Realm Therapeutics 20-F 10 Apr 19 2018 FY Annual report (foreign) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2018shares
Document And Entity Information [Abstract]
Document Type	20-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Entity Registrant Name	REALM THERAPEUTICS PLC
Entity Central Index Key	0001718903
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Shell Company	true
Entity Common Stock, Shares Outstanding	116,561,917

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 2,915	$ 9,508
Marketable securities	15,973	24,345
Royalty receivable	1,053	444
Prepaid expenses and other current assets	366	245
Total current assets	20,307	34,542
Property and equipment, net	202	246
Royalty receivable, net of current portion	1,016	0
Other assets	312	320
Total assets	21,837	35,108
Current liabilities:
Accounts payable	86	1,009
Accrued expenses	407	1,902
Total liabilities	493	2,911
Commitments (Note 6)
Shareholders’ equity:
Ordinary shares, £0.10 nominal value: 154,897,265 shares authorized; 116,561,917 ordinary shares issued and outstanding	24,259	24,259
Additional paid-in capital	197,992	197,722
Accumulated other comprehensive income (loss)	33	(11)
Accumulated deficit	(200,940)	(189,773)
Total shareholders’ equity	21,344	32,197
Total liabilities and shareholders’ equity	$ 21,837	$ 35,108

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - £ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Nominal value (in gbp per share)	£ 0.10	£ 0.10
Ordinary shares authorized (in shares)	154,897,265	154,897,265
Ordinary shares issued (in shares)	116,561,917	116,561,917
Common Stock, Shares, Outstanding	116,561,917	116,561,917

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenues	$ 253	$ 1,121
Operating expenses:
Research and development	8,570	8,189
General and administrative	4,907	3,622
Restructuring costs	805	0
Operating expenses	14,282	11,811
Loss from operations	(14,029)	(10,690)
Interest income	406	58
Loss from operations before income taxes	(13,623)	(10,632)
Income tax (expense) benefit	(4)	108
Net loss	(13,627)	(10,524)
Other comprehensive income (loss):
Unrealized gain on investments	14	13
Foreign exchange translation adjustment	43	(21)
Total comprehensive loss	$ (13,570)	$ (10,532)
Net loss per ordinary share - basic and diluted (in dollars per share)	$ (0.12)	$ (0.16)
Weighted average ordinary shares - basic and diluted (in shares)	116,561,917	65,081,903

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Ordinary Shares	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2016	$ 19,049	$ 15,492	$ 182,809	$ (3)	$ (179,249)
Beginning balance (in shares) at Dec. 31, 2016		50,165,432
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of ordinary shares and warrants, net of insurance costs (in shares)		66,396,485
Issuance of ordinary shares and warrants, net of insurance costs	23,225	$ 8,767	14,458
Share-based compensation expense	455		455
Unrealized gain on investments	13			13
Currency translation adjustments	(21)			(21)
Net loss	(10,524)				(10,524)
Ending balance at Dec. 31, 2017	32,197	$ 24,259	197,722	(11)	(189,773)
Ending balance (in shares) at Dec. 31, 2017		116,561,917
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share-based compensation expense	270		270
Unrealized gain on investments	1			1
Currency translation adjustments	43			43
Net loss	(13,627)				(13,627)
Ending balance at Dec. 31, 2018	$ 21,344	$ 24,259	$ 197,992	$ 33	$ (200,940)
Ending balance (in shares) at Dec. 31, 2018		116,561,917

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities:
Net loss	$ (13,627)	$ (10,524)
Adjustments to reconcile net loss to net cash used in operating activities
Loss on disposal of property and equipment	20	10
Depreciation and amortization	68	86
Noncash interest income	(131)	(4)
Share-based compensation	270	455
Changes in operating assets and liabilities:
Royalty receivable	966	(178)
Prepaid expenses and other assets	(113)	(153)
Accounts payable and accrued expenses	(2,418)	805
Net cash used in operating activities	(14,965)	(9,503)
Cash flows from investing activities:
Purchase of marketable securities	(37,762)	(29,324)
Proceeds from sale of marketable securities	46,135	5,000
Proceeds from sale of property and equipment	0	5
Purchases of property and equipment	(46)	(208)
Net cash provided by (used in) continuing investing activities	8,327	(24,527)
Net cash used in discontinued investing activities	0	(1,093)
Net cash provided by (used in) investing activities	8,327	(25,620)
Cash flows from financing activities:
Proceeds from the issuance of ordinary shares and warrants, net of costs	0	23,225
Net cash provided by financing activities	0	23,225
Effect of exchange rate changes on cash	45	(24)
Net decrease in cash and cash equivalents	(6,593)	(11,922)
Cash and cash equivalents, beginning of year	9,508	21,430
Cash and cash equivalents, end of year	2,915	9,508
Supplemental cash flow information:
Adjustment to royalty receivables upon adoption of ASC 606	$ (2,460)	$ 0

Nature of the business

Nature of the business	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of the business	Nature of the business Realm Therapeutics plc (the Company) is incorporated under the laws of England and Wales and is domiciled in the United Kingdom (U.K.) In August 2018, the Company reported top-line data from its Phase 2 clinical trial of product candidate PR022 in Atopic Dermatitis. In 2018, the primary focus of the business was completing the two Phase 2 clinical studies - one evaluating PR013 in Allergic Conjunctivitis and the other evaluating PR022 in Atopic Dermatitis. Both product candidates were developed based upon the Company’s propriety platform technology which is a high concentration, stabilized formulation of hypochlorous acid (HOCl). In March 2018, the Company announced that in the Phase 2 clinical trial for Allergic Conjunctivitis, its product candidate, PR013, did not demonstrate efficacy. As a result, the Company is no longer pursing the clinical development of PR013 and does do not intend to make any additional investments in this program. In July 2018, the Securities and Exchange Commission declared effective the Company’s registration statement with respect to American Depositary Shares (ADSs) representing the Company's ordinary shares, and Nasdaq approved the ADSs for listing and the ADSs were listed for trading thereon. The registration statement was filed to facilitate the creation of a trading market in the United States for ADSs and in satisfaction of Realm's obligations under a registration rights agreement entered into with investors who participated in the Company's October 2017 private placement. In August 2018, the reported top-line data from our Phase 2 clinical trial of PR022 in Atopic Dermatitis. In the study, PR022 showed no difference from vehicle in the primary endpoint of percent change in Eczema Area Severity Index (EASI) versus baseline. As a result, the Company is no longer pursing the clinical development of PR022 and, does not intend to make any additional investments in this program. In September 2018, the Company announced the commencement of a process to explore strategic alternatives for the Company, which might have included, without limitation, the sale of some or substantially all of the Company's assets, a sale of stock, a strategic merger or other business combination transaction or other transaction between the Company and a third party. The Company retained MTS Health Partners, L.P. to serve as the financial advisor to its Board of Directors in certain aspects of the process. In February 2019, the Company entered into an agreement to sell, subject to shareholder approval, certain assets, including its Vashe® wound care royalty stream, HOCl related equipment, intellectual property (including know-how, patents and copyrights), program records, and certain assigned contracts and intellectual property licenses (the Asset Disposal) to Urgo North America for gross proceeds of $10.0 million . The Company further announced its intention to delist its ordinary shares from admission to trading on AIM and to adopt an Investing Policy, both of which required shareholder approval. Shareholders approved all of these actions at a meeting held March 15, 2019. The AIM delisting became effective on March 27, 2019. The Asset Disposal closed on March 28, 2019 increasing the Company's cash resources for potential strategic transactions. The Investing Policy requires the Board to seek to invest in, partner with, acquire and/or be acquired by companies with meaningful development potential in the life sciences sector or with good overall business prospects; or, if a suitable transaction is not identified, to consider dissolving and liquidating the Company's remaining assets. In the event of dissolution, the Company would be required to pay all of its debts and contractual obligations and set aside certain reserves for potential future claims and would need to create distributable reserve in order to make any distributions to shareholders. If the Company dissolves and liquidates its assets, there can be no assurance as to the amount or timing of available cash that will remain for distribution to its shareholders. At December 31, 2018, the Company had cash, cash equivalents and marketable securities of $18.9 million , working capital of $19.8 million , and an accumulated deficit of $200.9 million . Our future operations are highly dependent on completing a strategic transaction with a third party. On April 5, 2019, the Company announced that it had received written notice from the Listing Qualifications Staff (the “Staff”) of Nasdaq Market indicating that, based upon the Company’s recent Assets Disposal, the Staff believes the Company is a “shell company” ( i.e. , a non-operating entity) and, as such, the continued listing of the Company's ADSs on Nasdaq is no longer warranted. The Company plans to timely request a hearing before the Nasdaq Hearings Panel (the “Panel”), which request will stay any suspension or delisting action by Nasdaq at least pending the ultimate outcome of the hearing.

Basis of presentation and summa

Basis of presentation and summary of significant accounting policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of presentation and summary of significant accounting policies	Basis of presentation and summary of significant accounting policies The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (U.S. GAAP). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Updates (ASU) of the Financial Accounting Standards Board (FASB). Principles of consolidation The consolidated financial statements include the accounts of Realm Therapeutics plc and its wholly‑owned subsidiaries: Realm Therapeutics, Inc., and non-operating entities PuriCore Europe Limited and PuriCore Scientific Limited. All inter‑company balances and transactions have been eliminated in consolidation. Use of estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Due to the uncertainty of factors surrounding the estimates or judgments used in the preparation of the consolidated financial statements, actual results may materially vary from these estimates. Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary. Foreign currency translation The Company’s reporting currency is the U.S. dollar given the majority of its operations are located in the U.S. and transactions are denominated in U.S. dollars. The functional currency of Realm Therapeutics plc, the parent, is the pound sterling and its assets and liabilities are translated at the rate of exchange at year-end, while the statements of operations are translated at the average exchange rates in effect during the year. The net effect of these translation adjustments is shown as a component of accumulated other comprehensive income (loss). Fair value of financial instruments At December 31, 2018 and 2017, the Company’s financial instruments included marketable securities, royalty receivable, accounts payable and accrued expenses. The carrying amount of the royalty receivable, accounts payable and accrued expenses approximates fair value due to the short-term maturities of these instruments. The carrying value of marketable securities is the estimated fair value. Cash and cash equivalents The Company considers all highly liquid investments purchased with an original maturity of 90 days or less to be cash equivalents. As of December 31, 2018, cash equivalents consisted of cash sweep funds and government-backed money market funds. As of December 31, 2017, cash equivalents consisted of certificates of deposit, U.S Treasuries and government‑backed money market funds. Marketable securities The Company determines the appropriate classification of its investments in debt and equity securities at the time of purchase and re-evaluates such determination at each balance sheet date. As of December 31, 2018 and 2017, all investments are classified as available for sale and carried at their estimated fair value. Unrealized gains and losses related to debt securities are recorded as a component of accumulated other comprehensive income (loss). The Company periodically reviews its investments for impairment and adjusts these investments to their fair value when a decline in market value is deemed to be other than temporary. If losses on these securities are considered to be other than temporary, the loss is recognized in earnings. Property and equipment Property and equipment are recorded at cost. Depreciation and amortization is determined using the straight-line method over the estimated useful lives ranging from 3 to 7 years . Leasehold improvements are amortized over the life of the lease or the estimated useful life of the assets, whichever is shorter. Expenditures for maintenance and repairs are expensed as incurred while renewals and betterments are capitalized. When property and equipment is sold or otherwise disposed of, the cost and related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in operations. Impairment of long-lived assets Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated. Impairment charges are recognized at the amount by which the carrying amount of an asset exceeds the fair value of the asset. Assets to be disposed of are reported at the lower of the carrying amount or the fair value less costs to sell. The Company has no t recognized any impairment of long-lived assets for the years ended December 31, 2018 and 2017. Revenue recognition The Company adopted ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) effective January 1, 2018 using the modified retrospective method with the impact of the adoption reflected in opening accumulated deficit. The impact of Topic 606 relates to the Company’s license and distribution agreement for Vashe, primarily regarding the recognition of the future minimum guaranteed royalty payments. Under Topic 606, minimum royalty payments are included in the transaction price as variable consideration, subject to a constraint. Therefore, the future minimum payments are recognized at a point in time rather than over the future periods. The revenue recognized is net of the effect of significant financing components calculated using customer-specific, risk-adjusted lending rates and will be recognized as interest income over time on an effective interest rate basis. The Company recognized the cumulative impact of the adoption of Topic 606 with a decrease of $2.5 million in the opening balance of its accumulated deficit on January 1, 2018 and a corresponding increase in royalty receivable. The comparative information for the prior period has not been restated and continues to be reported under the revenue recognition rules then in effect (Topic 605). Royalties in excess of the estimated future minimum royalty amount will be recognized if and when they are earned. The Company concluded that the minimum guaranteed royalty amounts are fixed in substance and are recognized upon transferring the license to the distributor under Topic 606 rather than upon billing under Topic 605. As a consequence of the acceleration of revenue recognition, the Company will not recognize royalty income until the minimum guaranteed amount has been achieved in the relevant contract period. Any royalties in excess of the minimum guarantee will be recognized as revenue in the period they are earned. Adoption of Topic 606 had no impact to cash provided by (used in) operating, investing, or financing activities within the Company’s consolidated statement of cash flows. In accordance with Topic 606, the disclosure of the impact of adoption to the Company’s consolidated statement of operations and consolidated balance sheet was as follows (in thousands): Year Ended December 31, 2018 As Reported Effect of Change Amounts under ASC 605 Revenue $ 253 $ 858 $ 1,111 Operating expenses Research and development 8,570 — 8,570 General and administrative 4,907 — 4,907 Restructuring costs 805 — 805 14,282 — 14,282 Loss from operations (14,029 ) 858 (13,171 ) Interest income 406 (132 ) 274 Loss from operations before income taxes (13,623 ) 726 (12,897 ) Income tax expense (4 ) — (4 ) Net loss $ (13,627 ) $ 726 $ (12,901 ) December 31, 2018 As Reported Effect of Change Amounts under ASC 605 Assets Royalty receivable $ 1,053 $ (718 ) $ 335 Royalty receivable, net of current portion $ 1,016 $ (1,016 ) $ — Shareholders' Equity Accumulated deficit $ (200,940 ) $ (1,734 ) $ (202,674 ) Research and development expenses Research and development costs are expensed as incurred and consist primarily of compensation paid to research and development focused employees and funds paid to third parties for the provision of services for product candidate development, clinical and pre-clinical development and related supply and manufacturing costs, and regulatory compliance costs. At the end of the reporting period, the Company compares payments made to third party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs. Upfront milestone payments made to third parties who perform research and development services on the Company’s behalf are expensed as services are rendered. Upon the Company’s decision to discontinue the clinical development of PR013, PR022, and all of its other product candidates, all research and development activities for those candidates have been suspended. Any remaining estimated costs associated with the discontinuance of clinical development have been accrued as of December 31, 2018. Restructuring costs Following the announcement in September 2018 that the Company was discontinuing its clinical development programs and seeking strategic alternatives, it implemented a workforce reduction to reduce operating expenses while it evaluates strategic alternatives. The majority of severance and benefits payments associated with this reduction were settled during the year ended December 31, 2018 and are classified within restructuring costs within the Company's consolidated statements of operations and comprehensive loss. The Company entered into agreements with certain employees necessary to complete its clinical operations and advance the strategic review process. Under these retention agreements, if the Company terminates these employees’ employment without cause and the employees sign a separation agreement, they are entitled to certain separation pay and benefits. The Company recognizes the restructuring expense for such agreements over the employees' retention service period. The Company also incurred professional fees associated with the strategic review, including legal fees, accounting, tax and other advisory fees and banker’s fees, which are included in restructuring costs. Share-based compensation The Company measures equity classified share-based awards granted to employees and directors based on the estimated fair value on the date of grant and recognizes compensation expense of those awards over the requisite service period, which is generally the vesting period of the respective award. The Company recognizes compensation expense for performance based awards when the performance condition is probable of achievement. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model, which is described more fully in Note 8. Stock-based awards granted to consultants and non-employees are measured based on the fair value of the award on the date on which the related services are completed. Compensation expense is recognized over the period during which services are rendered by such consultants and non-employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is remeasured using the then-current fair value of the Company’s common stock and updated assumption inputs in the Black-Scholes option-pricing model. Income taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A reduction in the carrying value of the net deferred tax assets is required when it is not more likely than not that such deferred tax assets are realizable. The Company has not recognized any deferred tax assets or liabilities. Net loss per ordinary share Basic loss per share is computed by dividing net loss by the weighted average number of ordinary shares outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as warrants and options which would result in the issuance of incremental ordinary shares. In computing basic and diluted net loss per share, the weighted average number of shares is the same for both calculations due to the fact that a net loss existed for the years ended December 31, 2018 and 2017. The following potentially dilutive securities outstanding as of December 31, 2018 and 2017 have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti-dilutive: Years Ended December 31, 2018 2017 Share options 10,068,744 11,418,175 Warrants 26,558,600 26,917,173 36,627,344 38,335,348 Recent accounting pronouncements In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Non-employe e Share-Based Payment Accounting . ASU 2018-07 is intended to reduce the cost and complexity and to improve financial reporting for non-employee share-based payments. The ASU expands the scope of Topic 718, Compensation-Stock Compensation (which currently only includes share-based payments to employees), to include share-based payments issued to non-employees for goods or services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. This update is effective for annual and interim periods beginning after December 15, 2018 with early adoption permitted. Upon transition, entities will remeasure unsettled liability-classified awards and any unmeasured equity-classified awards for non-employees at fair value as of the adoption date. A cumulative-effect adjustment to retained earnings will be required as of the beginning of the fiscal year of adoption. The Company is currently assessing the impact ASU 2018-07 will have on its consolidated financial statements and footnote disclosures thereto. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), which provided guidance on accounting for the federal tax rate change and other tax effects of the Tax Act. SAB 118 provided a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740, Income Taxes. In connection with our adoption of the Tax Act and in consideration of SAB 118, there were no changes made to the provisional amounts recognized in 2017 in connection with the enactment of the Tax Reform Act. The accounting for the income tax effects of the Tax Reform Act is complete as of December 31, 2018. In March 2016, the FASB issued ASU 2016‑09, Compensation — Improvements to Employee Share‑Based Payment Accounting, which simplifies several aspects of the accounting for employee share‑based payment transactions including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The new standard is effective for annual reporting periods beginning after December 15, 2017. The Company adopted this guidance on January 1, 2018 and it did not have a material impact to the consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . ASU No. 2016-15 addresses eight specific cash flow issues with the objective of reducing diversity in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The new standard is effective for fiscal years beginning after December 15, 2018 and interim periods within fiscal years beginning after December 15, 2018. Early adoption is permitted. The Company is currently evaluating the accounting, transition, and disclosure requirements of the standard and its impact on the Company’s consolidated statement of cash flows. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), with guidance regarding the accounting for and disclosure of leases. The update requires lessees to recognize all leases, including operating leases, with a term greater than twelve months on the balance sheet. This update also requires lessees and lessors to disclose key information about their leasing transactions. The guidance will be effective for annual and interim periods beginning after December 15, 2018. The Company is currently evaluating the effect that this guidance will have on its consolidated financial statements and related disclosures. While the Company continues to assess all the effects of adoption, the Company believes the most significant effect relates to the recognition of right-of-use assets and corresponding liabilities on its consolidated balance sheet, primarily related to its existing facility operating leases, and providing new disclosures with regards to the Company’s leasing activities.

Fair value and marketable secur

Fair value and marketable securities	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value and marketable securities	Fair value and marketable securities As of December 31, 2018, marketable securities were comprised of the following (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. Treasury bills $ 15,959 $ 14 $ — $ 15,973 As of December 31, 2017, marketable securities were comprised of the following (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. government agency $ 20,857 $ 14 $ — $ 20,871 Certificates of deposit 3,475 — (1 ) 3,474 $ 24,332 $ 14 $ (1 ) $ 24,345 The Company follows FASB’s accounting guidance on fair value measurements for financial assets and liabilities measured on a recurring basis. The guidance requires fair value measurements to be classified and disclosed in one of the following three categories: • Level 1 - Quoted prices (unadjusted in active markets for identical assets or liabilities) • Level 2 - Inputs other than quoted prices in active markets that are observable either directly or indirectly • Level 3 - Unobservable inputs in which there is little or no market data, which require the Company to develop its own assumptions This hierarchy requires the use of observable market data when available and to minimize the use of unobservable inputs when determining fair value. The Company has classified assets and liabilities measured at fair value on a recurring basis as follows (in thousands): December 31, 2018 Fair Value Measurement Based on Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents (1) $ 2,451 $ 2,451 $ 2,451 $ — $ — U.S. Treasury bills 15,973 15,973 15,973 — — $ 18,424 $ 18,424 $ 18,424 $ — $ — (1) Includes cash sweep accounts and U.S. Treasury money market mutual fund that have a maturity of 90 days or less from the original acquisition date. December 31, 2017 Fair Value Measurement Based on Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents (2) $ 8,978 $ 8,978 $ 8,978 $ — $ — U.S. government agency 20,871 20,871 — 20,871 — Certificates of deposit 3,474 3,474 3,474 — — $ 33,323 $ 33,323 $ 12,452 $ 20,871 $ — (2) Includes cash sweep accounts, U.S. Treasury money market mutual fund, and bank certificates of deposit and U.S. Treasury bills that have a maturity of 90 days or less from the original acquisition date.

Property and equipment

Property and equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property and equipment	Property and equipment Property and equipment, net, consisted of (in thousands): December 31, 2018 2017 Laboratory and other equipment $ 209 $ 271 Office equipment 76 68 Computer equipment and software 113 130 Leasehold improvements 58 57 456 526 Less: Accumulated depreciation and amortization (254 ) (280 ) $ 202 $ 246 Depreciation and amortization expense was $68,000 and $86,000 for the years ended December 31, 2018 and 2017, respectively.

Accrued expenses

Accrued expenses	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
Accrued expenses	Accrued expenses Accrued expenses consisted of (in thousands): December 31, 2018 2017 Compensation and related benefits $ 16 $ 994 Restructuring costs 276 — Consulting and professional fees — 105 Research and development expenses 25 745 Other 90 58 $ 407 $ 1,902

Commitments

Commitments	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments	Commitments Leases In April 2017, the Company entered into a 96 ‑month lease for office space. The Company recognizes rent expense on a straight-line basis over the lease period and has accrued for rent expense incurred but not yet paid. Landlord allowances for tenant improvements are deferred and recognized as a reduction to rent expense on a straight-line basis and over the entire lease term. The Company also leases office equipment with non-cancellable lease terms between five and seven years . Rent expense under operating leases was $0.1 million and $0.1 million for the years ended December 31, 2018 and 2017, respectively. Future minimum rental payments under non-cancellable operating leases at December 31, 2018 are as follows (in thousands): For the years ending December 31, 2019 $ 165 2020 165 2021 168 2022 171 2023 175 Thereafter 238 $ 1,082 Employment agreements The Company has entered into employment agreements with certain key executives and other employees involved in the strategic review process, providing for compensation and severance in certain circumstances, as defined in the agreements. Retirement plans The Company maintains a defined contribution 401(k) retirement plan, which covers all U.S. employees. Employees are eligible upon their date of hire. Under the 401(k) plan, participating employees may defer up to 100% of their pre‑tax salary but not more than statutory limits. The Company has a safe harbor plan and makes a contribution to employee accounts of 3% of compensation (as defined by the plan), subject to statutory limits, which vest immediately. During the years ended December 31, 2018 and 2017, the Company incurred costs of $68,000 and $67,000 , respectively, related to the retirement plan.

Shareholders' equity

Shareholders' equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Shareholders' equity	Shareholders’ equity Ordinary shares As of December 31, 2018, the Company had 154,897,265 ordinary shares authorized on a fully diluted share capital basis and 116,561,917 ordinary shares in issue. Each issued ordinary share entitles the holder to vote on all matters submitted to a vote of the Company’s shareholders. Ordinary shareholders are entitled to receive dividends, as may be declared by the board of directors. In October 2017, the Company completed a private placement with existing and new investors and issued 66.4 million units for net proceeds after expenses of $23.2 million . Each unit consisted of one ordinary share and one warrant to subscribe for 0.4 ordinary shares at a purchase price of 58 pence ( $0.78 ). Warrants to purchase ordinary shares As of December 31, 2018, there were 26,558,600 warrants to purchase ordinary shares outstanding, which were issued in connection with the October 2017 private placement, with an exercise price of 58 pence ( $0.78 ) that carry an expiration date of April 2020. During the year ended December 31, 2018, there were 358,573 warrants to purchase ordinary shares at 49 pence ( $0.66 ) that expired.

Share-based compensation

Share-based compensation	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based compensation	Share ‑ based compensation The Company operates the Realm Therapeutics 2016 Executive Omnibus Incentive Plan (the Plan), an equity compensation plan under which a variety of equity instruments can be issued to employees. As of December 31, 2018, there were 1,587,448 shares available for future issuance under the Plan. The amount and terms of grants are determined by the Company’s board of directors. The term of the options may be up to 10 years , and options are exercisable in cash or as otherwise determined by the board of directors. Generally, options vest annually over a three year period or, for certain key executives, vest upon the achievement of performance conditions measured over a three year period. All options granted have exercise prices equal to the fair value of the underlying ordinary shares on the date of the grant. The Company recorded share‑based compensation expense in the following expense categories of its consolidated statements of operations for the years ended December 31, 2018 and 2017 (in thousands): Years Ended December 31, 2018 2017 Research and development $ 146 $ 209 General and administrative 124 246 $ 270 $ 455 The fair value of options is estimated using the Black‑Scholes option pricing model, which takes into account inputs such as the exercise price, the value of the underlying ordinary shares at the grant date, expected term, expected volatility, risk‑free interest rate and dividend yield. The fair value of each grant of options during the year ended December 31, 2018 and 2017 was determined using the methods and assumptions discussed below. • The expected term of employee options is determined using the “simplified” method, as prescribed in SEC’s Staff Accounting Bulletin (SAB) No. 107, whereby the expected life equals the arithmetic average of the vesting term and the original contractual term of the option due to the Company’s lack of sufficient historical data. The expected term of nonemployee options is equal to the contractual term. • The expected volatility is based on historical volatility of the Company’s ordinary shares commensurate with the expected term assumption. • The risk‑free interest rate is based on the interest rate payable on U.S. Treasury securities in effect at the time of grant for a period that is commensurate with the assumed expected term. • The expected dividend yield is 0% because the Company has not historically paid, and does not expect for the foreseeable future to pay, a dividend on its common stock. For the years ended December 31, 2018 and 2017, the grant date fair value of all option grants was estimated at the time of grant using the Black‑Scholes option‑pricing model using the following weighted average assumptions: Years Ended December 31, 2018 2017 Expected term (in years) 6.0 3.7 Expected volatility 44.4 % 33.2 % Risk-free rate 2.8 % 1.8 % Dividend yield — — The per share weighted average fair value of the options granted during the years ended December 31, 2018 and 2017 was estimated at $0.20 and $0.15 per share, respectively. The following table summarizes the activity related to stock option grants to employees and nonemployees for the years ended December 31, 2018 and 2017: Number of Shares under Option Plan Weighted-Average Exercise Price per Option Weighted- Average Remaining Contractual Life (in years) Outstanding at January 1, 2017 4,250,668 $ 0.46 Granted 2,531,000 0.51 Anti-dilution adjustment to number of options 5,087,728 0.42 Expired (326,196 ) 1.21 Forfeited (125,025 ) 0.40 Outstanding at December 31, 2017 11,418,175 0.45 Granted 90,000 0.55 Expired (544,765 ) 1.00 Forfeited (894,666 ) 0.41 Outstanding at December 31, 2018 10,068,744 $ 0.40 3.51 Exercisable at December 31, 2018 6,652,354 $ 0.39 2.85 Vested and expected to vest at December 31, 2018 10,068,744 $ 0.40 3.51 As of December 31, 2018, there was $0.1 million in unrecognized compensation cost that is expected to be recognized over an estimated weighted‑average amortization period of 1.2 year. All options outstanding or exercisable as of December 31, 2018 had exercise prices in excess of the closing stock price reported on the last day for the year ending December 31, 2018.

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income taxes	Income taxes Loss from operations before income taxes was as follows (in thousands): Years Ended December 31, 2018 2017 U.K. $ (3,647 ) $ (1,297 ) U.S. (9,976 ) (9,335 ) $ (13,623 ) $ (10,632 ) Income tax (expense) benefit consists of the following (in thousands): Years Ended December 31, 2018 2017 Current tax (expense) benefit U.K. $ — $ — U.S. federal — 108 U.S. state and local (4 ) — Total current tax (expense) benefit (4 ) 108 Deferred tax (expense) benefit U.K. — — U.S. federal — — U.S. state and local — — Total deferred tax benefit — — Income tax (expense) benefit $ (4 ) $ 108 A reconciliation of income tax benefit from continuing operations as reflected in the financial statements was as follows: Years Ended December 31, 2018 2017 Income tax expense at U.K. statutory rate 19.0 % 19.3 % Foreign rate differential 0.9 11.4 State taxes, net of federal benefit 5.8 5.8 Permanent differences — (0.1 ) Tax Cuts and Jobs Act — (79.4 ) Change in valuation allowance (28.5 ) 43.5 Other 2.8 0.5 Effective tax rate — 1.0 % The principal components of the Company’s deferred tax assets and liabilities were as follows (in thousands): December 31, 2018 2017 Deferred income tax assets: Net operating losses $ 18,409 $ 15,261 Property and equipment 3 29 Accrued expenses and other 158 115 Tax credits 626 626 Valuation allowances (19,196 ) (16,031 ) Deferred income tax assets, net $ — $ — As of December 31, 2018, the Company had net operating loss (NOL) carry forwards of $14.5 million from its operations in the U.K., which are available to reduce certain future U.K. taxable income. As of December 31, 2018, the Company had U.S. federal and state NOLs of $68.8 million and $19.0 million , respectively. The Company has U.S. research and development credits of $0.6 million and refundable U.S. Alternative Minimum Tax credits of $0.1 million . The U.S. NOLs may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three‑year period in excess of 50%. This could limit the amount of NOLs and credits that the Company can utilize annually to offset future U.S. taxable income or tax liabilities, if any. The amount of the annual limitation, if any, will be determined based on the value of the Company immediately prior to the ownership change. Subsequent ownership changes may further affect the limitation in future years. While a comprehensive analysis has not been completed, the Company believes that the private placement completed in October 2017 likely caused an ownership change which would give rise to the limitations on the federal and state NOLs. These federal and state carry forwards will begin to expire in 2020 through 2038. ASC 740, Income Taxes , requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all the evidence, both positive and negative, the Company has recorded a full valuation allowance against its deferred tax assets at December 31, 2018 and 2017 because the Company’s management has determined that is it more likely than not that these assets will not be fully realized. The Company experienced a net increase in the valuation allowance of $3.2 million for the year ended December 31, 2018, primarily due to the increase in net operating losses generated. The Company files income tax returns in the U.K., the U.S., and various states within the U.S. In the normal course of business, the Company is subject to examination by federal, state and foreign jurisdictions, where applicable. The Company’s tax years in the U.S. are still open under statute from 2015 to present. However, applicable taxing authorities may review and adjust tax credit or NOL carryforwards generated in closed years that are utilized in open years. The Company’s policy is to record interest and penalties related to uncertain tax positions in income tax expense. As of December 31, 2018 and 2017, the Company had no accrued interest or penalties related to uncertain tax positions and no amounts have been recognized in the Company’s statement of operations. On December 22, 2017, the U.S. government enacted comprehensive tax legislation commonly referred to as the Tax Cuts and Jobs Act (the Tax Act). The Tax Act makes broad and complex changes to the U.S. tax code, including, but not limited to, reducing the top U.S. federal corporate tax rate from 35% to 21%; requiring companies to pay a onetime transition tax on certain un-repatriated earnings of foreign subsidiaries; generally eliminating U.S. federal income taxes on dividends from foreign subsidiaries; requiring a current inclusion in U.S. federal taxable income of certain earnings of controlled foreign corporations; eliminating the corporate alternative minimum tax (AMT) and changing how existing AMT credits can be realized; creating the base erosion anti-abuse tax (BEAT), a new minimum tax; creating a new limitation on deductible interest expense; and changing rules related to uses and limitations of net operating loss carryforwards created in tax years beginning after December 31, 2017. The Tax Act reduced the Company's U.S. corporate income tax rate from 35% to 21%, effective January 1, 2018. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. As a result of the reduction in the U.S. corporate income tax rate from 35% to 21% under the Tax Act, the Company revalued its ending net deferred tax assets and liabilities at December 31, 2017. The Tax Act provided for a one-time transition tax on the deemed repatriation of post-1986 undistributed foreign subsidiary earnings and profits (E&P). The Company has minimal operations at their controlled foreign corporation and, as such, had no transition tax liability. The global intangible low-taxed income tax and base erosion provisions are effective for taxable years beginning after December 31, 2017. The Company does not currently expect these provisions to have a material impact on its tax rate as there is minimal activity at their controlled foreign corporations and they are currently below the gross receipts threshold for purposes of the base erosion provisions. Due to the timing of the new tax law and the substantial changes it brings, the Staff of the U.S. Securities and Exchange Commission (the SEC) issued Staff Accounting Bulletin No. 118 (SAB 118), which provides registrants a measurement period to report the impact of the new U.S. tax law. During the measurement period, provisional amounts for the effects of the law are recorded to the extent a reasonable estimate can be made. The accounting for the income tax effects of the Tax Reform Act is complete as of December 31, 2018. There has been no material difference in actual amounts recorded compared to those recorded as provisional. The Company will continue to monitor for future updates to guidance or interpretations issued by the IRS.

Related party transactions

Related party transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related party transactions	Related party transactions During the year ended December 31, 2017, the Company received net proceeds of $23.2 million upon issuing ordinary shares and warrants for ordinary shares, of which $1.2 million was from existing investors and executives. In connection with providing scientific and business advisory services, the Company had engaged the consulting services of a director and compensation for services was provided at a fixed fee of $3,000 per month. The agreement terminated in April 2018.

Subsequent events

Subsequent events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent events	Subsequent events The Company has evaluated subsequent events from the balance sheet date through the date at which the consolidated financial statements were available to be issued, and determined there are no other items requiring disclosure beyond those already disclosed.

Basis of presentation and sum_2

Basis of presentation and summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of presentation	The accompanying consolidated financial statements have been prepared in conformity with generally accepted accounting principles in the United States (U.S. GAAP). Any reference in these notes to applicable guidance is meant to refer to U.S. GAAP as found in the Accounting Standards Codification (ASC) and Accounting Standards Updates (ASU) of the Financial Accounting Standards Board (FASB).
Principles of consolidation	The consolidated financial statements include the accounts of Realm Therapeutics plc and its wholly‑owned subsidiaries: Realm Therapeutics, Inc., and non-operating entities PuriCore Europe Limited and PuriCore Scientific Limited. All inter‑company balances and transactions have been eliminated in consolidation.
Use of estimates	The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Due to the uncertainty of factors surrounding the estimates or judgments used in the preparation of the consolidated financial statements, actual results may materially vary from these estimates. Estimates and assumptions are periodically reviewed and the effects of revisions are reflected in the consolidated financial statements in the period they are determined to be necessary.
Foreign currency translation	The Company’s reporting currency is the U.S. dollar given the majority of its operations are located in the U.S. and transactions are denominated in U.S. dollars. The functional currency of Realm Therapeutics plc, the parent, is the pound sterling and its assets and liabilities are translated at the rate of exchange at year-end, while the statements of operations are translated at the average exchange rates in effect during the year. The net effect of these translation adjustments is shown as a component of accumulated other comprehensive income (loss).
Fair value of financial instruments	At December 31, 2018 and 2017, the Company’s financial instruments included marketable securities, royalty receivable, accounts payable and accrued expenses. The carrying amount of the royalty receivable, accounts payable and accrued expenses approximates fair value due to the short-term maturities of these instruments. The carrying value of marketable securities is the estimated fair value.
Cash and cash equivalents	The Company considers all highly liquid investments purchased with an original maturity of 90 days or less to be cash equivalents. As of December 31, 2018, cash equivalents consisted of cash sweep funds and government-backed money market funds. As of December 31, 2017, cash equivalents consisted of certificates of deposit, U.S Treasuries and government‑backed money market funds.
Marketable securities	The Company determines the appropriate classification of its investments in debt and equity securities at the time of purchase and re-evaluates such determination at each balance sheet date. As of December 31, 2018 and 2017, all investments are classified as available for sale and carried at their estimated fair value. Unrealized gains and losses related to debt securities are recorded as a component of accumulated other comprehensive income (loss). The Company periodically reviews its investments for impairment and adjusts these investments to their fair value when a decline in market value is deemed to be other than temporary. If losses on these securities are considered to be other than temporary, the loss is recognized in earnings.
Property and equipment	Property and equipment are recorded at cost. Depreciation and amortization is determined using the straight-line method over the estimated useful lives ranging from 3 to 7 years . Leasehold improvements are amortized over the life of the lease or the estimated useful life of the assets, whichever is shorter. Expenditures for maintenance and repairs are expensed as incurred while renewals and betterments are capitalized. When property and equipment is sold or otherwise disposed of, the cost and related accumulated depreciation are eliminated from the accounts and any resulting gain or loss is reflected in operations.
Impairment of long-lived assets	Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated. Impairment charges are recognized at the amount by which the carrying amount of an asset exceeds the fair value of the asset. Assets to be disposed of are reported at the lower of the carrying amount or the fair value less costs to sell.
Revenue recognition	The Company adopted ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) effective January 1, 2018 using the modified retrospective method with the impact of the adoption reflected in opening accumulated deficit. The impact of Topic 606 relates to the Company’s license and distribution agreement for Vashe, primarily regarding the recognition of the future minimum guaranteed royalty payments. Under Topic 606, minimum royalty payments are included in the transaction price as variable consideration, subject to a constraint. Therefore, the future minimum payments are recognized at a point in time rather than over the future periods. The revenue recognized is net of the effect of significant financing components calculated using customer-specific, risk-adjusted lending rates and will be recognized as interest income over time on an effective interest rate basis. The Company recognized the cumulative impact of the adoption of Topic 606 with a decrease of $2.5 million in the opening balance of its accumulated deficit on January 1, 2018 and a corresponding increase in royalty receivable. The comparative information for the prior period has not been restated and continues to be reported under the revenue recognition rules then in effect (Topic 605). Royalties in excess of the estimated future minimum royalty amount will be recognized if and when they are earned. The Company concluded that the minimum guaranteed royalty amounts are fixed in substance and are recognized upon transferring the license to the distributor under Topic 606 rather than upon billing under Topic 605. As a consequence of the acceleration of revenue recognition, the Company will not recognize royalty income until the minimum guaranteed amount has been achieved in the relevant contract period. Any royalties in excess of the minimum guarantee will be recognized as revenue in the period they are earned.
Research and development expenses	Research and development costs are expensed as incurred and consist primarily of compensation paid to research and development focused employees and funds paid to third parties for the provision of services for product candidate development, clinical and pre-clinical development and related supply and manufacturing costs, and regulatory compliance costs. At the end of the reporting period, the Company compares payments made to third party service providers to the estimated progress toward completion of the research or development objectives. Such estimates are subject to change as additional information becomes available. Depending on the timing of payments to the service providers and the progress that the Company estimates has been made as a result of the service provided, the Company may record net prepaid or accrued expense relating to these costs. Upfront milestone payments made to third parties who perform research and development services on the Company’s behalf are expensed as services are rendered. Upon the Company’s decision to discontinue the clinical development of PR013, PR022, and all of its other product candidates, all research and development activities for those candidates have been suspended. Any remaining estimated costs associated with the discontinuance of clinical development have been accrued as of December 31, 2018.
Restructuring costs	Following the announcement in September 2018 that the Company was discontinuing its clinical development programs and seeking strategic alternatives, it implemented a workforce reduction to reduce operating expenses while it evaluates strategic alternatives. The majority of severance and benefits payments associated with this reduction were settled during the year ended December 31, 2018 and are classified within restructuring costs within the Company's consolidated statements of operations and comprehensive loss. The Company entered into agreements with certain employees necessary to complete its clinical operations and advance the strategic review process. Under these retention agreements, if the Company terminates these employees’ employment without cause and the employees sign a separation agreement, they are entitled to certain separation pay and benefits. The Company recognizes the restructuring expense for such agreements over the employees' retention service period. The Company also incurred professional fees associated with the strategic review, including legal fees, accounting, tax and other advisory fees and banker’s fees, which are included in restructuring costs.
Share-based compensation	The Company measures equity classified share-based awards granted to employees and directors based on the estimated fair value on the date of grant and recognizes compensation expense of those awards over the requisite service period, which is generally the vesting period of the respective award. The Company recognizes compensation expense for performance based awards when the performance condition is probable of achievement. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option pricing model, which is described more fully in Note 8. Stock-based awards granted to consultants and non-employees are measured based on the fair value of the award on the date on which the related services are completed. Compensation expense is recognized over the period during which services are rendered by such consultants and non-employees until completed. At the end of each financial reporting period prior to completion of the service, the fair value of these awards is remeasured using the then-current fair value of the Company’s common stock and updated assumption inputs in the Black-Scholes option-pricing model.
Income taxes	Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. A reduction in the carrying value of the net deferred tax assets is required when it is not more likely than not that such deferred tax assets are realizable. The Company has not recognized any deferred tax assets or liabilities.
Net loss per ordinary share	Basic loss per share is computed by dividing net loss by the weighted average number of ordinary shares outstanding during each period. Diluted loss per share includes the effect, if any, from the potential exercise or conversion of securities, such as warrants and options which would result in the issuance of incremental ordinary shares. In computing basic and diluted net loss per share, the weighted average number of shares is the same for both calculations due to the fact that a net loss existed for the years ended December 31, 2018 and 2017.
Recent accounting pronouncements	In June 2018, the FASB issued ASU No. 2018-07, Compensation—Stock Compensation (Topic 718): Improvements to Non-employe e Share-Based Payment Accounting . ASU 2018-07 is intended to reduce the cost and complexity and to improve financial reporting for non-employee share-based payments. The ASU expands the scope of Topic 718, Compensation-Stock Compensation (which currently only includes share-based payments to employees), to include share-based payments issued to non-employees for goods or services. Consequently, the accounting for share-based payments to non-employees and employees will be substantially aligned. This update is effective for annual and interim periods beginning after December 15, 2018 with early adoption permitted. Upon transition, entities will remeasure unsettled liability-classified awards and any unmeasured equity-classified awards for non-employees at fair value as of the adoption date. A cumulative-effect adjustment to retained earnings will be required as of the beginning of the fiscal year of adoption. The Company is currently assessing the impact ASU 2018-07 will have on its consolidated financial statements and footnote disclosures thereto. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”), which provided guidance on accounting for the federal tax rate change and other tax effects of the Tax Act. SAB 118 provided a measurement period that should not extend beyond one year from the Tax Act enactment date for companies to complete the accounting under ASC 740, Income Taxes. In connection with our adoption of the Tax Act and in consideration of SAB 118, there were no changes made to the provisional amounts recognized in 2017 in connection with the enactment of the Tax Reform Act. The accounting for the income tax effects of the Tax Reform Act is complete as of December 31, 2018. In March 2016, the FASB issued ASU 2016‑09, Compensation — Improvements to Employee Share‑Based Payment Accounting, which simplifies several aspects of the accounting for employee share‑based payment transactions including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The new standard is effective for annual reporting periods beginning after December 15, 2017. The Company adopted this guidance on January 1, 2018 and it did not have a material impact to the consolidated financial statements. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . ASU No. 2016-15 addresses eight specific cash flow issues with the objective of reducing diversity in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The new standard is effective for fiscal years beginning after December 15, 2018 and interim periods within fiscal years beginning after December 15, 2018. Early adoption is permitted. The Company is currently evaluating the accounting, transition, and disclosure requirements of the standard and its impact on the Company’s consolidated statement of cash flows. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), with guidance regarding the accounting for and disclosure of leases. The update requires lessees to recognize all leases, including operating leases, with a term greater than twelve months on the balance sheet. This update also requires lessees and lessors to disclose key information about their leasing transactions. The guidance will be effective for annual and interim periods beginning after December 15, 2018. The Company is currently evaluating the effect that this guidance will have on its consolidated financial statements and related disclosures. While the Company continues to assess all the effects of adoption, the Company believes the most significant effect relates to the recognition of right-of-use assets and corresponding liabilities on its consolidated balance sheet, primarily related to its existing facility operating leases, and providing new disclosures with regards to the Company’s leasing activities.
Fair value measurements	The Company follows FASB’s accounting guidance on fair value measurements for financial assets and liabilities measured on a recurring basis. The guidance requires fair value measurements to be classified and disclosed in one of the following three categories: • Level 1 - Quoted prices (unadjusted in active markets for identical assets or liabilities) • Level 2 - Inputs other than quoted prices in active markets that are observable either directly or indirectly • Level 3 - Unobservable inputs in which there is little or no market data, which require the Company to develop its own assumptions This hierarchy requires the use of observable market data when available and to minimize the use of unobservable inputs when determining fair value.

Basis of presentation and sum_3

Basis of presentation and summary of significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Schedule of Impact of Adoption of Topic 606	In accordance with Topic 606, the disclosure of the impact of adoption to the Company’s consolidated statement of operations and consolidated balance sheet was as follows (in thousands): Year Ended December 31, 2018 As Reported Effect of Change Amounts under ASC 605 Revenue $ 253 $ 858 $ 1,111 Operating expenses Research and development 8,570 — 8,570 General and administrative 4,907 — 4,907 Restructuring costs 805 — 805 14,282 — 14,282 Loss from operations (14,029 ) 858 (13,171 ) Interest income 406 (132 ) 274 Loss from operations before income taxes (13,623 ) 726 (12,897 ) Income tax expense (4 ) — (4 ) Net loss $ (13,627 ) $ 726 $ (12,901 ) December 31, 2018 As Reported Effect of Change Amounts under ASC 605 Assets Royalty receivable $ 1,053 $ (718 ) $ 335 Royalty receivable, net of current portion $ 1,016 $ (1,016 ) $ — Shareholders' Equity Accumulated deficit $ (200,940 ) $ (1,734 ) $ (202,674 )
Schedule of Potentially Dilutive Securities Outstanding	The following potentially dilutive securities outstanding as of December 31, 2018 and 2017 have been excluded from the computation of diluted weighted average shares outstanding, as they would be anti-dilutive: Years Ended December 31, 2018 2017 Share options 10,068,744 11,418,175 Warrants 26,558,600 26,917,173 36,627,344 38,335,348

Fair value and marketable sec_2

Fair value and marketable securities (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Marketable Securities	As of December 31, 2018, marketable securities were comprised of the following (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. Treasury bills $ 15,959 $ 14 $ — $ 15,973 As of December 31, 2017, marketable securities were comprised of the following (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value U.S. government agency $ 20,857 $ 14 $ — $ 20,871 Certificates of deposit 3,475 — (1 ) 3,474 $ 24,332 $ 14 $ (1 ) $ 24,345
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	The Company has classified assets and liabilities measured at fair value on a recurring basis as follows (in thousands): December 31, 2018 Fair Value Measurement Based on Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents (1) $ 2,451 $ 2,451 $ 2,451 $ — $ — U.S. Treasury bills 15,973 15,973 15,973 — — $ 18,424 $ 18,424 $ 18,424 $ — $ — (1) Includes cash sweep accounts and U.S. Treasury money market mutual fund that have a maturity of 90 days or less from the original acquisition date. December 31, 2017 Fair Value Measurement Based on Carrying Amount Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents (2) $ 8,978 $ 8,978 $ 8,978 $ — $ — U.S. government agency 20,871 20,871 — 20,871 — Certificates of deposit 3,474 3,474 3,474 — — $ 33,323 $ 33,323 $ 12,452 $ 20,871 $ — (2) Includes cash sweep accounts, U.S. Treasury money market mutual fund, and bank certificates of deposit and U.S. Treasury bills that have a maturity of 90 days or less from the original acquisition date.

Property and equipment (Tables)

Property and equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment, net, consisted of (in thousands): December 31, 2018 2017 Laboratory and other equipment $ 209 $ 271 Office equipment 76 68 Computer equipment and software 113 130 Leasehold improvements 58 57 456 526 Less: Accumulated depreciation and amortization (254 ) (280 ) $ 202 $ 246

Accrued expenses (Tables)

Accrued expenses (Tables)	12 Months Ended
	Dec. 31, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consisted of (in thousands): December 31, 2018 2017 Compensation and related benefits $ 16 $ 994 Restructuring costs 276 — Consulting and professional fees — 105 Research and development expenses 25 745 Other 90 58 $ 407 $ 1,902

Commitments (Tables)

Commitments (Tables)	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum rental payments under non-cancellable operating leases at December 31, 2018 are as follows (in thousands): For the years ending December 31, 2019 $ 165 2020 165 2021 168 2022 171 2023 175 Thereafter 238 $ 1,082

Share-based compensation (Table

Share-based compensation (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs	The Company recorded share‑based compensation expense in the following expense categories of its consolidated statements of operations for the years ended December 31, 2018 and 2017 (in thousands): Years Ended December 31, 2018 2017 Research and development $ 146 $ 209 General and administrative 124 246 $ 270 $ 455
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	For the years ended December 31, 2018 and 2017, the grant date fair value of all option grants was estimated at the time of grant using the Black‑Scholes option‑pricing model using the following weighted average assumptions: Years Ended December 31, 2018 2017 Expected term (in years) 6.0 3.7 Expected volatility 44.4 % 33.2 % Risk-free rate 2.8 % 1.8 % Dividend yield — —
Share-based Compensation, Stock Options, Activity	The following table summarizes the activity related to stock option grants to employees and nonemployees for the years ended December 31, 2018 and 2017: Number of Shares under Option Plan Weighted-Average Exercise Price per Option Weighted- Average Remaining Contractual Life (in years) Outstanding at January 1, 2017 4,250,668 $ 0.46 Granted 2,531,000 0.51 Anti-dilution adjustment to number of options 5,087,728 0.42 Expired (326,196 ) 1.21 Forfeited (125,025 ) 0.40 Outstanding at December 31, 2017 11,418,175 0.45 Granted 90,000 0.55 Expired (544,765 ) 1.00 Forfeited (894,666 ) 0.41 Outstanding at December 31, 2018 10,068,744 $ 0.40 3.51 Exercisable at December 31, 2018 6,652,354 $ 0.39 2.85 Vested and expected to vest at December 31, 2018 10,068,744 $ 0.40 3.51

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Schedule of Loss from Operations before Income Taxes	Loss from operations before income taxes was as follows (in thousands): Years Ended December 31, 2018 2017 U.K. $ (3,647 ) $ (1,297 ) U.S. (9,976 ) (9,335 ) $ (13,623 ) $ (10,632 )
Schedule of Components of Income Tax Expense (Benefit)	Income tax (expense) benefit consists of the following (in thousands): Years Ended December 31, 2018 2017 Current tax (expense) benefit U.K. $ — $ — U.S. federal — 108 U.S. state and local (4 ) — Total current tax (expense) benefit (4 ) 108 Deferred tax (expense) benefit U.K. — — U.S. federal — — U.S. state and local — — Total deferred tax benefit — — Income tax (expense) benefit $ (4 ) $ 108
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of income tax benefit from continuing operations as reflected in the financial statements was as follows: Years Ended December 31, 2018 2017 Income tax expense at U.K. statutory rate 19.0 % 19.3 % Foreign rate differential 0.9 11.4 State taxes, net of federal benefit 5.8 5.8 Permanent differences — (0.1 ) Tax Cuts and Jobs Act — (79.4 ) Change in valuation allowance (28.5 ) 43.5 Other 2.8 0.5 Effective tax rate — 1.0 %
Schedule of Deferred Tax Assets and Liabilities	The principal components of the Company’s deferred tax assets and liabilities were as follows (in thousands): December 31, 2018 2017 Deferred income tax assets: Net operating losses $ 18,409 $ 15,261 Property and equipment 3 29 Accrued expenses and other 158 115 Tax credits 626 626 Valuation allowances (19,196 ) (16,031 ) Deferred income tax assets, net $ — $ —

Nature of the business - Narrat

Nature of the business - Narrative (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 28, 2019USD ($)	Dec. 31, 2018USD ($)study	Dec. 31, 2017USD ($)
Subsequent Event [Line Items]
Number of Phase 2 clinical studies | study		2
Cash, cash equivalents and marketable securities		$ 18,900
Working capital		19,800
Accumulated deficit		$ 200,940	$ 189,773
Scenario, Forecast | Subsequent Event
Subsequent Event [Line Items]
Gross proceeds from sale of certain assets	$ 10,000

Basis of presentation and sum_4

Basis of presentation and summary of significant accounting policies - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2018
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of property and equipment	7 years

Basis of presentation and sum_5

Basis of presentation and summary of significant accounting policies - Impairment of Long-Lived Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Impairment of long-lived assets	$ 0	$ 0

Basis of presentation and sum_6

Basis of presentation and summary of significant accounting policies - Revenue Recognition, Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ 200,940	$ 189,773
Net cash provided by (used in) operating activities	(14,965)	(9,503)
Net cash provided by (used in) investing activities	8,327	(25,620)
Net cash provided by (used in) financing activities	0	$ 23,225
Accounting Standards Update 2014-09 | Effect of Change
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ 1,734		$ (2,500)
Royalty receivable			$ 2,500

Basis of presentation and sum_7

Basis of presentation and summary of significant accounting policies - Revenue Recognition, Schedule of Impact of Adoption of 606 (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2018
Income Statement [Abstract]
Revenues	$ 253	$ 1,121
Operating expenses:
Research and development	8,570	8,189
General and administrative	4,907	3,622
Restructuring costs	805	0
Operating expenses	14,282	11,811
Loss from operations	(14,029)	(10,690)
Interest income	406	58
Loss from operations before income taxes	(13,623)	(10,632)
Income tax expense	(4)	108
Net loss	(13,627)	(10,524)
Assets
Royalty receivable	1,053	444
Royalty receivable, net of current portion	1,016	0
Shareholders’ equity:
Accumulated deficit	(200,940)	$ (189,773)
Amounts under ASC 605
Income Statement [Abstract]
Revenues	1,111
Operating expenses:
Research and development	8,570
General and administrative	4,907
Restructuring costs	805
Operating expenses	14,282
Loss from operations	(13,171)
Interest income	274
Loss from operations before income taxes	(12,897)
Income tax expense	(4)
Net loss	(12,901)
Assets
Royalty receivable	335
Royalty receivable, net of current portion	0
Shareholders’ equity:
Accumulated deficit	(202,674)
Accounting Standards Update 2014-09 | Effect of Change
Income Statement [Abstract]
Revenues	858
Operating expenses:
Research and development	0
General and administrative	0
Restructuring costs	0
Operating expenses	0
Loss from operations	858
Interest income	(132)
Loss from operations before income taxes	726
Income tax expense	0
Net loss	726
Assets
Royalty receivable	(718)
Royalty receivable, net of current portion	(1,016)
Shareholders’ equity:
Accumulated deficit	$ (1,734)		$ 2,500

Basis of presentation and sum_8

Basis of presentation and summary of significant accounting policies - Schedule of Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	36,627,344	38,335,348
Share options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	10,068,744	11,418,175
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities outstanding	26,558,600	26,917,173

Fair value and marketable sec_3

Fair value and marketable securities - Marketable Securities (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		$ 24,332,000
Unrealized Gains		14,000
Unrealized Losses		(1,000)
Fair Value		24,345,000
U.S. Treasury bills
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 15,959,000
Unrealized Gains	14,000
Unrealized Losses	0
Fair Value	$ 15,973,000
U.S. government agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		20,857,000
Unrealized Gains		14,000
Unrealized Losses		0
Fair Value		20,871,000
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		3,475,000
Unrealized Gains		0
Unrealized Losses		(1,000)
Fair Value		$ 3,474,000

Fair value and marketable sec_4

Fair value and marketable securities - Schedule of Fair Value Measurement (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		$ 24,345
U.S. Treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 15,973
U.S. government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		20,871
Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		3,474
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	18,424	33,323
Carrying Amount | U.S. Treasury bills
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,973
Carrying Amount | U.S. government agency
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		20,871
Carrying Amount | Certificates of deposit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		3,474
Carrying Amount | Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,451	8,978
Fair Value | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	18,424	33,323
Fair Value | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	18,424	12,452
Fair Value | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	20,871
Fair Value | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	0	0
Fair Value | U.S. Treasury bills | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,973
Fair Value | U.S. Treasury bills | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	15,973
Fair Value | U.S. Treasury bills | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Fair Value | U.S. Treasury bills | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0
Fair Value | U.S. government agency | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		20,871
Fair Value | U.S. government agency | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0
Fair Value | U.S. government agency | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		20,871
Fair Value | U.S. government agency | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0
Fair Value | Certificates of deposit | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		3,474
Fair Value | Certificates of deposit | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		3,474
Fair Value | Certificates of deposit | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0
Fair Value | Certificates of deposit | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0
Fair Value | Cash Equivalents | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,451	8,978
Fair Value | Cash Equivalents | Fair Value, Measurements, Recurring | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,451	8,978
Fair Value | Cash Equivalents | Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Fair Value | Cash Equivalents | Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 0	$ 0

Property and equipment - Schedu

Property and equipment - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 456	$ 526
Less: Accumulated depreciation and amortization	(254)	(280)
Property and equipment, net	202	246
Laboratory and other equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	209	271
Office equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	76	68
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	113	130
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 58	$ 57

Property and equipment - Narrat

Property and equipment - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Depreciation and amortization	$ 68	$ 86

Accrued expenses - Schedule of

Accrued expenses - Schedule of Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Compensation and related benefits	$ 16	$ 994
Restructuring costs	276	0
Consulting and professional fees	0	105
Research and development expenses	25	745
Other	90	58
Total accrued expenses	$ 407	$ 1,902

Commitments - Narrative (Detail

Commitments - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Apr. 30, 2017
Loss Contingencies [Line Items]
Rent expense under operating leases	$ 100	$ 100
Maximum percent employees may defer	100.00%
Percent of compensation for employer match	3.00%
Costs incurred from retirement plan	$ 68	$ 67
Office space
Loss Contingencies [Line Items]
Operating lease period			96 months
Office equipment | Minimum
Loss Contingencies [Line Items]
Operating lease period	5 years
Office equipment | Maximum
Loss Contingencies [Line Items]
Operating lease period	7 years

Commitments - Schedule of Futur

Commitments - Schedule of Future Minimum Rental Payments for Operating Leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
2019	$ 165
2020	165
2021	168
2022	171
2023	175
Thereafter	238
Total future minimum rental payments due	$ 1,082

Shareholders' equity - Narrativ

Shareholders' equity - Narrative (Details) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2018$ / sharesshares	Dec. 31, 2018$ / shares£ / sharesshares	Dec. 31, 2018£ / sharesshares	Dec. 31, 2017shares	Oct. 31, 2017£ / sharesshares
Subsidiary, Sale of Stock [Line Items]
Ordinary shares authorized (in shares)		154,897,265	154,897,265	154,897,265	154,897,265
Ordinary shares issued (in shares)		116,561,917	116,561,917	116,561,917	116,561,917
Exercise price of warrant (in usd/gbp per share) | (per share)		$ 0.78	$ 0.78	£ 0.58
Number of warrants outstanding (in shares)		26,558,600	26,558,600	26,558,600
Number of warrants expired in the period (in shares)		358,573	358,573
Price of warrants expired (in usd/gbp per share) | (per share)		$ 0.66	$ 0.49
Private Placement
Subsidiary, Sale of Stock [Line Items]
Number of units issued from private placement (in units)	66,400,000
Net proceeds after expenses from private placement | $	$ 23.2
Number of ordinary shares included in each unit (in shares)	1
Number of warrants included in each unit (in shares)	1
Number of ordinary shares called from each warrant (in shares)	0.4					0.4
Exercise price of warrant (in usd/gbp per share) | (per share)	$ 0.78					£ 0.58

Share-based compensation - Narr

Share-based compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance (in shares)	1,587,448
Weighted average grant date fair value (in usd per share)	$ 0.20	$ 0.15
Unrecognized compensation cost	$ 0.1
Share options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of options	10 years
Vesting period	3 years
Performance period	3 years
Dividend yield	0.00%	0.00%
Weighted-average amortization period of unrecognized compensation cost	1 year 2 months 12 days

Share-based compensation - Shar

Share-based compensation - Share-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 270	$ 455
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	146	209
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense	$ 124	$ 246

Share-based compensation - Valu

Share-based compensation - Valuation Assumptions (Details) - Share options	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years	3 years 8 months 12 days
Expected volatility	44.40%	33.20%
Risk-free rate	2.80%	1.80%
Dividend yield	0.00%	0.00%

Share-based compensation - Stoc

Share-based compensation - Stock Option Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of Shares under Option Plan
Outstanding, beginning (in shares)	11,418,175	4,250,668
Granted (in shares)	90,000	2,531,000
Anti-dilution adjustment to number of options (in shares)		5,087,728
Expired (in shares)	(544,765)	(326,196)
Forfeited (in shares)	(894,666)	(125,025)
Outstanding, ending (in shares)	10,068,744	11,418,175
Exercisable (in shares)	6,652,354
Vested and expected to vest (in shares)	10,068,744
Weighted-Average Exercise Price per Option
Outstanding, beginning (in usd per share)	$ 0.45	$ 0.46
Granted (in usd per share)	0.55	0.51
Anti-dilution adjustment (in usd per share)		0.42
Expired (in usd per share)	1	1.21
Forfeited (in usd per share)	0.41	0.40
Outstanding, ending (in usd per share)	0.40	$ 0.45
Exercisable (in usd per share)	0.39
Vested and expected to vest (in usd per share)	$ 0.40
Weighted- Average Remaining Contractual Life (in years)
Outstanding (in years)	3 years 6 months 3 days
Exercisable (in years)	2 years 10 months 6 days
Vested and expected to vest (in years)	3 years 6 months 3 days

Income taxes - Schedule of Earn

Income taxes - Schedule of Earnings Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
U.K.	$ (3,647)	$ (1,297)
U.S.	(9,976)	(9,335)
Loss from operations before income taxes	$ (13,623)	$ (10,632)

Income taxes - Components of In

Income taxes - Components of Income Tax (Expense) Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Current tax (expense) benefit
U.K.	$ 0	$ 0
U.S. federal	0	108
U.S. state and local	(4)	0
Total current tax (expense) benefit	(4)	108
Deferred tax (expense) benefit
U.K.	0	0
U.S. federal	0	0
U.S. state and local	0	0
Total deferred tax benefit	0	0
Income tax (expense) benefit	$ (4)	$ 108

Income taxes - Schedule of Effe

Income taxes - Schedule of Effective Income Tax Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense at U.K. statutory rate	19.00%	19.30%
Foreign rate differential	0.90%	11.40%
State taxes, net of federal benefit	5.80%	5.80%
Permanent differences	0.00%	(0.10%)
Tax Cuts and Jobs Act	0.00%	(79.40%)
Change in valuation allowance	(28.50%)	43.50%
Other	2.80%	0.50%
Effective tax rate	0.00%	1.00%

Income taxes - Components of De

Income taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets:
Net operating losses	$ 18,409	$ 15,261
Property and equipment	3	29
Accrued expenses and other	158	115
Tax credits	626	626
Valuation allowances	(19,196)	(16,031)
Deferred income tax assets, net	$ 0	$ 0

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Net increase in valuation allowance	$ 3,200,000
Accrued interest or penalties related to uncertain tax positions	0	$ 0
U.K.
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	14,500,000
U.S. Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	68,800,000
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	19,000,000
Research and Development Credits
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	600,000
U.S. Alternative Minimum Tax Credits
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 100,000

Related party transactions - Na

Related party transactions - Narrative (Details) - USD ($)	4 Months Ended	12 Months Ended
	Apr. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Proceeds from the issuance of ordinary shares and warrants, net of costs		$ 0	$ 23,225,000
Existing investors and executives
Related Party Transaction [Line Items]
Proceeds from the issuance of ordinary shares and warrants, net of costs			$ 1,200,000
Consulting Services Fixed Fee | Director
Related Party Transaction [Line Items]
Fixed fee per month for consulting services	$ 3,000

Uncategorized Items - rlm-20181

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 2,460,000
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 2,460,000