0000950170-24-022256 | 10-K | XBRL Viewer

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Commitments and Contingencies - Additional Information (Detail) - USD ($)			12 Months Ended
	Sep. 01, 2022	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lessee Lease Description [Line Items]
Operating lease, right-of-use assets			$ 78,987,000	$ 82,737,000
Operating lease, short-term lease liability			17,891,000	12,829,000
Operating lease, long-term lease liability			$ 120,427,000	126,895,000
Finance lease, contractual lease term			3 years
Rent expense for operating and finance leases			$ 22,100,000	$ 21,600,000	$ 23,100,000
Lease Agreement
Lessee Lease Description [Line Items]
Operating lease, weighted average remaining lease term			9 years 8 months 12 days	10 years 8 months 12 days	11 years 8 months 12 days
Operating lease, weighted average discount rate			8.70%	8.70%	10.00%
Operating lease, cash paid included in net cash used in operating activities			$ 17,800,000	$ 24,100,000	$ 6,100,000
Financial lease estimated life			5 years
Finance Lease, Right-of-Use Asset			$ 1,800,000
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]			Property and equipment, net
Short term finance lease liability			$ 1,000,000
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]			Other current liabilities
Long term finance lease liability			$ 200,000
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]			Other non-current liabilities
Finance lease, weighted average remaining lease term			3 years	4 years	4 years 10 months 24 days
Finance lease, weighted average discount rate			9.50%	9.50%	9.50%
Finance lease payments			$ 900,000	$ 900,000	$ 0
Oyster Point Lease [Member] \| California [Member]
Lessee Lease Description [Line Items]
Operating lease, lease expiration date			Oct. 31, 2033
Operating lease, commencement date		Mar. 31, 2021
Radnor Lease [Member] \| Pennsylvania [Member]
Lessee Lease Description [Line Items]
Operating lease, lease expiration date			Jul. 31, 2027
Operating lease, commencement date	Sep. 01, 2022
Operating lease commenced, term description			one five-year option to extend the lease

Research and Development Arrangements

12 Months Ended

Dec. 31, 2023

Research and Development [Abstract]

Research and Development Arrangements

Note 3 — Research and Development Arrangements

2021 Ji Xing and RTW Transactions

In December 2021, we entered into the 2021 RTW Transactions as described below, related to omecamtiv mecarbil.

Ji Xing Omecamtiv Mecarbil License and Collaboration Agreement

On December 20, 2021, we entered into the Ji Xing OM License Agreement, pursuant to which we granted to Ji Xing an exclusive license to develop and commercialize omecamtiv mecarbil in China and Taiwan. Under the terms of the Ji Xing OM License Agreement, we are the beneficiary of a nonrefundable $50.0 million payment obligation from Ji Xing comprised of a $40.0 million payment as consideration for the rights granted by us to Ji Xing and $10.0 million attributable to our having submitted to the FDA an NDA for omecamtiv mecarbil. The $50.0 million payment was received by the Company in January 2022. We may be eligible to receive from Ji Xing additional payments totaling up to $330.0 million for the achievement of certain commercial milestone events in connection to omecamtiv mecarbil. In addition, Ji Xing will pay us tiered royalties in the mid-teens to the low twenties range on the net sales of pharmaceutical products containing omecamtiv mecarbil in China and Taiwan, subject to certain reductions for generic competition, patent expiration and payments for licenses to third party patents.

Ji Xing will be responsible for the development and commercialization of omecamtiv mecarbil at its own cost and is required to use diligent efforts to develop and commercialize omecamtiv mecarbil in China and Taiwan. The development of omecamtiv mecarbil will be initially focused on HFrEF, and Ji Xing will have the opportunity to participate in Cytokinetics’ global clinical trials of omecamtiv mecarbil. Cytokinetics will supply omecamtiv mecarbil to Ji Xing either as a finished product or as an active pharmaceutical ingredient. Ji Xing may reimburse Cytokinetics for certain costs related to development and supply activities that we perform on their behalf.

The Ji Xing OM License Agreement, unless terminated earlier, will continue on a market-by-market basis until expiration of the relevant royalty term. Ji Xing has the right to terminate the Ji Xing OM License Agreement for convenience. Each party may terminate the Ji Xing OM License Agreement for the other party’s uncured material breach, insolvency, or failure to perform due to extended force majeure events. Cytokinetics may also terminate the Ji Xing OM License Agreement if Ji Xing challenges Cytokinetics’ patents or undergoes certain change of control transactions. Rights granted to Ji Xing in relation to omecamtiv mecarbil will revert to Cytokinetics upon termination, and, under certain circumstances, subject to a low single digit royalty payment by the Company to Ji Xing on the net sales of the products containing the compound omecamtiv mecarbil in China and Taiwan. We assessed this arrangement in accordance with ASC 606 and concluded that there is one performance obligation relating to the license of functional intellectual property. The performance obligation was satisfied, and we recognized the residual allocation of arrangement consideration as revenue of $54.9 million in 2021. Due to the nature of development, including the inherent risk of development and approval by regulatory authorities, we are unable to estimate if and when the development milestone payments could be achieved or become due and, accordingly, we consider the milestone payments to be fully constrained and excluded any potential milestone payments from the initial transaction price.

The consideration related to sales-based milestone payments, including royalties, will be recognized when the related sales occur under the sales- and usage-based royalty exception as these amounts have been determined to relate predominantly to the license.

We re-evaluate the probability of achievement of development milestones and any related constraints each reporting period. We will include consideration, without constraint, in the transaction price to the extent it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur.

Common Stock Purchase Agreements

On December 20, 2021, as part of the 2021 RTW Transactions, we entered into common stock purchase agreements with each of the RTW Investors. These common stock purchase agreements provided for the sale and issuance of an aggregate of 511,182 shares of our common stock at a price per share of $39.125 and an aggregate purchase price of $20.0 million. The closing occurred on December 20, 2021. The RTW Investors have agreed to certain trading and other restrictions with respect to the shares of common stock they purchased pursuant to these agreements, including a restriction on sales or other transfers of the shares, subject to certain exceptions, for a period of one year from the closing date. The restrictions resulted in a premium paid by the RTW Investors of $4.9 million, which represents the excess amount paid over the fair value of the shares of common stock purchased. The premium was determined by analyzing the restrictions discount applied to the closing stock price as of December 20, 2021, which is a Level 2 fair value input. The cash received less the calculated premium is the $15.1 million fair value of the common stock recorded.

2020 Ji Xing and RTW Transactions

On July 14, 2020, we entered in the 2020 RTW Transactions, as described below, with RTW Royalty Holdings and Ji Xing, related to aficamten, our proprietary small molecule cardiac myosin inhibitor product, a novel cardiac myosin inhibitor, and other assets.

Ji Xing Aficamten License and Collaboration Agreement

On July 14, 2020, we entered into the Ji Xing Aficamten License Agreement with Ji Xing, pursuant to which we granted to Ji Xing an exclusive license to develop and commercialize aficamten in China and Taiwan. Under the terms of the Ji Xing Aficamten License Agreement, we received from Ji Xing a nonrefundable upfront payment of $25.0 million. We may be eligible to receive from Ji Xing milestone payments totaling up to $200.0 million for the achievement of certain development and commercial milestone events in connection to aficamten in the field of oHCM and/or nHCM and other indications. In addition, Ji Xing will pay us tiered royalties in the low-to-high teens range on the net sales of the products containing aficamten in China and Taiwan, subject to certain reductions for generic competition, patent expiration and payments for licenses to third party patents.

Ji Xing will be responsible for the development and commercialization of aficamten at its own cost and is required to use diligent efforts to develop and commercialize aficamten in China and Taiwan. The development of aficamten will be initially focused on HCM, and Ji Xing will have the opportunity to participate in Cytokinetics’ global pivotal clinical trials of aficamten. Cytokinetics or a designated supplier will supply aficamten to Ji Xing either as a finished product or as an active pharmaceutical ingredient.

The Ji Xing Aficamten License Agreement, unless terminated earlier, will continue on a market-by-market basis until expiration of the relevant royalty term. Ji Xing has the right to terminate the Ji Xing Aficamten License Agreement for convenience. Each party may terminate the Ji Xing Aficamten License Agreement for the other party’s uncured material breach, insolvency, or failure to perform due to extended force majeure events. Cytokinetics may also terminate the Ji Xing Aficamten License Agreement if Ji Xing challenges Cytokinetics’ patents or undergoes certain change of control transactions. Rights granted to Ji Xing in relation to aficamten will revert to Cytokinetics upon termination, and, under certain circumstances, subject to a low single digit royalty payment by the Company to Ji Xing on the net sales of the products containing the compound aficamten in China and Taiwan.

We assessed this arrangement in accordance with ASC 606 and concluded that there is one performance obligation relating to the license of functional intellectual property. The performance obligation was satisfied, and we recognized the residual allocation of arrangement consideration as revenue of $36.5 million for 2020. Due to the nature of development, including the inherent risk of development and approval by regulatory authorities, we are unable to estimate if and when the development milestone payments could be achieved or become due and, accordingly, we consider the milestone payments to be fully constrained and exclude the milestone payments from the initial transaction price.

The consideration related to sales-based milestone payments, including royalties, will be recognized when the related sales occur under the sales and usage-based royalty exception of ASC 606 as these amounts have been determined to relate predominantly to the license.

We recognized a $2.5 million milestone from Ji Xing in 2023 for the initiation of a phase 3 clinical trial for aficamten in nHCM which was collected in the fourth quarter of 2023.

We recognized a $5.0 million milestone from Ji Xing during the third quarter of 2021 for initiation of a phase 3 clinical trial for aficamten in oHCM. Although our contractual right to payment had not arisen under the Ji Xing Aficamten License Agreement, we determined recognition of the milestone in 2021 was appropriate based on our expected initiation of a phase 3 clinical trial of aficamten in oHCM and was recorded as a corresponding contract asset in other current assets in our consolidated balance sheet as of December 31, 2021.

Research and development revenue from Ji Xing for 2023 and 2022 was $1.3 million and $0.9 million, respectively, related to certain development cost reimbursements. We had no research and development revenue from Ji Xing in 2021.

We had accounts receivable from Ji Xing of $0.3 million as of December 31, 2023 and $0.1 million as of December 31, 2022.

Royalty Purchase Agreement

On July 14, 2020, we entered the RTW Royalty Purchase Agreement with RTW Royalty Holdings, pursuant to which we sold our Mavacamten Royalty, under the Research Collaboration Agreement, dated August 24, 2012, between us and MyoKardia, Inc. to RTW Royalty Holdings for a one-time payment of $85.0 million. The RTW Royalty Purchase Agreement transaction closed on November 13, 2020. On March 31, 2021, RTW Royalty Holdings assigned its rights and obligations under the RTW Royalty Purchase Agreement to its affiliate, RTW ICAV. We understand that on April 18, 2022, RTW ICAV and MyoKardia, Inc. entered into agreements, which purported to assign all of RTW ICAV's rights, title and interest to the Mavacamten Royalty to MyoKardia, Inc., and on April 25, 2022, we entered into a tripartite agreement with RTW ICAV and MyoKardia, Inc. acknowledging the release and discharge of any further obligations by us or MyoKardia, Inc. in connection to the Mavacamten Royalty.

The allocation of the consideration for the 2020 RTW Transactions resulted in $87.0 million being allocated to the RTW Royalty Purchase Agreement representing its fair value. The $87.0 million was initially recorded as deferred revenue. On April 25, 2022, as discussed above, we entered into a tripartite agreement with RTW ICAV and MyoKardia, Inc. acknowledging the release and discharge of any further obligations by us or MyoKardia, Inc. in connection to the Mavacamten Royalty. As a result of the full extinguishment of the Mavacamten Royalty, we recognized revenue of $87.0 million in 2022.

Astellas

Our strategic alliance with Astellas to advance novel therapies for diseases and medical conditions associated with skeletal muscle impairment and weakness commenced in 2013 under the Astellas Agreement.

On April 23, 2020, we and Astellas entered into the two agreements referenced below which, taken together, amend and restate the Company’s research, development and commercialization collaboration with Astellas under the Astellas Agreement.

Fast Skeletal Regulatory Activator Agreement

The Company and Astellas entered into the Astellas FSRA Agreement on April 23, 2020. As a result of the Astellas FSRA Agreement, the Company will now have exclusive control and responsibility for the Company's future development and commercialization of reldesemtiv, CK-601 and other FSRA compounds and products, and accordingly, Astellas has agreed to terminate its license to all FSRA compounds and related products.

Under the Astellas FSRA Agreement, Astellas agreed to pay one-third of the out-of-pocket clinical development costs which may be incurred in connection with the Company’s Phase 3 clinical trial of reldesemtiv in ALS, up to a maximum contribution by Astellas of $12 million. Astellas also agreed to non-cash contributions to the Company, which included the transfer of its existing inventories of active pharmaceutical ingredient of reldesemtiv and CK-601. As of December 31, 2023, we have billed and collected from Astellas up to the maximum contribution of $12.0 million. On March 31, 2023, we announced that we discontinued COURAGE-ALS, our Phase 3 clinical trial of reldesemtiv in patients with ALS, and COURAGE-ALS OLE.

Research and development revenue from Astellas for 2023, 2022, and 2021 was $2.7 million, $5.7 million, and $3.2 million, respectively.

We had no accounts receivable from Astellas as of December 31, 2023 and 2022.

Amgen

On November 23, 2020, we received written notice of termination from Amgen of the Amgen Agreement pertaining to the discovery, development and commercialization of novel small molecule therapeutics, including omecamtiv mecarbil, a novel cardiac myosin activator, and CK-136 (formerly AMG 594), a novel cardiac troponin activator. The termination of the Amgen Agreement was effective May 20, 2021.

We recognized research and development revenue for reimbursements from Amgen of both internal costs of certain full-time employee equivalents and other costs related to the Amgen Agreement, which terminated effective May 20, 2021. Research and development revenue from Amgen was $7.4 million in 2021 and consisted of reimbursement of costs we incurred related to METEORIC-HF. There was no research and development revenue from Amgen in 2023 and 2022.

Stockholders' Equity - Summary of Restricted Stock Unit Activity Including Performance Stock Units (Detail) - Restricted Stock Units (RSUs) Including Performance Stock Units (PSUs) - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Restricted Stock Units, Beginning Balance	1,214,264	1,414,827	1,116,642
Number of Restricted Stock Units, Granted	965,863	780,519	1,093,450
Number of Restricted Stock Units, Exercised	(721,215)	(707,772)	(606,240)
Number of Restricted Stock Units, Forfeited	(84,290)	(273,310)	(189,025)
Number of Restricted Stock Units, Ending Balance	1,374,622	1,214,264	1,414,827
Weighted Average Award Date Fair Value per Share, Beginning Balance	$ 30.07	$ 18.52	$ 11.88
Weighted Average Award Date Fair Value per Share, Granted	39.09	37.69	21.69
Weighted Average Award Date Fair Value per Share, Exercised	27.4	16.72	11.13
Weighted Average Award Date Fair Value per Share, Forfeited	35.46	26.65	21.32
Weighted Average Award Date Fair Value per Share, Ending Balance	$ 37.47	$ 30.07	$ 18.52

Stockholders' Equity - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 72,065	$ 47,853	$ 26,832
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	32,134	19,100	10,463
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 39,931	$ 28,753	$ 16,369

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Summary of Property and Equipment

Our property and equipment consisted of (in thousands):


	December 31,
	2023			2022
Property and equipment, net:
Laboratory equipment	$	18,839		$	18,490
Computer equipment and software		3,263			3,900
Office equipment, furniture and fixtures		6,061			6,056
Leasehold improvements		66,874			65,912
Construction in progress		220			741
Right-of-use assets, finance lease		1,839			2,448
Total property and equipment		97,096			97,547
Less: Accumulated depreciation		(28,348	)		(17,094	)
	$	68,748		$	80,453

Summary of Accrued Liabilities

Our accrued liabilities were as follows (in thousands):


	December 31,
	2023		2022
Accrued liabilities:
Clinical and preclinical costs	$	5,880	$	16,105
Compensation related		29,255		21,767
Other accrued expenses		7,506		6,224
Total accrued liabilities	$	42,641	$	44,096

Income Taxes - Additional Information (Detail) € in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2021 EUR (€)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Income Tax Contingency [Line Items]
Provision for income tax		$ 0	$ 0	$ 0
Increase (decrease) in valuation allowance		$ 128,600,000	116,500,000
Research and development credits and orphan drug credits, federal carryforwards will expire		2024
Unrecognized tax benefits		$ 24,500,000	$ 17,700,000	$ 10,300,000
Multinational enterprises with annual global revenue excess capital \| €	€ 750
Payment of a global minimum tax rate	15.00%
Revenue threshold \| €	€ 750
California Income Tax Purposes [Member]
Income Tax Contingency [Line Items]
Credit carryforwards for federal and state		22,800,000
Federal Tax [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		$ 955,700,000
Net operating loss carryforwards expiration		2024
Credit carryforwards for federal and state		$ 126,300,000
Federal and State Tax [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		$ 423,700,000
Net operating loss carryforwards expiration		2028
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Net operating loss carryforwards		$ 800,000
Net operating loss carryforwards expiration		2030

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 113,024	$ 65,582
Short-term investments	501,800	716,995
Accounts receivable	1,283	147
Prepaid expenses and other current assets	11,944	12,462
Total current assets	628,051	795,186
Long-term investments	40,534	46,708
Property and equipment, net	68,748	80,453
Operating lease right-of-use assets	78,987	82,737
Other assets	7,996	9,691
Total assets	824,316	1,014,775
Current liabilities:
Accounts payable	21,507	25,611
Accrued liabilities	42,641	44,096
Short-term operating lease liabilities	17,891	12,829
Current portion of long-term debt	10,080	958
Other current liabilities	10,559	1,123
Total current liabilities	102,678	84,617
Term loan, net	58,384	63,810
Convertible notes, net	548,989	545,808
Liabilities related to revenue participation right purchase agreements, net	379,975	300,501
Long-term operating lease liabilities	120,427	126,895
Other non-current liabilities	186	1,044
Total liabilities	1,210,639	1,122,675
Commitments and contingencies
Stockholders' deficit:
Preferred stock, $0.001 par value: Authorized: 10,000,000 shares; Issued and outstanding: none	0	0
Common stock, $0.001 par value: Authorized: 163,000,000 shares; Issued and outstanding: 101,637,922 shares at December 31, 2023 and 94,833,975 shares at December 31, 2022	102	94
Additional paid-in capital	1,725,823	1,481,590
Accumulated other comprehensive loss	(10)	(3,590)
Accumulated deficit	(2,112,238)	(1,585,994)
Total stockholders' deficit	(386,323)	(107,900)
Total liabilities and stockholders' deficit	$ 824,316	$ 1,014,775

Agreements with Royalty Pharma - Schedule of Initial Consideration (Detail) - 2022 Royalty Pharma Transactions [Member] $ in Thousands	Jan. 07, 2022 USD ($)
Debt Instrument [Line Items]
Consideration Fair Value	$ 116,385
Consideration proceeds	150,000
Consideration allocation	150,000
Revenue Participation Right Purchase Agreements [Member]
Debt Instrument [Line Items]
Consideration Fair Value	69,498
Consideration proceeds	100,000
Consideration allocation	89,571
Development Funding Loan Agreement [Member]
Debt Instrument [Line Items]
Consideration Fair Value	46,887
Consideration proceeds	50,000
Consideration allocation	$ 60,429

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1F

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1F

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Section 50
-Paragraph 1I
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Income Taxes - Summary of Deferred Tax Assets, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating loss carryforwards	$ 231,915	$ 202,459
Tax credits	119,815	98,292
Liability related to sale of future royalties	85,501	68,366
Reserves and accruals	35,466	23,950
Capitalized R&D	95,437	48,047
Long-term lease liability	28,634	28,901
Total noncurrent deferred tax assets	596,768	470,015
Deferred tax liabilities:
Depreciation and amortization	(6,842)	(7,909)
Operating lease right-of-use assets	(17,392)	(18,192)
Unrealized Loss	(6)	0
Total noncurrent deferred tax liabilities	(24,240)	(26,101)
Less: Valuation allowance	(572,528)	(443,914)
Net deferred tax assets	$ 0	$ 0

Balance Sheet Components - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property Plant And Equipment [Line Items]
Total property and equipment	$ 97,096	$ 97,547
Less: Accumulated depreciation	(28,348)	(17,094)
Total property and equipment, net	68,748	80,453
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	18,839	18,490
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	3,263	3,900
Office Equipment, Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	6,061	6,056
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	66,874	65,912
Construction in Progress [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	220	741
Right-of-Use Assets, Finance Lease [Member]
Property Plant And Equipment [Line Items]
Total property and equipment	$ 1,839	$ 2,448

Stockholders' Equity - Fair Value of Share-Based Payments was Estimated on Date of Grant Based on Assumptions (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Stock Option [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Risk-free interest rate, minimum	3.57%	1.41%	0.58%
Risk-free interest rate, maximum	4.60%	4.01%	1.28%
Volatility, minimum		66.00%	66.00%
Volatility, maximum		67.00%	67.00%
Volatility	67.00%
Expected term in years	6 years 3 months 18 days
Expected dividend yield	0.00%	0.00%	0.00%
Minimum [Member] \| Employee Stock Option [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Expected term in years		6 years 3 months 18 days	6 years 4 months 24 days
Maximum [Member] \| Employee Stock Option [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Expected term in years		6 years 4 months 24 days	6 years 6 months
ESPP [Member]
Deferred Compensation Arrangement With Individual Share Based Payments [Line Items]
Risk-free interest rate, minimum	5.33%	1.63%
Risk-free interest rate, maximum	5.44%	4.65%
Risk-free interest rate			0.05%
Volatility, minimum	49.00%	64.00%	66.00%
Volatility, maximum	50.00%	65.00%	67.00%
Expected term in years	6 months	6 months	6 months
Expected dividend yield	0.00%	0.00%	0.00%

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ (526,244)	$ (388,955)	$ (215,314)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stockholders' Equity - Additional Information (Detail)		1 Months Ended			12 Months Ended
Stockholders' Equity - Additional Information (Detail)	May 31, 2022 $ / shares shares	Jun. 30, 2022 $ / shares shares	May 31, 2021 Tranche $ / shares shares	May 31, 2020 shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Mar. 01, 2023 USD ($)	Feb. 28, 2023 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Intrinsic value of stock options outstanding \| $					$ 676,400,000
Allocated share based compensation expense \| $					$ 72,065,000	$ 47,853,000	$ 26,832,000
Outstanding warrants					12,957
Issuance of common stock under at-the-market offering, net of issuance costs, shares					101,637,922	94,833,975
Proceeds from issuance of common stock related to at-the-market offering, net of issuance costs \| $					$ 164,233,000
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock pursuant to ESPP, shares					136,065	98,153	108,780
Amended ATM Facility [Member] \| Cantor [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum offering price of common stock under At The Market agreement \| $								$ 300,000,000
Maximum percentage commission to be paid on gross proceedings under at the market agreement								3.00%
Issuance of common stock under at-the-market offering, net of issuance costs, shares					5,016,170
Proceeds from issuance of common stock related to at-the-market offering, net of issuance costs \| $					$ 164,200,000
Oxford and Silicon Valley Bank [Member] \| New Loan and Security Agreement [Member] \| 2019 Term Loan [Member] \| Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding warrants						28,306
Oxford and Silicon Valley Bank [Member] \| New Loan and Security Agreement [Member] \| 2019 Term Loan [Member] \| Warrants exercised in May 2022 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants exercise price \| $ / shares	$ 7.1
Warrants exercised	16,901
Oxford and Silicon Valley Bank [Member] \| New Loan and Security Agreement [Member] \| 2019 Term Loan [Member] \| Warrants exercised in June 2022 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants exercise price \| $ / shares		$ 9.76
Warrants exercised		9,226
Oxford and Silicon Valley Bank [Member] \| New Loan and Security Agreement [Member] \| 2019 Term Loan [Member] \| Warrants exercised in June 2022 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants exercise price \| $ / shares		$ 10.42
Warrants exercised		8,638
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation, vested restricted stock units, total fair value \| $					28,600,000
Unamortized/unrecognized stock-based compensation expense \| $					$ 29,200,000
Weighted-average period					1 year 7 months 6 days
Restricted Stock Units (RSUs) \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period					2 years
Restricted Stock Units (RSUs) \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period					3 years
Performance Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares available for grant			375,000
Per unit weighted average grant date fair value \| $ / shares			$ 25.32
Number of tranche \| Tranche			2
Performance Stock Units \| Tranche One
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share based payment award award vesting rights percentage			50.00%
Allocated share based compensation expense \| $						$ 700,000
Performance Stock Units \| Tranche Two
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation arrangement by share based payment award award vesting rights percentage			50.00%
Number of shares cancelled						182,500
Allocated share based compensation expense \| $						$ 0
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized/unrecognized stock-based compensation expense \| $					$ 102,200,000
Weighted-average period					2 years 6 months
2004 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option grant prices as percentage of the fair market value of the common stock					100.00%
Term to grant nonstatutory stock options and incentive stock options					10 years
Percentage of options grant to new employees					25.00%
Increase in number of authorized shares reserved for issuance	6,000,000
Shares available for grant					7,600,000
Share based compensation, options exercised, total intrinsic value \| $					$ 33,800,000	$ 46,300,000	$ 29,300,000
Intrinsic value of stock options outstanding \| $					$ 676,400,000
2004 Plan [Member] \| New Employee [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting right					Options granted to new employees generally vest 25% after one year and monthly thereafter over a period of four years
Period from percentage of stock option vested					1 year
Vesting period					4 years
Increase in number of authorized shares reserved for issuance	1,600,000								1,000,000
2004 Plan [Member] \| Existing Employee [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting right					Options granted to existing employees generally vest monthly over a period of four years
Vesting period					4 years
ESPP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option grant prices as percentage of the fair market value of the common stock					85.00%
Number of authorized shares reserved for issuance					103,822
Increase in common stock shares reserved for issuance				500,000
Issuance of common stock pursuant to ESPP, shares					136,065	98,153	108,780
Issuance of common stock pursuant to ESPP, per share \| $ / shares					$ 30.43	$ 32.89	$ 16.33

Debt (Tables)

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Schedule of Interest Cost Relating to Notes

The following table presents the total amount of interest cost recognized relating to the 2026 Notes (in thousands):


	Years Ended December 31,
	2023		2022		2021
Contractual interest expense	$	844	$	3,265	$	5,520
Accretion of debt discount		—		—		5,907
Amortization of debt issuance costs		108		355		59
Total interest expense recognized	$	952	$	3,620	$	11,486

The following table presents the total amount of interest cost recognized relating to the 2027 Notes (in thousands):


	2023		2022
Contractual interest expense	$	18,900	$	9,188
Amortization of debt issuance costs		3,074		1,542
Total interest expense recognized	$	21,974	$	10,730

Schedule of Maturities of Notes

Future minimum payments under the 2027 Notes and 2026 Notes are (in thousands):


Years ending December 31:	2027 Notes			2026 Notes			Total
2024	$	18,900		$	845		$	19,745
2025		18,900			845			19,745
2026		18,900			21,978			40,878
2027		558,900			—			558,900
Future minimum payments		615,600			23,668			639,268
Less: Interest		(75,600	)		(2,536	)		(78,136	)
Convertible notes, principal amount		540,000			21,132			561,132
Less: Debt issuance costs on the convertible notes		(11,799	)		(344	)		(12,143	)
Net carrying amount of the convertible notes	$	528,201		$	20,788		$	548,989

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During the fourth quarter ended December 31, 2023, none of our directors or officers (as defined in Rule 16a-1(f) under the Exchange Act) adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as those terms are defined in Item 408 of Regulation S-K.
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Total revenues	$ 7,530	$ 94,588	$ 70,428
Operating expenses:
Research and development	330,123	240,813	159,938
General and administrative	173,612	177,977	96,803
Total operating expenses	503,735	418,790	256,741
Operating loss	(496,205)	(324,202)	(186,313)
Interest expense	(28,306)	(19,414)	(16,440)
Loss on extinguishment of debt	0	(24,939)	0
Non-cash interest expense on liabilities related to revenue participation right purchase agreements	(29,362)	(31,742)	(12,892)
Interest and other income, net	27,629	11,342	331
Net loss	$ (526,244)	$ (388,955)	$ (215,314)
Net loss per share - basic	$ (5.45)	$ (4.33)	$ (2.8)
Net loss per share - diluted	$ (5.45)	$ (4.33)	$ (2.8)
Weighted-average number of shares used in computing net loss per share - basic	96,524	89,825	76,886
Weighted-average number of shares used in computing net loss per share - diluted	96,524	89,825	76,886
Other comprehensive gain (loss):
Unrealized gain (loss) on available-for-sale securities, net	$ 3,600	$ (2,721)	$ (1,018)
Foreign currency translation adjustments	(20)	0	0
Comprehensive loss	(522,664)	(391,676)	(216,332)
Research and Development Revenues [Member]
Revenues:
Total revenues	4,030	6,588	10,572
License Revenues [Member]
Revenues:
Total revenues	0	0	54,856
Milestone Revenues [Member]
Revenues:
Total revenues	3,500	1,000	5,000
Realization of Revenue Participation Right Purchase Agreement [Member]
Revenues:
Total revenues	$ 0	$ 87,000	$ 0

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments under Non-cancellable Lease

Future minimum lease payments under non-cancellable leases as of December 31, 2023 is as follows (in thousands):


Years ending December 31:	Operating Leases			Finance Leases
2024	$	18,738		$	990
2025		19,563			204
2026		20,180			-
2027		20,514			—
2028		20,738			—
Thereafter		109,981			—
Total future minimum lease payments		209,714			1,194
Less: Imputed interest		(71,396	)		(51	)
Total lease liability	$	138,318		$	1,143

Organization and Accounting Policies

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization and Accounting Policies

Note 1 — Organization and Accounting Policies

Organization

Cytokinetics, Incorporated (the “Company”, “we” or “our”) was incorporated under the laws of the state of Delaware on August 5, 1997. We are a late-stage biopharmaceutical company focused on the discovery and development of novel small molecule therapeutics that modulate muscle function for the potential treatment of serious diseases and medical conditions.

Our financial statements contemplate the conduct of our operations in the normal course of business. We have incurred an accumulated deficit of approximately $2.1 billion since inception and there can be no assurance that we will attain profitability. We had a net loss of $526.2 million and net cash used in operations of $414.3 million for the year ended December 31, 2023. Cash, cash equivalents, and investments decreased to $655.4 million as of December 31, 2023 from $829.3 million as of December 31, 2022. We anticipate that we will have operating losses and net cash outflows in future periods.

We are subject to risks common to late-stage biopharmaceutical companies including, but not limited to, development of new drug candidates, dependence on key personnel, and the ability to obtain additional capital as needed to fund our future plans. Our liquidity will be impaired if sufficient additional capital is not available on terms acceptable to us. To date, we have funded operations primarily through sales of our common stock, contract payments under our collaboration agreements, sales of future revenues and royalties, debt financing arrangements, government grants and interest income. Until we achieve profitable operations, we intend to continue to fund operations through payments from strategic collaborations, additional sales of equity securities, grants and debt financings. We have never generated revenues from commercial sales of our drugs and may not have drugs to market for several years, if ever. Our success is dependent on our ability to enter into new strategic collaborations and/or raise additional capital and to successfully develop and market one or more of our drug candidates. We cannot be certain that sufficient funds will be available from such a financing or through a collaborator when required or on satisfactory terms. Additionally, there can be no assurance that our drug candidates will be accepted in the marketplace or that any future products can be developed or manufactured at an acceptable cost. These factors could have a material adverse effect on our future financial results, financial position and cash flows.

Based on the current status of our research and development activities, we believe that our existing cash, cash equivalents, and investments will be sufficient to fund cash requirements for at least the next 12 months after the issuance of these consolidated financial statements. If, at any time, our prospects for financing our research and development programs decline, we may decide to reduce research and development expenses by delaying, discontinuing or reducing our funding of one or more of our research or development programs. Alternatively, we might raise funds through strategic collaborations, public or private financings or other arrangements. Such funding, if needed, may not be available on favorable terms, or at all. The financial statements do not include any adjustments that might result from the outcome of this uncertainty.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. We evaluate our estimates on an ongoing basis. We base our estimates on our historical experience and also on assumptions that we believe are reasonable; however, actual results could significantly differ from those estimates.

Basis of Presentation

The consolidated financial statements include the accounts of Cytokinetics, Incorporated and its wholly-owned subsidiaries and have been prepared in accordance with GAAP. Intercompany transactions and balances have been eliminated in consolidation. Certain prior period amounts have been reclassified to conform the prior period presentation to the current year.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of risk consist principally of cash, cash equivalents, restricted cash, investments, and accounts receivable.

Our cash, cash equivalents, restricted cash, and investments held with large financial institutions in the United States and deposits may exceed the Federal Deposit Insurance Corporation’s insurance limit.

Drug candidates we develop may require approvals or clearances from the FDA or other regulatory agencies prior to commercial sales. There can be no assurance that our drug candidates will receive any of the required approvals or clearances. If we were to be denied approval, or clearance or any such approval or clearance was to be delayed, it would have a material adverse impact on us.

Cash, Cash Equivalents, and Restricted Cash

We consider all highly liquid investments with a maturity of three months or less at the time of purchase to be cash equivalents, which consist of money market funds and repurchase agreements backed by U.S. Treasury securities. Repurchase agreements are collateralized by US Treasury securities for an amount not less than 102% of their value and are reported at a carrying value which approximates fair value due to their short duration.

A reconciliation of cash, cash equivalents, and restricted cash reported in our consolidated balance sheets to the amount reported within our consolidated statements of cash flows was as follows (in thousands):


	December 31,
	2023		2022
Cash and cash equivalents	$	113,024	$	65,582
Restricted cash		375		1,600
Total cash, cash equivalents, and restricted cash as reported within our consolidated statement of cash flows	$	113,399	$	67,182

As of December 31, 2023, our restricted cash balance of $0.4 million is used to collateralize letters of credit.

Investments

Our investments consist of U.S. Treasury securities, U.S. government agency securities, commercial paper, corporate obligations, and money market funds. We designate all investments as available-for-sale and report them at fair value, based on quoted market prices, with unrealized gains and losses recorded in accumulated other comprehensive loss. The cost of securities sold is based on the specific-identification method. Investments with original maturities greater than three months and remaining maturities of one year or less are classified as short-term investments. Investments with remaining maturities greater than one year are classified as long-term investments.

All of our available-for-sale investments are subject to a periodic impairment review. For each available-for-sale investment whose fair value is below its amortized cost, we determine if the impairment is a result of a credit-related loss or other factors using both quantitative and qualitative factors. If the impairment is a result of a credit-related loss, we recognize an allowance for credit losses. If the impairment is not a result of a credit loss, we recognize the loss in other comprehensive loss.

Property and Equipment, net

Property and equipment are stated at cost less accumulated depreciation and are depreciated on a straight-line basis over the estimated useful lives of the related assets, which are generally three years for computer equipment and software, five years for laboratory equipment and office equipment, and seven years for furniture and fixtures. Amortization of leasehold improvements and finance lease right-of-use assets are computed using the straight-line method over the shorter of the remaining lease term or the estimated useful life of the related assets, typically ranging from three to twelve years. Upon sale or retirement of assets, the costs and related accumulated depreciation and amortization are removed from the balance sheet and the resulting gain or loss is reflected in operations.

Impairment of Long-lived Assets

We review long-lived assets, including property, equipment and right-of-use assets, for impairment whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Impairment is measured as the amount by which the carrying amount of a long-lived asset exceeds its fair value. We would recognize an impairment loss when estimated undiscounted future cash flows expected to result from the use of the asset and its eventual disposition are less than its carrying amount.

Leases

We determine if the arrangement contains a lease at inception based on whether the contract conveys the right to control the use of an identified asset. The lease classification is determined at lease commencement, which is the date the underlying asset is available for use by the Company, and preliminary based on whether the arrangement is effectively a financed purchase of the underlying asset (finance lease) or not (operating lease). We determined the lease term at the commencement date by considering whether renewal options and termination options are reasonably assured of exercise. In addition to the fixed minimum lease payments required under the lease arrangements, certain leases include payments of operating expenses that may be revised based on the landlord’s estimate. These variable payments are excluded from the lease payments used to determine the right-of-use asset and lease liability and are recognized when the associated activity occurs.

We recognize right-of-use assets and short-term and long-term lease liabilities on our consolidated balance sheets for operating leases. The right-of-use asset and short-term and long-term lease liabilities for finance leases are recognized in property and equipment, other current liabilities, and other non-current liabilities, respectively, on the consolidated balance sheets.

In determining the present value of lease payments, we estimated our incremental borrowing rate based on information available upon commencement. We base the lease liabilities on the present value of remaining lease payments over the remaining terms of the leases using an estimated rate of interest that we would pay to borrow equivalent funds on a collateralized basis at the lease commencement date. The initial right-of-use asset, for both operating and finance leases, is measured based on the lease liability adjusted for any initial direct costs, lease prepayments, and lease incentives.

We recognize rent expense for operating leases on a straight-line basis over the lease term in operating expenses on the consolidated statements of operations. Finance lease right-of-use assets are amortized on a straight-line basis over the shorter of the expected useful life or the lease term, and the carrying amount of the lease liability is adjusted to reflect interest, which is recorded in interest expense.

We exclude from our consolidated balance sheets recognition of leases having a term of 12 months or less (short-term leases). We account for lease and non-lease components as a single component for our operating leases.

Revenue Recognition

We recognize revenue when we transfer promised goods or services to customers in an amount that reflects the consideration for those goods or services.

At contract inception, we assess the goods or services promised within each contract and assess whether each promised good or service is distinct and determine those that are performance obligations. For example, a license to our intellectual property is determined to be distinct from other performance obligations if licensee is able to use and benefit from the license on its own. Otherwise, licenses are bundled with other promises, such as ongoing research and development services, as combined performance obligation.

We enter into collaborative arrangements with partners that typically include payment to us for one of more of the following: (i) up-front license fees; (ii) milestone payments related to the achievement of developmental, regulatory, or commercial goals; (iii) royalties on net sales of licensed products; and (iv) research and development cost reimbursements. Up-front license fees are included in the transaction price. Development and regulatory milestone payments are included in the transaction price using the most likely amount method, if we conclude it is probable that a significant revenue reversal would not occur. For contracts that include sales-based royalties or sales-based milestones, we recognize revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty or sales-based milestone has been allocated has been satisfied.

Our joint programs with Astellas under the Astellas OSSA Agreement, and with Amgen under the Amgen Agreement (both of the Astellas OSSA Agreement and the Amgen Agreement having now been terminated), included promises of research and development services. We also entered into the Astellas FSRA Agreement on April 23, 2020. Under the Astellas FSRA Agreement, Astellas agreed to pay one-third of the out-of-pocket clinical development costs which may be incurred in connection with the Company’s Phase 3 clinical trial of reldesemtiv in ALS, up to a maximum contribution by Astellas of $12.0 million. We determined that these services collectively were distinct from any licenses provided to Astellas and Amgen under such agreements, and as such, these services were accounted for as a separate performance obligation recorded over time. We recognized revenue for these services as the performance obligations were satisfied, which we estimated using internal research and development costs incurred.

When a collaborative agreement has more than one performance obligation, we must develop estimates and assumptions that require judgment to determine the underlying stand-alone selling price for each performance obligation which determines how the transaction price is allocated among the performance obligations. The stand-alone selling price may include such items as, forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success, to determine the transaction price to allocate to each performance obligation.

For performance obligations that consist of the delivery of an intellectual property license, the revenue is recognized at the point in time that the license is delivered. For combined performance obligations consisting of an intellectual property license and research and development services, we recognize the combined performance obligation over time, using an input method, as the research and development services are performed.

We are required to make estimates related to the determination of the transaction price and our measurement of how revenue is recognized over time, using the input method. Any changes in these estimates are recorded on a cumulative catch-up basis, which would affect license, collaboration and other revenues and earnings in the period of adjustment.

Accrued Research and Development Expenditures

Clinical trial costs are a component of research and development expense. We accrue and expense clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research and manufacturing organizations and clinical sites. We determine the actual costs through monitoring patient enrollment, discussions with internal personnel and external service providers regarding the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.

Revenue Participation Right Purchase Agreements

We have entered into certain revenue participation right purchase agreements with certain investors, pursuant to which such investors purchased rights to royalties from certain revenue streams in exchange for consideration. We typically account for such agreements as liabilities to be amortized under the effective interest rate method over the life of the related royalty stream, when we have continuing involvement with the underlying R&D. We typically account for such agreements as deferred income to be amortized under the units-of-revenue method, when there is no continuing involvement with the underlying R&D. We are required to update our estimates, at each reporting period, related to the amount and timing of future royalty payments to be paid to the counterparties of the revenue participation right purchase agreements. The estimates of the future royalty payment determine the measurement of the non-cash interest expense and the carrying value of the liability.

Revenue participation right purchase agreements are measured using significant unobservable inputs. The estimates of future royalties requires the use of several assumptions such as: the probability of clinical success, the probability of regulatory approval, the estimated date of a product launch, estimates of eligible patient populations, estimates of prescribing behavior and patient compliance behavior, estimates of pricing, payor reimbursement and coverage, and sales ramp. As products containing aficamten and omecamtiv mecarbil have not yet been commercialized, the estimates are highly subjective.

In 2020, we entered into a royalty purchase agreement, pursuant to which we sold our right to receive certain payments on the net sales of products containing the compound mavacamten. The consideration received was deferred income to be amortized under the units-of-revenue method, as there was no continuing involvement with the underlying R&D. In 2022, we entered into a tripartite agreement with RTW ICAV and MyoKardia, Inc. acknowledging the release and discharge of any further obligations by us or MyoKardia, Inc. in connection to the Mavacamten Royalty and consequently we recognized the deferred revenue as Realization of revenue participation right purchase agreement on the income statement.

As of December 31, 2023, we have a total carrying value of approximately $380.0 million of liabilities related to revenue participation right purchase agreements.

Research and Development Expenditures

Research and development costs are charged to operations as incurred. Research and development expenses consist primarily of clinical manufacturing costs, preclinical study expenses, consulting and other third-party costs, employee compensation, supplies and materials, allocation of overhead and occupancy costs, facilities costs and depreciation of equipment.

Income Taxes

We account for income taxes under the asset and liability method. Under this method, deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to affect taxable income. Valuation allowances are established when necessary to reduce deferred tax assets to the amounts expected to be realized.

We recognize uncertain tax positions taken or expected to be taken on a tax return. Tax positions are initially recognized when it is more likely than not that the position will be sustained upon examination by the tax authorities. Such tax positions are initially and subsequently measured as the largest amount of tax benefit that is more likely than not of being realized upon ultimate settlement with the tax authority assuming full knowledge of the position and relevant facts.

We recognize interest accrued related to unrecognized tax benefits and penalties as income tax expense.

Stock-Based Compensation

We maintain equity incentive plans under which incentive stock options may be granted to employees and nonqualified stock options, restricted stock awards, performance-based stock units and stock appreciation rights may be granted to employees, directors, consultants and advisors. In addition, we maintain an ESPP under which employees may purchase shares of our common stock through payroll deductions.

Stock-based compensation expense related to stock options granted to employees and directors is recognized based on the grant date estimated fair values using the Black Scholes option pricing model. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service period.

Stock-based compensation expense related to performance-based stock units granted to employees is recognized based on the grant-date fair value of each award and recorded as expense over the vesting period using the ratable method when the underlying performance conditions are deemed probable.

Stock-based compensation expense related to the ESPP is recognized based on the fair value of each award estimated on the first day of the offering period using the Black Scholes option pricing model and recorded as expense over the service period using the straight-line method.

Debt

12 Months Ended

Dec. 31, 2023

Debt Disclosure [Abstract]

Debt

Note 7 — Debt

Silicon Valley Bank and Oxford Finance Term Loans

Prior to January 7, 2022, we maintained $45.0 million aggregate principal amount of the Term Loan Agreement with Silicon Valley Bank and Oxford Finance LLC.

The Term Loan Agreement was terminated, and all amounts thereunder repaid in connection to our entry into that certain RP Loan Agreement, between us and RPDF, as further described above.

As a result of the termination of the Term Loan Agreement and the repayment to the Lenders, in 2022, we recorded $2.7 million in loss on debt extinguishment in the consolidated statements of operations and comprehensive loss, consisting of the premium on debt repayments and the write-off of the remaining term loan fees and debt issuance costs.

Interest expense for the Term Loan Agreement was immaterial for 2022 because it represented approximately one week of interest before extinguishment. Interest expense for the Term Loan Agreement was $4.8 million for 2021.

Convertible Notes

On November 13, 2019, we issued $138.0 million aggregate principal amount of 2026 Notes. On July 6, 2022, we issued $540.0 million aggregate principal amount of 2027 Notes and used approximately $140.3 million of the net proceeds from the offering of 2027 Notes and issued 8,071,343 shares of common stock to repurchase approximately $116.9 million aggregate principal amount of the 2026 Notes pursuant to privately negotiated exchange agreements entered into with certain holders of the 2026 Notes concurrently with the pricing of the offering of the 2027 Notes. As a result of the partial repurchase of the 2026 Notes, the Company recorded an inducement loss of $22.2 million, consisting of the difference between the consideration to the holders pursuant to the exchange agreements and the if-converted value of the 2026 Notes under the original terms. As of December 31, 2023, there remain $21.1 million aggregate principal amount of 2026 Notes outstanding.

The 2026 Notes are unsecured obligations and bear interest at an annual rate of 4.0% per year, payable semi-annually on May 15 and December 15 of each year, beginning May 15, 2020. The 2026 Notes are governed by an indenture we entered into with U.S. Bank National Association, as trustee. The 2026 Notes will mature on November 15, 2026, unless earlier repurchased or redeemed by us or converted at the option of the holders. We may redeem the 2026 Notes prior to the maturity date but we are not required to and no sinking fund is provided for the 2026 Notes. The 2026 Notes may be converted, under certain circumstances as described below, based on an initial conversion rate of 94.7811 shares of common stock per $1,000 principal amount (which represents an initial conversion price of $10.55 per share). The conversion rate for the 2026 Notes will be subject to adjustment upon the occurrence of certain specified events. In addition, upon the occurrence of a make-whole fundamental change (as defined in the indenture), we will, in certain circumstances, increase the conversion rate by a number of additional shares for a holder that elects to convert its notes in connection with such make-whole fundamental change. The 2026 Notes are convertible at December 31, 2023 at the option of the holder.

The 2026 Notes will be redeemable, in whole or in part, at our option at any time, and from time to time, on or after November 20, 2023 and, in the case of any partial redemption, on or before the 60th scheduled trading day before the maturity date, at a cash redemption price equal to the principal amount of the 2026 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date but only if the last reported sale price per share of our common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date we may send the related redemption notice; and (2) the trading day immediately before the date we may send such notice. If a “fundamental change” (as defined in the indenture agreement, dated November 13, 2019 between us and U.S. Bank National Association, as trustee, as supplemented by the first supplemental indenture dated as of November 13, 2019 between us and such trustee) occurs, then, subject to certain exceptions, holders may require us to repurchase their 2026 Notes at a cash repurchase price equal to the principal amount of the 2026 Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date.

The following table presents the total amount of interest cost recognized relating to the 2026 Notes (in thousands):


	Years Ended December 31,
	2023		2022		2021
Contractual interest expense	$	844	$	3,265	$	5,520
Accretion of debt discount		—		—		5,907
Amortization of debt issuance costs		108		355		59
Total interest expense recognized	$	952	$	3,620	$	11,486

The effective interest rate of the 2026 Notes was 4.6% as of December 31, 2023 and 2022 and 12.5% as of December 31, 2021. As of December 31, 2023. the unamortized debt issuance cost for the 2026 Notes was $0.3 million and will be amortized over approximately 2.9 years.

The 2027 Notes ($540.0 million of aggregate principal) are our senior, unsecured obligations and are (i) senior in right of payment to our future indebtedness that is expressly subordinated to the 2027 Notes in right of payment; (ii) equal in right of payment with all of our indebtedness that is not so subordinated (including the 2026 Notes); (iii) effectively subordinated to our existing and future secured indebtedness, to the extent of the value of the collateral securing that indebtedness; and (iv) structurally subordinated to all existing and future indebtedness and other liabilities, including trade payables, and (to the extent we are not a holder thereof) preferred equity, if any, of our subsidiaries. The net proceeds of the 2027 Notes were approximately $523.6 million after deducting issuance costs related to the 2027 Notes. The 2027 Notes bear interest at a rate of 3.5% per year, payable semiannually in arrears on January 1 and July 1 of each year, beginning on January 1, 2023. The 2027 Notes will mature on July 1, 2027, unless earlier converted, redeemed or repurchased.

The 2027 Notes are convertible into cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, based on the applicable conversion rate(s). The initial conversion rate for the 2027 Notes is 19.5783 shares of our common stock per $1,000 principal amount of such Notes, which is equivalent to an initial conversion price of approximately $51.08 per share. Holders of the 2027 Notes may convert all or any portion of their convertible notes at their option only in the following circumstances: (i) during any calendar quarter (and only during such calendar quarter) commencing after the calendar quarter ending on September 30, 2022, if the last reported sale price per share of our common stock, $0.001 par value per share, exceeds 130% of the conversion price for each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (ii) during the five consecutive business days immediately after any 10 consecutive trading day period (such 10 consecutive trading day period, the “measurement period”) if the trading price per $1,000 principal amount of 2027 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of our common stock on such trading day and the conversion rate on such trading day; (iii) upon the occurrence of certain corporate events or distributions on our common stock, as described in the 2027 Indenture; (iv) if we call such 2027 Notes for redemption; and (v) at any time from, and including, March 1, 2027 until the close of business on the scheduled trading day immediately before the maturity date.

We may not redeem the 2027 Notes at our option at any time before July 7, 2025. The 2027 Notes will be redeemable, in whole or in part (subject to the “Partial Redemption Limitation” (as defined in the 2027 Indenture)), at our option at any time, and from time to time, on or after July 7, 2025 and, in the case of a partial redemption, on or before the 60th scheduled trading day immediately before the maturity date, at a cash redemption price equal to the principal amount of the 2027 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date, but only if the last reported sale price per share of our common stock exceeds 130% of the conversion price on (i) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date we may send the related redemption notice; and (ii) the trading day immediately before the date we may send such notice. In addition, calling any of the 2027 Notes for redemption will constitute a Make-Whole Fundamental Change with respect to that convertible note, in which case the conversion rate applicable to the conversion of that Note will be increased in certain circumstances if it is converted after it is called for redemption. The conversion rate for the 2027 Notes shall not exceed 25.4517 shares per $1,000 principal amount of such Notes, subject to certain customary anti-dilution adjustments (as defined in the 2027 indenture). Pursuant to the Partial Redemption Limitation, we may not elect to redeem less than all of the outstanding 2027 Notes unless at least $75.0 million aggregate principal amount of 2027 Notes are outstanding and not subject to redemption as of the time we may send the related redemption notice.

If a “Fundamental Change” (as defined in the 2027 Indenture) occurs, then, subject to a limited exception for certain cash mergers, noteholders may require us to repurchase their 2027 Notes at a cash repurchase price equal to the principal amount of the 2027 Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date. The definition of Fundamental Change includes certain business combination transactions involving us and certain de-listing events with respect to our common stock.

The following table presents the total amount of interest cost recognized relating to the 2027 Notes (in thousands):


	2023		2022
Contractual interest expense	$	18,900	$	9,188
Amortization of debt issuance costs		3,074		1,542
Total interest expense recognized	$	21,974	$	10,730

The effective interest rate of the 2027 Notes was 4.2% as of December 31, 2023 and 2022. As of December 31, 2023, the unamortized debt issuance cost for the 2027 Notes was $11.8 million and will be amortized over approximately 3.6 years. In 2023, the conditions allowing holders of the Notes to convert were not met. As a result, the 2027 Notes are not convertible at December 31, 2023.

Future minimum payments under the 2027 Notes and 2026 Notes are (in thousands):


Years ending December 31:	2027 Notes			2026 Notes			Total
2024	$	18,900		$	845		$	19,745
2025		18,900			845			19,745
2026		18,900			21,978			40,878
2027		558,900			—			558,900
Future minimum payments		615,600			23,668			639,268
Less: Interest		(75,600	)		(2,536	)		(78,136	)
Convertible notes, principal amount		540,000			21,132			561,132
Less: Debt issuance costs on the convertible notes		(11,799	)		(344	)		(12,143	)
Net carrying amount of the convertible notes	$	528,201		$	20,788		$	548,989

As of December 31, 2023, the estimated fair value of the 2027 Notes and 2026 Notes was $990.4 million and $168.4 million, respectively, and was based upon observable, Level 2 inputs, including pricing information from recent trades of the convertible notes.

Capped Call Transactions

In connection with the offering of the 2026 Notes, the Company entered into privately-negotiated capped call transactions with one of the underwriters in the offering or its affiliate. On October 24, 2022, we entered into a termination agreement in connection to the capped call transactions and thereby released the capped call counterparties of any further obligations in relation to the capped call transactions. As a result of the termination agreement and unwinding of the capped call transactions, we received gross proceeds of $26.4 million in cash.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Reconciliation of Statutory Federal Income Tax Rate to Effective Tax Rate

The following reconciles the statutory federal income tax rate to our effective tax rate:


	Years Ended December 31,
	2023			2022			2021
Tax at federal statutory tax rate		21	%		21	%		21	%
State tax, net of federal benefits		1	%		1	%		0	%
Change in state effected rates		0	%		0	%		(1	)%
Tax credits, net		4	%		4	%		3	%
Change in valuation allowance		(24	)%		(26	)%		(24	)%
Stock-based compensation		1	%		2	%		2	%
Other		(3	)%		(2	)%		(1	)%
Total		0	%		0	%		0	%

Summary of Deferred Tax Assets, Net

Deferred tax assets, net, reflecting the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes, were as follows (in thousands):


	As of December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	231,915		$	202,459
Tax credits		119,815			98,292
Liability related to sale of future royalties		85,501			68,366
Reserves and accruals		35,466			23,950
Capitalized R&D		95,437			48,047
Long-term lease liability		28,634			28,901
Total noncurrent deferred tax assets		596,768			470,015
Deferred tax liabilities:
Depreciation and amortization		(6,842	)		(7,909	)
Operating lease right-of-use assets		(17,392	)		(18,192	)
Unrealized Loss		(6	)		—
Total noncurrent deferred tax liabilities		(24,240	)		(26,101	)
Less: Valuation allowance		(572,528	)		(443,914	)
Net deferred tax assets	$	—		$	—

Schedule of Activity Related to our Gross Unrecognized Tax Benefits

Activity related to our gross unrecognized tax benefits were (in thousands):


	Years Ended December 31,
	2023			2022			2021
Balance at the beginning of the year	$	18,355		$	11,295		$	10,522
Increase related to prior year tax positions		—			4,438			—
Decrease related to prior year tax positions		(97	)		(1,804	)		(29	)
Increase related to current year tax positions		6,974			4,426			802
Balance at the end of the year	$	25,232		$	18,355		$	11,295

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Credit losses on debt securities	$ 0	$ 0

Income Taxes

12 Months Ended

Dec. 31, 2023

Income Tax Disclosure [Abstract]

Income Taxes

Note 10 — Income Taxes

We did not record an income tax provision in 2023, 2022, and 2021 because we had net taxable losses. Our significant jurisdictions are the United States and California.

The following reconciles the statutory federal income tax rate to our effective tax rate:


	Years Ended December 31,
	2023			2022			2021
Tax at federal statutory tax rate		21	%		21	%		21	%
State tax, net of federal benefits		1	%		1	%		0	%
Change in state effected rates		0	%		0	%		(1	)%
Tax credits, net		4	%		4	%		3	%
Change in valuation allowance		(24	)%		(26	)%		(24	)%
Stock-based compensation		1	%		2	%		2	%
Other		(3	)%		(2	)%		(1	)%
Total		0	%		0	%		0	%


	As of December 31,
	2023			2022
Deferred tax assets:
Net operating loss carryforwards	$	231,915		$	202,459
Tax credits		119,815			98,292
Liability related to sale of future royalties		85,501			68,366
Reserves and accruals		35,466			23,950
Capitalized R&D		95,437			48,047
Long-term lease liability		28,634			28,901
Total noncurrent deferred tax assets		596,768			470,015
Deferred tax liabilities:
Depreciation and amortization		(6,842	)		(7,909	)
Operating lease right-of-use assets		(17,392	)		(18,192	)
Unrealized Loss		(6	)		—
Total noncurrent deferred tax liabilities		(24,240	)		(26,101	)
Less: Valuation allowance		(572,528	)		(443,914	)
Net deferred tax assets	$	—		$	—

Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Based upon the weight of available evidence, which includes our historical operating performance, reported cumulative net losses since inception, expected future losses, and difficulty in accurately forecasting our future results and an assessment of both positive and negative evidence when determining whether it is more likely than not that deferred tax assets are recoverable, we maintained a full valuation allowance on the net deferred tax assets as of December 31, 2023 and 2022. The valuation allowance increased by $128.6 million in 2023 and increased by $116.5 million in 2022.

At December 31, 2023 federal NOL carryforwards were $955.7 million, apportioned state NOL carryforwards before federal benefits were $423.7 million, and foreign NOL carryforwards were $0.8 million. If not utilized, federal and state net operating loss carryforwards incurred prior to 2018 will begin to expire in various amounts beginning 2024 and 2028, respectively, and the foreign net operating loss carryforwards will begin to expire in 2030.

At December 31, 2023, tax credits of $126.3 million and $22.8 million for federal and California income tax purposes, respectively consisted of Research and Development Credits and Orphan Drug Credits. If not utilized, the federal carryforwards will expire in various amounts beginning in 2024. California based credit carryforwards do not expire.

In general, under Section 382, a corporation that undergoes an ‘ownership change’ is subject to limitations on its ability to utilize its pre-change net operating losses and tax credits to offset future taxable income. We do not believe it has experienced an ownership change since 2006, however, a portion of its NOLs and tax credits prior to 2007 will be subject to limitations under Section 382.

Activity related to our gross unrecognized tax benefits were (in thousands):


	Years Ended December 31,
	2023			2022			2021
Balance at the beginning of the year	$	18,355		$	11,295		$	10,522
Increase related to prior year tax positions		—			4,438			—
Decrease related to prior year tax positions		(97	)		(1,804	)		(29	)
Increase related to current year tax positions		6,974			4,426			802
Balance at the end of the year	$	25,232		$	18,355		$	11,295

We are subject to federal and various state & local and foreign income tax examinations for all fiscal years with unutilized NOLs and tax credit carryforwards. Included in the balance of unrecognized tax benefits as of December 31, 2023, 2022, and 2021 are $24.5 million, $17.7 million, and $10.3 million of tax benefits, respectively, that, if recognized, would result in adjustments to other tax accounts, primarily deferred taxes.

The Inflation Reduction Act of 2022, or IRA, was signed into law on August 16, 2022. The bill was meant to address the high inflation rate in the United States through various climate, energy, healthcare, and other incentives. These incentives are meant to be paid for by the tax provisions included in the IRA, such as a new 15 percent corporate minimum tax, a 1 percent new excise tax on stock buybacks, additional IRS funding to improve taxpayer compliance, and others. The IRA provisions are effective for tax years beginning after December 31, 2022. At this time, none of the IRA tax provisions are expected to have a material impact to our consolidated tax provision for the year ending December 31, 2023. The Company will continue to closely monitor any effects from future legislation.

In October 2021, the Organization for Economic Co-operation and Development (“OECD”)/G20 finalized the significant components of a two-pillar global tax reform plan, which has now been agreed to by the majority of OECD members. Pillar Two requires multinational enterprises with annual global revenue exceeding €750 million to pay a global minimum tax of 15%. The Company does not currently expect to meet the €750 million revenue threshold. The Company will continue to evaluate the potential impact on future periods of the Pillar Two framework and the implementation of the Pillar Two rules in the jurisdictions in which it operates.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480990/946-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//740/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-21

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482526/740-270-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-17

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482603/740-30-50-2

+ Details

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Summary of Stock Option Activity

Stock option activity in 2023, 2022, and 2021 was as follows:


	Stock Options Outstanding			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in millions)
Balance at December 31, 2020		8,501,949		$	10.02
Granted		2,513,350			22.43
Exercised		(1,346,194	)		9.01
Forfeited		(296,146	)		14.56
Balance at December 31, 2021		9,372,959		$	13.35
Granted		3,424,150			39.79
Exercised		(1,389,031	)		10.13
Forfeited		(415,675	)		28.94
Balance at December 31, 2022		10,992,403		$	22.13
Granted		2,447,225			38.59
Exercised		(1,200,895	)		12.13
Forfeited		(458,503	)		35.01
Balance at December 31, 2023		11,780,230		$	26.07		6.8	$	676.4
Exercisable at December 31, 2023		7,279,310		$	19.29		5.7	$	467.3

Summary of Restricted Stock Unit Activity Including Performance Stock Units

RSU, including PSU, activity in 2023, 2022, and 2021 was as follows:


	Number of Restricted Stock Units			Weighted Average Award Date Fair Value per Share
Balance at December 31, 2020		1,116,642		$	11.88
Granted		1,093,450			21.69
Exercised		(606,240	)		11.13
Forfeited		(189,025	)		21.32
Balance at December 31, 2021		1,414,827		$	18.52
Granted		780,519			37.69
Exercised		(707,772	)		16.72
Forfeited		(273,310	)		26.65
Balance at December 31, 2022		1,214,264		$	30.07
Granted		965,863			39.09
Exercised		(721,215	)		27.40
Forfeited		(84,290	)		35.46
Balance at December 31, 2023		1,374,622		$	37.47

Fair Value of Share-Based Payments was Estimated on Date of Grant Based on Assumptions

We use the Black-Scholes option pricing model to determine the fair value of stock option grants to employees and directors and employee stock purchase plan shares. The fair value of share-based payments was estimated on the date of grant based on the following assumptions:

         
        Year Ended December
31, 2023

        Year Ended December
31, 2022

        Year Ended December
31, 2021

         
        Options

        ESPP

        Options

        ESPP

        Options

        ESPP

        Risk-free interest rate

        3.57% to 4.6%

        5.33% to 5.44%

        1.41% to 4.01%

        1.63% to 4.65%

        0.58% to 1.28%

        0.05%

        Volatility

        67%

        49% to 50%

        66% to 67%

        64% to 65%

        66% to 67%

        66% to 67%

        Expected term in years

        6.3

        0.5

        6.3 to 6.4

        0.5

        6.4 to 6.5

        0.5

        Expected dividend yield

        0%

        0%

        0%

        0%

        0%

        0%

Summary of Stock-Based Compensation Expense

Stock-based compensation expense for 2023, 2022, and 2021 was as follows (in thousands):


	Years Ended December 31,
	2023		2022		2021
Research and development	$	32,134	$	19,100	$	10,463
General and administrative		39,931		28,753		16,369
	$	72,065	$	47,853	$	26,832

Summary of Warrants Outstanding to Purchase Shares of Common Stock

As of December 31, 2023 and 2022, we had the following warrants outstanding to purchase shares of our common stock:

        Issuance Date

        Expiration Date

        Exercise Price

        Warrants Outstanding at
 December 31, 2022

        Warrants Outstanding at
 December 31, 2023

January 2020

January 2030

10.42

12,957

12,957

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Summary of Fair Value of Financial Assets Consists of Cash Equivalents and Investments Classified as Available-for-sale Securities Measured on Recurring Basis

The follow tables set forth the fair value of our financial assets, which consists of cash equivalents and investments classified as available-for-sale securities, that were measured on a recurring basis (in thousands):


	December 31, 2023
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	77,429	$	—	$	—		$	77,429
U.S. Treasury securities	Level 1		34,625		13		(15	)		34,623
U.S. Government agency securities	Level 2		175,301		87		(133	)		175,255
Commercial paper	Level 2		252,956		156		(59	)		253,053
Corporate obligations	Level 2		92,384		103		(142	)		92,345
		$	632,695	$	359	$	(349	)	$	632,705


	December 31, 2022
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	45,887	$	—	$	—		$	45,887
U.S. Treasury securities	Level 1		172,568		—		(1,102	)		171,466
U.S. Treasury securities backed repurchase agreements	Level 2		16,003		—		—			16,003
U.S. Government agency securities	Level 2		129,174		12		(820	)		128,366
Foreign government agency securities	Level 2		7,599		—		(69	)		7,530
Commercial paper	Level 2		329,359		28		(431	)		328,956
Corporate obligations	Level 2		128,594		—		(1,209	)		127,385
		$	829,184	$	40	$	(3,631	)	$	825,593

Stockholders' Equity

12 Months Ended

Dec. 31, 2023

Equity [Abstract]

Stockholders' Equity

Note 8 — Stockholders’ Equity

Equity Incentive Plan

Our 2004 Plan provides for us to grant incentive stock options, non-statutory stock options, restricted stock, stock appreciation rights, restricted stock units, performance shares and performance units to employees, directors, and consultants. We may grant options for terms of up to ten years at prices not lower than 100% of the fair market value of our common stock on the date of grant. Options granted to new employees generally vest 25% after one year and monthly thereafter over a period of four years. Options granted to existing employees generally vest monthly over a period of four years.

In May 2022, our stockholders approved an amendment to the 2004 Plan to increase the number of authorized shares reserved for issuance under the 2004 Plan by an additional 6.0 million shares. In May 2022 and February 2023, our board of directors approved an amendment to the 2004 Plan to increase the number of authorized shares reserved for issuance under the 2004 Plan by an additional 1.6 million shares and 1.0 million shares, respectively, for inducement grants to new employees. As of December 31, 2023, the total authorized shares under the 2004 Plan available for grant was 7.6 million.

Our annual grant of stock-based compensation takes place during the first quarter of each year. Stock option activity in 2023, 2022, and 2021 was as follows:


	Stock Options Outstanding			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in millions)
Balance at December 31, 2020		8,501,949		$	10.02
Granted		2,513,350			22.43
Exercised		(1,346,194	)		9.01
Forfeited		(296,146	)		14.56
Balance at December 31, 2021		9,372,959		$	13.35
Granted		3,424,150			39.79
Exercised		(1,389,031	)		10.13
Forfeited		(415,675	)		28.94
Balance at December 31, 2022		10,992,403		$	22.13
Granted		2,447,225			38.59
Exercised		(1,200,895	)		12.13
Forfeited		(458,503	)		35.01
Balance at December 31, 2023		11,780,230		$	26.07		6.8	$	676.4
Exercisable at December 31, 2023		7,279,310		$	19.29		5.7	$	467.3

We have elected to account for forfeitures as they occur. The intrinsic value of stock options exercised, calculated based on the difference between the market value at the date of exercise and the exercise price, was $33.8 million for 2023, $46.3 million for 2022, and $29.3 million for 2021. The intrinsic value of stock options outstanding at December 31, 2023 was $676.4 million.

RSU, including PSU, activity in 2023, 2022, and 2021 was as follows:


	Number of Restricted Stock Units			Weighted Average Award Date Fair Value per Share
Balance at December 31, 2020		1,116,642		$	11.88
Granted		1,093,450			21.69
Exercised		(606,240	)		11.13
Forfeited		(189,025	)		21.32
Balance at December 31, 2021		1,414,827		$	18.52
Granted		780,519			37.69
Exercised		(707,772	)		16.72
Forfeited		(273,310	)		26.65
Balance at December 31, 2022		1,214,264		$	30.07
Granted		965,863			39.09
Exercised		(721,215	)		27.40
Forfeited		(84,290	)		35.46
Balance at December 31, 2023		1,374,622		$	37.47

RSUs generally vest annually over two to three years. For 2023, the fair value of RSUs vested, calculated based on the units vested multiplied by the closing price of our common stock on the date of vesting, was $28.6 million.

Performance Stock Units

In May 2021, the Compensation Committee granted a total of 375,000 PSUs to certain employees with a weighted average grant date fair value of $25.32 per unit. The fair value of the PSUs was determined on the grant date based on the fair value of the Company’s common stock at such time. The PSUs consist of two equal tranches with 50% of each tranche vesting upon achieving certain performance criteria and 50% vesting at the one-year anniversary of such achievement provided the recipient has been continuously employed by the Company. The first tranche vests upon certification by the Compensation Committee that the NDA for omecamtiv mecarbil has been filed and accepted by the FDA by December 31, 2021 or June 30, 2022 and the second tranche vests upon certification by the Compensation Committee that the FDA approval of the NDA is with an approved label that is consistent with the expectations underlying the Company’s commercial launch plans for omecamtiv mecarbil in effect immediately prior to such approval by June 30, 2022 or December 31, 2022.

In 2022, the performance target for the first tranche of PSUs was met. As a result, the Company recognized expense of $0.7 million in 2022 for the first tranche of PSUs. The performance target for the second tranche of PSUs was not met, and therefore, such second tranche of PSUs consisting of 182,500 PSUs were deemed forfeited as of December 31, 2022. No expense was recognized for the second tranche.

Employee Stock Purchase Plan

Under our ESPP, employees may purchase common stock up to a specified maximum amount at a price equal to 85% of the fair market value at certain plan-defined dates. In May 2020, the Company’s stockholders approved an amendment to the ESPP to increase the number of common stock shares reserved for issuance under the ESPP by 0.5 million shares.

We issued 136,065 shares at an average price of $30.43 per share during 2023, 98,153 shares at an average price of $32.89 per share in 2022, and 108,780 shares at an average price of $16.33 per share in 2021 pursuant to the ESPP. At December 31, 2023, we have 103,822 shares of common stock reserved for issuance under the ESPP.

Stock-Based Compensation Expense

         
        Year Ended December
31, 2023

        Year Ended December
31, 2022

        Year Ended December
31, 2021

         
        Options

        ESPP

        Options

        ESPP

        Options

        ESPP

        Risk-free interest rate

        3.57% to 4.6%

        5.33% to 5.44%

        1.41% to 4.01%

        1.63% to 4.65%

        0.58% to 1.28%

        0.05%

        Volatility

        67%

        49% to 50%

        66% to 67%

        64% to 65%

        66% to 67%

        66% to 67%

        Expected term in years

        6.3

        0.5

        6.3 to 6.4

        0.5

        6.4 to 6.5

        0.5

        Expected dividend yield

        0%

        0%

        0%

        0%

        0%

        0%

We use U.S. Treasury zero-coupon issues with remaining terms similar to the expected terms of the options for the risk-free interest rate. We use our own volatility history based on our stock trading history and our own historical exercise to estimate expected term for option grants. We do not anticipate paying dividends in the foreseeable future and use an expected dividend yield of zero. We do not estimate forfeitures in our stock-based compensation.

We measure compensation expense for restricted stock units at fair value on the date of grant and recognize the expense over the expected vesting period. We recognize stock-based compensation expense on a ratable basis over the requisite service period, generally the vesting period of the award for share-based awards.

Stock-based compensation expense for 2023, 2022, and 2021 was as follows (in thousands):


	Years Ended December 31,
	2023		2022		2021
Research and development	$	32,134	$	19,100	$	10,463
General and administrative		39,931		28,753		16,369
	$	72,065	$	47,853	$	26,832

As of December 31, 2023, we expect to recognize $102.2 million of unrecognized compensation cost related to unvested stock options over a weighted-average period of 2.5 years, $29.2 million of unrecognized compensation cost related to unvested restricted stock over a weighted-average period of 1.6 years.

Warrants

In May 2022, Silicon Valley Bank exercised 16,901 warrants issued pursuant to the Term Loan Agreement with a strike price of $7.10 per share and elected the cashless settlement method. In June 2022, Silicon Valley Bank exercised additional 9,226 warrants and 8,638 warrants with a strike price of $9.76 per share and $10.42 per share, respectively. Accordingly, in 2022, we issued to Silicon Valley Bank a total of 28,306 shares of our common stock.

As of December 31, 2023 and 2022, we had the following warrants outstanding to purchase shares of our common stock:

        Issuance Date

        Expiration Date

        Exercise Price

        Warrants Outstanding at
 December 31, 2022

        Warrants Outstanding at
 December 31, 2023

January 2020

January 2030

10.42

12,957

12,957

The remaining 12,957 warrants outstanding at December 31, 2023 were exercised in January 2024.

Controlled Equity Offering Sales Agreement with Cantor Fitzgerald & Co.

On March 1, 2023, we entered into the Amended ATM Facility, with Cantor, under which we may offer and sell, from time to time at our sole discretion, shares of the Common Stock having an aggregate offering price of up to $300.0 million through Cantor, as sales agent. The Amended ATM Facility amends, restates and supersedes the Controlled Equity Offering Sales Agreement dated as of March 6, 2019 between the Company and Cantor.

Cantor may sell the Common Stock by any method that is deemed to be an “at the market offering” as defined in Rule 415 of the Securities Act of 1933, as amended, including sales made directly on the Nasdaq Global Select Market or any other trading market for our common stock. Cantor will use commercially reasonable efforts to sell the Common Stock from time to time, based upon instructions from us (including any price, time or size limits or other customary parameters or conditions we may impose). We will pay Cantor a commission of up to 3.0% of the aggregate gross sales proceeds of any common stock sold through Cantor under the Amended ATM Facility, and also have provided Cantor with customary indemnification rights.

In 2023, we issued 5,016,170 shares of our common stock for net proceeds of $164.2 million under the Amended ATM Facility.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481062/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481004/946-505-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 50
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-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(e)(1))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
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-URI https://asc.fasb.org//1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
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-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-18

+ Details

Agreements with Royalty Pharma - Schedule of Future Minimum Payments under Term Loan Agreement (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Debt Instrument [Line Items]
2024	$ 19,745
2025	19,745
2026	40,878
2027	558,900
Less: Unamortized interest and loan costs	(12,143)
Term Loan, net	639,268
RP Loan Agreement [Member]
Debt Instrument [Line Items]
2024	10,080
2025	11,520
2026	11,520
2027	11,520
2028	11,520
Thereafter	37,440
Future minimum payments	93,600
Less: Unamortized interest and loan costs	(25,136)
Term Loan, net	$ 68,464

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (526,244)	$ (388,955)	$ (215,314)
Adjustments to reconcile net loss to net cash used in operating activities:
Non-cash interest expense on liabilities related to revenue participation right purchase agreement	29,474	31,858	13,004
Stock-based compensation expense	72,065	47,853	26,832
Non-cash lease expense	3,750	2,585	7,361
Impairment of right-of-use assets			2,844
Depreciation of property and equipment	11,892	5,814	2,276
Realized gain on investment, net	35	107
Interest receivable and amortization on investments	(15,735)	(4,710)	4,894
Non-cash interest expense related to debt	7,341	5,697	7,125
Loss on extinguishment of debt		2,693
Loss on inducement of convertible debt		22,246
Changes in operating assets and liabilities:
Accounts receivable	(1,136)	56,672	(47,399)
Prepaid and other assets	1,596	(7,414)	(7,381)
Accounts payable	(3,483)	4,524	1,055
Accrued and other liabilities	17,103	10,844	15,060
Deferred revenue		(87,000)
Operating lease liabilities	(1,406)	1,728	43,472
Other non-current liabilities	(9,585)	(4,058)	3,649
Net cash used in operating activities	(414,333)	(299,516)	(142,522)
Cash flows from investing activities:
Purchases of investments	(635,211)	(855,393)	(525,042)
Maturities of investments	870,905	604,594	422,837
Sales of investments	4,975		3,300
Purchases of property and equipment	(1,416)	(11,335)	(48,872)
Net cash provided by (used in) investing activities	239,253	(262,134)	(147,777)
Cash flows from financing activities:
Repayment of finance lease liabilities	(858)	(944)
Repayment of term loan		(47,651)
Debt extinguishment costs		(2,409)
Repayment of convertible debt		(140,330)
Proceeds from issuance of convertible debt, net		523,586
Proceeds from public offerings of common stock, net of discounts, commissions and offering cost			296,905
Proceeds from private placement, net			15,144
Proceeds from 2022 RPI Transactions, net	50,000	149,581
Proceeds from issuance of common stock related to at-the-market offering, net of issuance costs	164,233
Proceeds from issuance of common stock under equity incentive and stock purchase plans	18,459	17,543	12,380
Taxes paid related to net share settlement of equity awards	(10,517)	(9,602)	(4,449)
Cash Settlement of capped call options associated with 2026 Notes		26,392
Net cash provided by financing activities	221,317	516,166	319,980
Effect of exchange rate changes	(20)
Net increase (decrease) in cash, cash equivalents, and restricted cash	46,217	(45,484)	29,681
Cash, cash equivalents, and restricted cash, beginning of period	67,182	112,666	82,985
Cash, cash equivalents, and restricted cash, end of period	113,399	67,182	112,666
Supplemental cash flow disclosures:
Cash paid for interest	$ 10,295	15,165	9,175
Right-of-use assets recognized in exchange for operating lease obligations		10,904	80,395
Right-of-use assets recognized in exchange for finance lease obligations		1,055	1,294
Amounts unpaid for purchases of property and equipment		621	$ 11,982
Issuance of common stock in connection with repurchase of convertible note		$ 317,123

Consolidated Statements of Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2020	$ 113,383	$ 70	$ 1,105,470	$ 149	$ (992,306)
Beginning Balance, shares at Dec. 31, 2020		71,015,183
Exercise of stock options, value	11,020	$ 3	11,017	0	0
Exercise of stock options, shares		1,304,347
Shares withheld related to net share settlement of equity awards	(4,449)	$ 0	(4,449)	0	0
Shares withheld related to net share settlement of equity awards, shares		360,050
Net share settlement	(418)	$ 0	(418)	0	0
Issuance of common stock upon private placement, value	15,144		15,144	0	0
Issuance of common stock upon private placement, shares		511,182
Issuance under Employee Stock Purchase Plan, value	1,778	$ 0	1,778	0	0
Issuance under Employee Stock Purchase Plan, shares		108,780
Issuance of common stock under at-the-market offering/underwritten public offering	296,905	$ 11	296,894	0	0
Issuance of common stock under at-the-market offering/underwritten public offering, shares		11,500,000
Stock-based compensation	26,832	$ 0	26,832	0	0
Other comprehensive income (loss)	(1,018)	0	0	(1,018)	0
Net Income (Loss)	(215,314)	0	0	0	(215,314)
Ending Balance at Dec. 31, 2021	243,863	84	1,452,268	(869)	(1,207,620)
Ending Balance (ASU 2020-06 [Member]) at Dec. 31, 2021	(38,895)	$ 0	(49,476)	0	10,581
Ending Balance, shares at Dec. 31, 2021		84,799,542
Ending Balance, shares (ASU 2020-06 [Member]) at Dec. 31, 2021		0
Exercise of stock options, value	14,316	$ 2	14,314	0	0
Exercise of stock options, shares		1,389,031
Shares withheld related to net share settlement of equity awards	(9,602)	$ 0	(9,602)	0	0
Shares withheld related to net share settlement of equity awards, shares		(260,172)
Vesting of restricted stock units, value	0	$ 0	0	0	0
Vesting of restricted stock units, shares		707,772
Exercise of warrants, value	0	$ 0	0	0	0
Exercise of warrants, share		28,306
Issuance under Employee Stock Purchase Plan, value	3,227	$ 0	3,227	0	0
Issuance under Employee Stock Purchase Plan, shares		98,153
Induced conversion of convertible notes	(3,378)	$ 8	(3,386)	0	0
Induced conversion of convertible notes, shares		8,071,343
Settlement of capped call on 2026 Notes	26,392	$ 0	26,392	0	0
Stock-based compensation	47,853	0	47,853	0	0
Other comprehensive income (loss)	(2,721)	0	0	(2,721)	0
Net Income (Loss)	(388,955)	0	0	0	(388,955)
Ending Balance at Dec. 31, 2022	(107,900)	$ 94	1,481,590	(3,590)	(1,585,994)
Ending Balance, shares at Dec. 31, 2022		94,833,975
Exercise of stock options, value	14,319	$ 2	14,317	0	0
Exercise of stock options, shares		1,193,325
Shares withheld related to net share settlement of equity awards	(10,517)	$ 0	(10,517)	0	0
Shares withheld related to net share settlement of equity awards, shares		(262,829)
Vesting of restricted stock units, value		$ 1	0	0	0
Vesting of restricted stock units, shares		721,216
Issuance under Employee Stock Purchase Plan, value	4,140	$ 0	4,140	0	0
Issuance under Employee Stock Purchase Plan, shares		136,065
Issuance of common stock under at-the-market offering/underwritten public offering	164,233	$ 5	164,228	0	0
Issuance of common stock under at-the-market offering/underwritten public offering, shares		5,016,170
Stock-based compensation	72,065	$ 0	72,065	0	0
Other comprehensive income (loss)	3,580	0	0	3,580	0
Net Income (Loss)	(526,244)	0	0	0	(526,244)
Ending Balance at Dec. 31, 2023	$ (386,323)	$ 102	$ 1,725,823	$ (10)	$ (2,112,238)
Ending Balance, shares at Dec. 31, 2023		101,637,922

Commitments and Contingencies - Schedule of Future Minimum Lease Payments under Non-cancellable Lease (Detail) $ in Thousands	Dec. 31, 2023 USD ($)
Leases [Abstract]
2024	$ 18,738
2025	19,563
2026	20,180
2027	20,514
2028	20,738
Thereafter	109,981
Total future minimum lease payments	209,714
Less: Imputed interest	(71,396)
Total lease liability	138,318
2024	990
2025	204
2026	0
2027	0
2028	0
Thereafter	0
Total future minimum lease payments	1,194
Less: Imputed interest	(51)
Total lease liability	$ 1,143
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	us-gaap:OtherLiabilities

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	163,000,000	163,000,000
Common stock, shares issued	101,637,922	94,833,975
Common stock, shares outstanding	101,637,922	94,833,975

Balance Sheet Components

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Components

Note 5 — Balance Sheet Components

Our property and equipment consisted of (in thousands):


	December 31,
	2023			2022
Property and equipment, net:
Laboratory equipment	$	18,839		$	18,490
Computer equipment and software		3,263			3,900
Office equipment, furniture and fixtures		6,061			6,056
Leasehold improvements		66,874			65,912
Construction in progress		220			741
Right-of-use assets, finance lease		1,839			2,448
Total property and equipment		97,096			97,547
Less: Accumulated depreciation		(28,348	)		(17,094	)
	$	68,748		$	80,453

Depreciation expense was $11.9 million, $5.8 million, and $2.3 million for 2023, 2022, and 2021, respectively.

Our accrued liabilities were as follows (in thousands):


	December 31,
	2023		2022
Accrued liabilities:
Clinical and preclinical costs	$	5,880	$	16,105
Compensation related		29,255		21,767
Other accrued expenses		7,506		6,224
Total accrued liabilities	$	42,641	$	44,096

We sponsor a 401(k) defined contribution plan covering all employees and contributed $2.5 million, $1.8 million, and $1.1 million to this plan in 2023, 2022, and 2021, respectively.

Organization and Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Reconciliation of Cash, Cash Equivalents, and Restricted Cash


	December 31,
	2023		2022
Cash and cash equivalents	$	113,024	$	65,582
Restricted cash		375		1,600
Total cash, cash equivalents, and restricted cash as reported within our consolidated statement of cash flows	$	113,399	$	67,182

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
Document and Entity Information - USD ($) $ in Billions	Dec. 31, 2023	Feb. 27, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2023
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Trading Symbol	CYTK
Entity Registrant Name	CYTOKINETICS, INCORPORATED
Entity Central Index Key	0001061983
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		103,004,710
Entity Public Float			$ 2.0
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.001 par value
Security Exchange Name	NASDAQ
Entity File Number	000-50633
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	94-3291317
Entity Address, Address Line One	350 Oyster Point Boulevard
Entity Address, City or Town	South San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94080
City Area Code	650
Local Phone Number	624-3000
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Documents Incorporated by Reference	Portions of the Registrant’s Proxy Statement for its 2024 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission, no later than 120 days after the end of the fiscal year, are incorporated by reference into Part III of this Annual Report on Form 10-K.
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	San Jose, California

Debt - Additional Information (Detail)				12 Months Ended
Debt - Additional Information (Detail)	Oct. 24, 2022 USD ($)	Jul. 06, 2022 USD ($) $ / shares shares	Nov. 13, 2019 USD ($) $ / shares shares	Dec. 31, 2023 USD ($) Days $ / shares	Dec. 31, 2022 USD ($) $ / shares	Dec. 31, 2021 USD ($)	Jan. 06, 2022 USD ($)
Debt Instrument [Line Items]
Principal amount of original loan				$ 561,132,000
Loss on extinguishment of debt					$ 2,693,000
Interest expense				$ 28,306,000	$ 19,414,000	$ 16,440,000
Common stock, par value \| $ / shares				$ 0.001	$ 0.001
Oxford and Silicon Valley Bank [Member] \| Term Loan Agreement [Member]
Debt Instrument [Line Items]
Principal amount of original loan							$ 45,000,000
Loss on extinguishment of debt					$ 2,700,000
Oxford and Silicon Valley Bank [Member] \| 2019 Term Loan [Member] \| Term Loan Agreement [Member]
Debt Instrument [Line Items]
Interest expense						$ 4,800,000
2026 Notes [Member]
Debt Instrument [Line Items]
Principal amount of original loan			$ 138,000,000	$ 21,132,000
Issuance of shares of common stock \| shares		8,071,343
Repurchase of principal amount of original loan		$ 116,900,000
Inducement loss as a result of partial repurchase		22,200,000
Aggregate principal amount remaining				$ 21,100,000
Number of instalments description				payable semi-annually on May 15 and December 15 of each year, beginning May 15, 2020
Convertible notes, interest rate			4.00%
Convertible debt, fair value				$ 168,400,000
Convertible notes, maturity date			Nov. 15, 2026
Convertible notes, sinking fund			$ 0
Convertible notes, shares issued \| shares			94.7811
Convertible notes, principal amount			$ 1,000
Convertible notes, initial conversion price \| $ / shares			$ 10.55
Convertible notes, type of equity security issued				common stock
Convertible notes, conversion description				The 2026 Notes are convertible at December 31, 2023 at the option of the holder.
Convertible notes, redemption description				The 2026 Notes will be redeemable, in whole or in part, at our option at any time, and from time to time, on or after November 20, 2023 and, in the case of any partial redemption, on or before the 60th scheduled trading day before the maturity date, at a cash redemption price equal to the principal amount of the 2026 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date but only if the last reported sale price per share of our common stock exceeds 130% of the conversion price on (1) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date we may send the related redemption notice; and (2) the trading day immediately before the date we may send such notice. If a “fundamental change” (as defined in the indenture agreement, dated November 13, 2019 between us and U.S. Bank National Association, as trustee, as supplemented by the first supplemental indenture dated as of November 13, 2019 between us and such trustee) occurs, then, subject to certain exceptions, holders may require us to repurchase their 2026 Notes at a cash repurchase price equal to the principal amount of the 2026 Notes to be repurchased, plus accrued and unpaid interest, if any, to, but excluding, the fundamental change repurchase date.
Debt instrument, unamortized debt issuance cost				$ 300,000
Unamortized debt discount amortization period				2 years 10 months 24 days
Proceeds from termination of capped call options associated with convertible notes	$ 26,400,000
2026 Notes [Member] \| Liability [Member]
Debt Instrument [Line Items]
Debt instrument effective interest rate				4.60%	4.60%	12.50%
2027 Notes [Member]
Debt Instrument [Line Items]
Principal amount of original loan		540,000,000		$ 540,000,000
Payment associated with convertible notes		$ 140,300,000
Number of instalments description		payable semiannually in arrears on January 1 and July 1 of each year, beginning on January 1, 2023
Convertible notes, interest rate		3.50%
Convertible debt, fair value				990,400,000
Convertible notes, maturity date		Jul. 01, 2027
Convertible notes, shares issued \| shares		19.5783
Convertible notes, principal amount		$ 1,000		$ 1,000
Convertible notes, initial conversion price \| $ / shares		$ 51.08
Convertible notes, type of equity security issued				common stock
Net proceeds from convertible notes, net of debt discount and issuance costs		$ 523,600,000
Convertible notes, conversion description				The 2027 Notes are convertible into cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, based on the applicable conversion rate(s). The initial conversion rate for the 2027 Notes is 19.5783 shares of our common stock per $1,000 principal amount of such Notes, which is equivalent to an initial conversion price of approximately $51.08 per share. Holders of the 2027 Notes may convert all or any portion of their convertible notes at their option only in the following circumstances: (i) during any calendar quarter (and only during such calendar quarter) commencing after the calendar quarter ending on September 30, 2022, if the last reported sale price per share of our common stock, $0.001 par value per share, exceeds 130% of the conversion price for each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter; (ii) during the five consecutive business days immediately after any 10 consecutive trading day period (such 10 consecutive trading day period, the “measurement period”) if the trading price per $1,000 principal amount of 2027 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price per share of our common stock on such trading day and the conversion rate on such trading day; (iii) upon the occurrence of certain corporate events or distributions on our common stock, as described in the 2027 Indenture; (iv) if we call such 2027 Notes for redemption; and (v) at any time from, and including, March 1, 2027 until the close of business on the scheduled trading day immediately before the maturity date.
Convertible notes, redemption description				We may not redeem the 2027 Notes at our option at any time before July 7, 2025. The 2027 Notes will be redeemable, in whole or in part (subject to the “Partial Redemption Limitation” (as defined in the 2027 Indenture)), at our option at any time, and from time to time, on or after July 7, 2025 and, in the case of a partial redemption, on or before the 60th scheduled trading day immediately before the maturity date, at a cash redemption price equal to the principal amount of the 2027 Notes to be redeemed, plus accrued and unpaid interest, if any, to, but excluding, the redemption date, but only if the last reported sale price per share of our common stock exceeds 130% of the conversion price on (i) each of at least 20 trading days, whether or not consecutive, during the 30 consecutive trading days ending on, and including, the trading day immediately before the date we may send the related redemption notice; and (ii) the trading day immediately before the date we may send such notice. In addition, calling any of the 2027 Notes for redemption will constitute a Make-Whole Fundamental Change with respect to that convertible note, in which case the conversion rate applicable to the conversion of that Note will be increased in certain circumstances if it is converted after it is called for redemption. The conversion rate for the 2027 Notes shall not exceed 25.4517 shares per $1,000 principal amount of such Notes, subject to certain customary anti-dilution adjustments (as defined in the 2027 indenture). Pursuant to the Partial Redemption Limitation, we may not elect to redeem less than all of the outstanding 2027 Notes unless at least $75.0 million aggregate principal amount of 2027 Notes are outstanding and not subject to redemption as of the time we may send the related redemption notice.
Debt instrument, unamortized debt issuance cost				$ 11,800,000
Unamortized debt discount amortization period				3 years 7 months 6 days
2027 Notes [Member] \| Liability [Member]
Debt Instrument [Line Items]
Debt instrument effective interest rate				4.20%	4.20%
2027 Notes [Member] \| Debt Instrument Convertible Covenant One [Member]
Debt Instrument [Line Items]
Convertible notes, percentage of conversion price				130.00%
Convertible notes, trading days \| Days				20
Convertible notes, consecutive trading days \| Days				30
Common stock, par value \| $ / shares				$ 0.001
2027 Notes [Member] \| Debt Instrument Convertible Covenant Two [Member]
Debt Instrument [Line Items]
Convertible notes, percentage of last reported sale price of common stock				98.00%
Convertible notes, trading days \| Days				5
Convertible notes, consecutive trading days \| Days				10
2027 Notes [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Convertible notes, shares issued \| shares		25.4517
2027 Notes [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Aggregate principal amount of notes outstanding		$ 75,000,000

Organization and Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Summary Of Significant Accounting Policies [Line Items]
Accumulated deficit incurred	$ (2,112,238)	$ (1,585,994)
Net loss	(526,244)	(388,955)	$ (215,314)
Net cash used in operating activities	414,333	299,516	$ 142,522
Cash, cash equivalents and investments	$ 655,400	829,300
Cash requirements term	12 months
Restricted cash	$ 375	1,600
Liabilities related to revenue participation right purchase agreements, net	$ 379,975	$ 300,501
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of securities collateralized value	102.00%
Computer Equipment and Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	3 years
Laboratory Equipment and Office Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	5 years
Furniture and Fixtures [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	7 years
Leasehold Improvements [Member] \| Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	3 years
Leasehold Improvements [Member] \| Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Property and equipment estimated useful lives	12 years
Astellas [Member] \| Astellas FSRA Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Payment of development costs for clinical trials of reldesemtiv	$ 12,000

Agreements with Royalty Pharma - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended			3 Months Ended					12 Months Ended
	Jan. 07, 2022	Sep. 30, 2023	Mar. 31, 2022	Feb. 28, 2017	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jul. 01, 2023
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Arrangement consideration of debt transaction	$ 150,000
Long term debt					$ 639,268					$ 639,268
Debt Instrument, Face Amount					$ 561,132					$ 561,132
Purchase of common stock shares					101,637,922				94,833,975	101,637,922	94,833,975
Liabilities					$ 1,210,639				$ 1,122,675	$ 1,210,639	$ 1,122,675
RP Loan Agreement [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Long term debt					$ 68,464					$ 68,464
2022 Royalty Pharma Transactions [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Milestone payment	50,000
2022 Royalty Pharma Transactions [Member] \| RP Aficamten RPA, RPI ICAV [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Upfront payment	50,000
Purchased rights to certain revenue streams from net sales in consideration payment	$ 50,000
Percentage of net sales payable	4.50%
4.5% of net revenue to be receivable from annual worldwide net sales	$ 1,000,000
Percentage of net sales payable for excess of annual worldwide net sales	3.50%
3.5% of net sales payable for excess of annual worldwide net sales	$ 1,000,000
Imputed rate of interest on unamortized portion of liability					24.80%				22.40%	24.80%	22.40%
2022 Royalty Pharma Transactions [Member] \| RP Aficamten RPA, RPI ICAV [Member] \| oHCM [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Additional consideration amount paid of first pivotal clinical trail			$ 50,000
2022 Royalty Pharma Transactions [Member] \| RP Aficamten RPA, RPI ICAV [Member] \| nHCM [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Additional consideration amount paid of first pivotal clinical trail		$ 50,000
2022 Royalty Pharma Transactions [Member] \| RP Aficamten RPA, RPI ICAV [Member] \| Maximum [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Purchased rights to certain revenue streams from net sales in consideration payment	$ 150,000
2022 Royalty Pharma Transactions [Member] \| RP Aficamten RPA, RPI ICAV [Member] \| Change in Accounting Estimate [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Imputed rate of interest on unamortized liability		18.00%			24.80%	18.00%	19.00%	22.40%	22.40%	24.80%	22.40%
Non-cash interest expense recognized					$ 9,800	$ 5,400	$ 4,900	$ 5,400	$ 5,200	$ 25,500	$ 15,500
Increase in non-cash interest expense and net loss										$ 2,000
Increase (reduction) in net loss per share										$ 0.02
2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Term loan, maturity year	10 years
Debt instrument effective interest rate	7.65%
Applicable prepayment charges on term loan	$ 34,600
Debt Instrument, Face Amount	$ 50,000
Estimated fair value of long term debt					$ 59,900					$ 59,900
2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member] \| Term Loan Tranche 1, Tranche 4 and Tranche 5 [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Repayable loan percentage to principal amount Including interest and other fees	190.00%
2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member] \| Term Loan Tranche 2 and Tranche 3 [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Repayable loan percentage to principal amount Including interest and other fees	200.00%
2022 Royalty Pharma Transactions [Member] \| RP Aficamten RPA [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Additional consideration amount paid										$ 50,000
Royalty Purchase Finance Trust Agreement [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Imputed rate of interest on unamortized liability					0.10%				8.50%	0.10%	8.50%
Additional consideration amount paid										$ 0	$ 0	$ 0
Royalty Purchase Finance Trust Agreement [Member] \| RP OM RPA [Member] \| Maximum [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Increase in royalty rate					5.50%					5.50%
Royalty Purchase Finance Trust Agreement [Member] \| RP OM RPA [Member] \| Change in Accounting Estimate [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Imputed rate of interest on unamortized liability		2.90%			0.10%	2.90%	2.90%	1.90%	8.50%	0.10%	8.50%
Non-cash interest expense recognized					$ 100	$ 1,400	$ 1,400	$ 900	$ 4,000	$ 3,900	$ 16,200	$ 12,900
Increase in non-cash interest expense and net loss										$ 12,800
Increase (reduction) in net loss per share										$ 0.13
CRL Option [Member] \| 2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Term loan, maximum borrowing capacity	$ 300,000
Term loan, current borrowing capacity	50,000
Term loan, remaining borrowing capacity	250,000
CRL Option [Member] \| 2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member] \| Term Loan Tranche 2 [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Long term debt	50,000
CRL Option [Member] \| 2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member] \| Term Loan Tranche 3 [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Long term debt	25,000
CRL Option [Member] \| 2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member] \| Term Loan Tranche 4 [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Term loan, maximum borrowing capacity					75,000					$ 75,000
Long term debt	75,000
CRL Option [Member] \| 2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member] \| Term Loan Tranche 4 [Member] \| Minimum [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Term loan, current borrowing capacity					50,000					50,000
CRL Option [Member] \| 2022 Royalty Pharma Transactions [Member] \| RP Loan Agreement [Member] \| Term Loan Tranche 5 [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Term loan, remaining borrowing capacity					$ 100,000					$ 100,000
Long term debt	$ 100,000
CRL Option [Member] \| Royalty Purchase Finance Trust Agreement [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Cash payment under royalty agreement				$ 90,000
Purchase of common stock shares				875,656
Stock issued during period, value, issued for services				$ 10,000
Liabilities				$ 92,300
Additional percent of royalty on net sale				1.00%
CRL Option [Member] \| Royalty Purchase Finance Trust Agreement [Member] \| Minimum [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Percent of royalty on net sale	5.50%			4.50%
CRL Option [Member] \| Royalty Purchase Finance Trust Agreement [Member] \| Maximum [Member]
Liabilities Related to Revenue Participation Right Purchase Agreements [Line Items]
Increase in royalty rate													5.50%

Debt - Schedule of Future Minimum Payments under 2026 Notes (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Jul. 06, 2022	Nov. 13, 2019
Debt Instrument [Line Items]
2024	$ 19,745
2025	19,745
2026	40,878
2027	558,900
Future minimum payments	639,268
Less: Interest	(78,136)
Convertible notes, principal amount	561,132
Less: Debt issuance costs on the convertible notes	(12,143)
Net carrying amount of the convertible notes	548,989	$ 545,808
2026 Notes [Member]
Debt Instrument [Line Items]
2024	845
2025	845
2026	21,978
2027	0
Future minimum payments	23,668
Less: Interest	(2,536)
Convertible notes, principal amount	21,132			$ 138,000
Less: Debt issuance costs on the convertible notes	(344)
Net carrying amount of the convertible notes	20,788
2027 Notes [Member]
Debt Instrument [Line Items]
2024	18,900
2025	18,900
2026	18,900
2027	558,900
Future minimum payments	615,600
Less: Interest	(75,600)
Convertible notes, principal amount	540,000		$ 540,000
Less: Debt issuance costs on the convertible notes	(11,799)
Net carrying amount of the convertible notes	$ 528,201

Fair Value Measurements - Summary of Fair Value of Financial Assets Consists of Cash Equivalents and Investments Classified as Available-for-sale Securities Measured on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - Cash and Cash Equivalents and Investments [Member] - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	$ 632,695	$ 829,184
Unrealized Gains	359	40
Unrealized Losses	(349)	(3,631)
Fair Value	632,705	825,593
Money Market Funds [Member] \| Fair Value Measurements Using Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	77,429	45,887
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	77,429	45,887
U.S. Treasury Securities [Member] \| Fair Value Measurements Using Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	34,625	172,568
Unrealized Gains	13	0
Unrealized Losses	(15)	(1,102)
Fair Value	34,623	171,466
U.S. Government agency securities \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	175,301	129,174
Unrealized Gains	87	12
Unrealized Losses	(133)	(820)
Fair Value	175,255	128,366
U.S. Treasury Securities Backed Repurchase Agreements [Member] \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost		16,003
Unrealized Gains		0
Unrealized Losses		0
Fair Value		16,003
Foreign government agency securities \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost		7,599
Unrealized Gains		0
Unrealized Losses		(69)
Fair Value		7,530
Commercial Paper [Member] \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	252,956	329,359
Unrealized Gains	156	28
Unrealized Losses	(59)	(431)
Fair Value	253,053	328,956
Corporate Obligations [Member] \| Fair Value Measurements Using Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost	92,384	128,594
Unrealized Gains	103	0
Unrealized Losses	(142)	(1,209)
Fair Value	$ 92,345	$ 127,385

Stockholders' Equity - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, Beginning Balance	10,992,403	9,372,959	8,501,949
Stock Options Outstanding, Granted	2,447,225	3,424,150	2,513,350
Stock Options Outstanding, Forfeited	(458,503)	(415,675)	(296,146)
Stock Options Outstanding, Ending Balance	11,780,230	10,992,403	9,372,959
Stock Options Outstanding, Exercisable	7,279,310
Weighted Average Exercise Price per Share, Beginning Balance	$ 22.13	$ 13.35	$ 10.02
Weighted Average Exercise Price per Share, Granted	38.59	39.79	22.43
Weighted Average Exercise Price per Share, Exercised	12.13	10.13	9.01
Weighted Average Exercise Price per Share, Forfeited	35.01	28.94	14.56
Weighted Average Exercise Price per Share, Ending Balance	26.07	$ 22.13	$ 13.35
Weighted Average Exercise Price per Share, Exercisable	$ 19.29
Weighted Average Remaining Contractual Life	6 years 9 months 18 days
Weighted Average Remaining Contractual Life, Exercisable at December 31, 2023	5 years 8 months 12 days
Aggregate Intrinsic Value	$ 676.4
Aggregate Intrinsic Value, Exercisable at December 31, 2023	$ 467.3
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, Exercised	(1,200,895)	(1,389,031)	(1,346,194)

Subsequent Events - Additional Information (Details) - USD ($) $ in Thousands	2 Months Ended	12 Months Ended
	Feb. 27, 2024	Dec. 31, 2023	Dec. 31, 2022
Subsequent Event [Line Items]
Issuance of common stock under at-the-market offering, net of issuance costs, shares		101,637,922	94,833,975
Net proceeds of issuance of common stock		$ 164,233
Subsequent Event \| Amended ATM Facility [Member]
Subsequent Event [Line Items]
Issuance of common stock under at-the-market offering, net of issuance costs, shares	1,237,460
Net proceeds of issuance of common stock	$ 93,600

Commitments and Contingencies

12 Months Ended

Dec. 31, 2023

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 9 — Commitments and Contingencies

Operating Leases

In July 2019, we entered into the Oyster Point Lease of office and laboratory space at a facility located in South San Francisco, California, and we entered into amendments to the Oyster Point Lease in 2020, 2021, 2022, and 2023. The Oyster Point Lease commenced on March 31, 2021 and has an expiration date of October 31, 2033.

In January 2022, we entered into a series of lease agreements with the sub-landlord and landlord and leased an office space at a facility located in Radnor, Pennsylvania (the "Radnor Lease"). The Radnor Lease commenced on September 1, 2022, when the leasehold improvements were substantially completed, and we gained control over the use of the underlying assets. The Radnor Lease has an expiration date of July 31, 2027 with one five-year option to extend the lease.

The weighted-average remaining lease term of the operating leases was 9.7 years, 10.7 years, and 11.7 years as of December 31, 2023, 2022, and 2021, respectively. The weighted-average discount rate used to determine the related operating lease liabilities was 8.7% as of December 31, 2023 and 2022, and 10.0% as of December 31, 2021.

Cash paid for operating leases for the years ended December 31, 2023, 2022, and 2021 was $17.8 million, $24.1 million, and $6.1 million, respectively, and was included in net cash used in operating activities in our consolidated statements of cash flows.

Finance Leases

During the third quarter of 2021, we entered into a master lease agreement for laboratory equipment leases that commenced in the fourth quarter of 2021. The leases have an initial term of 3 years, commenced through the second quarter of 2022 and expire in 2025. The master lease agreement provides a purchase option with a bargain purchase price, which we expect to exercise at the end of the term. The Company classified the leases as finance leases.

Finance leases are accounted for on the consolidated balance sheets with right-of-use assets and lease liabilities recognized in property and equipment, other current liabilities, and other non-current liabilities, respectively. The finance lease cost is recognized as a combination of the amortization expense for the right-of-use assets calculated on a straight-line basis over the five-year estimated useful life for laboratory equipment and interest expense for the outstanding lease liabilities using the determined discount rates. As of December 31, 2023, we have recognized finance lease right-of-use assets of $1.8 million, short-term finance lease liabilities of $1.0 million, and long-term finance lease liabilities of $0.2 million.

As of December 31, 2023, 2022, and 2021, the weighted average remaining lease term for the finance leases is 3.0 years, 4.0 years, and 4.9 years, respectively. The weighted average discount rate used to determine the finance lease liabilities is 9.5% as of December 31, 2023, 2022, and 2021.

The cash paid for finance lease for the years ended December 31, 2023 and 2022 was $0.9 million and was included in financing activities in our consolidated statement of cash flows. No cash was paid for finance lease in 2021.

Future minimum lease payments under non-cancellable leases as of December 31, 2023 is as follows (in thousands):


Years ending December 31:	Operating Leases			Finance Leases
2024	$	18,738		$	990
2025		19,563			204
2026		20,180			-
2027		20,514			—
2028		20,738			—
Thereafter		109,981			—
Total future minimum lease payments		209,714			1,194
Less: Imputed interest		(71,396	)		(51	)
Total lease liability	$	138,318		$	1,143

Rent expense for operating and finance leases was $22.1 million, $21.6 million, and $23.1 million for 2023, 2022, and 2021, respectively.

Organization and Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash Equivalents (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 113,024	$ 65,582
Restricted cash	375	1,600
Total cash, cash equivalents, and restricted cash as reported within our consolidated statement of cash flows	$ 113,399	$ 67,182

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate to Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Tax at federal statutory tax rate	21.00%	21.00%	21.00%
State tax, net of federal benefits	1.00%	1.00%	0.00%
Change in state effected rates	0.00%	0.00%	(1.00%)
Tax credits, net	4.00%	4.00%	3.00%
Change in valuation allowance	(24.00%)	(26.00%)	(24.00%)
Stock-based compensation	1.00%	2.00%	2.00%
Other	(3.00%)	(2.00%)	(1.00%)
Total	0.00%	0.00%	0.00%

Agreements with Royalty Pharma

12 Months Ended

Dec. 31, 2023

Agreements with Royalty Pharma [Abstract]

Agreements with Royalty Pharma

Note 6 — Agreements with Royalty Pharma

On January 7, 2022, we announced that we had entered into the 2022 RPI Transactions with affiliates of Royalty Pharma International plc.

The RP Loan Agreement and the RP Aficamten RPA described below, are determined to be debt instruments subsequently measured at amortized cost and were entered into with parties that were at the time of our entry into the 2022 RPI Transactions affiliated and in contemplation of one another. We used the relative fair value method and made separate estimates of the fair value of each freestanding financial instrument and then allocated the proceeds in proportion to those fair value amounts. Arrangement consideration for the RP Loan Agreement and the RP Aficamten RPA totaled $150 million, consisting of the two $50 million upfront payments for the signing of the RP Loan Agreement and the RP Aficamten RPA and milestone of $50 million for initiation of the first pivotal trial in oHCM for aficamten that was deemed probable at the signing of the agreements.

The initial consideration was allocated as follows (in thousands):


	Fair Value		Proceeds		Allocation
Units of Accounting:
Revenue Participation Right Purchase Agreement	$	69,498	$	100,000	$	89,571
Development Funding Loan Agreement		46,887		50,000		60,429
Total consideration	$	116,385	$	150,000	$	150,000

2022 RP Loan Agreement

Under the RP Loan Agreement, we were initially entitled to receive up to $300.0 million in term loans, $50.0 million of which was disbursed to us on closing and the remaining $250.0 million scheduled to have been available to us upon our satisfaction of customary disbursement conditions and certain development conditions by specific deadlines, as follows:

•

$50.0 million of tranche 2 term loans during the one year period following the receipt on or prior to March 31, 2023 of marketing approval from FDA of omecamtiv mecarbil;

•

$25.0 million of tranche 3 term loans during the one year period following the commercial availability of a diagnostic test measuring levels of omecamtiv mecarbil to support the final FDA label language applicable to such drug, subject to such commercial availability and the conditions to the tranche 2 term loans having occurred on or prior to March 31, 2023;

•

$75.0 million of tranche 4 term loans during the one year period following the receipt on or prior to September 30, 2024 of positive results from SEQUOIA-HCM, the Phase 3 trial for aficamten; and

•

$100.0 million of tranche 5 term loans during the one year period following the acceptance by the FDA on or prior to March 31, 2025 of an NDA for aficamten, subject to the conditions to the tranche 4 term loans having occurred on or prior to September 30, 2024.

As a result of our receipt of a CRL on February 28, 2023, in connection to our NDA for omecamtiv mecarbil, we have not satisfied the conditions to the availability of the tranche 2 and tranche 3 loans under the RP Loan Agreement.

In December 2023, we announced positive topline results from SEQUOIA-HCM, the Phase 3 trial for aficamten. This entitled us to receive $75.0 million under tranche 4 during the one year period following the receipt of the positive results and requires us to complete a minimum mandatory draw of at least $50.0 million of the $75.0 million available.

The remaining $100.0 million under tranche 5 remains available for disbursement to us, subject to satisfaction of the conditions described above.

Each term loan under the RP Loan Agreement matures on the 10 year anniversary of the funding date for such term loan and is repayable in quarterly installments of principal, interest and fees commencing on the last business day of the seventh full calendar quarter following the calendar quarter of the applicable funding date for such term loan, with the aggregate amount payable in respect of each term loan (including interest and other applicable fees) equal to 190% of the principal amount of the term loan for the tranche 1, tranche 4 and tranche 5 term loans and 200% of the principal amount of the term loan for tranche 2 and tranche 3 term loans (such amount with respect to each term loan, “Final Payment Amount”). We accounted for amounts initially drawn under the RP Loan Agreement using the effective interest method which resulted in an effective interest rate of 7.65% over the ten-year term. As of the date of the prepayment or maturity of the term loan (or the date such prepayment or repayment is required to be paid), we will be required to pay an additional amount equal to $34.6 million accreted over the term of the loan. We have made our first payment in the fourth quarter of 2023.

We may prepay the term loans in full (but not in part) at any time at our option by paying an amount equal to the unpaid portion of Final Payment Amount for the outstanding term loans under the RP Loan Agreement; provided that if the conditions for either the tranche 4 term loans or the tranche 5 term loans have been met, we must have borrowed at least $50 million principal amount of the tranche 4 or 5 term loans. In addition, the term loans under the RP Loan Agreement are repayable in full at the option of either us or the lender in an amount equal to the unpaid portion of Final Payment Amount for the outstanding term loans upon a change of control of Cytokinetics.

Future minimum payments under the existing borrowing under RP Loan Agreement are (in thousands):


Years ending December 31:
2024	$	10,080
2025		11,520
2026		11,520
2027		11,520
2028		11,520
Thereafter		37,440
Future minimum payments		93,600
Less: Unamortized interest and loan costs		(25,136	)
Term Loan, net	$	68,464

As of December 31, 2023, the estimated fair value of our RP Loan Agreement was $59.9 million. The fair value was estimated based on Level 3 inputs.

Concurrent with our entry into the RP Loan Agreement discussed above, we terminated the Term Loan Agreement with Silicon Valley Bank and Oxford Finance LLC and repaid all amounts outstanding thereunder as further described in Note 7.

2022 RP Aficamten Royalty Purchase Agreement

In addition, on January 7, 2022, we entered into the RP Aficamten RPA with RPI ICAV, pursuant to which RPI ICAV purchased rights to certain revenue streams from net sales of pharmaceutical products containing aficamten by us, our affiliates and our licensees in exchange for up to $150.0 million in consideration, $50.0 million of which was paid on the closing date, $50.0 million of which was paid to us in March 2022 following the initiation of the first pivotal trial in oHCM for aficamten, and $50.0 million of which was paid to us in September 2023 following the initiation of the first pivotal clinical trial in nHCM for aficamten. The RP Aficamten RPA also provides that the parties will negotiate terms for additional funding if we achieve proof of concept results in certain other indications for aficamten, with a reduction in the applicable royalty if we and RPI ICAV fail to agree on such terms in certain circumstances.

Pursuant to the RP Aficamten RPA, RPI ICAV purchased the right to receive a percentage of net sales equal to 4.5% for annual worldwide net sales of pharmaceutical products containing aficamten up to $1 billion and 3.5% for annual worldwide net sales of pharmaceutical products containing aficamten in excess of $1 billion, subject to reduction in certain circumstances. Our liability to RPI ICAV is referred to as the “RP Aficamten Liability”.

We account for the RP Aficamten Liability as a liability primarily because we have significant continuing involvement in generating the related revenue stream from which the liability will be repaid. If and when aficamten is commercialized and royalties become due, we will recognize the portion of royalties paid to RPI ICAV as a decrease to the RP Aficamten Liability and a corresponding reduction in cash.

The carrying amount of the RP Aficamten Liability is based on our estimate of the future royalties to be paid to RPI ICAV over the life of the arrangement as discounted using an imputed rate of interest. The imputed rate of interest on the carrying value of the RP Aficamten Liability was approximately 24.8% as of December 31, 2023 and 22.4% as of December 31, 2022.

In 2023, we updated our analyses of the RP Aficamten RPA to reflect our assumptions resulting from ongoing global market research and to reflect other adjustments in connection with our anticipated commercialization, including the additional consideration of $50.0 million which was paid to us in September 2023 following the initiation of the first pivotal clinical trial in nHCM for aficamten. Our estimates regarding the amount of future royalty payments under the RP Aficamten RPA changed from the fourth quarter of 2022 due to changes in management’s estimates of unobservable inputs related to market conditions and timing to include projections of future royalty payments. The resulting probability-adjusted sales forecast for aficamten has increased year over year mainly due to the receipt of positive topline results from SEQUOIA-HCM, the Phase 3 trial for aficamten, in December 2023.

The change in estimates are accounted for on a prospective basis in our liability calculation and resulted in changes in our imputed interest rate and non-cash interest expense from 22.4% and $5.2 million in the fourth quarter of 2022, 22.4% and $5.4 million in the first quarter of 2023, 19.0% and $4.9 million in the second quarter of 2023, 18.0% and $5.4 million in the third quarter of 2023, to 24.8% and $9.8 million in the fourth quarter of 2023. The non-cash interest expense was $25.5 million and $15.5 million in 2023 and 2022, respectively. In 2023, the change in estimate increased our non-cash interest expense and net loss by $2.0 million. The change in accounting estimate increased the net loss per share by $0.02 in 2023.

2017 RP Omecamtiv Mecarbil Royalty Purchase Agreement

In February 2017, we entered into the RP OM RPA pursuant to which we sold a portion of our right to receive royalties from Amgen on future net sales of omecamtiv mecarbil to RPFT for a one-time payment of $90 million, which is non-refundable even if omecamtiv mecarbil is never commercialized. Concurrently, we entered into a common stock purchase agreement with RPFT through which RPFT purchased 875,656 shares of the Company’s common stock for $10.0 million. We allocated the consideration and issuance costs on a relative fair value basis to our liability to RPFT related to sale of future royalties under the RP OM RPA (the “RP OM Liability”) and the common stock sold to RPFT, which resulted in the RP OM Liability being initially recognized at $92.3 million. The RP OM RPA provides for the sale of a royalty to RPFT of 4.5% on worldwide net sales of omecamtiv mecarbil, subject to a potential increase of up to an additional 1% under certain circumstances. As a result of our receipt of a CRL on February 28, 2023 in connection to our NDA for omecamtiv mecarbil, pursuant to the terms of the RP OM RPA, the applicable royalty rate will increase to a maximum of 5.5% if omecamtiv approval obtains FDA approval at any time after June 30, 2023.

As a result of the termination of the Amgen Agreement and pursuant to our obligations under the RP OM RPA, we and RPFT amended the RP OM RPA on January 7, 2022 to preserve RPFT’s rights under the RP OM RPA by providing for direct payments by us to RPFT of up to 5.5% of our and our affiliates and licensees worldwide net sales of omecamtiv mecarbil. The RP OM RPA, as amended, had no impact on the original accounting for the $92.3 million associated with the RP OM Liability established in February 2017.

We account for the RP OM Liability as a liability primarily because we have significant continuing involvement in generating the related revenue stream from which the liability will be repaid. If and when omecamtiv mecarbil is commercialized and royalties become due, we will recognize the portion of royalties paid to RPFT as a decrease to the RP OM Liability and a corresponding reduction in cash.

The carrying amount of the RP OM Liability is based on our estimate of the future royalties to be paid to RPFT over the life of the arrangement as discounted using an imputed rate of interest. The excess of future estimated royalty payments over the $92.3 million of allocated proceeds, less issuance costs, is recognized as non-cash interest expense using the effective interest method. The imputed rate of interest on the carring value of the RP OM Liability was approximately 0.1% as of December 31, 2023 and 8.5% as of December 31, 2022.

In 2023, we updated our analyses of the RP OM RPA to reflect our current assumptions resulting from ongoing global market research and to reflect other adjustments in connection with our anticipated commercialization, including the result of our receipt of a CRL in connection to our NDA for omecamtiv mecarbil. As a consequence of our receipt of the CRL from FDA, the royalty rate under the RP OM RPA will increase to no more than 5.5%. The resulting probability-adjusted sales forecast for omecamtiv mecarbil has decreased year over year because commercialization and sales of omecamtiv mecarbil will be delayed.

Changes in estimates are accounted for on a prospective basis in our liability calculation and resulted in changes in our imputed interest rate and non-cash interest expense from 8.5% and $4.0 million in the fourth quarter of 2022, 1.9% and $0.9 million in the first quarter of 2023, 2.9% and $1.4 million in the second and third quarter of 2023, and to 0.1% and $0.1 million in the fourth quarter of 2023, respectively. The non-cash interest expense was $3.9 million, $16.2 million, and $12.9 million in 2023, 2022, and 2021, respectively. In 2023, the change in estimate decreased our non-cash interest expense and net loss by $12.8 million. The change in accounting estimate reduced the net loss per share by $0.13 in 2023.

Accounting for the Royalty Pharma Royalty Purchase Agreements

We periodically assess the amount and timing of expected royalty payments using a combination of internal projections and forecasts from external sources. To the extent such payments are greater or less than our initial estimates or the timing of such payments is materially different than its original estimates, we will prospectively adjust the amortization of the RP OM Liability and the RP Aficamten Liability and the effective interest rate.

There are a number of factors that could materially affect the amount and timing of royalty payments, a number of which are not within our control. The RP OM Liability and the RP Aficamten Liability are recognized using significant unobservable inputs. The estimates of future royalties requires the use of several assumptions such as: the probability of clinical success, the probability of regulatory approval, the estimated date of a product launch, estimates of eligible patient populations, estimates of prescribing behavior and patient compliance behavior, estimates of pricing, payor reimbursement and coverage, and sales ramp. A significant change in unobservable inputs could result in a material increase or decrease to the effective interest rate of the RP OM Liability and the RP Aficamten Liability.

We recorded $50.0 million of additional consideration associated with the 2022 RP Aficamten Royalty Purchase Agreement upon receipt of the cash in the third quarter of 2023.

We review our assumptions on a regular basis and our estimates may change in the future as we refine and reassess our assumptions.

Changes to the RP Aficamten Liability and the RP OM Liability are as follows (in thousands):


	RP Aficamten Liability				RP OM Liability
	2023		2022		2023		2022		2021
Beginning balance, January 1	$	105,117	$	—	$	195,384	$	179,072	$	166,068
Initial carrying value		—		89,571		—		—		—
Additional consideration		50,000		—		—		—		—
Interest accretion		25,474		15,546		3,888		16,196		12,892
Amortization of issuance costs		—		—		112		116		112
Ending balance, December 31	$	180,591	$	105,117	$	199,384	$	195,384	$	179,072

Agreements with Royalty Pharma (Tables)

12 Months Ended

Dec. 31, 2023

Agreements with Royalty Pharma [Abstract]

Schedule of Initial Consideration

The initial consideration was allocated as follows (in thousands):


	Fair Value		Proceeds		Allocation
Units of Accounting:
Revenue Participation Right Purchase Agreement	$	69,498	$	100,000	$	89,571
Development Funding Loan Agreement		46,887		50,000		60,429
Total consideration	$	116,385	$	150,000	$	150,000

Schedule of Future Minimum Payments under the Existing Borrowing Under Term Loan Agreement

Future minimum payments under the existing borrowing under RP Loan Agreement are (in thousands):


Years ending December 31:
2024	$	10,080
2025		11,520
2026		11,520
2027		11,520
2028		11,520
Thereafter		37,440
Future minimum payments		93,600
Less: Unamortized interest and loan costs		(25,136	)
Term Loan, net	$	68,464

Schedule of Activity within Liabilities Related to Sale of Future Royalties

Changes to the RP Aficamten Liability and the RP OM Liability are as follows (in thousands):


	RP Aficamten Liability				RP OM Liability
	2023		2022		2023		2022		2021
Beginning balance, January 1	$	105,117	$	—	$	195,384	$	179,072	$	166,068
Initial carrying value		—		89,571		—		—		—
Additional consideration		50,000		—		—		—		—
Interest accretion		25,474		15,546		3,888		16,196		12,892
Amortization of issuance costs		—		—		112		116		112
Ending balance, December 31	$	180,591	$	105,117	$	199,384	$	195,384	$	179,072

Income Taxes - Schedule of Activity Related to our Gross Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Balance at the beginning of the year	$ 18,355	$ 11,295	$ 10,522
Increase related to prior year tax positions		4,438
Decrease related to prior year tax positions	(97)	(1,804)	(29)
Increase related to current year tax positions	6,974	4,426	802
Balance at the end of the year	$ 25,232	$ 18,355	$ 11,295

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Depreciation expense	$ 11.9	$ 5.8	$ 2.3
Employer contributions under the plan	$ 2.5	$ 1.8	$ 1.1

Debt - Schedule of Interest Cost Relating to 2026 and 2027 Notes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
2026 Notes [Member]
Debt Instrument [Line Items]
Contractual interest expense	$ 844	$ 3,265	$ 5,520
Accretion of debt discount	0	0	5,907
Amortization of debt issuance costs	108	355	59
Total interest expense recognized	952	3,620	$ 11,486
2027 Notes [Member]
Debt Instrument [Line Items]
Contractual interest expense	18,900	9,188
Amortization of debt issuance costs	3,074	1,542
Total interest expense recognized	$ 21,974	$ 10,730

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accrued liabilities:
Clinical and preclinical costs	$ 5,880	$ 16,105
Compensation related	29,255	21,767
Other accrued expenses	7,506	6,224
Total accrued liabilities	$ 42,641	$ 44,096

Fair Value Measurements

12 Months Ended

Dec. 31, 2023

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 4 — Fair Value Measurements

We value our financial assets and liabilities at fair value, defined as the price that would be received for assets when sold or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). We utilize market data or assumptions that we believe market participants would use in pricing the asset or liability, including assumptions about risk and the risks inherent in the inputs to the valuation technique. These inputs can be readily observable, market corroborated or generally unobservable.

We primarily apply the market approach for recurring fair value measurements and endeavor to utilize the best information reasonably available. Accordingly, we use valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible and consider the security issuers’ and the third-party issuers’ credit risk in our assessment of fair value.

We classify fair value based on the observability of those inputs using a hierarchy that prioritizes the inputs used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurement) and the lowest priority to unobservable inputs (Level 3 measurement):

Level 1 — Observable inputs, such as quoted prices in active markets for identical assets or liabilities;

Level 2 — Inputs, other than the quoted prices in active markets, that are observable either directly or through corroboration with observable market data; and

Level 3 — Unobservable inputs, for which there is little or no market data for the assets or liabilities, such as internally-developed valuation models.

Fair Value of Financial Assets


	December 31, 2023
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	77,429	$	—	$	—		$	77,429
U.S. Treasury securities	Level 1		34,625		13		(15	)		34,623
U.S. Government agency securities	Level 2		175,301		87		(133	)		175,255
Commercial paper	Level 2		252,956		156		(59	)		253,053
Corporate obligations	Level 2		92,384		103		(142	)		92,345
		$	632,695	$	359	$	(349	)	$	632,705


	December 31, 2022
	Fair Value Hierarchy Level	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
Money market funds	Level 1	$	45,887	$	—	$	—		$	45,887
U.S. Treasury securities	Level 1		172,568		—		(1,102	)		171,466
U.S. Treasury securities backed repurchase agreements	Level 2		16,003		—		—			16,003
U.S. Government agency securities	Level 2		129,174		12		(820	)		128,366
Foreign government agency securities	Level 2		7,599		—		(69	)		7,530
Commercial paper	Level 2		329,359		28		(431	)		328,956
Corporate obligations	Level 2		128,594		—		(1,209	)		127,385
		$	829,184	$	40	$	(3,631	)	$	825,593

No credit losses on debt securities were recognized in 2023 or 2022. In its evaluation to determine expected credit losses, management considered all available historical and current information, expectations of future economic conditions, the type of security, the credit rating of the security, and the size of the loss position, as well as other relevant information. The Company does not intend to sell, and is unlikely to be required to sell, any of these available-for-sale investments before their effective maturity or market price recovery.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Organization and Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Organization

Use of Estimates

Basis of Presentation

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of risk consist principally of cash, cash equivalents, restricted cash, investments, and accounts receivable.

Cash, Cash Equivalents, and Restricted Cash


	December 31,
	2023		2022
Cash and cash equivalents	$	113,024	$	65,582
Restricted cash		375		1,600
Total cash, cash equivalents, and restricted cash as reported within our consolidated statement of cash flows	$	113,399	$	67,182

As of December 31, 2023, our restricted cash balance of $0.4 million is used to collateralize letters of credit.

Investments

Property and Equipment, net

Impairment of Long-lived Assets

Leases

Revenue Recognition

We recognize revenue when we transfer promised goods or services to customers in an amount that reflects the consideration for those goods or services.

Accrued Research and Development Expenditures

Revenue Participation Right Purchase Agreements

As of December 31, 2023, we have a total carrying value of approximately $380.0 million of liabilities related to revenue participation right purchase agreements.

Research and Development Expenditures

Income Taxes

We recognize interest accrued related to unrecognized tax benefits and penalties as income tax expense.

Stock-Based Compensation

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Instruments Excluded from the Computation of Diluted Net Loss Per Share

The following instruments were excluded from the computation of diluted net loss per share for the periods presented because their effect would have been antidilutive (in thousands):


	Years Ended December 31,
	2023		2022		2021
Options to purchase common stock		11,780		10,992		9,373
Warrants to purchase common stock		13		13		48
Restricted stock and performance units		1,375		1,260		1,415
Shares issuable related to the ESPP		16		13		8
Shares issuable upon conversion of 2026 Notes		2,003		2,003		16,675
Shares issuable upon conversion of 2027 Notes		10,572		10,572		—
Total shares		25,759		24,853		27,519

Agreements with Royalty Pharma - Schedule Represents Allocation of Transaction Consideration on a Relative Fair Value Basis to the Liability and the Common Stock (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
RP Aficamten Liability [Member]
Royalty Liability [Line Items]
Liabilities related to revenue participation right purchase agreements, net beginning balance	$ 105,117	$ 0
Initial carrying value	0	89,571
Additional consideration	50,000	0
Interest accretion	25,474	15,546
Amortization of issuance costs	0	0
Liabilities related to revenue participation right purchase agreements, net ending balance	180,591	105,117	$ 0
RPOM Liability [Member]
Royalty Liability [Line Items]
Liabilities related to revenue participation right purchase agreements, net beginning balance	195,384	179,072	166,068
Initial carrying value	0	0	0
Additional consideration	0	0	0
Interest accretion	3,888	16,196	12,892
Amortization of issuance costs	112	116	112
Liabilities related to revenue participation right purchase agreements, net ending balance	$ 199,384	$ 195,384	$ 179,072

Net Loss Per Share

12 Months Ended

Dec. 31, 2023

Earnings Per Share [Abstract]

Net Loss Per Share

Note 2 — Net Loss Per Share

Basic net loss per share is computed by dividing net loss by the weighted average number of vested common shares outstanding during the period. Diluted net loss per share is computed by giving effect to all potentially dilutive common shares, including outstanding stock options, unvested restricted stock, warrants, convertible preferred stock and shares issuable under our ESPP, during the period using the treasury stock method and convertible notes using the if-converted method.

The following instruments were excluded from the computation of diluted net loss per share for the periods presented because their effect would have been antidilutive (in thousands):


	Years Ended December 31,
	2023		2022		2021
Options to purchase common stock		11,780		10,992		9,373
Warrants to purchase common stock		13		13		48
Restricted stock and performance units		1,375		1,260		1,415
Shares issuable related to the ESPP		16		13		8
Shares issuable upon conversion of 2026 Notes		2,003		2,003		16,675
Shares issuable upon conversion of 2027 Notes		10,572		10,572		—
Total shares		25,759		24,853		27,519

Stockholders' Equity - Summary of Warrants Outstanding to Purchase Shares of Common Stock (Detail)	12 Months Ended
	Dec. 31, 2023 $ / shares shares
Class of Warrant or Right [Line Items]
Warrants Outstanding	12,957
Oxford and Silicon Valley Bank [Member] \| New Loan and Security Agreement [Member] \| 2019 Term Loan [Member] \| January 2020 [Member]
Class of Warrant or Right [Line Items]
Expiration Date	2030-01
Exercise Price \| $ / shares	$ 10.42
Warrants Outstanding	12,957

Research and Development Arrangements - Additional Information (Detail) - USD ($)			3 Months Ended	12 Months Ended
	Dec. 20, 2021	Apr. 23, 2020	Sep. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2022	Jul. 14, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues				$ 7,530,000	$ 94,588,000	$ 70,428,000
Accounts receivable				1,283,000	147,000
Amount received as milestone payment			$ 5,000,000	2,500,000
Net proceeds of issuance of common stock				164,233,000
Ji Xing Omecamtiv Mecarbil License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Nonrefundable payment obligation	$ 50,000,000
Amount received as milestone payment	$ 50,000,000
Ji Xing Aficamten License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable				300,000	100,000
Upfront payment received									$ 25,000,000
Royalty Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues					87,000,000
Sale of interest in future royalties									85,000,000
Fair Value of Royalty							$ 87,000,000
Long-term deferred revenue								$ 87,000,000
Common Stock Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Issuance of common stock upon private placement, shares	511,182
Shares Issued, price per share	$ 39.125
Net proceeds of issuance of common stock	$ 20,000,000
Common stock purchase agreement date	Dec. 20, 2021
Excess amount paid over the fair value of the shares	$ 4,900,000
Fair value of common stock	15,100,000
Maximum [Member] \| Ji Xing Omecamtiv Mecarbil License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential additional payments receivable	330,000,000
Maximum [Member] \| Ji Xing Aficamten License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential additional payments receivable									$ 200,000,000
2016 Astellas Amendment [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment of development costs for clinical trials of reldesemtiv		$ 12,000,000
Reimbursement of clinical development costs				12,000,000
Rights Granted [Member] \| Ji Xing Omecamtiv Mecarbil License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Nonrefundable payment obligation	40,000,000
New Drug Application [Member] \| Ji Xing Omecamtiv Mecarbil License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Nonrefundable payment obligation	$ 10,000,000
License Revenues [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues				0	0	54,856,000
License Revenues [Member] \| Ji Xing Aficamten License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues							$ 36,500,000
Research and Development Revenues [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues				4,030,000	6,588,000	10,572,000
Research and Development Revenues [Member] \| Ji Xing Aficamten License and Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues				1,300,000	900,000	0
Amgen \| Research And Development Milestone Grant And Other Revenues Net
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues				0	0	7,400,000
Astellas [Member] \| Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable				0	0
Astellas [Member] \| Research and Development Revenues [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenues				$ 2,700,000	$ 5,700,000	$ 3,200,000

Subsequent Events

12 Months Ended

Dec. 31, 2023

Subsequent Events [Abstract]

Subsequent Events

Note 11 — Subsequent Events

During the period January 1, 2024 through and inclusive of February 27, 2024, we sold 1,237,460 shares of our common stock for net proceeds of $93.6 million under the Amended ATM Facility.

Net Loss Per Share - Instruments Excluded from the Computation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	25,759	24,853	27,519
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	11,780	10,992	9,373
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	13	13	48
Restricted Stock and Performance Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	1,375	1,260	1,415
Shares Issuable Related to the ESSP [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	16	13	8
2026 Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	2,003	2,003	16,675
2027 Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total shares	10,572	10,572	0