Eloxx Pharmaceuticals (ELOX) 10-Q 9 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 03, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	ELOX
Entity Registrant Name	ELOXX PHARMACEUTICALS, INC.
Entity Central Index Key	0001035354
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		36,025,422
Entity Small Business	true
Entity Emerging Growth Company	false

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 44,576	$ 48,606
Marketable securities	8,928
Restricted bank deposit	45	45
Prepaid expenses and other current assets	1,911	1,690
Total current assets	55,460	50,341
Property and equipment, net	231	248
Operating lease right-of-use asset	1,106
Other long-term assets	94	129
Total assets	56,891	50,718
Current liabilities:
Accounts payable	2,240	747
Accrued expenses	4,597	6,938
Current portion of long-term debt	984
Current portion of operating lease liability	481
Taxes payable	122	122
Total current liabilities	8,424	7,807
Long-term debt	13,409
Operating lease liability	625
Stockholders’ equity:
Preferred stock, $0.01 par value per share, 5,000,000 shares authorized, no shares issued and outstanding at March 31, 2019 and December 31, 2018
Common stock, $0.01 par value per share, 500,000,000 shares authorized, 36,047,498 and 35,951,537 shares issued and 35,945,608 and 35,860,114 shares outstanding as of March 31, 2019 and December 31, 2018, respectively	361	360
Common stock in treasury, at cost, 101,890 and 91,423 shares at March 31, 2019 and December 31, 2018, respectively	(1,250)	(1,129)
Additional paid in capital	133,383	129,825
Accumulated other comprehensive income	1
Accumulated deficit	(98,062)	(86,145)
Total stockholders’ equity	34,433	42,911
Total liabilities and stockholders' equity	$ 56,891	$ 50,718

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 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	36,047,498	35,951,537
Common stock, shares outstanding	35,945,608	35,860,114
Common stock, treasury shares	101,890	91,423

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Other Comprehensive Loss - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Operating expenses:
Research and development		$ 6,019	$ 4,394
General and administrative		5,958	3,393
Reverse merger related expenses			761
Total operating expenses		11,977	8,548
Loss from operations		(11,977)	(8,548)
Other (income) expense, net		(60)	43
Net loss		(11,917)	(8,591)
Other Comprehensive Loss:
Net loss		(11,917)	(8,591)
Unrealized gain from available-for-sale securities		1
Comprehensive loss		$ (11,916)	$ (8,591)
Basic and diluted net loss per share		$ (0.33)	$ (0.31)
Weighted average number of common shares in computing basic and diluted net loss per share	[1]	35,910,270	27,527,738
[1]	The following potentially dilutive securities have been excluded from the computation of diluted weighted average shares outstanding as their effect would be anti-dilutive: Three months ended March 31, 2019 2018 Options to purchase common stock 3,921,823 2,498,617 Restricted stock units 618,548 — Warrants 388,075 411,615 Total potential common stock equivalents 4,928,446 2,910,232

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (11,917)	$ (8,591)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	2,658	735
Depreciation	33	21
Amortization of operating lease right-of-use asset	114
Amortization of debt discount	91
Amortization of premium and discount on investment	(5)
Change in operating assets and liabilities:
Prepaid expenses and other current assets	(183)	(90)
Accounts payable	1,493	643
Accrued expenses	(1,358)	1,585
Operating lease liabilities	(114)
Net cash used in operating activities	(9,188)	(5,697)
Cash flows from investing activities:
Purchases of property and equipment	(16)	(57)
Cash paid for long-term deposits	(3)
Net cash used in investing activities	(19)	(57)
Cash flows from financing activities:
Purchase of marketable securities	(8,923)
Proceeds from debt financing obligation	15,000
Payment of debt issuance costs	(276)
Payment for settlement of taxes upon vesting of Restricted Stock Securities	(1,104)
Proceeds from sale of Common Stock under Equity Sales Agreement	455
Proceeds from issuance of Common Stock on share-based compensation arrangements	25
Net cash provided by financing activities	5,177
Effect of exchange rate on cash		(5)
Increase in cash and cash equivalents	(4,030)	(5,759)
Cash, cash equivalents and restricted cash, beginning of year	48,651	24,049
Cash, cash equivalents and restricted cash, end of period	44,621	18,290
Reconciliation of cash, cash equivalents and restricted cash to condensed consolidated balance sheets
Cash and cash equivalents	44,576	18,290
Restricted cash included in restricted bank deposit	45	106
Total cash, cash equivalents and restricted cash	44,621	$ 18,396
Supplemental disclosure of non-cash financing activities
Non-cash acquisition of treasury shares	121
Fair value of warrants issued in connection with long-term debt	421
Cash paid during the year for interest	93
Final payment in connection with debt financing obligation	$ 900

Nature of the Business

Nature of the Business	3 Months Ended
	Mar. 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 wholly-owned subsidiary Eloxx Pharmaceuticals, Ltd. (collectively “Eloxx” or the “Company”), is a clinical-stage biopharmaceutical company developing novel ribonucleic acid (RNA)-modulating drug candidates (designed to be eukaryotic ribosomal selective glycosides (ERSG)) that are 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 are targeted to the ribosomes. ELX-02, the Company’s lead investigational drug product candidate, is a small molecule drug candidate designed to restore production of full-length functional proteins. ELX-02 is in the early stages of clinical development for systemic administration for cystic fibrosis and cystinosis. ELX-02 is an investigational drug that has not been approved by any global regulatory body. In addition, the Company recently announced a new program studying intravitreal administration of ERSG compounds for rare inherited retinal disorders with a focus on Usher Syndrome. 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. Eloxx is headquartered in Waltham, MA, with additional offices in New Jersey, Pennsylvania and Rehovot, Israel. The Company’s research and development strategy is to target rare or ultra-rare diseases where: a high unmet medical need exists, identified nonsense mutation-bearing patient population is identified, preclinical read-through can be established in predictive personalized medicine models, and a defined path through Organ Drug development, regulatory approval, patient access and commercialization is identified. The Company believes patient advocacy to be 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 focus for its lead investigational drug product candidate, ELX-02, is Cystic Fibrosis where the Company expects to complete its multiple ascending dose (“MAD”) study in the first half of 2019 and report top line results from its Phase 2 clinical trial in the second half of 2019. Eloxx has participated in the North American Cystic Fibrosis Foundation (CFF) CFTR Translation Read-through Workshop and is engaged with CFF on extending Cystic Fibrosis clinical studies to the United States. Eloxx presented positive new data for its lead investigational drug, ELX-02, at the European Cystic Fibrosis Society (ECFS) Basic Science Conference. In 2018, the European Cystic Fibrosis Society Clinical Trial Network assigned a “high priority” rating to Eloxx’s Phase 2 program. Eloxx has recently initiated a new program studying inherited retinal disease and is conducting IND enabling studies for several ERSG compounds from its library. Eloxx presented at the Sixth Annual Retinal Cell and Gene Therapy Innovation Summit and the Association for Research in Vision and Ophthalmology 2019 Annual Meeting. The Company entered into a multiyear partnership with the Foundation Fighting Blindness (FFB) to support its inherited retinal degenerative disease registry and educational programs. Eloxx presented as part of the FFB “Investing in Cures” 2019 meeting and believes that the ongoing R&D consultation and support provided by the FFB will accelerate the Company’s development programs that seek to support patients with ocular disease and high unmet medical need. Liquidity The Company has a history of net losses and negative cash flows from operating activities since inception, and as of March 31, 2019, had an accumulated deficit of $98.1 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 obtaining marketing approval and commercialization 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. 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. The Company believes that its cash, cash equivalents and marketable securities of $53.5 million at March 31, 2019 will enable it to meet anticipated cash needs required to reach top line Phase 2 data in cystic fibrosis and cystinosis in 2019 and maintain the Company’s current and planned operations into the second quarter of 2020.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of presentation and principles of consolidation The accompanying unaudited interim consolidated financial statements have been prepared by the Company 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 Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted, as permitted by such rules and regulations. These interim consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position, results of operations, and cash flows for the interim periods ended March 31, 2019 and 2018. The unaudited Condensed Consolidated Statements of Operations includes the Company’s operating expenses related to research and development and general and administrative which were substantially comprised of fees for professional services and employee compensation. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2018, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on March 14, 2018. Summary of Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2018, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K. During the three months ended March 31, 2019, the Company invested in marketable securities and as a result has provided the following updates. Marketable Securities —All investment instruments with an original maturity date, when purchased, in excess of three months but less than 1 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 condensed consolidated balance sheet, until such gains and losses are realized. Realized gains and losses on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific identification method. The Company periodically reviews the portfolio of securities to determine whether an other-than-temporary impairment has occurred. No such losses have occurred to date. There were no realized gains or losses on the sale of securities for the three months ended March 31, 2019. Below is a summary of cash, cash equivalents and marketable securities at March 31, 2019 (in thousands): Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents $ 44,576 $ — $ — $ 44,576 Marketable securities 8,927 1 — 8,928 Total cash, cash equivalents and marketable securities $ 53,503 $ 1 $ — $ 53,504 Fair Value Measurements —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. Authoritative guidance 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 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. 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. The Company has classified its cash, cash equivalents and marketable securities as Level 1. There were no transfers to Level 3 during the three months ended March 31, 2019. 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. Concentrations of Credit Risk and Off-Balance-Sheet Risk —Financial instruments that potentially subject the Company to credit risk primarily consist of cash and cash equivalents and available-for-sale 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 other securities, and the management of these investments is not discretionary on the part of the financial institution. The Company has no significant off-balance-sheet risks such as foreign exchange contracts, option contracts, or other hedging arrangements. Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases Leases

Prepaids and Other Current Asse

Prepaids and Other Current Assets	3 Months Ended
	Mar. 31, 2019
Prepaid And Other Current Assets [Abstract]
Prepaids and Other Current Assets	3. Prepaids and Other Current Assets Prepaids and other current assets as of March 31, 2019 and December 31, 2018 consisted of the following (in thousands): As of March 31, 2019 December 31, 2018 Prepaid insurance $ 325 $ 251 Other governmental agencies receivables 26 20 Prepaid research and development 1,215 864 Prepaid other 345 555 $ 1,911 $ 1,690

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2019
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment as of March 31, 2019 and December 31, 2018 consisted of the following (in thousands): As of March 31, 2019 December 31, 2018 Computers and software $ 146 $ 146 Office furniture and equipment 165 165 Leasehold improvements 157 141 468 452 Less: Accumulated depreciation 237 204 Property and equipment, net $ 231 $ 248 Depreciation expense was $33 thousand and $21 thousand for the three months ended March 31, 2019 and 2018, respectively.

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2019
Payables And Accruals [Abstract]
Accrued Expenses	5. Accrued Expenses Accrued expenses as of March 31, 2019 and December 31, 2018 consisted of the following (in thousands): As of March 31, 2019 December 31, 2018 Payroll and related expenses $ 1,060 $ 2,562 Research and development expenses 2,688 3,086 Professional services 583 985 Accrued interest on debt 103 — Accrued other 163 305 $ 4,597 $ 6,938

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	6. Leases The Company adopted 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 i) the renewal rate is at future market rate to be determined and ii) 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 three months ended March 31, 2019 was approximately $0.1 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 liability 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 ASC Topic 842, the Company recorded right to use assets of $1.2 million and a lease liability of $1.2 million. Operating lease assets and obligations are reflected within Operating lease right to use asset, and Operating lease liability, respectively, on the unaudited Condensed Consolidated Balance Sheet. The weighted average remaining lease term at March 31, 2019 was 2.3 years. The following table summarizes the Company’s maturities of operating lease liabilities as of March 31, 2019 (in thousands): Remainder of 2019 $ 413 2020 493 2021 310 Total lease payments 1,216 Less: present value discount (110 ) Total $ 1,106 For comparative purposes, 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	3 Months Ended
	Mar. 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”), collectively the Lenders. Under the SVB Loan Agreement, the Lenders agreed to extend term loans to the Company in an aggregate principal amount of $25 million, comprised of (i) an initial loan advance of $15 million; and (ii) a subsequent loan advance of $10 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 is 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. Any outstanding principal on the Term Loan Advances will accrue interest at a floating rate equal to the greater of (i) 5.25% per annum and (i) 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 March 31, 2019, the rate was 8%. The Company will be required to make principal payments on the outstanding balance of the Term Loan Advances commencing on February 1, 2020 (the “Term Loan Amortization Date”) in 36 equal monthly instalments, plus interest; provided that if the Company has achieved the milestones described above relating to the availability of the subsequent loan advance on or prior to December 31, 2019, then the Term Loan Amortization Date is automatically extended to February 1, 2021. 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 Loan Agreement. If the subsequent term loan is advanced, the Company will be obligated to issue Warrants to the Lender to purchase an aggregate of 27,222 shares of the Company’s common stock. 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 1.0% to 3.0% 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 March 31, 2019, the carrying value of the term loan consists of $15.0 million principal outstanding less the debt issuance costs of approximately $1.6 million. The debt issuance costs have been recorded as a debt discount which are being accreted to interest expense through the maturity date of the term loan. Interest expense relating to the term loan for the three months ended March 31 2019 was $0.2 million. Interest expense is calculated using the effective interest method, and is inclusive of non-cash amortization of capitalized loan costs. At March 31, 2019, the effective interest rate was 13.05%. 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. Future principal payments for the long-term debt are as follows (in thousands): March 31, 2019 Remainder of 2019 $ 917 2020 5,623 2021 5,659 2022 5,252 2023 420 17,871 Less amount representing interest (2,871 ) Less unamortized discount (1,507 ) Less loan payable, current, net of discount (984 ) 12,509 Final fee due at maturity in 2023 900 Long-term debt, net of current portion and discount $ 13,409

Legal and Other Contingencies

Legal and Other Contingencies	3 Months Ended
	Mar. 31, 2019
Commitments And Contingencies Disclosure [Abstract]
Legal and Other Contingencies	8. Legal and Other 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. Additionally, any litigation to which the Company may become subject could also require significant involvement of its senior management and may divert management’s attention from its business and operations. 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 periods ended March 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.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Stockholders' Equity	9. 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 condensed unaudited consolidated financial statements. Transactions related to stockholders’ equity of the Company during the three months ended March 31, 2019 were as follows (in thousands, except share amounts): Common stock Treasury stock Shares Amount Additional Paid-in Capital Accumulated Other Comprehensive Income Accumulated deficit Shares Amount Total stockholders' equity Balance at December 31, 2018 35,860,114 $ 360 $ 129,825 $ — $ (86,145 ) (91,423 ) $ (1,129 ) $ 42,911 Exercise of stock options 25,000 — 25 — — — — 25 Vesting of restricted shares 25,132 — — — — (10,467 ) (121 ) (121 ) Issuance of shares from at-the- market sales agreement 35,362 1 454 — — — — 455 Issuance of warrants — — 421 — — — — 421 Share-based compensation — — 2,658 — — — — 2,658 Change in unrealized gain (loss) on investments — — — 1 — — — 1 Net loss — — — — (11,917 ) — — (11,917 ) Balance at March 31, 2019 35,945,608 $ 361 $ 133,383 $ 1 $ (98,062 ) (101,890 ) $ (1,250 ) $ 34,433 Transactions related to stockholders’ equity of the Company during the three months ended March 31, 2018 were as follows (in thousands, except share amounts): Common stock Shares Amount Additional Paid-in Capital Accumulated deficit Total stockholders' equity Balance at December 31, 2017 27,527,738 $ 274 $ 60,047 $ (38,961 ) $ 21,360 Share-based compensation — — 735 — 735 Net loss — — — (8,591 ) (8,591 ) Balance at March 31, 2018 27,527,738 $ 274 $ 60,782 $ (47,552 ) $ 13,504 Warrants In connection with the 2019 issuance of debt, the Company granted 40,834 warrants to purchase 40,834 shares of common stock and recorded a charge in Accumulated paid in capital in the amount of $0.4 million reflecting the value of the warrants. Transactions related to warrants to purchase the Company’s common stock during the three months ended March 31, 2019, were as follows: Shares Weighted average exercise price Weighted average remaining contractual life Warrants outstanding and exercisable at December 31, 2018 347,241 $ 3.77 3.92 Granted 40,834 11.02 10.00 Exercised — Forfeited — Warrants outstanding and exercisable at March 31, 2019 388,075 $ 4.53 4.33

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation Stock Incentive Plans Prior to April 20, 2018, the Company had two equity compensation plans which provided 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 Compensation 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 all prior plans being assumed by the 2018 Plan and the total number of shares available for awards to employees, non-employee directors and other key personnel increased by 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 (the “Prior Plans”). Equity awards granted have a ten-year contractual life and, upon termination, vested options are generally exercisable between one and three months following the termination date, while unvested options are forfeited immediately. Summary of Option Activity Transactions related to the grant of options to employees and directors during the three months ended March 31, 2019 were as follows: Shares Weighted average exercise price Weighted average remaining contractual life Aggregate intrinsic value Options outstanding at December 31, 2018 3,261,719 $ 13.09 8.56 $ 11,650,373 Granted 804,100 11.71 Exercised (25,000 ) 1.00 Forfeited (118,996 ) 11.37 Options outstanding at March 31, 2019 3,921,823 $ 15.07 8.67 $ 10,417,568 Options exercisable at March 31, 2019 1,084,567 $ 10.49 7.17 $ 6,507,695 The aggregate intrinsic value represents the total intrinsic value (the difference between the deemed fair value of the Company’s Common Stock as of March 31, 2019, and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on March 31, 2019. This amount is impacted by the changes in the fair value of the Company’s shares. Summary of Restricted Stock Unit Activity Transactions related to the grant of restricted stock units to employees and directors during the three months ended March 31, 2019 were as follows: Shares Weighted average grant date fair value price Unvested at December 31, 2018 554,147 $ 9.34 Granted 100,000 11.53 Vested (35,599 ) 8.00 Forfeited — — Unvested at March 31, 2019 618,548 $ 9.77 In 2017, the Company issued an inducement award outside of the Prior Plans to the Company’s 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 Option Awards”). Subject to continued service through the vesting date, the Performance Option 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. For each of the three months ended March 31, 2019 and March 31, 2018, the Company recognized $24 thousand of expense associated with these awards. In addition, the Company issued an inducement award outside of the Prior Plans to the Company’s 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, 1/3 of the Time-Vesting Awards will vest and become immediately exercisable on the first anniversary of the effective date, with an additional 1/12 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. Stock-based compensation relates to options granted to employees, non-employee directors and non-employees, time-based restricted stock units granted to employees and performance-based 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 were recognized as follows: For the Three Months Ended March 31, 2019 2018 Research and development $ 525 $ 82 General and administrative 2,133 653 Total stock-based compensation expenses $ 2,658 $ 735

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The United States enacted the Tax Cuts and Jobs Act (“Tax Act”) on December 22, 2017, most provisions of which took effect in years beginning after December 31, 2017. The Tax Act made substantial changes to U.S. taxation of corporations, including lowering the U.S. federal corporate income tax rate from 34% 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 elected to record the U.S. income tax effect of future GILTI inclusions in the period in which they arise, if ever, and the Company has estimated that there will not be a GILTI inclusion for the year ended December 31, 2019. In accordance with ASC 740-270, Income Taxes – Interim Reporting, the Company is required at the end of each interim period to determine the best estimate of its annual effective tax rate and apply that rate to year-to-date ordinary income or loss. The resulting tax expense (or benefit) is adjusted for the tax effect of specific events, if any, required to be discretely recognized in the interim period as they occur. For both the three months ended March 31, 2019 and 2018, the Company recorded zero attributable to its operations in the U.S. The Company has not recorded net deferred tax assets as of March 31, 2019, or December 31, 2018, because it maintained a full valuation allowance against all material deferred tax assets, and management has determined that it is more likely than not, that the Company will be unable to realize those future benefits. The Company’s effective tax rate differs from the statutory rate of 21%, due to losses for which no future benefit is expected. As of March 31, 2019, and December 31, 2018, the Company had no uncertain tax positions recorded in its consolidated balance sheets.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	12. 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 periods, is as follows (amounts in thousands, except share numbers): Three months ended March 31, 2019 2018 Numerator: Net loss $ (11,917 ) $ (8,591 ) Denominator: Shares used in computing net loss per share of Common Stock, basic and diluted (1) 35,910,270 27,527,738 Net loss per share of Common Stock, basic and diluted $ (0.33 ) $ (0.31 ) (1) The following potentially dilutive securities have been excluded from the computation of diluted weighted average shares outstanding as their effect would be anti-dilutive: Three months ended March 31, 2019 2018 Options to purchase common stock 3,921,823 2,498,617 Restricted stock units 618,548 — Warrants 388,075 411,615 Total potential common stock equivalents 4,928,446 2,910,232

Reverse Merger

Reverse Merger	3 Months Ended
	Mar. 31, 2019
Business Combinations [Abstract]
Reverse Merger	13. Reverse Merger On December 19, 2017, Sevion Therapeutics, Inc. (“Sevion”) acquired Eloxx Pharmaceuticals, Limited (“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 pre-Closing. In connection with the Transaction, Sevion agreed to acquire all of the outstanding capital stock of Private Eloxx in exchange for the issuance of an aggregate 20,316,656 shares of the Sevion’s common stock, par value $0.01 per share, after giving effect to a 1-for-20 reverse split effected immediately prior to the Transaction. Immediately after giving effect to the Transaction, on December 19, 2017, Sevion changed its name to Eloxx Pharmaceuticals, Inc. The Reverse Merger was accounted for as a reverse recapitalization which is outside the scope of ASC Topic 805, “Business Combinations”. 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 capitalization and the accounts of Eloxx Limited since inception. The following summarizes the estimated fair value of 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 )

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of presentation and principles of consolidation	Basis of presentation and principles of consolidation The accompanying unaudited interim consolidated financial statements have been prepared by the Company 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 Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted, as permitted by such rules and regulations. These interim consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position, results of operations, and cash flows for the interim periods ended March 31, 2019 and 2018. The unaudited Condensed Consolidated Statements of Operations includes the Company’s operating expenses related to research and development and general and administrative which were substantially comprised of fees for professional services and employee compensation. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2018, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on March 14, 2018.
Summary of Accounting Policies	Summary of Accounting Policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2018, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K. During the three months ended March 31, 2019, the Company invested in marketable securities and as a result has provided the following updates.
Marketable Securities	Marketable Securities —All investment instruments with an original maturity date, when purchased, in excess of three months but less than 1 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 condensed consolidated balance sheet, until such gains and losses are realized. Realized gains and losses on available-for-sale securities are included in interest income. The cost of securities sold is based on the specific identification method. The Company periodically reviews the portfolio of securities to determine whether an other-than-temporary impairment has occurred. No such losses have occurred to date. There were no realized gains or losses on the sale of securities for the three months ended March 31, 2019. Below is a summary of cash, cash equivalents and marketable securities at March 31, 2019 (in thousands): Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents $ 44,576 $ — $ — $ 44,576 Marketable securities 8,927 1 — 8,928 Total cash, cash equivalents and marketable securities $ 53,503 $ 1 $ — $ 53,504
Fair Value Measurements	Fair Value Measurements —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. Authoritative guidance 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 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. 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. The Company has classified its cash, cash equivalents and marketable securities as Level 1. There were no transfers to Level 3 during the three months ended March 31, 2019. 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.
Concentration 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 primarily consist of cash and cash equivalents and available-for-sale 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 other securities, and the management of these investments is not discretionary on the part of the financial institution. The Company has no significant off-balance-sheet risks such as foreign exchange contracts, option contracts, or other hedging arrangements.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the FASB issued ASU 2016-02, Leases Leases

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 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 March 31, 2019 (in thousands): Amortized Unrealized Unrealized Fair Cost Gains Losses Value Cash and cash equivalents $ 44,576 $ — $ — $ 44,576 Marketable securities 8,927 1 — 8,928 Total cash, cash equivalents and marketable securities $ 53,503 $ 1 $ — $ 53,504

Prepaids and Other Current As_2

Prepaids and Other Current Assets (Tables)	3 Months Ended
	Mar. 31, 2019
Prepaid And Other Current Assets [Abstract]
Prepaids and Other Current Assets	Prepaids and other current assets as of March 31, 2019 and December 31, 2018 consisted of the following (in thousands): As of March 31, 2019 December 31, 2018 Prepaid insurance $ 325 $ 251 Other governmental agencies receivables 26 20 Prepaid research and development 1,215 864 Prepaid other 345 555 $ 1,911 $ 1,690

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2019
Property Plant And Equipment [Abstract]
Property and equipment	Property and equipment as of March 31, 2019 and December 31, 2018 consisted of the following (in thousands): As of March 31, 2019 December 31, 2018 Computers and software $ 146 $ 146 Office furniture and equipment 165 165 Leasehold improvements 157 141 468 452 Less: Accumulated depreciation 237 204 Property and equipment, net $ 231 $ 248

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2019
Payables And Accruals [Abstract]
Accrued expenses	Accrued expenses as of March 31, 2019 and December 31, 2018 consisted of the following (in thousands): As of March 31, 2019 December 31, 2018 Payroll and related expenses $ 1,060 $ 2,562 Research and development expenses 2,688 3,086 Professional services 583 985 Accrued interest on debt 103 — Accrued other 163 305 $ 4,597 $ 6,938

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 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 March 31, 2019 (in thousands): Remainder of 2019 $ 413 2020 493 2021 310 Total lease payments 1,216 Less: present value discount (110 ) Total $ 1,106
Summary of Future Minimum Non-Cancellable Commitments Under Operating Leases	For comparative purposes, 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)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of Future Principal Payments for Long-Term Debt	Future principal payments for the long-term debt are as follows (in thousands): March 31, 2019 Remainder of 2019 $ 917 2020 5,623 2021 5,659 2022 5,252 2023 420 17,871 Less amount representing interest (2,871 ) Less unamortized discount (1,507 ) Less loan payable, current, net of discount (984 ) 12,509 Final fee due at maturity in 2023 900 Long-term debt, net of current portion and discount $ 13,409

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Schedule of Transactions Related to Stockholders Equity	Transactions related to stockholders’ equity of the Company during the three months ended March 31, 2019 were as follows (in thousands, except share amounts): Common stock Treasury stock Shares Amount Additional Paid-in Capital Accumulated Other Comprehensive Income Accumulated deficit Shares Amount Total stockholders' equity Balance at December 31, 2018 35,860,114 $ 360 $ 129,825 $ — $ (86,145 ) (91,423 ) $ (1,129 ) $ 42,911 Exercise of stock options 25,000 — 25 — — — — 25 Vesting of restricted shares 25,132 — — — — (10,467 ) (121 ) (121 ) Issuance of shares from at-the- market sales agreement 35,362 1 454 — — — — 455 Issuance of warrants — — 421 — — — — 421 Share-based compensation — — 2,658 — — — — 2,658 Change in unrealized gain (loss) on investments — — — 1 — — — 1 Net loss — — — — (11,917 ) — — (11,917 ) Balance at March 31, 2019 35,945,608 $ 361 $ 133,383 $ 1 $ (98,062 ) (101,890 ) $ (1,250 ) $ 34,433 Transactions related to stockholders’ equity of the Company during the three months ended March 31, 2018 were as follows (in thousands, except share amounts): Common stock Shares Amount Additional Paid-in Capital Accumulated deficit Total stockholders' equity Balance at December 31, 2017 27,527,738 $ 274 $ 60,047 $ (38,961 ) $ 21,360 Share-based compensation — — 735 — 735 Net loss — — — (8,591 ) (8,591 ) Balance at March 31, 2018 27,527,738 $ 274 $ 60,782 $ (47,552 ) $ 13,504
Summary of Warrants Outstanding	Transactions related to warrants to purchase the Company’s common stock during the three months ended March 31, 2019, were as follows: Shares Weighted average exercise price Weighted average remaining contractual life Warrants outstanding and exercisable at December 31, 2018 347,241 $ 3.77 3.92 Granted 40,834 11.02 10.00 Exercised — Forfeited — Warrants outstanding and exercisable at March 31, 2019 388,075 $ 4.53 4.33

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Transactions Related to Grant of Options to Employees and Directors	Transactions related to the grant of options to employees and directors during the three months ended March 31, 2019 were as follows: Shares Weighted average exercise price Weighted average remaining contractual life Aggregate intrinsic value Options outstanding at December 31, 2018 3,261,719 $ 13.09 8.56 $ 11,650,373 Granted 804,100 11.71 Exercised (25,000 ) 1.00 Forfeited (118,996 ) 11.37 Options outstanding at March 31, 2019 3,921,823 $ 15.07 8.67 $ 10,417,568 Options exercisable at March 31, 2019 1,084,567 $ 10.49 7.17 $ 6,507,695
Transactions Related to Grant of Restricted Stock Units to Employees and Directors	Transactions related to the grant of restricted stock units to employees and directors during the three months ended March 31, 2019 were as follows: Shares Weighted average grant date fair value price Unvested at December 31, 2018 554,147 $ 9.34 Granted 100,000 11.53 Vested (35,599 ) 8.00 Forfeited — — Unvested at March 31, 2019 618,548 $ 9.77
Summary of Allocated Stock-based Compensation Expense	The total equity-based compensation expense related to all of the Company’s equity-based awards were recognized as follows: For the Three Months Ended March 31, 2019 2018 Research and development $ 525 $ 82 General and administrative 2,133 653 Total stock-based compensation expenses $ 2,658 $ 735

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 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 periods, is as follows (amounts in thousands, except share numbers): Three months ended March 31, 2019 2018 Numerator: Net loss $ (11,917 ) $ (8,591 ) Denominator: Shares used in computing net loss per share of Common Stock, basic and diluted (1) 35,910,270 27,527,738 Net loss per share of Common Stock, basic and diluted $ (0.33 ) $ (0.31 ) (1) The following potentially dilutive securities have been excluded from the computation of diluted weighted average shares outstanding as their effect would be anti-dilutive: Three months ended March 31, 2019 2018 Options to purchase common stock 3,921,823 2,498,617 Restricted stock units 618,548 — Warrants 388,075 411,615 Total potential common stock equivalents 4,928,446 2,910,232

Reverse Merger (Tables)

Reverse Merger (Tables)	3 Months Ended
	Mar. 31, 2019
Eloxx Limited [Member]
Summary of Estimated Fair Value of Assets Acquired and Liabilities Assumed	The following summarizes the estimated fair value of 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) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)Disease	Dec. 31, 2018USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of rare diseases | Disease	1,800
Accumulated deficit	$ (98,062)	$ (86,145)
Cash, cash equivalents and marketable securities	$ 53,504

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2019USD ($)
Accounting Policies [Abstract]
Realized gains or losses on the sale of securities	$ 0
Assets, transfer into level 3	0
Liabilities, transfer into level 3	$ 0

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Cash, Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Investments Debt And Equity Securities [Abstract]
Cash and cash equivalents	$ 44,576	$ 48,606	$ 18,290
Cash and cash equivalents, Fair Value	44,576
Marketable securities, Amortized Cost	8,927
Marketable securities, Unrealized Gains	1
Marketable securities, Fair Value	8,928
Total cash, cash equivalents and marketable securities, Amortized Cost	53,503
Total cash, cash equivalents and marketable securities, Unrealized Gains	1
Total cash, cash equivalents and marketable securities, Fair Value	$ 53,504

Prepaids and Other Current As_3

Prepaids and Other Current Assets - Schedule of Prepaids and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid insurance	$ 325	$ 251
Other governmental agencies receivables	26	20
Prepaid research and development	1,215	864
Prepaid other	345	555
Total	$ 1,911	$ 1,690

Property and Equipment - Proper

Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Cost	$ 468	$ 452
Less: Accumulated depreciation	237	204
Property and equipment, net	231	248
Computers and software [Member]
Property, Plant and Equipment [Line Items]
Cost	146	146
Office furniture and equipment [Member]
Property, Plant and Equipment [Line Items]
Cost	165	165
Leasehold improvement [Member]
Property, Plant and Equipment [Line Items]
Cost	$ 157	$ 141

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Property Plant And Equipment [Abstract]
Depreciation expenses	$ 33	$ 21

Accrued Expenses - Accrued Expe

Accrued Expenses - Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Payroll and related expenses	$ 1,060	$ 2,562
Research and development expenses	2,688	3,086
Professional services	583	985
Accrued interest on debt	103
Accrued other	163	305
Total	$ 4,597	$ 6,938

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
Leases [Line Items]
Operating lease cost	$ 100
Operating lease estimated incremental borrowings rate	8.00%
Operating lease, initial present value	$ 1,500
Operating lease, right-to-use asset	1,106
Operating lease, liability	$ 1,106
Weighted average remaining lease term	2 years 3 months 18 days
ASU 2016-02 [Member]
Leases [Line Items]
Operating lease, right-to-use asset		$ 1,200
Operating lease, liability		$ 1,200

Leases - Summary of Maturities

Leases - Summary of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
Remainder of 2019	$ 413
2020	493
2021	310
Total lease payments	1,216
Less: present value discount	(110)
Operating lease, liability	$ 1,106

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	Mar. 31, 2019USD ($)$ / sharesshares	Dec. 31, 2018$ / shares
Debt Instrument [Line Items]
Aggregate principal amount of initial loan advance		$ 17,871
Warrants issued to purchase shares of common stock | shares		40,834
Warrant exercise price | $ / shares		$ 4.53	$ 3.77
Term loan, final maturity payment		$ 900
Loan Agreement [Member]
Debt Instrument [Line Items]
Aggregate principal amount	$ 25,000
Debt instrument, interest rate terms	Any outstanding principal on the Term Loan Advances will accrue interest at a floating rate equal to the greater of (i) 5.25% per annum and (i) 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 (the “Term Loan Amortization Date”) in 36 equal monthly instalments, plus interest; provided that if the Company has achieved the milestones described above relating to the availability of the subsequent loan advance on or prior to December 31, 2019, then the Term Loan Amortization Date is automatically extended to February 1, 2021.
Term loan, floating interest rate	5.25%
Term loan, interest rate		8.00%
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, periodic principal payment, extended commencement date	Feb. 1, 2021
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, debt issuance costs		1,600
Term loan, interest expense		$ 200
Term loan, effective interest rate		13.05%
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
Warrants issued to purchase shares of common stock | shares	27,222
Loan Agreement [Member] | Subsequent Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Term loan, available date for funding	Dec. 31, 2019

Debt - Schedule of Future Princ

Debt - Schedule of Future Principal Payments for Long-Term Debt (Detail) $ in Thousands	Mar. 31, 2019USD ($)
Debt Disclosure [Abstract]
Remainder of 2019	$ 917
2020	5,623
2021	5,659
2022	5,252
2023	420
Total principal payments	17,871
Less amount representing interest	(2,871)
Less unamortized discount	(1,507)
Less loan payable, current, net of discount	(984)
Long term debt net of current portion and discount excluding final fee	12,509
Final fee due at maturity in 2023	900
Long-term debt, net of current portion and discount	$ 13,409

Stockholder's Equity - Schedule

Stockholder's Equity - Schedule of Transaction Related to Stockholder's Equity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Beginning balance	$ 42,911	$ 21,360
Beginning balance, shares	35,860,114
Exercise of stock options	$ 25
Exercise of stock options, shares	25,000
Vesting of restricted shares	$ (121)
Issuance of warrants	421
Share-based compensation	2,658	735
Change in unrealized gain (loss) on investments	1
Net loss	(11,917)	(8,591)
Ending balance	$ 34,433	13,504
Ending balance, shares	35,945,608
At-The-Market Sales Agreement [Member]
Issuance of shares from at-the- market sales agreement	$ 455
Additional Paid-in Capital
Beginning balance	129,825	60,047
Exercise of stock options	25
Issuance of warrants	421
Share-based compensation	2,658	735
Ending balance	133,383	60,782
Additional Paid-in Capital | At-The-Market Sales Agreement [Member]
Issuance of shares from at-the- market sales agreement	454
Accumulated Other Comprehensive Income [Member]
Change in unrealized gain (loss) on investments	1
Ending balance	1
Accumulated deficit [Member]
Beginning balance	(86,145)	(38,961)
Net loss	(11,917)	(8,591)
Ending balance	(98,062)	(47,552)
Treasury stock [Member]
Beginning balance	$ (1,129)
Beginning balance, shares	(91,423)
Vesting of restricted shares	$ (121)
Vesting of restricted shares, shares	(10,467)
Ending balance	$ (1,250)
Ending balance, shares	(101,890)
Common Stock
Beginning balance	$ 360	$ 274
Beginning balance, shares	35,860,114	27,527,738
Exercise of stock options, shares	25,000
Vesting of restricted shares, shares	25,132
Ending balance	$ 361	$ 274
Ending balance, shares	35,945,608	27,527,738
Common Stock | At-The-Market Sales Agreement [Member]
Issuance of shares from at-the- market sales agreement	$ 1
Issuance of stock, shares	35,362

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)shares
Stockholders Equity [Abstract]
Number of common stock in warrant	40,834
Warrant granted	40,834
Accumulated paid in capital | $	$ 421

Stockholder's Equity - Schedu_2

Stockholder's Equity - Schedule of Transaction Related to Warrants to Purchase Common Stock (Detail) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Stockholders Equity [Abstract]
Warrants outstanding and exercisable beginning balance, Shares	347,241
Warrants granted, Shares	40,834
Warrants outstanding and exercisable ending balance, Shares	388,075	347,241
Warrants outstanding and exercisable beginning balance, Weighted average exercise price	$ 3.77
Warrants granted, Weighted average exercise price	11.02
Warrants outstanding and exercisable ending balance, Weighted average exercise price	$ 4.53	$ 3.77
Warrants outstanding and exercisable Weighted average remaining contractual life	4 years 3 months 29 days	3 years 11 months 1 day
Warrants granted, Weighted average remaining contractual life	10 years

Stock-based Compensation - Addi

Stock-based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)$ / sharesshares	Mar. 31, 2018USD ($)	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	804,100
Exercise price per share | $ / shares	$ 11.71
Expense recognized associated with awards | $	$ 2,658	$ 735
Performance Option Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expense recognized associated with awards | $	$ 24	$ 24
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
Restricted stock unit	22,427
Exercise price per share | $ / shares	$ 8
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
Restricted stock unit	640,785
Exercise price per share | $ / shares	$ 8
Option vesting description	Subject to continued service through the vesting date, 1/3 of the Time-Vesting Awards will vest and become immediately exercisable on the first anniversary of the effective date, with an additional 1/12 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 equity awards 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 Options to Employees and Directors (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Amount
Options outstanding at December 31, 2018	3,261,719
Granted	804,100
Exercised	(25,000)
Forfeited	(118,996)
Options outstanding at March 31, 2019	3,921,823	3,261,719
Options exercisable at March 31, 2019	1,084,567
Weighted average exercise price
Options outstanding at December 31, 2018	$ 13.09
Granted	11.71
Exercised	1
Forfeited	11.37
Options outstanding at March 31, 2019	15.07	$ 13.09
Options exercisable at March 31, 2019	$ 10.49
Weighted average remaining contractual life
Options outstanding	8 years 8 months 1 day	8 years 6 months 21 days
Options exercisable	7 years 2 months 1 day
Aggregate intrinsic value
Options outstanding	$ 10,417,568	$ 11,650,373
Options exercisable	$ 6,507,695

Stock-based Compensation - Tr_2

Stock-based Compensation - Transactions Related to Grant of Restricted Stock Units to Employees and Directors (Detail) - Restricted Stock Units [Member]	3 Months Ended
	Mar. 31, 2019$ / sharesshares
Amount
Unvested at December 31, 2018 | shares	554,147
Granted | shares	100,000
Vested | shares	(35,599)
Unvested at March 31, 2019 | shares	618,548
Weighted average grant date fair value price
Unvested at December 31, 2018 | $ / shares	$ 9.34
Granted | $ / shares	11.53
Vested | $ / shares	8
Unvested at March 31, 2019 | $ / shares	$ 9.77

Stock-based Compensation - Summ

Stock-based Compensation - Summary of Allocated Stock-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	$ 2,658	$ 735
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	525	82
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	$ 2,133	$ 653

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Effective income tax rate reconciliation, at federal statutory income tax rate, percent	21.00%		34.00%
Deferred tax assets, net	$ 0			$ 0
Liability for uncertain tax positions	0			$ 0
Income tax expense (benefit)	$ 0	$ 0

Net Loss Per Share - Weighted A

Net Loss Per Share - Weighted Average Number of Shares Used in Computing Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net loss		$ (11,917)	$ (8,591)
Denominator:
Shares used in computing net loss per share of Common Stock, basic and diluted	[1]	35,910,270	27,527,738
Net loss per share of Common Stock, basic and diluted		$ (0.33)	$ (0.31)
[1]	The following potentially dilutive securities have been excluded from the computation of diluted weighted average shares outstanding as their effect would be anti-dilutive: Three months ended March 31, 2019 2018 Options to purchase common stock 3,921,823 2,498,617 Restricted stock units 618,548 — Warrants 388,075 411,615 Total potential common stock equivalents 4,928,446 2,910,232

Net Loss Per Share - Weighted_2

Net Loss Per Share - Weighted Average Number of Shares Used in Computing Basic and Diluted Net Loss Per Share (Parenthetical) (Detail) - shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential common stock equivalents	4,928,446	2,910,232
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential common stock equivalents	3,921,823	2,498,617
Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential common stock equivalents	618,548
Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Total potential common stock equivalents	388,075	411,615

Reverse Merger - Additional Inf

Reverse Merger - Additional Information (Detail)	Dec. 19, 2017$ / sharesshares	Mar. 31, 2019$ / shares	Dec. 31, 2018$ / shares
Business Acquisition [Line Items]
Common stock, par value		$ 0.01	$ 0.01
Eloxx Limited [Member]
Business Acquisition [Line Items]
Issuance of shares in exchange of all outstanding capital stock | shares	20,316,656
Common stock, par value	$ 0.01
Reverse stock split	0.05

Reverse Merger - Summary of Est

Reverse Merger - Summary of Estimated Fair Value of Assets Acquired and Liabilities Assumed (Detail) - Eloxx Limited [Member] $ in Thousands	Dec. 19, 2017USD ($)
Acquisition Date [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)