Protagonist Therapeutics (PTGX) 10-Q 14 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 31, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Trading Symbol	PTGX
Entity Registrant Name	PROTAGONIST THERAPEUTICS, INC.
Entity Central Index Key	1,377,121
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		16,714,453

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 96,024	$ 4,055
Restricted cash	10	10
Available-for-sale securities	2,499	7,868
Research and development tax incentive receivable	1,944	715
Prepaid expenses and other current assets	1,768	1,558
Total current assets	102,245	14,206
Property and equipment, net	564	609
Other assets	34	30
Total assets	102,843	14,845
Current liabilities:
Accounts payable	2,335	1,247
Accrued expenses and other payables	3,014	1,879
Total current liabilities	5,349	3,126
Redeemable convertible preferred stock tranche liability		1,643
Redeemable convertible preferred stock warrant liability		480
Total liabilities	5,349	5,249
Commitments and contingencies
Redeemable convertible preferred stock		36,996
Stockholders' equity (deficit):
Preferred stock, $0.00001 par value, 10,000,000 and 0 shares authorized as of September 30, 2016 (unaudited) and December 31, 2015, respectively; and no shares issued and outstanding as of September 30, 2016 (unaudited) and December 31, 2015
Common stock, $0.00001 par value, 90,000,000 and 160,000,000 shares authorized as of September 30, 2016 (unaudited) and December 31, 2015, respectively; 16,714,453 and 272,409 shares issued and outstanding as of September 30, 2016 (unaudited) and December 31, 2015, respectively	0	0
Additional paid-in capital	150,863	118
Accumulated other comprehensive loss	(24)	(102)
Accumulated deficit	(53,345)	(27,416)
Total stockholders' equity (deficit)	97,494	(27,400)
Total liabilities, redeemable convertible preferred stock and stockholders' equity (deficit)	$ 102,843	$ 14,845

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Redeemable convertible preferred stock, par value	$ 0.00001	$ 0.00001
Redeemable convertible preferred stock, shares authorized	0	126,374,911
Redeemable convertible preferred stock, shares issued	0	77,185,117
Redeemable convertible preferred stock, shares outstanding	0	77,185,117
Redeemable convertible preferred stock, redemption value		$ 41,538
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	90,000,000	160,000,000
Common stock, shares issued	16,714,453	272,409
Common stock, shares outstanding	16,714,453	272,409

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating expenses:
Research and development	$ 5,561	$ 3,158	$ 16,882	$ 7,638
General and administrative	1,577	863	4,387	2,155
Total operating expenses	7,138	4,021	21,269	9,793
Loss from operations	(7,138)	(4,021)	(21,269)	(9,793)
Interest income	54	1	93	2
Change in fair value of redeemable convertible preferred stock tranche and warrant liabilities		571	(4,719)	426
Other expense			(34)
Net loss	(7,084)	(3,449)	(25,929)	(9,365)
Net loss attributable to common stockholders	$ (7,377)	$ (3,485)	$ (26,487)	$ (9,401)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.87)	$ (12.79)	$ (8.62)	$ (38.32)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted	8,483,189	272,409	3,071,456	245,298

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (7,084)	$ (3,449)	$ (25,929)	$ (9,365)
Other comprehensive loss:
Loss (gain) on translation of foreign operations	75	(171)	73	(213)
Unrecognized gain on available-for-sale securities	1		5
Comprehensive loss	$ (7,008)	$ (3,620)	$ (25,851)	$ (9,578)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (25,929,000)	$ (9,365,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	242,000	160,000
Loss on disposal of property and equipment	34,000
Amortization of premium on available-for-sale securities	82,000
Stock-based compensation	610,000	62,000
Change in fair value associated with redeemable convertible preferred stock tranche liability	4,194,000	233,000
Change in fair value of redeemable convertible preferred stock warrant liability	525,000	(659,000)
Changes in operating assets and liabilities:
Research and development tax incentive receivable	(1,229,000)	(278,000)
Prepaid expenses and other current assets	(179,000)	(414,000)
Other assets	(4,000)
Accounts payable	157,000	431,000
Accrued expenses and other payables	1,205,000	184,000
Net cash used in operating activities	(20,292,000)	(9,646,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(327,000)	(179,000)
Purchase of available-for-sale securities	(6,396,000)
Proceeds from maturities of available-for-sale securities	11,688,000
Proceeds from sale of property and equipment	32,000
Net cash provided by (used in) investing activities	4,997,000	(179,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	22,508,000	17,362,000
Proceeds from issuance of common stock upon exercise of stock options	143,000	57,000
Proceeds from issuance of initial public offering, net of issuance cost	84,508,000
Net cash provided by financing activities	107,159,000	17,419,000
Effect on exchange rate changes on cash and cash equivalents	105,000	(206,000)
Net increase in cash and cash equivalents	91,969,000	7,388,000
Cash and cash equivalents, beginning of period	4,055,000	9,324,000
Cash and cash equivalents, end of period	96,024,000	16,712,000
SUPPLEMENTAL DISCLOSURES OF NON-CASH FINANCING INFORMATION
Settlement of fair value of redeemable convertible preferred stock liability	5,837,000
Tranche liability in connection with the Series C redeemable convertible preferred stock financing		1,017,000
Accretion of redeemable convertible preferred stock	558,000	$ 36,000
Conversion of redeemable convertible preferred stock to common stock at closing of initial public offering	66,904,000
Offering costs in accounts payable and accrued liabilities	860,000
Reclassification of preferred stock warrant liability to equity	$ 1,005,000

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business Protagonist Therapeutics, Inc. (the “Company”) was incorporated in the state of Delaware on August 22, 2006 and is headquartered in Milpitas, California. The Company is a clinical-stage biopharmaceutical company with a proprietary peptide technology platform focused on discovering and developing new chemical entities to address significant unmet medical needs. Protagonist Pty Ltd is a wholly-owned subsidiary located in Brisbane, Australia. The Company manages its operations as a single operating segment. Reverse Stock Split In July 2016, the Company’s board of directors approved an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of the Company’s issued and outstanding common stock at a 1-for-14.5 ratio, which was effected on August 1, 2016. The par value and authorized shares of common stock and convertible preferred stock were not adjusted as a result of the reverse split. All issued and outstanding common stock, options to purchase common stock and per share amounts contained in the condensed consolidated financial statements have been retroactively adjusted to reflect the reverse stock split for all periods presented. Initial Public Offering On August 10, 2016, the Company’s registration statement on Form S-1 (File Nos. 333-212476 and 333-213071) relating to its initial public offering (“IPO”) of common stock became effective. The IPO closed on August 16, 2016 at which time the Company issued 7,500,000 shares of its common stock at a price of $12.00 per share. In addition, upon closing the IPO, all outstanding shares of the redeemable convertible preferred stock converted into 8,577,571 shares of common stock and there are no shares of redeemable convertible preferred stock outstanding. In September 2016, the Company issued an additional 252,972 shares of common stock at a price of $12.00 per share following the underwriters’ exercise of their option to purchase additional shares. The Company received an aggregate of $83.6 million in cash, net of underwriting discounts and commissions, and after deducting offering costs paid by the Company.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Preparation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2015 has been derived from the audited consolidated financial statements at that date but does not include all of the information required by GAAP for complete consolidated financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and nine months ended September 30, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any other future year. The accompanying interim unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2015 included in the Company’s prospectus, filed with the SEC on August 12, 2016, pursuant to Rule 424(b) under the Securities Act. Principles of Consolidation The accompanying unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All significant intercompany transactions and balances have been eliminated upon consolidation. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to accruals for research and development activities, fair value of redeemable convertible preferred stock tranche liability, fair value of redeemable convertible preferred stock warrant liability, fair value of common stock, stock-based compensation and income taxes. Management bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. Actual results may differ from those estimates. Concentrations of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and available-for-sale securities. Substantially all the Company’s cash is held by one financial institution that management believes is of high credit quality. Such deposits may, at times, exceed federally insured limits. Cash Equivalents Cash equivalents that are readily convertible to cash are stated at cost, which approximates market value. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Cash equivalents consist of amounts invested in money market funds. Restricted Cash Restricted cash consisted of cash balances primarily held as security in connection with the Company’s corporate credit card. Available-for-Sale Securities All marketable securities have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its marketable securities at the time of purchase and reevaluates such designation as of each balance sheet date. Short-term marketable securities have maturities less than 365 days as of the balance sheet date. Long-term marketable securities have maturities greater than 365 days as of the balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest income. Fair Value of Financial Instruments Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the condensed consolidated financial statements on a recurring basis (at least annually). The carrying amount of the Company’s financial instruments, including cash equivalents, accounts payable and accrued expenses and other payables approximate fair value due to their short term maturities. See Note 3. Fair Value Measurements regarding the fair value of the Company’s available-for-sale securities, redeemable convertible preferred stock tranche liability and redeemable convertible preferred stock warrant liability. Accrued Research and Development Costs The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical studies and clinical trials, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced, and include these costs in accrued expenses and other payables in the condensed consolidated balance sheets and within research and development expense in the condensed consolidated statements of operations. These costs are a significant component of the Company’s research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers. The Company makes significant judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued costs and actual costs incurred. However, the status and timing of actual services performed, number of patients enrolled, and the rate of patient enrollments may vary from the Company’s estimates, resulting in adjustments to expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect the Company’s results of operations. Research and Development Costs Research and development costs are expensed as incurred and consist of salaries and benefits, stock-based compensation expense, lab supplies and facility costs, as well as fees paid to others that conduct certain research and development activities on the Company’s behalf. Research and Development Tax Incentive The Company is eligible under the AusIndustry research and development tax incentive program to obtain a cash amount from the Australian Taxation Office (“ATO”). The tax incentive is available to the Company on the basis of specific criteria with which the Company must comply. Specifically, the Company must have revenue of less than AUD 20.0 million and cannot be controlled by income tax exempt entities. These research and development tax incentives are recognized as contra research and development expense when the right to receive has been attained and funds are considered to be collectible. The tax incentive is denominated in Australian dollars and, therefore, the related receivable is remeasured into U.S. dollars as of each reporting date. Under certain conditions, research and development activities conducted outside Australia (“overseas finding”) also qualify for the research and development tax incentive. Funds received for overseas finding are at a risk of clawback until substantiation that less than 50% research and development expenditures for a project will be incurred overseas. A deferred tax incentive is recorded upon the cash receipt of the overseas finding funds and a reduction of research and development expense is not recognized until the Company can substantiate that more than 50% of the total project expenditure will occur in Australia. Net Loss per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, without consideration of potentially dilutive securities. The net loss attributable to common stockholders is calculated by adjusting the net loss of the Company for the accretion on the redeemable convertible preferred stock. Diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders for all periods presented since the effect of potentially dilutive securities are anti-dilutive given the net loss of the Company. Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326) In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) – Classification of Certain Cash Receipts and Cash Payments

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements Financial assets and liabilities are recorded at fair value. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The accounting guidance establishes a three-tiered hierarchy, which prioritizes the inputs used in the valuation methodologies in measuring fair value as follows: Level 1 Level 2— Level 3 In determining fair value, the Company utilizes quoted market prices, broker or dealer quotation, or valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible as well as considers counterparty credit risk in its assessment of fair value. The following table presents the fair value of the Company’s financial assets and liabilities determined using the inputs defined above (amounts in thousands). September 30, 2016 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 95,122 $ — $ — $ 95,122 Corporate bonds — 600 — 600 Commercial paper — 1,899 — 1,899 Total financial assets $ 95,122 $ 2,499 $ — $ 97,621 December 31, 2015 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 2,136 $ — $ — $ 2,136 Corporate bonds — 7,368 — 7,368 Commercial paper — 500 — 500 Total financial assets $ 2,136 $ 7,868 $ — $ 10,004 Liabilities: Redeemable convertible preferred stock tranche liability $ — $ — $ 1,643 $ 1,643 Redeemable convertible preferred stock warrant liability — — 480 480 Total financial liabilities $ — $ — $ 2,123 $ 2,123 The corporate bonds and commercial paper are classified as Level 2 as they were valued based upon quoted market prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets. Level 3 instruments are valued based on unobservable inputs that are supported by little or no market activity and reflect the Company’s assumptions in measuring fair value. The fair value measurements of the redeemable convertible preferred stock tranche liability and the redeemable convertible preferred stock warrant liability were based on significant inputs not observed in the market and thus represent a Level 3 measurement. The redeemable convertible preferred stock tranche liability stems from the initial sale of the Company’s Series C redeemable convertible preferred stock wherein the Company was obligated to sell additional shares in subsequent closings contingent upon a majority of the stockholders of the outstanding redeemable convertible preferred stock and/or the achievement of certain development milestones. The subsequent closings were deemed to be freestanding financial instruments that were at the option of the holders. The Company estimated the fair value of this liability using a one-step binomial lattice model in combination with the Option Pricing Model. The change in fair value was recognized as a gain or loss in the condensed consolidated statements of operations. See Note 10 for further discussion on the redeemable convertible preferred stock tranche liability and related valuations. The determination of the fair value of the redeemable convertible preferred stock warrant liability is discussed in Note 8. Generally, increases or decreases in the fair value of the underlying redeemable convertible preferred stock would result in a directionally similar impact in the fair value measurement of the warrant liability. The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial instruments as follows (in thousands): Redeemable Convertible Preferred Stock Tranche Liability: Balance at December 31, 2015 $ 1,643 Change in fair value upon revaluation 4,194 Settlement of redeemable convertible preferred stock tranche liability due to the issuance of Series C redeemable convertible preferred stock (5,837 ) Balance at September 30, 2016 $ — Redeemable Convertible Preferred Stock Warrant Liability: Balance at December 31, 2015 $ 480 Change in fair value upon revaluation 525 Reclassification of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock (1,005 ) Balance at September 30, 2016 $ —

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	4. Balance Sheet Components Cash Equivalents and Available-for-sale Securities Cash equivalents and available-for-sale securities consisted of the following (in thousands): September 30, 2016 Amortized Cost Gross Unrealized Gains Losses Fair Value Money market funds $ 95,122 $ — $ — $ 95,122 Corporate bonds 600 — — 600 Commercial paper 1,899 — — 1,899 Total cash equivalents and available-for-sale securities $ 97,621 $ — $ — $ 97,621 Classified as: Cash equivalents $ 95,122 Available-for-sale securities 2,499 Total cash equivalents and available-for-sale securities $ 97,621 December 31, 2015 Amortized Cost Gross Unrealized Gains Losses Fair Value Money market funds $ 2,136 $ — $ — $ 2,136 Corporate bonds 7,373 — (5 ) 7,368 Commercial paper 500 — — 500 Total cash equivalents and available-for-sale securities $ 10,009 $ — $ (5 ) $ 10,004 Classified as: Cash equivalents $ 2,136 Available-for-sale securities 7,868 Total cash equivalents and available-for-sale securities $ 10,004 All available-for-sale securities held as of September 30, 2016 and December 31, 2015 had contractual maturities of less than one year. There have been no material realized gains or losses on available-for-sale securities for the periods presented. Accrued Expenses and Other Payables Accrued expenses and other payables consisted of the following (in thousands): September 30, 2016 December 31, 2015 Accrued clinical and research related expenses $ 1,630 $ 976 Accrued employee related expenses 1,074 754 Other 310 149 Total accrued expenses and other payables $ 3,014 $ 1,879

Research Collaboration and Lice

Research Collaboration and License Agreement	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Research Collaboration and License Agreement	5. Research Collaboration and License Agreement In October 2013, the Company’s former collaboration partner decided to abandon a collaboration program with the Company and, pursuant to the terms of the agreement between the Company and the former collaboration partner, the Company elected to assume the responsibility for the development and commercialization of the product. Upon the former collaboration partner’s abandonment, it assigned to the Company certain intellectual property arising from the collaboration and also granted the Company an exclusive license to certain background intellectual property rights of the former collaboration partner that relate to the products assumed by the Company. Upon the nomination of PTG-300 as a development candidate, the Company owed the former collaboration partner a payment of $250,000. If the Company initiates a Phase 1 clinical trial for PTG-300, it will pay the former collaboration partner an additional $250,000. The Company has the right, but not the obligation, to further develop and commercialize the products and, if the Company successfully develops and commercializes PTG-300 without a partner, the Company will pay to the former collaboration partner up to an additional aggregate of $128.5 million for the achievement of certain development, regulatory and sales milestone events. In addition, the Company will pay to the former collaboration partner a low single digit royalty on worldwide net sales of the product until the later of ten years from the first commercial sale of the product or the expiration of the last patent covering the product. For the three and nine months ended September 30, 2016, the Company recorded research and development expense of zero and $250,000 under this agreement. There were no such costs incurred for the three and nine months ended September 30, 2015.

Government Programs

Government Programs	9 Months Ended
	Sep. 30, 2016
Business Combinations [Abstract]
Government Programs	6. Government Programs Research and Development Tax Incentive The Company recognized AUD 181,000 ($145,000) and AUD 1.6 million ($1.2 million), and AUD 194,000 ($127,000) and AUD 464,000 ($337,000) as a reduction of research and development expenses for the three and nine months ended September 30, 2016 and 2015, respectively, in connection with the research and development tax incentive from Australia. As of September 30, 2016 and December 31, 2015, the research and development tax incentive receivable was AUD 2.5 million ($1.9 million) and AUD 978,000 ($715,000), respectively. In March 2016, the Company received AUD 237,000 ($182,000) for overseas findings and recorded the funds as deferred tax incentive in accrued expenses and other payables on the condensed consolidated balance sheet due to the possibility that the funds could have to be repaid. SBIR Grant In September 2015, the Company was awarded a Phase 1 SBIR Grant from the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health (“NIH”) in support of research on orally stable peptide antagonists of the Interleukin-23 receptor (“IL-23R”) as potential treatments for inflammatory bowel diseases (“IBD”). The total grant award was $224,000 and is for the period from September 2015 to August 2016. In July 2016, the Company was awarded a Phase 1 SBIR Grant from the National Institute of Heart and Lung Diseases of the NIH in support of preclinical research aimed at discovering and optimizing lead molecules as novel peptide mimetics of the natural hepcidin hormone. The total grant award was $219,000 and is for the period from August 2016 to January 2017. The Company recognizes contra research and development when expenses related to the grants have been incurred and the grant funds become contractually due from NIH. The Company recorded $66,000 and $135,000 as a reduction of research and development expenses for the three and nine months ended September 30, 2016. There was no such reduction recorded for the three and nine months ended September 30, 2015. The Company recorded a receivable for $65,000 and $155,000 as of September 30, 2016 and December 31, 2015, respectively, to reflect the eligible costs incurred under the grants that are contractually due to the Company and such amounts are included in the prepaid expenses and other current assets on the condensed consolidated balance sheets.

Lease Agreement

Lease Agreement	9 Months Ended
	Sep. 30, 2016
Leases [Abstract]
Lease Agreement	7. Lease Agreement In April 2016, the Company entered into an amendment to its facility lease agreement to increase the leased space in Milpitas, California. Under the amended lease agreement, the Company will make additional lease payments of $80,000 through April 2018.

Preferred Stock Warrants

Preferred Stock Warrants	9 Months Ended
	Sep. 30, 2016
Text Block [Abstract]
Preferred Stock Warrants	8. Preferred Stock Warrants In connection with the Series B redeemable convertible preferred stock financing, the Company issued warrants to purchase 4,000,000 shares of Series B redeemable convertible preferred stock at an exercise price of $0.01 per share. These warrants would become exercisable only when certain milestones were met on programs begun as a result of collaborations entered into in 2011 and 2012. In particular, 50% of the warrants would become exercisable upon the Company publicly announcing its first Investigational New Drug (“IND”) candidate to the extent such IND candidate was the result of, or related to, the Company’s previous collaboration(s) with Ironwood Pharmaceuticals and/or Zealand Pharma A/S, and the balance would become exercisable upon the first dosing of a human patient in a clinical trial that was the result of, or related to, the Company’s previous collaboration(s) with Ironwood Pharmaceuticals and/or Zealand Pharma A/S. In August 2013, the initial closing date for the Series B financing, the Company issued 2,000,000 of the warrants (“First Tranche Warrants”). On August 15, 2014, in connection with the closing of the Series B second tranche financing, the Company issued the balance of the warrants (“Second Tranche Warrants”). The fair value of the warrants outstanding as of December 31, 2015 was remeasured at $480,000, determined using a one-step binomial lattice model in combination with the Option Pricing Model and the following assumptions: risk-free interest rate of 0.90%, expected life of 1.6 years and expected volatility of 57.0% and probability of exercisability of 95% and 0% for the first tranche and second tranche, respectively. In March 2016, the Company made a public announcement related to a preclinical candidate which triggered the achievement of the milestone and warrants to purchase 2,000,000 shares of Series B redeemable convertible preferred stock became exercisable as of that date. In April 2016, 1,999,998 shares of Series B redeemable convertible preferred stock were issued for cash proceeds of $20,000 in connection with the exercise of warrants. Immediately prior to the exercise of the warrants, the fair value of the warrants was remeasured at $1.0 million, determined using a hybrid method of the Option Pricing Model with a 67% weighted value per share and the probability-weighted expected return method (“PWERM”) with a 33% weighted value per share. The following assumptions were used in the Option Pricing Model: risk-free interest rate of 0.73%, expected life of 2.0 years and expected volatility of 52.0%. The PWERM method included probabilities of three IPO scenarios occurring in July 2016. The scenarios were weighted based on the Company’s estimate of each event occurring in deriving the estimated fair value. Upon the exercise of warrants, the redeemable convertible preferred stock warrant liability of $1.0 million was reclassified to redeemable convertible preferred stock. In May 2016, the remaining warrants for the purchase of 2,000,000 shares of Series B redeemable convertible preferred stock expired unexercised. The Company recorded a charge of zero and $525,000 for the three and nine months ended September 30, 2016, respectively, representing the increase in the fair value of the redeemable convertible preferred stock warrant liability in the condensed consolidated statements of operations. The Company recorded gains of $805,000 and $659,000 for the three and nine months ended September 30, 2015, respectively, representing the decrease in the fair value of the redeemable convertible preferred stock warrant liability in the condensed consolidated statements of operations.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	9 Months Ended
	Sep. 30, 2016
Text Block [Abstract]
Redeemable Convertible Preferred Stock	9. Redeemable Convertible Preferred Stock In April 2016, 1,999,998 shares of Series B redeemable convertible preferred stock were issued in connection with the exercise of warrants for cash proceeds of $20,000. Following the closing of the IPO, all outstanding shares of the redeemable convertible preferred stock converted into 8,577,571 shares of common stock and the related carrying value was reclassified to common stock and additional paid-in capital. There were no shares of redeemable convertible preferred stock outstanding as of September 30, 2016. The table below provides information on the Company’s redeemable convertible preferred stock as of December 31, 2015 (in thousands, except shares and original issue price): Shares Original Issue Price Authorized Issued and Outstanding Carrying Value Aggregate Liquidation Preference Series A $ 1.00 6,037,500 6,037,500 $ 1,751 $ 6,038 Series B $ 0.50 40,000,000 36,000,000 18,825 18,000 Series C $ 0.4979 80,337,411 35,147,617 16,420 17,500 Total redeemable convertible preferred stock 126,374,911 77,185,117 $ 36,996 $ 41,538 The Company recorded $293,000 and $558,000 for the accretion of the redeemable convertible preferred stock during the three and nine months ended September 30, 2016, respectively. The Company recorded $36,000 for the accretion of the redeemable convertible preferred stock during the three and nine months ended September 30, 2015.

Redeemable Convertible Prefer16

Redeemable Convertible Preferred Stock Tranche Liability	9 Months Ended
	Sep. 30, 2016
Text Block [Abstract]
Redeemable Convertible Preferred Stock Tranche Liability	10. Redeemable Convertible Preferred Stock Tranche Liability In July 2015, the Company entered into the Series C Preferred Stock Purchase Agreement (“the Series C Agreement”) for the issuance of up to 80,337,411 shares of Series C redeemable convertible preferred stock at a price of $0.4979 per share, in multiple closings. The initial closing occurred on July 10, 2015, whereby 35,147,617 shares of Series C redeemable convertible preferred stock were issued for gross proceeds of approximately $17.5 million. According to the initial terms of the Series C Agreement, the Company could issue 45,189,794 additional shares under the same terms as the initial closing, in a subsequent closing (“Series C Second Tranche”) contingent upon the achievement of certain development milestones. On the date of the initial closing, the Company recorded a Series C redeemable convertible preferred stock liability of $1.0 million, as the fair value of the obligation/right to complete the Series C Second Tranche. The fair value of the Series C redeemable convertible preferred stock liability on the date of the initial closing was determined using a one-step binomial lattice model in combination with the option pricing method based on the following assumptions: 90% probability of achievement of the development milestones, stock price of $0.4979 per share, expected term of 1.0 year, and risk-free rate of 0.5%. At December 31, 2015, the fair value of the Series C redeemable convertible preferred stock liability was remeasured and determined to be $1.6 million using a one-step binomial lattice model in combination with the Option Pricing Model based on the following assumptions: 95% probability of achievement of the development milestones, stock price of $0.4979 per share, expected term of 0.53 year, and risk-free rate of 0.9%. In March 2016, the Company completed the closing of the Series C Second Tranche and issued 45,189,794 shares of Series C redeemable convertible preferred stock for net cash proceeds of $22.5 million. At this time the Series C redeemable convertible preferred stock liability was remeasured at $5.8 million, determined using a hybrid method of the Option Pricing Model with a 67% weighted value per share and the PWERM with a 33% weighted value per share. The following assumptions were used in the Option Pricing Model: risk-free interest rate of 0.73%, expected life of 2.0 years and expected volatility of 52.0%. The PWERM method included probabilities of three IPO scenarios occurring in July 2016. The scenarios were weighted based on the Company’s estimate of each event occurring in deriving the estimated fair value. Upon the closing of the Series C Second Tranche, the Series C redeemable convertible preferred stock liability was terminated and the balance of the liability of $5.8 million was reclassified to redeemable convertible preferred stock. For the three and nine months ended September 30, 2016, the Company recorded a charge of zero and $4.2 million, respectively, for the change in the fair value of the Series C redeemable convertible preferred stock liability in the condensed consolidated statements of operations.

Common Stock

Common Stock	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Common Stock	11. Common Stock The Company had reserved shares of common stock for issuance, on an as-converted basis, as follows: September 30, 2016 December 31, 2015 Redeemable convertible preferred stock outstanding — 5,323,103 Options issued and outstanding 1,496,156 833,178 Options available for future grants 1,069,828 147,219 Redeemable convertible preferred stock warrants — 275,861 Total 2,565,984 6,579,361

Stock Option Plans

Stock Option Plans	9 Months Ended
	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Plans	12. Stock Option Plans Equity Incentive Plan In July 2016, the Company’s board of directors and stockholders approved the 2016 Equity Incentive Plan (the “2016 Plan”) to replace the 2007 Stock Option Plan and became effective upon the IPO. The 2016 Plan is administered by the Board of Directors or a committee appointed by the Board of Directors, which determines the types of awards to be granted, including the number of shares subject to the awards, the exercise price and the vesting schedule. Under the 2016 Plan, 1,200,000 shares of the Company’s common stock have been initially reserved for the issuance of stock options, restricted stock units and other awards to employees, directors and consultants. Options granted under the 2016 Plan expire no later than 10 years from the date of grant. The exercise price of each option may not be less than 100% of the fair market value of the common stock at the date of grant. Options may be granted to stockholders possessing more than 10% of the total combined voting power of all classes of stocks of the Company at an exercise price at least 110% of the fair value of the common stock at the date of grant and the options are not exercisable after the expiration of 10 years from the date of grant. Employee stock options generally vest 25% upon one year of continued service to the Company, with the remainder in monthly increments over three additional years. Upon adoption of the 2016 Plan, no additional stock awards will be issued under the 2007 Stock Option Plan. Options granted under the 2007 Stock Option Plan that were outstanding on the date the 2016 plan became effective remain subject to the terms of the 2007 Stock Option Plan. As of September 30, 2016, the Company has reserved 1,200,000 shares of common stock for issuance under the 2016 Plan. Employee Stock Purchase Plan In July 2016, the Company’s board of directors and stockholders approved the 2016 Employee Stock Purchase Plan (the “2016 ESPP”), which became effective upon the IPO. The 2016 ESPP is intended to qualify as an employee stock purchase plan under Section 423 of the Internal Revenue Code of 1986, as amended, and is administered by the Company’s board of directors and the Compensation Committee of the board of directors. Under the 2016 ESPP, 150,000 shares of the Company’s common stock have been initially reserved for employee purchases of the Company’s common stock, with an automatic annual increase to the shares issuable under the 2016 ESPP on the first day of each fiscal year for a period of up to 10 years in an amount equal to (i) the lesser of 1% of the total number of shares of common stock outstanding on December 31 of the preceding fiscal year and 300,000 shares of the Company’s common stock, or (ii) a lower number determined by the Board of Directors. The 2016 ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock at the beginning of the offering period or at the end of each applicable purchase period. Stock Options Activity under the Company’s stock option plan is set forth below: Options Outstanding Options Available for Grant Options Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Life (years) Aggregate Intrinsic Value (in thousands) Balances at December 31, 2015 147,219 833,178 $ 1.33 8.56 Additional options authorized 1,697,088 — Options granted (774,479 ) 774,479 5.55 Options exercised — (111,501 ) 1.28 Balances at September 30, 2016 1,069,828 1,496,156 3.52 8.65 $ 26,347 Options exercisable – September 30, 2016 338,784 1.97 7.26 $ 6,490 Options vested and expected to vest – September 30, 2016 1,481,620 3.51 8.64 $ 26,100 The aggregate intrinsic values of options outstanding, exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock on September 30, 2016. During the three months ended September 30, 2016, the estimated weighted-average grant-date fair value of common stock underlying options granted was $6.09 per share. No options were granted during the three months ended September 30, 2015. During the nine months ended September 30, 2016 and 2015, the estimated weighted-average grant-date fair value of common stock underlying options granted was $3.16 and $1.04 per share, respectively. Employee Stock Options Valuation The fair value of employee and director stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Expected term (in years) 4.16 - 5.70 — 4.16 - 5.94 5.89 Expected volatility 62.8 % — 62.5% - 64.8 % 59.8 % Risk-free interest rate 1.28 % — 1.27% - 1.38 % 1.57 % Dividend yield — — — — Stock Options Granted to Non-employees Stock-based compensation related to stock options granted to non-employees is recognized as the stock options are earned. The fair value of the stock options granted is calculated at each reporting date using the Black-Scholes option-pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Expected term (in years) 5.70 - 7.04 — 5.70 - 9.93 — Expected volatility 62.8 % — 62.5% - 62.8 % — Risk-free interest rate 1.29 % — 1.29% - 1.36 % — Dividend yield — — — — During the three and nine months ended September 30, 2016, the Company granted 7,752 shares and 25,647 shares, respectively, to non-employee consultants. No shares were granted to non-employee consultants during the three and nine months ended September 30, 2015. The Company recorded stock-based compensation expense during the three and nine months ended September 30, 2016 and 2015 of $226,000, $264,000, $4,000 and $14,000, respectively. Stock-Based Compensation Total stock-based compensation expense recognized for both employees and non-employees for stock options and the 2016 ESPP was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Research and development $ 285 $ 8 $ 360 $ 24 General and administrative 163 14 250 38 Total stock-based compensation expense $ 448 $ 22 $ 610 $ 62 As of September 30, 2016 there was $2.8 million of total unrecognized stock-based compensation costs related to stock options that the Company expects to recognize over a period of approximately 3.0 years.

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	9 Months Ended
	Sep. 30, 2016
Earnings Per Share [Abstract]
Net Loss per Share Attributable to Common Stockholders	13. Net Loss per Share Attributable to Common Stockholders As the Company had net losses for the three and nine months ended September 30, 2016 and 2015, all potential common shares were determined to be anti-dilutive. The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: Net loss $ (7,084 ) $ (3,449 ) $ (25,929 ) $ (9,365 ) Accretion of redeemable convertible preferred stock (293 ) (36 ) (558 ) (36 ) Net loss attributable to common stockholders $ (7,377 ) $ (3,485 ) $ (26,487 ) $ (9,401 ) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 8,483,189 272,409 3,071,456 245,298 Net loss per share attributable to common stockholders, basic and diluted $ (0.87 ) $ (12.79 ) $ (8.62 ) $ (38.32 ) The following outstanding shares of potentially dilutive securities have been excluded from diluted net loss per share calculations for the three and nine months ended September 30, 2016 and 2015, because their inclusion would be anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Redeemable convertible preferred stock on an as-converted basis — 5,323,103 — 5,323,103 Options to purchase common stock 1,496,156 468,546 1,496,156 468,546 Warrants to purchase redeemable convertible preferred stock on an as-converted basis — 275,861 — 275,861 Total 1,496,156 6,067,510 1,496,156 6,067,510

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events In October 2016, the Company received AUD 3.0 million ($2.2 million) including interest, in connection with the Australian research and development tax incentive. Of the funds received, $0.7 million will reduce the research and development tax incentive receivable and $1.5 million, which is for overseas findings, will be recorded as deferred tax incentive in accrued expenses and other payables as such funds are at risk of clawback until substantiation that less than 50% research and development expenditures for a project will be incurred overseas.

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Basis of Preparation	Basis of Preparation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2015 has been derived from the audited consolidated financial statements at that date but does not include all of the information required by GAAP for complete consolidated financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and nine months ended September 30, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any other future year. The accompanying interim unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2015 included in the Company’s prospectus, filed with the SEC on August 12, 2016, pursuant to Rule 424(b) under the Securities Act.
Principles of Consolidation	Principles of Consolidation The accompanying unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiary. All significant intercompany transactions and balances have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to accruals for research and development activities, fair value of redeemable convertible preferred stock tranche liability, fair value of redeemable convertible preferred stock warrant liability, fair value of common stock, stock-based compensation and income taxes. Management bases these estimates on historical and anticipated results, trends, and various other assumptions that the Company believes are reasonable under the circumstances, including assumptions as to future events. Actual results may differ from those estimates.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and available-for-sale securities. Substantially all the Company’s cash is held by one financial institution that management believes is of high credit quality. Such deposits may, at times, exceed federally insured limits.
Cash Equivalents	Cash Equivalents Cash equivalents that are readily convertible to cash are stated at cost, which approximates market value. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Cash equivalents consist of amounts invested in money market funds.
Restricted Cash	Restricted Cash Restricted cash consisted of cash balances primarily held as security in connection with the Company’s corporate credit card.
Available-for-Sale Securities	Available-for-Sale Securities All marketable securities have been classified as “available-for-sale” and are carried at estimated fair value as determined based upon quoted market prices or pricing models for similar securities. Management determines the appropriate classification of its marketable securities at the time of purchase and reevaluates such designation as of each balance sheet date. Short-term marketable securities have maturities less than 365 days as of the balance sheet date. Long-term marketable securities have maturities greater than 365 days as of the balance sheet date. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. Realized gains and losses and declines in fair value judged to be other than temporary, if any, on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific-identification method. Interest on marketable securities is included in interest income.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value accounting is applied for all financial assets and liabilities that are recognized or disclosed at fair value in the condensed consolidated financial statements on a recurring basis (at least annually). The carrying amount of the Company’s financial instruments, including cash equivalents, accounts payable and accrued expenses and other payables approximate fair value due to their short term maturities. See Note 3. Fair Value Measurements regarding the fair value of the Company’s available-for-sale securities, redeemable convertible preferred stock tranche liability and redeemable convertible preferred stock warrant liability.
Accrued Research and Development Costs	Accrued Research and Development Costs The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of preclinical studies and clinical trials, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated amount of services provided but not yet invoiced, and include these costs in accrued expenses and other payables in the condensed consolidated balance sheets and within research and development expense in the condensed consolidated statements of operations. These costs are a significant component of the Company’s research and development expenses. The Company accrues for these costs based on factors such as estimates of the work completed and in accordance with agreements established with its third-party service providers. The Company makes significant judgments and estimates in determining the accrued liabilities balance in each reporting period. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued costs and actual costs incurred. However, the status and timing of actual services performed, number of patients enrolled, and the rate of patient enrollments may vary from the Company’s estimates, resulting in adjustments to expense in future periods. Changes in these estimates that result in material changes to the Company’s accruals could materially affect the Company’s results of operations.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred and consist of salaries and benefits, stock-based compensation expense, lab supplies and facility costs, as well as fees paid to others that conduct certain research and development activities on the Company’s behalf.
Research and Development Tax Incentive	Research and Development Tax Incentive The Company is eligible under the AusIndustry research and development tax incentive program to obtain a cash amount from the Australian Taxation Office (“ATO”). The tax incentive is available to the Company on the basis of specific criteria with which the Company must comply. Specifically, the Company must have revenue of less than AUD 20.0 million and cannot be controlled by income tax exempt entities. These research and development tax incentives are recognized as contra research and development expense when the right to receive has been attained and funds are considered to be collectible. The tax incentive is denominated in Australian dollars and, therefore, the related receivable is remeasured into U.S. dollars as of each reporting date. Under certain conditions, research and development activities conducted outside Australia (“overseas finding”) also qualify for the research and development tax incentive. Funds received for overseas finding are at a risk of clawback until substantiation that less than 50% research and development expenditures for a project will be incurred overseas. A deferred tax incentive is recorded upon the cash receipt of the overseas finding funds and a reduction of research and development expense is not recognized until the Company can substantiate that more than 50% of the total project expenditure will occur in Australia.
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted average number of shares of common stock outstanding during the period, without consideration of potentially dilutive securities. The net loss attributable to common stockholders is calculated by adjusting the net loss of the Company for the accretion on the redeemable convertible preferred stock. Diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders for all periods presented since the effect of potentially dilutive securities are anti-dilutive given the net loss of the Company.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326) In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230) – Classification of Certain Cash Receipts and Cash Payments
Fair Value Measurements	The redeemable convertible preferred stock tranche liability stems from the initial sale of the Company’s Series C redeemable convertible preferred stock wherein the Company was obligated to sell additional shares in subsequent closings contingent upon a majority of the stockholders of the outstanding redeemable convertible preferred stock and/or the achievement of certain development milestones. The subsequent closings were deemed to be freestanding financial instruments that were at the option of the holders. The Company estimated the fair value of this liability using a one-step binomial lattice model in combination with the Option Pricing Model. The change in fair value was recognized as a gain or loss in the condensed consolidated statements of operations. See Note 10 for further discussion on the redeemable convertible preferred stock tranche liability and related valuations. The determination of the fair value of the redeemable convertible preferred stock warrant liability is discussed in Note 8. Generally, increases or decreases in the fair value of the underlying redeemable convertible preferred stock would result in a directionally similar impact in the fair value measurement of the warrant liability.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value	The following table presents the fair value of the Company’s financial assets and liabilities determined using the inputs defined above (amounts in thousands). September 30, 2016 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 95,122 $ — $ — $ 95,122 Corporate bonds — 600 — 600 Commercial paper — 1,899 — 1,899 Total financial assets $ 95,122 $ 2,499 $ — $ 97,621 December 31, 2015 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 2,136 $ — $ — $ 2,136 Corporate bonds — 7,368 — 7,368 Commercial paper — 500 — 500 Total financial assets $ 2,136 $ 7,868 $ — $ 10,004 Liabilities: Redeemable convertible preferred stock tranche liability $ — $ — $ 1,643 $ 1,643 Redeemable convertible preferred stock warrant liability — — 480 480 Total financial liabilities $ — $ — $ 2,123 $ 2,123
Summary of Changes in Fair Value of Company's Level 3 Financial Instruments	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial instruments as follows (in thousands): Redeemable Convertible Preferred Stock Tranche Liability: Balance at December 31, 2015 $ 1,643 Change in fair value upon revaluation 4,194 Settlement of redeemable convertible preferred stock tranche liability due to the issuance of Series C redeemable convertible preferred stock (5,837 ) Balance at September 30, 2016 $ — Redeemable Convertible Preferred Stock Warrant Liability: Balance at December 31, 2015 $ 480 Change in fair value upon revaluation 525 Reclassification of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock (1,005 ) Balance at September 30, 2016 $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Cash Equivalents and Available-for-sale Securities	Cash equivalents and available-for-sale securities consisted of the following (in thousands): September 30, 2016 Amortized Cost Gross Unrealized Gains Losses Fair Value Money market funds $ 95,122 $ — $ — $ 95,122 Corporate bonds 600 — — 600 Commercial paper 1,899 — — 1,899 Total cash equivalents and available-for-sale securities $ 97,621 $ — $ — $ 97,621 Classified as: Cash equivalents $ 95,122 Available-for-sale securities 2,499 Total cash equivalents and available-for-sale securities $ 97,621 December 31, 2015 Amortized Cost Gross Unrealized Gains Losses Fair Value Money market funds $ 2,136 $ — $ — $ 2,136 Corporate bonds 7,373 — (5 ) 7,368 Commercial paper 500 — — 500 Total cash equivalents and available-for-sale securities $ 10,009 $ — $ (5 ) $ 10,004 Classified as: Cash equivalents $ 2,136 Available-for-sale securities 7,868 Total cash equivalents and available-for-sale securities $ 10,004
Summary of Accrued Expenses and Other Payables	Accrued expenses and other payables consisted of the following (in thousands): September 30, 2016 December 31, 2015 Accrued clinical and research related expenses $ 1,630 $ 976 Accrued employee related expenses 1,074 754 Other 310 149 Total accrued expenses and other payables $ 3,014 $ 1,879

Redeemable Convertible Prefer24

Redeemable Convertible Preferred Stock (Tables)	9 Months Ended
	Sep. 30, 2016
Text Block [Abstract]
Summary of Redeemable Convertible Preferred Stock	The table below provides information on the Company’s redeemable convertible preferred stock as of December 31, 2015 (in thousands, except shares and original issue price): Shares Original Issue Price Authorized Issued and Outstanding Carrying Value Aggregate Liquidation Preference Series A $ 1.00 6,037,500 6,037,500 $ 1,751 $ 6,038 Series B $ 0.50 40,000,000 36,000,000 18,825 18,000 Series C $ 0.4979 80,337,411 35,147,617 16,420 17,500 Total redeemable convertible preferred stock 126,374,911 77,185,117 $ 36,996 $ 41,538

Common Stock (Tables)

Common Stock (Tables)	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Schedule of Common Stock Reserved for Issuance	The Company had reserved shares of common stock for issuance, on an as-converted basis, as follows: September 30, 2016 December 31, 2015 Redeemable convertible preferred stock outstanding — 5,323,103 Options issued and outstanding 1,496,156 833,178 Options available for future grants 1,069,828 147,219 Redeemable convertible preferred stock warrants — 275,861 Total 2,565,984 6,579,361

Stock Option Plans (Tables)

Stock Option Plans (Tables)	9 Months Ended
	Sep. 30, 2016
Schedule of Activity under Stock Option Plan	Activity under the Company’s stock option plan is set forth below: Options Outstanding Options Available for Grant Options Outstanding Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Life (years) Aggregate Intrinsic Value (in thousands) Balances at December 31, 2015 147,219 833,178 $ 1.33 8.56 Additional options authorized 1,697,088 — Options granted (774,479 ) 774,479 5.55 Options exercised — (111,501 ) 1.28 Balances at September 30, 2016 1,069,828 1,496,156 3.52 8.65 $ 26,347 Options exercisable – September 30, 2016 338,784 1.97 7.26 $ 6,490 Options vested and expected to vest – September 30, 2016 1,481,620 3.51 8.64 $ 26,100
Schedule of Stock-based Compensation Expense for Employees and Non-employees for Stock Options and the 2016 ESPP	Total stock-based compensation expense recognized for both employees and non-employees for stock options and the 2016 ESPP was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Research and development $ 285 $ 8 $ 360 $ 24 General and administrative 163 14 250 38 Total stock-based compensation expense $ 448 $ 22 $ 610 $ 62
Employee and Director [Member]
Schedule of Grant-date Fair Value of Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions	The fair value of employee and director stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Expected term (in years) 4.16 - 5.70 — 4.16 - 5.94 5.89 Expected volatility 62.8 % — 62.5% - 64.8 % 59.8 % Risk-free interest rate 1.28 % — 1.27% - 1.38 % 1.57 % Dividend yield — — — —
Non-employees [Member]
Schedule of Grant-date Fair Value of Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions	The fair value of the stock options granted is calculated at each reporting date using the Black-Scholes option-pricing model with the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Expected term (in years) 5.70 - 7.04 — 5.70 - 9.93 — Expected volatility 62.8 % — 62.5% - 62.8 % — Risk-free interest rate 1.29 % — 1.29% - 1.36 % — Dividend yield — — — —

Net Loss per Share Attributab27

Net Loss per Share Attributable to Common Stockholders (Tables)	9 Months Ended
	Sep. 30, 2016
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Net Loss per Share Attributable to Common Stockholders	The following table sets forth the computation of the basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Numerator: Net loss $ (7,084 ) $ (3,449 ) $ (25,929 ) $ (9,365 ) Accretion of redeemable convertible preferred stock (293 ) (36 ) (558 ) (36 ) Net loss attributable to common stockholders $ (7,377 ) $ (3,485 ) $ (26,487 ) $ (9,401 ) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 8,483,189 272,409 3,071,456 245,298 Net loss per share attributable to common stockholders, basic and diluted $ (0.87 ) $ (12.79 ) $ (8.62 ) $ (38.32 )
Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share	The following outstanding shares of potentially dilutive securities have been excluded from diluted net loss per share calculations for the three and nine months ended September 30, 2016 and 2015, because their inclusion would be anti-dilutive: Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Redeemable convertible preferred stock on an as-converted basis — 5,323,103 — 5,323,103 Options to purchase common stock 1,496,156 468,546 1,496,156 468,546 Warrants to purchase redeemable convertible preferred stock on an as-converted basis — 275,861 — 275,861 Total 1,496,156 6,067,510 1,496,156 6,067,510

Organization and Description 28

Organization and Description of Business - Additional Information (Detail) $ / shares in Units, $ in Thousands	Sep. 30, 2016USD ($)$ / sharesshares	Aug. 16, 2016$ / sharesshares	Jul. 31, 2016	Sep. 30, 2016USD ($)$ / sharesshares	Aug. 17, 2016shares	Dec. 31, 2015shares
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Reverse stock split description				In July 2016, the Company's board of directors approved an amendment to the Company's amended and restated certificate of incorporation to effect a reverse split of the Company's issued and outstanding common stock at a 1-for-14.5 ratio, which was effected on August 1, 2016.
Reverse stock split effective date				Aug. 1, 2016
Reverse stock split ratio			0.06896
Proceeds from stock issuance, net of underwriting discounts, commissions | $				$ 84,508
Number of shares converted					8,577,571
Preferred stock outstanding	0			0		0
Initial Public Offering [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Proceeds from stock issuance, net of underwriting discounts, commissions | $	$ 83,600
Common stock issued	252,972	7,500,000
Common stock price per share | $ / shares	$ 12	$ 12		$ 12
Redeemable Convertible Preferred Stock [Member] | Initial Public Offering [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of shares converted		8,577,571
Preferred stock outstanding		0

Summary of Significant Accoun29

Summary of Significant Accounting Policies - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2016AUD
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Research and development tax incentives	AUD 20,000,000
Tax incentive rate related to research and development	50.00%
Minimum [Member] | Australia [Member]
Summary Of Significant Accounting Policy [Line Items]
Tax incentive rate related to research and development	50.00%

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Assets and Liabilities Measured at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 97,621	$ 10,004
Total financial liabilities		2,123
Redeemable Convertible Preferred Stock Tranche Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities		1,643
Redeemable Convertible Preferred Stock Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities		480
Corporate Bonds Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	600	7,368
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	95,122	2,136
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	1,899	500
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	95,122	2,136
Level 1 [Member] | Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	95,122	2,136
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	2,499	7,868
Level 2 [Member] | Corporate Bonds Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	600	7,368
Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 1,899	500
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities		2,123
Level 3 [Member] | Redeemable Convertible Preferred Stock Tranche Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities		1,643
Level 3 [Member] | Redeemable Convertible Preferred Stock Warrant Liability [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial liabilities		$ 480

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Company's Level 3 Financial Instruments (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Fair Value Liabilities Measured On Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, beginning balance				$ 2,123,000
Change in fair value upon revaluation				(4,194,000)	$ (233,000)
Change in fair value upon revaluation		$ 0	$ 805,000	(525,000)	$ 659,000
Settlement of redeemable convertible preferred stock tranche liability due to the issuance of Series C redeemable convertible preferred stock	$ (5,800,000)			(5,837,000)
Reclassification of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock				(1,005,000)
Redeemable Convertible Preferred Stock Tranche Liability [Member]
Fair Value Liabilities Measured On Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, beginning balance				1,643,000
Redeemable Convertible Preferred Stock Warrant Liability [Member]
Fair Value Liabilities Measured On Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, beginning balance				480,000
Reclassification of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock				(1,000,000)
Level 3 [Member]
Fair Value Liabilities Measured On Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, beginning balance				2,123,000
Level 3 [Member] | Redeemable Convertible Preferred Stock Tranche Liability [Member]
Fair Value Liabilities Measured On Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, beginning balance				1,643,000
Change in fair value upon revaluation				4,194,000
Settlement of redeemable convertible preferred stock tranche liability due to the issuance of Series C redeemable convertible preferred stock				(5,837,000)
Level 3 [Member] | Redeemable Convertible Preferred Stock Warrant Liability [Member]
Fair Value Liabilities Measured On Recurring and Nonrecurring Basis [Line Items]
Financial liabilities, beginning balance				480,000
Change in fair value upon revaluation				525,000
Reclassification of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock				$ (1,005,000)

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Cash Equivalents and Available-for-sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	$ 97,621	$ 10,009
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	0	0
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses		(5)
Total cash equivalents and available-for-sale securities, Fair Value	97,621	10,004
Cash equivalents	95,122	2,136
Available-for-sale securities	2,499	7,868
Corporate Bonds Member]
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	600	7,373
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	0	0
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses		(5)
Total cash equivalents and available-for-sale securities, Fair Value	600	7,368
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	95,122	2,136
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	0	0
Total cash equivalents and available-for-sale securities, Fair Value	95,122	2,136
Commercial Paper [Member]
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	1,899	500
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	0	0
Total cash equivalents and available-for-sale securities, Fair Value	$ 1,899	$ 500

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Realized gains or losses on available-for-sale securities	$ 0	$ 0
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale securities contractual maturity	1 year	1 year

Balance Sheet Components - Su34

Balance Sheet Components - Summary of Accrued Expenses and Other Payables (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued clinical and research related expenses	$ 1,630	$ 976
Accrued employee related expenses	1,074	754
Other	310	149
Total accrued expenses and other payables	$ 3,014	$ 1,879

Research Collaboration and Li35

Research Collaboration and License Agreement - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development costs incurred under the agreement	$ 5,561,000	$ 3,158,000	$ 16,882,000	$ 7,638,000
Research Collaboration and License Agreement [Member] | PTG-300 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment based on agreement	250,000		250,000
Potential milestone payment on collaboration arrangement	250,000		250,000
Research and development costs incurred under the agreement	$ 0	$ 0	250,000	$ 0
Maximum [Member] | Research Collaboration and License Agreement [Member] | PTG-300 [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate milestone payment			$ 128,500,000

Government Programs - Additiona

Government Programs - Additional Information (Detail)

1 Months Ended

3 Months Ended

9 Months Ended

Jul. 31, 2016USD ($)

Sep. 30, 2015USD ($)

Sep. 30, 2016USD ($)

Sep. 30, 2016AUD

Mar. 31, 2016USD ($)

Mar. 31, 2016AUD

Sep. 30, 2015USD ($)

Sep. 30, 2015AUD

Sep. 30, 2016USD ($)

Sep. 30, 2016AUD

Sep. 30, 2015USD ($)

Sep. 30, 2015AUD

Sep. 30, 2016AUD

Dec. 31, 2015USD ($)

Dec. 31, 2015AUD

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Research and development tax incentive receivable

$ 1,944,000

$ 1,944,000

$ 715,000

SBIR Grant [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Reduction of research and development expenses related to tax

66,000

$ 0

135,000

$ 0

Research and development grants

$ 219,000

$ 224,000

Grants receivable

$ 155,000

65,000

155,000

65,000

155,000

Overseas Findings [Member] | Australian Taxation Office [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Research and development tax incentive receivable

1,900,000

1,900,000

AUD 2,500,000

$ 715,000

AUD 978,000

Deferred tax incentive

$ 182,000

AUD 237,000

Research and Development Tax Incentive [Member] | Australian Taxation Office [Member]

Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]

Reduction of research and development expenses related to tax

$ 145,000

AUD 181,000

$ 127,000

AUD 194,000

$ 1,200,000

AUD 1,600,000

$ 337,000

AUD 464,000

Lease Agreement - Additional In

Lease Agreement - Additional Information (Detail)	Apr. 30, 2016USD ($)
Lease Agreements [Member] | Milpitas [Member]
Leases [Line Items]
Additional lease payments	$ 80,000

Preferred Stock Warrants - Addi

Preferred Stock Warrants - Additional Information (Detail)	1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Jul. 31, 2016IPO	Apr. 30, 2016USD ($)shares	Aug. 31, 2013$ / sharesshares	Sep. 30, 2016USD ($)shares	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)shares	Sep. 30, 2015USD ($)	Dec. 31, 2015USD ($)shares	May 31, 2016shares	Mar. 31, 2016shares
Class of Warrant or Right [Line Items]
Redeemable convertible preferred stock, shares issued | shares				0		0		77,185,117
Redeemable convertible preferred stock, shares outstanding | shares				0		0		77,185,117
Proceeds from issuance of redeemable convertible preferred stock upon exercise of warrants | $						$ 22,508,000	$ 17,362,000
Remeasured fair value of warrants | $		$ 1,000,000
Reclassification of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock | $						1,005,000
Change in fair value of redeemable convertible preferred stock warrant liability | $				$ 0	$ (805,000)	525,000	$ (659,000)
Redeemable Convertible Preferred Stock Warrant Liability [Member]
Class of Warrant or Right [Line Items]
Reclassification of redeemable convertible preferred stock warrant liability to redeemable convertible preferred stock | $						$ 1,000,000
Option Pricing Model [Member]
Class of Warrant or Right [Line Items]
Percentage of weighted value per share		67.00%
PWERM [Member]
Class of Warrant or Right [Line Items]
Percentage of weighted value per share		33.00%
Fair value assumptions probabilities, number of IPO scenarios | IPO	3
First Tranche Warrants [Member]
Class of Warrant or Right [Line Items]
Number of convertible preferred stock issued upon exercise of stock warrants | shares			2,000,000
Second Tranche Warrants [Member]
Class of Warrant or Right [Line Items]
Warrants issued date						Aug. 15, 2014
Preferred Stock Warrant Liability [Member]
Class of Warrant or Right [Line Items]
Warrants outstanding, fair value | $								$ 480,000
Risk-free interest rate		0.73%						0.90%
Expected life		2 years						1 year 7 months 6 days
Expected volatility		52.00%						57.00%
First Tranche Warrants [Member]
Class of Warrant or Right [Line Items]
Probability of exercisability percentage								95.00%
Second Tranche Warrants [Member]
Class of Warrant or Right [Line Items]
Probability of exercisability percentage								0.00%
Series B Redeemable Convertible Preferred Stock [Member]
Class of Warrant or Right [Line Items]
Number of convertible preferred stock issued upon exercise of stock warrants | shares			4,000,000
Warrants exercise price | $ / shares			$ 0.01
Percentage of warrants exercisable upon new product announcement			50.00%
Redeemable convertible preferred stock, shares issued | shares		1,999,998
Redeemable convertible preferred stock, shares outstanding | shares										2,000,000
Proceeds from issuance of redeemable convertible preferred stock upon exercise of warrants | $		$ 20,000
Number of redeemable convertible preferred stock expired unexercised | shares									2,000,000

Redeemable Convertible Prefer39

Redeemable Convertible Preferred Stock - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Aug. 17, 2016	Mar. 31, 2016	Dec. 31, 2015
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued		0		0				77,185,117
Proceeds from issuance of redeemable convertible preferred stock upon exercise of warrants				$ 22,508,000	$ 17,362,000
Shares issued upon conversion of preferred stock						8,577,571
Redeemable convertible preferred stock, shares outstanding		0		0				77,185,117
Redeemable convertible preferred stock, period accretion		$ 293,000	$ 36,000	$ 558,000	$ 36,000
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued	1,999,998
Proceeds from issuance of redeemable convertible preferred stock upon exercise of warrants	$ 20,000
Redeemable convertible preferred stock, shares outstanding							2,000,000

Redeemable Convertible Prefer40

Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Jul. 31, 2015
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized	0	126,374,911
Convertible preferred stock, shares issued and outstanding		77,185,117
Convertible preferred stock, carrying value		$ 36,996
Convertible preferred stock, aggregate liquidation preference		$ 41,538
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price		$ 1
Convertible preferred stock, shares authorized		6,037,500
Convertible preferred stock, shares issued and outstanding		6,037,500
Convertible preferred stock, carrying value		$ 1,751
Convertible preferred stock, aggregate liquidation preference		$ 6,038
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price		$ 0.5000
Convertible preferred stock, shares authorized		40,000,000
Convertible preferred stock, shares issued and outstanding		36,000,000
Convertible preferred stock, carrying value		$ 18,825
Convertible preferred stock, aggregate liquidation preference		$ 18,000
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price		$ 0.4979	$ 0.4979
Convertible preferred stock, shares authorized		80,337,411
Convertible preferred stock, shares issued and outstanding		35,147,617
Convertible preferred stock, carrying value		$ 16,420
Convertible preferred stock, aggregate liquidation preference		$ 17,500

Redeemable Convertible Prefer41

Redeemable Convertible Preferred Stock Tranche Liability - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jul. 10, 2015	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Jul. 31, 2015
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued			0	0		77,185,117
Redeemable convertible preferred stock, proceeds				$ 22,508	$ 17,362
Fair value of redeemable convertible preferred stock liability reclassified		$ 5,800		5,837
Change in fair value of redeemable convertible preferred stock tranche liabilities				4,194	$ 233
Second Tranche Warrants [Member]
Temporary Equity [Line Items]
Probability of exercisability percentage						0.00%
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued		45,189,794
Redeemable convertible preferred stock, price per share						$ 0.4979	$ 0.4979
Redeemable convertible preferred stock, proceeds	$ 17,500	$ 22,500
Fair value of redeemable convertible preferred stock liability	$ 1,000	$ 5,800				$ 1,600
Probability of exercisability percentage	90.00%					95.00%
Fair value assumptions, expected term	1 year	2 years				6 months 11 days
Fair value assumptions, risk-free interest rate	0.50%	0.73%				0.90%
Fair value assumptions, expected volatility		52.00%
Change in fair value of redeemable convertible preferred stock tranche liabilities			$ 0	$ 4,200
Series C Redeemable Convertible Preferred Stock [Member] | Second Tranche Warrants [Member]
Temporary Equity [Line Items]
Additional shares to be issued upon the achievement of certain development milestones	45,189,794
Series C Redeemable Convertible Preferred Stock [Member] | Option Pricing Model [Member]
Temporary Equity [Line Items]
Fair value assumptions, weighted volatility rate		67.00%
Series C Redeemable Convertible Preferred Stock [Member] | PWERM [Member]
Temporary Equity [Line Items]
Fair value assumptions, weighted volatility rate		33.00%
Maximum [Member] | Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued	35,147,617						80,337,411

Common Stock - Schedule of Comm

Common Stock - Schedule of Common Stock Reserved for Issuance (Detail) - shares	Sep. 30, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Total	2,565,984	6,579,361
Redeemable Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Total		5,323,103
Options Issued and Outstanding [Member]
Class of Stock [Line Items]
Total	1,496,156	833,178
Redeemable Convertible Preferred Stock Warrant Liability [Member]
Class of Stock [Line Items]
Total		275,861
Options Available for Future Grants [Member]
Class of Stock [Line Items]
Total	1,069,828	147,219

Stock Option Plans - Additional

Stock Option Plans - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance		2,565,984		2,565,984		6,579,361
Options available for grant, options granted			0
Options, weighted-average grant-date fair value		$ 6.09		$ 3.16	$ 1.04
Stock-based compensation expense		$ 448,000	$ 22,000	$ 610,000	$ 62,000
Total unrecognized stock-based compensation costs related to stock options		$ 2,800,000		$ 2,800,000
Period of unrecognized stock-based compensation costs to be recognized				3 years
2016 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	1,200,000	1,200,000		1,200,000
Vesting percentage of requisite service period	25.00%
Additional vesting years	3 years
2016 Equity Incentive Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Exercise price as a percentage of the fair market value of common stock on grant date	100.00%
2016 Equity Incentive Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price as a percentage of the fair market value for option holding more than 10% total combined voting power	110.00%
Minimum percentage of voting right to grant stock option	10.00%
2016 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	150,000
Percentage of discount from fair market value of common stock on offering date	85.00%
Maximum percentage of outstanding stock issuance	1.00%
Maximum number of outstanding stock issuance	300,000
Maximum period for additional outstanding stock issuance	10 years
2016 Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum percentage of payroll deductions on eligible compensation	15.00%
Non-employee Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted		7,752	0	25,647	0
Stock-based compensation expense		$ 226,000	$ 4,000	$ 264,000	$ 14,000

Stock Option Plans - Schedule o

Stock Option Plans - Schedule of Activity under Stock Option Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Available for Grant, Options granted	0
2007 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Available for Grant, Beginning balance		147,219
Options Available for Grant, Additional options authorized		1,697,088
Options Available for Grant, Options granted		(774,479)
Options Available for Grant, Options exercised		0
Options Available for Grant, Ending balance		1,069,828	147,219
Number of Options Outstanding, Beginning balance		833,178
Number of Options Outstanding, Options granted		774,479
Number of Options Outstanding, Options exercised		(111,501)
Number of Options Outstanding, Ending balance		1,496,156	833,178
Number of Options Outstanding, Options exercisable		338,784
Number of Options Outstanding, Options vested and expected to vest		1,481,620
Weighted-Average Exercise Price Per Share, Beginning balance		$ 1.33
Weighted-Average Exercise Price Per Share, Options granted		5.55
Weighted-Average Exercise Price Per Share, Options exercised		1.28
Weighted-Average Exercise Price Per Share, Ending balance		3.52	$ 1.33
Weighted-Average Exercise Price Per Share, Options exercisable		1.97
Weighted-Average Exercise Price Per Share, Options vested and expected to vest		$ 3.51
Weighted-Average Remaining Contractual Life (years)		8 years 7 months 24 days	8 years 6 months 22 days
Weighted-Average Remaining Contractual Life (years), Options exercisable		7 years 3 months 4 days
Weighted-Average Remaining Contractual Life (years), Options vested and expected to vest		8 years 7 months 21 days
Aggregate Intrinsic Value, Options Outstanding		$ 26,347
Aggregate Intrinsic Value, Options exercisable		6,490
Aggregate Intrinsic Value, Options vested and expected to vest		$ 26,100

Stock Option Plans - Schedule45

Stock Option Plans - Schedule of Grant-date Fair Value of Employee and Director Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)				5 years 10 months 21 days
Expected volatility	62.80%			59.80%
Expected volatility, Minimum			62.50%
Expected volatility, Maximum			64.80%
Risk-free interest rate	1.28%			1.57%
Risk-free interest rate, Minimum			1.27%
Risk-free interest rate, Maximum			1.38%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	4 years 1 month 28 days		4 years 1 month 28 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 8 months 12 days		5 years 11 months 9 days

Stock Option Plans - Schedule46

Stock Option Plans - Schedule of Grant-date Fair Value of Non-employees Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)				5 years 10 months 21 days
Expected volatility	62.80%			59.80%
Expected volatility, Minimum			62.50%
Expected volatility, Maximum			64.80%
Risk-free interest rate	1.28%			1.57%
Risk-free interest rate, Minimum			1.27%
Risk-free interest rate, Maximum			1.38%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	4 years 1 month 28 days		4 years 1 month 28 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 8 months 12 days		5 years 11 months 9 days
Non-employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	62.80%
Expected volatility, Minimum			62.50%
Expected volatility, Maximum			62.80%
Risk-free interest rate	1.29%
Risk-free interest rate, Minimum			1.29%
Risk-free interest rate, Maximum			1.36%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Non-employees [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 8 months 12 days		5 years 8 months 12 days
Non-employees [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	7 years 15 days		9 years 11 months 5 days

Stock Option Plans - Schedule47

Stock Option Plans - Schedule of Stock-based Compensation Expense for Employees and Non-employees for Stock Options and the 2016 ESPP (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 448	$ 22	$ 610	$ 62
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	285	8	360	24
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 163	$ 14	$ 250	$ 38

Net Loss per Share Attributab48

Net Loss per Share Attributable to Common Stockholders - Schedule of Basic and Diluted Net Loss per Share Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net loss	$ (7,084)	$ (3,449)	$ (25,929)	$ (9,365)
Accretion of redeemable convertible preferred stock	(293)	(36)	(558)	(36)
Net loss attributable to common stockholders	$ (7,377)	$ (3,485)	$ (26,487)	$ (9,401)
Denominator:
Weighted-average shares used to compute net loss per common share, basic and diluted	8,483,189	272,409	3,071,456	245,298
Net loss per share attributable to common stockholders, basic and diluted	$ (0.87)	$ (12.79)	$ (8.62)	$ (38.32)

Net Loss per Share Attributab49

Net Loss per Share Attributable to Common Stockholders - Schedule of Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share	1,496,156	6,067,510	1,496,156	6,067,510
Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share		5,323,103		5,323,103
Warrants to Purchase Redeemable Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share		275,861		275,861
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share	1,496,156	468,546	1,496,156	468,546

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail)	1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 31, 2016USD ($)	Oct. 31, 2016AUD	Mar. 31, 2016USD ($)	Mar. 31, 2016AUD	Sep. 30, 2016AUD
Maximum [Member]
Subsequent Event [Line Items]
Research and development tax incentives | AUD					AUD 20,000,000
Tax incentive rate related to research and development					50.00%
Australian Taxation Office [Member] | Subsequent Event [Member] | Maximum [Member]
Subsequent Event [Line Items]
Tax incentive rate related to research and development	50.00%	50.00%
Australian Taxation Office [Member] | Overseas Findings [Member]
Subsequent Event [Line Items]
Deferred tax incentive			$ 182,000	AUD 237,000
Australian Taxation Office [Member] | Overseas Findings [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Research and development tax incentives	$ 2,200,000	AUD 3,000,000
Reduction of research and development expenses related to tax	700,000
Deferred tax incentive	$ 1,500,000