Protagonist Therapeutics (PTGX) 10-Q 15 Sep 16 2016 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Aug. 31, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q2
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		16,461,481

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 13,768,000	$ 4,055,000
Restricted cash	10,000	10,000
Available-for-sale securities	6,408,000	7,868,000
Research and development tax incentive receivable	1,744,000	715,000
Prepaid expenses and other current assets	487,000	1,558,000
Total current assets	22,417,000	14,206,000
Property and equipment, net	599,000	609,000
Deferred offering costs	1,466,000	0
Other assets	34,000	30,000
Total assets	24,516,000	14,845,000
Current liabilities:
Accounts payable	1,441,000	1,247,000
Accrued expenses and other payables	2,669,000	1,879,000
Total current liabilities	4,110,000	3,126,000
Redeemable convertible preferred stock tranche liability		1,643,000
Redeemable convertible preferred stock warrant liability		480,000
Total liabilities	4,110,000	5,249,000
Commitments and contingencies
Redeemable convertible preferred stock	66,610,000	36,996,000
Stockholders' deficit:
Common stock, $0.00001 par value, 160,000,000 shares authorized; 383,910 and 272,409 shares issued and outstanding as of June 30, 2016 (unaudited) and December 31, 2015, respectively	0	0
Additional paid-in capital	158,000	118,000
Accumulated other comprehensive loss	(101,000)	(102,000)
Accumulated deficit	(46,261,000)	(27,416,000)
Total stockholders' deficit	(46,204,000)	(27,400,000)
Total liabilities, redeemable convertible preferred stock and stockholders' deficit	$ 24,516,000	$ 14,845,000

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 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	126,374,911	126,374,911
Redeemable convertible preferred stock, shares issued	124,374,909	77,185,117
Redeemable convertible preferred stock, shares outstanding	124,374,909	77,185,117
Redeemable convertible preferred stock, redemption value	$ 65,038	$ 41,538
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	383,910	272,409
Common stock, shares outstanding	383,910	272,409

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating expenses:
Research and development	$ 5,696	$ 2,297	$ 11,321	$ 4,480
General and administrative	1,395	786	2,810	1,292
Total operating expenses	7,091	3,083	14,131	5,772
Loss from operations	(7,091)	(3,083)	(14,131)	(5,772)
Interest income	27		39	1
Change in fair value of redeemable convertible preferred stock tranche and warrant liabilities		(136)	(4,719)	(145)
Other expense	(34)		(34)
Net loss	(7,098)	(3,219)	(18,845)	(5,916)
Net loss attributable to common stockholders	$ (7,323)	$ (3,219)	$ (19,110)	$ (5,916)
Net loss per share attributable to common stockholders, basic and diluted	$ (19.07)	$ (13.78)	$ (56.90)	$ (25.55)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted	383,910	233,531	335,855	231,518

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (7,098)	$ (3,219)	$ (18,845)	$ (5,916)
Other comprehensive loss:
Loss on translation of foreign operations,	(4)	(26)	(2)	(42)
Unrecognized gain (loss) on available-for-sale securities	(1)		4
Comprehensive loss	$ (7,103)	$ (3,245)	$ (18,843)	$ (5,958)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($)	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (18,845,000)	$ (5,916,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	159,000	111,000
Loss on disposal of property and equipment	34,000
Amortization of premium on available-for-sale securities	72,000
Stock-based compensation	162,000	40,000
Change in fair value associated with redeemable convertible preferred stock tranche liability	4,194,000
Change in fair value of redeemable convertible preferred stock warrant liability	525,000	145,000
Changes in operating assets and liabilities:
Research and development tax credit receivable	(1,030,000)	(173,000)
Prepaid expenses and other current assets	1,134,000	(70,000)
Other assets	(4,000)
Accounts payable	85,000	160,000
Accrued expenses and other payables	202,000	(174,000)
Net cash used in operating activities	(13,312,000)	(5,877,000)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of property and equipment	(279,000)	(66,000)
Purchase of available-for-sale securities	(6,396,000)
Proceeds from maturities of available-for-sale securities	7,788,000
Net cash provided by (used in) investing activities	1,113,000	(66,000)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of redeemable convertible preferred stock, net of issuance costs	22,508,000
Proceeds from issuance of common stock upon exercise of stock options	143,000	57,000
Payments of deferred offering costs	(770,000)
Net cash provided by financing activities	21,881,000	57,000
Effect on exchange rate changes on cash and cash equivalents	31,000	(39,000)
Net increase (decrease) in cash and cash equivalents	9,713,000	(5,925,000)
Cash and cash equivalents, beginning of period	4,055,000	9,324,000
Cash and cash equivalents, end of period	13,768,000	$ 3,399,000
SUPPLEMENTAL DISCLOSURES OF NON-CASH FINANCING INFORMATION:
Settlement of fair value of redeemable convertible preferred stock liability	5,837,000
Accretion of redeemable convertible preferred stock	265,000
Deferred offering costs in accounts payable and accrued liabilities	696,000
Reclassification of preferred stock warrant liability to equity	$ 1,005,000

Organization and Description of

Organization and Description of Business	6 Months Ended
	Jun. 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 11, 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 No. 333-212476) 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. The Company received $83.7 million, net of underwriting discounts and commissions, but before deducting offering costs. 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 and received proceeds of $2.8 million, net of underwriting discounts and commissions.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 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 six months ended June 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 and assumptions 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 primarily 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. Deferred Offering Costs Deferred offering costs, which include legal, accounting, printer and filing fees, related to the IPO are capitalized. The deferred offering costs will be offset against proceeds from the IPO, to be recorded in the quarter ended September 30, 2016. As of June 30, 2016, $1.5 million of deferred offering costs were capitalized on the accompanying condensed consolidated balance sheet. There were no such costs capitalized as of December 31, 2015. 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 liabilities 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 Incentive Grant The Company is eligible under the AusIndustry research and tax 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 incentive grant. 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 issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses (Topic 326)

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 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). June 30, 2016 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 12,032 $ — $ — $ 12,032 Corporate bonds — 3,318 — 3,318 Commercial paper — 3,693 — 3,693 Total financial assets $ 12,032 $ 7,011 $ — $ 19,043 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 estimates the fair value of this liability using a one-step binomial lattice model in combination with Option Pricing Model. The change in fair value is 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 issue of Series C redeemable convertible preferred shares (5,837 ) Balance at June 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 June 30, 2016 $ —

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 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): June 30, 2016 Amortized Cost Gross Unrealized Gains Losses Fair Value Money market funds $ 12,032 $ — $ — $ 12,032 Corporate bonds 3,319 — (1 ) 3,318 Commercial paper 3,693 — — 3,693 Total cash equivalents and available-for-sale securities $ 19,044 $ — $ (1 ) $ 19,043 Classified as: Cash equivalents $ 12,635 Available-for-sale securities 6,408 Total cash equivalents and available-for-sale securities $ 19,043 December 31, 2015 Amortized 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 June 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 liabilities and other payables consisted of the following (in thousands): June 30, December 31, Accrued contract research $ 980 $ 976 Accrued employee related expenses 695 754 Accrued professional services fees 735 64 Accrued expenses and other payables 259 85 Total accrued liabilities $ 2,669 $ 1,879

Research Collaboration and Lice

Research Collaboration and License Agreement	6 Months Ended
	Jun. 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 six months ended June 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 six months ended June 30, 2015.

Government Grants

Government Grants	6 Months Ended
	Jun. 30, 2016
Text Block [Abstract]
Government Grants	6. Government Grants Research and Development Tax Incentive The Company recognized AUD 666,000 ($498,000) and AUD 1.4 million ($1.0 million), and AUD 143,000 ($110,000) and AUD 270,000 ($210,000) as a reduction of research and development expenses for the three and six months ended June 30, 2016 and 2015, respectively, in connection with the Research and Development Tax Incentive from Australia. As of June 30, 2016 and December 31, 2015, the research and development tax credit receivable was AUD 2.4 million ($1.7 million) and AUD 978,000 ($715,000), respectively. In March 2016, the Company received AUD 237,000 ($176,000) for overseas findings and recorded the funds as deferred revenue 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 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 Company recognizes contra research and development when expenses related to the grant have been incurred and the grant funds become contractually due from NIH. The total grant award was $224,000 and is for the period from September 2015 to August 2016. The Company recorded zero and $69,000 as a reduction of research and development expenses for the three and six months ended June 30, 2016. There was no such reduction recorded for the three and six months ended June 30, 2015. The Company recorded a receivable for $224,000 and $155,000 as of June 30, 2016 and December 31, 2015, respectively, to reflect the eligible costs incurred under the grant 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	6 Months Ended
	Jun. 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	6 Months Ended
	Jun. 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 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 charges of zero, $525,000, $136,000 and $145,000 for the three and six months ended June 30, 2016 and 2015, respectively, representing the change 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	6 Months Ended
	Jun. 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. The table below provides information on the Company’s redeemable convertible preferred stock as of June 30, 2016 (in thousands, except shares and original issue price): Shares Original Authorized Issued and Outstanding Carrying Aggregate Series A $ 1.00 6,037,500 6,037,500 $ 1,751 $ 6,038 Series B $ 0.50 40,000,000 37,999,998 19,850 19,000 Series C $ 0.4979 80,337,411 80,337,411 45,009 40,000 Total redeemable convertible preferred stock 126,374,911 124,374,909 $ 66,610 $ 65,038 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 Authorized Issued and Outstanding Carrying Aggregate 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 $225,000 and $265,000 for the accretion of the redeemable convertible preferred stock during the three and six months ended June 30, 2016, respectively. There was no accretion recorded for the three and six months ended June 30, 2015. The accretion was recorded as an offset to the additional paid-in capital.

Redeemable Convertible Prefer16

Redeemable Convertible Preferred Stock Tranche Liability	6 Months Ended
	Jun. 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 six months ended June 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	6 Months Ended
	Jun. 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: June 30, December 31, Redeemable convertible preferred stock outstanding 8,577,571 5,323,103 Options issued and outstanding 1,309,845 833,178 Options available for future grants 109,030 147,219 Redeemable convertible preferred stock warrants — 275,861 Total 9,996,446 6,579,361

Stock Option Plan

Stock Option Plan	6 Months Ended
	Jun. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock Option Plan	12. Stock Option Plan As of June 30, 2016, the Company has reserved 1,578,365 shares of common stock for issuance under the 2007 Stock Option Plan. Activity under the Company’s stock option plan is set forth below: Options Outstanding Options Options Weighted- Weighted- Aggregate (in thousands) Balances at December 31, 2015 147,219 833,178 $ 1.33 8.56 Additional options authorized 549,977 — Options granted (588,166 ) 588,166 3.89 Options exercised — (111,499 ) 1.28 Balances at June 30, 2016 109,030 1,309,845 2.48 8.73 $ 4,728 Options exercisable – June 30, 2016 233,785 1.56 6.84 $ 1,058 Options vested and expected to vest – June 30, 2016 1,295,163 2.48 8.73 $ 4,681 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, as determined by the Company’s Board of Directors, as of June 30, 2016. During the six months ended June 30, 2016 and 2015, the estimated weighted-average grant-date fair value of common stock underlying options granted was $2.27 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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Expected term (in years) 5.88 — 5.88 - 5.94 5.89 Expected volatility 62.5 % — 62.5% - 64.8 % 59.8 % Risk-free interest rate 1.38 % — 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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Expected term (in years) 6.83 — 6.83 — Expected volatility 62.5 % — 62.5 % — Risk-free interest rate 1.19 % — 1.19 % — Dividend yield — — — — During the three and six months ended June 30, 2016, the Company granted 17,894 shares, to non-employee consultants. No shares were granted to non-employee consultants during the three and six months ended June 30, 2015. The Company recorded stock-based compensation expense during the three and six months ended June 30, 2016 and 2015 of $18,000, $38,000, $4,000 and $9,000, respectively. Stock-Based Compensation Total stock-based compensation expense recognized for both employees and non-employee was as follows (in thousands): Three Months June 30, Six Months June 30, 2016 2015 2016 2015 Research and development $ 46 $ 8 $ 75 $ 16 General and administrative 60 13 87 24 Total stock-based compensation expense $ 106 $ 21 $ 162 $ 40 As of June 30, 2016 there was $1.6 million of total unrecognized stock-based compensation costs that the Company expects to recognize over a period of approximately 3.6 years.

Net Loss per Share Attributable

Net Loss per Share Attributable to Common Stockholders	6 Months Ended
	Jun. 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 six months ended June 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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Numerator: Net loss $ (7,098 ) $ (3,219 ) $ (18,845 ) $ (5,916 ) Accretion of redeemable convertible preferred stock (225 ) — (265 ) — Net loss attributable to common stockholders $ (7,323 ) $ (3,219 ) $ (19,110 ) $ (5,916 ) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 383,910 233,531 335,855 231,518 Net loss per share attributable to common stockholders, basic and diluted $ (19.07 ) $ (13.78 ) $ (56.90 ) $ (25.55 ) The following outstanding shares of potentially dilutive securities have been excluded from diluted net loss per share calculations for the three and six months ended June 30, 2016 and 2015, because their inclusion would be anti-dilutive: Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Redeemable convertible preferred stock on an as-converted basis 8,577,571 2,899,134 8,577,571 2,899,134 Options to purchase common stock 1,309,841 468,546 1,309,841 468,546 Warrants to purchase redeemable convertible preferred stock on an as-converted basis — 275,861 — 275,861 Total 9,887,412 3,643,541 9,887,412 3,643,541

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events In July 2016, the Company was awarded a Phase 1 SBIR Grant for $219,000 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. In July 2016, the Company’s board of directors and stockholders approved the 2016 Equity Incentive Plan (the “2016 Plan”). 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. In July 2016, the Company’s board of directors and stockholders approved the 2016 Employee Stock Purchase Plan (the “2016 ESPP”). 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. On August 1, 2016, the Company effected a 1-for-14.5 reverse split of its common stock. Upon the effectiveness of the reverse stock split, (i) every 14.5 shares of outstanding common stock was combined into 1 share of common stock, (ii) the number of shares of common stock for which each outstanding option or warrant to purchase common stock is exercisable was proportionally decreased on a 1-for-14.5 basis, (iii) the exercise price of each outstanding option to purchase common stock was proportionately increased on a 1-for-14.5 basis, and (iv) the conversion ratio for each share of preferred stock which was convertible into the Company’s common stock was proportionately reduced on a 1-for-14.5 basis. All of the outstanding common stock share numbers, warrants to purchase common stock, common stock share prices, common stock exercise prices and per share amounts have been adjusted, on a retroactive basis, to reflect this 1-for-14.5 reverse stock split for all periods presented. The par value per share, authorized number of shares of common stock, preferred stock and preferred stock warrants were not adjusted as a result of the reverse stock split. On August 10, 2016, the Company’s registration statements on Form S-1 (File Nos. 333-212476 and 333-213071) relating to the IPO 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. The Company received $83.7 million, net of underwriting discounts and commissions, but before deducting offering costs paid by the Company. 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 and received proceeds of $2.8 million, net of underwriting discounts and commissions.

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 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 six months ended June 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 and assumptions 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 primarily 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.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, which include legal, accounting, printer and filing fees, related to the IPO are capitalized. The deferred offering costs will be offset against proceeds from the IPO, to be recorded in the quarter ended September 30, 2016. As of June 30, 2016, $1.5 million of deferred offering costs were capitalized on the accompanying condensed consolidated balance sheet. There were no such costs capitalized as of December 31, 2015.
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 liabilities 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 Incentive Grant	Research and Development Incentive Grant The Company is eligible under the AusIndustry research and tax 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 incentive grant. 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 issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses (Topic 326)
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 estimates the fair value of this liability using a one-step binomial lattice model in combination with Option Pricing Model. The change in fair value is 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)	6 Months Ended
	Jun. 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). June 30, 2016 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 12,032 $ — $ — $ 12,032 Corporate bonds — 3,318 — 3,318 Commercial paper — 3,693 — 3,693 Total financial assets $ 12,032 $ 7,011 $ — $ 19,043 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 issue of Series C redeemable convertible preferred shares (5,837 ) Balance at June 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 June 30, 2016 $ —

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 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): June 30, 2016 Amortized Cost Gross Unrealized Gains Losses Fair Value Money market funds $ 12,032 $ — $ — $ 12,032 Corporate bonds 3,319 — (1 ) 3,318 Commercial paper 3,693 — — 3,693 Total cash equivalents and available-for-sale securities $ 19,044 $ — $ (1 ) $ 19,043 Classified as: Cash equivalents $ 12,635 Available-for-sale securities 6,408 Total cash equivalents and available-for-sale securities $ 19,043 December 31, 2015 Amortized 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 Liabilities and Other Payables	Accrued liabilities and other payables consisted of the following (in thousands): June 30, December 31, Accrued contract research $ 980 $ 976 Accrued employee related expenses 695 754 Accrued professional services fees 735 64 Accrued expenses and other payables 259 85 Total accrued liabilities $ 2,669 $ 1,879

Redeemable Convertible Prefer24

Redeemable Convertible Preferred Stock (Tables)	6 Months Ended
	Jun. 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 June 30, 2016 (in thousands, except shares and original issue price): Shares Original Authorized Issued and Outstanding Carrying Aggregate Series A $ 1.00 6,037,500 6,037,500 $ 1,751 $ 6,038 Series B $ 0.50 40,000,000 37,999,998 19,850 19,000 Series C $ 0.4979 80,337,411 80,337,411 45,009 40,000 Total redeemable convertible preferred stock 126,374,911 124,374,909 $ 66,610 $ 65,038 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 Authorized Issued and Outstanding Carrying Aggregate 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)	6 Months Ended
	Jun. 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: June 30, December 31, Redeemable convertible preferred stock outstanding 8,577,571 5,323,103 Options issued and outstanding 1,309,845 833,178 Options available for future grants 109,030 147,219 Redeemable convertible preferred stock warrants — 275,861 Total 9,996,446 6,579,361

Stock Option Plan (Tables)

Stock Option Plan (Tables)	6 Months Ended
	Jun. 30, 2016
Schedule of Activity under Stock Option Plan	Activity under the Company’s stock option plan is set forth below: Options Outstanding Options Options Weighted- Weighted- Aggregate (in thousands) Balances at December 31, 2015 147,219 833,178 $ 1.33 8.56 Additional options authorized 549,977 — Options granted (588,166 ) 588,166 3.89 Options exercised — (111,499 ) 1.28 Balances at June 30, 2016 109,030 1,309,845 2.48 8.73 $ 4,728 Options exercisable – June 30, 2016 233,785 1.56 6.84 $ 1,058 Options vested and expected to vest – June 30, 2016 1,295,163 2.48 8.73 $ 4,681
Schedule of Stock-based Compensation Expense for Employees and Non-employee	Total stock-based compensation expense recognized for both employees and non-employee was as follows (in thousands): Three Months June 30, Six Months June 30, 2016 2015 2016 2015 Research and development $ 46 $ 8 $ 75 $ 16 General and administrative 60 13 87 24 Total stock-based compensation expense $ 106 $ 21 $ 162 $ 40
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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Expected term (in years) 5.88 — 5.88 - 5.94 5.89 Expected volatility 62.5 % — 62.5% - 64.8 % 59.8 % Risk-free interest rate 1.38 % — 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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Expected term (in years) 6.83 — 6.83 — Expected volatility 62.5 % — 62.5 % — Risk-free interest rate 1.19 % — 1.19 % — Dividend yield — — — —

Net Loss per Share Attributab27

Net Loss per Share Attributable to Common Stockholders (Tables)	6 Months Ended
	Jun. 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 June 30, Six Months Ended June 30, 2016 2015 2016 2015 Numerator: Net loss $ (7,098 ) $ (3,219 ) $ (18,845 ) $ (5,916 ) Accretion of redeemable convertible preferred stock (225 ) — (265 ) — Net loss attributable to common stockholders $ (7,323 ) $ (3,219 ) $ (19,110 ) $ (5,916 ) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 383,910 233,531 335,855 231,518 Net loss per share attributable to common stockholders, basic and diluted $ (19.07 ) $ (13.78 ) $ (56.90 ) $ (25.55 )
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 six months ended June 30, 2016 and 2015, because their inclusion would be anti-dilutive: Three Months Ended June 30, Six Months Ended June 30, 2016 2015 2016 2015 Redeemable convertible preferred stock on an as-converted basis 8,577,571 2,899,134 8,577,571 2,899,134 Options to purchase common stock 1,309,841 468,546 1,309,841 468,546 Warrants to purchase redeemable convertible preferred stock on an as-converted basis — 275,861 — 275,861 Total 9,887,412 3,643,541 9,887,412 3,643,541

Organization and Description 28

Organization and Description of Business - Additional Information (Detail) $ / shares in Units, $ in Millions	Sep. 30, 2016USD ($)$ / sharesshares	Aug. 16, 2016USD ($)$ / sharesshares	Aug. 01, 2016	Jul. 31, 2016	Jun. 30, 2016
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 11, 2016.
Reverse stock split effective date					Aug. 11, 2016
Subsequent Event [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Reverse stock split ratio			0.06896	0.06896
Subsequent Event [Member] | Initial Public Offering [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Proceeds from stock issuance, net of underwriting discounts, commissions | $	$ 2.8	$ 83.7
Common stock issued	252,972	7,500,000
Common stock price per share | $ / shares	$ 12	$ 12
Subsequent Event [Member] | 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)	6 Months Ended
	Jun. 30, 2016AUD	Jun. 30, 2016USD ($)	Dec. 31, 2015USD ($)
Summary Of Significant Accounting Policy [Line Items]
Deferred offering costs | $		$ 1,466,000	$ 0
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Research and development tax incentives | AUD	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	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 19,043	$ 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	3,318	7,368
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	12,032	2,136
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	3,693	500
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	12,032	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	12,032	2,136
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	7,011	7,868
Level 2 [Member] | Corporate Bonds Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	3,318	7,368
Level 2 [Member] | Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 3,693	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		6 Months Ended
	Mar. 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 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)
Change in fair value upon revaluation		$ 0	$ (136,000)	(525,000)	$ (145,000)
Settlement of redeemable convertible preferred stock tranche liability due to issue of Series C redeemable convertible preferred shares	$ (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				(1,005,000)
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 issue of Series C redeemable convertible preferred shares				(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	Jun. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	$ 19,044	$ 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	(1)	(5)
Total cash equivalents and available-for-sale securities, Fair Value	19,043	10,004
Cash equivalents	12,635	2,136
Available-for-sale securities	6,408	7,868
Corporate Bonds Member]
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	3,319	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	(1)	(5)
Total cash equivalents and available-for-sale securities, Fair Value	3,318	7,368
Money Market Funds [Member]
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	12,032	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	12,032	2,136
Commercial Paper [Member]
Cash and Cash Equivalents [Line Items]
Total cash equivalents and available-for-sale securities, Amortized Cost	3,693	500
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	0	0
Total cash equivalents and available-for-sale securities, Fair Value	$ 3,693	$ 500

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 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 Liabilities and Other Payables (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued contract research	$ 980	$ 976
Accrued employee related expenses	695	754
Accrued professional services fees	735	64
Accrued expenses and other payables	259	85
Total accrued liabilities	$ 2,669	$ 1,879

Research Collaboration and Li35

Research Collaboration and License Agreement - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development costs incurred under the agreement	$ 5,696,000	$ 2,297,000	$ 11,321,000	$ 4,480,000
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 Grants - Additional

Government Grants - Additional Information (Detail)

3 Months Ended

6 Months Ended

12 Months Ended

Jun. 30, 2016USD ($)

Jun. 30, 2016AUD

Mar. 31, 2016USD ($)

Mar. 31, 2016AUD

Jun. 30, 2015USD ($)

Jun. 30, 2015AUD

Jun. 30, 2016USD ($)

Jun. 30, 2016AUD

Jun. 30, 2015USD ($)

Jun. 30, 2015AUD

Aug. 31, 2016USD ($)

Jun. 30, 2016AUD

Dec. 31, 2015USD ($)

Dec. 31, 2015AUD

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

Research and development tax incentive receivable

$ 1,744,000

$ 1,744,000

$ 715,000

SBIR Grant [Member]

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

Reduction of research and development expenses related to tax

0

$ 0

69,000

$ 0

Grants receivable

224,000

224,000

155,000

Subsequent Event [Member] | SBIR Grant [Member]

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

Reduction of research and development expenses related to tax

$ 224,000

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

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

Reduction of research and development expenses related to tax

$ 176,000

AUD 237,000

Research and development tax incentive receivable

1,700,000

1,700,000

AUD 2,400,000

$ 715,000

AUD 978,000

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

$ 498,000

AUD 666,000

$ 110,000

AUD 143,000

$ 1,000,000

AUD 1,400,000

$ 210,000

AUD 270,000

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		6 Months Ended		12 Months Ended
	Jul. 31, 2016IPO	Apr. 30, 2016USD ($)shares	Aug. 31, 2013$ / sharesshares	Jun. 30, 2016USD ($)shares	Jun. 30, 2015USD ($)	Jun. 30, 2016USD ($)shares	Jun. 30, 2015USD ($)	Dec. 31, 2015USD ($)shares	May 31, 2016shares	Mar. 31, 2016shares
Class of Warrant or Right [Line Items]
Redeemable convertible preferred stock, shares issued | shares				124,374,909		124,374,909		77,185,117
Redeemable convertible preferred stock, shares outstanding | shares				124,374,909		124,374,909		77,185,117
Proceeds from issuance of redeemable convertible preferred stock upon exercise of warrants | $						$ 22,508,000
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	$ 136,000	525,000	$ 145,000
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 | $						$ 1,005,000
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%
Subsequent Event [Member] | PWERM [Member]
Class of Warrant or Right [Line Items]
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		6 Months Ended
	Apr. 30, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued		124,374,909		124,374,909		77,185,117
Proceeds from issuance of redeemable convertible preferred stock upon exercise of warrants				$ 22,508,000
Redeemable convertible preferred stock, period accretion		$ 225,000	$ 0	$ 265,000	$ 0
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 Prefer40

Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jul. 31, 2015
Temporary Equity [Line Items]
Convertible preferred stock, shares authorized	126,374,911	126,374,911
Convertible preferred stock, shares issued and outstanding	124,374,909	77,185,117
Convertible preferred stock, carrying value	$ 66,610	$ 36,996
Convertible preferred stock, aggregate liquidation preference	$ 65,038	$ 41,538
Series A Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price	$ 1	$ 1
Convertible preferred stock, shares authorized	6,037,500	6,037,500
Convertible preferred stock, shares issued and outstanding	6,037,500	6,037,500
Convertible preferred stock, carrying value	$ 1,751	$ 1,751
Convertible preferred stock, aggregate liquidation preference	$ 6,038	$ 6,038
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price	$ 0.5000	$ 0.5000
Convertible preferred stock, shares authorized	40,000,000	40,000,000
Convertible preferred stock, shares issued and outstanding	37,999,998	36,000,000
Convertible preferred stock, carrying value	$ 19,850	$ 18,825
Convertible preferred stock, aggregate liquidation preference	$ 19,000	$ 18,000
Series C Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Convertible preferred stock, original issue price	$ 0.4979	$ 0.4979	$ 0.4979
Convertible preferred stock, shares authorized	80,337,411	80,337,411
Convertible preferred stock, shares issued and outstanding	80,337,411	35,147,617
Convertible preferred stock, carrying value	$ 45,009	$ 16,420
Convertible preferred stock, aggregate liquidation preference	$ 40,000	$ 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	Jun. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Jul. 31, 2015
Temporary Equity [Line Items]
Redeemable convertible preferred stock, shares issued			124,374,909	124,374,909	77,185,117
Redeemable convertible preferred stock, proceeds				$ 22,508
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
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	$ 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	Jun. 30, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Total	9,996,446	6,579,361
Redeemable Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Total	8,577,571	5,323,103
Options Issued and Outstanding [Member]
Class of Stock [Line Items]
Total	1,309,845	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	109,030	147,219

Stock Option Plan - Additional

Stock Option Plan - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	9,996,446		9,996,446		6,579,361
Options, weighted-average grant-date fair value			$ 2.27	$ 1.04
Stock-based compensation expense	$ 106,000	$ 21,000	$ 162,000	$ 40,000
Total unrecognized stock-based compensation costs	$ 1,600,000		$ 1,600,000
Period of unrecognized stock-based compensation costs to be recognized			3 years 7 months 6 days
2007 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance	1,578,365		1,578,365
Options granted			588,166
Non-employee Consultants [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted	17,894	0	17,894	0
Stock-based compensation expense	$ 18,000	$ 4,000	$ 38,000	$ 9,000

Stock Option Plan - Schedule of

Stock Option Plan - Schedule of Activity under Stock Option Plan (Detail) - 2007 Stock Option Plan [Member] $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016USD ($)$ / sharesshares	Dec. 31, 2015$ / sharesshares
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	549,977
Options Available for Grant, Options granted	(588,166)
Options Available for Grant, Options exercised	0
Options Available for Grant, Ending balance	109,030	147,219
Number of Options Outstanding, Beginning balance	833,178
Number of Options Outstanding, Options granted	588,166
Number of Options Outstanding, Options exercised	(111,499)
Number of Options Outstanding, Ending balance	1,309,845	833,178
Number of Options Outstanding, Options exercisable	233,785
Number of Options Outstanding, Options vested and expected to vest	1,295,163
Weighted-Average Exercise Price Per Share, Beginning balance | $ / shares	$ 1.33
Weighted-Average Exercise Price Per Share, Options granted | $ / shares	3.89
Weighted-Average Exercise Price Per Share, Options exercised | $ / shares	1.28
Weighted-Average Exercise Price Per Share, Ending balance | $ / shares	2.48	$ 1.33
Weighted-Average Exercise Price Per Share, Options exercisable | $ / shares	1.56
Weighted-Average Exercise Price Per Share, Options vested and expected to vest | $ / shares	$ 2.48
Weighted-Average Remaining Contractual Life (years)	8 years 8 months 23 days	8 years 6 months 22 days
Weighted-Average Remaining Contractual Life (years), Options exercisable	6 years 10 months 2 days
Weighted-Average Remaining Contractual Life (years), Options vested and expected to vest	8 years 8 months 23 days
Aggregate Intrinsic Value, Options Outstanding | $	$ 4,728
Aggregate Intrinsic Value, Options exercisable | $	1,058
Aggregate Intrinsic Value, Options vested and expected to vest | $	$ 4,681

Stock Option Plan - Schedule 45

Stock Option Plan - Schedule of Grant-date Fair Value of Employee and Director Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 10 months 17 days			5 years 10 months 21 days
Expected volatility	62.50%			59.80%
Expected volatility, Minimum			62.50%
Expected volatility, Maximum			64.80%
Risk-free interest rate	1.38%			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)			5 years 10 months 17 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)			5 years 11 months 9 days

Stock Option Plan - Schedule 46

Stock Option Plan - Schedule of Grant-date Fair Value of Non-employees Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	5 years 10 months 17 days			5 years 10 months 21 days
Expected volatility	62.50%			59.80%
Risk-free interest rate	1.38%			1.57%
Dividend yield	0.00%	0.00%	0.00%	0.00%
Non-employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 9 months 29 days		6 years 9 months 29 days
Expected volatility	62.50%		62.50%
Risk-free interest rate	1.19%		1.19%
Dividend yield	0.00%	0.00%	0.00%	0.00%

Stock Option Plan - Schedule 47

Stock Option Plan - Schedule of Stock-based Compensation Expense for Employees and Non-employee (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 106	$ 21	$ 162	$ 40
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	46	8	75	16
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 60	$ 13	$ 87	$ 24

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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Numerator:
Net loss	$ (7,098)	$ (3,219)	$ (18,845)	$ (5,916)
Accretion of redeemable convertible preferred stock	(225)		(265)
Net loss attributable to common stockholders	$ (7,323)	$ (3,219)	$ (19,110)	$ (5,916)
Denominator:
Weighted-average shares used to compute net loss per common share, basic and diluted	383,910	233,531	335,855	231,518
Net loss per share attributable to common stockholders, basic and diluted	$ (19.07)	$ (13.78)	$ (56.90)	$ (25.55)

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		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Dilutive securities excluded from computation of net loss per share	9,887,412	3,643,541	9,887,412	3,643,541
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	8,577,571	2,899,134	8,577,571	2,899,134
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	1,309,841	468,546	1,309,841	468,546

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail)	Sep. 30, 2016USD ($)$ / sharesshares	Aug. 16, 2016USD ($)$ / sharesshares	Aug. 01, 2016	Jul. 31, 2016USD ($)shares	Jun. 30, 2016shares	Dec. 31, 2015shares
Subsequent Event [Line Items]
Common stock reserved for issuance					9,996,446	6,579,361
Subsequent Event [Member]
Subsequent Event [Line Items]
Reverse stock split ratio			0.06896	0.06896
Subsequent Event [Member] | Initial Public Offering [Member]
Subsequent Event [Line Items]
Common stock issued	252,972	7,500,000
Common stock price per share | $ / shares	$ 12	$ 12
Proceeds from stock issuance, net of underwriting discounts, commissions | $	$ 2,800,000	$ 83,700,000
Subsequent Event [Member] | Over-Allotment Option [Member]
Subsequent Event [Line Items]
Common stock issued	252,972
Common stock price per share | $ / shares	$ 12
Proceeds from stock issuance, net of underwriting discounts, commissions | $	$ 2,800,000
Subsequent Event [Member] | 2016 Equity Incentive Plan [Member]
Subsequent Event [Line Items]
Common stock reserved for issuance				1,200,000
Subsequent Event [Member] | 2016 Employee Stock Purchase Plan [Member]
Subsequent Event [Line Items]
Common stock reserved for issuance				150,000
Subsequent Event [Member] | National Institutes of Heart and Lung Diseases [Member]
Subsequent Event [Line Items]
Reduction of research and development expenses related to tax | $				$ 219,000