Eiger BioPharmaceuticals (EIGRQ) 10-Q 4 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 01, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Trading Symbol	EIGR
Entity Registrant Name	Eiger BioPharmaceuticals, Inc.
Entity Central Index Key	0001305253
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		33,975,800
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	001-36183
Entity Tax Identification Number	33-0971591
Entity Address, Address Line One	2155 Park Boulevard
Entity Address, City or Town	Palo Alto
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94306
City Area Code	650
Local Phone Number	272-6138
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock (par value $0.001 per share)
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 49,255	$ 28,864
Short-term debt securities	36,051	99,976
Accounts receivable, net	2,762
Inventories	2,621	93
Prepaid expenses and other current assets	8,397	8,873
Total current assets	99,086	137,806
Long-term debt securities	35,093
Property and equipment, net	581	709
Operating lease right-of-use assets	777	1,176
Other assets	4,740	3,903
Total assets	140,277	143,594
Current liabilities:
Accounts payable	6,753	4,640
Accrued liabilities	11,579	11,405
Current portion of operating lease liabilities	608	582
Current portion of long-term debt, net	3,072
Total current liabilities	22,012	16,627
Long-term debt, net	28,524	31,194
Operating lease liabilities	276	738
Total liabilities	50,812	48,559
Stockholders’ equity:
Common stock	34	34
Additional paid-in capital	408,079	401,509
Accumulated other comprehensive income (loss)	1	(8)
Accumulated deficit	(318,649)	(306,500)
Total stockholders’ equity	89,465	95,035
Total liabilities and stockholders’ equity	$ 140,277	$ 143,594

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Product revenue, net	$ 3,039,000		$ 8,782,000
Costs and operating expenses:
Cost of sales	318,000		641,000
Research and development	18,106,000	$ 9,810,000	46,250,000	$ 29,045,000
Selling, general and administrative	6,466,000	5,027,000	17,916,000	15,141,000
Total costs and operating expenses	24,890,000	14,837,000	64,807,000	44,186,000
Loss from operations	(21,851,000)	(14,837,000)	(56,025,000)	(44,186,000)
Interest expense	(894,000)	(906,000)	(2,659,000)	(2,681,000)
Interest income	35,000	76,000	119,000	629,000
Other income (expense), net	503,000	(13,000)	46,462,000	(7,000)
Loss before provision for income taxes	(22,207,000)	(15,680,000)	(12,103,000)	(46,245,000)
Provision for income taxes	16,000	0	46,000	0
Net loss	$ (22,223,000)	$ (15,680,000)	$ (12,149,000)	$ (46,245,000)
Net loss per common share:
Basic and diluted	$ (0.65)	$ (0.52)	$ (0.36)	$ (1.74)
Weighted-average common shares outstanding:
Basic and diluted	33,946,559	29,879,135	33,922,080	26,639,201

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (22,223)	$ (15,680)	$ (12,149)	$ (46,245)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale debt securities, net	7	(29)	9	(26)
Comprehensive loss	$ (22,216)	$ (15,709)	$ (12,140)	$ (46,271)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ 56,480	$ 24	$ 297,863	$ 42	$ (241,449)
Balance, beginning of period, Shares at Dec. 31, 2019		24,523,381
Issuance of common stock upon exercise of stock options	30		30
Issuance of common stock upon exercise of stock options, Shares		2,895
Vesting of common stock issued under Product Development Agreement	53		53
Issuance of common stock upon ESPP purchase	83		83
Issuance of common stock upon ESPP purchase, Shares		11,332
Issuance of common stock upon offering at-the-market, net of issuance costs	191		191
Issuance of common stock upon offering at-the-market, net of issuance costs, Shares		32,751
Stock-based compensation expense	1,629		1,629
Unrealized (loss) gain on available-for-sale debt securities, net	(6)			(6)
Net loss	(15,239)				(15,239)
Balance at Mar. 31, 2020	43,221	$ 24	299,849	36	(256,688)
Balance, end of period, Shares at Mar. 31, 2020		24,570,359
Unrealized gain (loss) on available-for-sale debt securities, net	(6)			(6)
Balance at Dec. 31, 2019	56,480	$ 24	297,863	42	(241,449)
Balance, beginning of period, Shares at Dec. 31, 2019		24,523,381
Unrealized (loss) gain on available-for-sale debt securities, net	(26)
Net loss	(46,245)
Balance at Sep. 30, 2020	92,950	$ 32	380,596	16	(287,694)
Balance, end of period, Shares at Sep. 30, 2020		31,916,039
Unrealized gain (loss) on available-for-sale debt securities, net	(26)
Balance at Mar. 31, 2020	43,221	$ 24	299,849	36	(256,688)
Balance, beginning of period, Shares at Mar. 31, 2020		24,570,359
Issuance of common stock upon exercise of stock options	490		490
Issuance of common stock upon exercise of stock options, Shares		58,805
Vesting of common stock issued under Product Development Agreement	55		55
Issuance of common stock upon offering at-the-market, net of issuance costs	28,580	$ 3	28,577
Issuance of common stock upon offering at-the-market, net of issuance costs, Shares		2,612,476
Stock-based compensation expense	1,462		1,462
Unrealized (loss) gain on available-for-sale debt securities, net	9			9
Net loss	(15,326)				(15,326)
Balance at Jun. 30, 2020	58,491	$ 27	330,433	45	(272,014)
Balance, end of period, Shares at Jun. 30, 2020		27,241,640
Unrealized gain (loss) on available-for-sale debt securities, net	9			9
Vesting of common stock issued under Product Development Agreement	56		56
Issuance of common stock upon ESPP purchase	103		103
Issuance of common stock upon ESPP purchase, Shares		14,313
Issuance of common stock upon offering at-the-market, net of issuance costs	48,564	$ 5	48,559
Issuance of common stock upon offering at-the-market, net of issuance costs, Shares		4,660,086
Stock-based compensation expense	1,445		1,445
Unrealized (loss) gain on available-for-sale debt securities, net	(29)			(29)
Net loss	(15,680)				(15,680)
Balance at Sep. 30, 2020	92,950	$ 32	380,596	16	(287,694)
Balance, end of period, Shares at Sep. 30, 2020		31,916,039
Unrealized gain (loss) on available-for-sale debt securities, net	(29)			(29)
Balance at Dec. 31, 2020	95,035	$ 34	401,509	(8)	(306,500)
Balance, beginning of period, Shares at Dec. 31, 2020		33,878,486
Issuance of common stock upon exercise of stock options	166		166
Issuance of common stock upon exercise of stock options, Shares		19,150
Vesting of common stock issued under Product Development Agreement	53		53
Issuance of common stock upon ESPP purchase	136		136
Issuance of common stock upon ESPP purchase, Shares		19,928
Issuance of common stock upon release of restricted stock units, Shares		33,750
Stock-based compensation expense	1,549		1,549
Unrealized (loss) gain on available-for-sale debt securities, net	3			3
Net loss	29,248				29,248
Balance at Mar. 31, 2021	126,190	$ 34	403,413	(5)	(277,252)
Balance, end of period, Shares at Mar. 31, 2021		33,951,314
Unrealized gain (loss) on available-for-sale debt securities, net	3			3
Balance at Dec. 31, 2020	$ 95,035	$ 34	401,509	(8)	(306,500)
Balance, beginning of period, Shares at Dec. 31, 2020		33,878,486
Issuance of common stock upon exercise of stock options, Shares	25,945
Unrealized (loss) gain on available-for-sale debt securities, net	$ 9
Net loss	(12,149)
Balance at Sep. 30, 2021	89,465	$ 34	408,079	1	(318,649)
Balance, end of period, Shares at Sep. 30, 2021		33,975,800
Unrealized gain (loss) on available-for-sale debt securities, net	9
Balance at Mar. 31, 2021	126,190	$ 34	403,413	(5)	(277,252)
Balance, beginning of period, Shares at Mar. 31, 2021		33,951,314
Vesting of common stock issued under Product Development Agreement	52		52
Stock-based compensation expense	2,058		2,058
Unrealized (loss) gain on available-for-sale debt securities, net	(1)			(1)
Net loss	(19,174)				(19,174)
Balance at Jun. 30, 2021	109,125	$ 34	405,523	(6)	(296,426)
Balance, end of period, Shares at Jun. 30, 2021		33,951,314
Unrealized gain (loss) on available-for-sale debt securities, net	(1)			(1)
Issuance of common stock upon exercise of stock options	43		43
Issuance of common stock upon exercise of stock options, Shares		6,795
Vesting of common stock issued under Product Development Agreement	62		62
Issuance of common stock upon ESPP purchase	121		121
Issuance of common stock upon ESPP purchase, Shares		17,691
Stock-based compensation expense	2,330		2,330
Unrealized (loss) gain on available-for-sale debt securities, net	7			7
Net loss	(22,223)				(22,223)
Balance at Sep. 30, 2021	89,465	$ 34	$ 408,079	1	$ (318,649)
Balance, end of period, Shares at Sep. 30, 2021		33,975,800
Unrealized gain (loss) on available-for-sale debt securities, net	$ 7			$ 7

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020
Statement Of Stockholders Equity [Abstract]
Issuance of common stock upon offering at-the-market, net of issuance costs	$ 1,575	$ 786	$ 221

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flow (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net loss	$ (12,149)	$ (46,245)
Change in operating assets and liabilities:
Accounts receivable	(2,762)
Inventories	(2,528)
Prepaid expenses and other current assets	493	(4,418)
Other assets	(837)	(1,270)
Accounts payable	2,218	1,836
Accrued liabilities	257	(2,893)
Operating lease liabilities	(436)	(406)
Net cash used in operating activities	(54,577)	(47,670)
Gain from sale of priority review voucher	(46,493)
Income related to asset purchase agreement	(281)
Depreciation and amortization	203	112
Amortization of debt securities premiums and discounts	658	(33)
Non-cash interest expense	577	593
Amortization of operating lease right-of-use assets	399	354
Common stock issued under Product Development Agreement	167	164
Stock-based compensation	5,937	4,536
Investing activities
Purchase of debt securities available-for-sale	(71,447)	(92,480)
Proceeds from maturities of debt securities available-for-sale	99,630	74,767
Proceeds related to asset purchase agreement	281
Proceeds from sale of priority review voucher	95,000
Payments related to priority review voucher	(48,507)
Purchase of property and equipment	(92)	(107)
Net cash provided by (used in) investing activities	74,865	(17,820)
Financing activities
Issuance of common stock upon offering at-the-market, net of issuance costs		77,404
Proceeds from issuance of common stock upon stock option exercises	209	520
Proceeds from issuance of common stock upon ESPP purchase	277	186
Payment of debt issuance costs	(175)
Payment of deferred offering costs	(208)
Net cash provided by financing activities	103	78,110
Net increase in cash and cash equivalents	20,391	12,620
Cash and cash equivalents at beginning of period	28,864	39,373
Cash and cash equivalents at end of period	49,255	51,993
Supplemental disclosure of cash flow information:
Interest paid	$ 2,082	$ 2,089

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of Business	1. Description of Business Eiger BioPharmaceuticals, Inc. (the Company or Eiger) was incorporated in the State of Delaware on November 6, 2008. Eiger is a commercial-stage biopharmaceutical company focused on the development and commercialization of well-characterized drugs and biologics for serious rare and ultra-rare diseases with high unmet medical needs. Eiger has reported positive proof-of-concept clinical results across all of our programs. All five of our rare disease programs have FDA Breakthrough Therapy Designation. Eiger’s lead clinical programs are focused on the development of complementary, foundational treatments for Hepatitis Delta Virus (HDV), the most severe form of viral hepatitis, for which there is currently no FDA-approved therapy. Lonafarnib is a first-in-class oral farnesylation inhibitor and peginterferon lambda is a first-in-class, type III, well-tolerated interferon. Both lonafarnib and peginterferon lambda are in global Phase 3 trials. The FDA approved the Company’s first commercial product, Zokinvy ® LMNA ZMPSTE24 The Company is also developing avexitide, a well-characterized peptide, as a treatment for post-bariatric hypoglycemia (PBH), a debilitating and potentially life-threatening condition for which there is currently no approved therapy, and as a treatment for congenital hyperinsulinism (HI), an ultra-rare pediatric metabolic disorder. The Company’s principal operations are based in Palo Alto, California and it operates in one segment. Liquidity As of September 30, 2021, the Company had $85.3 million of cash, cash equivalents and short-term securities, comprised of $49.3 million of cash and cash equivalents and $36.0 million of short-term debt securities available-for-sale. As of September 30, 2021, the Company also had $35.1 million of long-term debt securities available-for-sale. The Company had an accumulated deficit of $318.6 million and negative cash flows from operating activities as of September 30, 2021. As the Company continues to incur losses, its transition to profitability will depend on the successful development, approval, and commercialization of product candidates and on the achievement of sufficient revenues to support its cost structure. The Company may never achieve profitability, and until it does, the Company will need to continue to raise additional capital Management believes that the currently available resources will be sufficient to fund its planned operations for at least the next 12 months following the issuance date of these condensed consolidated financial statements. However, if the Company’s anticipated operating results are not achieved in future periods, the Company believes that planned expenditures may need to be reduced or it would be required to raise funding in order to fund the operations. Additionally, the Company’s ability to raise additional capital may be adversely impacted by potential worsening global economic conditions and the recent disruptions to, and volatility in, the credit and financial markets in the United States and worldwide resulting from the ongoing COVID-19 pandemic.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The unaudited consolidated financial statements include the accounts of Eiger BioPharmaceuticals, Inc. and its wholly owned subsidiaries, EBPI Merger Inc., EB Pharma LLC, Eiger BioPharmaceuticals Europe Limited, and EigerBio Europe Limited, have been prepared in accordance with accounting principles generally accepted in the United States of America, (U.S. GAAP) and follow the requirements of the Securities and Exchange Commission (the SEC) for annual reporting. All intercompany balances and transactions have been eliminated in consolidation. Reclassifications Certain items on the unaudited condensed consolidated balance sheet have been reclassified to conform to current year presentation. Such items were not material. Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates. The Company bases its estimates on historical experience and on various other market-specific and relevant assumptions that the Company believes to be reasonable under the circumstances. Actual results could differ from those estimates. Debt Securities Short-term securities consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than 365 days from the date of acquisition. Long-term securities consist of debt securities classified as available-for-sale and have maturities greater than 365 days from the date of acquisition. All short-term and long-term securities are carried at fair value based upon quoted market prices. Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated other comprehensive loss. The cost of available-for-sale securities sold is based on the specific-identification method . Accounts Receivable Accounts receivable represent amounts billed to the Company’s customers, net of an allowance for doubtful accounts. Trade accounts receivable are recorded at invoiced amounts and do not bear interest. The expectation of collectability is based on a review of credit profiles of customers, contractual terms and conditions, current economic trends, and historical payment experience. The Company regularly reviews the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice and the collection history of each customer to determine the appropriate amount of allowance for doubtful accounts. The Company had no allowance as of September 30, 2021 and December 31, 2020. The Company had no bad debt expense for the three and nine months ended September 30, 2021 and 2020. Inventories Inventories are stated at the lower of cost, determined based on actual costs, or estimated net realizable value, on a first-in, first-out basis. Inventories consist of raw materials, work-in-process and finished goods. Prior to regulatory approval of the Company’s product candidates, expenses incurred to manufacture drug products are recorded as research and development expense. The Company begins capitalizing these expenses as inventory upon regulatory approval. The Company periodically assesses the recoverability of its inventory and reduces the carrying value of the inventory when items are determined to be obsolete, defective or in excess of forecasted sales requirements. Inventory write-downs for excess, defective, and obsolete inventory are recorded as a cost of sales. There have been no write-downs of inventories for the periods presented. Revenue Recognition The Company recognizes revenue upon transfer of control of promised products to customers in an amount that reflects the consideration it expects to receive in exchange for those products. Product Revenue The Company’s product revenue consists of sales of Zokinvy, which received FDA approval in November 2020 and was launched commercially in the United States in January 2021. Prior to 2021, the Company had no product revenue. The Company sells Zokinvy to a specialty pharmacy provider (the Customer) that subsequently dispenses the product directly to patients. As all sales of Zokinvy are currently in the United States, and the Company only has one customer, the Company discloses revenue on a total basis without further disaggregation. Additionally, the Company does not have any contract assets or liabilities, other than accounts receivable, related to its product revenue. The Company recognizes product revenue when the Customer obtains control of its product, which occurs at a point in time, typically upon delivery to the Customer as the delivery of the product is the Company’s only performance obligation. Shipping and handling activities are fulfillment activities rather than a separate performance obligation and are recorded in cost of sales. Product revenue is recorded at the net sales price (transaction price), which includes estimates of variable consideration resulting from rebates, prompt payment discounts, co-payment assistance, and returns. Amounts related to such items are estimated at contract inception and updated at the end of each reporting period as additional information becomes available. The amount of variable consideration may be constrained and is included in the transaction price only to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Product revenue is recorded after considering the impact of the following variable consideration amounts along with the constraint at the time of revenue recognition: Rebates: The Company’s products are subject to government mandated rebates for Medicaid Drug Rebate Program, Medicare Part D Prescription Drug Benefit Program, and other government health care programs in the United States. Rebate amounts are based upon contractual agreements or legal requirements with public sector benefit providers. The Company uses the expected-value method for estimating these rebates based on statutory discount rates and expected utilization. The expected utilization of rebates is estimated based on expected coverage of identified patients. Estimates for these rebates are adjusted quarterly to reflect the most recent information. The Company records an accrued liability for unpaid rebates related to products for which control has been transferred to the Customer. Prompt payment discounts: The Company provides a discount to the Customer if it pays for purchases within 30 days. The Company expects that its Customer will earn prompt payment discounts and uses the most likely amount method for estimating such discounts. As a result, when revenues are recognized, the Company deducts the full amount of the prompt payment discounts from total product revenues and record these discounts as a reduction of accounts receivable. Co-payment assistance: The Company provides co-payment assistance to patients who have commercial insurance and meet certain eligibility requirements. The Company uses the expected-value method for estimating co-payment assistance based on estimates of program redemption using data provided by third-party administrators. Estimates for the co-payment assistance are adjusted quarterly to reflect actual experience. The Company records an accrued liability for unredeemed co-payment assistance related to products for which control has been transferred to the Customer. Product returns: The Company offers limited product return rights and generally allows for the return of product that is damaged or defective, or within a few months prior to and up to a few months after the product expiration date. The Company considers several factors in the estimation of potential product returns, including expiration dates of the product shipped, the limited product return rights, third-party data in monitoring channel inventory levels, shelf life of the product, and other relevant factors. Cost of Sales Cost of sales consists primarily of direct and indirect costs related to the manufacturing of Zokinvy for commercial sale, including third-party manufacturing costs, packaging services, freight, storage costs, and write down of inventories. Costs incurred prior to FDA approval in November 2020 were previously recorded as research and development expense in the condensed consolidated statements of operations . Accrued Research and Development Costs The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued liabilities in the consolidated balance sheets and within research and development expenses in the consolidated statements of operations. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers. The Company makes judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. Leases The Company has a real estate lease for its office space in Palo Alto, California. The Company determines the initial classification and measurement of its right-of-use assets (ROU assets) and lease liabilities at the lease commencement date and thereafter if modified. The lease term includes any renewal options and termination options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its incremental borrowing rate. The incremental borrowing rate is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment. Rent expense for operating leases is recognized on a straight-line basis, unless the operating lease ROU assets have been impaired, over the reasonably assured lease term based on the total lease payments and is included in operating expenses in the condensed consolidated statements of operations. For operating leases that reflect impairment, the Company will recognize the amortization of the operating lease ROU assets on a straight-line basis over the remaining lease term with rent expense still included in selling, general and administrative expenses in the condensed consolidated statements of operations. The Company has elected the practical expedient to not separate lease and non-lease components. The Company’s non-lease components are primarily related to property maintenance and insurance, which varies based on future outcomes, and thus is recognized in selling, general and administrative expenses when incurred. Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) Codification Improvements to Topic 326, Financial Instruments – Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, Financial Instruments – Credit Losses (Topic 326), to irrevocably elect to measure certain individual financial assets at fair value instead of amortized cost In November 2019, the FASB issued ASU No. 2019-10, Financial Instruments – Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) defers the effective date for ASU No. 2016-13 for smaller reporting companies to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is evaluating the impact of the guidance on its consolidated financial statements. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848) The pronouncement is effective for all entities as of March 12, 2020 through December 31, 2022. In October 2021, the Company amended its Oxford Loan to replace its floating interest rate with the LIBOR replacement rate (see Notes 8 and 13). The Company will adopt this standard when LIBOR is discontinued and does not expect the adoption to have a material impact on its consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the financial statements on a recurring basis (at least annually). As of September 30, 2021 and December 31, 2020 Assets and liabilities recorded at fair value on a recurring basis in the unaudited condensed consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 : Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 : Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level 3 : Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. The Company’s money market funds are classified as Level 1 because they are valued using quoted market prices. The Company’s debt securities consist of available-for-sale securities and are classified as Level 2 because their value is based on valuations using significant inputs derived from or corroborated by observable market data. There were no There were no transfers into or out of Level 3 of the fair value hierarchy during the periods presented. The following tables present the fair value hierarchy for assets and liabilities measured at fair value (in thousands): September 30, 2021 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 42,394 $ — $ — $ 42,394 Corporate debt securities — 40,787 — 40,787 U.S. government bonds — 30,357 — 30,357 Total $ 42,394 $ 71,144 $ — $ 113,538 December 31, 2020 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 20,846 $ — $ — $ 20,846 Corporate debt securities — 33,941 — 33,941 Commercial paper — 21,980 — 21,980 U.S. treasury bills — 39,995 — 39,995 U.S. government bonds — 4,060 — 4,060 Total $ 20,846 $ 99,976 $ — $ 120,822 There were no financial liabilities as of September 30, 2021 and December 31, 2020 The following tables summarize the estimated value of the Company’s cash equivalents and debt securities and the gross unrealized holding gains and losses (in thousands): September 30, 2021 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market funds $ 42,394 $ — $ — $ 42,394 Total cash equivalents $ 42,394 $ — $ — $ 42,394 Debt securities: Corporate debt securities $ 40,799 $ — $ (12 ) $ 40,787 U.S. government bonds 30,344 13 — 30,357 Total debt securities $ 71,143 $ 13 $ (12 ) $ 71,144 Classified as: Cash equivalents $ 42,394 Short-term debt securities 36,051 Long-term debt securities 35,093 $ 113,538 December 31, 2020 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market funds $ 20,846 $ — $ — $ 20,846 Total cash equivalents $ 20,846 $ — $ — $ 20,846 Debt securities: Corporate debt securities $ 33,952 $ 1 $ (12 ) $ 33,941 Commercial paper 21,980 — — 21,980 U.S. treasury bills 39,992 3 — 39,995 U.S. government bonds 4,060 — — 4,060 Total debt securities $ 99,984 $ 4 $ (12 ) $ 99,976 Classified as: Cash equivalents 20,846 Short-term debt securities 99,976 $ 120,822 The Company periodically reviews the available-for-sale securities for impairment loss. The Company considers factors such as the duration, severity and the reason for the decline in value, the potential recovery period and its intent to sell. For debt securities, it also considers whether (i) it is more likely ot that the Company will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. During the nine months ended September 30, 2021, the Company did not recognize any impairment losses. All debt securities with unrealized losses have been in a loss position for 12 months.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4. Balance Sheet Components Inventories Inventories consist of the following (in thousands): September 30, December 31, 2021 2020 Raw materials $ 1,008 $ — Work-in-progress 1,498 34 Finished goods 115 59 Total inventories $ 2,621 $ 93 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): September 30, December 31, 2021 2020 Prepaid contract manufacturing costs $ 4,075 $ 6,126 Prepaid research costs 2,041 1,177 Prepaid insurance 927 448 Other 1,354 1,122 Total prepaid expenses and other current assets $ 8,397 $ 8,873 Accrued Liabilities Accrued liabilities consist of the following (in thousands): September 30, December 31, 2021 2020 Contract research costs $ 4,646 $ 6,062 Compensation and related benefits 2,241 3,169 Contract manufacturing costs 2,503 1,167 Product revenue reserves 1,380 — Other 809 1,007 Total accrued liabilities $ 11,579 $ 11,405

Product Development Agreement

Product Development Agreement	9 Months Ended
	Sep. 30, 2021
Product Development Agreement [Abstract]
Product Development Agreement	5. Product Development Agreement Product Development Agreement On August 11, 2018, the Company entered into a Product Development Agreement and a First Project Agreement (the Product Agreements), pursuant to which the Company will receive development program support services for its HDV program. The services are to be provided from July 1, 2018 through the new drug application (NDA) filing. As consideration, the Company has committed to pay fees of approximately $10.0 million in cash and stock over four years, including approximately $0.8 million for expert consultant fees and pass through costs to vendors, plus certain incentive-based regulatory milestone fees up to $1.0 million. As part of the aggregate payment, the Company issued 115,526 shares of common stock subject to quarterly vesting requirements related to successful performance of the services and achievement of budget timeline set forth in the Product Agreements. The Product Agreements can be terminated by either party due to material breach or by the Company without cause with Product Agreements. Additionally, as of September 30, 2021, the total unrecognized compensation expense related to unvested restricted shares was $0.1 million, which the Company expects to recognize over an estimated weighted-average period of .

Asset Purchase Agreements and R

Asset Purchase Agreements and Related License Agreements	9 Months Ended
	Sep. 30, 2021
Asset Purchase Agreements And Related License Agreements [Abstract]
Asset Purchase Agreements and Related License Agreements	6 . Asset Purchase Agreements and Related License Agreements Asset Purchase Agreement with AbbVie Inc. On November 20, 2020, Eiger entered into an asset purchase agreement (the APA) with AbbVie, Inc. (AbbVie) to sell its rare pediatric disease priority review voucher (the PRV), which was awarded on November 20, 2020 upon FDA approval of Zokinvy. The APA contains customary representations, warranties, covenants, and indemnification provisions subject to certain limitations. In consideration for the PRV, AbbVie agreed to pay the Company $95.0 million. The transaction closed in January 2021. Such consideration was shared with the Progeria Research Foundation (PRF) in accordance with the terms of the PRF Collaboration and Supply Agreement, pursuant to which the Company and PRF will equally share any net proceeds from the sale of a priority review voucher that the Company may receive as the sponsor of a rare pediatric disease product application. The Company retained $46.5 million of proceeds from the sale of the PRV, net of related payments, and recorded the amount in other income, net in the unaudited condensed consolidated statement of operations for the nine months ended September 30, 2021.

Sale of Assets

Sale of Assets	9 Months Ended
	Sep. 30, 2021
Discontinued Operations And Disposal Groups [Abstract]
Sale of Assets	7. Sale of Assets In May 2017, the Company and Theragene Pharmaceuticals, The Company has determined that the sale of the MYDICAR assets qualify as an asset sale and not a business. Concurrently with the execution of the Theragene APA, the Company became the owner of 475,000 shares of common stock of Theragene and held a put option for 225,000 shares of common stock of Theragene, which were recognized as a cost method investment with carrying value of zero. In September 2020, Theragene entered into an Asset Purchase Agreement with a third party for the sale of MYDICAR. Under the terms of the Theragene APA between the Company and Theragene, the Company is eligible to receive 25% of any upfront, licensee fee, milestone or other payment (other than royalty payments) received by Theragene from the sale or sublicense of MYDICAR, within 30 days of receipt of such payments by Theragene. As such, during the three and nine months ended September 30, 2021, the Company recognized zero and $0.3 million in other income, net, respectively. The Company expects to receive an additional $0.1 million subsequent to September 30, 2021.

Debt

Debt	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Debt	8 . Debt In December 2016, the Company entered into an aggregate $25.0 million loan with Oxford Finance LLC (the Oxford Loan) with a maturity date of July 1, 2021. and borrowed $5.0 million (Tranche B). On August 3, 2018, the Company On March 5, 2019, the Company entered into the third amendment to the Oxford Loan (the Amended Oxford Loan) to refinance the Oxford Loan. The Amended Oxford Loan increased the aggregate amount available to be borrowed to $35.0 million and extended the maturity date to March 1, 2024. On March 5, 2019, prior to entering into the Amended Oxford Loan, the outstanding balance of the Oxford Loan was $23.3 million. At the time of entering into the Amended Oxford Loan, the Company borrowed an additional $6.7 million in principal under the Amended Oxford Loan, which increased the total amount borrowed to $30.0 million (Amended Tranche A). The remaining $5.0 million (Amended Tranche B) was available to the Company provided that certain milestones are achieved by February 2021. The Company did not draw down the Amended Tranche B. On February 23, 2021, the Company entered into the fifth amendment to the Oxford Loan. The amendment extended the interest only period by 17 months until September 1, 2022, followed by 19 equal monthly payments of principal and interest. Upon the receipt of the Amended Tranche B, the interest only period for borrowed funds will be extended by six months until March 1, 2023, followed by 13 equal monthly payments of principal plus accrued interest. In addition, the Company paid an amendment fee of $0.2 million to the lender on the effective date of the fifth amendment, which was recorded as an additional debt discount and is being amortized over the remaining term of the Amended Oxford Loan. The Amended Tranche B is now available to the Company provided certain milestones are achieved by August 2022. The Amended Oxford Loan bears interest at a floating rate per annum equal to the greater of either the 30-day U.S. Dollar LIBOR reported in the Wall Street Journal plus 6.64% or 9.15%. the Company is required to pay an additional exit fee of $1.0 million The Company is also required to pay a 5.0% success fee of the total amount drawn under the Amended Oxford Loan The Amended Oxford Loan includes contingent interest features and mandatory prepayment features upon an event of default that meet the definition of a derivative but were not bifurcated from the debt instrument as their fair value was deemed to be insignificant . The refinancing of the Oxford Loan did not have a material impact on terms, conditions, representations, warranties, covenants or agreements set forth in the Oxford Loan. The loan is secured by the perfected first priority liens on the Company's assets, including a commitment by the Company to not allow any liens to be placed upon the Company’s intellectual property. The loan includes customary events of default, including failure to pay amounts due, breaches of covenants and warranties, material adverse effect events, certain cross defaults and judgments, and insolvency. If the Company is unable to comply with these covenants or if the Company defaults on any portion of the outstanding borrowings, the lenders can also impose a 5.0% penalty, restrict access to additional borrowings under the loan and security agreement, and accelerate the maturity of the debt. As of September 30, 2021, the Company was in compliance with all covenants. The Company is permitted to make voluntary prepayments of the Amended Oxford Loan with a prepayment fee, calculated as of the loan origination date, equal to (i) 2.0% of the loan prepaid during the first 12 months and (ii) 1.0% of the loan prepaid in months 13-24. The Company is required to make mandatory prepayments of the outstanding loan upon the acceleration by lender following the occurrence of an event of default, along with a payment of the final payment, the prepayment fee and any other obligations that are due and payable at the time of prepayment. The Company accounts for the amortization of the debt discount utilizing the effective interest method. Long-term debt and unamortized discount balances are as follows (in thousands): September 30, December 31, 2021 2020 Face value of long-term debt $ 30,000 $ 30,000 Exit fee 3,277 3,277 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (1,681 ) (2,083 ) Total long-term debt, net 31,596 31,194 Less: current portion of long-term debt (3,072 ) — Long-term debt, net $ 28,524 $ 31,194

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9 . Stock-Based Compensation During the second quarter of 2021, the Company approved the 2021 Inducement Plan to reserve 850,000 shares of its common stock to be used exclusively for grants of awards to individuals that were not previously employees or directors of the Company as a material inducement to such individuals’ entry into employment with the Company within the meaning of Rule 5635(c)(4) of the Nasdaq Listing Rules. As of September 30, 2021, there were 625,000 shares remaining available to be issued under the 2021 Inducement Plan. The following table summarizes stock option activity under the Company’s stock-based compensation plan s during the nine month s ended September 30 , 2021 (in thousands, except option and share data): Shares Available for Grant Number of Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value Outstanding as of December 31, 2020 1,021,109 3,697,075 $ 10.81 7.55 $ 9,048 Additional options authorized 2,543,924 Granted (1,723,785 ) 1,723,785 $ 9.13 Restricted stock units granted (371,500 ) — Performance stock units granted (240,000 ) — Exercised — (25,945 ) $ 8.07 Forfeited 16,823 (16,823 ) $ 9.41 Restricted stock units forfeited 1,875 — Outstanding as of September 30, 2021 1,248,446 5,378,092 $ 10.29 7.70 $ 1,489 Vested and exercisable as of September 30, 2021 2,768,024 $ 11.25 6.54 $ 1,016 During the three and nine months ended September 30, 2021, the weighted-average grant date fair value of options granted were $4.65 and $6.78 per share, respectively. During the three and nine months ended September 30, 2020, the weighted-average grant date fair value of options granted were $7.18 and $4.78 per share, respectively. The Company records stock-based compensation of stock options granted by estimating the fair value of stock-based awards using the Black-Scholes option pricing model and amortizes the fair value of the stock-based awards granted over the applicable vesting period of the awards on a straight-line basis. The fair value of stock options was estimated using the following weighted-average assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Expected term (in years) 5.77-6.08 6.08 5.27-6.08 5.27-6.08 Contractual term (in years) — — — 10.00 Volatility 70.72%-71.62% 74.00% 70.72%-100.87% 73.00%-77.00% Risk free interest rate 0.89%-1.15% 0.39% 0.62%-1.16% 0.39%-1.37% Dividend yield — — — — Restricted Stock Units and Performance Stock Units In the first quarter of 2020, the Company revised its non-employee director compensation policy to approve the granting of restricted stock units (RSUs) in accordance with the Restated 2013 Equity Incentive Plan (the Restated 2013 Plan). Each eligible director who has served for at least six months during the prior calendar year and continues to serve as a non-employee member of the board is granted RSUs. Each eligible director who has served on the Board for less than six months during the prior calendar year and who continues to serve as a non-employee member of the Board, is granted RSUs which are pro-rated for the period served during the prior calendar year. The RSUs granted to non-employee directors will vest on the one-year anniversary of the grant date, subject to the eligible director’s continuous services through the vesting date, and will vest in full upon a change in control, as defined under the Restated 2013 Plan. The RSUs granted to employees will begin vesting on the one-year anniversary through the two-year anniversary of the grant date. The fair value of all RSUs is measured at the grant date based on the closing market price of the Company’s common stock and is recognized as stock-based compensation expense on a straight-line basis over the vesting period. In the third quarter of 2021, the Company granted performance stock units (PSUs) pursuant to the Restated 2013 Plan. Each PSU, which is a stock award, is earned through the achievement of a performance-based metric over a defined performance period. The length of the defined performance period, the performance-based metric to be achieved during the defined performance period, and the measure of whether and to what degree such performance-based metric has been achieved will be conclusively determined by the compensation committee of the Company’s board of directors, in its sole discretion. The estimated fair value of equity awards that contain performance conditions is expensed over the term of the award once the Company has determined that it is probable that performance conditions will be satisfied. During the three and nine months ended September 30, 2021, the Company granted 240,000 PSUs with a weighted-average grant date fair value of $ 8.15 per share. As of September 30, 2021, no PSUs have vested as the performance-based metrics of the PSUs have not yet been achieved. During the three months ended September 30, 2021, the Company granted 168,000 RSUs with a weighted-average grant date fair value of $8.15 per share. There were no RSUs granted during the three months ended September 30, 2020. During the nine months ended September 30, 2021 and 2020, the Company granted 371,500 and 37,500 RSUs, respectively, with a weighted-average grant date fair value of $9.16 and $6.95 per share, respectively. In relation to the RSUs granted, the Company recognized $0.4 million and $0.1 million in stock-based compensation expense for the three months ended September 30, 2021 and 2020, respectively, and $0.7 million and $0.1 million in stock-based compensation expense for the nine months ended September 30, 2021 and 2020, respectively, which were included in selling, general and administrative expenses. As of September 30, 2021, the total unrecognized compensation expense related to unvested RSUs and PSUs was $4.7 million, which the Company expects to recognize over an estimated weighted-average period of 3.0 years The following table summarizes RSU and PSU activity and weighted average grant date fair value for the nine months ended September 30, 2021: Shares Weighted- Average Grant Date Fair Value Unvested shares as of December 31, 2020 37,500 $ 6.95 Granted 611,500 $ 8.76 Vested (33,750 ) $ 6.35 Forfeited (1,875 ) $ 9.99 Unvested shares as of September 30, 2021 613,375 $ 8.78 Stock-Based Compensation Expense Total stock-based compensation expense recognized was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 686 $ 367 $ 1,627 $ 1,154 Selling, general and administrative 1,644 1,078 4,310 3,382 Total $ 2,330 $ 1,445 $ 5,937 $ 4,536 As of September 30, 2021, the total unrecognized compensation expense related to unvested options was $16.8 million, which the Company expects to recognize over an estimated weighted average period of 2.8 years.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	10 . Income Taxes The Company’s provision for income taxes was approximately $16,000 and $46,000 for the three and nine months ended September 30, 2021, respectively, with an effective tax rate of 0.3% for the nine months ended September 30, 2021. The Company did not record tax expense for the three and nine months ended September 30, 2020 due to the Company’s loss position and full valuation allowance. The effective tax rate in each period differs from the U.S. statutory tax rate primarily due to the valuation allowances on the Company’s deferred tax assets as it is more likely than not that some or all of the Company’s deferred tax assets will not be realized. The tax expense recorded for the three and nine months ended September 30, 2021 relates to state taxes.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	1 1 . Commitments and Contingencies Lease Agreements In October 2017, the Company entered into a non-cancelable operating facility lease agreement for 8,029 square feet of office space located at 2155 Park Blvd. in Palo Alto, California. The lease commenced on March 1, 2018 and expires in February 2023. The lease has a three-year The maturity of the Company’s operating lease liabilities as of September 30, 2021 were as follows (in thousands): Undiscounted lease payments September 30, 2021 Remaining in 2021 $ 162 2022 662 2023 113 2024 1 Total undiscounted payments 938 Less: imputed interest 54 Present value of future lease payments 884 Less: current portion of operating lease liabilities 608 Operating lease liabilities $ 276 Rent expense recognized for the Company’s operating leases was $0.1 million and $0.2 million for the three months ended September 30, 2021 and 2020, respectively, and $0.4 million and $0.5 million for the nine months ended September 30, 2021 and 2020, respectively. Under the terms of the lease agreements, the Company is also responsible for certain variable lease payments that are not included in the measurement of the lease liability. Variable lease payments for the operating leases were $23,000 for the three months ended September 30, 2021 and 2020 and $0.1 million The operating cash outflows for the operating lease liabilities were $0.5 million and $0.5 million for the nine months ended September 30, 2021 and 2020, respectively. As of September 30, 2021 and December 31, 2020, the weighted-average remaining lease terms were 1.4 years and 2.1 years, and weighted-average discount rates were 9.15% and 9.15%, respectively.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	12. Net Loss Per Share Basic net loss per share of common stock is calculated by dividing the net loss by the weighted average number of shares of common stock outstanding during the period, without consideration for potentially dilutive securities. Since the Company was in a loss position for the three months ended September 30, 2021 and 2020, and nine months ended September 30, 2021 and 2020, diluted net loss per share is the same as basic net loss per share as the inclusion of all potential common shares outstanding would have been anti-dilutive. Dilutive potential common stock equivalents include the assumed exercise, vesting and issuance of employee stock awards using the treasury stock method. The following table sets forth the outstanding potentially dilutive securities which have been excluded in the calculation of diluted net loss per share because including such securities would be anti-dilutive (in common stock equivalent shares): Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 Options to purchase common stock 5,378,092 3,774,680 5,378,092 3,774,680 Restricted stock units (unvested) 627,088 37,500 627,088 37,500 ESPP 36,431 90,870 37,409 92,821 Total 6,041,611 3,903,050 6,042,589 3,905,001

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	1 3 . Subsequent Events On October 6, 2021, the Company entered into the sixth amendment to the Oxford Loan. Prior to the sixth amendment, the Amended Oxford Loan currently bears interest at a floating rate per annum equal to the greater of either the 30-day U.S. Dollar LIBOR reported in the Wall Street Journal plus 6.64% or 9.15%. The latest amendment replaces this rate with the LIBOR replacement rate upon a LIBOR transition event. As a result, the Amended Oxford Loan will bear interest at the LIBOR replacement rate which is the sum of the alternate benchmark rate and the LIBOR replacement spread. An estimate of the impact of the change to the LIBOR replacement rate on the financial statements cannot be made until the occurrence of the LIBOR transition event. The Company does not expect the impact of this change to be material.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited consolidated financial statements include the accounts of Eiger BioPharmaceuticals, Inc. and its wholly owned subsidiaries, EBPI Merger Inc., EB Pharma LLC, Eiger BioPharmaceuticals Europe Limited, and EigerBio Europe Limited, have been prepared in accordance with accounting principles generally accepted in the United States of America, (U.S. GAAP) and follow the requirements of the Securities and Exchange Commission (the SEC) for annual reporting. All intercompany balances and transactions have been eliminated in consolidation.
Reclassifications	Reclassifications Certain items on the unaudited condensed consolidated balance sheet have been reclassified to conform to current year presentation. Such items were not material.
Use of Estimates	Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates. The Company bases its estimates on historical experience and on various other market-specific and relevant assumptions that the Company believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Debt Securities	Debt Securities Short-term securities consist of debt securities classified as available-for-sale and have maturities greater than 90 days, but less than 365 days from the date of acquisition. Long-term securities consist of debt securities classified as available-for-sale and have maturities greater than 365 days from the date of acquisition. All short-term and long-term securities are carried at fair value based upon quoted market prices. Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated other comprehensive loss. The cost of available-for-sale securities sold is based on the specific-identification method .
Accounts Receivable	Accounts Receivable Accounts receivable represent amounts billed to the Company’s customers, net of an allowance for doubtful accounts. Trade accounts receivable are recorded at invoiced amounts and do not bear interest. The expectation of collectability is based on a review of credit profiles of customers, contractual terms and conditions, current economic trends, and historical payment experience. The Company regularly reviews the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice and the collection history of each customer to determine the appropriate amount of allowance for doubtful accounts. The Company had no allowance as of September 30, 2021 and December 31, 2020. The Company had no bad debt expense for the three and nine months ended September 30, 2021 and 2020.
Inventories	Inventories Inventories are stated at the lower of cost, determined based on actual costs, or estimated net realizable value, on a first-in, first-out basis. Inventories consist of raw materials, work-in-process and finished goods. Prior to regulatory approval of the Company’s product candidates, expenses incurred to manufacture drug products are recorded as research and development expense. The Company begins capitalizing these expenses as inventory upon regulatory approval. The Company periodically assesses the recoverability of its inventory and reduces the carrying value of the inventory when items are determined to be obsolete, defective or in excess of forecasted sales requirements. Inventory write-downs for excess, defective, and obsolete inventory are recorded as a cost of sales. There have been no write-downs of inventories for the periods presented.
Revenue Recognition	Revenue Recognition The Company recognizes revenue upon transfer of control of promised products to customers in an amount that reflects the consideration it expects to receive in exchange for those products. Product Revenue The Company’s product revenue consists of sales of Zokinvy, which received FDA approval in November 2020 and was launched commercially in the United States in January 2021. Prior to 2021, the Company had no product revenue. The Company sells Zokinvy to a specialty pharmacy provider (the Customer) that subsequently dispenses the product directly to patients. As all sales of Zokinvy are currently in the United States, and the Company only has one customer, the Company discloses revenue on a total basis without further disaggregation. Additionally, the Company does not have any contract assets or liabilities, other than accounts receivable, related to its product revenue. The Company recognizes product revenue when the Customer obtains control of its product, which occurs at a point in time, typically upon delivery to the Customer as the delivery of the product is the Company’s only performance obligation. Shipping and handling activities are fulfillment activities rather than a separate performance obligation and are recorded in cost of sales. Product revenue is recorded at the net sales price (transaction price), which includes estimates of variable consideration resulting from rebates, prompt payment discounts, co-payment assistance, and returns. Amounts related to such items are estimated at contract inception and updated at the end of each reporting period as additional information becomes available. The amount of variable consideration may be constrained and is included in the transaction price only to the extent it is probable that a significant reversal of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is resolved. Product revenue is recorded after considering the impact of the following variable consideration amounts along with the constraint at the time of revenue recognition: Rebates: The Company’s products are subject to government mandated rebates for Medicaid Drug Rebate Program, Medicare Part D Prescription Drug Benefit Program, and other government health care programs in the United States. Rebate amounts are based upon contractual agreements or legal requirements with public sector benefit providers. The Company uses the expected-value method for estimating these rebates based on statutory discount rates and expected utilization. The expected utilization of rebates is estimated based on expected coverage of identified patients. Estimates for these rebates are adjusted quarterly to reflect the most recent information. The Company records an accrued liability for unpaid rebates related to products for which control has been transferred to the Customer. Prompt payment discounts: The Company provides a discount to the Customer if it pays for purchases within 30 days. The Company expects that its Customer will earn prompt payment discounts and uses the most likely amount method for estimating such discounts. As a result, when revenues are recognized, the Company deducts the full amount of the prompt payment discounts from total product revenues and record these discounts as a reduction of accounts receivable. Co-payment assistance: The Company provides co-payment assistance to patients who have commercial insurance and meet certain eligibility requirements. The Company uses the expected-value method for estimating co-payment assistance based on estimates of program redemption using data provided by third-party administrators. Estimates for the co-payment assistance are adjusted quarterly to reflect actual experience. The Company records an accrued liability for unredeemed co-payment assistance related to products for which control has been transferred to the Customer. Product returns: The Company offers limited product return rights and generally allows for the return of product that is damaged or defective, or within a few months prior to and up to a few months after the product expiration date. The Company considers several factors in the estimation of potential product returns, including expiration dates of the product shipped, the limited product return rights, third-party data in monitoring channel inventory levels, shelf life of the product, and other relevant factors.
Cost of Sales	Cost of Sales Cost of sales consists primarily of direct and indirect costs related to the manufacturing of Zokinvy for commercial sale, including third-party manufacturing costs, packaging services, freight, storage costs, and write down of inventories. Costs incurred prior to FDA approval in November 2020 were previously recorded as research and development expense in the condensed consolidated statements of operations .
Accrued Research and Development Costs	Accrued Research and Development Costs The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical and clinical studies, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced and includes these costs in accrued liabilities in the consolidated balance sheets and within research and development expenses in the consolidated statements of operations. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers. The Company makes judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities.
Leases	Leases The Company has a real estate lease for its office space in Palo Alto, California. The Company determines the initial classification and measurement of its right-of-use assets (ROU assets) and lease liabilities at the lease commencement date and thereafter if modified. The lease term includes any renewal options and termination options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its incremental borrowing rate. The incremental borrowing rate is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment. Rent expense for operating leases is recognized on a straight-line basis, unless the operating lease ROU assets have been impaired, over the reasonably assured lease term based on the total lease payments and is included in operating expenses in the condensed consolidated statements of operations. For operating leases that reflect impairment, the Company will recognize the amortization of the operating lease ROU assets on a straight-line basis over the remaining lease term with rent expense still included in selling, general and administrative expenses in the condensed consolidated statements of operations. The Company has elected the practical expedient to not separate lease and non-lease components. The Company’s non-lease components are primarily related to property maintenance and insurance, which varies based on future outcomes, and thus is recognized in selling, general and administrative expenses when incurred.
Recent Accounting Pronouncements	Accounting Pronouncements Not Yet Adopted In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) Codification Improvements to Topic 326, Financial Instruments – Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, Financial Instruments – Credit Losses (Topic 326), to irrevocably elect to measure certain individual financial assets at fair value instead of amortized cost In November 2019, the FASB issued ASU No. 2019-10, Financial Instruments – Credit Losses (Topic 326), Derivatives and Hedging (Topic 815), and Leases (Topic 842) defers the effective date for ASU No. 2016-13 for smaller reporting companies to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. The Company is evaluating the impact of the guidance on its consolidated financial statements. In March 2020, the FASB issued ASU No. 2020-04, Reference Rate Reform (Topic 848) The pronouncement is effective for all entities as of March 12, 2020 through December 31, 2022. In October 2021, the Company amended its Oxford Loan to replace its floating interest rate with the LIBOR replacement rate (see Notes 8 and 13). The Company will adopt this standard when LIBOR is discontinued and does not expect the adoption to have a material impact on its consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Assets and Liabilities Measured at Fair Value	The following tables present the fair value hierarchy for assets and liabilities measured at fair value (in thousands): September 30, 2021 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 42,394 $ — $ — $ 42,394 Corporate debt securities — 40,787 — 40,787 U.S. government bonds — 30,357 — 30,357 Total $ 42,394 $ 71,144 $ — $ 113,538 December 31, 2020 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 20,846 $ — $ — $ 20,846 Corporate debt securities — 33,941 — 33,941 Commercial paper — 21,980 — 21,980 U.S. treasury bills — 39,995 — 39,995 U.S. government bonds — 4,060 — 4,060 Total $ 20,846 $ 99,976 $ — $ 120,822
Summary of Estimated Value of Cash Equivalents and Debt Securities and Gross Unrealized Holding Gains and Losses	The following tables summarize the estimated value of the Company’s cash equivalents and debt securities and the gross unrealized holding gains and losses (in thousands): September 30, 2021 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market funds $ 42,394 $ — $ — $ 42,394 Total cash equivalents $ 42,394 $ — $ — $ 42,394 Debt securities: Corporate debt securities $ 40,799 $ — $ (12 ) $ 40,787 U.S. government bonds 30,344 13 — 30,357 Total debt securities $ 71,143 $ 13 $ (12 ) $ 71,144 Classified as: Cash equivalents $ 42,394 Short-term debt securities 36,051 Long-term debt securities 35,093 $ 113,538 December 31, 2020 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market funds $ 20,846 $ — $ — $ 20,846 Total cash equivalents $ 20,846 $ — $ — $ 20,846 Debt securities: Corporate debt securities $ 33,952 $ 1 $ (12 ) $ 33,941 Commercial paper 21,980 — — 21,980 U.S. treasury bills 39,992 3 — 39,995 U.S. government bonds 4,060 — — 4,060 Total debt securities $ 99,984 $ 4 $ (12 ) $ 99,976 Classified as: Cash equivalents 20,846 Short-term debt securities 99,976 $ 120,822

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Inventory	Inventories consist of the following (in thousands): September 30, December 31, 2021 2020 Raw materials $ 1,008 $ — Work-in-progress 1,498 34 Finished goods 115 59 Total inventories $ 2,621 $ 93
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): September 30, December 31, 2021 2020 Prepaid contract manufacturing costs $ 4,075 $ 6,126 Prepaid research costs 2,041 1,177 Prepaid insurance 927 448 Other 1,354 1,122 Total prepaid expenses and other current assets $ 8,397 $ 8,873
Schedule of Components of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): September 30, December 31, 2021 2020 Contract research costs $ 4,646 $ 6,062 Compensation and related benefits 2,241 3,169 Contract manufacturing costs 2,503 1,167 Product revenue reserves 1,380 — Other 809 1,007 Total accrued liabilities $ 11,579 $ 11,405

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Schedule of Long-Term Debt and Unamortized Discount Balances	Long-term debt and unamortized discount balances are as follows (in thousands): September 30, December 31, 2021 2020 Face value of long-term debt $ 30,000 $ 30,000 Exit fee 3,277 3,277 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (1,681 ) (2,083 ) Total long-term debt, net 31,596 31,194 Less: current portion of long-term debt (3,072 ) — Long-term debt, net $ 28,524 $ 31,194

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2021
Stock Option Activity	The following table summarizes stock option activity under the Company’s stock-based compensation plan s during the nine month s ended September 30 , 2021 (in thousands, except option and share data): Shares Available for Grant Number of Options Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value Outstanding as of December 31, 2020 1,021,109 3,697,075 $ 10.81 7.55 $ 9,048 Additional options authorized 2,543,924 Granted (1,723,785 ) 1,723,785 $ 9.13 Restricted stock units granted (371,500 ) — Performance stock units granted (240,000 ) — Exercised — (25,945 ) $ 8.07 Forfeited 16,823 (16,823 ) $ 9.41 Restricted stock units forfeited 1,875 — Outstanding as of September 30, 2021 1,248,446 5,378,092 $ 10.29 7.70 $ 1,489 Vested and exercisable as of September 30, 2021 2,768,024 $ 11.25 6.54 $ 1,016
Summary of Non-cash Stock Based Compensation Expense	Total stock-based compensation expense recognized was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Research and development $ 686 $ 367 $ 1,627 $ 1,154 Selling, general and administrative 1,644 1,078 4,310 3,382 Total $ 2,330 $ 1,445 $ 5,937 $ 4,536
Employees and Non Employees Stock Option [Member]
Weighted-average assumptions used in Black-Scholes Model to estimate fair value of stock options granted	The fair value of stock options was estimated using the following weighted-average assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2021 2020 2021 2020 Expected term (in years) 5.77-6.08 6.08 5.27-6.08 5.27-6.08 Contractual term (in years) — — — 10.00 Volatility 70.72%-71.62% 74.00% 70.72%-100.87% 73.00%-77.00% Risk free interest rate 0.89%-1.15% 0.39% 0.62%-1.16% 0.39%-1.37% Dividend yield — — — —
Restricted Stock Units (RSU) [Member]
Schedule of Nonvested Restricted Stock Units and Performance Stock Units Activity and Weighted Average Grant Date Fair Value	The following table summarizes RSU and PSU activity and weighted average grant date fair value for the nine months ended September 30, 2021: Shares Weighted- Average Grant Date Fair Value Unvested shares as of December 31, 2020 37,500 $ 6.95 Granted 611,500 $ 8.76 Vested (33,750 ) $ 6.35 Forfeited (1,875 ) $ 9.99 Unvested shares as of September 30, 2021 613,375 $ 8.78

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Maturity of Operating Leases Liabilities and Future Minimum Lease Payments	The maturity of the Company’s operating lease liabilities as of September 30, 2021 were as follows (in thousands): Undiscounted lease payments September 30, 2021 Remaining in 2021 $ 162 2022 662 2023 113 2024 1 Total undiscounted payments 938 Less: imputed interest 54 Present value of future lease payments 884 Less: current portion of operating lease liabilities 608 Operating lease liabilities $ 276

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Summary of Potentially Dilutive Shares Excluded from Computation of Diluted Net Loss Per Share	The following table sets forth the outstanding potentially dilutive securities which have been excluded in the calculation of diluted net loss per share because including such securities would be anti-dilutive (in common stock equivalent shares): Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 Options to purchase common stock 5,378,092 3,774,680 5,378,092 3,774,680 Restricted stock units (unvested) 627,088 37,500 627,088 37,500 ESPP 36,431 90,870 37,409 92,821 Total 6,041,611 3,903,050 6,042,589 3,905,001

Description of Business - Addit

Description of Business - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)Segment	Dec. 31, 2020USD ($)
Description Of Business [Abstract]
Entity incorporation, date of incorporation	Nov. 6, 2008
Number of operating segments | Segment	1
Cash, cash equivalents and short-term investments	$ 85,300
Cash and cash equivalents	49,255	$ 28,864
Debt securities, available-for-sale	36,000
Long-term debt securities, available-for-sale	35,100
Accumulated deficit	$ (318,649)	$ (306,500)

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Accounting Policies [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 0		$ 0		$ 0
Bad debt expense	$ 0	$ 0	0	$ 0
Inventory Write-down			$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 113,538,000	$ 120,822,000
Financial liabilities	0	0
Other-than-temporary impairment losses	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Financial liabilities	0	0
Transfers in or out of level 3	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Financial assets:
Assets, Fair Value	$ 113,538	$ 120,822
US Treasury Bill Securities [Member]
Financial assets:
Assets, Fair Value		39,995
Corporate Debt Securities [Member]
Financial assets:
Assets, Fair Value	40,787	33,941
US Government Bonds [Member]
Financial assets:
Assets, Fair Value	30,357	4,060
Money Market Funds [Member]
Financial assets:
Assets, Fair Value	42,394	20,846
Commercial Paper [Member]
Financial assets:
Assets, Fair Value		21,980
Level 1 [Member]
Financial assets:
Assets, Fair Value	42,394	20,846
Level 1 [Member] | Money Market Funds [Member]
Financial assets:
Assets, Fair Value	42,394	20,846
Level 2 [Member]
Financial assets:
Assets, Fair Value	71,144	99,976
Level 2 [Member] | US Treasury Bill Securities [Member]
Financial assets:
Assets, Fair Value		39,995
Level 2 [Member] | Corporate Debt Securities [Member]
Financial assets:
Assets, Fair Value	40,787	33,941
Level 2 [Member] | US Government Bonds [Member]
Financial assets:
Assets, Fair Value	30,357	4,060
Level 2 [Member] | Commercial Paper [Member]
Financial assets:
Assets, Fair Value		21,980
Level 3 [Member]
Financial assets:
Assets, Fair Value	$ 0	$ 0

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Value of Cash Equivalents and Debt Securities and Gross Unrealized Holding Gains and Losses (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	$ 42,394	$ 20,846
Cash equivalents, Estimated Fair Value	42,394	20,846
Debt securities, Amortized cost	71,143	99,984
Debt securities, Unrealized gain	13	4
Debt securities, Unrealized loss	(12)	(12)
Debt securities, Estimated Fair Value	71,144	99,976
Assets, Fair Value	113,538	120,822
Short-Term Debt [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Estimated Fair Value	36,051	99,976
Long-Term Debt [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Estimated Fair Value	35,093
US Treasury Bill Securities [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost		39,992
Debt securities, Unrealized gain		3
Debt securities, Estimated Fair Value		39,995
Assets, Fair Value		39,995
Corporate Debt Securities [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	40,799	33,952
Debt securities, Unrealized gain		1
Debt securities, Unrealized loss	(12)	(12)
Debt securities, Estimated Fair Value	40,787	33,941
Assets, Fair Value	40,787	33,941
US Government Bonds [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	30,344	4,060
Debt securities, Unrealized gain	13
Debt securities, Estimated Fair Value	30,357	4,060
Assets, Fair Value	30,357	4,060
Money Market Funds [Member]
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	42,394	20,846
Cash equivalents, Estimated Fair Value	42,394	20,846
Assets, Fair Value	42,394	20,846
Cash Equivalents [Member]
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Estimated Fair Value	$ 42,394	20,846
Commercial Paper [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost		21,980
Debt securities, Estimated Fair Value		21,980
Assets, Fair Value		$ 21,980

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 1,008
Work-in-progress	1,498	$ 34
Finished goods	115	59
Total inventories	$ 2,621	$ 93

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaid contract manufacturing costs	$ 4,075	$ 6,126
Prepaid research costs	2,041	1,177
Prepaid insurance	927	448
Other	1,354	1,122
Total prepaid expenses and other current assets	$ 8,397	$ 8,873

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of Components of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Contract research costs	$ 4,646	$ 6,062
Compensation and related benefits	2,241	3,169
Contract manufacturing costs	2,503	1,167
Product revenue reserves	1,380
Other	809	1,007
Total accrued liabilities	$ 11,579	$ 11,405

Product Development Agreement -

Product Development Agreement - Additional Information (Detail) - USD ($) $ in Thousands	Aug. 11, 2018	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development		$ 18,106	$ 9,810	$ 46,250	$ 29,045
Weighted-average period for recognition (in years)				2 years 9 months 18 days
Product Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product development fees	$ 10,000
Expert consultant fees and pass through costs	800
Incentive-based regulatory milestone fees	$ 1,000
Number of common stock issued subject to quarterly vesting requirements	115,526
Product agreement termination notice period	90 days
Research and development		100		$ 200
Unrecognised compensation expense related to unvested restricted shares		$ 100		$ 100
Weighted-average period for recognition (in years)		6 months

Asset Purchase Agreements and_2

Asset Purchase Agreements and Related License Agreements - Additional Information (Detail) - AbbVie Asset Purchase Agreement [Member] $ in Millions	Nov. 20, 2020USD ($)
Asset Purchase Agreement And Related License Agreement [Line Items]
Payment for asset purchase agreement	$ 95
Progeria Research Foundation (PRF) Collaboration Agreement [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Proceeds from sale	$ 46.5

Sale of Assets - Additional Inf

Sale of Assets - Additional Information (Detail) - Disposal Group Not Discontinued Operations [Member] - MYDICAR [Member] - Theragene Pharmaceuticals, Inc. [Member] - USD ($)	Oct. 01, 2021	Sep. 30, 2020	May 31, 2017	Sep. 30, 2021	Sep. 30, 2021
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Cash payment received for sale of assets under asset purchase agreement			$ 200,000
Sale of assets number of common stock shares received			475,000	475,000	475,000
Maximum cumulative cash proceeds of counter party for issuance of additional shares			$ 4,000,000
Maximum consideration per share of counter party for issuance of additional shares			$ 6
Aggregate common stock consideration value			$ 2,900,000
Shares repurchase by counterparty based on exercise of put options			225,000		225,000
Cost method investment with carrying value				$ 0	$ 0
Upfront, licensee fee, milestone and other payments (excluding royalty payments) received, percentage		25.00%
Proceeds from upfront, licensee fee, milestone and other payments (excluding royalty payments) received				$ 0	$ 300,000
Subsequent Event [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Proceeds from upfront, licensee fee, milestone and other payments (excluding royalty payments) received	$ 100,000
Minimum [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Shares repurchase by counterparty based on exercise of put option value			$ 1,400,000
Maximum [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Asset purchase agreement contingent consideration receivable			$ 45,000,000
Royalty receivable percentage on net sales			8.00%

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($) $ in Thousands	Feb. 23, 2021	Mar. 05, 2019	Sep. 30, 2021	Dec. 31, 2020	Aug. 03, 2018	May 31, 2018	Dec. 31, 2016
Debt Instrument [Line Items]
Face value of term loan			$ 30,000	$ 30,000
Loan final repayment exit fees payable			$ (3,277)	$ (3,277)
Loan agreement, covenant noncompliance penalty			5.00%
Loan agreement, covenant description			The loan includes customary events of default, including failure to pay amounts due, breaches of covenants and warranties, material adverse effect events, certain cross defaults and judgments, and insolvency. If the Company is unable to comply with these covenants or if the Company defaults on any portion of the outstanding borrowings, the lenders can also impose a 5.0% penalty, restrict access to additional borrowings under the loan and security agreement,
Loan agreement, covenant compliance			and accelerate the maturity of the debt.
Oxford Loan [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity							$ 25,000
Loan, maturity period			Jul. 1, 2021
Repayments of loan agreement exit fee			$ 900
Oxford Loan [Member] | Tranche A [Member]
Debt Instrument [Line Items]
Face value of term loan							$ 15,000
Amendment [Member] | Tranche B [Member]
Debt Instrument [Line Items]
Face value of term loan						$ 5,000
Amendment [Member] | Tranche C [Member]
Debt Instrument [Line Items]
Face value of term loan					$ 5,000
Amended Oxford Loan [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity		$ 35,000
Loan, maturity period			Mar. 1, 2024
Loan outstanding		23,300
Borrowings from loan agreement		6,700
Loan agreement, floating rate terms			floating rate per annum equal to the greater of either the 30-day U.S. Dollar LIBOR reported in the Wall Street Journal plus 6.64% or 9.15%
Percentage of exit fee on principal balance			7.50%
Loan final repayment exit fees payable			$ 2,300
Loan final repayment additional exit fees payable			$ 1,000
Prepayment of loan fee, description			calculated as of the loan origination date, equal to (i) 2.0% of the loan prepaid during the first 12 months and (ii) 1.0% of the loan prepaid in months 13-24.
Amended Oxford Loan [Member] | Loan Prepaid During First 12 Months [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage			2.00%
Amended Oxford Loan [Member] | Loan Prepaid During 13 to 24 Months [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage			1.00%
Amended Oxford Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Loan agreement, interest rate			9.15%
Amended Oxford Loan [Member] | Food and Drug Administration [Member]
Debt Instrument [Line Items]
Percentage of success fee			5.00%
Success fees payable maximum period after approval			30 days
Amended Oxford Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Loan agreement, percentage to be added to the interest rate under condition			6.64%
Amended Oxford Loan [Member] | Amended Tranche A [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity		30,000
Amended Oxford Loan [Member] | Amended Tranche A [Member] | Food and Drug Administration [Member]
Debt Instrument [Line Items]
Fee payable maximum period from funding			10 years
Amended Oxford Loan [Member] | Amended Tranche B [Member]
Debt Instrument [Line Items]
Loan agreement, remaining borrowing capacity		$ 5,000
Fifth Amended Oxford Loan [Member]
Debt Instrument [Line Items]
Principal and interest payment period	19 years
Interest payment period	17 months
Amendment fees payment	$ 200
Fifth Amended Oxford Loan [Member] | Tranche B [Member]
Debt Instrument [Line Items]
Principal and interest payment period	13 years
Interest payment period	6 months

Debt - Schedule of Long-Term De

Debt - Schedule of Long-Term Debt and Unamortized Discount Balances (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Face value of long-term debt	$ 30,000	$ 30,000
Exit fee	3,277	3,277
Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees	(1,681)	(2,083)
Total long-term debt, net	31,596	31,194
Less: current portion of long-term debt	(3,072)
Long-term debt, net	$ 28,524	$ 31,194

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted				1,723,785
Total unrecognized compensation expense	$ 16,800			$ 16,800
Stock-based compensation expense	$ 2,330		$ 1,445	$ 5,937	$ 4,536
Weighted-average period for recognition (in years)				2 years 9 months 18 days
Stock options granted	1,248,446			1,248,446		1,021,109
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants	$ 4.65		$ 7.18	$ 6.78	$ 4.78
Restricted Stock Units (RSU) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants				$ 9.16	$ 6.95
Stock options granted	168,000		0	371,500	37,500
Total unrecognized compensation expense	$ 4,700			$ 4,700
Stock-based compensation expense	$ 400		$ 100	$ 700	$ 100
Weighted-average period for recognition (in years)				3 years
Performance Stock Units (PSU) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants	$ 8.15			$ 8.15
Total unrecognized compensation expense	$ 4,700			$ 4,700
Weighted-average period for recognition (in years)				3 years
Stock options granted	240,000			240,000
Inducement Plan 2021 [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock available for grant		850,000
Number of shares available to be issued	625,000			625,000

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021USD ($)$ / sharesshares	Dec. 31, 2020USD ($)$ / sharesshares
Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Exercise Price And Additional Disclosures [Abstract]
Shares Available for Grant, Outstanding, Beginning balance	1,021,109
Shares Available for Grant, Additional options authorized	2,543,924
Shares Available for Grant, Granted	(1,723,785)
Shares Available for Grant, Restricted stock units granted	(371,500)
Shares Available for Grant, Performance stock units granted	(240,000)
Shares Available for Grant, Forfeited	16,823
Shares Available for Grant, Restricted stock units forfeited	1,875
Shares Available for Grant, Outstanding, Ending balance	1,248,446	1,021,109
Number of Options, Outstanding, Beginning balance	3,697,075
Number of Options, Granted	1,723,785
Number of Options, Exercised	(25,945)
Number of Options, Forfeited	(16,823)
Number of Options, Outstanding, Ending balance	5,378,092	3,697,075
Number of Options, Vested and exercisable	2,768,024
Weighted-Average Exercise Price, Outstanding, Beginning balance | $ / shares	$ 10.81
Weighted-Average Exercise Price, Granted | $ / shares	9.13
Weighted-Average Exercise Price, Exercised | $ / shares	8.07
Weighted-Average Exercise Price, Forfeited | $ / shares	9.41
Weighted-Average Exercise Price, Outstanding, Ending balance | $ / shares	10.29	$ 10.81
Weighted-Average Exercise Price, vested and exercisable | $ / shares	$ 11.25
Weighted Average Remaining Contractual Life, Ending balance	7 years 8 months 12 days	7 years 6 months 18 days
Weighted Average Remaining Contractual Life, vested and exercisable	6 years 6 months 14 days
Aggregate Intrinsic Value | $	$ 1,489	$ 9,048
Aggregate Intrinsic Value, Vested and exercisable | $	$ 1,016

Stock-Based Compensation - Weig

Stock-Based Compensation - Weighted-average assumptions used in Black-Scholes Model to estimate fair value of stock options granted (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)			7 years 8 months 12 days		7 years 6 months 18 days
Employees Stock Option [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 9 months 7 days	6 years 29 days	5 years 3 months 7 days	5 years 3 months 7 days
Employees Stock Option [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days	6 years 29 days
Non-Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)				10 years
Employees and Non Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility, minimum	70.72%	74.00%	70.72%	73.00%
Volatility, maximum	71.62%		100.87%	77.00%
Risk free interest rate, minimum	0.89%	0.39%	0.62%	0.39%
Risk free interest rate, maximum	1.15%		1.16%	1.37%

Stock Based Compensation - Sche

Stock Based Compensation - Schedule of Nonvested Restricted Stock Units and Performance Stock Units Activity and Weighted Average Grant Date Fair Value (Detail)	9 Months Ended
	Sep. 30, 2021$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted	1,723,785
Restricted Stock Units and Performance Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested shares, beginning balance	37,500
Stock options granted	611,500
Vested, shares	(33,750)
Forfeited, shares	(1,875)
Unvested shares, ending balance	613,375
Weighted average grant-date fair value of options beginning balance | $ / shares	$ 6.95
Weighted-average grant date fair value of employee option grants | $ / shares	8.76
Weighted average grant-date fair value of options vested | $ / shares	6.35
Weighted average grant-date fair value of options forfeited | $ / shares	9.99
Weighted average grant-date fair value of options ending balance | $ / shares	$ 8.78

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Non-cash Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 2,330	$ 1,445	$ 5,937	$ 4,536
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	686	367	1,627	1,154
Selling General And Administrative Expenses [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 1,644	$ 1,078	$ 4,310	$ 3,382

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 16,000	$ 0	$ 46,000	$ 0
Effective tax rate			0.30%

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2017USD ($)ft²	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)	Dec. 31, 2020
Other Commitments [Line Items]
Rent expense recognized for company's operating leases		$ 100,000	$ 200,000	$ 400,000	$ 500,000
Variable lease payments for operating leases		$ 23,000	$ 23,000	100,000	100,000
Operating cash outflows for operating lease liabilities				$ 500,000	$ 500,000
Weighted-average remaining lease term		1 year 4 months 24 days		1 year 4 months 24 days		2 years 1 month 6 days
Weighted-average discount rate		9.15%		9.15%		9.15%
Palo Alto, California [Member]
Other Commitments [Line Items]
Total leased space | ft²	8,029
Lease commencement date	Mar. 1, 2018
Long-term operating lease expiry period month and year	2023-02
Lease renewal term	3 years
Security deposit of collateral for lease	$ 300,000

Commitments and Contingencies_2

Commitments and Contingencies - Maturity of Operating Leases Liabilities and Future Minimum Lease Payments (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Operating leases minimum payments, remaining in 2021	$ 162
Operating leases minimum payments, 2022	662
Operating leases minimum payments, 2023	113
Operating leases minimum payments, 2024	1
Total undiscounted payments	938
Less: imputed interest	54
Present value of future lease payments	884
Less: current portion of operating lease liabilities	608	$ 582
Operating lease liabilities	$ 276	$ 738

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Potentially Dilutive Shares Excluded from Computation of Diluted Net (Loss) Income Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities	6,041,611	3,903,050	6,042,589	3,905,001
Options Granted to Employees and Non Employees [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities	5,378,092	3,774,680	5,378,092	3,774,680
Restricted Stock Units (Unvested) [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities	627,088	37,500	627,088	37,500
ESPP [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities	36,431	90,870	37,409	92,821

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Amended Oxford Loan [Member]	Oct. 06, 2021	Sep. 30, 2021
Subsequent Event [Line Items]
Loan agreement, floating rate terms		floating rate per annum equal to the greater of either the 30-day U.S. Dollar LIBOR reported in the Wall Street Journal plus 6.64% or 9.15%
Subsequent Event [Member]
Subsequent Event [Line Items]
Loan agreement, floating rate terms	floating rate per annum equal to the greater of either the 30-day U.S. Dollar LIBOR reported in the Wall Street Journal plus 6.64% or 9.15%.