Eiger BioPharmaceuticals (EIGRQ) 10-Q 11 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Aug. 03, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Trading Symbol	EIGR
Entity Registrant Name	Eiger BioPharmaceuticals, Inc.
Entity Central Index Key	1,305,253
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		8,367,030

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 11,197	$ 27,756
Marketable securities	29,112	32,180
Prepaid expenses and other current assets	969	581
Total current assets	41,278	60,517
Property and equipment, net	101	76
Other assets	81	143
Total assets	41,460	60,736
Current liabilities:
Accounts payable	4,468	2,639
Accrued liabilities	1,422	2,649
Total current liabilities	5,890	5,288
Long term debt, net	14,898	14,727
Total liabilities	20,788	20,015
Stockholders’ equity:
Common stock	8	8
Additional paid-in capital	119,413	117,086
Accumulated other comprehensive loss	(6)	(15)
Accumulated deficit	(98,743)	(76,358)
Total stockholders’ equity	20,672	40,721
Total liabilities and stockholders’ equity	$ 41,460	$ 60,736

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating expenses:
Research and development	$ 8,131	$ 10,720	$ 15,595	$ 15,565
General and administrative	2,946	2,477	6,468	6,310
Total operating expenses	11,077	13,197	22,063	21,875
Loss from operations	(11,077)	(13,197)	(22,063)	(21,875)
Interest expense	(378)		(741)	(685)
Interest income	113		223
Other income (expense), net	196	(4)	196	(389)
Net loss	$ (11,146)	$ (13,201)	$ (22,385)	$ (22,949)
Net loss per common share, basic and diluted	$ (1.33)	$ (1.87)	$ (2.68)	$ (5.73)
Weighted-average common shares outstanding, basic and diluted	8,367,030	7,069,257	8,363,803	4,002,454

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,146)	$ (13,201)	$ (22,385)	$ (22,949)
Other comprehensive loss:
Unrealized gain on marketable securities, net	2		9
Comprehensive loss	$ (11,144)	$ (13,201)	$ (22,376)	$ (22,949)

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flow (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net loss	$ (22,385)	$ (22,949)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	19	9
Amortization of premiums on marketable securities	(73)
Non-cash interest expense	171	685
Stock-based compensation	2,270	512
Change in fair value of obligation to issue shares to Eiccose		204
Change in fair value of warrant liability		165
Issuance of common stock in connection with a license agreement		3,172
Change in operating assets and liabilities:
Prepaid expenses and other current assets	(388)	(253)
Other non-current assets	62	(91)
Accounts payable	1,829	(701)
Accrued and other liabilities	(1,427)	(284)
Net cash used in operating activities	(19,922)	(19,531)
Investing activities
Purchase of marketable securities	(17,550)
Proceeds from maturities of marketable securities	20,700
Proceeds from intellectual property sale	200
Proceeds from merger transaction		28,018
Purchase of property and equipment	(44)	(20)
Net cash provided by investing activities	3,306	27,998
Financing activities
Proceeds from issuance of common stock upon private placement, net of issuance cost		32,108
Proceeds from issuance of common stock upon ESPP purchase	57
Proceeds from issuance of common stock upon options exercises		39
Proceeds from issuance of common stock upon warrants exercises		7
Net cash provided by financing activities	57	32,154
Net (decrease) increase in cash and cash equivalents	(16,559)	40,621
Cash and cash equivalents at beginning of period	27,756	4,778
Cash and cash equivalents at end of period	$ 11,197	45,399
Non-cash 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
Eiccose LLC [Member]
Non-cash activities:
Issuance of common stock		$ 1,661

Description of Business

Description of Business	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Description of Business	1. Description of Business Eiger BioPharmaceuticals, Inc. (the “Company”) 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 orphan diseases. The Company has built a diverse portfolio of well-characterized product candidates with the potential to address diseases for which the unmet medical need is high, the biology for treatment is clear, and for which an effective therapy is urgently needed. The Company’s principal operations are based in Palo Alto, California and it operates in one segment. Liquidity As of June 30, 2017, the Company had $11.2 million of cash and cash equivalents, $29.1 million of short-term marketable securities, an accumulated deficit of $98.7 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 its operations for at least the next 12 months following the issuance date of these unaudited condensed consolidated financial statements. However, if the Company’s anticipated operating results are not achieved in future periods, management believes that planned expenditures will need to be reduced in order to extend the time period over which the then-available resources would be able to fund the Company’s operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The unaudited condensed consolidated financial statements include the accounts of Eiger BioPharmaceuticals, Inc. and its wholly owned subsidiaries, EBPI Merger Inc., EB Pharma LLC and Eiger BioPharmaceuticals Europe Limited, and have been prepared in accordance with accounting principles generally accepted in the United States of America, (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (the “SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or for any other interim period or for any other future year. The balance sheet as of December 31, 2016, has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, filed with the Securities and Exchange Commission on March 23, 2017. Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates, 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. Short-Term Marketable Securities Short-term marketable 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 marketable 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 . 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 unaudited condensed consolidated balance sheets and within research and development expense in the unaudited condensed 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. 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 Weighted-average common shares outstanding for the three and six month periods ended June 30, 2016, are impacted by the weighted effect of the conversion or issuance of 6,668,045 common shares in conjunction with the closing of the Merger Agreement on March 22, 2016. The following table sets forth the outstanding potentially dilutive securities which have been excluded in the calculation of diluted net loss per share because including such securities would be anti-dilutive (in common stock equivalent shares): Three Months Ended Six Months Ended June 30, June 30, 2017 2016 2017 2016 Options to purchase common stock 1,593,560 310,069 1,593,560 310,069 Warrants to purchase common stock 10,180 10,180 10,180 10,180 Total 1,603,740 320,249 1,603,740 320,249 Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), The Company is currently in the process of evaluating the impact that the standard will have on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting As a result of adopting this standard, the Company made an accounting policy election to account for forfeitures as they occur.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2017
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 June 30, 2017 and December 31, 2016, the carrying amount of prepaid expenses, accounts payable and accrued liabilities approximated their estimate fair value due to their relatively short maturities. Management believes the terms of long term debt reflect current market conditions for an instrument with similar terms and maturity, therefore the carrying value of the Company’s debt approximated its fair value. Assets and liabilities recorded at fair value on a recurring basis in the unaudited condensed consolidated balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level 1 : Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 : Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level 3 : Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. The Company’s money market funds are classified as Level 1 because they are valued using quoted market prices. The Company’s marketable 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 June 30, 2017 and December 31, 2016. 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): June 30, 2017 Level 1 Level 2 Level 3 Total Financial assets: Money market fund $ 4,794 $ — $ — $ 4,794 Corporate debt securities — 16,139 — 16,139 Commercial paper — 13,224 — 13,224 Total $ 4,794 $ 29,363 $ — $ 34,157 December 31, 2016 Level 1 Level 2 Level 3 Total Financial assets: Money market fund $ 9,657 $ — $ — $ 9,657 Corporate debt securities — 11,469 — 11,469 Commercial paper — 22,891 — 22,891 Total $ 9,657 $ 34,360 $ — $ 44,017 There were no financial liabilities as of June 30, 2017 and December 31, 2016. The following table summarizes the estimated value of the Company’s cash equivalents and marketable securities and the gross unrealized holding gains and losses (in thousands): June 30, 2017 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market fund $ 4,794 $ — $ — $ 4,794 Corporate debt securities 251 — — 251 Total cash equivalents $ 5,045 $ — $ — $ 5,045 Marketable securities: Corporate debt securities $ 15,893 $ 1 $ (6 ) $ 15,888 Commercial paper 13,225 — (1 ) 13,224 Total marketable securities $ 29,118 $ 1 $ (7 ) $ 29,112 December 31, 2016 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market fund $ 9,657 $ — $ — $ 9,657 Corporate debt securities 2,180 — — 2,180 Total cash equivalents $ 11,837 $ — $ — $ 11,837 Marketable securities: Corporate debt securities $ 9,294 $ — $ (5 ) $ 9,289 Commercial paper 22,901 3 (13 ) 22,891 Total marketable securities $ 32,195 $ 3 $ (18 ) $ 32,180 As of June 30, 2017 and December 31, 2016, the contractual maturity of the available-for-sale marketable securities is less than one year.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	4. Balance Sheet Components Accrued Liabilities Accrued liabilities consist of the following (in thousands): June 30, December 31, 2017 2016 Compensation and related benefits $ 828 $ 1,299 Contract research costs 449 834 Franchise tax 90 97 Consulting costs — 106 Contract manufacturing costs — 122 Other 55 191 Total accrued liabilities $ 1,422 $ 2,649

Debt

Debt	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Debt	5 . 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”). The remaining $10.0 million (“Tranche B”) will be available to the Company upon achievement of positive top line data from the lonafarnib Phase 2 trial in HDV, which was achieved in the fourth quarter of 2016, plus positive top line Phase 2 data from at least one of the following programs, including: (i) Lambda in HDV, (ii) Exendin 9-39 in PBH based on the Company’s own IND, (iii) ubenimex in PAH, or (iv) ubenimex in Lymphedema. 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 followed by 36 equal monthly payments of principal and interest commencing on the first day of the month following the funding of Tranche A. If the Company receives the Tranche B funds, then the interest only period is extended by six months followed by 30 equal monthly payments of principal plus accrued interest. At the time of final payment, the Company is required to pay an exit fee of 7.5% of the original principal balance of each tranche, which will be $1.1 million for Tranche A. The Company recorded as a liability and debt discount the exit fee at the origination of the term loan. In addition, the Company incurred loan origination fees and debt issuance costs of $0.3 million which were recorded as a direct deduction from the carrying amount of the related debt liability 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 $0.3 million and $0.6 million for the three and six months ended June 30, 2017. Long-term debt and unamortized discount balances are as follows (in thousands): June 30, December 31, 2017 2016 Face value of term loan $ 15,000 $ 15,000 Exit fee 1,125 1,125 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (1,227 ) (1,398 ) Term loan, net $ 14,898 $ 14,727

Sale of Assets

Sale of Assets	6 Months Ended
	Jun. 30, 2017
Discontinued Operations And Disposal Groups [Abstract]
Sale of Assets	6. 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. As of June 30, 2017, the Company received a cash payment of $0.2 million, which was recognized as other income. 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.

Stock Based Compensation

Stock Based Compensation	6 Months Ended
	Jun. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Compensation	7 . Stock Based Compensation The following table summarizes stock option activity under the Company’s stock based compensation plan during the six months ended June 30, 2017 (in thousands, except share data): Shares Available for Grant Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value Outstanding as of December 31, 2016 646,778 1,212,044 $ 14.06 $ 2,414 Additional options authorized 417,833 Granted (576,200 ) 576,200 $ 10.91 Canceled 194,684 (194,684 ) $ 13.45 Outstanding as of June 30, 2017 683,095 1,593,560 $ 13.00 8.54 $ 1,531 Vested and exercisable as of June 30, 2017 536,953 $ 14.95 7.46 $ 712 Stock Options Granted to Employees During the three and six months ended June 30, 2017, the Company granted employees stock options for 60,000 and 523,700 shares, respectively. The weighted-average grant date fair value of these options was $5.41 and $7.69 for the three and six months ended June 30, 2017, respectively. There were no stock options granted to employees during the three and six months ended June 30, 2016. 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 employee stock options was estimated using the following weighted-average assumptions: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Expected term (in years) 5.27-6.02 — 5.27-6.02 — Volatility 79.0%-80.0% — 79.0%-80.0% — Risk free interest rate 1.6%-1.9% — 1.6%-2.2% — Dividend yield — — — — Stock Options Granted to Non-Employees The Company grants stock options to non-employees in exchange for services rendered. During the three and six months ended June 30, 2017, the Company granted to non-employees stock options for 52,500 shares. During the three and six months ended June 30, 2016, the Company granted to non-employees stock options for zero and 48,544 shares, respectively. Stock-based compensation expense related to stock options granted to non-employees is recognized as the stock options are earned and will fluctuate as the estimated fair value of the common stock fluctuates until the awards vest. The Company believes that the estimated fair value of the stock options is more readily measurable than the fair value of the services rendered. The fair value of the stock options granted to non-employees is estimated at each reporting date using the Black-Scholes option-pricing model using similar assumptions as for employees except that the expected term is based on the options’ remaining contractual term instead of the simplified method: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Remaining contractual term (in years) 6.25-10.00 7.25-9.92 6.25-10.00 7.25-10.0 Volatility 88.0%-94.6% 89.4%-95.8% 87.4%-98.2% 89.4%-95.8% Risk free interest rate 1.9%-2.3% 1.4%-1.9% 1.9%-2.4% 1.4%-2.0% Dividend yield — — — — Stock-Based Compensation Expense Total stock-based compensation expense recognized for options granted to employees and non-employees was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Research and development 215 $ 69 498 $ 303 General and administrative 731 105 1,772 209 Total $ 946 $ 174 $ 2,270 $ 512 As of June 30, 2017, the total unrecognized compensation expense related to unvested employee options was $8.7 million, which the Company expects to recognize over an estimated weighted average period of 3.2 years.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	8 . Income Taxes Our tax expense for the three and six months ended June 30, 2017 was zero due to our loss position and full valuation allowance. This is consistent with our zero-tax expense for the three and six months ended June 30, 2016.

Legal Matters

Legal Matters	6 Months Ended
	Jun. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Legal Matters	9 . 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 and appellant filed his opening appellate brief. On July 5, 2017, defendants filed their answering appellate brief. 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. Due to the early stage of these proceedings, 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	6 Months Ended
	Jun. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10 . Commitments and Contingencies Lease Agreement In March 2017, the Company entered into a non-cancelable facility lease agreement for an office facility in Palo Alto, California. The lease commenced on April 1, 2017 and expires 12 months after the commencement date. The lease has one twelve-month renewal option prior to expiration and includes rent escalation clauses through the lease term. In April 2017, the Company provided a security deposit of $27,000 as collateral for the lease. The future minimum rent payable under the new lease agreement is approximately $0.3 million during the next year. There were no other changes in commitments and contingencies during the three and six months ended June 30, 2017.

Summary of Significant Accoun16

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements include the accounts of Eiger BioPharmaceuticals, Inc. and its wholly owned subsidiaries, EBPI Merger Inc., EB Pharma LLC and Eiger BioPharmaceuticals Europe Limited, and have been prepared in accordance with accounting principles generally accepted in the United States of America, (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (the “SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments, which are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or for any other interim period or for any other future year. The balance sheet as of December 31, 2016, has been derived from audited consolidated financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016, filed with the Securities and Exchange Commission on March 23, 2017.
Use of Estimates	Use of Estimates The preparation of unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates, 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.
Short-Term Marketable Securities	Short-Term Marketable Securities Short-term marketable 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 marketable 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 .
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 unaudited condensed consolidated balance sheets and within research and development expense in the unaudited condensed 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.
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 Weighted-average common shares outstanding for the three and six month periods ended June 30, 2016, are impacted by the weighted effect of the conversion or issuance of 6,668,045 common shares in conjunction with the closing of the Merger Agreement on March 22, 2016. The following table sets forth the outstanding potentially dilutive securities which have been excluded in the calculation of diluted net loss per share because including such securities would be anti-dilutive (in common stock equivalent shares): Three Months Ended Six Months Ended June 30, June 30, 2017 2016 2017 2016 Options to purchase common stock 1,593,560 310,069 1,593,560 310,069 Warrants to purchase common stock 10,180 10,180 10,180 10,180 Total 1,603,740 320,249 1,603,740 320,249
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), The Company is currently in the process of evaluating the impact that the standard will have on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation-Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting As a result of adopting this standard, the Company made an accounting policy election to account for forfeitures as they occur.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
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): Three Months Ended Six Months Ended June 30, June 30, 2017 2016 2017 2016 Options to purchase common stock 1,593,560 310,069 1,593,560 310,069 Warrants to purchase common stock 10,180 10,180 10,180 10,180 Total 1,603,740 320,249 1,603,740 320,249

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2017
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): June 30, 2017 Level 1 Level 2 Level 3 Total Financial assets: Money market fund $ 4,794 $ — $ — $ 4,794 Corporate debt securities — 16,139 — 16,139 Commercial paper — 13,224 — 13,224 Total $ 4,794 $ 29,363 $ — $ 34,157 December 31, 2016 Level 1 Level 2 Level 3 Total Financial assets: Money market fund $ 9,657 $ — $ — $ 9,657 Corporate debt securities — 11,469 — 11,469 Commercial paper — 22,891 — 22,891 Total $ 9,657 $ 34,360 $ — $ 44,017
Summary of Estimated Value of Cash Equivalents and Marketable Securities and Gross Unrealized Holding Gains and Losses	The following table summarizes the estimated value of the Company’s cash equivalents and marketable securities and the gross unrealized holding gains and losses (in thousands): June 30, 2017 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market fund $ 4,794 $ — $ — $ 4,794 Corporate debt securities 251 — — 251 Total cash equivalents $ 5,045 $ — $ — $ 5,045 Marketable securities: Corporate debt securities $ 15,893 $ 1 $ (6 ) $ 15,888 Commercial paper 13,225 — (1 ) 13,224 Total marketable securities $ 29,118 $ 1 $ (7 ) $ 29,112 December 31, 2016 Amortized cost Unrealized gain Unrealized loss Estimated Fair Value Cash equivalents: Money market fund $ 9,657 $ — $ — $ 9,657 Corporate debt securities 2,180 — — 2,180 Total cash equivalents $ 11,837 $ — $ — $ 11,837 Marketable securities: Corporate debt securities $ 9,294 $ — $ (5 ) $ 9,289 Commercial paper 22,901 3 (13 ) 22,891 Total marketable securities $ 32,195 $ 3 $ (18 ) $ 32,180

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Components of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): June 30, December 31, 2017 2016 Compensation and related benefits $ 828 $ 1,299 Contract research costs 449 834 Franchise tax 90 97 Consulting costs — 106 Contract manufacturing costs — 122 Other 55 191 Total accrued liabilities $ 1,422 $ 2,649

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2017
Debt Disclosure [Abstract]
Schedule of Long-Term Debt and Unamortized Discount Balances	Long-term debt and unamortized discount balances are as follows (in thousands): June 30, December 31, 2017 2016 Face value of term loan $ 15,000 $ 15,000 Exit fee 1,125 1,125 Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees (1,227 ) (1,398 ) Term loan, net $ 14,898 $ 14,727

Stock Based Compensation (Table

Stock Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2017
Stock Option Activity	The following table summarizes stock option activity under the Company’s stock based compensation plan during the six months ended June 30, 2017 (in thousands, except share data): Shares Available for Grant Number of Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Life (in Years) Aggregate Intrinsic Value Outstanding as of December 31, 2016 646,778 1,212,044 $ 14.06 $ 2,414 Additional options authorized 417,833 Granted (576,200 ) 576,200 $ 10.91 Canceled 194,684 (194,684 ) $ 13.45 Outstanding as of June 30, 2017 683,095 1,593,560 $ 13.00 8.54 $ 1,531 Vested and exercisable as of June 30, 2017 536,953 $ 14.95 7.46 $ 712
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): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Research and development 215 $ 69 498 $ 303 General and administrative 731 105 1,772 209 Total $ 946 $ 174 $ 2,270 $ 512
Employees Stock Option [Member]
Fair Value of Stock Option Granted Using Black-Scholes Option Pricing Model	The fair value of employee stock options was estimated using the following weighted-average assumptions: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Expected term (in years) 5.27-6.02 — 5.27-6.02 — Volatility 79.0%-80.0% — 79.0%-80.0% — Risk free interest rate 1.6%-1.9% — 1.6%-2.2% — Dividend yield — — — —
Non-Employees Stock Option [Member]
Fair Value of Stock Option Granted Using Black-Scholes Option Pricing Model	The fair value of the stock options granted to non-employees is estimated at each reporting date using the Black-Scholes option-pricing model using similar assumptions as for employees except that the expected term is based on the options’ remaining contractual term instead of the simplified method: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Remaining contractual term (in years) 6.25-10.00 7.25-9.92 6.25-10.00 7.25-10.0 Volatility 88.0%-94.6% 89.4%-95.8% 87.4%-98.2% 89.4%-95.8% Risk free interest rate 1.9%-2.3% 1.4%-1.9% 1.9%-2.4% 1.4%-2.0% Dividend yield — — — —

Description of Business - Addit

Description of Business - Additional Information (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2017USD ($)Segment	Dec. 31, 2016USD ($)	Jun. 30, 2016USD ($)	Dec. 31, 2015USD ($)
Description Of Business [Abstract]
Entity incorporation, date of incorporation	Nov. 6, 2008
Number of operating segments | Segment	1
Cash and cash equivalents	$ 11,197	$ 27,756	$ 45,399	$ 4,778
Short-term marketable securities	29,112	32,180
Accumulated deficit	$ (98,743)	$ (76,358)

Summary of Significant Accoun23

Summary of Significant Accounting Policies - Additional Information (Detail) - Merger Agreement [Member] - shares	Mar. 22, 2016	Jun. 30, 2017
Significant Accounting Policies [Line Items]
Weighted effect of the conversion or issuance of common shares	6,668,045
Merger agreement closing date		Mar. 22, 2016

Summary of Significant Accoun24

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings per Share (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	1,603,740	320,249	1,603,740	320,249
Warrants to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	10,180	10,180	10,180	10,180
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities	1,593,560	310,069	1,593,560	310,069

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 34,157,000	$ 44,017,000
Financial liabilities	0	$ 0
Transfers between levels	$ 0
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available- for-sale of marketable securities contractual maturity	1 year	1 year
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 0	$ 0
Financial liabilities	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets and Liabilities Measured at Fair Value (Detail) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Financial assets:
Assets, Fair Value	$ 34,157,000	$ 44,017,000
Corporate Debt Securities [Member]
Financial assets:
Assets, Fair Value	16,139,000	11,469,000
Money Market Fund [Member]
Financial assets:
Assets, Fair Value	4,794,000	9,657,000
Commercial Paper [Member]
Financial assets:
Assets, Fair Value	13,224,000	22,891,000
Level 1 [Member]
Financial assets:
Assets, Fair Value	4,794,000	9,657,000
Level 1 [Member] | Money Market Fund [Member]
Financial assets:
Assets, Fair Value	4,794,000	9,657,000
Level 2 [Member]
Financial assets:
Assets, Fair Value	29,363,000	34,360,000
Level 2 [Member] | Corporate Debt Securities [Member]
Financial assets:
Assets, Fair Value	16,139,000	11,469,000
Level 2 [Member] | Commercial Paper [Member]
Financial assets:
Assets, Fair Value	13,224,000	22,891,000
Level 3 [Member]
Financial assets:
Assets, Fair Value	$ 0	$ 0

Fair Value Measurements - Estim

Fair Value Measurements - Estimated Value of Cash Equivalents and Marketable Securities and Gross Unrealized Holding Gains and Losses (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Cash Equivalents and Marketable Securities [Line Items]
Cash equivalents, Amortized cost	$ 5,045	$ 11,837
Cash equivalents, Estimated Fair Value	5,045	11,837
Corporate Debt Securities [Member]
Cash Equivalents and Marketable Securities [Line Items]
Cash equivalents, Amortized cost	251	2,180
Cash equivalents, Estimated Fair Value	251	2,180
Money Market Fund [Member]
Cash Equivalents and Marketable Securities [Line Items]
Cash equivalents, Amortized cost	4,794	9,657
Cash equivalents, Estimated Fair Value	4,794	9,657
Marketable Securities [Member]
Cash Equivalents and Marketable Securities [Line Items]
Marketable securities, Amortized cost	29,118	32,195
Marketable securities, Unrealized gain	1	3
Marketable securities, Unrealized loss	(7)	(18)
Marketable securities, Estimated Fair Value	29,112	32,180
Marketable Securities [Member] | Corporate Debt Securities [Member]
Cash Equivalents and Marketable Securities [Line Items]
Marketable securities, Amortized cost	15,893	9,294
Marketable securities, Unrealized gain	1
Marketable securities, Unrealized loss	(6)	(5)
Marketable securities, Estimated Fair Value	15,888	9,289
Marketable Securities [Member] | Commercial Paper [Member]
Cash Equivalents and Marketable Securities [Line Items]
Marketable securities, Amortized cost	13,225	22,901
Marketable securities, Unrealized gain		3
Marketable securities, Unrealized loss	(1)	(13)
Marketable securities, Estimated Fair Value	$ 13,224	$ 22,891

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Components of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Compensation and related benefits	$ 828	$ 1,299
Contract research costs	449	834
Franchise tax	90	97
Consulting costs		106
Contract manufacturing costs		122
Other	55	191
Total accrued liabilities	$ 1,422	$ 2,649

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Face value of term loan	$ 15,000,000	$ 15,000,000	$ 15,000,000
Loan final repayment exit fees payable	1,125,000	1,125,000	1,125,000
Loan origination fees and debt issuance costs	1,227,000	1,227,000	1,398,000
Interest expense	300,000	$ 600,000
Oxford Loan [Member]
Debt Instrument [Line Items]
Loan agreement, aggregate borrowing capacity			$ 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	$ 300,000	$ 300,000
Loan agreement, covenant noncompliance penalty		5.00%	5.00%
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%	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
Interest only payment period		18 months
Principal and interest payment period		36 months
Percentage of exit fee on principal balance	7.50%	7.50%
Loan final repayment exit fees payable	$ 1,100,000	$ 1,100,000
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] | Tranche B [Member]
Debt Instrument [Line Items]
Loan agreement, remaining amount available for borrowing			$ 10,000,000
Interest only payment period		6 months
Principal and interest payment period		30 months
Percentage of exit fee on principal balance	7.50%	7.50%

Debt - Schedule of Long-Term De

Debt - Schedule of Long-Term Debt and Unamortized Discount Balances (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Face value of term loan	$ 15,000	$ 15,000
Exit fee	1,125	1,125
Unamortized debt discount associated with exit fee, debt issuance costs and loan origination fees	(1,227)	(1,398)
Term loan, net	$ 14,898	$ 14,727

Sale of Assets - Additional Inf

Sale of Assets - Additional Information (Detail) - MYDICAR [Member] - Disposal Group Not Discontinued Operations [Member] - Theragene Pharmaceuticals, Inc. [Member] - USD ($)	1 Months Ended	6 Months Ended
	May 31, 2017	Jun. 30, 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
Other Income [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

Stock Option Plan - Stock Optio

Stock Option Plan - Stock Option Activity (Detail) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)
Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Exercise Price And Additional Disclosures [Abstract]
Shares Available for Grant, Outstanding, Beginning balance	646,778
Shares Available for Grant, Additional options authorized	417,833
Shares Available for Grant, Granted	(576,200)
Shares Available for Grant, Canceled	194,684
Shares Available for Grant, Outstanding, Ending balance	683,095
Number of Options, Outstanding, Beginning balance	1,212,044
Number of Options, Granted	576,200
Number of Options, Canceled	(194,684)
Number of Options, Outstanding, Ending balance	1,593,560
Number of Options, Vested and exercisable	536,953
Weighted Average Exercise Price Per Share, Outstanding, Beginning balance | $ / shares	$ 14.06
Weighted Average Exercise Price Per Share, Granted | $ / shares	10.91
Weighted Average Exercise Price Per Share, Canceled | $ / shares	13.45
Weighted Average Exercise Price Per Share, Outstanding, Ending balance | $ / shares	13
Weighted Average Exercise Price Per Share, Vested and exercisable | $ / shares	$ 14.95
Weighted Average Remaining Contractual Life, Ending balance	8 years 6 months 14 days
Weighted Average Remaining Contractual Life, Vested and exercisable	7 years 5 months 16 days
Aggregate Intrinsic Value | $	$ 1,531	$ 2,414
Aggregate Intrinsic Value, Vested and exercisable | $	$ 712

Stock Based Compensation - Addi

Stock Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted			576,200
Total unrecognized compensation expense	$ 8.7		$ 8.7
Weighted average period expected to recognized compensation expense (in years)			3 years 2 months 12 days
Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted	60,000	0	523,700	0
Weighted-average grant date fair value of employee option grants	$ 5.41		$ 7.69
Non-Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted	52,500	0	52,500	48,544

Stock Based Compensation - Fair

Stock Based Compensation - Fair Value of Stock Option Granted Using Black-Scholes Option Pricing Model (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility, minimum	79.00%		79.00%
Volatility, maximum	80.00%		80.00%
Risk free interest rate, minimum	1.60%		1.60%
Risk free interest rate, maximum	1.90%		2.20%
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 8 days		5 years 3 months 8 days
Employees Stock Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 7 days		6 years 7 days
Non-Employees Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility, minimum	88.00%	89.40%	87.40%	89.40%
Volatility, maximum	94.60%	95.80%	98.20%	95.80%
Risk free interest rate, minimum	1.90%	1.40%	1.90%	1.40%
Risk free interest rate, maximum	2.30%	1.90%	2.40%	2.00%
Non-Employees Stock Option [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 2 months 30 days	7 years 2 months 30 days	6 years 2 months 30 days	7 years 2 months 30 days
Non-Employees Stock Option [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	10 years	9 years 11 months 1 day	10 years	10 years

Stock Based Compensation - Summ

Stock Based Compensation - Summary of Non-cash Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 946	$ 174	$ 2,270	$ 512
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	215	69	498	303
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 731	$ 105	$ 1,772	$ 209

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Tax expense	$ 0	$ 0	$ 0	$ 0

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) - USD ($)	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Apr. 30, 2017
Other Commitments [Line Items]
Changes in commitments and contingencies	$ 0	$ 0
Palo Alto, California [Member]
Other Commitments [Line Items]
Lease commencement date		Apr. 1, 2017
Long-term operating lease expiry period		12 months
Lease renewal term		1 year
Operating leases, future minimum rent payable during next year	$ 300,000	$ 300,000
Security deposit of collateral for lease			$ 27,000