Arcturus Therapeutics (ARCT) 10-Q 10 Aug 21 2021 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2021	Aug. 05, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
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	Large Accelerated Filer
Entity Small Business	false
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		26,327,077
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 433,574	$ 462,895
Accounts receivable	2,163	2,125
Prepaid expenses and other current assets	2,301	2,769
Total current assets	438,038	467,789
Property and equipment, net	3,407	3,378
Operating lease right-of-use asset, net	6,341	5,182
Equity-method investment	920
Non-current restricted cash	107	107
Total assets	448,813	476,456
Current liabilities:
Accounts payable	10,084	10,774
Accrued liabilities	42,614	20,639
Deferred revenue	18,071	18,108
Total current liabilities	70,769	49,521
Deferred revenue, net of current portion	9,850	12,512
Long-term debt, net of current portion	56,309	13,845
Operating lease liability, net of current portion	5,359	4,025
Other long-term liabilities	878
Total liabilities	143,165	79,903
Stockholders’ equity
Common stock: $0.001 par value; 60,000 shares authorized; 26,327 issued and outstanding at June 30, 2021 and 26,192 issued and outstanding at December 31, 2020	26	26
Additional paid-in capital	560,365	540,343
Accumulated deficit	(254,743)	(143,816)
Total stockholders’ equity	305,648	396,553
Total liabilities and stockholders’ equity	$ 448,813	$ 476,456

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	26,327,000	26,192,000
Common stock, shares outstanding	26,327,000	26,192,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement Of Income And Comprehensive Income [Abstract]
Collaboration revenue	$ 2,001	$ 2,322	$ 4,128	$ 4,968
Operating expenses:
Research and development, net	45,679	7,944	95,729	15,861
General and administrative	10,042	4,420	19,785	8,611
Total operating expenses	55,721	12,364	115,514	24,472
Loss from operations	(53,720)	(10,042)	(111,386)	(19,504)
(Loss) gain from equity-method investment	(328)	(100)	920	(263)
(Loss) gain from foreign currency	(13)		417
Finance expense, net	(520)	(121)	(878)	(273)
Net loss	$ (54,581)	$ (10,263)	$ (110,927)	$ (20,040)
Net loss per share, basic and diluted	$ (2.07)	$ (0.55)	$ (4.22)	$ (1.20)
Weighted-average shares outstanding, basic and diluted	26,323	18,794	26,284	16,657
Comprehensive loss:
Net loss	$ (54,581)	$ (10,263)	$ (110,927)	$ (20,040)
Comprehensive loss	$ (54,581)	$ (10,263)	$ (110,927)	$ (20,040)

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Ultragenyx [Member]	Common Stock [Member]	Common Stock [Member]Ultragenyx [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member]Ultragenyx [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ 25,792		$ 15		$ 97,445		$ (71,668)
Balance (in shares) at Dec. 31, 2019			15,138
Net loss	(20,040)						(20,040)
Issuance of common stock, net of issuance costs	75,305		$ 5		75,300
Issuance of common stock, net of issuance costs (in shares)			4,735
Issuance of common stock to Ultragenyx on option exercise		$ 9,600		$ 1		$ 9,599
Issuance of common stock to Ultragenyx on option exercise (in shares)				600
Share-based compensation expense	1,950				1,950
Issuance of common stock upon exercise of stock options	816				816
Issuance of common stock upon exercise of stock options (in shares)			137
Balance at Jun. 30, 2020	93,423		$ 21		185,110		(91,708)
Balance (in shares) at Jun. 30, 2020			20,610
Balance at Mar. 31, 2020	16,982		$ 15		98,412		(81,445)
Balance (in shares) at Mar. 31, 2020			15,157
Net loss	(10,263)						(10,263)
Issuance of common stock, net of issuance costs	75,305		$ 5		75,300
Issuance of common stock, net of issuance costs (in shares)			4,735
Issuance of common stock to Ultragenyx on option exercise		$ 9,600		$ 1		$ 9,599
Issuance of common stock to Ultragenyx on option exercise (in shares)				600
Share-based compensation expense	1,101				1,101
Issuance of common stock upon exercise of stock options	698				698
Issuance of common stock upon exercise of stock options (in shares)			118
Balance at Jun. 30, 2020	93,423		$ 21		185,110		(91,708)
Balance (in shares) at Jun. 30, 2020			20,610
Balance at Dec. 31, 2020	396,553		$ 26		540,343		(143,816)
Balance (in shares) at Dec. 31, 2020			26,192
Net loss	(110,927)						(110,927)
Issuance of common stock related to acquired in-process research and development	5,000				5,000
Issuance of common stock related to acquired in-process research and development (in shares)			75
Share-based compensation expense	14,527				14,527
Issuance of common stock upon exercise of stock options	495				495
Issuance of common stock upon exercise of stock options (in shares)			60
Balance at Jun. 30, 2021	305,648		$ 26		560,365		(254,743)
Balance (in shares) at Jun. 30, 2021			26,327
Balance at Mar. 31, 2021	352,607		$ 26		552,743		(200,162)
Balance (in shares) at Mar. 31, 2021			26,319
Net loss	(54,581)						(54,581)
Share-based compensation expense	7,540				7,540
Issuance of common stock upon exercise of stock options	82				82
Issuance of common stock upon exercise of stock options (in shares)			8
Balance at Jun. 30, 2021	$ 305,648		$ 26		$ 560,365		$ (254,743)
Balance (in shares) at Jun. 30, 2021			26,327

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
OPERATING ACTIVITIES:
Net loss	$ (110,927)	$ (20,040)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	594	394
Share-based compensation expense	14,527	1,950
Acquired in-process research and development expense	5,000
(Gain) loss from equity-method investment	(920)	263
Foreign currency transaction gain	(417)
Other non-cash expenses	1,583	654
Changes in operating assets and liabilities
Accounts receivable	(38)	(650)
Prepaid expense and other assets	468	(2,302)
Accounts payable	(791)	(1,442)
Accrued liabilities	17,727	3,619
Deferred revenue	(2,699)	(2,798)
Net cash used in operating activities	(75,893)	(20,352)
INVESTING ACTIVITIES:
Acquisition of property and equipment	(522)	(611)
Net cash used in investing activities	(522)	(611)
FINANCING ACTIVITIES:
Proceeds from debt	46,599
Proceeds from issuance of common stock, net of issuance costs		75,305
Proceeds from exercise of stock options	495	816
Net cash provided by financing activities	47,094	85,721
NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(29,321)	64,758
Cash, cash equivalents and restricted cash at beginning of the period	463,002	71,460
Cash, cash equivalents and restricted cash at end of the period	433,681	136,218
Supplemental disclosure of cash flow information
Cash paid for interest	173	180
Non-cash investing activities
Right-of-use asset obtained in exchange for lease liabilities	1,828	674
Acquisition of in-process research and development through issuance of common stock	5,000
Purchase of property and equipment in accounts payable	$ 101	44
Ultragenyx [Member]
FINANCING ACTIVITIES:
Proceeds from the issuance of common stock to Ultragenyx on option exercise		$ 9,600

Description of Business, Basis

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
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 global clinical-stage messenger RNA medicines company focused on development of infectious disease vaccines and significant opportunities within liver and respiratory rare diseases. The Company became a clinical stage company during 2020 when it announced that its Investigational New Drug (“IND”) application for ornithine transcarbamylase (“OTC”) deficiency was deemed allowed to proceed by the U.S. Food and Drug Administration (“FDA”), and its Clinical Trial Application (“CTA”) candidate LUNAR-COV19 was approved to proceed by the Singapore Health Sciences Authority. Basis of Presentation 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, 2020. These condensed consolidated financial statements are prepared in accordance with GAAP, which requires management to make estimates and assumptions regarding the valuation of debt instruments, the disclosure of contingent assets and liabilities at the date of the financial statements and Joint Ventures, Equity Method Investments and Variable Interest Entities Investments for which the Company exercises significant influence but does not have control are accounted for under the equity method. Equity method investment activity is related to a 49% joint venture with Axcelead, Inc. (see the following paragraph for further details) and a 12% ownership in Vallon Pharmaceuticals, Inc. (see “ Note 10, Related Party Transactions” In April 2021, Arcturus and Axcelead, Inc., a company existing under the laws of Japan (“Axcelead”), formed a joint venture entity, named Arcalis, Inc. (“JV Entity”), which operates as a corporation under the laws of Japan. Axcelead is an integrated drug discovery solutions provider to the pharmaceutical industry in Japan, having succeeded to a portion of the drug discovery research department of Takeda Pharmaceutical Company Limited on July 1, 2017. The goal of the joint venture entity is to be a contract development and manufacturing organization focused on mRNA manufacturing that would provide manufacturing services to the Company and also to third parties. The joint venture includes a shareholders agreement setting forth initial funding of the JV Entity and rights of the shareholders, including certain approval rights of Arcturus. As part of the joint venture, the Company entered into a License and Technology Transfer Agreement with the JV Entity, pursuant to which Arcturus grants to JV Entity a nonexclusive license to certain intellectual property for use at the JV Entity’s facilities, and obligates Arcturus to conduct certain technology transfer activities. The Company consolidates variable interest entities (“VIEs”) where it has been determined that the Company is the primary beneficiary of those entities’ operations. Management believes that power is shared between Arcturus and Axcelead, as unrelated parties. The consent of each of the parties is substantive and is required to make the decisions about the JV Entity’s significant activities. Management does not believe that Arcturus has the power to direct the activities of the JV Entity that most significantly impact the JV Entity’s economic performance. Therefore, the Company concluded it is not required to consolidate the JV Entity under the VIE model. The equity method of accounting is applicable for the JV Entity as the Company does not own more than 50% of voting power, but has influence over the operation and financial policies of the investee. The Company will account for its investment in the JV Entity using the equity method of accounting as specified in ASC 323 , Investments — Equity Method and Joint Ventures . Liquidity The Company has incurred significant operating losses since its inception. As of June 30, 2021 and December 31, 2020, the Company had an accumulated deficit of $254.7 million and $143.8 million, respectively. The Company’s activities since inception have consisted principally of research and development activities, general and administrative 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. From the Company’s inception through June 30, 2021, the Company has funded its operations principally with the sale of capital stock, revenues earned through collaboration agreements, and proceeds from long-term debt. During the first quarter of 2021, the Company elected to borrow and the Economic Development Board of the Republic of Singapore (the “EDB”) agreed to make a term loan of S$62.1 million (approximately USD$46.6 million) to support the manufacture of the LUNAR-COV19 vaccine candidate. Additionally, through underwritten public offerings during fiscal year 2020, the Company raised net proceeds of $423.8 million, after deducting underwriting discounts, commissions, and offering expenses. Management believes that it has sufficient working capital on hand to fund operations through at least the next twelve months from the date these condensed consolidated financial statements were available to be issued. There can be no assurance that the Company will be successful in securing additional funding, that the Company’s projections of its future working capital needs will prove accurate, or that any additional funding would be sufficient to continue operations in future years. 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 The Company determines revenue recognition for arrangements within the scope of Topic 606 by performing the following five steps: (i) identify the contract; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, the company satisfies a performance obligation. 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 See “Note 9, Commitments and Contingencies” Research and Development, Net All research and development costs are expensed as incurred. Research and development costs consist primarily of salaries, employee benefits, costs associated with preclinical studies and clinical trials (including amounts paid to clinical research organizations and other professional services), in process research and development expenses and license agreement expenses, net of any grants and prelaunch inventory. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. The Company records accruals for estimated research and development costs, comprising payments for work performed by third party contractors, laboratories, participating clinical trial sites, and others. Some of these contractors bill monthly based on actual services performed, while others bill periodically based upon achieving certain contractual milestones. For the latter, the Company accrues the expenses as goods or services are used or rendered. Clinical trial site costs related to patient enrollment are accrued as patients enter and progress through the trial. Pre-Launch Inventory Prior to obtaining initial regulatory approval for an investigational product candidate, the Company expenses costs relating to production of inventory as research and development expense in its condensed consolidated statements of operations, in the period incurred. When the Company believes regulatory approval and subsequent commercialization of an investigational product candidate is probable, and the Company also expects future economic benefit from the sales of the investigational product candidate to be realized, it will then capitalize the costs of production as inventory. 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) June 30, 2021 June 30, 2020 Cash and cash equivalents $ 433,574 $ 136,111 Non-current restricted cash 107 107 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 433,681 $ 136,218 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	6 Months Ended
	Jun. 30, 2021
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 The following table presents changes during the six months ended June 30, 2021 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, 2020 $ 2,125 Additions for revenue recognized from billings 1,429 Deductions for cash collections (1,391 ) BALANCE – June 30, 2021 $ 2,163 (in thousands) Contract Liabilities BALANCE - December 31, 2020 $ 30,620 Additions for advanced billings 1,429 Deductions for promised services provided in current period (4,128 ) BALANCE – June 30, 2021 $ 27,921 The following table summarizes the Company’s collaboration revenues for the periods indicated (in thousands). For the Three Months Ended June 30, For the Six Months Ended June 30, (Dollars in thousands) 2021 2020 2021 2020 Collaboration Partner – Janssen $ 769 $ 693 $ 1,593 $ 1,590 Collaboration Partner – Ultragenyx 925 913 1,850 1,824 Collaboration Partner – CureVac 247 231 472 540 Collaboration Partner – Other 60 485 213 1,014 Total collaboration revenue $ 2,001 $ 2,322 $ 4,128 $ 4,968 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”) to collaborate on developing candidates for treating HBV with RNA therapeutics. 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 up to $56.5 million, as well as royalty payments on any future licensed product sales. The next potential milestone to be achieved relates to demonstrating in vivo efficacy and safety. 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 will pay royalties as a low to mid-single digit percentage of net sales of licensed products, 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 Accounting Standards Codification (“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 2017 Agreement: (i) research services, (ii) license to use Arcturus technology and (iii) participation in a 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 June 3 0 , 202 1 , 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 15 months . None of the development and commercialization milestones were included in the transaction price as they 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 June 30, 2021 and December 31, 2020 for Janssen was $5.8 million and $5.9 million, respectively. 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 to certain Arcturus technology, which is 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 such 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, Ultragenyx 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. During the fourth quarter of 2020, Ultragenyx exercised its option to move forward with Preclinical Candidate Designation for its development target, Glycogen Storage Disease III, and paid an option fee to the Company of $0.5 million. The current potential development, regulatory and commercial milestone payments for the existing development targets as of June 30, 2021 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 June 30, 2021, 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 an option to purchase 0.6 million additional shares of common stock at $16.0 per share. In May 2020, the option was exercised. 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 were initially restricted for up to two years. These restrictions have since expired. 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 a 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 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 June 30, 2021, the transaction price included the upfront consideration received, option payments, 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 FDA 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. The transaction price is 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 (the “Development and Option Agreement”) with CureVac AG (“CureVac”). 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 LUNAR delivery technology (the “Arcturus Delivery Technology”), and CureVac patents and know-how related to mRNA technology. Prior to expiration of the initial term of eight years (which was subsequently amended, as discussed below), the Development and Option Agreement also includes an option to extend the term on an annual basis for up to three years, subject to payment by CureVac to Arcturus of a non-refundable annual extension fee. The Development and Option Agreement includes potential milestone payments from CureVac to the Company for selected targets. The current potential milestone payments for the remaining targets as of June 30, 2021 are $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 June 30, 2021, CureVac has not yet reached the clinical phase of the contract. Pursuant to a May 2018 amendment to the Development and Option Agreement (and 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. 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 that may 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. 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 a joint steering committee. The Company concluded that the promised goods/services are incapable of being distinct As of June 30, 2021, 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. As of June 30, 2021, 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 remaining 25 month contractual term as of June 30, 2021. Total deferred revenue as of June 30, 2021 and December 31, 2020 for CureVac was $1.9 million and $2.3 million, respectively. Other Agreements Other Collaboration Revenue The remaining revenue from smaller collaboration agreements and material transaction agreements primarily relates to the agreement with Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”). Total deferred revenue as of June 30, 2021 and December 31, 2020 for Takeda was $0.2 million and $0.4 million, respectively. Israeli Ministry of Health On August 17, 2020, the Company entered into an agreement with the Israeli Ministry of Health (“MOH”) to supply the Company’s COVID-19 vaccine candidate to Israel (the “Israel Supply Agreement”) subject to certain conditions, including applicable regulatory approvals. In October 2020, and in association with the Israel Supply Agreement, the Company received a non-refundable payment of $12.5 million from the MOH which is included in deferred revenue as of June 30, 2021. This payment of $12.5 million is associated with a specified clinical trial milestone and serves as an initial reserve payment for a specified number of doses of the LUNAR-COV19 vaccine candidate pursuant to the Israel Supply Agreement. As a result of the making of this payment, the MOH became bound to purchase an initial quantity of 500,000 reserved vaccine doses, as set forth in and subject to the terms and conditions of the Israel Supply Agreement.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2021
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 June 30, 2021 and December 31, 2020, 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	6 Months Ended
	Jun. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Note 4 Property and equipment, net balances as of June 30, 2021 and December 31, 2020 consisted of the following: (in thousands) June 30, 2021 December 31, 2020 Research equipment $ 6,162 $ 5,539 Computers and software 284 284 Office equipment and furniture 574 574 Leasehold improvements 44 44 Total 7,064 6,441 Less accumulated depreciation and amortization (3,657 ) (3,063 ) Property and equipment, net $ 3,407 $ 3,378 Depreciation and amortization expense was $0.3 million and $0.2 million Accrued liabilities consisted of the following as of June 30, 2021 and December 31, 2020: (in thousands) June 30, 2021 December 31, 2020 Accrued compensation $ 5,524 $ 2,097 Cystic Fibrosis Foundation Liability (Note 9) 5,036 6,585 Singapore Economic Development Board liability — 1,761 Vinbiocare deposit 10,000 — Current portion of operating lease liability 1,430 1,630 Current portion of long-term debt 5,000 1,250 Clinical accruals 7,717 4,067 Other accrued research and development expenses 7,907 3,249 Total $ 42,614 $ 20,639

Debt

Debt	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Debt	Note 5. Debt Manufacturing Supply Agreement On November 7, 2020, the Company’s wholly-owned subsidiary, Arcturus Therapeutics, Inc., entered into a Manufacturing Support Agreement (the “Support Agreement”) with the Economic Development Board of the Republic of Singapore (the “EDB”). Pursuant to the Support Agreement, the EDB agreed to make a term loan of S$62.1 million to the Company, subject to the satisfaction of customary deliveries, to support the manufacture of the LUNAR-COV19 vaccine candidates (the “Singapore Loan”). In June 2021, the EDB agreed to amend the Singapore Loan. The amendment includes certain loan covenants requiring (i) unused funds as of March 31, 2022 to be subsequently returned within thirty days, subject to any further agreed upon extension of the reconciliation date, (ii) the Company to provide a quarterly reconciliation report within forty-five days of each financial quarter end, (iii) an external audit of expenses paid through June 30, 2021 to be completed by September 30, 2021, and a projection of expenditures through March 31, 2022 followed by an audited statement of actual expenditures through March 31, 2022 by June 30, 2022, (iv) the Company to deliver 10 grams of LUNAR-COV19 vaccine candidate suitable for use in a phase 3 trial in two shipments with a partial shipment by June 30, 2022 and a remaining shipment by September 30, 2022, (v) the Company to provide EDB with a right of first refusal on GMP manufacturing slots of the LUNAR-COV19 vaccine candidate up to an agreed-upon maximum amount, (vi) and the obligation to repay the Singapore Loan will be secured by an interest in the raw materials and manufacturing equipment purchased by the Company with the funds from the Singapore Loan in form and substance satisfactory to the EDB in its sole discretion. The Company elected to borrow the full amount available under the Support Agreement of S$62.1 million ($46.6 million) on January 29, 2021. The Singapore Loan accrues interest at a rate of 4.5% per annum calculated on a daily basis. Subject to certain exceptions, the Singapore Loan is intended to be a limited recourse loan that will be repaid solely through a royalty payment of 10% of net sales proceeds of the LUNAR-COV19 vaccine candidate, up to the amount of the outstanding principal and interest under the Singapore Loan. However, all unpaid principal and interest under the Singapore Loan will be due and payable five years after draw date, if net sales of the LUNAR-COV19 vaccine exceed a certain minimum threshold during this five year period or the Company obtains clearance to sell the vaccine in specified jurisdictions. Unpaid principal and interest under the Singapore Loan will also become due and payable upon an event of default under the Support Agreement. The first vaccine sales, including the amount of net sales, shall be reported to EDB within 10 days of delivery and quarterly reports of aggregate vaccine sales, including net sales proceeds shall be provided within 30 days after quarter end. The Singapore Loan is forgivable if the Company has not obtained regulatory approval by the final repayment date and net sales of LUNAR-COV19 are less than $100 million. If, any portion of the Singapore Loan is required to be forgiven pursuant to the terms of the Support Agreement, the EDB has the right to take ownership of certain raw materials and equipment that were purchased by the Company with proceeds of the Singapore Loan (the “Specified Assets”). The Company entered into a security agreement (the “Security Agreement”) for the benefit of the EDB to provide that repayment of the Singapore Loan and related obligations are secured by a lien on the Specified Assets. In connection with the entry into the Support Agreement, the Company entered into a consent agreement with Western Alliance Bank (the “Bank”) and an amendment to the Loan and Security Agreement, dated as of October 12, 2018, between Western Alliance Bank and the Company (the “Loan”), to exclude the Specified Assets from Western Alliance Bank’s lien on certain assets of the Company. The Singapore Loan was initially recorded as long-term debt at $46.6 million, the amount of cash proceeds at the time the Company received the funding. As of June 30, 2021, the debt balance was adjusted to reflect the current exchange rate resulting in a debt balance of $46.2 million and a net foreign currency transaction gain of $0.4 million for the six months ended June 30, 2021. For the three and six months ended June 30, 2021, the Company recorded interest expense and a corresponding liability of $0.5 million and $0.9 million, respectively. As of June 30, 2021, the Company was in compliance with all covenants under the Singapore Loan and related commitments. Long-term debt with Western Alliance Bank On October 12, 2018, Arcturus Therapeutics, Inc. entered into the Loan with the Bank, whereby it received $ 10.0 million. The Loan is collateralized by all of the assets of Arcturus Therapeutics, Inc., 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 Arcturus Therapeutics, Inc.’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of its capital stock. In addition, Arcturus Therapeutics, Inc. is required to maintain at least 100% of its consolidated, unrestricted cash, or $15.0 million, whichever is lower, with the Bank. On October 30, 2019, Arcturus Therapeutics, Inc. and the Bank entered into a Third Amendment (the “Third Amendment”) to the Loan (as amended, the “Loan Agreement”). Pursuant to the amendment, the Bank agreed to make a term loan to Arcturus Therapeutics, Inc. on October 30, 2019, in the amount of $15.0 million (the “Term Loan”). The resulting net increase in the indebtedness of Arcturus Therapeutics, Inc. 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. Arcturus Therapeutics, Inc. will make monthly payments of interest only until October 1, 2021. Arcturus Therapeutics, Inc. 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, Arcturus Therapeutics, Inc. 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, subject to a prepayment fee ranging from 0.50% to 2.00% of the prepaid principal amount depending upon the date of the prepayment. Upon maturity or prepayment (as previously discussed), Arcturus Therapeutics, Inc. will be required to pay a 2% fee as a result of the FDA’s approval to proceed with the Company’s LUNAR-OTC program based on its IND submission. Such fee is accreted to the long-term 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 June 30, 2021, 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 are as follows as of June 30, 2021: 2021 $ 1,250,000 2022 7,500,000 2023 6,550,000 Total $ 15,300,000 The Company recognized interest expense related to its long-term debt of $0.7 million and $0.2 million during the three months ended June 30, 2021 and 2020, respectively, and $1.3 million and $0.5 million during the six months ended June 30, 2021 and 2020, respectively.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2021
Stockholders Equity Note [Abstract]
Stockholders' Equity	Note 6. Stockholders’ Equity Alexion Pharmaceuticals License Agreement On February 17, 2021, the Company entered into an exclusive license agreement with Alexion Pharmaceuticals, Inc. (“ Alexion ”) pursuant to which Alexion granted to the Company an exclusive, worldwide license to exploit certain specified Alexion patent applications. In accordance with the terms of the license agreement, and in exchange for the license, the Company issued 74,713 shares of its common stock to Alexion on February 19, 2021 valued at approximately $5.0 million. The number of shares issued under the agreement was calculated by dividing (i) five million dollars ($5.0 million) by (ii) the volume-weighted average price per share of the Company’s common stock on the Nasdaq Global Market for the thirty (30) trading days immediately preceding the Effective Date (rounded to the nearest whole share). The Company recorded the transaction as an asset purchase as management concluded that all of the value received was related to a single identifiable asset. Further, the Company concluded that there was no alternative future use for the asset and recorded a charge at the closing of the transaction for the full $5.0 million value assigned to the shares issued in connection with the license agreement. This non-cash charge was recorded as acquired in-process research and development expense in the statements of operations and comprehensive loss Net Loss per Share Dilutive securities that were not included in the calculation of diluted net loss per share for the three and six months ended June 30, 2021 as they were anti-dilutive totaled 1,011,031 and 1,242,987, respectively, and 1,505,244 and 903,949 for the three and six months ended June 30, 2020, respectively. For the three and six months ended 2020, the calculation of the weighted-average number of shares outstanding excludes 311,333 unvested restricted shares of common stock. There were no unvested restricted shares for the six months ended June 30, 2021.

Share-Based Compensation Expens

Share-Based Compensation Expense	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Share-Based Compensation	Note 7. Share-Based Compensation Expense In June 2020, the stockholders of the Company approved an increase to the number of shares authorized for use in making awards under the 2019 Omnibus Equity Incentive Plan (the “2019 Plan”) by 2,400,000 shares to 5,000,000. Accordingly, as of June 30, 2021, a total of 665,535 shares remain available for future issuance under the 2019 Plan, subject to the terms of the 2019 Plan. Employee Stock Purchase Plan In June 2020, the stockholders of the Company approved the 2020 Employee Stock Purchase Plan (“2020 Plan”) which provides for 600,000 shares of Company common stock reserved for future issuance. The first accumulation period under the 2020 Plan commenced on August 17, 2020. Under the 2020 Plan, eligible employees may purchase shares of the Company’s common stock at a discount annually, subject to a maximum of $25,000 per year. The discounted purchase price is equal to the lower of 85% of (i) the market value per share of the common stock on the first day of the accumulation period or (ii) the market value per share of common stock on the purchase date. Share-based compensation expense recognized under the 2020 Plan was $0.1 million and $0.2 million for the three and six months ended June 30, 2021, respectively. Stock Options Share-based compensation expense included in the Company’s condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2021 and 2020 was: For the Three Months Ended June 30, For the Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Research and development $ 3,582 $ 396 $ 6,828 $ 662 General and administrative 3,958 705 7,699 1,288 Total $ 7,540 $ 1,101 $ 14,527 $ 1,950

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
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. For the three and six months ended June 30, 2021 and 2020, the Company recorded no income tax expense. No tax benefit was provided for losses incurred in United States because those losses are offset by a full valuation allowance.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
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 (“Grant 1”) from the Singapore EDB 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$10.0 million using the exchange rate at the time the grant contract was entered into) in grants to support the development of the vaccine. On June 29, 2021 the EDB agreed to amend Grant 1 to update certain delivery and milestone timelines. The Grant has been paid in full by the EDB as a result of 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 have been recognized as contra research and development expense. The Company is liable for certain expenses during the program and is also subject to certain conditions including the completion of an external audit within 183 days of the conclusion of the claim period on February 20, 2021, or August 22, 2021, and delivery of 10 grams of LUNAR-COV19 vaccine candidate suitable for use in a phase 3 variant trial in two shipments with a partial shipment by June 30, 2022 and a remaining shipment by September 30, 2022. Additionally, the Company is required to pay an agreed upon royalty rate to Duke-NUS on future net sales of the LUNAR-COV19 vaccine candidate developed with Duke-NUS in markets or jurisdictions outside of Singapore. No contra research and development expense was recognized f or the three months ended June 30, 2021 and $ million was recognized for the three months ended June 30, 2020. F or the six months ended June 30, 2021 and 2020, the Company recognized $ million and $ million, respectively, of contra expense for Grant 1. At June 30, 2021, no amount remained in accrued expenses. On October 2, 2020, the Company was awarded another grant (“Grant 2”) from the Singapore EDB to support the further development of a potential COVID-19 vaccine. On June 29, 2021 the EDB agreed to amend Grant 2 to update certain delivery and milestone timelines. The grant provides for up to S$9.3 million (approximately US$6.7 million) to support the development of the vaccine candidate for costs incurred in Singapore subject to certain conditions including (i) completing an external audit within 183 days from March 31, 2021, or September 30, 2021, (ii) delivering 10 grams of LUNAR-COV19 vaccine candidate suitable for use in a phase 3 variant trial in two shipments with a partial shipment by June 30, 2022 and a remaining shipment by September 30, 2022 and (iii) creating an entity in Singapore which was completed during the fourth quarter of 2020, and (iv) initiating a clinical trial for a variant COVID-19 vaccine by March 31, 2022. The grant will be paid in two installments upon the achievement of certain milestones related to the progress of the development of the vaccine candidate. The Company received the first installment of $3.6 million in the fourth quarter of 2020. The funds received are recognized as contra research and development expense as costs are incurred. As of June 30, 2021, the Company recognized the remaining amount of the first installment as contra expense for Grant 2. 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 June 30, 2021 and 2020, the Company recognized contra expense of $0.9 million and $0.9 million, respectively, and for the six months ended June 30, 2021 and 2020, the Company recognized contra expense of $1.5 million and $2.9 million, respectively. As of June 30, 2021, $5.0 million remained 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 February 2020, the Company entered into a non-cancellable operating lease agreement for office space near its current headquarters. The lease extended for 13 months from the commencement date and included a right to extend the lease for one twelve-month period. In February 2021, the Company opted to extend the lease through March 2025 to coincide with the lease term of the Company’s headquarters In February 2021, the Company entered into a third non-cancellable operating lease agreement for office space near its current headquarters. The lease extends for 12 months from the commencement date with monthly base rent of approximately $11,000. 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 June 30, 2021, the remaining payments of the operating lease liability were as follows: (in thousands) Remaining Lease Payments 2021 $ 1,022 2022 1,987 2023 2,185 2024 2,250 Thereafter 521 Total remaining lease payments 7,965 Less: imputed interest (1,176 ) Total operating lease liabilities $ 6,789 Weighted-average remaining lease term 3.75 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 $0.5 million and $0.5 million for the three months ended June 30, 2021 and 2020, respectively, and $0.9 million and $0.9 million for the six months ended June 30, 2021 and 2020, respectively.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Party Transactions	Note 10. Related Party Transactions Ultragenyx On June 17, 2019, Arcturus and Ultragenyx executed Amendment 3 to the Ultragenyx Agreement. Pursuant to the amended Ultragenyx Agreement, the Company also granted Ultragenyx a two-year . 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 Vallon Pharmaceuticals, Inc. (“Vallon”) in consideration for the sale of the ADAIR technology. The Company has no requirement to invest further in Vallon. Vallon completed an initial public offering and began trading on The Nasdaq Stock Market in February 2021.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Note 11. Subsequent Events Vingroup Agreement On August 2, 2021, the Company announced an agreement with Vinbiocare Biotechnology Joint Stock Company (“Vinbiocare”), a member of Vingroup Joint Stock Company, regarding a collaboration to establish a manufacturing facility in Vietnam for the manufacture of Arcturus’ investigational COVID-19 vaccines, for sale and use within Vietnam. Under the terms of the arrangement, Vinbiocare will build out a manufacturing facility in Vietnam, and the Company will provide to Vinbiocare access to proprietary technologies and processes for the manufacture of Arcturus’ investigational COVID-19 vaccines. The Company will also provide Vinbiocare with an exclusive license to manufacture the vaccines in Vietnam at the facility solely for distribution in Vietnam. The license and technology transfer applies toward drug product manufacturing but not toward mRNA drug substance manufacturing. Vinbiocare will make an upfront payment of $40 million and be responsible for costs associated with the technology transfer. Vinbiocare will also pay for mRNA drug substance supplied by the Company and royalties on vaccines produced at the manufacturing facility. On June 11, 2021, the Company and Vinbiocare executed a deposit agreement whereby Vinbiocare paid the Company a $10 million deposit prior to June 30, 2021 to demonstrate its commitment to reach a mutual agreement on a technology transfer of Arcturus’ vaccine manufacturing technology (“Definitive Agreement”). In the event a Definitive Agreement was not signed, $500,000 of the deposit was non-refundable.

Description of Business, Basi_2

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation 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, 2020. These condensed consolidated financial statements are prepared in accordance with GAAP, which requires management to make estimates and assumptions regarding the valuation of debt instruments, the disclosure of contingent assets and liabilities at the date of the financial statements and
Joint Ventures, Equity Method Investments and Variable Interest Entities	Joint Ventures, Equity Method Investments and Variable Interest Entities Investments for which the Company exercises significant influence but does not have control are accounted for under the equity method. Equity method investment activity is related to a 49% joint venture with Axcelead, Inc. (see the following paragraph for further details) and a 12% ownership in Vallon Pharmaceuticals, Inc. (see “ Note 10, Related Party Transactions” In April 2021, Arcturus and Axcelead, Inc., a company existing under the laws of Japan (“Axcelead”), formed a joint venture entity, named Arcalis, Inc. (“JV Entity”), which operates as a corporation under the laws of Japan. Axcelead is an integrated drug discovery solutions provider to the pharmaceutical industry in Japan, having succeeded to a portion of the drug discovery research department of Takeda Pharmaceutical Company Limited on July 1, 2017. The goal of the joint venture entity is to be a contract development and manufacturing organization focused on mRNA manufacturing that would provide manufacturing services to the Company and also to third parties. The joint venture includes a shareholders agreement setting forth initial funding of the JV Entity and rights of the shareholders, including certain approval rights of Arcturus. As part of the joint venture, the Company entered into a License and Technology Transfer Agreement with the JV Entity, pursuant to which Arcturus grants to JV Entity a nonexclusive license to certain intellectual property for use at the JV Entity’s facilities, and obligates Arcturus to conduct certain technology transfer activities. The Company consolidates variable interest entities (“VIEs”) where it has been determined that the Company is the primary beneficiary of those entities’ operations. Management believes that power is shared between Arcturus and Axcelead, as unrelated parties. The consent of each of the parties is substantive and is required to make the decisions about the JV Entity’s significant activities. Management does not believe that Arcturus has the power to direct the activities of the JV Entity that most significantly impact the JV Entity’s economic performance. Therefore, the Company concluded it is not required to consolidate the JV Entity under the VIE model. The equity method of accounting is applicable for the JV Entity as the Company does not own more than 50% of voting power, but has influence over the operation and financial policies of the investee. The Company will account for its investment in the JV Entity using the equity method of accounting as specified in ASC 323 , Investments — Equity Method and Joint Ventures .
Liquidity	Liquidity The Company has incurred significant operating losses since its inception. As of June 30, 2021 and December 31, 2020, the Company had an accumulated deficit of $254.7 million and $143.8 million, respectively. The Company’s activities since inception have consisted principally of research and development activities, general and administrative 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. From the Company’s inception through June 30, 2021, the Company has funded its operations principally with the sale of capital stock, revenues earned through collaboration agreements, and proceeds from long-term debt. During the first quarter of 2021, the Company elected to borrow and the Economic Development Board of the Republic of Singapore (the “EDB”) agreed to make a term loan of S$62.1 million (approximately USD$46.6 million) to support the manufacture of the LUNAR-COV19 vaccine candidate. Additionally, through underwritten public offerings during fiscal year 2020, the Company raised net proceeds of $423.8 million, after deducting underwriting discounts, commissions, and offering expenses. Management believes that it has sufficient working capital on hand to fund operations through at least the next twelve months from the date these condensed consolidated financial statements were available to be issued. There can be no assurance that the Company will be successful in securing additional funding, that the Company’s projections of its future working capital needs will prove accurate, or that any additional funding would be sufficient to continue operations in future years.
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 The Company determines revenue recognition for arrangements within the scope of Topic 606 by performing the following five steps: (i) identify the contract; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when, or as, the company satisfies a performance obligation. 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 See “Note 9, Commitments and Contingencies”
Research and Development, Net	Research and Development, Net All research and development costs are expensed as incurred. Research and development costs consist primarily of salaries, employee benefits, costs associated with preclinical studies and clinical trials (including amounts paid to clinical research organizations and other professional services), in process research and development expenses and license agreement expenses, net of any grants and prelaunch inventory. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods or services are received. The Company records accruals for estimated research and development costs, comprising payments for work performed by third party contractors, laboratories, participating clinical trial sites, and others. Some of these contractors bill monthly based on actual services performed, while others bill periodically based upon achieving certain contractual milestones. For the latter, the Company accrues the expenses as goods or services are used or rendered. Clinical trial site costs related to patient enrollment are accrued as patients enter and progress through the trial.
Pre-Launch Inventory	Pre-Launch Inventory Prior to obtaining initial regulatory approval for an investigational product candidate, the Company expenses costs relating to production of inventory as research and development expense in its condensed consolidated statements of operations, in the period incurred. When the Company believes regulatory approval and subsequent commercialization of an investigational product candidate is probable, and the Company also expects future economic benefit from the sales of the investigational product candidate to be realized, it will then capitalize the costs of production as inventory.
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) June 30, 2021 June 30, 2020 Cash and cash equivalents $ 433,574 $ 136,111 Non-current restricted cash 107 107 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 433,681 $ 136,218
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)	6 Months Ended
	Jun. 30, 2021
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) June 30, 2021 June 30, 2020 Cash and cash equivalents $ 433,574 $ 136,111 Non-current restricted cash 107 107 Total cash, cash equivalents and restricted cash shown in the statement of cash flows $ 433,681 $ 136,218

Collaboration Revenue (Tables)

Collaboration Revenue (Tables)	6 Months Ended
	Jun. 30, 2021
Collaboration Agreements [Abstract]
Summary of Changes in Balances of Contract Assets and Contract Liability	The following table presents changes during the six months ended June 30, 2021 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, 2020 $ 2,125 Additions for revenue recognized from billings 1,429 Deductions for cash collections (1,391 ) BALANCE – June 30, 2021 $ 2,163 (in thousands) Contract Liabilities BALANCE - December 31, 2020 $ 30,620 Additions for advanced billings 1,429 Deductions for promised services provided in current period (4,128 ) BALANCE – June 30, 2021 $ 27,921
Summary of Collaboration Revenue	The following table summarizes the Company’s collaboration revenues for the periods indicated (in thousands). For the Three Months Ended June 30, For the Six Months Ended June 30, (Dollars in thousands) 2021 2020 2021 2020 Collaboration Partner – Janssen $ 769 $ 693 $ 1,593 $ 1,590 Collaboration Partner – Ultragenyx 925 913 1,850 1,824 Collaboration Partner – CureVac 247 231 472 540 Collaboration Partner – Other 60 485 213 1,014 Total collaboration revenue $ 2,001 $ 2,322 $ 4,128 $ 4,968

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	6 Months Ended
	Jun. 30, 2021
Balance Sheet Related Disclosures [Abstract]
Summary of Components of Property and Equipment, Net	Property and equipment, net balances as of June 30, 2021 and December 31, 2020 consisted of the following: (in thousands) June 30, 2021 December 31, 2020 Research equipment $ 6,162 $ 5,539 Computers and software 284 284 Office equipment and furniture 574 574 Leasehold improvements 44 44 Total 7,064 6,441 Less accumulated depreciation and amortization (3,657 ) (3,063 ) Property and equipment, net $ 3,407 $ 3,378
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following as of June 30, 2021 and December 31, 2020: (in thousands) June 30, 2021 December 31, 2020 Accrued compensation $ 5,524 $ 2,097 Cystic Fibrosis Foundation Liability (Note 9) 5,036 6,585 Singapore Economic Development Board liability — 1,761 Vinbiocare deposit 10,000 — Current portion of operating lease liability 1,430 1,630 Current portion of long-term debt 5,000 1,250 Clinical accruals 7,717 4,067 Other accrued research and development expenses 7,907 3,249 Total $ 42,614 $ 20,639

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Debt	Principal payments, including the final payment due at repayment, on the long-term debt are as follows as of June 30, 2021: 2021 $ 1,250,000 2022 7,500,000 2023 6,550,000 Total $ 15,300,000

Share-Based Compensation Expe_2

Share-Based Compensation Expense (Tables)	6 Months Ended
	Jun. 30, 2021
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Share-based Compensation Expenses	Share-based compensation expense included in the Company’s condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2021 and 2020 was: For the Three Months Ended June 30, For the Six Months Ended June 30, (in thousands) 2021 2020 2021 2020 Research and development $ 3,582 $ 396 $ 6,828 $ 662 General and administrative 3,958 705 7,699 1,288 Total $ 7,540 $ 1,101 $ 14,527 $ 1,950

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments And Contingencies Disclosure [Abstract]
Remaining Payments of Operating Lease Liability	As of June 30, 2021, the remaining payments of the operating lease liability were as follows: (in thousands) Remaining Lease Payments 2021 $ 1,022 2022 1,987 2023 2,185 2024 2,250 Thereafter 521 Total remaining lease payments 7,965 Less: imputed interest (1,176 ) Total operating lease liabilities $ 6,789 Weighted-average remaining lease term 3.75 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)	6 Months Ended		12 Months Ended
	Jun. 30, 2021USD ($)Segment	Jun. 30, 2020USD ($)	Dec. 31, 2020USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2021SGD ($)	Nov. 07, 2020USD ($)
Summary Of Significant Accounting Policy [Line Items]
Investment in joint venture	$ 9,200,000
Upfront fee/consideration	9,200,000
Cash consideration paid for equity interest in joint venture	$ 0
Percentage of equity interest in joint venture	49.00%
Accumulated deficit	$ 254,743,000		$ 143,816,000
Proceeds from issuance of common stock, net of issuance costs		$ 75,305,000
Number of operating segment for research and development | Segment	1
Dividends declared or paid	$ 0	$ 0
Underwritten Public Offering [Member]
Summary Of Significant Accounting Policy [Line Items]
Proceeds from issuance of common stock, net of issuance costs			$ 423,800,000
Singapore Economic Development Board [Member]
Summary Of Significant Accounting Policy [Line Items]
Term loan				$ 46,600,000	$ 62,100,000	$ 62,100,000
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Equity method ownership percentage	50.00%
Vallon Pharmaceuticals, Inc. [Member]
Summary Of Significant Accounting Policy [Line Items]
Percentage of owned shares	12.00%
Axcelead, Inc [Member]
Summary Of Significant Accounting Policy [Line Items]
Equity method ownership percentage	49.00%

Description of Business, Basi_5

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Cash and cash equivalents	$ 433,574	$ 462,895	$ 136,111
Non-current restricted cash	107	107	107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 433,681	$ 463,002	$ 136,218	$ 71,460

Collaboration Revenue - Summary

Collaboration Revenue - Summary of Changes in Balances of Contract Assets and Contract Liability (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2021USD ($)
Collaboration Agreements [Abstract]
Contract Assets, Balance	$ 2,125
Contract Assets, Additions for revenue recognized from billings	1,429
Contract Assets, Deductions for cash collections	(1,391)
Contract Assets, Balance	2,163
Contract Liabilities, Balance	30,620
Contract Liabilities, Additions for advanced billings	1,429
Deductions for promised services provided in current period	(4,128)
Contract Liabilities, Balance	$ 27,921

Collaboration Revenue - Summa_2

Collaboration Revenue - Summary of Collaboration Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 2,001	$ 2,322	$ 4,128	$ 4,968
Collaboration Partner - Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	769	693	1,593	1,590
Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	925	913	1,850	1,824
Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	247	231	472	540
Collaboration Partner – Other [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 60	$ 485	$ 213	$ 1,014

Collaboration Revenue (Details

Collaboration Revenue (Details Textual)	Jul. 26, 2019	Jun. 18, 2019USD ($)Target$ / sharesshares	Jun. 17, 2019$ / sharesshares	Oct. 31, 2017USD ($)	Dec. 31, 2020USD ($)shares	Jun. 30, 2021USD ($)VaccineDoseshares	Oct. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Jun. 16, 2019Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue					$ 30,620,000	$ 27,921,000
Purchase of common stock, shares | shares					26,192,000	26,327,000
Israeli Ministry of Health ("MOH") [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-refundable payment received							$ 12,500,000
Number of reserved vaccine doses | VaccineDose						500,000
Maximum [Member] | Collaboration Partner Cure Vac Entered Into Co Development Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	8 years
Minimum [Member] | Collaboration Partner Cure Vac Entered Into Co Development Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	4 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
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	5,800,000
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
Option exercise fee received					500,000
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	600,000
Purchase of additional shares of common stock price per share | $ / shares		$ 16	$ 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					9,200,000	$ 7,400,000
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.
Revenue recognition, reserve target exclusivity period						4 years
Research Collaboration And Exclusive License Agreement [Member] | Maximum [Member] | Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized				$ 56,500,000
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
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
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						2018-01
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						$ 1,900,000		$ 2,300,000
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						25 months
Other Collaboration Agreements [Member] | Takeda Pharmaceutical Company Limited [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue					$ 400,000	$ 200,000

Collaboration Revenue (Detail_2

Collaboration Revenue (Details Textual 1)	Jun. 30, 2021
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner Janssen [Member] | ASC 606 [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2021-04-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining research period	15 months

Balance Sheet Details - Summary

Balance Sheet Details - Summary of Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 7,064	$ 6,441
Less accumulated depreciation and amortization	(3,657)	(3,063)
Property and equipment, net	3,407	3,378
Research equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,162	5,539
Computer and software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	284	284
Office equipment and furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	574	574
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 44	$ 44

Balance Sheet Details (Details

Balance Sheet Details (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization	$ 300	$ 200	$ 594	$ 394

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Liabilities Current [Abstract]
Accrued compensation	$ 5,524	$ 2,097
Cystic Fibrosis Foundation Liability (Note 9)	5,036	6,585
Singapore Economic Development Board liability		1,761
Vinbiocare deposit	10,000
Current portion of operating lease liability	$ 1,430	$ 1,630
Operating Lease Liability Current Statement Of Financial Position Extensible List	Total	Total
Current portion of long-term debt	$ 5,000	$ 1,250
Clinical accruals	7,717	4,067
Other accrued research and development expenses	7,907	3,249
Total	$ 42,614	$ 20,639

Debt (Details Textual)

Debt (Details Textual)	Nov. 07, 2020USD ($)	Oct. 30, 2019USD ($)	Oct. 12, 2018USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Jun. 30, 2021USD ($)	Jun. 30, 2020USD ($)	Mar. 31, 2021USD ($)	Mar. 31, 2021SGD ($)	Jan. 29, 2021USD ($)	Jan. 29, 2021SGD ($)
Debt Instrument [Line Items]
Long-term debt				$ 15,300,000		$ 15,300,000
(Loss) gain from foreign currency				(13,000)		417,000
Interest expense related to long-term debt				700,000	$ 200,000	1,300,000	$ 500,000
Proceeds from debt						$ 46,599,000
Loan and Security Agreement [Member] | Western Alliance Bank [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Term loan		$ 15,000,000
Proceeds from long-term debt agreement			$ 10,000,000
Debt instrument, collateral						The Loan is collateralized by all of the assets of Arcturus Therapeutics, Inc., 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 Arcturus Therapeutics, Inc.’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of its capital stock. In addition, Arcturus Therapeutics, Inc. is required to maintain at least 100% of its consolidated, unrestricted cash, or $15.0 million, whichever is lower, with the Bank.
Debt instrument, collateral amount			15,000,000
Proceeds from debt		$ 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%
Singapore Economic Development Board [Member]
Debt Instrument [Line Items]
Term loan	$ 62,100,000							$ 46,600,000	$ 62,100,000
Term loan draw down										$ 46,600,000	$ 62,100,000
Loan accrues interest rate per annum, percentage	4.50%
Royalty payment percentage of proceeds from net sales	10.00%
Maximum LUNAR-COVID 19 sales required for Loans forgivable	$ 100,000,000
Long-term debt				46,200,000		$ 46,200,000				$ 46,600,000
(Loss) gain from foreign currency						400,000
Interest expense related to long-term debt				$ 500,000		$ 900,000

Debt - Summary of Final Payment

Debt - Summary of Final Payment Due at Repayment (Details)	Jun. 30, 2021USD ($)
Debt Disclosure [Abstract]
2021	$ 1,250,000
2022	7,500,000
2023	6,550,000
Total	$ 15,300,000

Stockholders' Equity (Details T

Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	Feb. 19, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Class Of Stock [Line Items]
Non-cash charge recorded in acquired in-process research and development expense				$ 5,000
Antidilutive securities excluded from computation of earnings per share		1,011,031	1,505,244	1,242,987	903,949
Unvested Restricted Ordinary Shares [Member]
Class Of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share			311,333	0	311,333
Alexion [Member]
Class Of Stock [Line Items]
Issuance of common stock	74,713
Common stock issued, value	$ 5,000
Non-cash charge recorded in acquired in-process research and development expense				$ 5,000

Share-Based Compensation Expe_3

Share-Based Compensation Expense (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 7,540,000	$ 1,101,000	$ 14,527,000	$ 1,950,000
2019 Omnibus Equity Incentive Plan [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized		2,400,000		2,400,000
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		5,000,000		5,000,000
2019 Omnibus Equity Incentive Plan [Member] | Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	665,535		665,535
2020 Employee Stock Purchase Plan [Member] | Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance		600,000		600,000
Maximum discounted purchase price			85.00%
Share-based compensation expenses	$ 100,000		$ 200,000
Maximum discounted amount per year			$ 25,000

Share-Based Compensation Expe_4

Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 7,540	$ 1,101	$ 14,527	$ 1,950
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	3,582	396	6,828	662
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 3,958	$ 705	$ 7,699	$ 1,288

Income Taxes (Details Textual)

Income Taxes (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0	$ 0	$ 0

Commitments and Contingencies_2

Commitments and Contingencies (Details Textual) $ in Millions

Oct. 02, 2020USD ($)Installment

Jul. 13, 2019USD ($)

Jul. 12, 2019USD ($)

Feb. 28, 2021USD ($)

Feb. 29, 2020

Oct. 31, 2017USD ($)

Jun. 30, 2021USD ($)

Dec. 31, 2020USD ($)

Jun. 30, 2020USD ($)

Jun. 30, 2021USD ($)

Jun. 30, 2020USD ($)

Oct. 02, 2020SGD ($)

Mar. 04, 2020USD ($)

Mar. 04, 2020SGD ($)

Commitment And Contingencies [Line Items]

Operating lease extended additional term

13 months

Lessee, operating leases, option to extend

one twelve-month period.

Monthly base rent

$ 11,000

Operating lease costs

$ 500,000

$ 500,000

$ 900,000

$ 900,000

COVID-19 Vaccine Development | Grant 1

Commitment And Contingencies [Line Items]

Contra research and development expense recognized

0

3,800,000

1,300,000

4,300,000

Contra expense remaining amount included in accrued expenses

0

COVID-19 Vaccine Development | Grant 2

Commitment And Contingencies [Line Items]

Grant, number of installments | Installment

2

Received first installment

$ 3,600,000

Underlying Agreement [Member] | Cystic Fibrosis Foundation [Member]

Commitment And Contingencies [Line Items]

Contra expense remaining amount included in accrued expenses

5,000,000

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

$ 900,000

$ 900,000

$ 1,500

$ 2,900

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] | COVID-19 Vaccine Development | Grant 1

Commitment And Contingencies [Line Items]

Grant awarded

$ 10,000,000

$ 14

Singapore Economic Development Board [Member] | Maximum [Member] | COVID-19 Vaccine Development | Grant 2

Commitment And Contingencies [Line Items]

Grant awarded

$ 6,700,000

$ 9.3

Commitments and Contingencies -

Commitments and Contingencies - Remaining Payments of Operating Lease Liability (Details) $ in Thousands	Jun. 30, 2021USD ($)
Leases [Abstract]
2021	$ 1,022
2022	1,987
2023	2,185
2024	2,250
Thereafter	521
Total remaining lease payments	7,965
Less: imputed interest	(1,176)
Total operating lease liabilities	$ 6,789
Weighted-average remaining lease term	3 years 9 months
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	Jun. 17, 2019	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Related Party Transaction [Line Items]
Collaboration revenue			$ 2,001	$ 2,322	$ 4,128	$ 4,968
Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Collaboration revenue			925	913	$ 1,850	1,824
Research Collaboration And Exclusive License Agreement [Member] | Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Ownership interest of common stock					8.40%
Collaboration revenue			$ 900	$ 900	$ 1,800	$ 1,800
Common stock shares restricted from selling period subsequent to issuance date		2 years
Purchase of additional shares of common stock	600,000	600,000
Purchase of additional shares of common stock price per share	$ 16	$ 16

Related Party Transactions - Eq

Related Party Transactions - Equity-Method Investment (Details Textual) - $ / shares	Jun. 30, 2021	Feb. 28, 2021	Jun. 30, 2018
Maximum [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage	50.00%
Vallon Pharmaceuticals, Inc. [Member]
Related Party Transaction [Line Items]
Percentage of owned shares	12.00%
ADAIR Technology [Member] | Vallon Pharmaceuticals, Inc. [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage			30.00%
Number of shares owned		843,750
Percentage of owned shares		12.00%
ADAIR Technology [Member] | Vallon Pharmaceuticals, Inc. [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Share price		$ 8

Subsequent Events (Details Text

Subsequent Events (Details Textual) - USD ($)	Aug. 02, 2021	Jun. 30, 2021	Jun. 11, 2021
Subsequent Event [Line Items]
Security deposit		$ 10,000,000
Vingroup Agreement
Subsequent Event [Line Items]
Security deposit			$ 10,000
Non-refundable deposit amount			$ 500,000
Vingroup Agreement | Subsequent Events
Subsequent Event [Line Items]
Upfront payment receivable	$ 40,000,000