Achaogen (AKAOQ) 10-Q 8 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 02, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	AKAO
Entity Registrant Name	Achaogen Inc
Entity Central Index Key	1,301,501
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		42,393,609

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 134,657	$ 118,964
Short-term investments	64,744	26,912
Contracts receivable	240	12,151
Prepaids and other current assets	6,245	2,189
Restricted cash	7,380	127
Total current assets	213,266	160,343
Property and equipment, net	12,972	3,261
Restricted cash	3,855	250
Deposit and other assets		71
Total assets	230,093	163,925
Current liabilities:
Accounts payable	5,820	5,739
Accrued liabilities	9,468	9,698
Loan payable, current portion	12,500	4,167
Deferred revenue	2,708
Other current liabilities		104
Total current liabilities	30,496	19,708
Loan payable, long-term	12,374	21,110
Warrant liability	15,681	13,874
Derivative liability	664	602
Deferred rent	7,596	1,896
Total liabilities	66,811	57,190
Commitments and contingencies (Note 10)
Contingently redeemable common stock (Note 9)	10,000
Stockholders' equity
Common stock, $0.001 par value, 290,000,000 shares authorized at September 30, 2017 and December 31, 2016; 42,360,929 and 35,638,052 shares issued and outstanding at September 30, 2017 and December 31, 2016, respectively	42	35
Preferred stock, $0.001 par value, 10,000,000 shares authorized and zero shares issued and outstanding at September 30, 2017 and December 31, 2016	0	0
Additional paid-in-capital	489,704	353,927
Accumulated deficit	(336,455)	(247,220)
Accumulated other comprehensive loss	(9)	(7)
Total stockholders’ equity	153,282	106,735
Total liabilities, contingently redeemable common stock and stockholders’ equity	$ 230,093	$ 163,925

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value (dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	290,000,000	290,000,000
Common stock, shares issued	42,360,929	35,638,052
Common stock, shares outstanding	42,360,929	35,638,052
Preferred stock, par value (dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Contract revenue	$ 577	$ 16,046	$ 9,306	$ 31,039
Operating expenses
Research and development	25,316	20,536	66,113	56,137
General and administrative	11,805	4,460	27,415	12,188
Total operating expenses	37,121	24,996	93,528	68,325
Loss from operations	(36,544)	(8,950)	(84,222)	(37,286)
Interest expense	(740)	(670)	(2,170)	(1,555)
Change in warrant and derivative liabilities	6,773	(1,499)	(3,957)	(2,881)
Other income, net	604	81	1,114	219
Net loss	$ (29,907)	$ (11,038)	$ (89,235)	$ (41,503)
Net loss per common share (Note 2):
Basic	$ (0.71)	$ (0.41)	$ (2.31)	$ (1.88)
Diluted	$ (0.85)	$ (0.41)	$ (2.31)	$ (1.88)
Weighted-average shares used to compute net loss per common share
Basic	42,259,001	26,789,397	38,709,811	22,046,368
Diluted	43,211,059	26,789,397	38,709,811	22,046,368

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (29,907)	$ (11,038)	$ (89,235)	$ (41,503)
Other comprehensive (loss) income:
Net unrealized gain (loss) on available-for-sale securities	33	(13)	(2)	40
Total comprehensive loss	$ (29,874)	$ (11,051)	$ (89,237)	$ (41,463)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net loss	$ (89,235)	$ (41,503)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	851	333
Amortization of (discount) premium on short-term investments	(144)	278
Stock-based compensation expense	10,297	2,726
Loss on fixed asset disposition	54
Change in warrant and derivative liabilities	3,958	2,881
Non-cash interest expense relating to notes payable	639	481
Change in operating assets and liabilities:
Contracts receivable	11,911	(9,854)
Prepaids and other assets	(3,985)	(340)
Accounts payable and accrued liabilities	(752)	10,062
Deferred revenue	2,708
Other liabilities	860	(60)
Net cash used in operating activities	(62,838)	(34,996)
Cash flows from investing activities:
Purchase of property and equipment	(5,277)	(434)
Purchase of short-term investments	(121,796)	(19,311)
Maturities of short-term investments	84,106	38,230
Net cash (used in) provided by investing activities	(42,967)	18,485
Cash flows from financing activities:
Proceeds from underwritten public offering, net of issuance costs	121,192
Proceeds from issuance of contingently redeemable common stock, net of issuance costs	10,000
Proceeds from issuance of common stock and warrants, net of issuance costs		28,095
Proceeds from the issuance of common stock in connection with equity incentive plans	1,789	181
Proceeds from issuance of loan payable		10,000
Proceeds from exercise of stock warrants	417
Repayment of loan payable	(1,042)
Net cash provided by financing activities	132,356	38,276
Net increase in cash, cash equivalents, and restricted cash	26,551	21,765
Cash, cash equivalents, and restricted cash at beginning of period	119,341	20,414
Cash, cash equivalents, and restricted cash at end of period	145,892	42,179
Supplemental disclosures of cash flow information
Interest paid	1,531	$ 1,074
Supplemental disclosures of noncash investing and financing information
Reclassification of warrant liability to additional paid-in capital	2,089
Purchases of property plant and equipment included in deferred rent	$ 4,736

Organization and Basis of Prese

Organization and Basis of Presentation and Consolidation	9 Months Ended
	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation and Consolidation	1. Organization and Basis of Presentation and Consolidation Achaogen, Inc. (together with its consolidated subsidiary, the “Company”) is a late-stage biopharmaceutical company passionately committed to the discovery, development, and commercialization of novel antibacterial treatments against multi-drug resistant gram-negative infections. The Company is developing plazomicin, its lead product candidate, for the treatment of bacterial infections due to multi-drug resistant Enterobacteriaceae, including carbapenem-resistant Enterobacteriaceae (“CRE”). The Company’s Phase 3 study of plazomicin in the treatment of patients with complicated urinary tract infections (“cUTI”) and acute pyelonephritis (“AP”), entitled EPIC (Evaluating Plazomicin In cUTI), is expected to serve as a single pivotal study required to support a new drug application (“NDA”) for plazomicin in the United States, which was submitted in October 2017. In addition, the Company’s Phase 3 study of plazomicin, the CARE (Combating Antibiotic Resistant Enterobacteriaceae) trial, is a resistant pathogen-specific trial designed to evaluate the efficacy and safety of plazomicin in patients with infections due to CRE. The Company is also developing an orally-available antibacterial candidate, C-Scape, a combination of an approved β-lactam and an approved β-lactamase inhibitor to address a serious unmet need for an effective oral treatment for patients with cUTI, including AP, caused by ESBL-producing Enterobacteriaceae. The Company began a Phase 1 study of C-Scape in the second quarter of 2017. In the event the Phase 1 trial is successful, the Company intends to initiate a single pivotal Phase 3 study in patients with cUTI, including AP, who are suitable for treatment with oral antibiotics, in 2018. The Company was incorporated in Delaware in 2002 and commenced operations in 2004. Since commencing operations in 2004, the Company has devoted substantially all its resources to identifying and developing its product candidates, including conducting preclinical studies and clinical trials and providing general and administrative support for these operations. Reclassifications The cash and cash equivalents on the condensed consolidated statements of cash flows for the nine-month period ended September 30, 2016 has been reclassified to include restricted cash to conform to the current period’s presentation. Such reclassifications did not impact the Company’s net loss or financial position. Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and 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. The results of operations for the three-month and nine-month periods ended September 30, 2017 are not necessarily indicative of the results to be expected for the full year or any other future period. 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. Intercompany accounts and transactions have been eliminated upon consolidation. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K. Liquidity and Going Concern In September 2017, the Company was awarded a contract (“C-Scape Contract”) valued at up to $18.0 million in grant funding from the Biomedical Advanced Research and Development Authority (“BARDA”) to support the development of C-Scape. The C-Scape Contract includes a base period with committed funding of $12.0 million and subsequent option periods that, if exercised, would bring the total value of the award to $18.0 million. On May 31, 2017, the Company completed an underwritten public offering of 5,750,000 shares of its common stock at a price to the public of $22.50 per share, including the closing of the full exercise of the underwriters’ option to purchase an additional 750,000 shares of common stock on June 9, 2017. The Company received net proceeds from the offering of $121.2 million, after deducting the underwriting discounts and commissions and offering expenses. On May 4, 2017, the Company entered into an agreement with the Bill & Melinda Gates Foundation (the “Gates Foundation”) to discover drug candidates against gram-negative bacterial pathogens intended to prevent neonatal sepsis (the “Grant Agreement”). Pursuant to the Grant Agreement, the Gates Foundation awarded the Company up to approximately $10.5 million in grant funding (“Grant Funds”) over a three-year research term, of which approximately $3.2 million was received in May 2017 (the “Advance Funds”). Concurrently with the Grant Agreement, the Company entered into a Common Stock Purchase Agreement (the “Gates Purchase Agreement”) with the Gates Foundation, pursuant to which the Company agreed to sell 407,331 shares of its contingently redeemable common stock to the Gates Foundation in a private placement at a purchase price per share equal to $24.55, for gross proceeds to the Company of $10.0 million (“Gates Investment”). In connection with the Grant Agreement and the Gates Investment, the Company entered into a strategic relationship with the Gates Foundation (the “Letter Agreement”). Under the terms of the Letter Agreement, the Gates Investment and Grant Funds may only be used to conduct mutually agreed upon work, including the scale up of the Company’s antibody platform technology to launch a product intended to prevent neonatal sepsis (the “NSP”). Pursuant to the Letter Agreement, the Company agreed to make the NSP available and accessible in certain developing countries and to grant the Gates Foundation a non-exclusive license to commercialize selected drug candidates in certain developing countries, which may only be exercised in the event of certain defaults as described in the Letter Agreement (the “Global Access Commitments”). The Global Access Commitments will continue in effect until the earlier of 25 years from the closing of the Gates Investment or 7 years following the termination of all funding provided by the Gates Foundation; provided, that the Global Access Commitments will continue for any products or services developed with funding provided by the Gates Foundation which continue to be developed or available in certain developing countries. The Company has incurred losses and negative cash flows from operations every year since its inception. As of September 30, 2017, the Company had unrestricted cash, cash equivalents and short-term investments of approximately $199.4 million and an accumulated deficit of approximately $336.5 million. Management expects that, based on its current operating plans, the Company’s existing cash, cash equivalents and short-term investments as of September 30, 2017 will be sufficient to fund its current planned operations for at least the next twelve months from the issuance of these financial statements. Management plans to raise additional funds through equity or debt financing arrangements, government contracts, and/or third party collaboration funding in the future to fund its operations, including the commercial development of plazomicin. However, there can be no assurance that such funding sources will be available at terms acceptable to the Company or at all. If the Company is unable to raise additional funding to meet its working capital needs, it will be forced to delay or reduce the scope of its research programs and/or limit or cease its operations. The accompanying financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The financial statements do not reflect any adjustments relating to the recoverability and reclassification of assets and liabilities that might be necessary if the Company is unable to continue as a going concern.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The accompanying financial statements have been prepared in accordance with U.S. GAAP. The preparation of financial statements in conformity with U.S. GAAP requires management to make judgments, assumptions and estimates that affect the reported amounts of assets, liabilities, revenues and expenses and related disclosures of contingent liabilities. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of liabilities, common stock and stock-based awards and income taxes. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates. Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, including cash and cash equivalents, contracts receivable, prepaid and other current assets, accounts payable, accrued liabilities, and other current liabilities approximate fair value due to their short-term maturities. Short-term investments consist of available-for-sale securities and are carried at fair value. Based upon the borrowing rates (which is a Level 2 input) currently available to the Company for loans with similar terms, the Company believes the carrying amount of the loan payable approximates its fair value. The warrant and derivative liabilities are recorded at estimated fair value with changes in estimated fair value recorded in the Company's statements of operations. Cash and Cash Equivalents Cash equivalents include only securities having a maturity of three months or less at the time of purchase. As of September 30, 2017 and December 31, 2016, cash and cash equivalents consisted of bank deposits, cash, commercial paper, money market funds, cash repurchase agreement investments and overnight cash sweep investments in government money market funds. Short-term Investments Short-term investments consist of debt securities with maturities greater than three months, but less than one year from the date of acquisition, and are classified as available for sale. Short-term investments are carried at fair value. Unrealized gains and losses on available-for-sale securities are excluded from earnings and reported as a component of net unrealized gain (loss) on available-for-sale securities in the Company's consolidated statements of comprehensive loss. The amortized cost of debt securities reflects amortization of purchase premiums and accretion of purchase discounts to date, which are included in interest income. The Company reviews all of its marketable securities on a regular basis to evaluate whether any security has experienced an other-than-temporary decline in fair value. Restricted Cash At September 30, 2017 and December 31, 2016, the Company had restricted cash of $11.2 million and $0.4 million, respectively. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in thousands): September 30, 2017 December 31, 2016 Cash and cash equivalents $ 134,657 $ 118,964 Restricted cash, current 7,380 127 Restricted cash, non-current 3,855 250 Total cash, cash equivalents, and restricted cash $ 145,892 $ 119,341 As of September 30, 2017 and December 31, 2016, the Company had $10.7 million and zero, respectively, of restricted cash related to the cash provided by the Gates Foundation, in connection with the Grant Agreement, Gates Purchase Agreement and Letter Agreement (see Note 1). As of September 30, 2017 and December 31, 2016, the Company had $0.5 million and $0.4 million, respectively, of restricted cash, which relates to the Company’s facility leases. Concurrently with the Grant Agreement, the Company entered into the Gates Purchase Agreement, pursuant to which the Company issued 407,331 shares of contingently redeemable common stock to the Gates Foundation for the Gates Investment (see Note 1). In addition, the Letter Agreement, among other things, restricts the Company’s use of both the Grant Funds and the Gates Investment to expenditures, including an allocation of overhead and administrative expenses, that are reasonably attributable to the activities required to support the research projects funded by the Gates Foundation. As a result of such restrictions, as of September 30, 2017, the Company classified the unspent portions of the Grant Funds and Gates Investment, held at one of the Company’s financial institutions, as restricted cash. The restricted cash related to the Company’s leases, which consists of a money market account with one of the Company’s financial institutions, serves as collateral for the letters of credit provided as security deposits under the Company’s facility lease and expire approximately 90 days from the end of their respective lease terms. Warrant Liability On June 3, 2016, the Company issued warrants to purchase 1,999,999 shares of its common stock in connection with a private placement financing transaction (the “Private Placement”). Each warrant has an exercise price of $3.66 per share and is exercisable for five years from the date of issuance. The Company accounts for these warrants as a liability instrument measured at estimated fair value. The initial fair value of the warrants was determined using a calibration model that involved using the Black-Scholes Pricing Model ("Black-Scholes"), which requires inputs such as the risk-free interest rate, expected share price volatility, underlying price per share of the Company's common stock and remaining term of the warrants. The warrants are subject to remeasurement at each balance sheet date, using Black-Scholes, with any changes in the fair value of the outstanding warrants recognized in the condensed consolidated statements of operations. As of September 30, 2017, warrants to purchase 1,178,782 shares of the Company’s common stock remain outstanding and unexercised. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. The Company has one operating segment. Customer Concentration For the three-month and nine-month periods ended September 30, 2017 and 2016, the Company’s revenue was generated from funding pursuant to U.S. government contracts and a non-profit foundation grant. All contracts receivable relate to funding from U.S. government contracts. Concentration of Credit Risk Financial instruments that potentially subject the Company to a significant concentration of credit risk consist of cash, cash equivalents and short-term investments. Cash and cash equivalents are deposited in checking, overnight sweep and money market accounts at one financial institution with balances that generally exceed federally insured limits. Management believes that the financial institution is financially sound, and, accordingly, minimal credit risk exists with respect to this financial institution. The Company’s investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of default by the institutions holding its cash and cash equivalents or issuing the debt securities. As of September 30, 2017 and December 31, 2016, the Company had not experienced any credit losses in such accounts or investments. Revenue Recognition The Company recognizes revenue when: (i) evidence of an arrangement exists, (ii) fees are fixed or determinable, (iii) services have been delivered, and (iv) collectability is reasonably assured. The Company currently generates revenue from government contracts and a non-profit foundation grant (collectively, the “Revenue Contracts”). Revenue Contracts are agreements that provide the Company with payments for certain types of expenditures in return for research and development activities over a contractually-defined period. Revenue from the Revenue Contracts is recognized in the period during which the related costs are incurred and the related services are rendered, provided that the applicable conditions under the government contracts have been met. Costs of contract revenue are recorded as a component of operating expenses in the Company's consolidated statement of operations. Funds received from third parties under contract arrangements are recorded as revenue if the Company is deemed to be the principal participant in the contract arrangements because the activities under the contracts are part of the Company’s development programs. If the Company is not the principal participant, the funds from contracts are recorded as a reduction to research and development expense. Contract funds received are not refundable and are recognized when the related qualified research and development costs are incurred and when there is reasonable assurance that the funds will be received. Funds billed and received in advance are recorded as deferred revenue. Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses include certain payroll and personnel expenses; laboratory supplies; consulting costs; external contract research and development expenses; and allocated overhead, including rent, equipment depreciation and utilities, and relate to both Company-sponsored programs as well as costs incurred pursuant to collaboration agreements and government contracts. The Company estimates preclinical study and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on its behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Payments made to third parties under these arrangements in advance of the receipt of the related services are recorded as prepaid expenses until the services are rendered. Advance payments for goods or services that will be used or rendered for future research and development activities are capitalized as prepaid expenses and other current assets and recognized as an expense as the goods are delivered or the related services are performed. Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which provides a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most current revenue recognition guidance. This ASU is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. This ASU defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP. The Company expects to adopt the new revenue standard as of January 1, 2018 using the modified retrospective method. The Company has completed its assessment of the first step which included identifying the Company’s customers. Through the remainder of 2017, the Company will continue to assess the potential impact of adopting this new standard on any current, new or significantly modified customer contracts. In subsequent quarters, the Company will complete its evaluation of additional disclosures that may be required upon adoption of the new standard. In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting Net Loss Per Share Basic net loss per common share is computed by dividing the net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share is computed by dividing the net loss by the weighted-average number of common shares and dilutive common share equivalents outstanding during the period. For purposes of this calculation, preferred stock, stock options, restricted stock units and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following tables set forth the computation of the Company’s basic and diluted net loss per share (in thousands, except shares and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Numerator: Net loss used to compute basic net loss per share $ (29,907 ) $ (11,038 ) $ (89,235 ) $ (41,503 ) Less: Gain on private placement warrants (6,795 ) - - - Net loss used to compute diluted net loss per share $ (36,702 ) $ (11,038 ) $ (89,235 ) $ (41,503 ) Denominator: Weighted-average shares used to compute basic net loss per share 42,259,001 26,789,397 38,709,811 22,046,368 Add: Private placement warrant shares 952,058 - - - Weighted-average shares used to compute diluted net loss per share 43,211,059 26,789,397 38,709,811 22,046,368 Net loss per share: Basic $ (0.71 ) $ (0.41 ) $ (2.31 ) $ (1.88 ) Diluted $ (0.85 ) $ (0.41 ) $ (2.31 ) $ (1.88 ) For the three-month and nine-month periods ended September 30, 2017 and 2016, potentially dilutive securities outstanding have been excluded from the computations of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported. The following potentially dilutive securities have been excluded from diluted net loss per share, because their effect would be antidilutive, as of September 30, 2017 and 2016: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Options to purchase common stock 4,793,775 3,416,136 4,793,775 3,416,136 Restricted stock units 845,705 561,428 845,705 561,428 Warrants to purchase common stock 17,514 2,030,023 1,196,296 2,030,023

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Financial assets and liabilities are recorded at fair value. The carrying amount of certain financial instruments, including cash and cash equivalents, restricted cash, contracts receivable, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. 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 : Quoted prices in active markets for identical assets or liabilities. Level 2 : Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices 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 assets or liabilities. Level 3 : Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. Where quoted prices are available in an active market, securities are classified as Level 1 of the valuation hierarchy, including cash held at overnight sweep accounts. The Company’s Level 2 valuations of marketable securities are generally derived from independent pricing services based upon quoted prices in active markets for similar securities, with prices adjusted for yield and number of days to maturity, or based on industry models using data inputs, such as interest rates and prices that can be directly observed or corroborated in active markets. In certain cases, where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3 within the valuation hierarchy. Level 3 liabilities that are measured at estimated fair value on a recurring basis consist of a derivative liability in connection with loan payable and a warrant liability in connection with the Private Placement. As of September 30, 2017 and December 31, 2016, financial assets and liabilities measured and recognized at fair value on a recurring basis and classified under the appropriate level of the fair value hierarchy as described above were as follows (in thousands): September 30, 2017 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Assets Level 1: Cash equivalents $ 126,267 $ — $ — $ 126,267 Restricted cash 11,235 — — 11,235 Subtotal 137,502 — — 137,502 Level 2: Corporate debt securities 8,664 — (2 ) 8,662 U.S. Treasury bills 21,004 — (8 ) 20,996 Commercial paper 43,475 1 — 43,476 Subtotal 73,143 1 (10 ) 73,134 Total $ 210,645 $ 1 $ (10 ) $ 210,636 Reported as: Cash and cash equivalents $ 134,657 Short-term investments $ 64,744 Restricted cash $ 11,235 Liabilities, Level 3 Warrant Liability $ 15,681 Derivative Liability $ 664 Total $ 16,345 December 31, 2016 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Assets Cash $ 3,728 $ — $ — $ 3,728 Level 1: Restricted cash 377 — — 377 Money market funds 115,236 — — 115,236 Subtotal 115,613 — — 115,613 Level 2: Corporate debt securities 12,969 — (7 ) 12,962 Commercial paper 13,950 — — 13,950 Subtotal 26,919 — (7 ) 26,912 Total $ 146,260 $ — $ (7 ) $ 146,253 Reported as: Cash and cash equivalents $ 118,964 Short-term investments $ 26,912 Restricted cash $ 377 Liabilities, Level 3 Warrant liability $ 13,874 Derivative liability $ 602 Total $ 14,476 All available-for-sale securities held as of September 30, 2017 had maturities less than one year from the date of acquisition. There were no sales of available-for-sale securities in any of the periods presented. The carrying value of debt securities that were in unrealized loss positions totaled $31.3 million as of September 30, 2017. The Company has determined that (i) it does not have the intent to sell any of these investments, and (ii) it is not more likely than not that it will be required to sell any of these investments before recovery of the entire amortized cost basis. The Company anticipates that it will recover the entire amortized cost basis of such debt securities and has determined that no other-than-temporary impairments associated with credit losses were required to be recognized during the three-month and nine-month periods ended September 30, 2017. Pursuant to the loan and security agreement with Solar Capital Ltd. (see Note 7), the Company entered into a Success Fee Agreement under which the Company agreed to pay $1.0 million in cash (the "Success Fee") if the Company obtains approval to market plazomicin from the Food and Drug Administration (the "FDA"). If such approval is obtained, the Success Fee shall be due the later of (i) August 5, 2019 or (ii) the date such FDA approval is obtained. The fair value of the Success Fee, approximately $602,000 at December 31, 2016, is recorded as a derivative liability and included in other long-term liabilities on the accompanying condensed consolidated balance sheet. The estimated fair value of the derivative liability as of September 30, 2017 increased by $21,000 and $62,000 to $664,000 from December 31, 2016, as a result of the time value of money, which is presented as change in warrant and derivative liabilities in the Company's condensed consolidated statements of operations for the three-month and nine-month periods ended September 30, 2017, respectively. The fair value of the derivative liability was determined using a discounted cash flow analysis, and is classified as a Level 3 measurement within the fair value hierarchy since the Company’s valuation utilized significant unobservable inputs. Specifically, the key assumptions included in the calculation of the estimated fair value of the derivative instrument include: i) the Company’s estimates of both the probability and timing of a potential $1.0 million payment to Solar Capital Ltd. as a result of FDA approval to market plazomicin, and ii) a discount rate of 13% which was derived from the Company's estimated cost of debt. The estimated fair value of the derivative liability is most sensitive to the probability of FDA approval. Should the probability of FDA approval change by 5%, the fair value of the derivative liability as of September 30, 2017 would change by approximately $39,000. For the three-month and nine-month periods ended September 30, 2017, there was no change to the key assumptions used in the calculation of the estimated fair value. Any changes in the estimated fair values are presented as changes in warrant and derivative liabilities in the Company's condensed consolidated statements of operations. Pursuant to the Private Placement (see Note 2), the Company issued warrants to purchase 1,999,999 shares of common stock at an exercise price of $3.66. The Company classified these warrants as a liability measured at fair value using Black-Scholes. Under certain entity conditions, the holder of a warrant may require the Company to settle the warrant in cash at its estimated fair value using Black-Scholes. On June 3, 2016, the closing date of the Private Placement, the $2.6 million initial estimated fair value of the warrants was recorded as a warrant liability on the accompanying condensed consolidated balance sheet. At September 30, 2017 and December 31, 2016, the estimated fair values of the outstanding warrants were approximately $15.7 million and $13.9 million, respectively. The change in the estimated fair value is primarily due to the change in the Company's stock price and is included in changes in warrant and derivative liabilities in the Company's condensed consolidated statements of operations. During the nine-month period ended September 30, 2017, certain holders of these warrants exercised warrants to purchase 113,948 shares of common stock. The Company received $0.4 million in proceeds from these warrant exercises. The Company is required to record the exercised warrants at its estimated fair value at the time of exercise, with any change included in changes in warrant and derivative liabilities in the Company’s condensed consolidated statements of operations. The Company estimated the fair value of these exercised warrants at their respective exercise dates to be $2.1 million, an increase of $0.9 million from its valuation, at December 31, 2016, of $1.2 million, primarily due to an increase in the Company’s stock price. The fair value of the warrant liability is classified as a Level 3 measurement within the fair value hierarchy since the Company’s valuation utilized significant unobservable inputs, including the risk-free interest rate, expected share price volatility, underlying price per share of the Company's common stock and remaining term of the warrants. At September 30, 2017 and December 31, 2016, the estimated fair values of the warrants were determined using Black-Scholes with the following assumptions: September 30, 2017 December 31, 2016 Expected volatility 80% 80% Expected term 3.7 years 4.2 years Risk-free interest rate 1.7% 1.8% Dividend yield —% —% The expected volatility is based on the Company's expected volatility. The expected term is based on the remaining life of the warrants. The risk-free interest rate is obtained from the yields on actively traded U.S. Treasury securities for a period equal to the expected term of the warrants. The dividend yield is zero because the Company has never paid cash dividends and has no present intention to pay cash dividends. Should the share price change by 5%, the fair value of the warrant liability as of September 30, 2017 would change by approximately $0.9 million. Changes in the fair value of recurring measurements included in Level 3 of the fair value hierarchy are presented as changes in warrant and derivative liabilities in the Company's condensed consolidated statements of operations and were as follows for the nine-month period ended September 30, 2017 (in thousands): Estimated Fair Value of Warrant Liability Estimated Fair Value of Derivative Liability Balance of Level 3 Liabilities at December 31, 2016 $ 13,874 $ 602 Change in estimated fair value of warrant liability 3,896 — Reclassification of warrant liability to additional paid in capital upon exercise of warrants (2,089 ) — Change in estimated fair value of derivative liability — 62 Balance of Level 3 Liabilities at September 30, 2017 $ 15,681 $ 664 Warrants outstanding as of September 30, 2017 and 2016 have a weighted-average exercise price of $3.78.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2017
Payables And Accruals [Abstract]
Balance Sheet Components	4. Balance Sheet Components Prepaids and other current assets Prepaids and other current assets consisted of the following (in thousands): September 30, 2017 December 31, 2016 Deferred research and development costs $ 4,457 $ 660 Prepaid expenses 1,490 1,390 Other current assets 298 139 $ 6,245 $ 2,189 Property and Equipment, net Property and equipment, net consisted of the following (in thousands): September 30, 2017 December 31, 2016 Office equipment $ 863 $ 644 Laboratory equipment 5,701 4,038 Leasehold improvements 8,055 1,072 Construction-in-progress 1,436 1,896 16,055 7,650 Less: accumulated depreciation and amortization (3,083 ) (4,389 ) Property and equipment, net $ 12,972 $ 3,261 Depreciation and amortization expense for the three-month periods ended September 30, 2017 September 30, 2017 Accrued Liabilities Accrued liabilities consisted of the following (in thousands): September 30, 2017 December 31, 2016 Accrued clinical and development expenses $ 2,188 $ 3,681 Payroll and related bonus expenses 6,242 4,941 Other 1,038 1,076 $ 9,468 $ 9,698

License and Collaboration Agree

License and Collaboration Agreements	9 Months Ended
	Sep. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License and Collaboration Agreements	5. License and Collaboration Agreements Thermo Fisher Scientific, Inc. In April 2016, the Company entered into an agreement with its collaboration partner, Microgenics Corporation (“Thermo Fisher”), a wholly owned subsidiary of Thermo Fisher Scientific, Inc., to develop and commercialize an assay to support plazomicin. If approved, the Company and Thermo Fisher plan to have a commercial assay for plazomicin available at launch to enable health care professionals to make decisions on safe and efficacious doses of plazomicin. In accordance with the terms of the agreement, the Company is required to make milestone payments with respect to research, development, regulatory and commercialization milestones (if any). All such milestone payments may total, in aggregate, up to but no more than approximately $6.5 million. In further consideration of this agreement, in the event of a successful commercialization of the assay, the Company is required to pay a minimum threshold annual revenue to Thermo Fisher. In February 2017, the Company announced the achievement of a strategic milestone in its ongoing collaboration to develop an assay enabling therapeutic drug management of plazomicin, and incurred $0.9 million of research and development expense related to this milestone. As of September 30, 2017, the Company has incurred $1.7 million in milestone payments and these costs were fully recorded as research and development expense. Crystal Biosciences, Inc. In May 2016, the Company entered into a collaboration and license agreement with Crystal Biosciences, Inc. (“Crystal”). Pursuant to the terms of this agreement, the Company and Crystal agreed to collaborate on the discovery of monoclonal antibodies against multiple targets. Crystal agreed to conduct the initial discovery work with its antibody platform and the Company has the right to develop and commercialize the antibodies discovered through this collaboration. The Company is required to provide signing and milestone payments with respect to research, development, regulatory and commercialization milestones (if any). All such milestone payments may total, in aggregate, up to but no more than approximately $20.6 million. The upfront signing fee, technology access fees and research funding were recorded as research and development expense. This collaboration and license agreement also provides that the Company shall pay royalties equal to a low single-digit percentage of annual worldwide net sales of the commercialized product. Ionis Pharmaceuticals In January 2006, the Company entered into a license agreement with Ionis Pharmaceuticals, Inc. (“Ionis”). Ionis granted the Company an exclusive, worldwide license with the right to grant and authorize sublicenses related to the research and development of aminoglycoside products. As an up-front fee, the Company issued 97,402 shares of Series A convertible preferred stock at a fair value of $15.40 per share. This license fee of $1,500,000 was recorded as research and development expense in 2006. In further consideration of this license, and in accordance with the terms of the agreement, the Company is required to make milestone payments with respect to development, regulatory and commercialization milestones, and to pay a percentage of revenue received from sublicensees (if any). All such milestone and sublicense revenue payments may total, in the aggregate, up to but no more than $19,500,000 for the first product and $9,750,000 following the second product commercialized under the agreement with Ionis. The Company is also required to pay additional milestone payments of up to $20,000,000 in the aggregate upon the first achievement of specified threshold levels of annual net sales of all aminoglycoside products in a calendar year. The license agreement also provides that the Company shall pay royalties equal to a low single-digit percentage of annual worldwide net sales of all licensed products, including, if applicable, plazomicin. Through September 30, 2017, the Company had compensated Ionis $7,000,000 in connection with the first three milestones under the license for the first aminoglycoside product candidate. As of September 30, 2017, the Company had no outstanding payments due under the license.

Revenue Contracts

Revenue Contracts	9 Months Ended
	Sep. 30, 2017
Contractors [Abstract]
Revenue Contracts	6. Revenue Contracts Certain of the Company’s drug discovery and development activities are performed under contracts with the Gates Foundation and U.S. government agencies. Management has determined that the Company is the principal participant in the following contract arrangements, and, accordingly, the Company records amounts earned under the arrangements as revenue. Costs incurred under the Revenue Contracts are recorded as operating expenses in the Company's consolidated statements of operations. Bill & Melinda Gates Foundation In May 2017, the Company entered into an agreement with the Gates Foundation to discover drug candidates against gram-negative bacterial pathogens intended to prevent neonatal sepsis (the “Grant Agreement”). The Gates Foundation awarded the Company up to approximately $10.5 million in grant funding (“Grant Funds”) over a three-year research term, of which approximately $3.2 million of committed funding was received in May 2017 (the “Advance Funds”). The Advance Funds are replenished by the Gates Foundation each calendar year, or sooner, following the Company’s submission of a progress report, including expenses incurred for the research activities. Under certain conditions, as described in the Grant Agreement, the Gates Foundation may terminate the Grant Agreement and the Company is obligated to return to the Gates Foundation any unused portion of the Advance Funds. In accordance with the Company’s significant accounting policies, the Advance Funds are recorded as deferred revenue. The Company recorded contract revenue of $0.3 million and $0.5 million, respectively, under this agreement during the three-month and nine-month periods ended Biomedical Advanced Research and Development Authority In August 2010, the Company was awarded a contract with the Biomedical Advanced Research and Development Authority (“BARDA”) for the development, manufacturing, nonclinical and clinical evaluation of, and regulatory filings for, plazomicin as a countermeasure for disease caused by antibiotic-resistant pathogens and biothreats. The original contract included committed funding of $27.6 million for the first two years of the contract and subsequent options exercisable by BARDA to provide additional funding. In September 2012, BARDA exercised an additional $15.8 million contract option ("Option 1"), which increased the total contract committed funding to $43.4 million through March 2014. In April 2013, the Company was awarded an additional $60.4 million under the contract to support its Phase 3 clinical trial of plazomicin ("Option 2") to increase the total committed funding under this contract to $103.8 million. On May 26, 2016, the Company was awarded an additional $20.0 million ("Option 3") under the contract to support its Phase 3 EPIC trial of plazomicin. In April 2017, BARDA modified Option 1 to allow for an additional $0.5 million of contract funding. This brings the total committed funding under this contract to $124.3 million. Through September 30, 2017, a total of $124.3 million has been recorded as revenue, with an insignificant amount of funding remaining under this BARDA contract. In September 2017, the Company was awarded the C-Scape Contract (“C-Scape Contract”) valued at up to $18.0 million from BARDA to support the development of C-Scape. The C-Scape Contract includes a base period with committed funding of $12.0 million and subsequent option periods that, if exercised, would bring the total value of the award to $18.0 million. Through September 30, 2017, the Company has recorded an insignificant amount to revenue, with $12.0 million remaining available from the funding currently commited under the C-Scape Contract. The Company recorded contract revenue of zero and $15.4 million under these agreements during the three-month periods ended September 30, 2017 and 2016, respectively, and $7.7 million and $29.2 million, respectively, during the nine-month periods ended September 30, 2017 and 2016. National Institute of Allergy and Infectious Diseases In July 2015, the Company was awarded a contract by the National Institute of Allergy and Infectious Diseases ("NIAID") to support the discovery and development of LpxC inhibitors for the treatment of bacterial infections for $1.5 million committed through June 30, 2016. In January 2016, an additional committed funding of $0.5 million was added. In April 2016, NIAID modified the contract to exercise the first option to increase the total contract committed funding to $4.4 million through February 2018. In April 2017, NIAID modified the contract to add committed funding of $0.3 million to the first option, bringing the total committed funding to $4.7 million. In June 2017, NIAID modified the contract to exercise the second option of $0.6 million, bringing the total committed funding to $5.3 million, of which $0.8 million remains available. During the third quarter of 2017, the Company decided to discontinue all research and development efforts on our preclinical LpxC inhibitor programs for gram-negative pathogens. The Company does not expect to draw further revenues under this contract. The Company recorded contract revenue of $0.3 million and $0.6 million under these agreements during the three-month periods ended September 30, 2017 and 2016, respectively, and $1.1 million and $1.8 million, respectively, during the nine-month periods ended September 30, 2017 and 2016.

Borrowings

Borrowings	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Borrowings	7. Borrowings Solar Capital Ltd. Loan Agreement On August 5, 2015, the Company entered into a loan and security agreement (the “Loan Agreement”) with Solar Capital Ltd. (the “Lender”) pursuant to which the Lender agreed to make available to the Company term loans in an aggregate principal amount of up to $25.0 million with a maturity date of August 5, 2019. An initial $15.0 million term loan was funded at closing on August 5, 2015, and a second $10.0 million term loan was funded on June 20, 2016. Borrowings under the term loans bear interest per annum at 6.99% plus the greater of 1% or the one-month LIBOR. Beginning on September 1, 2017 the Company is required to make monthly payments of interest plus equal monthly payments of principal over a term of 24 months. The Loan Agreement requires collateral by a security interest in all of the Company’s assets except intellectual property (which is subject to a negative pledge) and contains customary affirmative and negative covenants, and also includes standard events of default, including payment defaults. Upon the occurrence of an event of default, a default interest rate of an additional 4% may be applied to the outstanding loan balances, and the Lender may declare all outstanding obligations immediately due and payable and take such other actions as set forth in the Loan Agreement. There were no financial covenants attached to the loan. The Loan Agreement included a closing fee of $250,000 which was paid at closing, and the Company is obligated to pay a fee equal to 8% of the term loans funded upon the earliest to occur of the maturity date, the acceleration of the term loans or the voluntary prepayment of the term loans. The cost of these fees is being amortized as interest expense over the term of the loan using the effective-interest method. The Company may voluntarily prepay all, but not less than all, of the outstanding term loans. The Loan Agreement contains customary representations, warranties and covenants. In addition, the Loan Agreement contains customary events of default that entitle the Lender to cause the Company’s indebtedness under the Loan Agreement to become immediately due and payable. On August 5, 2015, pursuant to the Loan Agreement, the Company entered into a Success Fee Agreement with the Lender under which the Company agreed to pay the Lender $1.0 million if the Company obtains FDA approval to market plazomicin. If such approval is obtained, the Success Fee shall be due the later of (i) August 5, 2019 or (ii) the date such FDA approval is obtained. The fair value of the Success Fee at the date of issuance of approximately $356,000 was recorded as a debt discount and is being amortized as interest expense over the term of the loan using the effective-interest method. Future principal debt payments on the currently outstanding term loan are payable as follows (in thousands): September 30, 2017 2017 $ 3,125 2018 12,500 2019 8,333 Total principal payments 23,958 Final fee due at maturity in 2019 2,000 Total principal and final fee payments 25,958 Unamortized discount and debt issuance costs (1,084 ) Total loan obligation 24,874 Less current portion (12,500 ) Loan payable, long-term $ 12,374 The obligation includes a final fee of $2.0 million, representing 8% of the term loan currently funded, which accretes over the life of the loan as interest expense. The Company recorded interest expense related to the loan of $0.7 million and $0.7 million for the three-month periods ended September 30, 2017 and 2016, respectively, and $2.2 million and $1.6 million, respectively, for the nine-month periods ended September 30, 2017 and 2016.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stockholders' Equity	8. Stockholders' Equity On April 7, 2015, the Company filed a Registration Statement on Form S-3 (the “2015 Shelf Registration Statement”), which included a prospectus covering the offering, issuance and sale of up to $30.0 million of shares of the Company’s common stock from time to time in an “at-the-market” (“ATM”) equity offering. The Company entered into a Sales Agreement (the “Sales Agreement”) with Cowen and Company, LLC (“Cowen”), pursuant to which the Company may issue and sell shares of its common stock having aggregate sales proceeds of up to $30.0 million from time to time through an ATM equity program under which Cowen acts as sales agent. As of September 30, 2017, the Company had sold 1,105,549 shares of common stock under the Sales Agreement, at a weighted-average price of approximately $4.82 per share for aggregate gross proceeds of $5.3 million and net proceeds of $5.1 million after deducting the sales commissions and offering expenses. As of September 30, 2017, $24.7 million of common stock remained available to be sold under the Sales Agreement, subject to certain conditions specified therein. On June 3, 2016, the Company sold 7,999,996 shares of its common stock and warrants to purchase 1,999,999 shares of its common stock pursuant to the Purchase Agreement for aggregate gross proceeds of $25.4 million in the Private Placement. The warrants have an exercise price of $3.66 and are exercisable up to five years from the date of issuance. The Company's Chief Operating Officer, a related party, participated in the Private Placement by purchasing 141,453 shares of common stock and a warrant to purchase 35,363 shares of common stock for an aggregate purchase price of $0.5 million. Issuance costs of $0.3 million were offset against equity as a reduction from gross proceeds. At the close of the Private Placement, the estimated fair values of the common stock and warrants issued were $22.9 million and $2.6 million, respectively. At September 30, 2017, using Black-Scholes, the Company estimated the fair value of the remaining warrants outstanding to be $15.7 million and recorded a charge of $1.8 million and $11.3 million, for the increase in the liability, in the condensed consolidated statements of operations, for the nine-month period ended , On December 19, 2016, the Company completed an underwritten public offering of 7,475,000 shares of its common stock at a price to the public of $13.50 per share, including the full exercise of the underwriters’ option to purchase an additional 975,000 shares of common stock. The Company received net proceeds from the offering of $94.6 million, after deducting the underwriting discounts and commissions and estimated offering expenses. On May 31, 2017, the Company completed an underwritten public offering of 5,750,000 shares of its common stock at a price to the public of $22.50 per share, including the closing of the full exercise of the underwriters’ option to purchase an additional 750,000 shares of common stock on June 9, 2017. The Company received net proceeds from the offering of $121.2 million, after deducting the underwriting discounts and commissions and offering expenses. Equity Incentive Plans 2014 Equity Incentive Award Plan In February 2014, the Company’s stockholders approved the 2014 Equity Incentive Award Plan (the "2014 Plan"), which became effective as of March 11, 2014. Under the 2014 Plan, the Company may grant incentive stock options ("ISOs"), nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units ("RSUs") and other stock-based awards for the purchase of that number of shares of common stock. Effective January 1, 2017, the compensation committee of the Board of Directors approved an evergreen increase of 1,425,522 shares that may be granted in accordance with the terms of the 2014 Plan. As of September 30, 2017, 797,864 shares were available for future issuance under the 2014 Plan. Under the 2014 Plan, the terms of stock award agreements, including vesting requirements, are determined by the board of directors, subject to the provisions of the 2014 Plan. Options granted by the Company typically vest over a four year period and the exercise price may not be less than fair market value on the date of grant. Certain of the options are subject to acceleration of vesting in the event of certain change of control transactions. Options granted under the 2014 Plan expire no later than 10 years from the date of grant. 2014 Employment Commencement Incentive Plan In December 2014, the Company adopted a 2014 Employment Commencement Incentive Plan (the "Inducement Plan"). The Inducement Plan is designed to comply with the inducement exemption contained in Nasdaq’s Rule 5635(c)(4), which provides for the grant of non-qualified stock options, RSUs, restricted stock awards, performance awards, dividend equivalents, deferred stock awards, deferred stock units, stock payment and stock appreciation rights to a person not previously an employee or director of the Company, or following a bona fide period of non-employment, as an inducement material to the individual’s entering into employment with the Company. As of September 30, 2017, a total of 2,050,000 shares of common stock have been authorized under the Inducement Plan, including an additional 450,000 shares that became available resulting from an amendment adopted by the Board of Directors as of September 13, 2017. As of September 30, 2017, 338,073 shares were available for future issuance under the Inducement Plan. 2014 Employee Stock Purchase Plan In February 2014, the Company’s stockholders approved the 2014 Employee Stock Purchase Plan (the “ESPP”), which became effective as of March 11, 2014. Effective January 1, 2017, the compensation committee of the board of directors approved an evergreen increase of 178,190 shares that may be granted in accordance with the terms of the ESPP. As of September 30, 2017, 336,139 shares of common stock have been issued to employees participating in the ESPP and 350,528 shares are available for issuance under the ESPP. Amended and Restated 2003 Stock Plan The Company’s Amended and Restated 2003 Stock Plan (the "2003 Plan"), provided for the granting of incentive and non-statutory stock options to employees, directors and consultants at the discretion of the board of directors. The Company granted options under its 2003 Plan until January 2014 and it was terminated as to future awards in March 2014, although it continues to govern the terms of options that remain outstanding under the 2003 Plan. Options granted under the 2003 Plan expire no later than 10 years from the date of grant. Options granted under the 2003 Plan vest over periods determined by the board of directors, generally over four years. The 2003 Plan allows for early exercise of certain options prior to vesting. Upon termination of employment, the unvested shares are subject to repurchase at the original exercise price. Stock options granted or modified after March 21, 2002, that are subsequently exercised for cash prior to vesting, are not deemed to be issued until those shares vest. As of September 30, 2017 and December 31, 2016 there were no shares subject to repurchase relating to the early exercise of options. In connection with the board of directors’ and stockholders’ approval of the 2014 Plan, all remaining shares available for future awards under the 2003 Plan were transferred to the 2014 Plan, and the 2003 Plan was terminated as to future awards. As of September 30, 2017, a total of 829,586 shares of common stock are subject to options outstanding under the 2003 plan, which shares will become available under the 2014 Plan to the extent the options are forfeited or lapse unexercised. The following table summarizes stock option activity under the stock plans, excluding the ESPP, and related information: Shares Available for grant Shares Subject to Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Balance, December 31, 2016 639,374 3,540,293 $ 6.31 7.98 Additional shares authorized 2,325,522 — Options granted (1,641,757 ) 1,641,757 $ 21.96 Options exercised — (164,593 ) $ 7.50 Options cancelled 223,682 (223,682 ) $ 8.24 RSUs granted (470,076 ) — RSUs cancelled 59,192 — Balance, September 30, 2017 1,135,937 4,793,775 $ 11.54 7.86 Stock-based compensation expense recognized for stock options granted to employees and non-employee directors in the Company’s condensed consolidated statements of operations was as follows (in thousands): Three Months Ended September 30 Nine Months Ended September 30 2017 2016 2017 2016 Research and development $ 1,627 $ 542 $ 4,558 $ 1,511 General and administrative 2,179 432 5,258 1,215 Total $ 3,806 $ 974 $ 9,816 $ 2,726 Stock-based compensation expense for the nine-month period ended September 30, 2017 includes $0.6 million of expense that relates to stock options and restricted stock units held by the former Chief Medical Officer, which were modified upon his resignation in March 2017, including $0.7 million related to such modifications. As of September 30, 2017, approximately $23.6 million of total unrecognized stock-based compensation expense related to unvested stock options is expected to be recognized over a weighted-average period of 3.1 years. The estimated grant date fair value of employee stock options with time-based vesting terms was calculated using the Black-Scholes valuation model, based on the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected term 5.8–6.0 years 6.0 years 5.3–6.0 years 5.3–6.0 years Expected volatility 78-79% 67-68% 78-81% 67%–74% Risk-free interest rate 1.9%–2.1% 1.1%–1.3% 1.7%–2.1% 1.1%–1.5% Expected dividend yield —% —% —% —% Stock Options Granted to Non-Employees During the three-month and nine-month periods ended September 30, 2017, the Company granted to a non-employee consultant an option to purchase an aggregate of 3,000 shares of common stock and 1,500 RSUs, that vest upon the achievement of certain performance-based targets. The Company will record the estimated fair value of the awards at the time the performance-based targets are met, which has not occurred as of September 30, 2017. During the three-month and nine-month periods ended September 30, 2016, the Company granted 15,000 stock options and no RSUs to a non-employee consultant. The Company recorded non-employee stock-based compensation expense of approximately $67,000 and $6,000 for the three-month periods ended September 30, 2017 and 2016, respectively, and $481,000 and $6,000, respectively, for the the nine-month periods ended September 30, 2017 and 2016. The Company measures the estimated fair value of the award for each period until the award is fully vested. The non-employee stock-based compensation expense, during the three-month and nine-month periods ended September 30, 2017 , Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected term 0.25 years 1.01 years 0.25–0.51 years 1.01 years Expected volatility 60% 63% 48-77% 63% Risk-free interest rate 1.0 % 0.6% 0.9-1.0 % 0.6% Expected dividend yield —% —% —% —% Restricted Stock Units Granted to Employees During the nine-month period ended September 30, 2017, the Company granted RSUs to employees to receive 470,076 shares of common stock under the Company's stock plans with a weighted-average estimated grant-date fair value of $21.84 per share. RSUs generally vest annually over a 4-year service period and vesting is contingent on continued service. As of September 30, 2017, unrecognized compensation costs totaled $11.3 million related to outstanding RSUs, which are expected to be recognized over a weighted-average period of 2.9 years. A summary of RSU activity is as follows: RSU Awards Outstanding Number of Shares Weighted-Average Grant Date Fair Market Value Aggregate Intrinsic Value (in thousands) Balance, December 31, 2016 605,052 $ 5.60 $ 7,878 RSUs granted 470,076 $ 21.84 RSUs released (170,231 ) $ 5.91 RSUs cancelled (59,192 ) $ 7.73 Balance, September 30, 2017 845,705 $ 14.42 $ 13,489 Stock Options and Restricted Stock Units Granted to Employees that Contain Performance Conditions During the three-month periods ended September 30, 2017 and 2016, the Company granted options to purchase an aggregate of 22,500 and 129,000 shares of common stock, respectively, and during the nine-month periods ended The fair value was estimated at the grant date using a Monte-Carlo simulation model (“Monte-Carlo”), which requires the use of a range of assumptions. The expected life assumption is not used in Monte-Carlo, but the output of the model indicates an expected term. The associated stock-based compensation expense is being recognized on a straight-line basis over the implicit service period (expected time to vest) derived from Monte-Carlo. The fair value of awards granted to employees was estimated using Monte-Carlo with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected term 0.5–1.8 years 2.5–5.9 years 0.5–1.8 years 2.5–6.0 years Expected volatility 75% 70% 75% 70% Risk-free interest rate 2.4% 1.4-1.6% 2.4% 1.4-1.8% Expected dividend yield —% —% —% —%

Contingently Redeemable Common

Contingently Redeemable Common Stock	9 Months Ended
	Sep. 30, 2017
Temporary Equity Disclosure [Abstract]
Contingently Redeemable Common Stock	9. Contingently Redeemable Common Stock In May 2017, the Company entered into a Common Stock Purchase Agreement with the Gates Foundation, pursuant to which the Company agreed to sell 407,331 shares of its contingently redeemable common stock (the “Shares”) to the Gates Foundation in a private placement at a purchase price per share equal to $24.55, for gross proceeds to the Company of $10.0 million (“Gates Investment”). In connection with the Gates Investment, the Company entered into the Letter Agreement, which includes terms of Global Access Commitments (see Note 1). Under the Letter Agreement, if the Company defaults in its obligation to conduct certain mutually-agreed upon work with the proceeds from the Gates Investment, or otherwise triggers certain other events of default (“Charitable Default”), subject to a cure period, the Gates Foundation will have the right to request that (a) the Company redeem, or facilitate the purchase by a third party of, the Shares then held by the Gates Foundation at a price per share equal to the greater of (i) the fair market value of the common stock (if the Shares are freely tradable, the closing price of the Company’s common stock on the trading day prior to the redemption or purchase, as applicable), or (ii) an amount equal to $24.55 plus a compounded annual return of 5% from the date of issuance of the Shares, or (b) if the Shares then held by the Gates Foundation are not freely tradeable, the Company register the resale of the Shares held by the Gates Foundation on an effective registration statement, subject to certain conditions and qualifications. The Company concluded that certain potential events of the Charitable Default, as defined in the agreement, are not solely within the control of the Company and, accordingly, has classified the Shares outside of permanent equity, as temporary equity (the “Mezzanine Equity”). The 407,331 shares classified as Mezzanine Equity were recorded as contingently redeemable common stock at an initial carrying value equal to the gross proceeds of approximately $10 million, which approximated their fair value at the date of issuance. The Company has determined that the 407,331 shares of contingently redeemable common stock are not currently redeemable and that a Charitable Default is not currently probable. If, and at the time when, a Charitable Default becomes probable, then the Company will record a change in the carrying value to adjust it to the redemption value of the contingently redeemable common stock. At the time of such an occurrence, the contingently redeemable common stock will be adjusted to equal the redemption value at the end of each reporting period.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies Commercial Manufacturing Agreement In March 2017, the Company entered into a commercial validation and manufacturing agreement (the “Manufacturing Agreement”) with Hovione Limited (“Hovione”). Under the Manufacturing Agreement, Hovione has agreed to complete the validation program to validate and scale up the Company’s technology to manufacture the active pharmaceutical ingredient for plazomicin (the “Product”) and supply the Product to the Company. The Manufacturing Agreement has an initial term of seven years after the first delivery of the Product. Subject to the successful completion of the validation program and the Company’s launch of plazomicin, the Company has agreed to purchase a minimum quantity of the Product from Hovione depending on the Company’s requirements and the period of time following approval by the FDA. For the first three years following approval of plazomicin by the FDA, the Company is required to purchase at least 80% of its required quantity from Hovione. Following the initial three years after FDA approval, the Company is required to purchase between 40% and 66% of its required quantity from Hovione, depending on the amounts required during any such fiscal year. Contingent upon FDA’s approval of plazomicin, the Company has minimum annual purchase commitments from Hovione, beginning in 2020 through 2024. In connection with the Manufacturing Agreement, the Company executed certain work plans to carry out the validation and commercial manufacturing of plazomicin (the “Work Plans”). The Work Plans obligated the Company to make an aggregate amount of approximately $6.2 million in nonrefundable advance payments, of which $1.5 million was for the reservation of facilities and resources, plus procurement of long lead raw materials, paid in full under a separate agreement executed in July 2015. Such advance payments are initially capitalized as prepaid and other current assets and will be recognized as research and development expenses as goods are delivered and/or services are performed. The Company assesses such prepaid and other current assets for impairment if events or changes in circumstances indicate that the carrying amount may not be recoverable or may not provide future economic benefits. Further, the Work Plans include certain terms that require the Company to compensate Hovione if it chooses to cancel the Work Plans (“Cancellation Clause”). As of , $10.2 million is committed under the Cancellation Clause and the total aggregate amount of potential commitments, if all the services are rendered by Hovione, is approximately $28.1 million. As of and December 31, 2016, the Company has recorded approximately $4.5 million and $0.7 million, respectively as prepaid and other current assets and, during the three-month periods ended and 2016, has recognized $0.4 million and $0.2 million, respectively, and $1.9 million and $0.7 million, respectively, during the nine-month periods ended and 2016, as research and development expenses, related to the Work Plans. In December 2016, the Company entered into an agreement with Hovione to procure certain long lead raw materials to be used in the commercial production of plazomicin (the “Raw Material Agreement”). The Raw Material Agreement includes $1.2 million in nonrefundable advance payments. As of September 30, 2017 Facilities Lease Obligation In August 2016, the Company entered into a non-cancelable agreement (the "Lease") to lease 47,118 square feet of office, laboratory and research and development space (the “Original Space”) for the Company's new principal executive offices in South San Francisco. In July 2017, the Company entered into an amendment (the “Lease Amendment”) to lease an additional 51,866 square feet of space (the “Expansion Space”) for a total of 98,984 square feet (the “Premises”). The Lease commenced in March 2017, after the substantial completion of certain improvements ("Tenant Improvements") required under the Lease and the Company moved into the Original Space in April 2017. The lease for 18,888 square feet of the Expansion Space commenced in August 2017 and the remainder is expected to begin by the end of the second quarter 2018. The lease term for the Premises is through January 31, 2028 (the “Lease Term”) and contains an option to extend the Lease Term for an additional 5 years. Base rent for the first year for the Original Space is approximately $2.9 million. The base rent increases approximately 3.5% in each subsequent year of the Lease Term. The Lease also provides for rent abatement of approximately $1.8 million and $2.0 million for the first year of the Lease Term for the Original Space and Expansion Space, respectively. The Company has a one-time improvement allowance of $5.7 million for the Tenant Improvements (the "Original Allowance"). The Landlord disbursed the Original Allowance for the Tenant Improvements on behalf of the Company. At its election, the Company is also entitled to an additional improvements allowance of $0.9 million ("Original Additional Allowance"). Effective August 17, 2017, the Company elected to use the Original Additional Allowance and the base rent was increased by an aggregate of $1.7 million over the Lease Term. As of September 30, 2017, the Company has recorded approximately $6.6 million within leasehold improvements under property, plant and equipment, net and other current liabilities in the condensed consolidated balance sheet related to costs incurred under the Original Allowance and the Original Additional Allowance. The Lease Amendment provides for a one-time improvement allowance of $1.0 million for certain tenant improvements and, at its election, the Company is also entitled to an additional improvements allowance of $1.5 million (“Expansion Additional Allowance”). In the event the Company elects to use the Expansion Additional Allowance, the base rent will be increased as calculated in the Lease Amendment. Pursuant to the Lease Amendment, the Company holds the option to pay the balance of the Original Additional Allowance and Expansion Additional Allowance in full any time within the first 36 months of the Lease Term. Further, the Company had deposits of $0.5 million included in long-term restricted cash as of September 30, 2017, restricted from withdrawal and held in a money market account with one of the Company’s financial institutions in the form of collateral for letters of credit held as security for the Lease and the Lease Amendment. Future minimum lease payments under the operating leases as of September 30, 2017 are as follows (in thousands): Year Ending December 31, Amounts 2017 $ 272 2018 4,028 2019 6,201 2020 6,418 2021 6,644 Thereafter 45,657 Total minimum lease payments $ 69,220 The Company recognizes rent expense on a straight-line basis over the non-cancelable lease period. Rent expense was $0.9 million and $0.1 million for the three-month periods ended September 30, 2017 and 2016, respectively, and $2.0 million and $0.4 million, respectively, for the nine-month periods ended September 30, 2017 and 2016.

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Reclassifications	Reclassifications The cash and cash equivalents on the condensed consolidated statements of cash flows for the nine-month period ended September 30, 2016 has been reclassified to include restricted cash to conform to the current period’s presentation. Such reclassifications did not impact the Company’s net loss or financial position.
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and 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. The results of operations for the three-month and nine-month periods ended September 30, 2017 are not necessarily indicative of the results to be expected for the full year or any other future period. 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. Intercompany accounts and transactions have been eliminated upon consolidation. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2016 included in the Company’s Annual Report on Form 10-K.
Liquidity And Going Concern	Liquidity and Going Concern In September 2017, the Company was awarded a contract (“C-Scape Contract”) valued at up to $18.0 million in grant funding from the Biomedical Advanced Research and Development Authority (“BARDA”) to support the development of C-Scape. The C-Scape Contract includes a base period with committed funding of $12.0 million and subsequent option periods that, if exercised, would bring the total value of the award to $18.0 million. On May 31, 2017, the Company completed an underwritten public offering of 5,750,000 shares of its common stock at a price to the public of $22.50 per share, including the closing of the full exercise of the underwriters’ option to purchase an additional 750,000 shares of common stock on June 9, 2017. The Company received net proceeds from the offering of $121.2 million, after deducting the underwriting discounts and commissions and offering expenses. On May 4, 2017, the Company entered into an agreement with the Bill & Melinda Gates Foundation (the “Gates Foundation”) to discover drug candidates against gram-negative bacterial pathogens intended to prevent neonatal sepsis (the “Grant Agreement”). Pursuant to the Grant Agreement, the Gates Foundation awarded the Company up to approximately $10.5 million in grant funding (“Grant Funds”) over a three-year research term, of which approximately $3.2 million was received in May 2017 (the “Advance Funds”). Concurrently with the Grant Agreement, the Company entered into a Common Stock Purchase Agreement (the “Gates Purchase Agreement”) with the Gates Foundation, pursuant to which the Company agreed to sell 407,331 shares of its contingently redeemable common stock to the Gates Foundation in a private placement at a purchase price per share equal to $24.55, for gross proceeds to the Company of $10.0 million (“Gates Investment”). In connection with the Grant Agreement and the Gates Investment, the Company entered into a strategic relationship with the Gates Foundation (the “Letter Agreement”). Under the terms of the Letter Agreement, the Gates Investment and Grant Funds may only be used to conduct mutually agreed upon work, including the scale up of the Company’s antibody platform technology to launch a product intended to prevent neonatal sepsis (the “NSP”). Pursuant to the Letter Agreement, the Company agreed to make the NSP available and accessible in certain developing countries and to grant the Gates Foundation a non-exclusive license to commercialize selected drug candidates in certain developing countries, which may only be exercised in the event of certain defaults as described in the Letter Agreement (the “Global Access Commitments”). The Global Access Commitments will continue in effect until the earlier of 25 years from the closing of the Gates Investment or 7 years following the termination of all funding provided by the Gates Foundation; provided, that the Global Access Commitments will continue for any products or services developed with funding provided by the Gates Foundation which continue to be developed or available in certain developing countries. The Company has incurred losses and negative cash flows from operations every year since its inception. As of September 30, 2017, the Company had unrestricted cash, cash equivalents and short-term investments of approximately $199.4 million and an accumulated deficit of approximately $336.5 million. Management expects that, based on its current operating plans, the Company’s existing cash, cash equivalents and short-term investments as of September 30, 2017 will be sufficient to fund its current planned operations for at least the next twelve months from the issuance of these financial statements. Management plans to raise additional funds through equity or debt financing arrangements, government contracts, and/or third party collaboration funding in the future to fund its operations, including the commercial development of plazomicin. However, there can be no assurance that such funding sources will be available at terms acceptable to the Company or at all. If the Company is unable to raise additional funding to meet its working capital needs, it will be forced to delay or reduce the scope of its research programs and/or limit or cease its operations. The accompanying financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The financial statements do not reflect any adjustments relating to the recoverability and reclassification of assets and liabilities that might be necessary if the Company is unable to continue as a going concern.
Use of Estimates	Use of Estimates The accompanying financial statements have been prepared in accordance with U.S. GAAP. The preparation of financial statements in conformity with U.S. GAAP requires management to make judgments, assumptions and estimates that affect the reported amounts of assets, liabilities, revenues and expenses and related disclosures of contingent liabilities. On an ongoing basis, management evaluates its estimates, including those related to clinical trial accruals, fair value of liabilities, common stock and stock-based awards and income taxes. Management bases its estimates on historical experience and on various other assumptions that are believed to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities that are not readily apparent from other sources. Actual results may differ materially from those estimates.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of the Company’s financial instruments, including cash and cash equivalents, contracts receivable, prepaid and other current assets, accounts payable, accrued liabilities, and other current liabilities approximate fair value due to their short-term maturities. Short-term investments consist of available-for-sale securities and are carried at fair value. Based upon the borrowing rates (which is a Level 2 input) currently available to the Company for loans with similar terms, the Company believes the carrying amount of the loan payable approximates its fair value. The warrant and derivative liabilities are recorded at estimated fair value with changes in estimated fair value recorded in the Company's statements of operations.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash equivalents include only securities having a maturity of three months or less at the time of purchase. As of September 30, 2017 and December 31, 2016, cash and cash equivalents consisted of bank deposits, cash, commercial paper, money market funds, cash repurchase agreement investments and overnight cash sweep investments in government money market funds.
Short-term Investments	Short-term Investments Short-term investments consist of debt securities with maturities greater than three months, but less than one year from the date of acquisition, and are classified as available for sale. Short-term investments are carried at fair value. Unrealized gains and losses on available-for-sale securities are excluded from earnings and reported as a component of net unrealized gain (loss) on available-for-sale securities in the Company's consolidated statements of comprehensive loss. The amortized cost of debt securities reflects amortization of purchase premiums and accretion of purchase discounts to date, which are included in interest income. The Company reviews all of its marketable securities on a regular basis to evaluate whether any security has experienced an other-than-temporary decline in fair value.
Restricted Cash	Restricted Cash At September 30, 2017 and December 31, 2016, the Company had restricted cash of $11.2 million and $0.4 million, respectively. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in thousands): September 30, 2017 December 31, 2016 Cash and cash equivalents $ 134,657 $ 118,964 Restricted cash, current 7,380 127 Restricted cash, non-current 3,855 250 Total cash, cash equivalents, and restricted cash $ 145,892 $ 119,341 As of September 30, 2017 and December 31, 2016, the Company had $10.7 million and zero, respectively, of restricted cash related to the cash provided by the Gates Foundation, in connection with the Grant Agreement, Gates Purchase Agreement and Letter Agreement (see Note 1). As of September 30, 2017 and December 31, 2016, the Company had $0.5 million and $0.4 million, respectively, of restricted cash, which relates to the Company’s facility leases. Concurrently with the Grant Agreement, the Company entered into the Gates Purchase Agreement, pursuant to which the Company issued 407,331 shares of contingently redeemable common stock to the Gates Foundation for the Gates Investment (see Note 1). In addition, the Letter Agreement, among other things, restricts the Company’s use of both the Grant Funds and the Gates Investment to expenditures, including an allocation of overhead and administrative expenses, that are reasonably attributable to the activities required to support the research projects funded by the Gates Foundation. As a result of such restrictions, as of September 30, 2017, the Company classified the unspent portions of the Grant Funds and Gates Investment, held at one of the Company’s financial institutions, as restricted cash. The restricted cash related to the Company’s leases, which consists of a money market account with one of the Company’s financial institutions, serves as collateral for the letters of credit provided as security deposits under the Company’s facility lease and expire approximately 90 days from the end of their respective lease terms.
Warrant Liability	Warrant Liability On June 3, 2016, the Company issued warrants to purchase 1,999,999 shares of its common stock in connection with a private placement financing transaction (the “Private Placement”). Each warrant has an exercise price of $3.66 per share and is exercisable for five years from the date of issuance. The Company accounts for these warrants as a liability instrument measured at estimated fair value. The initial fair value of the warrants was determined using a calibration model that involved using the Black-Scholes Pricing Model ("Black-Scholes"), which requires inputs such as the risk-free interest rate, expected share price volatility, underlying price per share of the Company's common stock and remaining term of the warrants. The warrants are subject to remeasurement at each balance sheet date, using Black-Scholes, with any changes in the fair value of the outstanding warrants recognized in the condensed consolidated statements of operations. As of September 30, 2017, warrants to purchase 1,178,782 shares of the Company’s common stock remain outstanding and unexercised.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. The Company has one operating segment.
Customer Concentration	Customer Concentration For the three-month and nine-month periods ended September 30, 2017 and 2016, the Company’s revenue was generated from funding pursuant to U.S. government contracts and a non-profit foundation grant. All contracts receivable relate to funding from U.S. government contracts.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to a significant concentration of credit risk consist of cash, cash equivalents and short-term investments. Cash and cash equivalents are deposited in checking, overnight sweep and money market accounts at one financial institution with balances that generally exceed federally insured limits. Management believes that the financial institution is financially sound, and, accordingly, minimal credit risk exists with respect to this financial institution. The Company’s investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of default by the institutions holding its cash and cash equivalents or issuing the debt securities. As of September 30, 2017 and December 31, 2016, the Company had not experienced any credit losses in such accounts or investments.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when: (i) evidence of an arrangement exists, (ii) fees are fixed or determinable, (iii) services have been delivered, and (iv) collectability is reasonably assured. The Company currently generates revenue from government contracts and a non-profit foundation grant (collectively, the “Revenue Contracts”). Revenue Contracts are agreements that provide the Company with payments for certain types of expenditures in return for research and development activities over a contractually-defined period. Revenue from the Revenue Contracts is recognized in the period during which the related costs are incurred and the related services are rendered, provided that the applicable conditions under the government contracts have been met. Costs of contract revenue are recorded as a component of operating expenses in the Company's consolidated statement of operations. Funds received from third parties under contract arrangements are recorded as revenue if the Company is deemed to be the principal participant in the contract arrangements because the activities under the contracts are part of the Company’s development programs. If the Company is not the principal participant, the funds from contracts are recorded as a reduction to research and development expense. Contract funds received are not refundable and are recognized when the related qualified research and development costs are incurred and when there is reasonable assurance that the funds will be received. Funds billed and received in advance are recorded as deferred revenue.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses include certain payroll and personnel expenses; laboratory supplies; consulting costs; external contract research and development expenses; and allocated overhead, including rent, equipment depreciation and utilities, and relate to both Company-sponsored programs as well as costs incurred pursuant to collaboration agreements and government contracts. The Company estimates preclinical study and clinical trial expenses based on the services performed pursuant to contracts with research institutions and clinical research organizations that conduct and manage preclinical studies and clinical trials on its behalf. In accruing service fees, the Company estimates the time period over which services will be performed and the level of effort to be expended in each period. If the actual timing of the performance of services or the level of effort varies from the estimate, the Company will adjust the accrual accordingly. Payments made to third parties under these arrangements in advance of the receipt of the related services are recorded as prepaid expenses until the services are rendered. Advance payments for goods or services that will be used or rendered for future research and development activities are capitalized as prepaid expenses and other current assets and recognized as an expense as the goods are delivered or the related services are performed.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which provides a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and will supersede most current revenue recognition guidance. This ASU is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. This ASU defines a five-step process to achieve this core principle and, in doing so, it is possible more judgment and estimates may be required within the revenue recognition process than are required under existing GAAP. The Company expects to adopt the new revenue standard as of January 1, 2018 using the modified retrospective method. The Company has completed its assessment of the first step which included identifying the Company’s customers. Through the remainder of 2017, the Company will continue to assess the potential impact of adopting this new standard on any current, new or significantly modified customer contracts. In subsequent quarters, the Company will complete its evaluation of additional disclosures that may be required upon adoption of the new standard. In May 2017, the FASB issued ASU No. 2017-09, Compensation – Stock Compensation (Topic 718): Scope of Modification Accounting
Net Loss Per Share	Net Loss Per Share Basic net loss per common share is computed by dividing the net loss by the weighted-average number of common shares outstanding during the period. Diluted net loss per common share is computed by dividing the net loss by the weighted-average number of common shares and dilutive common share equivalents outstanding during the period. For purposes of this calculation, preferred stock, stock options, restricted stock units and warrants are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following tables set forth the computation of the Company’s basic and diluted net loss per share (in thousands, except shares and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Numerator: Net loss used to compute basic net loss per share $ (29,907 ) $ (11,038 ) $ (89,235 ) $ (41,503 ) Less: Gain on private placement warrants (6,795 ) - - - Net loss used to compute diluted net loss per share $ (36,702 ) $ (11,038 ) $ (89,235 ) $ (41,503 ) Denominator: Weighted-average shares used to compute basic net loss per share 42,259,001 26,789,397 38,709,811 22,046,368 Add: Private placement warrant shares 952,058 - - - Weighted-average shares used to compute diluted net loss per share 43,211,059 26,789,397 38,709,811 22,046,368 Net loss per share: Basic $ (0.71 ) $ (0.41 ) $ (2.31 ) $ (1.88 ) Diluted $ (0.85 ) $ (0.41 ) $ (2.31 ) $ (1.88 ) For the three-month and nine-month periods ended September 30, 2017 and 2016, potentially dilutive securities outstanding have been excluded from the computations of diluted weighted-average shares outstanding because such securities have an antidilutive impact due to losses reported. The following potentially dilutive securities have been excluded from diluted net loss per share, because their effect would be antidilutive, as of September 30, 2017 and 2016: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Options to purchase common stock 4,793,775 3,416,136 4,793,775 3,416,136 Restricted stock units 845,705 561,428 845,705 561,428 Warrants to purchase common stock 17,514 2,030,023 1,196,296 2,030,023

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Schedule of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in thousands): September 30, 2017 December 31, 2016 Cash and cash equivalents $ 134,657 $ 118,964 Restricted cash, current 7,380 127 Restricted cash, non-current 3,855 250 Total cash, cash equivalents, and restricted cash $ 145,892 $ 119,341
Schedule of Computation of Basic and Diluted Net Loss Per Share	The following tables set forth the computation of the Company’s basic and diluted net loss per share (in thousands, except shares and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Numerator: Net loss used to compute basic net loss per share $ (29,907 ) $ (11,038 ) $ (89,235 ) $ (41,503 ) Less: Gain on private placement warrants (6,795 ) - - - Net loss used to compute diluted net loss per share $ (36,702 ) $ (11,038 ) $ (89,235 ) $ (41,503 ) Denominator: Weighted-average shares used to compute basic net loss per share 42,259,001 26,789,397 38,709,811 22,046,368 Add: Private placement warrant shares 952,058 - - - Weighted-average shares used to compute diluted net loss per share 43,211,059 26,789,397 38,709,811 22,046,368 Net loss per share: Basic $ (0.71 ) $ (0.41 ) $ (2.31 ) $ (1.88 ) Diluted $ (0.85 ) $ (0.41 ) $ (2.31 ) $ (1.88 )
Schedule of Potentially Dilutive Securities Outstanding Excluded from the Computations of Diluted Weighted-Average Shares Outstanding	The following potentially dilutive securities have been excluded from diluted net loss per share, because their effect would be antidilutive, as of September 30, 2017 and 2016: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Options to purchase common stock 4,793,775 3,416,136 4,793,775 3,416,136 Restricted stock units 845,705 561,428 845,705 561,428 Warrants to purchase common stock 17,514 2,030,023 1,196,296 2,030,023

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Financial Assets and Liabilities Measured and Recognized at Fair Value	As of September 30, 2017 and December 31, 2016, financial assets and liabilities measured and recognized at fair value on a recurring basis and classified under the appropriate level of the fair value hierarchy as described above were as follows (in thousands): September 30, 2017 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Assets Level 1: Cash equivalents $ 126,267 $ — $ — $ 126,267 Restricted cash 11,235 — — 11,235 Subtotal 137,502 — — 137,502 Level 2: Corporate debt securities 8,664 — (2 ) 8,662 U.S. Treasury bills 21,004 — (8 ) 20,996 Commercial paper 43,475 1 — 43,476 Subtotal 73,143 1 (10 ) 73,134 Total $ 210,645 $ 1 $ (10 ) $ 210,636 Reported as: Cash and cash equivalents $ 134,657 Short-term investments $ 64,744 Restricted cash $ 11,235 Liabilities, Level 3 Warrant Liability $ 15,681 Derivative Liability $ 664 Total $ 16,345 December 31, 2016 Amortized Cost Unrealized Gains Unrealized Losses Fair Value Assets Cash $ 3,728 $ — $ — $ 3,728 Level 1: Restricted cash 377 — — 377 Money market funds 115,236 — — 115,236 Subtotal 115,613 — — 115,613 Level 2: Corporate debt securities 12,969 — (7 ) 12,962 Commercial paper 13,950 — — 13,950 Subtotal 26,919 — (7 ) 26,912 Total $ 146,260 $ — $ (7 ) $ 146,253 Reported as: Cash and cash equivalents $ 118,964 Short-term investments $ 26,912 Restricted cash $ 377 Liabilities, Level 3 Warrant liability $ 13,874 Derivative liability $ 602 Total $ 14,476
Schedule of Assumptions Used	the estimated fair values of the warrants were determined using Black-Scholes with the following assumptions: September 30, 2017 December 31, 2016 Expected volatility 80% 80% Expected term 3.7 years 4.2 years Risk-free interest rate 1.7% 1.8% Dividend yield —% —%
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation	Changes in the fair value of recurring measurements included in Level 3 of the fair value hierarchy are presented as changes in warrant and derivative liabilities in the Company's condensed consolidated statements of operations and were as follows for the nine-month period ended September 30, 2017 (in thousands): Estimated Fair Value of Warrant Liability Estimated Fair Value of Derivative Liability Balance of Level 3 Liabilities at December 31, 2016 $ 13,874 $ 602 Change in estimated fair value of warrant liability 3,896 — Reclassification of warrant liability to additional paid in capital upon exercise of warrants (2,089 ) — Change in estimated fair value of derivative liability — 62 Balance of Level 3 Liabilities at September 30, 2017 $ 15,681 $ 664

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2017
Payables And Accruals [Abstract]
Schedule of Prepaids and Other Current Assets	Prepaids and other current assets consisted of the following (in thousands): September 30, 2017 December 31, 2016 Deferred research and development costs $ 4,457 $ 660 Prepaid expenses 1,490 1,390 Other current assets 298 139 $ 6,245 $ 2,189
Schedule of Property and Equipment	Property and equipment, net consisted of the following (in thousands): September 30, 2017 December 31, 2016 Office equipment $ 863 $ 644 Laboratory equipment 5,701 4,038 Leasehold improvements 8,055 1,072 Construction-in-progress 1,436 1,896 16,055 7,650 Less: accumulated depreciation and amortization (3,083 ) (4,389 ) Property and equipment, net $ 12,972 $ 3,261
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): September 30, 2017 December 31, 2016 Accrued clinical and development expenses $ 2,188 $ 3,681 Payroll and related bonus expenses 6,242 4,941 Other 1,038 1,076 $ 9,468 $ 9,698

Borrowings (Tables)

Borrowings (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Schedule of Future Minimum Debt Obligation Payments	Future principal debt payments on the currently outstanding term loan are payable as follows (in thousands): September 30, 2017 2017 $ 3,125 2018 12,500 2019 8,333 Total principal payments 23,958 Final fee due at maturity in 2019 2,000 Total principal and final fee payments 25,958 Unamortized discount and debt issuance costs (1,084 ) Total loan obligation 24,874 Less current portion (12,500 ) Loan payable, long-term $ 12,374

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2017
Summary of Stock Option Activity	The following table summarizes stock option activity under the stock plans, excluding the ESPP, and related information: Shares Available for grant Shares Subject to Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Term (years) Balance, December 31, 2016 639,374 3,540,293 $ 6.31 7.98 Additional shares authorized 2,325,522 — Options granted (1,641,757 ) 1,641,757 $ 21.96 Options exercised — (164,593 ) $ 7.50 Options cancelled 223,682 (223,682 ) $ 8.24 RSUs granted (470,076 ) — RSUs cancelled 59,192 — Balance, September 30, 2017 1,135,937 4,793,775 $ 11.54 7.86
Schedule of Stock-based Compensation Expense for Stock Options Granted to Employees and Non-employees	Stock-based compensation expense recognized for stock options granted to employees and non-employee directors in the Company’s condensed consolidated statements of operations was as follows (in thousands): Three Months Ended September 30 Nine Months Ended September 30 2017 2016 2017 2016 Research and development $ 1,627 $ 542 $ 4,558 $ 1,511 General and administrative 2,179 432 5,258 1,215 Total $ 3,806 $ 974 $ 9,816 $ 2,726
Schedule of Estimated Grant Date Fair Value of Employee Stock Options	The estimated grant date fair value of employee stock options with time-based vesting terms was calculated using the Black-Scholes valuation model, based on the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected term 5.8–6.0 years 6.0 years 5.3–6.0 years 5.3–6.0 years Expected volatility 78-79% 67-68% 78-81% 67%–74% Risk-free interest rate 1.9%–2.1% 1.1%–1.3% 1.7%–2.1% 1.1%–1.5% Expected dividend yield —% —% —% —%
Schedule of Share-based Compensation, Restricted Stock Units Award Activity	A summary of RSU activity is as follows: RSU Awards Outstanding Number of Shares Weighted-Average Grant Date Fair Market Value Aggregate Intrinsic Value (in thousands) Balance, December 31, 2016 605,052 $ 5.60 $ 7,878 RSUs granted 470,076 $ 21.84 RSUs released (170,231 ) $ 5.91 RSUs cancelled (59,192 ) $ 7.73 Balance, September 30, 2017 845,705 $ 14.42 $ 13,489
Black Scholes
Schedule of Estimated Grant Date Fair Value of Employee Stock Options	The non-employee stock-based compensation expense, during the three-month and nine-month periods ended September 30, 2017 , Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected term 0.25 years 1.01 years 0.25–0.51 years 1.01 years Expected volatility 60% 63% 48-77% 63% Risk-free interest rate 1.0 % 0.6% 0.9-1.0 % 0.6% Expected dividend yield —% —% —% —%
Monte Carlo Simulation
Schedule of Estimated Grant Date Fair Value of Employee Stock Options	The fair value of awards granted to employees was estimated using Monte-Carlo with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Expected term 0.5–1.8 years 2.5–5.9 years 0.5–1.8 years 2.5–6.0 years Expected volatility 75% 70% 75% 70% Risk-free interest rate 2.4% 1.4-1.6% 2.4% 1.4-1.8% Expected dividend yield —% —% —% —%

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2017
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments	Future minimum lease payments under the operating leases as of September 30, 2017 are as follows (in thousands): Year Ending December 31, Amounts 2017 $ 272 2018 4,028 2019 6,201 2020 6,418 2021 6,644 Thereafter 45,657 Total minimum lease payments $ 69,220

Organization and Basis of Pre24

Organization and Basis of Presentation and Consolidation - Additional Information (Details) - USD ($)	Nov. 08, 2017	Jun. 09, 2017	May 31, 2017	May 04, 2017	Dec. 19, 2016	Jun. 03, 2016	Sep. 30, 2017	May 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Subsidiary, Sale of Stock [Line Items]
Research and development contract							$ 12,000,000
Research term								3 years
Advance amount received for research and development			$ 3,200,000					$ 3,200,000
Effective agreement terms									The Global Access Commitments will continue in effect until the earlier of 25 years from the closing of the Gates Investment or 7 years following the termination of all funding provided by the Gates Foundation; provided, that the Global Access Commitments will continue for any products or services developed with funding provided by the Gates Foundation which continue to be developed or available in certain developing countries.
Cash, cash equivalents and short-term investments							199,400,000		$ 199,400,000
Accumulated deficit							336,455,000		$ 336,455,000	$ 247,220,000
Bill & Melinda Gates Foundation
Subsidiary, Sale of Stock [Line Items]
Research term				3 years
Advance amount received for research and development				$ 3,200,000
Subsequent Event
Subsidiary, Sale of Stock [Line Items]
Research and development contract	$ 18,000,000
Maximum
Subsidiary, Sale of Stock [Line Items]
Research and development awarded grant funding							$ 18,000,000	$ 10,500,000
Maximum | Bill & Melinda Gates Foundation
Subsidiary, Sale of Stock [Line Items]
Research and development awarded grant funding				$ 10,500,000
Underwritten Public Offering
Subsidiary, Sale of Stock [Line Items]
Shares issued			5,750,000		7,475,000			5,750,000
Share price (dollars per share)			$ 22.50		$ 13.50			$ 22.50
Additional shares of common stock		750,000			975,000
Proceeds from offering net of underwriting discounts and commissions and offering expenses			$ 121,200,000		$ 94,600,000			$ 121,200,000
Private Placement
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance or sale of equity						$ 25,400,000
Private Placement | Bill & Melinda Gates Foundation
Subsidiary, Sale of Stock [Line Items]
Share price (dollars per share)				$ 24.55
Proceeds from issuance or sale of equity				$ 10,000,000
Private Placement | Redeemable Common Stock | Bill & Melinda Gates Foundation
Subsidiary, Sale of Stock [Line Items]
Shares issued				407,331

Summary of Significant Accoun25

Summary of Significant Accounting Policies - Additional Information (Details) $ / shares in Units, $ in Thousands	Jun. 03, 2016$ / sharesshares	Sep. 30, 2017USD ($)Segment$ / sharesshares	Dec. 31, 2016USD ($)	Sep. 30, 2016$ / shares
Summary of Significant Accounting Policies [Line Items]
Restricted cash		$ 11,200	$ 400
Restricted cash, current		$ 7,380	127
Facility lease expiration term		90 days
Warrants to purchase common stock, exercise price | $ / shares		$ 3.78		$ 3.78
Number of operating segments | Segment		1
Private Placement
Summary of Significant Accounting Policies [Line Items]
Warrants to purchase common stock, exercise price | $ / shares	$ 3.66
Weighted average contractual term	5 years
Contingently Redeemable Common Stock | Bill & Melinda Gates Foundation
Summary of Significant Accounting Policies [Line Items]
Shares issued | shares		407,331
Common Stock | Private Placement
Summary of Significant Accounting Policies [Line Items]
Number of shares authorized to be purchased | shares	1,999,999
Warrants to purchase common stock outstanding and unexercised | shares		1,178,782
Facility Leases
Summary of Significant Accounting Policies [Line Items]
Restricted cash, current		$ 500	400
Bill & Melinda Gates Foundation
Summary of Significant Accounting Policies [Line Items]
Restricted cash, current		$ 10,700	$ 0

Summary of Significant Accoun26

Summary of Significant Accounting Policies - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 134,657	$ 118,964
Restricted cash, current	7,380	127
Restricted cash, non-current	3,855	250
Total cash, cash equivalents, and restricted cash	$ 145,892	$ 119,341	$ 42,179	$ 20,414

Summary of Significant Accoun27

Summary of Significant Accounting Policies - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net loss used to compute basic net loss per share	$ (29,907)	$ (11,038)	$ (89,235)	$ (41,503)
Less: Gain on private placement warrants	(6,795)
Net loss used to compute diluted net loss per share	$ (36,702)	$ (11,038)	$ (89,235)	$ (41,503)
Denominator:
Basic	42,259,001	26,789,397	38,709,811	22,046,368
Add: Private placement warrant shares	952,058
Weighted-average shares used to compute diluted net loss per share	43,211,059	26,789,397	38,709,811	22,046,368
Net loss per share:
Basic	$ (0.71)	$ (0.41)	$ (2.31)	$ (1.88)
Diluted	$ (0.85)	$ (0.41)	$ (2.31)	$ (1.88)

Summary of Significant Accoun28

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Outstanding Excluded from the Computations of Diluted Weighted-Average Shares Outstanding (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding (shares)	4,793,775	3,416,136	4,793,775	3,416,136
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding (shares)	845,705	561,428	845,705	561,428
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding (shares)	17,514	2,030,023	1,196,296	2,030,023

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Measured and Recognized at Fair Value (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	$ 210,645	$ 146,260
Unrealized Gains	1
Unrealized Losses	(10)	(7)
Fair Value	210,636	146,253
Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	64,744	26,912
Restricted cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	11,235	377
Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	134,657	118,964
Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost		3,728
Fair Value		3,728
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	137,502	115,613
Fair Value	137,502	115,613
Level 1 | Cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	126,267
Fair Value	126,267
Level 1 | Restricted cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	11,235	377
Fair Value	11,235	377
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost		115,236
Fair Value		115,236
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	73,143	26,919
Unrealized Gains	1
Unrealized Losses	(10)	(7)
Fair Value	73,134	26,912
Level 2 | U.S. Treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	21,004
Unrealized Losses	(8)
Fair Value	20,996
Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	8,664	12,969
Unrealized Losses	(2)	(7)
Fair Value	8,662	12,962
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	43,475	13,950
Unrealized Gains	1
Fair Value	43,476	13,950
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrant Liability	15,681	13,874
Derivative Liability	664	602
Total	$ 16,345	$ 14,476

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($)	Jun. 03, 2016	Aug. 05, 2015	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sale of available-for-sale securities				$ 0		$ 0
Change in estimated fair value				3,958,000	$ 2,881,000
Potential payment to solar capital			$ 1,000,000	$ 1,000,000
Discount rate, percent				13.00%
Change in percent effecting fair value of derivative liability				5.00%
Effect in fair value of derivative liability due to change in percent of FDA approval probability			$ 900,000	$ 900,000
Warrants to purchase common stock, exercise price			$ 3.78	$ 3.78	$ 3.78
Proceeds from exercise of stock warrants				$ 417,000
Estimated fair value of warrants exercised			$ 2,100,000	2,100,000		$ 1,200,000
Increase in estimated fair value of warrants exercised				$ 900,000
Dividend yield				0.00%		0.00%
Private Placement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants to purchase common stock, exercise price	$ 3.66
Common Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Exercise of warrants to purchase common stock				113,948
Common Stock | Private Placement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Warrants to purchase common stock	1,999,999
Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability			664,000	$ 664,000		$ 602,000
Outstanding warrant liability			15,681,000	15,681,000		13,874,000
Fair value, derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Effect in fair value of derivative liability due to change in percent of FDA approval probability			39,000	39,000
Derivative | Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in estimated fair value			21,000	62,000
Derivative liability			664,000	664,000
Warrants to purchase common stock | Level 3 | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Change in estimated fair value				3,896,000
Issuance of derivative in connection with issuance of loan payable	$ 2,600,000			2,089,000
Secured Debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Success fee		$ 1,000,000
Fair value of success fee		$ 356,000
Secured Debt | Fair value, derivative liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of success fee						$ 602,000
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized loss position			$ 31,300,000	$ 31,300,000

Fair Value Measurements - Assum

Fair Value Measurements - Assumptions Used (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Expected volatility	80.00%	80.00%
Expected term	3 years 8 months 13 days	4 years 2 months 13 days
Risk-free interest rate	1.70%	1.80%
Dividend yield	0.00%	0.00%

Fair Value Measurements - Chang

Fair Value Measurements - Change in Fair Value of Recurring Measurements (Details) - USD ($)	Jun. 03, 2016	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Change in estimated fair value			$ 3,958,000	$ 2,881,000
Fair Value, Measurements, Recurring | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Estimated Fair Value, Beginning Balance			14,476,000
Estimated Fair Value, Ending Balance		$ 16,345,000	16,345,000
Warrants to purchase common stock | Fair Value, Measurements, Recurring | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Estimated Fair Value, Beginning Balance			13,874,000
Change in estimated fair value			3,896,000
Reclassification of warrant liability to additional paid in capital upon exercise of warrants	$ (2,600,000)		(2,089,000)
Estimated Fair Value, Ending Balance		15,681,000	15,681,000
Derivative | Fair Value, Measurements, Recurring | Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Estimated Fair Value, Beginning Balance			602,000
Change in estimated fair value		21,000	62,000
Estimated Fair Value, Ending Balance		$ 664,000	$ 664,000

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Prepaids and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Prepaid Expense And Other Assets Current [Abstract]
Deferred research and development costs	$ 4,457	$ 660
Prepaid expenses	1,490	1,390
Other current assets	298	139
Prepaids and other current assets	$ 6,245	$ 2,189

Balance Sheet Components - Sc34

Balance Sheet Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 16,055	$ 7,650
Less: accumulated depreciation and amortization	(3,083)	(4,389)
Property and equipment, net	12,972	3,261
Office equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	863	644
Laboratory equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	5,701	4,038
Leasehold improvements
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	8,055	1,072
Property and equipment, net	6,600
Construction-in-progress
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 1,436	$ 1,896

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Depreciation and amortization	$ 400	$ 100	$ 851	$ 333

Balance Sheet Components - Sc36

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued clinical and development expenses	$ 2,188	$ 3,681
Payroll and related bonus expenses	6,242	4,941
Other	1,038	1,076
Accrued liabilities	$ 9,468	$ 9,698

License and Collaboration Agr37

License and Collaboration Agreements - Additional Information (Details)	1 Months Ended				3 Months Ended		9 Months Ended
	Feb. 28, 2017USD ($)	May 31, 2016USD ($)	Apr. 30, 2016USD ($)	Jan. 31, 2006USD ($)$ / sharesshares	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)milestone	Sep. 30, 2016USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense					$ 25,316,000	$ 20,536,000	$ 66,113,000	$ 56,137,000
Thermo Fisher Scientific, Inc
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments for first commercialization product			$ 6,500,000
Research and development expense	$ 900,000						1,700,000
Crystal Biosciences, Inc
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments for first commercialization product		$ 20,600,000
Ionis Pharmaceuticals License Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments for first commercialization product				$ 19,500,000
Milestone payments for second commercialization product				9,750,000
Aggregate additional milestone payments				20,000,000
Cumulative milestones compensation							$ 7,000,000
Number of milestones paid in relation to license agreement | milestone							3
Payments due					$ 0		$ 0
Ionis Pharmaceuticals License Agreement | Up-front License Fee
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense				$ 1,500,000
Ionis Pharmaceuticals License Agreement | Series A Convertible Preferred Stock | Up-front License Fee
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued | shares				97,402
Shares issued price per share (dollars per share) | $ / shares				$ 15.40

Revenue Contracts - Additional

Revenue Contracts - Additional Information (Details) - USD ($)	Nov. 08, 2017	Sep. 30, 2017	Jun. 30, 2017	May 31, 2017	Apr. 30, 2017	May 26, 2016	Apr. 30, 2016	Jan. 31, 2016	Jul. 31, 2015	Apr. 30, 2013	Sep. 30, 2012	Aug. 31, 2010	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research term				3 years
Advance amount received for research and development				$ 3,200,000
Contracts revenue													$ 300,000			$ 500,000		$ 0
Research and development contract		$ 12,000,000
Subsequent Event
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development contract	$ 18,000,000
Biomedical Advanced Research and Development Authority
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contracts revenue													0	$ 15,400,000		7,700,000	$ 29,200,000
Research and development contract					$ 124,300,000					$ 103,800,000	$ 43,400,000	$ 27,600,000
Term of agreement, in years												2 years
Increase in research and development contract					500,000	$ 20,000,000				$ 60,400,000	$ 15,800,000
Research and development contract remaining available funding															$ 124,300,000
C-Scape Contract
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development contract		12,000,000
Research and development contract remaining available funding		12,000,000
C-Scape Contract | Subsequent Event
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development contract	$ 18,000,000
National Institute of Allergy and Infectious Diseases
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contracts revenue													$ 300,000	$ 600,000		$ 1,100,000	$ 1,800,000
Research and development contract			$ 5,300,000		4,700,000		$ 4,400,000		$ 1,500,000
Increase in research and development contract			600,000		$ 300,000			$ 500,000
Research and development contract remaining available funding			$ 800,000
Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development awarded grant funding		18,000,000		$ 10,500,000
Maximum | C-Scape Contract
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Research and development awarded grant funding		$ 18,000,000

Borrowings - Additional Informa

Borrowings - Additional Information (Details) - USD ($)	Jun. 20, 2016	Aug. 05, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Face amount			$ 23,958,000		$ 23,958,000
Proceeds from issuance of loan payable						$ 10,000,000
Final fee due at maturity in 2019			2,000,000		2,000,000
Interest expense			740,000	$ 670,000	2,170,000	1,555,000
Secured Debt
Debt Instrument [Line Items]
Debt, maturity date		Aug. 5, 2019
Proceeds from issuance of loan payable	$ 10,000,000	$ 15,000,000
Interest rate per annum (percent)		6.99%
Variable interest rate (percent)		1.00%
Repayment of debt term (months)		24 months
Increase in interest rate in event of default (percent)		4.00%
Closing fee		$ 250,000
Final fee (percent)		8.00%
Success fee		$ 1,000,000
Fair value of success fee		356,000
Final fee due at maturity in 2019		2,000,000
Interest expense			$ 700,000	$ 700,000	$ 2,200,000	$ 1,600,000
Secured Debt | Maximum
Debt Instrument [Line Items]
Face amount		$ 25,000,000

Borrowings - Future Minimum Deb

Borrowings - Future Minimum Debt Obligation Payments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2,017	$ 3,125
2,018	12,500
2,019	8,333
Total principal payments	23,958
Final fee due at maturity in 2019	2,000
Total principal and final fee payments	25,958
Unamortized discount and debt issuance costs	(1,084)
Total loan obligation	24,874
Less current portion	(12,500)	$ (4,167)
Loan payable, long-term	$ 12,374	$ 21,110

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	Jun. 09, 2017	May 31, 2017	Dec. 19, 2016	Jun. 03, 2016	May 31, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Apr. 07, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants to purchase common stock, exercise price						$ 3.78		$ 3.78
Warrants to purchase common stock | Level 3 | Fair Value, Measurements, Recurring
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Issuance of derivative in connection with issuance of loan payable				$ 2,600,000		$ 2,089,000
Remaining warrants outstanding						15,700,000
Change in estimated fair value of remaining warrants outstanding						$ 1,800,000	$ 11,300,000
Private Placement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from issuance or sale of equity				$ 25,400,000
Warrants to purchase common stock, exercise price				$ 3.66
Weighted average contractual term				5 years
Private Placement | Chief Operating Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued				141,453
Number of shares authorized to be purchased				35,363
Proceeds from issuance or sale of equity				$ 500,000
Payments of stock issuance costs				$ 300,000
Underwritten Public Offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued		5,750,000	7,475,000		5,750,000
Share price (dollars per share)		$ 22.50	$ 13.50		$ 22.50
Additional shares of common stock	750,000		975,000
Proceeds from offering net of underwriting discounts and commissions and offering expenses		$ 121,200,000	$ 94,600,000		$ 121,200,000
Maximum | Private Placement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average contractual term				5 years
ATM equity offering program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value authorized of equity instruments to be issued									$ 30,000,000
Shares issued						1,105,549
Proceeds from issuance of common stock, gross of issuance costs						$ 5,300,000
Proceeds from sale of stock, net of commissions and other transaction costs						5,100,000
Value of common stock remaining available to be sold						$ 24,700,000
ATM equity offering program | Weighted Average
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price (dollars per share)						$ 4.82
Common Stock | Private Placement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued				7,999,996
Number of shares authorized to be purchased				1,999,999
Estimated fair values of the common stock and warrants issued				$ 22,900,000
Cowen and Company, LLC | ATM equity offering program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Value authorized of equity instruments to be issued									$ 30,000,000

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Details) - USD ($)	Feb. 22, 2017	Jan. 02, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares authorized					2,325,522
Outstanding shares available for future issuance (shares)			1,135,937		1,135,937		639,374
Shares subject to options outstanding (shares)			4,793,775		4,793,775		3,540,293
Stock-based compensation expense					$ 10,297,000	$ 2,726,000
Options granted (shares)					1,641,757
Non-Employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense			$ 67,000	$ 6,000	$ 481,000	$ 6,000
Stock Options and Restricted Stock Units | Former Chief Medical Officer
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense					600,000
Stock-based compensation expense related to stock option and restricted units modification					700,000
Options to purchase common stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation			$ 23.6		$ 23.6
Weighted-average period of cost expected to be recognized					3 years 1 month 7 days
Equity Option | Non-Employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted (shares)			3,000	15,000	3,000	15,000
Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted (shares)					0
Shares granted					470,076
Weighted-average grant date fair market value, shares granted (dollars per share)					$ 21.84
Restricted stock units | Non-Employee
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted			1,500	0	1,500	0
Restricted stock units | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period					4 years
Weighted-average period of cost expected to be recognized					2 years 10 months 25 days
Shares granted					470,076
Weighted-average grant date fair market value, shares granted (dollars per share)					$ 21.84
Unrecognized compensation costs			$ 11,300,000		$ 11,300,000
Employee Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares authorized		178,190
Outstanding shares available for future issuance (shares)			350,528		350,528
Common stock issued (shares)					336,139
2014 Equity Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares authorized		1,425,522
Outstanding shares available for future issuance (shares)			797,864		797,864
Vesting period					4 years
Option expiration period					10 years
2014 Employment Commencement Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares authorized	450,000
Outstanding shares available for future issuance (shares)			338,073		338,073
Number of shares authorized (shares)			2,050,000		2,050,000
Stock Incentive Plan 2003
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period					4 years
Option expiration period					10 years
Shares subject to options outstanding (shares)			829,586		829,586
Employees That Contain Performance Conditions | Options to purchase common stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted (shares)			22,500	129,000	179,200	340,250
Employees That Contain Performance Conditions | Restricted stock units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted			5,000	6,750	33,950	56,925

Equity Incentive Plans - Summar

Equity Incentive Plans - Summary of Stock Option Activity (Detail) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Shares Available for grant
Beginning balance (shares)	639,374
Additional shares authorized (shares)	2,325,522
Options granted (shares)	(1,641,757)
Options exercised (shares)	0
Options cancelled (shares)	223,682
Ending balance (shares)	1,135,937	639,374
Shares Subject to Options Outstanding
Beginning balance (shares)	3,540,293
Additional shares authorized (shares)	0
Options granted (shares)	1,641,757
Options exercised (shares)	(164,593)
Options cancelled (shares)	(223,682)
Ending balance (shares)	4,793,775	3,540,293
Weighted- Average Exercise Price
Beginning balance (shares)	$ 6.31
Options granted (shares)	21.96
Options exercised (shares)	7.50
Options cancelled (shares)	8.24
Ending balance (shares)	$ 11.54	$ 6.31
Weighted- Average Remaining Contractual Term (years)	7 years 10 months 10 days	7 years 11 months 23 days
Restricted Stock Units
Shares Available for grant
Shares granted	(470,076)
Shares cancelled	59,192
Shares Subject to Options Outstanding
Options granted (shares)	0
Options cancelled (shares)	0

Equity Incentive Plans - Schedu

Equity Incentive Plans - Schedule of Stock-Based Compensation Expense for Stock Options Granted to Employees and Non-Employees (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense			$ 10,297	$ 2,726
Stock Options Granted To Employees And Non Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,806	$ 974	9,816	2,726
Stock Options Granted To Employees And Non Employee Directors | Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	1,627	542	4,558	1,511
Stock Options Granted To Employees And Non Employee Directors | General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,179	$ 432	$ 5,258	$ 1,215

Equity Incentive Plans - Sche45

Equity Incentive Plans - Schedule of Estimated Grant Date Fair Value of Employee Stock Options Using Black-Scholes Valuation Model (Detail) - Options to purchase common stock	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term		6 years
Expected volatility, minimum	78.00%	67.00%	78.00%	67.00%
Expected volatility, maximum	79.00%	68.00%	81.00%	74.00%
Risk-free interest rate, minimum	1.90%	1.10%	1.70%	1.10%
Risk-free interest rate, maximum	2.10%	1.30%	2.10%	1.50%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term	5 years 9 months 18 days		5 years 3 months 19 days	5 years 3 months 19 days
Maximum
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term	6 years		6 years	6 years

Equity Incentive Plans - Sche46

Equity Incentive Plans - Schedule of Estimated Stock-Based Compensation Expense (Details) - Black Scholes - Non-Employee	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term	3 months	1 year 4 days		1 year 4 days
Expected volatility	60.00%	63.00%		63.00%
Expected volatility, minimum			48.00%
Expected volatility, maximum			77.00%
Risk-free interest rate	1.00%	0.60%		0.60%
Risk-free interest rate, minimum			0.90%
Risk-free interest rate, maximum			1.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term			3 months
Maximum
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term			6 months 3 days

Equity Incentive Plans - Summ47

Equity Incentive Plans - Summary of Restricted Stock Activity (Details) - Restricted Stock Units $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)
Number of Shares
Beginning balance (shares) | shares	605,052
Shares granted | shares	470,076
Shares released | shares	(170,231)
Shares cancelled | shares	(59,192)
Ending balance (shares) | shares	845,705
Weighted-Average Grant Date Fair Market Value
Beginning balance (dollars per share) | $ / shares	$ 5.60
Weighted-average grant date fair market value, shares granted (dollars per share) | $ / shares	21.84
Shares released (dollars per share) | $ / shares	5.91
Shares canceled (dollars per share) | $ / shares	7.73
Ending balance (dollars per share) | $ / shares	$ 14.42
Aggregate Intrinsic Value (in thousands)
RSU Awards Outstanding, aggregate intrinsic value | $	$ 13,489	$ 7,878

Equity Incentive Plans - Sche48

Equity Incentive Plans - Schedule of Estimated Fair Value of Awards Granted to Employees using Monte-Carlo Assumptions (Details) - Monte Carlo Simulation	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected volatility	75.00%	70.00%	75.00%	70.00%
Risk-free interest rate	2.40%		2.40%
Risk-free interest rate, minimum		1.40%		1.40%
Risk-free interest rate, maximum		1.60%		1.80%
Expected dividend yield			0.00%	0.00%
Minimum
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term	6 months	2 years 6 months	6 months	2 years 6 months
Maximum
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Expected term	1 year 9 months 18 days	5 years 10 months 24 days	1 year 9 months 18 days	6 years

Contingently Redeemable Commo49

Contingently Redeemable Common Stock - Additional Information (Details) - Contingently Redeemable Common Stock $ / shares in Units, $ in Millions	1 Months Ended
	May 31, 2017USD ($)$ / sharesshares
Temporary Equity [Line Items]
Percentage of purchase price compounded annual interest	5.00%
Mezzanine Equity
Temporary Equity [Line Items]
Proceeds from issuance or sale of equity | $	$ 10
Shares issued | shares	407,331
Bill & Melinda Gates Foundation
Temporary Equity [Line Items]
Shares issued | shares	407,331
Share price (dollars per share) | $ / shares	$ 24.55
Proceeds from issuance or sale of equity | $	$ 10

Commitments and Contingencies -

Commitments and Contingencies - Commercial Manufacturing Agreement (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Mar. 31, 2017	Jul. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Loss Contingencies [Line Items]
Prepaid and other current assets	$ 6,245			$ 6,245		$ 6,245		$ 2,189
Research and development				25,316	$ 20,536	66,113	$ 56,137
Hovione Limited
Loss Contingencies [Line Items]
Commercial manufacturing agreement initial term		7 years
Percentage of long term purchase commitment minimum required quantity		80.00%
Number of years for minimum supply percentage after approval		3 years
Minimum annual purchase commitments beginning year		2,020
Annual purchase commitments ending Year		2,024
Advance payments			$ 1,500			6,200
Prepaid and other current assets	4,500			4,500		4,500		700
Commitment under Cancellation Clause	10,200			10,200		10,200
Aggregate amount of potential commitments						28,100
Research and development				$ 400	$ 200	$ 1,900	$ 700
Hovione Limited | Raw Material Agreement
Loss Contingencies [Line Items]
Advance payments								$ 1,200
Research and development	$ 1,200
Hovione Limited | Minimum
Loss Contingencies [Line Items]
Percentage of long term purchase commitment		40.00%
Hovione Limited | Maximum
Loss Contingencies [Line Items]
Percentage of long term purchase commitment		66.00%

Commitments and Contingencies51

Commitments and Contingencies - Facilities Lease Obligation (Details)	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2016USD ($)ft²	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Aug. 31, 2017ft²	Aug. 17, 2017USD ($)	Jul. 31, 2017USD ($)ft²	Dec. 31, 2016USD ($)
Operating Leased Assets [Line Items]
Square feet of office, laboratory and research and development space (sq feet) | ft²								98,984
Lease extended term date		Jan. 31, 2028
Expansion option (in years)		5 years
Lessor Leasing Arrangements, Operating Leases, Rental Increase, Percent	3.50%
One time improvement allowance	$ 5,700,000	$ 1,000		$ 1,000
Additional allowance	$ 900,000	1,500,000		1,500,000
Aggregate Increase in base rent							$ 1,700,000
Property and equipment, net		12,972,000		12,972,000					$ 3,261,000
Tenant Improvements Liabilities		6,600,000		$ 6,600,000
Period available to pay balance of Original Additional Allowance and Expansion Additional Allowance				36 months
Restricted cash, non current		500,000		$ 500,000
Rent expense		900,000	$ 100,000	2,000,000	$ 400,000
Leasehold improvements
Operating Leased Assets [Line Items]
Property and equipment, net		$ 6,600,000		$ 6,600,000
Original Space
Operating Leased Assets [Line Items]
Square feet of office, laboratory and research and development space (sq feet) | ft²	47,118
First year base rent	$ 2,900,000
One time, first year rent abatement	$ 1,800,000
Expansion Space
Operating Leased Assets [Line Items]
Square feet of office, laboratory and research and development space (sq feet) | ft²								51,866
Expected operating lease area of real estate property | ft²						18,888
One time, first year rent abatement								$ 2,000,000

Commitments and Contingencies52

Commitments and Contingencies - Schedule of Future Minimum Lease Payments (Details) $ in Thousands	Sep. 30, 2017USD ($)
Year Ending December 31,
2,017	$ 272
2,018	4,028
2,019	6,201
2,020	6,418
2,021	6,644
Thereafter	45,657
Total minimum lease payments	$ 69,220