Protagonist Therapeutics (PTGX) 10-Q 6 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Document And Entity Information
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Registrant Name	PROTAGONIST THERAPEUTICS, INC.
Entity Central Index Key	0001377121
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		27,206,447

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 50,195	$ 82,233
Restricted cash - current	10	10
Available-for-sale securities	87,497	46,620
Receivable from collaboration partner and contract asset - related party	1,945	4,587
Research and development tax incentive receivable, net	173	1,429
Prepaid expenses and other current assets	4,203	2,624
Total current assets	144,023	137,503
Property and equipment, net	1,734	861
Restricted cash - noncurrent	450	450
Operating lease right-of-use asset	6,295
Deferred tax asset	2,125	658
Total assets	154,627	139,472
Current liabilities:
Accounts payable	1,583	5,711
Payable to collaboration partner - related party	1,020	1,061
Accrued expenses and other payables	10,486	11,163
Operating lease liability - current	1,209
Deferred revenue - related party	16,478	8,223
Total current liabilities	30,776	26,158
Deferred revenue - related party - noncurrent	22,200
Operating lease liability - noncurrent	6,293
Deferred rent		799
Total liabilities	59,269	26,957
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.00001 par value, 10,000,000 shares authorized; no shares issued and outstanding
Common stock, $0.00001 par value, 90,000,000 shares authorized; 27,206,447 and 23,187,219 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively
Additional paid-in capital	295,672	253,222
Accumulated other comprehensive loss	(154)	(233)
Accumulated deficit	(200,160)	(140,474)
Total stockholders’ equity	95,358	112,515
Total liabilities and stockholders’ equity	$ 154,627	$ 139,472

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Condensed Consolidated Balance Sheets
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	90,000,000	90,000,000
Common stock, shares issued	27,206,447	23,187,219
Common stock, shares outstanding	27,206,447	23,187,219

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Consolidated Statements of Operations
License and collaboration revenue - related party	$ 4,141	$ 6,117	$ (2,488)	$ 28,572
Operating expenses:
Research and development	17,293	12,145	49,092	45,249
General and administrative	4,015	3,361	11,642	10,180
Total operating expenses	21,308	15,506	60,734	55,429
Loss from operations	(17,167)	(9,389)	(63,222)	(26,857)
Interest income and other, net	656	654	1,989	1,798
Loss before income tax benefit	(16,511)	(8,735)	(61,233)	(25,059)
Income tax benefit	102	0	1,547	0
Net loss	$ (16,409)	$ (8,735)	$ (59,686)	$ (25,059)
Net loss per share, basic and diluted	$ (0.61)	$ (0.38)	$ (2.36)	$ (1.15)
Weighted-average shares used to compute net loss per share, basic and diluted	26,956,957	22,912,279	25,315,512	21,750,562

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Consolidated Statements of Comprehensive Loss
Net loss	$ (16,409)	$ (8,735)	$ (59,686)	$ (25,059)
Other comprehensive loss:
Gain (loss) on translation of foreign operations	10	(63)	6	(149)
Unrealized gain on available-for-sale securities	3	46	73	52
Comprehensive loss	$ (16,396)	$ (8,752)	$ (59,607)	$ (25,156)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Total
Balance, Beginning at Dec. 31, 2017		$ 222,188	$ (6)	$ (101,550)	$ 120,632
Balance, Beginning (in shares) at Dec. 31, 2017	21,088,306
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense		4,847			4,847
Issuance of common stock upon private placement, net of issuance costs		21,679			21,679
Issuance of common stock upon private placement net of issuance costs(in shares)	2,750,000
Common stock issued pursuant to at-the-market offering, net of issuance costs		1,025			1,025
Common stock issued pursuant to at-the-market offering, net of issuance costs (in shares)	103,500
Common stock issued under equity incentive and employee stock purchase plans		931			931
Common stock issued under equity incentive and employee stock purchase plans (in shares)	196,296
Other comprehensive gain (loss)			(97)		(97)
Net loss				(25,059)	(25,059)
Balance, Ending at Sep. 30, 2018		250,670	(103)	(126,609)	123,958
Balance, Ending (in shares) at Sep. 30, 2018	24,138,102
Balance, Beginning at Jun. 30, 2018		225,622	(86)	(117,874)	107,662
Balance, Beginning (in shares) at Jun. 30, 2018	21,217,494
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense		2,017			2,017
Issuance of common stock upon private placement, net of issuance costs		21,679			21,679
Issuance of common stock upon private placement net of issuance costs(in shares)	2,750,000
Common stock issued pursuant to at-the-market offering, net of issuance costs		1,025			1,025
Common stock issued pursuant to at-the-market offering, net of issuance costs (in shares)	103,500
Common stock issued under equity incentive and employee stock purchase plans		327			327
Common stock issued under equity incentive and employee stock purchase plans (in shares)	67,108
Other comprehensive gain (loss)			(17)		(17)
Net loss				(8,735)	(8,735)
Balance, Ending at Sep. 30, 2018		250,670	(103)	(126,609)	123,958
Balance, Ending (in shares) at Sep. 30, 2018	24,138,102
Balance, Beginning at Dec. 31, 2018		253,222	(233)	(140,474)	$ 112,515
Balance, Beginning (in shares) at Dec. 31, 2018	23,187,219				23,187,219
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense		6,193			$ 6,193
Common stock issued pursuant to at-the-market offering, net of issuance costs		34,492			34,492
Common stock issued pursuant to at-the-market offering, net of issuance costs (in shares)	2,846,641
Common stock issued pursuant to exercise of Exchange Warrants (in shares)	599,997
Common stock issued under equity incentive and employee stock purchase plans		1,765			1,765
Common stock issued under equity incentive and employee stock purchase plans (in shares)	572,590
Other comprehensive gain (loss)			79		79
Net loss				(59,686)	(59,686)
Balance, Ending at Sep. 30, 2019		295,672	(154)	(200,160)	$ 95,358
Balance, Ending (in shares) at Sep. 30, 2019	27,206,447				27,206,447
Balance, Beginning at Jun. 30, 2019		268,234	(167)	(183,751)	$ 84,316
Balance, Beginning (in shares) at Jun. 30, 2019	24,967,603
Increase (Decrease) in Stockholders' Equity (Deficit)
Stock-based compensation expense		2,201			2,201
Common stock issued pursuant to at-the-market offering, net of issuance costs		23,949			23,949
Common stock issued pursuant to at-the-market offering, net of issuance costs (in shares)	1,924,957
Common stock issued under equity incentive and employee stock purchase plans		1,288			1,288
Common stock issued under equity incentive and employee stock purchase plans (in shares)	313,887
Other comprehensive gain (loss)			13		13
Net loss				(16,409)	(16,409)
Balance, Ending at Sep. 30, 2019		$ 295,672	$ (154)	$ (200,160)	$ 95,358
Balance, Ending (in shares) at Sep. 30, 2019	27,206,447				27,206,447

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net loss	$ (59,686)	$ (25,059)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	6,193	4,847
Operating lease right-of-use asset amortization	1,347
Change in deferred tax asset	(1,548)
Depreciation and amortization	501	399
Net (accretion of discount) amortization of premium on available-for-sale securities	(397)	304
Changes in operating assets and liabilities:
Research and development tax incentive receivable, net	1,237	96
Receivable from collaboration partner - related party	2,642	(2,770)
Prepaid expenses and other assets	(1,586)	526
Accounts payable	(4,165)	3,617
Payable to collaboration partner - related party	(41)	764
Accrued expenses and other payables	(781)	1,246
Operating lease liability	(1,409)
Deferred revenue - related party	30,455	(23,782)
Net cash used in operating activities	(27,238)	(39,812)
CASH FLOWS FROM INVESTING ACTIVITIES
Purchase of available-for-sale securities	(117,807)	(51,947)
Proceeds from maturities of available-for-sale securities	77,400	50,035
Purchases of property and equipment, net	(749)	(424)
Net cash used in investing activities	(41,156)	(2,336)
CASH FLOWS FROM FINANCING ACTIVITIES
Proceeds from issuance of common stock and warrants in private placement, net of issuance costs		21,679
Proceeds from at-the-market offering, net of issuance costs	34,492	1,025
Proceeds from issuance of common stock upon exercise of stock options and purchases under employee stock purchase plan	1,765	932
Net cash provided by financing activities	36,257	23,636
Effect of exchange rate changes on cash, cash equivalents and restricted cash	99	(90)
Net decrease in cash, cash equivalents and restricted cash	(32,038)	(18,602)
Cash, cash equivalents and restricted cash, beginning of period	82,693	106,489
Cash, cash equivalents and restricted cash, end of period	50,655	$ 87,887
SUPPLEMENTAL DISCLOSURES OF NON-CASH FINANCING AND INVESTING INFORMATION:
Purchases of property and equipment in accounts payable and accrued liabilities	$ 157

Organization and Description of

Organization and Description of Business	9 Months Ended
	Sep. 30, 2019
Organization and Description of Business
Organization and Description of Business	Note 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 Newark, California. The Company is a clinical-stage biopharmaceutical company with a proprietary technology platform that enables the discovery and development of novel constrained peptide-based drug candidates that address significant unmet medical needs. Protagonist Pty Limited (“Protagonist Australia”) is a wholly-owned subsidiary of the Company and is located in Brisbane, Queensland, Australia. Protagonist Australia was incorporated in Australia in September 2001. The Company manages its operations as a single operating segment. Liquidity The Company has incurred net losses from operations since inception and has an accumulated deficit of $200.2 million as of September 30, 2019. The Company’s ultimate success depends on the outcome of its research and development and collaboration activities. The Company expects to incur additional losses in the future and anticipates the need to raise additional capital to continue to execute its long-range business plan. Through September 30, 2019, the Company has financed its operations primarily through private placements of redeemable convertible preferred stock, offerings of common stock and payments received under license and collaboration agreements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies Basis of Presentation 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 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 consolidated balance sheet as of December 31, 2018 has been derived from the Company’s 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 of normal recurring adjustments) that are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other interim period or for any other future year. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2018 included in the Company’s Annual Report on Form 10‑K, filed with the SEC on March 12, 2019. Principles of Consolidation The accompanying unaudited interim condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All intercompany transactions and balances have been eliminated upon consolidation. Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, accruals for research and development activities, stock-based compensation, income taxes, research and development tax incentives, available-for-sale securities and leases. Estimates related to revenue recognition include actual costs incurred versus total estimated budgeted costs of the Company’s deliverables to determine percentage of completion, and application and estimates of constraints in the determination of the transaction price under its license and collaboration agreements. 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 forecasted amounts and future events. Actual results may differ significantly 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 of the Company’s cash is held by two financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The primary focus of the Company’s investment strategy is to preserve capital and to meet liquidity requirements. The Company’s cash equivalents and available-for-sale securities are managed by external managers within the guidelines of the Company’s investment policy. The Company’s investment policy addresses the level of credit exposure by limiting concentration in any one corporate issuer and establishing a minimum allowable credit rating. To manage its credit risk exposure, the Company maintains its portfolio of cash equivalents and available-for-sale securities in fixed income securities denominated and payable in U.S. dollars. Permissible investments of fixed income securities include obligations of the U.S. government and its agencies, money market instruments including commercial paper and negotiable certificates of deposit, and highly rated corporate debt obligations and money market funds. Cash Equivalents Cash equivalents that are readily convertible to cash are stated at cost, which approximates fair value. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. Restricted Cash Restricted cash consists of cash balances primarily held as security in connection with a letter of credit related to the Company’s facility lease entered into in March 2017 and the Company’s corporate credit card. Cash as Reported in Condensed Consolidated Statements of Cash Flows Cash as reported in the condensed consolidated statements of cash flows includes the aggregate amounts of cash and cash equivalents and the restricted cash as presented on the condensed consolidated balance sheets. Cash as reported in the condensed consolidated statements of cash flows consists of (in thousands): September 30, 2019 2018 Cash and cash equivalents $ 50,195 $ 87,427 Restricted cash - current 10 10 Restricted cash - noncurrent 450 450 Cash balance in condensed consolidated statements of cash flows $ 50,655 $ 87,887 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 greater than three months but no longer than 365 days as of the balance sheet date. Long-term marketable securities have maturities of 365 days or longer 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. Leases The Company adopted Accounting Standards Topic 842, Leases, (“ASC 842”) effective January 1, 2019. The Company determines if an arrangement is a lease at inception. Pursuant to ASC 842, operating leases are included in operating lease right-of-use (“ROU”) assets, operating lease liabilities, and noncurrent operating lease liabilities on the condensed consolidated balance sheets. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. If the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The operating lease ROU asset also includes any lease payments made and excludes lease incentives and initial direct costs incurred. Lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. The Company records tenant improvement allowances as a reduction to the ROU asset with the impact of the decrease recognized prospectively over the remaining lease term. The leasehold improvements will be amortized over the shorter of their useful life or the remaining term of the lease. Revenue Recognition The Company follows Accounting Standards Codification Topic 606, Revenue from Contracts with Customers (“ASC 606”). Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation. The Company applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligations when (or as) the performance obligations are satisfied. The Company constrains its estimate of the transaction price up to the amount (the “variable consideration constraint”) that a significant reversal of recognized revenue is not probable. Licenses of intellectual property: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in an arrangement, the Company recognizes revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring proportional performance for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of proportional performance each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement or amendment that includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price. ASC 606 suggests two alternatives to use when estimating the amount of variable consideration: the expected value method and the most likely amount method. Under the expected value method, an entity considers the sum of probability-weighted amounts in a range of possible consideration amounts. Under the most likely amount method, an entity considers the single most likely amount in a range of possible consideration amounts. Whichever method is used, it should be consistently applied throughout the life of the contract; however, it is not necessary for the Company to use the same approach for all contracts. The Company expects to use the most likely amount method for development and regulatory milestone payments. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis. The Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability or achievement of each such milestone and any related constraint, and if necessary, adjusts its estimates of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Upfront payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. Amounts payable to the Company and not yet billed to the collaboration partner are recorded as contract assets. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less. Contractual cost sharing payments made to a customer are accounted for as a reduction to the transaction price if such payments are not related to distinct goods or services received from the customer. Contracts may be amended to account for changes in contract specifications and requirements. The period between when the Company transfers control of promised goods or services and when the Company receives payment is expected to be one year or less, and that expectation is consistent with the Company’s historical experience. Upfront payment contract liabilities resulting from the Company’s license and collaboration agreements do not represent a financing component as the payment is not financing the transfer of goods and services, and the technology underlying the licenses granted reflects research and development expenses already incurred by the Company. As such, the Company does not adjust its revenues for the effects of a significant financing component. Research and Development Costs Research and development costs are expensed as incurred, unless there is an alternate future use in other research and development projects or otherwise. Research and development costs include salaries and benefits, stock-based compensation expense, laboratory supplies and facility-related overhead, outside contracted services including clinical trial costs, manufacturing and process development costs for both clinical and pre-clinical materials, research costs, development milestone payments under license and collaboration agreements, and other consulting services. The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of pre-clinical studies and clinical trials, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated services provided but not yet invoiced and includes these costs in accrued expenses and other payables in the condensed consolidated balance sheets and within research and development expense in the condensed consolidated statements of operations. 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. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued liabilities and actual costs incurred. However, the status and timing of actual services performed, number of patients enrolled, and the rate of patient enrollment 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 Tax Incentive The Company may be eligible under the AusIndustry research and development tax incentive program to obtain a cash refund from the Australian Taxation Office. The refundable cash tax incentive is available to the Company on the basis of specific criteria with which the Company must comply. Specifically, the Company must have annual turnover of less than AUD 20.0 million and cannot be controlled by income tax exempt entities. The refundable cash research and development tax incentive is recognized as a reduction to 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. The Company may alternatively be eligible for a taxable credit in the form of a non-cash tax incentive. The Company evaluates its eligibility under tax incentive programs as of each balance sheet date and makes accrual and related adjustments based on the most current and relevant data available. Net Loss per Share Basic net loss per share is calculated by dividing the Company’s net loss by the weighted average number of shares of common stock and Exchange Warrants outstanding during the period, without consideration of potentially dilutive securities. In accordance with Accounting Standards Codification Topic 260, Earnings Per Share , the Exchange Warrants are included in the computation of basic net loss per share because the exercise price is negligible, and they are fully vested and exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share for all periods presented since the effect of potentially dilutive securities is anti-dilutive given the net loss of the Company. See Note 9. Stockholder’s Equity for additional information regarding the Exchange Warrants. Recently Adopted Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016‑02, Leases (Topic 842). In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases , which provides clarification to ASU 2016-02. These ASUs (collectively, the new lease standard) require an entity to recognize a lease liability and a ROU asset on the balance sheet for leases with lease terms of more than twelve months. Lessor accounting is largely unchanged, while lessees are no longer provided with a source of off-balance sheet financing. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842) - Targeted Improvements, which allows entities to elect an optional transition method where entities may continue to apply the existing lease guidance during the comparative periods and apply the new lease requirements through a cumulative effect adjustment in the period of adoption rather than in the earliest period presented. The Company adopted the new lease standard using the modified retrospective approach effective January 1, 2019 and elected the package of transitional practical expedients, such that, for leases existing prior to the adoption of ASC 842, the Company did not need to reassess whether contracts are leases, retained historical lease classification and historical initial direct costs classification. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases. At January 1, 2019, the Company derecognized its deferred rent liability in the amount of $0.8 million and recognized a ROU asset and related lease liability in the amount of $7.5 million and $8.3 million, respectively. In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting , which is intended to simplify the accounting for nonemployee share-based payment transactions by expanding the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company adopted this guidance prospectively as of January 1, 2019. The adoption of this guidance did not have a material impact on the Company’s financial position, results of operations or liquidity. Recently Issued Accounting Pronouncements Not Yet Adopted as of September 30, 2019 In June 2016, the FASB issued ASU No. 2016‑13, Financial Instruments - Credit Losses (Topic 326) , which is intended to provide financial statement users with more useful information about expected credit losses on financial assets held by a reporting entity at each reporting date. In May 2019, the FASB issued ASU No. 2019-05, which amended the new standard by providing targeted transition relief. The new guidance replaces the existing incurred loss impairment methodology with a methodology that requires consideration of a broader range of reasonable and supportable forward-looking information to estimate all expected credit losses. This guidance is effective for the fiscal years and interim periods within those years beginning after December 15, 2019 and early adoption is permitted for fiscal years and interim periods within those years beginning after December 15, 2018. The Company is continuing to evaluate the impact of this new guidance on its receivable from collaboration partner and available-for-sale investment securities and does not expect the new guidance to have a material impact on its consolidated financial statements and related disclosures. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement , which modifies the disclosure requirements on fair value measurements and is intended to improve the effectiveness of disclosures, including the consideration of costs and benefits. The guidance is effective for the fiscal years and interim periods within those years beginning after January 1, 2020. Early adoption is permitted, and an entity is permitted to early adopt any removed or modified disclosures and delay adoption of additional disclosures until their effective date. The Company does not expect this new guidance to impact its consolidated financial statements and is currently evaluating the impact on its disclosures. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606 , which is intended to clarify the circumstances under which certain transactions in collaborative arrangements should be accounted for under the revenue recognition standard. Certain transactions between collaboration arrangement participants should be accounted for as revenue under ASC Topic 606 when the collaborative arrangement participant is a customer in the context of a unit of account. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this new guidance on its consolidated financial statements and disclosures.

License and Collaboration Agree

License and Collaboration Agreement	9 Months Ended
	Sep. 30, 2019
License and Collaboration Agreement
License and Collaboration Agreement
License and Collaboration Agreement	Note 3. License and Collaboration Agreement Agreement Terms On May 26, 2017, the Company and Janssen Biotech, Inc., (“Janssen”), one of the Janssen Pharmaceutical Companies of Johnson & Johnson, entered into an exclusive license and collaboration agreement (the “Janssen License and Collaboration Agreement”) for the development, manufacture and commercialization of PTG‑200 worldwide for the treatment of Crohn’s disease (“CD”) and ulcerative colitis (“UC”). Janssen is a related party to the Company as Johnson & Johnson Innovation - JJDC, Inc., a significant stockholder of the Company, and Janssen are both subsidiaries of Johnson & Johnson. PTG‑200 is the Company’s oral gut-restricted Interleukin 23 receptor (“IL‑23R”) antagonist drug candidate currently in development. The Janssen License and Collaboration Agreement became effective on July 13, 2017. Upon the effectiveness of the agreement, the Company received a non-refundable, upfront cash payment of $50.0 million from Janssen. Under the Janssen License and Collaboration Agreement, the Company granted to Janssen an exclusive worldwide license to develop, manufacture and commercialize PTG‑200 and related IL‑23R compounds for all indications, including CD and UC. The Company was responsible, at its own expense, for the conduct of the Phase 1 clinical trial for PTG-200, and Janssen is responsible for the conduct of the first Phase 2 clinical trial for PTG-200 in CD, including filing the U.S. Investigational New Drug application (“IND”). Development costs for the Phase 2 clinical trial are shared between the parties on an 80/20 basis, with Janssen assuming the larger share. The Company entered into an amendment (the “First Amendment”) to the Janssen License and Collaboration Agreement effective May 7, 2019. The First Amendment builds upon the Company’s ongoing development collaboration with Janssen for PTG-200 and, upon the effectiveness of the First Amendment, the Company became eligible to receive a $25.0 million payment from Janssen, which was received during the second quarter of 2019. The First Amendment expands the scope of the Janssen License and Collaboration Agreement by supporting research efforts towards identifying and developing second-generation IL-23 receptor antagonists (“second-generation compounds”). As part of the services added in the First Amendment, Janssen will pay certain costs and milestones related to advancing pre-clinical candidates from the second-generation research program into Phase 1 studies, including funding of a certain number of full-time equivalent employees (“FTEs”) at the Company for a set period of time. The Company will pay 100% of the costs for the Phase 1 studies for the first second-generation compound, and 50% of the costs of the Phase 1 studies for the second and third second-generation compounds; thereafter Janssen will pay 100% of any further Phase 1 development costs. Development costs for the Phase 2 clinical trials for second-generation compounds are shared between the parties on an 80/20 basis, with Janssen assuming the larger share. The Company’s Phase 1 and Phase 2 development costs are also limited by overall spending caps. The Company was eligible to receive a $25.0 million milestone payment upon Janssen’s filing of the IND. This amount was considered constrained up until the First Amendment became effective, at which time the Company became eligible to receive the $25.0 million payment from Janssen. Payments to the Company for research and development services are generally billed and collected as services are performed, including research activities and Phase 1 and Phase 2 development activities. Janssen bills the Company for its 20% share of the Phase 2 development costs as expenses are incurred by Janssen. Milestone payments are received after the related milestones are achieved. Pursuant to the First Amendment, the Company will be eligible to receive clinical development, regulatory and sales milestones, if and as achieved, and/or payments relating to Janssen’s elections to maintain or expand its license rights. The next such payment is a $50.0 million payment based on Phase 2a clinical trial results, as follows: · Janssen can elect to advance PTG-200 into Phase 2b following receipt of the top line results of the CD Phase 2a clinical trial for PTG-200 by paying a $50.0 million maintenance fee (the “Amended First Opt-in Election”); or · Janssen would make a $50.0 million milestone payment following dosing of the third patient in first Phase 2b clinical trial for CD for a second-generation product (the “Second-Generation Phase 2b Milestone”). Janssen can also then elect to receive exclusive, world-wide commercial rights for both PTG-200 and second-generation products following the Phase 2b completion date for PTG-200 or a second-generation product by paying a $50.0 million payment (the “Amended Second Opt-in Election”). Formerly, the first and second opt-in payments were $125.0 million and $200.0 million, respectively. If Janssen does not make the Amended Second Opt-in Election, with respect to either PTG-200 or a second-generation compound, the Janssen License and Collaboration Agreement would terminate. The Company will also be eligible for certain additional milestone payments including a potential payment of either $100.0 million upon a Phase 3 CD clinical trial meeting a primary clinical endpoint with respect to PTG-200 or $115.0 million upon a Phase 3 CD clinical trial meeting a primary clinical endpoint with respect to a second-generation compound. Pursuant to the First Amendment, the Company will be eligible to receive tiered royalties on net product sales at percentages ranging from mid-single digits to ten. Under the terms of the First Amendment, the Company will be eligible to receive up to $1.0 billion in research, development, regulatory and sales milestones. The Janssen License and Collaboration Agreement remains in effect until the royalty obligations cease following patent and regulatory expiry, unless terminated earlier. Upon a termination of the Janssen License and Collaboration Agreement, all rights revert back to the Company, and in certain circumstances, if such termination occurs during ongoing clinical trials, Janssen would, if requested, provide certain financial and operational support to the Company for the completion of such trials. Revenue Recognition The Company has concluded that the amended Janssen License and Collaboration Agreement continues to contain a single performance obligation including the development license; second-generation compound research services; Phase 1 development services for PTG-200 and two potential second-generation compounds; the Company’s services associated with Phase 2 development for PTG-200 until Phase 2a; the Company’s services associated with Phase 2 development for a second-generation product until the dosing of the third patient in Phase 2b; and all other such services that the Company may perform at the request of Janssen to support the development of PTG-200, second-generation research services, or the development of a second-generation compound. The Company concluded that the Amended First Opt-in Election and the Amended Second Opt-in Election options are not considered to be material rights. The Company determined that the license was not distinct from the added research and development services within the context of the agreement because the added research and development services significantly increase the utility of the intellectual property. The Company also determined that the remaining research and development services are not distinct from the partially delivered combined promise comprised under the agreement prior to the First Amendment of the development license and PTG-200 services, including compound supply and other services. Therefore, the First Amendment is treated as if it were part of the original Janssen License and Collaboration Agreement. The First Amendment will be accounted for as if it were an extension of services under the initial Janssen License and Collaboration Agreement by applying a cumulative catch-up adjustment to revenue. As of the effective date of the First Amendment, the Company calculated the adjusted cumulative revenue under the amended Janssen License and Collaboration Agreement by updating the transaction price for the incremental consideration to be received, net of the incremental development cost reimbursement to be paid to Janssen, and an updated percentage complete, which resulted in a cumulative adjustment recorded during the three months ended June 30, 2019 that reduced revenue by $9.4 million. The contract duration is defined as the period in which parties to the contract have present enforceable rights and obligations. For revenue recognition purposes, the Company determined that the duration of the Janssen License and Collaboration Agreement, as amended, began on the effective date of July 13, 2017 and ends upon the later of end of Phase 2a for PTG-200 or upon dosing of the third patient in Phase 2b for a second-generation compound. The Company uses the most likely amount method to estimate variable consideration included in the transaction price. Variable consideration after the First Amendment consists of future milestone payments and cost sharing payments from Janssen for agreed upon services offset by Phase 2 development costs reimbursement payable to Janssen. Cost sharing payments from Janssen relate to the agreed upon services for Phase 2 activities that the Company performs within the duration of the contract are included in the transaction price at an amount equal to 80% of the estimated budgeted costs for these activities, including primarily internal full-time equivalent effort and third party contract costs. Cost sharing payments to Janssen relate to agreed upon services for Phase 2 activities that Janssen performs within the duration of the contract are not a distinct service that Janssen transfers to the Company. Therefore, the consideration payable to Janssen is accounted for as a reduction in the transaction price. The Company determined that the new transaction price of the Janssen License and Collaboration Agreement was $110.8 million as of September 30, 2019, an increase of $1.6 million from the transaction price of $109.2 million at June 30, 2019 and $50.2 million from the transaction price of $60.6 million at March 31, 2019. In order to determine the transaction price, the Company evaluated all payments to be received during the duration of the contract, net of Phase 2 development costs reimbursement expected to be payable to Janssen. The Company determined that the transaction price includes the $50.0 million upfront payment, the $25.0 million payment received upon the effectiveness of the First Amendment, $18.4 million of reimbursement from Janssen for services performed for PTG-200 Phase 2 and for second-generation compound research costs and other services, and $17.4 million of estimated variable consideration. The Company evaluated whether the variable component of the transaction price should be constrained to ensure that a significant reversal of revenue recognized on a cumulative basis as of September 30, 2019 is not probable. The Company concluded that the variable consideration constraint does not further decrease the estimated transaction price as of September 30, 2019. The additional potential development, regulatory and sales milestone payments after the completion of Phase 2b activities that the Company is eligible to receive are outside the contract term and as such have been excluded from the transaction price. The increase in transaction price following the First Amendment was primarily due to the collection of the $25.0 million payment and increases in reimbursable costs related to new and extended research and development services, offset by Phase 2 development costs reimbursement payable to Janssen. The Company re-evaluates the transaction price, including variable consideration, at the end of each reporting period and as uncertain events are resolved or other changes in circumstances occur. The Company and Janssen make quarterly cost sharing payments to one another in amounts necessary to ensure that each party bears its contractual share of the overall shared costs incurred. The Company utilizes a cost-based input method to measure proportional performance and to calculate the corresponding amount of revenue to recognize. In applying the cost-based input methods of revenue recognition, the Company uses actual costs incurred relative to expected costs to fulfill the combined performance obligation. These costs consist primarily of internal full-time equivalent effort and third-party contract costs. Revenue will be recognized based on actual costs incurred as a percentage of total estimated costs as the Company completes its performance obligations. A cost-based input method of revenue recognition requires management to make estimates of costs to complete the Company’s performance obligations. The Company believes this is the best measure of progress because other measures do not reflect how the Company transfers its performance obligation to Janssen. In making such estimates, significant judgment is required to evaluate assumptions related to cost estimates. The cumulative effect of revisions to estimated costs to complete the Company’s performance obligations will be recorded in the period in which changes are identified and amounts can be reasonably estimated. A significant change in these assumptions and estimates could have a material impact on the timing and amount of revenue recognized in future periods. For the three months ended September 30, 2019, the Company recognized $4.1 million of license and collaboration revenue. For the three months ended September 30, 2018, the Company recognized $6.1 million of license and collaboration revenue. For the nine months ended September 30, 2019, the Company recorded a $9.4 million cumulative catchup adjustment reducing license and collaboration revenue, partially offset by $5.3 million of license and collaboration revenue following the contract modification for the First Amendment and $1.6 million of license and collaboration revenue recognized during the first quarter of 2019 under the original Janssen License and Collaboration agreement. For the nine months ended September 30, 2018, the Company recognized $28.6 million of license and collaboration revenue. The following tables present changes in the Company’s contract assets and liabilities during the periods presented (in thousands): Balance at Balance at Beginning of End of Nine Months Ended September 30, 2019 Period Additions Deductions Period Contract assets: Receivable from collaboration partner - related party $ 2,042 $ 30,882 $ (31,905) $ 1,019 Contract asset - related party $ 2,545 $ 926 $ (2,545) $ 926 Contract liabilities: Deferred revenue - related party $ 8,223 $ 36,441 $ (5,986) $ 38,678 Payable to collaboration partner - related party $ 1,061 $ 1,226 $ (1,267) $ 1,020 Balance at Balance at Beginning of End of Nine Months Ended September 30, 2018 Period Additions Deductions Period Contract assets: Receivable from collaboration partner - related party $ 1,816 $ 6,012 $ (3,242) $ 4,586 Contract liabilities: Deferred revenue - related party $ 31,752 $ 4,147 $ (27,929) $ 7,970 Payable to collaboration partner - related party $ — $ 1,068 $ (304) $ 764 During the three and nine months ended September 30, 2019, the Company recognized revenue of $2.9 million and $4.5 million, respectively from amounts included in the deferred revenue contract liability balance at the beginning of the period. During the three and nine months ended September 30, 2018, the Company recognized revenue of $5.9 million and $27.9 million, respectively, from amounts included in the contract liability balance at the beginning of the period. None of the costs to obtain or fulfill the contract were capitalized.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Measurements
Fair Value Measurements	Note 4. 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 —Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2— Inputs (other than quoted market prices included in Level 1) are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life. Level 3 —Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. In determining fair value, the Company utilizes quoted market prices, broker or dealer quotations, or valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible and considers counterparty credit risk in its assessment of fair value. The following table presents the fair value of the Company’s financial assets determined using the inputs defined above (in thousands). September 30, 2019 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 16,381 $ — $ — $ 16,381 Corporate bonds — 28,105 — 28,105 Commercial paper — 40,865 — 40,865 Government bonds — 46,596 — 46,596 Total financial assets $ 16,381 $ $ — $ December 31, 2018 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 25,390 $ — $ — $ 25,390 Corporate bonds — 8,989 — 8,989 Commercial paper — 59,730 — 59,730 Government bonds — 33,394 — 33,394 Total financial assets $ 25,390 $ $ — $ Investments in corporate bonds, commercial paper and government bonds 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.

Balance Sheet Components

Balance Sheet Components	9 Months Ended
	Sep. 30, 2019
Balance Sheet Components
Balance Sheet Components	Note 5. Balance Sheet Components Cash Equivalents and Available-for-sale Securities Cash equivalents and available-for-sale securities consisted of the following (in thousands): September 30, 2019 Amortized Gross Unrealized Cost Gains Losses Fair Value Money market funds $ 16,381 $ — $ — $ 16,381 Corporate bonds 28,083 23 (1) 28,105 Commercial paper 40,868 — (3) 40,865 Government bonds 46,579 17 — 46,596 Total cash equivalents and available-for-sale securities $ $ 40 $ (4) $ Classified as: Cash equivalents $ 44,450 Available-for-sale securities 87,497 Total cash equivalents and available-for-sale securities $ December 31, 2018 Amortized Gross Unrealized Cost Gains Losses Fair Value Money market funds $ 25,390 $ — $ — $ 25,390 Corporate bonds 8,997 — (8) 8,989 Commercial paper 59,730 — — 59,730 Government bonds 33,423 — (29) 33,394 Total cash equivalents and available-for-sale securities $ 127,540 $ — $ (37) $ 127,503 Classified as: Cash equivalents $ 80,883 Available-for-sale securities 46,620 Total cash equivalents and available-for-sale securities $ 127,503 Available-for-sale securities - current held as of September 30, 2019 and December 31, 2018 had contractual maturities of less than one year. There were no material realized gains or realized losses on available-for-sale securities for the periods presented. The Company has not experienced any material credit losses on its investments. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2019 2018 Laboratory equipment $ 3,006 $ 2,533 Furniture and computer equipment 487 338 Leasehold improvements 800 67 Total property and equipment 4,293 2,938 Less: accumulated depreciation and amortization (2,559) (2,077) Property and equipment, net $ 1,734 $ 861 Accrued Expenses and Other Payables Accrued expenses and other payables consisted of the following (in thousands): September 30, December 31, 2019 2018 Accrued clinical and research related expenses $ 6,420 $ 7,781 Accrued employee related expenses 3,480 2,726 Accrued professional service fees 376 61 Other 210 595 Total accrued expenses and other payables $ 10,486 $ 11,163

Research Collaboration and Lice

Research Collaboration and License Agreement	9 Months Ended
	Sep. 30, 2019
Research Collaboration and License Agreement
Research Collaboration and License Agreement
Research Collaboration and License Agreement	Note 6. 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 that relates to the products arising from the collaboration. Milestone payments to collaboration partners are recorded as research and development expenses in the period that the expense is incurred. The Company did not accrue any payments due to former collaboration partners for research and development expenses during the three and nine months ended September 30, 2019 and 2018.

Government Programs

Government Programs	9 Months Ended
	Sep. 30, 2019
Government Programs
Government Programs	Note 7. Government Programs Research and Development Tax Incentive The Company recognized AUD 1.8 million ($1.2 million) of research and development expenses for the nine months ended September 30, 2019 in connection with a reversal of previously recorded reductions to research and development expenses related to the research and development tax incentive from Australia. The Company determined that it had exceeded the annual turnover limit to claim such amounts following the receipt of certain payments under the Janssen License and Collaboration Agreement. No such amounts were recorded during the three months ended September 30, 2019. The Company recognized AUD 0.4 million ($0.3 million) and AUD 1.6 million ($1.3 million) as a reduction of research and development expenses for the three and nine months ended September 30, 2018, respectively, in connection with the research and development tax incentive from Australia. As of September 30, 2019 and December 31, 2018, the research and development tax incentive receivable, net was AUD 0.3 million ($0.2 million) and AUD 2.0 million ($1.4 million), respectively. Small Business Innovation Research (“SBIR”) Grants The Company has received SBIR grants from the National Institutes of Health (“NIH”) in support of research aimed at its product candidates. The Company recognizes a reduction to research and development expenses when expenses related to the grants have been incurred and the grant funds become contractually due from NIH. The Company recorded $0.6 million and $1.1 million as a reduction of research and development expenses for the three and nine months ended September 30, 2019, respectively. The Company recorded $0.2 million and $0.4 million as a reduction of research and development expenses for the three and nine months ended September 30, 2018, respectively. The Company recorded a receivable for $0.7 million and $0.3 million as of September 30, 2019 and December 31, 2018, respectively, to reflect the eligible costs incurred under the grants that are contractually due to the Company, and such amounts are included in prepaid expenses and other current assets on the condensed consolidated balance sheets.

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases
Leases	Note 8. Leases On January 1, 2019, the Company adopted ASC 842, which requires entities to recognize assets and liabilities for leases with lease terms of more than 12 months on the balance sheet. Adoption of ASC 842 resulted in the recording of operating lease assets of $7.5 million and operating lease liabilities of $8.3 million. The impact of the changes made to the consolidated balance sheet as of January 1, 2019 as a result of adopting the new guidance was as follows (in thousands): Balance at Adjustments Balance at December 31, Due to January 1, 2018 ASC 842 2019 Balance Sheet: Operating lease right-of-use asset - noncurrent $ — 7,499 $ 7,499 Operating lease liability - current $ — 1,080 $ 1,080 Operating lease liability - noncurrent $ — 7,219 $ 7,219 Deferred rent - noncurrent $ 799 (799) $ — The Company has one operating lease agreement entered into in March 2017 for laboratory and office space located in Newark, California. The Company provided the landlord with a $450,000 letter of credit collateralized by restricted cash as security deposit for the lease, which expires in May 2024. In March 2019, the Company recorded a receivable from the landlord of $469,000 related to eligible leasehold improvements made to the leased property, which the Company received in July 2019. Leases with terms of 12 months or less are not recorded on the balance sheet, as the related lease expenses are recognized on a straight-line basis over the lease term. During the three and nine months ended September 30, 2019, the Company recognized $21,000 and $42,000 of sublease income, respectively. The weighted average lease term and discount rate are as follows: September 30, 2019 Operating Lease Term and Discount Rate: Weighted-average remaining lease term 4.7 years Weighted-average discount rate 11.0% The following table summarizes the Company’s minimum lease payments and lease liability as of September 30, 2019 (in thousands): Year Ending December 31: Amount 2019 (remaining three months) $ 477 2020 1,941 2021 2,000 2022 2,059 2023 2,121 Thereafter 895 Total future minimum lease payments 9,493 Less: imputed interest (1,991) Present value of future minimum lease payments 7,502 Less: current portion of operating lease liability (1,209) Operating lease liability - noncurrent $ 6,293 As previously disclosed in the Company’s 2018 Annual Report on Form 10-K and under the previous lease accounting standard, future minimum lease payments for operating leases having initial or remaining noncancellable lease terms in excess of one year would have been as follows (in thousands): Year Ending December 31: Amount 2019 $ 1,941 2020 2,000 2021 2,059 2022 2,121 2023 2,185 Thereafter 922 Total $ 11,228 Supplemental lease cost information is as follows (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Operating lease cost $ 444 $ 1,347 Supplemental balance sheet information is as follows (in thousands): September 30, 2019 Operating Leases: Operating lease right-of-use asset, non-current $ 6,295 Operating lease liability - current $ 1,209 Operating lease liability - noncurrent 6,293 Total operating lease liabilities $ 7,502 Supplemental cash flow information is as follows (in thousands): Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flow used by operating leases $

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2019
Stockholders' Equity
Stockholders' Equity	Note 9. Stockholders’ Equity In September 2017, the Company filed a registration statement on Form S-3 with the Securities and Exchange Commission (“SEC”) (File No. 333-220314), that was declared effective as of October 5, 2017 and permits the offering, issuance, and sale by the Company of up to a maximum aggregate offering price of $200.0 million of its common stock, preferred stock and debt securities. Up to a maximum of $50.0 million of the maximum aggregate offering price of $200.0 million may be issued and sold pursuant to an at-the-market (“ATM”) financing facility under a sales agreement (the “Sales Agreement”). The Company sold 1,924,957 and 2,846,641 shares of its common stock pursuant to the Sales Agreement during the three and nine months ended September 30, 2019, respectively, for net proceeds of $23.9 million and $34.5 million, respectively, after deducting issuance costs. The Company sold 103,500 shares of its common stock pursuant to the Sales Agreement during the three and nine months ended September 30, 2018 for net proceeds of $1.0 million, after deducting issuance costs. As of September 30, 2019, a total of $72.0 million of common stock remained available for sale under the registration statement on Form S-3, $13.0 million of which remained available for sale under the ATM financing facility. On August 6, 2018, the Company entered into a Securities Purchase Agreement with certain accredited investors (each, an “Investor” and, collectively, the “Investors”), pursuant to which the Company sold an aggregate of 2,750,000 shares of its common stock at a price of $8.00 per share, for aggregate net proceeds of $21.7 million, after deducting offering expenses payable by the Company. In a concurrent private placement, the Company issued the Investors warrants to purchase an aggregate of 2,750,000 shares of its common stock (each, a “Warrant,” and collectively, the “Warrants”). Each Warrant is exercisable from August 8, 2018 through August 8, 2023. Warrants to purchase 1,375,000 shares of the Company’s common stock have an exercise price of $10.00 per share and Warrants to purchase 1,375,000 shares of the Company’s common stock have an exercise price of $15.00 per share. The exercise price and number of shares of common stock issuable upon the exercise of the Warrants (the “Warrant Shares”) are subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Warrants. Under certain circumstances, the warrants may be exercisable on a “cashless” basis. In connection with the issuance and sale of the common stock and Warrants, the Company granted the Investors certain registration rights with respect to the Warrants and the Warrant Shares. The common stock and warrants are classified as equity in accordance with Accounting Standards Codification Topic 480 , Distinguishing Liabilities from Equity, and the net proceeds from the transaction were recorded as a credit to additional paid-in capital. As of September 30, 2019, none of the warrants have been exercised. On December 21, 2018, the Company entered into an exchange agreement (the “Exchange Agreement”) with an Investor and its affiliates (the “Exchanging Stockholders”), pursuant to which the Company exchanged an aggregate of 1,000,000 shares of the Company’s common stock, par value $0.00001 per share, owned by the Exchanging Stockholders for pre-funded warrants (the “Exchange Warrants”) to purchase an aggregate of 1,000,000 shares of common stock (subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Exchange Warrants), with an exercise price of $0.00001 per share. The Exchange Warrants will expire ten years from the date of issuance. The Exchange Warrants are exercisable at any time prior to expiration except that the Exchange Warrants cannot be exercised by the Exchanging Stockholders if, after giving effect thereto, the Exchanging Stockholders would beneficially own more than 9.99% of the Company’s common stock, subject to certain exceptions. In accordance with Accounting Standards Codification Topic 505, Equity , the Company recorded the retirement of the common stock exchanged as a reduction of common shares outstanding and a corresponding debit to additional paid-in-capital at the fair value of the Exchange Warrants on the issuance date. The Exchange Warrants are classified as equity in accordance with Accounting Standards Codification Topic 480 , Distinguishing Liabilities from Equity, and fair value of the Exchange Warrants was recorded as a credit to additional paid-in capital and is not subject to remeasurement. The Company determined that the fair value of the Exchange Warrants is substantially similar to the fair value of the retired shares on the issuance date due to the negligible exercise price for the Exchange Warrants. During the nine months ended September 30, 2019, Exchange Warrants to purchase 600,000 shares of common stock were net exercised, resulting in the issuance of 599,997 shares of common stock. As of September 30, 2019, 400,000 Exchange Warrants remained unexercised.

Equity Plans

Equity Plans	9 Months Ended
	Sep. 30, 2019
Equity Plans
Equity Plans	Note 10. Equity Plans Equity Incentive Plans In July 2016, the Company’s board of directors and stockholders approved the Company’s 2016 Equity Incentive Plan (the “2016 Plan”) to replace the 2007 Stock Option Plan. The 2016 Plan is administered by the board of directors or a committee appointed by the board of directors, which determines the types of awards to be granted, including the number of shares subject to the awards, the exercise price and the vesting schedule. Awards granted under the 2016 Plan expire no later than ten years from the date of grant. As of September 30, 2019, approximately 579,220 shares were available for issuance under the 2016 Plan. Inducement Plan In May 2018, the Company’s board of directors approved the 2018 Inducement Plan, a non-stockholder approved stock plan, under which it reserved and authorized up to 750,000 shares of the Company’s common stock in order to award options and restricted stock unit awards to persons that were not previously employees or directors of the Company, or following a bona fide period of non-employment, as an inducement material to such persons entering into employment with the Company, within the meaning of Rule 5635(c)(4) of the NASDAQ Listing Rules. The 2018 Inducement Plan is administered by the board of directors or the Compensation Committee of the board, which determines the types of awards to be granted, including the number of shares subject to the awards, the exercise price and the vesting schedule. Awards granted under the 2018 Inducement Plan expire no later than ten years from the date of grant. As of September 30, 2019, approximately 280,000 shares were available for issuance under the 2018 Inducement Plan. Stock Options Stock options generally have an exercise price equal to the fair market value of the Company’s common stock on the grant date. Employee stock options generally vest over a period of four years. Employee stock option incentive awards granted in 2018 vest in three equal installments at six-month intervals over a period of 18 months. Non-employee director initial stock options generally vest over a period of three years, and non-employee director annual refresher stock options generally vest over a period of approximately one year. Non-employee consultant options generally vest over a period of one to four years. Stock option activity under the Company’s equity incentive and inducement plans is set forth below: Weighted- Weighted- Average Average Exercise Remaining Aggregate Options Price Per Contractual Intrinsic Outstanding Share Life (years) Value (1) (in millions) Balances at December 31, 2018 3,178,441 $ 12.23 7.52 Options granted 1,265,800 9.32 Options exercised (295,853) 3.91 Options forfeited (438,757) 13.30 Balances at September 30, 2019 3,709,631 $ 11.77 8.03 $ 10.7 Options exercisable – September 30, 2019 1,870,596 $ 11.98 7.14 $ 6.6 Options vested and expected to vest – September 30, 2019 3,709,631 $ 11.77 8.03 $ 10.7 (1) The aggregate intrinsic values were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock on September 30, 2019. The calculation excludes options with an exercise price higher than the closing price of the Company’s common stock on September 30, 2019. During the nine months ended September 30, 2019, the estimated weighted-average grant-date fair value of common stock underlying options granted to employees was $5.42 per share. Stock Options Valuation Assumptions The fair value of employee stock option awards was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions: Three Months Ended Nine Months Ended September 30, September 30, 2019 2018 2019 2018 Expected term (in years) 5.00 - 6.08 5.49 - 6.08 5.00 - 6.08 5.49 - 6.08 Expected volatility 61.0 - 63.4% 61.2 - 65.1% 61.0 - 63.4% 62.0 - 66.5% Risk-free interest rate 1.42 - 1.90% 2.75 - 2.98% 1.42 - 2.58% 2.42 - 2.98% Dividend yield — — — — Restricted Stock Units A restricted stock unit is an agreement to issue shares of the Company’s common stock at the time of vesting. Restricted stock unit annual refresher awards vest in four equal installments on approximately the first, second, third and fourth anniversaries of the grant date. Restricted stock unit incentive awards granted in 2018 vest in three equal installments at six-month intervals over a period of 18 months. Restricted stock unit activity under the Company’s equity incentive plans is set forth below: Weighted Average Number of Grant Date Shares Fair Value Unvested at December 31, 2018 418,450 $ 10.45 Restricted stock units granted 160,650 8.02 Restricted grant units vested (197,703) 9.29 Restricted grant units forfeited (96,952) 9.84 Unvested at September 30, 2019 284,445 $ 10.09 Employee Stock Purchase Plan The 2016 Employee Stock Purchase Plan (“2016 ESPP”) allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation. At the end of each offering period, eligible employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock at the beginning of the offering period or at the end of each applicable purchase period. As of September 30, 2019, a total of 181,984 shares of common stock have been issued under the 2016 ESPP, and 577,993 shares were available for issuance. Stock-Based Compensation Total stock-based compensation expense was as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2019 2018 2019 2018 Research and development $ 1,137 $ 1,046 $ 3,237 $ 2,424 General and administrative 1,064 971 2,956 2,423 Total stock-based compensation expense $ 2,201 $ 2,017 $ 6,193 $ 4,847 As of September 30, 2019, total unrecognized stock-based compensation expense was approximately $14.2 million, which the Company expects to recognize over a weighted-average period of approximately 2.6 years.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Taxes
Income Taxes	Note 11. Income Taxes The Company recorded income tax benefit of $0.1 million and $1.5 million for the three and nine months ended September 30, 2019, respectively, representing an effective income tax rate of 0.6% and 2.5%, respectively. Income tax benefit for the nine months ended September 30, 2019 included a discrete tax benefit of approximately $1.1 million for the 2017 Australia refundable R&D tax offset The Company’s effective income tax rate for the three and nine months ended September 30, 2019 differs from the Company’s federal statutory rate of 21%, primarily because its U.S. loss cannot be benefited due to the full valuation allowance position and reduced by foreign taxes. No income tax expense or benefit was recorded for the three and nine months ended September 30, 2018.

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2019
Net Loss per Share
Net Loss per Share	Note 12. Net Loss per Share As the Company had net losses for the three and nine months ended September 30, 2019 and 2018, all potential common shares were determined to be anti-dilutive. The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended Nine Months Ended September 30, September 30, 2019 2018 2019 2018 Numerator: Net loss $ (16,409) $ (8,735) $ (59,686) $ (25,059) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 26,956,957 22,912,279 25,315,512 21,750,562 Net loss per shares, basic and diluted $ (0.61) $ (0.38) $ (2.36) $ (1.15) The following outstanding shares of potentially dilutive securities have been excluded from diluted net loss per share computations for the periods presented because their inclusion would be anti-dilutive: September 30, 2019 2018 Options to purchase common stock 3,709,631 3,153,479 Common stock warrants 2,750,000 2,750,000 Restricted stock units 284,445 420,650 ESPP shares 41,263 52,682 Total 6,785,339 6,376,811

Subsequent Event

Subsequent Event	9 Months Ended
	Sep. 30, 2019
Subsequent Event.
Subsequent Event	Note 13. Subsequent Events Term Loan Credit Agreement On October 30, 2019, the Company entered into a credit and security agreement (the “Term Loan Credit Agreement”) agented by MidCap Financial Trust (“MidCap”) and the collateral agent (together with MidCap, the “Lenders”), pursuant to which the Lenders, including affiliates of MidCap and Silicon Valley Bank, agreed to provide a $50.0 million term loan facility for general corporate purposes. The Term Loan Credit Agreement provides for a $10.0 million term loan funded at the closing date, with the ability to access the remaining funding in two additional tranches (of $20.0 million each), subject to specified availability periods and the satisfaction of certain conditions (collectively, the “Term Loans”). The Term Loan Credit Agreement requires the Company to maintain cash and cash equivalents of at least 35% of the outstanding Term Loans at all times and the Credit Agreement is secured by a perfected security interest in all of the Company's assets except for intellectual property and certain other customary excluded property pursuant to the terms of the Term Loan Credit Agreement. Each Term Loan under the Term Loan Credit Agreement is subject to an origination fee of 0.25% of each funding and bear interest at an annual rate based on prime rate plus 2.91%, subject to a prime rate floor of 4.94%. Commencing November 1, 2019, the Company is required to make interest-only payments on the Term Loans for 24 months. Following the end of the interest-only payments, the Term Loans will begin amortizing on November 1, 2021, with equal monthly payments of principal plus interest being made by the Company to the Lenders for 24 consecutive monthly payments. All unpaid principal and accrued interest is due and payable in full no later than October 1, 2023. At the Company’s option, the Company may prepay the outstanding principal balance of the Term Loans in whole or in part, subject to a prepayment premium of 3.0% of any amount prepaid if the prepayment occurs through and including the first anniversary of the closing date (October 30, 2020), 2.0% of the amount prepaid if the prepayment occurs after the first anniversary of the closing date through and including the second anniversary of the closing date (October 30, 2021), and 1.0% of any amount prepaid after the second anniversary of the closing date and prior to October 1, 2023. An additional 2.85% of the amount of Term Loans advanced by the Lenders will be due upon prepayment or repayment of the Term Loans. Registration Statement on Form S-3 In October 2019, the Company filed a Registration Statement on Form S-3 (File no. 333-234414) (the “Shelf Registration Statement”) covering the offering of up to $250.0 million of common stock, preferred stock, debt securities and warrants. The Company may use the Shelf Registration Statement, when effective, at any time or from time to time to offer, in one or more offerings, common stock, preferred stock, debt securities and warrants.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation 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 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 consolidated balance sheet as of December 31, 2018 has been derived from the Company’s 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 of normal recurring adjustments) that are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019 or for any other interim period or for any other future year. The accompanying condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2018 included in the Company’s Annual Report on Form 10‑K, filed with the SEC on March 12, 2019.
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 intercompany transactions and balances have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of the condensed consolidated financial statements in conformity with GAAP requires management to make estimates, assumptions and judgments that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, accruals for research and development activities, stock-based compensation, income taxes, research and development tax incentives, available-for-sale securities and leases. Estimates related to revenue recognition include actual costs incurred versus total estimated budgeted costs of the Company’s deliverables to determine percentage of completion, and application and estimates of constraints in the determination of the transaction price under its license and collaboration agreements. 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 forecasted amounts and future events. Actual results may differ significantly 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 of the Company’s cash is held by two financial institutions that management believes are of high credit quality. Such deposits may, at times, exceed federally insured limits. The primary focus of the Company’s investment strategy is to preserve capital and to meet liquidity requirements. The Company’s cash equivalents and available-for-sale securities are managed by external managers within the guidelines of the Company’s investment policy. The Company’s investment policy addresses the level of credit exposure by limiting concentration in any one corporate issuer and establishing a minimum allowable credit rating. To manage its credit risk exposure, the Company maintains its portfolio of cash equivalents and available-for-sale securities in fixed income securities denominated and payable in U.S. dollars. Permissible investments of fixed income securities include obligations of the U.S. government and its agencies, money market instruments including commercial paper and negotiable certificates of deposit, and highly rated corporate debt obligations and money market funds.
Cash Equivalents	Cash Equivalents Cash equivalents that are readily convertible to cash are stated at cost, which approximates fair value. The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents.
Restricted Cash	Restricted Cash Restricted cash consists of cash balances primarily held as security in connection with a letter of credit related to the Company’s facility lease entered into in March 2017 and the Company’s corporate credit card.
Cash as Reported in Condensed Consolidated Statements of Cash Flows	Cash as Reported in Condensed Consolidated Statements of Cash Flows Cash as reported in the condensed consolidated statements of cash flows includes the aggregate amounts of cash and cash equivalents and the restricted cash as presented on the condensed consolidated balance sheets. Cash as reported in the condensed consolidated statements of cash flows consists of (in thousands): September 30, 2019 2018 Cash and cash equivalents $ 50,195 $ 87,427 Restricted cash - current 10 10 Restricted cash - noncurrent 450 450 Cash balance in condensed consolidated statements of cash flows $ 50,655 $ 87,887
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 greater than three months but no longer than 365 days as of the balance sheet date. Long-term marketable securities have maturities of 365 days or longer 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.
Leases	Leases The Company adopted Accounting Standards Topic 842, Leases, (“ASC 842”) effective January 1, 2019. The Company determines if an arrangement is a lease at inception. Pursuant to ASC 842, operating leases are included in operating lease right-of-use (“ROU”) assets, operating lease liabilities, and noncurrent operating lease liabilities on the condensed consolidated balance sheets. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. If the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The operating lease ROU asset also includes any lease payments made and excludes lease incentives and initial direct costs incurred. Lease terms include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. The Company records tenant improvement allowances as a reduction to the ROU asset with the impact of the decrease recognized prospectively over the remaining lease term. The leasehold improvements will be amortized over the shorter of their useful life or the remaining term of the lease.
Revenue Recognition	Revenue Recognition The Company follows Accounting Standards Codification Topic 606, Revenue from Contracts with Customers (“ASC 606”). Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation. The Company applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, the Company assesses the goods or services promised within each contract, determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligations when (or as) the performance obligations are satisfied. The Company constrains its estimate of the transaction price up to the amount (the “variable consideration constraint”) that a significant reversal of recognized revenue is not probable. Licenses of intellectual property: If a license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in an arrangement, the Company recognizes revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring proportional performance for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of proportional performance each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. Milestone payments: At the inception of each arrangement or amendment that includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price. ASC 606 suggests two alternatives to use when estimating the amount of variable consideration: the expected value method and the most likely amount method. Under the expected value method, an entity considers the sum of probability-weighted amounts in a range of possible consideration amounts. Under the most likely amount method, an entity considers the single most likely amount in a range of possible consideration amounts. Whichever method is used, it should be consistently applied throughout the life of the contract; however, it is not necessary for the Company to use the same approach for all contracts. The Company expects to use the most likely amount method for development and regulatory milestone payments. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis. The Company recognizes revenue as or when the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability or achievement of each such milestone and any related constraint, and if necessary, adjusts its estimates of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. Royalties: For arrangements that include sales-based royalties, including milestone payments based on the level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). Upfront payments and fees are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. Amounts payable to the Company and not yet billed to the collaboration partner are recorded as contract assets. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less. Contractual cost sharing payments made to a customer are accounted for as a reduction to the transaction price if such payments are not related to distinct goods or services received from the customer. Contracts may be amended to account for changes in contract specifications and requirements. The period between when the Company transfers control of promised goods or services and when the Company receives payment is expected to be one year or less, and that expectation is consistent with the Company’s historical experience. Upfront payment contract liabilities resulting from the Company’s license and collaboration agreements do not represent a financing component as the payment is not financing the transfer of goods and services, and the technology underlying the licenses granted reflects research and development expenses already incurred by the Company. As such, the Company does not adjust its revenues for the effects of a significant financing component.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred, unless there is an alternate future use in other research and development projects or otherwise. Research and development costs include salaries and benefits, stock-based compensation expense, laboratory supplies and facility-related overhead, outside contracted services including clinical trial costs, manufacturing and process development costs for both clinical and pre-clinical materials, research costs, development milestone payments under license and collaboration agreements, and other consulting services. The Company accrues for estimated costs of research and development activities conducted by third-party service providers, which include the conduct of pre-clinical studies and clinical trials, and contract manufacturing activities. The Company records the estimated costs of research and development activities based upon the estimated services provided but not yet invoiced and includes these costs in accrued expenses and other payables in the condensed consolidated balance sheets and within research and development expense in the condensed consolidated statements of operations. 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. As actual costs become known, the Company adjusts its accrued liabilities. The Company has not experienced any material differences between accrued liabilities and actual costs incurred. However, the status and timing of actual services performed, number of patients enrolled, and the rate of patient enrollment 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 Tax Incentive	Research and Development Tax Incentive The Company may be eligible under the AusIndustry research and development tax incentive program to obtain a cash refund from the Australian Taxation Office. The refundable cash tax incentive is available to the Company on the basis of specific criteria with which the Company must comply. Specifically, the Company must have annual turnover of less than AUD 20.0 million and cannot be controlled by income tax exempt entities. The refundable cash research and development tax incentive is recognized as a reduction to 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. The Company may alternatively be eligible for a taxable credit in the form of a non-cash tax incentive. The Company evaluates its eligibility under tax incentive programs as of each balance sheet date and makes accrual and related adjustments based on the most current and relevant data available.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the Company’s net loss by the weighted average number of shares of common stock and Exchange Warrants outstanding during the period, without consideration of potentially dilutive securities. In accordance with Accounting Standards Codification Topic 260, Earnings Per Share , the Exchange Warrants are included in the computation of basic net loss per share because the exercise price is negligible, and they are fully vested and exercisable after the original issuance date. Diluted net loss per share is the same as basic net loss per share for all periods presented since the effect of potentially dilutive securities is anti-dilutive given the net loss of the Company. See Note 9. Stockholder’s Equity for additional information regarding the Exchange Warrants.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Adopted	Recently Adopted Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016‑02, Leases (Topic 842). In July 2018, the FASB issued ASU No. 2018-10, Codification Improvements to Topic 842, Leases , which provides clarification to ASU 2016-02. These ASUs (collectively, the new lease standard) require an entity to recognize a lease liability and a ROU asset on the balance sheet for leases with lease terms of more than twelve months. Lessor accounting is largely unchanged, while lessees are no longer provided with a source of off-balance sheet financing. In July 2018, the FASB issued ASU No. 2018-11, Leases (Topic 842) - Targeted Improvements, which allows entities to elect an optional transition method where entities may continue to apply the existing lease guidance during the comparative periods and apply the new lease requirements through a cumulative effect adjustment in the period of adoption rather than in the earliest period presented. The Company adopted the new lease standard using the modified retrospective approach effective January 1, 2019 and elected the package of transitional practical expedients, such that, for leases existing prior to the adoption of ASC 842, the Company did not need to reassess whether contracts are leases, retained historical lease classification and historical initial direct costs classification. The Company did not elect the hindsight practical expedient to determine the lease term for existing leases. At January 1, 2019, the Company derecognized its deferred rent liability in the amount of $0.8 million and recognized a ROU asset and related lease liability in the amount of $7.5 million and $8.3 million, respectively. In June 2018, the FASB issued ASU No. 2018-07, Compensation – Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting , which is intended to simplify the accounting for nonemployee share-based payment transactions by expanding the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The Company adopted this guidance prospectively as of January 1, 2019. The adoption of this guidance did not have a material impact on the Company’s financial position, results of operations or liquidity. Recently Issued Accounting Pronouncements Not Yet Adopted as of September 30, 2019 In June 2016, the FASB issued ASU No. 2016‑13, Financial Instruments - Credit Losses (Topic 326) , which is intended to provide financial statement users with more useful information about expected credit losses on financial assets held by a reporting entity at each reporting date. In May 2019, the FASB issued ASU No. 2019-05, which amended the new standard by providing targeted transition relief. The new guidance replaces the existing incurred loss impairment methodology with a methodology that requires consideration of a broader range of reasonable and supportable forward-looking information to estimate all expected credit losses. This guidance is effective for the fiscal years and interim periods within those years beginning after December 15, 2019 and early adoption is permitted for fiscal years and interim periods within those years beginning after December 15, 2018. The Company is continuing to evaluate the impact of this new guidance on its receivable from collaboration partner and available-for-sale investment securities and does not expect the new guidance to have a material impact on its consolidated financial statements and related disclosures. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820) – Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement , which modifies the disclosure requirements on fair value measurements and is intended to improve the effectiveness of disclosures, including the consideration of costs and benefits. The guidance is effective for the fiscal years and interim periods within those years beginning after January 1, 2020. Early adoption is permitted, and an entity is permitted to early adopt any removed or modified disclosures and delay adoption of additional disclosures until their effective date. The Company does not expect this new guidance to impact its consolidated financial statements and is currently evaluating the impact on its disclosures. In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606 , which is intended to clarify the circumstances under which certain transactions in collaborative arrangements should be accounted for under the revenue recognition standard. Certain transactions between collaboration arrangement participants should be accounted for as revenue under ASC Topic 606 when the collaborative arrangement participant is a customer in the context of a unit of account. This guidance is effective for fiscal years and interim periods within those years beginning after December 15, 2020. Early adoption is permitted. The Company is in the process of assessing the impact of this new guidance on its consolidated financial statements and disclosures.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Summary of Significant Accounting Policies
Schedule of cash as reported in the consolidated statements of cash flows	Cash as reported in the condensed consolidated statements of cash flows consists of (in thousands): September 30, 2019 2018 Cash and cash equivalents $ 50,195 $ 87,427 Restricted cash - current 10 10 Restricted cash - noncurrent 450 450 Cash balance in condensed consolidated statements of cash flows $ 50,655 $ 87,887

License and Collaboration Agr_2

License and Collaboration Agreement (Tables)	9 Months Ended
	Sep. 30, 2019
License and Collaboration Agreement.
Schedule of changes in contract assets and liabilities	The following tables present changes in the Company’s contract assets and liabilities during the periods presented (in thousands): Balance at Balance at Beginning of End of Nine Months Ended September 30, 2019 Period Additions Deductions Period Contract assets: Receivable from collaboration partner - related party $ 2,042 $ 30,882 $ (31,905) $ 1,019 Contract asset - related party $ 2,545 $ 926 $ (2,545) $ 926 Contract liabilities: Deferred revenue - related party $ 8,223 $ 36,441 $ (5,986) $ 38,678 Payable to collaboration partner - related party $ 1,061 $ 1,226 $ (1,267) $ 1,020 Balance at Balance at Beginning of End of Nine Months Ended September 30, 2018 Period Additions Deductions Period Contract assets: Receivable from collaboration partner - related party $ 1,816 $ 6,012 $ (3,242) $ 4,586 Contract liabilities: Deferred revenue - related party $ 31,752 $ 4,147 $ (27,929) $ 7,970 Payable to collaboration partner - related party $ — $ 1,068 $ (304) $ 764

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Measurements
Schedule of fair value of financial assets	The following table presents the fair value of the Company’s financial assets determined using the inputs defined above (in thousands). September 30, 2019 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 16,381 $ — $ — $ 16,381 Corporate bonds — 28,105 — 28,105 Commercial paper — 40,865 — 40,865 Government bonds — 46,596 — 46,596 Total financial assets $ 16,381 $ $ — $ December 31, 2018 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 25,390 $ — $ — $ 25,390 Corporate bonds — 8,989 — 8,989 Commercial paper — 59,730 — 59,730 Government bonds — 33,394 — 33,394 Total financial assets $ 25,390 $ $ — $

Balance Sheet Components (Table

Balance Sheet Components (Tables)	9 Months Ended
	Sep. 30, 2019
Balance Sheet Components
Schedule of cash equivalents and available-for-sale securities	Cash equivalents and available-for-sale securities consisted of the following (in thousands): September 30, 2019 Amortized Gross Unrealized Cost Gains Losses Fair Value Money market funds $ 16,381 $ — $ — $ 16,381 Corporate bonds 28,083 23 (1) 28,105 Commercial paper 40,868 — (3) 40,865 Government bonds 46,579 17 — 46,596 Total cash equivalents and available-for-sale securities $ $ 40 $ (4) $ Classified as: Cash equivalents $ 44,450 Available-for-sale securities 87,497 Total cash equivalents and available-for-sale securities $ December 31, 2018 Amortized Gross Unrealized Cost Gains Losses Fair Value Money market funds $ 25,390 $ — $ — $ 25,390 Corporate bonds 8,997 — (8) 8,989 Commercial paper 59,730 — — 59,730 Government bonds 33,423 — (29) 33,394 Total cash equivalents and available-for-sale securities $ 127,540 $ — $ (37) $ 127,503 Classified as: Cash equivalents $ 80,883 Available-for-sale securities 46,620 Total cash equivalents and available-for-sale securities $ 127,503
Summary of Property and Equipment Net	Property and equipment, net consisted of the following (in thousands): September 30, December 31, 2019 2018 Laboratory equipment $ 3,006 $ 2,533 Furniture and computer equipment 487 338 Leasehold improvements 800 67 Total property and equipment 4,293 2,938 Less: accumulated depreciation and amortization (2,559) (2,077) Property and equipment, net $ 1,734 $ 861
Summary of Accrued Expenses and Other Payables	Accrued expenses and other payables consisted of the following (in thousands): September 30, December 31, 2019 2018 Accrued clinical and research related expenses $ 6,420 $ 7,781 Accrued employee related expenses 3,480 2,726 Accrued professional service fees 376 61 Other 210 595 Total accrued expenses and other payables $ 10,486 $ 11,163

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases
Schedule of weighted average lease term and discounts rate	September 30, 2019 Operating Lease Term and Discount Rate: Weighted-average remaining lease term 4.7 years Weighted-average discount rate 11.0%
Schedule of minimum lease payments and lease liabilities	The following table summarizes the Company’s minimum lease payments and lease liability as of September 30, 2019 (in thousands): Year Ending December 31: Amount 2019 (remaining three months) $ 477 2020 1,941 2021 2,000 2022 2,059 2023 2,121 Thereafter 895 Total future minimum lease payments 9,493 Less: imputed interest (1,991) Present value of future minimum lease payments 7,502 Less: current portion of operating lease liability (1,209) Operating lease liability - noncurrent $ 6,293
Schedule of future minimum lease payments for operating leases	As previously disclosed in the Company’s 2018 Annual Report on Form 10-K and under the previous lease accounting standard, future minimum lease payments for operating leases having initial or remaining noncancellable lease terms in excess of one year would have been as follows (in thousands): Year Ending December 31: Amount 2019 $ 1,941 2020 2,000 2021 2,059 2022 2,121 2023 2,185 Thereafter 922 Total $ 11,228
Schedule of least cost information	Supplemental lease cost information is as follows (in thousands): Three Months Ended Nine Months Ended September 30, 2019 September 30, 2019 Operating lease cost $ 444 $ 1,347
Schedule of balance sheet information	Supplemental balance sheet information is as follows (in thousands): September 30, 2019 Operating Leases: Operating lease right-of-use asset, non-current $ 6,295 Operating lease liability - current $ 1,209 Operating lease liability - noncurrent 6,293 Total operating lease liabilities $ 7,502
Schedule of cash flow information	Supplemental cash flow information is as follows (in thousands): Nine Months Ended September 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flow used by operating leases $
ASU 2016-02
Leases
Schedule of adopting new guidance	The impact of the changes made to the consolidated balance sheet as of January 1, 2019 as a result of adopting the new guidance was as follows (in thousands): Balance at Adjustments Balance at December 31, Due to January 1, 2018 ASC 842 2019 Balance Sheet: Operating lease right-of-use asset - noncurrent $ — 7,499 $ 7,499 Operating lease liability - current $ — 1,080 $ 1,080 Operating lease liability - noncurrent $ — 7,219 $ 7,219 Deferred rent - noncurrent $ 799 (799) $ —

Equity Plans (Tables)

Equity Plans (Tables)	9 Months Ended
	Sep. 30, 2019
Schedule of activity under equity incentive plans	Weighted- Weighted- Average Average Exercise Remaining Aggregate Options Price Per Contractual Intrinsic Outstanding Share Life (years) Value (1) (in millions) Balances at December 31, 2018 3,178,441 $ 12.23 7.52 Options granted 1,265,800 9.32 Options exercised (295,853) 3.91 Options forfeited (438,757) 13.30 Balances at September 30, 2019 3,709,631 $ 11.77 8.03 $ 10.7 Options exercisable – September 30, 2019 1,870,596 $ 11.98 7.14 $ 6.6 Options vested and expected to vest – September 30, 2019 3,709,631 $ 11.77 8.03 $ 10.7 (1) The aggregate intrinsic values were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock on September 30, 2019. The calculation excludes options with an exercise price higher than the closing price of the Company’s common stock on September 30, 2019.
Schedule of stock-based compensation expense	Total stock-based compensation expense was as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2019 2018 2019 2018 Research and development $ 1,137 $ 1,046 $ 3,237 $ 2,424 General and administrative 1,064 971 2,956 2,423 Total stock-based compensation expense $ 2,201 $ 2,017 $ 6,193 $ 4,847
Employee stock options
Black-Scholes option-pricing model assumptions	Three Months Ended Nine Months Ended September 30, September 30, 2019 2018 2019 2018 Expected term (in years) 5.00 - 6.08 5.49 - 6.08 5.00 - 6.08 5.49 - 6.08 Expected volatility 61.0 - 63.4% 61.2 - 65.1% 61.0 - 63.4% 62.0 - 66.5% Risk-free interest rate 1.42 - 1.90% 2.75 - 2.98% 1.42 - 2.58% 2.42 - 2.98% Dividend yield — — — —
Restricted stock units
Schedule of activity under equity incentive plans	Weighted Average Number of Grant Date Shares Fair Value Unvested at December 31, 2018 418,450 $ 10.45 Restricted stock units granted 160,650 8.02 Restricted grant units vested (197,703) 9.29 Restricted grant units forfeited (96,952) 9.84 Unvested at September 30, 2019 284,445 $ 10.09

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2019
Net Loss per Share
Schedule of computation of the basic and diluted net loss per share attributable to common stockholders	The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data): Three Months Ended Nine Months Ended September 30, September 30, 2019 2018 2019 2018 Numerator: Net loss $ (16,409) $ (8,735) $ (59,686) $ (25,059) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 26,956,957 22,912,279 25,315,512 21,750,562 Net loss per shares, basic and diluted $ (0.61) $ (0.38) $ (2.36) $ (1.15)
Schedule of potentially dilutive securities excluded from diluted net loss per share calculations	September 30, 2019 2018 Options to purchase common stock 3,709,631 3,153,479 Common stock warrants 2,750,000 2,750,000 Restricted stock units 284,445 420,650 ESPP shares 41,263 52,682 Total 6,785,339 6,376,811

Organization and Description _2

Organization and Description of Business - Liquidity (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)segment	Dec. 31, 2018USD ($)
Organization and Description of Business
Number of operating segments | segment	1
Net losses from operations since inception
Accumulated deficit | $	$ (200,160)	$ (140,474)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Concentrations of Credit Risk (Details)	Sep. 30, 2019Institution
Summary of Significant Accounting Policies
Number of financial institutions at which cash is held	2

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Aggregate amounts of cash and cash equivalents and the restricted cash
Cash and cash equivalents	$ 50,195	$ 82,233	$ 87,427
Restricted cash - current	10	10	10
Restricted cash - noncurrent	450	450	450
Cash balance in condensed consolidated statements of cash flows	$ 50,655	$ 82,693	$ 87,887	$ 106,489

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Research and Development Tax Incentive (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019AUD ($)
Revenue, Practical Expedient [Abstract]
Financing component	true
Maximum | Australian
Revenue, Practical Expedient [Abstract]
Revenue for availability of research and development tax incentive	$ 20

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Recently Adopted Accounting Pronouncements (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Recent Accounting Pronouncements
Practical expedients - package	true
Practical expedients - hindsight	false
Deferred rent liability			$ 799
Operating lease right-of-use asset	$ 6,295	$ 7,500
Lease liability	$ 7,502
ASU 2016-02
Recent Accounting Pronouncements
Operating lease right-of-use asset		7,499
Adjustment | ASU 2016-02
Recent Accounting Pronouncements
Deferred rent liability		(799)
Operating lease right-of-use asset		7,499
Lease liability		$ 8,300

License and Collaboration Agr_3

License and Collaboration Agreement (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	May 07, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 13, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments and fees	$ 22,200				$ 22,200
Revenue recognized	2,900			$ 5,900	4,500	$ 27,900
Deferred revenue - related party	16,478				16,478			$ 8,223
Receivable from collaboration partner and contract asset - related party	1,945				1,945			4,587
Payable to collaboration partner - related party	1,020				$ 1,020			1,061
License and Collaborative Revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost					20.00%
Second-Generation Analog, Phase 3 CD Clinical Trial Primary Clinical Endpoint [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost					80.00%
First Amendment | Development, regulatory and sales milestone payments
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to be received							$ 1,000,000
Janssen Biotech, Inc. | License and Collaborative Revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	4,100		$ (1,600)	6,100		28,600
Increase (decrease) in transaction price					$ (9,400)
Janssen Biotech, Inc. | Second-Generation Analog, Phase 3 CD Clinical Trial Primary Clinical Endpoint [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development cost					20.00%
Janssen Biotech, Inc. | License and Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue - related party	38,678			7,970	$ 38,678	7,970		8,223	$ 31,752
Payable to collaboration partner - related party	1,020			$ 764	1,020	764		$ 1,061
Transaction price recognized based on proportional performance		$ 109,200	$ 60,600		5,986	$ 27,929
Transaction price	110,800				$ 110,800
Development cost					80.00%
Increase (decrease) in transaction price	1,600	50,200
Janssen Biotech, Inc. | License and Collaboration Agreement | Upfront cash payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payments and fees										$ 50,000
Janssen Biotech, Inc. | First, second-generation compound | Second-Generation Analog, Phase 3 CD Clinical Trial Primary Clinical Endpoint [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research program cost					100.00%
Janssen Biotech, Inc. | Second and third, second-generation compounds | Second-Generation Analog, Phase 3 CD Clinical Trial Primary Clinical Endpoint [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research program cost					50.00%
Janssen Biotech, Inc. | Thereafter | Second-Generation Analog, Phase 3 CD Clinical Trial Primary Clinical Endpoint [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research program cost					100.00%
Janssen Biotech, Inc. | Phase 2 clinical trial | License and Collaborative Revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue					$ 18,400
Janssen Biotech, Inc. | First Opt-in Election
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Former opt-in payments					125,000
Janssen Biotech, Inc. | Second Opt-in Election
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Former opt-in payments					200,000
Janssen Biotech, Inc. | First Amendment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Increase (decrease) in transaction price					(9,400)
Janssen Biotech, Inc. | First Amendment | License and Collaborative Revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized		25,000			5,300
Janssen Biotech, Inc. | First Amendment | Development Milestone Payments
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to be received	50,000				50,000
Janssen Biotech, Inc. | First Amendment | Milestone payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized		$ 25,000
Janssen Biotech, Inc. | First Amendment | PTG-200, Phase 3 CD Clinical Trial Primary Clinical Endpoint
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to be received							100,000
Janssen Biotech, Inc. | First Amendment | Second-Generation Analog, Phase 3 CD Clinical Trial Primary Clinical Endpoint [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to be received							$ 115,000
Janssen Biotech, Inc. | First Amendment | Second-Generation Phase 2b Milestone Payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to be received	50,000				50,000
Janssen Biotech, Inc. | Amended First Opt-in | Upfront cash payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to be received	50,000				50,000
Janssen Biotech, Inc. | Amended Second Opt-in | Upfront cash payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Amount to be received	50,000				$ 50,000
Janssen Biotech, Inc. | Estimated variable consideration | License and Collaborative Revenue
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue	$ 17,400

License and Collaboration Agr_4

License and Collaboration Agreement - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Deferred revenue - related party
Balance at beginning of period			$ 8,223		$ 8,223
Balance at End of Period	$ 16,478				16,478
Payable to collaboration partner - related party
Balance at Beginning of Period			1,061		1,061
Balance at End of Period	1,020				1,020
Revenue recognized from contract liability balance at beginning of period	2,900			$ 5,900	4,500	$ 27,900
Costs to obtain or fulfill the contract that were capitalized	0			0	0	0
Janssen Biotech, Inc. | License and Collaboration Agreement
Receivable from collaboration partner - related party
Balance at beginning of period			2,042		2,042	1,816
Additions					30,882	6,012
Deductions					(31,905)	(3,242)
Balance at end of period	1,019			4,586	1,019	4,586
Contract asset - related party
Contract asset - related party, Balance at Beginning of Period			2,545		2,545
Contract asset - related party, Additions					926
Contract asset - related party, Deductions					(2,545)
Contract asset - related party, Balance at end of Period	926				926
Deferred revenue - related party
Balance at beginning of period			8,223		8,223	31,752
Additions					36,441	4,147
Deductions		$ (109,200)	(60,600)		(5,986)	(27,929)
Balance at End of Period	38,678			7,970	38,678	7,970
Payable to collaboration partner - related party
Balance at Beginning of Period			$ 1,061		1,061
Additions					1,226	1,068
Deductions					(1,267)	(304)
Balance at End of Period	$ 1,020			$ 764	$ 1,020	$ 764

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 131,947	$ 127,503
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	16,381	25,390
Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	28,105	8,989
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	40,865	59,730
Government Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	46,596	33,394
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	16,381	25,390
Level 1 | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	16,381	25,390
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	115,566	102,113
Level 2 | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	28,105	8,989
Level 2 | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	40,865	59,730
Level 2 | Government Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 46,596	$ 33,394

Balance Sheet Components - Cash

Balance Sheet Components - Cash Equivalents and Available-for-sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash Equivalents and Available-for-sale Securities
Total cash equivalents and available-for-sale securities, Amortized Cost	$ 131,911	$ 127,540
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	40
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses	(4)	(37)
Total cash equivalents and available-for-sale securities, Fair Value	131,947	127,503
Corporate Bonds
Cash Equivalents and Available-for-sale Securities
Total cash equivalents and available-for-sale securities, Amortized Cost	28,083	8,997
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	23
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses	(1)	(8)
Total cash equivalents and available-for-sale securities, Fair Value	28,105	8,989
Government Bonds
Cash Equivalents and Available-for-sale Securities
Total cash equivalents and available-for-sale securities, Amortized Cost	46,579	33,423
Total cash equivalents and available-for-sale securities, Gross Unrealized Gains	17
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses		(29)
Total cash equivalents and available-for-sale securities, Fair Value	46,596	33,394
Money Market Funds
Cash Equivalents and Available-for-sale Securities
Total cash equivalents and available-for-sale securities, Amortized Cost	16,381	25,390
Total cash equivalents and available-for-sale securities, Fair Value	16,381	25,390
Commercial Paper
Cash Equivalents and Available-for-sale Securities
Total cash equivalents and available-for-sale securities, Amortized Cost	40,868	59,730
Total cash equivalents and available-for-sale securities, Gross Unrealized Losses	(3)
Total cash equivalents and available-for-sale securities, Fair Value	$ 40,865	$ 59,730

Balance Sheet Components - Clas

Balance Sheet Components - Classification of Cash Equivalents and Available-for-sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Classified as:
Cash equivalents	$ 44,450	$ 80,883
Available-for-sale securities	87,497	46,620
Total cash equivalents and available-for-sale securities	$ 131,947	$ 127,503

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property and Equipment
Total property and equipment	$ 4,293	$ 2,938
Less: accumulated depreciation and amortization	(2,559)	(2,077)
Property and equipment, net	1,734	861
Laboratory equipment
Property and Equipment
Total property and equipment	3,006	2,533
Furniture and computer equipment
Property and Equipment
Total property and equipment	487	338
Leasehold improvements
Property and Equipment
Total property and equipment	$ 800	$ 67

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Expenses and Other Payables (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Balance Sheet Components
Accrued clinical and research related expenses	$ 6,420	$ 7,781
Accrued employee related expenses	3,480	2,726
Accrued professional service fees	376	61
Other	210	595
Total accrued expenses and other payables	$ 10,486	$ 11,163

Government Programs (Details)

Government Programs (Details) $ in Thousands, $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2019USD ($)	Sep. 30, 2018AUD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019AUD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018AUD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2018AUD ($)	Dec. 31, 2018USD ($)
Government Programs
Reduction of research and development expenses related to tax	$ 0	$ 0.4	$ 300			$ 1.6	$ 1,300
Research and development tax incentive receivable, net								$ 173		$ 1,429
SBIR Grant
Government Programs
Reduction of research and development expenses related to tax	$ 600		$ 200		$ 1,100		$ 400
Grants receivable								700		300
Australian
Government Programs
Reduction of research and development expenses related to tax				$ 1.8	$ 1,200
Overseas Findings | Australian
Government Programs
Research and development tax incentive receivable, net				$ 0.3				$ 200	$ 2	$ 1,400

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Leases
Operating lease right-of-use asset	$ 6,295	$ 7,500
Lease liability	7,502
Operating lease liability - current	1,209
Operating lease liability - noncurrent	$ 6,293
Deferred rent - noncurrent			$ 799
ASU 2016-02
Leases
Operating lease right-of-use asset		7,499
Operating lease liability - current		1,080
ASU 2016-02 | Adjustment
Leases
Operating lease right-of-use asset		7,499
Lease liability		8,300
Operating lease liability - current		1,080
Deferred rent - noncurrent		(799)
Noncurrent | ASU 2016-02
Leases
Operating lease liability - noncurrent		7,219
Noncurrent | ASU 2016-02 | Adjustment
Leases
Operating lease liability - noncurrent		$ 7,219

Leases - Agreement (Details)

Leases - Agreement (Details)	1 Months Ended		3 Months Ended	9 Months Ended
	Jul. 31, 2019USD ($)	Mar. 31, 2017USD ($)lease	Sep. 30, 2019USD ($)	Sep. 30, 2019USD ($)
Leases
Security deposit		$ 450,000
Tenant improvement allowances	$ 469,000
Sublease Income			$ 21,000	$ 42,000
Newark, California
Leases
Number of operating lease agreement | lease		1

Leases - Weighted average lease

Leases - Weighted average lease term and discount rate (Details)	Sep. 30, 2019
Leases
Weighted-average remaining lease term	4 years 8 months 12 days
Weighted-average discount rate	11.00%

Leases - Minimum lease payments

Leases - Minimum lease payments (Details) $ in Thousands	Sep. 30, 2019USD ($)
Minimum lease payments:
2019 (remaining three months)	$ 477
2020	1,941
2021	2,000
2022	2,059
2023	2,121
Thereafter	895
Total future minimum lease payments	9,493
Less: imputed interest	(1,991)
Present value of future minimum lease payments	7,502
Less: current portion of operating lease liability	(1,209)
Operating lease liability - noncurrent	$ 6,293

Leases - Future minimum lease p

Leases - Future minimum lease payments - ASC 840 (Details) $ in Thousands	Dec. 31, 2018USD ($)
Future minimum lease payments - ASC 840
2019	$ 1,941
2020	2,000
2021	2,059
2022	2,121
2023	2,185
Thereafter	922
Total	$ 11,228

Leases - Lease cost information

Leases - Lease cost information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Leases
Operating lease cost	$ 444	$ 1,347

Leases - Supplemental balance s

Leases - Supplemental balance sheet information (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019
Operating Leases:
Operating lease right-of-use asset	$ 6,295	$ 7,500
Financial position	us-gaap:OperatingLeaseRightOfUseAsset
Operating lease liability - current	$ 1,209
Financial position	us-gaap:OperatingLeaseLiabilityCurrent
Operating lease liability - noncurrent	$ 6,293
Financial position	us-gaap:OperatingLeaseLiabilityNoncurrent
Total operating lease liabilities	$ 7,502
Financial position	us-gaap:OperatingLeaseLiabilityCurrent us-gaap:OperatingLeaseLiabilityNoncurrent

Leases - Cash flow information

Leases - Cash flow information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Leases
Operating cash flow used by operating leases	$ 1,409

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 21, 2018	Aug. 06, 2018	Sep. 30, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Stock transactions
Net proceeds from sale of stock						$ 34,492	$ 1,025
Par value (per share)				$ 0.00001		$ 0.00001		$ 0.00001
Common Stock
Stock transactions
Common stock sold pursuant to Sales Agreement (in shares)				1,924,957	103,500	2,846,641	103,500
Common stock issued pursuant to exercise of Exchange Warrants (in shares)						599,997
Common Stock | Shelf offering
Stock transactions
Maximum aggregate offering price			$ 200,000
Common Stock | Private Placement
Stock transactions
Number of warrants exercised				0		0
Cantor Fitzgerald & Co. Sales Agreement
Stock transactions
Common stock available for sale				$ 72,000		$ 72,000
Cantor Fitzgerald & Co. Sales Agreement | At-the-market offering
Stock transactions
Maximum aggregate offering price			$ 50,000
Common stock available for sale				$ 13,000		$ 13,000
Cantor Fitzgerald & Co. Sales Agreement | Common Stock | At-the-market offering
Stock transactions
Common stock sold pursuant to Sales Agreement (in shares)				1,924,957	103,500	2,846,641	103,500
Net proceeds from sale of stock				$ 23,900	$ 1,000	$ 34,500	$ 1,000
Investors | Common Stock
Stock transactions
Common stock sold pursuant to Sales Agreement (in shares)		2,750,000
Price (in dollars per share)		$ 8
Aggregate gross proceeds		$ 21,700
Investors | Common Stock | Private Placement
Stock transactions
Warrants to purchase common stock, number of shares		2,750,000
Purchase of common stock		2,750,000
Exchange Agreement | Exchanging Stockholders
Stock transactions
Warrants to purchase common stock, number of shares	1,000,000
Warrants exercise price	$ 0.00001
Common stock exchanged for pre-funded warrants	1,000,000
Par value (per share)	$ 0.00001
Purchase of common stock	1,000,000
Exercise Price (per share)	$ 0.00001
Duration of warrants from date of issuance (in years)	10 years
Equity Method Investment, Ownership Percentage	9.99%
Exchange Agreement | Exchanging Stockholders | Common Stock
Stock transactions
Number of warrants exercised				600,000		600,000
Common stock issued pursuant to exercise of Exchange Warrants (in shares)						599,997
Exchange Warrants unexercised				400,000		400,000
Group one | Common Stock | Private Placement
Stock transactions
Number of shares to be converted for each warrant		1,375,000
Warrants exercise price		$ 10
Exercise Price (per share)		$ 10
Group two | Common Stock | Private Placement
Stock transactions
Number of shares to be converted for each warrant		1,375,000
Warrants exercise price		$ 15
Exercise Price (per share)		$ 15

Equity Plans - Description (Det

Equity Plans - Description (Details)	9 Months Ended
	Sep. 30, 2019installmentshares	May 31, 2018shares
2016 Equity Incentive Plan
Equity Plans
Number of shares available for issuance	579,220
2018 Inducement Plan
Equity Plans
Expiration period	10 years
Vesting period	18 months
Number of shares authorized		750,000
Number of shares available for issuance	280,000
Stock options - employees, consultants, directors | 2016 Equity Incentive Plan
Equity Plans
Expiration period	10 years
Employee stock options | 2016 Equity Incentive Plan
Equity Plans
Vesting period	4 years
Employee stock options | 2018 Inducement Plan
Equity Plans
Vesting period	18 months
Stock option units vesting, number of installments | installment	3
Non Employee Director Initial Stock Options | 2016 Equity Incentive Plan
Equity Plans
Vesting period	3 years
Nonemployee Director Annual Refresher Stock Options | 2016 Equity Incentive Plan
Equity Plans
Vesting period	1 year
Nonemployee Consultant Options | 2016 Equity Incentive Plan | Minimum
Equity Plans
Vesting period	1 year
Nonemployee Consultant Options | 2016 Equity Incentive Plan | Maximum
Equity Plans
Vesting period	4 years

Equity Plans - Activity (Detail

Equity Plans - Activity (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Options Outstanding
Options Outstanding, Beginning balance	3,178,441
Options Outstanding, Options granted	1,265,800
Options Outstanding, Options exercised	(295,853)
Options Outstanding, Options forfeited	(438,757)
Options Outstanding, Ending balance	3,709,631	3,178,441
Options Outstanding, Options exercisable	1,870,596
Options Outstanding, Options vested and expected to vest	3,709,631
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance	$ 12.23
Weighted-Average Exercise Price Per Share, Options granted	9.32
Weighted-Average Exercise Price Per Share, Options exercised	3.91
Weighted-Average Exercise Price Per Share, Options forfeited	13.30
Weighted-Average Exercise Price Per Share, Ending balance	11.77	$ 12.23
Weighted-Average Exercise Price Per Share, Options exercisable	11.98
Weighted-Average Exercise Price Per Share, Options vested and expected to vest	$ 11.77
Weighted-Average Remaining Contractual Life (years)
Weighted-Average Remaining Contractual Life (years)	8 years 11 days
Weighted-Average Remaining Contractual Life (years), Options exercisable	7 years 1 month 21 days
Weighted-Average Remaining Contractual Life (years), Options vested and expected to vest	8 years 11 days	7 years 6 months 7 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Options Outstanding	$ 10.7
Aggregate Intrinsic Value, Options exercisable	6.6
Aggregate Intrinsic Value, Options vested and expected to vest	$ 10.7
Options, weighted-average grant-date fair value	$ 5.42

Equity Plans - Employee Stock O

Equity Plans - Employee Stock Options Valuation Assumptions (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Equity Plans
Dividend yield	0.00%	0.00%	0.00%	0.00%
Employee stock options
Equity Plans
Expected volatility, Minimum	61.00%	61.20%	61.00%	62.00%
Expected volatility, Maximum	63.40%	65.10%	63.40%	66.50%
Risk-free interest rate, Minimum	1.42%	2.75%	1.42%	2.42%
Risk-free interest rate, Maximum	1.90%	2.98%	2.58%	2.98%
Employee stock options | Minimum
Equity Plans
Expected term	5 years	5 years 5 months 27 days	5 years	5 years 5 months 27 days
Employee stock options | Maximum
Equity Plans
Expected term	6 years 29 days	6 years 29 days	6 years 29 days	6 years 29 days

Equity Plans - Restricted Stock

Equity Plans - Restricted Stock Units - (Details)	9 Months Ended
	Sep. 30, 2019installment$ / sharesshares
Equity Plans
Restricted stock units vesting, number of equal installments | installment	4
Number of Shares
Number of shares, Unvested, Beginning balance | shares	418,450
Number of shares, Restricted stock units granted | shares	160,650
Number of shares, Restricted grant units vested | shares	(197,703)
Number of Shares, Restricted grant units forfeited | shares	(96,952)
Number of shares, Unvested, Ending balance | shares	284,445
Weighted-Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value, Unvested, Beginning balance | $ / shares	$ 10.45
Weighted-Average Grant Date Fair Value, Granted | $ / shares	8.02
Weighted-Average Grant Date Fair Value, Vested | $ / shares	9.29
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	9.84
Weighted-Average Grant Date Fair Value, Unvested, Ending balance | $ / shares	$ 10.09
2018 Inducement Plan
Equity Plans
Restricted stock units vesting, number of equal installments | installment	3
Vesting period	18 months

Equity Plans - ESPP Description

Equity Plans - ESPP Description and Rights Valuation Assumptions (Details) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Equity Plans
Dividend yield	0.00%	0.00%	0.00%	0.00%
2016 Employee Stock Purchase Plan
Equity Plans
Shares issued in period			181,984
Number of shares available for issuance	577,993		577,993
Maximum payroll deduction for share purchases (as a percent)	15.00%		15.00%
Purchase price of stock (as a percent)			85.00%

Equity Plans - Compensation Exp

Equity Plans - Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 2,201	$ 2,017	$ 6,193	$ 4,847
Total unrecognized stock-based compensation costs related to stock options	14,200		$ 14,200
Period of unrecognized stock-based compensation costs to be recognized			2 years 7 months 6 days
Research and Development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,137	1,046	$ 3,237	2,424
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,064	$ 971	$ 2,956	$ 2,423

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Effective tax rate of provision for income taxes difference from federal statutory rate
Income tax benefit	$ (102)	$ 0	$ (1,547)	$ 0
Effective income tax rate (as a percent)	0.60%		2.50%
Discrete tax benefit for 2017 Australia refundable R&D tax offset			$ 1,100
Federal statutory income tax rate (as a percent)	21.00%		21.00%

Net Loss per Share - Computatio

Net Loss per Share - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net loss	$ (16,409)	$ (8,735)	$ (59,686)	$ (25,059)
Denominator:
Weighted-average shares used to compute net loss per common share, basic and diluted	26,956,957	22,912,279	25,315,512	21,750,562
Net loss per shares, basic and diluted	$ (0.61)	$ (0.38)	$ (2.36)	$ (1.15)

Net Loss per Share - Antidiluti

Net Loss per Share - Antidilutive Securities (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	6,785,339	6,376,811
Employee stock options
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	3,709,631	3,153,479
Common stock warrants
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	2,750,000	2,750,000
Restricted stock units
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	284,445	420,650
ESPP rights
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	41,263	52,682

Subsequent Event (Details)

Subsequent Event (Details) - Subsequent Event $ in Millions	Oct. 30, 2019USD ($)item	Oct. 31, 2019USD ($)
Subsequent Event [Line Items]
Offering cost		$ 250
Term Loan Credit Agreement
Subsequent Event [Line Items]
Loan facility for general corporate	$ 50
Long-term Debt	$ 10
Number Of Tranches | item	2
Tranche Installment Amount	$ 20
Cash and cash equivalents ( In percentage)	35.00%
Loan Origination Fee (In Percentage)	0.25%
Period Of Interest Only Payments	24 months
Consecutive monthly payments	24 months
Additional Prepayment (In Percentage)	2.85%
Term Loan Credit Agreement | Debt Instrument Repayment On Or Before First Anniversary
Subsequent Event [Line Items]
Prepayment premium (In Percentage)	3.00%
Term Loan Credit Agreement | Debt Instrument Repayment Between First And Second Anniversary
Subsequent Event [Line Items]
Prepayment premium (In Percentage)	2.00%
Term Loan Credit Agreement | Debt Instrument Repayment After Second Anniversary
Subsequent Event [Line Items]
Prepayment premium (In Percentage)	1.00%
Term Loan Credit Agreement | Prime Rate
Subsequent Event [Line Items]
prime rate (In Percentage)	2.91%
Floor rate (In Percentage)	4.94%