Tarsus Pharmaceuticals (TARS) 10-K 31 Mar 21 2020 FY Annual report Financial data

Cover

Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Mar. 19, 2021	Oct. 16, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	012-34567
Entity Registrant Name	TARSUS PHARMACEUTICALS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	81-4717861
Entity Address, Address Line One	15440 Laguna Canyon Road, Suite 160
Entity Address, City or Town	Irvine
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92618
City Area Code	949
Local Phone Number	409-9820
Title of 12(b) Security	Common Stock, $0.0001 par value per share
Trading Symbol	TARS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Smaller Reporting Company	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		20,503,096
Entity Public Float			$ 312
Documents Incorporated by Reference	Portions of the information called for by Part III of this Annual Report on Form 10-K is hereby incorporated by reference to portions of the registrant’s definitive proxy statement for its 2021 annual meeting of stockholders, which will be filed with the Securities and Exchange Commission not later than 120 days after the registrant’s fiscal year ended December 31, 2020.
Amendment Flag	false
Entity Central Index Key	0001819790
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY

Balance Sheets

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 168,129	$ 57,952
Restricted cash	20	20
Other receivables	20	36
Prepaid Expense, Current	2,486	22
Total current assets	170,655	58,030
Property and equipment, net	548	154
Operating lease right-of-use assets	688	126
Other assets	81	6
Total assets	171,972	58,316
Current liabilities:
Accounts payable and other accrued liabilities	4,347	520
Accrued payroll and benefits	1,040	299
Total current liabilities	5,387	819
Other long-term liabilities	605	100
Total liabilities	5,992	919
Commitments and contingencies (Note 10)
Preferred stock	0	63,402
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 and no shares authorized at December 31, 2020 and December 31, 2019, respectively; no shares issued and outstanding at December 31, 2020 and December 31, 2019	0	0
Common stock, $0.0001 par value; 200,000,000 shares authorized; 20,502,576 shares issued and 20,323,201 outstanding, which excludes 179,375 shares subject to repurchase at December 31, 2020; 2,650,919 shares issued and 2,646,619 outstanding, which excludes 4,300 shares subject to repurchase at December 31, 2019	4	2
Additional paid-in capital	198,821	27
Accumulated deficit	(32,845)	(6,034)
Total stockholders’ equity (deficit)	165,980	(6,005)
Total liabilities, preferred stock and stockholders’ equity (deficit)	171,972	58,316
Series A Preferred Stock, $0.0001 par value; no shares authorized, issued and outstanding at December 31, 2020; 1,575,030 shares authorized, issued and outstanding at December 31, 2019; liquidation preference of $3,650 at December 31, 2019
Current liabilities:
Preferred stock	0	3,564
Series B Preferred Stock, $0.0001 par value; no shares authorized, issued and outstanding at December 31, 2020; 6,731,649 shares authorized and 6,674,909 shares issued and outstanding at December 31, 2019; liquidation preference of $60,010 at December 31, 2019
Current liabilities:
Preferred stock	$ 0	$ 59,838

Balance Sheets (Parenthetical)

Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Preferred stock, authorized (shares)		8,306,679
Preferred stock, issued (shares)	0
Preferred stock, outstanding (shares)	0	8,249,939
Preferred stock, liquidation preference		$ 63,660
Preferred stock, par value (usd per share)	$ 0.0001	$ 0.0001
Preferred stock, authorized (shares)	10,000,000	0
Preferred stock, issued (shares)	0	0
Preferred stock, outstanding (shares)	0	0
Common stock, par value (usd per share)	$ 0.0001	$ 0.0001
Common stock, authorized (shares)	200,000,000
Common stock, issued (shares)	20,502,576	2,650,919
Common stock, outstanding (shares)	20,323,201	2,646,619
Common stock, subject to repurchase (shares)	179,375	4,300
Series A Preferred Stock
Preferred stock, par value (usd per share)		$ 0.0001
Preferred stock, authorized (shares)	0	1,575,030
Preferred stock, issued (shares)	0	1,575,030
Preferred stock, outstanding (shares)	0	1,575,030
Preferred stock, liquidation preference		$ 3,650
Series B Preferred Stock
Preferred stock, par value (usd per share)		$ 0.0001
Preferred stock, authorized (shares)	0	6,731,649
Preferred stock, issued (shares)	0	6,674,909
Preferred stock, outstanding (shares)	0	6,674,909
Preferred stock, liquidation preference		$ 60,010

Statements of Operations and Co

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Operating expenses:
Research and development	$ 18,826	$ 3,162
General and administrative	8,172	1,136
Total operating expenses	26,998	4,298
Loss from operations before other income (expense) and income taxes	(26,998)	(4,298)
Other income (expense):
Interest income (expense), net	188	(40)
Loss on extinguishment of convertible notes	0	(255)
Change in fair value of derivative liabilities	0	(76)
Total other income (expense)	188	(371)
Provision for income taxes	(1)	(1)
Net loss	(26,811)	(4,670)
Comprehensive loss	$ (26,811)	$ (4,670)
Net loss per share attributable to common stockholders, basic and diluted (usd per share)	$ (4.32)	$ (1.98)
Weighted-average common shares outstanding, basic and diluted (shares)	6,207,367	2,362,768

Statements of Preferred and Com

Statements of Preferred and Common Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series A Preferred Stock	Series B Preferred Stock	Series C Preferred Stock, $0.0001 par value; 2,857,084 shares authorized and 2,857,079 shares issued and outstanding at September 30, 2020 (unaudited) and zero shares authorized, issued or outstanding at December 31, 2019; liquidation preference of $40,000 at September 30, 2020 (unaudited) and $0 at December 31, 2019	Common Stock	Additional Paid-In Capital	Accumulated Deficit
Beginning balance (shares) at Dec. 31, 2017	0
Beginning balance at Dec. 31, 2017	$ 0
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Preferred Stock (shares)		1,575,030
Issuance of Preferred Stock, net of issuance costs		$ 3,564
Ending balance (shares) at Dec. 31, 2018	1,575,030
Ending balance at Dec. 31, 2018	$ 3,564
Beginning balance (shares) at Dec. 31, 2017					1,434,027
Beginning balance at Dec. 31, 2017	(44)				$ 1	$ 0	$ (45)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(1,319)						(1,319)
Recognition of stock-based compensation expense	9					9
Issuance of common stock (in shares)					5,385
Vesting of founder shares subject to repurchase (shares)					538,532
Vesting of founder shares subject to repurchase	1				$ 1
Lapse of repurchase rights related to common stock issued pursuant to early exercises (shares)					100,974
Ending balance (shares) at Dec. 31, 2018					2,078,918
Ending balance at Dec. 31, 2018	$ (1,354)				$ 1	9	(1,364)
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Preferred Stock (shares)			6,406,853
Issuance of Preferred Stock, net of issuance costs			$ 57,428
Ending balance (shares) at Dec. 31, 2019	8,249,939	1,575,030	6,674,909
Ending balance at Dec. 31, 2019	$ 63,402	$ 3,564	$ 59,838
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(4,670)						(4,670)
Recognition of stock-based compensation expense	$ 18					18
Issuance of common stock upon exercise of vested stock options (shares)	0
Vesting of founder shares subject to repurchase (shares)					493,654
Lapse of repurchase rights related to common stock issued pursuant to early exercises (shares)					74,047
Issuance of Series B Preferred Stock upon conversion of Convertible Notes (shares)			268,056
Issuance of Series B Preferred Stock upon conversion of Convertible Notes			$ 2,410
Ending balance (shares) at Dec. 31, 2019	2,646,619				2,646,619
Ending balance at Dec. 31, 2019	$ (6,005)				$ 2	27	(6,034)
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of Preferred Stock (shares)				2,857,079
Issuance of Preferred Stock, net of issuance costs				$ 39,756
Conversion of preferred stock into common stock upon initial public offering (in shares)	(11,107,018)
Conversion of preferred stock into common stock upon initial public offering	$ (103,158)
Ending balance (shares) at Dec. 31, 2020	0	0	0
Ending balance at Dec. 31, 2020	$ 0	$ 0	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(26,811)						(26,811)
Recognition of stock-based compensation expense	839					839
Issuance of common stock (in shares)					6,325,000
Issuance of common stock	$ 91,674				$ 1	91,673
Issuance of common stock upon exercise of vested stock options (shares)	197,179				17,804
Issuance of common stock upon exercise of vested stock options	$ 10					10
Shares issued as consideration for in-license rights (Note 9 (b)) (shares)					222,460
Shares issued as consideration for in-license rights (Note 9 (b))	3,115					3,115
Lapse of repurchase rights related to common stock issued pursuant to early exercises (shares)					4,300
Conversion of preferred stock into common stock upon initial public offering (in shares)					11,107,018
Conversion of preferred stock into common stock upon initial public offering	$ 103,158				$ 1	103,157
Ending balance (shares) at Dec. 31, 2020	20,323,201				20,323,201
Ending balance at Dec. 31, 2020	$ 165,980				$ 4	$ 198,821	$ (32,845)

Statements of Preferred and C_2

Statements of Preferred and Common Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock issued, issuance costs	$ 2,442
Series A Preferred Stock
Stock issued, issuance costs			$ 86
Price per share (usd per share)		$ 2.3174
Series B Preferred Stock
Stock issued, issuance costs	28	$ 172
Price per share (usd per share)		$ 8.9904
Series C Preferred Stock
Stock issued, issuance costs	$ 243
Price per share (usd per share)	$ 14.0003

Statements of Cash Flows

Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Cash Flows From Operating Activities:
Net loss	$ (26,811)	$ (4,670)	$ (1,319)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	96	37
Stock-based compensation (Note 5)	839	18
Amortization of operating lease right-of-use asset (Note 10(a))	150	37
Impairment of operating lease right-of-use asset	15	0
Change in fair value of derivative liabilities (Note 9)	0	76
Stock issued for in-license agreement (Note 9(b))	3,115	0
Non-cash related party interest expense	0	89
Loss on extinguishment of convertible notes (Note 9)	0	255
Changes in operating assets and liabilities:
Other receivables	16	(32)
Prepaid expenses and other current assets	(2,464)	(18)
Other non-current assets	(75)	(6)
Accounts payable and other accrued liabilities	3,240	245
Accrued payroll and benefits	741	296
Net cash used in operating activities	(21,138)	(3,673)
Cash Flows From Investing Activities:
Purchases of property and equipment	(456)	(175)
Cash used in investing activities	(456)	(175)
Cash Flows From Financing Activities:
Proceeds from issuance of Series B Preferred Stock, net of issuance costs (Note 4)	(2,442)
Proceeds from issuance of convertible notes, net of issuance costs (Note 8)	0	1,989
Proceeds from issuance of common stock upon initial public offering, net of issuance costs	91,673	0
Proceeds from early exercise of stock options	360	0
Proceeds from issuance of common stock upon exercise of vested stock options	10	0
Net cash provided by financing activities	131,771	59,445
Net increase in cash, cash equivalents and restricted cash	110,177	55,597
Cash, cash equivalents, and restricted cash — beginning of year	57,972	2,375
Cash, cash equivalents, and restricted cash — end of year	168,149	57,972	2,375
Reconciliation of cash, cash equivalents and restricted cash
Cash and cash equivalents				$ 168,129	$ 57,952
Restricted cash				20	20
Cash, cash equivalents and restricted cash	57,972	57,972	$ 2,375	$ 168,149	$ 57,972
Supplemental Disclosures Noncash Investing and Financing Activities:
Conversion of Preferred Stock to common stock upon initial public offering	103,158	0
Stock issued for in-license agreement	3,115	0
Operating lease right-of-use asset obtained in exchange for operating lease liability	726	163
Settlement of derivative liabilities upon conversion of convertible notes (Note 8)	0	363
Additions of property and equipment in accounts payable and other accrued liabilities (Note 3(b))	34	10
Series B Preferred Stock issuance costs in accounts payable and other accrued liabilities	0	28
Conversion of convertible notes to Series B Preferred Stock (Note 8)	0	2,410
Series B Preferred Stock
Cash Flows From Financing Activities:
Proceeds from issuance of Series B Preferred Stock, net of issuance costs (Note 4)	(28)	(172)
Proceeds from issuance of Preferred Stock, net of issuance costs (Note 4)		57,456
Series C Preferred Stock
Cash Flows From Financing Activities:
Proceeds from issuance of Series B Preferred Stock, net of issuance costs (Note 4)	(243)
Proceeds from issuance of Preferred Stock, net of issuance costs (Note 4)	$ 39,756	$ 0

Description of Business and Pre

Description of Business and Presentation of Financial Statements	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Presentation of Financial Statements	DESCRIPTION OF BUSINESS AND PRESENTATION OF FINANCIAL STATEMENTS (a) Description of Business Tarsus Pharmaceuticals, Inc. (“Tarsus” or the “Company”) is a late clinical-stage biopharmaceutical company focused on the development and commercialization of novel therapeutic candidates to address large market opportunities initially in ophthalmic conditions where there are limited treatment alternatives. (b) Initial Public Offering and Reverse Stock Split On October 20, 2020, the Company completed its initial public offering "IPO" through an underwritten sale of 5,500,000 shares of its common stock at a price of $16.00 per share. The aggregate net proceeds received by the Company from the IPO, inclusive of an additional 825,000 common shares sold upon the full exercise of the underwriters’ purchase option totaled $91.7 million, after deducting underwriting discounts and commissions and other offering expenses. Concurrent with the closing of the Company's IPO, all then-outstanding shares of its convertible preferred stock (see Note 4 ) were automatically converted into an aggregate of 11,107,018 common shares. On October 8, 2020, the Company's Board of Directors approved a 1-for-7.4276 reverse stock split and a certificate of amendment was filed to restate the Company's certificate of incorporation to effect this reverse stock split. The par value was not adjusted as a result of the reverse stock split. All share and per share information included in the accompanying financial statements give retroactive effect to the reverse stock split for all periods presented. (c) Liquidity Risks The Company has no revenue and incurred losses and negative cash flows from operations since inception, resulting in an accumulated deficit of $32.8 million as of December 31, 2020, and the income potential of the Company's business and market are unproven. The Company’s cash and cash equivalents was $168.1 million and $58.0 million as of December 31, 2020 and December 31, 2019, respectively. The Company expects to continue to incur operating losses and negative cash flows and has historically financed its operations primarily through equity capital raises. The Company believes that existing capital resources, including the net proceeds from the IPO in October 2020, will be sufficient to meet projected operating requirements for at least 12 months from the date of issuance of the accompanying financial statements. The financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development activities. The Company’s operations have consisted primarily of its organization, securing financing, in-licensing intellectual property, and conducting preclinical and clinical studies. The Company faces risks associated with early-stage biotechnology companies whose product candidates are in development that require significant additional research and development efforts, including extensive preclinical and clinical testing and regulatory approval prior to commercialization. These efforts require the Company to expend large amounts of additional capital to complete research and development, achieve research and development objectives, defend intellectual property rights, and recruit and retain skilled personnel, including key members of management. The Company will be required to raise additional capital to fund future operations, however, no assurance can be given as to whether additional needed financing will be available on terms acceptable to the Company, if at all. If the Company raises additional funds by issuing equity securities, its stockholders may experience dilution. Any future debt financing into which the Company enters may impose additional covenants that restrict operations, including limitations on its ability to incur liens or additional debt, pay dividends, repurchase common stock, make certain investments or engage in certain merger, consolidation or asset sale transactions. Any debt financing or additional equity raise may contain terms that are not favorable to the Company or its stockholders. Further, adequate funding may not be available on acceptable terms, or at all. The Company’s potential inability to raise capital when needed could have a negative impact on its financial condition and ability to pursue planned business strategies. If the Company is unable to raise additional funds as required, it may need to delay, reduce, or terminate some or all its development programs and clinical trials. The Company may also be required to sell or license its rights to product candidates in certain territories or indications that it would otherwise prefer to develop and commercialize on its own. If the Company is required to enter into collaborations and other arrangements to address its liquidity needs, it may have to give up certain rights that limit its ability to develop and commercialize product candidates or may have other terms that are not favorable to the Company or its stockholders, which could materially and adversely affect its business and financial prospects. These factors may adversely impact the Company's ability to achieve its business objectives and would likely have an adverse effect on its future business prospects, or even its ability to remain a going concern. (d) Operating Segment To date, the Company has operated and managed its business and financial information on an aggregate basis for the purposes of evaluating financial performance and the allocation of resources. Accordingly, the Company’s management determined that it operates one reportable operating segment that is focused exclusively on developing pharmaceutical products for commercialization. (e) Emerging Growth Company Status The Company is an emerging growth company, as defined in the Jumpstart Our Business Startups Act of 2012 (the "JOBS Act"). Under the JOBS Act, emerging growth companies can delay adopting new or revised accounting standards issued subsequent to the enactment of the JOBS Act until such time as those standards apply to private companies. The Company has irrevocably elected to not take this exemption and, as a result, will adopt new or revised accounting standards on the relevant effective dates on which adoption of such standards is required for other public companies that are not emerging growth companies.

Summary of Significant Accounti

Summary of Significant Accounting Policies and Use of Estimates	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies and Use of Estimates	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND USE OF ESTIMATES (i) Basis of Presentation The preparation of financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) and with the rules and regulations of the Securities and Exchange Commission (“SEC”) requires management to make informed estimates and assumptions that impact the amounts reported in these financial statements and accompanying notes. These amounts may materially differ from the amounts ultimately realized and reported due to the inherent uncertainty of any estimate or assumption. On an on-going basis, management evaluates its most critical estimates and assumptions, including those related to the (i) fair value of stock awards and periodic expense recognition of stock-based compensation, (ii) the realization of income tax assets and estimates of tax liabilities, (iii) expense accruals related to research and development activities, including clinical trials, and, for periods prior to the IPO, (iv) valuation of convertible notes, derivative instruments, and preferred stock. Accounting policies and estimates that most significantly impact the presented amounts within these financial statements are further described below: (ii) Cash and Cash Equivalents Cash and cash equivalents consist of bank deposits and highly liquid investments, including money market fund accounts, with original maturities of three months or less from the purchase date. The carrying amounts reported in the balance sheets for cash and cash equivalents are valued at cost, which approximate their fair value. Cash equivalents may consist of money market funds. (iii) Restricted Cash Restricted cash represents cash held as collateral for the Company’s corporate credit card program. Any cash that is legally or contractually restricted from immediate use is classified as restricted cash. (iv) Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents in deposits at financial institutions that exceed federally insured limits. In March 2020, the World Health Organization declared a pandemic related to the global novel coronavirus disease 2019 (“COVID-19”) outbreak. The Company’s operations have not been significantly impacted by the COVID-19 pandemic. The Company has been carefully monitoring the potential impact COVID-19 may have on the Company’s business. However, the Company cannot at this time predict the specific extent, duration, or full impact that the COVID-19 outbreak will have on its financial condition and operations, including ongoing and planned clinical trials. The Company’s results of operations involve numerous risks and uncertainties. Factors that could adversely impact the Company’s operating results and business objectives include, but are not limited to, (1) uncertainty of results of clinical trials, (2) uncertainty of regulatory approval of the Company’s potential product candidates, including TP-03 for ophthalmic conditions, TP-04 for treatment of skin conditions and TP-05 for prophylaxis of Lyme and community malaria reduction, (3) uncertainty of market acceptance of its product candidates, (4) competition from substitute products and larger companies, (5) securing and protecting proprietary technology and strategic relationships, and (6) and dependence on key individuals and sole source suppliers. The Company’s product candidates require approvals from the U.S. Food and Drug Administration (“FDA”) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company is denied approval, approval is delayed or the Company is unable to maintain approval for any product candidate, it could have a materially adverse impact on the business. (v) Property and Equipment Property and equipment is stated at historical cost and is depreciated on a straight-line basis over an estimated useful life that corresponds with its designated asset category. Leasehold improvements are amortized on a straight-line basis over the shorter of the remaining lease term or the estimated useful lives of related improvements. The Company evaluates the recoverability of “long-lived assets” (which includes property and equipment) whenever events or changes in circumstances in the business indicate that the asset’s carrying amount may not be recoverable. Recoverability of these assets is measured by a comparison of the carrying amounts to the sum of the future undiscounted cash flows the assets are expected to generate over the remaining useful lives of the assets. If a long-lived asset fails a recoverability test, the Company measures the amount by which the carrying value of the asset exceeds its fair value. Other than the right-of-use ("ROU") asset impairment discussed in Note 9 , there were no events or changes in business circumstances during the years ended December 31, 2020 and 2019 that indicated the carrying amounts of any long-lived assets were not fully recoverable. (vi) Derivative Instruments The convertible notes issued in May 2019, August 2019, and October 2019 contained embedded derivative instruments, representing “contingent redemption options”. The contingent redemption options met the requirements for separate accounting and were accounted for as a single derivative instrument for each tranche of the convertible notes. The derivative instr uments were recorded at fair value at inception and were subject to remeasurement to fair value, with any changes in estimated fair value recognized as a component of “other (expense) income” in the Statements of Operations and Comprehensive Loss (see Note 7 ). As the Notes were converted in December 2019, no expense related to changes in fair value of derivative liabilities was recorded for the twelve months ended December 31, 2020. (vii) Research and Development Costs Research and development costs are expensed as incurred or as certain upfront or milestone payments become contractually due to licensors upon the achievement of clinical or regulatory events. These expenses also include internal costs directly attributable to in-development programs, including cost of certain salaries, payroll taxes, employee benefits, and stock-based compensation expense, as well as laboratory and clinical supplies, pre-clinical and clinical trial related expenses, and the cost of services provided by outside contractors. The Company recognizes expense for pre-clinical studies and clinical trial activities performed by these third parties. This is typically based upon estimates of the proportion of work completed over the term of the individual study or trial, as well as patient enrollment and dosing events in accordance with agreements established with clinical research organizations ("CROs") and clinical trial or pre-clinical study sites. The Company has entered, and may continue to enter into, license agreements to access and utilize intellectual property for drug development. In each case, the Company evaluates if the assets acquired in a transaction represent the acquisition of an as set or a business, as defined under applicable GAAP. The Company’s only executed in-license agreement (see Note 9(b) ) was evaluated and determined to represent an asset acquisition. Because this asset had not yet received regulatory approval and has no alternative future use, its purchase price was immediately recognized as research and development expense. In addition, any future milestone payments made before product regulatory approval (that do not meet the definition of a derivative) will also be immediately recognized as research and development expense when paid or become payable, provided there is no alternative future use of the rights in other research and development projects. (viii) Deferred Offering Costs Costs directly related to the Company’s IPO were deferred for expense recognition and instead capitalized and recorded on the accompanying balance sheets. These costs consisted of legal fees, accounting fees, and other applicable professional services. These deferred offering costs were reclassified to “additional paid in capital” and offset against IPO proceeds, upon closing of the IPO in October 2020. There were no deferred offering costs capitalized as of December 31, 2020 and 2019. (ix) Stock-Based Compensation Stock-based compensation expense is recognized for all equity awards granted to employees, consultants, and members of the Company’s Board of Directors and is recognized at fair value. For stock-based awards that vest subject to the satisfaction of a service requirement, the fair value measurement date is the date of grant and the related expense is recognized on a straight-line basis over each award’s actual or implied vesting period. For stock-based awards that vest subject to a performance condition, the Company recognizes compensation cost if and when it concludes that it is probable that the performance condition will be achieved and the related expense is recognized on an accelerated attribution method. As applicable, the Company reverses previously recognized expense for forfeitures of unvested awards in the period of occurrence. The Company uses the Black-Scholes option pricing model to estimate the fair value of stock-based awards as of the date of grant. The measurement of the fair value of stock-based awards and recognition of stock-based compensation expense requires assumptions to be estimated by management that involve inherent uncertainties and the application of management’s judgment, including (a) the fair value of the Company’s common stock on the date of the option grant, (b) the expected term of the stock option until its exercise by the recipient, (c) stock price volatility over the expected term, (d) the prevailing risk-free interest rate over the expected term, and (e) expected dividend payments over the expected term. Management estimates the expected term of awarded stock options utilizing the “simplified method” for awards as the Company does not yet have sufficient exercise history since its November 2016 formation. Further, prior to the IPO, the Company was privately-held and therefore lacked company-specific historical and implied volatility information of its stock. Accordingly, management estimated this expected volatility based on a designated peer-group of publicly-traded companies for a look-back period, as of the date of grant, that corresponded with the expected term of the awarded stock option. The Company estimates the risk-free interest rate based upon the U.S. Department of the Treasury yield curve in effect at award grant for time periods that correspond with the expected term of the awarded stock option. The Company’s expected dividend yield is zero because it has never paid cash dividends and does not expect to for the foreseeable future. Prior to the IPO, 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 its common stock. The factors included: (i) third-party valuations of the Company’s common stock; (ii) the Company’s stage of development; (iii) the status of research and development efforts; (iv) the rights, preferences and privileges of the Company’s preferred stock relative to common stock; (v) the Company’s operating results and financial condition, including the Company’s levels of available capital resources; (vi) equity market conditions affecting comparable public companies; (vii) general U.S. market conditions; and (viii) the lack of current marketability of the Company’s common stock. Subsequent to the IPO, the fair value of the Company’s common stock is based on the closing quoted market price of its common stock as reported by the NASDAQ Global Select Market on the date of grant. All stock-based compensation costs are recorded in the Statements of Operations and Comprehensive Loss based upon the underlying employee's role within the Company. (x) Income Taxes Income taxes are accounted for using the asset and liability method. Deferred tax assets and liabilities are recorded based on the estimated future tax effects of temporary differences between the tax basis of assets and liabilities and amounts reported in the financial statements, as well as operating losses and tax credit carry forwards using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period of enactment. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain due to the Company’s historical operating performance and recorded cumulative net losses in prior fiscal periods. A valuation allowance is recorded to reduce deferred tax assets, because based upon a weighting of positive and negative factors, it is more likely than not that these deferred tax assets will not be realized. If/when the Company were to determine that deferred tax assets are realizable, an adjustment to the corresponding valuation allowance would increase the net income in the period that such determination was made. In the event that the Company is assessed interest and/or penalties from taxing authorities that have not been previously accrued, such amounts would be included as a component of “income tax expense” within the Statements of Operations and Comprehensive Loss in the period the notice was received. To date there have been no interest or penalties charged. (xi) Preferred Stock The Company classified preferred stock outside of stockholders’ equity (deficit) on the accompanying balance sheets. The requirements of a deemed liquidation event, as defined within its amended and restated certificate of incorporation filed in September 2020 (the “2020 Amended and Restated Certificate of Incorporation”) were not entirely within the Company’s control. In the event of such a deemed liquidation event, the proceeds from the event are distributed in accordance with the liquidation preferences, provided that the holders of preferred stock have not converted their shares into common stock. The Company recorded the issuance of preferred stock at the issuance price less related issuance costs. As of December 31, 2019, the Company did not adjust the carrying value of outstanding preferred stock to its liquidation preference because a deemed liquidation event was not probable of occurring as of the end of the reporting period. All of the outstanding shares of preferred stock were automatically converted to common stock shares upon the closing of the IPO in October 2020. (xii) Net Loss per Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive shares of common stock. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method and if-converted method, as applicable. Basic and diluted net loss per share attributable to common stockholders is presented in conformity with the two-class method required for participating securities. The Company’s participating securities include preferred stock, unvested common stock to founders, and unvested common stock awards issued upon early exercise of certain stock options. The Company’s participating securities do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Shares of common stock subject to repurchase by the Company are excluded from the weighted-average shares. Due to net losses in all periods presented, all otherwise potentially dilutive securities are antidilutive. Accordingly, basic net loss per share equals diluted net loss per share for all period presented in the accompanying financial statements. (xiii) Fair Value Measurements 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: Quoted prices (unadjusted) in active markets for identical assets or liabilities that are publicly accessible at the measurement date. • Level 2: Observable prices that are based on inputs not quoted on active markets, but that are corroborated by market data. These inputs may include quoted prices for similar assets or liabilities or quoted market prices in markets that are not active to the general public. • 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. The carrying amounts for financial instruments consisting of cash and cash equivalents, accounts payable and accrued liabilities approximate fair value due to their short maturities. Derivative instruments are carried at fair value based on unobservable market inputs. (xiv) Comprehensive Loss Comprehensive loss represents all changes in stockholders’ equity (deficit), except those resulting from distributions to stockholders. For all periods presented, comprehensive loss was the same as reported net loss. (xv) Recently Issued or Effective Accounting Standards Recently issued or effective accounting pronouncements that impact, or may have an impact, on the Company’s financial statements have been discussed within the footnote to which each relates. Other recent accounting pronouncements not disclosed in these financial statements have been determined by the Company’s management to have no impact, or an immaterial impact, on its current and expected future financial position, results of operations, or cash flows.

Balance Sheet Account Detail

Balance Sheet Account Detail	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Account Detail	BALANCE SHEET ACCOUNT DETAIL The composition of select financial statement captions that comprise the accompanying balance sheets are summarized below: (a) Property and Equipment, net of Accumulated Depreciation “Property and equipment, net” consists of the following: December 31, 2020 2019 Furniture and fixtures $ 294 $ 5 Office equipment 74 26 Lab equipment 173 92 Leasehold improvements 141 69 Property and equipment, at cost 682 192 (Less): Accumulated depreciation and amortization 134 38 Property and equipment, net of accumulated depreciation $ 548 $ 154 Depreciation expense (included within “total operating expenses” in the accompanying Statements of Operations and Comprehensive Loss) for the years ended December 31, 2020 and 2019 was $0.1 million an d $37 thousand, res pectively. (b) Accounts Payable and Other Accrued Liabilities “Accounts payable and other accrued liabilities” consists of the following: December 31, 2020 2019 Trade accounts payable and other $ 2,237 $ 456 Operating lease liability, current portion 282 64 Accrued clinical studies 1,524 — Employee stock option early exercise liability, current portion 304 — Accounts payable and other accrued liabilities $ 4,347 $ 520 (c) Other Long-Term Liabilities “Other long-term liabilities” consists of the following: December 31, 2020 2019 Operating lease liability, non-current portion $ 549 $ 100 Employee stock option early exercise liability, non-current portion 56 — Other long-term liabilities $ 605 $ 100

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity	STOCKHOLDERS’ EQUITY Authorized Stock Under the October 2020 Amended and Restated Certificate of Incorporation, the Company is authorized to issue two classes of stock: common and preferred. The total number of shares authorized for issuance is 200.0 million of common shares and 10.0 million of preferred shares. Preferred Stock Overview Series A Preferred Stock Issuance In March and May 2018, the Company executed a private placement Series A Stock Purchase Agreement and issued 1.6 million shares of Series A Preferred Stock at $2.3174 per share for net proceeds of $3.6 million, after issuance costs of $0.1 million. Series B Preferred Stock Issuance In December 2019, the Company executed a private placement Series B Stock Purchase Agreement of 6.7 million shares of Series B Preferred Stock at $8.9904 per share for net proceeds of $57.4 million, after issuance costs of $0.2 million. Concurrently, convertible notes issued in May, August, and October 2019 for aggregate proceeds of $2.0 million were converted based on principal an d accrued interest, and the Company issued 0.3 million shares of Series B Preferred Stock at its contractual conversion price (see Note 8 ). Series C Preferred Stock Issuance In September 2020, the Company executed a private placement Series C Stock Purchase agreement of 2.9 million shares of Series C Preferred Stock at a purchase price of $14.0003 per share for net proceeds of $39.8 million, after issuance costs of $0.2 million. On October 20, 2020, upon the closing of the IPO, all outstanding shares of preferred stock were automatically converted into an aggregate 11,107,018 shares of the Company's common stock and $103.2 million of mezzanine equity was reclassified to common stock and additional paid-in capital. As of December 31, 2020, there were no shares of preferred stock issued and outstanding. The table below includes preferred stock details as of December 31, 2019. As of December 31, 2019 Authorized Outstanding Net Liquidation Original Series A Preferred Stock 1,575,030 1,575,030 $ 3,564 $ 3,650 $ 2.3174 Series B Preferred Stock 6,731,649 6,674,909 $ 59,838 $ 60,010 $ 8.9904 Total 8,306,679 8,249,939 $ 63,402 $ 63,660 Common Stock Overview and Reserve for Future Issuance Common stockholders have one vote for each share of common stock held and are entitled to receive any dividends declared by the Company’s Board of Directors when legally available for distribution, subject to the dividend rights of the holders of Series A, Series B, and Series C preferred stock discussed above. For the years ended December 31, 2020 and 2019, no dividends were declared. As of December 31, 2020 and 2019, the Company had 20.5 million and 2.7 million common shares issued, respectively. At December 31, 2020 and 2019, the Company had 20.3 million and 2.6 million, common shares outstanding, respectively. The following shares of common stock were reserved for issuance: December 31, 2020 2019 Preferred Stock outstanding — 8,249,939 Stock options issued and outstanding 1,836,739 297,142 Stock options reserved for future grant 9,414,091 2,150,867 Total shares of common stock reserved 11,250,830 10,697,948

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	STOCK-BASED COMPENSATION 2020 Equity Incentive Plan The Company's Board of Directors and stockholders adopted and approved the Company's 2020 Equity Incentive Plan (the “2020 Plan”) on October 8, 2020. The 2020 Plan replaces the 2016 Plan, however, awards outstanding under the 2016 Plan will continue to be governed by their existing terms. The number of shares of the Company's common stock available for issuance under the 2020 Plan equal the initial sum of 9,000,000 shares plus 2,432,980 shares remaining available for issuance under the 2016 Plan, or issued pursuant to or subject to awards granted under the 2016 Plan. The 2020 Plan provides for the following types of awards: incentive and non-statutory stock options, stock appreciation rights, restricted shares, and restricted stock units. The number of common shares reserved for issuance under the 2020 Plan are increased automatically on the first business day of each fiscal year, commencing in 2021 and ending in 2030, by a number equal to the lesser of: (i) 4% of the shares of common stock outstanding on the last business day of the prior fiscal year; or (ii) the number of shares determined by the Company's Board of Directors. In general, to the extent that any awards under the 2020 Plan are forfeited, terminate, expire or lapse without the issuance of shares, or if the Company reacquires the shares subject to awards granted under the 2020 Plan, those shares will again become available for issuance under the 2020 Plan, as will shares applied to pay the exercise or purchase price of an award or to satisfy tax withholding obligations related to any award. Prior to adopting the 2020 Plan, the Company had one active stockholder-approved stock-based compensation plan (the “2016 Plan”), adopted in December 2016, which permitted the grant of incentive stock options, nonqualified stock options, stock awards and certain other awards to its employees, members of its Board of Directors, and consultants. Stock-based awards are governed by agreements between the Company and the recipients. Incentive stock options and nonqualified stock options may be granted under the 2016 Plan and 2020 Plan at an exercise price of not less than 100% of the fair market value of common stock on the respective date of grant. The grant date is the date the terms of the award are formally approved by the Company’s Board of Directors or its designee. Through December 31, 2020, all awards issued under the 2016 Plan were in the form of stock options. These option agreements have service and/or performance conditions for vesting, unless immediately vested on the date of grant. Stock options granted typically have one Stock options must generally be exercised, if at all, no later than 10 years from the date of grant. Upon termination of employment, vested stock options may be exercised within 12 months after the date of termination upon death; six months after the date of termination upon disability; and three months after the date of termination for all other separations. Stock-Based Compensation Summary Stock-based compensation expense for the years ended December 31, 2020 and 2019 was as follows: Year Ended 2020 2019 Research and development $ 260 $ 6 General and administrative 579 12 Total stock-based compensation $ 839 $ 18 Valuation Assumptions of Stock Options The fair value of granted stock options was estimated as of the date of grant using the Black-Scholes option-pricing model, based on the following inputs: Year Ended 2020 2019 Exercise price (estimated fair value per common share on grant date) $2.01 to $10.99 $ 0.45 Expected term (in years) (a) 6.25 5.94 to 6.25 Risk-free interest rate (b) 0.38% to 0.47% 2.4% to 2.5% Expected volatility (c) 70.1% to 71.2% 82.5% to 89.4% Expected dividend yield (d) — — Weighted-average grant-date fair value per stock option $ 4.16 $ 0.34 (a) Determined using the “simplified method” under applicable GAAP ( SAB 107); the maximum contractual term of issued stock options is 10 years. (b) Based upon the U.S. Treasury yields in effect during the period which the options were granted (for a period equaling the stock options’ expected term). (c) Measured using the volatility of the stock price for the Company’s designated peer group of publicly-traded companies for a period equal to the expected option term. (d) Tarsus does not expect to declare any cash dividends in the foreseeable future. Stock Option Activity Stock option activity during the years ended December 31, 2020 and 2019 was as follows: Number of Weighted- Weighted- Aggregate Intrinsic Value (1) Outstanding - December 31, 2018 267,041 0.31 9.51 $ 37 Granted 32,793 0.45 Exercised — Forfeited (1,907) 0.45 Expired (785) 0.45 Outstanding - December 31, 2019 297,142 0.32 8.60 $ 37 Granted 1,741,384 4.16 Exercised (197,179) 1.88 Forfeited (4,608) 0.90 Expired — Outstanding - December 31, 2020 1,836,739 $ 3.77 9.15 $ 68,981 Vested - December 31, 2020 428,491 $ 1.68 8.47 $ 16,988 Unvested - December 31, 2020 1,408,248 $ 4.41 9.36 $ 51,993 ____________ (1) Represents the total difference between the estimated stock price fair value as of December 31, 2020 and the stock option exercise price, multiplied by the number of in-the-money options as of December 31, 2020. The amount of any intrinsic value will change in relation to any increases or decreases in the then-determined fair value of the Company’s common stock. The total grant-date fair value of options that vested during the years ended December 31, 2020 and 2019 was $0.7 million and $33 thousand , respectively. The following table summarizes information with respect to stock option grants as of December 31, 2020: As of December 31, 2020 Outstanding Exercisable Exercise Price Granted Aggregate Weighted- Granted Aggregate Weighted- $0.0007 83,809 $ 3,464 6.91 83,809 $ 3,464 6.91 $0.45 195,088 7,976 7.86 158,647 6,547 7.82 $2.01 1,143,868 44,982 9.33 1,085,376 44,566 9.34 $10.99 413,974 12,559 9.73 22,158 883 9.73 1,836,739 $ 68,981 9.15 1,349,990 $ 55,460 9.01 As of December 31, 2020, there was unrecognized compensation expense of $6.5 million related to unvested stock options, which the Company expects to recognize over a weighted average period of 2.8 years. Early Exercise Feature of Certain Stock Options The 2016 Plan permits certain option holders to exercise awarded options prior to vesting. Upon early exercise, the options become subject to a restricted stock agreement and remain subject to the same vesting provisions in the corresponding stock option award and unvested options are subject to repurchase by the Company upon termination at the same price exercised. These unvested shares are reported as issued, but not outstanding while subject to repurchase by the Company and are also excluded from the basic and diluted net loss per share calculation until the repurchase right lapses upon vesting. The Company initially records a liability for these early exercises that is subsequently reclassified into stockholders’ equity on a pro rata basis as vesting occurs. As of December 31, 2020 the Company has recorded the unvested portion of the exercise proceeds of $0.4 million as a liability from the early exercise in the accompanying Balance Sheets. During the years ended December 31, 2019, the Company repurchased 26,927 of unvested common stock options from a former consultant in connection with termination of his consulting agreement. As of December 31, 2019, all stock options with early exercise features were either vested or immaterial if early exercised and the Company reported no corresponding liability in the accompanying Balance Sheets.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Net Loss Per Share	NET LOSS PER SHARE Net loss per share attributable to common stockholders was computed by dividing net loss by the weighted-average number of common shares outstanding for the years ended December 31, 2020 and 2019: Year Ended December 31, 2020 2019 Net loss $ (26,811) $ (4,670) Weighted-average shares—basic and diluted 6,207,367 2,362,768 Net loss per share attributable to common $ (4.32) $ (1.98) The following outstanding potentially dilutive securities were excluded from the calculation of diluted net loss per share attributable to common stockholders because their impact under the “treasury stock method” and “if-converted method” would have been anti-dilutive for the periods presented: Year Ended December 31, 2020 2019 Stock options, unexercised—vested and unvested 1,836,739 297,142 Series A and Series B Preferred Stock, outstanding — 1,922,491 Stock options early-exercised and unvested 179,375 4,300 Convertible promissory notes — 93,421 Total 2,016,114 2,317,354

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The table below summarizes certain financial instruments measured at fair value that are included within the accompanying balance sheets, and their designation among the three fair value measurement categories (see Note 2(xiii) ): Year Ended December 31, 2020 Fair Value Measurements Level 1 Level 2 Level 3 Total Assets: Money market funds $ 168,129 $ — $ — $ 168,129 Total assets measured at fair value $ 168,129 $ — $ — $ 168,129 Year Ended December 31, 2019 Fair Value Measurements Level 1 Level 2 Level 3 Total Assets: Money market funds $ 57,952 $ — $ — $ 57,952 Total assets measured at fair value $ 57,952 $ — $ — $ 57,952 Money Market Funds Money market fund holdings are included in cash and cash equivalents on the accompanying balance sheets and are classified within Level 1 of the fair value hierarchy because they have readily-available market prices in active markets that are publicly accessible at the measurement date. These money market funds are invested in U.S. Treasury bills and notes, and other obligations issued or guaranteed as to principal and interest by the U.S. Government or its agencies. Convertible Promissory Notes – Derivative Liabilities The following table sets forth a summary of the changes in fair value of the bifurcated derivative liability associated with the convertible promissory notes issued and settled during 2019 to certain related parties (see Note 8 ). The measurement of the derivative liabilities represents a Level 3 financial instrument: Derivative Fair value as of December 31, 2018 $ — Initial fair value of derivative liability upon issuance of May 2019 Notes 28 Initial fair value of derivative liability upon issuance of August 2019 Notes 50 Initial fair value of derivative liability upon issuance of October 2019 Notes 209 Revaluation of derivative liabilities included in other income (expense), net within the Statement of Operations for the year ended December 31, 2019 76 Settlement of derivative liabilities through conversion of all Notes (363) Fair value as of December 31, 2019 $ — The fair values of the derivative liabilities presented above were estimated at the date of issuance and at subsequent balance sheet dates using a two-step approach to valuation. Management utilized a probability-weighted valuation method and then compared the instrument’s value with-and-without the derivative features in order to estimate their combined fair value, using unobservable inputs, which are classified as Level 3 within the fair value hierarchy. The significant inputs not included in the market and thus represents a Level 3 measurement in the valuation approach included the probability of achieving a settlement that provides the note holders the rights or the obligations to receive cash or a variable number of shares upon the completion of a then-future capital transaction. The convertible notes were issued and settled in full during the year ended December 31, 2019 (see Note 8 ).

Convertible Promissory Notes Pa

Convertible Promissory Notes Payable	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Convertible Promissory Notes Payable	CONVERTIBLE PROMISSORY NOTES PAYABLE Overview of Notes and Conversion in December 2019 In May 2019, the Company entered into a Note Purchase Agreement (the “May 2019 Purchase Agreement”) with its co-founders and certain other related parties (the “Note Holders”). Under the terms of the May 2019 Purchase Agreement, the Company received cash proceeds of $0.5 million and issued $0.5 million of convertible promissory notes (the “May 2019 Notes”) with a stated maturity of December 2020. These notes bore interest at a rate of 8.0% per annum, compounded annually, and payable at maturity. In the event of a qualified equity financing, the outstanding principal of the May 2019 Notes plus all accrued and previously unpaid interest would, at the option of the holder, either (i) automatically convert into shares of stock issued in the qualified equity financing based on a conversion price equal to 90% of the issuance price paid by these new investors, or (ii) be repaid in full. In August 2019, the Company amended and restated the May 2019 Purchase Agreement with the Note Holders and received an additional $0.5 million of proceeds and issued new $0.5 million convertible promissory notes to the same parties (the “August 2019 Notes”) with identical terms. In October 2019, the Company entered into a new Note Purchase Agreement (the “October 2019 Purchase Agreement”) with the Note Holders. Under the terms of the October 2019 Purchase Agreement, the Company received proceeds of $1.0 million and issued $1.0 million of convertible promissory notes (the “October 2019 Notes,” collectively with the May 2019 Notes and the August 2019 Notes, the “Notes”) with a conversion price equal to 80% of the issuance price in a qualified equity financing. In December 2019, the Company completed an issuance of Series B Preferred Stock (see Note 5 ). Upon this issuance, the $2.0 million of Note principal value, along with accrued interest, were converted into 0.3 million shares of Series B Preferred Stock under its contractual terms. The Company recorded “loss on extinguishment of convertible notes” (non-cash) of $0.3 million within “other income (expense)” in the accompanying Statements of Operations and Comprehensive Loss for the year ended December 31, 2019. Embedded Derivative and its Accounting The Notes allowed for redemption upon a qualified equity financing that was determined to be a contingent redemption feature that was not closely related to the Notes and was thus was required to be bifurcated as a derivative liability on the balance sheet. Based on the features of this derivative, the Company accounted for it as an implied discount in presenting the carrying value of these Notes. This discount was accreted over the term to maturity of the Notes using the effective interest method, resulting in aggregate interest expense recognition (non-cash) of $0.1 million for the year ended December 31, 2019. As the Notes were converted in December 2019, no interest expense was recorded for the year ended December 31, 2020. Changes in the embedded derivatives’ fair value at each reporting period were recognized in the accompanying statements of operations and comprehensive loss within “changes in fair value of derivative liabilities,” resulting in incremental “other expense” recognition (non-cash) of $0.1 million for the year ended December 31, 2019. As the Notes were converted in December 2019, no other expense related to changes in fair value of derivative liabilities was recorded for the year ended December 31, 2020.

Commitments & Contingencies

Commitments & Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments & Contingencies	COMMITMENTS & CONTINGENCIES (a) Facility Leases Overview In the ordinary course of business, the Company enters lease agreements with unaffiliated parties for the use of office and laboratory facilities and office equipment. As of December 31, 2019, the Company had one active facility lease in Irvine, California, that commenced on March 1, 2019 and expires April 30, 2022. This lease has a renewal option at the end of term, for which the Company was not reasonably certain to exercise at the lease commencement. As such, the renewal option was not included in the lease term used to calculate the right-of-use lease asset and lease liability. Prior to March 1, 2019, the Company did not have any material lease arrangements. As of December 31, 2020, the Company recorded an impairment of the operating lease right-of-use asset for this research and development facility of $15 thousand. The Company entered into two additional facility leases that commenced on June 1, 2020 for adjacent administrative and laboratory suites in Irvine, California. These leases expire on January 31, 2024. Both of these leases included a renewal option at the end of its term, for which the Company was not reasonably certain to exercise at the lease commencement. As such, the renewal option was not included in the lease term used to calculate the right-of-use lease asset and lease liability. In connectio n with these two leases the Company capitalized right-of-use assets along with an accompanying lease liability of $0.7 million. All of the Company’s facility leases have minimum annual rent, payable monthly, and carry fixed annual rent increases. Under the arrangements, real estate taxes, certain operating expenses, and common area maintenance are reimbursable to the lessor. These amounts are expensed as incurred, as they are variable in nature and therefore excluded from the measurement of the reported right-of-use asset and liability discussed below. During the years ended December 31, 2020 and 2019, the Company had no sublease arrangements with it as lessor. Adoption of New Lease Standard, Topic 842 Beginning January 1, 2019, the Company adopted ASU 2016-02 , Leases (“ Topic 842 ”). Under this new lease accounting standard, the Company recognized a right-of-use asset and lease liability on the accompanying Balance Sheets for all material leases. Management elected the “modified retrospective approach” with an effective transition date of January 1, 2018 upon adoption and the available practical expedients. The Company also elected to (1) not separate “lease components” from “non-lease components” in the measurement of minimum payments for its leases and (2) not recognize a lease asset and liability for a term of 12 months or less. Lease expense is recognized on a straight-line basis over the expected term of the lease. In March 2019, the Company capitalized a right-of-use asset of $0.2 million along with an accompanying $0.2 million lease liability. As part of applying Topic 842 , the Company determines if an arrangement is or contains a lease and the classification of that lease at contract execution. The classification of leases as “operating” or “finance” leases along with the initial measurement and recognition of the associated right-of-use assets and lease liabilities is performed at the lease commencement date. The measurement of lease liabilities is based on the present value of future lease payments over the lease term. Since an implicit rate for the operating lease for the Company’s Irvine facility was not determinable and was not implicit in the lease, the Company calculated an estimated incremental borrowing rate based upon what it would have to pay to borrow on a collateralized bases over a similar term and amount equal to the lease payments in a similar economic environment. The right-of-use lease asset is based on the corresponding lease liability and adjusted for (i) applicable payments made at or before the commencement date, (ii) initial direct costs incurred, and (iii) tenant incentives provided by the lessor. Components of Lease Expense The liability associated with each lease is amortized over the respective lease term using the effective interest rate method. The Company’s right-of-use assets are amortized over the lease term on a straight-line basis to lease expense, as reported on an allocated basis within “research and development” and “general and administrative” expenses in the accompanying Statements of Operations and Comprehensive Loss. For the years ended December 31, 2020 and 2019 the Company recognized $0.2 million and $0.1 million for lease expense, respectively. The Company had $25 thousand of variable lease payments, including non-lease components such as common area maintenance fees recognized as lease expense for the year ended December 31, 2020. There were no va riable lease payments for the year ended December 31, 2019. Weighted-Average Remaining Lease Term and Applied Discount Rate The Company had three active leases for its Irvine office and laboratory facility, with a remaining lease term of two years and four months as of December 31, 2019 and a remaining lease term of 1 year and 4 months a s of December 31, 2020. The Company had two additional facility leases commence on June 1, 2020, with remaining lease terms of 3 years, 1 month as of December 31, 2020. The weighted-average estimated incremental borrowing rate of 10% was utilized to present value future minimum lease payments since an implicit interest rate was not readily determinable for each lease. The weighted average remaining lease term for the Company’s leases as of December 31, 2020 is 2 years, 10 months . Future Contractual Lease Payments as of December 31, 2020 The below table summarizes the (i) minimum lease payments over the next five years and thereafter, (ii) lease arrangement imputed interest, and (iii) present value of future lease payments: Operating Leases - future payments December 31, 2020 2021 $ 349 2022 298 2023 281 2024 25 2025 — Total future lease payments, undiscounted $ 953 (Less): Imputed interest (122) Present value of operating lease payments $ 831 (b) In-License Agreements for Lotilaner Skin and Eye Disease or Conditions in Humans In January 2019, the Company entered into a license agreement with Elanco Tiergesundheit AG (“Elanco”), granting it a worldwide license to certain intellectual property for the development and commercialization of lotilaner for the treatment or cure of any eye or skin disease or condition in humans (the "January 2019 Agreement"). The Company has sole responsibility for related development, regulatory, and commercialization activities. The Company paid a $1.0 million upfront payment at the execution of the January 2019 Agreement, which is reported within “research and development” expense within the accompanying Statements of Operations and Comprehensive Loss for the year ended December 31, 2019. The Company also paid a re quired $1.0 million cl inical milestone payment in the September 2020 as part of an achieved Phase 2b/3 clinical trial milestone for the treatment of Demodex blepharitis; this amount is reported within “research and development” expense within the accompanying Statements of Operations and Comprehensive Loss for year ended December 31, 2020. The Company will make further payments to Elanco pursuant to the January 2019 Agreement upon achievement of various clinical milestones for an aggregate maximum of $5.0 million and various co mmercial and sales threshold milestones for an aggregate maximum of $79.0 million. In addition, the Company will be obligated to pay contractual royalties to Elanco in the single digits of its net sales. If the Company receives payments from any sublicensees, it will be obligated to pay Elanco a variable percentage in the low to mid double-digits of such proceeds, except for territories in which the Company achieved applicable regulatory approval prior to sublicense execution. All Other Disease or Conditions in Humans In September 2020, the Company executed an expanded license agreement with Elanco, granting it a worldwide license to certain intellectual property for the development and commercialization of lotilaner treatment or cure of all other diseases and conditions in humans – beyond that of the eye or skin (the “September 2020 Agreement”). The Company issued Ela nco 222,460 shares of its common stock as consideration for the license at the execution of the September 2020 Agreement. The value of these shares was $3.1 million ($14.0003 per share, approximating the Company's Series C preferred stock issuance price – see Note 4) and is reported within “research and development” expense within the accompanying Statements of Operations and Comprehensive Loss for the year ended December 31, 2020. In addi tion , in March 2021, the Company agreed to issue 187,500 shares of its common stock to Elanco during the second quarter of 2021 to maintain the September 2020 Agreement. The Company recorded the transaction as an asset acquisition as substantially all of the fair value of the gross assets acquired were concentrated in a group of similar identifiable assets thus satisfying the requirements of the screen test in ASU 2017-01 . The assets acquired in the transaction were measured based on the upfront payment to Elanco and the fair value of the common stock shares issued to Elanco, as the fair value of the consideration given was more readily determinable than the fair value of the assets received. Because the assets have not yet received regulatory approval and have no alternative future use, the fair value attributable to these assets were recorded as research and development expenses. The Company will make further payments to Elanco under the September 2020 Agreement upon achievement of various clinical milestones for an aggregate max imum of $4.5 million, and variou s commercial and sales threshold milestones for an aggregate maximum of $77.0 million. In addition, the Company will be obligated to pay contractual royalties to Elanco in the single digits of its net sales. If the Company receives payments from any sublicensees, it will be obligated to pay Elanco a variable percentage in the low to mid double-digits of such proceeds, except for territories in which the Company achieved applicable regulatory approval prior to sublicense execution. (c) Clinical Research Organization and Contract Manufacturer Agreements We enter into contracts in the normal course of business with clinical research organizations and clinical sites and with contract manufacturers for pre-clinical and clinical drug supply, as well as with various other vendors in operating our business. These contracts generally provide for termination provisions with requisite notice. (d) Employment Agreements The Company has entered into employment agreements with four of its named executive officers. These agreements provide for the payment of certain benefits upon separation of employment under specified circumstances, such as in connection with a change in control event or other significant transaction. (e) Other Contingencies From time to time, the Company may be subject to various litigation and related matters arising in the ordinary course of business. The Company is currently not aware of any such matters where there is at least a reasonable possibility that a material loss has been or will be incurred for financial statement recognition. (f) Indemnities and Guarantees The Company has certain indemnity commitments, under which it may be required to make payments to its officers and directors in relation to certain transactions to the maximum extent permitted under applicable laws. The duration of these indemnities varies, and in certain cases, is indefinite and does not provide for any limitation of maximum payments. The Company has not been obligated to make any such payments to date and no liabilities have been recorded for this contingency in the accompanying balance sheets.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	INCOME TAXESA reconciliation of income taxes was computed by applying the federal statutory income tax rate in each period to the pretax loss for the years ended December 31, 2020 and 2019, and adjusted for certain classes of transactions, as summarized below: Year Ended 2020 2019 Expected tax benefit at statutory rate $ (5,630) $ (981) State income tax, net of federal benefit 1 1 Permanent items 5 4 Research and development credits (632) (31) Loss on extinguishment of convertible notes — 54 Non-deductible interest — 35 Other 119 4 Change in valuation allowance 6,138 915 Income tax provision $ 1 $ 1 Significant components of the deferred tax assets and liabilities at December 31, 2020 and 2019, are presented below: Year Ended 2020 2019 Deferred tax assets: Net operating loss carry forwards $ 5,391 $ 961 Research and development credit carryforwards 710 88 Intangible assets 1,046 211 Other, net 476 104 Total deferred tax assets before valuation allowance 7,623 1,364 Less: valuation allowance (7,475) (1,338) Total deferred tax assets $ 148 $ 26 Deferred tax liabilities, net: Operating lease right-of-use assets (148) (26) Net deferred tax asset $ — $ — Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The Company maintains a valuation allowance against its net deferred tax assets due to the uncertainty that such assets will be realized and evaluates the recoverability of its deferred tax assets on at least an annual basis. The Company has determined that its deferred tax assets, with the exception of amounts supported by the reversal of taxable temporary differences, are not realizable. Consequently, the Company has recorded a valuation allowance on deferred tax assets of $7.5 million and $1.3 million at December 31, 2020 and 2019, respectively. At December 31, 2020, the Company has federal and California net operating loss carryforwards of approximat ely $25.3 million a nd $4.0 million, respectively. As a result of the Tax Cuts and Jobs Act of 2017 (the Tax Act), for U.S. income tax purposes, net operating losses generated prior to December 31, 2017 can be carried forward for up to 20 years, while net operating losses generated after December 31, 2017 can be carried forward indefinitely, but are limited to 80% utilization against taxable income. The Company’s total federal net operating loss of $25.3 million includes $45 thousand that will begin to expire in 2037 and $25.2 million that will not expire but will only be able to be offset 80% of future taxable income within each year. The California net operating losses will begin to expire in 2037. At December 31, 2020, the Company had federal and California research and development tax credits of $0.6 million and $0.4 million, respectively. The federal research and development tax credits begin to expire in 2037 unless previously utilized, and the California credit carryforwards are available indefinitely. The Internal Revenue Code (IRC) Sections 382 and 383 limit annual use of NOL and research and development credit carryforwards in the event a cumulative change in ownership of more than 50% occurs within a three-year period. The Company has not yet completed an ownership change analysis. If a requisite ownership change occurs, the amount of remaining tax attribute carryforwards available to offset taxable income and income tax expense in future years may be restricted or eliminated. If eliminated, the related asset would be removed from deferred tax assets with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by future ownership changes, if any, will not impact the Company’s effective tax rate. Uncertain tax positions are evaluated based upon the facts and circumstances that exist at each reporting period. Subsequent changes in judgement based upon new information may lead to changes in recognition, derecognition, and measurement. Adjustment may result, for example, upon resolution of an issue with the taxing authorities or expiration of a statute of limitations barring an assessment for an issue. The Company recognizes a tax benefit from an uncertain tax position when it is more-likely-than-not that it will be sustained upon examination by tax authorities. As of December 31, 2020, the Company had gross unrecognized tax benefits of $0.5 million, none of which would affect the effective tax rate if recognized. The Company does not anticipate any significant changes in its unrecognized tax benefits over the next 12 months. The Company's policy is to recognize the interest expense and/or penalties related to income tax matters as a component of income tax expense. The Company had no accrual for interest or penalties on its balance sheet at December 31, 2020 and has not recognized interest and/or penalties in its statement of operations for the year ended December 31, 2020 or 2019. The following table summarizes the changes to the gross unrecognized tax benefits for the years ended December 31, 2020 and 2019: Year Ended 2020 2019 Balance at beginning of year 33 20 Additions related to current year positions 217 13 Additions related to prior year positions 242 — Decreases related to prior year positions (4) — Balance at end of year 488 33 The Company is subject to taxation in the United States and California. All tax years from inception are subject to examination by federal and state tax authorities. The Company’s practice is to recognize interest and penalties related to income tax matters in income tax expense. No interest or penalties related to income tax matters have been incurred at December 31, 2020 and 2019 and the years then ended. Further, the Company is not currently under examination by any federal, state, or local tax authority.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	SUBSEQUENT EVENTSOut-license of TP-03 Commercial Rights in Greater China in March 2021On March 26, 2021, the Company executed an out-license agreement with LianBio Ophthalmology Limited ("LianBio"), granting exclusive commercial rights of TP-03 for the treatment of Demodex blepharitis and Meibomian Gland Disease (MGD) within The People’s Republic of China, Macau, Hong Kong, and Taiwan (the "Territory"). The Company is contractually entitled to receive (i) an aggregate $25 million by June 30, 2021, (ii) regulatory and sales milestone receipts totaling $75 million and $100 million, respectively, (iii) tiered royalties in the low double-digits on net sales of TP-03 within the Territory, and (iv) a minority interest in LianBio that vests upon the achievement of certain clinical and regulatory events.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies and Use of Estimates (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Operating Segment	Operating SegmentTo date, the Company has operated and managed its business and financial information on an aggregate basis for the purposes of evaluating financial performance and the allocation of resources. Accordingly, the Company’s management determined that it operates one reportable operating segment that is focused exclusively on developing pharmaceutical products for commercialization.
Basis of Presentation	Basis of PresentationThe preparation of financial statements in conformity with U.S. generally accepted accounting principles (“GAAP”) and with the rules and regulations of the Securities and Exchange Commission (“SEC”) requires management to make informed estimates and assumptions that impact the amounts reported in these financial statements and accompanying notes. These amounts may materially differ from the amounts ultimately realized and reported due to the inherent uncertainty of any estimate or assumption. On an on-going basis, management evaluates its most critical estimates and assumptions, including those related to the (i) fair value of stock awards and periodic expense recognition of stock-based compensation, (ii) the realization of income tax assets and estimates of tax liabilities, (iii) expense accruals related to research and development activities, including clinical trials, and, for periods prior to the IPO, (iv) valuation of convertible notes, derivative instruments, and preferred stock.
Cash and Cash Equivalents	Cash and Cash EquivalentsCash and cash equivalents consist of bank deposits and highly liquid investments, including money market fund accounts, with original maturities of three months or less from the purchase date. The carrying amounts reported in the balance sheets for cash and cash equivalents are valued at cost, which approximate their fair value. Cash equivalents may consist of money market funds.
Restricted Cash	Restricted CashRestricted cash represents cash held as collateral for the Company’s corporate credit card program. Any cash that is legally or contractually restricted from immediate use is classified as restricted cash.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents in deposits at financial institutions that exceed federally insured limits. In March 2020, the World Health Organization declared a pandemic related to the global novel coronavirus disease 2019 (“COVID-19”) outbreak. The Company’s operations have not been significantly impacted by the COVID-19 pandemic. The Company has been carefully monitoring the potential impact COVID-19 may have on the Company’s business. However, the Company cannot at this time predict the specific extent, duration, or full impact that the COVID-19 outbreak will have on its financial condition and operations, including ongoing and planned clinical trials. The Company’s results of operations involve numerous risks and uncertainties. Factors that could adversely impact the Company’s operating results and business objectives include, but are not limited to, (1) uncertainty of results of clinical trials, (2) uncertainty of regulatory approval of the Company’s potential product candidates, including TP-03 for ophthalmic conditions, TP-04 for treatment of skin conditions and TP-05 for prophylaxis of Lyme and community malaria reduction, (3) uncertainty of market acceptance of its product candidates, (4) competition from substitute products and larger companies, (5) securing and protecting proprietary technology and strategic relationships, and (6) and dependence on key individuals and sole source suppliers. The Company’s product candidates require approvals from the U.S. Food and Drug Administration (“FDA”) and comparable foreign regulatory agencies prior to commercial sales in their respective jurisdictions. There can be no assurance that any product candidates will receive the necessary approvals. If the Company is denied approval, approval is delayed or the Company is unable to maintain approval for any product candidate, it could have a materially adverse impact on the business.
Property and Equipment	Property and Equipment Property and equipment is stated at historical cost and is depreciated on a straight-line basis over an estimated useful life that corresponds with its designated asset category. Leasehold improvements are amortized on a straight-line basis over the shorter of the remaining lease term or the estimated useful lives of related improvements. The Company evaluates the recoverability of “long-lived assets” (which includes property and equipment) whenever events or changes in circumstances in the business indicate that the asset’s carrying amount may not be recoverable. Recoverability of these assets is measured by a comparison of the carrying amounts to the sum of the future undiscounted cash flows the assets are expected to generate over the remaining useful lives of the assets. If a long-lived asset fails a recoverability test, the Company measures the amount by which the carrying value of the asset exceeds its fair value. Other than the right-of-use ("ROU") asset impairment discussed in Note 9 , there were no events or changes in business circumstances during the years ended December 31, 2020 and 2019 that indicated the carrying amounts of any long-lived assets were not fully recoverable.
Derivative Instruments	Derivative Instruments The convertible notes issued in May 2019, August 2019, and October 2019 contained embedded derivative instruments, representing “contingent redemption options”. The contingent redemption options met the requirements for separate accounting and were accounted for as a single derivative instrument for each tranche of the convertible notes. The derivative instr uments were recorded at fair value at inception and were subject to remeasurement to fair value, with any changes in estimated fair value recognized as a component of “other (expense) income” in the Statements of Operations and Comprehensive Loss (see Note 7 ).
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred or as certain upfront or milestone payments become contractually due to licensors upon the achievement of clinical or regulatory events. These expenses also include internal costs directly attributable to in-development programs, including cost of certain salaries, payroll taxes, employee benefits, and stock-based compensation expense, as well as laboratory and clinical supplies, pre-clinical and clinical trial related expenses, and the cost of services provided by outside contractors. The Company recognizes expense for pre-clinical studies and clinical trial activities performed by these third parties. This is typically based upon estimates of the proportion of work completed over the term of the individual study or trial, as well as patient enrollment and dosing events in accordance with agreements established with clinical research organizations ("CROs") and clinical trial or pre-clinical study sites. The Company has entered, and may continue to enter into, license agreements to access and utilize intellectual property for drug development. In each case, the Company evaluates if the assets acquired in a transaction represent the acquisition of an as set or a business, as defined under applicable GAAP. The Company’s only executed in-license agreement (see Note 9(b) ) was evaluated and determined to represent an asset acquisition. Because this asset had not yet received regulatory approval and has no alternative future use, its purchase price was immediately recognized as research and development expense. In addition, any future milestone payments made before product regulatory approval (that do not meet the definition of a derivative) will also be immediately recognized as research and development expense when paid or become payable, provided there is no alternative future use of the rights in other research and development projects.
Deferred Offering Costs	Deferred Offering CostsCosts directly related to the Company’s IPO were deferred for expense recognition and instead capitalized and recorded on the accompanying balance sheets. These costs consisted of legal fees, accounting fees, and other applicable professional services. These deferred offering costs were reclassified to “additional paid in capital” and offset against IPO proceeds, upon closing of the IPO in October 2020. There were no deferred offering costs capitalized as of December 31, 2020 and 2019.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense is recognized for all equity awards granted to employees, consultants, and members of the Company’s Board of Directors and is recognized at fair value. For stock-based awards that vest subject to the satisfaction of a service requirement, the fair value measurement date is the date of grant and the related expense is recognized on a straight-line basis over each award’s actual or implied vesting period. For stock-based awards that vest subject to a performance condition, the Company recognizes compensation cost if and when it concludes that it is probable that the performance condition will be achieved and the related expense is recognized on an accelerated attribution method. As applicable, the Company reverses previously recognized expense for forfeitures of unvested awards in the period of occurrence. The Company uses the Black-Scholes option pricing model to estimate the fair value of stock-based awards as of the date of grant. The measurement of the fair value of stock-based awards and recognition of stock-based compensation expense requires assumptions to be estimated by management that involve inherent uncertainties and the application of management’s judgment, including (a) the fair value of the Company’s common stock on the date of the option grant, (b) the expected term of the stock option until its exercise by the recipient, (c) stock price volatility over the expected term, (d) the prevailing risk-free interest rate over the expected term, and (e) expected dividend payments over the expected term. Management estimates the expected term of awarded stock options utilizing the “simplified method” for awards as the Company does not yet have sufficient exercise history since its November 2016 formation. Further, prior to the IPO, the Company was privately-held and therefore lacked company-specific historical and implied volatility information of its stock. Accordingly, management estimated this expected volatility based on a designated peer-group of publicly-traded companies for a look-back period, as of the date of grant, that corresponded with the expected term of the awarded stock option. The Company estimates the risk-free interest rate based upon the U.S. Department of the Treasury yield curve in effect at award grant for time periods that correspond with the expected term of the awarded stock option. The Company’s expected dividend yield is zero because it has never paid cash dividends and does not expect to for the foreseeable future. Prior to the IPO, 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 its common stock. The factors included: (i) third-party valuations of the Company’s common stock; (ii) the Company’s stage of development; (iii) the status of research and development efforts; (iv) the rights, preferences and privileges of the Company’s preferred stock relative to common stock; (v) the Company’s operating results and financial condition, including the Company’s levels of available capital resources; (vi) equity market conditions affecting comparable public companies; (vii) general U.S. market conditions; and (viii) the lack of current marketability of the Company’s common stock. Subsequent to the IPO, the fair value of the Company’s common stock is based on the closing quoted market price of its common stock as reported by the NASDAQ Global Select Market on the date of grant. All stock-based compensation costs are recorded in the Statements of Operations and Comprehensive Loss based upon the underlying employee's role within the Company.
Income Taxes	Income Taxes Income taxes are accounted for using the asset and liability method. Deferred tax assets and liabilities are recorded based on the estimated future tax effects of temporary differences between the tax basis of assets and liabilities and amounts reported in the financial statements, as well as operating losses and tax credit carry forwards using enacted tax rates and laws that are expected to be in effect when the differences are expected to reverse. Deferred tax assets and liabilities are measured using the enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period of enactment. Realization of deferred tax assets is dependent upon future earnings, the timing and amount of which are uncertain due to the Company’s historical operating performance and recorded cumulative net losses in prior fiscal periods. A valuation allowance is recorded to reduce deferred tax assets, because based upon a weighting of positive and negative factors, it is more likely than not that these deferred tax assets will not be realized. If/when the Company were to determine that deferred tax assets are realizable, an adjustment to the corresponding valuation allowance would increase the net income in the period that such determination was made. In the event that the Company is assessed interest and/or penalties from taxing authorities that have not been previously accrued, such amounts would be included as a component of “income tax expense” within the Statements of Operations and Comprehensive Loss in the period the notice was received. To date there have been no interest or penalties charged.
Preferred Stock	Preferred StockThe Company classified preferred stock outside of stockholders’ equity (deficit) on the accompanying balance sheets. The requirements of a deemed liquidation event, as defined within its amended and restated certificate of incorporation filed in September 2020 (the “2020 Amended and Restated Certificate of Incorporation”) were not entirely within the Company’s control. In the event of such a deemed liquidation event, the proceeds from the event are distributed in accordance with the liquidation preferences, provided that the holders of preferred stock have not converted their shares into common stock. The Company recorded the issuance of preferred stock at the issuance price less related issuance costs. As of December 31, 2019, the Company did not adjust the carrying value of outstanding preferred stock to its liquidation preference because a deemed liquidation event was not probable of occurring as of the end of the reporting period. All of the outstanding shares of preferred stock were automatically converted to common stock shares upon the closing of the IPO in October 2020.
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common StockholdersBasic net loss per share attributable to common stockholders is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration for potential dilutive shares of common stock. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method and if-converted method, as applicable. Basic and diluted net loss per share attributable to common stockholders is presented in conformity with the two-class method required for participating securities. The Company’s participating securities include preferred stock, unvested common stock to founders, and unvested common stock awards issued upon early exercise of certain stock options. The Company’s participating securities do not have a contractual obligation to share in the Company’s losses. As such, the net loss was attributed entirely to common stockholders. Shares of common stock subject to repurchase by the Company are excluded from the weighted-average shares. Due to net losses in all periods presented, all otherwise potentially dilutive securities are antidilutive. Accordingly, basic net loss per share equals diluted net loss per share for all period presented in the accompanying financial statements.
Fair Value Measurements	Fair Value Measurements 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: Quoted prices (unadjusted) in active markets for identical assets or liabilities that are publicly accessible at the measurement date. • Level 2: Observable prices that are based on inputs not quoted on active markets, but that are corroborated by market data. These inputs may include quoted prices for similar assets or liabilities or quoted market prices in markets that are not active to the general public. • 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. The carrying amounts for financial instruments consisting of cash and cash equivalents, accounts payable and accrued liabilities approximate fair value due to their short maturities. Derivative instruments are carried at fair value based on unobservable market inputs.
Comprehensive Loss	Comprehensive LossComprehensive loss represents all changes in stockholders’ equity (deficit), except those resulting from distributions to stockholders. For all periods presented, comprehensive loss was the same as reported net loss.
Recently Issued or Effective Accounting Standards	Recently Issued or Effective Accounting StandardsRecently issued or effective accounting pronouncements that impact, or may have an impact, on the Company’s financial statements have been discussed within the footnote to which each relates. Other recent accounting pronouncements not disclosed in these financial statements have been determined by the Company’s management to have no impact, or an immaterial impact, on its current and expected future financial position, results of operations, or cash flows.

Balance Sheet Account Detail (T

Balance Sheet Account Detail (Tables)	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Property and equipment, net of accumulated depreciation	“Property and equipment, net” consists of the following: December 31, 2020 2019 Furniture and fixtures $ 294 $ 5 Office equipment 74 26 Lab equipment 173 92 Leasehold improvements 141 69 Property and equipment, at cost 682 192 (Less): Accumulated depreciation and amortization 134 38 Property and equipment, net of accumulated depreciation $ 548 $ 154
Accounts payable and accrued liabilities	“Accounts payable and other accrued liabilities” consists of the following: December 31, 2020 2019 Trade accounts payable and other $ 2,237 $ 456 Operating lease liability, current portion 282 64 Accrued clinical studies 1,524 — Employee stock option early exercise liability, current portion 304 — Accounts payable and other accrued liabilities $ 4,347 $ 520
Other long-term liabilities	“Other long-term liabilities” consists of the following: December 31, 2020 2019 Operating lease liability, non-current portion $ 549 $ 100 Employee stock option early exercise liability, non-current portion 56 — Other long-term liabilities $ 605 $ 100

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stock details	The table below includes preferred stock details as of December 31, 2019. As of December 31, 2019 Authorized Outstanding Net Liquidation Original Series A Preferred Stock 1,575,030 1,575,030 $ 3,564 $ 3,650 $ 2.3174 Series B Preferred Stock 6,731,649 6,674,909 $ 59,838 $ 60,010 $ 8.9904 Total 8,306,679 8,249,939 $ 63,402 $ 63,660 December 31, 2020 2019 Preferred Stock outstanding — 8,249,939 Stock options issued and outstanding 1,836,739 297,142 Stock options reserved for future grant 9,414,091 2,150,867 Total shares of common stock reserved 11,250,830 10,697,948

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-based compensation	Stock-based compensation expense for the years ended December 31, 2020 and 2019 was as follows: Year Ended 2020 2019 Research and development $ 260 $ 6 General and administrative 579 12 Total stock-based compensation $ 839 $ 18
Valuation assumptions of stock options	The fair value of granted stock options was estimated as of the date of grant using the Black-Scholes option-pricing model, based on the following inputs: Year Ended 2020 2019 Exercise price (estimated fair value per common share on grant date) $2.01 to $10.99 $ 0.45 Expected term (in years) (a) 6.25 5.94 to 6.25 Risk-free interest rate (b) 0.38% to 0.47% 2.4% to 2.5% Expected volatility (c) 70.1% to 71.2% 82.5% to 89.4% Expected dividend yield (d) — — Weighted-average grant-date fair value per stock option $ 4.16 $ 0.34 (a) Determined using the “simplified method” under applicable GAAP ( SAB 107); the maximum contractual term of issued stock options is 10 years. (b) Based upon the U.S. Treasury yields in effect during the period which the options were granted (for a period equaling the stock options’ expected term). (c) Measured using the volatility of the stock price for the Company’s designated peer group of publicly-traded companies for a period equal to the expected option term. (d) Tarsus does not expect to declare any cash dividends in the foreseeable future.
Stock option activity	Stock option activity during the years ended December 31, 2020 and 2019 was as follows: Number of Weighted- Weighted- Aggregate Intrinsic Value (1) Outstanding - December 31, 2018 267,041 0.31 9.51 $ 37 Granted 32,793 0.45 Exercised — Forfeited (1,907) 0.45 Expired (785) 0.45 Outstanding - December 31, 2019 297,142 0.32 8.60 $ 37 Granted 1,741,384 4.16 Exercised (197,179) 1.88 Forfeited (4,608) 0.90 Expired — Outstanding - December 31, 2020 1,836,739 $ 3.77 9.15 $ 68,981 Vested - December 31, 2020 428,491 $ 1.68 8.47 $ 16,988 Unvested - December 31, 2020 1,408,248 $ 4.41 9.36 $ 51,993 ____________ (1) Represents the total difference between the estimated stock price fair value as of December 31, 2020 and the stock option exercise price, multiplied by the number of in-the-money options as of December 31, 2020. The amount of any intrinsic value will change in relation to any increases or decreases in the then-determined fair value of the Company’s common stock.
Information with respect to stock option grants	The following table summarizes information with respect to stock option grants as of December 31, 2020: As of December 31, 2020 Outstanding Exercisable Exercise Price Granted Aggregate Weighted- Granted Aggregate Weighted- $0.0007 83,809 $ 3,464 6.91 83,809 $ 3,464 6.91 $0.45 195,088 7,976 7.86 158,647 6,547 7.82 $2.01 1,143,868 44,982 9.33 1,085,376 44,566 9.34 $10.99 413,974 12,559 9.73 22,158 883 9.73 1,836,739 $ 68,981 9.15 1,349,990 $ 55,460 9.01

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Net loss per share, basis and diluted	Net loss per share attributable to common stockholders was computed by dividing net loss by the weighted-average number of common shares outstanding for the years ended December 31, 2020 and 2019: Year Ended December 31, 2020 2019 Net loss $ (26,811) $ (4,670) Weighted-average shares—basic and diluted 6,207,367 2,362,768 Net loss per share attributable to common $ (4.32) $ (1.98)
Outstanding potentially dilutive securities	The following outstanding potentially dilutive securities were excluded from the calculation of diluted net loss per share attributable to common stockholders because their impact under the “treasury stock method” and “if-converted method” would have been anti-dilutive for the periods presented: Year Ended December 31, 2020 2019 Stock options, unexercised—vested and unvested 1,836,739 297,142 Series A and Series B Preferred Stock, outstanding — 1,922,491 Stock options early-exercised and unvested 179,375 4,300 Convertible promissory notes — 93,421 Total 2,016,114 2,317,354

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Financial instruments measured at fair value	The table below summarizes certain financial instruments measured at fair value that are included within the accompanying balance sheets, and their designation among the three fair value measurement categories (see Note 2(xiii) ): Year Ended December 31, 2020 Fair Value Measurements Level 1 Level 2 Level 3 Total Assets: Money market funds $ 168,129 $ — $ — $ 168,129 Total assets measured at fair value $ 168,129 $ — $ — $ 168,129 Year Ended December 31, 2019 Fair Value Measurements Level 1 Level 2 Level 3 Total Assets: Money market funds $ 57,952 $ — $ — $ 57,952 Total assets measured at fair value $ 57,952 $ — $ — $ 57,952
Changes in fair value of derivative liability	The measurement of the derivative liabilities represents a Level 3 financial instrument: Derivative Fair value as of December 31, 2018 $ — Initial fair value of derivative liability upon issuance of May 2019 Notes 28 Initial fair value of derivative liability upon issuance of August 2019 Notes 50 Initial fair value of derivative liability upon issuance of October 2019 Notes 209 Revaluation of derivative liabilities included in other income (expense), net within the Statement of Operations for the year ended December 31, 2019 76 Settlement of derivative liabilities through conversion of all Notes (363) Fair value as of December 31, 2019 $ —

Commitments & Contingencies (Ta

Commitments & Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Future contractual lease payments	The below table summarizes the (i) minimum lease payments over the next five years and thereafter, (ii) lease arrangement imputed interest, and (iii) present value of future lease payments: Operating Leases - future payments December 31, 2020 2021 $ 349 2022 298 2023 281 2024 25 2025 — Total future lease payments, undiscounted $ 953 (Less): Imputed interest (122) Present value of operating lease payments $ 831

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Reconciliation of income taxes	A reconciliation of income taxes was computed by applying the federal statutory income tax rate in each period to the pretax loss for the years ended December 31, 2020 and 2019, and adjusted for certain classes of transactions, as summarized below: Year Ended 2020 2019 Expected tax benefit at statutory rate $ (5,630) $ (981) State income tax, net of federal benefit 1 1 Permanent items 5 4 Research and development credits (632) (31) Loss on extinguishment of convertible notes — 54 Non-deductible interest — 35 Other 119 4 Change in valuation allowance 6,138 915 Income tax provision $ 1 $ 1
Significant components of deferred tax assets and liabilities	Significant components of the deferred tax assets and liabilities at December 31, 2020 and 2019, are presented below: Year Ended 2020 2019 Deferred tax assets: Net operating loss carry forwards $ 5,391 $ 961 Research and development credit carryforwards 710 88 Intangible assets 1,046 211 Other, net 476 104 Total deferred tax assets before valuation allowance 7,623 1,364 Less: valuation allowance (7,475) (1,338) Total deferred tax assets $ 148 $ 26 Deferred tax liabilities, net: Operating lease right-of-use assets (148) (26) Net deferred tax asset $ — $ —
Gross unrecognized tax benefits	The following table summarizes the changes to the gross unrecognized tax benefits for the years ended December 31, 2020 and 2019: Year Ended 2020 2019 Balance at beginning of year 33 20 Additions related to current year positions 217 13 Additions related to prior year positions 242 — Decreases related to prior year positions (4) — Balance at end of year 488 33

Description of Business and P_2

Description of Business and Presentation of Financial Statements (Details) $ / shares in Units, $ in Thousands	Oct. 20, 2020USD ($)$ / sharesshares	Oct. 08, 2020	Dec. 31, 2020USD ($)segment	Dec. 31, 2019USD ($)
Subsequent Event [Line Items]
Common stock issued upon conversion of preferred stock (shares)	11,107,018
Reverse stock split, conversion ratio		0.1346
Accumulated deficit | $			$ 32,845	$ 6,034
Cash and cash equivalents | $			$ 168,129	$ 57,952
Number of reportable segments | segment			1
Number of operating segments | segment			1
IPO
Subsequent Event [Line Items]
Stock issued (shares)	5,500,000
Price per share (usd per share) | $ / shares	$ 16
Stock issued, net proceeds | $	$ 91,700
Common stock issued upon conversion of preferred stock (shares)	11,107,018
Underwriters' option
Subsequent Event [Line Items]
Stock issued (shares)	825,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies and Use of Estimates (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Deferred offering costs	$ 0	$ 0
Expected dividend yield	0.00%	0.00%
Unrecognized tax benefits, interest and penalties expensed	$ 0	$ 0
Unrecognized tax benefits, interest and penalties accrued	$ 0	$ 0

Balance Sheet Account Detail -

Balance Sheet Account Detail - Property and Equipment, Net of Accumulated Depreciation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 682	$ 192
(Less): Accumulated depreciation and amortization	134	38
Property and equipment, net of accumulated depreciation	548	154
Depreciation	100	37
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	294	5
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	74	26
Lab equipment
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	173	92
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 141	$ 69

Balance Sheet Account Detail _2

Balance Sheet Account Detail - Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Trade accounts payable and other	$ 2,237	$ 456
Operating lease liability, current portion	282	64
Accrued clinical studies	1,524	0
Employee stock option early exercise liability, current portion	304	0
Accounts payable and other accrued liabilities	$ 4,347	$ 520
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accounts payable and other accrued liabilities	Accounts payable and other accrued liabilities

Balance Sheet Account Detail _3

Balance Sheet Account Detail - Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Operating lease liability, non-current portion	$ 549	$ 100
Employee stock option early exercise liability, non-current portion	56	0
Other long-term liabilities	$ 605	$ 100
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Thousands	Oct. 20, 2020USD ($)shares	Sep. 30, 2020USD ($)$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	May 31, 2018USD ($)$ / sharesshares	Dec. 31, 2020USD ($)vote$ / sharesshares	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)	Oct. 31, 2020shares
Class of Stock [Line Items]
Common stock, authorized (shares) | shares					200,000,000			200,000,000
Preferred stock, authorized (shares) | shares			0		10,000,000	0		10,000,000
Stock issued, issuance costs | $					$ 2,442
Common stock issued upon conversion of preferred stock (shares) | shares	11,107,018
Conversion of preferred stock into common stock upon initial public offering | $	$ 103,200				$ 103,158
Preferred stock, issued (shares) | shares					0
Common stock voting rights, number of votes | vote					1
Common stock dividends declared (usd per share) | $ / shares					$ 0	$ 0
Common stock, issued (shares) | shares			2,650,919		20,502,576	2,650,919
Common stock, outstanding (shares) | shares			2,646,619		20,323,201	2,646,619
Convertible notes payable
Class of Stock [Line Items]
Convertible notes converted | $			$ 2,000
Series A Preferred Stock
Class of Stock [Line Items]
Price per share (usd per share) | $ / shares			$ 2.3174			$ 2.3174
Stock issued, issuance costs | $							$ 86
Preferred stock, issued (shares) | shares			1,575,030		0	1,575,030
Series A Preferred Stock | Private placement
Class of Stock [Line Items]
Stock issued (shares) | shares				1,600,000
Price per share (usd per share) | $ / shares				$ 2.3174
Stock issued, net proceeds | $				$ 3,600
Stock issued, issuance costs | $				$ 100
Series B Preferred Stock
Class of Stock [Line Items]
Price per share (usd per share) | $ / shares			$ 8.9904			$ 8.9904
Stock issued, issuance costs | $					$ 28	$ 172
Preferred stock, issued (shares) | shares			6,674,909		0	6,674,909
Series B Preferred Stock | Private placement
Class of Stock [Line Items]
Stock issued (shares) | shares			6,700,000
Price per share (usd per share) | $ / shares			$ 8.9904			$ 8.9904
Stock issued, net proceeds | $			$ 57,400
Stock issued, issuance costs | $			$ 200
Series B Preferred Stock | Convertible notes payable
Class of Stock [Line Items]
Conversion of notes, preferred stock issued (shares) | shares			300,000
Series C Preferred Stock
Class of Stock [Line Items]
Price per share (usd per share) | $ / shares					$ 14.0003
Stock issued, issuance costs | $					$ 243
Series C Preferred Stock | Private placement
Class of Stock [Line Items]
Stock issued (shares) | shares		2,900,000
Price per share (usd per share) | $ / shares		$ 14.0003
Stock issued, net proceeds | $		$ 39,800
Stock issued, issuance costs | $		$ 200

Stockholders' Equity - Preferre

Stockholders' Equity - Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Preferred stock, authorized (shares)		8,306,679
Preferred stock, outstanding (shares)	0	8,249,939	1,575,030	0
Preferred stock, net carrying value	$ 0	$ 63,402	$ 3,564	$ 0
Preferred stock, liquidation preference		$ 63,660
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, authorized (shares)	0	1,575,030
Preferred stock, outstanding (shares)	0	1,575,030
Preferred stock, net carrying value	$ 0	$ 3,564
Preferred stock, liquidation preference		$ 3,650
Original issue price (usd per share)		$ 2.3174
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, authorized (shares)	0	6,731,649
Preferred stock, outstanding (shares)	0	6,674,909
Preferred stock, net carrying value	$ 0	$ 59,838
Preferred stock, liquidation preference		$ 60,010
Original issue price (usd per share)		$ 8.9904

Stockholders' Equity - Shares R

Stockholders' Equity - Shares Reserved for Issuance (Details) - shares	Dec. 31, 2020	Dec. 31, 2019
Equity [Abstract]
Preferred Stock outstanding (shares)	0	8,249,939
Stock options issued and outstanding (shares)	1,836,739	297,142
Stock options reserved for future grant (shares)	9,414,091	2,150,867
Total shares of common stock reserved (shares)	11,250,830	10,697,948

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)planshares	Oct. 08, 2020shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Total grant-date fair value of options that vested during period | $	$ 700,000	$ 33,000
Unrecognized compensation expense | $	$ 6,500,000
Unrecognized compensation expense, recognition period	2 years 9 months 18 days
Liability for early exercise of stock options | $	$ 400,000	$ 0
Repurchase of stock options (shares) | shares		26,927
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Expiration period, from date of termination upon death	12 months
Expiration period, from date of termination upon disability	6 months
Expiration period, from date of termination for all other separations	3 months
2020 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance (shares) | shares			9,000,000
Common stock reserved for issuance, increase percentage on first business day of each of next ten fiscal years	4.00%
2016 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock available for issuance (shares) | shares			2,432,980
Number of stock-based compensation plans | plan		1
Minimum exercise price, percent of fair market value	100.00%
2016 Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service condition for full vesting	1 year
2016 Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Service condition for full vesting	4 years

Stock-Based Compensation - Expe

Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 839	$ 18
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	260	6
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 579	$ 12

Stock-Based Compensation - Valu

Stock-Based Compensation - Valuation Assumptions of Stock Options (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Exercise price (estimated fair value per common share on grant date) (usd per share)		$ 0.45
Expected term	6 years 3 months
Risk-free interest rate, minimum	0.38%	2.40%
Risk-free interest rate, maximum	0.47%	2.50%
Expected volatility, minimum	70.10%	82.50%
Expected volatility, maximum	71.20%	89.40%
Expected dividend yield	0.00%	0.00%
Weighted-average grant-date fair value per stock option (usd per share)	$ 4.16	$ 0.34
Maximum contractual term	10 years
Minimum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Exercise price (estimated fair value per common share on grant date) (usd per share)	$ 2.01
Expected term		5 years 11 months 8 days
Maximum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Exercise price (estimated fair value per common share on grant date) (usd per share)	$ 10.99
Expected term		6 years 3 months

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Beginning balance (shares)	297,142	267,041
Granted (shares)	1,741,384	32,793
Exercised (shares)	(197,179)	0
Forfeited (shares)	(4,608)	(1,907)
Expired (shares)	0	(785)
Ending balance (shares)	1,836,739	297,142	267,041
Vested (shares)	428,491
Unvested (shares)	1,408,248
Weighted- Average Exercise Price/Share
Beginning balance (usd per share)	$ 0.32	$ 0.31
Granted (usd per share)	4.16	0.45
Exercised (usd per share)	1.88
Forfeited (usd per share)	0.90	0.45
Expired (usd per share)		0.45
Ending balance (usd per share)	3.77	$ 0.32	$ 0.31
Vested (usd per share)	1.68
Unvested (usd per share)	$ 4.41
Weighted-Average Remaining Contractual Term
Outstanding	9 years 1 month 24 days	8 years 7 months 6 days	9 years 6 months 3 days
Vested	8 years 5 months 19 days
Unvested	9 years 4 months 9 days
Aggregate Intrinsic Value (1)
Outstanding	$ 68,981	$ 37	$ 37
Vested	16,988
Unvested	$ 51,993

Stock-Based Compensation - Info

Stock-Based Compensation - Information With Respect to Stock Option Grants (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Outstanding
Granted stock options outstanding (in shares)	1,836,739
Aggregate Intrinsic Value	$ 68,981	$ 37	$ 37
Weighted- Average Remaining Contractual Life (Years)	9 years 1 month 24 days
Exercisable
Granted stock options exercisable (shares)	1,349,990
Aggregate Intrinsic Value	$ 55,460
Weighted- Average Remaining Contractual Life (Years)	9 years 3 days
0.0007
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price (usd per share)	$ 0.0007
Outstanding
Granted stock options outstanding (in shares)	83,809
Aggregate Intrinsic Value	$ 3,464
Weighted- Average Remaining Contractual Life (Years)	6 years 10 months 28 days
Exercisable
Granted stock options exercisable (shares)	83,809
Aggregate Intrinsic Value	$ 3,464
Weighted- Average Remaining Contractual Life (Years)	6 years 10 months 28 days
0.45
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price (usd per share)	$ 0.45
Outstanding
Granted stock options outstanding (in shares)	195,088
Aggregate Intrinsic Value	$ 7,976
Weighted- Average Remaining Contractual Life (Years)	7 years 10 months 9 days
Exercisable
Granted stock options exercisable (shares)	158,647
Aggregate Intrinsic Value	$ 6,547
Weighted- Average Remaining Contractual Life (Years)	7 years 9 months 25 days
2.01
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price (usd per share)	$ 2.01
Outstanding
Granted stock options outstanding (in shares)	1,143,868
Aggregate Intrinsic Value	$ 44,982
Weighted- Average Remaining Contractual Life (Years)	9 years 3 months 29 days
Exercisable
Granted stock options exercisable (shares)	1,085,376
Aggregate Intrinsic Value	$ 44,566
Weighted- Average Remaining Contractual Life (Years)	9 years 4 months 2 days
10.99
Share-based Payment Arrangement, Option, Exercise Price Range [Line Items]
Exercise price (usd per share)	$ 10.99
Outstanding
Granted stock options outstanding (in shares)	413,974
Aggregate Intrinsic Value	$ 12,559
Weighted- Average Remaining Contractual Life (Years)	9 years 8 months 23 days
Exercisable
Granted stock options exercisable (shares)	22,158
Aggregate Intrinsic Value	$ 883
Weighted- Average Remaining Contractual Life (Years)	9 years 8 months 23 days

Net Loss Per Share (Details)

Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net loss	$ (26,811)	$ (4,670)	$ (1,319)
Weighted-average shares—basic and diluted (shares)	6,207,367	2,362,768
Net loss per share attributable to common stockholders—basic and diluted (usd per share)	$ (4.32)	$ (1.98)

Net Loss Per Share - Outstandin

Net Loss Per Share - Outstanding Potentially Dilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	2,016,114,000	2,317,354,000
Stock options, unexercised—vested and unvested
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	1,836,739,000	297,142,000
Series A and Series B Preferred Stock, outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0	1,922,491,000
Stock options early-exercised and unvested
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	179,375,000	4,300,000
Convertible promissory notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total	0	93,421,000

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets:
Total assets measured at fair value	$ 168,129	$ 57,952
Money market funds
Assets:
Money market funds	168,129	57,952
Level 1
Assets:
Total assets measured at fair value	168,129	57,952
Level 1 | Money market funds
Assets:
Money market funds	168,129	57,952
Level 2
Assets:
Total assets measured at fair value	0	0
Level 2 | Money market funds
Assets:
Money market funds	0	0
Level 3
Assets:
Total assets measured at fair value	0	0
Level 3 | Money market funds
Assets:
Money market funds	$ 0	$ 0

Fair Value Measurements - Chang

Fair Value Measurements - Changes in Fair Value of Derivative Liability (Details) - Derivative Liabilities $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	$ 0
Revaluation of derivative liabilities included in other income (expense), net within the Statement of Operations	76
Settlement of derivative liabilities through conversion of all Notes	(363)
Fair value, end of period	0
May 2019 Notes
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Initial fair value of derivative liability upon issuance of notes	28
August 2019 Notes
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Initial fair value of derivative liability upon issuance of notes	50
October 2019 Notes
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Initial fair value of derivative liability upon issuance of notes	$ 209

Convertible Promissory Notes _2

Convertible Promissory Notes Payable (Details) - USD ($) shares in Millions	1 Months Ended				12 Months Ended
	Dec. 31, 2019	Oct. 31, 2019	Aug. 31, 2019	May 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Loss on extinguishment of convertible notes					$ 0	$ 255,000
Change in fair value of derivative liabilities					0	(76,000)
Convertible notes payable
Debt Instrument [Line Items]
Convertible notes converted	$ 2,000,000
Loss on extinguishment of convertible notes						300,000
Interest expense					0	100,000
Change in fair value of derivative liabilities					$ 0	$ (100,000)
Convertible notes payable | Series B Preferred Stock
Debt Instrument [Line Items]
Conversion of notes, preferred stock issued (shares)	0.3
Convertible notes payable | Founders and other related parties | May 2019 Notes
Debt Instrument [Line Items]
Cash proceeds from debt issuance				$ 500,000
Face amount of debt issued				$ 500,000
Interest rate				8.00%
Conversion price, percentage of issuance price				90.00%
Convertible notes payable | Founders and other related parties | August 2019 Notes
Debt Instrument [Line Items]
Cash proceeds from debt issuance			$ 500,000
Face amount of debt issued			$ 500,000
Convertible notes payable | Founders and other related parties | October 2019 Notes
Debt Instrument [Line Items]
Cash proceeds from debt issuance		$ 1,000,000
Face amount of debt issued		$ 1,000,000
Conversion price, percentage of issuance price		80.00%

Commitments & Contingencies - F

Commitments & Contingencies - Facility Leases (Details)	Jun. 01, 2020USD ($)contract	Dec. 31, 2020USD ($)contract	Dec. 31, 2019USD ($)contract	Mar. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Impairment of operating lease right-of-use asset		$ 15,000	$ 0
Operating lease right-of-use asset obtained in exchange for operating lease liability	$ 700,000	726,000	163,000
Operating lease right-of-use assets		688,000	126,000
Operating lease liability		831,000
Lease expense		200,000	100,000
Variable lease cost		$ 25,000	$ 0
Estimated incremental borrowing rate		10.00%
Weighted average remaining lease term		2 years 10 months
ASU 2016-02
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets				$ 200,000
Operating lease liability				$ 200,000
Irvine office and laboratory facility
Lessee, Lease, Description [Line Items]
Number of leases | contract		3	1
Remaining lease term		1 year 4 months	2 years 4 months
Other facility leases
Lessee, Lease, Description [Line Items]
Number of leases entered during period | contract	2
Remaining lease term		3 years 1 month

Commitments & Contingencies - I

Commitments & Contingencies - In-License Agreements for Lotilaner (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development		$ 18,826,000	$ 3,162,000
Common stock issued for license agreement, value		$ 3,115,000
License agreement | Elanco
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Research and development	$ 1,000,000		$ 1,000,000
Common stock issued for license agreement (shares)	222,460
Common stock issued for license agreement, value	$ 3,100,000
Common stock issued for license agreement, share price (usd per share)	$ 14.0003
Additional shares to be issued (shares)	187,500
License agreement | Clinical milestones | Elanco
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum milestone payments	$ 4,500,000			$ 5,000,000
License agreement | Commercial and sales milestones | Elanco
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum milestone payments	$ 77,000,000			$ 79,000,000

Commitments & Contingencies - E

Commitments & Contingencies - Employment Arrangements (Details)	Dec. 31, 2020arrangement
Commitments and Contingencies Disclosure [Abstract]
Number of employment arrangements with executive officers	4

Commitments & Contingencies -_2

Commitments & Contingencies - Future Contractual Lease Payments (Details) $ in Thousands	Dec. 31, 2020USD ($)
Commitments and Contingencies Disclosure [Abstract]
2021	$ 349
2022	298
2023	281
2024	25
2025	0
Total future lease payments, undiscounted	953
(Less): Imputed interest	(122)
Present value of operating lease payments	$ 831

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Expected tax benefit at statutory rate	$ (5,630)	$ (981)
State income tax, net of federal benefit	1	1
Permanent items	5	4
Research and development credits	(632)	(31)
Loss on extinguishment of convertible notes	0	54
Non-deductible interest	0	35
Other	119	4
Change in valuation allowance	6,138	915
Income tax provision	$ 1	$ 1

Income Taxes - Significant Comp

Income Taxes - Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating loss carry forwards	$ 5,391	$ 961
Research and development credit carryforwards	710	88
Intangible assets	1,046	211
Other, net	476	104
Total deferred tax assets before valuation allowance	7,623	1,364
Less: valuation allowance	(7,475)	(1,338)
Total deferred tax assets	148	26
Deferred tax liabilities, net:
Operating lease right-of-use assets	(148)	(26)
Net deferred tax asset	$ 0	$ 0

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Valuation allowance on deferred tax assets	$ 7,475,000	$ 1,338,000
Net operating loss carryforwards	25,300,000
Net operating loss carryforwards, subject to expiration	45,000
Net operating loss carryforwards, not subject to expiration	25,200,000
Unrecognized tax benefits	488,000	33,000	$ 20,000
Unrecognized tax benefits that would affect effective tax rate if recognized	0
Unrecognized tax benefits, interest and penalties accrued	0	0
Unrecognized tax benefits, interest and penalties expensed	0	$ 0
Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	25,300,000
California
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	4,000,000
Research and development tax credit carryforwards | Federal
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	600,000
Research and development tax credit carryforwards | California
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 400,000

Income Taxes - Gross Unrecogniz

Income Taxes - Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of year	$ 33
Additions related to current year positions	217	$ 13
Additions related to prior year positions	242	0
Decreases related to prior year positions	(4)	0
Balance at end of year	$ 488	$ 20

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event - License agreement - LianBo	Mar. 26, 2021USD ($)
Subsequent Event [Line Items]
Upfront payment receivable	$ 25,000,000
Regulatory milestone
Subsequent Event [Line Items]
Maximum milestone payments	75,000,000
Sales milestone
Subsequent Event [Line Items]
Maximum milestone payments	$ 100,000,000