0001193125-25-275758 | 10-Q | XBRL Viewer | Arcturus Therapeutics Holdings INC

Income Taxes	9 Months Ended
Sep. 30, 2025
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 rate is due to federal and state income tax expense offset by valuation allowance on the Company's deferred tax assets. The Company recorded negligible income tax expense for the three and nine months ended September 30, 2025. For the three months ended September 30, 2024, the Company recorded $0.2 million of income tax benefit and for the nine months ended September 30, 2024, the Company recorded no income tax benefit. No tax benefit was provided for losses incurred in the United States because those losses are offset by a full valuation allowance. Recent Tax Legislation On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law, which enacts significant changes to U.S. tax and related laws. Some of the provisions of the new tax law affecting corporations include but are not limited to current deduction of domestic research expenses, increasing the limit of the deduction of interest expense deduction to thirty percent of EBITDA, and one hundred percent bonus depreciation on eligible property acquired after January 19, 2025. The impact of the tax law changes from the OBBBA was included in the Company’s financial statements beginning in the three-months ending September 30, 2025.

Income Taxes

9 Months Ended

Sep. 30, 2025

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 rate is due to federal and state income tax expense offset by valuation allowance on the Company's deferred tax assets.

The Company recorded negligible income tax expense for the three and nine months ended September 30, 2025. For the three months ended September 30, 2024, the Company recorded $0.2 million of income tax benefit and for the nine months ended September 30, 2024, the Company recorded no income tax benefit. No tax benefit was provided for losses incurred in the United States because those losses are offset by a full valuation allowance.

Recent Tax Legislation

On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law, which enacts significant changes to U.S. tax and related laws. Some of the provisions of the new tax law affecting corporations include but are not limited to current deduction of domestic research expenses, increasing the limit of the deduction of interest expense deduction to thirty percent of EBITDA, and one hundred percent bonus depreciation on eligible property acquired after January 19, 2025. The impact of the tax law changes from the OBBBA was included in the Company’s financial statements beginning in the three-months ending September 30, 2025.

- Definition

The entire disclosure for income tax.

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+ Details

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 180,360	$ 237,028
Restricted cash	55,000	55,000
Accounts receivable	7,951	3,974
Prepaid expenses and other current assets	5,889	9,977
Total current assets	249,200	305,979
Property and equipment, net	7,419	9,531
Operating lease right-of-use assets, net	23,839	26,674
Non-current restricted cash	1,885	1,885
Total assets	282,343	344,069
Current liabilities:
Accounts payable	5,491	7,194
Accrued liabilities	19,382	38,781
Deferred revenue	6,826	19,514
Total current liabilities	31,699	65,489
Deferred revenue, net of current portion	4,220	12,604
Operating lease liability, net of current portion	21,865	24,998
Total liabilities	57,784	103,091
Stockholders’ equity
Common stock, $0.001 par value; 60,000 shares authorized; issued and outstanding shares were 27,235 at September 30, 2025 and 27,096 at December 31, 2024	27	27
Additional paid-in capital	710,043	689,758
Accumulated deficit	(485,511)	(448,807)
Total stockholders’ equity	224,559	240,978
Total liabilities and stockholders’ equity	$ 282,343	$ 344,069

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2025	Dec. 31, 2024
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	27,235,000	27,096,000
Common stock, shares outstanding	27,235,000	27,096,000

Revenue - Summary of Changes in Balances of Contract Assets Liability (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2025 USD ($)
Revenue from Contract with Customer [Abstract]
Accounts receivable, Balance	$ 3,974
Additions	53,189
Deductions	(49,212)
Accounts receivable, Balance	7,951
Deferred revenue, Balance	32,118
Additions	53,763
Deductions	(74,835)
Deferred revenue, Balance	$ 11,046

Stockholders' Equity (Details Textual) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
	Dec. 23, 2022	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Class Of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share		500,000	700,000	400,000	1,100,000
Wells Fargo Credit Agreement [Member]
Class Of Stock [Line Items]
Issuance of common stock		0		0
Wells Fargo Credit Agreement [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Common stock issued, value	$ 200

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

- Definition

Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering.

+ References + Details

Segment Information - Summary of Reported Segment Revenues, Segment Loss and Income, and Significant Segment Expenses (Details) - USD ($)
$ in Thousands

3 Months Ended

9 Months Ended

Sep. 30, 2025

Jun. 30, 2025

Mar. 31, 2025

Sep. 30, 2024

Jun. 30, 2024

Mar. 31, 2024

Sep. 30, 2025

Sep. 30, 2024

Segment Reporting Information [Line Items]

Revenue

$ 17,151

$ 41,673

$ 74,835

$ 129,544

Total research and development

23,265

39,134

87,736

151,376

General and administrative

10,398

13,276

32,052

40,443

Other

^[1]

(3,064)

(3,834)

(8,249)

(11,339)

Net loss

(13,448)

$ (9,180)

$ (14,076)

(6,903)

$ (17,216)

$ (26,817)

(36,704)

(50,936)

LUNAR-COVID [Member]

Segment Reporting Information [Line Items]

Total research and development

3,890

12,035

13,530

55,092

LUNAR-OTC [Member]

Segment Reporting Information [Line Items]

Total research and development

780

890

5,257

7,200

BARDA [Member]

Segment Reporting Information [Line Items]

Total research and development

1,043

1,347

5,983

6,949

LUNAR-CF, Net [Member]

Segment Reporting Information [Line Items]

Total research and development

3,210

5,502

14,987

12,307

Early-Stage Programs [Member]

Segment Reporting Information [Line Items]

Total research and development

370

2,100

536

14,566

Discovery Technologies [Member]

Segment Reporting Information [Line Items]

Total research and development

1,720

2,071

6,346

4,123

Payroll and Benefits [Member]

Segment Reporting Information [Line Items]

Total research and development

9,693

13,718

33,347

43,234

Facilities and Equipment [Member]

Segment Reporting Information [Line Items]

Total research and development

$ 2,559

$ 1,471

$ 7,750

$ 7,905

[1]	Primarily includes interest income.

Revenue

9 Months Ended

Sep. 30, 2025

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 nine months ended September 30, 2025 in the balances of contract assets and liabilities as compared to what was disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024.


(in thousands)	December 31, 2024		Additions		Deductions			September 30, 2025
Contract Assets:
Accounts receivable	$	3,974	$	53,189	$	(49,212	)	$	7,951
Contract Liabilities:
Deferred revenue	$	32,118	$	53,763	$	(74,835	)	$	11,046

The following table summarizes the Company’s revenues for the periods indicated.


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(in thousands)	2025		2024		2025		2024
Collaboration Revenue:
CSL Seqirus	$	13,553	$	38,786	$	63,453	$	117,078
Other collaboration revenue		600		29		687		311
Total collaboration revenue	$	14,153	$	38,815	$	64,140	$	117,389
Grant revenue:
BARDA	$	1,895	$	2,858	$	9,591	$	12,155
Gates Foundation		1,103		—		1,104		—
Total grant revenue	$	2,998	$	2,858	$	10,695	$	12,155

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 processes. CSL Seqirus will lead the 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 infectious diseases. In September 2024, our COVID-19 vaccine KOSTAIVE® became the world’s first approved and commercially available self-amplifying RNA (sa-mRNA) vaccine.

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 is entitled to potentially receive up to $3.0 billion in commercial milestones based on “net sales” 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 for pandemic preparedness and against seasonal influenza as well as three other infectious disease pathogens. During the third quarter of 2025, the Company invoiced $4.1 million in upfront payments related to the CSL Collaboration Agreement. All amounts were included in accounts receivable as of September 30, 2025.

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 the delivery of the vaccine license, research and development services for COVID-19 and non-COVID-19 vaccines and regulatory activities for COVID-19 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 September 30, 2025, the transaction price consisted of upfront consideration received and milestones achieved. Additional variable consideration was not included in the transaction price as of September 30, 2025, 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 third quarter of 2025 relates to the license delivered, milestones achieved and services performed through September 30, 2025.

Total deferred revenue as of September 30, 2025 and December 31, 2024 for the CSL Collaboration Agreement was $8.7 million and $30.7 million, respectively.

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 September 30, 2025, the Company recognized $1.4 million related to the performance obligation, which was fully satisfied during the period.

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 Company recognized $5.3 million in revenue related to this customer option during the third quarter of 2024 upon the transfer of vaccine product to CSL Seqirus. The remaining $5.1 million, along with an estimated adjustment for costs in excess of previously invoiced amounts, was recognized as revenue during the quarter ended March 31, 2025 when the remaining vaccine product was 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

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 loss.

As of September 30, 2025, the remaining available funding net of revenue earned was $30.3 million.

Gates Foundation

During the three months ended September 30, 2025, the Company recognized $1.1 million of grant revenue related to cost reimbursement under two grants awarded by the Gates Foundation.

The grants support development of (i) a therapeutic HPV vaccine candidate and (ii) durability assessments of self-amplifying mRNA COVID-19 vaccine platforms. Grant funding is conditional upon achievement of defined milestones and submission of periodic progress and financial reports. Revenue is recognized as qualifying costs, including employee FTE labor and related expenses, are incurred in accordance with the terms of each agreement.

Unspent or uncommitted amounts remain deferred until the associated performance obligations are satisfied. As of September 30, 2025, deferred grant revenue related to these agreements totaled $2.3 million.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Other Balance Sheet Details - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Accrued Liabilities, Current [Abstract]
Accrued compensation	$ 4,956	$ 13,305
Cystic Fibrosis Foundation liability	6,577	7,443
Current portion of operating lease liability	$ 4,122	$ 3,552
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total	Total
Clinical trial accruals	$ 349	$ 2,828
Vinbiocare contractual liabilities	386	2,421
Legal accrual		130
Other accrued research and development expenses	2,992	9,102
Total	$ 19,382	$ 38,781

Related Party Transactions

9 Months Ended

Sep. 30, 2025

Related Party Transactions

Note 11. Related Party Transactions

Equity-method Investment - ARCALIS, Inc.

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. The Company’s share of the investees’ results is presented as either income or loss from equity-method investees in the accompanying consolidated statements of operations and comprehensive loss. As of September 30, 2025, the carrying value of the equity-method investment in ARCALIS remained at zero.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
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-Section 50
-Paragraph 1
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Commitments and Contingencies

9 Months Ended

Sep. 30, 2025

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, (i) CFF increased the amount it will award to advance LUNAR-CF to $24.6 million from approximately $15.6 million, and (ii) the Company agreed to incur at least $15.0 million toward activities under the research plan. During the fourth quarter of 2023, the Company received the full payment from CFF related to the amendment. Total contra expense recognized was $0.2 million and $0.9 million for the three and nine months ended September 30, 2025, respectively. A total expense of $0.3 million and a total contra expense of $0.5 million were recognized during the three and nine months ended September 30, 2024, respectively. As of September 30, 2025 and December 31, 2024, $6.6 million and $7.4 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. The Company was still engaged in the lease for the property and obligated to make the remaining lease payments through March 31, 2025, and therefore recorded an impairment loss in the amount of $1.3 million during the three months ended March 31, 2024, as there was no 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 the premises.

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 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 September 30, 2025, the remaining payments of the operating lease liability were as follows:


(in thousands)	Remaining Lease Payments
2025 (remainder of year)	$	1,287
2026		5,274
2027		4,132
2028		3,822
2029		3,937
Thereafter		11,813
Total remaining lease payments		30,265
Less: imputed interest		(4,278	)
Total operating lease liabilities	$	25,987
Weighted-average remaining lease term		6.6
Weighted-average discount rate		4.6	%

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 $1.3 million and $3.8 million for the three and nine months ended September 30, 2025, respectively, and $1.3 million and $4.1 million for the three and nine months ended September 30, 2024, respectively.

Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 5,729	$ 9,493	$ 18,591	$ 29,005
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	3,342	4,395	10,414	13,575
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 2,387	$ 5,098	$ 8,177	$ 15,430

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

Related Party Transactions - Equity-Method Investment (Details Textual)	Sep. 30, 2025 USD ($)
ARCALIS [Member]
Related Party Transaction [Line Items]
Carrying value of the equity-method investment	$ 0

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References + Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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+ Details

Share-Based Compensation Expense (Details Textual) - shares	Sep. 30, 2025	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	1,586,213
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	151,215

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Other Balance Sheet Details - Summary of Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 19,390	$ 21,342
Less accumulated depreciation and amortization	(11,971)	(11,811)
Property and equipment, net	7,419	9,531
Research equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	15,105	16,864
Computer and software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,069	1,131
Office equipment and furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	604	703
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,612	$ 2,644

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Operating activities
Net loss	$ (36,704)	$ (50,936)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,343	2,725
Share-based compensation expense	18,591	29,005
Foreign currency transaction loss	319	643
Changes in assets and liabilities:
Accounts receivable	(3,977)	1,865
Prepaid expense and other assets	4,088	(923)
Right-of-use assets	2,835	3,638
Accounts payable	(1,616)	4,852
Accrued liabilities	(19,718)	(625)
Deferred revenue	(21,072)	(47,051)
Lease liabilities	(3,133)	(2,656)
Net cash used in operating activities	(58,044)	(59,463)
Investing activities
Acquisition of property and equipment	(318)	(648)
Net cash used in investing activities	(318)	(648)
Financing activities
Proceeds from exercise of stock options	1,109	4,602
Proceeds from the issuance of common stock under equity plans	585	682
Proceeds from debt	15,000
Payments on debt obligations	(15,000)
Net cash provided by financing activities	1,694	5,284
Net decrease in cash, cash equivalents and restricted cash	(56,668)	(54,827)
Cash, cash equivalents and restricted cash at beginning of the period	293,913	348,890
Cash, cash equivalents and restricted cash at end of the period	237,245	294,063
Non-cash investing activities
Non-cash asset disposal	2,183	473
Right-of-use assets acquired through operating leases		$ 2,736
Purchase of property and equipment in accounts payable	$ (87)

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Sep. 30, 2025
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	Rule 10b5-1 Trading Arrangements During the three months ended September 30, 2025, none of our directors or officers, as defined in Rule 16a-1(f) of the Exchange Act, 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.
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Revenue - Summary of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation Of Revenue [Line Items]
Total revenue	$ 17,151	$ 41,673	$ 74,835	$ 129,544
Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	14,153	38,815	64,140	117,389
Grant Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	2,998	2,858	10,695	12,155
CSL Seqirus [Member] \| Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	13,553	38,786	63,453	117,078
Other Collaboration Revenue [Member] \| Collaboration Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	600	29	687	311
BARDA [Member] \| Grant Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	1,895	$ 2,858	9,591	$ 12,155
Gates Foundation [Member] \| Grant Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 1,103		$ 1,104

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

Other Balance Sheet Details - Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 180,360	$ 237,028	$ 237,178
Restricted cash	55,000	55,000	55,000
Non-current restricted cash	1,885	1,885	1,885
Total cash, cash equivalents and restricted cash	$ 237,245	$ 293,913	$ 294,063	$ 348,890

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2025
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, 2024. 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. There were no significant changes to our significant accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024.
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 (“FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. 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. In November 2024, the FASB issued ASU 2024-03, Income Statement–Reporting Comprehensive Income–Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, which requires public entities to disclose specified information about certain costs and expenses on an interim and annual basis. ASU 2024-03 is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the impact that adoption of ASU 2024-03 will have on the financial statement disclosures. In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures. The new standard requires a company to expand its existing income tax disclosures, specifically related to the rate reconciliation and income taxes paid. The standard is effective for the Company beginning in fiscal year 2025, with early adoption permitted. The Company does not expect to early adopt the new standard. The new standard is expected to be applied prospectively, but retrospective application is permitted. The Company is currently evaluating the impact of ASU 2023-09 on the financial statements and related disclosures.

Share-Based Compensation Expense

9 Months Ended

Sep. 30, 2025

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 approved 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 September 30, 2025, a total of 1,586,213 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. Pursuant to the terms of the plan, shares underlying awards that are forfeited, cancelled, or terminated without issuance are returned to the share reserve. As of September 30, 2025, a total of 151,215 shares remain available for future issuance under the 2021 Plan, subject to the terms of the 2021 Plan.

Share-Based Compensation

Share-based compensation expense included in the Company’s condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2025 and 2024 was as follows:


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(in thousands)	2025		2024		2025		2024
Research and development	$	3,342	$	4,395	$	10,414	$	13,575
General and administrative		2,387		5,098		8,177		15,430
Total	$	5,729	$	9,493	$	18,591	$	29,005

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2025

Commitments and Contingencies Disclosure [Abstract]

Remaining Payments of Operating Lease Liability

As of September 30, 2025, the remaining payments of the operating lease liability were as follows:


(in thousands)	Remaining Lease Payments
2025 (remainder of year)	$	1,287
2026		5,274
2027		4,132
2028		3,822
2029		3,937
Thereafter		11,813
Total remaining lease payments		30,265
Less: imputed interest		(4,278	)
Total operating lease liabilities	$	25,987
Weighted-average remaining lease term		6.6
Weighted-average discount rate		4.6	%

Segment Information - Additional Information (Details)	9 Months Ended
Segment Information - Additional Information (Details)	Sep. 30, 2025 Segment
Segment Reporting [Abstract]
Number of business segment	1
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description	The Company’s CODM is its Chief Executive Officer, who reviews and evaluates consolidated net loss for purposes of assessing performance, making operating decisions, allocating resources, and planning and forecasting for future periods.

Segment Information (Tables)

9 Months Ended

Sep. 30, 2025

Segment Reporting [Abstract]

Summary of Reported Segment Revenues, Segment Loss and Income, and Significant Segment Expenses

The following table presents information about reported segment revenues, segment loss and income, and significant segment expenses:


	For the Three Months Ended September 30,						For the Nine Months Ended September 30,
(in thousands)	2025			2024			2025			2024
Revenues	$	17,151		$	41,673		$	74,835		$	129,544
Less:
Research and development:
LUNAR-COVID		3,890			12,035			13,530			55,092
LUNAR-OTC		780			890			5,257			7,200
BARDA		1,043			1,347			5,983			6,949
LUNAR-CF, net		3,210			5,502			14,987			12,307
Early-stage programs		370			2,100			536			14,566
Discovery technologies		1,720			2,071			6,346			4,123
Payroll and benefits		9,693			13,718			33,347			43,234
Facilities and equipment		2,559			1,471			7,750			7,905
Total research and development		23,265			39,134			87,736			151,376
General and administrative		10,398			13,276			32,052			40,443
Other (1)		(3,064	)		(3,834	)		(8,249	)		(11,339	)
Net loss	$	(13,448	)	$	(6,903	)	$	(36,704	)	$	(50,936	)

(1) Primarily includes interest income.

Revenue (Details Textual) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
Revenue (Details Textual) - USD ($) $ in Thousands	Nov. 01, 2022	Aug. 31, 2022	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2024	Mar. 31, 2024
Revenue [Line Items]
Deferred revenue			$ 11,046		$ 11,046			$ 32,118
Revenue recognized					(74,835)
Seqirus Inc [Member] \| COVID-19 Vaccine [Member]
Revenue [Line Items]
Revenue recognized				$ 5,100		$ 5,300
BARDA [Member]
Revenue [Line Items]
Total grant revenue		$ 63,200
Grant revenue outstanding					30,300
Gates Foundation [Member] \| Grant Revenue [Member]
Revenue [Line Items]
Deferred revenue			2,300		2,300
Revenue recognized			1,100
Research Collaboration And License Agreement [Member] \| Seqirus Inc [Member]
Revenue [Line Items]
Upfront payment received	$ 200,000
Research Collaboration And License Agreement [Member] \| Seqirus Inc [Member] \| COVID-19 Vaccine [Member]
Revenue [Line Items]
Net profits percentage	40.00%
Development milestones received advance payment							$ 5,300		$ 5,100
Research Collaboration And License Agreement [Member] \| Maximum [Member] \| Seqirus Inc [Member]
Revenue [Line Items]
Eligible to receive development milestone payment	$ 1,300,000
Eligible to receive commercial milestone payment	$ 3,000,000
CSL Collaboration Agreement [Member]
Revenue [Line Items]
Upfront payments invoiced			4,100
Deferred revenue			8,700		$ 8,700			$ 30,700
CSL Collaboration Agreement [Member] \| Phase I Clinical Study [Member]
Revenue [Line Items]
Milestone payments							17,500
Revenue recognized			$ 1,400
CSL Collaboration Agreement [Member] \| Maximum [Member] \| Phase I Clinical Study [Member]
Revenue [Line Items]
Additional payments upon meeting certain clinical milestones							$ 1,500

Revenue (Tables)

9 Months Ended

Sep. 30, 2025

Revenue from Contract with Customer [Abstract]

Summary of Changes in Balances of Receivables and Contract Liability


(in thousands)	December 31, 2024		Additions		Deductions			September 30, 2025
Contract Assets:
Accounts receivable	$	3,974	$	53,189	$	(49,212	)	$	7,951
Contract Liabilities:
Deferred revenue	$	32,118	$	53,763	$	(74,835	)	$	11,046

Schedule of Revenue

The following table summarizes the Company’s revenues for the periods indicated.


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(in thousands)	2025		2024		2025		2024
Collaboration Revenue:
CSL Seqirus	$	13,553	$	38,786	$	63,453	$	117,078
Other collaboration revenue		600		29		687		311
Total collaboration revenue	$	14,153	$	38,815	$	64,140	$	117,389
Grant revenue:
BARDA	$	1,895	$	2,858	$	9,591	$	12,155
Gates Foundation		1,103		—		1,104		—
Total grant revenue	$	2,998	$	2,858	$	10,695	$	12,155

Fair Value Measurements

9 Months Ended

Sep. 30, 2025

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 relatively short maturities.

As of September 30, 2025 and December 31, 2024, 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.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
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+ Details

Share-Based Compensation Expense (Tables)

9 Months Ended

Sep. 30, 2025

Share-Based Payment Arrangement [Abstract]

Schedule of Share-based Compensation Expenses


	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(in thousands)	2025		2024		2025		2024
Research and development	$	3,342	$	4,395	$	10,414	$	13,575
General and administrative		2,387		5,098		8,177		15,430
Total	$	5,729	$	9,493	$	18,591	$	29,005

Commitments and Contingencies - Remaining Payments of Operating Lease Liability (Details) $ in Thousands	Sep. 30, 2025 USD ($)
Leases [Abstract]
2025 (remainder of year)	$ 1,287
2026	5,274
2027	4,132
2028	3,822
2029	3,937
Thereafter	11,813
Total remaining lease payments	30,265
Less: imputed interest	(4,278)
Total operating lease liabilities	$ 25,987
Weighted-average remaining lease term	6 years 7 months 6 days
Weighted-average discount rate	4.60%

Debt

9 Months Ended

Sep. 30, 2025

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 in 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 amounts were drawn down under the Loan during the three months ended September 30, 2025.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

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Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Commitments and Contingencies (Details Textual) - USD ($) $ in Millions		1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended	50 Months Ended
	Aug. 01, 2019	Sep. 30, 2021	Oct. 31, 2017	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Sep. 25, 2023	Feb. 29, 2020
Commitment And Contingencies [Line Items]
Operating lease costs				$ 1.3		$ 1.3	$ 3.8	$ 4.1
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			$ 0.1
Security deposit			$ 0.1
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					$ 1.3
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		$ 2.0
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Contra expense remaining amount included in accrued expenses							$ 6.6		$ 7.4
Minimum amount agreed to incur under research plan										$ 15.0
Total expense recognized period						$ 0.3
Contra expense included in research and development expense				$ 0.2			$ 0.9	$ 0.5
Underlying Agreement [Member] \| LUNAR-CF [Member] \| Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Payments for advance	$ 15.6									$ 24.6
Maximum [Member] \| September 2021 Lease Agreement [Member]
Commitment And Contingencies [Line Items]
Monthly base rent		0.4
Minimum [Member] \| September 2021 Lease Agreement [Member]
Commitment And Contingencies [Line Items]
Monthly base rent		$ 0.3

Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Income Taxes (Details Textual) - USD ($) $ in Thousands	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	$ (217)	$ 4	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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+ Details

Subsequent Events

9 Months Ended

Sep. 30, 2025

Subsequent Events [Abstract]

Subsequent Events

Note 12. Subsequent Events

Change of Corporate Headquarters

On November 6, 2025, the Company changed its corporate headquarters from 10628 Science Center Drive, Suite 250 San Diego, California 92121, to 10285 Science Center Drive, San Diego, California 92121 (the “Address Change”) in order to order to consolidate administrative operations into a single facility. There was no material impact on the Company’s operations, financial position, or results of operations as a result of the Address Change.

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, 2023	$ 278,513	$ 27	$ 646,352	$ (367,866)
Balance (in shares) at Dec. 31, 2023		26,828
Net 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 loss	(50,936)
Balance at Sep. 30, 2024	261,866	$ 27	680,641	(418,802)
Balance (in shares) at Sep. 30, 2024		27,084
Balance at Mar. 31, 2024	263,972	$ 27	658,628	(394,683)
Balance (in shares) at Mar. 31, 2024		26,917
Net 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
Net loss	(6,903)			(6,903)
Share-based compensation expense	9,493		9,493
Issuance of common stock upon exercise of stock options	11		11
Issuance of common stock upon exercise of stock options (in shares)		2
Issuance of common stock under equity plans	682		682
Issuance of common stock under equity plans (in shares)		40
Balance at Sep. 30, 2024	261,866	$ 27	680,641	(418,802)
Balance (in shares) at Sep. 30, 2024		27,084
Balance at Dec. 31, 2024	240,978	$ 27	689,758	(448,807)
Balance (in shares) at Dec. 31, 2024		27,096
Net loss	(14,076)			(14,076)
Share-based compensation expense	6,662		6,662
Issuance of common stock upon exercise of stock options	195		195
Issuance of common stock upon exercise of stock options (in shares)		25
Balance at Mar. 31, 2025	233,759	$ 27	696,615	(462,883)
Balance (in shares) at Mar. 31, 2025		27,121
Balance at Dec. 31, 2024	240,978	$ 27	689,758	(448,807)
Balance (in shares) at Dec. 31, 2024		27,096
Net loss	(36,704)
Balance at Sep. 30, 2025	224,559	$ 27	710,043	(485,511)
Balance (in shares) at Sep. 30, 2025		27,235
Balance at Mar. 31, 2025	233,759	$ 27	696,615	(462,883)
Balance (in shares) at Mar. 31, 2025		27,121
Net loss	(9,180)			(9,180)
Share-based compensation expense	6,200		6,200
Issuance of common stock upon exercise of stock options	274		274
Issuance of common stock upon exercise of stock options (in shares)		27
Balance at Jun. 30, 2025	231,053	$ 27	703,089	(472,063)
Balance (in shares) at Jun. 30, 2025		27,148
Net loss	(13,448)			(13,448)
Share-based compensation expense	5,729		5,729
Issuance of common stock upon exercise of stock options	640		640
Issuance of common stock upon exercise of stock options (in shares)		52
Issuance of common stock under equity plans	585		585
Issuance of common stock under equity plans (in shares)		35
Balance at Sep. 30, 2025	$ 224,559	$ 27	$ 710,043	$ (485,511)
Balance (in shares) at Sep. 30, 2025		27,235

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

- Definition

Amount of equity (deficit) attributable to parent. Excludes temporary equity and equity attributable to noncontrolling interest.

+ References

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+ Details

Other Balance Sheet Details (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
Other Balance Sheet Details (Details Textual) - USD ($)	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Apr. 21, 2023
Public Utilities, Inventory [Line Items]
Depreciation and amortization expenses	$ 800,000	$ 900,000	$ 2,343,000	$ 2,725,000
Cash proceeds from disposed of fully depreciated assets	0
Non-current restricted cash	1,885,000	1,885,000	1,885,000	1,885,000	$ 1,885,000
Property Leases in San Diego [Member]
Public Utilities, Inventory [Line Items]
Non-current restricted cash	1,900,000	$ 1,900,000	1,900,000	$ 1,900,000
Wells Fargo Credit Agreement [Member]
Public Utilities, Inventory [Line Items]
Debt instrument, collateral amount	$ 55,000,000		$ 55,000,000			$ 55,000,000

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Pay vs Performance Disclosure
Net Income (Loss)	$ (13,448)	$ (9,180)	$ (14,076)	$ (6,903)	$ (17,216)	$ (26,817)	$ (36,704)	$ (50,936)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Segment Information

9 Months Ended

Sep. 30, 2025

Segment Reporting [Abstract]

Segment Information

Note 10. Segment Information

The Company operates in one business segment, which includes all activities related to the discovery, development and commercialization of messenger RNA medicines. The determination of a single business segment is consistent with the consolidated financial information regularly provided to the Company’s chief operating decision maker (“CODM”). The Company’s CODM is its Chief Executive Officer, who reviews and evaluates consolidated net loss for purposes of assessing performance, making operating

decisions, allocating resources, and planning and forecasting for future periods. The CODM does not evaluate the operating segment using asset or liability information.

The following table presents information about reported segment revenues, segment loss and income, and significant segment expenses:


	For the Three Months Ended September 30,						For the Nine Months Ended September 30,
(in thousands)	2025			2024			2025			2024
Revenues	$	17,151		$	41,673		$	74,835		$	129,544
Less:
Research and development:
LUNAR-COVID		3,890			12,035			13,530			55,092
LUNAR-OTC		780			890			5,257			7,200
BARDA		1,043			1,347			5,983			6,949
LUNAR-CF, net		3,210			5,502			14,987			12,307
Early-stage programs		370			2,100			536			14,566
Discovery technologies		1,720			2,071			6,346			4,123
Payroll and benefits		9,693			13,718			33,347			43,234
Facilities and equipment		2,559			1,471			7,750			7,905
Total research and development		23,265			39,134			87,736			151,376
General and administrative		10,398			13,276			32,052			40,443
Other (1)		(3,064	)		(3,834	)		(8,249	)		(11,339	)
Net loss	$	(13,448	)	$	(6,903	)	$	(36,704	)	$	(50,936	)

(1) Primarily includes interest income.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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-Section 50
-Paragraph 21
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+ Details

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2025

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 commercial messenger RNA medicines company focused on the development of liver and respiratory rare disease therapeutics and infectious disease vaccines. Arcturus became a clinical stage company in 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. In 2023, our COVID-19 vaccine, ARCT-154 (also referred to as KOSTAIVE®), received marketing authorization approval in Japan for adults 18 years and older, and in September 2024 KOSTAIVE became the world’s first approved and commercially available self-amplifying RNA (sa-mRNA) vaccine.

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, 2024.

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.

There were no significant changes to our significant accounting policies as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024.

Recently Issued Accounting Standards Not Yet Adopted

From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) or other standard setting bodies and adopted by the Company as of the specified effective date. 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.

In November 2024, the FASB issued ASU 2024-03, Income Statement–Reporting Comprehensive Income–Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, which requires public entities to disclose specified information about certain costs and expenses on an interim and annual basis. ASU 2024-03 is effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the impact that adoption of ASU 2024-03 will have on the financial statement disclosures.

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740) - Improvements to Income Tax Disclosures. The new standard requires a company to expand its existing income tax disclosures, specifically related to the rate reconciliation and income taxes paid. The standard is effective for the Company beginning in fiscal year 2025, with early adoption permitted. The Company does not expect to early adopt the new standard. The new standard is expected to be applied prospectively, but retrospective application is permitted. The Company is currently evaluating the impact of ASU 2023-09 on the financial statements and related disclosures.

Debt (Details Textual) - Wells Fargo Credit Agreement [Member] - USD ($)			3 Months Ended
	Jun. 26, 2024	Apr. 21, 2023	Sep. 30, 2025
Debt Instrument [Line Items]
Revolving credit line available		$ 50,000,000
Loans interest rate, percentage		2.00%
Term of agreement		2 years
Extended term period	1 year
Option for renewal term		1 year
Non-refundable commitment fee, percentage		0.25%
Loan accrued interest rate per annum, percentage		1.00%
Debt instrument, collateral amount		$ 55,000,000	$ 55,000,000
Repayment of loan			$ 0

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Revenue:
Total revenue	$ 17,151	$ 41,673	$ 74,835	$ 129,544
Operating expenses:
Research and development, net	23,265	39,134	87,736	151,376
General and administrative	10,398	13,276	32,052	40,443
Total operating expenses	33,663	52,410	119,788	191,819
Loss from operations	(16,512)	(10,737)	(44,953)	(62,275)
Loss from foreign currency	(170)	(201)	(319)	(642)
Finance income, net	3,234	3,818	8,572	11,981
Net loss before income taxes	(13,448)	(7,120)	(36,700)	(50,936)
Provision (benefit) for income taxes		(217)	4	0
Net loss	$ (13,448)	$ (6,903)	$ (36,704)	$ (50,936)
Net loss per share:
Basic	$ (0.49)	$ (0.26)	$ (1.35)	$ (1.89)
Diluted	$ (0.49)	$ (0.26)	$ (1.35)	$ (1.89)
Weighted-average shares outstanding:
Basic	27,188	27,062	27,142	26,970
Diluted	27,188	27,062	27,142	26,970
Comprehensive loss:
Net loss	$ (13,448)	$ (6,903)	$ (36,704)	$ (50,936)
Comprehensive loss	(13,448)	(6,903)	(36,704)	(50,936)
Collaboration Revenue [Member]
Revenue:
Total revenue	14,153	38,815	64,140	117,389
Grant Revenue [Member]
Revenue:
Total revenue	$ 2,998	$ 2,858	$ 10,695	$ 12,155

Other Balance Sheet Details (Tables)

9 Months Ended

Sep. 30, 2025

Balance Sheet Related Disclosures [Abstract]

Summary of Components of Property and Equipment, Net

Property and equipment, net balances consisted of the following:


(in thousands)	September 30, 2025			December 31, 2024
Research equipment	$	15,105		$	16,864
Computers and software		1,069			1,131
Office equipment and furniture		604			703
Leasehold improvements		2,612			2,644
Total		19,390			21,342
Less accumulated depreciation and amortization		(11,971	)		(11,811	)
Property and equipment, net	$	7,419		$	9,531

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following:


(in thousands)	September 30, 2025		December 31, 2024
Accrued compensation	$	4,956	$	13,305
Cystic Fibrosis Foundation liability		6,577		7,443
Current portion of operating lease liability		4,122		3,552
Clinical trial accruals		349		2,828
Vinbiocare contractual liabilities		386		2,421
Legal accrual		—		130
Other accrued research and development expenses		2,992		9,102
Total	$	19,382	$	38,781

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 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 September 30, 2025 and 2024:


(in thousands)	September 30, 2025		September 30, 2024
Cash and cash equivalents	$	180,360	$	237,178
Restricted cash		55,000		55,000
Non-current restricted cash		1,885		1,885
Total cash, cash equivalents and restricted cash	$	237,245	$	294,063

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2025	Nov. 05, 2025
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	Q3
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	10285 Science Center Drive
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		28,412,537
Document Quarterly Report	true
Document Transition Report	false
Former Address [Member]
Document Information [Line Items]
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

Other Balance Sheet Details

9 Months Ended

Sep. 30, 2025

Balance Sheet Related Disclosures [Abstract]

Other Balance Sheet Details

Note 4. Other Balance Sheet Details

Property and equipment, net balances consisted of the following:


(in thousands)	September 30, 2025			December 31, 2024
Research equipment	$	15,105		$	16,864
Computers and software		1,069			1,131
Office equipment and furniture		604			703
Leasehold improvements		2,612			2,644
Total		19,390			21,342
Less accumulated depreciation and amortization		(11,971	)		(11,811	)
Property and equipment, net	$	7,419		$	9,531

Depreciation and amortization expense was $0.8 million and $2.3 million for the three and nine months ended September 30, 2025, respectively, and $0.9 million and $2.7 million for the three and nine months ended September 30, 2024, respectively. During the three months ended September 30, 2025, the Company disposed of certain fully depreciated assets with no cash proceeds.

Accrued liabilities consisted of the following:


(in thousands)	September 30, 2025		December 31, 2024
Accrued compensation	$	4,956	$	13,305
Cystic Fibrosis Foundation liability		6,577		7,443
Current portion of operating lease liability		4,122		3,552
Clinical trial accruals		349		2,828
Vinbiocare contractual liabilities		386		2,421
Legal accrual		—		130
Other accrued research and development expenses		2,992		9,102
Total	$	19,382	$	38,781


(in thousands)	September 30, 2025		September 30, 2024
Cash and cash equivalents	$	180,360	$	237,178
Restricted cash		55,000		55,000
Non-current restricted cash		1,885		1,885
Total cash, cash equivalents and restricted cash	$	237,245	$	294,063

Restricted cash includes collateral pledged and held in the Company’s securities accounts pursuant to a security agreement with Wells Fargo Bank, National Association (“Wells Fargo”) (Note 5). As of September 30, 2025, 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 of the Company’s offices. As of September 30, 2025 and 2024, the Company had restricted cash of $1.9 million in conjunction with property leases in San Diego, California, and such restriction is expected to be removed at the end of the lease term.

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Details Textual)	9 Months Ended
	Sep. 30, 2025
Accounting Policies [Abstract]
COVID vaccination age limit	adults 18 years and older

Stockholders' Equity

9 Months Ended

Sep. 30, 2025

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 as they were anti-dilutive totaled 0.5 million and 0.4 million for three and nine months ended September 30, 2025, respectively, and 0.7 million and 1.1 million for the three and nine months ended September 30, 2024, 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 million from time to time through Cantor, Wells Fargo Securities, or William Blair, each acting as the Company's sales agent. During the three and nine months ended September 30, 2025 the Company did not offer or sell any shares of common stock pursuant to the Sales Agreement.

- Definition

The entire disclosure for equity.

+ References

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+ Details