Protagonist Therapeutics (PTGX) 10-Q 3 Aug 23 2023 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2023	Jul. 31, 2023
Document And Entity Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2023
Document Transition Report	false
Entity File Number	001-37852
Entity Registrant Name	PROTAGONIST THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	98-0505495
Entity Address, Address Line One	7707 Gateway Boulevard, Suite 140
Entity Address, City or Town	Newark
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94560-1160
City Area Code	510
Local Phone Number	474-0170
Title of 12(b) Security	Common Stock
Trading Symbol	PTGX
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		57,530,242
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001377121
Amendment Flag	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 235,382	$ 125,744
Marketable securities	78,019	111,611
Receivable from collaboration partner	39	10
Prepaid expenses and other current assets	3,501	5,712
Total current assets	316,941	243,077
Property and equipment, net	1,263	1,565
Restricted cash - noncurrent	225	225
Operating lease right-of-use asset	2,037	3,061
Total assets	320,466	247,928
Current liabilities:
Accounts payable	4,573	3,640
Payable to collaboration partner	10	69
Accrued expenses and other payables	19,369	24,955
Operating lease liability - current	2,446	2,515
Total current liabilities	26,398	31,179
Operating lease liability - noncurrent		1,141
Total liabilities	26,398	32,320
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; 57,494,185 and 49,339,252 shares issued and outstanding as of June 30, 2023 and December 31, 2022, respectively	1
Additional paid-in capital	903,205	752,722
Accumulated other comprehensive loss	(198)	(359)
Accumulated deficit	(608,940)	(536,755)
Total stockholders' equity	294,068	215,608
Total liabilities and stockholders' equity	$ 320,466	$ 247,928

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2023	Dec. 31, 2022
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	57,494,185	49,339,252
Common stock, shares outstanding	57,494,185	49,339,252

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Condensed Consolidated Statements of Operations
License and collaboration revenue	$ 0	$ 859	$ 0	$ 26,581
Revenue from Contract with Customer, Product and Service [Extensible List]	License and Collaboration Agreement	License and Collaboration Agreement	License and Collaboration Agreement	License and Collaboration Agreement
Operating expenses:
Research and development	$ 33,182	$ 34,611	$ 60,598	$ 70,929
General and administrative	9,172	7,691	17,777	18,206
Total operating expenses	42,354	42,302	78,375	89,135
Loss from operations	(42,354)	(41,443)	(78,375)	(62,554)
Interest income	3,913	484	6,404	652
Other expense, net	(19)	(78)	(214)	(65)
Net loss	$ (38,460)	$ (41,037)	$ (72,185)	$ (61,967)
Net loss per share, basic	$ (0.68)	$ (0.84)	$ (1.34)	$ (1.27)
Net loss per share, diluted	$ (0.68)	$ (0.84)	$ (1.34)	$ (1.27)
Weighted-average shares used to compute net loss per share, basic	56,775,742	49,049,902	53,691,965	48,902,047
Weighted-average shares used to compute net loss per share, diluted	56,775,742	49,049,902	53,691,965	48,902,047

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Condensed Consolidated Statements of Comprehensive Loss
Net loss	$ (38,460)	$ (41,037)	$ (72,185)	$ (61,967)
Other comprehensive loss:
(Loss) gain on translation of foreign operations		(209)	194	(114)
Unrealized loss on marketable securities	(76)	(39)	(33)	(307)
Comprehensive loss	$ (38,536)	$ (41,285)	$ (72,024)	$ (62,388)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholder's Equity - USD ($) $ in Thousands	Common Stock At-the-market offering	Common Stock Public offerings	Common Stock	Additional Paid-In Capital At-the-market offering	Additional Paid-In Capital Public offerings	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Gain	Accumulated Deficit	At-the-market offering	Public offerings	Total
Balance, Beginning at Dec. 31, 2021						$ 709,682	$ (299)	$ (409,362)			$ 300,021
Balance, Beginning (in shares) at Dec. 31, 2021			47,838,330
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of issuance costs				$ 14,553					$ 14,553
Issuance of common stock, net of issuance costs (in shares)	422,367
Issuance of common stock under equity incentive and employee stock purchase plans						3,213					3,213
Issuance of common stock under equity incentive and employee stock purchase plans (in shares)			430,960
Shares withheld for net settlement of tax withholding upon vesting of restricted stock units						(186)					(186)
Shares withheld for net settlement of tax withholding upon vesting of restricted stock units (in shares)			(7,726)
Stock-based compensation expense						12,740					12,740
Issuance costs related to prior period common stock offering						25					25
Other comprehensive gain (loss)							(421)				(421)
Net loss								(61,967)			(61,967)
Balance, Ending at Jun. 30, 2022						740,027	(720)	(471,329)			267,978
Balance, Ending (in shares) at Jun. 30, 2022			48,683,931
Balance, Beginning at Dec. 31, 2021						709,682	(299)	(409,362)			300,021
Balance, Beginning (in shares) at Dec. 31, 2021			47,838,330
Balance, Ending at Dec. 31, 2022						752,722	(359)	(536,755)			$ 215,608
Balance, Ending (in shares) at Dec. 31, 2022			49,339,252								49,339,252
Balance, Beginning at Mar. 31, 2022						732,542	(472)	(430,292)			$ 301,778
Balance, Beginning (in shares) at Mar. 31, 2022			48,552,102
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under equity incentive and employee stock purchase plans						655					655
Issuance of common stock under equity incentive and employee stock purchase plans (in shares)			131,829
Stock-based compensation expense						6,805					6,805
Issuance costs related to prior period common stock offering						25					25
Other comprehensive gain (loss)							(248)				(248)
Net loss								(41,037)			(41,037)
Balance, Ending at Jun. 30, 2022						740,027	(720)	(471,329)			267,978
Balance, Ending (in shares) at Jun. 30, 2022			48,683,931
Balance, Beginning at Dec. 31, 2022						752,722	(359)	(536,755)			$ 215,608
Balance, Beginning (in shares) at Dec. 31, 2022			49,339,252								49,339,252
Balance, Ending at Mar. 31, 2023			$ 1			786,768	(122)	(570,480)			$ 216,167
Balance, Ending (in shares) at Mar. 31, 2023			51,440,503
Balance, Beginning at Dec. 31, 2022						752,722	(359)	(536,755)			$ 215,608
Balance, Beginning (in shares) at Dec. 31, 2022			49,339,252								49,339,252
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of issuance costs	$ 1			$ 24,301	$ 107,790				$ 24,302	$ 107,790
Issuance of common stock, net of issuance costs (in shares)	1,749,199	5,750,000
Issuance of common stock under equity incentive and employee stock purchase plans						3,234					$ 3,234
Issuance of common stock under equity incentive and employee stock purchase plans (in shares)			687,697
Shares withheld for net settlement of tax withholding upon vesting of restricted stock units						(769)					(769)
Shares withheld for net settlement of tax withholding upon vesting of restricted stock units (in shares)			(31,963)
Stock-based compensation expense						15,927					15,927
Other comprehensive gain (loss)							161				161
Net loss								(72,185)			(72,185)
Balance, Ending at Jun. 30, 2023			$ 1			903,205	(198)	(608,940)			$ 294,068
Balance, Ending (in shares) at Jun. 30, 2023			57,494,185								57,494,185
Balance, Beginning at Mar. 31, 2023			$ 1			786,768	(122)	(570,480)			$ 216,167
Balance, Beginning (in shares) at Mar. 31, 2023			51,440,503
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of issuance costs					$ 107,790					$ 107,790
Issuance of common stock, net of issuance costs (in shares)		5,750,000
Issuance of common stock under equity incentive and employee stock purchase plans						973					973
Issuance of common stock under equity incentive and employee stock purchase plans (in shares)			329,486
Shares withheld for net settlement of tax withholding upon vesting of restricted stock units						(669)					(669)
Shares withheld for net settlement of tax withholding upon vesting of restricted stock units (in shares)			(25,804)
Stock-based compensation expense						8,343					8,343
Other comprehensive gain (loss)							(76)				(76)
Net loss								(38,460)			(38,460)
Balance, Ending at Jun. 30, 2023			$ 1			$ 903,205	$ (198)	$ (608,940)			$ 294,068
Balance, Ending (in shares) at Jun. 30, 2023			57,494,185								57,494,185

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash Flows from Operating Activities
Net loss	$ (72,185)	$ (61,967)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	15,927	12,740
Operating lease right-of-use asset amortization	1,168	1,168
(Accretion) amortization of discount/premium on marketable securities	(2,215)	454
Depreciation	485	508
Other	194
Changes in operating assets and liabilities:
Receivable from collaboration partner	(29)	1,523
Prepaid expenses and other assets	2,211	(255)
Accounts payable	933	(184)
Payable to collaboration partner	(59)	(819)
Accrued expenses and other payables	(5,661)	(1,553)
Deferred revenue		(1,601)
Operating lease liability	(1,354)	(1,315)
Net cash used in operating activities	(60,585)	(51,301)
Cash Flows from Investing Activities
Purchase of marketable securities	(34,122)	(102,121)
Proceeds from maturities of marketable securities	69,896	132,942
Purchases of property and equipment	(186)	(563)
Net cash provided by investing activities	35,588	30,258
Cash Flows from Financing Activities
Proceeds from public offering of common stock, net of issuance costs	107,868
Proceeds from at-the-market offering, net of issuance costs	24,302	14,553
Proceeds from issuance of common stock upon exercise of stock options and purchases under employee stock purchase plan	3,234	3,213
Tax withholding payments related to net settlement of restricted stock units	(769)	(186)
Issuance costs related to prior period common stock offering		25
Net cash provided by financing activities	134,635	17,605
Effect of exchange rate changes on cash, cash equivalents and restricted cash		10
Net increase (decrease) in cash, cash equivalents and restricted cash	109,638	(3,428)
Cash, cash equivalents and restricted cash, beginning of period	125,969	123,890
Cash, cash equivalents and restricted cash, end of period	235,607	120,462
Supplemental Disclosure of Non-Cash Financing and Investing Information:
Purchases of property and equipment in accounts payable and accrued liabilities	61	$ 122
Issuance costs related to common stock offering included in accrued liabilities and other payables	$ 78

Organization and Description of

Organization and Description of Business	6 Months Ended
	Jun. 30, 2023
Organization and Description of Business
Organization and Description of Business	PROTAGONIST THERAPEUTICS, INC. Notes to Unaudited Condensed Consolidated Financial Statements Note 1. Protagonist Therapeutics, Inc. (the “Company”) is headquartered in Newark, California. The Company is a biopharmaceutical company with peptide-based new chemical entities rusfertide and JNJ-2113 (formerly PN-235) in different stages of clinical development, both derived from the Company’s proprietary technology platform. The Company’s Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by the Chief Executive Officer, the Company’s chief operating decision maker, in deciding how to allocate resources and assessing performance. Liquidity As of June 30, 2023, the Company had cash, cash equivalents and marketable securities of $313.4 million. The Company has incurred net losses from operations since inception and had an accumulated deficit of $608.9 million as of June 30, 2023. The Company’s ultimate success depends upon 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. Since the Company’s initial public offering in August 2016, it has financed its operations primarily through proceeds from offerings of common stock and payments received under license and collaboration agreements. Risks and Uncertainties The Company is currently operating in a period of economic uncertainty and capital markets disruption, which has been impacted by the COVID-19 pandemic, domestic and global monetary and fiscal policy, geopolitical instability, including the ongoing military conflict between Russia and Ukraine and rising tensions between China and Taiwan, a recessionary environment, historically high domestic and global inflation and of failures of banking and other financial institutions. The Company has experienced delays in its existing and planned clinical trials due to worldwide impacts related to the COVID-19 pandemic, and its future results of operations and liquidity could be adversely impacted by outbreaks of disease, epidemics and pandemics, including further delays in existing and planned clinical trials, difficulty in recruiting patients for these clinical trials, delays in manufacturing and collaboration activities and supply chain disruptions. The conflict in Ukraine has exacerbated market disruptions, including significant volatility in commodity prices as well as supply chain interruptions, and has contributed to record inflation globally. The U.S. Federal Reserve and other central banks may be unable to contain inflation through more restrictive monetary policy and inflation may increase or continue for a prolonged period of time. Inflationary factors, such as increases in the cost of clinical supplies, interest rates, overhead costs and transportation costs may adversely affect the Company’s operating results. In addition, the failure of Silicon Valley Bank and other regional banks in the United States during the first half of 2023 has given rise to uncertainty in the security of amounts in deposit accounts uninsured by the Federal Deposit Insurance Corporation. The Company continues to monitor these events and the potential impact on its business. Although the Company does not believe that inflation has had a material impact on its financial position or results of operations to date, it may be adversely affected in the future due to global monetary and fiscal policy, macroeconomic factors, supply chain constraints, the ongoing conflict between Russia and Ukraine and other factors, and such factors may lead to increases in the cost of manufacturing for and initiation of studies in the Company’s product candidates.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2023
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“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 condensed consolidated balance sheet as of June 30, 2023 has been derived from the Company’s unaudited 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 presentation of the Company’s condensed consolidated financial statements. The results of operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results to be expected for the year ending December 31, 2023 or for any future period. Effective January 1, 2023, the financial statements of Protagonist Australia use the U.S. dollar as the functional currency due to the expected nature of the ongoing operations of this subsidiary. The cumulative translation adjustment as of January 1, 2023 related to this subsidiary was not material. Prior to January 1, 2023, the financial statements of Protagonist Australia used the Australian dollar as the functional currency since the majority of expense transactions occurred in such currency. Foreign currency translation gains and losses are reported as a component of stockholders’ equity in accumulated other comprehensive loss on the condensed consolidated balance sheets. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2022 included in the Company’s Annual Report on Form 10-K, filed with the SEC on March 15, 2023. 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 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, marketable securities and leases. Estimates related to revenue recognition include actual costs incurred versus total estimated costs of the Company’s deliverables to determine percentage of completion in addition to the application and estimates of potential revenue 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 could differ materially from these estimates. There has been uncertainty and disruption in the global economy and financial markets due to a number of factors, including the COVID-19 pandemic, geopolitical instability, inflationary pressures and domestic and global monetary and fiscal policy. The Company has taken into consideration any known impacts in its accounting estimates to date and is not aware of any additional specific events or circumstances that would require any additional updates to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of the issuance of this report. These estimates may change as new events occur and additional information is obtained. Actual results could differ materially from these estimates under different assumptions or conditions. 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ 2023 2022 Cash and cash equivalents ​ $ 235,382 ​ $ 120,237 Restricted cash - noncurrent ​ 225 ​ 225 Total cash reported on condensed consolidated statements of cash flows ​ $ 235,607 ​ $ 120,462 ​ Investment Impairment ​ As of each reporting date, the Company assesses each of its investments in available-for-sale debt securities whose fair value is below its cost basis to determine if the investment’s impairment is due to credit-related factors or noncredit-related factors. Factors considered in determining whether an impairment is credit-related include the extent to which the investment’s fair value is less than its cost basis, declines in published credit ratings, issuer default on interest or principal payments, and declines in the financial condition and near-term prospects of the issuer. Credit-related impairments on available-for-sale debt securities are recognized as an allowance for credit losses with a corresponding adjustment to other income (expense), net. The portion of the impairment that is not credit-related is recorded as a reduction of other comprehensive income (loss), net of applicable taxes. ​ The Company has elected to exclude accrued interest from both the fair value and the amortized cost basis of the available-for-sale debt securities for the purposes of identifying and measuring an impairment. The Company writes off accrued interest as a reduction of interest income when an issuer has defaulted on interest payments due on a security. ​ Significant Accounting Policies ​ Other than the change in Protagonist Australia functional currency from the Australian dollar to the U.S. dollar effective January 1, 2023 and the investment impairment policy, as discussed above, there have been no material changes to the Company’s significant accounting policies during the three and six months ended June 30, 2023 as compared to those disclosed in Note 2. Summary of Significant Accounting Policies included in our Annual Report on Form 10-K for the year ended December 31, 2022. ​ Recently Adopted Accounting Pronouncement In June 2016, the Financial Accounting Standard Board (“FASB”) issued Accounting Standard Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326) Financial Instruments – Credit Losses (Topic 326): Effective Dates

License and Collaboration Agree

License and Collaboration Agreement	6 Months Ended
	Jun. 30, 2023
License and Collaboration Agreement..
License and Collaboration Agreement
License and Collaboration Agreement	Note 3. License and Collaboration Agreement Agreement Terms On July 27, 2021, the Company entered into an Amended and Restated License and Collaboration Agreement (the “Restated Agreement”) with Janssen Biotech, Inc., a Pennsylvania corporation (“Janssen”), which amended and restated the License and Collaboration Agreement, effective July 13, 2017, by and between the Company and Janssen (the “Original Agreement”), as amended by the first amendment, effective May 7, 2019 (the “First Amendment”). Prior to January 1, 2023, Janssen was a related party to the Company as Johnson & Johnson Innovation - JJDC, Inc. was a significant (greater than 5%) stockholder of the Company, and both companies are subsidiaries of Johnson & Johnson. Upon the effectiveness of the Original Agreement, the Company received a non-refundable, upfront cash payment of $50.0 million from Janssen. Upon the effectiveness of the First Amendment, the Company received a $25.0 million payment from Janssen in 2019. The Company received a $5.0 million payment triggered by the successful nomination of a second-generation oral Interleukin (“IL”)-23 receptor antagonist development compound (“second-generation compound”) during the first quarter of 2020 and received a $7.5 million payment triggered by the completion of data collection activities for the first Phase 1 clinical trial of a second-generation compound during the fourth quarter of 2021. The Company received a $25.0 million milestone payment in connection with the dosing of the third patient in the first Phase 2 clinical trial for a second-generation compound during the second quarter of 2022. The Restated Agreement relates to the development, manufacture and commercialization of oral IL-23 receptor antagonist drug candidates. The candidates nominated for initial development pursuant to the Restated Agreement included PTG-200 (JNJ-67864238), PN-232 (JNJ-75105186) and JNJ-2113 (JNJ-77242113) (formerly PN-235). PTG-200 is an oral IL-23 receptor antagonist that was in Phase 2a development for the treatment of Crohn’s disease (“CD”). During the fourth quarter of 2021, following a pre-specified interim analysis criteria, a portfolio decision was made by Janssen to stop further development of both PTG-200 and PN-232 in favor of advancing JNJ-2113, based on its superior potency and overall pharmacokinetic and pharmacodynamic profile. Janssen is primarily responsible for the conduct of all future trials, including anticipated Phase 2 and Phase 3 trials, and the Company is primarily responsible for the conduct of the second-generation Phase 1 trials. ​ The Restated Agreement enables Janssen to develop collaboration compounds for multiple indications. Under the Restated Agreement, Janssen is required to use commercially reasonable efforts to develop at least one collaboration compound for at least two indications. Upcoming potential development milestones for second-generation compounds include: ● $50.0 million upon the dosing of the third patient in a Phase 3 clinical trial for a second-generation compound for any indication; ● $115.0 million upon a Phase 3 clinical trial for a second-generation compound for any indication meeting its primary clinical endpoint; ● $35.0 million upon the filing of a New Drug Application (“NDA”) for a second-generation compound with the U.S. Food and Drug Administration (the “FDA”); ● $50.0 million upon FDA approval of an NDA for a second-generation compound; ● $10.0 million upon the dosing of the third patient in the first Phase 2 clinical trial for any second-generation compound for a second indication (i.e., an indication different than the indication which triggered the $25.0 million milestone received during the second quarter of 2022 described above); and ● $15.0 million upon the dosing of the third patient in a Phase 3 clinical trial for a second-generation compound for a second indication. Pursuant to the Restated Agreement, the Company remains eligible to receive tiered royalties on net product sales at percentages ranging from six percent to ten percent. The sales milestone payments in the Original Agreement also remain the same in the Restated Agreement. Pursuant to both the Original and Restated Agreements, payments to the Company for research and development services are generally billed and collected as services are performed or assets are delivered, including research activities and Phase 1 and Phase 2 development activities. Janssen bills the Company for its share of the PTG-200 Phase 2a development costs as expenses are incurred by Janssen. Milestone payments are received after the related milestones are achieved. Janssen retains exclusive, worldwide rights to develop and commercialize IL-23 receptor antagonist compounds derived from the research collaboration conducted under the Original Agreement, or Janssen’s further research under the Restated Agreement. Any further research and development will be conducted by Janssen. The Company will have the right to co-detail (for CD and ulcerative colitis indications) up to two of the IL-23 receptor antagonist compounds under the collaboration in the U.S. market. The Restated Agreement remains in effect until the royalty obligations cease following patent and regulatory expiry, unless terminated earlier. Upon a termination of the Restated 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 Restated Agreement contains a single performance obligation for the development license; Phase 1 development services for PTG-200, PN-232 and JNJ-2113 (formerly PN-235); the Company’s services associated with Phase 2a development for PTG-200 in CD; the initial year of second-generation compound research services; and all other such services that the Company may perform at the request of Janssen to support the development of PTG-200 through Phase 2a and PN-232 and JNJ-2113 through Phase 1. Under the Restated Agreement, development services performed by the Company for PTG-200 beyond Phase 2a and PN-232 and JNJ-2113 beyond Phase 1 are no longer required. 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 duration of the Restated Agreement for the identified single initial performance obligation began on the Original Agreement’s effective date of July 13, 2017 and ended upon the completion of Phase 1 clinical trials for PN-232 and JNJ-2113. Final activities related to these trials were completed as of June 30, 2022. The transaction price of the initial performance obligation under the Restated Agreement was $131.7 million as of June 30, 2022, an increase of $0.2 million from the transaction price of $131.5 million as of March 31, 2022. In order to determine the transaction price, the Company evaluated all payments to be received during the duration of the contract, net of development costs reimbursement expected to be payable to Janssen. The transaction price as of June 30, 2022 included $112.5 million of nonrefundable payments received to date, $17.9 million of reimbursement from Janssen for services performed for IL-23 receptor antagonist compound research costs and other services, and variable consideration consisting of $8.2 million of development cost reimbursement from Janssen, partially offset by $6.9 million of net cost reimbursement due to Janssen for services performed. The Company concluded that the variable consideration constraint was appropriately reflected in the estimated transaction price as of June 30, 2022, and that the achievement of future milestones was subject to additional development and/or regulatory uncertainty and therefore it was not probable at June 30, 2022 that a material reversal of such revenues would not occur. Janssen also opted in for certain additional services to be performed by the Company that were outside the initial performance obligation. Revenue for these additional services was recognized as these services were performed. No license and collaboration revenue was recognized for the three and six months ended June 30, 2023 because the Company completed its performance obligation under the collaboration as of June 30, 2022. For the three and six months ended June 30, 2022, the Company recognized license and collaboration revenue of $0.9 million and $26.6 million, respectively. License and collaboration revenue for the three and six months ended June 30, 2022 was primarily related to the transaction price recognized under the Restated Agreement based on proportional performance. 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 Six Months Ended June 30, 2023 Period ​ Additions Deductions Period Contract assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Receivable from collaboration partner ​ $ 10 ​ $ 41 ​ ​ (12) ​ $ 39 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Payable to collaboration partner ​ $ 69 ​ $ 11 ​ ​ (70) ​ $ 10 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ Beginning of ​ ​ ​ ​ ​ End of Six Months Ended June 30, 2022 Period ​ Additions Deductions Period Contract assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Receivable from collaboration partner ​ $ 1,566 ​ $ 25,165 ​ $ (26,688) ​ $ 43 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue ​ $ 1,601 ​ $ 25,757 ​ $ (27,358) ​ $ — Payable to collaboration partner ​ $ 899 ​ $ 30 ​ $ (849) ​ $ 80 ​ During the three and six months ended June 30, 2022, the Company recognized revenue of $0.9 million from amounts included in the deferred revenue contract liability balance at the beginning of each period. None of the costs to obtain or fulfill the contract were capitalized.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2023
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 Level 2— Level 3 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 tables present the fair value of the Company’s financial assets determined using the inputs defined above (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2023 ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 64,578 ​ $ — ​ $ — $ 64,578 Commercial paper ​ — ​ ​ 132,955 ​ — 132,955 Corporate debt securities ​ ​ — ​ ​ 6,408 ​ ​ — ​ ​ 6,408 U.S. Treasury and agency securities ​ ​ — ​ ​ 101,851 ​ ​ — ​ ​ 101,851 Total financial assets ​ $ 64,578 ​ $ 241,214 $ — $ 305,792 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 54,292 ​ $ — ​ $ — $ 54,292 Commercial paper ​ — ​ 110,227 ​ — 110,227 Corporate debt securities ​ — ​ 10,741 — 10,741 U.S. Treasury and agency securities ​ ​ ​ ​ ​ 57,242 ​ ​ — 57,242 Total financial assets ​ $ 54,292 ​ $ 178,210 $ — $ 232,502 ​ The Company’s commercial paper, corporate debt securities, and U.S. Treasury and agency securities, including U.S. Treasury bills, 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. The carrying amount of the Company’s remaining financial assets and liabilities, including cash, receivables and payables, approximates their fair value due to their short-term nature.

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	6 Months Ended
	Jun. 30, 2023
Cash Equivalents and Marketable Securities
Cash Equivalents and Marketable Securities	Note 5. Cash Equivalents and Marketable Securities ​ Cash equivalents and marketable securities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2023 ​ ​ Amortized ​ Gross Unrealized ​ ​ Cost Gains Losses Fair Value Money market funds ​ $ 64,578 ​ $ — ​ $ — ​ $ 64,578 Commercial paper ​ 133,007 ​ ​ — ​ ​ (52) ​ 132,955 Corporate debt securities ​ ​ 6,422 ​ ​ — ​ ​ (14) ​ ​ 6,408 U.S. Treasury and agency securities ​ ​ 101,872 ​ ​ 22 ​ ​ (43) ​ ​ 101,851 Total cash equivalents and marketable securities ​ $ 305,879 ​ $ 22 $ (109) ​ $ 305,792 Classified as: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ ​ ​ ​ ​ ​ ​ $ 227,773 Marketable securities ​ ​ ​ ​ ​ ​ ​ 78,019 Total cash equivalents and marketable securities ​ ​ ​ ​ ​ ​ ​ $ 305,792 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ Amortized ​ Gross Unrealized ​ ​ Cost Gains Losses Fair Value Money market funds ​ $ 54,292 ​ $ — $ — ​ $ 54,292 Commercial paper ​ 110,257 ​ — (30) ​ 110,227 Corporate debt securities ​ 10,756 ​ — (15) ​ 10,741 U.S. Treasury and agency securities ​ ​ 57,251 ​ ​ 27 ​ ​ (36) ​ ​ 57,242 Total cash equivalents and marketable securities ​ $ 232,556 ​ $ 27 $ (81) ​ $ 232,502 Classified as: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ ​ ​ ​ ​ ​ ​ $ 120,891 Marketable securities ​ ​ ​ ​ ​ ​ ​ 111,611 Total cash equivalents and marketable securities ​ ​ ​ ​ ​ ​ ​ $ 232,502 ​ Marketable securities of $78.0 million and $111.6 million held at June 30, 2023 and December 31, 2022, respectively, had contractual maturities of less than one year. The Company does not intend to sell its securities that are in an unrealized loss position, and it is not more likely than not that the Company will be required to sell its securities before recovery of their amortized cost basis, which may be at maturity. There were no material realized gains or realized losses on marketable securities for the periods presented. The Company evaluated securities with unrealized losses to determine whether such losses, if any, are due to credit-related factors and determined that there were no credit-related losses to be recognized as of June 30, 2023.

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2023
Balance Sheet Components
Balance Sheet Components	Note 6. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2023 ​ 2022 Prepaid clinical and research related expenses ​ $ 796 ​ $ 2,746 Prepaid insurance ​ ​ 827 ​ ​ 1,417 Prepaid license ​ ​ 607 ​ ​ 489 Other prepaid expenses ​ 1,260 ​ 1,018 Other receivable ​ ​ 11 ​ ​ 42 Prepaid expenses and other current assets ​ $ 3,501 ​ $ 5,712 ​ Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2023 ​ 2022 Laboratory equipment ​ $ 4,982 ​ $ 4,817 Furniture and computer equipment ​ 1,089 ​ 1,089 Leasehold improvements ​ 913 ​ 913 Total property and equipment ​ 6,984 ​ 6,819 Accumulated depreciation ​ (5,721) ​ (5,254) Property and equipment, net ​ $ 1,263 ​ $ 1,565 ​ ​ Accrued Expenses and Other Payables Accrued expenses and other payables consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2023 ​ 2022 Accrued clinical and research related expenses ​ $ 14,703 ​ $ 19,109 Accrued employee related expenses ​ 3,633 ​ 4,967 Accrued professional service fees ​ ​ 868 ​ ​ 464 Other ​ 165 ​ 415 Total accrued expenses and other payables ​ $ 19,369 ​ $ 24,955 ​

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2023
Stockholders' Equity
Stockholders' Equity	Note 7. Stockholders’ Equity In April 2023, the Company completed an underwritten public offering of 5,000,000 shares of its common stock at a public offering price of $20.00 per share and issued an additional 750,000 shares of common stock at a price of $20.00 per share following the underwriters’ exercise of their option to purchase additional shares. Net proceeds, after deducting underwriting commissions and offering costs paid by the Company, were approximately $107.8 million. ​ In August 2022, the Company entered into an Open Market Sale Agreement SM (the “Sales Agreement”), pursuant to which the Company may offer and sell up to $100.0 million of shares of common stock from time to time in “at-the-market” offerings (the “2022 ATM Facility”). There were no sales of the Company’s common stock under the 2022 ATM Facility during the year ended December 31, 2022. During the three months ended March 31, 2023, the Company sold 1,749,199 shares of its common stock under the 2022 ATM Facility for net proceeds of $24.3 million, after deducting issuance costs. There were no sales of the Company’s common stock under the 2022 ATM Facility during the three months ended June 30, 2023. ​ In November 2019, the Company entered into an Open Market Sale Agreement SM (the “Prior Sales Agreement”), pursuant to which the Company could offer and sell up to $75.0 million of shares of common stock from time to time in “at-the-market” offerings (the “2019 ATM Facility”). During the year ended December 31, 2022, the Company sold 422,367 shares of its common stock under the 2019 ATM Facility for net proceeds of $14.6 million, after deducting issuance costs. The Prior Sales Agreement was terminated in connection with and replaced by the Sales Agreement in August 2022. In August 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 (“ASC 480”)

Equity Plans

Equity Plans	6 Months Ended
	Jun. 30, 2023
Equity Plans
Equity Plans	Note 8. Equity Plans Equity Incentive Plan In July 2016, the Company’s Board of Directors (“the Board”) 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, or a committee appointed by 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 2016 Plan expire no later than ten years from the date of grant. As of June 30, 2023, 841,577 shares of common stock were available for issuance under the 2016 Plan. Inducement Plan In May 2018, the Board approved the Company’s 2018 Inducement Plan (as subsequently amended, the “2018 Inducement Plan”), a non-stockholder approved stock plan, under which the Company awards 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 or the Compensation Committee of the Board (the “Compensation Committee”), 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 June 30, 2023, 575,961 shares of common stock were available for issuance under the 2018 Inducement Plan. Stock Options 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 Value (1) ​ ​ ​ ​ ​ ​ ​ (years) (in millions) Balances at December 31, 2022 6,240,509 $ 19.03 ​ ​ ​ Options granted 2,262,750 ​ ​ 12.61 ​ ​ Options exercised (220,771) ​ ​ 12.27 ​ ​ ​ Options forfeited ​ (157,679) ​ ​ 26.14 ​ ​ ​ ​ ​ Balances at June 30, 2023 8,124,809 $ 17.29 ​ 7.53 ​ $ 92.2 Options exercisable – June 30, 2023 ​ 4,410,899 $ 16.81 ​ 6.33 ​ ​ 51.9 Options vested and expected to vest – June 30, 2023 ​ 8,124,809 ​ $ 17.29 7.53 ​ $ 92.2 (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 June 30, 2023. The calculation excludes options with an exercise price higher than the closing price of the Company’s common stock on June 30, 2023. The estimated weighted-average grant-date fair value of common stock underlying options granted to employees during the six months ended June 30, 2023 was $10.40 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 ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2023 ​ 2022 ​ 2023 ​ 2022 Expected term (in years) 6.08 - 6.08 5.50 - 6.08 ​ 5.27 - 6.08 5.27- 6.08 Expected volatility 106.2% - 107.5% ​ 96.3% - 99.9% ​ 106.2% - 107.5% ​ 96.3% - 99.9% Risk-free interest rate 3.71% - 4.04% ​ 2.71% - 2.93% ​ 3.57% - 4.04% ​ 1.64% - 2.93% Dividend yield — — ​ — — ​ In determining the fair value of the options granted, the Company uses the Black-Scholes option-pricing model and assumptions discussed below. Each of these inputs is subjective and generally requires judgment to determine. Expected Term Expected Volatility Risk-Free Interest Rate Expected Dividend Restricted Stock Units Restricted stock unit (“RSU”) activity under the Company’s equity incentive plans is set forth below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ Number of ​ Grant Date ​ Shares Fair Value Unvested RSUs at December 31, 2022 ​ 637,436 ​ $ 19.29 Granted ​ 396,775 ​ ​ 12.17 Vested ​ (284,321) ​ ​ 14.20 Forfeited ​ (12,901) ​ ​ 16.28 Unvested RSUs at June 30, 2023 ​ 736,989 ​ $ 18.37 ​ Performance Stock Units Performance stock unit (“PSU”) activity under the Company’s equity incentive plans is set forth below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ Number of ​ Grant Date ​ Shares Fair Value Unvested PSUs at December 31, 2022 ​ 199,500 ​ $ 14.59 Granted — ​ ​ — Vested ​ (114,000) ​ ​ 8.76 Forfeited ​ — ​ ​ — Unvested PSUs at June 30, 2023 ​ 85,500 ​ $ 23.57 ​ The terms of the PSUs provide for 100% of shares to be earned based on the achievement of certain pre-determined performance objectives, subject to the participant’s continued employment. The PSUs will vest, if at all, upon certification by the Compensation Committee of the actual achievement of the related performance objectives, subject to specified change of control exceptions. ​ Stock-based compensation expense associated with PSUs is based on the fair value of the Company’s common stock on the grant date, which equals the closing price of the Company’s common stock on the grant date. The Company recognizes compensation expense over the vesting period of the awards that are ultimately expected to vest when the achievement of the related performance objectives becomes probable. ​ During the three and six months ended June 30, 2023, the Compensation Committee certified the actual achievement of performance objectives related to certain PSUs. As a result, recipients earned a total of 114,000 shares of common stock. The total fair market value of PSUs on vest date during the three and six months ended June 30, 2023 was $3.0 million. ​ The total grant date fair value of unvested PSUs outstanding as of June 30, 2023 was $2.0 million. As of June 30, 2023, the achievement of the related performance objectives was deemed not probable and, accordingly, no stock-based compensation for unvested PSUs has been recognized as expense as of June 30, 2023. Employee Stock Purchase Plan ​ The Company’s 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. During the six months ended June 30, 2023, a total of 68,605 shares of common stock were issued under the 2016 ESPP, and 1,486,685 shares of common stock remained available for issuance as of June 30, 2023. Stock-Based Compensation ​ Total stock-based compensation expense was as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2023 2022 2023 2022 Research and development ​ $ 4,809 ​ $ 4,106 ​ $ 9,391 ​ $ 7,432 General and administrative ​ 3,534 ​ 2,699 ​ 6,536 ​ 5,308 Total stock-based compensation expense ​ $ 8,343 ​ $ 6,805 ​ $ 15,927 ​ $ 12,740 ​ As of June 30, 2023, total unrecognized stock-based compensation expense was approximately $60.7 million, which the Company expects to recognize over a weighted-average period of approximately 2.7 years.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2023
Net Loss per Share
Net Loss per Share	Note 9. Net Loss per Share As the Company had net losses for the three and six months ended June 30, 2023 and 2022, all potential weighted average dilutive 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 ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2023 2022 2023 2022 Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (38,460) ​ $ (41,037) ​ $ (72,185) ​ $ (61,967) Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares used to compute net loss per common share, basic and diluted ​ 56,775,742 ​ 49,049,902 ​ 53,691,965 48,902,047 Net loss per share, basic and diluted ​ $ (0.68) ​ $ (0.84) ​ $ (1.34) ​ $ (1.27) ​ 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: ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ 2023 2022 Options to purchase common stock ​ 8,124,809 6,825,121 Common stock warrants ​ 2,750,000 ​ 2,750,000 Restricted stock units ​ 736,989 ​ 766,090 Performance stock units ​ 85,500 ​ 219,000 ESPP shares ​ 24,998 ​ 19,103 Total 11,722,296 10,579,314 ​

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2023
Summary of Significant Accounting Policies
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“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 condensed consolidated balance sheet as of June 30, 2023 has been derived from the Company’s unaudited 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 presentation of the Company’s condensed consolidated financial statements. The results of operations for the three and six months ended June 30, 2023 are not necessarily indicative of the results to be expected for the year ending December 31, 2023 or for any future period. Effective January 1, 2023, the financial statements of Protagonist Australia use the U.S. dollar as the functional currency due to the expected nature of the ongoing operations of this subsidiary. The cumulative translation adjustment as of January 1, 2023 related to this subsidiary was not material. Prior to January 1, 2023, the financial statements of Protagonist Australia used the Australian dollar as the functional currency since the majority of expense transactions occurred in such currency. Foreign currency translation gains and losses are reported as a component of stockholders’ equity in accumulated other comprehensive loss on the condensed consolidated balance sheets. The accompanying unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto for the year ended December 31, 2022 included in the Company’s Annual Report on Form 10-K, filed with the SEC on March 15, 2023.
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 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, marketable securities and leases. Estimates related to revenue recognition include actual costs incurred versus total estimated costs of the Company’s deliverables to determine percentage of completion in addition to the application and estimates of potential revenue 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 could differ materially from these estimates. There has been uncertainty and disruption in the global economy and financial markets due to a number of factors, including the COVID-19 pandemic, geopolitical instability, inflationary pressures and domestic and global monetary and fiscal policy. The Company has taken into consideration any known impacts in its accounting estimates to date and is not aware of any additional specific events or circumstances that would require any additional updates to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of the issuance of this report. These estimates may change as new events occur and additional information is obtained. Actual results could differ materially from these estimates under different assumptions or conditions.
Cash as Reported in 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): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ 2023 2022 Cash and cash equivalents ​ $ 235,382 ​ $ 120,237 Restricted cash - noncurrent ​ 225 ​ 225 Total cash reported on condensed consolidated statements of cash flows ​ $ 235,607 ​ $ 120,462
Investment Impairment	Investment Impairment ​ As of each reporting date, the Company assesses each of its investments in available-for-sale debt securities whose fair value is below its cost basis to determine if the investment’s impairment is due to credit-related factors or noncredit-related factors. Factors considered in determining whether an impairment is credit-related include the extent to which the investment’s fair value is less than its cost basis, declines in published credit ratings, issuer default on interest or principal payments, and declines in the financial condition and near-term prospects of the issuer. Credit-related impairments on available-for-sale debt securities are recognized as an allowance for credit losses with a corresponding adjustment to other income (expense), net. The portion of the impairment that is not credit-related is recorded as a reduction of other comprehensive income (loss), net of applicable taxes. ​ The Company has elected to exclude accrued interest from both the fair value and the amortized cost basis of the available-for-sale debt securities for the purposes of identifying and measuring an impairment. The Company writes off accrued interest as a reduction of interest income when an issuer has defaulted on interest payments due on a security.
Recently Adopted Accounting Pronouncement	Recently Adopted Accounting Pronouncement In June 2016, the Financial Accounting Standard Board (“FASB”) issued Accounting Standard Update (“ASU”) 2016-13, Financial Instruments - Credit Losses (Topic 326) Financial Instruments – Credit Losses (Topic 326): Effective Dates

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2023
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): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ 2023 2022 Cash and cash equivalents ​ $ 235,382 ​ $ 120,237 Restricted cash - noncurrent ​ 225 ​ 225 Total cash reported on condensed consolidated statements of cash flows ​ $ 235,607 ​ $ 120,462

License and Collaboration Agr_2

License and Collaboration Agreement (Tables)	6 Months Ended
	Jun. 30, 2023
License and Collaboration Agreement.
Schedule of changes in contract assets and liabilities	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ Balance at ​ ​ Beginning of ​ ​ ​ ​ ​ End of Six Months Ended June 30, 2023 Period ​ Additions Deductions Period Contract assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Receivable from collaboration partner ​ $ 10 ​ $ 41 ​ ​ (12) ​ $ 39 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Payable to collaboration partner ​ $ 69 ​ $ 11 ​ ​ (70) ​ $ 10 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ ​ ​ ​ ​ ​ Balance at ​ ​ Beginning of ​ ​ ​ ​ ​ End of Six Months Ended June 30, 2022 Period ​ Additions Deductions Period Contract assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Receivable from collaboration partner ​ $ 1,566 ​ $ 25,165 ​ $ (26,688) ​ $ 43 Contract liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Deferred revenue ​ $ 1,601 ​ $ 25,757 ​ $ (27,358) ​ $ — Payable to collaboration partner ​ $ 899 ​ $ 30 ​ $ (849) ​ $ 80

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2023
Fair Value Measurements
Schedule of fair value of financial assets	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2023 ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 64,578 ​ $ — ​ $ — $ 64,578 Commercial paper ​ — ​ ​ 132,955 ​ — 132,955 Corporate debt securities ​ ​ — ​ ​ 6,408 ​ ​ — ​ ​ 6,408 U.S. Treasury and agency securities ​ ​ — ​ ​ 101,851 ​ ​ — ​ ​ 101,851 Total financial assets ​ $ 64,578 ​ $ 241,214 $ — $ 305,792 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ Level 1 Level 2 Level 3 Total Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Money market funds ​ $ 54,292 ​ $ — ​ $ — $ 54,292 Commercial paper ​ — ​ 110,227 ​ — 110,227 Corporate debt securities ​ — ​ 10,741 — 10,741 U.S. Treasury and agency securities ​ ​ ​ ​ ​ 57,242 ​ ​ — 57,242 Total financial assets ​ $ 54,292 ​ $ 178,210 $ — $ 232,502

Cash Equivalents and Marketab_2

Cash Equivalents and Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2023
Cash Equivalents and Marketable Securities
Schedule of cash equivalents and marketable securities	Cash equivalents and marketable securities consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2023 ​ ​ Amortized ​ Gross Unrealized ​ ​ Cost Gains Losses Fair Value Money market funds ​ $ 64,578 ​ $ — ​ $ — ​ $ 64,578 Commercial paper ​ 133,007 ​ ​ — ​ ​ (52) ​ 132,955 Corporate debt securities ​ ​ 6,422 ​ ​ — ​ ​ (14) ​ ​ 6,408 U.S. Treasury and agency securities ​ ​ 101,872 ​ ​ 22 ​ ​ (43) ​ ​ 101,851 Total cash equivalents and marketable securities ​ $ 305,879 ​ $ 22 $ (109) ​ $ 305,792 Classified as: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ ​ ​ ​ ​ ​ ​ $ 227,773 Marketable securities ​ ​ ​ ​ ​ ​ ​ 78,019 Total cash equivalents and marketable securities ​ ​ ​ ​ ​ ​ ​ $ 305,792 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2022 ​ ​ Amortized ​ Gross Unrealized ​ ​ Cost Gains Losses Fair Value Money market funds ​ $ 54,292 ​ $ — $ — ​ $ 54,292 Commercial paper ​ 110,257 ​ — (30) ​ 110,227 Corporate debt securities ​ 10,756 ​ — (15) ​ 10,741 U.S. Treasury and agency securities ​ ​ 57,251 ​ ​ 27 ​ ​ (36) ​ ​ 57,242 Total cash equivalents and marketable securities ​ $ 232,556 ​ $ 27 $ (81) ​ $ 232,502 Classified as: ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents ​ ​ ​ ​ ​ ​ ​ $ 120,891 Marketable securities ​ ​ ​ ​ ​ ​ ​ 111,611 Total cash equivalents and marketable securities ​ ​ ​ ​ ​ ​ ​ $ 232,502

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2023
Balance Sheet Components
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2023 ​ 2022 Prepaid clinical and research related expenses ​ $ 796 ​ $ 2,746 Prepaid insurance ​ ​ 827 ​ ​ 1,417 Prepaid license ​ ​ 607 ​ ​ 489 Other prepaid expenses ​ 1,260 ​ 1,018 Other receivable ​ ​ 11 ​ ​ 42 Prepaid expenses and other current assets ​ $ 3,501 ​ $ 5,712
Summary of Property and Equipment Net	Property and equipment, net consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2023 ​ 2022 Laboratory equipment ​ $ 4,982 ​ $ 4,817 Furniture and computer equipment ​ 1,089 ​ 1,089 Leasehold improvements ​ 913 ​ 913 Total property and equipment ​ 6,984 ​ 6,819 Accumulated depreciation ​ (5,721) ​ (5,254) Property and equipment, net ​ $ 1,263 ​ $ 1,565
Schedule of Accrued Expenses and Other Payables	Accrued expenses and other payables consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ 2023 ​ 2022 Accrued clinical and research related expenses ​ $ 14,703 ​ $ 19,109 Accrued employee related expenses ​ 3,633 ​ 4,967 Accrued professional service fees ​ ​ 868 ​ ​ 464 Other ​ 165 ​ 415 Total accrued expenses and other payables ​ $ 19,369 ​ $ 24,955

Equity Plans (Tables)

Equity Plans (Tables)	6 Months Ended
	Jun. 30, 2023
Schedule of activity under equity incentive plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ Weighted- ​ ​ ​ ​ ​ ​ Average ​ Average ​ ​ ​ ​ ​ ​ Exercise ​ Remaining ​ Aggregate ​ ​ Options ​ Price Per ​ Contractual ​ Intrinsic ​ Outstanding Share Life Value (1) ​ ​ ​ ​ ​ ​ ​ (years) (in millions) Balances at December 31, 2022 6,240,509 $ 19.03 ​ ​ ​ Options granted 2,262,750 ​ ​ 12.61 ​ ​ Options exercised (220,771) ​ ​ 12.27 ​ ​ ​ Options forfeited ​ (157,679) ​ ​ 26.14 ​ ​ ​ ​ ​ Balances at June 30, 2023 8,124,809 $ 17.29 ​ 7.53 ​ $ 92.2 Options exercisable – June 30, 2023 ​ 4,410,899 $ 16.81 ​ 6.33 ​ ​ 51.9 Options vested and expected to vest – June 30, 2023 ​ 8,124,809 ​ $ 17.29 7.53 ​ $ 92.2 (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 June 30, 2023. The calculation excludes options with an exercise price higher than the closing price of the Company’s common stock on June 30, 2023.
Schedule of stock-based compensation expense	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2023 2022 2023 2022 Research and development ​ $ 4,809 ​ $ 4,106 ​ $ 9,391 ​ $ 7,432 General and administrative ​ 3,534 ​ 2,699 ​ 6,536 ​ 5,308 Total stock-based compensation expense ​ $ 8,343 ​ $ 6,805 ​ $ 15,927 ​ $ 12,740
Options to Purchase Common Stock
Black-Scholes option-pricing model assumptions	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2023 ​ 2022 ​ 2023 ​ 2022 Expected term (in years) 6.08 - 6.08 5.50 - 6.08 ​ 5.27 - 6.08 5.27- 6.08 Expected volatility 106.2% - 107.5% ​ 96.3% - 99.9% ​ 106.2% - 107.5% ​ 96.3% - 99.9% Risk-free interest rate 3.71% - 4.04% ​ 2.71% - 2.93% ​ 3.57% - 4.04% ​ 1.64% - 2.93% Dividend yield — — ​ — —
Restricted stock units
Schedule of activity under equity incentive plans	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ Number of ​ Grant Date ​ Shares Fair Value Unvested RSUs at December 31, 2022 ​ 637,436 ​ $ 19.29 Granted ​ 396,775 ​ ​ 12.17 Vested ​ (284,321) ​ ​ 14.20 Forfeited ​ (12,901) ​ ​ 16.28 Unvested RSUs at June 30, 2023 ​ 736,989 ​ $ 18.37
Performance Stock Units
Schedule of performance stock unit activity	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted ​ ​ ​ ​ Average ​ ​ Number of ​ Grant Date ​ Shares Fair Value Unvested PSUs at December 31, 2022 ​ 199,500 ​ $ 14.59 Granted — ​ ​ — Vested ​ (114,000) ​ ​ 8.76 Forfeited ​ — ​ ​ — Unvested PSUs at June 30, 2023 ​ 85,500 ​ $ 23.57

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2023
Net Loss per Share
Schedule of computation of the basic and diluted net loss per share attributable to common stockholders	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ 2023 2022 2023 2022 Numerator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net loss ​ $ (38,460) ​ $ (41,037) ​ $ (72,185) ​ $ (61,967) Denominator: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-average shares used to compute net loss per common share, basic and diluted ​ 56,775,742 ​ 49,049,902 ​ 53,691,965 48,902,047 Net loss per share, basic and diluted ​ $ (0.68) ​ $ (0.84) ​ $ (1.34) ​ $ (1.27)
Schedule of potentially dilutive securities excluded from diluted net loss per share calculations	​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ 2023 2022 Options to purchase common stock ​ 8,124,809 6,825,121 Common stock warrants ​ 2,750,000 ​ 2,750,000 Restricted stock units ​ 736,989 ​ 766,090 Performance stock units ​ 85,500 ​ 219,000 ESPP shares ​ 24,998 ​ 19,103 Total 11,722,296 10,579,314

Organization and Description _2

Organization and Description of Business - Liquidity (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2023 USD ($) segment	Dec. 31, 2022 USD ($)
Organization and Description of Business
Number of operating segments | segment	1
Net losses from operations since inception
Cash, cash equivalents and marketable securities	$ 313,400
Accumulated deficit	$ (608,940)	$ (536,755)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022	Jun. 30, 2022	Dec. 31, 2021
Aggregate amounts of cash and cash equivalents and the restricted cash
Cash and cash equivalents	$ 235,382	$ 125,744	$ 120,237
Restricted cash - noncurrent	225	225	225
Total cash reported on condensed consolidated statements of cash flows	$ 235,607	$ 125,969	$ 120,462	$ 123,890

License and Collaboration Agr_3

License and Collaboration Agreement - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jul. 27, 2021	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2020	May 07, 2019	Jul. 13, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and collaboration revenue		$ 0	$ 859	$ 0	$ 26,581
Revenue recognized			900		900
Janssen | Services performed for IL-23 receptor antagonist compound research costs and other services
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement for services performed			17,900		17,900
Janssen | License and Collaboration Agreement | Three phase 1 studies of second-generation compounds
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible amount received							$ 7,500
Janssen | License and Collaboration Agreement | 3rd patient in the first Phase 2 clinical trial for any second-generation compound for a second indication
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible amount received			25,000		25,000
Janssen | Original Agreement | Upfront cash payment
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment										$ 50,000
Janssen | Restated Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Contract modification, increase (decrease) in adjustment to revenue			200
Upfront payment			112,500		112,500
Development cost payable			6,900		6,900
Reimbursement for services performed			8,200		8,200
Final transaction price			$ 131,700		$ 131,700	$ 131,500
Janssen | Restated Agreement | Second-generation Oral Interleukin ("IL")-23 Receptor Antagonist Development Compound
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible amount received								$ 5,000
Janssen | Restated Agreement | Minimum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalties on net product sales	6%
Janssen | Restated Agreement | Maximum
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalties on net product sales	10%
Janssen | Restated Agreement | License and Collaboration Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Eligible amount received									$ 25,000
Janssen | Restated Agreement | License and Collaboration Agreement | Dosing of the 3rd patient in a Phase 3 clinical trial for a second-generation compound for any indication
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upcoming potential development milestones		50,000		50,000
Janssen | Restated Agreement | License and Collaboration Agreement | Phase 3 clinical trial for a second-generation compound for any indication
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upcoming potential development milestones		115,000		115,000
Janssen | Restated Agreement | License and Collaboration Agreement | Filing of New Drug Application ("NDA") for second-generation compound with the U.S. Food and Drug Administration
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upcoming potential development milestones		35,000		35,000
Janssen | Restated Agreement | License and Collaboration Agreement | FDA approval of NDA for second-generation compound
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upcoming potential development milestones		50,000		50,000
Janssen | Restated Agreement | License and Collaboration Agreement | Phase 2 studies for second-generation products
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upcoming potential development milestones		25,000		25,000
Janssen | Restated Agreement | License and Collaboration Agreement | 3rd patient in the first Phase 2 clinical trial for any second-generation compound for a second indication
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upcoming potential development milestones		10,000		10,000
Janssen | Restated Agreement | License and Collaboration Agreement | Dosing Of Third Patient In Phase 3 Clinical Trial For Second Generation Compound For A Second Indication [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upcoming potential development milestones		$ 15,000		$ 15,000

License and Collaboration Agr_4

License and Collaboration Agreement - Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Payable to collaboration partner - related party
Balance at Beginning of Period	$ 69
Balance at End of Period	10
License and Collaboration Agreement
Receivable from collaboration partner - related party
Balance at Beginning of Period	10	$ 1,566
Additions	41	25,165
Deductions	(12)	(26,688)
Balance at End of Period	39	43
Deferred revenue - related party
Balance at Beginning of Period		1,601
Additions		25,757
Deductions		(27,358)
Payable to collaboration partner - related party
Balance at Beginning of Period	69	899
Additions	11	30
Deductions	(70)	(849)
Balance at End of Period	$ 10	$ 80

Fair Value Measurements (Detail

Fair Value Measurements (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 305,792	$ 232,502
Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	64,578	54,292
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	132,955	110,227
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	6,408	10,741
U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	101,851	57,242
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	64,578	54,292
Level 1 [Member] | Money Market Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	64,578	54,292
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	241,214	178,210
Level 2 [Member] | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	132,955	110,227
Level 2 [Member] | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	6,408	10,741
Level 2 [Member] | U.S. Treasury and agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total financial assets	$ 101,851	$ 57,242

Cash Equivalents and Marketab_3

Cash Equivalents and Marketable Securities - Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Cash Equivalents and Marketable Securities
Total cash equivalents and marketable securities, Amortized Cost	$ 305,879	$ 232,556
Total cash equivalents and marketable securities, Gross Unrealized Gains	22	27
Total cash equivalents and marketable securities, Gross Unrealized Losses	(109)	(81)
Total cash equivalents and marketable securities, Fair Value	305,792	232,502
Corporate debt securities
Cash Equivalents and Marketable Securities
Total cash equivalents and marketable securities, Amortized Cost	6,422	10,756
Total cash equivalents and marketable securities, Gross Unrealized Losses	(14)	(15)
Total cash equivalents and marketable securities, Fair Value	6,408	10,741
U.S. Treasury and agency securities
Cash Equivalents and Marketable Securities
Total cash equivalents and marketable securities, Amortized Cost	101,872	57,251
Total cash equivalents and marketable securities, Gross Unrealized Gains	22	27
Total cash equivalents and marketable securities, Gross Unrealized Losses	(43)	(36)
Total cash equivalents and marketable securities, Fair Value	101,851	57,242
Money Market Funds
Cash Equivalents and Marketable Securities
Total cash equivalents and marketable securities, Amortized Cost	64,578	54,292
Total cash equivalents and marketable securities, Fair Value	64,578	54,292
Commercial Paper
Cash Equivalents and Marketable Securities
Total cash equivalents and marketable securities, Amortized Cost	133,007	110,257
Total cash equivalents and marketable securities, Gross Unrealized Losses	(52)	(30)
Total cash equivalents and marketable securities, Fair Value	$ 132,955	$ 110,227

Cash Equivalents and Marketab_4

Cash Equivalents and Marketable Securities - Classification of Cash Equivalents and Marketable Securities (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Classified as:
Cash equivalents	$ 227,773,000	$ 120,891,000
Marketable securities - current	78,019,000	111,611,000
Total cash equivalents and marketable securities	$ 305,792,000	$ 232,502,000
Contractual maturities
Maximum period of current contractual maturities	1 year	1 year
Realized Gain (loss)	$ 0	$ 0
Credit-related losses to be recognized	$ 0

Balance Sheet Components - Prep

Balance Sheet Components - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Prepaid Expense and Other Assets, Current [Abstract]
Prepaid clinical and research related expenses	$ 796	$ 2,746
Prepaid insurance	827	1,417
Prepaid licenses	607	489
Other prepaid expenses	1,260	1,018
Other receivable	11	42
Prepaid expenses and other current assets	$ 3,501	$ 5,712

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Property and Equipment
Total property and equipment	$ 6,984	$ 6,819
Accumulated depreciation	(5,721)	(5,254)
Property and equipment, net	1,263	1,565
Laboratory equipment
Property and Equipment
Total property and equipment	4,982	4,817
Furniture and computer equipment
Property and Equipment
Total property and equipment	1,089	1,089
Leasehold improvements
Property and Equipment
Total property and equipment	$ 913	$ 913

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Expenses and Other Payables (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Accrued Expenses and Other Payables
Accrued clinical and research related expenses	$ 14,703	$ 19,109
Accrued employee related expenses	3,633	4,967
Accrued professional service fees	868	464
Other	165	415
Total accrued expenses and other payables	$ 19,369	$ 24,955

Stockholders' Equity (Details)

Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended					3 Months Ended		6 Months Ended	12 Months Ended
	Aug. 08, 2018	Apr. 30, 2023	Aug. 31, 2022	Jan. 31, 2022	Nov. 30, 2019	Aug. 31, 2018	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Stock transactions
Common stock sold, price per share		$ 20
Common stock issued (in shares)		5,000,000
Proceeds from public offering of common stock, net of issuance costs		$ 107,800							$ 107,868
2019 Sales Agreement
Stock transactions
Common stock issued (in shares)				422,367
Maximum aggregate offering price					$ 75,000
Proceeds from public offering of common stock, net of issuance costs				$ 14,600
2022 Sales Agreement
Stock transactions
Common stock issued (in shares)							0	1,749,199		0
Maximum aggregate offering price			$ 100,000
Aggregate net proceeds								$ 24,300
Over-Allotment Option
Stock transactions
Common stock sold, price per share		$ 20
Common stock issued (in shares)		750,000
Common Stock | Private Placement
Stock transactions
Number of warrants exercised							0		0
Investors | Private Placement
Stock transactions
Aggregate shares of common stock sold						2,750,000
Common stock sold, price per share						$ 8
Net proceeds from sale of common stock						$ 21,700
Warrants issued to purchase common stock, number of shares	2,750,000
Warrants exercisable date	Aug. 08, 2023
$10.00 per share | Investors | Private Placement
Stock transactions
Warrants to purchase common stock (in shares)	1,375,000
Exercise Price (per share)	$ 10
$15.00 per share | Investors | Private Placement
Stock transactions
Warrants to purchase common stock (in shares)	1,375,000
Exercise Price (per share)	$ 15

Equity Plans - Narrative (Detai

Equity Plans - Narrative (Details) - shares	1 Months Ended		6 Months Ended
	May 31, 2018	Jul. 31, 2016	Jun. 30, 2023
Equity Plans
Dividend yield			0%
2016 Equity Incentive Plan
Equity Plans
Expiration period		10 years
Number of shares available for issuance			841,577
2018 Inducement Plan
Equity Plans
Expiration period	10 years
Number of shares available for issuance			575,961

Equity Plans - Stock Option Act

Equity Plans - Stock Option Activity (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($) $ / shares shares
Options Outstanding
Options Outstanding, Beginning balance | shares	6,240,509
Options Outstanding, Options granted | shares	2,262,750
Options Outstanding, Options exercised | shares	(220,771)
Options Outstanding, Options forfeited | shares	(157,679)
Options Outstanding, Ending balance | shares	8,124,809
Options Outstanding, Options exercisable | shares	4,410,899
Options Outstanding, Options vested and expected to vest | shares	8,124,809
Weighted-Average Exercise Price Per Share
Weighted-Average Exercise Price Per Share, Beginning balance	$ 19.03
Weighted-Average Exercise Price Per Share, Options granted	12.61
Weighted-Average Exercise Price Per Share, Options exercised	12.27
Weighted-Average Exercise Price Per Share, Options forfeited	26.14
Weighted-Average Exercise Price Per Share, Ending balance	17.29
Weighted-Average Exercise Price Per Share, Options exercisable	16.81
Weighted-Average Exercise Price Per Share, Options vested and expected to vest	$ 17.29
Weighted-Average Remaining Contractual Life (years)
Weighted-Average Remaining Contractual Life (years)	7 years 6 months 10 days
Weighted-Average Remaining Contractual Life (years), Options exercisable	6 years 3 months 29 days
Weighted-Average Remaining Contractual Life (years), Options vested and expected to vest	7 years 6 months 10 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value, Options Outstanding | $	$ 92.2
Aggregate Intrinsic Value, Options exercisable | $	51.9
Aggregate Intrinsic Value, Options vested and expected to vest | $	$ 92.2
Options, weighted-average grant-date fair value	$ 10.40

Equity Plans - Stock Options Va

Equity Plans - Stock Options Valuation Assumptions (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Equity Plans
Dividend yield			0%
Options to Purchase Common Stock
Equity Plans
Expected volatility, Minimum	106.20%	96.30%	106.20%	96.30%
Expected volatility, Maximum	107.50%	99.90%	107.50%	99.90%
Risk-free interest rate, Minimum	3.71%	2.71%	3.57%	1.64%
Risk-free interest rate, Maximum	4.04%	2.93%	4.04%	2.93%
Expected Volatility, Percentage Of Mix Allocated To Peer Companies					25%
Expected Volatility, Percentage Of Mix Allocated To Entity Stock Price					75%
Options to Purchase Common Stock | Minimum
Equity Plans
Expected term (in years)	6 years 29 days	5 years 6 months	5 years 3 months 7 days	5 years 3 months 7 days
Options to Purchase Common Stock | Maximum
Equity Plans
Expected term (in years)	6 years 29 days	6 years 29 days	6 years 29 days	6 years 29 days

Equity Plans - Restricted and P

Equity Plans - Restricted and Performance Stock Units - (Details) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($) $ / shares shares
Restricted stock units
Number of Shares
Number of shares, Unvested, Beginning balance | shares	637,436
Number of shares, Granted | shares	396,775
Number of shares, Vested | shares	(284,321)
Number of Shares, Forfeited | shares	(12,901)
Number of shares, Unvested, Ending balance | shares	736,989
Weighted-Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value, Unvested, Beginning balance | $ / shares	$ 19.29
Weighted-Average Grant Date Fair Value, Granted | $ / shares	12.17
Weighted-Average Grant Date Fair Value, Vested | $ / shares	14.20
Weighted-Average Grant Date Fair Value, Forfeited | $ / shares	16.28
Weighted-Average Grant Date Fair Value, Unvested, Ending balance | $ / shares	$ 18.37
Performance Stock Units
Number of Shares
Number of shares, Unvested, Beginning balance | shares	199,500
Number of shares, Vested | shares	(114,000)
Number of shares, Unvested, Ending balance | shares	85,500
Weighted-Average Grant Date Fair Value
Weighted-Average Grant Date Fair Value, Unvested, Beginning balance | $ / shares	$ 14.59
Weighted-Average Grant Date Fair Value, Vested | $ / shares	8.76
Weighted-Average Grant Date Fair Value, Unvested, Ending balance | $ / shares	$ 23.57
Aggregate fair value of restricted stock units that vested | $	$ 2

Equity Plans - Performance Stoc

Equity Plans - Performance Stock Units (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Equity Plans
Stock-based compensation			$ 15,927,000	$ 12,740,000
Common Stock
Equity Plans
Number of shares issued	329,486	131,829	687,697	430,960
Performance Stock Units
Equity Plans
Vesting percentage of requisite service period			100%		100%
Stock-based compensation			$ 0
Fair value of units vested			2,000,000
Performance Stock Units | Common Stock
Equity Plans
Fair value of units vested	$ 3,000,000		$ 3,000,000
Number of shares issued			114,000

Equity Plans - Employee Stock P

Equity Plans - Employee Stock Purchase Plan 2016 ESPP (Details)	6 Months Ended
	Jun. 30, 2023 shares
Equity Plans
Dividend yield	0%
2016 Employee Stock Purchase Plan
Equity Plans
Maximum payroll deduction for share purchases (as a percent)	15%
Purchase price of stock (as a percent)	85%
Shares issued in period	68,605
Number of shares available for issuance	1,486,685

Equity Plans - Stock-based Comp

Equity Plans - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 8,343	$ 6,805	$ 15,927	$ 12,740
Total unrecognized stock-based compensation costs related to stock options	60,700		$ 60,700
Period of unrecognized stock-based compensation costs to be recognized			2 years 8 months 12 days
Research and Development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	4,809	4,106	$ 9,391	7,432
General and Administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 3,534	$ 2,699	$ 6,536	$ 5,308

Net Loss per Share - Computatio

Net Loss per Share - Computation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Numerator:
Net loss	$ (38,460)	$ (41,037)	$ (72,185)	$ (61,967)
Denominator:
Weighted-average shares used to compute net loss per common share, Basic	56,775,742	49,049,902	53,691,965	48,902,047
Weighted-average shares used to compute net loss per common share, Diluted	56,775,742	49,049,902	53,691,965	48,902,047
Net loss per share, basic	$ (0.68)	$ (0.84)	$ (1.34)	$ (1.27)
Net loss per share, diluted	$ (0.68)	$ (0.84)	$ (1.34)	$ (1.27)

Net Loss per Share - Antidiluti

Net Loss per Share - Antidilutive Securities (Details) - shares	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	11,722,296	10,579,314
Options to Purchase Common Stock
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	8,124,809	6,825,121
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)	736,989	766,090
Performance Stock Units
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	85,500	219,000
ESPP shares
Potentially dilutive securities have been excluded from diluted net loss per share calculations
Anti-dilutive securities (in shares)	24,998	19,103