Oruka Therapeutics (ORKA) 10-Q 14 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 12, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	ARCA Biopharma, Inc.
Entity Central Index Key	907,654
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Period Focus	Q3
Trading Symbol	ABIO
Document Fiscal Year Focus	2,018
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		13,924,058

BALANCE SHEETS (Unaudited)

BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 8,056	$ 8,702
Marketable securities		3,050
Other current assets	336	547
Total current assets	8,392	12,299
Property and equipment, net	29	42
Other assets	24	24
Total assets	8,445	12,365
Current liabilities:
Accounts payable	217	622
Accrued compensation and employee benefits	184	757
Accrued expenses and other liabilities	577	691
Total current liabilities	978	2,070
Deferred rent, net of current portion	4	20
Total liabilities	982	2,090
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.001 par value; 100 million shares authorized at September 30, 2018 and December 31, 2017; 13,923,825 and 11,775,062 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	14	12
Additional paid-in capital	144,894	141,266
Accumulated other comprehensive loss		(2)
Accumulated deficit	(137,445)	(131,001)
Total stockholders’ equity	7,463	10,275
Total liabilities and stockholders’ equity	$ 8,445	$ 12,365

BALANCE SHEETS (Unaudited) (Par

BALANCE SHEETS (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	13,923,825	11,775,062
Common stock, shares outstanding	13,923,825	11,775,062

STATEMENTS OF OPERATIONS AND CO

STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Costs and expenses:
Research and development	$ 740	$ 3,488	$ 3,614	$ 11,242
General and administrative	922	987	2,977	3,173
Total costs and expenses	1,662	4,475	6,591	14,415
Loss from operations	(1,662)	(4,475)	(6,591)	(14,415)
Interest and other income	40	44	124	128
Interest expense	(2)	(2)	(8)	(6)
Loss before income taxes	(1,624)	(4,433)	(6,475)	(14,293)
Benefit from income taxes	31		31
Net loss	(1,593)	(4,433)	(6,444)	(14,293)
Change in unrealized loss on marketable securities		2	2	16
Comprehensive loss	$ (1,593)	$ (4,431)	$ (6,442)	$ (14,277)
Net loss per share:
Basic and diluted	$ (0.11)	$ (0.39)	$ (0.47)	$ (1.43)
Weighted average shares outstanding:
Basic and diluted	13,923,825	11,502,654	13,823,793	9,982,739

STATEMENTS OF STOCKHOLDERS' EQU

STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2016	$ 22,194	$ 9	$ 134,715	$ (19)	$ (112,511)
Beginning Balance, shares at Dec. 31, 2016		9,082,366
Issuance of common stock for cash, net of offering costs	69		69
Issuance of common stock for cash, net of offering costs, shares		85,068
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		5,434
Share-based compensation	101		101
Change in unrealized loss on marketable securities	10			10
Net loss	(4,338)				(4,338)
Ending Balance at Mar. 31, 2017	18,036	$ 9	134,885	(9)	(116,849)
Ending Balance, shares at Mar. 31, 2017		9,172,868
Beginning Balance at Dec. 31, 2016	22,194	$ 9	134,715	(19)	(112,511)
Beginning Balance, shares at Dec. 31, 2016		9,082,366
Change in unrealized loss on marketable securities	16
Net loss	(14,293)
Ending Balance at Sep. 30, 2017	14,352	$ 12	141,147	(3)	(126,804)
Ending Balance, shares at Sep. 30, 2017		11,750,744
Beginning Balance at Mar. 31, 2017	18,036	$ 9	134,885	(9)	(116,849)
Beginning Balance, shares at Mar. 31, 2017		9,172,868
Issuance of common stock for cash, net of offering costs	2,110	$ 1	2,109
Issuance of common stock for cash, net of offering costs, shares		934,214
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		9,504
Share-based compensation	119		119
Change in unrealized loss on marketable securities	4			4
Net loss	(5,522)				(5,522)
Ending Balance at Jun. 30, 2017	14,747	$ 10	137,113	(5)	(122,371)
Ending Balance, shares at Jun. 30, 2017		10,116,586
Issuance of common stock for cash, net of offering costs	3,917	$ 2	3,915
Issuance of common stock for cash, net of offering costs, shares		1,634,158
Share-based compensation	119		119
Change in unrealized loss on marketable securities	2			2
Net loss	(4,433)				(4,433)
Ending Balance at Sep. 30, 2017	14,352	$ 12	141,147	(3)	(126,804)
Ending Balance, shares at Sep. 30, 2017		11,750,744
Issuance of common stock for cash, net of offering costs, shares		24,085
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		233
Share-based compensation	119		119
Change in unrealized loss on marketable securities	1			1
Net loss	(4,197)				(4,197)
Ending Balance at Dec. 31, 2017	$ 10,275	$ 12	141,266	(2)	(131,001)
Ending Balance, shares at Dec. 31, 2017	11,775,062	11,775,062
Issuance of common stock for cash, net of offering costs	$ 3,415	$ 2	3,413
Issuance of common stock for cash, net of offering costs, shares		2,133,828
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		5,430
Share-based compensation	97		97
Change in unrealized loss on marketable securities	2			2
Net loss	(2,735)				(2,735)
Ending Balance at Mar. 31, 2018	11,054	$ 14	144,776		(133,736)
Ending Balance, shares at Mar. 31, 2018		13,914,320
Beginning Balance at Dec. 31, 2017	$ 10,275	$ 12	141,266	(2)	(131,001)
Beginning Balance, shares at Dec. 31, 2017	11,775,062	11,775,062
Change in unrealized loss on marketable securities	$ 2
Net loss	(6,444)
Ending Balance at Sep. 30, 2018	$ 7,463	$ 14	144,894		(137,445)
Ending Balance, shares at Sep. 30, 2018	13,923,825	13,923,825
Beginning Balance at Mar. 31, 2018	$ 11,054	$ 14	144,776		(133,736)
Beginning Balance, shares at Mar. 31, 2018		13,914,320
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		9,505
Share-based compensation	60		60
Net loss	(2,116)				(2,116)
Ending Balance at Jun. 30, 2018	8,998	$ 14	144,836		(135,852)
Ending Balance, shares at Jun. 30, 2018		13,923,825
Share-based compensation	58		58
Net loss	(1,593)				(1,593)
Ending Balance at Sep. 30, 2018	$ 7,463	$ 14	$ 144,894		$ (137,445)
Ending Balance, shares at Sep. 30, 2018	13,923,825	13,923,825

STATEMENTS OF CASH FLOWS (Unaud

STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (6,444)	$ (14,293)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation	17	21
Amortization of other assets		269
Amortization of premiums and discounts on marketable securities	2	109
Share-based compensation	215	339
Change in operating assets and liabilities:
Other current assets	522	186
Accounts payable	(405)	29
Accrued compensation and employee benefits	(573)	(526)
Accrued expenses and other liabilities	(235)	590
Net cash used in operating activities	(6,901)	(13,276)
Cash flows from investing activities:
Purchases of property and equipment	(4)	(2)
Purchases of marketable securities		(5,471)
Proceeds from maturities of marketable securities	3,050	13,650
Net cash provided by investing activities	3,046	8,177
Cash flows from financing activities:
Proceeds from the issuance of common stock	3,532	6,515
Common stock offering costs	(117)	(419)
Repayment of principal on vendor finance agreement	(206)	(256)
Net cash provided by financing activities	3,209	5,840
Net (decrease) increase in cash and cash equivalents	(646)	741
Cash and cash equivalents, beginning of period	8,702	7,401
Cash and cash equivalents, end of period	8,056	8,142
Supplemental cash flow information:
Interest paid	6	6
Income tax refund received	31
Supplemental disclosure of noncash investing and financing transactions:
Vendor finance agreement	105
Change in unrealized loss on marketable securities	$ 2	$ 16

The Company and Summary of Sign

The Company and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
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 biopharmaceutical company applying a precision medicine approach to developing genetically-targeted therapies for cardiovascular diseases. The Company’s lead product candidate, Gencaro™ (bucindolol hydrochloride), is an investigational, pharmacologically unique beta-blocker and mild vasodilator that ARCA is developing for the potential treatment of heart failure (HF) patients at risk for atrial fibrillation (AF). In February 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 patients with heart failure with reduced left ventricular ejection fraction (HFrEF) and mid-range left ventricle ejection fraction (HFmrEF) against an active comparator, the beta-blocker TOPROL-XL (metoprolol succinate), a drug indicated for treating HFrEF that is also prescribed, but not approved, for treating AF in patients with HFrEF. Enrollment in GENETIC-AF was limited to patients that possess the specific genotype that the Company believes enhances Gencaro’s potential therapeutic effects. The planned development program of Gencaro is, in part, based on the results of our 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. GENETIC-AF was a Phase 2B, multi-center, randomized, double-blind, clinical superiority trial comparing the safety and efficacy of Gencaro against TOPROL-XL, that enrolled 267 patients. The Company reported top-line Phase 2B trial data in February 2018. Overall, Gencaro demonstrated a similar treatment benefit compared to the active comparator, metoprolol succinate; however, trends for benefit in favor of bucindolol were observed in multiple subpopulations of patients in the trial. Based on these data, the Company believes further clinical development of Gencaro is warranted. In July 2018, the Company received guidance from the U.S. Food and Drug Administration (FDA) following an End-of-Phase 2 meeting regarding the Phase 3 program for Gencaro as a potential genetically-targeted treatment for AF patients with HF with a specific genotype. Based on review of the Phase 2 GENETIC-AF 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. The Company, in consultation with the FDA, developed key elements of the Phase 3 clinical trial needed to support a potential New Drug Application (NDA), details of which were submitted for evaluation and confirmation via the FDA’s Special Protocol Assessment (SPA) process. In late October 2018, the Company received a No Agreement letter from the FDA on its SPA. After further correspondence and following provision of information regarding the SPA, the FDA has agreed to reconsider the SPA request. To facilitate this process, the Company has requested a meeting with the FDA, which, if granted, is expected to occur in December 2018. At this time, the Company does not know when the FDA will provide a further decision on its SPA request. During 2018, ARCA initiated Investigational New Drug enabling development activities with AB171, a thiol-substituted isosorbide mononitrate, as a potential genetically-targeted treatment for peripheral arterial disease and for HF. 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, through the end of the first quarter of 2019. 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 could delay or cancel certain planned expenditures related to its drug development programs and/or implement 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. On April 11, 2018, the Company received notification from Nasdaq of potential delisting of its shares from the Nasdaq Capital Market because the closing bid price of its common stock had not met the minimum closing bid price of $1.00 per share during the preceding 30 days. On October 9, 2018, ARCA received a written notification from NASDAQ granting an additional 180 calendar day period, until April 8, 2019, to regain compliance with the minimum bid price requirement. The minimum bid price requirement will be met if the Common Stock has a closing bid of at least $1.00 per share for a minimum of 10 consecutive business days during the 180 day period. If the Company is not able to regain compliance with the closing bid requirement in such period, the Company may be subject to delisting from the Nasdaq Capital Market. If delisted, it could substantially impact the Company’s access to the capital markets, and any limitation on market liquidity or reduction in the price of the common stock as a result of that delisting could adversely affect the Company’s ability to raise capital on acceptable terms, or at all. On October 18, 2018, the Company held a special meeting of its stockholders, at which stockholders authorized the Company’s board of directors to amend the Company’s restated certificate of incorporation, as amended, to effect a reverse split of the Company’s outstanding common stock, if, in the judgment of the Company’s board of directors, it is deemed necessary to maintain NASDAQ compliance or for other reasons. The Company’s board of directors has not selected a ratio for the reverse split. Basis of Presentation The accompanying unaudited financial statements of the Company were prepared in accordance with generally accepted accounting principles for interim financial information and instructions to Form 10-Q and pursuant to Regulation S-X. Accordingly, these financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America (GAAP) for complete financial statements. In the opinion of management, these financial statements include all normal and recurring adjustments considered necessary for a fair presentation of these interim financial statements. The results of operations for the nine months ended September 30, 2018 are not necessarily indicative of results expected for the full year ending December 31, 2018. The Company has generated no revenue to date and its activities have consisted of seeking regulatory approval, research and development, exploring strategic alternatives for further developing and commercializing Gencaro, and raising capital. These unaudited financial statements should be read in conjunction with the audited financial statements and footnotes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission. Amounts presented are rounded to the nearest thousand, where indicated, except per share data and par values. 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. Accrued Expenses As part of the process of preparing its financial statements, the Company is required to estimate accrued 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 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 professional service fees, such as attorneys, consultants, and clinical research organizations. The Company develops estimates of liabilities using its judgment based upon the facts and circumstances known at the time. Recent Accounting Pronouncements In January 2016, Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) In July 2018, FASB issued ASU No. 2018‑11, Topic 842 - Targeted Improvements . The update requires modified retrospective transition, with the option to initially apply the new standard at the adoption date and recognize a cumulative-effect adjustment and elect various practical expedients. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification requirements under Regulation S-K and Regulation S-X under the Securities Exchange Act of 1934, as amended, on the analy

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Loss Per Share	(2) Net Loss Per Share The Company calculates basic earnings per share by dividing net loss by the weighted average common shares outstanding during the period. Diluted earnings 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, restricted stock units and warrants for common stock . Because the Company reported a net loss for the three and nine months ended September 30, 2018 and 2017, all potentially dilutive shares of common stock have been excluded from the computation of the dilutive net loss per share for all periods presented. September 30, 2018 2017 Potentially dilutive securities, excluded: Outstanding stock options 604,265 820,587 Unvested restricted stock units 233 15,401 Warrants to purchase common stock 2,669,855 3,656,978 3,274,353 4,492,966

Marketable Securities and Fair

Marketable Securities and Fair Value Disclosures	9 Months Ended
	Sep. 30, 2018
Marketable Securities And Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value Disclosures	(3) Marketable Securities and Fair Value Disclosures There were no marketable securities as of September 30, 2018. Marketable securities consisted of the following as of December 31, 2017 (in thousands): December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Short-term available-for-sale securities: Corporate bonds $ 3,052 $ — $ (2 ) $ 3,050 Total $ 3,052 $ — $ (2 ) $ 3,050 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. The following table identifies the Company’s assets that were measured at fair value on a recurring basis (in thousands): Balance Level 1 Level 2 Level 3 September 30, 2018 Money market $ 8,078 $ 8,078 $ — $ — Total $ 8,078 $ 8,078 $ — $ — December 31, 2017 Money market $ 8,189 $ 8,189 $ — $ — Corporate bonds 3,725 — 3,725 — Total $ 11,914 $ 8,189 $ 3,725 $ — As of September 30, 2018 and December 31, 2017, the Company had $8.1 million and $8.9 million, respectively, of cash equivalents consisting of money market funds and commercial paper 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 and equity securities with Level 1 inputs through quoted market prices. There were no transfers of assets between fair value hierarchy levels during the nine-month period ended September 30, 2018. Fair Value of Other Financial Instruments The carrying amount of other financial instruments, including accounts payable and notes payable approximated fair value due to their short maturities.

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Property and Equipment	(4) Property and Equipment Property and equipment consist of the following (in thousands): Estimated Life September 30, 2018 December 31, 2017 Computer equipment 3 years $ 65 $ 74 Lab equipment 5 years 142 142 Furniture and fixtures 5 years 83 83 Computer software 3 years 83 85 Leasehold improvements Lesser of useful life or life of the lease 59 59 432 443 Accumulated depreciation and amortization (403 ) (401 ) Property and equipment, net $ 29 $ 42 For the nine months ended September 30, 2018 and 2017, depreciation and amortization expense was $17,000 and $21,000, respectively.

Related Party Arrangements

Related Party Arrangements	9 Months Ended
	Sep. 30, 2018
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 nine months ended September 30, 2018 and 2017 was $274,000 and $301,000 respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
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 the 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. Below is a summary of the future minimum lease payments committed for the Company’s facility in Westminster, Colorado as of September 30, 2018 (in thousands): Remainder of 2018 $ 22 2019 83 Total future minimum lease payments $ 105 Rent expense for the nine months ended September 30, 2018 and 2017 was $62,000 and $62,000, respectively. 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 bought 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, discussed above. The acquisition cost of this interest did not have a material impact on the Company’s financial statements.

Equity Financings and Warrants

Equity Financings and Warrants	9 Months Ended
	Sep. 30, 2018
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 this Sales Agreement, the Company sold an aggregate of 4,811,353 shares of Common Stock pursuant to the terms of such Sales Agreement, as amended, for aggregate gross proceeds of approximately $10.1 million and net proceeds received were approximately $9.5 million, including initial expenses for executing the “at the market offering” and commissions to the placement agent. As of September 30, 2018, 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 previously 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 September 30, 2018, these warrants, by year of expiration, are summarized below: Year of Expiration Number of Warrants Weighted Average Exercise Price 2019 224,323 $ 15.73 2020 44,299 15.96 2022 2,401,233 6.10 2,669,855 $ 7.07

Share-based Compensation

Share-based Compensation	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-based Compensation	(8) Share-based Compensation For the three and nine month periods ended September 30, 2018 and 2017, the Company recognized the following non-cash, share-based compensation expense in the statements of operations (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Research and development $ 26 $ 44 $ 92 $ 124 General and administrative 32 75 123 215 Total $ 58 $ 119 $ 215 $ 339 Stock option transactions for the nine month period ended September 30, 2018 under the Company’s stock incentive plans were as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Options outstanding at December 31, 2017 611,975 $ 6.00 8.14 Granted 40,000 0.72 Exercised — — Forfeited and cancelled (47,710 ) 8.37 Options outstanding at September 30, 2018 604,265 $ 5.47 7.54 Options exercisable at September 30, 2018 447,317 $ 6.50 7.29 Options vested and expected to vest 604,014 $ 5.47 7.54 Stock award transactions related to restricted stock units for the nine month period ended September 30, 2018 under the Company’s stock incentive plans were as follows: Number of Shares Weighted Average Grant Date Fair Value Restricted stock units outstanding at December 31, 2017 15,168 $ 7.94 Granted — — Vested and released (14,935 ) 7.98 Forfeited and cancelled — — Restricted stock units outstanding at September 30, 2018 233 $ 5.23

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	(9) Income Taxes In accordance with GAAP, a valuation allowance should be provided if it is more likely than not that some or all of the Company’s deferred tax assets will not be realized. The Company’s ability to realize the benefit of its deferred tax assets will depend on the generation of future taxable income. Due to the uncertainty of future profitable operations and taxable income, the Company has recorded a full valuation allowance against its net deferred tax assets. The Company believes its tax filing positions and deductions related to tax periods subject to examination will be sustained upon audit and, therefore, has no reserve for uncertain tax positions. Income tax benefit of $31,000 for the nine months ended September 30, 2018 was related to a federal research and experimentation income tax credit related to the Protecting Americans from Tax Hikes Act of 2015 (PATH Act) which allows qualified small businesses to monetize up to $250,000 of research and experimentation tax credits through payroll tax refunds. The PATH Act refunds were not effective until 2017.

The Company and Summary of Si_2

The Company and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
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 biopharmaceutical company applying a precision medicine approach to developing genetically-targeted therapies for cardiovascular diseases. The Company’s lead product candidate, Gencaro™ (bucindolol hydrochloride), is an investigational, pharmacologically unique beta-blocker and mild vasodilator that ARCA is developing for the potential treatment of heart failure (HF) patients at risk for atrial fibrillation (AF). In February 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 patients with heart failure with reduced left ventricular ejection fraction (HFrEF) and mid-range left ventricle ejection fraction (HFmrEF) against an active comparator, the beta-blocker TOPROL-XL (metoprolol succinate), a drug indicated for treating HFrEF that is also prescribed, but not approved, for treating AF in patients with HFrEF. Enrollment in GENETIC-AF was limited to patients that possess the specific genotype that the Company believes enhances Gencaro’s potential therapeutic effects. The planned development program of Gencaro is, in part, based on the results of our 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. GENETIC-AF was a Phase 2B, multi-center, randomized, double-blind, clinical superiority trial comparing the safety and efficacy of Gencaro against TOPROL-XL, that enrolled 267 patients. The Company reported top-line Phase 2B trial data in February 2018. Overall, Gencaro demonstrated a similar treatment benefit compared to the active comparator, metoprolol succinate; however, trends for benefit in favor of bucindolol were observed in multiple subpopulations of patients in the trial. Based on these data, the Company believes further clinical development of Gencaro is warranted. In July 2018, the Company received guidance from the U.S. Food and Drug Administration (FDA) following an End-of-Phase 2 meeting regarding the Phase 3 program for Gencaro as a potential genetically-targeted treatment for AF patients with HF with a specific genotype. Based on review of the Phase 2 GENETIC-AF 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. The Company, in consultation with the FDA, developed key elements of the Phase 3 clinical trial needed to support a potential New Drug Application (NDA), details of which were submitted for evaluation and confirmation via the FDA’s Special Protocol Assessment (SPA) process. In late October 2018, the Company received a No Agreement letter from the FDA on its SPA. After further correspondence and following provision of information regarding the SPA, the FDA has agreed to reconsider the SPA request. To facilitate this process, the Company has requested a meeting with the FDA, which, if granted, is expected to occur in December 2018. At this time, the Company does not know when the FDA will provide a further decision on its SPA request. During 2018, ARCA initiated Investigational New Drug enabling development activities with AB171, a thiol-substituted isosorbide mononitrate, as a potential genetically-targeted treatment for peripheral arterial disease and for HF. 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, through the end of the first quarter of 2019. 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 could delay or cancel certain planned expenditures related to its drug development programs and/or implement 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. On April 11, 2018, the Company received notification from Nasdaq of potential delisting of its shares from the Nasdaq Capital Market because the closing bid price of its common stock had not met the minimum closing bid price of $1.00 per share during the preceding 30 days. On October 9, 2018, ARCA received a written notification from NASDAQ granting an additional 180 calendar day period, until April 8, 2019, to regain compliance with the minimum bid price requirement. The minimum bid price requirement will be met if the Common Stock has a closing bid of at least $1.00 per share for a minimum of 10 consecutive business days during the 180 day period. If the Company is not able to regain compliance with the closing bid requirement in such period, the Company may be subject to delisting from the Nasdaq Capital Market. If delisted, it could substantially impact the Company’s access to the capital markets, and any limitation on market liquidity or reduction in the price of the common stock as a result of that delisting could adversely affect the Company’s ability to raise capital on acceptable terms, or at all. On October 18, 2018, the Company held a special meeting of its stockholders, at which stockholders authorized the Company’s board of directors to amend the Company’s restated certificate of incorporation, as amended, to effect a reverse split of the Company’s outstanding common stock, if, in the judgment of the Company’s board of directors, it is deemed necessary to maintain NASDAQ compliance or for other reasons. The Company’s board of directors has not selected a ratio for the reverse split.
Basis of Presentation	Basis of Presentation The accompanying unaudited financial statements of the Company were prepared in accordance with generally accepted accounting principles for interim financial information and instructions to Form 10-Q and pursuant to Regulation S-X. Accordingly, these financial statements do not include all of the information and footnotes required by accounting principles generally accepted in the United States of America (GAAP) for complete financial statements. In the opinion of management, these financial statements include all normal and recurring adjustments considered necessary for a fair presentation of these interim financial statements. The results of operations for the nine months ended September 30, 2018 are not necessarily indicative of results expected for the full year ending December 31, 2018. The Company has generated no revenue to date and its activities have consisted of seeking regulatory approval, research and development, exploring strategic alternatives for further developing and commercializing Gencaro, and raising capital. These unaudited financial statements should be read in conjunction with the audited financial statements and footnotes thereto for the year ended December 31, 2017 included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission. Amounts presented are rounded to the nearest thousand, where indicated, except per share data and par values.
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.
Accrued Expenses	Accrued Expenses As part of the process of preparing its financial statements, the Company is required to estimate accrued 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 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 professional service fees, such as attorneys, consultants, and clinical research organizations. The Company develops estimates of liabilities using its judgment based upon the facts and circumstances known at the time.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In January 2016, Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) In July 2018, FASB issued ASU No. 2018‑11, Topic 842 - Targeted Improvements . The update requires modified retrospective transition, with the option to initially apply the new standard at the adoption date and recognize a cumulative-effect adjustment and elect various practical expedients. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification requirements under Regulation S-K and Regulation S-X under the Securities Exchange Act of 1934, as amended, on the analy

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Summary of Potentially Dilutive Shares of Common Stock	Because the Company reported a net loss for the three and nine months ended September 30, 2018 and 2017, all potentially dilutive shares of common stock have been excluded from the computation of the dilutive net loss per share for all periods presented. September 30, 2018 2017 Potentially dilutive securities, excluded: Outstanding stock options 604,265 820,587 Unvested restricted stock units 233 15,401 Warrants to purchase common stock 2,669,855 3,656,978 3,274,353 4,492,966

Marketable Securities and Fai_2

Marketable Securities and Fair Value Disclosures (Tables)	9 Months Ended
	Sep. 30, 2018
Marketable Securities And Fair Value Disclosures [Abstract]
Summary of Marketable Securities	Marketable securities consisted of the following as of December 31, 2017 (in thousands): December 31, 2017 Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value Short-term available-for-sale securities: Corporate bonds $ 3,052 $ — $ (2 ) $ 3,050 Total $ 3,052 $ — $ (2 ) $ 3,050
Summary of Assets Measured at Fair Value on Recurring Basis	The following table identifies the Company’s assets that were measured at fair value on a recurring basis (in thousands): Balance Level 1 Level 2 Level 3 September 30, 2018 Money market $ 8,078 $ 8,078 $ — $ — Total $ 8,078 $ 8,078 $ — $ — December 31, 2017 Money market $ 8,189 $ 8,189 $ — $ — Corporate bonds 3,725 — 3,725 — Total $ 11,914 $ 8,189 $ 3,725 $ —

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2018
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	Property and equipment consist of the following (in thousands): Estimated Life September 30, 2018 December 31, 2017 Computer equipment 3 years $ 65 $ 74 Lab equipment 5 years 142 142 Furniture and fixtures 5 years 83 83 Computer software 3 years 83 85 Leasehold improvements Lesser of useful life or life of the lease 59 59 432 443 Accumulated depreciation and amortization (403 ) (401 ) Property and equipment, net $ 29 $ 42

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Future Minimum Lease Payments	Below is a summary of the future minimum lease payments committed for the Company’s facility in Westminster, Colorado as of September 30, 2018 (in thousands): Remainder of 2018 $ 22 2019 83 Total future minimum lease payments $ 105

Equity Financings and Warrants

Equity Financings and Warrants (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Summary of Warrants by Year of Expiration	As of September 30, 2018, these warrants, by year of expiration, are summarized below: Year of Expiration Number of Warrants Weighted Average Exercise Price 2019 224,323 $ 15.73 2020 44,299 15.96 2022 2,401,233 6.10 2,669,855 $ 7.07

Share-based Compensation (Table

Share-based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Non-cash, Share-based Compensation Expense	For the three and nine month periods ended September 30, 2018 and 2017, the Company recognized the following non-cash, share-based compensation expense in the statements of operations (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Research and development $ 26 $ 44 $ 92 $ 124 General and administrative 32 75 123 215 Total $ 58 $ 119 $ 215 $ 339
Summary of Stock Option Activities	Stock option transactions for the nine month period ended September 30, 2018 under the Company’s stock incentive plans were as follows: Number of Options Weighted Average Exercise Price Weighted Average Remaining Contractual Term (in years) Options outstanding at December 31, 2017 611,975 $ 6.00 8.14 Granted 40,000 0.72 Exercised — — Forfeited and cancelled (47,710 ) 8.37 Options outstanding at September 30, 2018 604,265 $ 5.47 7.54 Options exercisable at September 30, 2018 447,317 $ 6.50 7.29 Options vested and expected to vest 604,014 $ 5.47 7.54
Summary of RSU Activity	Stock award transactions related to restricted stock units for the nine month period ended September 30, 2018 under the Company’s stock incentive plans were as follows: Number of Shares Weighted Average Grant Date Fair Value Restricted stock units outstanding at December 31, 2017 15,168 $ 7.94 Granted — — Vested and released (14,935 ) 7.98 Forfeited and cancelled — — Restricted stock units outstanding at September 30, 2018 233 $ 5.23

The Company and Summary of Si_3

The Company and Summary of Significant Accounting Policies (Details Textual)	Oct. 09, 2018$ / shares	Apr. 11, 2018$ / shares	Sep. 30, 2018USD ($)Patients
Company And Summary Of Significant Accounting Policies Table [Line Items]
Revenues | $			$ 0
Concentrations of credit risk | $			$ 0
Nasdaq Capital Market
Company And Summary Of Significant Accounting Policies Table [Line Items]
Common stock not met minimum closing bid price, preceding days		30 days
Common stock bid price, description			On April 11, 2018, the Company received notification from Nasdaq of potential delisting of its shares from the Nasdaq Capital Market because the closing bid price of its common stock had not met the minimum closing bid price of $1.00 per share during the preceding 30 days. On October 9, 2018, ARCA received a written notification from NASDAQ granting an additional 180 calendar day period, until April 8, 2019, to regain compliance with the minimum bid price requirement. The minimum bid price requirement will be met if the Common Stock has a closing bid of at least $1.00 per share for a minimum of 10 consecutive business days during the 180 day period.
Nasdaq Capital Market | Minimum
Company And Summary Of Significant Accounting Policies Table [Line Items]
Minimum closing bid price | $ / shares		$ 1
Nasdaq Capital Market | Subsequent Event
Company And Summary Of Significant Accounting Policies Table [Line Items]
Minimum consecutive business days	10 days
Additional granted days for common stock to meet minimum bid price	180 days
Nasdaq Capital Market | Subsequent Event | Minimum
Company And Summary Of Significant Accounting Policies Table [Line Items]
Minimum closing bid price | $ / shares	$ 1
Phase 2B | GENETIC-AF Trial
Company And Summary Of Significant Accounting Policies Table [Line Items]
Number of patients enrolled | Patients			267

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Potentially Dilutive Shares of Common Stock (Details) - shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	3,274,353	4,492,966
Outstanding stock options
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	604,265	820,587
Unvested restricted stock units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	233	15,401
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	2,669,855	3,656,978

Marketable Securities and Fai_3

Marketable Securities and Fair Value Disclosures (Details Textual) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 0
Transfers of assets between fair value hierarchy levels	0
Fair Value Measurements, Recurring | Level 1 | Money Market Funds | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents consisting of money market funds and commercial paper	$ 8,100,000	$ 8,900,000

Marketable Securities and Fai_4

Marketable Securities and Fair Value Disclosures - Summary of Marketable securities (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 0
Short-term available-for-sale securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 3,052,000
Gross Unrealized Losses		(2,000)
Fair Value		3,050,000
Short-term available-for-sale securities | Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		3,052,000
Gross Unrealized Losses		(2,000)
Fair Value		$ 3,050,000

Marketable Securities and Fai_5

Marketable Securities and Fair Value Disclosures - Summary of Assets Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 8,078	$ 11,914
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		3,725
Money market
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	8,078	8,189
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	8,078	8,189
Level 1 | Money market
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value	$ 8,078	8,189
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		3,725
Level 2 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets measured at fair value		$ 3,725

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and Equipment, Gross	$ 432	$ 443
Accumulated depreciation and amortization	(403)	(401)
Property and equipment, net	$ 29	42
Computer Equipment
Property Plant And Equipment [Line Items]
Estimated Life	3 years
Property and Equipment, Gross	$ 65	74
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	$ 83	83
Computer Software
Property Plant And Equipment [Line Items]
Estimated Life	3 years
Property and Equipment, Gross	$ 83	85
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	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	$ 17	$ 21

Related Party Arrangements (Det

Related Party Arrangements (Details Textual) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Chief Executive Officer | Research Grants
Related Party Transaction [Line Items]
Total expense	$ 274	$ 301

Commitments and Contingencies_2

Commitments and Contingencies (Details Textual) $ in Thousands	Mar. 02, 2016	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Aug. 01, 2013ft²
Commitments And Contingencies [Line Items]
Area of office facilities taken on lease | ft²				5,300
Additional operating lease term	38 months
Lease renewal start date	Oct. 1, 2016
Lease expiration date	Nov. 30, 2019
Rent expense		$ 62	$ 62
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%

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Lease Payments (Details) $ in Thousands	Sep. 30, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
Remainder of 2018	$ 22
2,019	83
Total future minimum lease payments	$ 105

Equity Financings and Warrant_2

Equity Financings and Warrants (Details Textual) - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Aug. 21, 2017	Jan. 11, 2017
Equity Financing And Warrants [Line Items]
Common stock, par value	$ 0.001		$ 0.001
Common stock, shares issued	13,923,825		11,775,062
Proceeds from the issuance of common stock	$ 3,532,000	$ 6,515,000
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	4,811,353
Proceeds from the issuance of common stock	$ 10,100,000
Net proceeds from issuance of common stock	$ 9,500,000
Sales Agreement | JonesTrading
Equity Financing And Warrants [Line Items]
Common stock, par value					$ 0.001
Aggregate offering price of common stock authorized				$ 10,200,000	$ 7,300,000

Equity Financings and Warrant_3

Equity Financings and Warrants - Summary of Warrants by Year of Expiration (Details)	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Class Of Warrant Or Right [Line Items]
Number of Warrants | shares	2,669,855
Weighted Average Exercise Price | $ / shares	$ 7.07
2,019
Class Of Warrant Or Right [Line Items]
Year of Expiration	2,019
Number of Warrants | shares	224,323
Weighted Average Exercise Price | $ / shares	$ 15.73
2,020
Class Of Warrant Or Right [Line Items]
Year of Expiration	2,020
Number of Warrants | shares	44,299
Weighted Average Exercise Price | $ / shares	$ 15.96
2,022
Class Of Warrant Or Right [Line Items]
Year of Expiration	2,022
Number of Warrants | shares	2,401,233
Weighted Average Exercise Price | $ / shares	$ 6.10

Share-based Compensation - Summ

Share-based Compensation - Summary of Non-cash, Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	$ 58	$ 119	$ 215	$ 339
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	26	44	92	124
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total expenses	$ 32	$ 75	$ 123	$ 215

Share-based Compensation - Su_2

Share-based Compensation - Summary of Stock Option Activities (Details) - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Number of Stock Options
Number of Options, Options outstanding, beginning of period	611,975
Number of Options, Granted	40,000
Number of Options, Forfeited and cancelled	(47,710)
Number of Options, Options outstanding, end of period	604,265	611,975
Number of Options, Options exercisable, end of period	447,317
Number of Options, Options vested and expected to vest	604,014
Stock Options, Weighted Average Exercise Price
Weighted Average Exercise Price, Options outstanding, beginning of period	$ 6
Weighted Average Exercise Price, Granted	0.72
Weighted Average Exercise Price, Forfeited and cancelled	8.37
Weighted Average Exercise Price, Options outstanding, end of period	5.47	$ 6
Weighted Average Exercise Price, Options exercisable, end of period	6.50
Weighted Average Exercise Price, Options vested and expected to vest, end of period	$ 5.47
Stock Options, Weighted Average Remaining Contractual Term
Weighted Average Remaining Contractual Term (in years), Options outstanding	7 years 6 months 14 days	8 years 1 month 20 days
Weighted Average Remaining Contractual Term (in years), Options exercisable	7 years 3 months 14 days
Weighted Average Remaining Contractual Term (in years), Options vested and expected to vest	7 years 6 months 14 days

Share-based Compensation - Su_3

Share-based Compensation - Summary of RSU Activity (Details)	9 Months Ended
	Sep. 30, 2018$ / sharesshares
Restricted Stock Awards, Number of Shares
Restricted stock units outstanding, beginning of period | shares	15,168
Vested and released | shares	(14,935)
Restricted stock units outstanding, end of period | shares	233
Restricted Stock Awards, Weighted Average Grant Date Fair Value
Restricted stock units outstanding, beginning of period | $ / shares	$ 7.94
Vested and released | $ / shares	7.98
Restricted stock units outstanding, end of period | $ / shares	$ 5.23

Income Taxes (Details Textual)

Income Taxes (Details Textual)	3 Months Ended	9 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2018USD ($)
Income Tax [Line Items]
Reserve for uncertain tax positions	$ 0	$ 0
Income tax benefit	31,000	31,000
Research Tax Credit Carryforward | Federal | Protecting Americans from Tax Hikes Act of 2015
Income Tax [Line Items]
Income tax benefit		31,000
Research Tax Credit Carryforward | Federal | Protecting Americans from Tax Hikes Act of 2015 | Maximum
Income Tax [Line Items]
Research and experimentation credits	$ 250,000	$ 250,000