89bio (ETNB) 10-Q 12 Nov 21 2021 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Nov. 08, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Entity Registrant Name	89bio, Inc.
Entity Central Index Key	0001785173
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		20,282,212
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Title of 12(b) Security	Common stock, par value $0.001 per share
Trading Symbol	ETNB
Security Exchange Name	NASDAQ
Entity File Number	001-39122
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-4946844
Entity Address, Address Line One	142 Sansome Street
Entity Address, Address Line Two	Second Floor
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94104
City Area Code	415
Local Phone Number	500-4614
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 39,695	$ 98,183
Restricted cash	25	25
Short-term available-for-sale securities	117,638	106,446
Prepaid and other current assets	9,678	5,548
Total current assets	167,036	210,202
Property and equipment, net	146	166
Other assets	874	706
Total assets	168,056	211,074
Current liabilities:
Accounts payable	12,526	2,065
Accrued expenses	7,319	6,048
Total current liabilities	19,845	8,113
Term loan, non-current, net	1,441
Total liabilities	21,286	8,113
Commitments and contingencies (Note 5)
Stockholders’ equity:
Common stock	20	20
Additional paid-in capital	333,673	326,046
Accumulated other comprehensive income (loss)	6	(10)
Accumulated deficit	(186,929)	(123,095)
Total stockholders’ equity	146,770	202,961
Total liabilities and stockholders’ equity	$ 168,056	$ 211,074

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Operating expenses:
Research and development	$ 23,590	$ 11,208	$ 49,351	$ 27,429
General and administrative	4,622	3,225	14,151	9,379
Total operating expenses	28,212	14,433	63,502	36,808
Loss from operations	(28,212)	(14,433)	(63,502)	(36,808)
Other expenses, net	(117)	(146)	(332)	(87)
Net loss before tax	(28,329)	(14,579)	(63,834)	(36,895)
Income tax expense		(24)		(23)
Net loss	(28,329)	(14,603)	(63,834)	(36,918)
Other comprehensive income (loss):
Unrealized (loss) gain on available-for-sale securities	(4)	7	5	7
Foreign currency translation adjustments	6	(10)	11	(10)
Total other comprehensive income (loss)	2	(3)	16	(3)
Comprehensive loss	$ (28,327)	$ (14,606)	$ (63,818)	$ (36,921)
Net loss per share, basic and diluted	$ (1.41)	$ (0.86)	$ (3.18)	$ (2.49)
Weighted-average shares used to compute net loss per share, basic and diluted	20,092,094	16,884,244	20,043,301	14,809,131

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2019	$ 89,944	$ 14	$ 163,526	$ 0	$ (73,596)
Beginning balance, shares at Dec. 31, 2019		13,788,982
Issuance of common stock upon exercise of stock options	9		9	0
Issuance of common stock upon exercise of stock options, shares		4,876
Stock-based compensation	493		493	0
Net loss	(10,544)			0	(10,544)
Ending balance at Mar. 31, 2020	79,902	$ 14	164,028	0	(84,140)
Ending balance, shares at Mar. 31, 2020		13,793,858
Beginning balance at Dec. 31, 2019	89,944	$ 14	163,526	0	(73,596)
Beginning balance, shares at Dec. 31, 2019		13,788,982
Issuance of common stock warrant in connection with term loan facility	634
Net loss	(36,918)
Other comprehensive income	(3)
Ending balance at Sep. 30, 2020	214,004	$ 20	324,501	(3)	(110,514)
Ending balance, shares at Sep. 30, 2020		19,878,852
Beginning balance at Mar. 31, 2020	79,902	$ 14	164,028	0	(84,140)
Beginning balance, shares at Mar. 31, 2020		13,793,858
Issuance of common stock upon exercise of stock options	21		21	0
Issuance of common stock upon exercise of stock options, shares		6,919
Issuance of common stock upon ESPP Purchase	75		75	0
Issuance of common stock upon ESPP purchase, shares		4,427
Issuance of common stock warrant in connection with term loan facility	634		634	0
Stock-based compensation	910		910	0
Net loss	(11,771)			0	(11,771)
Ending balance at Jun. 30, 2020	69,771	$ 14	165,668	0	(95,911)
Ending balance, shares at Jun. 30, 2020		13,805,204
Issuance of common stock	157,680	$ 6	157,674	0
Issuance of common stock, shares		6,072,040
Issuance of common stock upon exercise of stock options	5		5	0
Issuance of common stock upon exercise of stock options, shares		1,608
Stock-based compensation	1,154		1,154	0
Net loss	(14,603)			0	(14,603)
Other comprehensive income	(3)			(3)
Ending balance at Sep. 30, 2020	214,004	$ 20	324,501	(3)	(110,514)
Ending balance, shares at Sep. 30, 2020		19,878,852
Beginning balance at Dec. 31, 2020	202,961	$ 20	326,046	(10)	(123,095)
Beginning balance, shares at Dec. 31, 2020		19,931,660
Issuance of common stock upon exercise of stock options	216		216	0
Issuance of common stock upon exercise of stock options, shares		103,170
Stock-based compensation	1,793		1,793	0
Net loss	(14,782)			0	(14,782)
Other comprehensive income	7			7
Ending balance at Mar. 31, 2021	190,195	$ 20	328,055	(3)	(137,877)
Ending balance, shares at Mar. 31, 2021		20,034,830
Beginning balance at Dec. 31, 2020	$ 202,961	$ 20	326,046	(10)	(123,095)
Beginning balance, shares at Dec. 31, 2020		19,931,660
Issuance of common stock upon exercise of stock options, shares	167,286
Issuance of common stock warrant in connection with term loan facility	$ 574
Net loss	(63,834)
Other comprehensive income	16
Ending balance at Sep. 30, 2021	146,770	$ 20	333,673	6	(186,929)
Ending balance, shares at Sep. 30, 2021		20,104,153
Beginning balance at Mar. 31, 2021	190,195	$ 20	328,055	(3)	(137,877)
Beginning balance, shares at Mar. 31, 2021		20,034,830
Issuance of common stock upon exercise of stock options	152		152	0
Issuance of common stock upon exercise of stock options, shares		40,628
Issuance of common stock upon ESPP Purchase	83		83	0
Issuance of common stock upon ESPP purchase, shares		5,207
Issuance of common stock warrant in connection with term loan facility	574		574	0
Stock-based compensation	2,417		2,417	0
Net loss	(20,723)			0	(20,723)
Other comprehensive income	7			7
Ending balance at Jun. 30, 2021	172,705	$ 20	331,281	4	(158,600)
Ending balance, shares at Jun. 30, 2021		20,080,665
Issuance of common stock upon exercise of stock options	78		78	0
Issuance of common stock upon exercise of stock options, shares		23,488
Stock-based compensation	2,314		2,314	0
Net loss	(28,329)			0	(28,329)
Other comprehensive income	2			2
Ending balance at Sep. 30, 2021	$ 146,770	$ 20	$ 333,673	$ 6	$ (186,929)
Ending balance, shares at Sep. 30, 2021		20,104,153

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parenthetical) $ in Thousands	3 Months Ended
	Sep. 30, 2020USD ($)
Statement Of Stockholders Equity [Abstract]
Stock issuance costs	$ 1,208

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (Unaudited) $ in Thousands	9 Months Ended
	Sep. 30, 2021USD ($)	Sep. 30, 2020USD ($)
Cash flows from operating activities:
Net loss	$ (63,834)	$ (36,918)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	58	47
Stock-based compensation	6,524	2,557
Amortization of premium on available-for-sale securities	704	85
Amortization of debt issuance costs	392	154
Changes in operating assets and liabilities:
Prepaid and other current assets	(4,119)	(1,404)
Other assets	4
Accounts payable	10,459	2,804
Accrued expenses	1,271	459
Net cash used in operating activities	(48,541)	(32,216)
Cash flows from investing activities:
Purchases of available-for-sale securities	(119,518)	(78,705)
Proceeds from sales and maturities of available-for-sale securities	107,627	1,025
Purchases of property and equipment	(36)	(124)
Net cash used in investing activities	(11,927)	(77,804)
Cash flows from financing activities:
Proceeds from issuance of common stock upon public offerings, net of issuance costs		158,287
Proceeds from term loan facility, net of issuance costs	1,451
Proceeds from issuance of common stock upon stock option exercises	446	35
Payment of debt issuance costs		(161)
Net cash provided by financing activities	1,980	158,236
Net change in cash and cash equivalents, and restricted cash	(58,488)	48,216
Cash and cash equivalents, and restricted cash at beginning of period	98,208	93,360
Cash and cash equivalents, and restricted cash at end of period	39,720	141,576
Components of cash and cash equivalents, and restricted cash:
Cash and cash equivalents	39,695	141,551
Restricted cash	25	25
Cash and cash equivalents, and restricted cash at end of period	39,720	141,576
Supplemental cash flow disclosures:
Issuance of common stock warrant in connection with term loan facility	574	634
Offering costs included in accounts payable and accrued expenses		607
Cash paid for income taxes		135
ESPP Purchase
Cash flows from financing activities:
Proceeds from issuance of common stock	$ 83	$ 75

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation Description of Business 89bio, Inc. (“89bio” or the “Company”) is a clinical-stage biopharmaceutical company focused on the development and commercialization of innovative therapies for the treatment of liver and cardio-metabolic diseases. The Company’s lead product candidate, BIO89-100, a specifically engineered glycoPEGylated analog of fibroblast growth factor 21, is currently being developed for the treatment of nonalcoholic steatohepatitis and for the treatment of severe hypertriglyceridemia. 89bio was formed as a Delaware corporation in June 2019 Public Offerings In July 2020, the Company completed an underwritten public offering of 3,047,040 shares of its common stock, at the public offering price of $27.50 per share. The Company raised a total of $78.2 million in net proceeds after deducting underwriting discounts and commissions of $5.0 million and offering costs of $0.6 million. In September 2020, the Company completed an underwritten public offering of 3,025,000 shares of its common stock, at a public offering price of $28.00 per share. The Company raised a total of $79.5 million in net proceeds after deducting underwriting discounts and commissions of $4.6 million and offering costs of $0.6 million Sales Agreement In March 2021, we entered into a sales agreement (the “Sales Agreement”) with SVB Leerink LLC and Cantor Fitzgerald & Co. (the “Sales Agents”) pursuant to which we may offer and sell up to $75.0 million of shares of our common stock, from time to time, in “at-the-market” offerings (the “ATM Facility”). The Sales Agents are entitled to compensation at a commission equal to 3.0% of the aggregate gross sales price per share sold under the Sales Agreement. During the three and nine months ended September 30, 2021, we did not sell any shares of common stock pursuant to the Sales Agreement. Liquidity The accompanying condensed consolidated financial statements have been prepared assuming the Company will continue as a going concern, which contemplates the realization of assets and liquidation of liabilities in the normal course of business. To date, the Company has not generated revenues from its activities and has incurred substantial operating losses. Management expects the Company to continue to generate substantial operating losses for the foreseeable future until it completes development of its products and seeks regulatory approvals to market such products. The Company had cash and cash equivalents and short-term available-for-sale securities of $157.3 million as of September 30, 2021. The Company expects that its cash and cash equivalents and short-term available-for-sale securities as of September 30, 2021, together with proceeds available from the Company’s term loan facility (see Note 6) and ATM Facility, will be sufficient to fund operating expenses and capital expenditure requirements for a period of at least one year from the date these unaudited condensed consolidated financial statements are filed with the Securities and Exchange Commission (“SEC”).

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Unaudited Condensed Consolidated Financial Statements The accompanying interim unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. The accompanying interim condensed consolidated financial statements are unaudited. The interim unaudited condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements as of and for the year ended December 31, 2020 and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position, results of operations and comprehensive loss, and cash flows. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 202 1 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 20 20 was derived from the audited financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements included in the Annual Report on Form 10-K for the year ended December 31, 20 20 , which was filed with the SEC on March 2 5 , 202 1 . Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include but are not limited to the fair value of stock options and certain accrued expenses. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates. Fair Value Measurements Financial assets and liabilities are recorded at fair value on a recurring basis in the condensed consolidated balance sheets. The carrying values of Company’s financial assets and liabilities, including cash and cash equivalents, restricted cash, prepaid and other current assets, accounts payable and accrued expenses approximate to their fair value due to the short-term nature of these instruments. The fair value of the Company’s term loan approximates its carrying value, or amortized cost, due to the short-term nature of this obligation and the market rates of interest rates it bears. Level 1 —Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 —Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable inputs for similar assets or liabilities. These include quoted prices for identical or similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active; and Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Risks and Uncertainties The ongoing COVID-19 pandemic has disrupted and may continue to disrupt the Company’s business and delay its preclinical and clinical programs and timelines. The Company does not yet know the full extent of potential delays to clinical trials, which could prevent or delay the Company from obtaining approval for BIO89-100. The extent to which the COVID-19 pandemic may impact the Company’s future operating results and financial condition is uncertain. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market funds and commercial paper that are stated at fair value. Investments Investments 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 available-for-sale investments in debt securities at the time of purchase. Generally, investments with original maturities beyond three months at the date of purchase are classified as short-term because it is management’s intent to use the investments to fund current operations or to make them available for current operations. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. The Company periodically evaluates whether declines in fair values of its available-for-sale securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the available-for-sale security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any available-for-sale securities before recovery of its amortized cost basis. 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 other expenses, net. The cost of investments sold is based on the specific-identification method. There are no material realized gains or losses on investments for the periods presented. Interest on available-for-sale securities is included in other expenses, net. Comprehensive Loss The Company’s comprehensive loss is comprised of net loss and changes in unrealized gains or losses on available-for-sale securities and foreign currency translation adjustments. Recent Accounting Pronouncements In February 2016, the Financial Standards Accounting Board (the “ ”) Accounting Standards Update (“ ”) Leases In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) , which replaces the existing incurred loss impairment model with an expected credit loss model and requires a financial asset measured at amortized cost to be presented at the net amount expected to be collected. The standard is effective for public entities for fiscal years beginning after December 15, 2019 and for nonpublic entities for fiscal years beginning after December 15, 2022. As an emerging growth company, ASU 2016-13 is effective for the Company for the year ending December 31, 2023 and interim periods within that fiscal year and must be adopted using a modified retrospective approach, with certain exceptions. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following table presents the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy as of September 30, 2021 (in thousands): September 30, 2021 Valuation Amortized Unrealized Unrealized Hierarchy Cost Gains Losses Fair Value Money market funds Level 1 $ 31,382 $ — $ — $ 31,382 Commercial paper Level 2 71,961 3 (1 ) 71,963 U.S. government bonds Level 2 19,180 8 (1 ) 19,187 Corporate debt securities Level 2 11,633 — (1 ) 11,632 Agency bonds Level 2 9,756 4 — 9,760 Municipal bonds Level 2 5,578 1 — 5,579 Non-U.S. debt securities Level 2 2,516 — — 2,516 Total cash equivalents and available-for-sale securities $ 152,006 $ 16 $ (3 ) $ 152,019 Classified as: Cash equivalents $ 34,381 Short-term available-for-sale securities 117,638 Total cash equivalents and available-for-sale securities $ 152,019 The following table summarizes the Company’s available-for-sale securities by contractual maturity as of September 30, 2021 (in thousands): September 30, 2021 Within one year $ 130,215 After one year through two years 21,804 Total cash equivalents and available-for-sale securities $ 152,019 The following table presents the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy as of December 31, 2020 (in thousands): December 31, 2020 Valuation Amortized Unrealized Unrealized Hierarchy Cost Gains Losses Fair Value Money market funds Level 1 $ 46,134 $ — $ — $ 46,134 Commercial paper Level 2 76,605 — (2 ) 76,603 Agency bonds Level 2 29,654 15 — 29,669 Corporate debt securities Level 2 11,890 — (6 ) 11,884 U.S. government bonds Level 2 7,093 — — 7,093 Municipal bonds Level 2 5,592 2 (1 ) 5,593 U.S. treasury bills Level 2 4,680 — — 4,680 Agency discount securities Level 2 200 — — 200 Total cash equivalents and available-for-sale securities $ 181,848 $ 17 $ (9 ) $ 181,856 Classified as: Cash equivalents $ 75,410 Short-term available-for-sale securities 106,446 Total cash equivalents and available-for-sale securities $ 181,856 The following table summarizes the Company’s available-for-sale securities by contractual maturity as of December 31, 2020 (in thousands): December 31, 2020 Within one year $ 160,304 After one year through two years 21,552 Total cash equivalents and available-for-sale securities $ 181,856

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies Leases In July 2021, the Company amended the lease agreement for its San Francisco office to extend the term of the lease, which was scheduled to expire in January 2022, to January 2023, with an option to renew the term for one year. Future minimum September 30, 2021 Remainder of 2021 $ 67 2022 212 2023 7 Total future minimum annual payments $ 286 Rent expense was $70,000 and $61,000 for the three months ended September 30, 2021 and 2020, respectively. Rent expense was $215,000 and $208,000 for the nine months ended September 30, 2021 and 2020, respectively. Asset Transfer and License Agreement with Teva Pharmaceutical Industries Ltd In April 2018, the Company concurrently entered into two Asset Transfer and License Agreements (the “Teva Agreements”) with Teva Pharmaceutical Industries Ltd (“Teva”) under which it acquired certain patents and intellectual property relating to two programs: (1) Teva’s glycoPEGylated FGF21 program, including the compound TEV-47948 (BIO89-100), a glycoPEGylated long-acting FGF21 and (2) Teva’s development program of small molecule inhibitors of fatty acid synthase. Pursuant to the Teva Agreements, the Company paid Teva an initial nonrefundable upfront payment of $6.0 million and the Company could be obligated to pay Teva up to $67.5 million under each program, for a total of $135.0 million, upon the achievement of certain clinical development and commercial milestones. In addition, the Company is obligated to pay Teva tiered royalties at percentages in the low-to-mid single-digits on worldwide net sales on all products containing the Teva compounds. The Teva Agreements can be terminated (i) by the Company without cause, after the first anniversary of the effective date, upon 120 days’ written notice to Teva, (ii) by either party, if the other party materially breaches any of its obligations under the Teva Agreements and fails to cure such breach within 60 days after receiving notice thereof, or (iii) by either party, if a bankruptcy petition is filed against the other party and is not dismissed within 60 days. In addition, Teva can also terminate the agreement related to the Company’s glycoPEGylated FGF21 program in the event the Company, or any of its affiliates or sublicensees, challenges any of the Teva patents licensed to the Company, and the challenge is not withdrawn within 30 days of written notice from Teva. During the three and nine months ended September 30, 2021 and 2020, there were no license payment expenses related to the Teva Agreements.

Term Loan

Term Loan	9 Months Ended
	Sep. 30, 2021
Debt Disclosure [Abstract]
Term Loan	6. Term Loan Loan and Security Agreement In April 2020, the Company entered into a Loan and Security Agreement, (the “Loan Agreement”) with the lenders referred to therein (the “Lenders”), and Silicon Valley Bank (“SVB”), as collateral agent. The Loan Agreement provided for (i) a secured term A loan facility (the “Term A Loan Facility”) of up to $10.0 million and (ii) a secured term B loan facility (the “Term B Loan Facility”) of up to $5.0 million that became available upon the satisfaction of certain milestones, each of which was available to be drawn through May 31, 2021 pursuant to an amendment executed in April 2021. In April 2020, in connection with the execution of the Loan Agreement, the Company issued SVB a warrant to purchase 25,000 shares of the Company’s common stock with a warrant exercise price of $22.06 per share that is immediately exercisable. The initial expiration date of April 7, 2030 was changed to June 30, 2025 in connection with the July 2020 offering. Upon issuance, the fair value allocated to the warrant of $0.6 million met the requirements for equity classification within additional paid-in capital on the condensed consolidated balance sheets. Additionally, the Company incurred $0.2 million in closing costs, which together with the value of the warrants, were recorded as debt issuance costs classified within other assets on the condensed consolidated balance sheets. In May 2021, the parties further amended the Loan Agreement (as amended, the “2021 Loan Agreement”). The 2021 Loan Agreement increased the Term A Loan Facility to up to $20.0 million thereby increasing the total term loan facility from $15.0 million to $25.0 million. Further, the Term B Loan Facility of up to $5.0 million remains available to be drawn upon the achievement of certain additional milestones, and each loan facility is available to be drawn upon on or before September 30, 2022. Concurrent with the closing and as a condition of the 2021 Loan Agreement, the Company drew $1.5 million under the Term A Loan Facility. The 2021 Loan Agreement provides for interest only payments to October 1, 2022, followed by consecutive monthly payments of principal and interest starting on October 1, 2022 and continuing through the maturity date of the term loan of September 1, 2024. The interest only period may be extended to April 1, 2023, if on or before September 20, 2022, the Company receives net cash proceeds of at least $75.0 million from the sale of its equity securities. The term loan bears interest at the greater of (i) 4.25% and (ii) the sum of (a) the Prime Rate as reported in The Wall Street Journal plus (b) 1.00% (or 4.25% initially and as of September 30, 2021). In addition, a final payment fee of 5% of the principal amount of the loan is due when the term loan becomes due or upon prepayment of the term loan. If the Company elects to prepay the loan, there is also a prepayment fee of between 1% and 3% of the principal amount of the term loan depending on the timing of prepayment. In May 2021, in connection with the execution of the 2021 Loan Agreement, the Company issued SVB a warrant to purchase 33,923 shares of the Company’s common stock with a warrant exercise price of $19.12 per share that is immediately exercisable and expires on May 28, 2031. The Company determined the fair value of the warrant at the issuance date by using the Black-Scholes option-pricing model with the following assumptions: risk-free interest rate of 1.6%, no dividends, expected volatility of 98.6% and expected term of 10.0 years. Upon issuance, the fair value of the warrant of $0.6 million was recorded as a debt issuance cost and met the requirements for equity classification within additional paid-in capital on the condensed consolidated balance sheets. An additional warrant to purchase 11,305 shares of the Company’s common stock will be issued in connection with the Term B Loan Facility, if funded, with the exercise price determined on the Company’s stock price at the time of issuance. Additionally, the Company incurred closing costs that were not material. The 2021 Loan Agreement was accounted for as a modification to a credit facility. The related debt issuance costs incurred in May 2021, including the fair value of the warrant, together with the remaining unamortized debt issuance costs related to the Loan Agreement of $0.4 million are recorded as deferred assets and recognized on a straight-line basis as interest expense over the availability of the draw period. As amounts are drawn under the credit facility, a portion of the then carrying value of the debt issuance costs are allocated to the amounts drawn as a debt discount and, together with the final payment fee, are recognized using the effective interest method. Interest expense is recorded within other expenses, net on the condensed consolidated statement of operations and comprehensive loss. As of September 30, 2021, the remaining unamortized debt issuance costs classified within other assets on the condensed consolidated balance sheet is $0.7 million.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ Equity Equity Incentive Plan The Company’s board of directors approved the 2019 Equity Incentive Plan (the “2019 Plan”), which became effective in September 2019. The Company initially reserved 2,844,193 shares of common stock for issuance under the 2019 Plan. In addition, the number of shares of common stock reserved for issuance under the 2019 Plan will automatically increase on the first day of January for a period of up to ten years, commencing on January 1, 2020, in an amount equal to 4% of the total number of shares of the Company’s capital stock outstanding on the immediately preceding December 31, or a lesser number of shares determined by the Company’s board of directors. As of September 30, 2021, there were 1,447,655 shares of common stock available for issuance as future option grants under the 2019 Plan. Employee Stock Purchase Plan In October 2019, the Company adopted the 2019 Employee Stock Purchase Plan (“ESPP”), which became effective in November 2019. The Company initially reserved 225,188 shares of common stock for purchase under the ESPP. The number of shares of common stock reserved for issuance under the ESPP will automatically increase on the first day of January for a period of up to ten years, in an amount equal to 1% of the total number of shares of the Company’s common stock outstanding on the immediately preceding December 31, or a lesser number of shares determined by the Company’s board of directors. Purchases will be accomplished through the participation of discrete offering periods and each offering is expected to be 6 months long. For each offering period, ESPP participants will purchase shares of common stock at a price per share equal to 85% of the lesser of the fair market value of the Company’s common stock on (1) the first trading day of the applicable offering period or (2) the last trading day of the applicable offering period. The first six month offering period under the ESPP commenced on January 1, 2020. As of September 30, 2021, there were 549,915 shares of common stock available for issuance under the ESPP. The Company recorded stock-based compensation for the periods indicated as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 Research and development $ 856 $ 359 $ 2,253 $ 848 General and administrative 1,458 795 4,271 1,709 Total stock-based compensation $ 2,314 $ 1,154 $ 6,524 $ 2,557 The fair value of option awards granted for the periods indicated was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions: Nine Months Ended September 30, 2021 2020 Stock Options Expected term (years) 5.5 - 6.1 4.0 - 6.1 Contractual term (years) 10.0 10.0 Expected volatility 94.0 - 97.6 % 86.4 - 93.7 % Risk-free interest rate 0.7 - 1.0 % 0.2 - 1.5 % Expected dividend — — The following table summarizes stock option activity for the nine months ended September 30, 2021: Weighted Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Options Price Term Value (In years) (In thousands) Balance outstanding as of December 31, 2020 1,898,395 $ 12.79 8.60 $ 25,918 Granted 766,513 22.55 Exercised (167,286 ) 2.67 Cancelled (93,889 ) 19.03 Balance outstanding as of September 30, 2021 2,403,733 16.36 8.34 $ 16,813 Exercisable as of September 30, 2021 829,994 7.62 $ 10,103 Restricted Stock Units (“RSUs”) In February 2021, the Company granted 56,545 service based RSUs to its employees with a total grant date fair value of $1.3 million. The RSUs vest annually over a three-year In February 2021, the Company granted 61,500 performance based RSUs to certain executives, one-third of which vest on each one-year

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	8. Net Loss Per Share Basic net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding for the period. Since the Company was in a loss position for all periods presented, diluted net loss per share is the same as basic net loss per share for all periods as the inclusion of all potential shares of common stock outstanding would have been anti-dilutive. The following outstanding potentially dilutive common stock equivalents have been excluded from the calculation of diluted net loss per share for the periods presented due to their anti-dilutive effect: Nine Months Ended September 30, 2021 2020 Stock options to purchase common stock 2,403,733 1,260,943 Unvested restricted stock units 110,978 — Warrants to purchase common stock 58,923 — Employee stock purchase plan 3,568 2,093 Total 2,577,202 1,263,036

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2021
Accounting Policies [Abstract]
Unaudited Condensed Consolidated Financial Statements	Unaudited Condensed Consolidated Financial Statements The accompanying interim unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“U.S. GAAP”) and applicable rules and regulations of the SEC regarding interim financial reporting. The accompanying interim condensed consolidated financial statements are unaudited. The interim unaudited condensed consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements as of and for the year ended December 31, 2020 and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s consolidated financial position, results of operations and comprehensive loss, and cash flows. The results of operations for the three and nine months ended September 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 202 1 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 20 20 was derived from the audited financial statements as of that date. These condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements included in the Annual Report on Form 10-K for the year ended December 31, 20 20 , which was filed with the SEC on March 2 5 , 202 1 .
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the condensed consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include but are not limited to the fair value of stock options and certain accrued expenses. The Company evaluates its estimates and assumptions on an ongoing basis using historical experience and other factors and adjusts those estimates and assumptions when facts and circumstances dictate. Actual results could differ from those estimates.
Fair Value Measurements	Fair Value Measurements Financial assets and liabilities are recorded at fair value on a recurring basis in the condensed consolidated balance sheets. The carrying values of Company’s financial assets and liabilities, including cash and cash equivalents, restricted cash, prepaid and other current assets, accounts payable and accrued expenses approximate to their fair value due to the short-term nature of these instruments. The fair value of the Company’s term loan approximates its carrying value, or amortized cost, due to the short-term nature of this obligation and the market rates of interest rates it bears. Level 1 —Observable inputs such as unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level 2 —Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable inputs for similar assets or liabilities. These include quoted prices for identical or similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active; and Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.
Risk and Uncertainties	Risks and Uncertainties The ongoing COVID-19 pandemic has disrupted and may continue to disrupt the Company’s business and delay its preclinical and clinical programs and timelines. The Company does not yet know the full extent of potential delays to clinical trials, which could prevent or delay the Company from obtaining approval for BIO89-100. The extent to which the COVID-19 pandemic may impact the Company’s future operating results and financial condition is uncertain.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of three months or less from the purchase date to be cash equivalents. Cash equivalents consist primarily of amounts invested in money market funds and commercial paper that are stated at fair value.
Investments	Investments Investments 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 available-for-sale investments in debt securities at the time of purchase. Generally, investments with original maturities beyond three months at the date of purchase are classified as short-term because it is management’s intent to use the investments to fund current operations or to make them available for current operations. Unrealized gains and losses are excluded from earnings and are reported as a component of comprehensive loss. The Company periodically evaluates whether declines in fair values of its available-for-sale securities below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the available-for-sale security until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any available-for-sale securities before recovery of its amortized cost basis. 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 other expenses, net. The cost of investments sold is based on the specific-identification method. There are no material realized gains or losses on investments for the periods presented. Interest on available-for-sale securities is included in other expenses, net.
Comprehensive Loss	Comprehensive Loss The Company’s comprehensive loss is comprised of net loss and changes in unrealized gains or losses on available-for-sale securities and foreign currency translation adjustments.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Standards Accounting Board (the “ ”) Accounting Standards Update (“ ”) Leases In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326) : Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”) , which replaces the existing incurred loss impairment model with an expected credit loss model and requires a financial asset measured at amortized cost to be presented at the net amount expected to be collected. The standard is effective for public entities for fiscal years beginning after December 15, 2019 and for nonpublic entities for fiscal years beginning after December 15, 2022. As an emerging growth company, ASU 2016-13 is effective for the Company for the year ending December 31, 2023 and interim periods within that fiscal year and must be adopted using a modified retrospective approach, with certain exceptions. The Company is currently evaluating the impact of this standard on its consolidated financial statements and related disclosures.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2021
Fair Value Disclosures [Abstract]
Summary of Financial Assets Measured at Fair Value on Recurring Basis	The following table presents the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy as of September 30, 2021 (in thousands): September 30, 2021 Valuation Amortized Unrealized Unrealized Hierarchy Cost Gains Losses Fair Value Money market funds Level 1 $ 31,382 $ — $ — $ 31,382 Commercial paper Level 2 71,961 3 (1 ) 71,963 U.S. government bonds Level 2 19,180 8 (1 ) 19,187 Corporate debt securities Level 2 11,633 — (1 ) 11,632 Agency bonds Level 2 9,756 4 — 9,760 Municipal bonds Level 2 5,578 1 — 5,579 Non-U.S. debt securities Level 2 2,516 — — 2,516 Total cash equivalents and available-for-sale securities $ 152,006 $ 16 $ (3 ) $ 152,019 Classified as: Cash equivalents $ 34,381 Short-term available-for-sale securities 117,638 Total cash equivalents and available-for-sale securities $ 152,019 The following table presents the Company’s financial assets measured at fair value on a recurring basis by level within the fair value hierarchy as of December 31, 2020 (in thousands): December 31, 2020 Valuation Amortized Unrealized Unrealized Hierarchy Cost Gains Losses Fair Value Money market funds Level 1 $ 46,134 $ — $ — $ 46,134 Commercial paper Level 2 76,605 — (2 ) 76,603 Agency bonds Level 2 29,654 15 — 29,669 Corporate debt securities Level 2 11,890 — (6 ) 11,884 U.S. government bonds Level 2 7,093 — — 7,093 Municipal bonds Level 2 5,592 2 (1 ) 5,593 U.S. treasury bills Level 2 4,680 — — 4,680 Agency discount securities Level 2 200 — — 200 Total cash equivalents and available-for-sale securities $ 181,848 $ 17 $ (9 ) $ 181,856 Classified as: Cash equivalents $ 75,410 Short-term available-for-sale securities 106,446 Total cash equivalents and available-for-sale securities $ 181,856
Schedule of Contractual Maturities of Available-for-Sale Securities	The following table summarizes the Company’s available-for-sale securities by contractual maturity as of September 30, 2021 (in thousands): September 30, 2021 Within one year $ 130,215 After one year through two years 21,804 Total cash equivalents and available-for-sale securities $ 152,019 The following table summarizes the Company’s available-for-sale securities by contractual maturity as of December 31, 2020 (in thousands): December 31, 2020 Within one year $ 160,304 After one year through two years 21,552 Total cash equivalents and available-for-sale securities $ 181,856

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments Under Non-cancellable Operating Lease Obligations	Future minimum September 30, 2021 Remainder of 2021 $ 67 2022 212 2023 7 Total future minimum annual payments $ 286

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2021
Equity [Abstract]
Summary of Stock-Based Compensation	The Company recorded stock-based compensation for the periods indicated as follows (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2021 2020 2021 2020 Research and development $ 856 $ 359 $ 2,253 $ 848 General and administrative 1,458 795 4,271 1,709 Total stock-based compensation $ 2,314 $ 1,154 $ 6,524 $ 2,557
Summary of Estimated Fair Value of Option Awards Granted Using Black-Scholes Option-Pricing Model	The fair value of option awards granted for the periods indicated was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions: Nine Months Ended September 30, 2021 2020 Stock Options Expected term (years) 5.5 - 6.1 4.0 - 6.1 Contractual term (years) 10.0 10.0 Expected volatility 94.0 - 97.6 % 86.4 - 93.7 % Risk-free interest rate 0.7 - 1.0 % 0.2 - 1.5 % Expected dividend — —
Summary of Stock Option Activity	The following table summarizes stock option activity for the nine months ended September 30, 2021: Weighted Weighted Average Average Remaining Aggregate Number of Exercise Contractual Intrinsic Options Price Term Value (In years) (In thousands) Balance outstanding as of December 31, 2020 1,898,395 $ 12.79 8.60 $ 25,918 Granted 766,513 22.55 Exercised (167,286 ) 2.67 Cancelled (93,889 ) 19.03 Balance outstanding as of September 30, 2021 2,403,733 16.36 8.34 $ 16,813 Exercisable as of September 30, 2021 829,994 7.62 $ 10,103

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2021
Earnings Per Share [Abstract]
Schedule of Outstanding Potentially Dilutive Securities Excluded From Calculation of Diluted Net Loss	The following outstanding potentially dilutive common stock equivalents have been excluded from the calculation of diluted net loss per share for the periods presented due to their anti-dilutive effect: Nine Months Ended September 30, 2021 2020 Stock options to purchase common stock 2,403,733 1,260,943 Unvested restricted stock units 110,978 — Warrants to purchase common stock 58,923 — Employee stock purchase plan 3,568 2,093 Total 2,577,202 1,263,036

Organization and Basis of Pre_2

Organization and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended
	Mar. 31, 2021	Sep. 30, 2020	Jul. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021
Subsidiary Sale Of Stock [Line Items]
Date of incorporation						Jun. 30, 2019
Issuance of common stock					$ 157,680
Cash and Cash equivalents and short term available-for-sale securities				$ 157,300		$ 157,300
ATM Facility | Maximum
Subsidiary Sale Of Stock [Line Items]
Issuance of common stock	$ 75,000
S V B Leerink L L C And Cantor Fitzgerald Co
Subsidiary Sale Of Stock [Line Items]
Shares issued and sold				0		0
Selling Commission Per Shares Sold Percentage	3.00%
Common Stock
Subsidiary Sale Of Stock [Line Items]
Shares issued and sold					6,072,040
Issuance of common stock					$ 6
Underwritten public offering | Common Stock
Subsidiary Sale Of Stock [Line Items]
Shares issued and sold		3,025,000	3,047,040
Proceeds from issuance of common stock, net of underwriters discount and commissions		$ 79,500	$ 78,200
IPO price per share		$ 28	$ 27.50		$ 28
Payment of underwriting discounts, commissions		$ 4,600	$ 5,000
Other offering expenses		$ 600	$ 600

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details)	9 Months Ended
	Sep. 30, 2021USD ($)
Accounting Policies [Abstract]
Realized gains or losses on investments	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Aggregated Fair Value	$ 152,019	$ 181,856
Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	152,006	181,848
Short-term investments, Gross Unrealized Holding Gains	16	17
Short-term investments, Gross Unrealized Holding Losses	(3)	(9)
Short-term investments, Aggregated Fair Value	152,019	181,856
Recurring | Cash equivalents
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Aggregated Fair Value	34,381	75,410
Recurring | Short-term available for sale securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Aggregated Fair Value	117,638	106,446
Recurring | Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	31,382	46,134
Short-term investments, Aggregated Fair Value	31,382	46,134
Recurring | Level 2 | Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	71,961	76,605
Short-term investments, Gross Unrealized Holding Gains	3
Short-term investments, Gross Unrealized Holding Losses	(1)	(2)
Short-term investments, Aggregated Fair Value	71,963	76,603
Recurring | Level 2 | Corporate Debt
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	11,633	11,890
Short-term investments, Gross Unrealized Holding Losses	(1)	(6)
Short-term investments, Aggregated Fair Value	11,632	11,884
Recurring | Level 2 | Agency bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	9,756	29,654
Short-term investments, Gross Unrealized Holding Gains	4	15
Short-term investments, Aggregated Fair Value	9,760	29,669
Recurring | Level 2 | U.S. government bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	19,180	7,093
Short-term investments, Gross Unrealized Holding Gains	8
Short-term investments, Gross Unrealized Holding Losses	(1)
Short-term investments, Aggregated Fair Value	19,187	7,093
Recurring | Level 2 | Non-US debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	2,516
Short-term investments, Aggregated Fair Value	2,516
Recurring | Level 2 | Municipal Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost	5,578	5,592
Short-term investments, Gross Unrealized Holding Gains	1	2
Short-term investments, Gross Unrealized Holding Losses		(1)
Short-term investments, Aggregated Fair Value	$ 5,579	5,593
Recurring | Level 2 | U.S. treasury bills
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost		4,680
Short-term investments, Aggregated Fair Value		4,680
Recurring | Level 2 | Agency discount securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments, Amortized Cost		200
Short-term investments, Aggregated Fair Value		$ 200

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Contractual Maturities of Available-for-Sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Within one year	$ 130,215	$ 160,304
After one year through two years	21,804	21,552
Total cash equivalents and available-for-sale securities	$ 152,019	$ 181,856

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2018	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Loss Contingencies [Line Items]
Operating leases, rent expense		$ 70,000	$ 61,000	$ 215,000	$ 208,000
Teva Agreements
Loss Contingencies [Line Items]
Nonrefundable upfront payment	$ 6,000,000
Payment upon achievement of certain clinical and commercial milestones	135,000,000
Asset transfer and license agreement, termination period after written notice				120 days
Asset transfer and license agreement, termination period notice of breach				60 days
Asset transfer and license agreement termination notice period if bankruptcy petition filed				60 days
Teva Agreements | Research and Development Expenses
Loss Contingencies [Line Items]
License payment expenses		$ 0	$ 0	$ 0	$ 0
Teva Agreements | Teva's GlycoPEGylated FGF21 Program
Loss Contingencies [Line Items]
Payment upon achievement of certain clinical and commercial milestones	67,500,000
Teva Agreements | Teva's Development Program
Loss Contingencies [Line Items]
Payment upon achievement of certain clinical and commercial milestones	$ 67,500,000
San Francisco Office
Loss Contingencies [Line Items]
Lessee, Operating Lease, Renewal Term		1 year		1 year

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancellable Operating Lease Obligations (Details) $ in Thousands	Sep. 30, 2021USD ($)
Commitments And Contingencies Disclosure [Abstract]
Remainder of 2021	$ 67
2022	212
2023	7
Total future minimum annual payments	$ 286

Term Loan - Additional Informat

Term Loan - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended		9 Months Ended
	May 31, 2021USD ($)$ / sharesshares	Apr. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2021USD ($)	Jul. 31, 2020
Debt Instrument [Line Items]
Percentage of fee on loan			5.00%
Loan Agreement
Debt Instrument [Line Items]
Line of credit facility, description	In May 2021, the parties further amended the Loan Agreement (as amended, the “2021 Loan Agreement”). The 2021 Loan Agreement increased the Term A Loan Facility to up to $20.0 million thereby increasing the total term loan facility from $15.0 million to $25.0 million. Further, the Term B Loan Facility of up to $5.0 million remains available to be drawn upon the achievement of certain additional milestones, and each loan facility is available to be drawn upon on or before September 30, 2022.	In April 2020, the Company entered into a Loan and Security Agreement, (the “Loan Agreement”) with the lenders referred to therein (the “Lenders”), and Silicon Valley Bank (“SVB”), as collateral agent. The Loan Agreement provided for (i) a secured term A loan facility (the “Term A Loan Facility”) of up to $10.0 million and (ii) a secured term B loan facility (the “Term B Loan Facility”) of up to $5.0 million that became available upon the satisfaction of certain milestones, each of which was available to be drawn through May 31, 2021 pursuant to an amendment executed in April 2021.
Warrants to purchase common stock | shares	33,923
Warrant exercise price | $ / shares	$ 19.12
Warrant expiration date	May 28, 2031	Apr. 7, 2030		Jun. 30, 2025
Debt issuance costs, gross	$ 600	$ 600
Line of credit facility increase in borrowing capacity	15,000
Proceeds from sale of available-for-sale securities, equity			$ 75,000
Deferred tax assets	400
Debt issuance costs, net			$ 700
Loan Agreement | Dividends
Debt Instrument [Line Items]
Fair value of warrant assumptions, dividends	$ 0
Loan Agreement | Black Scholes Option Pricing Model | Risk-free Interest Rate
Debt Instrument [Line Items]
Fair measurement input	0.016
Loan Agreement | Black Scholes Option Pricing Model | Expected Volatility
Debt Instrument [Line Items]
Fair measurement input	0.986
Loan Agreement | Black Scholes Option Pricing Model | Expected Term (Years)
Debt Instrument [Line Items]
Fair measurement input	10 years
Loan Agreement | Prime Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate			1.00%
Loan Agreement | Maximum
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 25,000
Loan Agreement | Minimum [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate			4.25%
Loan Agreement | Other Assets
Debt Instrument [Line Items]
Debt issuance costs, gross		200
Loan Agreement | Term A Loan Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	20,000	$ 10,000
Warrants to purchase common stock | shares		25,000
Warrant exercise price | $ / shares		$ 22.06
Term loan amount drawn			$ 1,500
Credit facility maturity date			Sep. 1, 2024
Loan Agreement | Term B Loan Facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000	$ 5,000
Warrants to purchase common stock | shares	11,305

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended
	Feb. 28, 2021	Oct. 31, 2019	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stockholders' Equity [Line Items]
Number of common shares issuable under the plan (in shares)					2,844,193
Percentage of increase in number of shares of capital stock issued and outstanding					4.00%
Common stock reserved and available for issuance as future option grants			1,447,655		1,447,655
Shares granted					766,513
Share base compensation expense			$ 2,314,000	$ 1,154,000	$ 6,524,000	$ 2,557,000
Service-based RSUs | Employee
Stockholders' Equity [Line Items]
Shares granted	56,545
Total grant date fair value	$ 1,300,000
Share base compensation expense			100,000		200,000
Vesting period	3 years
Performance RSUs | Executive Officer
Stockholders' Equity [Line Items]
Shares granted	61,500
Total grant date fair value	$ 1,400,000
Share base compensation expense			$ 200,000		$ 600,000
Vesting period	1 year
ESPP Purchase
Stockholders' Equity [Line Items]
Number of common shares issuable under the plan (in shares)		225,188
Percentage of increase in number of shares of capital stock issued and outstanding		1.00%
Percent of purchase shares of common stock		85.00%
Number of shares of common stock available for issuance under ESPP			549,915		549,915
Maximum
Stockholders' Equity [Line Items]
Period for increase in number of shares of common stock reserved for issuance					10 years
Maximum | ESPP Purchase
Stockholders' Equity [Line Items]
Period for increase in number of shares of common stock reserved for issuance		10 years

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 2,314	$ 1,154	$ 6,524	$ 2,557
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	856	359	2,253	848
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation	$ 1,458	$ 795	$ 4,271	$ 1,709

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Estimated Fair Value of Option Awards Granted Using Black-Scholes Option-Pricing Model (Details)	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Contractual term (years)	10.0	10 years
Expected volatility, minimum	94.00%	86.40%
Expected volatility, maximum	97.60%	93.70%
Risk-free interest rate, minimum	0.70%	0.20%
Risk-free interest rate, maximum	1.00%	1.50%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	5 years 6 months	4 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (years)	6 years 1 month 9 days	6 years 1 month 9 days

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Number of Options
Outstanding, Beginning Balance	1,898,395
Granted	766,513
Exercised	(167,286)
Cancelled	(93,889)
Outstanding, Ending Balance	2,403,733	1,898,395
Exercisable as of September 30, 2021	829,994
Weighted Average Exercise Price
Weighted Average Exercise Price Outstanding, Beginning Balance	$ 12.79
Weighted Average Exercise Price, Granted	22.55
Weighted Average Exercise Price, Exercised	2.67
Weighted Average Exercise Price, Cancelled	19.03
Weighted Average Exercise Price Outstanding, Ending Balance	$ 16.36	$ 12.79
Weighted Average Remaining Contractual Term (In years)
Weighted Average Remaining Contractual Term (In years), Outstanding	8 years 4 months 2 days	8 years 7 months 6 days
Weighted Average Remaining Contractual Term (In years), Exercisable as of September 30, 2021	7 years 7 months 13 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value Outstanding	$ 25,918
Aggregate Intrinsic Value Outstanding	16,813	$ 25,918
Aggregate Intrinsic Value, Exercisable as of September 30, 2021	$ 10,103

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Outstanding Potentially Dilutive Securities Excluded From Calculation of Diluted Net Loss (Details) - shares	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	2,577,202	1,263,036
Stock Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	2,403,733	1,260,943
Unvested Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	110,978
Warrants to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	58,923
ESPP Purchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive common stock equivalents excluded from calculation of diluted net loss per share	3,568	2,093