Impel Pharmaceuticals (IMPL) 10-Q 7 Jun 21 2021 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2021	Jun. 04, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Registrant Name	IMPEL NEUROPHARMA, INC.
Entity Central Index Key	0001445499
Entity Current Reporting Status	No
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		22,276,271
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	IMPL
Security Exchange Name	NASDAQ
Entity File Number	001-40353
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-3058238
Entity Address, Address Line One	201 Elliott Avenue West
Entity Address, Address Line Two	Suite 260
Entity Address, City or Town	Seattle
Entity Address, State or Province	WA
Entity Address, Postal Zip Code	98119
City Area Code	206
Local Phone Number	568-1466
Document Quarterly Report	true
Document Transition Report	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheet (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash	$ 4,467	$ 7,095
Prepaid expenses and other current assets	1,792	1,077
Total current assets	6,259	8,172
Property and equipment, net	3,512	3,700
Other assets	1,711	187
Total assets	11,482	12,059
Current liabilities:
Accounts payable	6,425	4,314
Accrued liabilities	2,625	3,173
Current portion of term debt	1,667	417
Redeemable convertible preferred stock warrant liabilities	2,677	2,622
Total current liabilities	13,394	10,526
Convertible notes at fair value	8,366	0
Long-term debt	6,963	7,994
Total liabilities	28,723	18,520
Commitments and contingencies (Note 5)
Redeemable convertible preferred stock, $0.001 par value; 204,198,489 shares authorized at March 31, 2021 and December 31, 2020; 202,009,981 shares issued and outstanding at March 31, 2021 and December 31, 2020; aggregate liquidation preference of $128,922 at March 31, 2021 and December 31, 2020	127,168	127,039
Stockholders’ deficit:
Common stock, $0.001 par value; 266,833,885 shares authorized at March 31, 2021 and December 31, 2020; 763,573 and 755,478 shares issued and outstanding at March 31, 2021 and December 31, 2020, respectively	0	0
Additional paid-in capital	5,144	4,762
Accumulated deficit	149,553	(138,262)
Total stockholders’ deficit	(144,409)	(133,500)
Total liabilities, redeemable convertible preferred stock and stockholders’ deficit	$ 11,482	$ 12,059

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheet (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Redeemable convertible preferred stock, par value	$ 0.001	$ 0.001
Redeemable convertible preferred stock, shares authorized	204,198,489	204,198,489
Redeemable convertible preferred stock, shares issued	202,009,981	202,009,981
Redeemable convertible preferred stock, shares outstanding	202,009,981	202,009,981
Redeemable convertible preferred stock, aggregate liquidation preference	$ 128,922	$ 128,922
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	266,833,885	266,833,885
Common stock, shares issued	763,573	755,478
Common stock, shares outstanding	763,573	755,478

Condensed Consolidated Statemen

Condensed Consolidated Statement of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating expenses:
Research and development	$ 4,098	$ 6,354
General and administrative	5,771	3,452
Total operating expenses	9,869	9,805
Loss from operations	(9,869)	(9,805)
Interest income (expense), net	(298)	33
Other expense, net	(1,124)	14
Loss before income taxes	(11,291)	(9,758)
Provision for income taxes	0	1
Net loss and comprehensive loss	(11,291)	(9,759)
Accretion on redeemable convertible preferred stock	129	128
Net loss attributable to common stockholders	$ (11,420)	$ (9,887)
Net loss per share attributable to common stockholders, basic and diluted	$ (15)	$ (27)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted	756,986	360,808

Condensed Consolidated Statem_2

Condensed Consolidated Statement of Changes in Redeemable Convertible Preferred Stock and Stockholders' Deficit (Unaudited) - USD ($) $ in Thousands	Total	Redeemable Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Beginning Balance at Dec. 31, 2019		$ 125,647
Beginning Balance, Shares at Dec. 31, 2019		201,335,862
Beginning Balance at Dec. 31, 2019	$ (91,704)			$ 760	$ (92,464)
Beginning Balance, Shares at Dec. 31, 2019			360,115
Accretion on preferred stock	(128)	$ 129		(128)
Stock-based compensation expense	298			298
Issuance of common stock upon the exercise of stock options	8			8
Issuance of common stock upon the exercise of stock options, Shares			3,569
Net loss and comprehensive loss	(9,759)				(9,759)
Ending Balance at Mar. 31, 2020		$ 125,776
Ending Balance, Shares at Mar. 31, 2020		201,335,862
Ending Balance at Mar. 31, 2020	(101,285)			938	(102,223)
Ending Balance, Shares at Mar. 31, 2020			363,684
Beginning Balance at Dec. 31, 2020	$ 127,039	$ 127,039
Beginning Balance, Shares at Dec. 31, 2020	202,009,981	202,009,981
Beginning Balance at Dec. 31, 2020	$ (133,500)			4,762	(138,262)
Beginning Balance, Shares at Dec. 31, 2020			755,478
Accretion on preferred stock	(129)	$ 129		(129)
Stock-based compensation expense	493			493
Issuance of common stock upon the exercise of stock options	$ 18			18
Issuance of common stock upon the exercise of stock options, Shares	8,095		8,095
Net loss and comprehensive loss	$ (11,291)				(11,291)
Ending Balance at Mar. 31, 2021	$ 127,168	$ 127,168
Ending Balance, Shares at Mar. 31, 2021	202,009,981	202,009,981
Ending Balance at Mar. 31, 2021	$ (144,409)			$ 5,144	$ (149,553)
Ending Balance, Shares at Mar. 31, 2021			763,573

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash flows from operating activities:
Net loss	$ (11,291)	$ (9,759)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	250	219
Stock-based compensation	493	298
Change in fair value of redeemable convertible preferred stock warrant liabilities	55	(44)
Noncash Interest	27
Amortization of debt discount	219	0
Change in fair value of convertible notes	839
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(715)	(238)
Other assets	0	(187)
Accounts payable	1,277	105
Accrued liabilities	(1,064)	(1,025)
Net cash used in operating activities	(9,910)	(10,631)
Cash flows from investing activities:
Purchases of property and equipment	(27)	(418)
Net cash used in investing activities	(27)	(418)
Cash flows from financing activities:
Payment of deferred offering costs	(209)
Proceeds from issuance of common stock upon exercise of stock options	18	8
Proceeds from issuance of redeemable convertible preferred stock upon the exercise of redeemable convertible preferred stock warrants	7,500	0
Net cash provided by financing activities	7,309	8
Net decrease in cash	(2,628)	(11,041)
Cash — Beginning of period	7,095	37,001
Cash — End of period	4,467	25,959
Supplemental disclosures of cash flow information:
Accretion on preferred stock	129	128
Property and equipment included in accounts payable and accrued liabilities	35	222
Deferred offering costs included in accounts payable and accrued liabilities	$ 1,315	$ 0

Organization and Description of

Organization and Description of Business	3 Months Ended
	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business Impel Neuropharma, Inc., or the Company, is a late-stage pharmaceutical company focused on the development and commercialization of transformative therapies for patients suffering from diseases with high unmet medical needs, with an initial focus on diseases of the central nervous system, or CNS. The Company’s strategy is to pair its proprietary Precision Olfactory Delivery, or POD, upper nasal delivery technology with well-understood therapeutics or other therapeutics where rapid vascular absorption is preferred to drive therapeutic benefit, improve patient outcomes, reduce drug development risk and expand the commercial opportunity within its target diseases. The Company was incorporated under the laws of the State of Delaware on July 24, 2008 , maintains its headquarters and principal operations in Seattle, Washington, and performs certain of its research and development activities in Australia. Initial Public Offering On April 22, 2021, the Company’s Registration Statement on Form S-1 relating to its initial public offering, or IPO, was declared effective by the Securities and Exchange Commission, or the SEC, and the shares of its common stock began trading on the Nasdaq Global Select Market on April 23, 2021. The IPO closed on April [27], 2021, pursuant to which the Company issued and sold 5,333,334 shares of its common stock at a public offering price of $ 15.00 per share. The Company received net proceeds of approximately [$ 71.4 ] million from the IPO, after deducting underwriting discounts and commissions of $ 5.6 million and offering costs of $ 3.0 million. Prior to the completion of the IPO, all shares of redeemable convertible preferred stock then outstanding were converted into 12,605,800 shares of common stock. In addition, the warrant held by Avenue Venture Opportunities Fund, L.P., or Avenue, was exchanged for 107,663 shares of common stock and warrants to purchase 1,987,348 shares of redeemable convertible preferred stock automatically converted into warrants to purchase 1,987,348 shares of common stock. Such warrants were then net exercised into 52,974 shares of common stock. The convertible notes issued in March 2021 for an aggregate principal amount of $ 7.5 million (see Note 6) were also converted into 559,585 shares of common stock at a 10 % discount of the IPO price. Reverse Stock Split In April 2021, the Company’s board of directors and stockholders approved an amendment to the Company’s certificate of incorporation to effect a reverse split of shares of the Company’s common stock on an one-for-16.37332 basis, which was effected on April 16, 2021 (the “Reverse Stock Split”). The number of authorized shares and the par values of the common stock and redeemable convertible preferred stock were not adjusted as a result of the Reverse Stock Split. In connection with the Reverse Stock Split, the conversion ratio for the Company’s outstanding redeemable convertible preferred stock was proportionately adjusted such that the common stock issuable upon conversion of such preferred stock was decreased in proportion to the Reverse Stock Split . All references to common stock and options to purchase common stock share data, per share data and related information contained in the condensed consolidated financial statements have been retroactively adjusted to reflect the effect of the Reverse Stock Split for all periods presented. Liquidity and Capital Resources The Company raised $ 71.4 million in net proceeds from its IPO in April 2021 and from the Company’s inception through March 31, 2021, it raised an aggregate of $ 142.5 million in gross cash proceeds from the sale and issuance of redeemable convertible preferred stock, convertible notes, debt and warrants. The Company had a cash balance of $ 4.5 million as of March 31, 2021. Based upon the Company’s current operating plan, it estimates that its cash as of March 31, 2021, combined with the net proceeds from its IPO, are together sufficient for the Company to fund operating, investing, and financing cash flow needs for at least one year from the issuance date of these interim financial statements. Additionally, given the completion of the IPO, the Company has $ 10.0 million of available capacity on the Avenue debt facility through December 31, 2021 (see Note 6). In the event of an FDA approval, the Company will be required to raise additional capital. If sufficient funds on acceptable terms are not available when needed, the Company could be required to reduce operating expenses and delay, reduce the scope of, or eliminate one or more of its development programs or planned product launch plans. Failure to manage discretionary spending or raise additional financing, as needed, may adversely impact the Company’s ability to achieve its intended business objectives. The accompanying financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The accompanying financial statements do not reflect any adjustments relating to the recoverability and reclassifications of assets and liabilities that might be necessary if the Company is unable to continue as a going concern.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or U.S. GAAP. The condensed consolidated financial statements include the operations of Impel Neuropharma, Inc., and its wholly owned Australian subsidiary. All intercompany balances and transactions have been eliminated upon consolidation. The condensed consolidated balance sheet as of March 31, 2021, the condensed consolidated statements of operations and comprehensive loss, changes in redeemable convertible preferred stock and stockholders’ deficit and cash flows for the three months ended March 31, 2021 and 2020 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements 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 as of March 31, 2021 and its results of operations and cash flows for the three months ended March 31, 2021 and 2020. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three-month periods are also unaudited. The results of operations for the three months ended March 31, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2020 included herein 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 prospectus dated April 23, 2021 that forms a part of the Company's Registration Statement on Form S-1 (File No. 333-254999), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended. 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 amounts reported in the financial statements and accompanying notes. On an ongoing basis, management evaluates such estimates and assumptions for continued reasonableness. In particular, management makes estimates with respect to the fair values of common stock, redeemable convertible preferred stock warrant liabilities, stock-based compensation expense, convertible debt and income taxes. Appropriate adjustments, if any, to the estimates used are made prospectively based upon such periodic evaluation. Actual results could differ from those estimates. Segments The Company’s chief operating decision maker is its Chief Executive Officer. The Chief Executive Officer reviews financial information on an aggregate basis for the purposes of evaluating financial performance and allocating the Company’s resources. Accordingly, the Company has determined that it operates in one segment. Cash The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents. At March 31, 2021 and December 31, 2020, cash consisted of cash in bank deposits held at financial institutions. Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash. The Company’s cash is deposited with high credit quality financial institutions. At times such deposits may be in excess of the Federal Depository Insurance Corporation insured limits. Fair Value Measurement Assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: 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 for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active; 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. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the accompanying consolidated balance sheets for cash, other current assets, accounts payable, and accrued liabilities approximate their fair values, due to their short-term nature. Convertible Notes In March 2021, the Company issued convertible promissory notes to various investors for an aggregate amount of $ 7.5 million. As permitted under Accounting Standards Codification ("ASC") 825, Financial Instruments ("ASC 825"), the Company has elected the fair value option for recognition of the convertible notes. The Company elected the fair value option to allow the Company to eliminate the burden of complying with the requirements for derivative accounting. Under the fair value option, the convertible notes are remeasured at fair value in each reporting period until their conversion in April 2021, with changes in the fair value recognized in the Company’s condensed consolidated statement of operations as other (expense) income, net. Accrued interest on the convertible notes is recorded in interest (expense) income, net. Deferred Offering Costs The Company has deferred offering costs consisting of legal, accounting and other fees and costs directly attributable to the Company’s IPO. The deferred offering costs will be offset against the proceeds received upon the completion of the IPO. As of March 31, 2021, $ 1.5 million of deferred offering costs were included in other assets on the condensed consolidated balance sheet. There were no deferred offering costs as of December 31, 2020. Redeemable Convertible Preferred Stock Warrant Liabilities Freestanding warrants to purchase shares of the Company’s redeemable convertible preferred stock are accounted for as liabilities at fair value, because the shares underlying the warrants contain contingent redemption features outside the control of the Company. Warrants classified as liabilities are recorded on the Company’s condensed consolidated balance sheets at their fair value on the date of issuance and remeasured to fair value on each subsequent reporting period, with the changes in fair value recognized as a component of other (expense) income, net in the accompanying condensed consolidated statements of operations. The Company will continue to adjust the liability for changes in the fair value of these warrants until the earlier of the exercise of the warrants, the expiration of the warrants, or until such time as the warrants are no longer considered liability instruments. Research and Development Research and development costs are expensed as incurred and consist primarily of salaries, benefits and other staff-related costs, including associated stock-based compensation, laboratory supplies, nonclinical and clinical studies and trials and related clinical manufacturing costs, costs related to manufacturing preparation, fees paid to other entities that conduct certain research and development activities on the Company’s behalf. Non-refundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized as prepaid expenses until the related goods are delivered or services are performed. Such payments are evaluated for current or long-term classification based on when such services are expected to be received. Advance Payments for Research and Development Services and Accruals As part of the process of preparing its condensed consolidated financial statements, the Company is required to estimate its expenses resulting from its obligation under contracts with vendors and consultants and clinical site agreements in connection with its research and development efforts. The financial terms of these contracts are subject to negotiations which vary contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company’s objective is to reflect the appropriate research and development expenses in its condensed consolidated financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of its research and development efforts. The Company determines advance payments for research and development services and accrual estimates through discussion with applicable personnel and outside service providers as to the progress of clinical trials, or other services completed. The Company adjusts its rate of research and development expense recognition if actual results differ from its estimates. The Company makes estimates of its advance payments and accrued expenses as of each balance sheet date in its condensed consolidated financial statements based on facts and circumstances known at that time. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of status and timing of services performed relative to the actual status and timing of services performed may vary and may result in the Company reporting amounts that are too high or too low for any particular period. Through March 31, 2021, there had been no material adjustments to the Company’s prior period estimates of advance payments and accruals for research and development expenses. The Company’s research and development advance payments and accruals are dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors. Stock-Based Compensation The Company recognizes stock-based compensation expense for stock options and restricted stock unit awards on a straight-line basis over the requisite service period. The Company’s stock-based compensation costs are based upon the grant date fair value of options estimated using the Black-Scholes-Merton option pricing model. This model utilizes as inputs the estimated fair value of the underlying common stock at the measurement date, the estimated term of the stock options (weighted-average period of time that the options granted are expected to be outstanding), risk-free interest rates, expected dividends, and the expected volatility of the Company’s common stock. The Company has elected to recognize forfeitures of share-based payment awards as they occur. The Company recognizes stock-based compensation expense for stock options granted to nonemployees based on the estimated fair value of the award as it is more readily measurable than the fair value of the services received. Net Loss Per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period, without consideration of potentially dilutive securities. Diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders since the effect of potentially dilutive securities is anti-dilutive given the net loss of the Company. Comprehensive Loss Comprehensive loss represents the change in the Company’s stockholders’ deficit from all sources other than investments by or distributions to stockholders. The Company has no items of other comprehensive loss; as such, net loss equals comprehensive loss. Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2016-02, Leases , or Topic 842, which supersedes the guidance in former ASC 840, Leases . This standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less may be accounted for similar to existing guidance for operating leases today. In May 2020, the FASB issued ASU No. 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities, which deferred the effective dates for non-public entities. Therefore, this standard is effective for annual reporting periods, and interim periods within those years, for public entities beginning after December 15, 2018 and for private entities beginning after December 15, 2021. Originally, a modified retrospective transition approach was required for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. In July 2018, the FASB issued guidance to permit an alternative transition method for Topic 842, which allows transition to the new lease standard by recognizing a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Entities may elect to apply either approach. There are also a number of optional practical expedients that entities may elect to apply. The Company is currently assessing the impact of this standard on its condensed consolidated financial statements. The Company expects to record a material right-of-use asset and lease liability in connection with adopting this standard on January 1, 2022. Recently Adopted Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity , or ASU 2020-06, which simplifies accounting for convertible instruments by removing major separation models required under current U.S. GAAP. ASU 2020-06 removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception and it also simplifies the diluted earnings per share calculation in certain areas. ASU 2020-06 is effective for the Company for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020 and adoption must be as of the beginning of the Company’s annual fiscal year. The Company early adopted this standard on January 1, 2021 and the adoption of the standard did not have a significant impact on its consolidated financial statements.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The following table summarizes the fair value of the Company’s financial liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): March 31, 2021 Level 1 Level 2 Level 3 Total Liabilities: Redeemable convertible preferred stock warrant liabilities $ — $ — $ 2,677 $ 2,677 Convertible notes $ — $ — $ 8,366 $ 8,366 Total financial liabilities $ — $ — $ 11,043 $ 11,043 December 31, 2020 Level 1 Level 2 Level 3 Total Liabilities: Redeemable convertible preferred stock warrant liabilities $ — $ — $ 2,622 $ 2,622 Total financial liabilities $ — $ — $ 2,622 $ 2,622 The carrying value of the Company’s term loan (see Note 6) approximates the fair value as the term loan was recently issued in November 2020. The following table summarizes the change in the fair value of the redeemable convertible preferred stock warrant liabilities for the three months ended March 31, 2021 (in thousands): Beginning balance as of December 31, 2020 $ 2,622 Losses from changes in fair value 55 Ending balance as of March 31, 2021 $ 2,677 The following table summarizes the change in the fair value of the convertible notes for the three months ended March 31, 2021 (in thousands): Beginning balance as of December 31, 2020 $ — Issuance of convertible notes 7,500 Interest 27 Losses from changes in fair value 839 Ending balance as of March 31, 2021 $ 8,366 Fair values of the Company’s redeemable convertible preferred stock warrant liabilities and convertible notes are based on significant inputs not observed in the market, and thus represent a Level 3 measurement. Refer to Note 6 and Note 7 for the valuation techniques and assumptions used in estimating the fair value of the convertible notes and warrants, respectively.

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4. Balance Sheet Components Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): March 31, December 31, Refundable clinical deposits $ 825 $ 627 Tax refund receivable 229 229 Prepaid insurance 178 47 Other prepaids and current assets 560 129 Total prepaid expenses and other current assets $ 1,792 $ 1,077 Accrued Liabilities Accrued liabilities consisted of the following (in thousands): March 31, December 31, Accrued professional services $ 1,079 $ 192 Accrued compensation 1,274 2,393 Accrued other liabilities 195 333 Accrued construction in progress 77 255 Total accrued liabilities $ 2,625 $ 3,173

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	5. Commitments and Contingencies Operating Leases The Company leases office and laboratory space in Seattle, Washington. In September 2017, the Company entered into a non-cancelable operating lease for 11,256 square feet of office and laboratory space. Rent is payable monthly, increasing by approximately 3 % each year. As of March 31, 2021, the remaining future minimum lease payments were $ 1.0 million through the expiration date of August 31, 2022 . Rent expense for the three months ended March 31, 2021 and 2020 was $ 174,000 and $ 150,000 , respectively. Legal Proceedings From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of its business activities. The Company accrues a liability for such matters when it is probable that future expenditures will be made and that such expenditures can be reasonably estimated. Significant judgment is required to determine both probability and the estimated amount. Indemnifications In the ordinary course of business, the Company enters into agreements that may include indemnification provisions. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company intends to enter into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently has directors’ and officers’ insurance coverage that reduces its exposure and enables the Company to recover a portion of any future amounts paid. The Company believes the estimated fair value of these indemnification agreements in excess of applicable insurance coverage is minimal. COVID-19 In March 2020, the COVID-19 disease was declared a pandemic by the World Health Organization. Management continues to evaluate the potential impacts of the COVID-19 pandemic on the development of its product candidates, and business. The Company is working closely with its manufacturing vendors to maintain adequate product supply and with healthcare providers as future studies are planned to mitigate risk to patients while adhering to regulatory, institutional and government guidance and policies. The Company remains committed to its development plans and acknowledges the potential risk for delays in the product supply chain and in anticipated timelines for its preclinical studies and clinical trials.

Debt

Debt	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Debt	6. Debt Term Loan On November 5, 2020 the Company entered into a debt and equity financing agreement with Avenue Venture Opportunities Fund, L.P., or Avenue. The agreement provides for a 36 -month term loan of up to $ 20.0 million, of which $ 10.0 million was funded at close and (b) an additional $ 10.0 million is available at the Company’s request until December 31, 2021, subject to (i) completion of an underwritten public offering with gross proceeds of at least $ 75.0 million, or a Qualified Offering, (ii) receipt of FDA approval of TRUDHESA and (iii) approval by Avenue’s investment committee. The term loan bears interest at the higher of the prime rate or 11 %. Under the agreement, Avenue also has the right to invest up to $ 10.0 million in a private placement concurrent with an IPO (at the IPO price) or special purpose acquisition company, or SPAC, transaction (at the effective price per share), in each case, subject to mutual agreement and Avenue investment committee approval. Payments for the term loan are interest only for the initial 12 months and can be extended to (i) 24 months upon achieving a qualified IPO with gross proceeds of at least $ 75.0 million or (ii) 36 months upon achieving the first interest only period extension and FDA approval of TRUDHESA. The term loan will amortize in equal payments of principal from the end of the interest only period to the expiration of the 36-month term on November 1, 2023 and includes a final payment of $ 450,000 due upon the maturity of the term loan. In connection with the agreement, the Company granted Avenue warrants for the purchase of shares of 1,762,810 shares of Series D redeemable convertible preferred stock, as disclosed in Note 7. Avenue is eligible to receive additional warrants upon the drawdown of the remaining $ 10.0 million under the agreement. The Company’s obligations are secured by a security interest in substantially all of the Company’s assets, excluding the. Company’s intellectual property after completion of the Company’s IPO. The agreement contains customary representations, warranties and covenants, including covenants by the Company limiting additional indebtedness, liens, including on intellectual property, guaranties, mergers and consolidations, substantial asset sales, investments and loans, certain corporate changes, transactions with affiliates and fundamental changes. The agreement provides for events of default customary for term loans of this type, including but not limited to non-payment, breaches or defaults in the performance of covenants, insolvency and bankruptcy. The net proceeds from the issuance of the term loan were initially allocated to the warrants at an amount equal to their fair value of $ 1.5 million and the remainder to the term loan. The Company incurred financing costs of $ 299,000 which, together with the fair value of the warrants and the final payment, are recorded as a debt discount and are being amortized over the contractual term using the effective interest method. During the three months ended March 31, 2021, the Company recorded interest expense of $ 491,000 . The term loan consists of the following (in thousands): March 31, December 31, Face value of term loan $ 10,000 $ 10,000 Final payment 450 450 Unamortized debt discount associated with final payment, ( 1,820 ) ( 2,039 ) Total debt, net $ 8,630 $ 8,411 Less: short-term debt 1,667 417 Long-term debt $ 6,963 $ 7,994 Convertible Promissory Notes In March 2021, the Company issued unsecured convertible promissory notes to various investors for an aggregate amount of $ 7.5 million which are accounted for at fair value. The notes bear interest at a rate of 5.0 % per annum and mature on the earlier of (a) December 31, 2021 and (b) a change of control. The notes are (i) automatically convertible into shares of the Company’s common stock upon the closing of a firm-commitment underwritten public offering, at a per share price of at least $ 1.0636 , resulting in at least $ 50.0 million in net proceeds, or a Qualified Public Offering, or a SPAC transaction at 90% of the price per share in such transactions, (ii) convertible at the holder’s option or upon a change of control into shares of Series D redeemable convertible preferred stock at the Series D original issuance price, and (iii) convertible at the holder’s option upon a new redeemable convertible preferred stock financing into shares of redeemable preferred stock issued in such financing at 90% of the price per share. The agreement contains customary representations, warranties and covenants, including covenants by the Company limiting additional indebtedness, liens, including on intellectual property, guaranties, mergers and consolidations, substantial asset sales, investments and loans, certain corporate changes, transactions with affiliates and fundamental changes. The agreement provides for events of default customary for term loans of this type, including but not limited to non-payment, breaches or defaults in the performance of covenants, insolvency and bankruptcy. Accrued interest on the convertible notes totaled $ 27,000 during the three months ended March 31, 2021 and is recorded in interest (expense) income, net. On March 31, 2021, the notes were remeasured to their settlement amount at the IPO date excluding accrued interest due to the proximity of the settlement date to the end of the reporting period. The loss on the increase in fair value on the convertible notes totaled $ 839,000 from their issuance through March 31, 2021 and is classified as other (expense) income, net in the accompanying condensed consolidated statements of operations. The carrying value of the convertible notes of $ 8.4 million immediately prior to the Company’s IPO subsequently converted into 559,585 shares of common stock upon completion of the IPO.

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock Warrant Liabilities	3 Months Ended
	Mar. 31, 2021
Warrants And Rights Note Disclosure [Abstract]
Redeemable Convertible Preferred Stock Warrant Liabilities	7. Redeemable Convertible Preferred Stock Warrant Liabilities The key terms of the outstanding redeemable convertible preferred stock warrant liabilities as of March 31, 2021 and December 31, 2020 are summarized in the following table: Number of shares as of Exercisable into: March 31, December 31, Exercise Expiration Series A-2 redeemable convertible preferred stock 862,471 862,471 $ 0.4996 September 30, 2021 Series C-1 redeemable convertible preferred stock 1,124,877 1,124,877 0.5289 November 16, 2021 Series D redeemable convertible preferred stock 1,762,810 1,762,810 0.7091 October 31, 2021 Total 3,750,158 3,750,158 The fair value of the warrants was determined using an option pricing model. Under this model, the estimated equity value of the Company as of the measurement date is allocated to various classes of financial instruments (such as common and redeemable convertible preferred stock and warrants to purchase redeemable convertible preferred stock) based on their rights and preferences in an assumed liquidity scenario, which was estimated to occur in two years. Other assumptions used included stock volatility ranging from 46.4 % to 103.0 % during the three months ended March 31, 2021 and 46.0 % to 64.1 % during the three months ended March 31, 2020, and risk-free interest rates ranging from 0.04 % to 0.24 % during the three months ended March 31, 2021 and 0.15 % to 2.81 % during the three months ended March 31, 2020. In April 2021, upon completion of the IPO, the Series A-2 and C-1 redeemable convertible preferred stock warrants were net exercised into 52,974 shares of common stock. The Series D redeemable convertible preferred stock warrants were exchanged for 107,663 shares of common stock.

Redeemable Convertible Prefer_2

Redeemable Convertible Preferred Stock	3 Months Ended
	Mar. 31, 2021
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	8. Redeemable Convertible Preferred Stock Redeemable convertible preferred stock consisted of the following (in thousands, except share amounts): Redeemable Convertible Shares Authorized Shares Issued and Carrying Value at Carrying Value at Aggregate Series A-1 746,426 746,426 238 $ 238 $ 305 Series A-2 9,869,218 8,805,587 4,147 4,147 4,399 Series B 3,968,775 3,968,775 4,016 3,980 4,421 Series C-1 43,278,699 42,153,822 21,056 20,975 22,297 Series C-2 26,537,826 26,537,826 15,390 15,390 15,000 Series C-3 24,605,790 24,605,790 14,975 14,973 15,000 Series D 95,191,755 95,191,755 67,346 67,336 67,500 Total 204,198,489 202,009,981 127,168 $ 127,039 $ 128,922 Classification The Company has classified its redeemable convertible preferred stock as mezzanine equity on the condensed consolidated balance sheets as the shares are contingently redeemable with passage of time or upon deemed liquidation events, such as a change in control. As only the passage of time is required for Series B, C-1, C-2, C-3, and D preferred stock to become redeemable, the Company is accreting the carrying value of the preferred stock shares to their redemption value, using the effective interest method, over the period from issuance to the earliest payment dates. With respect to Series A-1 and A-2, no accretion was recorded during the three months ended March 31, 2021 and 2020, as a deemed liquidation event was no t probable. Amounts recorded for the accretion of redeemable convertible preferred stock during the three months ended March 31, 2021 and 2020 were $ 129,000 and $ 128,000 , respectively. The accretion is recorded as a deemed dividend and a charge to additional paid-in capital. In April 2021, immediately prior to the completion of the IPO (see Note 1), all outstanding shares of redeemable convertible preferred stock were automatically converted into 12,605,800 shares of common stock. Upon conversion into common stock, the carrying value of the redeemable convertible preferred stock of $ 127.2 million was reclassified to equity.

Common Stock

Common Stock	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Common Stock	9. Common Stock Each share of common stock has the right to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors, subject to the prior rights of holders of all classes of stock outstanding having priority rights as to dividends. No cash dividends have been declared by the board of directors from inception. The Company has reserved the following shares of common stock for issuance, on an as-converted basis, as follows: March 31, December 31, Stock incentive plans 2,778,250 2,786,345 Redeemable convertible preferred stock 12,605,800 12,605,800 Convertible notes 559,585 — Redeemable convertible preferred stock warrants 229,034 229,034 Total 16,172,669 15,621,179

Stock Incentive Plan

Stock Incentive Plan	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Incentive Plan	10. Stock Incentive Plan 2008 Plan In September 2008, the Company’s board of directors adopted the 2008 Stock Incentive Plan, or the 2008 Plan, which provides for the granting of incentive stock options, nonqualified stock options, and restricted stock awards to its employees, directors and consultants. Options granted or shares issued under the 2008 Plan that were outstanding on the date the 2018 Equity Incentive Plan, or the 2018 Plan, became effective will remain subject to the terms of the 2008 Plan. The 2008 Plan terminated in 2018 as it reached its ten-year term. New grants issued after the termination of the 2008 plan will be under the 2018 plan. At March 31, 2021 and December 31, 2020, options to purchase 627,285 and 634,788 shares, respectively, under the 2008 plan remained outstanding. 2018 Plan In November 2018, the Company’s board of directors adopted the 2018 Equity Incentive Plan. The 2018 Plan provides for the granting of incentive stock options, nonqualified stock options, restricted stock units, and other forms of stock awards to its employees, directors and consultants. The 2018 Plan is administered by the board of directors or a committee appointed by the board of directors, which determines the types of awards to be granted, including the number of shares subject to the awards, the exercise price and the vesting schedule. The exercise price of incentive stock options and nonqualified stock options will be no less than 100% of the fair value per share of the Company’s common stock on the date of grant. If an individual owns capital stock representing more than 10% of the voting shares and the grant is an incentive stock option, the price of each share will be at least 110% of the fair value on the date of grant . Options expire after 10 years ( five years for incentive stock options granted to stockholders owning greater than 10% of the voting stock). The term and vesting periods for options granted under the 2018 Plan are determined by the Company’s board of directors or a committee appointed by the board of directors. Options granted generally vest over four years . Options must be exercised within a 10-year period or sooner if so specified within the option agreement. Under the 2018 Plan, the Company initially reserved 753,645 shares of common stock for issuance. In addition, any authorized shares not issued or subject to outstanding grants under the 2008 Plan and any shares subject to outstanding stock options that are cancelled without being exercised or expire under the 2008 Plan are added to the shares authorized and reserved for issuance under the 2018 Plan. At March 31, 2021 and December 31, 2020, options to purchase 2,082,425 and 1,807,101 shares, respectively, under 2018 Plan remained outstanding. The Company had 68,540 and 344,456 shares available for future grant under the 2018 Plan as of March 31, 2021 and December 31, 2020, respectively. Stock Option Activity A summary of the Company’s stock option activity under its stock option plans was as follows (in thousands, except share and per share data and years): Options Outstanding Shares Number of Weighted Remaining Aggregate Balance — December 31, 2020 344,456 2,441,889 $ 5.17 8.02 $ 14,844 Authorized — — $ — - $ — Granted ( 276,843 ) 276,843 $ 12.95 - $ — Exercised — ( 8,095 ) $ 2.19 - $ — Cancelled 927 ( 927 ) $ 2.82 - $ — Balance — March 31, 2021 68,540 2,709,710 $ 5.97 9.01 $ 21,079 Exercisable — March 31, 2021 — 1,079,601 $ 3.28 6.79 $ 11,308 In May 2020, the Company’s board of directors increased the pool of stock options available for future grant by 596,414 shares and appointed an existing member of the board of directors as the Company’s Chief Executive Officer. In connection with this change, the Company granted 715,358 stock options to its Chief Executive Officer at an exercise price of $ 7.86 per share that will vest ratably over 48 months. Vesting of the Chief Executive Officer’s options accelerate upon a termination without cause. The Company recognized $ 2.1 million of expense related to a modification upon the acceleration of the former Chief Executive Officer’s outstanding options upon his departure from the Company. The total intrinsic value of options exercised was $ 94,000 and $ 21,000 during the three months ended March 31, 2021 and 2020, respectively. The intrinsic value is the difference between the estimated fair value of the Company’s common stock at the time of exercise, as determined by the board of directors, and the exercise price of the stock option. The total fair value of options that vested during the three months ended March 31, 2021 and 2020 was $ 367,000 and $ 434,000 , respectively. The grant date fair value of options granted during the three months ended March 31, 2021 and 2020 was $ 2.0 million and $ 0.7 million, respectively. The weighted-average grant date fair value of employee options granted during the three months ended March 31, 2021 and 2020 was $ 7.07 and $ 4.47 per share, respectively. Stock-Based Compensation Expense Stock-based compensation expense recognized was as follows (in thousands): Three Months Ended 2021 2020 Research and development $ 119 $ 119 General and administrative 374 179 Total stock-based compensation expense $ 493 $ 298 As of March 31, 2021, there was $ 6.9 million of total unrecognized compensation cost related to unvested options that are expected to vest. The cost is expected to be recognized over a weighted-average period of 3.0 years. In determining the fair value of the stock options granted, the Company uses the Black-Scholes-Merton option-pricing model and assumptions discussed below. Each of these inputs is subjective. Fair Value of Common Stock— Given the absence of a public trading market, the Company’s board of directors with input from management considered numerous objective and subjective factors to determine the fair value of common stock. The factors included, but were not limited to: (1) third-party valuations of the Company’s common stock; (2) the Company’s stage of development; (3) the status of research and development efforts; (4) the rights, preferences and privileges of the Company’s preferred stock relative to those of the Company’s common stock; (5) the Company’s operating results and financial condition, including the Company’s levels of available capital resources; and (6) equity market conditions affecting comparable public companies; (7) general U.S. market conditions; and (8) the lack of marketability of the Company’s common stock. Expected Term —The Company’s expected term represents the period that the Company’s stock-based awards are expected to be outstanding. The Company used the simplified method (based on the mid-point between the vesting date and the end of the contractual term) to determine the expected term. Expected Volatility —Since the Company is privately held and does not have any trading history for its common stock, the expected volatility was estimated based on the average historical volatilities for comparable publicly traded pharmaceutical companies over a period equal to the expected term of the stock option grants. The comparable companies were chosen based on their similar size, stage in the life cycle and area of specialty. The Company will continue to apply this process until a sufficient amount of historical information regarding the volatility of its own stock price becomes available. Risk-Free Interest Rate —The risk-free interest rate is based on the U.S. Treasury zero coupon issues in effect at the time of grant for periods corresponding with the expected term of option. Expected Dividend —The Company has never paid dividends on its common stock and has no plans to pay dividends on its common stock. Therefore, the Company used an expected dividend yield of zero . The fair value of stock option awards granted to employees was estimated at the date of grant using a Black-Scholes-Merton option pricing model with the following assumptions: Three Months Ended 2021 2020 Expected term (in years) 6.1 6.1 Expected volatility 59.2 % 57.6 % Risk-free interest rate 0.42 – 0.92 % 1.5 5 Expected dividends — —

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes To calculate the interim tax provision, at the end of each interim period the Company estimates the annual effective tax rate and applies that to its quarterly earnings from continuing operations. The effect of changes in the enacted tax laws or rates is recognized in the interim period in which the change occurs. The computation of the annual estimated effective tax rate at each interim period requires certain estimates and judgments including, but not limited to, the expected operating income for the year, projections of the proportion of income earned and taxed in foreign jurisdictions, permanent differences between book and tax amounts, and the likelihood of recovering deferred tax assets generated in the current year. The accounting estimates used to compute the provision for income taxes may change as new events occur, additional information is obtained, or the tax environment changes. The Company’s effective tax rate for the three months ended March 31, 2021 and 2020 differs from the U.S. statutory rate due to the U.S. valuation allowance and foreign income taxed at local statutory rates. During the three months ended March 31, 2021, the Company reported U.S. pre-tax losses, consistent with prior years to date. The Company has not yet been able to establish a sustained level of profitability in the U.S. or other sufficient significant positive evidence to conclude that its U.S. deferred tax assets are more likely than not to be realized. Therefore, the Company continues to maintain a valuation allowance against its U.S. deferred tax assets.

Defined Contribution Plan

Defined Contribution Plan	3 Months Ended
	Mar. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Defined Contribution Plan	12. Defined Contribution Plan The Company has a defined contribution retirement savings plan under Section 401(k) of the IRC. This plan allows eligible employees to defer a portion of their annual compensation on a pre-tax or after-tax basis. The Company makes discretionary matching contributions of up to 4 % of a participating employee’s salary. For the three months ended March 31, 2021 and 2020, the amount expensed under the plan was $ 111,000 and $ 95,000 , respectively.

Net Loss Per Share Attributable

Net Loss Per Share Attributable to Common Stockholders	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share Attributable to Common Stockholders	13. Net Loss Per Share Attributable to Common Stockholders The following outstanding shares of potentially dilutive securities were excluded from the computation of the diluted net loss per share attributable to common stockholders for the periods presented because their effect would have been anti-dilutive: Three Months Ended 2021 2020 Redeemable convertible preferred stock on an as-converted 12,605,800 12,539,109 Redeemable convertible preferred stock warrants on an as- 229,034 193,583 Convertible notes on an as-converted basis 559,585 — Stock options to purchase common stock 2,709,710 2,464,335 Total 16,104,129 15,197,027

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events The Company adopted its 2021 Stock Incentive Plan, or the 2021 Plan, which became effective on the date immediately prior to the date of effectiveness of the IPO and will serve as the successor to its 2018 Plan. The 2021 Plan authorizes the award of stock options, RSUs, restricted stock awards, stock bonus awards, stock appreciation rights, performance awards, and cash awards. The Company initially reserved 2,205,000 shares of its common stock, plus any reserved shares not issued or subject to outstanding grants under the 2018 Plan on the effective date of the 2021 Plan, for issuance pursuant to awards granted under its 2021 Plan. The number of shares reserved for issuance under its 2021 Plan will increase automatically on January 1 of each of 2022 through 2031 by the number of shares equal to the lesser of 5% of the total number of outstanding shares of all classes of its common stock as of the immediately preceding December 31, or a number as may be determined by its board of directors .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with United States generally accepted accounting principles, or U.S. GAAP. The condensed consolidated financial statements include the operations of Impel Neuropharma, Inc., and its wholly owned Australian subsidiary. All intercompany balances and transactions have been eliminated upon consolidation. The condensed consolidated balance sheet as of March 31, 2021, the condensed consolidated statements of operations and comprehensive loss, changes in redeemable convertible preferred stock and stockholders’ deficit and cash flows for the three months ended March 31, 2021 and 2020 are unaudited. These unaudited condensed consolidated financial statements have been prepared on the same basis as the annual consolidated financial statements 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 as of March 31, 2021 and its results of operations and cash flows for the three months ended March 31, 2021 and 2020. The financial data and the other financial information contained in these notes to the condensed consolidated financial statements related to the three-month periods are also unaudited. The results of operations for the three months ended March 31, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other future annual or interim period. The condensed consolidated balance sheet as of December 31, 2020 included herein 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 prospectus dated April 23, 2021 that forms a part of the Company's Registration Statement on Form S-1 (File No. 333-254999), as filed with the SEC pursuant to Rule 424(b)(4) promulgated under the Securities Act of 1933, as amended.
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 amounts reported in the financial statements and accompanying notes. On an ongoing basis, management evaluates such estimates and assumptions for continued reasonableness. In particular, management makes estimates with respect to the fair values of common stock, redeemable convertible preferred stock warrant liabilities, stock-based compensation expense, convertible debt and income taxes. Appropriate adjustments, if any, to the estimates used are made prospectively based upon such periodic evaluation. Actual results could differ from those estimates.
Segments	Segments The Company’s chief operating decision maker is its Chief Executive Officer. The Chief Executive Officer reviews financial information on an aggregate basis for the purposes of evaluating financial performance and allocating the Company’s resources. Accordingly, the Company has determined that it operates in one segment.
Cash	Cash The Company considers all highly liquid investments with original maturities of three months or less from the date of purchase to be cash equivalents. At March 31, 2021 and December 31, 2020, cash consisted of cash in bank deposits held at financial institutions.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash. The Company’s cash is deposited with high credit quality financial institutions. At times such deposits may be in excess of the Federal Depository Insurance Corporation insured limits.
Fair Value Measurement	Fair Value Measurement Assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: 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 for the asset or liability. These include quoted prices for similar assets or liabilities in active markets and quoted prices for identical or similar assets or liabilities in markets that are not active; 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. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The carrying amounts reflected in the accompanying consolidated balance sheets for cash, other current assets, accounts payable, and accrued liabilities approximate their fair values, due to their short-term nature.
Convertible Notes	Convertible Notes In March 2021, the Company issued convertible promissory notes to various investors for an aggregate amount of $ 7.5 million. As permitted under Accounting Standards Codification ("ASC") 825, Financial Instruments ("ASC 825"), the Company has elected the fair value option for recognition of the convertible notes. The Company elected the fair value option to allow the Company to eliminate the burden of complying with the requirements for derivative accounting. Under the fair value option, the convertible notes are remeasured at fair value in each reporting period until their conversion in April 2021, with changes in the fair value recognized in the Company’s condensed consolidated statement of operations as other (expense) income, net. Accrued interest on the convertible notes is recorded in interest (expense) income, net.
Deferred Offering Costs	Deferred Offering Costs The Company has deferred offering costs consisting of legal, accounting and other fees and costs directly attributable to the Company’s IPO. The deferred offering costs will be offset against the proceeds received upon the completion of the IPO. As of March 31, 2021, $ 1.5 million of deferred offering costs were included in other assets on the condensed consolidated balance sheet. There were no deferred offering costs as of December 31, 2020.
Redeemable Convertible Preferred Stock Warrant Liabilities	Redeemable Convertible Preferred Stock Warrant Liabilities Freestanding warrants to purchase shares of the Company’s redeemable convertible preferred stock are accounted for as liabilities at fair value, because the shares underlying the warrants contain contingent redemption features outside the control of the Company. Warrants classified as liabilities are recorded on the Company’s condensed consolidated balance sheets at their fair value on the date of issuance and remeasured to fair value on each subsequent reporting period, with the changes in fair value recognized as a component of other (expense) income, net in the accompanying condensed consolidated statements of operations. The Company will continue to adjust the liability for changes in the fair value of these warrants until the earlier of the exercise of the warrants, the expiration of the warrants, or until such time as the warrants are no longer considered liability instruments.
Research and Development	Research and Development Research and development costs are expensed as incurred and consist primarily of salaries, benefits and other staff-related costs, including associated stock-based compensation, laboratory supplies, nonclinical and clinical studies and trials and related clinical manufacturing costs, costs related to manufacturing preparation, fees paid to other entities that conduct certain research and development activities on the Company’s behalf. Non-refundable advance payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized as prepaid expenses until the related goods are delivered or services are performed. Such payments are evaluated for current or long-term classification based on when such services are expected to be received.
Advance Payments for Research and Development Services and Accruals	Advance Payments for Research and Development Services and Accruals As part of the process of preparing its condensed consolidated financial statements, the Company is required to estimate its expenses resulting from its obligation under contracts with vendors and consultants and clinical site agreements in connection with its research and development efforts. The financial terms of these contracts are subject to negotiations which vary contract to contract and may result in payment flows that do not match the periods over which materials or services are provided to the Company under such contracts. The Company’s objective is to reflect the appropriate research and development expenses in its condensed consolidated financial statements by matching those expenses with the period in which services and efforts are expended. The Company accounts for these expenses according to the progress of its research and development efforts. The Company determines advance payments for research and development services and accrual estimates through discussion with applicable personnel and outside service providers as to the progress of clinical trials, or other services completed. The Company adjusts its rate of research and development expense recognition if actual results differ from its estimates. The Company makes estimates of its advance payments and accrued expenses as of each balance sheet date in its condensed consolidated financial statements based on facts and circumstances known at that time. Although the Company does not expect its estimates to be materially different from amounts actually incurred, its understanding of status and timing of services performed relative to the actual status and timing of services performed may vary and may result in the Company reporting amounts that are too high or too low for any particular period. Through March 31, 2021, there had been no material adjustments to the Company’s prior period estimates of advance payments and accruals for research and development expenses. The Company’s research and development advance payments and accruals are dependent upon the timely and accurate reporting of contract research organizations and other third-party vendors.
Stock-Based Compensation	Stock-Based Compensation The Company recognizes stock-based compensation expense for stock options and restricted stock unit awards on a straight-line basis over the requisite service period. The Company’s stock-based compensation costs are based upon the grant date fair value of options estimated using the Black-Scholes-Merton option pricing model. This model utilizes as inputs the estimated fair value of the underlying common stock at the measurement date, the estimated term of the stock options (weighted-average period of time that the options granted are expected to be outstanding), risk-free interest rates, expected dividends, and the expected volatility of the Company’s common stock. The Company has elected to recognize forfeitures of share-based payment awards as they occur. The Company recognizes stock-based compensation expense for stock options granted to nonemployees based on the estimated fair value of the award as it is more readily measurable than the fair value of the services received.
Net Loss Per Share Attributable to Common Stockholders	Net Loss Per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding for the period, without consideration of potentially dilutive securities. Diluted net loss per share attributable to common stockholders is the same as basic net loss per share attributable to common stockholders since the effect of potentially dilutive securities is anti-dilutive given the net loss of the Company.
Comprehensive Loss	Comprehensive Loss Comprehensive loss represents the change in the Company’s stockholders’ deficit from all sources other than investments by or distributions to stockholders. The Company has no items of other comprehensive loss; as such, net loss equals comprehensive loss.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2016-02, Leases , or Topic 842, which supersedes the guidance in former ASC 840, Leases . This standard requires lessees to apply a dual approach, classifying leases as either finance or operating leases based on the principle of whether or not the lease is effectively a financed purchase by the lessee. This classification will determine whether lease expense is recognized based on an effective interest method or on a straight-line basis over the term of the lease. A lessee is also required to record a right-of-use asset and a lease liability for all leases with a term of greater than 12 months regardless of their classification. Leases with a term of 12 months or less may be accounted for similar to existing guidance for operating leases today. In May 2020, the FASB issued ASU No. 2020-05, Revenue from Contracts with Customers (Topic 606) and Leases (Topic 842): Effective Dates for Certain Entities, which deferred the effective dates for non-public entities. Therefore, this standard is effective for annual reporting periods, and interim periods within those years, for public entities beginning after December 15, 2018 and for private entities beginning after December 15, 2021. Originally, a modified retrospective transition approach was required for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. In July 2018, the FASB issued guidance to permit an alternative transition method for Topic 842, which allows transition to the new lease standard by recognizing a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Entities may elect to apply either approach. There are also a number of optional practical expedients that entities may elect to apply. The Company is currently assessing the impact of this standard on its condensed consolidated financial statements. The Company expects to record a material right-of-use asset and lease liability in connection with adopting this standard on January 1, 2022. Recently Adopted Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40): Accounting for Convertible Instruments and Contracts in an Entity’s Own Equity , or ASU 2020-06, which simplifies accounting for convertible instruments by removing major separation models required under current U.S. GAAP. ASU 2020-06 removes certain settlement conditions that are required for equity contracts to qualify for the derivative scope exception and it also simplifies the diluted earnings per share calculation in certain areas. ASU 2020-06 is effective for the Company for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted, but no earlier than fiscal years beginning after December 15, 2020 and adoption must be as of the beginning of the Company’s annual fiscal year. The Company early adopted this standard on January 1, 2021 and the adoption of the standard did not have a significant impact on its consolidated financial statements.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Summary of Fair Value, Liabilities Measured on Recurring Basis	The following table summarizes the fair value of the Company’s financial liabilities measured at fair value on a recurring basis by level within the fair value hierarchy (in thousands): March 31, 2021 Level 1 Level 2 Level 3 Total Liabilities: Redeemable convertible preferred stock warrant liabilities $ — $ — $ 2,677 $ 2,677 Convertible notes $ — $ — $ 8,366 $ 8,366 Total financial liabilities $ — $ — $ 11,043 $ 11,043 December 31, 2020 Level 1 Level 2 Level 3 Total Liabilities: Redeemable convertible preferred stock warrant liabilities $ — $ — $ 2,622 $ 2,622 Total financial liabilities $ — $ — $ 2,622 $ 2,622
Summary of Change in Fair Value of Redeemable Convertible Preferred Stock Warrant Liabilities and Convertible notes	The following table summarizes the change in the fair value of the redeemable convertible preferred stock warrant liabilities for the three months ended March 31, 2021 (in thousands): Beginning balance as of December 31, 2020 $ 2,622 Losses from changes in fair value 55 Ending balance as of March 31, 2021 $ 2,677 The following table summarizes the change in the fair value of the convertible notes for the three months ended March 31, 2021 (in thousands): Beginning balance as of December 31, 2020 $ — Issuance of convertible notes 7,500 Interest 27 Losses from changes in fair value 839 Ending balance as of March 31, 2021 $ 8,366

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): March 31, December 31, Refundable clinical deposits $ 825 $ 627 Tax refund receivable 229 229 Prepaid insurance 178 47 Other prepaids and current assets 560 129 Total prepaid expenses and other current assets $ 1,792 $ 1,077
Schedule of Accrued Liabilities	Accrued Liabilities Accrued liabilities consisted of the following (in thousands): March 31, December 31, Accrued professional services $ 1,079 $ 192 Accrued compensation 1,274 2,393 Accrued other liabilities 195 333 Accrued construction in progress 77 255 Total accrued liabilities $ 2,625 $ 3,173

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Schedule of Term Loan	The term loan consists of the following (in thousands): March 31, December 31, Face value of term loan $ 10,000 $ 10,000 Final payment 450 450 Unamortized debt discount associated with final payment, ( 1,820 ) ( 2,039 ) Total debt, net $ 8,630 $ 8,411 Less: short-term debt 1,667 417 Long-term debt $ 6,963 $ 7,994

Redeemable Convertible Prefer_3

Redeemable Convertible Preferred Stock Warrant Liabilities (Tables)	3 Months Ended
	Mar. 31, 2021
Warrants And Rights Note Disclosure [Abstract]
Schedule of Outstanding Redeemable Convertible Preferred Stock Warrant Liabilities	The key terms of the outstanding redeemable convertible preferred stock warrant liabilities as of March 31, 2021 and December 31, 2020 are summarized in the following table: Number of shares as of Exercisable into: March 31, December 31, Exercise Expiration Series A-2 redeemable convertible preferred stock 862,471 862,471 $ 0.4996 September 30, 2021 Series C-1 redeemable convertible preferred stock 1,124,877 1,124,877 0.5289 November 16, 2021 Series D redeemable convertible preferred stock 1,762,810 1,762,810 0.7091 October 31, 2021 Total 3,750,158 3,750,158

Redeemable Convertible Prefer_4

Redeemable Convertible Preferred Stock (Tables)	3 Months Ended
	Mar. 31, 2021
Summary of Redeemable Convertible Preferred Stock	Redeemable convertible preferred stock consisted of the following (in thousands, except share amounts): Redeemable Convertible Shares Authorized Shares Issued and Carrying Value at Carrying Value at Aggregate Series A-1 746,426 746,426 238 $ 238 $ 305 Series A-2 9,869,218 8,805,587 4,147 4,147 4,399 Series B 3,968,775 3,968,775 4,016 3,980 4,421 Series C-1 43,278,699 42,153,822 21,056 20,975 22,297 Series C-2 26,537,826 26,537,826 15,390 15,390 15,000 Series C-3 24,605,790 24,605,790 14,975 14,973 15,000 Series D 95,191,755 95,191,755 67,346 67,336 67,500 Total 204,198,489 202,009,981 127,168 $ 127,039 $ 128,922

Common Stock (Tables)

Common Stock (Tables)	3 Months Ended
	Mar. 31, 2021
Equity [Abstract]
Schedule of Reserved Shares of Common Stock for Issuance, on an as-Converted Basis	The Company has reserved the following shares of common stock for issuance, on an as-converted basis, as follows: March 31, December 31, Stock incentive plans 2,778,250 2,786,345 Redeemable convertible preferred stock 12,605,800 12,605,800 Convertible notes 559,585 — Redeemable convertible preferred stock warrants 229,034 229,034 Total 16,172,669 15,621,179

Stock Incentive Plan (Tables)

Stock Incentive Plan (Tables)	3 Months Ended
	Mar. 31, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity under Stock Option Plans	A summary of the Company’s stock option activity under its stock option plans was as follows (in thousands, except share and per share data and years): Options Outstanding Shares Number of Weighted Remaining Aggregate Balance — December 31, 2020 344,456 2,441,889 $ 5.17 8.02 $ 14,844 Authorized — — $ — - $ — Granted ( 276,843 ) 276,843 $ 12.95 - $ — Exercised — ( 8,095 ) $ 2.19 - $ — Cancelled 927 ( 927 ) $ 2.82 - $ — Balance — March 31, 2021 68,540 2,709,710 $ 5.97 9.01 $ 21,079 Exercisable — March 31, 2021 — 1,079,601 $ 3.28 6.79 $ 11,308
Schedule of Stock-Based Compensation Expense Recognized	Stock-based compensation expense recognized was as follows (in thousands): Three Months Ended 2021 2020 Research and development $ 119 $ 119 General and administrative 374 179 Total stock-based compensation expense $ 493 $ 298
Schedule of Share-Based Payment Award Stock Options Valuation Assumptions	The fair value of stock option awards granted to employees was estimated at the date of grant using a Black-Scholes-Merton option pricing model with the following assumptions: Three Months Ended 2021 2020 Expected term (in years) 6.1 6.1 Expected volatility 59.2 % 57.6 % Risk-free interest rate 0.42 – 0.92 % 1.5 5 Expected dividends — —

Net Loss Per Share Attributab_2

Net Loss Per Share Attributable to Common Stockholders (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders	The following outstanding shares of potentially dilutive securities were excluded from the computation of the diluted net loss per share attributable to common stockholders for the periods presented because their effect would have been anti-dilutive: Three Months Ended 2021 2020 Redeemable convertible preferred stock on an as-converted 12,605,800 12,539,109 Redeemable convertible preferred stock warrants on an as- 229,034 193,583 Convertible notes on an as-converted basis 559,585 — Stock options to purchase common stock 2,709,710 2,464,335 Total 16,104,129 15,197,027

Organization and Description _2

Organization and Description of Business - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Apr. 23, 2021	Apr. 30, 2021	Mar. 31, 2021	Mar. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Date of incorporation				Jul. 24, 2008
Payment of underwriting discounts, commissions				$ 209
Reverse stock split, description				effect a reverse split of shares of the Company’s common stock on an one-for-16.37332 basis, which was effected on April 16, 2021 (the “Reverse Stock Split”). The number of authorized shares and the par values of the common stock and redeemable convertible preferred stock were not adjusted as a result of the Reverse Stock Split. In connection with the Reverse Stock Split, the conversion ratio for the Company’s outstanding redeemable convertible preferred stock was proportionately adjusted such that the common stock issuable upon conversion of such preferred stock was decreased in proportion to the Reverse Stock Split
Proceeds from issuance or sale of equity, debt and warrants				$ 142,500
Cash			$ 4,500	4,500
Common Stock | Subsequent Events [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Conversion of redeemable convertible preferred stock to common stock	12,605,800
Common Stock | Avenue Venture Opportunities Fund L P | Subsequent Events [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Conversion of warrant, shares converted	107,663
Warrant exercised	52,974
Warrant to Purchase Common Stock [Member] | Avenue Venture Opportunities Fund L P | Subsequent Events [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Conversion of warrant, shares converted	1,987,348
Convertible Notes [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Conversion of redeemable convertible preferred stock to common stock			559,585
Conversion of convertible notes, amount converted			$ 7,500
Discount of Initial Public Offering price			10.00%
IPO [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Remaining borrowing capacity			$ 10,000	$ 10,000
IPO [Member] | Subsequent Events [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Shares issued and sold	5,333,334
Shares price per share	$ 15
Proceeds from issuance of common stock, net of underwriters discount and commissions	$ 71,400	$ 71,400
Payments of stock issuance offering costs	3,000
Payment of underwriting discounts, commissions	$ 5,600

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)Segment	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount	$ 10,000	$ 10,000
Deferred offering costs	$ 1,500	$ 0
Number of operating segments | Segment	1
Convertible Promissory Notes
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount	$ 7,500

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Fair Value, Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Liabilities:
Total financial liabilities	$ 11,043	$ 2,622
Redeemable Convertible Preferred Stock Warrant Liability [Member]
Liabilities:
Total financial liabilities	2,677	2,622
Convertible Notes [Member]
Liabilities:
Total financial liabilities	8,366	0
Level 1 [Member]
Liabilities:
Total financial liabilities	0	0
Level 1 [Member] | Redeemable Convertible Preferred Stock Warrant Liability [Member]
Liabilities:
Total financial liabilities	0	0
Level 1 [Member] | Convertible Notes [Member]
Liabilities:
Total financial liabilities	0
Level 2 [Member]
Liabilities:
Total financial liabilities	0	0
Level 2 [Member] | Redeemable Convertible Preferred Stock Warrant Liability [Member]
Liabilities:
Total financial liabilities	0	0
Level 2 [Member] | Convertible Notes [Member]
Liabilities:
Total financial liabilities	0
Level 3 [Member]
Liabilities:
Total financial liabilities	11,043	2,622
Level 3 [Member] | Redeemable Convertible Preferred Stock Warrant Liability [Member]
Liabilities:
Total financial liabilities	2,677	$ 2,622
Level 3 [Member] | Convertible Notes [Member]
Liabilities:
Total financial liabilities	$ 8,366

Fair Value Measurements - Sum_2

Fair Value Measurements - Summary of Change in Fair Value of Redeemable Convertible Preferred Stock Warrant Liabilities and Convertible notes (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning balance	$ 2,622
Ending balance	11,043
Convertible Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning balance	0
Issuance of convertible notes	7,500
Interest	27
Losses from changes in fair value	839
Ending balance	8,366
Redeemable Convertible Preferred Stock Warrant Liability [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Beginning balance	2,622
Losses from changes in fair value	55
Ending balance	$ 2,677

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Refundable clinical deposits	$ 825	$ 627
Tax refund receivable	229	229
Prepaid insurance	178	47
Other prepaids and current assets	560	129
Total prepaid expenses and other current assets	$ 1,792	$ 1,077

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Accrued professional services	$ 1,079	$ 192
Accrued compensation	1,274	2,393
Accrued other liabilities	195	333
Accrued construction in progress	77	255
Total accrued liabilities	$ 2,625	$ 3,173

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	1 Months Ended	3 Months Ended
	Sep. 30, 2017ft²	Mar. 31, 2021USD ($)	Mar. 31, 2020USD ($)
Commitments And Contingencies Disclosure [Abstract]
Non cancelable operating lease area | ft²	11,256
Remaining future minimum lease payments		$ 1,000,000
Increase in rent payable monthly, percentage	3.00%
Operating lease expiration date		Aug. 31, 2022
Rent expenses		$ 174,000	$ 150,000

Debt - Additional Information (

Debt - Additional Information (Details) - USD ($)	Nov. 05, 2020	Mar. 31, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Final principal payment	$ 450,000
Face value of term loan		$ 10,000,000	$ 10,000,000
Debt instrument, aggregate principal amount		10,000,000	$ 10,000,000
IPO [Member]
Debt Instrument [Line Items]
Remaining borrowing capacity		10,000,000
Maximum [Member] | IPO [Member]
Debt Instrument [Line Items]
Right to invest in a private placement	$ 10,000,000
Term Loan [Member]
Debt Instrument [Line Items]
Term of loan	36 months
Current borrowing capacity	$ 10,000,000
Remaining borrowing capacity	10,000,000
Gross proceeds	$ 75,000,000
Debt instrument interest rate stated percentage	11.00%
Long term debt draw down	$ 10,000,000
Net proceeds from issuance of term loan	1,500,000
Financing cost	$ 299,000
Interest expense		$ 491,000
Debt Instrument Interest Rate Stated Percentage	11.00%
Term Loan [Member] | Series D Preferred Stock [Member]
Debt Instrument [Line Items]
Granted warrants for the purchase of shares	1,762,810
Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Maximum credit commitment	$ 20,000,000
Term Loan [Member] | Minimum [Member] | IPO [Member]
Debt Instrument [Line Items]
Gross proceeds	$ 75,000,000
Convertible Promissory Notes
Debt Instrument [Line Items]
Debt instrument interest rate stated percentage		5.00%
Proceeds from issuance of debt		$ 50,000,000
Face value of term loan		$ 7,500,000
Debt Instrument Interest Rate Stated Percentage		5.00%
Debt instrument, aggregate principal amount		$ 7,500,000
Debt instrument, maturity date		Dec. 31, 2021
Shares price per share		$ 1.0636
Debt instrument, convertible terms		The notes are (i) automatically convertible into shares of the Company’s common stock upon the closing of a firm-commitment underwritten public offering, at a per share price of at least $1.0636, resulting in at least $50.0 million in net proceeds, or a Qualified Public Offering, or a SPAC transaction at 90% of the price per share in such transactions, (ii) convertible at the holder’s option or upon a change of control into shares of Series D redeemable convertible preferred stock at the Series D original issuance price, and (iii) convertible at the holder’s option upon a new redeemable convertible preferred stock financing into shares of redeemable preferred stock issued in such financing at 90% of the price per share.
Accrued interest on convertible notes		$ 27,000
Increase in fair value on the convertible notes		839,000
Carrying value of convertible notes		$ 8,400,000
Conversion of convertible notes into common stock (in shares)		559,585

Debt - Schedule of Term Loan (D

Debt - Schedule of Term Loan (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Face value of term loan	$ 10,000	$ 10,000
Final payment	450	450
Unamortized debt discount associated with final payment, issuance date warrant fair value, and financing costs	(1,820)	(2,039)
Total debt, net	8,630	8,411
Less: short-term debt	1,667	417
Long-term debt	$ 6,963	$ 7,994

Redeemable Convertible Prefer_5

Redeemable Convertible Preferred Stock Warrant Liabilities - Schedule of Outstanding Redeemable Convertible Preferred Stock Warrant Liabilities (Details) - $ / shares	Mar. 31, 2021	Dec. 31, 2020
Class Of Warrant Or Right [Line Items]
Redeemable convertible preferred stock warrant liabilities, Number of shares outstanding	3,750,158	3,750,158
Series A-2 Redeemable Convertible Preferred Stock [Member]
Class Of Warrant Or Right [Line Items]
Redeemable convertible preferred stock warrant liabilities, Number of shares outstanding	862,471	862,471
Redeemable convertible preferred stock warrant liabilities, Exercise Price	$ 0.4996
Redeemable convertible preferred stock warrant liabilities, Expiration	Sep. 30, 2021
Series C-1 Redeemable Convertible Preferred Stock [Member]
Class Of Warrant Or Right [Line Items]
Redeemable convertible preferred stock warrant liabilities, Number of shares outstanding	1,124,877	1,124,877
Redeemable convertible preferred stock warrant liabilities, Exercise Price	$ 0.5289
Redeemable convertible preferred stock warrant liabilities, Expiration	Nov. 16, 2021
Series D Redeemable Convertible Preferred Stock [Member]
Class Of Warrant Or Right [Line Items]
Redeemable convertible preferred stock warrant liabilities, Number of shares outstanding	1,762,810	1,762,810
Redeemable convertible preferred stock warrant liabilities, Exercise Price	$ 0.7091
Redeemable convertible preferred stock warrant liabilities, Expiration	Oct. 31, 2021

Redeemable Convertible Prefer_6

Redeemable Convertible Preferred Stock Warrant Liabilities - Additional Information (Details) - shares	1 Months Ended	3 Months Ended
	Apr. 30, 2021	Mar. 31, 2021	Mar. 31, 2020
Class Of Warrant Or Right [Line Items]
Expected volatility rate, minimum		46.40%	46.00%
Expected volatility rate, maximum		103.00%	64.10%
Risk-free interest rate, minimum		0.04%	0.15%
Risk-free interest rate, maximum		0.24%	2.81%
Series D Redeemable Convertible Preferred Stock [Member]
Class Of Warrant Or Right [Line Items]
Warrants for purchase of shares exercised		107,663
Subsequent Event [Member] | Series A-2 Redeemable Convertible Preferred Stock [Member]
Class Of Warrant Or Right [Line Items]
Warrants for purchase of shares exercised	52,974

Redeemable Convertible Prefer_7

Redeemable Convertible Preferred Stock - Summary of Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Temporary Equity [Line Items]
Shares Authorized	204,198,489	204,198,489
Shares Issued and Outstanding	202,009,981
Carrying Value	$ 127,168	$ 127,039
Redeemable convertible preferred stock, aggregate liquidation preference	$ 128,922	128,922
Series A-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	746,426
Shares Issued and Outstanding	746,426
Carrying Value	$ 238	238
Redeemable convertible preferred stock, aggregate liquidation preference	$ 305
Series A-2 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	9,869,218
Shares Issued and Outstanding	8,805,587
Carrying Value	$ 4,147	4,147
Redeemable convertible preferred stock, aggregate liquidation preference	$ 4,399
Series B Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	3,968,775
Shares Issued and Outstanding	3,968,775
Carrying Value	$ 4,016	3,980
Redeemable convertible preferred stock, aggregate liquidation preference	$ 4,421
Series C-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	43,278,699
Shares Issued and Outstanding	42,153,822
Carrying Value	$ 21,056	20,975
Redeemable convertible preferred stock, aggregate liquidation preference	$ 22,297
Series C-2 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	26,537,826
Shares Issued and Outstanding	26,537,826
Carrying Value	$ 15,390	15,390
Redeemable convertible preferred stock, aggregate liquidation preference	$ 15,000
Series C-3 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	24,605,790
Shares Issued and Outstanding	24,605,790
Carrying Value	$ 14,975	14,973
Redeemable convertible preferred stock, aggregate liquidation preference	$ 15,000
Series D Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Shares Authorized	95,191,755
Shares Issued and Outstanding	95,191,755
Carrying Value	$ 67,346	$ 67,336
Redeemable convertible preferred stock, aggregate liquidation preference	$ 67,500

Redeemable Convertible Prefer_8

Redeemable Convertible Preferred Stock - Additional Information (Details) - USD ($)	Apr. 30, 2021	Mar. 31, 2021	Mar. 31, 2020
Series A-1 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity, accretion to redemption value		$ 0	$ 0
Series A-2 Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity, accretion to redemption value		0	0
Redeemable Convertible Preferred Stock [Member]
Temporary Equity [Line Items]
Temporary equity, accretion to redemption value		0	0
Temporary equity, accretion of dividends		$ 129,000	$ 128,000
Redeemable Convertible Preferred Stock [Member] | Subsequent Events [Member]
Temporary Equity [Line Items]
Number of common stock shares issued upon conversion	12,605,800
Carrying value reclassified to equity	$ 127,200,000

Common Stock - Additional Infor

Common Stock - Additional Information (Details) - Common Stock [Member]	3 Months Ended
	Mar. 31, 2021USD ($)
Common stock, voting rights	Each share of common stock has the right to one vote.
Cash dividends declared	$ 0

Common Stock - Schedule of Rese

Common Stock - Schedule of Reserved Shares of Common Stock for Issuance, on an as-Converted Basis (Details) - shares	Mar. 31, 2021	Dec. 31, 2020
Common stock reserved for future issuance	16,172,669	15,621,179
Stock Incentive Plans [Member]
Common stock reserved for future issuance	2,778,250	2,786,345
Redeemable Convertible Preferred Stock [Member]
Common stock reserved for future issuance	12,605,800	12,605,800
Convertible Notes [Member]
Common stock reserved for future issuance	559,585	0
Redeemable Convertible Preferred Stock Warrant [Member]
Common stock reserved for future issuance	229,034	229,034

Stock Incentive Plan - Addition

Stock Incentive Plan - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended
	May 31, 2020	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options outstanding		2,709,710		2,441,889
Common stock reserved for future issuance		16,172,669		15,621,179
Number of shares available for grant		68,540		344,456
Stock options, grants in period		276,843
Stock options, grants in period, weighted-average exercise price		$ 12.95
Unvested stock options, cost not yet recognized, amount		$ 6,900
Unvested award, cost not yet recognized, period for recognition		3 years
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares available for future grant	596,414
Accelerated cost	$ 2,100
Stock options, exercises in period, total intrinsic value		$ 94,000	$ 21,000
Stock options, vested in period, fair value		367,000	434,000
Stock options. grants in period, grant date fair value		$ 2,000	$ 700
Stock options, grants in period, weighted-average grant date fair value		$ 7.07	$ 4.47
Expected dividend yield		0.00%	0.00%
Stock Options [Member] | Chief Executive Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period	48 months
Stock options, grants in period	715,358
Stock options, grants in period, weighted-average exercise price	$ 7.86
2008 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Plan term		10 years
Stock options outstanding		627,285		634,788
2018 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options outstanding		2,082,425		1,807,101
Terms of award		The exercise price of incentive stock options and nonqualified stock options will be no less than 100% of the fair value per share of the Company’s common stock on the date of grant. If an individual owns capital stock representing more than 10% of the voting shares and the grant is an incentive stock option, the price of each share will be at least 110% of the fair value on the date of grant
Award expiration period		10 years
Stockholders owning greater than 10% of voting stock, award expiration period		5 years
Award vesting period		4 years
Options exercised period		10 years
Common stock reserved for future issuance		753,645
Number of shares available for grant		68,540		344,456

Stock Incentive Plan - Summary

Stock Incentive Plan - Summary of Stock Option Activity under Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares Available for Grant, Beginning Balance	344,456
Shares Available for Grant, Authorized	0
Shares Available for Grant, Granted	276,843
Shares Available for Grant, Exercised	0
Shares Available for Grant, Cancelled	927
Shares Available for Grant, Ending Balance	68,540	344,456
Shares Available for Grant, Exercisable	0
Number of Options, Beginning Balance	2,441,889
Number of Options, Authorized	0
Number of Options, Granted	276,843
Number of Options, Exercised	8,095
Number of Options, Cancelled	927
Number of Options, Ending Balance	2,709,710	2,441,889
Number of Options, Exercisable	1,079,601
Weighted-Average Exercise Price, Beginning Balance	$ 5.17
Weighted Average Exercise Price, Authorized	0
Weighted-Average Exercise Price, Granted	12.95
Weighted-Average Exercise Price, Exercised	2.19
Weighted-Average Exercise Price, Cancelled	2.82
Weighted-Average Exercise Price, Ending Balance	5.97	$ 5.17
Weighted-Average Exercise Price, Exercisable	$ 3.28
Remaining Contractual Term (Years), Balance	9 years 3 days	8 years 7 days
Remaining Contractual Term (Years), Exercisable	6 years 9 months 14 days
Aggregate Intrinsic Value, Beginning Balance	$ 14,844
Aggregate Intrinsic Value, Ending Balance	21,079	$ 14,844
Aggregate Intrinsic Value, Exercisable	$ 11,308

Stock Incentive Plan - Schedule

Stock Incentive Plan - Schedule of Stock-Based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 493	$ 298
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	119	119
General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 374	$ 179

Stock Incentive Plan - Schedu_2

Stock Incentive Plan - Schedule of Share-Based Payment Award Stock Options Valuation Assumptions (Details) - Stock Options [Member]	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	59.20%	57.60%
Risk-free interest rate		1.55%
Expected dividends	0.00%	0.00%
Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.42%
Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Risk-free interest rate	0.92%

Defined Contribution Plan - Add

Defined Contribution Plan - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Compensation And Retirement Disclosure [Abstract]
Maximum employee's contribution, percentage	4.00%
Defined contribution plan amount expensed	$ 111,000	$ 95,000

Net Loss Per Share Attributab_3

Net Loss Per Share Attributable to Common Stockholders - Schedule of Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share Attributable to Common Stockholders (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	16,104,129	15,197,027
Redeemable Convertible Preferred Stock on an as-Converted Basis [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	12,605,800	12,539,109
Redeemable Convertible Preferred Stock Warrants on an as Converted Basis [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	229,034	193,583
Convertible notes on an as-converted basis
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	559,585	0
Stock Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	2,709,710	2,464,335

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - shares	1 Months Ended
	Apr. 30, 2021	Mar. 31, 2021	Dec. 31, 2020
Subsequent Event [Line Items]
Common Stock Capital Shares Reserved For Future Issuance		16,172,669	15,621,179
Subsequent Events [Member]
Subsequent Event [Line Items]
Subsequent event, description	The number of shares reserved for issuance under its 2021 Plan will increase automatically on January 1 of each of 2022 through 2031 by the number of shares equal to the lesser of 5% of the total number of outstanding shares of all classes of its common stock as of the immediately preceding December 31, or a number as may be determined by its board of directors
Common Stock Capital Shares Reserved For Future Issuance	2,205,000