Eiger BioPharmaceuticals (EIGRQ) 10-K 13 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 05, 2020	Jun. 30, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
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	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
Documents Incorporated by Reference	Part III incorporates certain information by reference from the registrant’s proxy statement for the 2020 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, 2019.
Entity Common Stock, Shares Outstanding		24,559,027
Entity Public Float			$ 255,497,853

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 39,373	$ 61,262
Debt securities, available-for-sale	55,621	39,091
Prepaid expenses and other current assets	5,390	1,492
Total current assets	100,384	101,845
Property and equipment, net	590	167
Operating lease right-of-use assets	1,654
Other assets	2,511	436
Total assets	105,139	102,448
Current liabilities:
Accounts payable	6,414	5,830
Accrued liabilities	10,001	4,194
Current portion of operating lease liabilities	534
Total current liabilities	16,949	10,024
Long term debt, net	30,390	25,620
Operating lease liabilities	1,320
Other long term liabilities		212
Total liabilities	48,659	35,856
Commitments and contingencies (Note 13)
Stockholders’ equity:
Common stock, $0.001 par value, 200,000,000 shares authorized as of December 31, 2019 and 2018; 24,523,381 and 19,211,759 shares issued and outstanding as of December 31, 2019 and 2018, respectively	24	19
Additional paid-in capital	297,863	237,795
Accumulated other comprehensive income (loss)	42	(25)
Accumulated deficit	(241,449)	(171,197)
Total stockholders’ equity	56,480	66,592
Total liabilities and stockholders’ equity	$ 105,139	$ 102,448

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
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	24,523,381	19,211,759
Common stock, shares outstanding	24,523,381	19,211,759

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development	$ 51,791	$ 37,091	$ 29,519
General and administrative	17,113	13,956	12,001
Total operating expenses	68,904	51,047	41,520
Loss from operations	(68,904)	(51,047)	(41,520)
Interest expense	(3,406)	(2,329)	(1,524)
Interest income	2,073	997	410
Other (expense) income, net	(15)	(12)	186
Net loss	$ (70,252)	$ (52,391)	$ (42,448)
Net loss per common share, basic and diluted	$ (3.08)	$ (3.84)	$ (4.86)
Weighted-average common shares outstanding, basic and diluted	22,785,611	13,634,152	8,727,935

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (70,252)	$ (52,391)	$ (42,448)
Other comprehensive loss:
Unrealized gain (loss) on available-for-sale debt securities, net	67	(22)	12
Comprehensive loss	$ (70,185)	$ (52,413)	$ (42,436)

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, 2016	$ 40,721	$ 8	$ 117,086	$ (15)	$ (76,358)
Beginning Balance, Shares at Dec. 31, 2016		8,356,659
Issuance of common stock upon public offering, net of issuance costs	19,800	$ 3	19,797
Issuance of common stock upon public offering, net of issuance costs, shares		2,143,525
Issuance of common stock upon ESPP purchase	142		142
Issuance of common stock upon ESPP purchase, Shares		16,186
Issuance of common stock upon stock option exercise	52		52
Issuance of common stock upon stock option exercises, Shares		10,229
Stock-based compensation expense	4,243		4,243
Unrealized gain on debt securities, net	12			12
Net loss	(42,448)				(42,448)
Ending Balance at Dec. 31, 2017	22,522	$ 11	141,320	(3)	(118,806)
Ending Balance, Shares at Dec. 31, 2017		10,526,599
Issuance of common stock upon public offering, net of issuance costs	90,642	$ 8	90,634
Issuance of common stock upon public offering, net of issuance costs, shares		8,510,918
Issuance of common stock upon ESPP purchase	96		96
Issuance of common stock upon ESPP purchase, Shares		17,508
Issuance of common stock upon stock option exercise	310		310
Issuance of common stock upon stock option exercises, Shares		41,208
Issuance of common stock under Product Development Agreement	428		428
Issuance of common stock under Product Development Agreement, Shares		115,526
Stock-based compensation expense	5,007		5,007
Unrealized gain on debt securities, net	(22)			(22)
Net loss	(52,391)				(52,391)
Ending Balance at Dec. 31, 2018	$ 66,592	$ 19	237,795	(25)	(171,197)
Ending Balance, Shares at Dec. 31, 2018	19,211,759	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	120,921
Issuance of common stock under Product Development Agreement	$ 226		226
Stock-based compensation expense	5,679		5,679
Unrealized gain on 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	24,523,381

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Stockholders Equity [Abstract]
Issuance of common stock upon public offering, issuance costs	$ 3,731	$ 5,357	$ 376

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net loss	$ (70,252)	$ (52,391)	$ (42,448)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	68	54	41
Amortization of debt securities discounts	(467)	(426)	(53)
Stock-based compensation	5,679	5,007	4,243
Non-cash interest expense	723	592	366
Gain on intellectual property sale			(200)
Amortization of operating lease right-of-use assets	418
Common stock issued under Product Development Agreement	226	428
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(3,698)	(780)	(131)
Other assets	(2,075)	(124)	(169)
Accounts payable	584	2,647	544
Accrued liabilities	5,610	2,110	(565)
Operating lease liabilities	(430)
Other long term liabilities		212
Net cash used in operating activities	(63,614)	(42,671)	(38,372)
Investing Activities
Purchase of debt securities available-for-sale	(96,267)	(57,193)	(24,524)
Proceeds from maturities of debt securities available-for-sale	80,271	28,250	47,025
Proceeds from intellectual property sale			200
Purchase of property and equipment	(475)	(142)	(44)
Net cash (used in) provided by investing activities	(16,471)	(29,085)	22,657
Financing Activities
Proceeds from issuance of common stock upon public offering, net of issuance costs	53,194	90,642	19,800
Proceeds from borrowings in connection with term loan, net of issuance costs	6,627	9,935
Repayment of accrued exit fee and second amendment fee	(913)
Repayment of term loan	(1,667)
Proceeds from issuance of common stock upon ESPP purchase	130	96	142
Proceeds from issuance of common stock upon stock option exercises	844	310	52
Payment of deferred offering costs	(19)
Net cash provided by financing activities	58,196	100,983	19,994
Net (decrease) increase in cash and cash equivalents	(21,889)	29,227	4,279
Cash and cash equivalents at beginning of year	61,262	32,035	27,756
Cash and cash equivalents at end of year	39,373	61,262	32,035
Supplemental disclosure of cash flow information:
Interest paid	$ 2,638	$ 1,652	$ 1,038

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2019
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 late-stage biopharmaceutical company focused on the development and commercialization of well-characterized drugs for life-threatening, rare and ultra-rare diseases with high unmet medical needs and no approved therapies. Eiger has reported positive proof-of-concept clinical results in four programs: lonafarnib monotherapy, lonafarnib boosted with ritonavir, peginterferon lambda monotherapy and in combination with lonafarnib boosted with ritonavir, and avexitide, all with first-in-class drugs, now advancing into submission for regulatory approvals or Phase 3 clinical development. Eiger’s lead program is in Phase 3, developing lonafarnib, a first-in-class prenylation inhibitor, boosted with ritonavir, for the treatment of Hepatitis Delta Virus (HDV) infection, the most severe form of human viral hepatitis for which there is currently no approved therapy. The Company is also developing lonafarnib monotherapy for treatment of Progeria and Progeroid Laminopathies. Progeria, also known as Hutchinson-Gilford Progeria Syndrome (HGPS), and Progeroid Laminopathies, are ultra-rare and rapidly fatal genetic conditions of accelerated aging in children. Peginterferon lambda (lambda) is the Company’s second program treating HDV. Lambda is a well-characterized, late-stage, first in class, type III interferon. The Company is developing avexitide, a well-characterized peptide, as a treatment for post-bariatric hypoglycemia (PBH). PBH is a debilitating and potentially life-threatening condition for which there is currently no approved therapy. Avexitide has also demonstrated clinical proof of concept for treatment of Congenital Hyperinsulinism (CHI), 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, 2019, the Company had $95.0 million of cash, cash equivalents and investments, comprised of $39.4 million of cash and cash equivalents and $55.6 million of debt securities available-for-sale. The additional $5.0 million will be available to the Company under the Amended Oxford Loan upon the latest to occur of (i) achievement of positive lonafarnib Phase 3 HDV topline data sufficient to file new drug application and (ii) January 1, 2021 (Note 8). The Company had an accumulated deficit of $241.4 million and negative cash flows from operating activities as of December 31, 2019. The Company expects to continue to incur losses for the next several years. Management believes that the currently available resources will be sufficient to fund its operations for at least the next 12 months following the issuance date of these consolidated financial statements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Consolidation 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 following 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 expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates, including those related to clinical trial accrued liabilities, stock-based compensation, operating lease liabilities and income taxes. 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. 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. For each product candidate, the Company relies on one supply chain for each of the four 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. 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. All short-term securities are carried at fair value based upon quoted market prices. Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated other comprehensive loss. The cost of available-for-sale securities sold is based on the specific-identification method . 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 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, 2019, the Company has not impaired any long-lived assets. 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 expense in the consolidated statements of operations. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers. The Company makes judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. Leases The Company has a real estate lease for its office space in Palo Alto, California. The Company determines the initial classification and measurement of its right-of-use assets (ROU assets) and lease liabilities at the lease commencement date and thereafter if modified. The lease term includes any renewal options and termination options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its incremental borrowing rate. The incremental borrowing rate is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment. Rent expense for operating leases is recognized on a straight-line basis, unless the operating lease ROU assets have been impaired, over the reasonably assured lease term based on the total lease payments and is included in operating expenses in the 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 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 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 expense. 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, 2019 2018 2017 Options to purchase common stock 2,767,617 1,996,211 1,467,051 Warrants to purchase common stock — — 10,180 Total 2,767,617 1,996,211 1,477,231 Immaterial Error Correction In connection with the preparation of the consolidated statements of operations for the year ended December 31, 2019, the Company identified immaterial errors in the calculation of number of d, for the year ended December 31, 2018, resulting in an overstatement in the weighted average common shares outstanding and an understatement in the net loss per share, basic and diluted Year Ended December 31, 2018 As Reported Adjustment As Revised Weighted average common shares outstanding, basic and diluted 13,711,034 (76,882 ) 13,634,152 Net loss per share, basic and diluted $ (3.82 ) $ (0.02 ) $ (3.84 ) Recently Adopted Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842), Targeted Improvements to Leases (Topic 842) Codification Improvements to Leases (Topic 842) Codification Improvements to Leases (Topic 842) In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes 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. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) The Company is currently in the process of evaluating the impact the standard will have on its consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2019
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, 2019 and 2018, the carrying amount of prepaid expenses and other current assets, accounts payable and accrued liabilities approximated their estimate 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, 2019 and 2018. There were no transfers between Level 1, Level 2 or 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, 2019 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 35,854 $ — $ — $ 35,854 Corporate debt securities — 16,644 — 16,644 Commercial paper — 7,457 — 7,457 U.S. government bonds — 31,520 — 31,520 Total $ 35,854 $ 55,621 $ — $ 91,475 December 31, 2018 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 45,441 $ — $ — $ 45,441 Corporate debt securities — 23,474 — 23,474 Commercial paper — 15,617 — 15,617 Total $ 45,441 $ 39,091 $ — $ 84,532 There were no financial liabilities as of December 31, 2019 and 2018. 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, 2019 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 35,854 $ — $ — $ 35,854 Total cash equivalents $ 35,854 $ — $ — $ 35,854 Debt securities: Corporate debt securities $ 16,633 $ 11 $ — $ 16,644 Commercial paper 7,457 — — 7,457 U.S. government bonds 31,489 31 — 31,520 Total debt securities $ 55,579 $ 42 $ — $ 55,621 December 31, 2018 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 45,441 $ — $ — $ 45,441 Total cash equivalents $ 45,441 $ — $ — $ 45,441 Debt securities: Corporate debt securities $ 23,489 $ 1 $ (16 ) $ 23,474 Commercial paper 15,627 — (10 ) 15,617 Total debt securities $ 39,116 $ 1 $ (26 ) $ 39,091 As of December 31, 2019, the contractual maturity of the available-for-sale debt securities is less than one year. The Company periodically reviews the available-for-sale investments 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, 2019, 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, 2019
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4. Balance Sheet Components Property and Equipment, Net Property and equipment, net consist of the following (in thousands): December 31, 2019 2018 Computer equipment and software $ 160 $ 138 Furniture 111 98 Leasehold improvements 61 56 Lab equipment 36 36 Construction in progress 436 — Total property and equipment 804 328 Less: accumulated depreciation (214 ) (161 ) Property and equipment, net $ 590 $ 167 Depreciation expense for the years ended December 31, 2019, 2018 and 2017 was $68,000, $54,000 and $41,000, respectively. Accrued Liabilities Accrued liabilities consist of the following (in thousands): December 31, 2019 2018 Contract research costs $ 5,288 $ 2,191 Contract manufacturing costs 2,510 — Compensation and related benefits 1,707 1,705 Consulting costs 97 258 Franchise tax 40 40 Other 359 — Total accrued liabilities $ 10,001 $ 4,194

License, Collaboration, and Pro

License, Collaboration, and Product Development Agreements	12 Months Ended
	Dec. 31, 2019
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, sublicenseable, 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, 2019. 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. IQVIA General Services Agreement On November 7, 2018, the Company entered into a General Services Agreement (the GSA) with IQVIA RDS, Inc. (IQVIA), pursuant to which the Company will receive professional services for the project management of the phase III EIG-LNG-011 clinical trial (the Study). The services are to be provided through November 2021. As consideration, the Company agreed to pay $14.2 million for the professional services to be performed and $12.2 million for pass-through and miscellaneous expense over the term of the GSA. The GSA can be terminated by either party due to material health risk to the Study, a material breach, or by the Company without cause with 45 days prior written notice. 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 hepatitis Delta virus (HDV) program. The services are to be provided from July 1, 2018 through the completion of the Phase 3 Clinical Study Reports and the subsequent 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 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. Clinigen Master Service Agreement On April 26, 2018, the Company entered into a master service agreement with Clinigen Healthcare Ltd. (Clinigen) in anticipation of its obligations under the PRF Collaboration Agreement to establish an Expanded Access Program (EAP) for children with progeria and progeroid laminopathies. On May 23, 2018, the Company entered into the first statement of work (SOW) under the agreement. Pursuant to the SOW, Clinigen became an authorized non-exclusive worldwide distributor of lonafarnib, the unlicensed pharmaceutical product (the Product). The Company is responsible for supply of the Product to Clinigen, and Clinigen is responsible for providing the Product to patients as part of the patient support program. Clinigen is also obligated to set up, manage and close-out the patient support program. The agreement will continue on a country-by-country basis until the Product is commercially available in that country. 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. The next potential milestone relating to this agreement is a $3.0 million payment, payable if and when the Company is able to successfully demonstrate proof of concept, as defined by the BMS License Agreement, in a Phase 2 clinical trial or if and when the Company initiates a Phase 3 clinical trial. If the milestone is triggered on the initiation of a Phase 3 clinical trial, the amount payable increases by $5.0 million. 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, 2019. 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. 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, 2019
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, the 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, 2019, 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, 2019, 2018 and 2017, the Company recognized $0.1 million, $0.1 million and $44,000 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, 2019, 2018 and 2017. 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, 2017, upon the successful completion of the Phase 2 trials, the development milestone was achieved and the Company paid the related milestone payment of $0.1 million to each of the Sellers.

Sale of Assets

Sale of Assets	12 Months Ended
	Dec. 31, 2019
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 $2.85 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 $1.35 million or the aggregate fair market value of the Option Shares as of the date of the receipt 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 20 th The Company has determined that the sale of the MYDICAR assets qualify as an asset sale and not a business. During the year ended December 31, 2017, the Company received a cash payment of $0.2 million, which was recognized as other (expense) income, net in the consolidated statement of operations. 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. As of December 31, 2019, there was no change in the fair value of the Company’s equity investment in Theragene.

Debt

Debt	12 Months Ended
	Dec. 31, 2019
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). 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 The Oxford Loan bears interest at a floating rate per annum equal to the greater of either the 30-day U.S. Dollar LIBOR reported in the Wall Street Journal plus 6.41% or 6.95%. The interest only period for borrowed funds is until February 1, 2019, followed by 30 equal monthly payments of principal plus accrued interest. 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 $1.9 million. In addition, at the time of final payment of Tranche B, the Company is required to pay an additional exit fee of $0.1 million. The Company recorded as a liability and debt discount the exit fee at the origination of the term loan. In addition, the Company incurred loan origination fees and debt issuance costs of $0.4 million which were recorded as a direct deduction from the carrying amount of the related debt liability as a debt discount. 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) will be available to the Company upon the latest to occur of (i) achievement of positive lonafarnib Phase 3 HDV topline data sufficient to file new drug application (Clinical Milestone) and (ii) January 1, 2021. The Amended Oxford Loan bears interest at a floating rate per annum equal to the greater of either the 30-day U.S. Dollar LIBOR reported in the Wall Street Journal plus 6.64% or 9.15%. The Amended Oxford Loan has an interest only period until April 1, 2021, followed by 36 equal monthly payments of principal and interest. Upon the receipt of Amended Tranche B, the interest only period for borrowed funds will be extended by one year until April 1, 2022, followed by 24 equal monthly payments of principal plus accrued interest. 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 term 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, 2019, the Company did not meet a customary affirmative reporting covenant. In March 2020, the Company received a full waiver for such breach from Oxford. 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, 2019 2018 Face value of long term debt $ 30,000 $ 25,000 Exit fee 3,277 1,960 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (2,887 ) (1,340 ) Long term debt, net $ 30,390 $ 25,620 As of December 31, 2019, future minimum payments of principal, exit fee and interest expense under the Oxford Loan were as follows (in thousands): Year ending December 31, 2020 $ 2,790 2021 10,051 2022 11,662 2023 10,734 2024 5,816 Total future payments 41,053 Less: unamortized interest (7,776 ) Less: exit fee (2,887 ) Face value of term loan $ 30,390

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
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, 2019, no dividends had been declared by the Board of Directors. On April 17, 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 Eiger’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. The Company had reserved shares of common stock for issuance as follows: December 31, 2019 2018 Options issued and outstanding 2,767,617 1,996,211 Options available for future grants 823,598 755,337 Total 3,591,215 2,751,548

Equity Incentive Plans

Equity Incentive Plans	12 Months Ended
	Dec. 31, 2019
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. The following table summarizes stock option activity under both the Company’s stock-based compensation plans during the year ended December 31, 2019 (in thousands, except share and per share data): Shares Available for Grant Number of Options Weighted- Average Exercise Price Per Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value Outstanding as of December 31, 2018 755,337 1,996,211 $ 11.80 7.54 $ 2,347 Additional options authorized 960,588 Granted (1,170,750 ) 1,170,750 $ 13.06 Exercised (120,921 ) $ 7.61 Forfeited or cancelled 278,423 (278,423 ) $ 15.52 Outstanding as of December 31, 2019 823,598 2,767,617 $ 12.14 7.94 $ 8,218 Vested and exercisable as of December 31, 2019 1,397,413 $ 11.90 7.15 $ 4,685 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 $14.90 as of December 31, 2019. The aggregate intrinsic value of stock options exercised in 2019, 2018 and 2017 was $0.6 million, $0.2 million and $0.1 million, respectively. During the years ended December 31, 2019, 2018 and 2017, the Company granted employee stock options for the purchase of 1,141,750, 799,500 and 579,700 shares of the Company’s common stock, respectively, with a weighted-average grant date fair value of $8.98, $7.50 and $7.66 per share, respectively. The Company records stock-based compensation on stock options by estimating the fair value of stock-based awards using the Black-Scholes option pricing model and amortizing 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, 2019 2018 2017 Expected term (in years) 5.27 - 6.08 5.27 - 6.08 5.27 - 6.08 Contractual term (in years) 10.00 9.67 - 9.84 6.00 - 10.00 Volatility 73.14% - 83.19% 84.00% - 95.00% 79.00% - 80.00% Risk free interest rate 1.42% - 2.57% 1.67% - 2.68% 1.63% - 2.23% 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). Upon adoption of ASU 2018-07, the Company elected to use 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. Modification of Stock Awards In December 2018, the Company entered into a Separation Agreement with its former Chief Financial Officer which resulted in the acceleration in the vesting of certain unvested stock options as well as the extension of the exercise period for all vested options. As a result of the modification, the Company recorded stock-based compensation expense of $0.3 million during the year ended December 31, 2018 to reflect the revised service period for the stock options and related vesting of shares that would otherwise not have vested. 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, 2019, a total of 453,831 shares are reserved for issuance under the 2013 ESPP. The Company had 404,436 shares available for future issuance under the 2013 ESPP as of December 31, 2019. During the years ended December 31, 2019 and December 31, 2018, employees purchased 15,701 shares for $0.1 million and 17,508 shares for $0.1 million, respectively, under the 2013 ESPP. Stock-Based Compensation Expense Total stock-based compensation expense recognized for options granted to employees and non-employees was as follows (in thousands): Year Ended December 31, 2019 2018 2017 Research and development $ 1,550 $ 1,500 $ 1,214 General and administrative 4,129 3,507 3,029 Total stock-based compensation expense $ 5,679 $ 5,007 $ 4,243 As of December 31, 2019, the total unrecognized compensation expense related to unvested options was $11.3 million, which the Company expects to recognize over an estimated weighted average period of 2.7 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes No provision for income taxes was recorded for the years ended December 31, 2019, 2018 and 2017. 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, 2019 2018 2017 Federal statutory income tax rate 21.00 % 21.00 % 34.00 % Change in valuation allowance (27.42 ) (26.02 ) (8.04 ) Tax credits 7.27 5.52 5.10 State income taxes, net of federal benefit 0.25 0.27 0.36 Stock-based compensation (0.89 ) (0.77 ) (1.06 ) Other, net (0.21 ) — — Change in tax law — — (30.36 ) Provision (benefit) for income taxes — % — % — % The components of the deferred tax assets and liabilities are as follows (in thousands): December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 42,761 $ 30,268 Tax credits 7,157 12,536 Depreciation and amortization 1,602 1,526 Stock-based compensation 1,912 1,524 Accruals and reserves 319 381 Lease liabilities 389 — Gross deferred tax assets 54,140 46,235 Valuation allowance (53,793 ) (46,235 ) Total deferred tax assets 347 — Deferred tax liabilities: Right-of-use assets (347 ) — Total deferred tax liabilities (347 ) — 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, 2019 and 2018. The net change in the valuation allowance for the years ended December 31, 2019 and 2018 increased by $7.6 million and $13.6 million, respectively. As of December 31, 2019, the Company had approximately $195.8 million and $24.7 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, 2019, the Company also had research and development tax credit carryforwards of approximately $30,000 and $1.5 million for federal and state purposes, respectively, available to offset future taxable income tax. If not utilized, the federal carryforwards will expire in various amounts beginning in 2038, and the state credits can be carried forward indefinitely. As of December 31, 2019, the Company also had orphan drug tax credit carryforwards of approximately $9.2 million for federal purposes available to offset future taxable income tax. If not utilized, the federal carryforwards will begin to expire in 2038. 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 August 5, 2019. Based upon this assessment, the Company experienced ownership changes on April 20, 2016 and October 18, 2018. 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, 2019, 2018 and 2017 is as follows (in thousands): Year Ended December 31, 2019 2018 2017 Balance at beginning of year $ 4,634 $ 3,218 $ 1,831 Additions based on tax positions related to prior year — (61 ) — Additions based on tax positions related to current year 2,443 1,477 1,387 Reductions based on tax positions related to prior year (3,800 ) — — Reductions based on tax positions related to current year — — — Balance at end of year $ 3,277 $ 4,634 $ 3,218 If the $3.3 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, 2019, 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 statement 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, 2019, 2018 and 2017.

Legal Matters

Legal Matters	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Legal Matters	12. 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, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	13. Commitments and Contingencies Lease Agreement 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 94306. The lease commenced on March 1, 2018 and expires in February 2023. The lease has a three-year renewal option prior to expiration; however, the Company is not reasonably assured to exercise this option. The lease includes rent escalation clauses throughout the lease term. In October 2017, the Company provided a security deposit of $0.3 million. The Company also has additional operating leases that are included in its lease accounting but are not considered significant for disclosure. The maturity of the Company’s operating lease liabilities as of December 31, 2019 and future minimum lease payments as of December 31, 2018 were as follows (in thousands): Undiscounted lease payments December 31, 2019 December 31, 2018 2019 $ — $ 593 2020 676 610 2021 674 629 2022 662 647 2023 113 109 Total undiscounted payments 2,125 $ 2,588 Less: imputed interest 271 Present value of future lease payments 1,854 Less: current portion of operating lease liabilities 534 Operating lease liabilities $ 1,320 Rent expense recognized for the Company’s operating leases was $0.6 million, $0.8 million, and $0.6 million for the years ended December 31, 2019, 2018, and 2017, 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 million for the year ended December 31, 2019. The operating cash outflows for the operating lease liabilities were $0.6 million for the year ended December 31, 2019. As of December 31, 2019, the weighted-average remaining lease term and weighted-average discount rate were 3.1 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.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Transactions	14. 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, 2019
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation 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 following 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 expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates, including those related to clinical trial accrued liabilities, stock-based compensation, operating lease liabilities and income taxes. 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.
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. For each product candidate, the Company relies on one supply chain for each of the four 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.
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. All short-term securities are carried at fair value based upon quoted market prices. Unrealized gains and losses on available-for-sale securities are excluded from earnings and are reported as a component of accumulated other comprehensive loss. The cost of available-for-sale securities sold is based on the specific-identification method .
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 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, 2019, the Company has not impaired any long-lived assets.
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 expense in the consolidated statements of operations. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers. The Company makes judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities.
Leases	Leases The Company has a real estate lease for its office space in Palo Alto, California. The Company determines the initial classification and measurement of its right-of-use assets (ROU assets) and lease liabilities at the lease commencement date and thereafter if modified. The lease term includes any renewal options and termination options that the Company is reasonably assured to exercise. The present value of lease payments is determined by using the interest rate implicit in the lease, if that rate is readily determinable; otherwise, the Company uses its incremental borrowing rate. The incremental borrowing rate is determined by using the rate of interest that the Company would pay to borrow on a collateralized basis an amount equal to the lease payments for a similar term and in a similar economic environment. Rent expense for operating leases is recognized on a straight-line basis, unless the operating lease ROU assets have been impaired, over the reasonably assured lease term based on the total lease payments and is included in operating expenses in the 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 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 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 expense.
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, 2019 2018 2017 Options to purchase common stock 2,767,617 1,996,211 1,467,051 Warrants to purchase common stock — — 10,180 Total 2,767,617 1,996,211 1,477,231
Immaterial Error Correction	Immaterial Error Correction In connection with the preparation of the consolidated statements of operations for the year ended December 31, 2019, the Company identified immaterial errors in the calculation of number of d, for the year ended December 31, 2018, resulting in an overstatement in the weighted average common shares outstanding and an understatement in the net loss per share, basic and diluted Year Ended December 31, 2018 As Reported Adjustment As Revised Weighted average common shares outstanding, basic and diluted 13,711,034 (76,882 ) 13,634,152 Net loss per share, basic and diluted $ (3.82 ) $ (0.02 ) $ (3.84 )
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-02, Leases (Topic 842), Targeted Improvements to Leases (Topic 842) Codification Improvements to Leases (Topic 842) Codification Improvements to Leases (Topic 842) In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes
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. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) The Company is currently in the process of evaluating the impact the standard will have on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
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 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, 2019 2018 2017 Options to purchase common stock 2,767,617 1,996,211 1,467,051 Warrants to purchase common stock — — 10,180 Total 2,767,617 1,996,211 1,477,231
Schedule of Error Corrections and Prior Period Adjustments	In connection with the preparation of the consolidated statements of operations for the year ended December 31, 2019, the Company identified immaterial errors in the calculation of number of d, for the year ended December 31, 2018, resulting in an overstatement in the weighted average common shares outstanding and an understatement in the net loss per share, basic and diluted Year Ended December 31, 2018 As Reported Adjustment As Revised Weighted average common shares outstanding, basic and diluted 13,711,034 (76,882 ) 13,634,152 Net loss per share, basic and diluted $ (3.82 ) $ (0.02 ) $ (3.84 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 35,854 $ — $ — $ 35,854 Corporate debt securities — 16,644 — 16,644 Commercial paper — 7,457 — 7,457 U.S. government bonds — 31,520 — 31,520 Total $ 35,854 $ 55,621 $ — $ 91,475 December 31, 2018 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 45,441 $ — $ — $ 45,441 Corporate debt securities — 23,474 — 23,474 Commercial paper — 15,617 — 15,617 Total $ 45,441 $ 39,091 $ — $ 84,532
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, 2019 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 35,854 $ — $ — $ 35,854 Total cash equivalents $ 35,854 $ — $ — $ 35,854 Debt securities: Corporate debt securities $ 16,633 $ 11 $ — $ 16,644 Commercial paper 7,457 — — 7,457 U.S. government bonds 31,489 31 — 31,520 Total debt securities $ 55,579 $ 42 $ — $ 55,621 December 31, 2018 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 45,441 $ — $ — $ 45,441 Total cash equivalents $ 45,441 $ — $ — $ 45,441 Debt securities: Corporate debt securities $ 23,489 $ 1 $ (16 ) $ 23,474 Commercial paper 15,627 — (10 ) 15,617 Total debt securities $ 39,116 $ 1 $ (26 ) $ 39,091

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment	Property and equipment, net consist of the following (in thousands): December 31, 2019 2018 Computer equipment and software $ 160 $ 138 Furniture 111 98 Leasehold improvements 61 56 Lab equipment 36 36 Construction in progress 436 — Total property and equipment 804 328 Less: accumulated depreciation (214 ) (161 ) Property and equipment, net $ 590 $ 167
Schedule of Components of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2019 2018 Contract research costs $ 5,288 $ 2,191 Contract manufacturing costs 2,510 — Compensation and related benefits 1,707 1,705 Consulting costs 97 258 Franchise tax 40 40 Other 359 — Total accrued liabilities $ 10,001 $ 4,194

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 2018 Face value of long term debt $ 30,000 $ 25,000 Exit fee 3,277 1,960 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (2,887 ) (1,340 ) Long term debt, net $ 30,390 $ 25,620
Schedule of Future Minimum Payments of Principal, Exit Fee and Interest Expense under Oxford Term Loan	As of December 31, 2019, future minimum payments of principal, exit fee and interest expense under the Oxford Loan were as follows (in thousands): Year ending December 31, 2020 $ 2,790 2021 10,051 2022 11,662 2023 10,734 2024 5,816 Total future payments 41,053 Less: unamortized interest (7,776 ) Less: exit fee (2,887 ) Face value of term loan $ 30,390

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Common Stock Reserved for Issuance	The Company had reserved shares of common stock for issuance as follows: December 31, 2019 2018 Options issued and outstanding 2,767,617 1,996,211 Options available for future grants 823,598 755,337 Total 3,591,215 2,751,548

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	12 Months Ended
	Dec. 31, 2019
Stock Option Activity	The following table summarizes stock option activity under both the Company’s stock-based compensation plans during the year ended December 31, 2019 (in thousands, except share and per share data): Shares Available for Grant Number of Options Weighted- Average Exercise Price Per Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value Outstanding as of December 31, 2018 755,337 1,996,211 $ 11.80 7.54 $ 2,347 Additional options authorized 960,588 Granted (1,170,750 ) 1,170,750 $ 13.06 Exercised (120,921 ) $ 7.61 Forfeited or cancelled 278,423 (278,423 ) $ 15.52 Outstanding as of December 31, 2019 823,598 2,767,617 $ 12.14 7.94 $ 8,218 Vested and exercisable as of December 31, 2019 1,397,413 $ 11.90 7.15 $ 4,685
Summary of Non-cash Stock Based Compensation Expense	Total stock-based compensation expense recognized for options granted to employees and non-employees was as follows (in thousands): Year Ended December 31, 2019 2018 2017 Research and development $ 1,550 $ 1,500 $ 1,214 General and administrative 4,129 3,507 3,029 Total stock-based compensation expense $ 5,679 $ 5,007 $ 4,243
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, 2019 2018 2017 Expected term (in years) 5.27 - 6.08 5.27 - 6.08 5.27 - 6.08 Contractual term (in years) 10.00 9.67 - 9.84 6.00 - 10.00 Volatility 73.14% - 83.19% 84.00% - 95.00% 79.00% - 80.00% Risk free interest rate 1.42% - 2.57% 1.67% - 2.68% 1.63% - 2.23% Dividend yield — — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 2018 2017 Federal statutory income tax rate 21.00 % 21.00 % 34.00 % Change in valuation allowance (27.42 ) (26.02 ) (8.04 ) Tax credits 7.27 5.52 5.10 State income taxes, net of federal benefit 0.25 0.27 0.36 Stock-based compensation (0.89 ) (0.77 ) (1.06 ) Other, net (0.21 ) — — Change in tax law — — (30.36 ) Provision (benefit) for income taxes — % — % — %
Components of Deferred Tax Assets and Liabilities	The components of the deferred tax assets and liabilities are as follows (in thousands): December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 42,761 $ 30,268 Tax credits 7,157 12,536 Depreciation and amortization 1,602 1,526 Stock-based compensation 1,912 1,524 Accruals and reserves 319 381 Lease liabilities 389 — Gross deferred tax assets 54,140 46,235 Valuation allowance (53,793 ) (46,235 ) Total deferred tax assets 347 — Deferred tax liabilities: Right-of-use assets (347 ) — Total deferred tax liabilities (347 ) — 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, 2019, 2018 and 2017 is as follows (in thousands): Year Ended December 31, 2019 2018 2017 Balance at beginning of year $ 4,634 $ 3,218 $ 1,831 Additions based on tax positions related to prior year — (61 ) — Additions based on tax positions related to current year 2,443 1,477 1,387 Reductions based on tax positions related to prior year (3,800 ) — — Reductions based on tax positions related to current year — — — Balance at end of year $ 3,277 $ 4,634 $ 3,218

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
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, 2019 and future minimum lease payments as of December 31, 2018 were as follows (in thousands): Undiscounted lease payments December 31, 2019 December 31, 2018 2019 $ — $ 593 2020 676 610 2021 674 629 2022 662 647 2023 113 109 Total undiscounted payments 2,125 $ 2,588 Less: imputed interest 271 Present value of future lease payments 1,854 Less: current portion of operating lease liabilities 534 Operating lease liabilities $ 1,320

Description of Business - Addit

Description of Business - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)Segment	Dec. 31, 2018USD ($)
Description Of Business [Line Items]
Entity incorporation, date of incorporation	Nov. 6, 2008
Number of operating segments | Segment	1
Cash, Cash Equivalents, and Investments	$ 95,000
Cash and cash equivalents	39,373	$ 61,262
Debt securities, available-for-sale	55,621	39,091
Accumulated deficit	(241,449)	$ (171,197)
Amended Oxford Loan [Member]
Description Of Business [Line Items]
Loan agreement, remaining borrowing capacity	$ 5,000

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019USD ($)SupplyChainProductCandidate	Jan. 01, 2019USD ($)
Significant Accounting Policies [Line Items]
Impairment of long-lived assets	$ 0
Interest charged in relation to unrecognized tax benefits	0
Penalties charged in relation to unrecognized tax benefits	0
Operating lease right-of-use assets	1,654,000
Operating lease liabilities	$ 1,854,000
ASU 2016-02 [Member]
Significant Accounting Policies [Line Items]
Operating lease right-of-use assets		$ 2,000,000
Operating lease liabilities		$ 2,200,000
Supplier Concentration Risk [Member]
Significant Accounting Policies [Line Items]
Concentration risk, supplier	For each product candidate, the Company relies on one supply chain for each of the four 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
Number of product candidates. | ProductCandidate	4

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, 2019
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

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	2,767,617	1,996,211	1,477,231
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities			10,180
Options Granted to Employees and Non Employees [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	2,767,617	1,996,211	1,467,051

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Schedule of Error Corrections and Prior Period Adjustments (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted-average common shares outstanding, basic and diluted	22,785,611	13,634,152	8,727,935
Net loss per common share, basic and diluted	$ (3.08)	$ (3.84)	$ (4.86)
As Reported [Member]
Weighted-average common shares outstanding, basic and diluted		13,711,034
Net loss per common share, basic and diluted		$ (3.82)
Adjustment [Member]
Weighted-average common shares outstanding, basic and diluted		(76,882)
Net loss per common share, basic and diluted		$ (0.02)

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 91,475,000	$ 84,532,000
Financial liabilities	0	0
Transfers between levels	0	0
Other-than-temporary impairment losses	$ 0
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available- for-sale of debt securities contractual maturity	1 year
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 0	0
Financial liabilities	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Financial Assets:
Assets, Fair Value	$ 91,475,000	$ 84,532,000
Corporate Debt Securities [Member]
Financial Assets:
Assets, Fair Value	16,644,000	23,474,000
U S Government Bonds [Member]
Financial Assets:
Assets, Fair Value	31,520,000
Money Market Funds [Member]
Financial Assets:
Assets, Fair Value	35,854,000	45,441,000
Commercial Paper [Member]
Financial Assets:
Assets, Fair Value	7,457,000	15,617,000
Level 1 [Member]
Financial Assets:
Assets, Fair Value	35,854,000	45,441,000
Level 1 [Member] | Money Market Funds [Member]
Financial Assets:
Assets, Fair Value	35,854,000	45,441,000
Level 2 [Member]
Financial Assets:
Assets, Fair Value	55,621,000	39,091,000
Level 2 [Member] | Corporate Debt Securities [Member]
Financial Assets:
Assets, Fair Value	16,644,000	23,474,000
Level 2 [Member] | U S Government Bonds [Member]
Financial Assets:
Assets, Fair Value	31,520,000
Level 2 [Member] | Commercial Paper [Member]
Financial Assets:
Assets, Fair Value	7,457,000	15,617,000
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, 2019	Dec. 31, 2018
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	$ 35,854	$ 45,441
Cash equivalents, Estimated Fair Value	35,854	45,441
Debt securities, Amortized cost	55,579	39,116
Debt securities, Unrealized gain	42	1
Debt securities, Unrealized loss		(26)
Debt securities, Estimated Fair Value	55,621	39,091
Corporate Debt Securities [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	16,633	23,489
Debt securities, Unrealized gain	11	1
Debt securities, Unrealized loss		(16)
Debt securities, Estimated Fair Value	16,644	23,474
U S Government Bonds [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	31,489
Debt securities, Unrealized gain	31
Debt securities, Estimated Fair Value	31,520
Money Market Funds [Member]
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	35,854	45,441
Cash equivalents, Estimated Fair Value	35,854	45,441
Commercial Paper [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	7,457	15,627
Debt securities, Unrealized loss		(10)
Debt securities, Estimated Fair Value	$ 7,457	$ 15,617

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 804	$ 328
Property and equipment, accumulated depreciation	(214)	(161)
Property and equipment, net	590	167
Lab Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	36	36
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	160	138
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	111	98
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	61	$ 56
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 436

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Depreciation [Abstract]
Depreciation expense	$ 68	$ 54	$ 41

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Components of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Contract research costs	$ 5,288	$ 2,191
Contract manufacturing costs	2,510
Compensation and related benefits	1,707	1,705
Consulting costs	97	258
Franchise tax	40	40
Other	359
Total accrued liabilities	$ 10,001	$ 4,194

License, Collaboration, and P_2

License, Collaboration, and Product Development Agreements - Additional Information (Detail) - USD ($)	Nov. 07, 2018	Aug. 11, 2018	May 15, 2018	Apr. 20, 2016	May 31, 2015	Sep. 30, 2010	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development							$ 51,791,000	$ 37,091,000	$ 29,519,000
Weighted-average period for recognition (in years)							2 years 8 months 12 days
Aggregate fair value of shares issued							$ 24,000	$ 19,000
Common stock, shares issued							24,523,381	19,211,759
Common Stock [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sale of common stock							5,175,000	8,510,918	2,143,525
UPenn/CHOP Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-Refundable Issue Fee							$ 1,000,000
Milestone payment obligations							0
UPenn/CHOP Agreement [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License maintenance fee							2,500,000
UPenn/CHOP Agreement [Member] | Commercial Sales [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations							18,000,000
IQVIA General Services Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Professional services fees	$ 14,200,000
Pass through and miscellaneous expense	$ 12,200,000
Termination of agreement notice period	45 days
Product Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Product development fees		$ 10,000,000
Expert consultant fees and pass through costs		800,000
Incentive-based regulatory milestone fees		$ 1,000,000
Number of common stock issued subject to quarterly vesting requirements		115,526
Product agreement termination notice period		90 days
Research and development							200,000
Unrecognised compensation expense related to unvested restricted shares							$ 500,000
Weighted-average period for recognition (in years)							2 years 3 months 18 days
Progeria Research Foundation (PRF) Collaboration Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development			$ 2,000,000
Collaboration agreement initial term			10 years
Collaboration agreement subsequent renewal terms			2 years
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				$ 3,200,000
BMS Transaction [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment				2,000,000
BMS Transaction [Member] | Commercial Sales [Member] | Maximum [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations				128,000,000
BMS Transaction [Member] | Development and Regulatory Milestones [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations				61,000,000
BMS Transaction [Member] | Development Phase 2 [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations				3,000,000
BMS Transaction [Member] | Development Phase 3 [Member] | Maximum [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase in milestone payment obligations				$ 5,000,000
Merck Transaction [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate fair value of shares issued						$ 500,000
Common stock, shares issued						27,350
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.
Milestone payments					$ 1,000,000		$ 0
Merck Transaction [Member] | Development [Member] | Maximum [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payment obligations						$ 27,000,000

Asset Purchase Agreements and_2

Asset Purchase Agreements and Related License Agreements - Additional Information (Detail) - USD ($)	Mar. 22, 2016	Sep. 30, 2015	Dec. 31, 2010	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Asset Purchase Agreement And Related License Agreement [Line Items]
Compensation expense related to the time-vested/milestone vested options				$ 5,679,000	$ 5,007,000	$ 4,243,000
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			$ 400,000
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			$ 500,000
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		$ 200,000
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				$ 100,000	$ 100,000	44,000
License agreement milestone payments paid						$ 100,000
Avexitide Purchase Agreement [Member] | Maximum [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Aggregate potential milestone payments		$ 1,000,000

Sale of Assets - Additional Inf

Sale of Assets - Additional Information (Detail) - MYDICAR [Member] - Theragene Pharmaceuticals, Inc. [Member] - Disposal Group Not Discontinued Operations [Member] - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2017	Dec. 31, 2019	Dec. 31, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Cash payment received for sale of assets under asset purchase agreement	$ 200,000
Sale of assets number of common stock shares received	475,000		475,000
Maximum cumulative cash proceeds of counter party for issuance of additional shares	$ 4,000,000
Maximum consideration per share of counter party for issuance of additional shares	$ 6
Aggregate common stock consideration value	$ 2,850,000
Shares repurchase by counterparty based on exercise of put options	225,000
Put options outstanding			225,000
Cost method investment with carrying value			$ 0
Change in fair value of equity investment		$ 0
Other Income (Expense), Net [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Cash payment received for sale of assets under asset purchase agreement			$ 200,000
Maximum [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Asset purchase agreement contingent consideration receivable	$ 45,000,000
Royalty receivable percentage on net sales	8.00%
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	$ 1,350,000

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Mar. 05, 2019	Aug. 03, 2018	May 31, 2018	Dec. 31, 2016
Debt Instrument [Line Items]
Face value of term loan	$ 30,000,000	$ 25,000,000
Loan final repayment exit fees payable	$ 3,277,000	$ 1,960,000
Loan agreement, covenant noncompliance penalty	5.00%
Loan agreement, covenant description	The loan includes customary events of default, including failure to pay amounts due, breaches of covenants and warranties, material adverse effect events, certain cross defaults and judgments, and insolvency. If the Company is unable to comply with these covenants or if the Company defaults on any portion of the outstanding borrowings, the lenders can also impose a 5.0% penalty, restrict access to additional borrowings under the loan and security agreement, and accelerate the maturity of the debt.
Loan agreement, covenant compliance	As of December 31, 2019, the Company did not meet a customary affirmative reporting covenant. In March 2020, the Company received a full waiver for such breach from Oxford.
Oxford Loan [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity						$ 25,000,000
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 6.41% or 6.95%.
Principal and interest payment period		30 months
Percentage of exit fee on principal balance	7.50%
Loan final repayment exit fees payable		$ 1,900,000
Loan origination fees and debt issuance costs						400,000
Repayments of loan agreement exit fee	$ 900,000
Oxford Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Loan agreement, interest rate		6.95%
Oxford Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Loan agreement, percentage to be added to the interest rate under condition		6.41%
Oxford Loan [Member] | Tranche A [Member]
Debt Instrument [Line Items]
Face value of term loan						$ 15,000,000
Oxford Loan [Member] | Tranche B [Member]
Debt Instrument [Line Items]
Loan final repayment exit fees payable	100,000
Oxford Loan [Member] | Amended Tranche A [Member]
Debt Instrument [Line Items]
Face value of term loan	30,390,000
Loan final repayment exit fees payable	$ 2,887,000
Amendment [Member] | Amended Tranche B [Member]
Debt Instrument [Line Items]
Face value of term loan					$ 5,000,000
Amendment [Member] | Tranche C [Member]
Debt Instrument [Line Items]
Face value of term loan				$ 5,000,000
Amended Oxford Loan [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity			$ 35,000,000
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%.
Principal and interest payment period	36 months
Percentage of exit fee on principal balance	7.50%
Loan final repayment exit fees payable	$ 2,300,000
Loan origination fees and debt issuance costs	$ 200,000
Loan, maturity period	Mar. 1, 2024
Loan outstanding			23,300,000
Borrowings from loan agreement	$ 6,700,000
Loan agreement, remaining borrowing capacity	5,000,000
Loan final repayment additional exit fees payable	$ 1,000,000
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] | Minimum [Member]
Debt Instrument [Line Items]
Loan agreement, interest rate	9.15%
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 B [Member]
Debt Instrument [Line Items]
Principal and interest payment period	24 months
Loan agreement, remaining borrowing capacity			5,000,000
Extended term of interest only payment period	1 year
Amended Oxford Loan [Member] | Amended Tranche A [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity			$ 30,000,000
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

Debt - Schedule of Long-Term De

Debt - Schedule of Long-Term Debt and Unamortized Discount Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Disclosure [Abstract]
Face value of long term debt	$ 30,000	$ 25,000
Exit fee	3,277	1,960
Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees	(2,887)	(1,340)
Long term debt, net	$ 30,390	$ 25,620

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, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Less: exit fee	$ (3,277)	$ (1,960)
Face value of term loan	30,000	25,000
Oxford Loan [Member]
Debt Instrument [Line Items]
Less: exit fee		$ (1,900)
Oxford Loan [Member] | Amended Tranche A [Member]
Debt Instrument [Line Items]
2020	2,790
2021	10,051
2022	11,662
2023	10,734
2024	5,816
Total future payments	41,053
Less: unamortized interest	(7,776)
Less: exit fee	(2,887)
Face value of term loan	$ 30,390

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Apr. 17, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividends declared		$ 0
Proceeds from issuance of common stock upon public offering, net of issuance costs		$ 53,194,000	$ 90,642,000	$ 19,800,000
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		5,175,000	8,510,918	2,143,525
Underwriting Agreement [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Proceeds from issuance of common stock upon public offering, net of issuance costs	$ 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, 2019	Dec. 31, 2018
Equity [Abstract]
Options issued and outstanding	2,767,617	1,996,211
Options available for future grants	823,598	755,337
Total	3,591,215	2,751,548

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Closing price of common stock	$ 14.90
Aggregate intrinsic value of options exercised	$ 600	$ 200	$ 100
Stock options granted	1,170,750
Expected dividend yield	0.00%
Stock-based compensation	$ 5,679	$ 5,007	4,243
Common Stock Reserved for Issuance	3,591,215	2,751,548
Number of additional shares authorized	960,588
Options available for future grants	823,598	755,337
Issuance of common stock upon ESPP purchase	$ 130	$ 96	$ 142
Total unrecognized compensation expense	$ 11,300
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]
Stock options granted	1,141,750	799,500	579,700
Weighted-average grant date fair value of employee option grants	$ 8.98	$ 7.50	$ 7.66
Grant date fair value of employee options vested	5,700,000	4,700,000	5,000,000
Non-Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options granted	29,000	68,000	72,500
Modification of Stock Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation		$ 300
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	3,479,273
2013 Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common Stock Reserved for Issuance	453,831			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	404,436
Issuance of common stock upon ESPP purchase, Shares	15,701	17,508
Issuance of common stock upon ESPP purchase	$ 100	$ 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, 2019, a total of 453,831 shares are reserved for issuance under the 2013 ESPP. The Company had 404,436 shares available for future issuance under the 2013 ESPP as of December 31, 2019. During the years ended December 31, 2019 and December 31, 2018, employees purchased 15,701 shares for $0.1 million and 17,508 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, 2019	Dec. 31, 2018
Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Exercise Price And Additional Disclosures [Abstract]
Shares Available for Grant, Outstanding, Beginning balance	755,337
Shares Available for Grant, Additional options authorized	960,588
Shares Available for Grant, Granted	(1,170,750)
Shares Available for Grant, Forfeited or cancelled	278,423
Shares Available for Grant, Outstanding, Ending balance	823,598	755,337
Number of Options, Outstanding, Beginning balance	1,996,211
Number of Options, Granted	1,170,750
Number of Options, Exercised	(120,921)
Number of Options, Forfeited or cancelled	(278,423)
Number of Options, Outstanding, Ending balance	2,767,617	1,996,211
Number of Options, Vested and exercisable	1,397,413
Weighted Average Exercise Price Per Option, Outstanding, Beginning balance	$ 11.80
Weighted Average Exercise Price Per Option, Granted	13.06
Weighted Average Exercise Price Per Option, Exercised	7.61
Weighted Average Exercise Price Per Option, Forfeited or cancelled	15.52
Weighted Average Exercise Price Per Option, Outstanding, Ending balance	12.14	$ 11.80
Weighted Average Exercise Price Per Option, Vested and exercisable	$ 11.90
Weighted Average Remaining Contractual Life, Ending balance	7 years 11 months 8 days	7 years 6 months 14 days
Weighted Average Remaining Contractual Life, Vested and exercisable	7 years 1 month 24 days
Aggregate Intrinsic Value	$ 8,218	$ 2,347
Aggregate Intrinsic Value, Vested and exercisable	$ 4,685

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, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)	7 years 11 months 8 days	7 years 6 months 14 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 3 months 7 days	5 years 3 months 7 days
Employees Stock Option [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days
Non-Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)	10 years
Non-Employees Stock Option [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)		9 years 8 months 1 day	6 years
Non-Employees Stock Option [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (in years)		9 years 10 months 2 days	10 years
Employees and Non Employees Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Volatility, minimum	73.14%	84.00%	79.00%
Volatility, maximum	83.19%	95.00%	80.00%
Risk free interest rate, minimum	1.42%	1.67%	1.63%
Risk free interest rate, maximum	2.57%	2.68%	2.23%

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Non-cash Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 5,679	$ 5,007	$ 4,243
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	1,550	1,500	1,214
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total stock-based compensation expense	$ 4,129	$ 3,507	$ 3,029

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Provision for income taxes	$ 0	$ 0	$ 0
Valuation allowance	7,600,000	13,600,000
Tax credits	9,200,000
Unrecognized tax benefits impact on effective tax rate	3,300,000
Accrued interest and penalties associated with uncertain tax positions	0	$ 0	$ 0
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 195,800,000
Operating loss carryforwards expiration year	2030
Tax credits	$ 30,000
Federal [Member] | Research and Development Tax Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credits expiration year	2038
Federal [Member] | Orphan Drug Tax Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credits expiration year	2038
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 24,700,000
Operating loss carryforwards expiration year	2028
Tax credits	$ 1,500,000

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%	34.00%
Change in valuation allowance	(27.42%)	(26.02%)	(8.04%)
Tax credits	7.27%	5.52%	5.10%
State income taxes, net of federal benefit	0.25%	0.27%	0.36%
Stock-based compensation	(0.89%)	(0.77%)	(1.06%)
Other, net	(0.21%)
Change in tax law			(30.36%)
Provision (benefit) for income taxes	0.00%	0.00%	0.00%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss carryforwards	$ 42,761	$ 30,268
Tax credits	7,157	12,536
Depreciation and amortization	1,602	1,526
Stock-based compensation	1,912	1,524
Accruals and reserves	319	381
Lease liabilities	389
Gross deferred tax assets	54,140	46,235
Valuation allowance	(53,793)	(46,235)
Total deferred tax assets	347
Deferred tax liabilities:
Right-of-use assets	(347)
Total deferred tax liabilities	(347)
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, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 4,634	$ 3,218	$ 1,831
Additions based on tax positions related to prior year		(61)
Additions based on tax positions related to current year	2,443	1,477	1,387
Reductions based on tax positions related to prior year	(3,800)
Balance at end of year	$ 3,277	$ 4,634	$ 3,218

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2017USD ($)ft²	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)
Other Commitments [Line Items]
Rent expense recognized for company's operating leases		$ 0.6	$ 0.8	$ 0.6
Variable lease payments for operating leases		0.1
Operating cash outflows for operating lease liabilities		$ 0.6
Weighted-average remaining lease term		3 years 1 month 6 days
Weighted-average discount rate		9.15%
Palo Alto, California [Member]
Other Commitments [Line Items]
Total leased space | ft²	8,029
Lease commencement date	Mar. 1, 2018
Long-term operating lease expiry period month and year	2023-02
Lease renewal term	3 years
Security deposit of collateral for lease	$ 0.3

Commitments and Contingencies_2

Commitments and Contingencies - Maturity of Operating Leases Liabilities and Future Minimum Lease Payments (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Operating leases minimum payments, 2020	$ 676
Operating leases minimum payments, 2021	674
Operating leases minimum payments, 2022	662
Operating leases minimum payments, 2023	113
Total undiscounted payments	2,125
Less: imputed interest	271
Present value of future lease payments	1,854
Less: current portion of operating lease liabilities	534
Operating lease liabilities	$ 1,320
Future minimum lease payments, 2019		$ 593
Future minimum lease payments, 2020		610
Future minimum lease payments, 2021		629
Future minimum lease payments, 2022		647
Future minimum lease payments, 2023		109
Total minimum payments		$ 2,588