Oruka Therapeutics (ORKA) 10-K 18 Feb 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Feb. 13, 2020	Jun. 28, 2019
Cover [Abstract]
Entity Registrant Name	ARCA Biopharma, Inc.
Entity Central Index Key	0000907654
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Period Focus	FY
Trading Symbol	ABIO
Document Fiscal Year Focus	2019
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 10,588,328
Entity Common Stock, Shares Outstanding		1,594,070
Entity Interactive Data Current	Yes
Entity File Number	000-22873
Entity Tax Identification Number	36-3855489
Entity Address, Address Line One	11080 CirclePoint Road
Entity Address, Address Line Two	Suite 140
Entity Address, City or Town	Westminster
Entity Address, State or Province	CO
Entity Address, Postal Zip Code	80020
City Area Code	720
Local Phone Number	940-2200
Document Annual Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE

BALANCE SHEETS

BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 8,363	$ 6,608
Other current assets	117	169
Total current assets	8,480	6,777
Right-of-use asset - operating	22
Property and equipment, net	10	24
Other assets	24	24
Total assets	8,536	6,825
Current liabilities:
Accounts payable	418	230
Accrued compensation and employee benefits	129	150
Accrued expenses and other liabilities	379	413
Total current liabilities	926	793
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value; 5 million shares authorized; no shares issued or outstanding at December 31, 2019 and 2018
Common stock, $0.001 par value; 100 million shares authorized at December 31, 2019 and 2018; 1,594,070 and 773,558 shares issued and outstanding at December 31, 2019 and 2018, respectively	2	1
Additional paid-in capital	152,024	144,965
Accumulated deficit	(144,416)	(138,934)
Total stockholders’ equity	7,610	6,032
Total liabilities and stockholders’ equity	$ 8,536	$ 6,825

BALANCE SHEETS (Parenthetical)

BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued	0	0
Preferred stock, outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	1,594,070	773,558
Common stock, shares outstanding	1,594,070	773,558

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Costs and expenses:
Research and development	$ 1,833	$ 4,239
General and administrative	3,981	3,879
Total costs and expenses	5,814	8,118
Loss from operations	(5,814)	(8,118)
Interest and other income	172	162
Interest expense	(7)	(8)
Loss before income taxes	(5,649)	(7,964)
Income tax benefit	167	31
Net loss	(5,482)	(7,933)
Change in unrealized loss on marketable securities		2
Comprehensive loss	$ (5,482)	$ (7,931)
Net loss per share:
Basic and diluted	$ (4.15)	$ (10.31)
Weighted average shares outstanding:
Basic and diluted	1,321,234	769,392

STATEMENTS OF STOCKHOLDERS' EQU

STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2017	$ 10,275	$ 1	$ 141,277	$ (2)	$ (131,001)
Beginning Balance, shares at Dec. 31, 2017		654,170
Issuance of common stock for cash, net of offering costs	3,415		3,415
Issuance of common stock for cash, net of offering costs, shares		118,546
Issuance of common stock upon vesting of Restricted Stock Units, value	0	$ 0	0	0	0
Issuance of common stock upon vesting of Restricted Stock Units, shares		842
Share-based compensation	273		273
Change in unrealized loss on marketable securities	2			$ 2
Net loss	(7,933)				(7,933)
Ending Balance at Dec. 31, 2018	$ 6,032	$ 1	144,965		(138,934)
Ending Balance, shares at Dec. 31, 2018	773,558	773,558
Issuance of common stock for cash, net of offering costs	$ 6,909	$ 1	6,908
Issuance of common stock for cash, net of offering costs, shares		820,561
Adjustment for fractional shares		(49)
Share-based compensation	151		151
Net loss	(5,482)				(5,482)
Ending Balance at Dec. 31, 2019	$ 7,610	$ 2	$ 152,024		$ (144,416)
Ending Balance, shares at Dec. 31, 2019	1,594,070	1,594,070

STATEMENTS OF CASH FLOWS

STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net loss	$ (5,482)	$ (7,933)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	18	22
Amortization of right-of-use asset - operating	71
Amortization of premiums and discounts on marketable securities		2
Share-based compensation	151	273
Change in operating assets and liabilities:
Other current assets	401	689
Accounts payable	188	(392)
Accrued compensation and employee benefits	(21)	(607)
Accrued expenses and other liabilities	(127)	(298)
Net cash used in operating activities	(4,801)	(8,244)
Cash flows from investing activities:
Purchase of property and equipment	(4)	(4)
Proceeds from maturities of marketable securities		3,050
Net cash (used in) provided by investing activities	(4)	3,046
Cash flows from financing activities:
Proceeds from the issuance of common stock	7,281	3,532
Common stock offering costs	(372)	(117)
Repayment of principal on vendor finance agreement	(349)	(311)
Net cash provided by financing activities	6,560	3,104
Net (decrease) increase in cash and cash equivalents	1,755	(2,094)
Cash and cash equivalents, beginning of year	6,608	8,702
Cash and cash equivalents, end of year	8,363	6,608
Supplemental cash flow information:
Interest paid	7	8
Income tax refund received	167	54
Supplemental disclosure of noncash investing and financing transactions:
Leased assets obtained in exchange for operating lease liabilities, upon adoption and extension	$ 93
Change in unrealized loss on marketable securities		$ 2

The Company and Summary of Sign

The Company and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
The Company and Summary of Significant Accounting Policies	(1) The Company and Summary of Significant Accounting Policies Description of Business ARCA biopharma, Inc. (the Company or ARCA), a Delaware corporation, is headquartered in Westminster, Colorado. The Company is a clinical-stage biopharmaceutical company applying a precision medicine approach to the development and commercialization of genetically targeted therapies for cardiovascular diseases. The Company’s lead product candidate, Gencaro™ (bucindolol hydrochloride), is a pharmacogenetically-targeted beta-adrenergic receptor antagonist with mild vasodilator properties that ARCA is developing to treat cardiovascular disease, focusing on atrial fibrillation (AF) in patients with chronic heart failure (HF). In 2018, the Company completed its Phase 2B clinical superiority trial, known as GENETIC-AF, in which the Company evaluated Gencaro for the treatment of AF in HF patients. In the trial, Gencaro was evaluated against an active comparator, the beta-blocker TOPROL-XL (metoprolol succinate), a drug indicated for the treatment of HF patients that is commonly prescribed for HF patients with AF. Enrollment in GENETIC-AF was limited to patients that possess the specific genotype that the Company believes responds best to Gencaro. The planned development program of Gencaro is, in part, based on the results of the Company’s completed GENETIC-AF Phase 2B clinical trial and a prospectively designed DNA substudy of adrenergic receptor polymorphisms in the BEST trial, a previous Phase 3 study of HF patients. Following review of the Phase 2B GENETIC-AF clinical trial results, as well as its alignment with previous Phase 3 pharmacogenetic substudy data from the BEST trial, the FDA stated that data from a single pivotal Phase 3 clinical trial may be sufficient to support approval of Gencaro for the treatment of AF in patients with HF. In 2019, the Company reached an agreement with the U.S. Food and Drug Administration (FDA) known as a Special Protocol Assessment (SPA), for the requirements of the Gencaro Phase 3 clinical trial. Based on the SPA agreement, the planned Phase 3 clinical trial, if successful, may support a New Drug Application (NDA) for the marketing approval of Gencaro. The Company’s other product candidate, AB171, is a thiol-substituted isosorbide mononitrate, which ARCA plans to develop as a genetically-targeted treatment for HF and peripheral arterial disease. The Company will need to raise additional capital to fund future operations and any additional development of Gencaro or AB171. If the Company is unable to obtain additional funding or is unable to complete a strategic transaction, it may have to discontinue development activities on Gencaro or discontinue its operations. Liquidity and Going Concern The Company devotes substantially all of its efforts towards obtaining regulatory approval and raising capital necessary to fund its operations and it is subject to a number of risks associated with clinical research and development, including dependence on key individuals, the development of and regulatory approval of commercially viable products, the need to raise adequate additional financing necessary to fund the development and commercialization of its products, and competition from larger companies. The Company has not generated revenue to date and has incurred substantial losses and negative cash flows from operations since its inception. The Company has historically funded its operations through issuances of common and preferred stock. The Company believes that its current cash and cash equivalents will be sufficient to fund its operations, at its projected cost structure, after giving effect to potential cost reductions, through the end of the third quarter of 2020. In light of the significant uncertainties regarding clinical development timelines and costs for developing drugs such as Gencaro, the Company will need to raise additional capital to finance the Company’s future operations and any additional development of Gencaro or any other product candidates. If the Company is delayed in completing or is unable to complete additional financing and/or a strategic transaction, the Company may discontinue its development activities or operations. Due to the current status of the Gencaro development program, the current amount of cash and cash equivalents held, the anticipated costs to be incurred for existing operations as well as exploring other corporate strategic alternatives, and the uncertainty of the Company’s ability to raise a significant amount of capital, management has determined there is substantial doubt about the Company’s ability to continue as a going concern from one year after the Company’s financial statements have been issued. The Company has implemented efforts to reduce personnel costs, including reduction of executive management salaries. The Company could delay or cancel certain planned expenditures related to its drug development programs and/or implement additional cost reduction measures to conserve its cash balances; however, there is no assurance that those measures would be adequate to allow the Company to continue as a going concern for a period beyond one year from the issuance of these financial statements. These financial statements have been prepared with the assumption that the Company will continue as a going concern and will be able to realize its assets and discharge its liabilities in the normal course of business and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that may result from the inability of the Company to continue as a going concern. The Company may not be able to raise sufficient capital on acceptable terms, or at all, to continue development of Gencaro or to otherwise continue operations and may not be able to execute any strategic transaction. The Company’s liquidity, and its ability to raise additional capital or complete any strategic transaction, depends on a number of factors, including, but not limited to, the following: • the costs and timing for the potential additional clinical trials in order to gain possible regulatory approval for Gencaro or any other product candidate; • the market price of the Company’s stock and the availability and cost of additional equity capital from existing and potential new investors; • the Company’s ability to retain the listing of its common stock on the Nasdaq Capital Market; • general economic and industry conditions affecting the availability and cost of capital; • the Company’s ability to control costs associated with its operations; • the costs of filing, prosecuting, defending and enforcing any patent claims and other intellectual property rights; and • the terms and conditions of the Company’s existing collaborative and licensing agreements. The sale of additional equity or convertible debt securities would likely result in substantial additional dilution to the Company’s stockholders. If the Company raises additional funds through the incurrence of indebtedness, the obligations related to such indebtedness would be senior to rights of holders of the Company’s capital stock and could contain covenants that would restrict the Company’s operations. The Company also cannot predict what consideration might be available, if any, to the Company or its stockholders, in connection with any strategic transaction. Should strategic alternatives or additional capital not be available to the Company, or not be available on acceptable terms, the Company may be unable to realize value from its assets and discharge its liabilities in the normal course of business which may, among other alternatives, cause the Company to further delay, substantially reduce or discontinue operational activities to conserve its cash resources. Reverse Stock Split On April 3, 2019, the Company completed a 1-for-18 reverse stock split of its common stock. All common shares and per common share amounts in the financial statements and footnotes have been adjusted retroactively to reflect the effects of this action. Basis of Presentation The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) and include all adjustments necessary for the fair presentation of our financial position, results of operations and cash flows for the periods presented. Management has performed an evaluation of the Company’s activities through the date of filing of this Annual Report on Form 10-K. Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Updated (ASU) No. 2016-02, Leases (Topic 842) Targeted Improvements The Company reviewed all other recently issued accounting pronouncements and concluded that they were either not applicable or not expected to have a significant impact to the financial statements. Accounting Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America 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. The Company bases estimates on various assumptions that are believed to be reasonable under the circumstances. The Company believes significant judgment was involved in estimating the clinical trial accruals, and in estimating other accrued liabilities, stock-based compensation, and income taxes. Management is continually evaluating and updating these estimates, and it is possible that these estimates will change in the future or that actual results may differ from these estimates. Cash Equivalents Cash equivalents generally consist of money market funds and debt securities with maturities of 90 days or less at the time of purchase. The Company invests its excess cash in securities with strong ratings and has established guidelines relative to diversification and maturity with the objective of maintaining safety of principal and liquidity. Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company has no off-balance-sheet concentrations of credit risk, such as foreign exchange contracts, option contracts, or foreign currency hedging arrangements. The Company maintains cash and cash equivalent balances in the form of bank demand deposits and money market fund accounts with financial institutions that management believes are creditworthy. Such balances may at times exceed the insured amount. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Cost includes expenditures for equipment, leasehold improvements, replacements, and renewals. Maintenance and repairs are charged to expense as incurred. When assets are sold, retired, or otherwise disposed of, the cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in operations. The cost of property and equipment is depreciated using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are amortized over the shorter of the life of the lease or the estimated useful life of the assets. Accrued Outsourcing Expenses As part of the process of preparing its financial statements, the Company is required to estimate accrued outsourcing expenses. This process involves identifying services that third parties have performed on the Company’s behalf and estimating the level of service performed and the associated cost incurred for these services as of the balance sheet date. Examples of estimated accrued outsourcing expenses include contract service fees, such as fees payable to contract manufacturers in connection with the production of materials related to the Company’s drug product, and service fees from clinical research organizations. The Company develops estimates of liabilities using its judgment based upon the facts and circumstances known at the time. Segments The Company operates in one segment. Management uses one measure of profitability and does not segment its business for internal reporting. Research and Development Research and development costs are expensed as incurred. These consist primarily of salaries, contract services, and supplies. Costs related to clinical trial and drug manufacturing activities are based upon estimates of the services received and related expenses incurred by contract research organizations (CROs), clinical study sites, drug manufacturers, collaboration partners, laboratories, consultants, or otherwise. Related contracts vary significantly in length, and could be for a fixed amount, a variable amount based on actual costs incurred, capped at a certain limit, or for a combination of these elements. Activity levels are monitored through communications with the vendors, including detailed invoices and task completion review, analysis of expenses against budgeted amounts, and pre-approval of any changes in scope of the services to be performed. Certain significant vendors may also provide an estimate of costs incurred but not invoiced on a periodic basis. Expenses related to the CROs and clinical studies, as well as contract drug manufacturers, are primarily based on progress made against specified milestones or targets in each period. In accordance with certain research and development agreements, we are obligated to make certain upfront payments upon execution of the agreement. We record these upfront payments as prepaid research and development expenses, which are included in Other current assets or Other assets in the accompanying Balance Sheets. Such payments are recorded to research and development expense as services are performed. We evaluate on a quarterly basis whether events and circumstances have occurred that may indicate impairment of remaining prepaid research and development expenses. Stock-Based Compensation The Company’s stock-based compensation cost recognized is based on the estimated grant date fair value. The Company recognizes compensation costs for its stock-based awards on a straight-line basis over the requisite service period for the entire award, as adjusted for expected forfeitures. Income Taxes The current benefit for income taxes represents actual or estimated amounts payable or refundable on tax returns filed or to be filed each year. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. The overall change in deferred tax assets and liabilities for the period measures the deferred tax expense or benefit for the period. The measurement of deferred tax assets may be reduced by a valuation allowance based on judgmental assessment of available evidence if deemed more likely than not that some or all of the deferred tax assets will not be realized.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	(2) Net Loss Per Share The Company calculates basic loss per share by dividing net loss by the weighted average common shares outstanding during the period. Diluted loss per share is computed by dividing net loss by the weighted average number of common shares outstanding during the period increased to include, if dilutive, the number of additional common shares that would have been outstanding if the potential common shares had been issued. The Company’s potentially dilutive shares include stock options and warrants for common stock. Because the Company reported a net loss for the years ended December 31, 2019 and 2018, all potentially dilutive shares of common stock have been excluded from the computation of the dilutive net loss per share for all periods presented. Such potentially dilutive shares of common stock consist of the following: Years Ended December 31, 2019 2018 Potentially dilutive securities, excluded: Outstanding stock options 31,136 33,503 Warrants to purchase common stock 135,862 148,325 166,998 181,828

Fair Value Disclosures

Fair Value Disclosures	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Fair Value Disclosures	(3) Fair Value Disclosures Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). Inputs used to measure fair value are classified into the following hierarchy: • Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities. The Company’s Level 1 assets consist of money market investments. The Company does not have any Level 1 liabilities. • Level 2—Unadjusted quoted prices in active markets for similar assets or liabilities; unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active; or inputs other than quoted prices that are observable for the asset or liability. The Company’s Level 2 assets consist of corporate bonds and commercial paper securities. The Company does not have any Level 2 liabilities. • Level 3—Unobservable inputs for the asset or liability. The Company does not have any Level 3 assets or liabilities. As of December 31, 2019 and 2018, the Company had $8.3 million and $6.5 million, respectively, of cash equivalents consisting of money market funds with original maturities of 90 days or less. The Company has the ability to liquidate these investments without restriction. The Company determines fair value for these money market funds with Level 1 inputs through quoted market prices. There were no transfers between any fair value hierarchy levels in 2019 or 2018. Fair Value of Other Financial Instruments The carrying amount of other financial instruments, including accounts payable, approximated fair value due to their short maturities. As of December 31, 2019 and 2018, the Company did not have any debt outstanding.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment	(4) Property and Equipment Property and equipment consist of the following (in thousands): Estimated Life December 31, 2019 December 31, 2018 Computer equipment 3 years $ 54 $ 65 Lab equipment 5 years 142 142 Furniture and fixtures 5 years 61 62 Computer software 3 years 61 70 Leasehold improvements Lesser of useful life or life of the lease 59 59 377 398 Accumulated depreciation and amortization (367 ) (374 ) Property and equipment, net $ 10 $ 24 For the years ended December 31, 2019 and 2018, depreciation and amortization expense was $18,000 and $22,000, respectively.

Related Party Arrangements

Related Party Arrangements	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Party Arrangements	(5) Related Party Arrangements Transactions with the Company’s President and Chief Executive Officer The Company has entered into unrestricted research grants with its President and Chief Executive Officer’s academic research laboratory at the University of Colorado. Funding of any unrestricted research grants is contingent upon the Company’s financial condition, and can be deferred or terminated at the Company’s discretion. Total expense under these arrangements for the years ended December 31, 2019 and 2018 was $286,000 and $325,000, respectively, of which $111,000 was unpaid and included in accrued expenses and other liabilities as of December 31, 2018.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	(6) Commitments and Contingencies The Company has or is subject to the following commitments and contingencies: Employment Agreements The Company maintains employment agreements with several key executive employees. The agreements may be terminated at any time by the Company with or without cause upon written notice to the employee, and entitle the employee to wages in lieu of notice for periods not exceeding one calendar year from date of termination without cause or by the employee for good reason. Certain of these agreements also provide for payments to be made under certain conditions related to a change in control of the Company. Operating Lease On August 1, 2013 the Company entered into a lease agreement for approximately 5,300 square feet of office facilities in Westminster, Colorado which has served as the Company’s primary business office since October 1, 2013. Effective March 2, 2016, the lease was renewed for an additional 38 month term beginning October 1, 2016 and expiring on November 30, 2019. Effective October 10, 2019, the lease was renewed for an additional four month term beginning December 1, 2019 and expiring on March 31, 2020 (the October 2019 Amendment). Additional future undiscounted minimum lease payments under the October 2019 Amendment are $34,000. Under the October 2019 Amendment, the Company has no further rights to extend or renew this lease agreement. The lease includes real estate taxes and insurance, which is not a lease component and is not included in the lease obligation. In addition, common area maintenance charges are based on actual costs incurred and are a non-lease component that is not included in the lease obligation. Future minimum lease payments committed for the Company’s facility in Westminster, Colorado as of December 31, 2018 were $83,000. Below is a summary of the future undiscounted minimum lease payments committed for the Company’s facility in Westminster, Colorado as of December 31, 2019 (in thousands): 2020 $ 25 Total future minimum lease payments $ 25 Rent expense, which is included in general and administrative expense, under this lease for the years ended December 31, 2019 and 2018 was $74,000 and $82,000, respectively. As of December 31, 2019, the lease liability was $25,000 and included in accrued expenses and other liabilities. Cash paid for amounts included in the measurement of lease liabilities and the operating cash flows from operating leases for the year ended December 31, 2019 were $91,000. The weighted-average remaining lease term for the operating lease as of December 31, 2019 is 0.2 years. The weighted-average discount rate for the operating lease is 7.5%. Cardiovascular Pharmacology and Engineering Consultants, LLC ARCA has licensed worldwide rights to all preclinical and clinical data from development of bucindolol through the BEST trial from Cardiovascular Pharmacology and Engineering Consultants, LLC (CPEC), who has licensed rights to this data from Bristol Myers Squib (BMS). CPEC is a licensing subsidiary of Indevus Pharmaceuticals Inc. (a wholly owned subsidiary of Endo Pharmaceuticals), holding ownership rights to certain clinical trial data of Gencaro. Under the terms of its license agreement with CPEC, the Company will incur milestone and royalty obligations upon the occurrence of certain events. If the FDA grants marketing approval for Gencaro, the license agreement states that the Company will owe CPEC a milestone payment of $8.0 million within six months after FDA approval. The license agreement states that a milestone payment of up to $5.0 million in the aggregate shall be paid upon regulatory marketing approval in Europe and Japan. The license agreement also states that the Company’s royalty obligation ranges from 12.5% to 25% of revenue from the related product based on achievement of specified product sales levels, including a 5% royalty that CPEC is obligated to pay under its original license agreement for Gencaro. The agreement states that the Company has the right to buy down the royalties to a range of 12.5% to 17% by making a payment to CPEC within six months of regulatory approval. In October 2017, the Company entered into an agreement with CPEC’s minority owner, Aeolus Pharmaceuticals, Inc. (Aeolus) pursuant to which the Company acquired Aeolus’ minority membership interest in CPEC. The transaction effectively buys-out Aeolus’ royalty interest thereby reducing or eliminating the stated milestone and royalty obligations that could be payable by the Company, if Gencaro receives regulatory approval and is commercialized. As a result of this transaction, the Company, together with Endo Pharmaceuticals, Inc., indirectly hold the remaining licensee rights of CPEC to certain Gencaro clinical data, as discussed above. The acquisition cost of this interest did not have a material impact on the Company’s annual financial statements.

Equity Financings and Warrants

Equity Financings and Warrants	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Equity Financings and Warrants	(7) Equity Financings and Warrants At the Market Equity Financing On January 11, 2017, the Company entered into a Capital on Demand TM Under the amended Sales Agreement, JonesTrading may sell the Shares by any method permitted by law and deemed to be an “at the market offering” as defined in Rule 415 promulgated under the Securities Act of 1933, as amended, including sales made directly on or through The NASDAQ Capital Market, on any other existing trading market for the Common Stock or to or through a market maker. In addition, under the amended Sales Agreement, JonesTrading may sell the Shares by any other method permitted by law, including in negotiated transactions. The Company may instruct JonesTrading not to sell Shares if the sales cannot be effected at or above the price designated by the Company from time to time. The Company is not obligated to make any sales of the Shares under the amended Sales Agreement. The offering of Shares pursuant to the amended Sales Agreement will terminate upon the earlier of (a) the sale of all of the Shares subject to the amended Sales Agreement or (b) the termination of the amended Sales Agreement by JonesTrading or the Company, as permitted therein. The Company paid JonesTrading a commission rate equal to 3.0% of the aggregate gross proceeds from each sale of Shares and agreed to provide JonesTrading with customary indemnification and contribution rights. The Company will also reimburse JonesTrading for certain specified expenses in connection with entering into and amending the Sales Agreement. Under the amended Sales Agreement, the Company sold an aggregate of 820,561 and 118,546 shares of Common Stock pursuant to the terms of such Sales Agreement, as amended, for net proceeds of approximately $6.9 million and $3.4 million during the years ended December 31, 2019 and 2018, respectively, including initial expenses for executing the “at the market offering” and commissions to the placement agent. As of December 31, 2019, the Company had sold all shares available for this offering under its prospectus to the Company’s registration statement on Form S-3 (No. 333-217459). Warrants Warrants to purchase shares of common stock were granted as part of various financing and business agreements. All outstanding warrants were recorded in additional paid-in capital at their estimated fair market value at the date of grant using a Black-Scholes option-pricing model. As of December 31, 2019, these warrants, by year of expiration, are summarized below: Year of Expiration Number of Warrants Weighted Average Exercise Price 2020 2,461 $ 287.28 2022 133,401 109.80 135,862 $ 113.04

Share-based Compensation

Share-based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based Compensation	(8) Share-based Compensation Stock Plans The Company’s equity incentive plan, the 2013 Equity Incentive Plan The Equity Plan provides for the granting of stock options (including indexed options), restricted stock units, stock appreciation rights, restricted stock purchase rights, restricted stock bonuses, performance shares, performance units and deferred stock units. Under the Equity Plan, awards may be granted to employees, directors and consultants of ARCA, except for incentive stock options, which may be granted only to employees. As of December 31, 2019, options to purchase 30,914 shares with a weighted average exercise price of $73.14 per share were outstanding under the Equity Plan, and 36,511 shares were reserved for future awards. In general, the Equity Plan authorizes the grant of stock options that vest at rates set by the Board of Directors or the Compensation Committee thereof. Generally, stock options granted by ARCA under the equity incentive plans become exercisable ratably for a period of three to four years from the date of grant and have a maximum term of ten years. The exercise prices of stock options under the equity incentive plan generally meet the following criteria: the exercise price of incentive stock options must be at least 100% of the fair market value on the grant date and exercise price of options granted to 10% (or greater) stockholders must be at least 110% of the fair market value on the grant date. In conjunction with the adoption of the Equity Plan, the Company discontinued grants under its previous plan, the Amended and Restated ARCA biopharma, Inc. 2004 Equity Incentive Plan The Company granted no options to purchase shares of common stock in the year ended December 31, 2019 and options to purchase an aggregate of 2,220 shares of common stock in the year ended December 31, 2018, respectively. The fair values of employee stock options granted in the year ended December 31, 2018 were estimated at the date of grant using the Black-Scholes model with the following assumptions and had the following estimated weighted average grant date fair value per share: Year Ended December 31, 2018 Expected term 5.3 years Expected volatility 90 % Risk-free interest rate 2.59 % Expected dividend yield 0 % Weighted-average grant date fair value per share $ 9.34 A summary of ARCA’s stock option activities for the years ended December 31, 2019 and 2018, and related information as of December 31, 2019, is as follows: Options Outstanding Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Options outstanding - December 31, 2017 33,938 $ 107.37 Granted 2,220 12.96 Exercised — — Forfeited and cancelled (2,655 ) 169.17 Options outstanding - December 31, 2018 33,503 $ 96.22 7.29 $ — Granted — — Exercised — — Forfeited and cancelled (2,367 ) 250.36 Options outstanding - December 31, 2019 31,136 $ 84.50 6.26 $ — Options exercisable - December 31, 2019 30,074 $ 86.42 6.24 $ — Options vested and expected to vest - December 31, 2019 31,136 $ 84.50 6.26 $ — The aggregate intrinsic value in the table above represents the total intrinsic value, based on our closing price as of December 31 of the respective year, which would have been received by the option holders had all the option holders with in-the-money options exercised as of that date. Restricted Stock Units The Company began granting restricted stock units (RSUs) to employees during 2013 in conjunction with the adoption of the Equity Plan. The fair value of RSU awards is the closing price of the Company’s common stock on the date of grant and was recognized as compensation expense on a straight-line basis over the respective vesting period. The stock awards granted had a requisite service period between three and four years with annual vesting on the grant anniversary date. There was no RSU activity for the year ended December 31, 2019. A summary of RSU activity for the year ended December 31, 2018 is presented below: Restricted Stock Units Outstanding Number of Shares Weighted Average Grant Date Fair Value RSUs outstanding - December 31, 2017 842 $ 142.92 Granted — — Vested and released (842 ) 142.92 Forfeited and cancelled — — RSUs outstanding - December 31, 2018 — $ — As of December 31, 2018, all compensation cost related to stock awards was recognized. Non-cash Stock-based Compensation For the years ended December 31, 2019 and 2018, the Company recognized the following non-cash, share-based compensation expense (in thousands): Years Ended December 31, 2019 2018 Research and development $ 71 $ 117 General and administrative 80 156 Total $ 151 $ 273 ARCA did not recognize any tax benefit related to employee stock-based compensation cost as a result of the full valuation allowance on its net deferred tax assets.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	(9) Employee Benefit Plans The Company has a 401(k) plan and makes a matching contribution equal to 100% of the employee’s first 3% of the employee’s contributions and 50% of the employee’s next 2% of contributions. The Company adopted the plan in 2006 and contributed $77,000 and $115,000 for the years ended December 31, 2019 and 2018, respectively.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	( 10) Income Taxes Effective June 1, 2005, the Company changed from an S-Corporation to a C-Corporation. As an S-Corporation, the net operating loss carryforwards were distributed to the Company’s stockholders; such amounts were not significant. As of December 31, 2019, the Company has net operating loss carryforwards of approximately $170.3 million, and approximately $1.7 million of research and development credits that may be used to offset future taxable income. The Company’s net operating loss carryforwards through December 31, 2017 will expire beginning 2025 through 2037. The net operating loss carryforwards beginning in 2018, have no expiration, but are limited to 80% of taxable income. Utilization of net operating losses and tax credits, including those acquired as a result of the Merger, will be subject to an annual limitation due to ownership change limitations provided by Internal Revenue Code Section 382. The Company believes that an ownership change limitation as defined under Section 382 of the U.S. Internal Revenue Code occurred as a result of its various historical financing transactions, including its offering of common stock completed in June 2015. Future utilization of the federal net operating losses and tax credit carryforwards accumulated from June 2005 to the change in ownership date will be subject to annual limitations to offset future taxable income. The annual limitation may result in the expiration of the net operating losses and credits before utilization. As such, a portion of the Company’s net operating loss carryforwards may be limited. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the period in which those temporary differences become deductible. Management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. Due primarily to the Company’s history of operating losses, management is unable to conclude that it is more likely than not that the Company will realize the benefits of these deductible differences, and accordingly has provided a valuation allowance against the entire net deferred tax asset of approximately $44.6 million at December 31, 2019, reflecting an increase of approximately $1.1 million from December 31, 2018. The deferred tax assets are primarily comprised of net operating loss carryforwards and research and experimentation credit carryforwards. As of December 31, 2019, the Company has not performed an Internal Revenue Code Section 382 limitation study. Depending on the outcome of such a study, the gross amount of net operating losses recognizable in future tax periods could be limited. A limitation in the carryforwards would decrease the carrying amount of the gross amount of the net operating loss carryforwards, with a corresponding decrease in the valuation allowance recorded against these gross deferred tax assets. Income tax benefit for the years ended December 31, 2019 and 2018 primarily were related to the reduction in the recorded valuation allowance as a result of the realization of research and experimentation credit carryforwards under the Protecting Americans from Tax Hikes Act of 2015, or PATH Act. As of December 31, 2019, the Company has realized the full amount available under the PATH Act. Income tax benefit attributable to our loss from operations before income taxes differs from the amounts computed by applying the U.S. federal statutory income tax rate of 21% for 2019 and 2018, as a result of the following (in thousands): Years ended December 31, 2019 2018 U.S. federal income tax benefit at statutory rates $ (1,151 ) $ (1,666 ) State income tax benefit, net of federal benefit (201 ) (290 ) Research and experimentation credits (31 ) (144 ) Deferred tax asset adjustment 3 34 Other 115 134 Change in valuation allowance 1,098 1,901 Income tax benefit $ (167 ) $ (31 ) Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting and the amounts used for income tax purposes, as well as operating loss and tax credit carryforwards. The income tax effects of temporary differences and carryforwards that give rise to significant portions of the Company’s net deferred tax assets consisted of the following (in thousands): As of December 31, 2019 2018 Net operating loss carryforwards $ 41,989 $ 40,742 Charitable contribution carryforwards 439 433 Research and experimentation credits 1,668 1,796 Capitalized intangibles 387 409 Stock-based compensation 119 127 Depreciation and amortization — 1 Accrued compensation 16 20 Other 9 1 Total deferred tax assets 44,627 43,529 Valuation allowance (44,627 ) (43,529 ) Net deferred tax assets $ — $ — Since the Company is in a loss carryforward position, the Company is generally subject to U.S. federal and state income tax examinations by tax authorities for all years for which a loss carryforward is available. Thus, the Company’s open tax years extend back to 2009. The Company believes that its tax filing positions and deductions related to tax periods subject to examination will be sustained upon audit and does not anticipate any adjustment will result in a material adverse effect on the Company’s financial condition, result of operations, or cash flow. For the years ended December 31, 2019 and 2018, the Company has no reserve for uncertain tax positions. The Company does not expect that the total amounts of unrecognized tax benefits will significantly increase or decrease within the subsequent twelve months. In the event the Company concludes it is subject to interest or penalties arising from uncertain tax positions, the Company will record interest and penalties as a component of other income and expense. No interest or penalties were recognized in the financial statements for the years ended December 31, 2019 and 2018.

The Company and Summary of Si_2

The Company and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Description of Business	Description of Business ARCA biopharma, Inc. (the Company or ARCA), a Delaware corporation, is headquartered in Westminster, Colorado. The Company is a clinical-stage biopharmaceutical company applying a precision medicine approach to the development and commercialization of genetically targeted therapies for cardiovascular diseases. The Company’s lead product candidate, Gencaro™ (bucindolol hydrochloride), is a pharmacogenetically-targeted beta-adrenergic receptor antagonist with mild vasodilator properties that ARCA is developing to treat cardiovascular disease, focusing on atrial fibrillation (AF) in patients with chronic heart failure (HF). In 2018, the Company completed its Phase 2B clinical superiority trial, known as GENETIC-AF, in which the Company evaluated Gencaro for the treatment of AF in HF patients. In the trial, Gencaro was evaluated against an active comparator, the beta-blocker TOPROL-XL (metoprolol succinate), a drug indicated for the treatment of HF patients that is commonly prescribed for HF patients with AF. Enrollment in GENETIC-AF was limited to patients that possess the specific genotype that the Company believes responds best to Gencaro. The planned development program of Gencaro is, in part, based on the results of the Company’s completed GENETIC-AF Phase 2B clinical trial and a prospectively designed DNA substudy of adrenergic receptor polymorphisms in the BEST trial, a previous Phase 3 study of HF patients. Following review of the Phase 2B GENETIC-AF clinical trial results, as well as its alignment with previous Phase 3 pharmacogenetic substudy data from the BEST trial, the FDA stated that data from a single pivotal Phase 3 clinical trial may be sufficient to support approval of Gencaro for the treatment of AF in patients with HF. In 2019, the Company reached an agreement with the U.S. Food and Drug Administration (FDA) known as a Special Protocol Assessment (SPA), for the requirements of the Gencaro Phase 3 clinical trial. Based on the SPA agreement, the planned Phase 3 clinical trial, if successful, may support a New Drug Application (NDA) for the marketing approval of Gencaro. The Company’s other product candidate, AB171, is a thiol-substituted isosorbide mononitrate, which ARCA plans to develop as a genetically-targeted treatment for HF and peripheral arterial disease. The Company will need to raise additional capital to fund future operations and any additional development of Gencaro or AB171. If the Company is unable to obtain additional funding or is unable to complete a strategic transaction, it may have to discontinue development activities on Gencaro or discontinue its operations.
Liquidity and Going Concern	Liquidity and Going Concern The Company devotes substantially all of its efforts towards obtaining regulatory approval and raising capital necessary to fund its operations and it is subject to a number of risks associated with clinical research and development, including dependence on key individuals, the development of and regulatory approval of commercially viable products, the need to raise adequate additional financing necessary to fund the development and commercialization of its products, and competition from larger companies. The Company has not generated revenue to date and has incurred substantial losses and negative cash flows from operations since its inception. The Company has historically funded its operations through issuances of common and preferred stock. The Company believes that its current cash and cash equivalents will be sufficient to fund its operations, at its projected cost structure, after giving effect to potential cost reductions, through the end of the third quarter of 2020. In light of the significant uncertainties regarding clinical development timelines and costs for developing drugs such as Gencaro, the Company will need to raise additional capital to finance the Company’s future operations and any additional development of Gencaro or any other product candidates. If the Company is delayed in completing or is unable to complete additional financing and/or a strategic transaction, the Company may discontinue its development activities or operations. Due to the current status of the Gencaro development program, the current amount of cash and cash equivalents held, the anticipated costs to be incurred for existing operations as well as exploring other corporate strategic alternatives, and the uncertainty of the Company’s ability to raise a significant amount of capital, management has determined there is substantial doubt about the Company’s ability to continue as a going concern from one year after the Company’s financial statements have been issued. The Company has implemented efforts to reduce personnel costs, including reduction of executive management salaries. The Company could delay or cancel certain planned expenditures related to its drug development programs and/or implement additional cost reduction measures to conserve its cash balances; however, there is no assurance that those measures would be adequate to allow the Company to continue as a going concern for a period beyond one year from the issuance of these financial statements. These financial statements have been prepared with the assumption that the Company will continue as a going concern and will be able to realize its assets and discharge its liabilities in the normal course of business and do not include any adjustments to reflect the possible future effects on the recoverability and classification of assets or the amounts and classification of liabilities that may result from the inability of the Company to continue as a going concern. The Company may not be able to raise sufficient capital on acceptable terms, or at all, to continue development of Gencaro or to otherwise continue operations and may not be able to execute any strategic transaction. The Company’s liquidity, and its ability to raise additional capital or complete any strategic transaction, depends on a number of factors, including, but not limited to, the following: • the costs and timing for the potential additional clinical trials in order to gain possible regulatory approval for Gencaro or any other product candidate; • the market price of the Company’s stock and the availability and cost of additional equity capital from existing and potential new investors; • the Company’s ability to retain the listing of its common stock on the Nasdaq Capital Market; • general economic and industry conditions affecting the availability and cost of capital; • the Company’s ability to control costs associated with its operations; • the costs of filing, prosecuting, defending and enforcing any patent claims and other intellectual property rights; and • the terms and conditions of the Company’s existing collaborative and licensing agreements. The sale of additional equity or convertible debt securities would likely result in substantial additional dilution to the Company’s stockholders. If the Company raises additional funds through the incurrence of indebtedness, the obligations related to such indebtedness would be senior to rights of holders of the Company’s capital stock and could contain covenants that would restrict the Company’s operations. The Company also cannot predict what consideration might be available, if any, to the Company or its stockholders, in connection with any strategic transaction. Should strategic alternatives or additional capital not be available to the Company, or not be available on acceptable terms, the Company may be unable to realize value from its assets and discharge its liabilities in the normal course of business which may, among other alternatives, cause the Company to further delay, substantially reduce or discontinue operational activities to conserve its cash resources.
Reverse Stock Split	Reverse Stock Split On April 3, 2019, the Company completed a 1-for-18 reverse stock split of its common stock. All common shares and per common share amounts in the financial statements and footnotes have been adjusted retroactively to reflect the effects of this action.
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in accordance with U.S. generally accepted accounting principles (U.S. GAAP) and include all adjustments necessary for the fair presentation of our financial position, results of operations and cash flows for the periods presented. Management has performed an evaluation of the Company’s activities through the date of filing of this Annual Report on Form 10-K.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Updated (ASU) No. 2016-02, Leases (Topic 842) Targeted Improvements The Company reviewed all other recently issued accounting pronouncements and concluded that they were either not applicable or not expected to have a significant impact to the financial statements.
Accounting Estimates in the Preparation of Financial Statements	Accounting Estimates in the Preparation of Financial Statements The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America 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. The Company bases estimates on various assumptions that are believed to be reasonable under the circumstances. The Company believes significant judgment was involved in estimating the clinical trial accruals, and in estimating other accrued liabilities, stock-based compensation, and income taxes. Management is continually evaluating and updating these estimates, and it is possible that these estimates will change in the future or that actual results may differ from these estimates.
Cash Equivalents	Cash Equivalents Cash equivalents generally consist of money market funds and debt securities with maturities of 90 days or less at the time of purchase. The Company invests its excess cash in securities with strong ratings and has established guidelines relative to diversification and maturity with the objective of maintaining safety of principal and liquidity.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents. The Company has no off-balance-sheet concentrations of credit risk, such as foreign exchange contracts, option contracts, or foreign currency hedging arrangements. The Company maintains cash and cash equivalent balances in the form of bank demand deposits and money market fund accounts with financial institutions that management believes are creditworthy. Such balances may at times exceed the insured amount.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Cost includes expenditures for equipment, leasehold improvements, replacements, and renewals. Maintenance and repairs are charged to expense as incurred. When assets are sold, retired, or otherwise disposed of, the cost and accumulated depreciation are removed from the accounts and any resulting gain or loss is reflected in operations. The cost of property and equipment is depreciated using the straight-line method over the estimated useful lives of the related assets. Leasehold improvements are amortized over the shorter of the life of the lease or the estimated useful life of the assets.
Accrued Outsourcing Expenses	Accrued Outsourcing Expenses As part of the process of preparing its financial statements, the Company is required to estimate accrued outsourcing expenses. This process involves identifying services that third parties have performed on the Company’s behalf and estimating the level of service performed and the associated cost incurred for these services as of the balance sheet date. Examples of estimated accrued outsourcing expenses include contract service fees, such as fees payable to contract manufacturers in connection with the production of materials related to the Company’s drug product, and service fees from clinical research organizations. The Company develops estimates of liabilities using its judgment based upon the facts and circumstances known at the time.
Segments	Segments The Company operates in one segment. Management uses one measure of profitability and does not segment its business for internal reporting.
Research and Development	Research and Development Research and development costs are expensed as incurred. These consist primarily of salaries, contract services, and supplies. Costs related to clinical trial and drug manufacturing activities are based upon estimates of the services received and related expenses incurred by contract research organizations (CROs), clinical study sites, drug manufacturers, collaboration partners, laboratories, consultants, or otherwise. Related contracts vary significantly in length, and could be for a fixed amount, a variable amount based on actual costs incurred, capped at a certain limit, or for a combination of these elements. Activity levels are monitored through communications with the vendors, including detailed invoices and task completion review, analysis of expenses against budgeted amounts, and pre-approval of any changes in scope of the services to be performed. Certain significant vendors may also provide an estimate of costs incurred but not invoiced on a periodic basis. Expenses related to the CROs and clinical studies, as well as contract drug manufacturers, are primarily based on progress made against specified milestones or targets in each period. In accordance with certain research and development agreements, we are obligated to make certain upfront payments upon execution of the agreement. We record these upfront payments as prepaid research and development expenses, which are included in Other current assets or Other assets in the accompanying Balance Sheets. Such payments are recorded to research and development expense as services are performed. We evaluate on a quarterly basis whether events and circumstances have occurred that may indicate impairment of remaining prepaid research and development expenses.
Stock-Based Compensation	Stock-Based Compensation The Company’s stock-based compensation cost recognized is based on the estimated grant date fair value. The Company recognizes compensation costs for its stock-based awards on a straight-line basis over the requisite service period for the entire award, as adjusted for expected forfeitures.
Income Taxes	Income Taxes The current benefit for income taxes represents actual or estimated amounts payable or refundable on tax returns filed or to be filed each year. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in the period that includes the enactment date. The overall change in deferred tax assets and liabilities for the period measures the deferred tax expense or benefit for the period. The measurement of deferred tax assets may be reduced by a valuation allowance based on judgmental assessment of available evidence if deemed more likely than not that some or all of the deferred tax assets will not be realized.

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Summary of Potentially Dilutive Shares of Common Stock	Because the Company reported a net loss for the years ended December 31, 2019 and 2018, all potentially dilutive shares of common stock have been excluded from the computation of the dilutive net loss per share for all periods presented. Such potentially dilutive shares of common stock consist of the following: Years Ended December 31, 2019 2018 Potentially dilutive securities, excluded: Outstanding stock options 31,136 33,503 Warrants to purchase common stock 135,862 148,325 166,998 181,828

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	Property and equipment consist of the following (in thousands): Estimated Life December 31, 2019 December 31, 2018 Computer equipment 3 years $ 54 $ 65 Lab equipment 5 years 142 142 Furniture and fixtures 5 years 61 62 Computer software 3 years 61 70 Leasehold improvements Lesser of useful life or life of the lease 59 59 377 398 Accumulated depreciation and amortization (367 ) (374 ) Property and equipment, net $ 10 $ 24

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	Below is a summary of the future undiscounted minimum lease payments committed for the Company’s facility in Westminster, Colorado as of December 31, 2019 (in thousands): 2020 $ 25 Total future minimum lease payments $ 25

Equity Financings and Warrants

Equity Financings and Warrants (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Warrants by Year of Expiration	As of December 31, 2019, these warrants, by year of expiration, are summarized below: Year of Expiration Number of Warrants Weighted Average Exercise Price 2020 2,461 $ 287.28 2022 133,401 109.80 135,862 $ 113.04

Share-based Compensation (Table

Share-based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Estimated Weighted Average Grant Date Fair Value per Share	The Company granted no options to purchase shares of common stock in the year ended December 31, 2019 and options to purchase an aggregate of 2,220 shares of common stock in the year ended December 31, 2018, respectively. The fair values of employee stock options granted in the year ended December 31, 2018 were estimated at the date of grant using the Black-Scholes model with the following assumptions and had the following estimated weighted average grant date fair value per share: Year Ended December 31, 2018 Expected term 5.3 years Expected volatility 90 % Risk-free interest rate 2.59 % Expected dividend yield 0 % Weighted-average grant date fair value per share $ 9.34
Summary of Stock Option Activities	A summary of ARCA’s stock option activities for the years ended December 31, 2019 and 2018, and related information as of December 31, 2019, is as follows: Options Outstanding Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Options outstanding - December 31, 2017 33,938 $ 107.37 Granted 2,220 12.96 Exercised — — Forfeited and cancelled (2,655 ) 169.17 Options outstanding - December 31, 2018 33,503 $ 96.22 7.29 $ — Granted — — Exercised — — Forfeited and cancelled (2,367 ) 250.36 Options outstanding - December 31, 2019 31,136 $ 84.50 6.26 $ — Options exercisable - December 31, 2019 30,074 $ 86.42 6.24 $ — Options vested and expected to vest - December 31, 2019 31,136 $ 84.50 6.26 $ —
Summary of RSU Activity	There was no RSU activity for the year ended December 31, 2019. A summary of RSU activity for the year ended December 31, 2018 is presented below: Restricted Stock Units Outstanding Number of Shares Weighted Average Grant Date Fair Value RSUs outstanding - December 31, 2017 842 $ 142.92 Granted — — Vested and released (842 ) 142.92 Forfeited and cancelled — — RSUs outstanding - December 31, 2018 — $ —
Summary of Non-cash, Share-based Compensation Expense	For the years ended December 31, 2019 and 2018, the Company recognized the following non-cash, share-based compensation expense (in thousands): Years Ended December 31, 2019 2018 Research and development $ 71 $ 117 General and administrative 80 156 Total $ 151 $ 273

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Tax Benefit Attributable to Our Loss from Operations	Income tax benefit attributable to our loss from operations before income taxes differs from the amounts computed by applying the U.S. federal statutory income tax rate of 21% for 2019 and 2018, as a result of the following (in thousands): Years ended December 31, 2019 2018 U.S. federal income tax benefit at statutory rates $ (1,151 ) $ (1,666 ) State income tax benefit, net of federal benefit (201 ) (290 ) Research and experimentation credits (31 ) (144 ) Deferred tax asset adjustment 3 34 Other 115 134 Change in valuation allowance 1,098 1,901 Income tax benefit $ (167 ) $ (31 )
Net Deferred Tax Assets	Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting and the amounts used for income tax purposes, as well as operating loss and tax credit carryforwards. The income tax effects of temporary differences and carryforwards that give rise to significant portions of the Company’s net deferred tax assets consisted of the following (in thousands): As of December 31, 2019 2018 Net operating loss carryforwards $ 41,989 $ 40,742 Charitable contribution carryforwards 439 433 Research and experimentation credits 1,668 1,796 Capitalized intangibles 387 409 Stock-based compensation 119 127 Depreciation and amortization — 1 Accrued compensation 16 20 Other 9 1 Total deferred tax assets 44,627 43,529 Valuation allowance (44,627 ) (43,529 ) Net deferred tax assets $ — $ —

The Company and Summary of Si_3

The Company and Summary of Significant Accounting Policies (Details Textual)	Apr. 03, 2019	Dec. 31, 2019USD ($)Segment	Jan. 01, 2019USD ($)
Company And Summary Of Significant Accounting Policies Table [Line Items]
Revenues		$ 0
Right-of-use asset		22,000
Concentrations of credit risk		$ 0
Number of segments | Segment		1
ASU 2016-02
Company And Summary Of Significant Accounting Policies Table [Line Items]
Lease lability			$ 80,000
Right-of-use asset			60,000
Remaining lease payments			$ 83,000
Discount rate			7.50%
Accrued rent			$ 20,000
Common Stock
Company And Summary Of Significant Accounting Policies Table [Line Items]
Reverse stock split description	1-for-18
Reverse stock split conversion ratio1	0.056

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Potentially Dilutive Shares of Common Stock (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	166,998	181,828
Outstanding stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	31,136	33,503
Warrants to purchase common stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	135,862	148,325

Fair Value Disclosures (Details

Fair Value Disclosures (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfers of assets between fair value hierarchy levels	$ 0	$ 0
Debt outstanding	0	0
Fair Value Measurements, Recurring | Level 1 | Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents consisting of money market funds and commercial paper	$ 8,300,000	$ 6,500,000

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and Equipment, Gross	$ 377	$ 398
Accumulated depreciation and amortization	(367)	(374)
Property and equipment, net	$ 10	24
Computer Equipment
Property Plant And Equipment [Line Items]
Estimated Life	3 years
Property and Equipment, Gross	$ 54	65
Lab Equipment
Property Plant And Equipment [Line Items]
Estimated Life	5 years
Property and Equipment, Gross	$ 142	142
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Estimated Life	5 years
Property and Equipment, Gross	$ 61	62
Computer Software
Property Plant And Equipment [Line Items]
Estimated Life	3 years
Property and Equipment, Gross	$ 61	70
Leasehold Improvements
Property Plant And Equipment [Line Items]
Estimated Life	Lesser of useful life or life of the lease
Property and Equipment, Gross	$ 59	$ 59

Property and Equipment (Details

Property and Equipment (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 18	$ 22

Related Party Arrangements (Det

Related Party Arrangements (Details Textual) - Chief Executive Officer - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Accrued Expenses and Other Liabilities
Related Party Transaction [Line Items]
Unpaid expense		$ 111
Research Grants
Related Party Transaction [Line Items]
Total expense	$ 286	$ 325

Commitments and Contingencies_2

Commitments and Contingencies (Details Textual) $ in Thousands	Oct. 10, 2019USD ($)	Mar. 02, 2016	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)	Aug. 01, 2013ft²
Commitments And Contingencies [Line Items]
Area of office facilities taken on lease | ft²					5,300
Additional operating lease term	4 months	38 months
Lease renewal start date	Dec. 1, 2019	Oct. 1, 2016
Lease expiration date	Mar. 31, 2020	Nov. 30, 2019
Future undiscounted minimum lease payments	$ 34
Lease renewal option			Under the October 2019 Amendment, the Company has no further rights to extend or renew this lease agreement.
Lessee, Operating Lease, Existence of Option to Extend [true false]			false
Future minimum lease payments			$ 25
Lessee, operating lease, assumptions and judgments, allocation of lease and nonlease component			The lease includes real estate taxes and insurance, which is not a lease component and is not included in the lease obligation. In addition, common area maintenance charges are based on actual costs incurred and are a non-lease component that is not included in the lease obligation.
Lease liability			$ 25
Operating lease, liability, current, statement of financial position [Extensible List]			us-gaap:OtherAccruedLiabilitiesCurrent
Operating lease, cash paid for measurement of lease liabilities			$ 91
Weighted-average remaining lease term			2 months 12 days
Weighted-average discount rate			7.50%
Royalty buy down due period			6 months
Minimum
Commitments And Contingencies [Line Items]
Percentage of royalty obligation			12.50%
Percentage of range of royalties that can be bought down			12.50%
Maximum
Commitments And Contingencies [Line Items]
Percentage of royalty obligation			25.00%
Percentage of range of royalties that can be bought down			17.00%
Upon Food and Drug Administration Approval
Commitments And Contingencies [Line Items]
Expected milestone payments due upon approval			$ 8,000
Upon Regulatory Marketing Approval
Commitments And Contingencies [Line Items]
Expected milestone payments due upon approval			$ 5,000
CPEC
Commitments And Contingencies [Line Items]
Percentage of royalty obligation			5.00%
General and Administrative Expense
Commitments And Contingencies [Line Items]
Rent expense			$ 74
Rent expense				$ 82
Westminster, Colorado
Commitments And Contingencies [Line Items]
Future minimum lease payments				$ 83

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
2020	$ 25
Total future minimum lease payments	$ 25

Equity Financings and Warrant_2

Equity Financings and Warrants (Details Textual) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jun. 28, 2019	Jan. 11, 2017
Equity Financing And Warrants [Line Items]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares issued	1,594,070	773,558
JonesTrading
Equity Financing And Warrants [Line Items]
Percentage of selling commission per additional shares sold				3.00%
Sales Agreement
Equity Financing And Warrants [Line Items]
Common stock, shares issued	820,561	118,546
Net proceeds from issuance of common stock	$ 6.9	$ 3.4
Sales Agreement | JonesTrading
Equity Financing And Warrants [Line Items]
Common stock, par value				$ 0.001
Aggregate offering price of common stock authorized			$ 17.5	$ 7.3

Equity Financings and Warrant_3

Equity Financings and Warrants - Summary of Warrants by Year of Expiration (Details)	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Class Of Warrant Or Right [Line Items]
Number of Warrants | shares	135,862
Weighted Average Exercise Price | $ / shares	$ 113.04
2020
Class Of Warrant Or Right [Line Items]
Year of Expiration	2020
Number of Warrants | shares	2,461
Weighted Average Exercise Price | $ / shares	$ 287.28
2022
Class Of Warrant Or Right [Line Items]
Year of Expiration	2022
Number of Warrants | shares	133,401
Weighted Average Exercise Price | $ / shares	$ 109.80

Share-based Compensation (Detai

Share-based Compensation (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding under Equity plan		31,136	33,503	33,938
Weighted Average exercise Price of Options Outstanding		$ 84.50	$ 96.22	$ 107.37
Stock options award, expiration		10 years
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to unvested options		$ 25
Maturity period of weighted average period of compensation expenses		6 months
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options award, vesting period		3 years
Percentage holding for stock options exercise price		10.00%
Minimum | Incentive Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price of stock option		100.00%
Minimum | Incentive Stock Option | Stockholders
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price of stock option		110.00%
Minimum | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted Stock Units award, requisite service period		3 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options award, vesting period		4 years
Maximum | Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted Stock Units award, requisite service period		4 years
2013 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares reserve for issuance under amended Equity Plan	55,555
Number of shares issuable under Equity plan	73,412
Number of shares outstanding under Equity plan		30,914
Weighted Average exercise Price of Options Outstanding		$ 73.14
Shares reserved for future		36,511
Options granted		0	2,220
Two Thousand And Four Stock Option Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares outstanding under Equity plan		222
Weighted Average exercise Price of Options Outstanding		$ 1,665.68

Share-based Compensation - Esti

Share-based Compensation - Estimated Weighted Average Grant Date Fair Value Per Share (Details)	12 Months Ended
	Dec. 31, 2018$ / shares
Estimated weighted average grant date fair value per share
Expected term	5 years 3 months 18 days
Expected volatility	90.00%
Risk-free interest rate	2.59%
Expected dividend yield	0.00%
Weighted-average grant date fair value per share	$ 9.34

Share-based Compensation - Summ

Share-based Compensation - Summary of Stock Option Activities (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Number of Stock Options
Number of Options, Options outstanding, beginning of period	33,503	33,938
Number of Options, Granted		2,220
Number of Options, Forfeited and cancelled	(2,367)	(2,655)
Number of Options, Options outstanding, end of period	31,136	33,503
Number of Options, Options exercisable, end of period	30,074
Number of Options, Options vested and expected to vest	31,136
Stock Options, Weighted Average Exercise Price
Weighted Average Exercise Price, Options outstanding, beginning of period	$ 96.22	$ 107.37
Weighted Average Exercise Price, Granted		12.96
Weighted Average Exercise Price, Forfeited and cancelled	250.36	169.17
Weighted Average Exercise Price, Options outstanding, end of period	84.50	$ 96.22
Weighted Average Exercise Price, Options exercisable, end of period	86.42
Weighted Average Exercise Price, Options vested and expected to vest, end of period	$ 84.50
Stock Options, Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years), Options outstanding	6 years 3 months 3 days	7 years 3 months 14 days
Weighted Average Remaining Contractual Term (in years), Options exercisable	6 years 2 months 26 days
Weighted Average Remaining Contractual Term (in years), Options vested and expected to vest	6 years 3 months 3 days

Share-based Compensation - Su_2

Share-based Compensation - Summary of RSU Activity (Details)	12 Months Ended
	Dec. 31, 2018$ / sharesshares
Restricted Stock Awards, Number of Shares
Restricted stock units outstanding, beginning of period | shares	842
Vested and released | shares	(842)
Restricted Stock Awards, Weighted Average Grant Date Fair Value
Restricted stock units outstanding, beginning of period | $ / shares	$ 142.92
Vested and released | $ / shares	$ 142.92

Share-based Compensation - Su_3

Share-based Compensation - Summary of Non-cash, Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	$ 151	$ 273
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	71	117
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	$ 80	$ 156

Employee Benefit Plans (Details

Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Contribution Plan Disclosure [Line Items]
Matching contribution	matching contribution equal to 100% of the employee’s first 3% of the employee’s contributions and 50% of the employee’s next 2% of contributions.
Company's contribution	$ 77	$ 115
First 3% of pay contributed
Defined Contribution Plan Disclosure [Line Items]
Benefit Plan, Percentage of Match	100.00%
Employer matching contribution percentage	3.00%
Next 2% of pay contributed
Defined Contribution Plan Disclosure [Line Items]
Benefit Plan, Percentage of Match	50.00%
Employer matching contribution percentage	2.00%

Income Taxes (Details Textual)

Income Taxes (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Line Items]
Net operating loss carryforwards		$ 170,300,000
Tax Credit Carryforward, Description	The net operating loss carryforwards beginning in 2018, have no expiration, but are limited to 80% of taxable income.
Percentage limited to taxable income on operating loss carryforward	80.00%
Valuation allowance	$ 44,627,000	$ 43,529,000
Increase net deferred tax asset	$ 1,100,000
Federal statutory income tax rate	21.00%	21.00%
Reserve for uncertain tax positions	$ 0	$ 0
Interest or penalties recognized	$ 0	0
Open tax year	2009
Research Tax Credit Carryforward
Income Tax [Line Items]
Research and experimentation credits		$ 1,700,000
Operating loss carryforwards, limitations on use	Utilization of net operating losses and tax credits, including those acquired as a result of the Merger, will be subject to an annual limitation due to ownership change limitations provided by Internal Revenue Code Section 382. The Company believes that an ownership change limitation as defined under Section 382 of the U.S. Internal Revenue Code occurred as a result of its various historical financing transactions, including its offering of common stock completed in June 2015. Future utilization of the federal net operating losses and tax credit carryforwards accumulated from June 2005 to the change in ownership date will be subject to annual limitations to offset future taxable income. The annual limitation may result in the expiration of the net operating losses and credits before utilization. As such, a portion of the Company’s net operating loss carryforwards may be limited
Tax credit carryforward, limitations on use	Utilization of net operating losses and tax credits, including those acquired as a result of the Merger, will be subject to an annual limitation due to ownership change limitations provided by Internal Revenue Code Section 382. The Company believes that an ownership change limitation as defined under Section 382 of the U.S. Internal Revenue Code occurred as a result of its various historical financing transactions, including its offering of common stock completed in June 2015. Future utilization of the federal net operating losses and tax credit carryforwards accumulated from June 2005 to the change in ownership date will be subject to annual limitations to offset future taxable income. The annual limitation may result in the expiration of the net operating losses and credits before utilization. As such, a portion of the Company’s net operating loss carryforwards may be limited
Earliest Tax Year
Income Tax [Line Items]
Operating loss carryforwards expiration year			2025
Latest Tax Year
Income Tax [Line Items]
Operating loss carryforwards expiration year			2037

Income Taxes - Income Tax Benef

Income Taxes - Income Tax Benefit Attributable to Our Loss from Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Effective Income Tax Rate Reconciliation, Amount [Abstract]
U.S. federal income tax benefit at statutory rates	$ (1,151)	$ (1,666)
State income tax benefit, net of federal benefit	(201)	(290)
Research and experimentation credits	(31)	(144)
Deferred tax asset adjustment	3	34
Other	115	134
Change in valuation allowance	1,098	1,901
Income tax benefit	$ (167)	$ (31)

Income Taxes - Net deferred tax

Income Taxes - Net deferred tax assets (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 41,989	$ 40,742
Charitable contribution carryforwards	439	433
Research and experimentation credits	1,668	1,796
Capitalized intangibles	387	409
Stock-based compensation	119	127
Depreciation and amortization		1
Accrued compensation	16	20
Other	9	1
Total deferred tax assets	44,627	43,529
Valuation allowance	(44,627)	(43,529)
Net deferred tax assets	$ 0	$ 0