Eiger BioPharmaceuticals (EIGRQ) 10-K 10 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2021	Mar. 07, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Trading Symbol	EIGR
Entity Registrant Name	Eiger BioPharmaceuticals, Inc.
Entity Central Index Key	0001305253
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-36183
Entity Incorporation, State or Country Code	DE
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
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	false
Entity Common Stock, Shares Outstanding		34,639,884
Entity Public Float			$ 285,874,670
Auditor Name	KPMG LLP
Auditor Location	San Francisco, CA
Auditor Firm ID	185
Documents Incorporated by Reference	Part III incorporates certain information by reference from the registrant’s proxy statement for the 2022 Annual Meeting of Shareholders. Such proxy statement will be filed no later than 120 days after the close of the registrant’s fiscal year ended December 31, 2021.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 22,221	$ 28,864
Short-term debt securities	66,594	99,976
Accounts receivable, net	2,576
Inventories	2,612	93
Prepaid expenses and other current assets	9,361	8,873
Total current assets	103,364	137,806
Long-term debt securities	17,262
Property and equipment, net	613	709
Operating lease right-of-use assets	653	1,176
Other assets	4,510	3,903
Total assets	126,402	143,594
Current liabilities:
Accounts payable	7,765	4,640
Accrued liabilities	13,699	11,405
Current portion of operating lease liabilities	628	582
Current portion of long-term debt, net	7,809
Total current liabilities	29,901	16,627
Long-term debt, net	23,986	31,194
Operating lease liabilities	116	738
Total liabilities	54,003	48,559
Commitments and contingencies (Note 13)
Stockholders’ equity:
Common stock, $0.001 par value, 200,000,000 shares authorized as of December 31, 2021 and 2020; 34,568,821 and 33,878,486 shares issued and outstanding as of December 31, 2021 and 2020, respectively	35	34
Additional paid-in capital	412,930	401,509
Accumulated other comprehensive loss	(149)	(8)
Accumulated deficit	(340,417)	(306,500)
Total stockholders’ equity	72,399	95,035
Total liabilities and stockholders’ equity	$ 126,402	$ 143,594

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	34,568,821	33,878,486
Common stock, shares outstanding	34,568,821	33,878,486

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Product revenue, net	$ 12,142,000
Costs and operating expenses:
Cost of sales	745,000
Research and development	64,436,000	$ 41,590,000	$ 51,791,000
Selling, general and administrative	23,900,000	20,559,000	17,113,000
Total costs and operating expenses	89,081,000	62,149,000	68,904,000
Loss from operations	(76,939,000)	(62,149,000)	(68,904,000)
Interest expense	(3,559,000)	(3,594,000)	(3,406,000)
Interest income	158,000	704,000	2,073,000
Other income (expense), net	46,487,000	(12,000)	(15,000)
Loss before provision for income taxes	(33,853,000)	(65,051,000)	(70,252,000)
Provision for income taxes	64,000	0	0
Net loss	$ (33,917,000)	$ (65,051,000)	$ (70,252,000)
Net loss per common share, basic and diluted	$ (1)	$ (2.31)	$ (3.08)
Weighted-average common shares outstanding, basic and diluted	33,944,342	28,143,391	22,785,611

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (33,917)	$ (65,051)	$ (70,252)
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale debt securities, net	(141)	(50)	67
Comprehensive loss	$ (34,058)	$ (65,101)	$ (70,185)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2018	$ 66,592	$ 19	$ 237,795	$ (25)	$ (171,197)
Beginning Balance, Shares at Dec. 31, 2018		19,211,759
Issuance of common stock upon public offering, net of issuance costs	53,194	$ 5	53,189
Issuance of common stock upon public offering, net of issuance costs, shares		5,175,000
Issuance of common stock upon ESPP purchase	130		130
Issuance of common stock upon ESPP purchase, Shares		15,701
Issuance of common stock upon stock option exercise	844		844
Issuance of common stock upon stock option exercises, Shares		120,921
Issuance of common stock under Product Development Agreement	226		226
Stock-based compensation expense	5,679		5,679
Unrealized (loss) gain on available-for-sale debt securities, net	67			67
Net loss	(70,252)				(70,252)
Ending Balance at Dec. 31, 2019	56,480	$ 24	297,863	42	(241,449)
Ending Balance, Shares at Dec. 31, 2019		24,523,381
Issuance of common stock upon public offering, net of issuance costs	96,760	$ 10	96,750
Issuance of common stock upon public offering, net of issuance costs, shares		9,267,760
Issuance of common stock upon ESPP purchase	186		186
Issuance of common stock upon ESPP purchase, Shares		25,645
Issuance of common stock upon stock option exercise	520		520
Issuance of common stock upon stock option exercises, Shares		61,700
Issuance of common stock under Product Development Agreement	217		217
Stock-based compensation expense	5,973		5,973
Unrealized (loss) gain on available-for-sale debt securities, net	(50)			(50)
Net loss	(65,051)				(65,051)
Ending Balance at Dec. 31, 2020	$ 95,035	$ 34	401,509	(8)	(306,500)
Ending Balance, Shares at Dec. 31, 2020	33,878,486	33,878,486
Issuance of common stock upon public offering, net of issuance costs	$ 2,685	$ 1	2,684
Issuance of common stock upon public offering, net of issuance costs, shares		565,938
Issuance of common stock upon ESPP purchase	257		257
Issuance of common stock upon ESPP purchase, Shares		37,619
Issuance of common stock upon stock option exercise	$ 361		361
Issuance of common stock upon stock option exercises, Shares	53,028	53,028
Issuance of common stock upon release of restricted stock units, Shares		33,750
Issuance of common stock under Product Development Agreement	$ 218		218
Stock-based compensation expense	7,901		7,901
Unrealized (loss) gain on available-for-sale debt securities, net	(141)			(141)
Net loss	(33,917)				(33,917)
Ending Balance at Dec. 31, 2021	$ 72,399	$ 35	$ 412,930	$ (149)	$ (340,417)
Ending Balance, Shares at Dec. 31, 2021	34,568,821	34,568,821

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Stockholders Equity [Abstract]
Issuance of common stock upon public offering, issuance costs	$ 417	$ 3,231	$ 3,731

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities
Net loss	$ (33,917)	$ (65,051)	$ (70,252)
Adjustments to reconcile net loss to net cash used in operating activities:
Gain from sale of priority review vouches	(46,493)
Income related to asset purchase agreement	(281)
Depreciation and amortization	276	167	68
Amortization of debt securities premiums and discounts	996	124	(467)
Stock-based compensation	7,901	5,973	5,679
Non-cash interest expense	776	804	723
Amortization of operating lease right-of-use assets	523	478	418
Common stock issued under Product Development Agreement	218	217	226
Changes in operating assets and liabilities:
Accounts receivable	(2,576)
Inventories	(2,424)
Prepaid expenses and other current assets	(701)	(3,563)	(3,698)
Other assets	(607)	(1,392)	(2,075)
Accounts payable	3,234	(1,899)	584
Accrued liabilities	2,309	1,491	5,610
Operating lease liabilities	(576)	(534)	(430)
Net cash used in operating activities	(71,342)	(63,185)	(63,614)
Investing Activities
Purchase of debt securities available-for-sale	(84,647)	(128,295)	(96,267)
Proceeds from maturities of debt securities available-for-sale	99,630	83,766	80,271
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	(225)	(258)	(475)
Net cash provided by (used) in investing activities	61,532	(44,787)	(16,471)
Financing Activities
Issuance of common stock upon offering at-the-market, net of commissions	3,040	96,779
Proceeds from issuance of common stock upon stock option exercises	361	520	844
Proceeds from issuance of common stock upon ESPP purchase	257	186	130
Payment of debt issuance costs	(175)
Common stock offering costs	(316)	(22)	(19)
Proceeds from borrowings in connection with term loan, net of issuance costs			6,627
Repayment of accrued exit fee and second amendment fee			(913)
Repayment of term loan			(1,667)
Net cash provided by financing activities	3,167	97,463	58,196
Net decrease in cash and cash equivalents	(6,643)	(10,509)	(21,889)
Cash and cash equivalents at beginning of year	28,864	39,373	61,262
Cash and cash equivalents at end of year	22,221	28,864	39,373
Supplemental disclosure of cash flow information:
Interest paid	$ 2,783	$ 2,791	2,638
Public Offering [Member]
Financing Activities
Issuance of common stock upon offering at-the-market, net of commissions			$ 53,194

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 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 of innovative therapies to treat and cure Hepatitis Delta Virus (HDV), the most severe form of viral hepatitis, and other serious diseases. All five of our rare disease programs have FDA Breakthrough Therapy Designation. The Eiger HDV platform includes two first-in-class therapies in Phase 3 that target critical host processes involved in viral replication. Lonafarnib is a first-in-class oral farnesylation inhibitor and peginterferon lambda (lambda) is a first-in-class, type III, well-tolerated interferon. Both lonafarnib and lambda are in global Phase 3 trials. The FDA approved the Company’s first commercial product, Zokinvy (lonafarnib) for treatment of Progeria and processing-deficient progeroid laminopathies, ultra-rare and rapidly fatal genetic conditions of accelerated aging in children, on November 20, 2020. Eiger’s Marketing Authorization Application (MAA) is under review with the European Medicines Agency (EMA), with a decision expected in the second half of 2022 . 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 December 31, 2021, the Company had $88.8 million of cash, cash equivalents and short-term securities, comprised of $22.2 million of cash and cash equivalents and $66.6 million of short-term debt securities available-for-sale. As of December 31, 2021, the Company had $17.3 million of long-term debt securities available-for-sale. The Company had an accumulated deficit of $340.4 million and negative cash flows from operating activities as of December 31, 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 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 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	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The 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. Use of Estimates The preparation of 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 revenue and 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. Reclassifications Certain items on the consolidated balance sheet have been reclassified to conform to current year presentation. Such items were not material. Concentrations of Risk Financial instruments that potentially subject the Company to a concentration of credit risk consists of cash, cash equivalents and investments. The Company’s cash is held by a financial institution in the United States. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institution is financially sound, and accordingly, minimal credit risk exists with respect to the financial institution. The Company relies on one supply chain for each of its product candidates. If any of the single source suppliers in any of the supply chains fail to satisfy the Company’s requirements on a timely basis, it could suffer delays in its clinical development programs and activities, which could adversely affect its operating results. Two customers accounted for approximately 66 percent and 34 percent of the Company’s accounts receivable as of December 31, 2021. One customer accounted for approximately 94 percent of product revenue during the year ended December 31, 2021. The Company did not have accounts receivable or revenue in 2020. Cash and Cash Equivalents Cash and cash equivalents include all cash balances and highly liquid investments with original maturities of three months or less from the date of purchase. Cash equivalents consists primarily of amounts invested in money market funds held at financial institutions and corporate debt securities. The recorded carrying amount of cash equivalents approximates their fair value. 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 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 income (loss). The cost of available-for-sale securities sold is based on the specific-identification method . Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Depreciation expense is computed using the straight-line method over the estimated useful lives of the assets. Depreciation begins at the time the asset is placed into service. Maintenance and repairs are charged to operations as incurred. Property and equipment purchased for specific research and development projects with no alternative uses are expensed as incurred. The useful lives of the property and equipment are as follows: Lab equipment 5 years Furniture 5 years Leasehold improvements Shorter of remaining lease term or 5 years Computer equipment and software 3 years Impairment of Long-Lived Assets The Company evaluates its long-lived assets, including property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying value of these assets may not be recoverable. The Company assesses the recoverability of long-lived assets by determining whether or not the carrying value of such assets will be recovered through undiscounted expected future cash flows. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. Through December 31, 2021, the Company has not impaired any long-lived assets. 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 December 31, 2021 and 2020. The Company had no bad debt expense for the year ended December 31, 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. In the United States, the Company sells Zokinvy to a single specialty pharmacy provider that subsequently dispenses the product directly to patients. 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. In June 2021, the French National Agency for Medicines and Health Products Safety (ANSM) granted Zokinvy (lonafarnib) a Temporary Authorizations for Use (Autorisation Temporaire d'Utilisation or ATU) for a term of one year. Pursuant to this program, the Company sells product to a distributor who in turn ships product to pharmacies after receiving requests from physicians for patients in France. In November 2021, the Company began distributing and recognizing revenue from sales of Zokinvy (lonafarnib) through a reimbursed early access program in France. The revenue from sale of product under the ATU program is less than ten p ercent of total revenue for the year ended December 31, 2021 . The Company recognizes product revenue when a customer obtains control of its product, which occurs at a point in time, typically upon delivery to a 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 product is 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 a customer. Prompt payment discounts: The Company provides a discount to a customer if it pays for purchases within 30 days. The Company expects that its customers 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 records 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 a 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. Product costs incurred prior to FDA approval in November 2020 were previously recorded as research and development expense in the 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 Under Accounting Standards Codification (“ASC”) 842, 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 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 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. Deferred Financing Costs Financing costs incurred with securing a term debt are recorded in the Company’s consolidated balance sheets as an offset to the term debt and amortized to interest expense in the Company’s consolidated statements of operations over the contractual life of the loan using the effective interest method. Research and Development Costs Research and development costs are expensed as incurred and consist of payroll expenses, stock-based compensation expense, lab supplies and allocated facility costs, as well as fees paid to third parties that conduct certain research and development and manufacturing activities on the Company’s behalf. Amounts incurred in connection with license and asset purchase agreements are also included in research and development expenses. Manufacturing costs related to products undergoing regulatory approval are expensed as research and development costs until receipt of such approval. Stock-Based Compensation Stock-based awards to employees and directors, including stock options, are recorded at fair value as of the grant date using the Black-Scholes option pricing model and recognized as expense on a straight line-basis over the employee’s or director’s requisite service period (generally the vesting period). Stock-based awards to non-employees are recorded at their fair value as of the grant date, using the Black-Scholes option pricing model and recognized as expense over the period in which the related services are received. The determination of fair value for stock-based awards on the date of grant using an option pricing model requires management to make certain assumptions for Black-Scholes option pricing model inputs. The Company accounts for forfeitures of stock-based awards when they occur. Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company must then assess the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s lack of earnings history, the net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on their technical merits, as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to unrecognized tax benefits. Internal Revenue Code Section 382 limits the use of net operating loss and tax credit carryforwards in certain situations where changes occur in the stock ownership of a company. In the event that the Company experiences a change of ownership, utilization of the net operating loss and tax credit carryforwards may be restricted. Comprehensive Loss Comprehensive loss represents all changes in stockholders' equity except those resulting from and distributions to stockholders. The Company’s unrealized gains and losses on debt securities represent the only component of other comprehensive loss that are excluded from the reported net loss and that are presented in the consolidated statements of comprehensive loss. 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 all periods presented, diluted net loss per share is the same as basic net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. 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): December 31, 2021 2020 2019 Options to purchase common stock 5,262,185 3,697,075 2,767,617 Restricted stock units (unvested) 623,000 37,500 — ESPP 48,159 81,169 36,493 Total 5,933,344 3,815,744 2,804,110 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 Note 8). 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	12 Months Ended
	Dec. 31, 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). At December 31, 2021 and 2020, the carrying amount of accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities approximated their estimated fair value due to their relatively short maturities. Management believes the terms of its long-term debt reflect current market conditions for an instrument with similar terms and maturity, therefore the carrying value of the Company’s debt approximated its fair value. Assets and liabilities recorded at fair value on a recurring basis in the 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 assets or liabilities classified as Level 3 as of December 31, 2021 and 2020. 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): December 31, 2021 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 13,520 $ — $ — $ 13,520 Corporate debt securities — 41,511 — 41,511 U.S. government bonds — 42,345 — 42,345 Total $ 13,520 $ 83,856 $ — $ 97,376 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 December 31, 2021 and 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): December 31, 2021 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 13,520 $ — $ — $ 13,520 Total cash equivalents $ 13,520 $ — $ — $ 13,520 Debt securities: Corporate debt securities $ 41,576 $ — $ (65 ) $ 41,511 U.S. government bonds 42,429 — (84 ) 42,345 Total debt securities $ 84,005 $ — $ (149 ) $ 83,856 Classified as: Cash equivalents $ 13,520 Short-term debt securities 66,594 Long-term debt securities 17,262 $ 97,376 December 31, 2020 Amortized cost Unrealized gain Unrealized loss Estimated 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. As of December 31, 2021 and 2020, 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	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4. Balance Sheet Components Inventories Inventories consist of the following (in thousands): December 31, 2021 2020 Raw materials $ 1,056 $ — Work-in-progress 1,468 34 Finished goods 88 59 Total inventories $ 2,612 $ 93 Property and Equipment, Net Property and equipment, net consist of the following (in thousands): December 31, 2021 2020 Computer equipment and software $ 669 $ 520 Furniture 116 111 Leasehold improvements 101 80 Lab equipment 271 271 Construction in progress 59 69 Total property and equipment 1,216 1,051 Less: accumulated depreciation (603 ) (342 ) Property and equipment, net $ 613 $ 709 Depreciation expense for the years ended December 31, 2021, 2020 and 2019 was approximately $0.3 million, $0.2 million and $0.1 million, respectively. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2021 2020 Prepaid contract manufacturing costs $ 3,695 $ 6,126 Prepaid research costs 3,253 1,177 Prepaid insurance 631 448 Other 1,782 1,122 Total prepaid expenses and other current assets $ 9,361 $ 8,873 Accrued Liabilities Accrued liabilities consist of the following (in thousands): December 31, 2021 2020 Contract research costs $ 4,760 $ 6,062 Contract manufacturing costs 3,288 1,167 Compensation and related benefits 3,131 3,169 Product revenue reserves 1,846 — Other 674 1,007 Total accrued liabilities $ 13,699 $ 11,405

License, Collaboration, and Pro

License, Collaboration, and Product Development Agreements	12 Months Ended
	Dec. 31, 2021
Collaboration And License Agreements [Abstract]
License, Collaboration, and Product Development Agreements	5. License, Collaboration, and Product Development Agreements License Agreement with the Trustees of the University of Pennsylvania and the Children’s Hospital of Philadelphia In May 2019, the Company entered into a license agreement (the UPenn/CHOP Agreement) with the Trustees of the University of Pennsylvania (UPenn) and the Children’s Hospital of Philadelphia (CHOP), under which the Company obtained an exclusive, royalty-bearing, worldwide license to develop, manufacture and sell certain Glucagon Like Peptide-1 (GLP-1) receptor antagonist(s) products to treat all human and animal conditions. The Company also obtained an exclusive, royalty-bearing, sublicensable, worldwide license to certain data developed by CHOP. The Company is responsible for the development and commercialization of the licensed products at its sole cost and expense. As part of the consideration for the rights granted to the Company under the UPenn/CHOP Agreement, the Company paid UPenn a one-time, non-refundable issue fee of $1.0 million, which is recorded in research and development expenses for the year ended December 31, 2019. In addition, the Company is obligated to pay UPenn a specified annual license maintenance fee, up to $2.5 million in certain regulatory milestones, and up to $18.0 million in commercial milestones. The Company will also be required to pay UPenn a flat royalty in the low-single digits on net sales of all licensed products by the Company, subject to specified reductions and offsets, and specified minimum annual royalty payments. The Company’s obligation to pay royalties expires on a product-by-product and country-by-country basis, on the later of: (i) the expiration of the last valid claim in the licensed patents in any country, or (ii) the tenth anniversary of the first commercial sale of the product in such country. No milestones have been achieved as of December 31, 2021. The Company may terminate the UPenn/CHOP Agreement in its entirety for any reason by providing prior written notice to UPenn and CHOP. UPenn or CHOP may terminate the UPenn/CHOP Agreement, upon a written notice, for the Company’s failure to achieve the specified diligence milestones within the specified periods, subject to the Company’s extension rights. 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. Product Agreements Progeria Research Foundation (PRF) Collaboration Agreement On May 15, 2018, the Company entered into a Collaboration and Supply Agreement (the PRF Collaboration Agreement) with PRF. Under the PRF Collaboration Agreement, the parties agreed to collaborate with respect to the development and pursuit of regulatory approval of lonafarnib for the treatment of progeria and progeroid laminopathies in humans. PRF granted the Company a non-exclusive, world-wide, royalty-free, sub-licensable license pertaining to all intellectual property and data controlled by PRF to prepare and file any NDA for a product containing lonafarnib for progeria and progeroid laminopathies. The Company is obligated to: (i) exclusively supply lonafarnib to PRF for use in clinical trials and non-clinical research in progeria and progeroid laminopathies at the Company’s expense, (ii) prepare and be the sponsor of any NDA submission for lonafarnib for the treatment of progeria and progeroid laminopathies to the FDA, (iii) use commercially reasonable efforts to file a NDA for progeria and progeroid laminopathies by a specified date, (iv) submit a rare pediatric disease designation and a request for expedited approval in connection with a NDA filing, (v) establish a patient support program in progeria and progeroid laminopathies, and (vi) use commercially reasonable efforts to develop a pediatric formulation of lonafarnib for use in progeria and progeroid laminopathies. Under the PRF Collaboration Agreement, the Company is solely responsible for any additional studies necessary for obtaining an NDA for progeria and progeroid laminopathies and is also responsible for any additional costs for such studies up to $2.0 million. The PRF Collaboration Agreement continues for an initial term of ten years and automatically renews for subsequent renewal terms of two years each unless either party terminates earlier. Bristol-Meyers Squibb License Agreement On April 20, 2016, the Company and Bristol-Myers Squibb Company (BMS) entered into a License Agreement (the BMS License Agreement) and a Common Stock Purchase Agreement (the BMS Purchase Agreement). Under the BMS License Agreement, BMS granted the Company an exclusive, worldwide, license to research, develop, manufacture, and sell products containing PEG-interferon Lambda-1a (the Licensed Product) for all therapeutic and diagnostic uses in humans and animals. The Company is responsible for the development and commercialization of the Licensed Product at its sole cost and expense. The Company paid BMS $2.0 million and issued 157,587 shares of its common stock at an aggregate fair value of $3.2 million in April 2016. The BMS License Agreement also includes development and regulatory milestone payments totaling $61.0 million and commercial sales milestones of up to $128.0 million. The Company is obligated to pay BMS annual net sales royalties in the range of mid-single to mid-teens, depending on net sales levels. In fourth quarter 2020, the Company recorded in research and development expense a $3.0 million milestone, triggered on successful demonstration of proof of concept, as defined by the BMS License Agreement, in a Phase 2 clinical trial. The next milestone of $5.0 million is related to the initiation of a Phase 3 clinical trial, as defined by the BMS License Agreement, and is expected to be achieved in the first quarter of 2022. Merck License Agreement In September 2010, the Company entered into an exclusive license agreement with Schering Corporation, subsequently acquired by Merck & Co., Inc. (Merck), which provides the Company with the exclusive right to develop, manufacture, and sell products containing the compounds lonafarnib for the treatment of all human viruses except certain specified viruses such as hepatitis B and hepatitis C alone. As part of consideration, the Company issued 27,350 shares of common stock with a fair value of $0.5 million. The Company is obligated to pay Merck up to an aggregate of $27.0 million in development milestones and will be required to pay tiered royalties based on aggregate annual net sales of all licensed products ranging from mid-single to low double-digit royalties on net sales. In May 2015, the first regulatory milestone was achieved and the Company paid the related milestone payment of $1.0 million to Merck. No additional milestones have been achieved as of December 31, 2021. The next milestone of $1.0 million is triggered on positive Phase 3 data, which is expected by end of 2022. On May 15, 2018, the Company entered into an amendment to the exclusive license agreement with Merck, which provides for expansion of the existing exclusively licensed field of use under the license agreement with Merck to include all uses of lonafarnib related to the treatment of Hutchinson-Gilford Progeria Syndrome (HGPS or Progeria) in humans at no cost to the Company. On November 3, 2020, the Company entered into an amendment to the exclusive license agreement with Merck which expanded the definition of progeria to also include progeroid laminopathies. The Company has the sole responsibility and the continuing obligation for the manufacture and supply of lonafarnib to the PRF. Merck will not receive milestone payments in relation to lonafarnib for the treatment of progeria and progeroid laminopathies or any royalty payments for sales of a specified quantity of lonafarnib to treat the currently estimated progeria and progeroid laminopathies patient population worldwide.

Asset Purchase Agreements and R

Asset Purchase Agreements and Related License Agreements	12 Months Ended
	Dec. 31, 2020
Asset Purchase Agreements And Related License Agreements [Abstract]
Asset Purchase Agreements and Related License Agreements	6. Asset Purchase Agreements and Related License Agreements EGI Asset Purchase Agreement In December 2010, the Company entered into an asset purchase agreement with Eiger Group International, Inc. (EGI). Dr. Jeffrey Glenn, a founder and director of the Company, is the sole owner of EGI. Pursuant to the agreement, the Company purchased all of the assets including the intellectual property rights related to the use of farnesyl transferase inhibitors as anti-viral agents and methods to treat viral infections with those inhibitors and inhibitors of prenylation, prenyl cysteine methyltranferase and a protease as anti-viral agents and methods to treat viral infection with those inhibitors. The Company paid EGI an upfront payment of $ 0.4 million when the agreement was executed in December 2010. Additionally, t he Company will pay EGI a low single-digit royalty based on aggregate annual net sales of products developed using the intellectual property. Within the first ten years after commercialization, the Company may make a one-time payment of $ 0.5 million for each contract for the three types of product related to such intellectual property that would reduce the payment term for the three products to the tenth anniversary of the first commercial sale. The obligation to pay royalties expires on a country-by-country and product-by-product basis on the later of either when the product is no longer sold in any country or the earliest of the tenth anniversary of the first commercial sale of the product. As of December 31, 2021 , the product has not achieved regulatory approval. Avexitide Purchase Agreement and Related Stanford License Agreement In September 2015, the Company entered into an asset purchase agreement with two individuals, Dr. Tracey McLaughlin and Dr. Colleen Craig, (the Sellers), whereby the Company purchased all of the assets related to the compound avexitide (formerly known as exendin 9-39) including any related intellectual property from the Sellers (the Exendin APA). The Company also entered into a consulting agreement with the Sellers as part of the agreement. The Company issued 15,378 shares of common stock that were valued at $0.2 million and with the option to purchase 46,134 shares of common stock with an exercise price of $2.06 per share when the agreement was executed in September 2015. Of the 46,134 options to purchase common stock, 15,378 shares vest monthly over four years as services are provided by the Sellers and 30,756 vest upon the earlier of the first commercial sale of the product or the approval of new drug application by the U.S. Food and Drug Administration (the milestone-vested options). On March 22, 2016, immediately following the closing of the merger, the Company issued additional top-up options to the Sellers to purchase an aggregate of 48,544 shares of common stock, pursuant to the terms of the Exendin APA, with an exercise price of $17.25 per share. The top-up options consist of both time-vested and milestone-vested options. The fair value of the time-vested options is recognized as stock-based compensation expense as the awards vest over time. The fair value of the milestone-vested options will be recognized as research and development expense when it is probable that the earliest milestone will be achieved at their fair value as of the ASU 2018-07 adoption date. During the years ended December 31, 2021, 2020 and 2019, the Company recognized $0.1 million, $0.1 million and $0.1 million of compensation expense related to the time-vested options, respectively. No expense was recognized for the milestone vested options during the years ended December 31, 2021, 2020 and 2019. The Company is also obligated to pay development milestone payments in an aggregate amount of up to $1.0 million to each Seller. Additionally, the Company is obligated to pay each Seller royalties of low single-digits based on aggregate annual net sales of all products developed based on avexitide, subject to certain reductions and exceptions. The Company’s obligation to pay royalties expires on the expiration of the last to expire patent assigned to the Company under the agreement. Additionally, the Company has assumed the license agreement the Sellers had previously entered into with the Board of Trustees of the Leland Stanford Junior University (Stanford). The Company is obligated to pay a royalty to Stanford in the low single-digits on annual net sales after the first commercial sale of any products developed based on avexitide. As of December 31, 2021, the Company has paid a total of $0.1 million in milestone payments to each of the Sellers related to the successful completion of the Phase 2 trials. 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 consolidated statement of operations for the year ended December 31, 2021.

Sale of Assets

Sale of Assets	12 Months Ended
	Dec. 31, 2021
Discontinued Operations And Disposal Groups [Abstract]
Sale of Assets	7. Sale of Assets In May 2017, the Company and Theragene Pharmaceuticals, Inc. (Theragene) entered into an asset purchase agreement (Theragene APA), whereby the Company sold all of the assets related to MYDICAR including any related intellectual property for a cash payment of $0.2 million and 475,000 shares of common stock of Theragene. At any time after the Theragene APA execution date and until Theragene has received cumulative gross proceeds of $4.0 million (Proceeds Date) from all equity financing transactions occurring after the Theragene APA execution date, if Theragene issues additional shares of its common stock without consideration or for a consideration per share less than $6.00 per share then Theragene will issue additional shares of its common stock to the Company concurrently with such issue, in an amount such that the per share consideration multiplied by the aggregate number of common stock shares issued to the Company will equal $2.9 million. Additionally, the Company may exercise a put option at any time after the Proceeds Date, where upon written notice from the Company, Theragene will repurchase the 225,000 shares of its common stock held by the Company (Option Shares) at an aggregate purchase price equal to the greater of $1.4 million or the aggregate fair market value of the Option Shares as of the date of the receipt of such notice. The Company is also eligible to receive contingent consideration up to a maximum $45.0 million in cash, based upon Theragene achieving certain specified future milestones. In addition, the Company is also eligible to receive up to 8% royalties on net sales of any future Theragene products covered by or involving the related patents or know-how until the twentieth anniversary of the Theragene APA. 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 year ended December 31, 2021, the Company recognized $0.3 million in other income (expense), net. The Company expects to receive an additional $0.1 million subsequent to December 31, 2021.

Debt

Debt	12 Months Ended
	Dec. 31, 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. The Company borrowed $15.0 million in December 2016 (Tranche A). In May 2018, the Company entered into an amendment to the Oxford Loan and borrowed 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 d id 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. On October 6, 2021, the Company entered into the sixth amendment to the Oxford Loan. Prior to the sixth amendment, the Amended Oxford Loan bore 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. At the time of final payment, the Company is required to pay an exit fee of 7.5% of the original principal balance of borrowed funds, or $2.3 million. In addition, 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. As of December 31, 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): 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 (1,482 ) (2,083 ) Total long term debt, net 31,795 31,194 Less: current portion of long-term debt (7,809 ) — Long-term debt, net $ 23,986 $ 31,194 As of December 31, 2021, future minimum payments of principal, exit fee and interest expense under the Oxford Loan were as follows (in thousands): Year ending December 31, 2022 10,555 2023 20,189 2024 6,471 Total future payments 37,215 Less: unamortized interest (3,938 ) Less: exit fee (1,482 ) Face value of term loan $ 31,795

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Stockholders' Equity	9. Stockholders’ Equity Common Stock The holders of the Company’s common stock have one vote for each share of common stock. Common stockholders are entitled to dividends when, as, and if declared by the Board of Directors, subject to the prior rights of the convertible preferred stockholders. As of December 31, 2021, no dividends had been declared by the Board of Directors. In April 2019, the Company completed an underwritten public offering of 5,175,000 shares of its common stock, including 675,000 shares sold upon full exercise of the underwriters’ option to purchase additional shares of common stock, at a price of $11.00 per share. The offering was made under the Company’s effective shelf registration statement and resulted in net proceeds to the Company of $53.2 million, after deducting underwriting discounts and commissions and offering expenses. In December 2019, the Company filed a shelf registration statement on Form S-3 (File No. 333-235655) with the Securities and Exchange Commission, which permits the offering, issuance and sale of up to a maximum aggregate offering price of $150.0 million of the Company’s common stock, preferred stock, debt securities and warrants. Up to a maximum of $50.0 million of the maximum aggregate offering price of $150.0 million may be issued and sold pursuant to an at-the-market (ATM) financing facility (2019 ATM Facility) under a sales agreement with Jefferies LLC (Jefferies). In August 2020, the Company entered into a new sales agreement with Jefferies for up to $50.0 million of the remaining amount on the shelf registration statement which may be sold pursuant to an ATM financing facility (2020 ATM Facility). As of December 31, 2020, the Company had sold all shares available under both the 2019 ATM Facility and the 2020 ATM Facility for a total of 9,267,760 shares resulting in $97.3 million in net proceeds, after deducting commissions. In December 2020, the Company filed a new shelf registration statement on Form S-3 (File No. 333-251497) with the Securities and Exchange Commission, which permits the offering, issuance and sale by the Company up to a maximum aggregate offering price of $ 200.0 million of its common stock, preferred stock, debt securities and warrants. Up to a maximum of $ 50.0 million of the maximum aggregate offering price of $ 200.0 mil lion may be issued and sold pursuant to a n ATM financing facility ( the ATM Facility) under a sales agreement with Jefferies. In December 2021, the Company completed ATM offerings for a total of 565,938 shares of common stock under the ATM Facility . The offerings were made under Eiger’s effective shelf registration statement and resulted in net proceeds to the Company of $ 3.0 million, after deducting commissions. The Company had reserved shares of common stock for issuance as follows: December 31, 2021 2020 Options issued and outstanding 5,262,185 3,697,075 Options available for future grants 1,327,645 1,021,109 Restricted and performance stock units outstanding 623,000 37,500 Shares available for issuance under ESPP 671,172 543,791 Total 7,884,002 5,299,475

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plans	10 . Equity Incentive Plans Restated 2013 Equity Incentive Plan In June 2016, the Company’s Board of Directors adopted and in August 2016 the Company’s stockholders approved the Amended and Restated 2013 Equity Incentive Plan (the Restated 2013 Plan). Under the terms of the Restated 2013 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then employees, officers, non-employee directors or consultants of the Company. Under the terms of the Plan, options may be granted at an exercise price not less than fair market value. For employees holding more than 10% of the voting rights of all classes of stock, the exercise prices for incentive and non-statutory stock options may not be less than 110% of fair market value, as determined by the Board of Directors. The terms of options granted under the Rested 2013 Plan may not exceed ten years. The vesting schedule of newly issued option grants is generally four years. 2021 Inducement Plan 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 December 31, 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 plans during the year ended December 31, 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 (1,866,785 ) 1,866,785 $ 8.92 Restricted stock units granted (371,500 ) — Performance stock units granted (270,000 ) — Exercised — (53,028 ) $ 6.81 Forfeited or cancelled 248,647 (248,647 ) $ 9.52 Restricted stock units forfeited 22,250 — $ — Outstanding as of December 31, 2021 1,327,645 5,262,185 $ 10.24 7.25 $ 530 Vested and exercisable as of December 31, 2021 2,983,332 $ 11.20 6.11 $ 482 The aggregate intrinsic values of options outstanding, exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock of $5.19 as of December 31, 2021. The aggregate intrinsic value of stock options exercised in 2021, 2020 and 2019 was $0.1 million, $0.3 million and $0.6 million, respectively. During the years ended December 31, 2021, 2020 and 2019, the weighted-average grant date fair value of options granted were $5.58, $4.78 and $8.98 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: Year Ended December 31, 2021 2020 2019 Expected term (in years) 5.27 - 6.08 5.00 - 6.08 5.27 - 6.08 Contractual term (in years) — 10.00 10.00 Volatility 68.96% - 71.40% 73.00% - 77.00% 73.14% - 83.19% Risk free interest rate 0.62% - 1.35% 0.39% - 1.37% 1.42% - 2.57% Dividend yield — — — Expected Term : The Company’s expected term represents the period that the Company’s stock-based awards are expected to be outstanding and is determined using the simplified method (based on the mid-point between the vesting date and the end of the contractual term for employee options). The Company uses the contractual term to determine the non-employee award fair value at the grant date. The contractual term of options granted under the Restated 2013 Plan is ten years. Expected Volatility : Since the Company does not have a long trading history for its common stock, the expected volatility was estimated based on the average volatility for comparable publicly traded biotechnology companies over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on their similar size, or stage in the life cycle. Beginning in the third quarter of 2019, as the Company had been publicly traded for four and a half years, the Company began to layer in its historical volatility in the calculation of expected volatility. Risk-Free Interest Rate : The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of option. Expected Dividend : The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero. 2013 Employee Stock Purchase Plan In 2013, the Company’s board of directors adopted and in 2016, upon the merger with Celladon, the Company amended and approved the 2013 Employee Stock Purchase Plan (2013 ESPP). The 2013 ESPP is intended to qualify as an employee stock purchase plan under Section 423 of the U.S. Internal Revenue Code and is administered by the Company’s board of directors. The number of shares of common stock initially reserved for issuance under the 2013 ESPP was 100,000 shares with an automatic annual increase to the shares issuable under the 2013 ESPP to the lower of (i) 1% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, and (ii) 165,000 shares of common stock, unless a lower number determined by the board of directors. As of December 31, 2021, a total of 783,831 shares are reserved for issuance and 671,172 shares available for future issuance under the 2013 ESPP. During the years ended December 31, 2021, 2020 and 2019, employees purchased 37,619 shares for $0.3 million, 25,645 shares for $0.2 million and 15,701 shares for $0.1 million, respectively, under the 2013 ESPP. 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 vest annually on the one-year, two-year, and three-year anniversaries 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. The performance stock units (PSUs) are also available for grant 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 year ended December 31, 2021, the Company granted 270,000 PSUs with a weighted-average grant date fair value of $7.92 per share. The performance-based metrics include the achievement of certain revenue targets and clinical and regulatory milestones. During the year ended December 31, 2021, the Company recorded $0.2 million of stock-based compensation expense related to the PSUs as it is expected that all milestones will be achieved by the target dates. This expense is included in selling, general and administrative expenses. No stock-based compensation expense was recognized during the year ended December 31, 2020 in relation to the PSUs. During the year ended December 31, 2021, the Company granted 371,500 RSUs with a weighted-average grant date fair value of $9.16 per share. In relation to the RSUs granted, the Company recognized $0.9 million and $0.2 million in stock-based compensation expense for the years ended December 31, 2021 and 2020, respectively, which is included in selling, general and administrative expenses. As of December 31, 2021, the total unrecognized compensation expense related to unvested RSUs and PSUs was $4.3 million, which the Company expects to recognize over an estimated weighted-average period of 2.8 years. The following table summarizes RSU and PSU activity and weighted average grant date fair value for the year ended December 31, 2021: Shares Weighted- Average Grant Date Fair Value Unvested shares as of December 31, 2020 37,500 $ 6.95 Granted 641,500 8.64 Vested (33,750 ) 6.35 Forfeited (22,250 ) 9.49 Unvested shares as of December 31, 2021 623,000 $ 8.63 Stock-Based Compensation Expense Total stock-based compensation expense recognized was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 2,252 $ 1,494 $ 1,550 Selling, general and administrative 5,649 4,479 4,129 Total $ 7,901 $ 5,973 $ 5,679 As of December 31, 2021, the total unrecognized compensation expense related to unvested options was $12.6 million, which the Company expects to recognize over an estimated weighted average period of 2.7 years.
Schedule of Nonvested Restricted 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 year ended December 31, 2021: Shares Weighted- Average Grant Date Fair Value Unvested shares as of December 31, 2020 37,500 $ 6.95 Granted 641,500 8.64 Vested (33,750 ) 6.35 Forfeited (22,250 ) 9.49 Unvested shares as of December 31, 2021 623,000 $ 8.63

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	11 . Income Taxes The Company’s provision for income taxes was approximately $64,000 for the year ended December 31, 2021, with an effective tax rate of -0.19% for the year ended December 31, 2021. No provision for income taxes was recorded for the years ended December 31, 2020 and 2019. The Company has incurred net operating losses (NOL) for all the periods presented. The Company has not reflected any benefit of such NOL carryforwards in the accompanying consolidated financial statements. The Company has established a full valuation allowance against its deferred tax assets due to the uncertainty surrounding the realization of such assets. The effective tax rate of the provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2021 2020 2019 Federal statutory income tax rate 21.00 % 21.00 % 21.00 % Change in valuation allowance (31.07 ) (26.75 ) (27.42 ) Tax credits 12.14 6.43 7.27 State income taxes, net of federal benefit 0.73 0.33 0.25 Stock-based compensation (3.02 ) (1.00 ) (0.89 ) Other, net 0.03 (0.01 ) (0.21 ) Provision for income taxes (0.19 )% — % — % The components of the deferred tax assets and liabilities are as follows (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 60,273 $ 54,523 Tax credits 5,486 1,068 Depreciation and amortization 1,863 2,067 Stock-based compensation 3,004 2,452 Accruals and reserves 646 606 Lease liabilities 156 278 Gross deferred tax assets 71,428 60,994 Valuation allowance (71,291 ) (60,747 ) Total deferred tax assets 137 247 Deferred tax liabilities: Right-of-use assets (137 ) (247 ) Total deferred tax liabilities (137 ) (247 ) Net deferred tax assets $ — $ — Due to the Company’s lack of earnings history, the deferred tax assets have been fully offset by a valuation allowance as of December 31, 2021 and 2020. The net change in the valuation allowance for the years ended December 31, 2021 and 2020 increased by $10.5 million and $7.0 million, respectively. As of December 31, 2021, the Company had approximately $279.1 million and $25.4 million, respectively, of federal and state NOL carryforwards available to reduce future taxable income that will begin to expire in 2030 and 2028, respectively, for federal and state tax purposes. As of December 31, 2021, the Company also had research and development tax credit carryforwards of $0.2 million and $2.3 million for federal and state purposes available to offset future taxable income tax. If not utilized, the state credits can be carried forward indefinitely. The Company’s ability to utilize NOL carryforwards or other tax attributes, such as research tax credits, in any taxable year may be limited if the Company has experienced an ownership change under Section 382 of the Internal Revenue Code (the Code) of 1986, as amended. The Company’s merger with Celladon resulted in such an ownership change and, accordingly, Celladon’s NOL carryforwards and certain other tax attributes will be subject to further limitations on their use. The Company assessed whether it had an ownership change, as defined by Section 382 of the Code from its formation through December 31, 2021. Based upon this assessment, the Company experienced ownership changes on April 20, 2016, October 18, 2018 and December 31, 2020. Due to these ownership changes, reductions were made to the Company’s NOL and tax credit carryforwards under these rules Additional ownership changes in the future could result in additional limitations on the Company’s NOL and tax credit carryforwards. Tax benefits from uncertain tax positions are recognized when it is more likely than not that the position will be sustained upon examination, including resolutions of any related appeals or litigation processes, based on the technical merits. The amount recognized is measured as the largest amount of tax benefit that is greater than 50 percent likely of being realized upon effective settlement. Uncertain Tax Positions A reconciliation of the Company’s unrecognized tax benefits for the years ended December 31, 2021, 2020 and 2019 is as follows (in thousands): Year Ended December 31, 2021 2020 2019 Balance at beginning of year $ 451 $ 3,277 $ 4,634 Additions based on tax positions related to prior year — — — Additions based on tax positions related to current year 1,499 81 2,443 Reductions based on tax positions related to prior year — (2,907 ) (3,800 ) Reductions based on tax positions related to current year — — — Balance at end of year $ 1,950 $ 451 $ 3,277 If the $2.0 million of unrecognized tax benefits is recognized, there would not be an effect on the effective tax rate. The Company does not expect the unrecognized tax benefits to change significantly over the next 12 months. As of December 31, 2021, the unrecognized tax benefits for uncertain tax positions were offset against deferred tax assets and would not affect the income tax rate if recognized due to the Company being in a full valuation allowance position. The Company’s policy is to account for interest and penalties in tax expense on the consolidated statements of operations. The Company files income tax returns in the U.S. federal and state jurisdictions. All periods since inception are subject to examination by U.S. federal and state jurisdictions. There were no such interest or penalties during the years ended December 31, 2021, 2020 and 2019.

Legal Matters

Legal Matters	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Legal Matters	1 2 . Legal Matters From time to time in the ordinary course of business the Company becomes involved in various lawsuits, claims and proceedings, including those pertaining to the defense and enforcement of the Company’s patent or other intellectual property rights and contractual rights. These proceedings are costly and time consuming. Additionally, successful challenges to the Company’s patent or other intellectual property rights through these proceedings could result in a loss of rights in the relevant jurisdiction and may allow third parties to use the Company’s proprietary technologies without a license from the Company or its collaborators. The outcome of such matters, which the Company believes, after consultation with legal counsel, will not have a material adverse effect on its financial condition, results of operations or liquidity. However, due to the risks and uncertainties inherent in legal proceedings, actual results could differ from current expected results. All legal costs associated with litigation are expensed as incurred.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	13 . 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 December 31, 2021 were as follows (in thousands): Undiscounted lease payments December 31, 2021 2022 $ 665 2023 115 2024 1 2025 1 Total undiscounted payments 782 Less: imputed interest (38 ) Present value of future lease payments 744 Less: current portion of operating lease liabilities (628 ) Operating lease liabilities $ 116 Rent expense recognized for the Company’s operating leases was $0.6 million, $0.6 million, and $0.6 million for the years ended December 31, 2021, 2020, and 2019, 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 $0.1 The operating cash outflows for the operating lease liabilities were $0.6 million, $0.7 million and $0.6 million for the years ended December 31, 2021, 2020 and 2019, respectively. As of December 31, 2021, the weighted-average remaining lease term and weighted-average discount rate were 1.2 years and 9.15%, respectively. Other Commitments The Company is obligated to make future payments to third parties under asset purchase and license agreements, including royalties and payments that become due and payable on the achievement of certain development and commercialization milestones. However, the amount and timing of these payments are not known. Manufacturing Service Agreement In 2020, the Company entered into a Master Manufacturing Services Agreement (MMSA) and Product Agreement with Patheon, Inc. (Patheon) for the manufacturing of lonafarnib capsules and packaging of bottles for commercial sale. Under the terms of the agreements, the Company is required to provide Patheon with annual volume forecasts of capsules and Patheon will manufacture 80% of actual manufacturing volume. If the Company orders more than 20 percent of manufacturing volume from other manufacturers, the Company is required to pay 70% of purchase price to Patheon for the shortfall. The initial terms of the MMSA and Product Agreement end on December 31, 2025 with automatic renewal for successive two-year terms, unless earlier terminated pursuant to the terms of each agreement, or upon either party’s notice of termination to the other.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Party Transactions	14. Related Party Transactions As disclosed in Note 6, the Company entered into license agreements with EGI, which is owned by the founder of the Company.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The 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.
Use of Estimates	Use of Estimates The preparation of 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 revenue and 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.
Reclassifications	Reclassifications Certain items on the consolidated balance sheet have been reclassified to conform to current year presentation. Such items were not material.
Concentrations of Risk	Concentrations of Risk Financial instruments that potentially subject the Company to a concentration of credit risk consists of cash, cash equivalents and investments. The Company’s cash is held by a financial institution in the United States. Amounts on deposit may at times exceed federally insured limits. Management believes that the financial institution is financially sound, and accordingly, minimal credit risk exists with respect to the financial institution. The Company relies on one supply chain for each of its product candidates. If any of the single source suppliers in any of the supply chains fail to satisfy the Company’s requirements on a timely basis, it could suffer delays in its clinical development programs and activities, which could adversely affect its operating results. Two customers accounted for approximately 66 percent and 34 percent of the Company’s accounts receivable as of December 31, 2021. One customer accounted for approximately 94 percent of product revenue during the year ended December 31, 2021. The Company did not have accounts receivable or revenue in 2020.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include all cash balances and highly liquid investments with original maturities of three months or less from the date of purchase. Cash equivalents consists primarily of amounts invested in money market funds held at financial institutions and corporate debt securities. The recorded carrying amount of cash equivalents approximates their fair value.
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 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 income (loss). The cost of available-for-sale securities sold is based on the specific-identification method .
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation. Depreciation expense is computed using the straight-line method over the estimated useful lives of the assets. Depreciation begins at the time the asset is placed into service. Maintenance and repairs are charged to operations as incurred. Property and equipment purchased for specific research and development projects with no alternative uses are expensed as incurred. The useful lives of the property and equipment are as follows: Lab equipment 5 years Furniture 5 years Leasehold improvements Shorter of remaining lease term or 5 years Computer equipment and software 3 years
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company evaluates its long-lived assets, including property and equipment, for impairment whenever events or changes in circumstances indicate that the carrying value of these assets may not be recoverable. The Company assesses the recoverability of long-lived assets by determining whether or not the carrying value of such assets will be recovered through undiscounted expected future cash flows. If the asset is considered to be impaired, the amount of any impairment is measured as the difference between the carrying value and the fair value of the impaired asset. Through December 31, 2021, the Company has not impaired any long-lived assets.
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 December 31, 2021 and 2020. The Company had no bad debt expense for the year ended December 31, 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. In the United States, the Company sells Zokinvy to a single specialty pharmacy provider that subsequently dispenses the product directly to patients. 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. In June 2021, the French National Agency for Medicines and Health Products Safety (ANSM) granted Zokinvy (lonafarnib) a Temporary Authorizations for Use (Autorisation Temporaire d'Utilisation or ATU) for a term of one year. Pursuant to this program, the Company sells product to a distributor who in turn ships product to pharmacies after receiving requests from physicians for patients in France. In November 2021, the Company began distributing and recognizing revenue from sales of Zokinvy (lonafarnib) through a reimbursed early access program in France. The revenue from sale of product under the ATU program is less than ten p ercent of total revenue for the year ended December 31, 2021 . The Company recognizes product revenue when a customer obtains control of its product, which occurs at a point in time, typically upon delivery to a 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 product is 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 a customer. Prompt payment discounts: The Company provides a discount to a customer if it pays for purchases within 30 days. The Company expects that its customers 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 records 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 a 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. Product costs incurred prior to FDA approval in November 2020 were previously recorded as research and development expense in the 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 Under Accounting Standards Codification (“ASC”) 842, 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 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 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.
Deferred Financing Costs	Deferred Financing Costs Financing costs incurred with securing a term debt are recorded in the Company’s consolidated balance sheets as an offset to the term debt and amortized to interest expense in the Company’s consolidated statements of operations over the contractual life of the loan using the effective interest method.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred and consist of payroll expenses, stock-based compensation expense, lab supplies and allocated facility costs, as well as fees paid to third parties that conduct certain research and development and manufacturing activities on the Company’s behalf. Amounts incurred in connection with license and asset purchase agreements are also included in research and development expenses. Manufacturing costs related to products undergoing regulatory approval are expensed as research and development costs until receipt of such approval.
Stock-Based Compensation	Stock-Based Compensation Stock-based awards to employees and directors, including stock options, are recorded at fair value as of the grant date using the Black-Scholes option pricing model and recognized as expense on a straight line-basis over the employee’s or director’s requisite service period (generally the vesting period). Stock-based awards to non-employees are recorded at their fair value as of the grant date, using the Black-Scholes option pricing model and recognized as expense over the period in which the related services are received. The determination of fair value for stock-based awards on the date of grant using an option pricing model requires management to make certain assumptions for Black-Scholes option pricing model inputs. The Company accounts for forfeitures of stock-based awards when they occur.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes. Under this method, deferred tax assets and liabilities are determined based on the differences between the financial reporting and the tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. The Company must then assess the likelihood that the resulting deferred tax assets will be realized. A valuation allowance is provided when it is more likely than not that some portion or all of a deferred tax asset will not be realized. Due to the Company’s lack of earnings history, the net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes benefits of uncertain tax positions if it is more likely than not that such positions will be sustained upon examination based solely on their technical merits, as the largest amount of benefit that is more likely than not to be realized upon the ultimate settlement. The Company’s policy is to recognize interest and penalties related to the underpayment of income taxes as a component of income tax expense or benefit. To date, there have been no interest or penalties charged in relation to unrecognized tax benefits. Internal Revenue Code Section 382 limits the use of net operating loss and tax credit carryforwards in certain situations where changes occur in the stock ownership of a company. In the event that the Company experiences a change of ownership, utilization of the net operating loss and tax credit carryforwards may be restricted.
Comprehensive Loss	Comprehensive Loss Comprehensive loss represents all changes in stockholders' equity except those resulting from and distributions to stockholders. The Company’s unrealized gains and losses on debt securities represent the only component of other comprehensive loss that are excluded from the reported net loss and that are presented in the consolidated statements of comprehensive loss.
Net Loss per Share	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 all periods presented, diluted net loss per share is the same as basic net loss per share for all periods as the inclusion of all potential common shares outstanding would have been anti-dilutive. 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): December 31, 2021 2020 2019 Options to purchase common stock 5,262,185 3,697,075 2,767,617 Restricted stock units (unvested) 623,000 37,500 — ESPP 48,159 81,169 36,493 Total 5,933,344 3,815,744 2,804,110
Accounting Pronouncements Not Yet Adopted	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 Note 8). 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.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Schedule of Estimated Useful Lives of Property and Equipment	The useful lives of the property and equipment are as follows: Lab equipment 5 years Furniture 5 years Leasehold improvements Shorter of remaining lease term or 5 years Computer equipment and software 3 years
Schedule of Antidilutive Securities Excluded from Computation of Earnings 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): December 31, 2021 2020 2019 Options to purchase common stock 5,262,185 3,697,075 2,767,617 Restricted stock units (unvested) 623,000 37,500 — ESPP 48,159 81,169 36,493 Total 5,933,344 3,815,744 2,804,110

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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): December 31, 2021 Level 1 Level 2 Level 3 Total Financial assets: Money market funds $ 13,520 $ — $ — $ 13,520 Corporate debt securities — 41,511 — 41,511 U.S. government bonds — 42,345 — 42,345 Total $ 13,520 $ 83,856 $ — $ 97,376 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): December 31, 2021 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 13,520 $ — $ — $ 13,520 Total cash equivalents $ 13,520 $ — $ — $ 13,520 Debt securities: Corporate debt securities $ 41,576 $ — $ (65 ) $ 41,511 U.S. government bonds 42,429 — (84 ) 42,345 Total debt securities $ 84,005 $ — $ (149 ) $ 83,856 Classified as: Cash equivalents $ 13,520 Short-term debt securities 66,594 Long-term debt securities 17,262 $ 97,376 December 31, 2020 Amortized cost Unrealized gain Unrealized loss Estimated 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)	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Inventory	Inventories consist of the following (in thousands): December 31, 2021 2020 Raw materials $ 1,056 $ — Work-in-progress 1,468 34 Finished goods 88 59 Total inventories $ 2,612 $ 93
Schedule of Property and Equipment	Property and equipment, net consist of the following (in thousands): December 31, 2021 2020 Computer equipment and software $ 669 $ 520 Furniture 116 111 Leasehold improvements 101 80 Lab equipment 271 271 Construction in progress 59 69 Total property and equipment 1,216 1,051 Less: accumulated depreciation (603 ) (342 ) Property and equipment, net $ 613 $ 709
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following (in thousands): December 31, 2021 2020 Prepaid contract manufacturing costs $ 3,695 $ 6,126 Prepaid research costs 3,253 1,177 Prepaid insurance 631 448 Other 1,782 1,122 Total prepaid expenses and other current assets $ 9,361 $ 8,873
Schedule of Components of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2021 2020 Contract research costs $ 4,760 $ 6,062 Contract manufacturing costs 3,288 1,167 Compensation and related benefits 3,131 3,169 Product revenue reserves 1,846 — Other 674 1,007 Total accrued liabilities $ 13,699 $ 11,405

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 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): 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 (1,482 ) (2,083 ) Total long term debt, net 31,795 31,194 Less: current portion of long-term debt (7,809 ) — Long-term debt, net $ 23,986 $ 31,194
Schedule of Future Minimum Payments of Principal, Exit Fee and Interest Expense under Oxford Term Loan	As of December 31, 2021, future minimum payments of principal, exit fee and interest expense under the Oxford Loan were as follows (in thousands): Year ending December 31, 2022 10,555 2023 20,189 2024 6,471 Total future payments 37,215 Less: unamortized interest (3,938 ) Less: exit fee (1,482 ) Face value of term loan $ 31,795

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Summary of Common Stock Reserved for Issuance	The Company had reserved shares of common stock for issuance as follows: December 31, 2021 2020 Options issued and outstanding 5,262,185 3,697,075 Options available for future grants 1,327,645 1,021,109 Restricted and performance stock units outstanding 623,000 37,500 Shares available for issuance under ESPP 671,172 543,791 Total 7,884,002 5,299,475

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2021
Stock Option Activity	The following table summarizes stock option activity under the Company’s stock-based compensation plans during the year ended December 31, 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 (1,866,785 ) 1,866,785 $ 8.92 Restricted stock units granted (371,500 ) — Performance stock units granted (270,000 ) — Exercised — (53,028 ) $ 6.81 Forfeited or cancelled 248,647 (248,647 ) $ 9.52 Restricted stock units forfeited 22,250 — $ — Outstanding as of December 31, 2021 1,327,645 5,262,185 $ 10.24 7.25 $ 530 Vested and exercisable as of December 31, 2021 2,983,332 $ 11.20 6.11 $ 482
Summary of Non-cash Stock Based Compensation Expense	Total stock-based compensation expense recognized was as follows (in thousands): Year Ended December 31, 2021 2020 2019 Research and development $ 2,252 $ 1,494 $ 1,550 Selling, general and administrative 5,649 4,479 4,129 Total $ 7,901 $ 5,973 $ 5,679
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: Year Ended December 31, 2021 2020 2019 Expected term (in years) 5.27 - 6.08 5.00 - 6.08 5.27 - 6.08 Contractual term (in years) — 10.00 10.00 Volatility 68.96% - 71.40% 73.00% - 77.00% 73.14% - 83.19% Risk free interest rate 0.62% - 1.35% 0.39% - 1.37% 1.42% - 2.57% Dividend yield — — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Effective Income Tax Rate	The effective tax rate of the provision for income taxes differs from the federal statutory rate as follows: Year Ended December 31, 2021 2020 2019 Federal statutory income tax rate 21.00 % 21.00 % 21.00 % Change in valuation allowance (31.07 ) (26.75 ) (27.42 ) Tax credits 12.14 6.43 7.27 State income taxes, net of federal benefit 0.73 0.33 0.25 Stock-based compensation (3.02 ) (1.00 ) (0.89 ) Other, net 0.03 (0.01 ) (0.21 ) Provision for income taxes (0.19 )% — % — %
Components of Deferred Tax Assets and Liabilities	The components of the deferred tax assets and liabilities are as follows (in thousands): December 31, 2021 2020 Deferred tax assets: Net operating loss carryforwards $ 60,273 $ 54,523 Tax credits 5,486 1,068 Depreciation and amortization 1,863 2,067 Stock-based compensation 3,004 2,452 Accruals and reserves 646 606 Lease liabilities 156 278 Gross deferred tax assets 71,428 60,994 Valuation allowance (71,291 ) (60,747 ) Total deferred tax assets 137 247 Deferred tax liabilities: Right-of-use assets (137 ) (247 ) Total deferred tax liabilities (137 ) (247 ) Net deferred tax assets $ — $ —
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the Company’s unrecognized tax benefits for the years ended December 31, 2021, 2020 and 2019 is as follows (in thousands): Year Ended December 31, 2021 2020 2019 Balance at beginning of year $ 451 $ 3,277 $ 4,634 Additions based on tax positions related to prior year — — — Additions based on tax positions related to current year 1,499 81 2,443 Reductions based on tax positions related to prior year — (2,907 ) (3,800 ) Reductions based on tax positions related to current year — — — Balance at end of year $ 1,950 $ 451 $ 3,277

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 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 December 31, 2021 were as follows (in thousands): Undiscounted lease payments December 31, 2021 2022 $ 665 2023 115 2024 1 2025 1 Total undiscounted payments 782 Less: imputed interest (38 ) Present value of future lease payments 744 Less: current portion of operating lease liabilities (628 ) Operating lease liabilities $ 116

Description of Business - Addit

Description of Business - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 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 Investments	$ 88,800
Cash and cash equivalents	22,221	$ 28,864
Debt securities, available-for-sale	66,600
Long-term debt securities, available-for-sale	17,300
Accumulated deficit	$ (340,417)	$ (306,500)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021USD ($)SupplyChain	Dec. 31, 2020USD ($)
Significant Accounting Policies [Line Items]
Impairment of long-lived assets	$ 0
Accounts receivable, allowance for doubtful accounts	0	$ 0
Bad debt expense	0	$ 0
Inventory Write-down	0
Interest charged in relation to unrecognized tax benefits	0
Penalties charged in relation to unrecognized tax benefits	$ 0
Supplier Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration risk, supplier	The Company relies on one supply chain for each of its product candidates. If any of the single source suppliers in any of the supply chains fail to satisfy the Company’s requirements on a timely basis, it could suffer delays in its clinical development programs and activities, which could adversely affect its operating results.
Number of supply chains for each product candidate | SupplyChain	1
Supplier Concentration Risk [Member] | Revenue Member]
Significant Accounting Policies [Line Items]
Percentage Of Amount Accounted For Customer	94.00%
Supplier Concentration Risk [Member] | Customer 1 | Accounts Receivable [Member]
Significant Accounting Policies [Line Items]
Percentage Of Amount Accounted For Customer	66.00%
Supplier Concentration Risk [Member] | Customer 2 | Accounts Receivable [Member]
Significant Accounting Policies [Line Items]
Percentage Of Amount Accounted For Customer	34.00%

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2021
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	3 years
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life	5 years
Property, Plant and Equipment, Useful Life, Minimum	Shorter of remaining lease term

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	5,933,344	3,815,744	2,804,110
Options Granted to Employees and Non Employees [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	5,262,185	3,697,075	2,767,617
Restricted Stock Units, Unvested [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	623,000	37,500
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	48,159	81,169	36,493

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 97,376	$ 120,822
Financial liabilities	0	0
Other-than-temporary impairment losses	0	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	Dec. 31, 2021	Dec. 31, 2020
Financial assets:
Assets, Fair Value	$ 97,376	$ 120,822
US Treasury Bill Securities [Member]
Financial assets:
Assets, Fair Value		39,995
Corporate Debt Securities [Member]
Financial assets:
Assets, Fair Value	41,511	33,941
US Government Bonds [Member]
Financial assets:
Assets, Fair Value	42,345	4,060
Money Market Funds [Member]
Financial assets:
Assets, Fair Value	13,520	20,846
Commercial Paper [Member]
Financial assets:
Assets, Fair Value		21,980
Level 1 [Member]
Financial assets:
Assets, Fair Value	13,520	20,846
Level 1 [Member] | Money Market Funds [Member]
Financial assets:
Assets, Fair Value	13,520	20,846
Level 2 [Member]
Financial assets:
Assets, Fair Value	83,856	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	41,511	33,941
Level 2 [Member] | US Government Bonds [Member]
Financial assets:
Assets, Fair Value	42,345	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	Dec. 31, 2021	Dec. 31, 2020
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	$ 13,520	$ 20,846
Cash equivalents, Estimated Fair Value	13,520	20,846
Debt securities, Amortized cost	84,005	99,984
Debt securities, Unrealized gain		4
Debt securities, Unrealized loss	(149)	(12)
Debt securities, Estimated Fair Value	83,856	99,976
Assets, Fair Value	97,376	120,822
Debt securities, Amortized cost	84,005	99,984
$20,846	149	12
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
Debt securities, Amortized cost		39,992
Short-Term Debt [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Estimated Fair Value	66,594	99,976
Long-Term Debt [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Estimated Fair Value	17,262
Corporate Debt Securities [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	41,576	33,952
Debt securities, Unrealized gain		1
Debt securities, Unrealized loss	(65)	(12)
Debt securities, Estimated Fair Value	41,511	33,941
Assets, Fair Value	41,511	33,941
Debt securities, Amortized cost	41,576	33,952
$20,846	65	12
US Government Bonds [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost		4,060
Debt securities, Estimated Fair Value		4,060
Assets, Fair Value	42,345	4,060
Debt securities, Amortized cost		4,060
US Government Bonds [Member] | US Treasury Bill Securities [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	42,429
Debt securities, Unrealized loss	(84)
Debt securities, Estimated Fair Value	42,345
Debt securities, Amortized cost	42,429
$20,846	84
Money Market Funds [Member]
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	13,520	20,846
Cash equivalents, Estimated Fair Value	13,520	20,846
Assets, Fair Value	13,520	20,846
Cash Equivalents [Member]
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Estimated Fair Value	$ 13,520	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
Debt securities, Amortized cost		$ 21,980

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 1,056
Work-in-progress	1,468	$ 34
Finished goods	88	59
Total inventories	$ 2,612	$ 93

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 1,216	$ 1,051
Property and equipment, accumulated depreciation	(603)	(342)
Property and equipment, net	613	709
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	271	271
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	669	520
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	116	111
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	101	80
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 59	$ 69

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Depreciation [Abstract]
Depreciation expense	$ 0.3	$ 0.2	$ 0.1

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Prepaid Expense And Other Assets Current [Abstract]
Prepaid contract manufacturing costs	$ 3,695	$ 6,126
Prepaid research costs	3,253	1,177
Prepaid insurance	631	448
Other	1,782	1,122
Total prepaid expenses and other current assets	$ 9,361	$ 8,873

Balance Sheet Components - Sc_4

Balance Sheet Components - Schedule of Components of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Payables And Accruals [Abstract]
Contract research costs	$ 4,760	$ 6,062
Contract manufacturing costs	3,288	1,167
Compensation and related benefits	3,131	3,169
Product revenue reserves	1,846
Other	674	1,007
Total accrued liabilities	$ 13,699	$ 11,405

License, Collaboration, and P_2

License, Collaboration, and Product Development Agreements - Additional Information (Detail) - USD ($) $ in Thousands	Aug. 11, 2018	May 15, 2018	Apr. 20, 2016	Mar. 15, 2018	May 31, 2015	Sep. 30, 2010	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development									$ 64,436	$ 41,590	$ 51,791
Weighted-average period for recognition (in years)									2 years 8 months 12 days
Aggregate fair value of shares issued									$ 35	$ 34
Common stock, shares issued									34,568,821	33,878,486
Common Stock [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sale of common stock									565,938	9,267,760	5,175,000
UPenn/CHOP Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-Refundable Issue Fee											$ 1,000
Milestone payment obligations									$ 0
UPenn/CHOP Agreement [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License maintenance fee									2,500
UPenn/CHOP Agreement [Member] | Commercial Sales [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations									18,000
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									$ 200	$ 200	$ 200
Weighted-average period for recognition (in years)									3 months 18 days
Progeria Research Foundation (PRF) Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development				$ 2,000
Collaboration agreement initial term		10 years
Collaboration agreement subsequent renewal terms		2 years
BMS Transaction [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment			$ 2,000
BMS Transaction [Member] | Common Stock [Member] | BMS Purchase Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sale of common stock			157,587
Aggregate fair value of shares issued			$ 3,200
BMS Transaction [Member] | Commercial Sales [Member] | Maximum [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations			128,000
BMS Transaction [Member] | Development and Regulatory Milestones [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations			$ 61,000
BMS Transaction [Member] | Development Phase 2 [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations										$ 3,000
BMS Transaction [Member] | Development Phase 3 [Member] | Licensing Agreements [Member] | Subsequent Event [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations							$ 5,000
Merck Transaction [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate fair value of shares issued						$ 500
Common stock, shares issued						27,350
Milestone payments					$ 1,000				$ 0
Royalties expiration description										The Company is obligated to pay Merck up to an aggregate of $27.0 million in development milestones and will be required to pay tiered royalties based on aggregate annual net sales of all licensed products ranging from mid-single to low double-digit royalties on net sales.
Merck Transaction [Member] | Licensing Agreements [Member] | Subsequent Event [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payments								$ 1,000
Merck Transaction [Member] | Development [Member] | Maximum [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payment obligations						$ 27,000

Asset Purchase Agreements and_2

Asset Purchase Agreements and Related License Agreements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Nov. 20, 2020	Mar. 22, 2016	Sep. 30, 2015	Dec. 31, 2010	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Asset Purchase Agreement And Related License Agreement [Line Items]
Compensation expense related to the time-vested/milestone vested options					$ 7,901	$ 5,973	$ 5,679
Milestone Vested Options [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Compensation expense related to the time-vested/milestone vested options					$ 0	0	0
Asset Purchase Agreement [Member] | EIG Transaction [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Upfront payment				$ 400
Asset purchase description					Within the first ten years after commercialization, the Company may make a one-time payment of $0.5 million for each contract for the three types of product related to such intellectual property that would reduce the payment term for the three products to the tenth anniversary of the first commercial sale.
One-time payment				$ 500
Asset Purchase Agreement [Member] | EIG Transaction [Member] | Farnesyl Transferase Inhibitors and Related Intellectual Property [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Royalties expiration description					The obligation to pay royalties expires on a country-by-country and product-by-product basis on the later of either when the product is no longer sold in any country or the earliest of the tenth anniversary of the first commercial sale of the product.
Avexitide Purchase Agreement [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Shares issued for purchased assets			15,378
Common stock, value			$ 200
Options to purchase common stock		48,544	46,134
Options to purchase of common stock exercise price		$ 17.25	$ 2.06
Options to purchase common stock vesting period			4 years
Vesting of options to purchase common stock			30,756
Compensation expense related to the time-vested/milestone vested options					$ 100	$ 100	$ 100
License agreement milestone payments paid					$ 100
Avexitide Purchase Agreement [Member] | Maximum [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Aggregate potential milestone payments			$ 1,000
AbbVie Asset Purchase Agreement [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Payment for asset purchase agreement	$ 95,000
AbbVie Asset Purchase Agreement [Member] | Progeria Research Foundation (PRF) Collaboration Agreement [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Proceeds from sale	$ 46,500

Sale of Assets - Additional Inf

Sale of Assets - Additional Information (Detail) - Disposal Group Not Discontinued Operations [Member] - MYDICAR [Member] - Theragene Pharmaceuticals, Inc. [Member] - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2022	Sep. 30, 2020	May 31, 2017	Dec. 31, 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			$ 0.2
Sale of assets number of common stock shares received			475,000	475,000
Maximum cumulative cash proceeds of counter party for issuance of additional shares			$ 4
Maximum consideration per share of counter party for issuance of additional shares			$ 6
Aggregate common stock consideration value			$ 2.9
Shares repurchase by counterparty based on exercise of put options			225,000	225,000
Cost method investment with carrying value				$ 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				$ 0.3
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	$ 0.1
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			$ 1.4
Maximum [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Asset purchase agreement contingent consideration receivable			$ 45
Royalty receivable percentage on net sales			8.00%

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($) $ in Thousands	Oct. 06, 2021	Feb. 23, 2021	Mar. 05, 2019	Dec. 31, 2016	Dec. 31, 2021	Dec. 31, 2020	Aug. 03, 2018	May 31, 2018
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.
Loan agreement, covenant compliance					and accelerate the maturity of the debt.
Minimum [Member]
Debt Instrument [Line Items]
Loan agreement, interest rate	9.15%
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
Oxford Loan [Member] | Amended Tranche A [Member]
Debt Instrument [Line Items]
Face value of term loan					31,795
Loan final repayment exit fees payable					$ 1,482
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] | 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	Dec. 31, 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	(1,482)	(2,083)
Total long term debt, net	31,795	31,194
Total long term debt, net	31,795	31,194
Less: current portion of long-term debt	(7,809)
Long-term debt, net	$ 23,986	$ 31,194

Debt - Schedule of Future Minim

Debt - Schedule of Future Minimum Payments of Principal, Exit Fee and Interest Expense under Oxford Term Loan (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Exit fee	$ 3,277	$ 3,277
Face value of term loan	30,000	$ 30,000
Oxford Loan [Member] | Amended Tranche A [Member]
Debt Instrument [Line Items]
2022	10,555
2023	20,189
2024	6,471
Total future payments	37,215
Less: unamortized interest	(3,938)
Exit fee	(1,482)
Face value of term loan	$ 31,795

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Aug. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Apr. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividends declared					$ 0
Net proceeds from issuance of common stock					$ 3,040,000	$ 96,779,000
Equity, debt, warrants and units, maximum aggregate offering amount		$ 200,000,000	$ 150,000,000
At-The-Market Offering [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock upon public offering, net of issuance costs, shares					565,938	9,267,760
Net proceeds from issuance of common stock					$ 3,000	$ 97,300,000
Equity, debt, warrants and units, maximum aggregate offering amount		200,000,000	150,000,000
Equity, debt, warrants and units, maximum issued and sale		$ 50,000,000	$ 50,000,000
Amount of common stock available for sale	$ 50,000,000
Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock upon public offering, net of issuance costs, shares					565,938	9,267,760	5,175,000
Underwriting Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Net proceeds from issuance of common stock				$ 53,200,000
Underwriting Agreement [Member] | Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock upon public offering, net of issuance costs, shares				5,175,000
Number of additional common stock issued				675,000
Common stock, offering price per share				$ 11

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Common Stock Reserved for Issuance (Detail) - shares	Dec. 31, 2021	Dec. 31, 2020
Equity [Abstract]
Options issued and outstanding	5,262,185	3,697,075
Options available for future grants	1,327,645	1,021,109
Restricted and performance stock units outstanding	623,000	37,500
Shares available for issuance under ESPP	671,172	543,791
Total	7,884,002	5,299,475

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of common stock	$ 5.19
Aggregate intrinsic value of options exercised	$ 100	$ 300	$ 600
Expected dividend yield	0.00%
Common Stock Reserved for Issuance	7,884,002	5,299,475
Number of additional shares authorized	2,543,924
Options available for future grants	1,327,645	1,021,109
Issuance of common stock upon ESPP purchase	$ 257	$ 186	130
Stock options granted	1,866,785
Stock-based compensation expense	$ 7,901	$ 5,973	$ 5,679
Total unrecognized compensation expense	$ 12,600
Weighted-average period for recognition (in years)	2 years 8 months 12 days
Weighted average period expected to recognized compensation expense (in years)	2 years 8 months 12 days
Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants	$ 5.58	$ 4.78	$ 8.98
Grant date fair value of employee options vested	6,900,000	5,600,000	5,700,000
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	$ 7.92
Options available for future grants	270,000
Stock-based compensation expense	$ 200	$ 0
Restricted Stock Units, Unvested [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant date fair value of employee option grants	$ 9.16
Stock options granted	371,500
Stock-based compensation expense	$ 900	$ 200
Total unrecognized compensation expense	$ 4,300
Weighted-average period for recognition (in years)	2 years 9 months 18 days
Weighted average period expected to recognized compensation expense (in years)	2 years 9 months 18 days
Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Issuance of common stock authorized	6,399,366
2013 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock Reserved for Issuance	783,831			100,000
Percentage increase in number of shares of common stock reserved for issuance	1.00%
Number of additional shares authorized	165,000
Options available for future grants	671,172
Issuance of common stock upon ESPP purchase, Shares	37,619	25,645	15,701
Issuance of common stock upon ESPP purchase	$ 300	$ 200	$ 100
Share-based compensation arrangement by share-based payment award, description	The number of shares of common stock initially reserved for issuance under the 2013 ESPP was 100,000 shares with an automatic annual increase to the shares issuable under the 2013 ESPP to the lower of (i) 1% of the total number of shares of common stock outstanding on December 31 of the preceding calendar year, and (ii) 165,000 shares of common stock, unless a lower number determined by the board of directors. As of December 31, 2021, a total of 783,831 shares are reserved for issuance and 671,172 shares available for future issuance under the 2013 ESPP. During the years ended December 31, 2021, 2020 and 2019, employees purchased 37,619 shares for $0.3 million, 25,645 shares for $0.2 million and 15,701 shares for $0.1 million, respectively, under the 2013 ESPP.
Minimum [Member] | Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Threshold ownership percentage of shareholder for grant of options at pre determined exercise price	10.00%
Minimum [Member] | Holders Of Ten Percent Or More Of Voting Power | Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	110.00%
Maximum [Member] | Restated 2013 Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual terms of options granted under the Plan	10 years

Equity Incentive Plans - Stock

Equity Incentive Plans - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
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	(1,866,785)
Shares Available for Grant, Restricted stock units granted	(371,500)
Performance stock units granted	(270,000)
Shares Available for Grant, Forfeited or cancelled	248,647
Restricted stock units forfeited	22,250
Shares Available for Grant, Outstanding, Ending balance	1,327,645	1,021,109
Vested and exercisable as of December 31, 2021	2,983,332
Number of Options, Outstanding, Beginning balance	3,697,075
Number of Options, Granted	1,866,785
Number of Options, Exercised	(53,028)
Number of Options, Forfeited or cancelled	(248,647)
Number of Options, Outstanding, Ending balance	5,262,185	3,697,075
Weighted Average Exercise Price Per Option, Outstanding, Beginning balance	$ 10.81
Weighted Average Exercise Price Per Option, Granted	8.92
Weighted Average Exercise Price Per Option, Exercised	6.81
Weighted Average Exercise Price Per Option, Forfeited or cancelled	9.52
Weighted Average Exercise Price Per Option, Outstanding, Ending balance	10.24	$ 10.81
Weighted Average Exercise Price Per Option, Vested and exercisable	$ 11.20
Outstanding as of December 31, 2020	7 years 3 months	7 years 6 months 18 days
Vested and exercisable as of December 31, 2021	6 years 1 month 9 days
Aggregate Intrinsic Value	$ 530	$ 9,048
Aggregate Intrinsic Value, Vested and exercisable	$ 482

Equity Incentive Plans - Weight

Equity Incentive Plans - Weighted-average assumptions used in Black-Scholes Model to estimate fair value of stock options granted (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)	7 years 3 months	7 years 6 months 18 days
Dividend yield	0.00%
Employees Stock Option [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 7 days	5 years	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
Non-Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)		10 years	10 years
Employees and Non Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility, minimum	68.96%	73.00%	73.14%
Volatility, maximum	71.40%	77.00%	83.19%
Risk free interest rate, minimum	0.62%	0.39%	1.42%
Risk free interest rate, maximum	1.35%	1.37%	2.57%

Equity Incentive Plans - Schedu

Equity Incentive Plans - Schedule of Nonvested Restricted Stock Units Activity and Weighted Average Grant Date Fair Value (Detail)	12 Months Ended
	Dec. 31, 2021$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted	1,866,785
Restricted Stock Units And Performance Stock Unit
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested shares, beginning balance	37,500
Stock options granted	641,500
Vested, shares	(33,750)
Forfeited, shares	(22,250)
Unvested shares, ending balance	623,000
Weighted average grant-date fair value of options beginning balance | $ / shares	$ 6.95
Weighted-average grant date fair value of employee option grants | $ / shares	8.64
Weighted average grant-date fair value of options vested | $ / shares	6.35
Weighted average grant-date fair value of options forfeited | $ / shares	9.49
Weighted average grant-date fair value of options ending balance | $ / shares	$ 8.63

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Non-cash Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 7,901	$ 5,973	$ 5,679
Compensation expense related to the time-vested/milestone vested options	7,901	5,973	5,679
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	2,252	1,494	1,550
Compensation expense related to the time-vested/milestone vested options	2,252	1,494	1,550
Selling General And Administrative Expenses [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	5,649	4,479	4,129
Compensation expense related to the time-vested/milestone vested options	$ 5,649	$ 4,479	$ 4,129

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Provision for income taxes	$ 64,000	$ 0	$ 0
Effective tax rate	(0.19%)
Valuation allowance	$ 10,500,000	7,000,000
Unrecognized tax benefits impact on effective tax rate	2,000,000
Accrued interest and penalties associated with uncertain tax positions	0	$ 0	$ 0
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 279,100,000
Operating loss carryforwards expiration year	2030
Tax credits	$ 200,000
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 25,400,000
Operating loss carryforwards expiration year	2028
Tax credits	$ 2,300,000

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%	21.00%
Change in valuation allowance	(31.07%)	(26.75%)	(27.42%)
Tax credits	12.14%	6.43%	7.27%
State income taxes, net of federal benefit	0.73%	0.33%	0.25%
Stock-based compensation	(3.02%)	(1.00%)	(0.89%)
Other, net	0.03%	(0.01%)	(0.21%)
Provision for income taxes	(0.19%)

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforwards	$ 60,273	$ 54,523
Tax credits	5,486	1,068
Depreciation and amortization	1,863	2,067
Stock-based compensation	3,004	2,452
Accruals and reserves	646	606
Lease liabilities	156	278
Gross deferred tax assets	71,428	60,994
Valuation allowance	(71,291)	(60,747)
Total deferred tax assets	137	247
Deferred tax liabilities:
Right-of-use assets	(137)	(247)
Total deferred tax liabilities	(137)	(247)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits Roll Forward (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 451	$ 3,277	$ 4,634
Additions based on tax positions related to current year	1,499	81	2,443
Reductions based on tax positions related to prior year		(2,907)	(3,800)
Balance at end of year	$ 1,950	$ 451	$ 3,277

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2017USD ($)ft²	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Other Commitments [Line Items]
Rent expense recognized for company's operating leases		$ 0.6	$ 0.6	$ 0.6
Variable lease payments for operating leases		0.1	0.1	0.1
Operating cash outflows for operating lease liabilities		$ 0.6	$ 0.7	$ 0.6
Weighted-average remaining lease term		1 year 2 months 12 days
Weighted-average discount rate		9.15%
Patheon, Inc. [Member] | Master Manufacturing Services Agreement [Member]
Other Commitments [Line Items]
Percentage of product manufactured on the basics of annual forecasts		80.00%
Percentage of purchase price		70.00%
Product agreement date of expiration		Dec. 31, 2025
Product agreement renewal term		2 years
Maximum [Member] | Patheon, Inc. [Member] | Master Manufacturing Services Agreement [Member]
Other Commitments [Line Items]
Percentage of product manufactured on the basics of annual forecasts		20.00%
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	$ 0.3

Commitments and Contingencies_2

Commitments and Contingencies - Maturity of Operating Leases Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Operating leases minimum payments, 2022	$ 665
Operating leases minimum payments, 2023	115
Operating leases minimum payments, 2024	1
Operating leases minimum payments, 2025	1
Total undiscounted payments	782
Less: imputed interest	(38)
Present value of future lease payments	744
Less: current portion of operating lease liabilities	(628)	$ (582)
Operating lease liabilities	$ 116	$ 738