Arcturus Therapeutics (ARCT) 10-Q 5 Aug 24 2024 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2024	Aug. 02, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2024
Document Fiscal Year Focus	2024
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	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		27,042,246
Document Quarterly Report	true
Document Transition Report	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 260,329	$ 292,005
Restricted cash	55,000	55,000
Accounts receivable	24,085	32,064
Prepaid expenses and other current assets	7,594	7,521
Total current assets	347,008	386,590
Property and equipment, net	11,182	12,427
Operating lease right-of-use assets, net	28,533	28,500
Non-current restricted cash	1,885	1,885
Total assets	388,608	429,402
Current liabilities:
Accounts payable	13,905	5,279
Accrued liabilities	35,450	31,881
Deferred revenue	42,362	44,829
Total current liabilities	91,717	81,989
Deferred revenue, net of current portion	11,344	42,496
Operating lease liability, net of current portion	26,964	25,907
Other non-current liabilities		497
Total liabilities	130,025	150,889
Stockholders’ equity
Common stock, $0.001 par value; 60,000 shares authorized; issued and outstanding shares were 27,042 at June 30, 2024 and 26,828 at December 31, 2023	27	27
Additional paid-in capital	670,455	646,352
Accumulated deficit	(411,899)	(367,866)
Total stockholders’ equity	258,583	278,513
Total liabilities and stockholders’ equity	$ 388,608	$ 429,402

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2024	Dec. 31, 2023
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	27,042,000	26,828,000
Common stock, shares outstanding	27,042,000	26,828,000

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, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenue:
Total revenue	$ 49,859	$ 10,519	$ 87,871	$ 90,804
Operating expenses:
Research and development, net	58,669	52,668	112,242	104,436
General and administrative	12,316	13,225	27,167	26,987
Total operating expenses	70,985	65,893	139,409	131,423
Loss from operations	(21,126)	(55,374)	(51,538)	(40,619)
(Loss) gain from foreign currency	(388)	149	(441)	(179)
Gain on debt extinguishment				33,953
Finance income, net	4,148	3,252	8,164	5,729
Net loss before income taxes	(17,366)	(51,973)	(43,815)	(1,116)
Provision for income taxes	(150)	577	218	680
Net loss	$ (17,216)	$ (52,550)	$ (44,033)	$ (1,796)
Net loss per share:
Basic	$ (0.64)	$ (1.98)	$ (1.64)	$ (0.07)
Diluted	$ (0.64)	$ (1.98)	$ (1.64)	$ (0.07)
Weighted-average shares outstanding:
Basic	26,967	26,563	26,923	26,557
Diluted	26,967	26,563	26,923	26,557
Comprehensive loss:
Net loss	$ (17,216)	$ (52,550)	$ (44,033)	$ (1,796)
Comprehensive loss	(17,216)	(52,550)	(44,033)	(1,796)
Collaboration Revenue [Member]
Revenue:
Total revenue	45,976	9,565	78,574	89,294
Grant Revenue [Member]
Revenue:
Total revenue	$ 3,883	$ 954	$ 9,297	$ 1,510

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2022	$ 270,312	$ 27	$ 608,426	$ (338,141)
Balance (in shares) at Dec. 31, 2022		26,555
Net Income (Loss)	50,754			50,754
Share-based compensation expense	8,182		8,182
Balance at Mar. 31, 2023	329,248	$ 27	616,608	(287,387)
Balance (in shares) at Mar. 31, 2023		26,555
Balance at Dec. 31, 2022	270,312	$ 27	608,426	(338,141)
Balance (in shares) at Dec. 31, 2022		26,555
Net Income (Loss)	(1,796)
Balance at Jun. 30, 2023	285,175	$ 27	625,085	(339,937)
Balance (in shares) at Jun. 30, 2023		26,574
Balance at Mar. 31, 2023	329,248	$ 27	616,608	(287,387)
Balance (in shares) at Mar. 31, 2023		26,555
Net Income (Loss)	(52,550)			(52,550)
Share-based compensation expense	8,383		8,383
Issuance of common stock upon exercise of stock options	94		94
Issuance of common stock upon exercise of stock options (in shares)		19
Balance at Jun. 30, 2023	285,175	$ 27	625,085	(339,937)
Balance (in shares) at Jun. 30, 2023		26,574
Balance at Dec. 31, 2023	278,513	$ 27	646,352	(367,866)
Balance (in shares) at Dec. 31, 2023		26,828
Net Income (Loss)	(26,817)			(26,817)
Share-based compensation expense	10,088		10,088
Issuance of common stock upon exercise of stock options	2,188		2,188
Issuance of common stock upon exercise of stock options (in shares)		89
Balance at Mar. 31, 2024	263,972	$ 27	658,628	(394,683)
Balance (in shares) at Mar. 31, 2024		26,917
Balance at Dec. 31, 2023	278,513	$ 27	646,352	(367,866)
Balance (in shares) at Dec. 31, 2023		26,828
Net Income (Loss)	(44,033)
Balance at Jun. 30, 2024	258,583	$ 27	670,455	(411,899)
Balance (in shares) at Jun. 30, 2024		27,042
Balance at Mar. 31, 2024	263,972	$ 27	658,628	(394,683)
Balance (in shares) at Mar. 31, 2024		26,917
Net Income (Loss)	(17,216)			(17,216)
Share-based compensation expense	9,424		9,424
Issuance of common stock upon exercise of stock options	2,403		2,403
Issuance of common stock upon exercise of stock options (in shares)		125
Balance at Jun. 30, 2024	$ 258,583	$ 27	$ 670,455	$ (411,899)
Balance (in shares) at Jun. 30, 2024		27,042

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Operating activities
Net loss	$ (44,033)	$ (1,796)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	1,813	1,315
Share-based compensation expense	19,512	16,565
Foreign currency translation loss	441	160
Gain on debt extinguishment		(33,953)
Other non-cash expenses		502
Changes in assets and liabilities:
Accounts receivable	7,979	(35)
Prepaid expense and other assets	(73)	4,712
Right-of-use assets	2,703	1,992
Accounts payable	8,626	5,593
Accrued liabilities	2,631	(2,983)
Deferred revenue	(33,619)	24,969
Lease liabilities	(1,679)	(2,105)
Net cash (used in) provided by operating activities	(35,699)	14,936
Investing activities
Acquisition of property and equipment	(568)	(1,045)
Net cash used in investing activities	(568)	(1,045)
Financing activities
Proceeds from exercise of stock options	4,591	94
Payments on debt obligations		(27,364)
Net cash provided by (used in) financing activities	4,591	(27,270)
Net decrease in cash, cash equivalents and restricted cash	(31,676)	(13,379)
Cash, cash equivalents and restricted cash at beginning of the period	348,890	393,977
Cash, cash equivalents and restricted cash at end of the period	317,214	380,598
Supplemental disclosure of cash flow information
Cash paid for interest		2,102
Non-cash investing activities
Non-cash asset disposal	473
Right-of-use assets acquired through operating leases	$ 2,736
Purchase of property and equipment in accounts payable and accrued expenses		$ 577

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (17,216)	$ (26,817)	$ (52,550)	$ 50,754	$ (44,033)	$ (1,796)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Jun. 30, 2024 shares
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	Rule 10b5-1 Trading Arrangements During the three months ended June 30, 2024 , none of our directors or officers adopted or terminated a "Rule 10b5-1 trading arrangement" (as defined in Item 408 of Regulation S-K of the Exchange Act) intended to satisfy the affirmative defense conditions of Rule 10b5-1(c) under the Exchange Act, other than as follows: • Lance Kurata , our Chief Legal Officer , adopted a Rule 10b5-1 trading arrangement as of June 12, 2024 . Mr. Kurata's trading arrangement provides for the exercise of up to an aggregate of 35,000 options to purchase shares of common stock and subsequent sale of such underlying shares of common stock, until June 12, 2025 .
Directors or Officers [Member]
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Lance Kurata [Member]
Trading Arrangements, by Individual
Name	Lance Kurata
Title	Chief Legal Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	June 12, 2024
Expiration Date	June 12, 2025
Aggregate Available	35,000

Description of Business, Basis

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2024
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” or "Arcturus") is a global messenger RNA medicines company focused on the development of infectious disease vaccines and significant addressing unmet medical needs 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 and its Clinical Trial Application (“CTA”) for candidate LUNAR-COV19 were approved by applicable health authorities. Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of Arcturus 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 consolidated financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. These condensed consolidated financial statements are prepared in accordance with GAAP, which requires management to make estimates and assumptions regarding the valuation of certain debt and equity instruments, share-based compensation, accruals for liabilities, income taxes, revenue and deferred revenue, leases, and other matters that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Although these estimates are based on management’s knowledge of current events and actions the Company may undertake in the future, actual results may ultimately differ from these estimates and assumptions. 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 the Company's joint venture in ARCALIS, Inc. with Axcelead, Inc. (“Axcelead”). The Company’s share of the investee's results is presented as either income or loss from equity-method investment in the accompanying condensed consolidated statements of operations and comprehensive loss. Liquidity The Company has incurred significant operating losses since its inception. As of June 30, 2024 and December 31, 2023, the Company had an accumulated deficit of $ 411.9 million and $ 367.9 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, 2024, the Company has funded its operations principally with the proceeds from revenues earned through collaboration agreements, the sale of capital stock, expense reimbursements from government contracts and proceeds from long-term debt. At June 30, 2024, the Company’s balance of cash and cash equivalents, including restricted cash, was $ 317.2 million. 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 At contract inception, the Company analyzes its collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of Accounting Standards Codification (“ASC”) Topic 808, Collaborative Arrangements (“ASC 808”). For collaboration arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the collaboration reflect a vendor-customer relationship and are therefore within the scope of ASC 606. The Company determines revenue recognition for arrangements within the scope of ASC 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 revenue agreements include license fees, upfront payments, development or regulatory milestone payments, profit-sharing arrangements, reimbursement for research and development activities, option exercise fees, drug substance and drug product supply fees, consulting and related technology transfer fees and royalties on sales of commercialized products. 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 ASC 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. For performance obligations that are recognized over time, the Company measures the progress using an input method. The input methods used are based on the effort expended or costs incurred toward the satisfaction of the performance obligation. The Company estimates the amount of effort expended, including the time estimated it will take to complete the activities, or costs incurred in a given period, relative to the estimated total effort or costs to satisfy the performance obligation. This approach requires the Company to make numerous estimates and use significant judgment. If estimates or judgments change over the course of the collaboration, a cumulative catch up of revenue is recognized in the period such changes are identified. See “Note 2, Revenue” for specific details surrounding the Company’s arrangements. Leases The Company determines if an arrangement is a lease at inception. Lease right-of-use assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's obligation to make lease payments arising from the lease. For operating leases with an initial term greater than 12 months, the Company recognizes operating lease right-of-use assets and operating lease liabilities based on the present value of lease payments over the lease term at the commencement date. Operating lease right-of-use assets are comprised of the lease liability plus any lease payments made and excludes lease incentives. Lease terms include options to renew or terminate the lease when the Company is reasonably certain that the renewal option will be exercised or when it is reasonably certain that the termination option will not be exercised. For the Company's operating leases, if the interest rate used to determine the present value of future lease payments is not readily determinable, the Company estimates its incremental borrowing rate as the discount rate for the lease. The Company's incremental borrowing rate is estimated to approximate the interest rate on a collateralized basis with similar terms and payments, and in similar economic environments. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has elected the practical expedient to not separate lease and non-lease components. See “Note 9, Commitments and Contingencies” for specific details surrounding the Company’s leases. Research and Development Costs, 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, pre-launch inventory and license agreement expenses. Research and development expenses are presented net of any grants. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods are received or the services are performed. 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 activities performed by third parties are accrued and expensed based upon estimates of the proportion of work completed over the life of the individual clinical trial and patient enrollment rates in accordance with agreements established with Clinical Research Organizations ("CROs") and clinical trial sites. Estimates are determined by reviewing contracts, vendor agreements and purchase orders, and through discussions with internal clinical personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services. 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 and comprehensive loss, 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. Restricted Cash Restricted cash includes collateral pledged and held at the Company’s securities accounts pursuant to a security agreement with Wells Fargo Bank, National Association (“Wells Fargo”) (Note 5). At June 30, 2024 , such collateral amounted to $ 55.0 million. Restricted cash also includes cash required to be set aside as security for lease payments and to maintain a letter of credit for the benefit of the landlord for the Company’s offices. At June 30, 2024 and 2023 , the Company had restricted cash of $ 1.9 million and $ 2.1 million, respectively, in conjunction with property leases in San Diego, California, and such restriction is expected to be removed at the end of the lease term. The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the unaudited condensed consolidated balance sheets that sum to the total of the same such amounts shown in the unaudited condensed consolidated statement of cash flows as of June 30, 2024 and 2023 : (in thousands) June 30, 2024 June 30, 2023 Cash and cash equivalents $ 260,329 $ 323,471 Restricted cash 55,000 55,000 Non-current restricted cash 1,885 2,127 Total cash, cash equivalents and restricted $ 317,214 $ 380,598 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 treasury-stock method. Dilutive shares of common stock for the three and six months ended June 30, 2024 were comprised of stock options and restricted stock units. Dilutive shares of common stock for the three and six months ended June 30, 2023 were comprised of stock options. No dividends were declared or paid during the reported periods. Recently Issued Accounting Standards Not Yet Adopted From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the condensed consolidated financial statements and disclosures.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue	Note 2. Revenue The Company has entered into license agreements and collaborative research and development arrangements with pharmaceutical and biotechnology companies, as well as consulting, related technology transfer, product revenue and government grant agreements. Under these arrangements, the Company is entitled to receive license fees, consulting fees, product fees, technological transfer fees, upfront payments, milestone payments if and when certain research and development milestones, technology transfer milestones or success-based milestones are achieved, royalties on approved product sales and reimbursement for research and development activities. The Company’s costs of performing these services are included within research and development expenses. The Company’s milestone payments are typically defined by achievement of certain preclinical, clinical, and commercial success criteria. Preclinical milestones may include in vivo proof of concept in disease animal models, lead candidate identification, and completion of IND-enabling toxicology studies. Clinical milestones may, for example, include successful enrollment of the first patient in or completion of Phase 1, 2 and 3 clinical trials, and commercial milestones are often tiered based on net or aggregate sale amounts. The Company cannot guarantee the achievement of these milestones due to risks associated with preclinical and clinical activities required for development of nucleic acid medicine-based therapeutics and vaccines. The following table presents changes during the six months ended June 30, 2024 in the balances of contract assets and liabilities as compared to what was disclosed in the Company’s Annual Report. (in thousands) December 31, 2023 Additions Deductions June 30, 2024 Contract Assets: Accounts receivable $ 32,064 $ 55,132 $ ( 63,111 ) $ 24,085 Contract Liabilities: Deferred revenue $ 87,325 $ 54,252 $ ( 87,871 ) $ 53,706 The following table summarizes the Company’s revenues for the periods indicated. For the Three Months For the Six Months (in thousands) 2024 2023 2024 2023 Collaboration Revenue: CSL Seqirus $ 45,911 $ 7,607 $ 78,292 $ 85,824 Janssen — 170 — 660 Other collaboration revenue 65 1,788 282 2,810 Total collaboration revenue $ 45,976 $ 9,565 $ 78,574 $ 89,294 Grant revenue: BARDA $ 3,883 $ 954 $ 9,297 $ 1,510 Total grant revenue $ 3,883 $ 954 $ 9,297 $ 1,510 The following paragraphs provide information regarding the nature and purpose of the Company’s most significant collaboration and grant arrangements. CSL Seqirus On November 1, 2022, the Company entered into a Collaboration and License Agreement (as amended, the “CSL Collaboration Agreement”) with Seqirus, Inc., a part of CSL Limited (“CSL Seqirus”), for the global exclusive rights to research, develop, manufacture, and commercialize vaccines. Under the terms of the CSL Collaboration Agreement, the Company provides CSL Seqirus with an exclusive global license to its mRNA technology (including STARR ® ) and LUNAR ® lipid-mediated delivery, along with mRNA drug substance and drug product manufacturing process. CSL Seqirus will lead development and commercialization of vaccines under the collaboration. The collaboration plans to advance vaccines against SARS-CoV-2 (COVID-19), influenza, pandemic preparedness as well as three other respiratory infectious diseases. The Company received a $ 200.0 million upfront payment and is eligible to receive over $ 1.3 billion in development milestones if all products are registered in the licensed fields and entitled to potentially receive up to $ 3.0 billion in commercial milestones based on “net sale” of vaccines in the various fields. In addition, the Company is eligible to receive a 40 % net profit share for COVID-19 vaccine products and up to low double-digit royalties for vaccines against flu, pandemic preparedness and three other respiratory pathogens. During the second quarter of 2024, the Company achieved a $ 17.0 million development milestone related to the CSL Collaboration Agreement which was included in accounts receivable as of June 30, 2024. In evaluating the CSL Collaboration Agreement in accordance with ASC 606, the Company concluded that CSL Seqirus is a customer. The Company identified all promised goods/services within the CSL Collaboration Agreement, and when combining certain promised goods/services, the Company concluded that there are five distinct performance obligations. The nature of the performance obligations consists of delivery of the vaccine license, research and development services for COVID and non-COVID vaccines and regulatory activities for COVID vaccines. For each performance obligation, the Company estimated the standalone selling price based on 1) in the case of the license, the fair value using costs to recreate plus margin method and 2) in the case of research and development services and regulatory activities, cost plus margin for estimated full-time equivalent (“FTE”) costs, direct costs including laboratory supplies, contractors, and other out-of-pocket expenses for research and development services and regulatory activities. As of June 30, 2024, the transaction price consisted of upfront consideration received and milestones achieved. Additional variable consideration was not included in the transaction price at June 30, 2024 because the Company could not conclude that it is probable that including the variable consideration will not result in a significant revenue reversal. The Company allocated the transaction price to the performance obligations in proportion to their standalone selling price. The vaccine license was recognized at the point in time it was transferred in 2022. The research and development and regulatory activities performance obligations are recognized over a period of time based on the percentage of services rendered using the input method, meaning actual costs incurred divided by total costs budgeted to satisfy the performance obligation. Any consideration related to sales-based royalties will be recognized when the amounts are probable of non-reversal, provided that the reported sales are reliably measurable and the Company has no remaining promised goods/services, as they are constrained and therefore have also been excluded from the transaction price. The revenue recognized in the second quarter of 2024 relates to the license delivered, milestones achieved and services performed through June 30, 2024. Total deferred revenue as of June 30, 2024 and December 31, 2023 for the CSL Collaboration Agreement was $ 53.7 million and $ 87.1 million, respectively. During 2023, the Company also received an advance payment of $ 23.6 million for the manufacturing and supply of ARCT-154 drug product. The advance payment was for specified manufacturing runs of ARCT-154 which include the drug substance utilized, as well as the reservation fees and related manufacturing requirements. The Company concluded that the promise to manufacture and supply ARCT-154 drug product is a customer option as part of the CSL Collaboration Agreement and is accounted for as a separate contract. The Company recognized $ 18.0 million in revenue related to this customer option during the second quarter of 2024. No amount related to this customer option remained in deferred revenue as of June 30, 2024. During 2023, the Company entered into an amendment to the CSL Collaboration Agreement, pursuant to which the Company agreed to sponsor and conduct a Phase 1 clinical study in the influenza field. As part of the amendment, the Company received $ 17.5 million from CSL Seqirus. The amendment also provides for up to $ 1.5 million in additional payments which are achievable upon meeting certain clinical milestones relating to the Phase 1 clinical study in the influenza field. The Company previously concluded that the expansion of research and development support services under the CSL Collaboration Agreement represented an option that was not a material right. Therefore the Company concluded the promise to sponsor and conduct the Phase 1 clinical study is a separate contract and the sole performance obligation under the new arrangement. During the quarter ended June 30, 2024 , the Company recognized $ 3.0 million related to the performance obligation and the remaining amount of $ 9.8 million is included in deferred revenue. During the fourth quarter of 2023, the Company received an advance payment of $ 5.3 million from CSL Seqirus for manufacturing activities related to COVID-19 vaccine product. During the first quarter of 2024, the Company received an additional advance payment of $ 5.1 million from CSL Seqirus for manufacturing activities related to COVID-19 vaccine product. The Company concluded that the promise to perform manufacturing activities is a customer option as part of the CSL Collaboration Agreement and is accounted for as a separate contract. The advance payments are included in deferred revenue as of June 30, 2024 and will be recognized as revenue when the vaccine product is transferred to CSL Seqirus. In March 2024, the Company entered into an amendment to the CSL Collaboration Agreement, pursuant to which the parties agreed to, among other things, adjust (i) the development plans for certain product candidates, (ii) various development milestones related to such product candidates, (iii) provisions of the CSL Collaboration Agreement related to specific royalty payments, (iii) provisions of the CSL Collaboration Agreement related to distributors, and (iv) proprietary payment calculations related to the foregoing. BARDA Grant In August 2022, the Company entered into a cost reimbursement contract (the “BARDA Contract”) with the Biomedical Advanced Research and Development Authority ("BARDA"), a division of the Office of the Assistant Secretary for Preparedness and Response (ASPR) within the U.S. Department of Health and Human Services (HHS) for an award of up to $ 63.2 million for the development of a pandemic influenza vaccine using the Company's STARR ® self-amplifying mRNA vaccine platform technology. The Company earns grant revenue for performing tasks under the agreement. The Company determined that the BARDA Contract is not in the scope of ASC 808 or ASC 606. Applying International Accounting Standards No. 20 ("IAS 20"), Accounting for Government Grants and Disclosure of Government Assistance, by analogy, the Company recognizes grant revenue from the reimbursement of direct out-of-pocket expenses, overhead allocations and fringe benefits for research costs associated with the grant. The costs associated with these reimbursements are reflected as a component of research and development expense in the Company’s condensed consolidated statements of operations and comprehensive income (loss). The Company rec ognized $ 3.9 million and $ 1.0 million o f revenue during the three months ended June 30, 2024 and 2023, respectively. As of June 30, 2024, the remaining available funding net of revenue e arned was $ 44.5 million.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2024
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 established 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. As of June 30, 2024 and December 31, 2023 , 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, 2024
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Note 4. Balance Sheet Details Property and equipment, net balances consisted of the following: (in thousands) June 30, 2024 December 31, 2023 Research equipment $ 16,784 $ 16,046 Computers and software 1,131 1,275 Office equipment and furniture 703 958 Leasehold improvements 2,644 2,655 Construction in progress — 233 Total 21,262 21,167 Less accumulated depreciation and amortization ( 10,080 ) ( 8,740 ) Property and equipment, net $ 11,182 $ 12,427 Depreciation and amortization expense was $ 0.9 mi llion and $ 1.8 million for the three and six months ended June 30, 2024, respectively, and $ 0.7 m illion and $ 1.3 million for the three and six months ended June 30, 2023, respectively. Construction in progress is primarily comprised of research equipment not yet placed in service. Accrued liabilities consisted of the following: (in thousands) June 30, 2024 December 31, 2023 Accrued compensation $ 9,206 $ 5,918 Cystic Fibrosis Foundation liability 6,870 7,633 Income tax payable — 641 Current portion of operating lease liability 3,917 4,309 Clinical trial accruals 968 2,333 Vinbiocare contractual liabilities 2,514 2,514 Other accrued research and development expenses 11,975 8,533 Total $ 35,450 $ 31,881

Debt

Debt	6 Months Ended
	Jun. 30, 2024
Debt Disclosure [Abstract]
Debt	Note 5. Debt Wells Fargo Credit Agreement The Company’s wholly-owned subsidiary, Arcturus Therapeutics, Inc. (“Arcturus Therapeutics”) entered into a credit agreement with Wells Fargo Bank on April 21, 2023, and amended on June 26, 2024 , whereby Wells Fargo will make a $ 50.0 million revolving credit line available to the Company (the “Loan”) and each draw on the Loan evidenced by a revolving line of credit note (the “Note”). Borrowings under the agreement will bear interest at a rate of 1.00 % above either the Daily Simple SOFR or Term SOFR (as such terms are defined in the Note), with “SOFR” being the rate per annum equal to the secured overnight financing rate as administered by the Federal Reserve Bank of New York. If an Event of Default (as defined in the agreement) occurs, then all Loans shall bear interest at a rate equal to 2.00 % above the interest rate applicable immediately prior to the occurrence of the Event of Default. The term of the agreement was originally two years , with an option for one-year renewals subject to Wells Fargo approval and Arcturus Therapeutics furnishing to Wells Fargo a non-refundable commitment fee equal to 0.25 % of the Loan amount for each such renewal. There is no penalty for terminating the facility prior to the maturity date of the Note. As collateral, the Company has agreed to pledge $ 55.0 million in cash to be held at the Company’s securities accounts with Wells Fargo Securities, LLC, an affiliate of Wells Fargo, pursuant to a security agreement. In June 2024, Arcturus Therapeutics and Wells Fargo entered into an amendment to the Note, whereby the term of the Note was extended by one year to April 2026. No borrowings were outstanding as of June 30, 2024 .

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2024
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Note 6. Stockholders’ Equity Net Loss per Share Potentially dilutive securities that were not included in the calculation of diluted net loss per share for the three and six months ended June 30, 2024 as they were anti-dilutive totaled 1.1 million and 1.3 million, respectively, and 1.0 million and 0.8 million for the three and six months ended June 30, 2023, respectively. Sales Agreement On December 23, 2022, the Company entered into a Controlled Equity Offering℠ Sales Agreement, which was amended on August 7, 2023 (as amended, the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor”),Wells Fargo Securities, LLC (“Wells Fargo Securities”), and William Blair & Company, L.L.C. (“William Blair”) relating to shares of the Company's common stock. In accordance with the terms of the Sales Agreement, the Company may offer and sell shares of its common stock having an aggregate offering price of up to $ 200,000,000 from time to time through Cantor, Wells Fargo Securities, or William Blair, each acting as the Company's sales agent. During the period ended June 30, 2024 the Company did no t offer or sell any shares of common stock pursuant to the Sales Agreement.

Share-Based Compensation Expens

Share-Based Compensation Expense	6 Months Ended
	Jun. 30, 2024
Share-Based Payment Arrangement [Abstract]
Share-Based Compensation Expense	Note 7. Share-Based Compensation Expense In June 2024 at the Company’s 2024 Annual Meeting of Stockholders (the "2024 Annual Meeting"), the stockholders of the Company appro ved an amendment to the Company’s 2019 Omnibus Equity Incentive Plan (as amended, the “2019 Plan”) which, among other things, increased the aggregate number of shares authorized for use in making awards to eligible persons under the 2019 Plan by 2,000,000 shares, for a total of up to 10,750,000 shares available for issuance. As of June 30, 2024 , following the 2024 Annual Meeting, a total of 2,236,360 shares remain available for future issuance under the 2019 Plan, subject to the terms of the 2019 Plan. In October 2021, the Company adopted the 2021 Inducement Equity Incentive Plan which covers the award of up to 1,000,000 shares of common stock (the “2021 Plan”) effective as of October 15, 2021. Approval of the Company’s stockholders is not required as a condition to the effectiveness of the 2021 Plan for so long as the plan is in compliance with applicable Nasdaq inducement plan rules. In April 2022, the compensation committee of the Company’s board of directors approved a proposal to reduce the total number of shares available for future issuance under the 2021 Plan to 130,000 . As of June 30, 2024 , a total of 124,697 shares remain available for future issuance under the 2021 Plan, subject to the terms of the 2021 Plan. 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, 2024 and 2023 was as follows: For the Three Months For the Six Months (in thousands) 2024 2023 2024 2023 Research and development $ 4,378 $ 3,741 $ 9,180 $ 7,249 General and administrative 5,046 4,642 10,332 9,316 Total $ 9,424 $ 8,383 $ 19,512 $ 16,565

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2024
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 is due to federal and state income tax expense offset by valuation allowance on the Company's deferred tax assets. For the three and six months ended June 30, 2024, the Company recorded $ ( 0.2 ) million and $ 0.2 million of income tax expense, respectively. For the three and six months ended June 30, 2023, the Company recorded $ 0.6 million and $ 0.7 million of income tax expense, respectively. 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, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 9. Commitments and Contingencies Cystic Fibrosis Foundation Agreement On September 25, 2023, the Company amended its Development Program Letter Agreement, dated May 16, 2017 and as amended July 13, 2018 and August 1, 2019, with the Cystic Fibrosis Foundation (“CFF”). Pursuant to the amendment, CFF increased the amount it will award to advance LUNAR-CF to $ 24.6 million from approximately $ 15.6 million and the Company agreed to incur at least $ 15.0 million toward activities under the research plan. Total contra expense of $ 0.8 million was recognized during the three and six months ended June 30, 2024. For the three and six months ended June 30, 2023, the Company recognized no contra expense related to the agreement. As of June 30, 2024 and December 31, 2023, $ 6.9 million and $ 7.6 million, respectively, remained in accrued liabilities. 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 $ 0.1 million. In March 2024, the Company negotiated with the lessor to extend the lease through March 2027. The Company entered into an irrevocable standby letter of credit with the landlord for a security deposit of $ 0.1 million 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 second 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 January 2024, the Company vacated this office space with no intention of operating out of the location in the future. Because Arcturus was still engaged in the lease for the property and obligated to make the remaining lease payment through March 31, 2025, the Company recorded an impairment loss in the amount of $ 1.3 million during the three months ended March 31, 2024, as it would not receive any future economic benefit from the lease. In July 2024, the Company terminated the existing lease agreement, in accordance with its terms, thereby ending their contractual obligation to pay for premise. In September 2021, the Company entered into a third non-cancellable lease agreement for office, research and development, engineering and laboratory space near its current headquarters, and such lease term commenced during the second quarter of 2022. The initial term of this lease extends ten years and eight months from the date of possession, and the Company has the right to extend the term of the lease for an additional five-year period. When the lease term was determined for the operating lease right-of-use assets and lease liabilities, the extension option for the lease was not included. The lease has a monthly base rent ranging from $ 0.3 million to $ 0.4 million which escalates over the lease term. The Company received a free rent period of four months and also pays for various operating costs, including utilities and real property taxes. The Company entered into an irrevocable standby letter of credit with the landlord for a security deposit of $ 2.0 million 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. 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, 2024, the remaining payments of the operating lease liability were as follows: (in thousands) Remaining Lease Payments 2024 $ 2,838 2025 5,019 2026 5,274 Thereafter 23,703 Total remaining lease payments 36,834 Less: imputed interest ( 5,953 ) Total operating lease liabilities $ 30,881 Weighted-average remaining lease term 7.5 Weighted-average discount rate 4.8 % 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 term s. Operating lease costs were $ 1.5 million and $ 2.9 million for the three and six months ended June 30, 2024, respectively, and $ 1.4 million and $ 2.8 million for the three and six months ended June 30, 2023, respectively.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2024
Related Party Transactions [Abstract]
Related Party Transactions	Note 10. Related Party Transactions See “Note 1, Joint Ventures, Equity Method Investments and Variable Interest Entities” for specific details surrounding the Company’s agreement with Axcelead to form the joint venture entity, ARCALIS, Inc.

Description of Business, Basi_2

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements include the accounts of Arcturus 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 consolidated financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. These condensed consolidated financial statements are prepared in accordance with GAAP, which requires management to make estimates and assumptions regarding the valuation of certain debt and equity instruments, share-based compensation, accruals for liabilities, income taxes, revenue and deferred revenue, leases, and other matters that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting periods. Although these estimates are based on management’s knowledge of current events and actions the Company may undertake in the future, actual results may ultimately differ from these estimates and assumptions.
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 the Company's joint venture in ARCALIS, Inc. with Axcelead, Inc. (“Axcelead”). The Company’s share of the investee's results is presented as either income or loss from equity-method investment in the accompanying condensed consolidated statements of operations and comprehensive loss.
Liquidity	Liquidity The Company has incurred significant operating losses since its inception. As of June 30, 2024 and December 31, 2023, the Company had an accumulated deficit of $ 411.9 million and $ 367.9 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, 2024, the Company has funded its operations principally with the proceeds from revenues earned through collaboration agreements, the sale of capital stock, expense reimbursements from government contracts and proceeds from long-term debt. At June 30, 2024, the Company’s balance of cash and cash equivalents, including restricted cash, was $ 317.2 million. 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 At contract inception, the Company analyzes its collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of Accounting Standards Codification (“ASC”) Topic 808, Collaborative Arrangements (“ASC 808”). For collaboration arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the collaboration reflect a vendor-customer relationship and are therefore within the scope of ASC 606. The Company determines revenue recognition for arrangements within the scope of ASC 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 revenue agreements include license fees, upfront payments, development or regulatory milestone payments, profit-sharing arrangements, reimbursement for research and development activities, option exercise fees, drug substance and drug product supply fees, consulting and related technology transfer fees and royalties on sales of commercialized products. 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 ASC 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. For performance obligations that are recognized over time, the Company measures the progress using an input method. The input methods used are based on the effort expended or costs incurred toward the satisfaction of the performance obligation. The Company estimates the amount of effort expended, including the time estimated it will take to complete the activities, or costs incurred in a given period, relative to the estimated total effort or costs to satisfy the performance obligation. This approach requires the Company to make numerous estimates and use significant judgment. If estimates or judgments change over the course of the collaboration, a cumulative catch up of revenue is recognized in the period such changes are identified. See “Note 2, Revenue” for specific details surrounding the Company’s arrangements.
Leases	Leases The Company determines if an arrangement is a lease at inception. Lease right-of-use assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's obligation to make lease payments arising from the lease. For operating leases with an initial term greater than 12 months, the Company recognizes operating lease right-of-use assets and operating lease liabilities based on the present value of lease payments over the lease term at the commencement date. Operating lease right-of-use assets are comprised of the lease liability plus any lease payments made and excludes lease incentives. Lease terms include options to renew or terminate the lease when the Company is reasonably certain that the renewal option will be exercised or when it is reasonably certain that the termination option will not be exercised. For the Company's operating leases, if the interest rate used to determine the present value of future lease payments is not readily determinable, the Company estimates its incremental borrowing rate as the discount rate for the lease. The Company's incremental borrowing rate is estimated to approximate the interest rate on a collateralized basis with similar terms and payments, and in similar economic environments. Lease expense for lease payments is recognized on a straight-line basis over the lease term. The Company has elected the practical expedient to not separate lease and non-lease components. See “Note 9, Commitments and Contingencies” for specific details surrounding the Company’s leases.
Research and Development Costs, Net	Research and Development Costs, 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, pre-launch inventory and license agreement expenses. Research and development expenses are presented net of any grants. Payments made prior to the receipt of goods or services to be used in research and development are capitalized until the goods are received or the services are performed. 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 activities performed by third parties are accrued and expensed based upon estimates of the proportion of work completed over the life of the individual clinical trial and patient enrollment rates in accordance with agreements established with Clinical Research Organizations ("CROs") and clinical trial sites. Estimates are determined by reviewing contracts, vendor agreements and purchase orders, and through discussions with internal clinical personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.
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 and comprehensive loss, 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.
Restricted Cash	Restricted Cash Restricted cash includes collateral pledged and held at the Company’s securities accounts pursuant to a security agreement with Wells Fargo Bank, National Association (“Wells Fargo”) (Note 5). At June 30, 2024 , such collateral amounted to $ 55.0 million. Restricted cash also includes cash required to be set aside as security for lease payments and to maintain a letter of credit for the benefit of the landlord for the Company’s offices. At June 30, 2024 and 2023 , the Company had restricted cash of $ 1.9 million and $ 2.1 million, respectively, in conjunction with property leases in San Diego, California, and such restriction is expected to be removed at the end of the lease term. The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the unaudited condensed consolidated balance sheets that sum to the total of the same such amounts shown in the unaudited condensed consolidated statement of cash flows as of June 30, 2024 and 2023 : (in thousands) June 30, 2024 June 30, 2023 Cash and cash equivalents $ 260,329 $ 323,471 Restricted cash 55,000 55,000 Non-current restricted cash 1,885 2,127 Total cash, cash equivalents and restricted $ 317,214 $ 380,598
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 treasury-stock method. Dilutive shares of common stock for the three and six months ended June 30, 2024 were comprised of stock options and restricted stock units. Dilutive shares of common stock for the three and six months ended June 30, 2023 were comprised of stock options. No dividends were declared or paid during the reported periods.
Recently Issued Accounting Standards Not Yet Adopted	Recently Issued Accounting Standards Not Yet Adopted From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board or other standard setting bodies and adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the condensed consolidated financial statements and disclosures.

Description of Business, Basi_3

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2024
Accounting Policies [Abstract]
Schedule of Cash and Cash Equivalents and Restricted Cash	(in thousands) June 30, 2024 June 30, 2023 Cash and cash equivalents $ 260,329 $ 323,471 Restricted cash 55,000 55,000 Non-current restricted cash 1,885 2,127 Total cash, cash equivalents and restricted $ 317,214 $ 380,598

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2024
Revenue from Contract with Customer [Abstract]
Summary of Changes in Balances of Receivables and Contract Liability	The following table presents changes during the six months ended June 30, 2024 in the balances of contract assets and liabilities as compared to what was disclosed in the Company’s Annual Report. (in thousands) December 31, 2023 Additions Deductions June 30, 2024 Contract Assets: Accounts receivable $ 32,064 $ 55,132 $ ( 63,111 ) $ 24,085 Contract Liabilities: Deferred revenue $ 87,325 $ 54,252 $ ( 87,871 ) $ 53,706
Schedule of Revenue	The following table summarizes the Company’s revenues for the periods indicated. For the Three Months For the Six Months (in thousands) 2024 2023 2024 2023 Collaboration Revenue: CSL Seqirus $ 45,911 $ 7,607 $ 78,292 $ 85,824 Janssen — 170 — 660 Other collaboration revenue 65 1,788 282 2,810 Total collaboration revenue $ 45,976 $ 9,565 $ 78,574 $ 89,294 Grant revenue: BARDA $ 3,883 $ 954 $ 9,297 $ 1,510 Total grant revenue $ 3,883 $ 954 $ 9,297 $ 1,510

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	6 Months Ended
	Jun. 30, 2024
Balance Sheet Related Disclosures [Abstract]
Summary of Components of Property and Equipment, Net	Property and equipment, net balances consisted of the following: (in thousands) June 30, 2024 December 31, 2023 Research equipment $ 16,784 $ 16,046 Computers and software 1,131 1,275 Office equipment and furniture 703 958 Leasehold improvements 2,644 2,655 Construction in progress — 233 Total 21,262 21,167 Less accumulated depreciation and amortization ( 10,080 ) ( 8,740 ) Property and equipment, net $ 11,182 $ 12,427
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following: (in thousands) June 30, 2024 December 31, 2023 Accrued compensation $ 9,206 $ 5,918 Cystic Fibrosis Foundation liability 6,870 7,633 Income tax payable — 641 Current portion of operating lease liability 3,917 4,309 Clinical trial accruals 968 2,333 Vinbiocare contractual liabilities 2,514 2,514 Other accrued research and development expenses 11,975 8,533 Total $ 35,450 $ 31,881

Share-Based Compensation Expe_2

Share-Based Compensation Expense (Tables)	6 Months Ended
	Jun. 30, 2024
Share-Based Payment Arrangement [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, 2024 and 2023 was as follows: For the Three Months For the Six Months (in thousands) 2024 2023 2024 2023 Research and development $ 4,378 $ 3,741 $ 9,180 $ 7,249 General and administrative 5,046 4,642 10,332 9,316 Total $ 9,424 $ 8,383 $ 19,512 $ 16,565

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Remaining Payments of Operating Lease Liability	As of June 30, 2024, the remaining payments of the operating lease liability were as follows: (in thousands) Remaining Lease Payments 2024 $ 2,838 2025 5,019 2026 5,274 Thereafter 23,703 Total remaining lease payments 36,834 Less: imputed interest ( 5,953 ) Total operating lease liabilities $ 30,881 Weighted-average remaining lease term 7.5 Weighted-average discount rate 4.8 %

Description of Business, Basi_4

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Details Textual)	6 Months Ended
	Jun. 30, 2024 USD ($) Segment	Jun. 30, 2023 USD ($)	Jun. 26, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Summary Of Significant Accounting Policy [Line Items]
Accumulated deficit	$ 411,899,000			$ 367,866,000
Cash and cash equivalents, including restricted cash	$ 317,214,000	$ 380,598,000		348,890,000	$ 393,977,000
Number of operating segment for research and development | Segment	1
Non-current restricted cash	$ 1,885,000	2,127,000		$ 1,885,000
Dividends declared or paid	0	$ 0
Wells Fargo Credit Agreement [Member]
Summary Of Significant Accounting Policy [Line Items]
Debt instrument, collateral amount	$ 55,000,000		$ 55,000,000

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, 2024	Dec. 31, 2023	Jun. 30, 2023	Dec. 31, 2022
Accounting Policies [Abstract]
Cash and cash equivalents	$ 260,329	$ 292,005	$ 323,471
Restricted cash	55,000		55,000
Non-current restricted cash	1,885	1,885	2,127
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 317,214	$ 348,890	$ 380,598	$ 393,977

Revenue - Summary of Changes in

Revenue - Summary of Changes in Balances of Receivables and Contract Liability (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2024 USD ($)
Revenue from Contract with Customer [Abstract]
Accounts receivable, Balance	$ 32,064
Additions	55,132
Deductions	(63,111)
Accounts receivable, Balance	24,085
Deferred revenue, Balance	87,325
Additions	54,252
Deductions	(87,871)
Deferred revenue, Balance	$ 53,706

Revenue - Summary of Revenues (

Revenue - Summary of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation Of Revenue [Line Items]
Total revenue	$ 49,859	$ 10,519	$ 87,871	$ 90,804
Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	45,976	9,565	78,574	89,294
Grant Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	3,883	954	9,297	1,510
CSL Seqirus [Member] | Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	45,911	7,607	78,292	85,824
Janssen [Member] | Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue		170		660
Other Collaboration Revenue [Member] | Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	65	1,788	282	2,810
BARDA [Member] | Grant Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 3,883	$ 954	$ 9,297	$ 1,510

Revenue (Details Textual)

Revenue (Details Textual) - USD ($)		1 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Nov. 01, 2022	Aug. 31, 2022	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Dec. 31, 2023	Mar. 31, 2024
Revenue [Line Items]
Deferred revenue			$ 53,706,000		$ 53,706,000	$ 87,325,000
Revenue recognized					(87,871,000)
BARDA [Member]
Revenue [Line Items]
Revenue recognized			3,900,000	$ 1,000,000
Total grant revenue		$ 63,200,000
Grant revenue outstanding					44,500,000
Research Collaboration And License Agreement [Member] | Seqirus Inc [Member]
Revenue [Line Items]
Upfront payment received	$ 200,000,000
Research Collaboration And License Agreement [Member] | Seqirus Inc [Member] | COVID-19 Vaccine [Member]
Revenue [Line Items]
Net profits percentage	40%
Development milestones received advance payment						5,300,000	$ 5,100,000
Research Collaboration And License Agreement [Member] | Seqirus Inc [Member] | Manufacturing and Supply of ARCT-154 Drug Product [Member]
Revenue [Line Items]
Deferred revenue			0		0
Revenue recognized			18,000,000
Development milestones received advance payment						23,600,000
Research Collaboration And License Agreement [Member] | Maximum [Member] | Seqirus Inc [Member]
Revenue [Line Items]
Eligible to receive development milestone payment	$ 1,300,000,000
Eligible to receive commercial milestone payment	$ 3,000,000,000
CSL Collaboration Agreement [Member]
Revenue [Line Items]
Development milestones achieved					17,000,000
Deferred revenue			53,700,000		53,700,000	87,100,000
CSL Collaboration Agreement [Member] | Phase I Clinical Study [Member]
Revenue [Line Items]
Deferred revenue			9,800,000		9,800,000
Milestone payments						17,500,000
Remaining performance obligation			$ 3,000,000		$ 3,000,000
CSL Collaboration Agreement [Member] | Maximum [Member] | Phase I Clinical Study [Member]
Revenue [Line Items]
Additional payments upon meeting certain clinical milestones						$ 1,500,000

Balance Sheet Details - Summary

Balance Sheet Details - Summary of Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 21,262	$ 21,167
Less accumulated depreciation and amortization	(10,080)	(8,740)
Property and equipment, net	11,182	12,427
Research equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	16,784	16,046
Computer and software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,131	1,275
Office equipment and furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	703	958
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,644	2,655
Construction in progress [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross		$ 233

Balance Sheet Details (Details

Balance Sheet Details (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization	$ 900	$ 700	$ 1,813	$ 1,315

Balance Sheet Details - Schedul

Balance Sheet Details - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Accrued Liabilities, Current [Abstract]
Accrued compensation	$ 9,206	$ 5,918
Cystic Fibrosis Foundation liability	6,870	7,633
Income tax payable		641
Current portion of operating lease liability	$ 3,917	$ 4,309
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total	Total
Clinical trial accruals	$ 968	$ 2,333
Vinbiocare contractual liabilities	2,514	2,514
Other accrued research and development expenses	11,975	8,533
Total	$ 35,450	$ 31,881

Debt (Details Textual)

Debt (Details Textual) - Wells Fargo Credit Agreement [Member] - USD ($)		1 Months Ended
	Jun. 26, 2024	Jun. 30, 2024
Debt Instrument [Line Items]
Revolving credit line available	$ 50,000,000
Loans interest rate, percentage	2%
Term of agreement	2 years
Extended term period		1 year
Option for renewal term	1 year
Non-refundable commitment fee, percentage	0.25%
Long-term debt		$ 0
Debt instrument, collateral amount	$ 55,000,000	$ 55,000,000
SOFR [Member]
Debt Instrument [Line Items]
Loan accrued interest rate per annum, percentage	1%

Stockholders' Equity (Details T

Stockholders' Equity (Details Textual) - USD ($)		3 Months Ended		6 Months Ended
	Dec. 23, 2022	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Class Of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share		1,100,000	1,000,000	1,300,000	800,000
Wells Fargo Credit Agreement [Member]
Class Of Stock [Line Items]
Issuance of common stock				0
Wells Fargo Credit Agreement [Member] | Maximum [Member]
Class Of Stock [Line Items]
Common stock issued, value	$ 200,000,000

Share-Based Compensation Expe_3

Share-Based Compensation Expense (Details Textual) - shares	Jun. 30, 2024	Apr. 30, 2022	Oct. 15, 2021
2019 Omnibus Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized	2,000,000
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	10,750,000
2019 Omnibus Equity Incentive Plan [Member] | Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	2,236,360
2021 Inducement Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Reduction in number of common stock shares available for future issuance		130,000
2021 Inducement Equity Incentive Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available			1,000,000
2021 Inducement Equity Incentive Plan [Member] | Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	124,697

Share-Based Compensation Expe_4

Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 9,424	$ 8,383	$ 19,512	$ 16,565
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	4,378	3,741	9,180	7,249
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 5,046	$ 4,642	$ 10,332	$ 9,316

Income Taxes (Details Textual)

Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Income Tax Disclosure [Abstract]
Income tax expense	$ (150)	$ 577	$ 218	$ 680

Commitments and Contingencies_2

Commitments and Contingencies (Details Textual) - USD ($)		1 Months Ended		3 Months Ended			6 Months Ended		12 Months Ended	50 Months Ended
	Aug. 01, 2019	Sep. 30, 2021	Oct. 31, 2017	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023	Sep. 25, 2023	Feb. 29, 2020
Commitment And Contingencies [Line Items]
Operating lease costs				$ 1,500,000		$ 1,400,000	$ 2,900,000	$ 2,800,000
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			$ 100,000
Security deposit			$ 100,000
February 2020 Lease Agreement [Member]
Commitment And Contingencies [Line Items]
Operating lease extended additional term											13 months
Lessee, operating leases, option 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.
Impairment loss					$ 1,300,000
September 2021 Lease Agreement [Member]
Commitment And Contingencies [Line Items]
Operating lease extended additional term		10 years 8 months
Lessee, operating leases, option to extend							the Company has the right to extend the term of the lease for an additional five-year period.
Security deposit		$ 2,000,000
Underlying Agreement [Member] | Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Contra expense remaining amount included in accrued expenses							$ 6,900,000		$ 7,600,000
Minimum amount agreed to incur under research plan										$ 15,000,000
Contra expense included in research and development expense				$ 800,000		$ 0	$ 800,000	$ 0
Underlying Agreement [Member] | LUNAR-CF [Member] | Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Payments for advance	$ 15,600,000									$ 24,600,000
Maximum [Member] | September 2021 Lease Agreement [Member]
Commitment And Contingencies [Line Items]
Monthly base rent		400,000
Minimum [Member] | September 2021 Lease Agreement [Member]
Commitment And Contingencies [Line Items]
Monthly base rent		$ 300,000

Commitments and Contingencies -

Commitments and Contingencies - Remaining Payments of Operating Lease Liability (Details) $ in Thousands	Jun. 30, 2024 USD ($)
Leases [Abstract]
2024	$ 2,838
2025	5,019
2026	5,274
Thereafter	23,703
Total remaining lease payments	36,834
Less: imputed interest	(5,953)
Total operating lease liabilities	$ 30,881
Weighted-average remaining lease term	7 years 6 months
Weighted-average discount rate	4.80%