Eiger BioPharmaceuticals (EIGRQ) 10-K 14 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2018	Mar. 11, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
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	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		19,260,443
Entity Public Float			$ 122,624,067

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 61,262	$ 32,035
Debt securities, available-for-sale	39,091	9,744
Prepaid expenses and other current assets	1,492	712
Total current assets	101,845	42,491
Property and equipment, net	167	79
Other assets	436	312
Total assets	102,448	42,882
Current liabilities:
Accounts payable	5,830	3,183
Accrued liabilities	4,194	2,084
Current portion of long term debt		2,002
Total current liabilities	10,024	7,269
Long term debt, net	25,620	13,091
Other long term liabilities	212
Total liabilities	35,856	20,360
Commitments and contingencies (Note 15)
Stockholders’ equity:
Common stock, $0.001 par value, 200,000,000 shares authorized as of December 31, 2018 and 2017; 19,211,759 and 10,526,599 shares issued and outstanding as of December 31, 2018 and 2017, respectively	19	11
Additional paid-in capital	237,795	141,320
Accumulated other comprehensive loss	(25)	(3)
Accumulated deficit	(171,197)	(118,806)
Total stockholders’ equity	66,592	22,522
Total liabilities and stockholders’ equity	$ 102,448	$ 42,882

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
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	19,211,759	10,526,599
Common stock, shares outstanding	19,211,759	10,526,599

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating expenses:
Research and development	$ 37,091	$ 29,519	$ 33,014
General and administrative	13,956	12,001	13,106
Total operating expenses	51,047	41,520	46,120
Loss from operations	(51,047)	(41,520)	(46,120)
Interest expense	(2,329)	(1,524)	(690)
Interest income	997	410	97
Other (expense) income, net	(12)	186	(374)
Net loss	$ (52,391)	$ (42,448)	$ (47,087)
Net loss per common share, basic and diluted	$ (3.82)	$ (4.86)	$ (7.84)
Weighted-average common shares outstanding, basic and diluted	13,711,034	8,727,935	6,007,027

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (52,391)	$ (42,448)	$ (47,087)
Other comprehensive loss:
Unrealized (loss) gain on available-for-sale debt securities, net	(22)	12	(15)
Comprehensive loss	$ (52,413)	$ (42,436)	$ (47,102)

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Eiccose LLC [Member]	Convertible Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member]Eiccose LLC [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member]Eiccose LLC [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2015	$ (5,152)					$ 1,552			$ (29,271)
Preferred stock, Beginning balance, Shares at Dec. 31, 2015			2,609,102
Preferred stock, Beginning balance at Dec. 31, 2015			$ 22,567
Beginning Balance, Shares at Dec. 31, 2015				273,993
Issuance of common stock upon private placement, net of $1,300 of issuance cost	32,108			$ 2		32,106
Issuance of common stock upon private placement, net of $1,300 of issuance cost, Shares				1,954,390
Issuance of common stock upon conversion of convertible promissory note	6,129					6,129
Issuance of common stock upon conversion of convertible promissory note, Shares				350,040
Issuance of common stock upon exercise of warrants	1,057					1,057
Issuance of common stock upon exercise of warrants, Shares				61,254
Issuance of common stock to Eiccose upon private placement		$ 1,661					$ 1,661
Issuance of common stock to Eiccose upon private placement, Shares					96,300
Conversion of preferred stock into common stock			$ (22,567)	$ 3		22,564
Conversion of preferred stock into common stock, Shares			(2,609,102)	2,609,102
Issuance of common stock upon reverse merger	27,390			$ 2		27,388
Issuance of common stock upon reverse merger, Shares				1,596,959
Issuance of common stock upon execution of license agreement	3,172					3,172
Issuance of common stock upon execution of license agreement, Shares				157,587
Issuance of stock	18,229			$ 1		18,228
Issuance of stock, Shares				1,250,000
Issuance of common stock upon stock option exercises	39					39
Issuance of common stock upon stock option exercises, Shares				7,034
Stock-based compensation expense	3,190					3,190
Unrealized gain (loss) on debt securities, net	(15)							$ (15)
Net loss	(47,087)								(47,087)
Ending Balance at Dec. 31, 2016	40,721			$ 8		117,086		(15)	(76,358)
Ending Balance, Shares at Dec. 31, 2016				8,356,659
Issuance of stock	19,800			$ 3		19,797
Issuance of stock, 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 exercises	52					52
Issuance of common stock upon stock option exercises, Shares				10,229
Stock-based compensation expense	4,243					4,243
Unrealized gain (loss) 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			10,526,599
Issuance of stock	$ 90,642			$ 8		90,634
Issuance of stock, 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 exercises	$ 310					310
Issuance of common stock upon stock option exercises, Shares	41,208			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 (loss) 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

Consolidated Statements of St_2

Consolidated Statements of Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Private Placement [Member]
Issuance of common stock, issuance stock			$ 1,300
Initial Public Offering [Member]
Issuance of common stock, issuance stock	$ 5,357	$ 376	$ 1,800

Consolidated Statements of Cash

Consolidated Statements of Cash Flow - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating Activities
Net loss	$ (52,391)	$ (42,448)	$ (47,087)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	54	41	23
Amortization of debt securities discounts	(426)	(53)	(41)
Stock-based compensation	5,007	4,243	3,190
Non-cash interest expense	592	366	685
Gain on intellectual property sale		(200)
Issuance of common stock in connection with license, asset purchase, and product development agreements	428		3,172
Change in fair value of obligation to issue shares to Eiccose			204
Change in fair value of warrants liability			165
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(780)	(131)	326
Other non-current assets	(124)	(169)	(89)
Accounts payable	2,647	544	699
Accrued liabilities	2,110	(565)	783
Other long term liabilities	212
Net cash used in operating activities	(42,671)	(38,372)	(37,970)
Investing Activities
Purchase of debt securities available-for-sale	(57,193)	(24,524)	(34,154)
Proceeds from maturities of debt securities available-for-sale	28,250	47,025	2,000
Proceeds from intellectual property sale		200
Cash received from merger transaction			28,018
Purchase of property and equipment	(142)	(44)	(58)
Net cash (used in) provided by investing activities	(29,085)	22,657	(4,194)
Financing Activities
Proceeds from issuance of common stock upon public offering, net of issuance costs	90,642	19,800	18,229
Proceeds from borrowings in connection with term loan, net of issuance costs	9,935		14,759
Proceeds from issuance of common stock upon private placement, net of issuance costs			32,108
Proceeds from issuance of common stock upon ESPP purchase	96	142
Proceeds from issuance of common stock upon stock option exercises	310	52	39
Proceeds from issuance of common stock upon warrants exercises			7
Net cash provided by financing activities	100,983	19,994	65,142
Net increase in cash and cash equivalents	29,227	4,279	22,978
Cash and cash equivalents at beginning of period	32,035	27,756	4,778
Cash and cash equivalents at end of period	61,262	32,035	27,756
Non-cash investing and financing activities:
Conversion of warrant liability to common stock upon private placement			1,050
Issuance of common stock			3,172
Non-cash net liabilities assumed in reverse merger			671
Conversion of convertible promissory note to common stock upon private placement			6,129
Conversion of preferred stock to common stock upon reverse merger			22,567
Interest paid	$ 1,652	$ 1,038
Eiccose LLC [Member]
Non-cash investing and financing activities:
Issuance of common stock			$ 1,661

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2018
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. The Company is a clinical-stage biopharmaceutical company committed to bringing to market novel products for the treatment of rare diseases. The Company’s mission is to systematically reduce the time and cost of the drug development process to more rapidly deliver important medicines to patients with rare diseases. Lonafarnib is the Company’s lead compound advancing into 1) Phase 3 in a single, pivotal trial to treat Hepatitis Delta Virus (“HDV”) infection by the end of the year, 2) a new drug application (“NDA”) and 3) a marketing authorization application (“MAA”) for the treatment of Hutchinson-Gilford Progeria Syndrome (“HGPS” or “Progeria”) in 2019. The Company’s principal operations are based in Palo Alto, California and it operates in one segment. Liquidity As of December 31, 2018, the Company had $61.3 million of cash and cash equivalents and $39.1 million of short-term debt securities. In addition, the Company had an accumulated deficit of $171.2 million and negative cash flows from operating activities. 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 the Company’s planned operations for at least the next 12 months following the issuance date of these financial statements and through the anticipated readout of the Phase 3 D-LIVR study.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
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 subsidiary EB Pharma LLC, have been prepared in conformity with accounting principles generally accepted in the United States of America, (“U.S. GAAP”). 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 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. Short-Term 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 debt 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, 2018, 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. 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 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). Share-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 regarding subjective variables. 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 had 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, 2018 2017 2016 Options to purchase common stock 1,996,211 1,467,051 1,212,044 Warrants to purchase common stock — 10,180 10,180 Total 1,996,211 1,477,231 1,222,224 Recently Adopted Accounting Pronouncements In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments. The Company has adopted this guidance during the quarter ended March 31, 2018. The adoption of this guidance did not have a significant impact on the statement of cash flows when adopted. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718) Revenue from Contracts with Customers Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), Targeted Improvements to Leases (Topic 842) Codification Improvements to Leases (Topic 842) In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) 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, 2018
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, 2018 and 2017, 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 long term debt reflects 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, 2018 and 2017. 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, 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 December 31, 2017 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 19,612 $ — $ — $ 19,612 Corporate debt securities — 6,501 — 6,501 Commercial paper — 3,243 — 3,243 Total $ 19,612 $ 9,744 $ — $ 29,356 There were no financial liabilities as of December 31, 2018 and 2017. 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, 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 December 31, 2017 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 19,612 $ — $ — $ 19,612 Total cash equivalents $ 19,612 $ — $ — $ 19,612 Debt securities: Corporate debt securities $ 6,503 $ — $ (2 ) $ 6,501 Commercial paper 3,244 — (1 ) 3,243 Total debt securities $ 9,747 $ — $ (3 ) $ 9,744 As of December 31, 2018, 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, 2018, the Company did not recognize any impairment losses. All debt securities with unrealized losses have been in a loss position for twelve months.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2018
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, 2018 2017 Lab equipment $ 36 $ 36 Computer equipment and software 138 116 Furniture 98 34 Leasehold improvements 56 — Total property and equipment 328 186 Less: accumulated depreciation (161 ) (107 ) Property and equipment, net $ 167 $ 79 Depreciation expense for the years ended December 31, 2018, 2017 and 2016 was $54,000, $41,000 and $23,000, respectively. Accrued Liabilities Accrued liabilities consist of the following (in thousands): December 31, 2018 2017 Compensation and related benefits $ 1,705 $ 1,262 Contract research costs 2,191 634 Consulting costs 258 87 Franchise tax 40 56 Contract manufacturing costs — 4 Other — 41 Total accrued liabilities $ 4,194 $ 2,084

Reverse Merger

Reverse Merger	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Reverse Merger	5. Reverse Merger On March 22, 2016, Eiger completed the Merger with Celladon as discussed in Note 1. For accounting purposes, Eiger is considered to have acquired Celladon in the Merger. Eiger was determined to be the accounting acquirer based upon the terms of the Merger and other factors including; (i) Eiger security holders owned approximately 78% of the combined company immediately following the closing of the Merger, (ii) Eiger directors held all of the board seats in the combined company, and (iii) Eiger management held all key positions in the management of the combined company. The Merger was accounted for as an asset acquisition rather than business combination because the assets acquired and liabilities assumed by Eiger did not meet the definition of a business as defined by U.S. GAAP. The net assets acquired in connection with this transaction were recorded at their estimated acquisition date fair values as of March 22, 2016, the date the Merger with Celladon was completed. Immediately prior to the effective date of the Merger and in connection with the Private Placement, the Notes converted into shares of common stock of Eiger. Further, all of the Warrants were exercised for common stock (see Note 9) and all shares of preferred stock of Eiger converted into shares of common stock of Eiger. At the effective date of the Merger, Celladon issued shares of its common stock to Eiger stockholders, at an exchange rate of approximately 0.09 shares of common stock, after taking into account the Reverse Stock Split, in exchange for each share of Eiger common stock outstanding immediately prior to the Merger. The exchange rate was calculated by a formula that was determined through arms-length negotiations between Celladon and Eiger. The combined Company assumed all of the outstanding options, whether or not vested, under the Eiger 2009 Equity Incentive Plan (the “Eiger Plan”) with such options henceforth representing the right to purchase a number of shares of Celladon common stock equal to approximately 0.09 multiplied by the number of shares of Eiger common stock previously represented by such options. Immediately after the Reverse Stock Split and the Merger on March 22, 2016, there were 6,945,401 shares of the combined Company’s common stock outstanding. In addition, immediately after the Merger, pre-Merger Eiger stockholders, warrant holders and option holders owned approximately 78% of the aggregate number of shares of the combined Company’s common stock, and the stockholders of Celladon immediately prior to the Merger owned approximately 22% of the aggregate number of shares of the combined Company’s common stock (on a fully diluted basis). On March 22, 2016, Celladon had 1,596,959 shares of common stock outstanding and a market capitalization of $27.5 million. The estimated fair value of the net assets of Celladon on March 22, 2016 was $27.3 million. The fair value of Celladon’s common stock on the Merger closing date was above the fair value of Celladon’s net assets. As Celladon’s net assets were predominantly comprised of cash offset by current liabilities, the fair value of Celladon’s net assets as of March 22, 2016 was considered to be the best indicator of the fair value and, therefore, the estimated purchase consideration. The following table summarizes the net assets acquired based on their estimated fair values as of March 22, 2016 (in thousands): Cash and cash equivalents $ 28,018 Prepaid and other assets 198 Current liabilities (857 ) Non-current liabilities (12 ) Net acquired tangible assets 27,347 Estimated total purchase consideration $ 27,347

License, Collaboration, and Pro

License, Collaboration, and Product Development Agreements	12 Months Ended
	Dec. 31, 2018
Collaboration And License Agreements [Abstract]
License, Collaboration, and Product Development Agreements	6. License, Collaboration, and Product Development Agreements 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 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 new drug application (“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 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 the proprietary BMS molecule known as 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 License Agreement required the Company to make an upfront payment of $2.0 million in cash and issue $3.0 million in Company common stock (see below) and includes development and regulatory milestone payments totaling $61.0 million and commercial sales milestones of up to $128.0 million. The Company is obligated to pay BMS annual net sales royalties in the range of mid-single to mid-teens, depending on net sales levels. In addition, if the Company grants a sublicense, the Company is obligated to pay BMS a portion of the sublicensing income received. 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 in a Phase 2 clinical trial. The Company paid BMS an upfront payment of $2.0 million in cash in April 2016, which was charged to research and development expense in the consolidated statement of operations as there is no future alternative use for the intellectual property licensed. The Company issued BMS $3.0 million in common stock as an element of the upfront payment. The BMS Purchase Agreement provided for the issuance of 157,587 shares of common stock of the Company to BMS in consideration of the license granted to the Company under the BMS License Agreement. The BMS Purchase Agreement grants BMS certain registration rights with respect to the shares of common stock delivered, and BMS has agreed to certain trading and other restrictions with respect to the shares issued. In April 2016, the Company issued 157,587 common shares to BMS for an aggregate fair value of $3.2 million, which was charged to research and development expense in the consolidated statement of operations as there is no future alternative use for the intellectual property licensed. 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 consideration for such exclusive right, the Company issued Private Eiger convertible preferred stock with a fair value of $0.5 million when the agreement was executed in September 2010. This preferred stock was converted to 27,350 shares of common stock upon the Merger. In addition, 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. The Company’s obligation to pay royalties to Merck expires on a country-by-country and product-by-product basis on the later of the expiration of the last to expire patent assigned to the Company under the agreement, which is estimated to be on the tenth anniversary of the first commercial sale of the product. 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, 2018. 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 Progeria Research Foundation (“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. Janssen License Agreement In December 2014, the Company entered into a license agreement with Janssen Pharmaceutica NV, (“Janssen”), which provides to the Company with the exclusive worldwide license to develop, manufacture, and sell products containing the compound tipifarnib for all therapeutic and diagnostic uses in humans, including any such uses for human virology diseases, but excluding oncology diseases. The Company is responsible for the development of at least one product in a major market country and for commercialization of products in all countries where necessary authorization is obtained, at its sole cost and expense. The Company may manufacture, develop, and commercialize the products itself or grant one or more sublicenses for such purposes. However, for a period of time following completion of the proof of concept trial, Janssen has a first right of negotiation for an exclusive license back from the Company to develop and commercialize tipifarnib in any country in the world. The agreement will continue for so long as the Company owe royalty payments to Janssen under the agreement or for so long as there is a valid patent claim under the agreement, whichever is longer. In connection with this license agreement, the Company is obligated to make development milestone payments in aggregate of up to $38.0 million, sales milestone payments in aggregate up to $65.8 million 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 of net sales. As of December 31, 2018, the Company is not engaged in any product development related to this compound and does not perceive that it will pay any milestone payments in the near future.

Asset Purchase Agreements and R

Asset Purchase Agreements and Related License Agreements	12 Months Ended
	Dec. 31, 2018
Asset Purchase Agreements And Related License Agreements [Abstract]
Asset Purchase Agreements and Related License Agreements	7. 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, 2018, the product has not achieved regulatory approval. In November 2012, the Company entered into an agreement with EGI whereby the Company sold all of the assets related to the compound clemizole, including any related intellectual property. EGI will pay to the Company a high single-digit royalty on future aggregate annual net sales, subject to certain reductions and exceptions. EGI’s obligation to pay royalties expires on a country-by-country and product-by-product basis on the later of either expiration of the last to expire patent sold to EGI under the agreement or the earliest of the tenth anniversary of the first commercial sale of the product. As of December 31, 2018, 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 options 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 Dr. Tracey McLaughlin and Dr. Colleen Craig 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 share-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, 2018, 2017 and 2016, the Company recognized $0.1 million, $44,000 and $0.3 million of compensation expense related to the time-vested options, respectively. No expense was recognized for the milestone vested options during the years ended December 31, 2018, 2017 and 2016. 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. Eiccose Purchase Agreement and Related Stanford and Nippon License Agreements In October 2015, the Company entered into an asset purchase agreement with Eiccose whereby Eiccose sold all of the assets related to the treatment of pulmonary arterial hypertension (“PAH”), treatment of lymphedema and products containing ubenimex for the treatment of disorders involving LTB4, and any related intellectual property to the Company (the “Eiccose APA”). David Cory, the President, Chief Executive Officer and a director of the Company, is the sole managing member and significant equity interest holder of Eiccose. The Company made a payment to Eiccose of $0.1 million representing reimbursement of certain previously incurred expenses, including payments and accrued amounts owed to Stanford in connection with the license agreement for the treatment of Lymphedema (the “Lymphedema License Agreement”) and the license agreement for the treatment of PAH (the “PAH License Agreement”). The Eiccose APA also provided that, upon a next round of financing pursuant to which the Company sold shares of capital stock resulting in gross proceeds to the Company of at least $25.0 million, the Company would issue to Eiccose fully vested shares of the Company’s common stock equal to 1.75% of the total number of the Company’s outstanding capital stock, before Merger. In October 2015, the Company recorded $1.5 million in research and development expenses and a corresponding liability representing the fair value of the Company’s obligation to issue common stock to Eiccose. On March 22, 2016, the Company issued to Eiccose 96,300 fully vested shares of the Company’s common stock pursuant to the terms of the Eiccose APA. In connection with this transaction the Company remeasured the fair value of the obligation to issue common stock at the settlement date and the change in fair value of $0.2 million was recognized within other income (expense), net in the consolidated statement of operations during the year ended December 31, 2016. Upon the settlement of the obligation with the issuance of shares on March 22, 2016, the liability was reclassified to common stock and additional paid-in capital within stockholders’ equity. The Company is also obligated to pay to Eiccose an aggregate of up to a maximum of $10.0 million of commercial milestones in connection with future sales of the product and royalties in the low single-digits based on aggregate annual net sales following the first commercial sale of any product. In June 2017, Eiccose was disbanded. The Company’s commercial milestone obligations and sales royalties remain, however have been transferred to the previous shareholders of Eiccose. As of December 31, 2018, the product has not reached commercialization and no milestones have been paid. In June 2017, Eiccose was disbanded. The Company’s commercial milestone obligations and sales royalties remain, however have been transferred to the previous shareholders of Eiccose. In addition, as a result of this agreement, the Company has assumed the license agreements Eiccose had previously entered into. These include the PAH License Agreement, the Lymphedema License Agreement for the treatment of lymphedema and the license agreement with Nippon Kayaku Co., Ltd, (“Nippon”). As part of the agreement, Nippon is obligated to make a payment for royalties in the low single-digits of sales to the Company. In connection with the PAH License Agreement and the Lymphedema License Agreement, the Company is obligated to make development and commercial milestone payments of up to $0.5 million in the aggregate under each contract, increasing annual license maintenance fees ranging from $10,000 to $75,000 over the term of each license agreement and royalty payments in low single-digits on annual net sales after the first commercial sale of a product under each license .

Debt

Debt	12 Months Ended
	Dec. 31, 2018
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 loan matures on July 1, 2021. The Company borrowed $15.0 million in December 2016 (“Tranche A”). In May 2018, the Company entered into an amendment to the Oxford Loan (the “Amendment”) 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 Company is required to repay the Tranche A in 18 monthly interest only payments, and starting on August 1, 2018, 36 equal monthly payments of principal and interest. Upon the receipt of Amended Tranche B, the interest only period for borrowed funds was extended by six months until February 1, 2019, followed by 30 equal monthly payments of principal plus accrued interest. at the time of final payment of Amended Tranche B, the Company is required to pay an additional exit fee of $0.1 million direct deduction from the carrying amount of the related debt liability as a debt discount 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 Oxford 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 and restrict access to additional borrowings under the loan and security agreement. The Company is permitted to make voluntary prepayments of the Oxford Loan with a prepayment fee, calculated as of the loan origination date, equal to (i) 3.0% of the loan prepaid during the first 12 months, (ii) 2.0% of the loan prepaid in months 13-24 and (iii) 1.0% of the loan prepaid thereafter. 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. The Company recorded interest expense of $1.7 million, $1.1 million, and $5,000 for the years ended December 31, 2018, 2017, and 2016, respectively. Long-term debt and unamortized discount balances are as follows (in thousands): December 31, 2018 2017 Face value of long term debt $ 25,000 $ 15,000 Exit fee 1,960 1,125 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (1,340 ) (1,032 ) Total long term debt 25,620 15,093 Less: current portion of long term debt (1) — (2,002 ) Long term debt, net $ 25,620 $ 13,091 (1) As of December 31, 2018, future minimum payments of principal, exit fee and interest expense under the Oxford Loan were as follows (in thousands): Year ending December 31, 2019 $ 11,047 2020 11,002 2021 7,965 Total future payments 30,014 Less: unamortized interest (3,054 ) Less: exit fee (1,960 ) Face value of term loan $ 25,000

Convertible Promissory Note and

Convertible Promissory Note and Warrant Purchase Agreement	12 Months Ended
	Dec. 31, 2018
Disclosure Of Convertible Promissory Note And Warrant Purchase Agreement [Abstract]
Convertible Promissory Note and Warrant Purchase Agreement	9. Convertible Promissory Note and Warrant Purchase Agreement On November 12, 2015, the Company entered into a convertible note and warrant purchase agreement (the “Note and Warrant Purchase Agreement”) with three lenders under which the Company issued the Notes for an aggregate principal amount of $6.0 million and the Warrants exercisable for shares of the Company’s equity securities at a purchase price of $0.11 per share, on a post-Merger and post-Reverse Stock Split basis. The terms of the Notes included a provision whereby the Notes would be automatically converted into equity securities from a qualified financing with proceeds of at least $25.0 million. The terms of the Warrants included a provision whereby the Warrants would be automatically exercised if the Company consummated a public offering including a reverse merger (“PO”). If the PO did not occur on or prior to February 28, 2016, the warrant coverage amount was equal to 17.5% of the outstanding principal balance of the Notes. The number of warrant shares into which the Warrants could be exercised was equal to the warrant coverage amount divided by the per share price of the equity securities sold in a qualified financing for an exercise price of $0.11 per share, on a post-Merger and post-Reverse Stock Split basis. The Warrants also include a provision whereby in the event of a PO which would result in the automatic exercise of the Warrants and the automatic conversion of the Notes, the exercise price of the warrants would be paid by cancelling any unpaid interest on the Notes. Upon the closing of the Private Placement on March 22, 2016, immediately prior to the closing of the Merger, the outstanding balance of the Notes totaling approximately $6.0 million was converted into 350,040 shares of the Company’s common stock. The Warrants were exercised for 61,254 shares of the Company’s common stock. During the year ended December 31, 2016, the Company recognized a loss related to the change in fair value of the Warrants of $0.2 million. The warrant liability was reclassified to common stock and additional paid-in capital within stockholders’ equity, upon the exercise of the Warrants and issuance of shares on March 22, 2016. For the year ended December 31, 2016, the Company recognized $0.7 million related to the accrued interest and amortization of the debt discount within interest expense on the Company’s consolidated statements of operations. The discount was fully amortized upon the conversion of the Notes.

Sale of Assets

Sale of Assets	12 Months Ended
	Dec. 31, 2018
Discontinued Operations And Disposal Groups [Abstract]
Sale of Assets	10. 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 income (expense), net in the consolidated statement of operations. Concurrently with the execution of the Theragene APA, the Company became an owner of 475,000 shares of common stock of Theragene and 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, 2018, there was no change in the fair value of our equity investment in Theragene.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	1 1 . 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, 2018, no dividends had been declared by the Board of Directors. The Company had reserved shares of common stock for issuance as follows: December 31, 2018 2017 Options issued and outstanding 1,996,211 1,467,051 Options available for future grants 755,337 799,375 Warrants to purchase common stock issued and outstanding — 10,180 Total 2,751,548 2,276,606 Warrants The Company issued the Warrants in connection with the issuance of the Notes (see Note 9). As of December 31, 2015, the Company accounted for the Warrants as a liability at fair value as the number of shares were not fixed and determinable at the issuance date. The Company adjusted the liability for changes in fair value until the exercise of the Warrants in March 2016, when the number of shares to be exercised became fixed, and the Warrants were automatically exercised into common stock. The warrant liability was immediately reclassified to common stock and additional paid in capital within stockholders’ equity. The change in fair value of the warrant liability was recognized as a component of other income (expense), net in the consolidated statements of operations. The Company assumed from Celladon fully exercisable Warrants outstanding for the purchase of 10,180 shares of common stock with an exercise price of $84.15 per share. The Warrants expired in October 2018.

Stock Option Plan

Stock Option Plan	12 Months Ended
	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Option Plan	1 2 . Stock Option Plan In 2009, the Company adopted the 2009 Equity Incentive Plan or the Plan. Under the Plan, shares of the Company’s common stock have been reserved for the issuance of stock options to employees, directors, and consultants under terms and provisions established by the Board of Directors. 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 Plan may not exceed ten years. The vesting schedule of newly issued option grants is generally four years. As discussed in Note 5, the Company assumed all of the outstanding options, whether or not vested, under the Eiger Plan, with such options henceforth representing the right to purchase a number of shares of the Company’s common stock equal to approximately 0.09 multiplied by the number of shares of Eiger common stock previously represented by such options. For accounting purposes, however, the Company is deemed to have assumed the Celladon 2013 Equity Incentive Plan. Because the Company is considered to be the acquirer for accounting purposes, the pre-Merger vested stock options granted by Celladon are deemed to have been exchanged for equity awards of the Company and, as such, the portion of the acquisition date fair value of these equity awards attributable to pre-Merger service to Celladon were accounted for as a component of the consideration transferred, which was inconsequential to the consolidated financial statements. The exchange of options to purchase shares of Eiger common stock for options to purchase shares of the Combined Company, was accounted for as a modification of the awards because the legal exchange of the awards is considered a modification of Eiger stock options. The modification of the stock options did not result in any incremental compensation expense as 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”), which increased the number of shares reserved for grant by 1,296,683 shares. 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. All awards granted prior to the approval of the Restated 2013 Plan remain subject to the terms of the previous plans and the applicable award agreements. The following table summarizes stock option activity under both the Company’s stock-based compensation plans during the year ended December 31, 2018 (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, 2017 799,375 1,467,051 $ 12.70 8.41 $ 4,511 Additional options authorized 526,330 Granted (867,500 ) 867,500 $ 10.34 Exercised (41,208 ) $ 7.52 Forfeited or cancelled 297,132 (297,132 ) $ 12.63 Outstanding as of December 31, 2018 755,337 1,996,211 $ 11.80 7.54 $ 2,347 Vested and exercisable as of December 31, 2018 1,004,316 $ 12.36 6.52 $ 1,647 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 $10.16 as of December 31, 2018. The aggregate intrinsic value of stock options exercised in 2018, 2017 and 2016 was $0.2 million, $0.1 million and $0.1 million, respectively. During the years ended December 31, 2018, 2017 and 2016, the Company granted employee stock options for the purchase of 799,500, 579,700 and 902,028 shares of the Company’s common stock, respectively, with a weighted-average grant date fair value of $7.50, $7.66 and $10.40 per share, respectively. The Company records stock-based compensation of stock options granted to employees 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, 2018 2017 2016 Expected term (in years) 5.27 - 6.08 5.27 - 6.08 5.27 - 6.08 Contractual term (in years) 9.67 - 9.84 6.00 - 10.00 6.75 - 10.00 Volatility 84.00% - 95.00% 79.00% - 80.00% 73.91% - 78.00% Risk free interest rate 1.67% - 2.68% 1.63% - 2.23% 1.21% - 2.27% Dividend yield — — — Each of these inputs is subjective and generally requires judgment to determine. Fair Value of Common Stock : Prior to the Merger, the fair value of the shares of common stock underlying stock options was determined by the Company’s Board of Directors. In order to determine the fair value of the common stock at the time of grant of the option, the Board of Directors considered, among other things, valuations performed by an independent third-party. Because there was no public market for the Company’s common stock, the Board of Directors exercised reasonable judgment and considered a number of objective and subjective factors to determine the best estimate of the fair value of the Company’s common stock, including important developments in the Company’s operations, sales of convertible preferred stock, actual operating results and financial performance, the conditions in the life sciences industry and the economy in general, the stock price performance and volatility of comparable public companies, and the lack of liquidity of the Company’s common stock, among other factors. Following the Merger, the Company’s Board of Directors determined the fair value of each share of underlying common stock based on the closing price of the Company’s common stock as reported on the date of grant. 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 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. 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. 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, 2018 2017 2016 Research and development $ 1,500 $ 1,214 $ 737 General and administrative 3,507 3,029 2,453 Total stock-based compensation expense $ 5,007 $ 4,243 $ 3,190 As of December 31, 2018, the total unrecognized compensation expense related to unvested options was $8.5 million, which the Company expects to recognize over an estimated weighted average period of 2.6 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	1 3 . Income Taxes No provision for income taxes was recorded for the years ended December 31, 2018, 2017 and 2016. The Company has incurred net operating losses for all the periods presented. The Company has not reflected any benefit of such net operating loss 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, 2018 2017 2016 Federal statutory income tax rate 21.00 % 34.00 % 34.00 % Change in valuation allowance (26.02 ) (8.04 ) (36.67 ) Federal and state tax credits 5.52 5.10 4.68 State income taxes, net of federal benefit 0.27 0.36 (0.21 ) Stock-based compensation (0.77 ) (1.06 ) (1.26 ) Other, net — — (0.54 ) 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, 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 30,268 $ 20,230 Tax credits 12,536 9,514 Depreciation and amortization 1,526 1,700 Stock-based compensation 1,524 913 Accruals and reserves 381 245 Gross deferred tax assets 46,235 32,602 Valuation allowance (46,235 ) (32,602 ) 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, 2018 and 2017. The valuation allowance increased by $13.6 million and $3.4 million during the years ended December 31, 2018 and 2017, respectively. As of December 31, 2018, the Company had approximately $136.3 million and $24.7 million, respectively, of federal and state operating loss carryforwards available to reduce future taxable income that will begin to expire in 2030 and 2028, respectively, for federal and state tax purposes. The 2018 federal net operating loss can be carried forward indefinitely. As of December 31, 2018, the Company also had research and development tax credit carryforwards of approximately $0.3 million and $1.2 million for federal and state purposes available to offset future taxable income tax, respectively. If not utilized, the federal carryforwards will expire in various amounts beginning in 2028, and the state credits can be carried forward indefinitely. As of December 31, 2018, the Company had orphan drug tax credit carryforwards of approximately $15.9 million for federal purposes available to offset future taxable income tax. If not utilized, the federal carryforwards will begin to expire in 2033. Utilization of the NOL and tax credit carryforwards may be subject to a substantial annual limitation due to ownership change limitations that have occurred or that could occur in future, as required by Section 382 of the Code, as well as similar state and foreign provisions. These ownership changes may limit the amount of NOL and tax credit carryforwards that can be utilized annually to offset future taxable income and tax, respectively. The Company assessed whether an ownership change, as defined by Section 382 of the Code, occurred from its formation through December 31, 2018. Based upon this assessment, no reduction was made to the federal and state NOL carryforwards or federal and state tax credit carryforwards under these rules. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118, Income Tax Accounting Implications of the Tax Cuts and Jobs Act (SAB 118) (the “Act”), which allows companies to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. Since the Act was passed late in the fourth quarter of 2017, and ongoing guidance and accounting interpretation was yet to be issued, the Company’s accounting of the transition tax and deferred tax re-measurements were incomplete as of December 31, 2017. The Company filed its 2017 Federal corporate income tax return in the third quarter of 2018. The Company’s final analysis and impact of the Act is reflected in the tax provision and related tax disclosures for the year ended December 31, 2018. There was no change to the originally estimated $30.4 million re-measurement of deferred tax assets. Uncertain Tax Positions A reconciliation of the Company’s unrecognized tax benefits for the years ended December 31, 2018, 2017 and 2016 is as follows (in thousands): Year Ended December 31, 2018 2017 2016 Balance at beginning of year $ 3,218 $ 1,831 $ 404 Additions based on tax positions related to prior year (61 ) — 19 Additions based on tax positions related to current year 1,477 1,387 1,408 Balance at end of year $ 4,634 $ 3,218 $ 1,831 If the $4.6 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. At December 31, 2018, 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, 2018, 2017 and 2016.

Legal Matters

Legal Matters	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Legal Matters	1 4 . Legal Matters In July 2015, following Celladon’s announcements of the negative CUPID 2 data and the suspension of further research and development activities and the subsequent declines of the price of its common stock, three putative class actions were filed in the U.S. District Court for the Southern District of California against Celladon and certain of its current and former officers. The complaints generally alleged that the defendants violated Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), by making materially false and misleading statements regarding the clinical trial program for MYDICAR, thereby artificially inflating the price of Celladon’s common stock. The complaints sought unspecified monetary damages and other relief, including attorneys’ fees. On December 9, 2015, the district court consolidated the three On October 7, 2016, the district court granted defendants’ motion to dismiss the consolidated amended complaint and granted leave to amend within 60 days from the date of the district court’s order. The lead plaintiff subsequently filed a notice of intent not to amend the consolidated amended complaint and instead indicated that it intended to appeal the district court’s decision. On December 9, 2016, the district court closed the case. On December 28, 2016, the lead plaintiff filed a notice to the United States Court of Appeals for the Ninth Circuit appealing the district court’s order dismissing the consolidated amended complaint. On May 5, 2017, the lead plaintiff filed his opening brief. On July 5, 2017, the defendants filed their appellate brief response. The Plaintiff subsequently filed their response to the Company’s July 5, 2017 filing on August 19, 2017. Oral arguments were heard on August 28, 2018 before the Ninth Circuit Court of Appeals, and on September 17, 2018, the court ruled that the lower court ruling was re-affirmed. The plaintiff had two weeks to file a petition for a rehearing and such filing was not made within the allowed time, effectively terminating the shareholder lawsuit. It is possible that additional suits will be filed, or allegations made by stockholders, with respect to these same or other matters and also naming the Company and/or Celladon’s former officers and directors as defendants. The Company believes that it has meritorious defenses and intends to defend these lawsuits vigorously. The Company is not able to predict or reasonably estimate the ultimate outcome or possible losses relating to these claims.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	1 5 . Commitments and Contingencies Lease Agreement In October 2017, the Company entered into a non-cancelable 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 five years after the commencement date. The lease has one three-year renewal option prior to expiration and includes rent escalation clauses through the lease term. In October 2017, the Company provided a security deposit of $0.3 million, which is included in other assets in the Company’s consolidated balance sheet as of December 31, 2018 and 2017. Future aggregate minimum lease payments under the non-cancelable operating leases are as follows (in thousands): Year ending December 31, Amounts 2019 $ 593 2020 610 2021 629 2022 647 2023 109 Total minimum payments $ 2,588 Rent expense was $0.8 million, $0.6 million and $0.3 million for the years ended December 31, 2018, 2017 and 2016, 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. The Company has not included these potential payment obligations in the table above as the amount and timing of such payments are not known.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	1 6 . As disclosed in Note 7, the Company entered into license agreements with EGI, which is owned by the founder of the Company. As disclosed in Note 7, in 2015 the Company entered into an asset purchase agreement with Eiccose, for which the Company’s chief executive officer was the sole managing member and significant equity interest holder. In June 2017, Eiccose was disbanded. The Company’s commercial milestone obligations and sales royalties remain, and have been transferred to the previous shareholders of Eiccose.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	17. On March 5, 2019, the Company entered into an amendment to the Oxford Loan (the “New Oxford Loan”) to refinance its term loan. As amended, the New Oxford Loan has been increased to $35.0 million in aggregate commitments, maturing on March 1, 2024. The Company received gross proceeds of $30.0 million (“New Tranche A”) at the amendment date. The remaining $5.0 million will be available to the Company upon achievement of certain clinical milestone. The New Oxford Loan will bear interest at a floating rate 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 interest only period for the borrowed funds is until April 1, 2021, followed by 36 equal monthly payments of principal plus accrued interest. If the Company receives the remaining funds, then the interest only period will be extended by one year followed by 24 equal monthly payments of principal plus accrued interest. There was no other material impact on terms, conditions, representations, warranties, covenants or agreements set forth in the Oxford Loan.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
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 subsidiary EB Pharma LLC, have been prepared in conformity with accounting principles generally accepted in the United States of America, (“U.S. GAAP”). 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 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.
Short-Term Debt Securities	Short-Term 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 debt 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, 2018, 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.
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 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). Share-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 regarding subjective variables.
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 had 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, 2018 2017 2016 Options to purchase common stock 1,996,211 1,467,051 1,212,044 Warrants to purchase common stock — 10,180 10,180 Total 1,996,211 1,477,231 1,222,224
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In January 2016, the FASB issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) Classification of Certain Cash Receipts and Cash Payments. The Company has adopted this guidance during the quarter ended March 31, 2018. The adoption of this guidance did not have a significant impact on the statement of cash flows when adopted. In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718) Revenue from Contracts with Customers Accounting Pronouncements Not Yet Adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), Targeted Improvements to Leases (Topic 842) Codification Improvements to Leases (Topic 842) In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments—Credit Losses (Topic 326) 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, 2018
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, 2018 2017 2016 Options to purchase common stock 1,996,211 1,467,051 1,212,044 Warrants to purchase common stock — 10,180 10,180 Total 1,996,211 1,477,231 1,222,224

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
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, 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 December 31, 2017 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 19,612 $ — $ — $ 19,612 Corporate debt securities — 6,501 — 6,501 Commercial paper — 3,243 — 3,243 Total $ 19,612 $ 9,744 $ — $ 29,356
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, 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 December 31, 2017 Amortized cost Unrealized gain Unrealized loss Estimated Cash equivalents: Money market funds $ 19,612 $ — $ — $ 19,612 Total cash equivalents $ 19,612 $ — $ — $ 19,612 Debt securities: Corporate debt securities $ 6,503 $ — $ (2 ) $ 6,501 Commercial paper 3,244 — (1 ) 3,243 Total debt securities $ 9,747 $ — $ (3 ) $ 9,744

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Schedule of Property and Equipment	Property and equipment, net consist of the following (in thousands): December 31, 2018 2017 Lab equipment $ 36 $ 36 Computer equipment and software 138 116 Furniture 98 34 Leasehold improvements 56 — Total property and equipment 328 186 Less: accumulated depreciation (161 ) (107 ) Property and equipment, net $ 167 $ 79
Schedule of Components of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2018 2017 Compensation and related benefits $ 1,705 $ 1,262 Contract research costs 2,191 634 Consulting costs 258 87 Franchise tax 40 56 Contract manufacturing costs — 4 Other — 41 Total accrued liabilities $ 4,194 $ 2,084

Reverse Merger (Tables)

Reverse Merger (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Summary of Net Assets Acquired Based on Estimated Fair Values	The following table summarizes the net assets acquired based on their estimated fair values as of March 22, 2016 (in thousands): Cash and cash equivalents $ 28,018 Prepaid and other assets 198 Current liabilities (857 ) Non-current liabilities (12 ) Net acquired tangible assets 27,347 Estimated total purchase consideration $ 27,347

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 2017 Face value of long term debt $ 25,000 $ 15,000 Exit fee 1,960 1,125 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (1,340 ) (1,032 ) Total long term debt 25,620 15,093 Less: current portion of long term debt (1) — (2,002 ) Long term debt, net $ 25,620 $ 13,091 (1)
Schedule of Future Minimum Payments of Principal, Exit Fee and Interest Expense under Oxford Term Loan	As of December 31, 2018, future minimum payments of principal, exit fee and interest expense under the Oxford Loan were as follows (in thousands): Year ending December 31, 2019 $ 11,047 2020 11,002 2021 7,965 Total future payments 30,014 Less: unamortized interest (3,054 ) Less: exit fee (1,960 ) Face value of term loan $ 25,000

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Summary of Common Stock Reserved for Issuance	The Company had reserved shares of common stock for issuance as follows: December 31, 2018 2017 Options issued and outstanding 1,996,211 1,467,051 Options available for future grants 755,337 799,375 Warrants to purchase common stock issued and outstanding — 10,180 Total 2,751,548 2,276,606

Stock Option Plan (Tables)

Stock Option Plan (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 (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, 2017 799,375 1,467,051 $ 12.70 8.41 $ 4,511 Additional options authorized 526,330 Granted (867,500 ) 867,500 $ 10.34 Exercised (41,208 ) $ 7.52 Forfeited or cancelled 297,132 (297,132 ) $ 12.63 Outstanding as of December 31, 2018 755,337 1,996,211 $ 11.80 7.54 $ 2,347 Vested and exercisable as of December 31, 2018 1,004,316 $ 12.36 6.52 $ 1,647
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, 2018 2017 2016 Research and development $ 1,500 $ 1,214 $ 737 General and administrative 3,507 3,029 2,453 Total stock-based compensation expense $ 5,007 $ 4,243 $ 3,190
Employees and Non Employees Stock Option [Member]
Fair Value of Stock Option Granted Using Black-Scholes Option Pricing Model	The fair value of stock options was estimated using the following weighted-average assumptions: Year Ended December 31, 2018 2017 2016 Expected term (in years) 5.27 - 6.08 5.27 - 6.08 5.27 - 6.08 Contractual term (in years) 9.67 - 9.84 6.00 - 10.00 6.75 - 10.00 Volatility 84.00% - 95.00% 79.00% - 80.00% 73.91% - 78.00% Risk free interest rate 1.67% - 2.68% 1.63% - 2.23% 1.21% - 2.27% Dividend yield — — —

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
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, 2018 2017 2016 Federal statutory income tax rate 21.00 % 34.00 % 34.00 % Change in valuation allowance (26.02 ) (8.04 ) (36.67 ) Federal and state tax credits 5.52 5.10 4.68 State income taxes, net of federal benefit 0.27 0.36 (0.21 ) Stock-based compensation (0.77 ) (1.06 ) (1.26 ) Other, net — — (0.54 ) 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, 2018 2017 Deferred tax assets: Net operating loss carryforwards $ 30,268 $ 20,230 Tax credits 12,536 9,514 Depreciation and amortization 1,526 1,700 Stock-based compensation 1,524 913 Accruals and reserves 381 245 Gross deferred tax assets 46,235 32,602 Valuation allowance (46,235 ) (32,602 ) 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, 2018, 2017 and 2016 is as follows (in thousands): Year Ended December 31, 2018 2017 2016 Balance at beginning of year $ 3,218 $ 1,831 $ 404 Additions based on tax positions related to prior year (61 ) — 19 Additions based on tax positions related to current year 1,477 1,387 1,408 Balance at end of year $ 4,634 $ 3,218 $ 1,831

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Lease Payments under Non-cancelable Operating Leases	Future aggregate minimum lease payments under the non-cancelable operating leases are as follows (in thousands): Year ending December 31, Amounts 2019 $ 593 2020 610 2021 629 2022 647 2023 109 Total minimum payments $ 2,588

Description of Business - Addit

Description of Business - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018USD ($)Segment	Dec. 31, 2017USD ($)
Description Of Business [Abstract]
Entity incorporation, date of incorporation	Nov. 6, 2008
Number of operating segments | Segment	1
Cash and cash equivalents	$ 61,262	$ 32,035
Short-term debt securities	39,091	9,744
Accumulated deficit	$ (171,197)	$ (118,806)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)SupplyChainProductCandidate
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
ASU 2016-02 [Member] | Subsequent Event [Member]
Significant Accounting Policies [Line Items]
Impact of change in operating leases	$ 2,000,000
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, 2018
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, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	1,996,211	1,477,231	1,222,224
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities		10,180	10,180
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	1,996,211	1,467,051	1,212,044

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Financial assets	$ 84,532,000	$ 29,356,000
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
Fair Value, Inputs, Level 3
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, 2018	Dec. 31, 2017
Financial Assets:
Assets, Fair Value	$ 84,532,000	$ 29,356,000
Corporate Debt Securities [Member]
Financial Assets:
Assets, Fair Value	23,474,000	6,501,000
Money Market Funds [Member]
Financial Assets:
Assets, Fair Value	45,441,000	19,612,000
Commercial Paper [Member]
Financial Assets:
Assets, Fair Value	15,617,000	3,243,000
Level 1 [Member]
Financial Assets:
Assets, Fair Value	45,441,000	19,612,000
Level 1 [Member] | Money Market Funds [Member]
Financial Assets:
Assets, Fair Value	45,441,000	19,612,000
Level 2 [Member]
Financial Assets:
Assets, Fair Value	39,091,000	9,744,000
Level 2 [Member] | Corporate Debt Securities [Member]
Financial Assets:
Assets, Fair Value	23,474,000	6,501,000
Level 2 [Member] | Commercial Paper [Member]
Financial Assets:
Assets, Fair Value	15,617,000	3,243,000
Fair Value, Inputs, Level 3
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, 2018	Dec. 31, 2017
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	$ 45,441	$ 19,612
Cash equivalents, Estimated Fair Value	45,441	19,612
Debt securities, Amortized cost	39,116	9,747
Debt securities, Unrealized gain	1
Debt securities, Unrealized loss	(26)	(3)
Debt securities, Estimated Fair Value	39,091	9,744
Corporate Debt Securities [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	23,489	6,503
Debt securities, Unrealized gain	1
Debt securities, Unrealized loss	(16)	(2)
Debt securities, Estimated Fair Value	23,474	6,501
Money Market Funds [Member]
Cash Equivalents and Investment Securities [Line Items]
Cash equivalents, Amortized cost	45,441	19,612
Cash equivalents, Estimated Fair Value	45,441	19,612
Commercial Paper [Member]
Cash Equivalents and Investment Securities [Line Items]
Debt securities, Amortized cost	15,627	3,244
Debt securities, Unrealized loss	(10)	(1)
Debt securities, Estimated Fair Value	$ 15,617	$ 3,243

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 328	$ 186
Property and equipment, accumulated depreciation	(161)	(107)
Property and equipment, net	167	79
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	138	116
Furniture [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	98	$ 34
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 56

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Depreciation [Abstract]
Depreciation expense	$ 54	$ 41	$ 23

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Components of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Compensation and related benefits	$ 1,705	$ 1,262
Contract research costs	2,191	634
Consulting costs	258	87
Franchise tax	40	56
Contract manufacturing costs		4
Other		41
Total accrued liabilities	$ 4,194	$ 2,084

Reverse Merger - Additional Inf

Reverse Merger - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 22, 2016
Reverse Merger Transactions [Line Items]
Combined shares of common stock outstanding	19,211,759	10,526,599
Estimated fair value of assets			$ 27,347
Celladon Europe [Member]
Reverse Merger Transactions [Line Items]
Combined shares of common stock outstanding			1,596,959
Market capitalization			$ 27,500
Estimated fair value of assets			$ 27,300
Reverse Stock Split [Member]
Reverse Merger Transactions [Line Items]
Common stock exchange price per share			$ 0.09
Combined shares of common stock outstanding			6,945,401
Reverse Merger [Member]
Reverse Merger Transactions [Line Items]
Date of acquisition	Mar. 22, 2016
Reverse Merger [Member] | Eiger BioPharmaceuticals, Inc [Member]
Reverse Merger Transactions [Line Items]
Ownership percentage			78.00%
Reverse Merger [Member] | Eiger BioPharmaceuticals, Inc [Member] | Celladon Europe [Member]
Reverse Merger Transactions [Line Items]
Percentage of shares acquired by share holders of Celladon			22.00%

Reverse Merger - Summary of Net

Reverse Merger - Summary of Net Assets Acquired Based on Estimated Fair Values (Detail) $ in Thousands	Mar. 22, 2016USD ($)
Business Combinations [Abstract]
Cash and cash equivalents	$ 28,018
Prepaid and other assets	198
Current liabilities	(857)
Non-current liabilities	(12)
Net acquired tangible assets	27,347
Estimated total purchase consideration	$ 27,347

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	Dec. 31, 2014	Sep. 30, 2010	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development								$ 37,091,000	$ 29,519,000	$ 33,014,000
Weighted-average period for recognition (in years)								2 years 7 months 6 days
Aggregate fair value of shares issued								$ 19,000	$ 11,000
Common Stock [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sale of common stock								8,510,918	2,143,525	1,250,000
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								$ 400,000
Unrecognised compensation expense related to unvested restricted shares								$ 700,000
Weighted-average period for recognition (in years)								3 years 3 months
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] | Licensing Agreements [Member] | Development and Regulatory Milestones [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations				61,000,000
BMS Transaction [Member] | Licensing Agreements [Member] | Commercial Sales [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations				128,000,000
BMS Transaction [Member] | Licensing Agreements [Member] | Development Phase 2 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations				3,000,000
BMS Transaction [Member] | Licensing Agreements [Member] | Common Stock [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
New shares issued during period, value upfront payment				$ 3,000,000
Merck Transaction [Member] | Licensing Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalties expiration description								The Company’s obligation to pay royalties to Merck expires on a country-by-country and product-by-product basis on the later of the expiration of the last to expire patent assigned to the Company under the agreement, which is estimated to be on the tenth anniversary of the first commercial sale of the product.
Milestone payments					$ 1,000,000			$ 0
Merck Transaction [Member] | Licensing Agreements [Member] | Private Eiger [Member] | Convertible Preferred Stock [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Fair value of shares issued							$ 500,000
Conversion of preferred stock into common stock upon merger							27,350
Merck Transaction [Member] | Licensing Agreements [Member] | Development [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Development milestone payment obligations							$ 27,000,000
Janssen Transaction [Member] | Licensing Agreements [Member] | Development [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations						$ 38,000,000
Janssen Transaction [Member] | Licensing Agreements [Member] | Sales [Member] | Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment obligations						$ 65,800,000

Asset Purchase Agreements and_2

Asset Purchase Agreements and Related License Agreements - Additional Information (Detail) - USD ($)	Mar. 22, 2016	Oct. 31, 2015	Sep. 30, 2015	Dec. 31, 2010	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Asset Purchase Agreement And Related License Agreement [Line Items]
Compensation expense related to the time-vested/milestone vested options					$ 5,007,000	$ 4,243,000	$ 3,190,000
Research and development expense					37,091,000	29,519,000	33,014,000
Eiccose Purchase Agreement [Member] | Eiccose APA [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
License agreement milestone payments paid					0
Reimbursement of expenses incurred		$ 100,000
Gross proceeds to company's capital stock		$ 25,000,000
Share based compensation issued and outstanding shares percentage		1.75%
Research and development expense		$ 1,500,000
Number of fully vested shares issued	96,300
Change in fair value recognized in other income (expense)							200,000
Maximum [Member] | Eiccose Purchase Agreement [Member] | Eiccose APA [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Aggregate potential milestone payments	$ 10,000,000
Share-based Compensation Award, Tranche Two [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.
Asset Purchase Agreement [Member] | EIG Transaction [Member] | Clemizole and Related Intellectual Property [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Royalties expiration description					EGI’s obligation to pay royalties expires on a country-by-country and product-by-product basis on the later of either expiration of the last to expire patent sold to EGI under the agreement 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]
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
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
Avexitide Purchase Agreement [Member] | Share-based Compensation Award, Tranche Two [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Shares issued for purchased assets			15,378
Avexitide Purchase Agreement [Member] | Share-based Compensation Award, Tranche One [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Vesting of options to purchase common stock			30,756
Compensation expense related to the time-vested/milestone vested options					$ 100,000	44,000	$ 300,000
Licensing Agreements [Member] | Eiccose Purchase Agreement [Member] | Eiccose APA [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Reimbursement of expenses incurred					$ 0	$ 0
Licensing Agreements [Member] | Maximum [Member] | Eiccose Purchase Agreement [Member] | Eiccose APA [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Aggregate development and commercial potential milestone payments		500,000
Annual sublicense maintenance fee payable		75,000
Licensing Agreements [Member] | Minimum [Member] | Eiccose Purchase Agreement [Member] | Eiccose APA [Member]
Asset Purchase Agreement And Related License Agreement [Line Items]
Annual sublicense maintenance fee payable		$ 10,000

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	May 31, 2018	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Aug. 03, 2018
Debt Instrument [Line Items]
Interest expense			$ 1,700,000	$ 1,100,000	$ 5,000
Oxford Loan [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity		$ 25,000,000			25,000,000
Loan, maturity period			Jul. 1, 2021
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%.
Loan origination fees and debt issuance costs		400,000			400,000
Loan agreement, covenant noncompliance penalty			5.00%	5.00%
Loan agreement, covenant description			The Oxford 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 and restrict access to additional borrowings under the loan and security agreement.
Loan agreement, covenant compliance			The Company was in compliance with the terms under the Oxford Loan as of December 31, 2018 and 2017.
Prepayment of loan fee, description			Calculated as of the loan origination date, equal to (i) 3.0% of the loan prepaid during the first 12 months, (ii) 2.0% of the loan prepaid in months 13-24 and (iii) 1.0% of the loan prepaid thereafter.
Oxford Loan [Member] | Loan Prepaid During First 12 Months [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage			3.00%
Oxford Loan [Member] | Loan Prepaid During 13 to 24 Months [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage			2.00%
Oxford Loan [Member] | Loan Prepaid After 24 Months [Member]
Debt Instrument [Line Items]
Debt instrument prepayment fee percentage			1.00%
Oxford Loan [Member] | Minimum [Member]
Debt Instrument [Line Items]
Loan agreement, interest rate			6.95%
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
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		$ 15,000,000	$ 15,000,000
Interest only payment period		18 months
Principal and interest payment period		36 months
Percentage of exit fee on principal balance			7.50%
Loan final repayment exit fees payable			$ 1,100,000	$ 1,125,000
Oxford Loan [Member] | Tranche A [Member] | Food And Drug Administration [Member]
Debt Instrument [Line Items]
Fee payable maximum period from funding			10 years
Oxford Loan [Member] | Amended Tranche B [Member]
Debt Instrument [Line Items]
Principal and interest payment period	30 months
Extended term of interest only payment period	6 months
Percentage of exit fee on principal balance			7.50%
Loan final repayment exit fees payable			$ 400,000
Loan final repayment fee payable			100,000
Oxford Loan [Member] | Amended Tranche C [Member]
Debt Instrument [Line Items]
Loan final repayment exit fees payable			$ 400,000
Amendment [Member] | Amended Tranche B [Member]
Debt Instrument [Line Items]
Face value of term loan	$ 5,000,000
Amendment [Member] | Amended Tranche C [Member]
Debt Instrument [Line Items]
Face value of term loan						$ 5,000,000

Debt - Schedule of Long-Term De

Debt - Schedule of Long-Term Debt and Unamortized Discount Balances (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Less: current portion of long term debt		$ (2,002)
Long term debt, net	$ 25,620	13,091
Oxford Loan [Member] | Tranche A, B and C [Member]
Debt Instrument [Line Items]
Face value of long term debt	25,000
Exit fee	1,960
Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees	(1,340)
Total long term debt	25,620
Long term debt, net	25,620
Oxford Loan [Member] | Tranche A [Member]
Debt Instrument [Line Items]
Face value of long term debt		15,000	$ 15,000
Exit fee	$ 1,100	1,125
Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees		(1,032)
Total long term debt		15,093
Less: current portion of long term debt		(2,002)
Long term debt, net		$ 13,091

Debt - Schedule of Future Minim

Debt - Schedule of Future Minimum Payments of Principal, Exit Fee and Interest Expense under Oxford Term Loan (Detail) - Oxford Loan [Member] - Tranche A, B and C [Member] $ in Thousands	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
2019	$ 11,047
2020	11,002
2021	7,965
Total future payments	30,014
Less: unamortized interest	(3,054)
Less: exit fee	(1,960)
Face value of term loan	$ 25,000

Convertible Promissory Note a_2

Convertible Promissory Note and Warrant Purchase Agreement - Additional Information (Detail) $ / shares in Units, $ in Thousands	Mar. 22, 2016USD ($)shares	Nov. 12, 2015USD ($)Lender$ / shares	Dec. 31, 2018	Dec. 31, 2016USD ($)	Dec. 31, 2017$ / shares
Convertible Promissory Note [Line Items]
Warrant exercise price | $ / shares					$ 84.15
Warrants exercisable date			Mar. 22, 2016
Fair value of warrants				$ 165
Interest Expense [Member]
Convertible Promissory Note [Line Items]
Accrued interest				700
Amortization of debt discount				$ 700
Private Placement [Member]
Convertible Promissory Note [Line Items]
Outstanding balance of notes	$ 6,000
Common Stock [Member]
Convertible Promissory Note [Line Items]
Conversion of warrants | shares	61,254
Common Stock [Member] | Private Placement [Member]
Convertible Promissory Note [Line Items]
Notes converted in to common stock | shares	350,040
Convertible Promissory Note and Warrant Purchase Agreement [Member]
Convertible Promissory Note [Line Items]
Number of lenders | Lender		3
Convertible Promissory Note and Warrant Purchase Agreement [Member] | Minimum [Member]
Convertible Promissory Note [Line Items]
Qualified financing for warrants to convert		$ 25,000
Convertible Promissory Note and Warrant Purchase Agreement [Member] | If the PO or Reverse Merger did not occur by February 28, 2016 [Member]
Convertible Promissory Note [Line Items]
Percentage of warrant equals outstanding principal balance of notes		17.50%
Convertible Promissory Note and Warrant Purchase Agreement [Member] | Convertible Debt [Member]
Convertible Promissory Note [Line Items]
Conversion of notes		$ 6,000
Convertible Promissory Note and Warrant Purchase Agreement [Member] | Warrants to Purchase Common Stock [Member]
Convertible Promissory Note [Line Items]
Purchase price per share | $ / shares		$ 0.11
Warrant exercise price | $ / shares		$ 0.11

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, 2018	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

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Dividends declared	$ 0
Warrants outstanding	0	10,180
Warrants outstanding, Exercise Price		$ 84.15
Warrants outstanding, Expiration Date	2018-10

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Common Stock Reserved for Issuance (Detail) - shares	Dec. 31, 2018	Dec. 31, 2017
Equity [Abstract]
Options issued and outstanding	1,996,211	1,467,051
Options available for future grants	755,337	799,375
Warrants to purchase common stock issued and outstanding	0	10,180
Total	2,751,548	2,276,606

Stock Option Plan - Additional

Stock Option Plan - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2009
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion rate representing right to purchase number of shares of Company's common stock		0.09%
Increased number of shares reserved for grant		526,330
Closing price of common stock		$ 10.16
Aggregate intrinsic value of options exercised		$ 0.2	$ 0.1	$ 0.1
Stock options granted		867,500
Expected dividend yield		0.00%
Total unrecognized compensation expense		$ 8.5
Weighted average period expected to recognized compensation expense (in years)		2 years 7 months 6 days
Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted		799,500	579,700	902,028
Weighted-average grant date fair value of employee option grants		$ 7.50	$ 7.66	$ 10.40
Grant date fair value of employee options vested		4,700,000	5,000,000	2,000,000
Non-Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted		68,000	72,500	48,544
Two Thousand Nine Equity And 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
Two Thousand Nine Equity And Incentive Plan [Member] | Holders Of Ten Percent Or More Of Voting Rights of All Classes of Stock [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%
Two Thousand Nine Equity And Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual terms of options granted under the Plan					10 years
Amended and Restated 2013 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increased number of shares reserved for grant	1,296,683

Stock Option Plan - Stock Optio

Stock Option Plan - Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Exercise Price And Additional Disclosures [Abstract]
Shares Available for Grant, Outstanding, Beginning balance	799,375
Shares Available for Grant, Additional options authorized	526,330
Shares Available for Grant, Granted	(867,500)
Shares Available for Grant, Forfeited or cancelled	297,132
Shares Available for Grant, Outstanding, Ending balance	755,337	799,375
Number of Options, Outstanding, Beginning balance	1,467,051
Number of Options, Granted	867,500
Number of Options, Exercised	(41,208)
Number of Options, Forfeited or cancelled	(297,132)
Number of Options, Outstanding, Ending balance	1,996,211	1,467,051
Number of Options, Vested and exercisable	1,004,316
Weighted Average Exercise Price Per Option, Outstanding, Beginning balance	$ 12.70
Weighted Average Exercise Price Per Option, Granted	10.34
Weighted Average Exercise Price Per Option, Exercised	7.52
Weighted Average Exercise Price Per Option, Forfeited or cancelled	12.63
Weighted Average Exercise Price Per Option, Outstanding, Ending balance	11.80	$ 12.70
Weighted Average Exercise Price Per Option, Vested and exercisable	$ 12.36
Weighted Average Remaining Contractual Life, Ending balance	7 years 6 months 14 days	8 years 4 months 28 days
Weighted Average Remaining Contractual Life, Vested and exercisable	6 years 6 months 7 days
Aggregate Intrinsic Value	$ 2,347	$ 4,511
Aggregate Intrinsic Value, Vested and exercisable	$ 1,647

Stock Option Plan - Fair Value

Stock Option Plan - Fair Value of Stock Option Granted Using Black-Scholes Option Pricing Model (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term (in years)	7 years 6 months 14 days	8 years 4 months 28 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] | 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	6 years 9 months
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	10 years
Employees and Non Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility, minimum	84.00%	79.00%	73.91%
Volatility, maximum	95.00%	80.00%	78.00%
Risk free interest rate, minimum	1.67%	1.63%	1.21%
Risk free interest rate, maximum	2.68%	2.23%	2.27%

Stock Option Plan - Summary of

Stock Option Plan - Summary of Non-cash Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 5,007	$ 4,243	$ 3,190
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1,500	1,214	737
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 3,507	$ 3,029	$ 2,453

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Provision for income taxes	$ 0	$ 0	$ 0
Valuation allowance	13,600,000	3,400,000
Tax credits	15,900,000
Reduction in net operating loss carryforwards	0
Net deferred tax assets	0	0
Unrecognized tax benefits impact on effective tax rate	4,600,000
Accrued interest and penalties associated with uncertain tax positions	0	$ 0	$ 0
Re-Measurement [Member]
Income Taxes [Line Items]
Net deferred tax assets	30,400,000
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 136,300,000
Operating loss carryforwards expiration year	2030
Tax credits	$ 300,000
Federal [Member] | Research and Development Tax Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credits expiration year	2028
Federal [Member] | Orphan Drug Tax Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credits expiration year	2033
State [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 24,700,000
Operating loss carryforwards expiration year	2028
Tax credits	$ 1,200,000
Tax credits expiration description	state credits can be carried forward indefinitely

Income Taxes - Schedule of Reco

Income Taxes - Schedule of Reconciliation of Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	34.00%	34.00%
Change in valuation allowance	(26.02%)	(8.04%)	(36.67%)
Federal and state tax credits	5.52%	5.10%	4.68%
State income taxes, net of federal benefit	0.27%	0.36%	(0.21%)
Stock-based compensation	(0.77%)	(1.06%)	(1.26%)
Other, net			(0.54%)
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, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 30,268	$ 20,230
Tax credits	12,536	9,514
Depreciation and amortization	1,526	1,700
Stock-based compensation	1,524	913
Accruals and reserves	381	245
Gross deferred tax assets	46,235	32,602
Valuation allowance	(46,235)	(32,602)
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, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Balance at beginning of year	$ 3,218	$ 1,831	$ 404
Additions based on tax positions related to prior year	(61)		19
Additions based on tax positions related to current year	1,477	1,387	1,408
Balance at end of year	$ 4,634	$ 3,218	$ 1,831

Legal Matters - Additional Info

Legal Matters - Additional Information (Detail) - 3 Putative Securities Class Action Complaints [Member] - Claim	Dec. 09, 2015	Jul. 31, 2015
Loss Contingencies [Line Items]
Loss contingency, new claims filed, number		3
Loss contingency, claims consolidated, number	3

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2017USD ($)ft²	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Other Commitments [Line Items]
Rent expense		$ 0.8	$ 0.6	$ 0.3
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	5 years
Lease renewal term	3 years
Security deposit of collateral for lease	$ 0.3

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Lease Payments under Non-cancelable Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
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

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - New Oxford Loan [Member] - USD ($) $ in Millions	Mar. 05, 2019	Dec. 31, 2018
Subsequent Event [Line Items]
Loan agreement, floating rate terms		floating rate 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%.
Frequency of payments		The interest only period for the borrowed funds is until April 1, 2021, followed by 36 equal monthly payments of principal plus accrued interest. If the Company receives the remaining funds, then the interest only period will be extended by one year followed by 24 equal monthly payments of principal plus accrued interest.
Subsequent Event [Member]
Subsequent Event [Line Items]
Loan agreement, aggregate borrowing capacity	$ 35
Loan, maturity date	Mar. 1, 2024
Loan agreement, remaining borrowing capacity	$ 5
Extended term of interest only payment period	1 year
Extended term of principal and interest payment period	24 months
Subsequent Event [Member] | Minimum [Member]
Subsequent Event [Line Items]
Loan agreement, interest rate	9.15%
Subsequent Event [Member] | LIBOR [Member]
Subsequent Event [Line Items]
Loan agreement, percentage to be added to the interest rate under condition	6.64%
New Tranche A [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Proceeds from loan agreement	$ 30
Interest only payment period	Apr. 1, 2021
Principal and interest payment period	36 months