Arcturus Therapeutics (ARCT) 10-Q 8 May 20 2020 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2020	May 06, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Trading Symbol	ARCT
Entity Registrant Name	ARCTURUS THERAPEUTICS HOLDINGS INC.
Entity Central Index Key	0001768224
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-38942
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	32-0595345
Entity Address, Address Line One	10628 Science Center Drive
Entity Address, Address Line Two	Suite 250
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	900-2660
Entity Common Stock, Shares Outstanding		19,892,287
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 59,471	$ 71,353
Accounts receivable	2,351	2,179
Prepaid expenses and other current assets	1,937	758
Total current assets	63,759	74,290
Property and equipment, net	2,571	2,349
Operating lease right-of-use asset, net	5,567	5,134
Equity-method investment	100	263
Non-current restricted cash	107	107
Total assets	72,104	82,143
Current liabilities:
Accounts payable	3,779	5,793
Accrued liabilities	9,775	7,134
Deferred revenue	8,096	8,397
Total current liabilities	21,650	21,324
Deferred revenue, net of current portion	13,815	15,182
Long-term debt	15,028	14,995
Operating lease liability, net of current portion	4,629	4,850
Total liabilities	55,122	56,351
Stockholders’ equity
Common stock: $0.001 par value; 30,000 shares authorized; 15,157 issued and outstanding at March 31, 2020; $0.001 par value; 30,000 shares authorized, 15,138 issued and outstanding at December 31, 2019	15	15
Additional paid-in capital	98,412	97,445
Accumulated deficit	(81,445)	(71,668)
Total stockholders’ equity	16,982	25,792
Total liabilities and stockholders’ equity	$ 72,104	$ 82,143

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	30,000,000	30,000,000
Common stock, shares issued	15,157,000	15,138,000
Common stock, shares outstanding	15,157,000	15,138,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Collaboration revenue	$ 2,646	$ 4,350
Operating expenses:
Research and development, net	7,917	7,324
General and administrative	4,191	3,534
Total operating expenses	12,108	10,858
Loss from operations	(9,462)	(6,508)
Loss from equity-method investment	(163)	(288)
Finance expense, net	(152)	(88)
Net loss	$ (9,777)	$ (6,884)
Net loss per share, basic and diluted	$ (0.67)	$ (0.68)
Weighted-average shares outstanding, basic and diluted	14,521	10,095
Comprehensive loss:
Net loss	$ (9,777)	$ (6,884)
Comprehensive loss	$ (9,777)	$ (6,884)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2018	$ 13,642	$ 214	$ 58,302	$ (44,874)
Balance (in shares) at Dec. 31, 2018		10,762
Net loss	(6,884)			(6,884)
Share-based compensation	399		399
Effect of adoption of ASU 2014-09	(803)			(803)
Balance at Mar. 31, 2019	6,354	$ 214	58,701	(52,561)
Balance (in shares) at Mar. 31, 2019		10,762
Balance at Dec. 31, 2019	25,792	$ 15	97,445	(71,668)
Balance (in shares) at Dec. 31, 2019		15,138
Net loss	(9,777)			(9,777)
Share-based compensation	849		849
Issuance of common stock upon exercise of stock options	118		118
Issuance of common stock upon exercise of stock options (in shares)		19
Balance at Mar. 31, 2020	$ 16,982	$ 15	$ 98,412	$ (81,445)
Balance (in shares) at Mar. 31, 2020		15,157

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES:
Net loss	$ (9,777)	$ (6,884)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	182	172
Share-based compensation expense	849	399
Loss from equity-method investment	163	288
Other non-cash expenses	274	212
Changes in operating assets and liabilities
Accounts receivable	(172)	24
Prepaid expense and other assets	(1,179)	(291)
Accounts payable	(2,276)	1,585
Accrued liabilities	1,746	(2,060)
Deferred revenue	(1,668)	1,144
Net cash used in operating activities	(11,858)	(5,411)
INVESTING ACTIVITIES:
Acquisition of property and equipment	(142)	(78)
Net cash used in investing activities	(142)	(78)
FINANCING ACTIVITIES:
Proceeds from exercise of stock options	118
Net cash provided by financing activities	118
NET DECREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(11,882)	(5,489)
Cash, cash equivalents and restricted cash at beginning of the period	71,460	36,816
Cash, cash equivalents and restricted cash at end of the period	59,578	31,327
Supplemental disclosure of cash flow information
Cash paid for interest	228	167
Non-cash investing activities
Right-of-use asset obtained in exchange for lease liabilities	674	5,868
Purchase of property and equipment in accounts payable	$ 262	$ 135

Description of Business, Basis

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Description of Business, Basis of Presentation and Summary of Significant Accounting Policies	Note 1. Description of Business, Basis of Presentation and Summary of Significant Accounting Policies Description of Business Arcturus Therapeutics Holdings Inc. (the “Company”) is a clinical-stage messenger RNA medicines company focused on the development of infectious disease vaccines utilizing our Self-Transcribing and Replicating RNA (“STARR”) technology and significant opportunities in liver and respiratory rare diseases. In addition to the Company’s internal messenger RNA (“mRNA”) platform, its proprietary lipid nanoparticle delivery system, LUNAR, may enable multiple nucleic acid medicines. In April 2020, the Company became a clinical stage Company when it announced that its Investigational New Drug (“IND”) application for a Phase 1b study in patients with ornithine transcarbamylase (“OTC”) deficiency was deemed allowed to proceed by the U.S. Food and Drug Administration (“FDA”), and an additional Clinical Trial Application (“CTA”) for a Phase 1 study in healthy volunteers was approved by the New Zealand Medicines and Medical Devices Safety Authority. In March 2020, the Company was awarded a grant (the “Grant”) from the Singapore Economic Development Board to support the co-development of a potential COVID-19 vaccine with the Duke-NUS Medical School. The grant provides for up to S$14.0 million (approximately US$10 million using the exchange rate on the date the grant was awarded) in grants to support the development of the vaccine. A portion of the Grant will be paid by the Economic Development Board in advance and the remainder of the Grant will be paid to the Company upon the achievement of certain milestones related to the progress of the development of the vaccine, as set forth in the award agreement. The Company has agreed to pay Duke-NUS Medical School a royalty based on annual net sales of the vaccine in markets or jurisdictions outside of Singapore. Basis of Presentation The financial statements for periods prior to June 17, 2019 Arcturus Therapeutics Ltd., Arcturus Therapeutics Ltd The accompanying condensed consolidated financial statements include the accounts of Arcturus Therapeutics Holdings Inc. and its subsidiaries and are unaudited. All intercompany accounts and transactions have been eliminated in consolidation. These condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In management’s opinion, the accompanying condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation of the results for the interim periods presented. Interim financial results are not necessarily indicative of results anticipated for the full year. These condensed consolidated financial statements should be read in conjunction with the audited financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. These condensed consolidated financial statements are prepared in accordance with GAAP, which requires management to make estimates and assumptions regarding the valuation of certain debt and equity instruments, the disclosure of contingent assets and liabilities at the date of the financial statements and Liquidity The Company’s activities since inception have consisted principally of performing research and development activities, general and administration activities, and raising capital. The Company’s activities are subject to significant risks and uncertainties, including failing to secure additional funding before the Company achieves sustainable revenues and profit from operations. The Company is a clinical-stage bioscience company that is dependent on obtaining external equity and debt financings to fund its operations. Historically, the Company’s primary sources of financing have been through the sale of its securities, through issuance of debt and through collaboration agreements. As mentioned above, the Company was recently awarded a grant from the Singapore Economic Development Board of up to $10.0 million to support the co-development of a potential COVID-19 vaccine with the Duke-NUS Medical School, approximately $5.0 million of which was awarded during the quarter ended March 31, 2020 and subsequently received in April 2020. Additionally, in April 2020 the Company completed an underwritten public offering of 4,735,297 shares of common stock (including the underwriters’ overallotment option) at a price of $17.00 per share. The Company received net proceeds of approximately $75.5 million in the offering. In March 2020, the Company entered into an at-the-market Sales Agreement with Stifel, Nicolaus & Company, Incorporated (the “ATM”). The ATM was terminated simultaneously with the consummation of the underwritten public offering in April 2020. Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company and its chief operating decision-maker view the Company’s operations and manage its business in one operating segment, which is the research and development of medical applications for the Company’s nucleic acid-focused technology. Revenue Recognition Effective January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) (“Topic 606”), The terms of the Company’s collaborative research and development agreements include license fees, upfront payments, milestone payments, and reimbursement for research and development activities, option exercise fees, and royalties on sales of commercialized products. Arrangements that include upfront payments are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs obligations under these arrangements. The event-based milestone payments represent variable consideration, and the Company uses the most likely amount method to estimate this variable consideration because the Company will either receive the milestone payment or will not, which makes the potential milestone payment a binary event. The most likely amount method requires the Company to determine the likelihood of earning the milestone payment. Given the high degree of uncertainty around achievement of these milestones, the Company determines the milestone amounts to be fully constrained and does not recognize revenue until the uncertainty associated with these payments is resolved. The Company will recognize revenue from sales-based royalty payments when or as the sales occur. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved and other changes in circumstances occur. A performance obligation is a promise in a contract to transfer a distinct good or service to the collaborative partner and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation based on relative standalone selling price and recognized as revenue when, or as, the performance obligation is satisfied. See “Note 2, Collaboration Revenue” Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize most leases on the balance sheet as lease liabilities with corresponding right-of-use assets and to disclose key information about leasing arrangements. The Company adopted Topic 842 on its effective date in the first quarter of 2019 using a modified retrospective approach. The Company elected the available package of practical expedients upon adoption, which allowed it to carry forward historical assessments of whether existing agreements contained a lease and the classification of existing operating leases. See “Note 8, Commitments and Contingences” Research and Development, Net Research and development costs are expensed as incurred. These expenses result from the Company’s independent research and development efforts as well as efforts associated with collaboration arrangements. Research and development costs include salaries and personnel-related costs, consulting fees, fees paid for contract research and manufacturing services, the costs of laboratory supplies, equipment and facilities, preclinical studies and other external costs are shown net of any grants. Statement of Cash Flows The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the condensed consolidated balance sheet to the total of the same such amounts shown in the condensed consolidated statement of cash flows: (in thousands) March 31, 2020 March 31, 2019 Cash and cash equivalents $ 59,471 $ 31,220 Non-current restricted cash 107 107 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 59,578 $ 31,327 Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period determined using the treas ury-stock method. Dilutive shares of common stock are comprised of stock options. No dividends were declared or paid during the reported periods.

Collaboration Revenue

Collaboration Revenue	3 Months Ended
	Mar. 31, 2020
Collaboration Agreements [Abstract]
Collaboration Revenue	Note 2. Collaboration Revenue The Company has entered into license agreements and collaborative research and development arrangements with pharmaceutical and biotechnology companies. Under these arrangements, the Company is entitled to receive license fees, upfront payments, milestone payments if and when certain research and development milestones or technology transfer milestones are achieved, royalties on approved product sales and reimbursement for research and development activities. The Company’s costs of performing these services are included within research and development expenses. The Company’s milestone payments are typically defined by achievement of certain preclinical, clinical, and commercial success criteria. Preclinical milestones may include in vivo proof of concept in disease animal models, lead candidate identification, and completion of IND-enabling toxicology studies. Clinical milestones may, for example, include successful enrollment of the first patient in or completion of Phase I, II, and III clinical trials, and commercial milestones are often tiered based on net or aggregate sale amounts. The Company cannot guarantee the achievement of these milestones due to risks associated with preclinical and clinical activities required for development of nucleic acid medicine-based therapeutics. The following table presents changes during the three months ended March 31, 2020 in the balances of contract assets, including receivables from collaborative partners, and contract liabilities, including deferred revenue, as compared to what was disclosed in the Company’s Annual Report. (in thousands) Contract Assets BALANCE - December 31, 2019 $ 2,179 Additions for revenue recognized from billings 978 Deductions for cash collections (806 ) BALANCE – March 31, 2020 $ 2,351 (in thousands) Contract Liabilities BALANCE - December 31, 2019 $ 23,579 Additions for advanced billings 978 Deductions for promised goods/services provided in current period (2,646 ) BALANCE – March 31, 2020 $ 21,911 The following table summarizes the Company’s collaboration revenues for the periods indicated (in thousands). For the Three Months Ended March 31, (Dollars in thousands) 2020 2019 Collaboration Partner – Janssen $ 897 $ 513 Collaboration Partner – Ultragenyx 911 1,388 Collaboration Partner – CureVac 309 1,894 Collaboration Partner – Takeda and other 529 555 Total collaboration revenue $ 2,646 $ 4,350 The following paragraphs provide information regarding the nature and purpose of the Company’s most significant collaboration arrangements. Collaboration Partner – Janssen In October 2017, the Company entered into a research collaboration and license agreement with Janssen (the “2017 Agreement”). The 2017 Agreement allocated discovery, development, funding obligations, and ownership of related intellectual property among the Company and Janssen Pharmaceuticals, Inc. (“Janssen”). The Company received an upfront payment of $7.7 million and may receive preclinical, development and sales milestone payments of $56.5 million, as well as royalty payments on any future licensed product sales. Janssen began reimbursing the Company for research costs during the first quarter of 2019 upon the completion of the first of three research periods. Janssen may also pay option exercise fees within the $1.0 million to $5.0 million range per target. Janssen will pay royalties on annual net sales of licensed products in the low to mid-single digits range, subject to reduction on a country-by-country and licensed-product-by-licensed-product basis and subject to certain events, such as expiration of program patents. In addition, the 2017 Agreement includes an exclusivity period. In evaluating the 2017 Agreement in accordance with ASC Topic 606, the Company concluded that the contract counterparty, Janssen, is a customer. The Company identified the following promised goods/services as of the inception of the Agreement: (i) research services, (ii) license to use Arcturus technology and (iii) participation in the Joint Research Committee. The Company concluded that the promised goods/services are incapable of being distinct and consequently do not have any value on a standalone basis. Accordingly, they are determined to represent a single performance obligation. The Company concluded that Janssen’s options to select additional collaboration targets and to license rights to selected targets are not priced at a discount and therefore do not represent performance obligations for which the transaction price would be allocated. As of March 31, 2020, the remaining transaction price, consisting of upfront consideration received and budgeted reimbursable out-of-pocket costs, is expected to be recognized using an input method over the remaining research period of 30 months. None of the development and commercialization milestones were included in the transaction price, as all milestone amounts were not estimated to be met, are outside the control of the Company and contingent upon success in future clinical trials and the collaborator’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur, provided that the reported sales are reliably measurable, and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to Janssen and therefore have also been excluded from the transaction price. Total deferred revenue as of March 31, 2020 and December 31, 2019 for Janssen was $5.9 million. Collaboration Partner – Ultragenyx In October 2015 the Company entered into a research collaboration and license agreement with Ultragenyx (the “Ultragenyx Agreement”), whereby Arcturus granted to Ultragenyx a co-exclusive license under Arcturus technology and shall be in effect only during the reserve target exclusivity term as discussed in the following paragraphs. This collaboration agreement was amended in 2017, 2018 and during the second quarter of 2019. During the initial phase of the collaboration, the Company will design and optimize therapeutics for certain rare disease targets. Ultragenyx has the option under the Ultragenyx Agreement to add additional rare disease targets during the collaborative development period. Additionally, during the collaborative development period, the Company will participate with Ultragenyx in a joint steering committee. The Ultragenyx Agreement also includes an initial exclusivity period with an option to extend this period. As part of the Ultragenyx Agreement and related amendments, Ultragenyx has paid $27.9 million in upfront fees, exclusivity extension fees and additional consideration. Ultragenyx also reimburses the Company for all internal and external development costs incurred, pursuant to the Ultragenyx Agreement, is required to make additional payments upon exercise of the Ultragenyx expansion option or exclusivity extension (if any) and if Ultragenyx achieves certain, clinical, regulatory and sales milestones, then the Company is eligible to receive royalty payments $0.5 million to $1.5 million. The current potential development, regulatory and commercial milestone payments for the existing development targets as of March 31, 2020 are $138.0 million. Ultragenyx will pay royalties as a single-digit percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term. As of March 31, 2020, Ultragenyx has not yet reached the clinical phase of the contract. On June 18, 2019, Arcturus and Ultragenyx amended the collaboration agreement for a third time (“Amendment 3”). As part of Amendment 3, the total number of targets was increased from 10 to 12, and reserve targets will be exclusively reserved for Ultragenyx with no fees for four years after execution of the amendment. An equity component was also added as part of Amendment 3 wherein Ultragenyx purchased 2.4 million shares of common stock at a premium price. Along with the equity purchase, Ultragenyx received the option to purchase 0.6 million additional shares of common stock at $16 per share within two years of executing the amendment (Note 6). The consideration received from Ultragenyx as a result of Amendment 3 was equal to $30.0 million and was comprised of a $24.0 million common stock purchase and a $6.0 million upfront payment. Specifically for Amendment 3, management determined the transaction price to be $14.4 million. See further discussion below regarding determining the transaction price. Management determined the fair value of the premium received by using the opening stock price subsequent to execution of Amendment 3 and applying a lack of marketability discount as the shares received by Ultragenyx are restricted for up to two years (subject to reduction upon the exercise of the option). In evaluating the Ultragenyx agreement in accordance with ASC Topic 606, the Company concluded that the contract counterparty, Ultragenyx, is a customer. The Company has identified the following promised goods/services as part of the initial agreement and subsequent amendments: (i) research services, (ii) license to use Arcturus technology, (iii) exclusivity and (iv) participation in the Joint Steering Committee. The Company concluded that the promised goods/services are incapable of being distinct and consequently do not have any value on a standalone basis. Accordingly, they are determined to represent a single performance obligation. The Company concluded that Ultragenyx’s options to extend exclusivity and options to select additional collaboration targets and to license rights to selected targets are not priced at a discount and therefore do not represent performance obligations for which the transaction price would be allocated. At March 31, 2020, the transaction price included the upfront consideration received, exclusivity extension payments and additional consideration received pursuant to Amendment 3. The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that the consideration is outside the control of the Company and contingent upon success in future clinical trials, approval from the Food and Drug Administration and the collaborator’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur as they are constrained, provided that the reported sales are reliably measurable and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to Ultragenyx and therefore have also been excluded from the transaction price. Amendment 3 was deemed a contract modification and accounted for as part of the original Ultragenyx Agreement and the Company recorded a cumulative catch-up adjustment of $1.1 million on the modification date. The transaction price will be recognized to revenue on a straight-line basis using an input method over the 4-year reserve target exclusivity period. The reserve target exclusivity period represents the timing over which promised goods/services Collaboration Partner – CureVac In January 2018, the Company entered into a Development and Option Agreement with CureVac, (the “Development and Option Agreement”). Under the terms of the Development and Option Agreement, the parties agreed to conduct joint preclinical development programs once CureVac makes a payment to pull down a target on the basis of which CureVac is granted options for taking a license on pre-agreed license terms to develop and commercialize certain products incorporating the Company’s patents and know-how related to delivery technology (the LUNAR platform) (the “Arcturus Delivery Technology”), and CureVac patents and know-how related to mRNA technology. Subject to certain restrictions, the parties will have an undivided one-half interest in the patents and know-how developed jointly by the parties during the course of the Development and Option Agreement. Pursuant to the terms of the Development and Option Agreement, CureVac will have a number of target options to co-develop from a reserved target list to enter into licenses under the Arcturus Delivery Technology with respect to the development, manufacture and commercialization of licensed products (which can include products identified for development by the Company, unless the Company is permitted by the terms of the Development and Option Agreement to place such products on a restricted list). A separate notice and fee will be required for each license agreement. If the target to which the license agreement relates is chosen by the parties for co-development under the Co-Development Agreement (as defined below and discussed in the following paragraph) the license agreement will terminate as such programs will be covered under the Co-Development Agreement discussed below, and therefore CureVac will be given a credit for any exercise fees, milestone payments already paid and all other payments made in relation to the license agreement towards future such payments incurred with respect to future licenses under the Arcturus Delivery Technology. Prior to expiration of the initial term of 8 years (which was subsequently amended, as discussed below), the Agreement also includes an option to extend the term on an annual basis for up to 3 years, subject to payment by CureVac to Arcturus of a non-refundable annual extension fee. The agreement included potential milestone payments for selected targets from CureVac to the Company. The current potential milestone payments for the remaining targets as of March 31, 2020 is $14.0 million for rare disease targets and $23.0 million for non-rare disease targets. CureVac will pay royalties as a percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term in the low single-digit range. As of March 31, 2020, CureVac has not yet reached the clinical phase of the contract. Pursuant to a May 2018 amendment to the Development and Option Agreement (as amended and restated on September 28, 2018), the Company increased the number of targets available to CureVac under the Development and Option Agreement and agreed upon the license forms to be executed upon selection of the targets by CureVac. Concurrently with the Development and Option Agreement, the Company entered into a Co-Development and Co-Commercialization Agreement (the “Co-Development Agreement”) which the Company considered a combined contract with the Development and Option Agreement for purposes of revenue recognition. However, on February 11, 2019, the Company announced the termination of the obligations of CureVac for the preclinical development of ARCT-810, effective as of August 4, 2019 and the re-assumption by the Company of the worldwide rights thereto. As a result, On July 26, 2019, the Company entered into an amendment (“CureVac Amendment”) to its Development and Option Agreement with CureVac (as amended, the “Development and Option Agreement”), pursuant to which the Company and CureVac agreed to shorten the time period during which CureVac may select potential targets to be licensed from the Company from eight years to four years, and to reduce the overall number of maximum targets to be reserved and licensed. In connection with the July 2019 CureVac Amendment, the Company and CureVac also entered into a Termination Agreement (the “Termination Agreement”) terminating the January 1, 2018 Co-Development Agreement between the Company and CureVac. Pursuant to the Termination Agreement CureVac agreed to make a one-time payment to Arcturus in the amount of $4.0 million, which was made in July 2019. In evaluating the CureVac Development and Option Agreement and Co-Development Agreement in accordance with ASC Topic 606, the Company concluded that the contract counterparty, CureVac, is a customer. The Company has identified the following promised goods/services as part of the initial agreement with CureVac and subsequent amendments: (i) research services, (ii) license to use Arcturus technology, (iii) exclusivity and (iv) participation in the Joint Steering Committee. The Company concluded that the promised goods/services are incapable of being distinct At March 31, 2020, the transaction price included the upfront consideration received. The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the collaborator’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur as they are constrained, provided that the reported sales are reliably measurable and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to CureVac and therefore have also been excluded from the transaction price. For the three months ended March 31, 2020, no adjustments were made to the transaction price. The upfront consideration of $5.0 million was recorded as deferred revenue in the Company’s balance sheet upon receipt and is currently being recognized as revenue on a straight-line basis using an input method over the amended forty-six month contractual term as of March 31, 2020. As a result of Amendment 3, the Company recorded a cumulative catch up adjustment of $0.4 million on the modification date, July 26, 2019. Total deferred revenue as of March 31, 2020 and December 31, 2019 for CureVac was $3.0 million and $3.2 million, respectively. No adjustment was necessary upon adoption of Topic 606 Other Collaboration Revenue The remaining revenue from smaller collaboration agreements relates to the agreement with Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”). Under the agreement with Takeda, the Company recognized $0.5 million related to amortization of an upfront payment during the first quarter of 2020 related to research and development activities. The current agreement was entered into on March 18, 2019 and is expected to be completed by the end of 2020.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Note 3. Fair Value Measurements The Company establishes the fair value of its assets and liabilities using the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company establishes a fair value hierarchy based on the inputs used to measure fair value. The three levels of the fair value hierarchy are as follows: Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly. Level 3: Unobservable inputs in which little or no market data exists and are therefore determined using estimates and assumptions developed by the Company, which reflect those that a market participant would use. The carrying value of cash, restricted cash, accounts receivable, accounts payable, and accrued liabilities approximate their respective fair values due to their relative short maturities. The carrying amounts of long-term debt for the amount drawn on the Company’s debt facility approximates fair value as the interest rate is variable and reflects current market rates. As of March 31, 2020 and December 31, 2019, all assets measured at fair value on a recurring basis consisted of cash equivalents and money market funds, which were classified within Level 1 of the fair value hierarchy. The fair value of these financial instruments was measured based on quoted prices.

Balance Sheet Details

Balance Sheet Details	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Note 4 Prepaid expenses and other current assets consisted of the following as of March 31, 2020 and December 31, 2019: (in thousands) March 31, 2020 December 31, 2019 Prepaid expenses $ 1,344 $ 720 Other current assets 593 38 Total $ 1,937 $ 758 Property and equipment, net for the same periods consisted of the following: (in thousands) March 31, 2020 December 31, 2019 Research equipment $ 4,045 $ 3,658 Computers and software 271 271 Office equipment and furniture 574 561 Leasehold improvements 44 40 Total 4,934 4,530 Less accumulated depreciation and amortization (2,363 ) (2,181 ) Property and equipment, net $ 2,571 $ 2,349 Depreciation and amortization expense was $0.2 million and $0.2 million Accrued liabilities consisted of the following as of March 31, 2020 and December 31, 2019: (in thousands) March 31, 2020 December 31, 2019 Accrued compensation $ 1,635 $ 1,608 Cystic Fibrosis Foundation Liability (Note 9) 1,921 1,949 Current portion of operating lease liability 1,474 827 Other accrued research and development expenses 4,745 2,750 Total $ 9,775 $ 7,134

Debt

Debt	3 Months Ended
	Mar. 31, 2020
Debt Disclosure [Abstract]
Debt	Note 5. Debt Long-term debt with Western Alliance Bank On October 12, 2018, the Company entered into a Loan and Security Agreement with Western Alliance Bank (the “Bank”), whereby the Company received $10.0 million under a long-term debt agreement (the “Loan”). The Loan is collateralized by all of the assets of the Company, excluding intellectual property, which is subject to a negative pledge. The Loan contains customary conditions of borrowing, events of default and covenants, including covenants that restrict the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. In addition, the Company is required to maintain at least 100% of its consolidated, unrestricted cash, or $15 million, whichever is lower, with the Bank. On October 30, 2019, the Company and the Bank entered into a Third Amendment (the “Third Amendment”) to the Loan and Security Agreement dated as of October 12, 2018 (as amended, the “Loan Agreement”). Pursuant to the amendment, the Bank agreed to make a term loan to the Company on October 30, 2019, in the amount of $15 million (the “Term Loan”). The resulting net increase in the indebtedness of the Company was $5.0 million. The Term Loan bears interest at a floating rate ranging from 1.25% to 2.75% above the prime rate. The amendment further provides that the Term Loan has a maturity date of October 30, 2023. The Company shall make monthly payments of interest only until the interest-only end date of October 1, 2021. The Company paid a loan origination fee of $54,000 which was recorded as a debt discount along with the remaining loan origination fee from the Loan and is being accreted over the term of the Term Loan. In addition, the Company is required to pay a fee of $525,000 upon certain change of control events. The Term Loan may be prepaid in full at any time, provided that a prepayment fee is required to be paid by the Company upon prepayment. The prepayment fee ranges from 0.50% to 2.00% of the prepaid principal amount depending upon the date on which the prepayment is made. In connection with the Third Amendment, the Company guaranteed the obligations under the Loan Agreement and pledged substantially all of its assets as security under the Loan Agreement. The Term Loan also includes covenants which includes the Company’s submission of a clinical candidate for IND application made to the U.S. Food and Drug Administration by May 31, 2020 and have it accepted by June 30, 2020. This covenant has been satisfied. Upon maturity or prepayment (as previously discussed), the Company will be required to pay a 2% fee as a result of the FDA’s approval to proceed with the Company’s the LUNAR-OTC (ARCT-810) program based on its IND submission. Such fee is accreted to the debt balance using the effective interest method over the term of the Loan Agreement. Should an event of default occur, including the occurrence of a material adverse effect, the Company could be liable for immediate repayment of all obligations under the Loan Agreement. As of March 31, 2020, the Company was in compliance with all covenants under the Loan Agreement. Principal payments, including the final payment due at repayment, on the long-term debt for fiscal years 2021, 2022 and 2023 are $4.0 million, $6.0 million and $5.5 million, respectively, with no principal payments due in 2020. The Company recognized interest expense related to its long-term debt of $0.3 million and $0.2 million during the three months ended March 31, 2020 and 2019, respectively.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2020
Stockholders Equity Note [Abstract]
Stockholders' Equity	Note 6. Stockholders’ Equity Restricted Common Shares In March 2013, the founders of the Company purchased 2,783,686 shares of common stock for $0.0068 per share. Of the shares purchased, 1,538,353 were subject to a repurchase option whereby the Company has an option for two months after date of termination of service to repurchase any or all of the unvested shares at the original purchase price per share. The repurchase option shall be deemed to be automatically exercised by the Company as of the end of the two-month period unless the Company notifies the purchaser that it does not intend to exercise its option. The shares will be vested (1) 25% after obtaining suitable siRNA license; (2) 25% after in vivo 622,667 Net Loss per Share Dilutive securities that were not included in the calculation of diluted net loss per share for the three months ended March 31, 2020 and 2019 as they were anti-dilutive totaled 316,957 and 67,051, respectively. For the quarters ended March 31, 2020 and 2019, the calculation of the weighted-average number of shares outstanding excludes unvested restricted shares of common stock of 622,667.

Share-Based Compensation

Share-Based Compensation	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	Note 7. Share-Based Compensation In August 2018, the Company adopted the 2018 Omnibus Equity Incentive Plan (“2018 Plan”). Under the 2018 Plan, the Company was authorized to issue up to a maximum of Stock Options Share-based compensation expenses included in the Company’s condensed statements of operations and comprehensive loss for the three months ended March 31, 2020 and 2019 were: For the Three Months Ended March 31, (in thousands) 2020 2019 Research and development $ 266 $ 152 General and administrative 583 247 Total $ 849 $ 399

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Note 8. Income Taxes The Company is subject to taxation in the United States and various states. The Company computes its quarterly income tax provision by using a forecasted annual effective tax rate and adjusts for any discrete items arising during the quarter. The primary difference between the effective tax rate and the federal statutory tax rate relates to the valuation allowances on the Company’s net operating losses. No tax benefit was provided for losses incurred in the United States because those losses are offset by a full valuation allowance. For the three months ended March 31, 2020, the Company recorded income tax expense of $0 million. No tax benefit was provided for losses incurred in United States because those losses are offset by a full valuation allowance. On March 27, 2020, the United States enacted the Coronavirus Aid, Relief and Economic Security Act (CARES Act). The Cares Act is an emergency economic stimulus package that includes spending and tax breaks to strengthen the United States economy and fund a nationwide effort to curtail the effect of COVID-19. While the CARES Act provides sweeping tax changes in response to the COVID-19 pandemic, some of the more significant provisions which are expected to impact the Company’s financial statements include removal of certain limitations on utilization of net operating losses, increasing the loss carryback period for certain losses to five years, and increasing the ability to deduct interest expense, as well as amending certain provisions of the previously enacted Tax Cuts and Jobs Act. As of the quarter ended March 31, 2020 the Company has estimated that the impact of the CARES Act will be immaterial to its tax position. Due to the recent enactment of the CARES Act, the Company will continue to analyze the impact that the CARES Act will have in subsequent quarters on its financial position, results of operations or cash flows .

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 9. Commitments and Contingencies COVID-19 Vaccine Development On March 4, 2020, the Company was awarded a grant (the “Grant”) from the Singapore Economic Development Board to support the co-development of a potential COVID-19 vaccine with the Duke-NUS Medical School. The Grant provides for up to S$14.0 million (approximately US$10 million using the March 2, 2020 exchange rate) in grants to support the development of the vaccine. A portion of the Grant will be paid by the Economic Development Board in advance and the remainder of the Grant will be paid to the Company upon the achievement of certain milestones related to the progress of the development of the vaccine, as set forth in the award agreement. The funds received will be recognized as contra research and development expense in proportion to the percentage covered by the Economic Development Board of the overall budget. The Company is liable for certain expenses during the program period and any unused funds are required to be repaid upon completion of the program. For the three months ended March 31, 2020, the Company recognized $0.5 million of contra expense. Cystic Fibrosis Foundation Agreement On August 1, 2019, the Company amended its Development Program Letter Agreement, dated May 16, 2017 and as amended July 13, 2018, with the Cystic Fibrosis Foundation (“CFF”). Pursuant to the amendment, (i) CFF increased the amount it will award to advance LUNAR-CF to $15.0 million from approximately $3.2 million, (ii) the Company will provide $5.0 million in matching funds for remaining budgeted costs and (iii) the related disbursement schedule from CFF to Arcturus was modified such that (a) $4.0 million was disbursed upon execution of the CFF Amendment, (b) $2.0 million will be disbursed within 30 days of the first day of each of January, April, July and October 2020 upon Arcturus invoicing CFF to meet project goals, and (c) the last payment of $3.0 million less the prior award previously paid out, equaling approximately $2.3 million, will be disbursed upon Arcturus Therapeutics, Inc. invoicing CFF to meet good manufacturing practices and opening an Investigational New Drug (“IND”) application. The funds received from CFF will be recognized as contra research and development expense in proportion to the percentage covered by CFF of the overall budget. For the three months ended March 31, 2020, the Company recognized $2.0 million of contra expense with $1.9 million remaining in accrued expenses. Leases In October 2017, the Company entered into a non-cancellable operating lease agreement for office space adjacent to its previously occupied headquarters. The commencement of the lease began in March 2018 and the lease extends for approximately 84 months from the commencement date with a remaining lease term through March 2025. Monthly rental payments are due under the lease and there are escalating rent payments during the term of the lease. The Company is also responsible for its proportional share of operating expenses of the building and common areas. In conjunction with the new lease, the Company received free rent for four months and received a tenant improvement allowance of $74,000. The lease may be extended for one five-year period at the then current market rate with annual escalations; however, the Company deemed the extension option not reasonably certain to be exercised and therefore excluded the option from the lease terms. The Company entered into an irrevocable standby letter of credit with the landlord for a security deposit of $96,000 upon executing the lease which is included (along with additional funds required to secure the letter of credit) in the balance of non-current restricted cash. In January 2020, the Company entered into a non-cancellable operating lease agreement for office space near its current headquarters. The commencement of the lease began in February 2020 and the lease extends for 13 months from the commencement date. In conjunction with the new lease, the Company received free rent for one month. The lease may be extended for one twelve-month period; however, the Company deemed the extension option not reasonably certain to be exercised and therefore excluded the option from the lease terms Operating lease right-of-use asset and liability on the condensed consolidated balance sheets represent the present value of remaining lease payments over the remaining lease terms. The Company does not allocate lease payments to non-lease components; therefore, payments for common-area-maintenance and administrative services are not included in the operating lease right-of-use asset and liability. The Company uses its incremental borrowing rate to calculate the present value of the lease payments, as the implicit rate in the lease is not readily determinable. As of March 31, 2020, the payments of the operating lease liability were as follows: (in thousands) Remaining Lease Payments 2020 (remaining) $ 1,489 2021 1,427 2022 1,349 2023 1,390 2024 1,432 Thereafter 314 Total remaining lease payments 7,401 Less: imputed interest (1,298 ) Total operating lease liabilities $ 6,103 Weighted-average remaining lease term 4.7 years Weighted-average discount rate 8.4 % Operating lease costs consist of the fixed lease payments included in operating lease liability and are recorded on a straight-line basis over the lease terms. Operating lease costs were $0.4 million and $0.3 million for the three months ended March 31, 2020 and 2019, respectively.

Related Party Transactions

Related Party Transactions	3 Months Ended
	Mar. 31, 2020
Related Party Transactions [Abstract]
Related Party Transactions	Note 10. Related Party Transactions Ultragenyx In June 2019, Arcturus and Ultragenyx executed Amendment 3 to the Ultragenyx Agreement. In addition, as a result of the amended Ultragenyx Agreement, Ultragenyx owns 15.8% of the outstanding common stock of the Company as of March 31, 2020. Pursuant to the amended Ultragenyx Agreement, the Company also granted Ultragenyx a two-year option (the “Option”) to purchase up to 600,000 additional shares of common stock at a price of $16.00 per share. Equity-Method Investment In June 2018, the Company completed the sale of its intangible asset related to the ADAIR technology. Pursuant to the asset purchase agreement for ADAIR, the Company received a 30% ownership interest in the common stock of a privately held company in consideration for the sale of the ADAIR technology. The Company has no requirement to invest further in this private company. During the third quarter of 2019, the equity-method investee issued shares of its common stock at a share price greater than the initial investment which resulted in the Company recording a gain in its equity-method investment. The gain has been offset by additional losses incurred by the equity-method investee and calculated on a lag. For the three months ended March 31, 2020, the Company recorded a loss of $0.2 million. Subsequent to the equity-method investee issuing shares of its common stock, the Company’s ownership was reduced to 19%. As the Company continues to have the ability to exercise significant influence over the operating and financial policies of the investee, the Company will continue to account for the investment as an equity-method investment.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	Note 11. Subsequent Events Acceptance of Investigational New Drug Application for ARCT-810 In April 2020, the Company’s IND application for a Phase 1b study in patients with OTC deficiency was deemed allowed to proceed by the U.S. Food and Drug Administration, and an additional Clinical Trial Application for a Phase 1 study in healthy volunteers was approved by the New Zealand Medicines and Medical Devices Safety Authority. Underwritten Public Offering of Common Stock See discussion of underwritten public offering of common stock at Note 1.

Description of Business, Basi_2

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The financial statements for periods prior to June 17, 2019 Arcturus Therapeutics Ltd., Arcturus Therapeutics Ltd The accompanying condensed consolidated financial statements include the accounts of Arcturus Therapeutics Holdings Inc. and its subsidiaries and are unaudited. All intercompany accounts and transactions have been eliminated in consolidation. These condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In management’s opinion, the accompanying condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation of the results for the interim periods presented. Interim financial results are not necessarily indicative of results anticipated for the full year. These condensed consolidated financial statements should be read in conjunction with the audited financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. These condensed consolidated financial statements are prepared in accordance with GAAP, which requires management to make estimates and assumptions regarding the valuation of certain debt and equity instruments, the disclosure of contingent assets and liabilities at the date of the financial statements and
Liquidity	Liquidity The Company’s activities since inception have consisted principally of performing research and development activities, general and administration activities, and raising capital. The Company’s activities are subject to significant risks and uncertainties, including failing to secure additional funding before the Company achieves sustainable revenues and profit from operations. The Company is a clinical-stage bioscience company that is dependent on obtaining external equity and debt financings to fund its operations. Historically, the Company’s primary sources of financing have been through the sale of its securities, through issuance of debt and through collaboration agreements. As mentioned above, the Company was recently awarded a grant from the Singapore Economic Development Board of up to $10.0 million to support the co-development of a potential COVID-19 vaccine with the Duke-NUS Medical School, approximately $5.0 million of which was awarded during the quarter ended March 31, 2020 and subsequently received in April 2020. Additionally, in April 2020 the Company completed an underwritten public offering of 4,735,297 shares of common stock (including the underwriters’ overallotment option) at a price of $17.00 per share. The Company received net proceeds of approximately $75.5 million in the offering. In March 2020, the Company entered into an at-the-market Sales Agreement with Stifel, Nicolaus & Company, Incorporated (the “ATM”). The ATM was terminated simultaneously with the consummation of the underwritten public offering in April 2020.
Segment Information	Segment Information Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company and its chief operating decision-maker view the Company’s operations and manage its business in one operating segment, which is the research and development of medical applications for the Company’s nucleic acid-focused technology.
Revenue Recognition	Revenue Recognition Effective January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) (“Topic 606”), The terms of the Company’s collaborative research and development agreements include license fees, upfront payments, milestone payments, and reimbursement for research and development activities, option exercise fees, and royalties on sales of commercialized products. Arrangements that include upfront payments are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs obligations under these arrangements. The event-based milestone payments represent variable consideration, and the Company uses the most likely amount method to estimate this variable consideration because the Company will either receive the milestone payment or will not, which makes the potential milestone payment a binary event. The most likely amount method requires the Company to determine the likelihood of earning the milestone payment. Given the high degree of uncertainty around achievement of these milestones, the Company determines the milestone amounts to be fully constrained and does not recognize revenue until the uncertainty associated with these payments is resolved. The Company will recognize revenue from sales-based royalty payments when or as the sales occur. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved and other changes in circumstances occur. A performance obligation is a promise in a contract to transfer a distinct good or service to the collaborative partner and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation based on relative standalone selling price and recognized as revenue when, or as, the performance obligation is satisfied. See “Note 2, Collaboration Revenue”
Leases	Leases In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize most leases on the balance sheet as lease liabilities with corresponding right-of-use assets and to disclose key information about leasing arrangements. The Company adopted Topic 842 on its effective date in the first quarter of 2019 using a modified retrospective approach. The Company elected the available package of practical expedients upon adoption, which allowed it to carry forward historical assessments of whether existing agreements contained a lease and the classification of existing operating leases. See “Note 8, Commitments and Contingences”
Research and Development, Net	Research and Development, Net Research and development costs are expensed as incurred. These expenses result from the Company’s independent research and development efforts as well as efforts associated with collaboration arrangements. Research and development costs include salaries and personnel-related costs, consulting fees, fees paid for contract research and manufacturing services, the costs of laboratory supplies, equipment and facilities, preclinical studies and other external costs are shown net of any grants.
Statement of Cash Flows	Statement of Cash Flows The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the condensed consolidated balance sheet to the total of the same such amounts shown in the condensed consolidated statement of cash flows: (in thousands) March 31, 2020 March 31, 2019 Cash and cash equivalents $ 59,471 $ 31,220 Non-current restricted cash 107 107 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 59,578 $ 31,327
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period determined using the treas ury-stock method. Dilutive shares of common stock are comprised of stock options. No dividends were declared or paid during the reported periods.

Description of Business, Basi_3

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2020
Accounting Policies [Abstract]
Schedule of Cash and Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the condensed consolidated balance sheet to the total of the same such amounts shown in the condensed consolidated statement of cash flows: (in thousands) March 31, 2020 March 31, 2019 Cash and cash equivalents $ 59,471 $ 31,220 Non-current restricted cash 107 107 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 59,578 $ 31,327

Collaboration Revenue (Tables)

Collaboration Revenue (Tables)	3 Months Ended
	Mar. 31, 2020
Collaboration Agreements [Abstract]
Summary of Changes in Balances of Contract Assets and Contract Liability	The following table presents changes during the three months ended March 31, 2020 in the balances of contract assets, including receivables from collaborative partners, and contract liabilities, including deferred revenue, as compared to what was disclosed in the Company’s Annual Report. (in thousands) Contract Assets BALANCE - December 31, 2019 $ 2,179 Additions for revenue recognized from billings 978 Deductions for cash collections (806 ) BALANCE – March 31, 2020 $ 2,351 (in thousands) Contract Liabilities BALANCE - December 31, 2019 $ 23,579 Additions for advanced billings 978 Deductions for promised goods/services provided in current period (2,646 ) BALANCE – March 31, 2020 $ 21,911
Summary of Collaboration Revenue	The following table summarizes the Company’s collaboration revenues for the periods indicated (in thousands). For the Three Months Ended March 31, (Dollars in thousands) 2020 2019 Collaboration Partner – Janssen $ 897 $ 513 Collaboration Partner – Ultragenyx 911 1,388 Collaboration Partner – CureVac 309 1,894 Collaboration Partner – Takeda and other 529 555 Total collaboration revenue $ 2,646 $ 4,350

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	3 Months Ended
	Mar. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following as of March 31, 2020 and December 31, 2019: (in thousands) March 31, 2020 December 31, 2019 Prepaid expenses $ 1,344 $ 720 Other current assets 593 38 Total $ 1,937 $ 758
Summary of Components of Property and Equipment, Net	Property and equipment, net for the same periods consisted of the following: (in thousands) March 31, 2020 December 31, 2019 Research equipment $ 4,045 $ 3,658 Computers and software 271 271 Office equipment and furniture 574 561 Leasehold improvements 44 40 Total 4,934 4,530 Less accumulated depreciation and amortization (2,363 ) (2,181 ) Property and equipment, net $ 2,571 $ 2,349
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following as of March 31, 2020 and December 31, 2019: (in thousands) March 31, 2020 December 31, 2019 Accrued compensation $ 1,635 $ 1,608 Cystic Fibrosis Foundation Liability (Note 9) 1,921 1,949 Current portion of operating lease liability 1,474 827 Other accrued research and development expenses 4,745 2,750 Total $ 9,775 $ 7,134

Share-Based Compensation (Table

Share-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Share-based Compensation Expenses	Share-based compensation expenses included in the Company’s condensed statements of operations and comprehensive loss for the three months ended March 31, 2020 and 2019 were: For the Three Months Ended March 31, (in thousands) 2020 2019 Research and development $ 266 $ 152 General and administrative 583 247 Total $ 849 $ 399

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Payments of Operating Lease Liability	As of March 31, 2020, the payments of the operating lease liability were as follows: (in thousands) Remaining Lease Payments 2020 (remaining) $ 1,489 2021 1,427 2022 1,349 2023 1,390 2024 1,432 Thereafter 314 Total remaining lease payments 7,401 Less: imputed interest (1,298 ) Total operating lease liabilities $ 6,103 Weighted-average remaining lease term 4.7 years Weighted-average discount rate 8.4 %

Description of Business, Basi_4

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Details Textual) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2020USD ($)shares	Mar. 31, 2020USD ($)Segment	Mar. 31, 2019USD ($)	Apr. 20, 2020$ / shares	Mar. 04, 2020USD ($)	Mar. 04, 2020SGD ($)
Summary Of Significant Accounting Policy [Line Items]
Number of operating segment for research and development | Segment		1
Dividends declared or paid		$ 0	$ 0
Subsequent Event [Member]
Summary Of Significant Accounting Policy [Line Items]
Grant received	$ 5,000,000
Underwritten Public Offering [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policy [Line Items]
Shares issued in public offering | shares	4,735,297
Common stock, price per share | $ / shares				$ 17
Minimum [Member] | Underwritten Public Offering [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policy [Line Items]
Net proceeds from offering	$ 75,500,000
Singapore Economic Development Board [Member] | Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Grant awarded					$ 10,000,000	$ 14

Schedule of Cash and Cash Equiv

Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 59,471	$ 71,353	$ 31,220
Non-current restricted cash	107	107	107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 59,578	$ 71,460	$ 31,327	$ 36,816

Collaboration Revenue - Summary

Collaboration Revenue - Summary of Changes in Balances of Contract Assets and Contract Liability (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020USD ($)
Collaboration Agreements [Abstract]
Contract Assets, Balance	$ 2,179
Contract Assets, Additions for revenue recognized from billings	978
Contract Assets, Deductions for cash collections	(806)
Contract Assets, Balance	2,351
Contract Liabilities, Balance	23,579
Contract Liabilities, Additions for advanced billings	978
Contract Liabilities, Deductions for promised goods/services provided in current period	(2,646)
Contract Liabilities, Balance	$ 21,911

Collaboration Revenue - Summa_2

Collaboration Revenue - Summary of Collaboration Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 2,646	$ 4,350
Collaboration Partner - Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	897	513
Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	911	1,388
Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	309	1,894
Collaboration Partner - Takeda and Other [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 529	$ 555

Collaboration Revenue (Details

Collaboration Revenue (Details Textual)	Jul. 26, 2019USD ($)	Jun. 18, 2019USD ($)Target$ / sharesshares	Feb. 11, 2019	Mar. 31, 2020USD ($)shares	Dec. 31, 2017USD ($)	Dec. 31, 2019USD ($)shares	Jun. 16, 2019Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue				$ 21,911,000		$ 23,579,000
Purchase of common stock, shares | shares				15,157,000		15,138,000
Minimum [Member] | Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	4 years
Maximum [Member] | Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	8 years
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received				$ 7,700,000
Revenue recognition potential milestone revenue recognized				56,500,000
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner Janssen [Member] | ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation				0
Deferred revenue				5,900,000		$ 5,900,000
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received		$ 6,000,000		27,900,000
Revenue recognition potential milestone revenue recognized				$ 138,000,000
Royalty payment term description				Ultragenyx will pay royalties as a single-digit percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term.
Number of targets | Target		12					10
Purchase of common stock, shares | shares		2,400,000
Purchase of additional shares of common stock | shares		600,000
Purchase of additional shares of common stock price per share | $ / shares		$ 16
Consideration received		$ 30,000,000
Consideration received for common stock purchase		24,000,000
Transaction price		$ 14,400,000
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner - Ultragenyx [Member] | ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation				$ 0
Deferred revenue				$ 11,800,000		12,700,000
Revenue, practical expedient description				The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained.
Cumulative catch up adjustment				$ 1,100,000
Revenue recognition, reserve target exclusivity period				4 years
Research Collaboration And Exclusive License Agreement [Member] | Minimum [Member] | Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target					$ 1,000,000
Research Collaboration And Exclusive License Agreement [Member] | Minimum [Member] | Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target				$ 500,000
Research Collaboration And Exclusive License Agreement [Member] | Maximum [Member] | Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target					$ 5,000,000
Research Collaboration And Exclusive License Agreement [Member] | Maximum [Member] | Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target				$ 1,500,000
Lack of marketability discount restricted period		2 years
mRNA Technology [Member] | Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment term description				CureVac will pay royalties as a percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term in the low single-digit range
Development and option agreement date				Jan. 31, 2018
Expiration of initial term				8 years
Option to extend initial term on an annual basis				3 years
mRNA Technology [Member] | Collaboration Partner - CureVac [Member] | Rare Disease Targets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized				$ 14,000,000
mRNA Technology [Member] | Collaboration Partner - CureVac [Member] | Non-Rare Disease Targets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized				23,000,000
mRNA Technology [Member] | Collaboration Partner - CureVac [Member] | ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation				0
Deferred revenue				$ 3,000,000		$ 3,200,000
Revenue, practical expedient description				The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained.
Adjustments to transaction price				$ 0
Upfront fee received				$ 5,000,000
Contractual term				46 months
Cumulative catch up adjustment				$ 400,000
mRNA Technology [Member] | Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement termination date			Feb. 11, 2019
Percentage of global rights reassumed			100.00%
Termination Agreement [Member] | Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement settlement obligation one-time settled amount	$ 4,000,000
Other Collaboration Agreements [Member] | Takeda Pharmaceutical Company Limited [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue related to amortization of upfront payment				$ 500,000

Collaboration Revenue (Detail_2

Collaboration Revenue (Details Textual 1)	Mar. 31, 2020
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner Janssen [Member] | ASC 606 [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining research period	30 months

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Prepaid Expenses And Other Current Assets [Abstract]
Prepaid expenses	$ 1,344	$ 720
Other current assets	593	38
Total	$ 1,937	$ 758

Balance Sheet Details - Summary

Balance Sheet Details - Summary of Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 4,934	$ 4,530
Less accumulated depreciation and amortization	(2,363)	(2,181)
Property and equipment, net	2,571	2,349
Research equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,045	3,658
Computer and software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	271	271
Office equipment and furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	574	561
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 44	$ 40

Balance Sheet Details (Details

Balance Sheet Details (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization	$ 182	$ 172

Balance Sheet Details - Sched_2

Balance Sheet Details - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Accrued compensation	$ 1,635	$ 1,608
Cystic Fibrosis Foundation Liability (Note 9)	1,921	1,949
Current portion of operating lease liability	1,474	827
Other accrued research and development expenses	4,745	2,750
Total	$ 9,775	$ 7,134

Debt (Details Textual)

Debt (Details Textual) - USD ($)	Oct. 30, 2019	Oct. 12, 2018	Mar. 31, 2020	Mar. 31, 2019
Debt Instrument [Line Items]
Repayment of long-term debt for remainder of fiscal year			$ 0
Repayment of long-term debt for year, 2021			4,000,000
Repayment of long-term debt for year, 2022			6,000,000
Repayment of long-term debt for year, 2023			5,500,000
Interest expense related to long-term debt			$ 300,000	$ 200,000
Loan and Security Agreement [Member] | Western Alliance Bank [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Proceeds from long-term debt agreement		$ 10,000,000
Debt instrument, collateral		The Loan is collateralized by all of the assets of the Company, excluding intellectual property, which is subject to a negative pledge. The Loan contains customary conditions of borrowing, events of default and covenants, including covenants that restrict the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. In addition, the Company is required to maintain at least 100% of its consolidated, unrestricted cash, or $15 million, whichever is lower, with the Bank.
Debt instrument, collateral amount		$ 15,000,000
Term loan	$ 15,000,000
Net increase in indebtedness	$ 5,000,000
Loan maturity date	Oct. 30, 2023
Loan interest-only payment extended maturity date	Oct. 1, 2021
Loan origination fee paid		54,000
Warrant fee payable		$ 525,000
Prepayment fee percentage			2.00%
Loan and Security Agreement [Member] | Western Alliance Bank [Member] | Long-term Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Percentage required to be maintain in consolidated, unrestricted cash		100.00%
Interest of the prime rate plus	1.25%
Prepayment fee percentage	0.50%
Loan and Security Agreement [Member] | Western Alliance Bank [Member] | Long-term Debt [Member] | Maximum [Member]
Debt Instrument [Line Items]
Interest of the prime rate plus	2.75%
Prepayment fee percentage	2.00%

Stockholders' Equity (Details T

Stockholders' Equity (Details Textual)	1 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2013$ / sharesshares	Mar. 31, 2020shares	Mar. 31, 2019shares	Dec. 31, 2017USD ($)Milestoneshares	May 01, 2020shares	Dec. 31, 2016Milestone	Dec. 31, 2014shares
Class Of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share		316,957	67,051
Unvested Restricted Ordinary Shares [Member]
Class Of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share		622,667	622,667
Restricted Common Shares [Member]
Class Of Stock [Line Items]
Stock issued during period	2,783,686
Share price of stock issued | $ / shares	$ 0.0068
Shares subject to repurchase option	1,538,353
Share based compensation arrangement by share based payment award period from termination date of employee or consultant for repurchase of shares	2 months
Number of milestones achieved | Milestone				2		2
Common shares, unvested		622,667	622,667				769,176
Accelerated ordinary shares vested				146,510
Modification expense resulting from accelerated vesting of ordinary shares | $				$ 1,495,000
Subsequent Event [Member] | Restricted Common Shares [Member]
Class Of Stock [Line Items]
Common shares, unvested					311,333
Vested After Obtaining Suitable siRNA License [Member] | Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%
Vested After in Vivo Proof-of-concept Achieved [Member] | Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%
Vested After IND Application Completed [Member] | Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%
Vested After in Human Efficacy Achieved [Member] | Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%

Share-Based Compensation (Detai

Share-Based Compensation (Details Textual) - shares	Mar. 31, 2020	Jun. 30, 2019	Aug. 31, 2018
2018 Omnibus Equity Incentive Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized			1,100,000
2019 Omnibus Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	353,332
2019 Omnibus Equity Incentive Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized		2,600,000

Share-Based Compensation (Det_2

Share-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 849	$ 399
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	266	152
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 583	$ 247

Income Taxes (Details Textual)

Income Taxes (Details Textual) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Income Tax Disclosure [Abstract]
Income tax expense	$ 0

Commitments and Contingencies_2

Commitments and Contingencies (Details Textual) $ in Millions	Jul. 13, 2019USD ($)	Jul. 12, 2019USD ($)	Jan. 31, 2020	Oct. 31, 2017USD ($)	Mar. 31, 2020USD ($)	Mar. 31, 2019USD ($)	Mar. 04, 2020USD ($)	Mar. 04, 2020SGD ($)
Commitment And Contingencies [Line Items]
Operating lease extended additional term			13 months
Operating lease, remaining lease term					4 years 8 months 12 days
Lessee, operating lease, term of contract			1 month
Lessee, operating leases, option to extend			The lease may be extended for one twelve-month period;
Operating lease costs					$ 400,000	$ 300,000
COVID-19 Vaccine Development
Commitment And Contingencies [Line Items]
Contra research and development expense recognized					500,000
Underlying Agreement [Member] | Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Payments for matching funds for remaining budgeted costs	$ 5,000,000
Disbursed amount upon execution of amendment	4,000,000
Final payment of disbursement amount	3,000,000
Disbursement payment upon achievement of required manufacturing practices and IND application	2,300,000
Contra expense included in research and development expense					2,000,000
Contra expense remaining amount included in accrued expenses					$ 1,900,000
Underlying Agreement [Member] | Cystic Fibrosis Foundation [Member] | Disbursement Due January 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
Underlying Agreement [Member] | Cystic Fibrosis Foundation [Member] | Disbursement Due April 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
Underlying Agreement [Member] | Cystic Fibrosis Foundation [Member] | Disbursement Due July 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
Underlying Agreement [Member] | Cystic Fibrosis Foundation [Member] | Disbursement Due October 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
Underlying Agreement [Member] | LUNAR-CF [Member] | Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Payments for advance	$ 15,000,000	$ 3,200,000
October 2017 Lease Amendment [Member]
Commitment And Contingencies [Line Items]
Operating lease extended additional term				84 months
Lessee, operating lease, term of contract				4 months
Tenant improvement allowance				$ 74,000
Lessee, operating leases, option to extend				The lease may be extended for one five-year period at the then current market rate with annual escalations;
Security deposit				$ 96,000
Singapore Economic Development Board [Member] | Maximum [Member]
Commitment And Contingencies [Line Items]
Grant awarded							$ 10,000,000	$ 14
Singapore Economic Development Board [Member] | Maximum [Member] | COVID-19 Vaccine Development
Commitment And Contingencies [Line Items]
Grant awarded							$ 10,000,000	$ 14

Commitments and Contingencies -

Commitments and Contingencies - Payments of Operating Lease Liability (Details) $ in Thousands	Mar. 31, 2020USD ($)
Leases [Abstract]
2020 (remaining)	$ 1,489
2021	1,427
2022	1,349
2023	1,390
2024	1,432
Thereafter	314
Total remaining lease payments	7,401
Less: imputed interest	(1,298)
Total operating lease liabilities	$ 6,103
Weighted-average remaining lease term	4 years 8 months 12 days
Weighted-average discount rate	8.40%

Related Party Transactions - Ul

Related Party Transactions - Ultragenyx (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	Jun. 18, 2019	Mar. 31, 2020	Mar. 31, 2019
Related Party Transaction [Line Items]
Collaboration revenue		$ 2,646	$ 4,350
Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Collaboration revenue		$ 911	1,388
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Ownership interest of common stock		15.80%
Collaboration revenue		$ 900	$ 1,400
Common stock shares restricted from selling period subsequent to issuance date	2 years
Purchase of additional shares of common stock	600,000
Purchase of additional shares of common stock price per share	$ 16

Related Party Transactions - Eq

Related Party Transactions - Equity-Method Investment (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Related Party Transaction [Line Items]
Share of gain (losses) for investee	$ (163)	$ (288)
ADAIR Technology [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage	30.00%
Share of gain (losses) for investee	$ (200)
ADAIR Technology [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage	19.00%