Compass Therapeutics (CMPX) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 02, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Entity Registrant Name	COMPASS THERAPEUTICS, INC.
Entity Central Index Key	0001738021
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Common Stock, Shares Outstanding		52,123,374
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity File Number	000-55939
Entity Tax Identification Number	82-4876496
Entity Address, Address Line One	245 First Street
Entity Address, Address Line Two	3rd Floor
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	500-8099
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of each class	Common Stock, $0.0001 par value per share
No Trading Symbol	true

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (unaudited) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 55,518	$ 25,303
Prepaid expenses and other current assets	2,314	935
Total current assets	57,832	26,238
Property and equipment, net	2,418	3,751
Restricted cash	263	263
Other assets	177	129
Total assets	60,690	30,381
Current liabilities:
Current portion of long-term debt	7,461	5,576
Accounts payable	854	629
Accrued expenses	1,358	3,122
Derivative liability related to loan		494
Total current liabilities	9,673	9,821
Long-term debt, net of current portion	3,730	9,293
Total liabilities	13,403	19,114
Commitments and contingencies (Note 11)
Convertible preferred stock - 207,164,404 authorized, issued, and outstanding as of December 31, 2019. No shares authorized, issued, and outstanding as of September 30, 2020.		129,870
Stockholders' equity (deficit):
Preferred stock, $0.0001 par value: 10,000,000 shares authorized and no shares issued and outstanding as of September 30, 2020; no shares issued and outstanding as of December 31, 2019
Common stock, $0.0001 par value: 300,000,000 shares authorized; 52,123,374 and 9,073,002 shares issued at September 30, 2020 and December 31, 2019, respectively; 51,672,326 and 7,034,047 shares outstanding at September 30, 2020 and December 31, 2019, respectively	5	1
Additional paid-in-capital	190,299	3,304
Accumulated deficit	(143,017)	(121,908)
Total stockholders' equity (deficit)	47,287	(118,603)
Total liabilities and stockholders' equity (deficit)	$ 60,690	$ 30,381

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) (unaudited) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Convertible preferred stock, shares authorized	0	207,164,404
Convertible preferred stock, shares issued	0	207,164,404
Convertible preferred stock, shares outstanding	0	207,164,404
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	52,120,062	9,073,002
Common stock, shares outstanding	51,024,270	7,034,047

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Operating expenses:
Research and development	$ 3,670	$ 5,979	$ 10,498	$ 19,146
General and administrative	5,291	2,404	9,364	8,504
Total operating expenses	8,961	8,383	19,862	27,650
Loss from operations	(8,961)	(8,383)	(19,862)	(27,650)
Other income (expense):
Interest income	22	176	70	647
Interest expense	(212)	(312)	(730)	(944)
Change in fair value of derivative liability		(7)	(556)	(96)
Realized foreign exchange loss	1		1	(8)
Total other expense	(189)	(143)	(1,215)	(401)
Loss before income tax expense	(9,150)	(8,526)	(21,077)	(28,051)
Income tax expense		(26)	(32)	(81)
Net loss	$ (9,150)	$ (8,552)	$ (21,109)	$ (28,132)
Net loss per share - basic and diluted	$ (0.18)	$ (1.27)	$ (0.88)	$ (4.26)
Basic and diluted weighted average shares outstanding	50,939,657	6,752,143	23,968,408	6,601,951

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Convertible Preferred Stock
Temporary equity, Beginning Balance at Dec. 31, 2018					$ 129,870
Temporary equity, Beginning Balance, Shares at Dec. 31, 2018					207,164,404
Temporary equity, Ending Balance at Mar. 31, 2019					$ 129,870
Temporary equity, Ending Balance, Shares at Mar. 31, 2019					207,164,404
Beginning Balance at Dec. 31, 2018	$ (84,774)	$ 1	$ 2,389	$ (87,164)
Beginning Balance, Shares at Dec. 31, 2018		6,355,377
Vesting of share-based awards		223,072
Stock-based compensation expense	255		255
Net loss	(10,771)			(10,771)
Ending Balance at Mar. 31, 2019	(95,290)	$ 1	2,644	(97,935)
Ending Balance, Shares at Mar. 31, 2019		6,578,449
Temporary equity, Beginning Balance at Dec. 31, 2018					$ 129,870
Temporary equity, Beginning Balance, Shares at Dec. 31, 2018					207,164,404
Temporary equity, Ending Balance at Sep. 30, 2019					$ 129,870
Temporary equity, Ending Balance, Shares at Sep. 30, 2019					207,164,404
Beginning Balance at Dec. 31, 2018	(84,774)	$ 1	2,389	(87,164)
Beginning Balance, Shares at Dec. 31, 2018		6,355,377
Net loss	(28,132)
Ending Balance at Sep. 30, 2019	(112,217)	$ 1	3,078	(115,296)
Ending Balance, Shares at Sep. 30, 2019		6,911,983
Temporary equity, Beginning Balance at Mar. 31, 2019					$ 129,870
Temporary equity, Beginning Balance, Shares at Mar. 31, 2019					207,164,404
Temporary equity, Ending Balance at Jun. 30, 2019					$ 129,870
Temporary equity, Ending Balance, Shares at Jun. 30, 2019					207,164,404
Beginning Balance at Mar. 31, 2019	(95,290)	$ 1	2,644	(97,935)
Beginning Balance, Shares at Mar. 31, 2019		6,578,449
Vesting of share-based awards		105,127
Stock-based compensation expense	185		185
Net loss	(8,809)			(8,809)
Ending Balance at Jun. 30, 2019	(103,914)	$ 1	2,829	(106,744)
Ending Balance, Shares at Jun. 30, 2019		6,683,576
Temporary equity, Ending Balance at Sep. 30, 2019					$ 129,870
Temporary equity, Ending Balance, Shares at Sep. 30, 2019					207,164,404
Vesting of share-based awards		228,407
Stock-based compensation expense	249		249
Net loss	(8,552)			(8,552)
Ending Balance at Sep. 30, 2019	(112,217)	$ 1	3,078	(115,296)
Ending Balance, Shares at Sep. 30, 2019		6,911,983
Temporary equity, Beginning Balance at Dec. 31, 2019	$ 129,870				$ 129,870
Temporary equity, Beginning Balance, Shares at Dec. 31, 2019	207,164,404				207,164,404
Temporary equity, Ending Balance at Mar. 31, 2020					$ 129,870
Temporary equity, Ending Balance, Shares at Mar. 31, 2020					207,164,404
Beginning Balance at Dec. 31, 2019	$ (118,603)	$ 1	3,304	(121,908)
Beginning Balance, Shares at Dec. 31, 2019		7,034,047
Vesting of share-based awards		88,080
Stock-based compensation expense	247		247
Net loss	(6,402)			(6,402)
Ending Balance at Mar. 31, 2020	(124,758)	$ 1	3,551	(128,310)
Ending Balance, Shares at Mar. 31, 2020		7,122,127
Temporary equity, Beginning Balance at Dec. 31, 2019	$ 129,870				$ 129,870
Temporary equity, Beginning Balance, Shares at Dec. 31, 2019	207,164,404				207,164,404
Temporary equity, Ending Balance, Shares at Sep. 30, 2020	0				0
Beginning Balance at Dec. 31, 2019	$ (118,603)	$ 1	3,304	(121,908)
Beginning Balance, Shares at Dec. 31, 2019		7,034,047
Conversion of Compass Therapeutics LLC preferred shares into common shares upon consummation of the reverse merger, Shares		30,629,606
Net loss	(21,109)
Ending Balance at Sep. 30, 2020	47,287	$ 5	190,299	(143,017)
Ending Balance, Shares at Sep. 30, 2020		51,024,270
Temporary equity, Beginning Balance at Mar. 31, 2020					$ 129,870
Temporary equity, Beginning Balance, Shares at Mar. 31, 2020					207,164,404
Temporary equity, Conversion of Compass Therapeutics LLC preferred shares into common shares upon consummation of the reverse merger					$ (129,870)
Temporary equity, Conversion of Compass Therapeutics LLC preferred shares into common shares upon consummation of the reverse merger, Shares					(207,164,404)
Beginning Balance at Mar. 31, 2020	(124,758)	$ 1	3,551	(128,310)
Beginning Balance, Shares at Mar. 31, 2020		7,122,127
Common shares issued to former shareholders of Olivia Ventures Inc., Shares		1,000,000
Conversion of Compass Therapeutics LLC preferred shares into common shares upon consummation of the reverse merger	129,870	$ 3	129,867
Conversion of Compass Therapeutics LLC preferred shares into common shares upon consummation of the reverse merger, Shares		30,629,606
Common shares issued in private placement, net of issuance costs of $6,902	53,581	$ 1	53,580
Common shares issued in private placement, net of issuance costs of $6,902, Shares		12,096,442
Payment to non-participating Compass Therapeutics LLC members upon consummation of Merger	(69)		(69)
Payment to non-participating Compass Therapeutics LLC members upon consummation of Merger, Shares		(13,640)
Vesting of share-based awards		62,298
Stock-based compensation expense	183		183
Net loss	(5,557)			(5,557)
Ending Balance at Jun. 30, 2020	$ 53,250	$ 5	187,112	(133,867)
Ending Balance, Shares at Jun. 30, 2020		50,896,833
Temporary equity, Ending Balance, Shares at Sep. 30, 2020	0				0
Adjustment to issuance costs related to June 2020 private placement	$ 651		651
Vesting of share-based awards		127,437
Stock-based compensation expense	2,536		2,536
Net loss	(9,150)			(9,150)
Ending Balance at Sep. 30, 2020	$ 47,287	$ 5	$ 190,299	$ (143,017)
Ending Balance, Shares at Sep. 30, 2020		51,024,270

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) (unaudited)	3 Months Ended
	Jun. 30, 2020USD ($)
Statement Of Stockholders Equity [Abstract]
Stock issuance costs	$ 6,902

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (21,109)	$ (28,132)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,335	1,599
Loss on disposal of equipment	8	5
Noncash interest expense	72	93
Share-based compensation	2,966	689
Change in fair value of derivative liability	556	96
Changes in operating assets and liabilities:
Prepaid expenses and other current assets	(1,379)	228
Other long-term assets	25	(26)
Accounts payable	194	(1,103)
Accrued expenses	(1,848)	401
Settlement of derivative liability	(1,050)
Net cash used in operating activities	(20,230)	(26,150)
Cash flows from investing activities:
Purchases of property and equipment	(23)	(281)
Proceeds from sale of equipment	55
Net cash provided by (used in) investing activities	32	(281)
Cash flows from financing activities:
Proceeds from issuance of common units	60,482
Issuance costs from issuance of common units	(6,319)
Repayment of borrowings under loan	(3,750)
Net cash provided by financing activities	50,413
Net change in cash, cash equivalents and restricted cash	30,215	(26,431)
Cash, cash equivalents and restricted cash at beginning of period	25,566	57,773
Cash, cash equivalents and restricted cash at end of period	55,781	31,342
Supplemental disclosure of cash flow information
Cash paid for interest	686	$ 851
Supplemental disclosure of financing activities
Conversion of preferred units	129,870
Deferred offering costs included in accrued expenses	$ (116)

Nature of Business and Basis of

Nature of Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of Business and Basis of Presentation	1. Nature of Business and Basis of Presentation Compass Therapeutics, Inc. (“Compass” or the “Company”) is a clinical-stage biopharmaceutical company developing proprietary antibody therapeutics intended to engage the immune system to treat both solid tumors and hematological malignancies. The Company immuno-oncology product candidates include a clinical-stage monoclonal antibody and a portfolio of bispecific antibodies. The Company was incorporated as Olivia Ventures, Inc. (“Olivia”) in the State of Delaware on March 20, 2018. Prior to the Merger (as defined below), Olivia was a “shell company” (as defined in Rule 12b-2 of the Securities Exchange Act of 1934, as amended). On June 17, 2020, the Company’s Board of Directors and the Company’s pre-Merger (defined below) stockholders approved an amended and restated certificate of incorporation, which, among other things, increased authorized capital stock from 50,000,000 shares of common stock par value $0.0001 and 5,000,000 shares of preferred stock, par value $0.0001 per share, to 300,000,000 shares of common stock, par value $0.0001 per share, and 10,000,000 shares of preferred stock, par value $0.0001 per share. On June 17, 2020, the Company completed a merger (the “Merger”) of a wholly-owned subsidiary Compass Therapeutics LLC (“Compass LLC”) pursuant to an Agreement and Plan of Merger and Reorganization (the “Merger Agreement”), by and among the Company, Olivia Ventures, Inc., Acquisition Sub, Compass Therapeutics, Blockers, Blockers Merger Subs and Blocker Holders and, as a result of, Compass LLC became a wholly-owned subsidiary of the Company. At the effective time of the Merger and the applicable effective time of each Blocker Merger, collectively, the Effective Time, an aggregate of 31,627,139 shares of its common stock were issued to holders of common membership interests of Compass LLC (including common membership interests issued upon the conversion of preferred membership interests) and 7,428,217 shares of its common stock were issued to the holders of equity interests of the Blockers. The issuances of shares of the Company’s common stock to the security holders of Compass LLC and the Blockers are collectively referred to as the Share Conversion. In addition, 2,930,836 shares of the Company’s common stock were reserved for issuance under its 2020 Stock Option and Incentive Plan. Immediately prior to the Effective Time, an aggregate of 4,000,000 of the 5,000,000 shares of the Company’s common stock held by pre-Merger stockholders of Olivia Ventures, Inc. were forfeited and surrendered for cancellation, or the Stock Forfeiture. No fractional shares of the Company’s common stock were issued in connection with the Merger, and holders of Compass LLC Units received cash in lieu thereof. The Merger and the Blocker Mergers were treated as a recapitalization and reverse acquisition for financial reporting purposes. Compass Therapeutics is considered the acquirer for accounting purposes, and the Company’s historical financial statements before the Merger have been replaced with the historical financial statements of Compass Therapeutics in this and future filings with the SEC. As a result, the vested and outstanding common units held by Compass LLC members have been presented as outstanding shares of the Company’s common stock for all periods presented. All outstanding preferred units of Compass LLC are presented as convertible preferred stock for all periods and until such units were converted into shares of the Company’s common stock at the time of the Merger. On June 19, 2020, the Company completed a private placement and sold 12,096,442 shares of its common stock The Company is subject to risks and uncertainties common to companies in the biotechnology and pharmaceutical industries. There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s technology will be obtained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. The Company operates in an environment of rapid change in technology and substantial competition from pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees and consultants.

Liquidity Uncertainties and Goi

Liquidity Uncertainties and Going Concern	9 Months Ended
	Sep. 30, 2020
Liquidity Uncertainties And Going Concern [Abstract]
Liquidity, Uncertainties and Going Concern	2. Liquidity, Uncertainties and Going Concern The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about its ability to continue as a going concern within one year after the date that the condensed consolidated financial statements are issued. Since its inception, the Company has funded its operations primarily with proceeds from the sale of its equity securities and borrowings under loan agreements. The Company has incurred recurring losses since its inception and had an accumulated deficit of $143.0 million at September 30, 2020. The Company expects to continue to generate operating losses for the foreseeable future. The Company expects that its cash and cash equivalents will be sufficient to fund its operating expenses and capital expenditure requirements into the first quarter of 2022. The future viability of the Company beyond that point is dependent on its ability to raise additional capital to finance its operations. In December 2019, a novel strain of coronavirus (“COVID-19”) was reported to have surfaced in Wuhan, China. As of May 2020, COVID-19 has spread to Europe, the United States and many other countries, and has been declared a pandemic by the World Health Organization. In an effort to contain the spread of COVID-19, the United States, Europe and Asia have implemented severe travel restrictions, social distancing requirements, stay-at-home or shelter-in-place orders and have delayed the commencement of non-COVID-19-related clinical trials, among other restrictions. As a result, the COVID-19 pandemic has presented a substantial public health and economic challenge around the world and is affecting the Company’s employees, communities and business operations, as well as contributing to significant volatility and negative pressure on the U.S. economy and in financial markets. The full extent to which the COVID-19 pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition will depend on future developments that are highly uncertain and cannot be accurately predicted, including new information that may emerge concerning COVID-19, the actions taken to contain it or mitigate its impact, and the economic impact on local, regional, national and international markets. Due to the evolving and uncertain global impacts of the COVID-19 pandemic, the Company cannot precisely determine or quantify the impact this pandemic will have on its business operations for the remainder of fiscal 2020. The extent to which COVID-19 may impact the Company’s results of operations will depend on a variety of factors and future developments, which are highly uncertain and cannot be predicted with confidence, including the ultimate geographic spread of the disease, the duration, scope and severity of the pandemic, the duration and extent of travel restrictions and social distancing in the U.S. and other countries, business closures or business disruptions and the effectiveness of actions taken in the U.S. and other countries to contain and treat COVID-19. For ongoing and planned clinical trials, the Company has experienced some temporary delays or disruptions due to the COVID-19 pandemic, including limited or reduced patient access to trial investigators, hospitals and trial sites, delayed initiation of new clinical trial sites and limited on-site personnel support at various trial sites, which could adversely impact the Company’s development plans, including the initiation of planned clinical trials and its ability to conduct ongoing clinical trials. There may also be local orders affecting one or more trial sites, which may trigger mandated changes to the Company’s clinical trial protocols or temporary suspensions in the affected trial sites. In addition, quarantines, stay-at-home, executive and similar government orders, or the perception that such orders, shutdowns or other restrictions on the conduct of business operations have occurred and could continue to occur or be expanded in scope or duration, which could adversely impact ongoing and planned clinical trials, employees and business operations, personnel at third-party suppliers and other vendors in the U.S. and other countries, the availability, cost or supply of materials, which may cause delays or disruptions to development plans for the Company’s product candidates, and sales and marketing activities for any product candidates for which the Company may receive marketing approval in the U.S. or other geographies in the future.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. Summary of Significant Accounting Policies Basis of Presentation The accompanying condensed consolidated financial statements are presented in U.S. dollars and have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and as amended by Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all normal and recurring adjustments (which consist primarily of accruals, estimates and assumptions that impact the financial statements) considered necessary to present fairly the Company’s financial position as of September 30, 2020 and its results of operations and changes in convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2020 and 2019 and cash flows for the nine months ended September 30, 2020 and 2019. Operating results for the nine months ended September 30, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020. The condensed consolidated balance sheet at December 31, 2019 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by GAAP for complete financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements of Compass Therapeutics LLC and related footnotes for the year ended December 31, 2019, included as Exhibit 99.1 in the Company’s Form 8-K filed with the SEC on June 23, 2020. Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of Compass Therapeutics, Inc., and its wholly-owned subsidiaries Compass Therapeutics LLC and Compass Therapeutics Advisors Inc. All intercompany accounts and transactions have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, the accrual of research and development expenses, the valuation of the embedded derivative, the valuation of common stock and estimates associated with stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from those estimates. Changes in estimates are recorded in the period that they become known. Segment Information Operating segments are defined as components of an enterprise for which separate and discrete information is available for evaluation by the chief operating decision-maker in deciding how to allocate resources and assess performance. The Company has one operating segment. The Company’s chief operating decision-maker, its chief executive officer, manages the Company’s operations on a consolidated basis for the purpose of allocating resources. All of the Company’s long-lived assets are held in the United States. Cash and Cash Equivalents The Company considers all highly liquid investments that are readily convertible into cash with original maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents include cash held in banks and amounts held in money market funds. Cash equivalents are stated at cost, which approximates market value. C Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and restricted cash. The Company maintains its cash, cash equivalents and restricted cash with financial institutions that management believes to be of high-credit quality. The Company has Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the related assets as follows: Asset Classification Estimated Useful Life Equipment 5 years Furniture and fixtures 7 years Software 5 years Leasehold improvements Lesser of estimated useful life or lease term Estimated useful lives are periodically assessed to determine if changes are appropriate. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are eliminated from the condensed consolidated balance sheet and any resulting gains or losses are included in the condensed consolidated statement of operations in the period of disposal. Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service. Assets held under capital leases are stated at the lesser of the present value of future minimum lease payments or the fair value of the leased asset at the inception of the lease. Amortization of assets held under capital leases is computed using the straight-line method over the shorter of the estimated useful life of the asset or the period of the related lease. Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized in the condensed consolidated statements of operations when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. The Company did not record any impairment losses on long-lived assets during the nine months ended September 30, 2020 and 2019. Fair Value Measurements Certain assets and liabilities of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) 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. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1 – Quoted prices in active markets for identical assets or liabilities. • Level 2 – Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets and liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. An entity may choose to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected are reported in earnings. The Company’s cash equivalents are carried at fair value according to the fair value hierarchy described above and were determined based on Level 1 measurements (see Note 4). The Company’s restricted cash is carried at fair value according to the fair value hierarchy described above and were determined based on Level 2 measurements (see Note 4). The carrying values of other current assets and accounts payable approximate their fair value due to the short‑term nature of these assets and liabilities. The carrying values of the Company’s loan approximated its fair value as of September 30, 2020 and December 31, 2019 due to its variable interest rate. The fair value of the loan related embedded derivative (see Note 4) was determined based on Level 3 measurements. Research and Development Costs Costs associated with internal research and development and external research and development services, including drug development and preclinical studies, are expensed as incurred. Research and development expenses include costs for salaries, employee benefits, subcontractors, facility-related expenses, depreciation and amortization, stock-based compensation, third-party license fees, laboratory supplies, and external costs of outside vendors engaged to conduct discovery, preclinical and clinical development activities and clinical trials as well as to manufacture clinical trial materials, and other costs. The Company recognizes external research and development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. Such prepaid expenses are recognized as an expense when the goods have been delivered or the related services have been performed, or when it is no longer expected that the goods will be delivered, or the services rendered. Costs associated with licenses of technology acquired as part of collaborative arrangements are expensed as incurred and are generally included in research and development expense in the condensed consolidated statements of operations if it is determined the license has no alternative future use. Accrued Research and Development Expenses The Company has entered into various research and development and other agreements with commercial firms, researchers, universities and others for provisions of goods and services. These agreements are generally cancelable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs. Stock-Based Compensation Prior to the Merger, Compass Therapeutics LLC issued Class A and Class C common units to various employees, directors and consultants. The units constituted “profits interests” for tax purposes and were accounted for as share-based payment arrangements. Upon consummation of the Merger, all outstanding vested units were converted into shares of common stock and all outstanding unvested units were converted into shares of restricted stock that continue to vest over the remaining term of the original award. Subsequent to the Merger, the Company has granted stock options to various employees, directors and consultants. The Company recognizes the grant‑date fair value of stock‑based awards issued to employees and nonemployee board members as compensation expense on a straight‑line basis over the vesting period of the award. The Company uses the Black‑Scholes option pricing model to determine the grant‑date fair value of stock options and adjusts expense for forfeitures in the periods they occur. Net Loss per Share Basic loss per share is computed by dividing net loss by the weighted average number of shares of common stock outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock, stock options, unvested restricted stock and common stock warrants that would result in the issuance of incremental shares of common stock. In computing the basic and diluted net loss per share, the weighted average number of shares remains the same for both calculations due to the fact that when a net loss exists, dilutive shares are not included in the calculation as the impact is anti-dilutive. The following potentially dilutive securities outstanding as of September 30, 2020 and 2019 have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti-dilutive: September 30, 2020 2019 Convertible preferred stock — 30,629,606 Stock options 1,625,469 — Nonvested restricted stock 1,095,792 1,916,891 Common stock warrants — 3,114,145 Total 2,721,261 35,660,642 Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016‑02, Leases In August 2018, the FASB issued ASU No. 2018‑13, Disclosure Framework Changes to the Disclosure Requirements for Fair Value Measurements In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606 In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The following tables present information about the Company’s financial assets and liabilities that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): Fair Value Measurements as of September 30, 2020 Using: Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable Assets Inputs Inputs (Level 1) (Level 2) (Level 3) Fair Value Assets Cash equivalents - money market funds $ 52,175 $ — $ — $ 52,175 Restricted cash — 263 — 263 Total assets $ 52,175 $ 263 $ — $ 52,438 Liabilities Derivative liability related to loan $ — $ — $ — $ — Total liabilities $ — $ — $ — $ — Fair Value Measurements as of December 31, 2019 Using: Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable Assets Inputs Inputs (Level 1) (Level 2) (Level 3) Fair Value Assets Cash equivalents - money market funds $ 22,784 $ — $ — $ 22,784 Restricted cash — 263 — 263 Total assets $ 22,784 $ 263 $ — $ 23,047 Liabilities Derivative liability related to loan $ — $ — $ 494 $ 494 Total liabilities $ — $ — $ 494 $ 494 Valuation of Derivative Liability The Company’s derivative liability was comprised of the contingent interest rate reset features and a contingent feature to pay a success fee upon the occurrence of certain liquidity events, each of which met the definition of a derivative instrument, which terms are included in the loan and security agreement (refer to Note 7). The Company classified these instruments as a liability on the condensed consolidated balance sheets because these features were not clearly and closely related to its host instrument and met the definition of a derivative. The derivative liability was initially recorded at fair value upon issuance of the loan and was being subsequently remeasured to fair value at each reporting date. Changes in the fair value of the derivative liability were recognized as a component of other income (expense), net in the condensed consolidated statements of operations. The success fee was paid in full following the closing of the Merger in June 2020. The fair value of the derivative liability recognized was determined based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The fair value of the derivative liability was determined using the probability-weighted expected return method, which considered as inputs the type, timing and probability of occurrence of a change-of-control event, the future equity financing and cash settlement of the loans; the potential amount of the payment under each of these potential settlement scenarios; and the risk-adjusted discount rate reflecting the expected risk profile for each of the potential settlement scenarios. The following table provides a roll forward of the aggregate fair values of the Company’s derivative liability (in thousands): Derivative Liability Balance at December 31, 2019 $ 494 Change in fair value 556 Payment of success fee (1,050 ) Balance at September 30, 2020 $ —

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Property and Equipment	5. Property and Equipment Property and equipment consist of the following (in thousands): September 30, December 31, 2020 2019 Equipment $ 7,040 $ 7,230 Furniture and fixtures 629 629 Leasehold improvements 896 896 Software 912 669 Assets not yet placed in service — 230 Total property and equipment–at cost 9,477 9,654 Less: Accumulated depreciation (7,059 ) (5,903 ) Property and equipment, net $ 2,418 $ 3,751 Total depreciation and amortization expense for three months ended September 30, 2020 and 2019, was $0.4 million and $0.5 million, respectively. Total depreciation and amortization expense for nine months ended September 30, 2020 and 2019, was $1.3 million and $1.6 million, respectively.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2020
Payables And Accruals [Abstract]
Accrued Expenses	6 . Accrued Expenses Accrued expenses consist of the following (in thousands): September 30, December 31, 2020 2019 Compensation and benefits $ 605 $ 1,759 Research and development expenses 26 249 Legal and professional fees 507 417 Sales taxes — 554 Other 220 143 Total accrued expenses $ 1,358 $ 3,122

Loan Payable

Loan Payable	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Loan Payable	7. Loan Payable The aggregate principal amount of debt outstanding consisted of the following (in thousands): September 30, December 31, 2020 2019 Current portion of debt $ 7,500 $ 5,625 Less: unamortized debt discount (39 ) (49 ) Current portion of debt, net of debt discount $ 7,461 $ 5,576 Long-term debt, net of current portion $ 3,750 $ 9,375 Less: unamortized debt discount (20 ) (82 ) Long-term debt, net of current portion $ 3,730 $ 9,293 The Company entered into, and subsequently amended, a term loan facility with Pacific Western Bank, Inc. (“PWB”), and received $15.0 million debt proceeds. The loans bear interest at the greater of (i) 6.25% and (ii) the prime rate plus an applicable margin of 2.0%. The interest rate was 6.25% at September 30, 2020. In an event of default, as defined in the agreement, the interest rate applicable to borrowings would be increased by 5.0%. The Company made interest-only payments through March 31, 2020. Beginning in April 2020, the Company is obligated to make equal monthly principal payments of $625,000 through March 31, 2022 when the notes mature. The loan agreement allows for prepayment of the outstanding principal at any time, subject to a prepayment charge that is dependent on the prepayment date. The debt agreement contained provisions whereby the Company was obligated to pay a success fee of $1.1 million upon the achievement of certain liquidity events. Upon consummation of the Merger, the Company success fee payment became due and was paid in its entirety in June 2020. The 2018 Credit Facility contains a negative pledge on the Company’s intellectual property and also contains customary indemnification obligations and customary events of default, including, among other things, (i) non‑payment, (ii) breach of warranty, (iii) non‑performance of covenants and obligations, (iv) default on other indebtedness, (v) judgments, (iv) change of control, (vii) bankruptcy and insolvency, (viii) impairment of security, (ix) key permit events, (x) key person event, (xi) regulatory matters, (xii) and key contracts. In addition, the Company must maintain a minimum cash balance of $6.0 million beginning in April 2020. In the event of default under the 2018 Credit Facility, the Company would be required to pay interest on principal and all other due and unpaid obligations at the current rate in effect plus 5%. The borrowings are collateralized by substantially all of the Company’s assets, excluding intellectual property, and contains affirmative and negative covenants including restrictions on the Company’s ability to incur additional indebtedness, pay dividends, encumber its property, or engage in certain fundamental business transactions, such as mergers or acquisitions of other businesses. The Company must maintain a minimum cash balance of $6.0 million beginning in April 2020. The Company was in compliance with its covenants as of September 30, 2020. The Company recognized interest expense of $0.2 million and $0.3 million during the three months ended September 30, 2020 and 2019 and $0.7 million and $0.9 million during the nine months ended September 30, 2020 and 2019, respectively. As of September 30, 2020, the aggregate minimum future principal payments due in connection with the 2018 Loan Agreement, as amended, are as follows (in thousands): Year Ending December 31, 2020 $ 1,875 2021 7,500 2022 1,875 $ 11,250

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders' Equity (Deficit)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Convertible Preferred Stock and Stockholders' Equity (Deficit)	8 . Convertible Preferred Stock and Stockholders’ Equity (Deficit) Convertible Preferred Stock In connection with the Merger, as discussed in Note 1, the Company issued 30,629,606 shares of its common stock to holders of convertible preferred interests of Compass Therapeutics LLC. No convertible preferred securities were outstanding as of September 30, 2020. As of December 31, 2019, convertible preferred stock consisted of the following shares outstanding: Preferred Stock Shares Issued and Outstanding Series A-1 64,704,832 Series A-2 36,782,734 Series A-3 23,467,151 Series A-4 15,253,415 Series A4B 22,216,583 Series A-5 44,739,689 207,164,404 Common Stock In connection with the Merger, as discussed in Note 1, the Company issued 1,000,000 shares of common stock to the former shareholders of Olivia Ventures Inc. The Company paid $69,000 to several nonaccredited investors of Compass Therapeutics LLC in lieu of issuing shares. In addition, 2,930,836 shares of the Company’s common stock were reserved for issuance under the 2020 Stock Option and Incentive Plan. The Company also sold 12,096,442 shares of its common stock pursuant to the closing of a private placement offering at a purchase price of $5.00 per share.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	9. Stock-Based Compensation Stock-based compensation expense for the three and nine months ended September 30, 2020 and 2019 was classified in the consolidated statement of operations and comprehensive loss as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 374 $ 103 $ 486 $ 278 General and administrative 2,162 146 2,480 411 Total $ 2,536 $ 249 $ 2,966 $ 689 Estimating Fair Value of Equity Awards The fair value of each equity award was determined by the Company on the date of grant and by using the methods and assumptions discussed below. Certain of these inputs are subjective and generally require judgment to determine. Expected Term : The expected term of the equity award represents the weighted average period the award is expected to be outstanding. The Company uses the simplified method for estimating the expected term as provided by the Securities and Exchange Commission. The simplified method calculates the expected term as the average time to vesting and the contractual life of the award. Expected volatility – Due to the Company’s limited operating history and lack of company-specific historical or implied volatility, the expected volatility assumption was determined by examining the historical volatilities of a group of industry peers whose share prices are publicly available. Risk-free interest rate – The risk-free rate assumption is based on the U.S. Treasury instruments, the terms of which were consistent with the expected term of the Company’s equity award. Expected dividend – The Company has not paid and does not intend to pay dividends. Following the closing of the Merger and upon establishing a public trading market for the Company’s securities, the fair value of the Company’s common stock used to value equity awards will be based on the closing price of the Company’s common stock as reported on the date of the grant. Restricted Stock Prior to the Merger, Compass LLC maintained an incentive pool of unit-based awards that were granted to board members, employees and consultants and accounted for as unit-based compensation. Upon consummation of the Merger, all outstanding vested profits interests units were converted into shares of the Company’s common stock. Unvested units were converted into restricted shares of the Company’s common stock and will continue to vest under the same terms as the original profits interests. A summary of the Company’s restricted share activity during the nine months ended September 30, 2020 is as follows: Weighted Average Estimated Grant Date Fair Value Fair Value Shares Per Share Nonvested, January 1, 2020 2,038,955 $ 2.04 Granted 879 $ 2.34 Vested (277,815 ) $ 1.51 Forfeited or canceled (666,227 ) $ 1.78 Nonvested, September 30, 2020 1,095,792 $ 2.34 The weighted-average grant-date fair value for Compass LLC profits interests granted was $2.34 per unit. No restricted share awards have been granted following the Merger. As of September 30, 2020, remaining unrecognized compensation cost related to unvested restricted stock awards to be recognized in future periods totaled $1.8 million, which is expected to be recognized over a weighted average period of 1.9 years. The fair value of each profits interest was estimated on the date of grant using the weighted average assumptions in the table below: Nine Months Ended September 30, 2020 2019 Expected term (in years) 6.0 6.0 Risk-free rate 0.36 % 1.75 % Expected volatility 140.45 % 65.06 % Expected dividend yield 0 % 0 % Stock Options In June 2020, the Company’s board of directors adopted the 2020 Stock Option and Incentive Plan (the “2020 Plan”) and reserved 2,930,836 shares of common stock for issuance under this plan and subject to automatic annual increases as defined in the plan. As of September 30, 2020, 1,305,367 shares remain available for future grant. The 2020 Plan authorizes the board of directors or a committee of the board to grant incentive stock options, nonqualified stock options and restricted stock awards to eligible officers, employees, consultants and directors of the Company. Options generally vest over a period of four years and have a contractual life of ten years from the date of grant. The following table summarizes the stock option activity for the 2020 Plan: Weighted Weighted Average Number of Average Remaining Nonvested Exercise Price Contractual Options Per Share Life (in years) Outstanding at January 1, 2020 — $ — Granted 1,633,000 $ 5.00 Exercise — $ — Forfeited/cancelled (7,531 ) $ 5.00 Outstanding at September 30, 2020 1,625,469 $ 5.00 9.9 Vested at September 30, 2020 647,707 $ 5.00 9.8 For the nine months ended September 30, 2020, the weighted average grant date fair value for options granted was $3.42. The aggregate intrinsic value for options vested and outstanding as of and for the nine months ended September 30, 2020 was de minimis. As of September 30, 2020, the unrecognized compensation cost related to outstanding options was $3.3 million, expected to be recognized over a weighted average period of approximately 2.1 years. The weighted average assumptions used in the Black-Scholes option pricing model to determine the fair value of stock options granted to employees and directors during the nine months ended September 30, 2020 were as follows: September 30, 2020 Expected term (in years) 5.4 Risk-free rate 0.22 % Expected volatility 86.2 % Expected dividend yield 0.00 %

License, Research and Collabora

License, Research and Collaboration Agreements	9 Months Ended
	Sep. 30, 2020
License Research And Collaboration Agreements [Abstract]
License, Research and Collaboration Agreements	10. License, Research and Collaboration Agreements Collaboration Agreements Adimab Agreement The Company entered into a collaboration agreement with Adimab, LLC on October 16, 2014. As of September 30, 2020, future milestone payments in connection with this agreement amounted to $2.0 million. The agreement also includes provisions for payment of royalties at rates ranging in the single digits as a percentage of future net sales within a specified term from the first commercial sale. There were no milestone payments made during the three and nine months ended September 30, 2020. The Company made milestone payments of Other License and Research Agreements The Company has entered into several license agreements with various academic and healthcare institutions to in-license certain intellectual property rights and know-how relevant to its programs. As part of the consideration related to these license agreements, the Company made cash payments of $63,000 and $0.2 million during the three and nine months ended September 30, 2020, respectively. The Company recorded research and development expense of $64,000 and $79,000 during the three months ended September 30, 2020 and 2019, respectively, and $0.2 million and $0.4 million during the nine months ended September 30, 2020 and 2019, respectively. In addition, the Company also committed to make certain clinical and regulatory milestone payments in the aggregate of $0.5 million associated with the in-licensed technology.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	11. Commitments and Contingencies Operating Leases The Company leases laboratory and office space in Cambridge, MA. The Company also leases a vivarium and storage space in Cambridge, MA. The leases expire January 31, 2021. The lease agreements have annual scheduled payment increases and the Company is recognizing the rent expense on a straight‑line basis over the lease term. Rental expense was $0.5 million and $0.5 million for the three months ended September 30, 2020 and 2019, respectively, and $1.5 million and $1.4 million for the nine months ended September 30, 2020 and 2019, respectively. The future minimum rental payments under the leases as of September 30, 2020 are as follows: Amount Year Ending December 31, 2020 $ 481 2021 160 $ 641

Related Parties and Related-Par

Related Parties and Related-Party Transactions	9 Months Ended
	Sep. 30, 2020
Related Party Transactions [Abstract]
Related Parties and Related-Party Transactions	12. Related Parties and Related-Party Transactions On October 16, 2014, the Company entered into a collaboration agreement with Adimab, LLC. The Company’s co-founder has a direct ownership interest in Adimab, LLC. The Company recorded research and development expense of $0 million and $1.5 in connection with this agreement during nine months ended September 30, 2020 and 2019, respectively. On September 18, 2017, the Company entered into a software license and services agreement with StackWave, LLC. A former employee of the Company is the co-founder and has a direct ownership interest in StackWave, LLC. The Company recorded research and development expense of $17,000 for the nine months ended September 30, 2020 and capitalized software of $0.2 million and $0.7 million for the nine months ended September 30, 2020 and 2019, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements are presented in U.S. dollars and have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”). Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification (“ASC”) and as amended by Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all normal and recurring adjustments (which consist primarily of accruals, estimates and assumptions that impact the financial statements) considered necessary to present fairly the Company’s financial position as of September 30, 2020 and its results of operations and changes in convertible preferred stock and stockholders’ equity (deficit) for the three and nine months ended September 30, 2020 and 2019 and cash flows for the nine months ended September 30, 2020 and 2019. Operating results for the nine months ended September 30, 2020 are not necessarily indicative of the results that may be expected for the year ending December 31, 2020. The condensed consolidated balance sheet at December 31, 2019 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by GAAP for complete financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the consolidated financial statements of Compass Therapeutics LLC and related footnotes for the year ended December 31, 2019, included as Exhibit 99.1 in the Company’s Form 8-K filed with the SEC on June 23, 2020.
Principles of Consolidation	Principles of Consolidation The accompanying condensed consolidated financial statements include the accounts of Compass Therapeutics, Inc., and its wholly-owned subsidiaries Compass Therapeutics LLC and Compass Therapeutics Advisors Inc. All intercompany accounts and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these financial statements include, but are not limited to, the accrual of research and development expenses, the valuation of the embedded derivative, the valuation of common stock and estimates associated with stock-based awards. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Actual results could differ from those estimates. Changes in estimates are recorded in the period that they become known.
Segment Information	Segment Information Operating segments are defined as components of an enterprise for which separate and discrete information is available for evaluation by the chief operating decision-maker in deciding how to allocate resources and assess performance. The Company has one operating segment. The Company’s chief operating decision-maker, its chief executive officer, manages the Company’s operations on a consolidated basis for the purpose of allocating resources. All of the Company’s long-lived assets are held in the United States.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments that are readily convertible into cash with original maturities of three months or less from the date of purchase to be cash equivalents. Cash and cash equivalents include cash held in banks and amounts held in money market funds. Cash equivalents are stated at cost, which approximates market value. C
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and restricted cash. The Company maintains its cash, cash equivalents and restricted cash with financial institutions that management believes to be of high-credit quality. The Company has
Property and Equipment	Property and Equipment Property and equipment are stated at cost, net of accumulated depreciation and amortization. Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the related assets as follows: Asset Classification Estimated Useful Life Equipment 5 years Furniture and fixtures 7 years Software 5 years Leasehold improvements Lesser of estimated useful life or lease term Estimated useful lives are periodically assessed to determine if changes are appropriate. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are eliminated from the condensed consolidated balance sheet and any resulting gains or losses are included in the condensed consolidated statement of operations in the period of disposal. Costs for capital assets not yet placed into service are capitalized as construction-in-progress and depreciated once placed into service. Assets held under capital leases are stated at the lesser of the present value of future minimum lease payments or the fair value of the leased asset at the inception of the lease. Amortization of assets held under capital leases is computed using the straight-line method over the shorter of the estimated useful life of the asset or the period of the related lease.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist of property and equipment. Long-lived assets to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset group for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset group to its carrying value. An impairment loss would be recognized in the condensed consolidated statements of operations when estimated undiscounted future cash flows expected to result from the use of an asset group are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset group over its fair value, determined based on discounted cash flows. The Company did not record any impairment losses on long-lived assets during the nine months ended September 30, 2020 and 2019.
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) 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. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1 – Quoted prices in active markets for identical assets or liabilities. • Level 2 – Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets and liabilities, or other inputs that are observable or can be corroborated by observable market data. • Level 3 – Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. An entity may choose to measure many financial instruments and certain other items at fair value at specified election dates. Subsequent unrealized gains and losses on items for which the fair value option has been elected are reported in earnings. The Company’s cash equivalents are carried at fair value according to the fair value hierarchy described above and were determined based on Level 1 measurements (see Note 4). The Company’s restricted cash is carried at fair value according to the fair value hierarchy described above and were determined based on Level 2 measurements (see Note 4). The carrying values of other current assets and accounts payable approximate their fair value due to the short‑term nature of these assets and liabilities. The carrying values of the Company’s loan approximated its fair value as of September 30, 2020 and December 31, 2019 due to its variable interest rate. The fair value of the loan related embedded derivative (see Note 4) was determined based on Level 3 measurements.
Research and Development Costs	Research and Development Costs Costs associated with internal research and development and external research and development services, including drug development and preclinical studies, are expensed as incurred. Research and development expenses include costs for salaries, employee benefits, subcontractors, facility-related expenses, depreciation and amortization, stock-based compensation, third-party license fees, laboratory supplies, and external costs of outside vendors engaged to conduct discovery, preclinical and clinical development activities and clinical trials as well as to manufacture clinical trial materials, and other costs. The Company recognizes external research and development costs based on an evaluation of the progress to completion of specific tasks using information provided to the Company by its service providers. Nonrefundable advance payments for goods or services to be received in the future for use in research and development activities are recorded as prepaid expenses. Such prepaid expenses are recognized as an expense when the goods have been delivered or the related services have been performed, or when it is no longer expected that the goods will be delivered, or the services rendered. Costs associated with licenses of technology acquired as part of collaborative arrangements are expensed as incurred and are generally included in research and development expense in the condensed consolidated statements of operations if it is determined the license has no alternative future use.
Accrued Research and Development Expenses	Accrued Research and Development Expenses The Company has entered into various research and development and other agreements with commercial firms, researchers, universities and others for provisions of goods and services. These agreements are generally cancelable, and the related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies or clinical trials, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company’s estimates. The Company’s historical accrual estimates have not been materially different from the actual costs.
Stock-Based Compensation	Stock-Based Compensation Prior to the Merger, Compass Therapeutics LLC issued Class A and Class C common units to various employees, directors and consultants. The units constituted “profits interests” for tax purposes and were accounted for as share-based payment arrangements. Upon consummation of the Merger, all outstanding vested units were converted into shares of common stock and all outstanding unvested units were converted into shares of restricted stock that continue to vest over the remaining term of the original award. Subsequent to the Merger, the Company has granted stock options to various employees, directors and consultants. The Company recognizes the grant‑date fair value of stock‑based awards issued to employees and nonemployee board members as compensation expense on a straight‑line basis over the vesting period of the award. The Company uses the Black‑Scholes option pricing model to determine the grant‑date fair value of stock options and adjusts expense for forfeitures in the periods they occur.
Net Loss per Share	Net Loss per Share Basic loss per share is computed by dividing net loss by the weighted average number of shares of common stock outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as convertible preferred stock, stock options, unvested restricted stock and common stock warrants that would result in the issuance of incremental shares of common stock. In computing the basic and diluted net loss per share, the weighted average number of shares remains the same for both calculations due to the fact that when a net loss exists, dilutive shares are not included in the calculation as the impact is anti-dilutive. The following potentially dilutive securities outstanding as of September 30, 2020 and 2019 have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti-dilutive: September 30, 2020 2019 Convertible preferred stock — 30,629,606 Stock options 1,625,469 — Nonvested restricted stock 1,095,792 1,916,891 Common stock warrants — 3,114,145 Total 2,721,261 35,660,642
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016‑02, Leases In August 2018, the FASB issued ASU No. 2018‑13, Disclosure Framework Changes to the Disclosure Requirements for Fair Value Measurements In November 2018, the FASB issued ASU No. 2018-18, Collaborative Arrangements (Topic 808): Clarifying the Interaction Between Topic 808 and Topic 606 In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Schedule of Estimated Useful Lives of Assets	Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the related assets as follows: Asset Classification Estimated Useful Life Equipment 5 years Furniture and fixtures 7 years Software 5 years Leasehold improvements Lesser of estimated useful life or lease term
Schedule of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Weighted Average Shares Outstanding	The following potentially dilutive securities outstanding as of September 30, 2020 and 2019 have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti-dilutive: September 30, 2020 2019 Convertible preferred stock — 30,629,606 Stock options 1,625,469 — Nonvested restricted stock 1,095,792 1,916,891 Common stock warrants — 3,114,145 Total 2,721,261 35,660,642

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Summary of Financial Assets and Liabilities are Measured at Fair Value on Recurring Basis	The following tables present information about the Company’s financial assets and liabilities that are measured at fair value on a recurring basis and indicate the level of the fair value hierarchy utilized to determine such fair values (in thousands): Fair Value Measurements as of September 30, 2020 Using: Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable Assets Inputs Inputs (Level 1) (Level 2) (Level 3) Fair Value Assets Cash equivalents - money market funds $ 52,175 $ — $ — $ 52,175 Restricted cash — 263 — 263 Total assets $ 52,175 $ 263 $ — $ 52,438 Liabilities Derivative liability related to loan $ — $ — $ — $ — Total liabilities $ — $ — $ — $ — Fair Value Measurements as of December 31, 2019 Using: Quoted Prices in Active Significant Markets for Other Significant Identical Observable Unobservable Assets Inputs Inputs (Level 1) (Level 2) (Level 3) Fair Value Assets Cash equivalents - money market funds $ 22,784 $ — $ — $ 22,784 Restricted cash — 263 — 263 Total assets $ 22,784 $ 263 $ — $ 23,047 Liabilities Derivative liability related to loan $ — $ — $ 494 $ 494 Total liabilities $ — $ — $ 494 $ 494
Schedule of Aggregate Fair Values of Derivative Liability	The following table provides a roll forward of the aggregate fair values of the Company’s derivative liability (in thousands): Derivative Liability Balance at December 31, 2019 $ 494 Change in fair value 556 Payment of success fee (1,050 ) Balance at September 30, 2020 $ —

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment consist of the following (in thousands): September 30, December 31, 2020 2019 Equipment $ 7,040 $ 7,230 Furniture and fixtures 629 629 Leasehold improvements 896 896 Software 912 669 Assets not yet placed in service — 230 Total property and equipment–at cost 9,477 9,654 Less: Accumulated depreciation (7,059 ) (5,903 ) Property and equipment, net $ 2,418 $ 3,751

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2020
Payables And Accruals [Abstract]
Components of Accrued Expenses	Accrued expenses consist of the following (in thousands): September 30, December 31, 2020 2019 Compensation and benefits $ 605 $ 1,759 Research and development expenses 26 249 Legal and professional fees 507 417 Sales taxes — 554 Other 220 143 Total accrued expenses $ 1,358 $ 3,122

Loan Payable (Tables)

Loan Payable (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Schedule of Aggregate Principal Amount of Debt Outstanding	The aggregate principal amount of debt outstanding consisted of the following (in thousands): September 30, December 31, 2020 2019 Current portion of debt $ 7,500 $ 5,625 Less: unamortized debt discount (39 ) (49 ) Current portion of debt, net of debt discount $ 7,461 $ 5,576 Long-term debt, net of current portion $ 3,750 $ 9,375 Less: unamortized debt discount (20 ) (82 ) Long-term debt, net of current portion $ 3,730 $ 9,293
Schedule of Aggregate Minimum Future Principal Payments	As of September 30, 2020, the aggregate minimum future principal payments due in connection with the 2018 Loan Agreement, as amended, are as follows (in thousands): Year Ending December 31, 2020 $ 1,875 2021 7,500 2022 1,875 $ 11,250

Convertible Preferred Stock a_2

Convertible Preferred Stock and Stockholders' Equity (Deficit) (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Summary of Convertible Preferred Stock Shares Outstanding	As of December 31, 2019, convertible preferred stock consisted of the following shares outstanding: Preferred Stock Shares Issued and Outstanding Series A-1 64,704,832 Series A-2 36,782,734 Series A-3 23,467,151 Series A-4 15,253,415 Series A4B 22,216,583 Series A-5 44,739,689 207,164,404

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Schedule of Stock-Based Compensation Expense	Stock-based compensation expense for the three and nine months ended September 30, 2020 and 2019 was classified in the consolidated statement of operations and comprehensive loss as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2020 2019 2020 2019 Research and development $ 374 $ 103 $ 486 $ 278 General and administrative 2,162 146 2,480 411 Total $ 2,536 $ 249 $ 2,966 $ 689
Schedule of Restricted Share Activity	A summary of the Company’s restricted share activity during the nine months ended September 30, 2020 is as follows: Weighted Average Estimated Grant Date Fair Value Fair Value Shares Per Share Nonvested, January 1, 2020 2,038,955 $ 2.04 Granted 879 $ 2.34 Vested (277,815 ) $ 1.51 Forfeited or canceled (666,227 ) $ 1.78 Nonvested, September 30, 2020 1,095,792 $ 2.34
2020 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Stock Option Activity	The following table summarizes the stock option activity for the 2020 Plan: Weighted Weighted Average Number of Average Remaining Nonvested Exercise Price Contractual Options Per Share Life (in years) Outstanding at January 1, 2020 — $ — Granted 1,633,000 $ 5.00 Exercise — $ — Forfeited/cancelled (7,531 ) $ 5.00 Outstanding at September 30, 2020 1,625,469 $ 5.00 9.9 Vested at September 30, 2020 647,707 $ 5.00 9.8
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Schedule of Fair Value Profits Interest Estimated on Weighted Average Assumptions	The fair value of each profits interest was estimated on the date of grant using the weighted average assumptions in the table below: Nine Months Ended September 30, 2020 2019 Expected term (in years) 6.0 6.0 Risk-free rate 0.36 % 1.75 % Expected volatility 140.45 % 65.06 % Expected dividend yield 0 % 0 %
Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Schedule of Fair Value Profits Interest Estimated on Weighted Average Assumptions	The weighted average assumptions used in the Black-Scholes option pricing model to determine the fair value of stock options granted to employees and directors during the nine months ended September 30, 2020 were as follows: September 30, 2020 Expected term (in years) 5.4 Risk-free rate 0.22 % Expected volatility 86.2 % Expected dividend yield 0.00 %

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Rental Payments under Leases	The future minimum rental payments under the leases as of September 30, 2020 are as follows: Amount Year Ending December 31, 2020 $ 481 2021 160 $ 641

Nature of Business and Basis _2

Nature of Business and Basis of Presentation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 19, 2020	Jun. 17, 2020	Jun. 30, 2020	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Class Of Stock [Line Items]
Entity incorporation, date of incorporation				Mar. 20, 2018
Common stock, shares authorized		300,000,000		300,000,000	50,000,000	300,000,000
Common stock, par value		$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized		10,000,000		10,000,000	5,000,000	10,000,000
Preferred stock par value		$ 0.0001		$ 0.0001	$ 0.0001	$ 0.0001
2020 Plan
Class Of Stock [Line Items]
Number of common stock reserved for issuance		2,930,836		1,305,367
Common Stock
Class Of Stock [Line Items]
Common stock shares issued under common membership interests		31,627,139
Aggregate number of common stock forfeited and surrendered for cancellation		4,000,000
Common stock held by pre-merger stockholders		5,000,000
Shares of common stock sold			12,096,442
Common Stock | Private Placement Offering
Class Of Stock [Line Items]
Shares of common stock sold	12,096,442			12,096,442
Purchase price per share	$ 5			$ 5
Net proceeds from private placement	$ 54.2
Common Stock | 2020 Plan
Class Of Stock [Line Items]
Number of common stock reserved for issuance				2,930,836
Common Stock | Blockers
Class Of Stock [Line Items]
Common stock shares issued under equity interest		7,428,217

Liquidity, Uncertainties and Go

Liquidity, Uncertainties and Going Concern - Additional Information (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Liquidity Uncertainties And Going Concern [Abstract]
Accumulated deficit	$ 143,017	$ 121,908

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	9 Months Ended
	Sep. 30, 2020USD ($)Segment	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment	1
Impairment losses on long-lived assets	$ 0	$ 0
ASU 2018-13
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted	true
Change in accounting principle, accounting standards update, adoption date	Jan. 1, 2020
Change in accounting principle, accounting standards update, immaterial effect	true
Money Market Funds
Summary Of Significant Accounting Policies [Line Items]
Cash equivalents	$ 52,200,000		$ 22,800,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Estimated Useful Lives of Assets (Details)	9 Months Ended
	Sep. 30, 2020
Equipment
Property Plant And Equipment [Line Items]
Estimated useful life	5 years
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Estimated useful life	7 years
Software
Property Plant And Equipment [Line Items]
Estimated useful life	5 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated useful life	Lesser of estimated useful life or lease term

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Weighted Average Shares Outstanding (Details) - shares	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted weighted average shares outstanding	2,721,261	35,660,642
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted weighted average shares outstanding		30,629,606
Stock Options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted weighted average shares outstanding	1,625,469
Nonvested Restricted Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted weighted average shares outstanding	1,095,792	1,916,891
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted weighted average shares outstanding		3,114,145

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Financial Assets and Liabilities are Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Liabilities
Derivative liability related to loan		$ 494
Fair Value Measurements Recurring
Assets
Restricted cash	$ 263	263
Total assets	52,438	23,047
Liabilities
Derivative liability related to loan		494
Total liabilities		494
Fair Value Measurements Recurring | Money Market Funds
Assets
Cash equivalents - money market funds	52,175	22,784
Fair Value Measurements Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Total assets	52,175	22,784
Fair Value Measurements Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Money Market Funds
Assets
Cash equivalents - money market funds	52,175	22,784
Fair Value Measurements Recurring | Significant Other Observable Inputs (Level 2)
Assets
Restricted cash	263	263
Total assets	$ 263	263
Fair Value Measurements Recurring | Significant Unobservable Inputs (Level 3)
Liabilities
Derivative liability related to loan		494
Total liabilities		$ 494

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Aggregate Fair Values of Derivative Liability (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020USD ($)
Fair Value Disclosures [Abstract]
Balance at December 31, 2019	$ 494
Change in fair value	556
Payment of success fee	$ (1,050)

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	$ 9,477	$ 9,654
Less: Accumulated depreciation	(7,059)	(5,903)
Property and equipment, net	2,418	3,751
Equipment
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	7,040	7,230
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	629	629
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	896	896
Software
Property Plant And Equipment [Line Items]
Total property and equipment–at cost	$ 912	669
Assets Not Yet Placed in Service
Property Plant And Equipment [Line Items]
Total property and equipment–at cost		$ 230

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Total depreciation and amortization expense	$ 0.4	$ 0.5	$ 1.3	$ 1.6

Accrued Expenses - Components o

Accrued Expenses - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Compensation and benefits	$ 605	$ 1,759
Research and development expenses	26	249
Legal and professional fees	507	417
Sales taxes		554
Other	220	143
Total accrued expenses	$ 1,358	$ 3,122

Loan Payable - Schedule of Aggr

Loan Payable - Schedule of Aggregate Principal Amount of Debt Outstanding (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Current portion of debt	$ 7,500	$ 5,625
Less: unamortized debt discount	(39)	(49)
Current portion of debt, net of debt discount	7,461	5,576
Long-term debt, net of current portion	3,750	9,375
Less: unamortized debt discount	(20)	(82)
Long-term debt, net of current portion	$ 3,730	$ 9,293

Loan Payable - Additional Infor

Loan Payable - Additional Information (Details) - Pacific Western Bank, Inc - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Apr. 01, 2020
Term Loan Facility
Debt Instrument [Line Items]
Debt proceeds			$ 15,000,000
Debt instrument, interest rate	6.25%		6.25%
Debt instrument, interest rate during period			6.25%
Increase in interest rate in case of default			5.00%
Term loan facility payment terms			The Company made interest-only payments through March 31, 2020. Beginning in April 2020, the Company is obligated to make equal monthly principal payments of $625,000 through March 31, 2022 when the notes mature.
Frequency of periodic payment			monthly
Date of first required payment			2020-04
Equal monthly principal payments			$ 625,000
Debt instrument, maturity date			Mar. 31, 2022
Success fee payment	$ 1,100,000		$ 1,100,000
Interest expense	$ 200,000	$ 300,000	$ 700,000	$ 900,000
Term Loan Facility | Prime Rate
Debt Instrument [Line Items]
Debt instrument, applicable margin interest rate			2.00%
2018 Credit Facility
Debt Instrument [Line Items]
Minimum cash balance					$ 6,000,000
Debt instrument, interest rate, effective percentage	5.00%		5.00%

Loan Payable - Schedule of Ag_2

Loan Payable - Schedule of Aggregate Minimum Future Principal Payments (Details) - 2018 Loan Agreement $ in Thousands	Sep. 30, 2020USD ($)
Debt Instrument [Line Items]
2020	$ 1,875
2021	7,500
2022	1,875
Long-term debt	$ 11,250

Convertible Preferred Stock a_3

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($)	Jun. 19, 2020	Jun. 30, 2020	Sep. 30, 2020	Jun. 17, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Convertible preferred stock, shares outstanding			0			207,164,404
Common stock, shares issued			52,120,062			9,073,002
Payment to several nonaccredited investors			$ 69,000
2020 Stock Option and Incentive Plan
Class Of Stock [Line Items]
Common stock reserved for issuance			1,305,367	2,930,836
Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares outstanding			0		207,164,404	207,164,404	207,164,404	207,164,404	207,164,404	207,164,404
Common Stock
Class Of Stock [Line Items]
Conversion of Compass Therapeutics LLC preferred shares into common shares upon consummation of the reverse merger, Shares		30,629,606	30,629,606
Shares of common stock sold		12,096,442
Common Stock | Private Placement Offering
Class Of Stock [Line Items]
Shares of common stock sold	12,096,442		12,096,442
Purchase price per share	$ 5		$ 5
Common Stock | Olivia Ventures Inc
Class Of Stock [Line Items]
Common stock, shares issued			1,000,000
Common Stock | 2020 Stock Option and Incentive Plan
Class Of Stock [Line Items]
Common stock reserved for issuance			2,930,836

Convertible Preferred Stock a_4

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Summary of Convertible Preferred Stock Shares Outstanding (Details) - shares	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Class Of Stock [Line Items]
Convertible preferred stock, shares issued	0		207,164,404
Convertible preferred stock, shares outstanding	0		207,164,404
Series A-1
Class Of Stock [Line Items]
Convertible preferred stock, shares issued			64,704,832
Convertible preferred stock, shares outstanding			64,704,832
Series A-2
Class Of Stock [Line Items]
Convertible preferred stock, shares issued			36,782,734
Convertible preferred stock, shares outstanding			36,782,734
Series A-3
Class Of Stock [Line Items]
Convertible preferred stock, shares issued			23,467,151
Convertible preferred stock, shares outstanding			23,467,151
Series A-4
Class Of Stock [Line Items]
Convertible preferred stock, shares issued			15,253,415
Convertible preferred stock, shares outstanding			15,253,415
Series A4B
Class Of Stock [Line Items]
Convertible preferred stock, shares issued			22,216,583
Convertible preferred stock, shares outstanding			22,216,583
Series A-5
Class Of Stock [Line Items]
Convertible preferred stock, shares issued			44,739,689
Convertible preferred stock, shares outstanding			44,739,689
Convertible Preferred Stock
Class Of Stock [Line Items]
Convertible preferred stock, shares issued			207,164,404
Convertible preferred stock, shares outstanding	0	207,164,404	207,164,404	207,164,404	207,164,404	207,164,404	207,164,404

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,536	$ 249	$ 2,966	$ 689
Research and Development
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	374	103	486	278
General and Administrative
Employee Service Share Based Compensation Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,162	$ 146	$ 2,480	$ 411

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Restricted Share Activity (Details) - Restricted Stock - $ / shares	Jun. 17, 2020	Sep. 30, 2020
Shares
Nonvested at the beginning		2,038,955
Nonvested, Granted	0	879
Nonvested, Vested		(277,815)
Nonvested, Forfeited or canceled		(666,227)
Nonvested at the ending		1,095,792
Estimated Fair Value Per Share
Nonvested at the beginning		$ 2.04
Nonvested, Granted		2.34
Nonvested, Vested		1.51
Nonvested, Forfeited or canceled		1.78
Nonvested at the ending		$ 2.34

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jun. 17, 2020	Sep. 30, 2020	Jun. 30, 2020
2020 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of common stock reserved for issuance			2,930,836
Number of common stock reserved for issuance	2,930,836	1,305,367
Stock options, vesting period		4 years
Stock options, contractual life		10 years
Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant-date fair value for profits interests granted		$ 2.34
Share awards granted	0	879
Unrecognized compensation cost relating to unvested restricted stock awards		$ 1.8
Unvested stock expected to be recognized over a weighted-average period		1 year 10 months 24 days
Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested stock expected to be recognized over a weighted-average period		2 years 1 month 6 days
Weighted average grant date fair value for options granted		$ 3.42
Unrecognized compensation cost relating to outstanding options		$ 3.3
Stock Option | 2020 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options, contractual life		9 years 10 months 24 days

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Fair Value Profits Interest Estimated on Weighted Average Assumptions (Details) - Restricted Stock	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years	6 years
Risk-free rate	0.36%	1.75%
Expected volatility	140.45%	65.06%
Expected dividend yield	0.00%	0.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Option Activity (Details) - 2020 Plan	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Weighted Average Remaining Contractual Life (in years)
Outstanding, Weighted Average Remaining Contractual Life at September 30, 2020	10 years
Stock Option
Number of Nonvested Options
Granted | shares	1,633,000
Forfeited/cancelled | shares	(7,531)
Outstanding at September 30, 2020 | shares	1,625,469
Vested at September 30, 2020 | shares	647,707
Weighted Average Exercise Price Per Share
Granted | $ / shares	$ 5
Forfeited/cancelled | $ / shares	5
Outstanding at September 30, 2020 | $ / shares	5
Vested at September 30, 2020 | $ / shares	$ 5
Weighted Average Remaining Contractual Life (in years)
Outstanding, Weighted Average Remaining Contractual Life at September 30, 2020	9 years 10 months 24 days
Vested, Weighted Average Remaining Contractual Life at September 30, 2020	9 years 9 months 18 days

Stock-Based Compensation - Sc_4

Stock-Based Compensation - Schedule of Weighted Average Assumptions on Grant Date Fair Value for Options Granted (Details) - Stock Option	9 Months Ended
	Sep. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 4 months 24 days
Risk-free rate	0.22%
Expected volatility	86.20%
Expected dividend yield	0.00%

License, Research and Collabo_2

License, Research and Collaboration Agreements - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development	$ 3,670,000	$ 5,979,000	$ 10,498,000	$ 19,146,000
Adimab Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement date			Oct. 16, 2014
Future milestone payments	2,000,000		$ 2,000,000
Milestone payments	0		0
Research and development milestone payments		1,000,000		1,500,000
Other License and Research Agreements
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cash payment for license agreement	63,000		200,000
Research and development	64,000	$ 79,000	200,000	$ 400,000
Clinical and regulatory milestone payments	$ 500,000		$ 500,000

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Lease expiration date			Jan. 31, 2021
Rental expense	$ 0.5	$ 0.5	$ 1.5	$ 1.4

Commitments and Contingencies_2

Commitments and Contingencies - Future Minimum Rental Payments under Leases (Details) $ in Thousands	Sep. 30, 2020USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020	$ 481
2021	160
Total future minimum rental payments	$ 641

Related Parties and Related-P_2

Related Parties and Related-Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Research and development expense	$ 3,670,000	$ 5,979,000	$ 10,498,000	$ 19,146,000
Adimab, LLC | Collaboration Agreement
Related Party Transaction [Line Items]
Research and development expense			0	1,500,000
StackWave, LLC | Software License and Services Agreement
Related Party Transaction [Line Items]
Research and development expense			17,000
Capitalized software	$ 200,000	$ 700,000	$ 200,000	$ 700,000