Eloxx Pharmaceuticals (ELOX) 10-K 6 Mar 20 2019 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Mar. 01, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	ELOX
Entity Registrant Name	ELOXX PHARMACEUTICALS, INC.
Entity Central Index Key	0001035354
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		40,118,481
Entity Public Float			$ 268,970,171
Entity Small Business	true
Entity Emerging Growth Company	false
Entity File Number	001-31326
Entity Tax Identification Number	84-1368850
Entity Address, Address Line One	950 Winter Street
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02451
City Area Code	781
Local Phone Number	577-5300
Entity Shell Company	false
Document Annual Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, $0.01 par value
Security Exchange Name	NASDAQ
Entity Interactive Data Current	Yes
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Certain information required by Part III, Items 10-14 of this Form 10-K is incorporated by reference to the Registrant’s definitive Proxy Statement for the 2020 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this Form 10-K, provided that if such Proxy Statement is not filed within such period, such information will be included in an amendment to this Form 10-K to be filed within such 120-day period.

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 22,493	$ 48,606
Marketable securities	33,783
Restricted cash	43	45
Prepaid expenses and other current assets	1,390	1,690
Total current assets	57,709	50,341
Property and equipment, net	201	248
Operating lease right-of-use asset	924
Other long-term assets	113	129
Total assets	58,947	50,718
Current liabilities
Accounts payable	1,871	747
Accrued expenses	4,655	6,938
Current portion of long-term debt	4,336
Advances from collaboration partners	403
Current portion of operating lease liability	499
Taxes payable	43	122
Total current liabilities	11,807	7,807
Long-term debt	10,502
Operating lease liability	425
Total liabilities	22,734	7,807
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value per share, 5,000,000 authorized, no shares issued or outstanding as of December 31, 2019 and 2018, respectively
Common stock, $0.01 par value per share, 500,000,000 shares authorized, 40,186,469 and 35,951,537 shares issued and 40,030,763 and 35,860,114 shares outstanding as of December 31, 2019 and 2018, respectively	402	360
Common stock in treasury, at cost, 155,706 and 91,423 shares as of December 31, 2019 and 2018, respectively	(1,703)	(1,129)
Additional paid-in capital	174,515	129,825
Accumulated other comprehensive income	18
Accumulated deficit	(137,019)	(86,145)
Total stockholders’ equity	36,213	42,911
Total liabilities and stockholders’ equity	$ 58,947	$ 50,718

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred Stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	40,186,469	35,951,537
Common stock, shares outstanding	40,030,763	35,860,114
Common stock, treasury shares	155,706	91,423

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($)		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating expenses:
Research and development, net		$ 25,842,000	$ 20,489,000	$ 16,398,000
General and administrative		24,713,000	26,482,000	2,702,000
Reverse merger related expenses			594,000	1,290,000
Total operating expenses		50,555,000	47,565,000	20,390,000
Loss from operations		(50,555,000)	(47,565,000)	(20,390,000)
Other (income) expense, net		319,000	(502,000)	824,000
Loss before income taxes		(50,874,000)	(47,063,000)	(21,214,000)
Provision for income taxes		0	122,000
Net loss		(50,874,000)	(47,185,000)	(21,214,000)
Less: dividends accumulated for the period	[1]			(2,404,000)
Net loss attributable to common stockholders		$ (50,874,000)	$ (47,185,000)	$ (23,618,000)
Net loss per share, basic and diluted		$ (1.34)	$ (1.45)	$ (4.75)
Weighted average number of shares of common stock used in computing net loss per share, basic and diluted		38,063,173	32,436,506	4,976,377
Comprehensive loss:
Net loss attributable to common stockholders		$ (50,874,000)	$ (47,185,000)	$ (23,618,000)
Other comprehensive gain (loss):
Unrealized gain (loss) from available-for-sale securities		18,000
Comprehensive loss		$ (50,856,000)	$ (47,185,000)	$ (23,618,000)
[1]	The net loss used for the computation of basic and diluted net loss per share includes 8% per share per annum compounded annually which was related to distributions for preferred stockholders of Eloxx Limited. On December 19, 2017 in conjunction with the Reverse Merger, all preferred shares were converted to common shares.

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	Public Offering [Member]	At-the-market Sale Agreement [Member]	Series C Preferred Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member]Series C Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member]Public Offering [Member]	Common Stock [Member]At-the-market Sale Agreement [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]Public Offering [Member]	Additional Paid-in Capital [Member]At-the-market Sale Agreement [Member]	Additional Paid-in Capital [Member]Series C Preferred Stock [Member]	Accumulated Other Comprehensive Income [Member]	Treasury stock [Member]	Accumulated deficit [Member]
Balance at Dec. 31, 2016	$ 610				$ 76		$ 42			$ 18,238						$ (17,746)
Balance, shares at Dec. 31, 2016					7,638,263		4,205,278
Issuance of stock	17,006			$ 18,427		$ 63	$ 63			16,943			$ 18,364
Issuance of stock, shares						6,311,076	6,333,333
Conversion of convertible loan into Series C preferred stock				$ 3,168		$ 8							$ 3,160
Conversion of convertible loan into Series C preferred stock, shares						825,213
Exercise of options into Common Stock	17									17
Exercise of options into Common Stock, shares							16,699
Stock-based compensation expense	101									101
Conversion of Series A, B-1, B-2 and C preferred stock into common stock with respect to the Reverse Merger					$ (147)		$ 147
Conversion of Series A, B-1, B-2 and C preferred stock into common stock with respect to the Reverse Merger, shares					(14,774,552)		14,774,552
Shares issued with respect to the Reverse Merger	(170)						$ 22			(192)
Shares issued with respect to the Reverse Merger, shares							2,197,876
Provision related to the Technion exit fee	3,416									3,416
Net loss	(21,214)															(21,214)
Balance at Dec. 31, 2017	21,361						$ 274			60,047						(38,960)
Balance, shares at Dec. 31, 2017							27,527,738
Issuance of stock		$ 53,573						$ 60			$ 53,513
Issuance of stock, shares								5,899,500	201,100
Exercise of options into Common Stock	446						$ 14			432
Exercise of options into Common Stock, shares							1,334,522
Issuance of common stock upon Technion settlement							$ 6			(6)
Issuance of common stock Techion settlement, shares							569,395
Issuance of shares upon execution of warrants							$ 1			51					$ (52)
Issuance of shares upon execution of warrants, shares							60,989								(3,385)
Issuance of common stock from at-the-market sales agreement			$ 2,423						$ 2			$ 2,421
Repurchase of common stock	(31)														$ (31)
Repurchase of common stock, shares							(5,076)								(5,000)
Vesting of restricted stock units	(1,046)						$ 3			(3)					$ (1,046)
Vesting of restricted shares, Shares							271,946								(83,038)
Stock-based compensation expense	13,370									13,370
Net loss	(47,185)															(47,185)
Balance at Dec. 31, 2018	$ 42,911						$ 360			129,825					$ (1,129)	(86,145)
Balance, shares at Dec. 31, 2018	35,860,114						35,860,114								(91,423)
Issuance of stock		$ 32,172						$ 38			$ 32,134
Issuance of stock, shares								3,833,334	35,362
Exercise of options into Common Stock	$ 169						$ 1			168
Exercise of options into Common Stock, shares	116,327						116,327
Issuance of shares upon execution of warrants							$ 1			178					$ (179)
Issuance of shares upon execution of warrants, shares							44,814								(14,893)
Issuance of common stock from at-the-market sales agreement			$ 455									$ 455
Issuance of warrants	$ 421									421
Vesting of restricted stock units	(395)						$ 2			(2)					$ (395)
Vesting of restricted shares, Shares							140,812								(49,390)
Stock-based compensation expense	11,336									11,336
Unrealized gain (loss) on investments	18													$ 18
Net loss	(50,874)															(50,874)
Balance at Dec. 31, 2019	$ 36,213						$ 402			$ 174,515				$ 18	$ (1,703)	$ (137,019)
Balance, shares at Dec. 31, 2019	40,030,763						40,030,763								(155,706)

Consolidated Statements of Co_2

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)$ / shares
Issuance expenses	$ 494
Series C Preferred Stock [Member]
Issuance expenses	$ 573
Conversion of convertible preferred stock par value | $ / shares	$ 0.01

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (50,874)	$ (47,185)	$ (21,214)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	11,336	13,370	101
Depreciation	87	216	39
Loss (gain) on sales and disposals of property and equipment	(2)	12
Amortization of operating lease right-of-use asset	472
Amortization of debt discount	535
Amortization of premiums and discounts on investments	(301)
Amortization and revaluation of discount in respect to convertible loan			668
Provision related to the Technion exit fee			3,416
Change in operating assets and liabilities:
Prepaid expenses and other current assets	83	(1,080)	709
Other assets		(41)
Accounts payable	1,124	(780)	(583)
Accrued expenses	(1,300)	3,999	929
Operating lease liabilities	(472)
Taxes payable	(79)	122
Net cash used in operating activities	(39,391)	(31,367)	(15,935)
Cash flows from investing activities:
Purchases of marketable securities	(67,214)
Proceeds from maturity of marketable securities	33,750
Purchase of property and equipment	(40)	(235)	(237)
Proceeds from sales of property and equipment	2	6
Cash paid for long-term deposits	(22)	(88)
Cash received upon the Reverse Merger			123
Net cash used in investing activities	(33,524)	(317)	(114)
Cash flows from financing activities:
Proceeds from issuance of common stock			17,006
Proceeds from debt financing obligation	15,000
Payment of debt issuance costs	(276)
Proceeds from share-based compensation arrangements	169	446	17
Payment for settlement of taxes upon vesting of restricted stock securities	(1,378)
Proceeds from convertible loan and related financial derivative into Series C preferred stock			2,500
Proceeds from advances from collaboration partners	403
Net cash provided by financing activities	46,800	56,184	37,950
(Decrease) increase in cash, cash equivalents and restricted cash	(26,115)	24,500	21,901
Cash, cash equivalents and restricted cash at the beginning of the year	48,651	24,151	2,250
Cash, cash equivalents and restricted cash at the end of the year	22,536	48,651	24,151
Reconciliation of cash, cash equivalents and restricted cash to consolidated balance sheet:
Cash and cash equivalents	22,493	48,606	24,049
Restricted cash	43	45	102
Cash, cash equivalents and restricted cash at the end of the year	22,536	48,651	24,151
Supplemental disclosure of cash flow activities:
Cash paid for interest	986
Cash paid for income taxes, net of refunds received	36
Supplemental disclosure of non-cash financing activities:
Non-cash acquisition of treasury stock		1,129
Non-cash issuance of common stock upon exercise of warrants	179
Fair value of warrants issued in connection with long-term debt	421
Remeasurement of operating leases	176
Conversion of convertible loan into Series C preferred stock			3,168
Proceeds receivable from equity sales agreement		255
Underwritten Public Offering [Member]
Cash flows from financing activities:
Proceeds from issuance of common stock	32,172	53,573
Equity Sales Agreement [Member]
Cash flows from financing activities:
Proceeds from issuance of common stock	$ 710	$ 2,165
Series C Preferred Stock [Member]
Cash flows from financing activities:
Proceeds from issuance of preferred stock			18,427
Supplemental disclosure of non-cash financing activities:
Issuance expenses of Series C Preferred Shares			$ 242

Nature of the Business

Nature of the Business	12 Months Ended
	Dec. 31, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Nature of the Business	1. Nature of the Business Eloxx Pharmaceuticals, Inc., together with its subsidiaries (collectively “Eloxx” or the “Company”), is a clinical-stage biopharmaceutical company developing novel ribonucleic acid (RNA)-modulating drug candidates, each designed to be a eukaryotic ribosomal selective glycoside (ERSG), formulated to treat rare and ultra-rare premature stop codon diseases. Premature stop codons are point mutations that disrupt the stability of the impacted messenger RNA (mRNA) and the protein synthesis from that mRNA. As a consequence, patients with premature stop codon diseases have reduced levels of, or no, protein from a gene whose product performs an essential function. This type of mutation accounts for some of the most severe phenotypes across genetic diseases. Nonsense mutations have been identified in over 1,800 rare and ultra-rare diseases. Read-through therapeutic development is focused on increasing mRNA stability and enabling functional protein synthesis. As opposed to a typical gene therapy approach of targeting a single, unique mutation in a target disease, this small molecule strategy enables targeting an entire class of mutations across the rare disease landscape. The small molecule approach has the potential to address a range of different premature stop codons in a single gene since the ERSG compounds are targeted to the ribosomes. ELX-02, the Company’s lead investigational drug product candidate, is a small molecule designed to restore production of full-length functional proteins. ELX-02 is in clinical development for systemic administration for cystic fibrosis and nephropathic cystinosis. ELX-02 is an investigational drug that has not been approved by any global regulatory body. In addition, during 2019 the Company announced a new program studying intravitreal administration of ERSG compounds for rare inherited retinal disorders (IRDs) with an initial focus on Usher Syndrome. During the year, the Company advanced its clinical program for ELX-02 into Phase 2 studies in cystic fibrosis and nephropathic cystinosis. The Company also completed a renal impairment study with ELX-02 in subjects with mild, moderate, and severe renal impairment. The results from the renal impairment study provide support for both continuing the Company’s clinical development programs and evaluating the suitability of its ERSG library for development in additional renal disorders, including autosomal dominant polycystic kidney disease and cystinuria. The Company’s preclinical candidate pool consists of a library of novel ERSG drug candidates identified based on read-through potential and cytoplasmic ribosomal selectivity. The Company’s research and development strategy is to target rare or ultra-rare diseases where a high unmet medical need exists, a nonsense mutation-bearing patient population is established, preclinical read-through can be established in predictive personalized medicine models, and a defined path through Orphan Drug development, regulatory approval, patient access and commercialization is identified. The Company believes patient advocacy is an important element of patient focused drug development and seeks opportunities to collaborate with patient advocacy groups throughout the discovery and development process. The Company’s current clinical program for its lead investigational drug product candidate, ELX-02, includes studies in both cystic fibrosis and nephropathic cystinosis. During the third quarter of 2019, the Company announced that the Cystic Fibrosis Foundation (the “CF Foundation”) is providing funding for a portion of the U.S. Phase 2 cystic fibrosis clinical trial and that it will form a joint program advisory group with the CF Foundation focused on the development of ELX-02 for cystic fibrosis. The Cystic Fibrosis Therapeutics Development Network (“TDN”) has sanctioned the Phase 2 study protocol, which is being conducted at TDN member sites. Eloxx Pharmaceuticals, Ltd. (“Eloxx Limited”) was incorporated in Israel on September 17, 2013 and acquired by the Company in a reverse merger described below. The Company focuses its activity on the discovery, development and commercialization of compounds for the treatment of genetic diseases caused by nonsense mutations primarily through a license agreement (the “Technion Agreement”) with the Technion Research and Development Foundation Ltd. (“TRDF”) entered into in 2013. For more information relating to the Technion Agreement, see Note 9, “Legal and Other Contingencies”. Reverse Merger On December 19, 2017, Sevion Therapeutics, Inc. (“Sevion”) acquired Eloxx Limited pursuant to a merger between the companies (the “Transaction” or “Reverse Merger”). Upon consummation of the Transaction (the “Closing”), Sevion adopted the business plan of Eloxx Limited and discontinued the pursuit of Sevion’s business plan. In connection with the Transaction, Sevion acquired all of the outstanding capital stock of Eloxx Limited in exchange for the issuance of an aggregate 20,316,656 shares of Sevion’s common stock, par value $0.01 per share (the “Common Stock”), after giving effect to a 1-for-20 reverse split immediately prior to the Transaction. As a result of the Transaction, Eloxx Limited became a wholly-owned subsidiary of Sevion. While Sevion was the legal acquirer in the transaction, Eloxx Limited was deemed the accounting acquirer. Immediately after giving effect to the Transaction, on December 19, 2017, Sevion changed its name to Eloxx Pharmaceuticals, Inc. The annual consolidated financial statements of the Company reflect the operations of the acquirer for accounting purposes, together with a deemed issuance of shares, equivalent to the shares held by the former stockholders of the legal acquirer and a recapitalization of the equity of the accounting acquirer. The annual consolidated financial statements include the accounts of the Company since the effective date of the reverse capitalization and the accounts of Eloxx Limited since inception. Liquidity The Company has a history of net losses and negative cash flows from operating activities since inception, and as of December 31, 2019, had an accumulated deficit of $(137.0) million. The Company expects to continue to incur net losses and use cash in its operations for the foreseeable future. To date, the Company has not generated revenue from the sale of any product or service and does not expect to generate significant revenue unless and until it obtains marketing approval for and commercializes one or more of its product candidates currently in development. Successful transition to profitable operations is dependent upon achieving a level of revenue adequate to support the Company’s cost structure. The Company has financed its operations primarily from the sale of equity securities and to a lesser extent, loans and grants. The Company may never achieve profitability, and unless and until it does, the Company will continue to need to raise additional capital to fund its operations. As discussed in Note 17, on February 24, 2020, the Company’ Board of Directors approved a leadership and organizational realignment, aimed at supporting the Company’s efforts to improve operating performance, and concentrate development efforts on the Company’s core programs. The Company believes that its cash, cash equivalents and marketable securities of $56.3 million at December 31, 2019 will enable it to meet anticipated cash needs required to maintain the Company’s current and planned operations through at least the next 12 months from the issuance of the financial statements for the year ended December 31, 2019. Management intends to fund future operations through private or public debt or equity financing transactions and may seek additional capital through arrangements with strategic partners or from other sources. If the Company is unable to obtain financing, it will evaluate options which may include reducing or deferring operating expenses, which may have a material adverse effect on the Company’s operations and future prospects.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The Company has prepared its consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) promulgated by the Financial Accounting Standards Board (“FASB”). Principles of Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. Intercompany balances and transactions have been eliminated upon consolidation. Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates, judgments and assumptions. The Company’s management believes that the estimates, judgments and assumptions used are reasonable based upon information available at the time they are made. These estimates, judgments and assumptions can affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of the consolidated financial statements, and the reported amounts of expenses during the reporting period. The Company evaluates estimates on an ongoing basis in light of changes in circumstances, facts and experiences. Actual results could materially differ from those estimates. Foreign Currency The functional currency of the Company is the U.S. dollar. Accordingly, monetary accounts maintained in other currencies are re-measured into U.S. dollars in accordance with ASC Topic 830, “Foreign Currency Matters”. All foreign currency transaction gains and losses arising from transactions denominated in foreign currencies, whether realized or unrealized, are recorded in the statements of operation as other income or expenses . Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss consists of net loss and other comprehensive loss. Other comprehensive loss consists of unrealized gains and losses from available-for-sale securities. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. The Company’s cash and cash equivalents include holdings in checking and overnight sweep accounts. The Company’s cash equivalents, which are money market funds held in a sweep account, are measured at fair value on a recurring basis. As of December 31, 2019 and 2018 the balance of cash and cash equivalents was $22.5 million and $48.6 million, respectively, which approximates fair value and was determined based upon Level 1 inputs. The sweep account is valued using quoted market prices with no valuation adjustments applied. Accordingly, these securities are categorized as Level 1. Marketable Securities All investment instruments with an original maturity date, when purchased, in excess of three months but less than one year have been classified as current marketable securities. The Company classifies securities that are available to fund current operations as current assets. These marketable securities are classified as available-for-sale and are carried at fair value. The Company records unrealized gains and losses on available-for-sale debt securities as a component of accumulated other comprehensive income, which is a separate component of stockholders’ equity on its consolidated balance sheet, until such gains and losses are realized. Realized gains and losses on available-for-sale securities are included in other income. The cost of securities sold is based on the specific identification method. The Company periodically reviews its portfolio of securities to determine whether an other-than-temporary impairment loss has occurred. No such losses have occurred to date. There were no realized gains or losses on sales of securities for the year ended December 31, 2019. Below is a summary of cash, cash equivalents and marketable securities at December 31, 2019 (in thousands): Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents $ 22,493 $ — $ — $ 22,493 Marketable securities - U.S. treasuries 33,765 19 (1 ) 33,783 Total cash, cash equivalents and marketable securities $ 56,258 $ 19 $ (1 ) $ 56,276 Restricted Cash At December 31, 2019, and 2018, restricted cash consisted of bank guarantees related to Eloxx Limited’s corporate facilities lease and credit card program. Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially subject the Company to credit risk consist primarily of cash and cash equivalents and marketable securities. The Company mitigates its risk with respect to cash and cash equivalents and marketable securities by maintaining its deposits and investments at high-quality financial institutions. The Company invests any excess cash in money market funds and U.S. treasuries, and the management of these investments is not discretionary on the part of the financial institution. The Company has no off-balance-sheet concentration of credit risk such as foreign exchange contracts, option contracts or other foreign hedging arrangements. Property and Equipment Property and equipment are recorded at cost, less accumulated depreciation. Leasehold improvements are amortized over the lesser of the estimated useful life or the expected term of the related lease. Costs associated with maintenance and repairs are expensed as incurred. Depreciation expense is computed on a straight-line method over the estimated useful lives of the respective assets, as follows: Useful Life (Years) Computers and software 3 years Office furniture and equipment 5 to 12 years Laboratory equipment 5 years Leasehold improvement Over the shorter of the expected lease term or estimated useful life Upon sale or disposition of property and equipment, the cost and related accumulated depreciation are eliminated from the accounts and any resultant gain or loss is credited or charged to operations. Impairment of Long-Lived Assets Property and equipment subject to depreciation are reviewed for impairment in accordance with ASC Topic 360, “Accounting for the Impairment or Disposal of Long-Lived Assets,” whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If such assets are considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds their fair value. The Company continually evaluates whether events or circumstances have occurred that indicate that the remaining useful life of its long-lived assets may warrant revision or that the carrying value of these assets may be impaired. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. Evaluation of recoverability of the asset or asset group is based on an estimate of undiscounted future cash flows resulting from the use of the asset or asset group and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the asset or asset group, the assets are written down to their estimated fair value. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. As of each balance sheet date presented, none of the Company’s long-lived assets were impaired. The Company has not recorded any impairment losses to date. Legal and Other Contingencies The Company accounts for its contingent liabilities in accordance with ASC Topic 450, “Contingencies”. A provision is recorded when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. With respect to legal matters, provisions are reviewed and adjusted to reflect the impact of negotiations, estimated settlements, legal rulings, advice of legal counsel and other information and events pertaining to a particular matter. For the years ended December 31, 2019, 2018 and 2017 the Company was not a party to any litigation that could have a material adverse effect on the Company’s business, financial position, results of operations or cash flows (see also Note 9, “Legal and Other Contingencies”). Legal costs incurred in connection with loss contingencies are expensed as incurred. Research and Development Expenses Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries, stock-based compensation and benefits for employees performing such activities, certain facilities costs, depreciation, third-party license fees, and external costs of vendors engaged to conduct preclinical development activities and clinical trials. Research and development expenses are expensed as incurred and include the Company’s costs of performing services in connection with its collaboration agreements and research grants. Non-refundable prepayments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized in prepaid expenses and other current assets. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered, or the services rendered. The Company enters into arrangements with contract research organizations in connection with clinical trials. Such arrangements often provide for payment prior to commencing the project or based upon predetermined milestones throughout the period during which services are expected to be performed. As part of the process of preparing the Company’s financial statements, management is required to estimate accrued expenses. The date on which services commence, the level of services performed on or before a given date, and the cost of such services are often determined based on subjective judgments informed by the facts and circumstances know to management from the terms of the contract and the Company’s ongoing monitoring of service performance. The Company makes these judgments based upon the facts and circumstances known to management based on the terms of the contract and the Company’s ongoing monitoring of service performance. Government Grants Eloxx Limited has received royalty-bearing grants for the years ended December 31, 2015, 2016 and 2017 totaling $2.6 million, which represents participation in approved research and development programs of the Israeli Innovation Authority (“IIA”, previously known as the Office of the Chief Scientist of the Ministry of Economy). These amounts are recognized on the accrual basis as a reduction of research and development expenses as such expenses are incurred. Fair Value of Financial Instruments Fair value is determined based on the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal market for the asset or liability in an orderly transaction between market participants. U.S. GAAP specifies a hierarchy of valuation techniques based upon whether the inputs to those valuation techniques reflect assumptions other market participants would use based upon market data obtained from independent sources (observable inputs) or reflect the Company’s own assumptions of market participant valuation (unobservable inputs). The fair value hierarchy consists of three levels: Level 1 - Quoted prices (unadjusted) in active markets that are unadjusted and accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2 - Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Financial assets and liabilities are classified within the fair value hierarchy based on the lowest level of input that is significant to the fair value measurement. The authoritative guidance requires the use of observable market data if such data is available without undue cost and effort. When available, the Company uses unadjusted quoted market prices to measure fair value and classify such items within Level 1. If quoted market prices are not available, fair value is based upon internally developed models that use, where possible, current market-based or independently-sourced market parameters, such as interest and currency rates and comparable transactions. Items valued using internally generated models are classified according to the lowest level input or value driver that is significant to the valuation. Thus, items may be classified in Level 3 even though there may be inputs that are readily observable. If quoted market prices are not available, the valuation model used generally depends on the specific asset or liability being valued. At December 31, 2019 and 2018, the Company’s financial assets valued based on Level 1 inputs consisted of cash, cash equivalents and marketable securities (U.S. treasuries). The Company did not have any transfers of financial assets between Level 2 and 3 during 2019. The carrying amounts of cash and cash equivalents, restricted bank deposits, prepaids and other current assets, accounts payables and accrued expenses approximate their fair value due to the short-term maturities of such instruments. Some assets and liabilities are required to be recorded at fair value on a recurring basis, while other assets and liabilities are recorded at fair value on a nonrecurring basis. The carrying amounts of current financial instruments, which include accounts payable, accrued expenses, lease obligation liability and debt, approximate their fair values due to the short-term nature of these instruments. Stock-Based Compensation The Company accounts for stock-based compensation in accordance with ASC Topic 718, “Compensation-Stock Compensation” (“ASC 718”), which requires companies to estimate the fair value of equity-based payment awards on the date of grant using an option-pricing model. The Company recognizes compensation expenses for the value of its awards granted based on the straight-line method over the requisite service period of each of the awards or over the implicit service period when a performance condition affects the vesting, and it is considered probable that the performance condition will be achieved. The Company determines the fair value of each stock option award at its grant date using the Black-Scholes option pricing model for options awarded in 2019, and using the . The Company determines the fair value of each stock unit, or RSU, at its grant date based on the closing market price of the Company’s common stock on that date. Income Taxes The Company accounts for income taxes in accordance with ASC Topic 740, “Income Taxes” (“ASC 740”), which prescribes the use of the asset and liability method whereby deferred tax assets and liability account balances are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to be recovered or settled. The Company provides a valuation allowance, if necessary, to reduce deferred tax assets to their estimated realizable value if it is more likely than not that a portion or all of the deferred tax assets will not be realized. The Company considers many factors when assessing the likelihood of future realization of deferred tax assets, including recent earnings results, expectations of future taxable income, carryforward periods available and other relevant factors. The Company records changes in the required valuation allowance in the period that the determination is made. Based on ASC 740, a two-step approach is used to recognize and measure uncertain tax positions. The first step is to evaluate the tax position taken or expected to be taken in a tax return by determining if the weight of available evidence indicates that it is more likely than not that, on an evaluation of the technical merits, the tax position will be sustained on audit, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement. As of December 31, 2019 and 2018, no liability for unrecognized tax positions has been recorded. Accordingly, no interest or penalties related to uncertain tax positions are recorded, either. The Company’s policy is to record any interest or penalties associated with unrecognized tax positions as a component of income tax expense. Net Loss per Share For the year ended December 31, 2017, the Company applied the two-class method as required by ASC Topic 260-10, “Earnings Per Share” (“ASC 260-10”), which requires the income or loss per share for each class of shares (ordinary and preferred shares) to be calculated assuming 100% of the Company’s earnings are distributed as dividends to each class of shares based on their contractual rights. For the years ended December 31, 2019 and 2018, the Company had no outstanding preferred shares and was not required to apply the two-class method under ASC 260-10. No dividends were declared or paid during the reported periods. According to the provisions of ASC 260-10, the Company’s preferred shares are not participating securities in losses and, therefore, are not included in the computation of net loss per share. Basic loss per share is computed by dividing the loss for the period applicable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. In computing diluted income per share, weighted average shares used in computing basic earnings per share are adjusted to reflect the potential dilution that could occur upon the exercise of outstanding stock options and upon conversion of restricted stock units and warrants issued to investors and service providers using the “treasury stock method”. Recent Accounting Pronouncements - Adopted In February 2016, the FASB issued ASU 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 establishes ASC Topic 842 (“Topic 842”) which replaces ASC 840, Leases, by introducing a lessee model that requires balance sheet recognition for most leases and the disclosure of key information about leasing arrangements. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement. Topic 842 provides several optional practical expedients in transition. The Company elected the package of practical expedients which allowed the Company to not reassess its existing conclusions on lease identification, classification and initial direct costs. Further, the Company elected the hindsight practical expedient and utilized the short-term lease exemption for all leases with an original term of 12 months or less for purposes of applying the recognition and measurement requirements of the new standard. The Company also elected the practical expedient which allowed it to not separate lease and non-lease components for all its leases. The Company adopted the new standard on January 1, 2019 and applied the effective date as its date of initial application and has not updated disclosures required under the new standard for dates and periods prior to January 1, 2019. Also see Note 6, “Leases”. Recent Accounting Pronouncements - Pending Adoption In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). This standard requires that for most financial assets, losses must be based on an expected loss approach which includes estimates of losses over the life of exposure that considers historical, current and forecasted information. Expanded disclosures related to the methods used to estimate the losses as well as a specific disaggregation of balances for financial assets are also required. This standard is effective for annual periods beginning after December 15, 2019 and interim periods within those annual periods, with early adoption permitted for annual periods beginning after December 15, 2018. The Company is assessing the impact the adoption of ASU 2016-13 may have on its consolidated financial statements.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2019
Prepaid And Other Current Assets [Abstract]
Prepaid Expenses and Other Current Assets	3. Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): December 31, 2019 2018 Research and development $ 448 $ 864 Other 699 555 Insurance 217 251 Other governmental agency receivables 26 20 $ 1,390 $ 1,690

Property and Equipment, net

Property and Equipment, net	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment, net	4. Property and Equipment, net Property and equipment, net consisted of the following (in thousands): December 31, 2019 2018 Computers and software $ 166 $ 146 Office furniture and equipment 164 165 Leasehold improvements 158 141 488 452 Less: Accumulated depreciation (287 ) (204 ) Property and equipment, net $ 201 $ 248 Depreciation expense was $87 thousand, $216 thousand and $39 thousand

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses consisted of the following (in thousands): December 31, 2019 2018 Research and development expenses $ 1,560 $ 3,086 Payroll, bonus and other employee-related expenses 2,200 2,562 Professional services 664 985 Other 137 305 Interest on debt 94 — $ 4,655 $ 6,938

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	6. Leases The Company adopted the new lease accounting standard, Topic 842, effective January 1, 2019. The Company has elected the ‘package of practical expedients’, which permits it not to reassess under the new standard its prior conclusions about lease identification, lease classification and initial direct costs. In addition, the Company elected not to apply Topic 842 to arrangements with lease terms of 12 months or less. The Company has operating leases for its principal offices in the U.S. and Israel. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent the Company’s obligation to make lease payments arising from its operating leases. In determining the length of the lease term to its long-term lease, the Company determined not to consider an embedded renewal option for one operating lease primarily due to the facts that (i) the renewal rate is at a future market rate to be determined, and (ii) the Company does not have significant leasehold improvements that would restrict its ability to consider relocation. The Company applied its incremental borrowing rate based upon information available in determining the present value of the lease payments. The Company’s incremental borrowing rate is determined using a secured borrowing rate for the same currency and term as the associated lease. Operating lease costs under the leases for the year ended December 31, 2019 were approximately $0.5 million. Lease expense for these leases is recognized on a straight-line basis over the lease term, with variable lease payments recognized in the period those payments are incurred. At lease commencement date, the Company estimated the lease liabilities and the right-of-use assets at present value using the Company’s estimated incremental borrowing rate of 8% and determined the initial present value, at inception, of $1.5 million. On January 1, 2019, upon adoption of Topic 842, the Company recorded right-of-use assets of $1.2 million and lease liabilities of $1.2 million. These assets and obligations are reflected within ‘Operating lease right-of-use asset’, and ‘Operating lease liability’ (current and noncurrent), respectively, on the Consolidated Balance Sheet. The weighted average remaining lease term at December 31, 2019 was 1.81 years. The Company made payments of $0.5 million for the year ended December 31, 2019, and recorded a $0.2 million remeasurement, which increased the respective assets and obligations balances. The following table summarizes the Company’s maturities of operating lease liabilities as of December 31, 2019 (in thousands): 2020 $ 556 2021 404 2022 32 Total lease payments 992 Less: present value discount (68 ) Total $ 924 The Company’s aggregate future minimum non-cancellable commitments under operating leases as of December 31, 2018 were as follows (in thousands): 2019 $ 541 2020 490 2021 310 Total minimum lease payments $ 1,341

Debt

Debt	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Debt	7. Debt On January 30, 2019, the Company entered into a Loan and Security Agreement (the “SVB Loan Agreement”) with Silicon Valley Bank (“SVB”) and WestRiver Innovation Lending Fund VIII, L.P. (“WestRiver”, and together with SVB, the “Lenders”). Under the SVB Loan Agreement, the Lenders agreed to extend term loans to the Company in an aggregate principal amount of $25.0 million, comprised of (i) an initial loan advance of $15.0 million; and (ii) a subsequent loan advance of $10.0 million, subject to first achieving certain conditions (collectively, the “Term Loan Advances”). The initial term loan was funded on January 30, 2019. The subsequent term loan advance was available until December 31, 2019 at the Company’s election after the occurrence of certain milestone events relating to data from the Company’s clinical trials and receipt by the Company of certain minimum cash proceeds of at least $75 million from an additional equity offering through a private placement or a public offering. These events did not occur, and thus the Company did not draw the second advance. Outstanding principal on the Term Loan Advances accrues interest at a floating rate equal to the greater of (i) 5.25% per annum and (ii) the sum of 2.5% plus the prime rate, as published in the Wall Street Journal. Interest payments are payable monthly following the funding of a Term Loan advance. On December 31, 2019, the rate was 7.25%. The Company will be required to make principal payments on the outstanding balance of the Term Loan Advances commencing on February 1, 2020 in 36 equal monthly installments, plus interest. Any amounts outstanding under the Term Loan Advances, if not repaid sooner, are due and payable on January 1, 2023 (the “Maturity Date”). In conjunction with the initial loan advance, the Company issued warrants (the “Warrants”) to SVB and WestRiver to purchase an aggregate of 40,834 shares of the Company’s common stock at a warrant exercise price of $11.02 (subject to certain adjustments), which price was calculated using the 10-day average bid price of the Company’s common stock prior to the date of the SVB Loan Agreement. The Company may prepay the outstanding principal balance of the term loans advanced by SVB in whole but not in part, subject to a prepayment fee ranging from 1% to 3% of any amount prepaid, depending upon when the prepayment occurs. The Company will also pay a final payment fee equal to 6% of the total term loans advanced, due upon the earliest of maturity or termination of the SVB Loan Agreement. Under the terms of the SVB Loan Agreement, the Company granted first priority liens and security interests in substantially all of the Company’s assets (excluding all of its intellectual property, which is subject to a negative pledge) and a pledge by the Company of the shares of one of its wholly-owned subsidiaries as collateral for the obligations thereunder. The SVB Loan Agreement also contains representations and warranties by the Company and SVB and indemnification provisions in favor of SVB and customary covenants (including limitations on other indebtedness, liens, acquisitions, investments and dividends, but no financial covenants), and events of default (including payment defaults, breaches of covenants following any applicable cure period, a material impairment in the perfection or priority of SVB’s security interest in the collateral, and events relating to bankruptcy or insolvency). As of December 31, 2019, the carrying value of the term loan consists of $15.0 million principal outstanding less the unamortized debt issuance costs of approximately $1.1 million. The debt issuance costs have been recorded as a debt discount and are being accreted to interest expense through the maturity date of the term loan. Interest expense relating to the term loan for the period ended December 31, 2019 was $1.6 million. Interest expense is calculated using the effective interest method and is inclusive of non-cash amortization of capitalized loan costs. At December 31, 2019, the effective interest rate was 12.40%. The final maturity payment of $0.9 million is recognized over the life of the term loan through interest expense using the effective interest method. The Company’s scheduled future principal payments for the long-term debt are as follows (in thousands): December 31, 2019 2020 $ 4,583 2021 5,000 2022 5,000 2023 417 Total future principal payments 15,000 Less: unamortized discount (1,062 ) Carrying value of long-term debt 13,938 Less: current portion (4,336 ) Add: final fee due at maturity in 2023 900 Long-term portion $ 10,502

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2019
Related Party Transactions [Abstract]
Related Parties	8. Related Parties On August 29, 2013, the Company entered into the Technion Agreement with TRDF, with respect to certain technology relating to aminoglycosides and the redesign of aminoglycosides for the treatment of human genetic diseases caused by premature stop mutations and further results of the research of the technology, in order to develop and commercialize products based on such technology. Under the Technion Agreement, TRDF is obligated to provide the Company with research services for an estimated annual payment of $0.1 million, the precise amount to be agreed by the parties prior to the beginning of each year of the research period. During the year ended December 31, 2017, the Company recorded general and administrative expenses In addition, TRDF granted the Company a license to use, market, sell or sub-license the rights of the product developed under the TRDF research results (the “Licensed Product”), as fully defined in the Technion Agreement, for the following considerations: (i) milestone payments up to total consideration of $6.1 million, to be transferred upon meeting certain milestones as defined in the Technion Agreement; (ii) certain royalties in the low- to mid-single-digit percentage of net sales (subject to change in the case of (a) sublicensing to a big pharmaceutical or biotechnology company, or (b) payment of royalties to third parties, or (c) commercialization by a third party of an authorized generic to a licensed product), for a period until the later of (i) the expiration of a valid claim on the Licensed Product in each country the Licensed Product is sold to, or (ii) a certain amount of years from the date of the first commercial sale of the Licensed Product in such country; and (iii) a low- to mid-double-digit percentage of any non-royalty sub-license income received by the Company from a sub-licensed entity. In addition, the Company shall pay certain fee to TRDF upon an exit event as described in the Technion Agreement. Moreover, upon the closing of an exit event which is not an Initial Public Offering (“IPO”), as defined in the Technion Agreement, TRDF shall be entitled to an amount equal to 3% of all non-refundable, non-contingent consideration, whether in cash or in kind, actually received by the Company and/or its shareholders. Upon the closing of an exit event which is an IPO, as defined in the Technion Agreement, TRDF shall be entitled to a number of Ordinary Shares of the Company representing 3% of the Company’s outstanding shares on a fully diluted basis immediately prior to the closing of such IPO. On August 9, 2017 the Company received a letter from TRDF regarding TRDF’s alleged entitlement to an exit fee in accordance with the Technion Agreement. The Company recorded $3.4 million in research and development expense with an offsetting adjustment to additional paid-in capital for the year ended December 31, 2017 related to the planned issuance of shares to TRDF at fair market value on the purported date of the exit event. On June 13, 2018, the Company entered into an amendment to the license agreement providing that in exchange for the issuance by the Company to TRDF of 569,395 shares, the Company and TRDF agreed to terminate (i) TRDF’s rights to receive payments from the Company upon the Company’s consummation of certain business transactions such as a merger or an initial public offering, (ii) certain preemptive rights provided by the Articles of Association of Eloxx Limited, and (iii) TRDF’s right to designate an observer to the Company’s board of directors.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	9. Commitments and Contingencies Royalty Commitments to the IIA To date, the Company has received research and development grants from the IIA totaling $2.6 million, including $0.9 million Under the research and development agreements with the IIA and pursuant to applicable law, the Company is required to pay royalties at the rate of 3% on sales to end customers of products candidates developed with funds provided by the IIA, up to an amount equal to 100% of the IIA research and development grants received, plus interest based on the 12-month LIBOR rate. If the Company does not generate sales of products developed with funds provided by the IIA, the Company is not obligated to pay royalties or repay the grants. As of December 31, 2019, the Company has not commenced the payment obligation of the royalties and has a contingent obligation with respect to royalty-bearing participation received or accrued, amounting to $2.7 million, including accrued LIBOR interest. Commitments to TRDF Since August 29, 2013, the Company has had an ongoing agreement with TRDF. Refer to Note 8, “Related Parties”, for further information. Contingencies From time to time, the Company may become involved in various lawsuits and legal proceedings, which arise in the ordinary course of business. The Company is currently unaware of any material pending legal proceedings to which it is a party or of which its property is the subject. However, the Company may at times in the future become involved in litigation in the ordinary course of business, which may include actions related to or based on its intellectual property and its use, customer claims, employment practices and employee complaints and other events arising out of its operations. When appropriate in management’s estimation, the Company will record adequate reserves in its financial statements for pending litigation. Litigation is subject to inherent uncertainties, and an adverse result in any such matters could adversely impact its reputation, operations, and its financial operating results or overall financial condition. The Company accounts for contingent liabilities in accordance with ASC Topic 450, “Contingencies”. A provision is recorded when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. With respect to legal matters, provisions are reviewed and adjusted to reflect the impact of negotiations, estimated settlements, legal rulings, advice of legal counsel and other information and events pertaining to a particular matter. As of December 31, 2019 and 2018, the Company was not a party to any litigation that is reasonably possible to have a material adverse effect on the Company’s business, financial position, results of operations or cash flows. Legal costs incurred in connection with loss contingencies are expensed as incurred. During 2019, the Company received a funding award from the Cystic Fibrosis Foundation and entered into an agreement relating to the award and provision of other services. Payment of award amounts are subject to the achievement of certain milestones in connection with the Company’s cystic fibrosis development program in the U.S. The funding provided to the Company is accounted for as an advance from a collaboration partner within the scope of ASC Topic 730, “Research and Development.” The Company recorded a liability for advances from collaboration partners of $0.4 million as of December 31, 2019.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Stockholders' Equity	10. Stockholders’ Equity For accounting purposes, all common stock, preferred stock, warrants, options to purchase common stock and loss per share amounts have been adjusted to give retroactive effect to the exchange ratio and reverse stock split for all periods presented in these consolidated financial statements. As of December 31, 2019, the Company had 500,000,000 shares authorized of common stock, $0.01 par value, of which 40,030,763 shares were outstanding and 5,000,000 shares authorized of preferred stock, $0.01 par value, of which no shares were issued or outstanding. Common Stock Public Offering On April 30, 2018, the Company closed an underwritten public offering of 5,899,500 shares of its common stock, including the exercise in full by the underwriter of its overallotment option to purchase an additional 769,500 shares, at the public offering price of $9.75 per share for gross proceeds of approximately $57.5 million, before deducting the underwriting discounts and commissions and offering expenses of approximately $3.9 million. The shares of common stock were offered by the Company pursuant to a shelf registration statement on Form S-3 (File No. 333-224207) that was filed with the U.S. Securities and Exchange Commission (the “SEC”) on April 10, 2018 and declared effective on April 20, 2018, which covers the offering, issuance and sale of up to $125 million of its common stock, preferred stock, debt securities or warrants and other securities, either individually or in combination (the “April 2018 Shelf”). On June 24, 2019, the Company completed an underwritten public offering of 3,833,334 shares of common stock of the Company at the public offering price of $9.00 per share and received net proceeds of approximately $32.2 million after deducting underwriting discounts and commissions of $2.1 million and estimated offering expenses of $0.2 million. Form S-3 and Equity Sales Agreement In November 2018, the Company entered into an Equity Distribution Agreement (the “Agreement”) with Citigroup Global Markets Inc. and Cantor Fitzgerald & Co. (collectively, the “Sales Agents”), pursuant to which the Company may sell and issue shares of its common stock up to an aggregate of $50 million through the Sales Agents. The shares were offered pursuant to the April 2018 Shelf. The Company agreed to pay the Sales Agents a commission of up to 3% of the gross proceeds of any sales of common stock pursuant to the Agreement. The Company incurred approximately $0.3 million related to legal, accounting and other fees in connection with the Agreement. For the year ended December 31, 2018, under the Agreement, the Company sold 201,100 shares of common stock and received net proceeds of $2.2 million. On November 16, 2018, the Company filed a shelf registration statement (the “November 2018 Shelf”) on Form S-3 with the SEC. The November 2018 Shelf (File No. 333-228430) was declared effective on November 26, 2018 and covers the offering, issuance and sale of up to $200 million of the Company’s common stock, preferred stock, debt securities or warrants and other securities, either individually or in combination. Preferred and Common Stock In February 2016, Eloxx Limited issued shares of preferred stock to purchase shares of preferred stock for an aggregate gross amount of $6.0 million. In August 2016, Technion Investment Opportunities Fund L.P (the “TIOF”) and TRDF exercised 124,786 and 311,964 warrants, respectively, to purchase shares of preferred stock for total consideration of $0.4 million. In September 2016, Eloxx Limited achieved a milestone in connection with the prior issuance of securities, pursuant to which Eloxx Limited paid a $0.1 million milestone payment and issued to investors additional shares of preferred stock and warrants to purchase preferred stock for an aggregate amount of $3.7 million. In May 2017, Eloxx Limited entered into a Share Purchase Agreement (the “2017 SPA”) with certain existing and new investors, whereby an aggregate gross amount of $21.5 million, which included the conversion of the loan (as detailed in Note 16), was received by Eloxx Limited in exchange for the issuance of preferred stock including shares of preferred stock that were issued as a result of the anti-dilution effect of the Reverse Merger. The related issuance costs recorded in 2017 were $0.6 million. Upon the closing of the Reverse Merger in December 2017, the Company issued 6,333,333 shares of common stock related to the 2017 SPA for an aggregate gross amount of $17.5 million. Additionally, Sevion raised $1.5 million prior to the Reverse Merger. The related issuance costs for these transactions recorded in 2017 were $0.5 million. Warrants Eloxx Limited issued warrants to purchase shares in conjunction with the Share Purchase Agreements prior to the Transaction. During the year ended December 31, 2019, transactions related to warrants were as follows: Shares Weighted average exercise price Weighted average remaining contractual life (years) Warrants outstanding at December 31, 2018 347,241 $ 3.77 3.92 Granted 40,834 Exercised (59,707 ) Forfeited (4,474 ) Warrants outstanding at December 31, 2019 323,894 $ 4.32 3.74 Warrants exercisable at December 31, 2019 323,894 $ 4.32 3.74

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	11. Stock-Based Compensation Stock Incentive Plans Prior to April 20, 2018, the Company had two equity compensation plans which provided that options to purchase ordinary shares of Eloxx Limited, or ordinary shares of Eloxx Limited, may be granted to employees, officers, directors, service providers and consultants of Eloxx Limited: the Sevion 2008 Incentive Plan (the “2008 Plan”) and the Eloxx Limited 2013 Share Ownership and Option Plan (the “2013 Plan”). On March 12, 2018, the Company’s Board of Directors (the “Board”) adopted the 2018 Equity Incentive Plan (the “2018 Plan”). The 2018 Plan became effective on April 20, 2018 upon approval by the stockholders of the Company with the outstanding options and shares available for future grant under the 2008 Plan and the 2013 Plan being assumed by the 2018 Plan. The initial total number of shares available under the 2018 Plan for awards to employees, non-employee directors and other key personnel was 5,000,000 shares. Upon the 2018 Plan becoming effective, the Company ceased granting awards under each of the 2008 Plan and the 2013 Plan. Stock options granted have a ten-year contractual life and, upon termination of service, vested options are generally exercisable between one and three months following the termination date, while unvested options are forfeited immediately. In 2017, the Company issued an inducement award outside of its stock plans to its Chief Executive Officer in the form of an option to purchase 22,427 shares of the Company’s common stock with an exercise price per share equal to $8.00, and an award of restricted stock units for 22,427 shares of the Company’s common stock (collectively, the “Performance Awards”). Subject to continued service through the vesting date, the Performance Awards will vest and become immediately exercisable upon the date that marks the first successful completion of a Phase 2B study with respect to any indication. The Company recognized $0.1 million of expense associated with these awards during each of the years ended December 31, 2019 and 2018. In addition, the Company issued an inducement award outside of its stock plans to its Chief Executive Officer in the form of an option to purchase 640,785 shares of the Company’s common stock with an exercise price per share equal to $8.00, and an award of restricted stock units for 640,785 shares of the Company’s common stock (collectively, the “Time-Vesting Awards”). Subject to continued service through the vesting date, one-third of the Time-Vesting Awards will vest and become immediately exercisable on the first anniversary of the effective date, with an additional one-twelfth of the Time-Vesting Awards vesting on each quarterly anniversary of the effective date, provided that vesting of the Time-Vesting Awards shall be subject to acceleration following the achievement of certain milestones. Summary of Stock Option Activity Transactions related to stock options granted to employees and directors during the year ended December 31, 2019, were as follows: Amount Weighted average exercise price Weighted average remaining contractual life (years) Aggregate intrinsic value Options outstanding as of December 31, 2018 3,261,719 $ 13.09 8.56 $ 11,650,373 Granted 1,842,990 9.31 Exercised (116,327 ) 4.27 Forfeited (250,712 ) 10.35 Options outstanding as of December 31, 2019 4,737,670 $ 11.17 8.54 $ 3,629,073 Options exercisable at December 31, 2019 1,785,477 $ 11.78 7.55 $ 2,498,968 As of December 31, 2019, the unrecognized compensation cost related to the outstanding options was $18.4 million and is expected to be recognized over a weighted-average period of 2.68 years. The weighted average grant date fair values of stock options granted during the years ended December 31, 2019, 2018, and 2017 were $6.28, $18.06 and $3.68 The following table presents the assumptions used to estimate the fair values of stock options granted in the periods presented: Year ended December 31, 2019 2018 2017 Dividend yield 0% 0% 0% Volatility 76%-92% 90%-92% 87%-117% Risk-free interest rate 1.51%-2.62% 2.55%-3.20% 1.22%-2.50% Expected term (years) 5.5-6.0 — — Contractual term (years) 10 10 10 Forfeiture rate post-vesting — 10% 10% Suboptimal exercise — 2.3 2.3 Summary of Restricted Stock Unit Activity Transactions related to restricted stock units granted to employees during the year ended December 31, 2019, were as follows: Shares Weighted average grant date fair value per share Unvested at December 31, 2018 554,147 $ 9.34 Granted 100,000 11.53 Vested (190,202 ) 8.09 Forfeited — — Unvested at December 31, 2019 463,945 $ 9.45 As of December 31, 2019, the unrecognized compensation cost related to the outstanding options was $4.0 million and is expected to be recognized over a weighted-average period of 2.27 years. Stock-based Compensation Expense Stock-based compensation expense relates to stock options granted to employees, non-employee directors and non-employees, time-based restricted stock units granted to employees and performance-based stock options and restricted stock units granted to an employee. The total equity-based compensation expense related to all of the Company’s equity-based awards was recognized as follows (in thousands): Year ended December 31, 2019 2018 2017 Research and development $ 2,458 $ 1,745 $ 39 General and administrative 8,878 11,625 62 Total stock-based compensation expense $ 11,336 $ 13,370 $ 101

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The components of income (loss) before taxes on income are as follows (in thousands): Year ended December 31, 2019 2018 2017 U.S. $ (22,242 ) $ (24,439 ) $ (21 ) Israel (28,632 ) (22,624 ) (21,145 ) Loss before taxes on income $ (50,874 ) $ (47,063 ) $ (21,166 ) There were no taxes on income during the year ended December 31, 2019. Taxes on income during the year ended December 31, 2018 resulted primarily from subsidiary income as a result of the implementation of an intercompany cost-plus arrangement. The current income tax provision consisted of the following (in thousands): Year ended December 31, 2019 2018 2017 Federal $ — $ 94 $ — State and local — 28 — Foreign — — — Income tax provision $ — $ 122 $ — The significant components of the Company’s deferred tax assets were comprised of the following (in thousands): December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 38,357 $ 29,521 Stock-based compensation 2,801 1,001 Reserves and allowances 615 377 U.S. tax credits and other credits 2,980 714 Research and development credits 1,831 4,216 Operating lease right-of-use assets (169 ) — Operating lease liabilities 169 — Other 98 40 Total deferred tax assets 46,682 35,869 Valuation allowance (46,682 ) (35,869 ) Net deferred tax assets $ — $ — Deferred taxes are recognized for temporary differences between the basis of assets and liabilities for financial statements and income tax purposes. The Company has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets. As of December 31, 2019 and 2018, based on the Company’s history of operating losses, the Company has concluded that it is not more likely than not that the benefit of the deferred tax assets will not be realized. Accordingly, the Company has provided a full valuation allowance for deferred tax assets as of December 31, 2019 and 2018. As of December 31, 2019 and 2018, the Company provided valuation allowances of approximately $46.7 million and $35.9 million, respectively, on U.S. federal, U.S. state and Israeli tax jurisdiction deferred tax assets to reduce the carrying amounts of these assets to zero. The net changes in the Company’s valuation allowances were increases of $10.8 million and $7.7 million For the year ended December 31, 2019, the expected tax expense based on the federal statutory rate reconciled with the actual tax expense as follows: Year ended December 31, 2019 2018 U.S. federal statutory rate 21.0 % 21.0 % State tax rate, net of federal benefit 0.9 2.4 Permanent differences (1.5 ) (3.0 ) Adjustments to deferred taxes — (1.8 ) Effect of rate differences from statutory 1.1 0.8 Tax reform - federal tax rate change — 0.1 Tax reform - change in valuation allowance — (0.1 ) Change in valuation allowance (21.5 ) (19.5 ) Other — (0.2 ) Income tax provision 0.0 % -0.3 % The main reconciling item between the statutory tax rate and the Company’s effective tax rate is the recognition of valuation allowances in respect to deferred taxes related to accumulated net operating losses carried forward and temporary differences due to the uncertainty of the realization of such deferred taxes. For the years ended December 31, 2019 and 2018, the Company had U.S. federal net operating loss (“NOL”) carryforwards of $99.4 million and $89.8 million. U.S. federal NOL carryforwards will begin to expire, if not utilized, beginning in 2020 through 2037. Included in the U.S. federal NOL carryforward are $23.5 million of NOLs generated after the effective date of the Tax Cuts and Jobs Act of 2017 (the “Tax Act”), which are not subject to expiration but may not be carried back and are only eligible to offset up to a maximum of 80% of taxable income generated in a given year. It is uncertain if and to what extent various U.S. states will conform their net operating loss rules to the Tax Act. For the years ended December 31, 2019 and 2018, the Company had U.S. state NOL carryforwards of $31.9 million and $40.0 million, respectively, which may be available to offset future income tax liabilities. As of December 31, 2019 and 2018, the Company had federal research tax credit carryforwards of $3.0 million and $0.7 million, respectively, available to reduce future tax liabilities and which expire at dates beginning in 2027 through 2037. As of December 31, 2019 and 2018, the Company had Israeli NOL carryforwards of $73.7 million, and $34.6 million, respectively, which carry forward indefinitely. The enactment of the Tax Act in December 2017, as further discussed below, resulted in the remeasurement of the Company’s net deferred tax assets due to the reduction in the corporate statutory rate from 35% to 21%. The effect on deferred tax assets and liabilities of a change in law or tax rates is recognized in income in the period that includes the enactment date. The Tax Act also includes a provision designed to currently tax global intangible low-taxed income (“GILTI”). The Company will record the U.S. income tax effect of future GILTI inclusions in the period in which they arise, if ever. After the enactment of the Tax Act, the SEC issued Staff Accounting Bulletin No. 118 (“SAB 118”) which provided guidance on accounting for the enactment effect of the Tax Act. SAB 118 addressed the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. SAB 118 provided for a measurement period of up to one year from the Tax Act enactment date for companies to complete their accounting under ASC 740. The Company had calculated a provisional estimate of deferred tax expense of $10.2 million related to the remeasurement of its U.S. deferred tax assets in the future, which was fully and equally offset by a corresponding reduction in the valuation allowance. During the quarter ended December 31, 2018, the Company completed the accounting for the income tax effects of the Tax Act, which resulted in an immaterial change in the net deferred tax asset, before valuation allowance, as of the enactment date. Under the provisions of the Internal Revenue Code (“IRC”), the net operating loss and tax credit carryforwards are subject to review and potential adjustments by the Internal Revenue Service and state tax authorities. Under Section 382 of the Internal Revenue Code and corresponding provisions of state law, if a corporation undergoes an “ownership change,” which is generally defined as a greater than 50 percent change, by value, in its equity ownership over a three-year period, the corporation’s ability to use its pre-change NOL carryforwards and other pre-change tax attributes to offset its post-change income or taxes may be limited. The Company may have experienced ownership changes in the past, including the Reverse Merger of Sevion Therapeutics, Inc. on December 19, 2017 at which time the Company’s pre-change U.S. federal NOL carryforward was $77.2 million, and its research tax credit was $0.7 million. The Company may experience additional ownership changes in the future as a result of subsequent shifts in its stock ownership, some of which may be outside of its control. Although the Company has not completed its analysis, it is reasonably possible that its federal NOLs available to offset future taxable income could materially decrease. This reduction would be offset by an adjustment to the existing valuation allowance for an equal and offsetting amount. Additionally, the state NOLs available to offset future state income could similarly decrease, which would also be offset by an equal and offsetting adjustment to the existing valuation allowance. Given the offsetting adjustments to the existing valuation allowance, any ownership change is not expected to have an adverse material effect on the Company’s Consolidated Financial Statements. The Company is subject to income taxes in the United States and Israel. The Company files income tax returns in the U.S. and in several states. The federal and state tax returns are generally subject to tax examination by taxing authorities for tax years beginning in June 30, 2015 to present. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	13. Net Loss Per Share The loss and the weighted average number of shares used in computing basic and diluted net loss per share for the years ended December 31, 2019, 2018, and 2017, are as follows (in thousands, except share and per share data): Year ended December 31, 2019 2018 2017 Numerator: Net loss $ (50,874 ) $ (47,185 ) $ (21,214 ) Less: Dividends accumulated for the period (1) — — (2,404 ) Net loss attributable to common stockholders $ (50,874 ) $ (47,185 ) $ (23,618 ) Denominator: Weighted average number of shares common stock used in computing net loss per share, basic and diluted 38,063,173 32,436,506 4,976,377 Net loss per share, basic and diluted $ (1.34 ) $ (1.45 ) $ (4.75 ) (1) The net loss used for the computation of basic and diluted net loss per share includes 8% per share per annum compounded annually which was related to distributions for preferred stockholders of Eloxx Limited. On December 19, 2017 in conjunction with the Reverse Merger, all preferred shares were converted to common shares. For the years ended December 31, 2019, 2018, and 2017, the totals of outstanding preferred stock, stock options, stock warrants and restricted stock units, as applicable, excluded from the calculation of the diluted net loss per share due to their anti-dilutive effect were 5,525,509, 4,163,107 and 19,027,306

Other (Income) Expense, net

Other (Income) Expense, net	12 Months Ended
	Dec. 31, 2019
Other Income And Expenses [Abstract]
Other (Income) Expense, net	14. Other (Income) Expense, net Other (income) expense consisted of the following (in thousands): Year ended December 31, 2019 2018 2017 Interest and other income $ (1,072 ) $ (601 ) $ — Foreign currency exchange gains 76 92 156 Amortization and revaluation of embedded conversion feature in respect to convertible loan — — 625 Investment income, net (301 ) — — Interest and other expense 1,616 7 43 Total other expense (income), net $ 319 $ (502 ) $ 824

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2019
Segment Reporting [Abstract]
Segment and Geographic Information	15. Segment and Geographic Information Operating segments are defined as components of an enterprise (business activity from which it earns revenue and incurs expenses) about which discrete financial information is available and regularly reviewed by the chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is its Chief Executive Officer. The chief operating decision maker reviews consolidated operating results to make decisions about allocating resources and assessing performance for the entire company. The Company views its operations and manages its business as one operating segment; however, it operates in two geographic regions: the U.S. and Israel. Substantially all of the Company’s assets are located in the U.S.

Reverse Merger

Reverse Merger	12 Months Ended
	Dec. 31, 2019
Business Combinations [Abstract]
Reverse Merger	16. Reverse Merger As described in Note 1, “Nature of the Business,” the Reverse Merger was accounted for as a reverse recapitalization which is outside the scope of ASC Topic 805, Business Combinations (“ASC 805”). Under reverse capitalization accounting, Eloxx Limited is considered the acquirer for accounting and financial reporting purposes and acquired the assets and assumed the liabilities of the Company. The assets acquired and liabilities assumed are reported at their historical amounts. The annual consolidated financial statements of the Company reflect the operations of the acquirer for accounting purposes together with a deemed issuance of shares, equivalent to the shares held by the former stockholders of the legal acquirer and a recapitalization of the equity of the accounting acquirer. The annual consolidated financial statements include the accounts of the Company since the effective date of the reverse merger and the accounts of Eloxx Limited since inception. The following table summarizes the assets and liabilities assumed at the date of the Reverse Merger (in thousands): December 19, 2017 Cash and cash equivalents $ 123 Prepaid expenses and other current assets 220 Property, plant and equipment, net 39 Restricted bank deposits 6 Total assets acquired 388 Accounts payable (215 ) Accrued expenses (343 ) Total liabilities acquired (558 ) Total net liabilities acquired $ (170 ) The Company incurred approximately

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events On February 24, 2020, the Company’s Board of Directors approved a leadership and organizational realignment aimed at supporting the Company’s efforts to improve operating performance and concentrate development efforts on the Company’s core programs. The organizational realignment reduces managerial layers and consolidates roles across the organization, resulting in the elimination of 13 full-time positions. These changes will take place throughout March 2020. The Company expects to incur a one-time pre-tax charge, during the first quarter of 2020, consisting of employee separation costs of approximately $1.7 million, primarily relating to severance and benefits costs. The Company also expects to incur a one-time non-cash stock compensation charge, during the first quarter of 2020, relating to accelerated vesting of executive stock awards, of approximately $2.5 million

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company has prepared its consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASUs”) promulgated by the Financial Accounting Standards Board (“FASB”).
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. Intercompany balances and transactions have been eliminated upon consolidation.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates, judgments and assumptions. The Company’s management believes that the estimates, judgments and assumptions used are reasonable based upon information available at the time they are made. These estimates, judgments and assumptions can affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the dates of the consolidated financial statements, and the reported amounts of expenses during the reporting period. The Company evaluates estimates on an ongoing basis in light of changes in circumstances, facts and experiences. Actual results could materially differ from those estimates.
Foreign Currency	Foreign Currency The functional currency of the Company is the U.S. dollar. Accordingly, monetary accounts maintained in other currencies are re-measured into U.S. dollars in accordance with ASC Topic 830, “Foreign Currency Matters”. All foreign currency transaction gains and losses arising from transactions denominated in foreign currencies, whether realized or unrealized, are recorded in the statements of operation as other income or expenses .
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources. Comprehensive loss consists of net loss and other comprehensive loss. Other comprehensive loss consists of unrealized gains and losses from available-for-sale securities.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. The Company’s cash and cash equivalents include holdings in checking and overnight sweep accounts. The Company’s cash equivalents, which are money market funds held in a sweep account, are measured at fair value on a recurring basis. As of December 31, 2019 and 2018 the balance of cash and cash equivalents was $22.5 million and $48.6 million, respectively, which approximates fair value and was determined based upon Level 1 inputs. The sweep account is valued using quoted market prices with no valuation adjustments applied. Accordingly, these securities are categorized as Level 1.
Marketable Securities	Marketable Securities All investment instruments with an original maturity date, when purchased, in excess of three months but less than one year have been classified as current marketable securities. The Company classifies securities that are available to fund current operations as current assets. These marketable securities are classified as available-for-sale and are carried at fair value. The Company records unrealized gains and losses on available-for-sale debt securities as a component of accumulated other comprehensive income, which is a separate component of stockholders’ equity on its consolidated balance sheet, until such gains and losses are realized. Realized gains and losses on available-for-sale securities are included in other income. The cost of securities sold is based on the specific identification method. The Company periodically reviews its portfolio of securities to determine whether an other-than-temporary impairment loss has occurred. No such losses have occurred to date. There were no realized gains or losses on sales of securities for the year ended December 31, 2019. Below is a summary of cash, cash equivalents and marketable securities at December 31, 2019 (in thousands): Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents $ 22,493 $ — $ — $ 22,493 Marketable securities - U.S. treasuries 33,765 19 (1 ) 33,783 Total cash, cash equivalents and marketable securities $ 56,258 $ 19 $ (1 ) $ 56,276
Restricted Cash	Restricted Cash At December 31, 2019, and 2018, restricted cash consisted of bank guarantees related to Eloxx Limited’s corporate facilities lease and credit card program.
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk Financial instruments that potentially subject the Company to credit risk consist primarily of cash and cash equivalents and marketable securities. The Company mitigates its risk with respect to cash and cash equivalents and marketable securities by maintaining its deposits and investments at high-quality financial institutions. The Company invests any excess cash in money market funds and U.S. treasuries, and the management of these investments is not discretionary on the part of the financial institution. The Company has no off-balance-sheet concentration of credit risk such as foreign exchange contracts, option contracts or other foreign hedging arrangements.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost, less accumulated depreciation. Leasehold improvements are amortized over the lesser of the estimated useful life or the expected term of the related lease. Costs associated with maintenance and repairs are expensed as incurred. Depreciation expense is computed on a straight-line method over the estimated useful lives of the respective assets, as follows: Useful Life (Years) Computers and software 3 years Office furniture and equipment 5 to 12 years Laboratory equipment 5 years Leasehold improvement Over the shorter of the expected lease term or estimated useful life Upon sale or disposition of property and equipment, the cost and related accumulated depreciation are eliminated from the accounts and any resultant gain or loss is credited or charged to operations.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Property and equipment subject to depreciation are reviewed for impairment in accordance with ASC Topic 360, “Accounting for the Impairment or Disposal of Long-Lived Assets,” whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. If such assets are considered to be impaired, the impairment to be recognized is measured as the amount by which the carrying amount of the assets exceeds their fair value. The Company continually evaluates whether events or circumstances have occurred that indicate that the remaining useful life of its long-lived assets may warrant revision or that the carrying value of these assets may be impaired. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends, and significant changes or planned changes in the use of the assets. Evaluation of recoverability of the asset or asset group is based on an estimate of undiscounted future cash flows resulting from the use of the asset or asset group and its eventual disposition. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the asset or asset group, the assets are written down to their estimated fair value. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. As of each balance sheet date presented, none of the Company’s long-lived assets were impaired. The Company has not recorded any impairment losses to date.
Legal and Other Contingencies	Legal and Other Contingencies The Company accounts for its contingent liabilities in accordance with ASC Topic 450, “Contingencies”. A provision is recorded when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. With respect to legal matters, provisions are reviewed and adjusted to reflect the impact of negotiations, estimated settlements, legal rulings, advice of legal counsel and other information and events pertaining to a particular matter. For the years ended December 31, 2019, 2018 and 2017 the Company was not a party to any litigation that could have a material adverse effect on the Company’s business, financial position, results of operations or cash flows (see also Note 9, “Legal and Other Contingencies”). Legal costs incurred in connection with loss contingencies are expensed as incurred.
Research and Development Expenses	Research and Development Expenses Research and development expenses are comprised of costs incurred in performing research and development activities, including salaries, stock-based compensation and benefits for employees performing such activities, certain facilities costs, depreciation, third-party license fees, and external costs of vendors engaged to conduct preclinical development activities and clinical trials. Research and development expenses are expensed as incurred and include the Company’s costs of performing services in connection with its collaboration agreements and research grants. Non-refundable prepayments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized in prepaid expenses and other current assets. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered, or the services rendered. The Company enters into arrangements with contract research organizations in connection with clinical trials. Such arrangements often provide for payment prior to commencing the project or based upon predetermined milestones throughout the period during which services are expected to be performed. As part of the process of preparing the Company’s financial statements, management is required to estimate accrued expenses. The date on which services commence, the level of services performed on or before a given date, and the cost of such services are often determined based on subjective judgments informed by the facts and circumstances know to management from the terms of the contract and the Company’s ongoing monitoring of service performance. The Company makes these judgments based upon the facts and circumstances known to management based on the terms of the contract and the Company’s ongoing monitoring of service performance.
Government Grants	Government Grants Eloxx Limited has received royalty-bearing grants for the years ended December 31, 2015, 2016 and 2017 totaling $2.6 million, which represents participation in approved research and development programs of the Israeli Innovation Authority (“IIA”, previously known as the Office of the Chief Scientist of the Ministry of Economy). These amounts are recognized on the accrual basis as a reduction of research and development expenses as such expenses are incurred.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Fair value is determined based on the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal market for the asset or liability in an orderly transaction between market participants. U.S. GAAP specifies a hierarchy of valuation techniques based upon whether the inputs to those valuation techniques reflect assumptions other market participants would use based upon market data obtained from independent sources (observable inputs) or reflect the Company’s own assumptions of market participant valuation (unobservable inputs). The fair value hierarchy consists of three levels: Level 1 - Quoted prices (unadjusted) in active markets that are unadjusted and accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2 - Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3 - Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Financial assets and liabilities are classified within the fair value hierarchy based on the lowest level of input that is significant to the fair value measurement. The authoritative guidance requires the use of observable market data if such data is available without undue cost and effort. When available, the Company uses unadjusted quoted market prices to measure fair value and classify such items within Level 1. If quoted market prices are not available, fair value is based upon internally developed models that use, where possible, current market-based or independently-sourced market parameters, such as interest and currency rates and comparable transactions. Items valued using internally generated models are classified according to the lowest level input or value driver that is significant to the valuation. Thus, items may be classified in Level 3 even though there may be inputs that are readily observable. If quoted market prices are not available, the valuation model used generally depends on the specific asset or liability being valued. At December 31, 2019 and 2018, the Company’s financial assets valued based on Level 1 inputs consisted of cash, cash equivalents and marketable securities (U.S. treasuries). The Company did not have any transfers of financial assets between Level 2 and 3 during 2019. The carrying amounts of cash and cash equivalents, restricted bank deposits, prepaids and other current assets, accounts payables and accrued expenses approximate their fair value due to the short-term maturities of such instruments. Some assets and liabilities are required to be recorded at fair value on a recurring basis, while other assets and liabilities are recorded at fair value on a nonrecurring basis. The carrying amounts of current financial instruments, which include accounts payable, accrued expenses, lease obligation liability and debt, approximate their fair values due to the short-term nature of these instruments.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation in accordance with ASC Topic 718, “Compensation-Stock Compensation” (“ASC 718”), which requires companies to estimate the fair value of equity-based payment awards on the date of grant using an option-pricing model. The Company recognizes compensation expenses for the value of its awards granted based on the straight-line method over the requisite service period of each of the awards or over the implicit service period when a performance condition affects the vesting, and it is considered probable that the performance condition will be achieved. The Company determines the fair value of each stock option award at its grant date using the Black-Scholes option pricing model for options awarded in 2019, and using the . The Company determines the fair value of each stock unit, or RSU, at its grant date based on the closing market price of the Company’s common stock on that date.
Income Taxes	Income Taxes The Company accounts for income taxes in accordance with ASC Topic 740, “Income Taxes” (“ASC 740”), which prescribes the use of the asset and liability method whereby deferred tax assets and liability account balances are determined based on differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to be recovered or settled. The Company provides a valuation allowance, if necessary, to reduce deferred tax assets to their estimated realizable value if it is more likely than not that a portion or all of the deferred tax assets will not be realized. The Company considers many factors when assessing the likelihood of future realization of deferred tax assets, including recent earnings results, expectations of future taxable income, carryforward periods available and other relevant factors. The Company records changes in the required valuation allowance in the period that the determination is made. Based on ASC 740, a two-step approach is used to recognize and measure uncertain tax positions. The first step is to evaluate the tax position taken or expected to be taken in a tax return by determining if the weight of available evidence indicates that it is more likely than not that, on an evaluation of the technical merits, the tax position will be sustained on audit, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement. As of December 31, 2019 and 2018, no liability for unrecognized tax positions has been recorded. Accordingly, no interest or penalties related to uncertain tax positions are recorded, either. The Company’s policy is to record any interest or penalties associated with unrecognized tax positions as a component of income tax expense.
Net Loss per Share	Net Loss per Share For the year ended December 31, 2017, the Company applied the two-class method as required by ASC Topic 260-10, “Earnings Per Share” (“ASC 260-10”), which requires the income or loss per share for each class of shares (ordinary and preferred shares) to be calculated assuming 100% of the Company’s earnings are distributed as dividends to each class of shares based on their contractual rights. For the years ended December 31, 2019 and 2018, the Company had no outstanding preferred shares and was not required to apply the two-class method under ASC 260-10. No dividends were declared or paid during the reported periods. According to the provisions of ASC 260-10, the Company’s preferred shares are not participating securities in losses and, therefore, are not included in the computation of net loss per share. Basic loss per share is computed by dividing the loss for the period applicable to ordinary shareholders by the weighted average number of ordinary shares outstanding during the period. In computing diluted income per share, weighted average shares used in computing basic earnings per share are adjusted to reflect the potential dilution that could occur upon the exercise of outstanding stock options and upon conversion of restricted stock units and warrants issued to investors and service providers using the “treasury stock method”.
Recent Accounting Pronouncements	Recent Accounting Pronouncements - Adopted In February 2016, the FASB issued ASU 2016-02, Leases (“ASU 2016-02”). ASU 2016-02 establishes ASC Topic 842 (“Topic 842”) which replaces ASC 840, Leases, by introducing a lessee model that requires balance sheet recognition for most leases and the disclosure of key information about leasing arrangements. Leases will be classified as finance or operating, with classification affecting the pattern and classification of expense recognition in the income statement. Topic 842 provides several optional practical expedients in transition. The Company elected the package of practical expedients which allowed the Company to not reassess its existing conclusions on lease identification, classification and initial direct costs. Further, the Company elected the hindsight practical expedient and utilized the short-term lease exemption for all leases with an original term of 12 months or less for purposes of applying the recognition and measurement requirements of the new standard. The Company also elected the practical expedient which allowed it to not separate lease and non-lease components for all its leases. The Company adopted the new standard on January 1, 2019 and applied the effective date as its date of initial application and has not updated disclosures required under the new standard for dates and periods prior to January 1, 2019. Also see Note 6, “Leases”. Recent Accounting Pronouncements - Pending Adoption In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). This standard requires that for most financial assets, losses must be based on an expected loss approach which includes estimates of losses over the life of exposure that considers historical, current and forecasted information. Expanded disclosures related to the methods used to estimate the losses as well as a specific disaggregation of balances for financial assets are also required. This standard is effective for annual periods beginning after December 15, 2019 and interim periods within those annual periods, with early adoption permitted for annual periods beginning after December 15, 2018. The Company is assessing the impact the adoption of ASU 2016-13 may have on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2019
Accounting Policies [Abstract]
Summary of Cash, Cash Equivalents and Marketable Securities	Below is a summary of cash, cash equivalents and marketable securities at December 31, 2019 (in thousands): Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents $ 22,493 $ — $ — $ 22,493 Marketable securities - U.S. treasuries 33,765 19 (1 ) 33,783 Total cash, cash equivalents and marketable securities $ 56,258 $ 19 $ (1 ) $ 56,276
Summary of Useful Lives of Principal Classes of Assets	Depreciation expense is computed on a straight-line method over the estimated useful lives of the respective assets, as follows: Useful Life (Years) Computers and software 3 years Office furniture and equipment 5 to 12 years Laboratory equipment 5 years Leasehold improvement Over the shorter of the expected lease term or estimated useful life

Prepaid Expenses and Other Cu_2

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2019
Prepaid And Other Current Assets [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): December 31, 2019 2018 Research and development $ 448 $ 864 Other 699 555 Insurance 217 251 Other governmental agency receivables 26 20 $ 1,390 $ 1,690

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	12 Months Ended
	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Property and equipment, net	Property and equipment, net consisted of the following (in thousands): December 31, 2019 2018 Computers and software $ 166 $ 146 Office furniture and equipment 164 165 Leasehold improvements 158 141 488 452 Less: Accumulated depreciation (287 ) (204 ) Property and equipment, net $ 201 $ 248

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued expenses	Accrued expenses consisted of the following (in thousands): December 31, 2019 2018 Research and development expenses $ 1,560 $ 3,086 Payroll, bonus and other employee-related expenses 2,200 2,562 Professional services 664 985 Other 137 305 Interest on debt 94 — $ 4,655 $ 6,938

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Summary of Maturities of Operating Lease Liabilities	The following table summarizes the Company’s maturities of operating lease liabilities as of December 31, 2019 (in thousands): 2020 $ 556 2021 404 2022 32 Total lease payments 992 Less: present value discount (68 ) Total $ 924
Summary of Future Minimum Non-Cancellable Commitments Under Operating Leases	The Company’s aggregate future minimum non-cancellable commitments under operating leases as of December 31, 2018 were as follows (in thousands): 2019 $ 541 2020 490 2021 310 Total minimum lease payments $ 1,341

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2019
Debt Disclosure [Abstract]
Schedule of Future Principal Payments for Long-Term Debt	The Company’s scheduled future principal payments for the long-term debt are as follows (in thousands): December 31, 2019 2020 $ 4,583 2021 5,000 2022 5,000 2023 417 Total future principal payments 15,000 Less: unamortized discount (1,062 ) Carrying value of long-term debt 13,938 Less: current portion (4,336 ) Add: final fee due at maturity in 2023 900 Long-term portion $ 10,502

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2019
Equity [Abstract]
Summary of Warrants Outstanding	Eloxx Limited issued warrants to purchase shares in conjunction with the Share Purchase Agreements prior to the Transaction. During the year ended December 31, 2019, transactions related to warrants were as follows: Shares Weighted average exercise price Weighted average remaining contractual life (years) Warrants outstanding at December 31, 2018 347,241 $ 3.77 3.92 Granted 40,834 Exercised (59,707 ) Forfeited (4,474 ) Warrants outstanding at December 31, 2019 323,894 $ 4.32 3.74 Warrants exercisable at December 31, 2019 323,894 $ 4.32 3.74

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Transactions Related to Grant of Stock Options to Employees and Directors	Transactions related to stock options granted to employees and directors during the year ended December 31, 2019, were as follows: Amount Weighted average exercise price Weighted average remaining contractual life (years) Aggregate intrinsic value Options outstanding as of December 31, 2018 3,261,719 $ 13.09 8.56 $ 11,650,373 Granted 1,842,990 9.31 Exercised (116,327 ) 4.27 Forfeited (250,712 ) 10.35 Options outstanding as of December 31, 2019 4,737,670 $ 11.17 8.54 $ 3,629,073 Options exercisable at December 31, 2019 1,785,477 $ 11.78 7.55 $ 2,498,968
Assumptions Used to Estimate Fair Values of Stock Options Granted	The following table presents the assumptions used to estimate the fair values of stock options granted in the periods presented: Year ended December 31, 2019 2018 2017 Dividend yield 0% 0% 0% Volatility 76%-92% 90%-92% 87%-117% Risk-free interest rate 1.51%-2.62% 2.55%-3.20% 1.22%-2.50% Expected term (years) 5.5-6.0 — — Contractual term (years) 10 10 10 Forfeiture rate post-vesting — 10% 10% Suboptimal exercise — 2.3 2.3
Transactions Related to Grant of Restricted Stock Units to Employees	Transactions related to restricted stock units granted to employees during the year ended December 31, 2019, were as follows: Shares Weighted average grant date fair value per share Unvested at December 31, 2018 554,147 $ 9.34 Granted 100,000 11.53 Vested (190,202 ) 8.09 Forfeited — — Unvested at December 31, 2019 463,945 $ 9.45
Summary of Allocated Stock-based Compensation Expense	Stock-based compensation expense relates to stock options granted to employees, non-employee directors and non-employees, time-based restricted stock units granted to employees and performance-based stock options and restricted stock units granted to an employee. The total equity-based compensation expense related to all of the Company’s equity-based awards was recognized as follows (in thousands): Year ended December 31, 2019 2018 2017 Research and development $ 2,458 $ 1,745 $ 39 General and administrative 8,878 11,625 62 Total stock-based compensation expense $ 11,336 $ 13,370 $ 101

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Components of Income (Loss) Before Taxes	The components of income (loss) before taxes on income are as follows (in thousands): Year ended December 31, 2019 2018 2017 U.S. $ (22,242 ) $ (24,439 ) $ (21 ) Israel (28,632 ) (22,624 ) (21,145 ) Loss before taxes on income $ (50,874 ) $ (47,063 ) $ (21,166 )
Current Income Tax Provision	There were no taxes on income during the year ended December 31, 2019. Taxes on income during the year ended December 31, 2018 resulted primarily from subsidiary income as a result of the implementation of an intercompany cost-plus arrangement. The current income tax provision consisted of the following (in thousands): Year ended December 31, 2019 2018 2017 Federal $ — $ 94 $ — State and local — 28 — Foreign — — — Income tax provision $ — $ 122 $ —
Significant Components of Deferred Tax Assets	The significant components of the Company’s deferred tax assets were comprised of the following (in thousands): December 31, 2019 2018 Deferred tax assets: Net operating loss carryforwards $ 38,357 $ 29,521 Stock-based compensation 2,801 1,001 Reserves and allowances 615 377 U.S. tax credits and other credits 2,980 714 Research and development credits 1,831 4,216 Operating lease right-of-use assets (169 ) — Operating lease liabilities 169 — Other 98 40 Total deferred tax assets 46,682 35,869 Valuation allowance (46,682 ) (35,869 ) Net deferred tax assets $ — $ —
Reconciliation of Expected Tax Expense with Actual Tax Expense	For the year ended December 31, 2019, the expected tax expense based on the federal statutory rate reconciled with the actual tax expense as follows: Year ended December 31, 2019 2018 U.S. federal statutory rate 21.0 % 21.0 % State tax rate, net of federal benefit 0.9 2.4 Permanent differences (1.5 ) (3.0 ) Adjustments to deferred taxes — (1.8 ) Effect of rate differences from statutory 1.1 0.8 Tax reform - federal tax rate change — 0.1 Tax reform - change in valuation allowance — (0.1 ) Change in valuation allowance (21.5 ) (19.5 ) Other — (0.2 ) Income tax provision 0.0 % -0.3 %

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2019
Earnings Per Share [Abstract]
Schedule of Loss and Weighted Average Number of Shares Used in Computing Basic and Diluted Net Loss Per Share	The loss and the weighted average number of shares used in computing basic and diluted net loss per share for the years ended December 31, 2019, 2018, and 2017, are as follows (in thousands, except share and per share data): Year ended December 31, 2019 2018 2017 Numerator: Net loss $ (50,874 ) $ (47,185 ) $ (21,214 ) Less: Dividends accumulated for the period (1) — — (2,404 ) Net loss attributable to common stockholders $ (50,874 ) $ (47,185 ) $ (23,618 ) Denominator: Weighted average number of shares common stock used in computing net loss per share, basic and diluted 38,063,173 32,436,506 4,976,377 Net loss per share, basic and diluted $ (1.34 ) $ (1.45 ) $ (4.75 ) (1) The net loss used for the computation of basic and diluted net loss per share includes 8% per share per annum compounded annually which was related to distributions for preferred stockholders of Eloxx Limited. On December 19, 2017 in conjunction with the Reverse Merger, all preferred shares were converted to common shares.

Other (Income) Expense, net (Ta

Other (Income) Expense, net (Tables)	12 Months Ended
	Dec. 31, 2019
Other Income And Expenses [Abstract]
Schedule of Other (Income) Expense	Other (income) expense consisted of the following (in thousands): Year ended December 31, 2019 2018 2017 Interest and other income $ (1,072 ) $ (601 ) $ — Foreign currency exchange gains 76 92 156 Amortization and revaluation of embedded conversion feature in respect to convertible loan — — 625 Investment income, net (301 ) — — Interest and other expense 1,616 7 43 Total other expense (income), net $ 319 $ (502 ) $ 824

Reverse Merger (Tables)

Reverse Merger (Tables)	12 Months Ended
	Dec. 31, 2019
Eloxx Limited [Member]
Summary of Assets and Liabilities Assumed	The following table summarizes the assets and liabilities assumed at the date of the Reverse Merger (in thousands): December 19, 2017 Cash and cash equivalents $ 123 Prepaid expenses and other current assets 220 Property, plant and equipment, net 39 Restricted bank deposits 6 Total assets acquired 388 Accounts payable (215 ) Accrued expenses (343 ) Total liabilities acquired (558 ) Total net liabilities acquired $ (170 )

Nature of the Business - Additi

Nature of the Business - Additional Information (Detail) $ / shares in Units, $ in Thousands	Dec. 19, 2017$ / sharesshares	Dec. 31, 2019USD ($)Disease$ / shares	Dec. 31, 2018USD ($)$ / shares
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Number of rare diseases | Disease		1,800
Common stock, par value | $ / shares		$ 0.01	$ 0.01
Accumulated deficit | $		$ (137,019)	$ (86,145)
Cash, cash equivalents and marketable securities | $		$ 56,276
Eloxx Limited [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Common stock, par value | $ / shares	$ 0.01
Issuance of shares in exchange of all outstanding capital stock | shares	20,316,656
Reverse stock split	0.05

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended		36 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Line Items]
Cash equivalents	$ 22,493,000	$ 48,606,000	$ 24,049,000
Realized gains or losses on the sale of securities	0
Impairment of long-lived assets	0
Asset Impairment	0
Assets, transfer from level 2 to level 3	0
Liability for unrecognized tax benefits	0	0
Interest or penalties related to uncertain tax positions	$ 0	$ 0
Preferred shares, outstanding	0	0
Dividends	$ 0	$ 0
Payment of dividends	$ 0	$ 0
Eloxx Limited [Member]
Accounting Policies [Line Items]
Proceeds from royalty-bearing grants			$ 2,600,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Cash, Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Cash and cash equivalents	$ 22,493	$ 48,606	$ 24,049
Cash and cash equivalents, Fair Value	22,493
Total cash, cash equivalents and marketable securities, Amortized Cost	56,258
Total cash, cash equivalents and marketable securities, Unrealized Gains	19
Total cash, cash equivalents and marketable securities, Unrealized Losses	(1)
Total cash, cash equivalents and marketable securities, Fair Value	56,276
U.S. treasuries [Member]
Schedule Of Available For Sale Securities [Line Items]
Marketable securities, Amortized Cost	33,765
Marketable securities, Unrealized Gains	19
Marketable securities, Unrealized Losses	(1)
Marketable securities, Fair Value	$ 33,783

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Useful Lives of Principal Classes of Assets (Detail)	12 Months Ended
	Dec. 31, 2019
Computers and software [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	3 years
Office furniture and equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	5 years
Office furniture and equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	12 years
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	5 years
Leasehold improvement [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of asset, description	Over the shorter of the expected lease term or estimated useful life

Prepaid Expenses and Other Cu_3

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Research and development	$ 448	$ 864
Other	699	555
Insurance	217	251
Other governmental agency receivables	26	20
Total	$ 1,390	$ 1,690

Property and Equipment, net - P

Property and Equipment, net - Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Cost	$ 488	$ 452
Less: Accumulated depreciation	(287)	(204)
Property and equipment, net	201	248
Computers and software [Member]
Property, Plant and Equipment [Line Items]
Cost	166	146
Office furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	164	165
Leasehold improvement [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 158	$ 141

Property and Equipment, net - A

Property and Equipment, net - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Depreciation expenses	$ 87	$ 216	$ 39

Accrued Expenses - Accrued Expe

Accrued Expenses - Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Research and development expenses	$ 1,560	$ 3,086
Payroll, bonus and other employee-related expenses	2,200	2,562
Professional services	664	985
Other	137	305
Interest on debt	94
Total	$ 4,655	$ 6,938

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019
Leases [Line Items]
Operating lease cost	$ 500
Operating lease estimated incremental borrowings rate	8.00%
Operating lease, initial present value	$ 1,500
Operating lease, right-of-use asset	924
Operating lease, liabilities	$ 924
Weighted average remaining lease term	1 year 9 months 21 days
Operating lease, payments	$ 500
Remeasurement of operating leases	$ 176
ASU 2016-02 [Member]
Leases [Line Items]
Operating lease, right-of-use asset		$ 1,200
Operating lease, liabilities		$ 1,200

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Dec. 31, 2019USD ($)
Leases [Abstract]
2020	$ 556
2021	404
2022	32
Total lease payments	992
Less: present value discount	(68)
Operating lease, liabilities	$ 924

Leases - Summary of Future Mini

Leases - Summary of Future Minimum Non-Cancellable Commitments Under Operating Leases (Detail) $ in Thousands	Dec. 31, 2018USD ($)
Leases [Abstract]
2019	$ 541
2020	490
2021	310
Total minimum lease payments	$ 1,341

Debt - Additional Information (

Debt - Additional Information (Detail) $ / shares in Units, $ in Thousands	Jan. 30, 2019USD ($)Installment$ / sharesshares	Dec. 31, 2019USD ($)$ / shares	Dec. 31, 2018$ / shares
Debt Instrument [Line Items]
Aggregate principal amount of initial loan advance		$ 13,938
Warrant exercise price | $ / shares		$ 4.32	$ 3.77
Term loan, principal outstanding		$ 15,000
Term loan, final maturity payment		$ 900
Loan Agreement [Member]
Debt Instrument [Line Items]
Aggregate principal amount	$ 25,000
Debt instrument, interest rate terms	Outstanding principal on the Term Loan Advances accrues interest at a floating rate equal to the greater of (i) 5.25% per annum and (ii) the sum of 2.5% plus the prime rate, as published in the Wall Street Journal. Interest payments are payable monthly following the funding of a Term Loan advance.
Debt instrument, payment terms	The Company will be required to make principal payments on the outstanding balance of the Term Loan Advances commencing on February 1, 2020 in 36 equal monthly installments, plus interest.
Term loan, floating interest rate	5.25%
Term loan, interest rate		7.25%
Term loan, frequency of periodic payment	monthly
Term loan, number of repayment installments | Installment	36
Term loan, periodic principal payment commencement date	Feb. 1, 2020
Term loan, maturity date	Jan. 1, 2023
Warrant exercise price | $ / shares	$ 11.02
Common stock average closing bid price number of trading days	10 days
Term loan, final payment fee percentage	6.00%
Term loan, principal outstanding		$ 15,000
Term loan, unamortized debt issuance costs		1,100
Term loan, interest expense		$ 1,600
Term loan, effective interest rate		12.40%
Term loan, final maturity payment		$ 900
Loan Agreement [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Term loan, floating interest rate	2.50%
Loan Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Term loan, prepayment fee percentage	1.00%
Loan Agreement [Member] | Minimum [Member] | Private Placement or Public Offering [Member]
Debt Instrument [Line Items]
Cash proceeds from an additional equity offering	$ 75,000
Loan Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Term loan, prepayment fee percentage	3.00%
Loan Agreement [Member] | Initial Loan [Member]
Debt Instrument [Line Items]
Aggregate principal amount of initial loan advance	$ 15,000
Warrants issued to purchase shares of common stock | shares	40,834
Loan Agreement [Member] | Subsequent Loan [Member]
Debt Instrument [Line Items]
Aggregate principal amount of subsequent loan advance	$ 10,000

Debt - Schedule of Future Princ

Debt - Schedule of Future Principal Payments for Long-Term Debt (Detail) $ in Thousands	Dec. 31, 2019USD ($)
Debt Disclosure [Abstract]
2020	$ 4,583
2021	5,000
2022	5,000
2023	417
Total future principal payments	15,000
Less: unamortized discount	(1,062)
Carrying value of long-term debt	13,938
Less: current portion	(4,336)
Add: final fee due at maturity in 2023	900
Long-term portion	$ 10,502

Related Parties - Additional In

Related Parties - Additional Information (Detail) - USD ($)	Jun. 30, 2018	Jun. 13, 2018	Aug. 29, 2013	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Related Party Transaction Details [Line Items]
Research and development expense				$ 25,842,000	$ 20,489,000	$ 16,398,000
General and administrative expenses				24,713,000	26,482,000	2,702,000
Accrued expenses				$ 4,655,000	6,938,000
Technion Research and Development Foundation Ltd [Member]
Schedule Of Related Party Transaction Details [Line Items]
Research and development expense						3,400,000
Collaborative arrangement additional consideration receivable as percentage of all non-refundable, non-contingent consideration				3.00%
Collaborative arrangement additional consideration receivable as percentage of non-refundable, non-contingent consideration received				3.00%
Technion Agreement [Member] | Technion Research and Development Foundation Ltd [Member]
Schedule Of Related Party Transaction Details [Line Items]
Research and development expense			$ 100,000	$ 200,000	100,000	3,500,000
General and administrative expenses				0	0	$ 7,000
Accrued expenses				142,000	$ 25,000
Aggregate milestone payment				$ 6,100,000
Shares issued	569,395	569,395

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended			48 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2018
Legal And Other Contingencies [Line Items]
Advances from collaboration partners	$ 403,000
Research and Development Agreements [Member]
Legal And Other Contingencies [Line Items]
R&D grants received	$ 0	$ 0	$ 900,000	$ 2,600,000
Royalty payment as percentage of net sales	3.00%
Repayment percentage of grants received	100.00%
Royalty received including accrued LIBOR interest	$ 2,700,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Jun. 24, 2019	Apr. 30, 2018	Dec. 19, 2017	Jan. 31, 2019	Nov. 30, 2018	May 31, 2017	Sep. 30, 2016	Aug. 31, 2016	Feb. 29, 2016	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Nov. 16, 2018	Apr. 20, 2018	Dec. 18, 2017	Dec. 31, 2016
Common stock, shares authorized										500,000,000	500,000,000
Common stock, par value										$ 0.01	$ 0.01
Common stock, shares outstanding										40,030,763	35,860,114
Preferred Stock, shares authorized										5,000,000	5,000,000
Preferred stock, par value										$ 0.01	$ 0.01
Preferred stock, shares issued							0.1			0	0
Preferred Stock, shares outstanding										0	0
Net proceeds from common stock shares issued at public offering												$ 17,006,000
Offering expenses												494,000
Proceeds from issuance of preferred stock							$ 3,700,000		$ 6,000,000
Warrant exercised										59,707
Common stock, shares issued										40,186,469	35,951,537
Sevion Therapeutics Inc [Member]
Equity method investments															$ 1,500,000
Equity Sales Agreement [Member]
Issuance of stock, shares				35,362							201,100
Net proceeds from common stock shares issued at public offering				$ 700,000						$ 710,000	$ 2,165,000
Legal,accounting and other fees					$ 300,000
2017 Share Purchase Agreement [Member]
Proceeds from issuance of preferred stock						$ 21,500,000
Stock issuance costs						$ 600,000
2017 Share Purchase Agreement [Member] | After Merger [Member]
Net proceeds from common stock shares issued at public offering			$ 17,500,000
Stock issuance costs												$ 500,000
Common stock, shares issued			6,333,333
Common Stock [Member]
Common stock, shares outstanding										40,030,763	35,860,114	27,527,738				4,205,278
Issuance of stock, shares												6,333,333
Preferred Stock [Member]
Common stock, shares outstanding																7,638,263
Preferred Stock [Member] | TIOF [Member]
Warrant exercised								124,786
Preferred Stock [Member] | TRDF [Member]
Warrant exercised								311,964
Preferred Stock [Member] | TIOF and TRDF [Member]
Total consideration								$ 400,000
Maximum [Member]
Shelf registration statement securities value													$ 200,000,000	$ 125,000,000
Maximum [Member] | Equity Sales Agreement [Member] | Citigroup Global Markets Inc. and Cantor Fitzgerald & Co. [Member]
Aggregate offering price					$ 50,000,000
Percentage of sales agents commission					3.00%
Underwritten Public Offering [Member]
Underwriting discounts and commissions and offering expenses		$ 3,900,000
Net proceeds from common stock shares issued at public offering										$ 32,172,000	$ 53,573,000
Underwritten Public Offering [Member] | Common Stock [Member]
Issuance of stock, shares	3,833,334	5,899,500
Common stock public offering price	$ 9	$ 9.75
Gross proceeds from common stock shares issued at public offering		$ 57,500,000
Net proceeds from common stock shares issued at public offering	$ 32,200,000
Underwriting discounts and commissions	2,100,000
Offering expenses	$ 200,000
Over-Allotment Option [Member]
Common stock, shares issued		769,500

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Transaction Related to Warrants to Purchase Common Stock (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Stockholders Equity [Abstract]
Warrants outstanding beginning balance, Shares	347,241
Warrants granted, Shares	40,834
Warrants exercised,Shares	(59,707)
Warrants forfeited, Shares	(4,474)
Warrants outstanding ending balance, Shares	323,894	347,241
Warrants exercisable, Shares	323,894
Warrants outstanding beginning balance, Weighted average exercise price	$ 3.77
Warrants outstanding ending balance,Weighted average exercise price	4.32	$ 3.77
Warrants exercisable, Weighted average exercise price	$ 4.32
Warrants outstanding and exercisable Weighted average remaining contractual life	3 years 8 months 26 days	3 years 11 months 1 day
Warrants exercisable, Weighted average remaining contractual life	3 years 8 months 26 days

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018USD ($)$ / shares	Dec. 31, 2017USD ($)$ / sharesshares	Apr. 20, 2018shares	Apr. 19, 2018CompensationPlan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity compensation plans | CompensationPlan					2
Options to purchase common stock granted	1,842,990
Exercise price per share | $ / shares	$ 9.31
Expense recognized associated with awards | $	$ 11,336	$ 13,370	$ 101
Unrecognized compensation cost related to outstanding options | $	$ 18,400
Unrecognized compensation cost expected to be recognized over a weighted-average period	2 years 8 months 4 days
Weighted average grant date fair value of options granted | $ / shares	$ 6.28	$ 18.06	$ 3.68
Performance Option Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized associated with awards | $	$ 100	$ 100
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock unit	100,000
Unrecognized compensation cost expected to be recognized over a weighted-average period	2 years 3 months 7 days
Unrecognized compensation cost related to outstanding other than options | $	$ 4,000
Chief Executive Officer [Member] | Performance Option Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase common stock granted			22,427
Exercise price per share | $ / shares			$ 8
Restricted stock unit			22,427
Chief Executive Officer [Member] | Time Vesting Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options to purchase common stock granted			640,785
Exercise price per share | $ / shares			$ 8
Restricted stock unit			640,785
Option vesting description	Subject to continued service through the vesting date, one-third of the Time-Vesting Awards will vest and become immediately exercisable on the first anniversary of the effective date, with an additional one-twelfth of the Time-Vesting Awards vesting on each quarterly anniversary of the effective date
Chief Executive Officer [Member] | Time Vesting Awards [Member] | First Anniversary of Effective Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, percentage	0.33%
Chief Executive Officer [Member] | Time Vesting Awards [Member] | Each Quarterly Anniversary of Effective Date [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights, quarterly percentage	0.083%
2018 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance				5,000,000
Contractual life of stock options granted	10 years
2018 Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercisable period of vested options	1 month
2018 Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercisable period of vested options	3 months

Stock-based Compensation - Tran

Stock-based Compensation - Transactions Related to Grant of Stock Options to Employees and Directors (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Amount
Options outstanding as of December 31, 2018	3,261,719
Granted	1,842,990
Exercised	(116,327)
Forfeited	(250,712)
Options outstanding as of December 31, 2019	4,737,670	3,261,719
Options exercisable at December 31, 2019	1,785,477
Weighted average exercise price
Options outstanding as of December 31, 2018	$ 13.09
Granted	9.31
Exercised	4.27
Forfeited	10.35
Options outstanding as of December 31, 2019	11.17	$ 13.09
Options exercisable at December 31, 2019	$ 11.78
Weighted average remaining contractual life
Options outstanding	8 years 6 months 14 days	8 years 6 months 21 days
Options exercisable	7 years 6 months 18 days
Aggregate intrinsic value
Options outstanding	$ 3,629,073	$ 11,650,373
Options exercisable	$ 2,498,968

Stock-based Compensation - Assu

Stock-based Compensation - Assumptions Used to Estimate Fair Values of Stock Options Granted (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Volatility, minimum	76.00%	90.00%	87.00%
Volatility, maximum	92.00%	92.00%	117.00%
Risk free interest rate, minimum	1.51%	2.55%	1.22%
Risk free interest rate, maximum	2.62%	3.20%	2.50%
Contractual term (years)	10 years	10 years	10 years
Forfeiture rate post-vesting		10.00%	10.00%
Suboptimal exercise		$ 2.3	$ 2.3
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	5 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years

Stock-based Compensation - Tr_2

Stock-based Compensation - Transactions Related to Grant of Restricted Stock Units to Employees (Detail) - Restricted Stock Units [Member]	12 Months Ended
	Dec. 31, 2019$ / sharesshares
Amount
Unvested at December 31, 2018 | shares	554,147
Granted | shares	100,000
Vested | shares	(190,202)
Unvested at December 31, 2019 | shares	463,945
Weighted average grant date fair value price
Unvested at December 31, 2018 | $ / shares	$ 9.34
Granted | $ / shares	11.53
Vested | $ / shares	8.09
Unvested at December 31, 2019 | $ / shares	$ 9.45

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Allocated Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 11,336	$ 13,370	$ 101
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,458	1,745	39
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 8,878	$ 11,625	$ 62

Income Taxes - Components of In

Income Taxes - Components of Income (Loss) Before Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S.	$ (22,242)	$ (24,439)	$ (21)
Israel	(28,632)	(22,624)	(21,145)
Loss before taxes on income	$ (50,874)	$ (47,063)	$ (21,166)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 23, 2017	Dec. 19, 2017
Income Tax Disclosure [Line Items]
Taxes on income	$ 0	$ 122,000
Deferred tax assets, valuation allowance	46,682,000	35,869,000
Net deferred tax asset	0	0	$ 0
Change in valuation allowance	10,800,000	7,700,000
Federal research tax credit carryforwards	$ 3,000,000	$ 700,000			$ 700,000
U.S. federal corporate income tax rate	21.00%	21.00%	35.00%
Provisional estimate of deferred tax expense			$ 10,200,000
Income tax examination, description	The Company is subject to income taxes in the United States and Israel. The Company files income tax returns in the U.S. and in several states. The federal and state tax returns are generally subject to tax examination by taxing authorities for tax years beginning in June 30, 2015 to present. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by the Internal Revenue Service or state tax authorities to the extent utilized in a future period. The Israeli income tax returns remain open to examination beginning in 2013 to present. If and when the Company claims NOL carryforwards from any prior years against future taxable income, those losses may be examined by the taxing authorities.
Earliest Tax Year [Member]
Income Tax Disclosure [Line Items]
Federal research tax credit expiry, beginning period	2027
Latest Tax Year [Member]
Income Tax Disclosure [Line Items]
Federal research tax credit expiry, beginning period	2037
Federal [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 99,400,000	$ 89,800,000			$ 77,200,000
U.S. federal NOL carryforwards, not subject to expiration				$ 23,500,000
Net operating loss carryforwards eligible to offset taxable income, maximum	80.00%
Federal [Member] | Earliest Tax Year [Member]
Income Tax Disclosure [Line Items]
U.S. net operating loss expiry, beginning period	2020
Federal [Member] | Latest Tax Year [Member]
Income Tax Disclosure [Line Items]
U.S. net operating loss expiry, beginning period	2037
State [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 31,900,000	40,000,000
Israel Tax Authority [Member]
Income Tax Disclosure [Line Items]
Net operating loss carryforwards	$ 73,700,000	$ 34,600,000

Income Taxes - Current Income T

Income Taxes - Current Income Tax Provision (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal		$ 94,000
State and local		28,000
Income tax provision	$ 0	$ 122,000

Income Taxes - Significant Comp

Income Taxes - Significant Components of Deferred Tax Assets (Detail) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating loss carryforwards	$ 38,357,000	$ 29,521,000
Stock-based compensation	2,801,000	1,001,000
Reserves and allowances	615,000	377,000
U.S. tax credits and other credits	2,980,000	714,000
Research and development credits	1,831,000	4,216,000
Operating lease right-of-use assets	(169,000)
Operating lease liabilities	169,000
Other	98,000	40,000
Total deferred tax assets	46,682,000	35,869,000
Valuation allowance	(46,682,000)	(35,869,000)
Net deferred tax assets	$ 0	$ 0	$ 0

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Expected Tax Expense with Actual Tax Expense (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.S. federal statutory rate	21.00%	21.00%	35.00%
State tax rate, net of federal benefit	0.90%	2.40%
Permanent differences	(1.50%)	(3.00%)
Adjustments to deferred taxes		(1.80%)
Effect of rate differences from statutory	1.10%	0.80%
Tax reform - federal tax rate change		0.10%
Tax reform - change in valuation allowance		(0.10%)
Change in valuation allowance	(21.50%)	(19.50%)
Other		(0.20%)
Income tax provision	0.00%	(0.30%)

Net Loss Per Share - Schedule o

Net Loss Per Share - Schedule of Loss and Weighted Average Number of Shares Used in Computing Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss		$ (50,874)	$ (47,185)	$ (21,214)
Less: Dividends accumulated for the period	[1]			(2,404)
Net loss attributable to common stockholders		$ (50,874)	$ (47,185)	$ (23,618)
Denominator:
Weighted average number of shares common stock used in computing net loss per share, basic and diluted		38,063,173	32,436,506	4,976,377
Net loss per share, basic and diluted		$ (1.34)	$ (1.45)	$ (4.75)
[1]	The net loss used for the computation of basic and diluted net loss per share includes 8% per share per annum compounded annually which was related to distributions for preferred stockholders of Eloxx Limited. On December 19, 2017 in conjunction with the Reverse Merger, all preferred shares were converted to common shares.

Net Loss Per Share - Schedule_2

Net Loss Per Share - Schedule of Loss and Weighted Average Number of Shares Used in Computing Basic and Diluted Net Loss Per Share (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Percentage of dividend rate	8.00%	8.00%	8.00%

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Shares excluded from the calculation of the diluted net loss per share	5,525,509	4,163,107	19,027,306

Other (Income) Expense, net - S

Other (Income) Expense, net - Schedule of Other (Income) Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Income And Expenses [Abstract]
Interest and other income	$ (1,072)	$ (601)
Foreign currency exchange gains	76	92	$ 156
Amortization and revaluation of embedded conversion feature in respect to convertible loan			625
Investment income, net	(301)
Interest and other expense	1,616	7	43
Total other expense (income), net	$ 319	$ (502)	$ 824

Segment and Geographic Inform_2

Segment and Geographic Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019SegmentRegion
Segment Reporting [Abstract]
Number of operating segment | Segment	1
Number of geographic regions | Region	2

Reverse Merger - Summary of Ass

Reverse Merger - Summary of Assets and Liabilities Assumed (Detail) - Eloxx Limited [Member] $ in Thousands	Dec. 19, 2017USD ($)
Business Acquisition [Line Items]
Cash and cash equivalents	$ 123
Prepaid expenses and other current assets	220
Property, plant and equipment, net	39
Restricted bank deposits	6
Total assets acquired	388
Accounts payable	(215)
Accrued expenses	(343)
Total liabilities acquired	(558)
Total net liabilities acquired	$ (170)

Reverse Merger - Additional Inf

Reverse Merger - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Eloxx Limited [Member]
Business Acquisition [Line Items]
Professional fees	$ 0	$ 600,000	$ 1,300,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) $ in Millions	Feb. 24, 2020Employee	Mar. 31, 2020USD ($)
Forecast [Member]
Subsequent Event [Line Items]
Vesting of executive stock awards		$ 2.5
Forecast [Member] | Severance and Benefits [Member]
Subsequent Event [Line Items]
Expect to incur of employee separation costs		$ 1.7
Subsequent Event [Member]
Subsequent Event [Line Items]
Elimination of managerial full time positions | Employee	13