0001564590-20-052527 | 10-Q | XBRL Viewer | Arcturus Therapeutics Holdings INC

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Share-Based Compensation (Details Textual) - shares	Sep. 30, 2020	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	5,526,998
2019 Omnibus Equity Incentive Plan [Member] \| Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	2,388,340
2019 Omnibus Equity Incentive Plan [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized		2,400,000
2019 Omnibus Equity Incentive Plan [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized		5,000,000	2,600,000
2020 Employee Stock Purchase Plan [Member] \| Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance		600,000

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 307,023	$ 71,353
Accounts receivable	2,447	2,179
Prepaid expenses and other current assets	4,630	758
Total current assets	314,100	74,290
Property and equipment, net	3,451	2,349
Operating lease right-of-use asset, net	4,862	5,134
Equity-method investment		263
Non-current restricted cash	107	107
Total assets	322,520	82,143
Current liabilities:
Accounts payable	6,478	5,793
Accrued liabilities	15,838	7,134
Deferred revenue	5,698	8,397
Total current liabilities	28,014	21,324
Deferred revenue, net of current portion	13,645	15,182
Long-term debt	15,076	14,995
Operating lease liability, net of current portion	4,155	4,850
Total liabilities	60,890	56,351
Stockholders' equity
Common stock: $0.001 par value; 30,000 shares authorized; 24,473 and 15,138 issued and outstanding at September 30, 2020 and December 31, 2019, respectively.	25	15
Additional paid-in capital	374,317	97,445
Accumulated deficit	(112,712)	(71,668)
Total stockholders' equity	261,630	25,792
Total liabilities and stockholders' equity	$ 322,520	$ 82,143

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Ultragenyx [Member]	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Common Stock [Member] Ultragenyx [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Ultragenyx [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]
Balance at Dec. 31, 2018	$ 13,642		$ (803)	$ 214		$ 58,302		$ (44,874)	$ (803)
Balance (in shares) at Dec. 31, 2018				10,762
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201409Member
Net loss	$ (15,002)							(15,002)
Treasury Stock (in shares)				(43)
Issuance of common stock, net of issuance costs	21,278			$ 2		21,276
Issuance of common stock, net of issuance costs (in shares)				1,995
Issuance of common stock upon exercise of stock options	50					50
Issuance of common stock upon exercise of stock option (in shares)				12
Share-based compensation	1,185					1,185
Redomiciliation share exchange				$ (203)		203
Issuance of common stock to Ultragenyx and option, net of issuance costs		$ 15,545			$ 2		$ 15,543
Issuance of common stock to Ultragenyx and option, net of issuance costs (in shares)					2,400
Balance at Sep. 30, 2019	35,895			$ 15		96,559		(60,679)
Balance (in shares) at Sep. 30, 2019				15,126
Balance at Jun. 30, 2019	21,618			$ 13		74,851		(53,246)
Balance (in shares) at Jun. 30, 2019				13,120
Net loss	(7,433)							(7,433)
Issuance of common stock, net of issuance costs	21,278			$ 2		21,276
Issuance of common stock, net of issuance costs (in shares)				1,995
Issuance of common stock upon exercise of stock options	49					49
Issuance of common stock upon exercise of stock option (in shares)				11
Share-based compensation	383					383
Balance at Sep. 30, 2019	35,895			$ 15		96,559		(60,679)
Balance (in shares) at Sep. 30, 2019				15,126
Balance at Dec. 31, 2019	25,792			$ 15		97,445		(71,668)
Balance (in shares) at Dec. 31, 2019				15,138
Net loss	(41,044)							(41,044)
Issuance of common stock, net of issuance costs	261,883			$ 9		261,874
Issuance of common stock, net of issuance costs (in shares)				8,489
Issuance of common stock upon exercise of stock options	1,461					1,461
Issuance of common stock upon exercise of stock option (in shares)				246
Share-based compensation	3,938					3,938
Issuance of common stock to Ultragenyx and option, net of issuance costs		$ 9,600			$ 1		$ 9,599
Issuance of common stock to Ultragenyx and option, net of issuance costs (in shares)					600
Balance at Sep. 30, 2020	261,630			$ 25		374,317		(112,712)
Balance (in shares) at Sep. 30, 2020				24,473
Balance at Jun. 30, 2020	93,423			$ 21		185,110		(91,708)
Balance (in shares) at Jun. 30, 2020				20,610
Net loss	(21,004)							(21,004)
Issuance of common stock, net of issuance costs	186,578			$ 4		186,574
Issuance of common stock, net of issuance costs (in shares)				3,754
Issuance of common stock upon exercise of stock options	645					645
Issuance of common stock upon exercise of stock option (in shares)				109
Share-based compensation	1,988					1,988
Balance at Sep. 30, 2020	$ 261,630			$ 25		$ 374,317		$ (112,712)
Balance (in shares) at Sep. 30, 2020				24,473

Collaboration Revenue

9 Months Ended

Sep. 30, 2020

Collaboration Agreements [Abstract]

Collaboration Revenue

Note 2. Collaboration Revenue

The Company has entered into license agreements and collaborative research and development arrangements with pharmaceutical and biotechnology companies. Under these arrangements, the Company is entitled to receive license fees, upfront payments, milestone payments if and when certain research and development milestones or technology transfer milestones are achieved, royalties on approved product sales and reimbursement for research and development activities. The Company’s costs of performing these services are included within research and development expenses. The Company’s milestone payments are typically defined by achievement of certain preclinical, clinical, and commercial success criteria. Preclinical milestones may, for example, 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.

The following table presents changes during the nine months ended September 30, 2020 in the balances of contract assets, including receivables from collaborative partners, and contract liabilities, including deferred revenue, as compared to what was disclosed in the Company’s 2019 Annual Report on Form 10-K.

(in thousands)	Contract Assets
BALANCE - December 31, 2019	$	2,179
Additions for revenue recognized from billings		3,065
Deductions for cash collections		(2,797	)
BALANCE – September 30, 2020	$	2,447

(in thousands)	Contract Liabilities
BALANCE - December 31, 2019	$	23,579
Additions for advanced billings		3,065
Deductions for promised services provided in current period		(7,301	)
BALANCE – September 30, 2020	$	19,343

The following table summarizes the Company’s collaboration revenues for the periods indicated (in thousands).

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(Dollars in thousands)	2020		2019		2020		2019
Collaboration Partner – Janssen	$	879	$	966	$	2,469	$	2,101
Collaboration Partner – Ultragenyx		912		922		2,736		4,854
Collaboration Partner – CureVac		241		1,057		782		6,360
Collaboration Partner – Other		301		373		1,314		4,506
Total collaboration revenue	$	2,333	$	3,318	$	7,301	$	17,821

The following paragraphs provide information regarding the nature and purpose of the Company’s most significant collaboration arrangements.

Collaboration Partner – Janssen

In October 2017, the Company entered into a research collaboration and license agreement with Janssen (the “2017 Agreement”). The 2017 Agreement allocated discovery, development, funding obligations, and ownership of related intellectual property among the Company and Janssen Pharmaceuticals, Inc. (“Janssen”). The Company received an upfront payment of $7.7 million and may receive preclinical, development and sales milestone payments of up to $56.5 million, as well as royalty payments on any future licensed product sales. Janssen began reimbursing the Company for research costs during the first quarter of 2019 upon the completion of the first of three research periods. Janssen may also pay option exercise fees within the $1.0 million to $5.0 million range per target. Janssen will pay royalties as a low to mid-single digit percentage of net sales of licensed products, subject to reduction on a country-by-country and licensed-product-by-licensed-product basis and subject to certain events, such as expiration of program patents. In addition, the 2017 Agreement includes an exclusivity period.

In evaluating the 2017 Agreement in accordance with Accounting Standards Codification (“ASC”) Topic 606, the Company concluded that the contract counterparty, Janssen, is a customer. The Company identified the following promised goods/services as of the inception of the 2017 Agreement: (i) research services, (ii) license to use Arcturus technology and (iii) participation in a joint research committee. The Company concluded that the promised goods/services are incapable of being distinct and consequently do not have any value on a standalone basis. Accordingly, they are determined to represent a single performance obligation. The Company concluded that Janssen’s options to select additional collaboration targets and to license rights to selected targets are not priced at a discount and therefore do not represent performance obligations for which the transaction price would be allocated.

As of September 30, 2020, the remaining transaction price, consisting of upfront consideration received and budgeted reimbursable out-of-pocket costs, is expected to be recognized using an input method over the remaining research period of 24 months. None of the development and commercialization milestones were included in the transaction price, as all milestone amounts were not estimated to be met, are outside the control of the Company and contingent upon success in future clinical trials and Janssen’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur, provided that the reported sales are reliably measurable, and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to Janssen and therefore have also been excluded from the transaction price.

Total deferred revenue as of September 30, 2020 and December 31, 2019 for Janssen was $5.9 million.

Collaboration Partner – Ultragenyx

In October 2015 the Company entered into a research collaboration and license agreement with Ultragenyx (the “Ultragenyx Agreement”), whereby Arcturus granted to Ultragenyx a co-exclusive license to certain Arcturus technology, which is in effect only during the reserve target exclusivity term as discussed in the following paragraphs. This collaboration agreement was amended in 2017, 2018 and during the second quarter of 2019. During the initial phase of the collaboration, the Company will design and optimize therapeutics for certain rare disease targets. Ultragenyx has the option under the Ultragenyx Agreement to add additional rare disease targets during the collaborative development period. Additionally, during the collaborative development period, the Company will participate with Ultragenyx in a joint steering committee. The Ultragenyx Agreement also includes an initial exclusivity period with an option to extend such period.

As part of the Ultragenyx Agreement and related amendments, Ultragenyx has paid $27.9 million in upfront fees, exclusivity extension fees and additional consideration. Ultragenyx also reimburses the Company for all internal and external development costs incurred. Pursuant to the Ultragenyx Agreement, Ultragenyx is required to make additional payments upon exercise of the Ultragenyx expansion option or exclusivity extension (if any) and if Ultragenyx achieves certain, clinical, regulatory and sales milestones, then the Company is eligible to receive royalty payments. For each development target for which Ultragenyx exercises its option, Ultragenyx will pay the Company a one-time option exercise fee that increases based upon the number of development targets selected by Ultragenyx and ranges from $0.5 million to $1.5 million.

The current potential development, regulatory and commercial milestone payments for the existing development targets as of September 30, 2020 are $138.0 million. Ultragenyx will pay royalties as a single-digit percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term. As of September 30, 2020, Ultragenyx has not yet reached the clinical phase of the contract.

On June 18, 2019, Arcturus and Ultragenyx amended the collaboration agreement for a third time (“Amendment 3”). As part of Amendment 3, the total number of targets was increased from 10 to 12, and reserve targets will be exclusively reserved for Ultragenyx with no fees for four years after execution of the amendment. An equity component was also added as part of Amendment 3 wherein Ultragenyx purchased 2.4 million shares of common stock at a premium price. Along with the equity purchase, Ultragenyx received an option to purchase 0.6 million additional shares of common stock at $16 per share. In May 2020, the option was exercised.

The consideration received from Ultragenyx as a result of Amendment 3 was equal to $30.0 million and was comprised of a $24.0 million common stock purchase and a $6.0 million upfront payment. Specifically for Amendment 3, management determined the transaction price to be $14.4 million. See further discussion below regarding determining the transaction price. Management determined the fair value of the premium received by using the opening stock price subsequent to execution of Amendment 3 and applying a lack of marketability discount, as the shares received by Ultragenyx were initially restricted for up to two years. Pursuant to the terms of the equity purchase agreement between the Company and Ultragenyx, the transfer restrictions will terminate on November 20, 2020 as a result of the purchase of the 0.6 million option shares.

In evaluating the Ultragenyx agreement in accordance with ASC Topic 606, the Company concluded that the contract counterparty, Ultragenyx, is a customer. The Company has identified the following promised goods/services as part of the initial agreement and subsequent amendments: (i) research services, (ii) license to use Arcturus technology, (iii) exclusivity and (iv) participation in a joint steering committee. The Company concluded that the promised goods/services are incapable of being distinct and consequently do not have any value on a standalone basis. Accordingly, they are determined to represent a single performance obligation. The Company concluded that Ultragenyx’s options to extend exclusivity and select additional collaboration targets and to license rights to selected targets are not priced at a discount and therefore do not represent performance obligations for which the transaction price would be allocated.

As of September 30, 2020, the transaction price included the upfront consideration received, exclusivity extension payments and additional consideration received pursuant to Amendment 3. The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that the consideration is outside the control of the Company and contingent upon success in future clinical trials, approval from the FDA and the collaborator’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur as they are constrained, provided that the reported sales are reliably measurable and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to Ultragenyx and therefore have also been excluded from the transaction price.

Amendment 3 was deemed a contract modification and accounted for as part of the original Ultragenyx Agreement and the Company recorded a cumulative catch-up adjustment of $1.1 million on the modification date. The transaction price is recognized to revenue on a straight-line basis using an input method over the 4-year reserve target exclusivity period. The reserve target exclusivity period represents the timing over which promised goods/services will be provided. Total deferred revenue at September 30, 2020 and December 31, 2019 from Ultragenyx was $10.0 million and $12.7 million, respectively.

Collaboration Partner – CureVac

In January 2018, the Company entered into a Development and Option Agreement (the “Development and Option Agreement”) with CureVac AG (“CureVac”). Under the terms of the Development and Option Agreement, the parties agreed to conduct joint preclinical development programs once CureVac makes a payment to pull down a target on the basis of which CureVac is granted options for taking a license on pre-agreed license terms to develop and commercialize certain products incorporating the Company’s patents and know-how related to LUNAR delivery technology (the “Arcturus Delivery Technology”), and CureVac patents and know-how related to mRNA technology. Subject to certain restrictions, the parties will have an undivided one-half interest in the patents and know-how developed jointly by the parties during the course of the Development and Option Agreement. Pursuant to the terms of the Development and Option Agreement, CureVac will have a number of target options to co-develop from a reserved target list to enter into licenses under the Arcturus Delivery Technology with respect to the development, manufacture and commercialization of licensed products (which can include products identified for development by the Company, unless the Company is permitted by the terms of the Development and Option Agreement to place such products on a restricted list). A separate notice and fee will be required for each license agreement. If the target to which the license agreement relates is chosen by the parties for co-development under the Co-Development Agreement (as defined below and discussed in the following paragraph) the license agreement will terminate, as such programs will be covered under the Co-Development Agreement discussed below, and therefore CureVac will be given a credit for any exercise fees, milestone payments already paid and all other payments made in relation to the license agreement towards future such payments incurred with respect to future licenses under the Arcturus Delivery Technology.

Prior to expiration of the initial term of eight years (which was subsequently amended, as discussed below), the Development and Option Agreement also includes an option to extend the term on an annual basis for up to three years, subject to payment by CureVac to Arcturus of a non-refundable annual extension fee. The Development and Option Agreement includes potential milestone payments from CureVac to the Company for selected targets. The current potential milestone payments for the remaining targets as of September 30, 2020 are $14.0 million for rare disease targets and $23.0 million for non-rare disease targets. CureVac will pay royalties as a percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term in the low single-digit range. As of September 30, 2020, CureVac has not yet reached the clinical phase of the contract. Pursuant to a May 2018 amendment to the Development and Option Agreement (and as amended and restated on September 28, 2018), the Company increased the number of targets available to CureVac under the Development and Option Agreement and agreed upon the license forms to be executed upon selection of the targets by CureVac.

Concurrently with the Development and Option Agreement, the Company entered into a Co-Development and Co-Commercialization Agreement (the “Co-Development Agreement”) which the Company considered a combined contract with the Development and Option Agreement for purposes of revenue recognition. However, on February 11, 2019, the Company announced the termination of the obligations of CureVac for the preclinical development of ARCT-810, effective as of August 4, 2019, and the re-assumption by the Company of the worldwide rights thereto. As a result, Arcturus reassumed 100% global rights for clinical development candidate ARCT-810, a mRNA drug to treat OTC deficiency.

On July 26, 2019, the Company entered into an amendment (“CureVac Amendment”) to its Development and Option Agreement with CureVac (as amended, the “Development and Option Agreement”), pursuant to which the Company and CureVac agreed to shorten the time period during which CureVac may select potential targets to be licensed from the Company from eight years to four years, and to reduce the overall number of maximum targets that may be reserved and licensed.

In connection with the July 2019 CureVac Amendment, the Company and CureVac also entered into a Termination Agreement (the “Termination Agreement”) terminating the January 1, 2018 Co-Development Agreement between the Company and CureVac. Pursuant to the Termination Agreement, CureVac agreed to make a one-time payment to Arcturus in the amount of $4.0 million, which was made in July 2019.

In evaluating the CureVac Development and Option Agreement and Co-Development Agreement in accordance with ASC Topic 606, the Company concluded that the contract counterparty, CureVac, is a customer. The Company has identified the following promised goods/services as part of the initial agreement with CureVac and subsequent amendments: (i) research services, (ii) license to use Arcturus technology, (iii) exclusivity and (iv) participation in a joint steering committee. The Company concluded that the promised goods/services are incapable of being distinct and consequently do not have any value on a standalone basis. Accordingly, they are determined to represent a single performance obligation. The Company concluded that CureVac’s options to extend the research term and options to select additional collaboration targets and to license rights to selected targets are not priced at a discount and therefore do not represent performance obligations for which the transaction price would be allocated.

As of September 30, 2020, the transaction price included the upfront consideration received. The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the collaborator’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur as they are constrained, provided that the reported sales are reliably measurable and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to CureVac and therefore have also been excluded from the transaction price. For the three months ended September 30, 2020, no adjustments were made to the transaction price.

The upfront consideration of $5.0 million was recorded as deferred revenue in the Company’s balance sheet upon receipt and is currently being recognized as revenue on a straight-line basis using an input method over the remaining 34 month contractual term as of September 30, 2020. As a result of Amendment 3, the Company recorded a cumulative catch up adjustment of $0.4 million on the modification date, July 26, 2019. Total deferred revenue as of September 30, 2020 and December 31, 2019 for CureVac was $2.5 million and $3.2 million, respectively.

Other Collaboration Revenue

The remaining revenue from smaller collaboration agreements primarily relates to the agreements with Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”) and Synthetic Genomics, Inc. (“SGI”). Under the agreement with Takeda, the Company recognized $0.8 million during the first three quarters of 2020 which relates to the amortization of an upfront payment for research and development activities. The current agreement with Takeda was entered into on March 18, 2019 and is expected to be completed in the second quarter of 2021. Under the agreement with SGI, the Company recognized $0.3 million during the first three quarters of 2020 related to sublicensed technology.

Commitments and Contingencies

9 Months Ended

Sep. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 9. Commitments and Contingencies

COVID-19 Vaccine Development

On March 4, 2020, the Company was awarded a grant (the “Grant”) from the Singapore Economic Development Board to support the co-development of a potential COVID-19 vaccine with the Duke-NUS Medical School. The Grant provides for up to S$14.0 million (approximately US$10.1 million using the exchange rate at the time the grant contract was entered into) in grants to support the development of the vaccine. The Company entered into an amendment to the Grant on September 24, 2020 to update certain delivery and milestone timelines. The Grant has been paid in full by the Economic Development Board as a result of the achievement of certain milestones related to the progress of the development of the vaccine, as set forth in the award agreement. The funds received have been recognized as contra research and development expense in proportion to the percentage covered by the Economic Development Board of the overall budget. The Company is liable for certain expenses during the program. For the three and nine months ended September 30, 2020, the Company recognized $3.7 million and $7.9 million of contra expense, respectively, with $2.1 million remaining in accrued expenses.

On October 2, 2020, the Company was awarded another grant from the Singapore Economic Development Board to support the further development of a potential COVID-19 vaccine. The grant provides for up to S$9.3 million (approximately US$6.7 million) to support the development of the vaccine candidate. The grant will be paid in two installments upon the achievement of certain milestones related to the progress of the development of the vaccine candidate.

Cystic Fibrosis Foundation Agreement

On August 1, 2019, the Company amended its Development Program Letter Agreement, dated May 16, 2017 and as amended July 13, 2018, with the Cystic Fibrosis Foundation (“CFF”). Pursuant to the amendment, (i) CFF increased the amount it will award to advance LUNAR-CF to $15.0 million from approximately $3.2 million, (ii) the Company will provide $5.0 million in matching funds for remaining budgeted costs and (iii) the related disbursement schedule from CFF to Arcturus was modified such that (a) $4.0 million was disbursed upon execution of the CFF Amendment, (b) $2.0 million was disbursed within 30 days of the first day of each of January, April, July and October 2020 upon Arcturus invoicing CFF to meet project goals, and (c) the last payment of $3.0 million less the prior award previously paid out, equaling approximately $2.3 million, will be disbursed upon Arcturus Therapeutics, Inc. (i) invoicing CFF in order to allow it to meet good manufacturing practices and (ii) opening an IND application. The funds received from CFF will be recognized as contra research and development expense in proportion to the percentage covered by CFF of the overall budget. For the three and nine months ended September 30, 2020, the Company recognized $0.7 million and $3.7 million of contra expense, respectively, with $4.2 million remaining in accrued expenses. For the three and nine months ended September 30, 2019, the Company recognized $0.7 million of contra expense.

Leases

In October 2017, the Company entered into a non-cancellable operating lease agreement for office space adjacent to its previous headquarters. The commencement of the lease began in March 2018 and the lease extends for approximately 84 months from the commencement date with a remaining lease term through March 2025. Monthly rental payments are due under the lease and there are escalating rent payments during the term of the lease. The Company is also responsible for its proportional share of operating expenses of the building and common areas. In conjunction with the new lease, the Company received free rent for four months and received a tenant improvement allowance of $74,000. The lease may be extended for one five-year period at the then current market rate with annual escalations; however, the Company deemed the extension option not reasonably certain to be exercised and therefore excluded the option from the lease terms. The Company entered into an irrevocable standby letter of credit with the landlord for a security deposit of $96,000 upon executing the lease which is included (along with additional funds required to secure the letter of credit) in the balance of non-current restricted cash.

In February 2020, the Company entered into a non-cancellable operating lease agreement for office space near its current headquarters. The lease extends for 13 months from the commencement date. In conjunction with the new lease, the Company received free rent for one month. The lease may be extended for one twelve-month period, and in November 2020 the Company deemed the extension option reasonably certain to be exercised and will include the option in the lease terms beginning in October 2020.

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 September 30, 2020, the payments of the operating lease liability were as follows:

(in thousands)	Remaining Lease Payments
2020 (remaining)	$	496
2021		1,427
2022		1,349
2023		1,390
2024		1,432
Thereafter		314
Total remaining lease payments		6,408
Less: imputed interest		(1,055	)
Total operating lease liabilities	$	5,353
Weighted-average remaining lease term	4.3 years
Weighted-average discount rate		8.4	%

Operating lease costs consist of the fixed lease payments included in operating lease liability and are recorded on a straight-line basis over the lease term. Operating lease costs were $0.5 million and $1.3 million for the three and nine months ended September 30, 2020, respectively, and $0.3 million and $0.9 million for the three and nine months ended September 30, 2019, respectively.

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Details Textual) $ / shares in Units, $ in Millions	1 Months Ended			9 Months Ended
	Jul. 31, 2020 USD ($) $ / shares shares	May 31, 2020 USD ($) $ / shares shares	Apr. 30, 2020 USD ($) shares	Sep. 30, 2020 USD ($) Segment shares	Sep. 30, 2019 USD ($)	Oct. 31, 2020 USD ($)	Oct. 02, 2020 USD ($)	Oct. 02, 2020 SGD ($)	Apr. 20, 2020 $ / shares	Mar. 04, 2020 USD ($)	Mar. 04, 2020 SGD ($)	Dec. 31, 2019 shares
Summary Of Significant Accounting Policy [Line Items]
Proceeds from issuance of common stock, net of issuance costs				$ 261,883,000	$ 21,278,000
Common stock, shares issued \| shares				24,473,002								15,138,000
Number of operating segment for research and development \| Segment				1
Dividends declared or paid				$ 0	$ 0
ASU 2014-09 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted				true
Change in accounting principle, accounting standards update, adoption date				Jan. 01, 2019
ASU 2016-02 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in accounting principle, accounting standards update, adopted				true
Change in accounting principle, accounting standards update, adoption date				Mar. 31, 2019
Ultragenyx [Member]
Summary Of Significant Accounting Policy [Line Items]
Common stock, price per share \| $ / shares		$ 16
Common stock, shares issued \| shares		600,000
Proceeds from issuance of common stock on option exercise		$ 9,600,000
Co-Development and Phase 1/2 Clinical Trials [Member]
Summary Of Significant Accounting Policy [Line Items]
Funds received				$ 10,000,000
Underwritten Public Offering [Member]
Summary Of Significant Accounting Policy [Line Items]
Issuance of common stock, net of issuance costs (in shares) \| shares	3,753,773		4,735,297
Common stock, price per share \| $ / shares	$ 53.00								$ 17.00
Proceeds from issuance of common stock, net of issuance costs	$ 186,600,000
Minimum [Member] \| Underwritten Public Offering [Member]
Summary Of Significant Accounting Policy [Line Items]
Proceeds from issuance of common stock, net of issuance costs			$ 75,500,000
Singapore Economic Development Board [Member] \| Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Grant awarded										$ 10,100,000	$ 14.0
Singapore Economic Development Board [Member] \| Maximum [Member] \| Co-Development and Phase 1/2 Clinical Trials [Member]
Summary Of Significant Accounting Policy [Line Items]
Grant awarded										$ 16,800,000
Singapore Economic Development Board [Member] \| Maximum [Member] \| Subsequent Event [Member]
Summary Of Significant Accounting Policy [Line Items]
Grant awarded							$ 6,700,000	$ 9.3
Israeli Ministry of Health (“MOH”) [Member] \| Subsequent Event [Member]
Summary Of Significant Accounting Policy [Line Items]
Non-refundable payment received						$ 12,500,000

Commitments and Contingencies (Tables)

9 Months Ended

Sep. 30, 2020

Commitments And Contingencies Disclosure [Abstract]

Payments of Operating Lease Liability

As of September 30, 2020, the payments of the operating lease liability were as follows:

(in thousands)	Remaining Lease Payments
2020 (remaining)	$	496
2021		1,427
2022		1,349
2023		1,390
2024		1,432
Thereafter		314
Total remaining lease payments		6,408
Less: imputed interest		(1,055	)
Total operating lease liabilities	$	5,353
Weighted-average remaining lease term	4.3 years
Weighted-average discount rate		8.4	%

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

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

Basis of Presentation

The financial statements for periods prior to June 17, 2019, the effective date of the Company’s Redomiciliation to the United States (as described in the Company’s annual report on Form 10-K for the year ended December 31, 2019 (the “2019 Annual Report”)), relate to its predecessor, Arcturus Therapeutics Ltd., and for the periods from and after June 17, 2019 relate to Arcturus Therapeutics Holdings Inc. Unless stated otherwise or the context otherwise requires, references to the “Company,” “Arcturus,” “we,” “our” and “us” mean Arcturus Therapeutics Holdings Inc. and its consolidated subsidiaries from and after the effective time of the Redomiciliation and, prior to that time Arcturus Therapeutics Ltd.

The accompanying condensed consolidated financial statements include the accounts of Arcturus Therapeutics Holdings Inc. and its subsidiaries and, for the three and nine months ended September 30, 2020 and 2019, are unaudited. All intercompany accounts and transactions have been eliminated in consolidation. These condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. In management’s opinion, the accompanying condensed consolidated financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation of the results for the interim periods presented.

Interim financial results are not necessarily indicative of results anticipated for the full year. These condensed consolidated financial statements should be read in conjunction with the audited financial statements and footnotes included in the Company’s 2019 Annual Report.

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, deferred revenue, 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.

Liquidity

The Company’s activities since inception have consisted principally of research and development activities, general and administration activities, and raising capital. The Company’s activities are subject to significant risks and uncertainties, including failing to secure additional funding before the Company achieves sustainable revenues and profit from operations.

The Company is a clinical-stage bioscience company that is dependent on obtaining external equity and debt financings to fund its operations. Historically, the Company’s primary sources of financing have been through the sale of its securities, through issuance of debt and through collaboration agreements.

As mentioned above, the Company was recently awarded grants from the Singapore Economic Development Board of up to approximately $16.8 million in the aggregate to support the co-development and Phase 1/2 clinical trials of the LUNAR-COV19 vaccine candidate, part of which is being conducted with the Duke-NUS Medical School. Approximately $10.0 million of these grants were funded as of September 30, 2020. Additionally, in April 2020, the Company completed an underwritten public offering of 4,735,297 shares of common stock (including the underwriters’ overallotment option) at a price of $17.00 per share. The Company received net proceeds of approximately $75.5 million in the offering.

In May 2020, Ultragenyx Pharmaceutical Inc. (“Ultragenyx”) exercised its option to purchase 600,000 shares of the Company’s common stock at $16 per share. The Company received proceeds of $9.6 million as a result of the option exercise.

In July 2020 the Company completed an additional underwritten public offering of 3,753,773 shares of common stock (including the underwriters’ overallotment option) at a price of $53.00 per share. The Company received net proceeds of approximately $186.6 million in the offering.

Segment Information

Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company and its chief operating decision-maker view the Company’s operations and manage its business in one operating segment, which is the research and development of medical applications for the Company’s nucleic acid-focused technology.

Revenue Recognition

Effective January 1, 2019, the Company adopted Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) (“Topic 606”), using the modified retrospective transition method. Topic 606 provides a unified model to determine how revenue is recognized and the Company applied the standard to collaborative research and technology agreements that were in progress as of the effective date, January 1, 2019. The Company determines revenue recognition for arrangements within the scope of Topic 606 by performing the following five steps: (i) identify the contract, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations in the contract, and (v) recognize revenue when, or as, the Company satisfies a performance obligation.

The terms of the Company’s collaborative research and development agreements include license fees, upfront payments, milestone payments, reimbursement for research and development activities, option exercise fees, and royalties on sales of commercialized products. Arrangements that include upfront payments are recorded as deferred revenue upon receipt or when due and may require deferral of revenue recognition to a future period until the Company performs its obligations under these arrangements. The event-based milestone payments represent variable consideration, and the Company uses the most likely amount method to estimate this variable consideration because the potential milestone payment is a binary event, as the Company will either receive the milestone payment or it will not. 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 counterparty and is the unit of account under Topic 606. A contract’s transaction price is allocated to each distinct performance obligation based on relative standalone selling price and recognized as revenue when, or as, the performance obligation is satisfied.

See “Note 2, Collaboration Revenue” for specific details surrounding the Company’s collaboration arrangements.

Leases

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842), which requires lessees to recognize most leases on the balance sheet as lease liabilities with corresponding right-of-use assets and to disclose key information about leasing arrangements. The Company adopted Topic 842 on its effective date in the first quarter of 2019 using a modified retrospective approach. The Company elected the available package of practical expedients upon adoption, which allowed it to carry forward historical assessments of whether existing agreements contained a lease and the classification of existing operating leases.

See “Note 8, Commitments and Contingences” for specific details surrounding the Company’s leases.

Research and Development, Net

Research and development costs are expensed as incurred. These expenses result from the Company’s independent research and development efforts as well as efforts associated with collaboration arrangements. Research and development costs include salaries and personnel-related costs, consulting fees, fees paid for contract research and manufacturing services, the costs of laboratory supplies, equipment and facilities, preclinical studies and other external costs, net of any grants.

Pre-Launch Inventory

Prior to obtaining initial regulatory approval for an investigational product candidate, the Company expenses costs relating to production of inventory as research and development expense in its condensed consolidated statements of operations, in the period incurred. When the Company believes regulatory approval and subsequent commercialization of an investigational product candidate is probable, and the Company also expects future economic benefit from the sales of the investigational product candidate to be realized, it will then capitalize the costs of production as inventory.

Statement of Cash Flows

The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the condensed consolidated balance sheet to the total of the same such amounts shown in the condensed consolidated statement of cash flows:

(in thousands)	September 30, 2020		September 30, 2019
Cash and cash equivalents	$	307,023	$	74,172
Non-current restricted cash		107		107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$	307,130	$	74,279

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 of 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 are comprised of stock options.

No dividends were declared or paid during the reported periods.

Share-Based Compensation

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

Note 7. Share-Based Compensation

In June 2019, the Company adopted the 2019 Omnibus Equity Incentive Plan (“2019 Plan”), which was ratified by stockholders at the Company’s 2019 annual meeting. Under the 2019 Plan, the Company is authorized to issue up to a maximum of 2,600,000 shares of common stock pursuant to the exercise of incentive stock options or other awards provided for therein. In June 2020, the stockholders of the Company approved an increase to the number of shares authorized for use in making awards under the 2019 Plan by 2,400,000 shares to 5,000,000. Accordingly, as of September 30, 2020, a total of 2,388,340 shares remain available for future issuance under the 2019 Plan, subject to the terms of the 2019 Plan.

In June 2020, the stockholders of the Company approved the 2020 Employee Stock Purchase Plan (“2020 Plan”) which provides for 600,000 shares of Company common stock reserved for future issuance. The first accumulation period under the 2020 Plan commenced on August 17, 2020.

Stock Options

Share-based compensation expenses included in the Company’s condensed consolidated statements of operations and comprehensive loss for the three and nine months ended September 30, 2020 and 2019 were:

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(in thousands)	2020		2019		2020		2019
Research and development	$	798	$	158	$	1,460	$	466
General and administrative		1,190		225		2,478		719
Total	$	1,988	$	383	$	3,938	$	1,185

Balance Sheet Details (Tables)

9 Months Ended

Sep. 30, 2020

Balance Sheet Related Disclosures [Abstract]

Summary of Components of Property and Equipment, Net

Property and equipment, net consisted of the following:

(in thousands)	September 30, 2020			December 31, 2019
Research equipment	$	5,343		$	3,658
Computers and software		284			271
Office equipment and furniture		574			561
Leasehold improvements		44			40
Total		6,245			4,530
Less accumulated depreciation and amortization		(2,794	)		(2,181	)
Property and equipment, net	$	3,451		$	2,349

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following as of September 30, 2020 and December 31, 2019:

(in thousands)	September 30, 2020		December 31, 2019
Accrued compensation	$	3,099	$	1,608
Cystic Fibrosis Foundation Liability		4,236		1,949
Singapore Economic Development Board Liability		2,106		—
Current portion of operating lease liability		1,198		827
Clinical accruals		1,352		—
Other accrued research and development expenses		3,847		2,750
Total	$	15,838	$	7,134

Income Taxes

9 Months Ended

Sep. 30, 2020

Income Tax Disclosure [Abstract]

Income Taxes

Note 8. Income Taxes

The Company is subject to taxation in the United States and various states. The primary difference between the effective tax rate and the federal statutory tax rate relates to the valuation allowances on the Company’s net operating losses. No tax benefit was provided for losses incurred in the United States because those losses are offset by a full valuation allowance.

For the three and nine months ended September 30, 2020, the Company did not record any income tax expense. No tax benefit was provided for losses incurred in United States because those losses are offset by a full valuation allowance.

On March 27, 2020, the United States enacted the Coronavirus Aid, Relief and Economic Security Act (the “CARES Act”). The CARES Act is an emergency economic stimulus package that includes spending and tax breaks to strengthen the United States economy and fund a nationwide effort to curtail the effect of COVID-19. While the CARES Act provides sweeping tax changes in response to the COVID-19 pandemic, some of the more significant provisions which are expected to impact the Company’s financial statements include removing of certain limitations on utilization of net operating losses, increasing the loss carryback period for certain losses to five years, and increasing the ability to deduct interest expense, as well as amending certain provisions of the previously enacted Tax Cuts and Jobs Act. For the nine months ended September 30, 2020, the Company estimated that the impact of the CARES Act will be immaterial to its tax position. The Company will continue to analyze the impact that the CARES Act will have in subsequent quarters on its financial position, results of operations or cash flows.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References + Details

Commitments and Contingencies - Payments of Operating Lease Liability (Details) $ in Thousands	Sep. 30, 2020 USD ($)
Leases [Abstract]
2020 (remaining)	$ 496
2021	1,427
2022	1,349
2023	1,390
2024	1,432
Thereafter	314
Total remaining lease payments	6,408
Less: imputed interest	(1,055)
Total operating lease liabilities	$ 5,353
Weighted-average remaining lease term	4 years 3 months 18 days
Weighted-average discount rate	8.40%

Stockholders' Equity (Details Textual)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
Stockholders' Equity (Details Textual)	Mar. 31, 2013 $ / shares shares	Sep. 30, 2020 shares	Sep. 30, 2019 shares	Sep. 30, 2020 shares	Sep. 30, 2019 shares	Dec. 31, 2017 USD ($) Milestone shares	Nov. 10, 2020 shares	Dec. 31, 2019 shares	Dec. 31, 2016 Milestone	Dec. 31, 2014 shares
Class Of Stock [Line Items]
Common stock, shares authorized		30,000,000		30,000,000				30,000,000
Common stock, shares issued		24,473,002		24,473,002				15,138,000
Common stock reserved for future issuance		5,526,998		5,526,998
Antidilutive securities excluded from computation of earnings per share		1,405,378	166,921	1,129,949	96,615
Restricted Common Shares [Member]
Class Of Stock [Line Items]
Stock issued during period	2,783,686
Share price of stock issued \| $ / shares	$ 0.0068
Shares subject to repurchase option	1,538,353
Share based compensation arrangement by share based payment award period from termination date of employee or consultant for repurchase of shares	2 months
Number of milestones achieved \| Milestone						2			2
Common shares, unvested										769,176
Accelerated ordinary shares vested						146,510
Common shares, vested				all
Modification expense resulting from accelerated vesting of ordinary shares \| $						$ 1,495,000
Vested After Obtaining Suitable siRNA License [Member] \| Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%
Vested After in Vivo Proof-of-concept Achieved [Member] \| Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%
Vested After IND Application Completed [Member] \| Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%
Vested After in Human Efficacy Achieved [Member] \| Restricted Common Shares [Member]
Class Of Stock [Line Items]
Shares vesting percentage	25.00%
Scenario Forecast [Member]
Class Of Stock [Line Items]
Common stock, shares authorized							60,000,000

Related Party Transactions - Equity-Method Investment (Details Textual) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2018
Related Party Transaction [Line Items]
Share of losses for investee	$ (303)	$ 263	$ (15)
ADAIR Technology [Member] \| Vallon Pharmaceuticals, Inc. [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage				30.00%
Share of losses for investee		$ 300
ADAIR Technology [Member] \| Vallon Pharmaceuticals, Inc. [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage		19.00%

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2020	Nov. 02, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
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	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NASDAQ
Entity File Number	001-38942
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	32-0595345
Entity Address, Address Line One	10628 Science Center Drive
Entity Address, Address Line Two	Suite 250
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	858
Local Phone Number	900-2660
Entity Common Stock, Shares Outstanding		24,493,084
Document Quarterly Report	true
Document Transition Report	false

Balance Sheet Details (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization	$ 200	$ 200	$ 613	$ 531

Collaboration Revenue (Tables)

9 Months Ended

Sep. 30, 2020

Collaboration Agreements [Abstract]

Summary of Changes in Balances of Contract Assets and Contract Liability

(in thousands)	Contract Assets
BALANCE - December 31, 2019	$	2,179
Additions for revenue recognized from billings		3,065
Deductions for cash collections		(2,797	)
BALANCE – September 30, 2020	$	2,447

(in thousands)	Contract Liabilities
BALANCE - December 31, 2019	$	23,579
Additions for advanced billings		3,065
Deductions for promised services provided in current period		(7,301	)
BALANCE – September 30, 2020	$	19,343

Summary of Collaboration Revenue

The following table summarizes the Company’s collaboration revenues for the periods indicated (in thousands).

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(Dollars in thousands)	2020		2019		2020		2019
Collaboration Partner – Janssen	$	879	$	966	$	2,469	$	2,101
Collaboration Partner – Ultragenyx		912		922		2,736		4,854
Collaboration Partner – CureVac		241		1,057		782		6,360
Collaboration Partner – Other		301		373		1,314		4,506
Total collaboration revenue	$	2,333	$	3,318	$	7,301	$	17,821

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	30,000,000	30,000,000
Common stock, shares issued	24,473,002	15,138,000
Common stock, shares outstanding	24,473,000	15,138,000

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

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

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

Note 1. Description of Business, Basis of Presentation and Summary of Significant Accounting Policies

Description of Business

Arcturus Therapeutics Holdings Inc. (the “Company”) is a clinical-stage messenger RNA medicines company focused on significant opportunities within liver and respiratory rare diseases, and the development of infectious disease vaccines utilizing its Self-Transcribing and Replicating RNA (“STARR”) technology. In addition to the Company’s internal messenger RNA (“mRNA”) platform, its proprietary lipid nanoparticle delivery system, LUNAR, has the potential to enable multiple nucleic acid medicines.

In April 2020, the Company became a clinical stage Company when it announced that its Investigational New Drug (“IND”) application for a Phase 1b study in patients with ornithine transcarbamylase (“OTC”) deficiency was deemed allowed to proceed by the U.S. Food and Drug Administration (“FDA”), and an additional Clinical Trial Application (“CTA”) for a Phase 1 study in healthy volunteers was approved by the New Zealand Medicines and Medical Devices Safety Authority.

In March 2020, the Company was awarded a grant (the “Grant”) from the Singapore Economic Development Board to support the co-development of a potential COVID-19 vaccine with the Duke-NUS Medical School. The grant provides for up to S$14.0 million (approximately US$10.1 million using the exchange rate at the time the grant contract was entered into) in grants to support the development of the vaccine. The Company entered into an amendment to the Grant on September 24, 2020 to update certain delivery and milestone timelines. The Grant has been paid in full by the Economic Development Board as a result of the achievement of certain milestones related to the progress of the development of the vaccine, as set forth in the award agreement. The Company has agreed to pay Duke-NUS Medical School a royalty based on annual net sales of the vaccine in markets or jurisdictions outside of Singapore. In July 2020, the Company and Duke-NUS Medical School announced that the CTA for COVID-19 vaccine candidate (referred to herein as the LUNAR-COV19 vaccine candidate) had been approved to proceed by the Singapore Health Sciences Authority ("HSA").

On October 2, 2020, the Company was awarded another grant from the Singapore Economic Development Board to support the further development of the LUNAR-COV19 vaccine candidate. The grant provides for up to S$9.3 million (approximately US$6.7 million using the exchange rate at the time the grant contract was entered into) to support the development of the LUNAR-COV19 vaccine candidate.

On August 17, 2020, the Company entered into an agreement with the Israeli Ministry of Health (“MOH”) to supply the Company’s COVID-19 vaccine candidate to Israel (the “Israel Supply Agreement”) subject to certain conditions, including applicable regulatory approvals. In October 2020, and in association with the Israel Supply Agreement, the Company received a non-refundable payment of $12.5 million from the MOH. This payment of $12.5 million is associated with a specified clinical trial milestone and serves as an initial reserve payment for a specified number of doses of the LUNAR-COV19 vaccine candidate pursuant to the Israel Supply Agreement. As a result of the making of this payment, the MOH has become bound to purchase an initial quantity of reserved vaccine doses, as set forth in and subject to the terms and conditions of the Israel Supply Agreement.

Basis of Presentation

Liquidity

Segment Information

Revenue Recognition

See “Note 2, Collaboration Revenue” for specific details surrounding the Company’s collaboration arrangements.

Leases

See “Note 8, Commitments and Contingences” for specific details surrounding the Company’s leases.

Research and Development, Net

Pre-Launch Inventory

Statement of Cash Flows

(in thousands)	September 30, 2020		September 30, 2019
Cash and cash equivalents	$	307,023	$	74,172
Non-current restricted cash		107		107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$	307,130	$	74,279

Net Loss per Share

No dividends were declared or paid during the reported periods.

Commitments and Contingencies (Details Textual) $ in Millions				1 Months Ended		3 Months Ended		9 Months Ended
	Oct. 02, 2020 USD ($) Installment	Jul. 13, 2019 USD ($)	Jul. 12, 2019 USD ($)	Feb. 29, 2020	Oct. 31, 2017 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Oct. 02, 2020 SGD ($)	Mar. 04, 2020 USD ($)	Mar. 04, 2020 SGD ($)
Commitment And Contingencies [Line Items]
Operating lease extended additional term				13 months
Operating lease, remaining lease term						4 years 3 months 18 days		4 years 3 months 18 days
Lessee, operating lease, term of contract				1 month
Lessee, operating leases, option to extend				The lease may be extended for one twelve-month period, and in November 2020 the Company deemed the extension option reasonably certain to be exercised and will include the option in the lease terms beginning in October 2020.
Operating lease costs						$ 500,000	$ 300,000	$ 1,300,000	$ 900,000
COVID-19 Vaccine Development [Member]
Commitment And Contingencies [Line Items]
Contra research and development expense recognized						3,700,000		7,900,000
Contra expense remaining amount included in accrued expenses						2,100,000		2,100,000
COVID-19 Vaccine Development [Member] \| Subsequent Event [Member]
Commitment And Contingencies [Line Items]
Grant, number of installments \| Installment	2
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Contra expense remaining amount included in accrued expenses						4,200,000		4,200,000
Payments for matching funds for remaining budgeted costs		$ 5,000,000
Disbursed amount upon execution of amendment		4,000,000
Final payment of disbursement amount		3,000,000
Disbursement payment upon achievement of required manufacturing practices and IND application		2,300,000
Contra expense included in research and development expense						$ 700,000	$ 700,000	$ 3,700,000	$ 700,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due January 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal		2,000,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due April 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal		2,000,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due July 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal		2,000,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due October 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal		2,000,000
Underlying Agreement [Member] \| LUNAR-CF [Member] \| Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Payments for advance		$ 15,000,000	$ 3,200,000
October 2017 Lease Amendment [Member]
Commitment And Contingencies [Line Items]
Operating lease extended additional term					84 months
Lessee, operating lease, term of contract					4 months
Tenant improvement allowance					$ 74,000
Lessee, operating leases, option to extend					The lease may be extended for one five-year period at the then current market rate with annual escalations;
Security deposit					$ 96,000
Singapore Economic Development Board [Member] \| Maximum [Member]
Commitment And Contingencies [Line Items]
Grant awarded											$ 10,100,000	$ 14.0
Singapore Economic Development Board [Member] \| Maximum [Member] \| Subsequent Event [Member]
Commitment And Contingencies [Line Items]
Grant awarded	$ 6,700,000									$ 9.3
Singapore Economic Development Board [Member] \| Maximum [Member] \| COVID-19 Vaccine Development [Member]
Commitment And Contingencies [Line Items]
Grant awarded											$ 10,100,000	$ 14.0
Singapore Economic Development Board [Member] \| Maximum [Member] \| COVID-19 Vaccine Development [Member] \| Subsequent Event [Member]
Commitment And Contingencies [Line Items]
Grant awarded	$ 6,700,000									$ 9.3

Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Cash and cash equivalents	$ 307,023	$ 71,353	$ 74,172
Non-current restricted cash	107	107	107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 307,130	$ 71,460	$ 74,279	$ 36,816

Debt (Details Textual) - USD ($)			3 Months Ended		9 Months Ended
Debt (Details Textual) - USD ($)	Oct. 30, 2019	Oct. 12, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Debt Instrument [Line Items]
Repayment of long-term debt for remainder of fiscal year			$ 0		$ 0
Repayment of long-term debt for year, 2021			1,300,000		1,300,000
Repayment of long-term debt for year, 2022			7,500,000		7,500,000
Repayment of long-term debt for year, 2023			6,500,000		6,500,000
Interest expense related to long-term debt			$ 200,000	$ 200,000	$ 700,000	$ 600,000
Loan and Security Agreement [Member] \| Western Alliance Bank [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Proceeds from long-term debt agreement		$ 10,000,000
Debt instrument, collateral		The Loan is collateralized by all of the assets of Arcturus Therapeutics, Inc., excluding intellectual property, which is subject to a negative pledge. The Loan contains customary conditions of borrowing, events of default and covenants, including covenants that restrict Arcturus Therapeutics, Inc.’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of its capital stock. In addition, Arcturus Therapeutics, Inc. is required to maintain at least 100% of its consolidated, unrestricted cash, or $15.0 million, whichever is lower, with the Bank.
Debt instrument, collateral amount		$ 15,000,000
Term loan	$ 15,000,000
Net increase in indebtedness	$ 5,000,000
Loan maturity date	Oct. 30, 2023
Loan interest-only payment extended maturity date	Oct. 01, 2021
Loan origination fee paid		54,000
Warrant fee payable		$ 525,000
Prepayment fee percentage					2.00%
Loan and Security Agreement [Member] \| Western Alliance Bank [Member] \| Long-term Debt [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Percentage required to be maintain in consolidated, unrestricted cash		100.00%
Interest of the prime rate plus	1.25%
Prepayment fee percentage	0.50%
Loan and Security Agreement [Member] \| Western Alliance Bank [Member] \| Long-term Debt [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Interest of the prime rate plus	2.75%
Prepayment fee percentage	2.00%

Subsequent Events

9 Months Ended

Sep. 30, 2020

Subsequent Events [Abstract]

Subsequent Events

Note 11. Subsequent Events

On November 7, 2020, the Company’s wholly-owned subsidiary, Arcturus Therapeutics, Inc., entered into a Manufacturing Support Agreement (the “Support Agreement”) with the Economic Development Board of the Republic of Singapore (the “EDB”). Pursuant to the Support Agreement, the EDB has agreed to make a term loan of up to $45.0 million (the “Singapore Loan”) to the Company, subject to the entry into an agreed upon security agreement (described below) and satisfaction of other customary deliveries, to support the development of the LUNAR-COV19 vaccine candidate. Outstanding balances on the Singapore Loan will earn interest, compounding annually, and the Company may prepay all or part of the Singapore Loan without penalty upon advance notice.

Subject to certain exceptions, the Singapore Loan is intended to be a limited recourse loan that is intended to be repaid solely through a royalty payment on sales of the LUNAR-COV19 vaccine candidate, with a portion of the proceeds on all such vaccine sales being applied on a quarterly basis to prepay outstanding principal and interest under the Singapore Loan. However, all unpaid principal and interest under the Singapore Loan will be due and payable five years after draw date, if net sales of the LUNAR-COV19 vaccine exceed a certain minimum threshold during this five year period or the Company obtains clearance to sell the vaccine in specified jurisdictions. Unpaid principal and interest under the Singapore Loan will also become due and payable upon an event of default under the Support Agreement.

If, any portion of the Singapore Loan is required to be forgiven pursuant to the terms of the Support Agreement, the EDB has the right to take ownership of certain raw materials and equipment that were purchased by the Company with proceeds of the Singapore Loan (the “Specified Assets”) and the Company is required to enter into a security agreement (the “Security Agreement”) for the benefit of the EDB before the Singapore Loan is drawn to provide that repayment of the Singapore Loan and related obligations are secured by a lien on the Specified Assets.

In connection with the entry into the Support Agreement, the Company entered into a consent agreement with Western Alliance Bank which provides Western Alliance Bank’s consent to enter into the Singapore Loan and its commitment to amend the Loan and Security Agreement, dated as of October 12, 2018, between Western Alliance Bank and the Company, concurrently with the entry into the Security Agreement to exclude the Specified Assets from Western Alliance Bank’s lien on certain assets of the Company.

The foregoing description of the Support Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Support Agreement, which is filed as an exhibit to this Quarterly Report on Form 10-Q.

Collaboration Revenue - Summary of Changes in Balances of Contract Assets and Contract Liability (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($)
Collaboration Agreements [Abstract]
Contract Assets, Balance	$ 2,179
Contract Assets, Additions for revenue recognized from billings	3,065
Contract Assets, Deductions for cash collections	(2,797)
Contract Assets, Balance	2,447
Contract Liabilities, Balance	23,579
Contract Liabilities, Additions for advanced billings	3,065
Contract Liabilities, Deductions for promised services provided in current period	(7,301)
Contract Liabilities, Balance	$ 19,343

Related Party Transactions

9 Months Ended

Sep. 30, 2020

Related Party Transactions

Note 10. Related Party Transactions

Ultragenyx

On June 17, 2019, Arcturus and Ultragenyx executed Amendment 3 to the Ultragenyx Agreement. Pursuant to the amended Ultragenyx Agreement, the Company also granted Ultragenyx a two-year option (the “Option”) to purchase up to 600,000 additional shares of common stock at a price of $16.00 per share (the “Additional Shares”). Ultragenyx exercised the Option in May 2020, and as a result, owns 12.3% of the outstanding common stock of the Company as of September 30, 2020. For the three and nine months ended September 30, 2020, the Company has recognized revenue of $0.9 million and $2.7 million, respectively, and for the three and nine months ended September 30, 2019, the Company recognized revenue of $0.9 million and $4.9 million, respectively. As of September 30, 2020 and 2019, the Company holds accounts receivable balances of negligible amounts related to the Ultragenyx Agreement.

Equity-Method Investment

In June 2018, the Company completed the sale of its intangible asset related to the ADAIR technology. Pursuant to the asset purchase agreement for ADAIR, the Company received a 30% ownership interest in the common stock of Vallon Pharmaceuticals, Inc. (“Vallon”) in consideration for the sale of the ADAIR technology. The Company has no requirement to invest further in Vallon. During the third quarter of 2019, Vallon issued shares of its common stock at a share price greater than the initial investment which resulted in the Company recording a gain in its equity-method investment. The gain has been offset by additional losses incurred by Vallon. On October 23, 2020, Vallon filed with the Securities and Exchange Commission a registration statement on Form S-1 for an initial public offering of shares of common stock. For the nine months ended September 30, 2020, the Company recorded losses of $0.3 million. Subsequent to Vallon issuing shares of its common stock, the Company’s ownership was reduced to 19%. As the Company continues to have the ability to exercise significant influence over the operating and financial policies of the investee, the Company will continue to account for the investment as an equity-method investment.

Share-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Share-based Compensation Expenses

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(in thousands)	2020		2019		2020		2019
Research and development	$	798	$	158	$	1,460	$	466
General and administrative		1,190		225		2,478		719
Total	$	1,988	$	383	$	3,938	$	1,185

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Collaboration revenue	$ 2,333	$ 3,318	$ 7,301	$ 17,821
Operating expenses:
Research and development, net	17,699	7,053	33,560	21,646
General and administrative	5,572	3,881	14,183	10,871
Total operating expenses	23,271	10,934	47,743	32,517
Loss from operations	(20,938)	(7,616)	(40,442)	(14,696)
Loss from equity-method investment		303	(263)	15
Finance expense, net	(66)	(120)	(339)	(321)
Net loss	$ (21,004)	$ (7,433)	$ (41,044)	$ (15,002)
Net loss per share, basic and diluted	$ (0.92)	$ (0.56)	$ (2.19)	$ (1.33)
Weighted-average shares outstanding, basic and diluted	22,938	13,201	18,766	11,248
Comprehensive loss:
Net loss	$ (21,004)	$ (7,433)	$ (41,044)	$ (15,002)
Comprehensive loss	$ (21,004)	$ (7,433)	$ (41,044)	$ (15,002)

Description of Business, Basis of Presentation and Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2020

Accounting Policies [Abstract]

Schedule of Cash and Cash Equivalents and Restricted Cash

(in thousands)	September 30, 2020		September 30, 2019
Cash and cash equivalents	$	307,023	$	74,172
Non-current restricted cash		107		107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$	307,130	$	74,279

Collaboration Revenue (Details Textual)					1 Months Ended	3 Months Ended	9 Months Ended
Collaboration Revenue (Details Textual)	Jul. 26, 2019 USD ($)	Jun. 18, 2019 USD ($) Target $ / shares shares	Jun. 17, 2019 $ / shares shares	Feb. 11, 2019	Oct. 31, 2017 USD ($)	Sep. 30, 2020 USD ($) shares	Sep. 30, 2020 USD ($) shares	Dec. 31, 2019 USD ($) shares	Jun. 16, 2019 Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue						$ 19,343,000	$ 19,343,000	$ 23,579,000
Purchase of common stock, shares \| shares						24,473,002	24,473,002	15,138,000
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received					$ 7,700,000
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member] \| ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation						$ 0	$ 0
Deferred revenue						$ 5,900,000	5,900,000	$ 5,900,000
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received		$ 6,000,000					27,900,000
Revenue recognition potential milestone revenue recognized							$ 138,000,000
Royalty payment term description							Ultragenyx will pay royalties as a single-digit percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term.
Number of targets \| Target		12							10
Purchase of common stock, shares \| shares		2,400,000				600,000	600,000
Purchase of additional shares of common stock \| shares		600,000	600,000
Purchase of additional shares of common stock price per share \| $ / shares		$ 16	$ 16.00
Consideration received		$ 30,000,000
Consideration received for common stock purchase		24,000,000
Transaction price		$ 14,400,000
Collaboration agreement transfer restrictions termination date.							Nov. 20, 2020
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member] \| ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation						$ 0	$ 0
Deferred revenue						10,000,000	$ 10,000,000	12,700,000
Revenue, practical expedient description							The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained.
Cumulative catch up adjustment							$ 1,100,000
Revenue recognition, reserve target exclusivity period							4 years
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment term description							CureVac will pay royalties as a percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term in the low single-digit range
Development and option agreement date							Jan. 31, 2018
Expiration of initial term							8 years
Option to extend initial term on an annual basis							3 years
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member] \| Rare Disease Targets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized							$ 14,000,000
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member] \| Non-Rare Disease Targets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized							23,000,000
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member] \| ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation						0	0
Deferred revenue						2,500,000	$ 2,500,000	$ 3,200,000
Revenue, practical expedient description							The Company recognizes the reimbursement of labor and expenses as costs are incurred and none of the development and commercialization milestones were included in the transaction price, as all milestone amounts were fully constrained.
Adjustments to transaction price						$ 0
Upfront fee received							$ 5,000,000
Contractual term							34 months
Cumulative catch up adjustment	$ 400,000
mRNA Technology [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement termination date				Feb. 11, 2019
Percentage of global rights reassumed				100.00%
Termination Agreement [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement settlement obligation one-time settled amount	$ 4,000,000
Other Collaboration Agreements [Member] \| Takeda Pharmaceutical Company Limited [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue related to amortization of upfront payment							$ 800,000
Other Collaboration Agreements [Member] \| Synthetic Genomics Inc. [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Sublicense revenue recognized							300,000
Maximum [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	8 years
Maximum [Member] \| Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized					$ 56,500,000
Option exercise revenue range per target							5,000,000
Maximum [Member] \| Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target							1,500,000
Lack of marketability discount restricted period		2 years
Minimum [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	4 years
Minimum [Member] \| Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target							1,000,000
Minimum [Member] \| Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target							$ 500,000

Fair Value Measurements

9 Months Ended

Sep. 30, 2020

Fair Value Disclosures [Abstract]

Fair Value Measurements

Note 3. Fair Value Measurements

The Company establishes the fair value of its assets and liabilities using the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company establishes a fair value hierarchy based on the inputs used to measure fair value.

The three levels of the fair value hierarchy are as follows:

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly.

Level 3: Unobservable inputs for 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, cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued liabilities approximate their respective fair values due to their relative short maturities. The carrying amount of long-term debt for the amount drawn on the Company’s debt facility approximates fair value as the interest rate is variable and reflects current market rates.

As of September 30, 2020 and December 31, 2019, all assets measured at fair value on a recurring basis consisted of cash equivalents and money market funds, which were classified within Level 1 of the fair value hierarchy. The fair value of these financial instruments was measured based on quoted prices.

- 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 + Details

Debt

9 Months Ended

Sep. 30, 2020

Debt Disclosure [Abstract]

Debt

Note 5. Debt

Long-term debt with Western Alliance Bank

On October 12, 2018, Arcturus Therapeutics, Inc. entered into a Loan and Security Agreement with Western Alliance Bank (the “Bank”), whereby it received $10.0 million under a long-term debt agreement (the “Loan”).

The Loan is collateralized by all of the assets of Arcturus Therapeutics, Inc., excluding intellectual property, which is subject to a negative pledge. The Loan contains customary conditions of borrowing, events of default and covenants, including covenants that restrict Arcturus Therapeutics, Inc.’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of its capital stock. In addition, Arcturus Therapeutics, Inc. is required to maintain at least 100% of its consolidated, unrestricted cash, or $15.0 million, whichever is lower, with the Bank.

On October 30, 2019, Arcturus Therapeutics, Inc. and the Bank entered into a Third Amendment (the “Third Amendment”) to the Loan (as amended, the “Loan Agreement”).

Pursuant to the amendment, the Bank agreed to make a term loan to Arcturus Therapeutics, Inc. on October 30, 2019, in the amount of $15.0 million (the “Term Loan”). The resulting net increase in the indebtedness of Arcturus Therapeutics, Inc. was $5.0 million. The Term Loan bears interest at a floating rate ranging from 1.25% to 2.75% above the prime rate. The amendment further provides that the Term Loan has a maturity date of October 30, 2023. Arcturus Therapeutics, Inc. will make monthly payments of interest only until October 1, 2021.

Arcturus Therapeutics, Inc. paid a loan origination fee of $54,000 which was recorded as a debt discount along with the remaining loan origination fee from the Loan and is being accreted over the term of the Term Loan. In addition, Arcturus Therapeutics, Inc. is required to pay a fee of $525,000 upon certain change of control events.

The Term Loan may be prepaid in full at any time, subject to a prepayment fee ranging from 0.50% to 2.00% of the prepaid principal amount depending upon the date of the prepayment. In connection with the Third Amendment, the Company guaranteed the obligations under the Loan Agreement and pledged substantially all of its assets as security under the Loan Agreement.

Upon maturity or prepayment (as previously discussed), Arcturus Therapeutics, Inc. will be required to pay a 2% fee as a result of the FDA’s approval to proceed with the Company’s LUNAR-OTC (ARCT-810) program based on its IND submission. Such fee is accreted to the long-term debt balance using the effective interest method over the term of the Loan Agreement.

Should an event of default occur, including the occurrence of a material adverse effect, the Company could be liable for immediate repayment of all obligations under the Loan Agreement. As of September 30, 2020, the Company was in compliance with all covenants under the Loan Agreement.

Principal payments, including the final payment due at repayment, on the long-term debt for fiscal years 2021, 2022 and 2023 are $1.3 million, $7.5 million and $6.5 million, respectively, with no principal payments due in 2020.

The Company recognized interest expense related to its long-term debt of $0.2 million and $0.7 million for the three and nine months ended September 30, 2020, respectively, and $0.2 million and $0.6 million for the three and nine months ended September 30, 2019, respectively.

Collaboration Revenue (Details Textual 1)	Sep. 30, 2020
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member] \| ASC 606 [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining research period	24 months

Collaboration Revenue - Summary of Collaboration Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 2,333	$ 3,318	$ 7,301	$ 17,821
Collaboration Partner - Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	879	966	2,469	2,101
Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	912	922	2,736	4,854
Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	241	1,057	782	6,360
Collaboration Partner – Other [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 301	$ 373	$ 1,314	$ 4,506

- 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: 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 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
OPERATING ACTIVITIES:
Net loss	$ (41,044)	$ (15,002)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	613	531
Share-based compensation expense	3,938	1,185
Loss (gain) from equity-method investment	263	(15)
Other non-cash interest expense	1,027	649
Changes in operating assets and liabilities
Accounts receivable	(268)	1,856
Prepaid expense and other assets	(3,872)	(1,973)
Accounts payable	15	1,489
Accrued liabilities	7,335	1,432
Deferred revenue	(4,236)	10,941
Net cash (used in) provided by operating activities	(36,229)	1,093
INVESTING ACTIVITIES:
Acquisition of property and equipment	(1,045)	(503)
Net cash used in investing activities	(1,045)	(503)
FINANCING ACTIVITIES:
Proceeds from issuance of common stock, net of issuance costs	261,883	21,278
Proceeds from exercise of stock options	1,461	50
Net cash provided by financing activities	272,944	36,873
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	235,670	37,463
Cash, cash equivalents and restricted cash at beginning of the period	71,460	36,816
Cash, cash equivalents and restricted cash at end of the period	307,130	74,279
Supplemental disclosure of cash flow information
Cash paid for interest	173	508
Non-cash investing activities
Right-of-use asset obtained in exchange for lease liabilities	674	5,868
Purchase of property and equipment in accounts payable	670	126
Ultragenyx [Member]
FINANCING ACTIVITIES:
Proceeds from the issuance of common stock to Ultragenyx and option exercise	$ 9,600	$ 15,545

Related Party Transactions - Ultragenyx (Details Textual) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Jun. 18, 2019	Jun. 17, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Related Party Transaction [Line Items]
Collaboration revenue			$ 2,333	$ 3,318	$ 7,301	$ 17,821
Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Collaboration revenue			912	922	$ 2,736	4,854
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Common stock shares restricted from selling period subsequent to issuance date		2 years
Purchase of additional shares of common stock	600,000	600,000
Purchase of additional shares of common stock price per share	$ 16	$ 16.00
Ownership interest of common stock					12.30%
Collaboration revenue			$ 900	$ 900	$ 2,700	$ 4,900

- Definition

+ References

+ Details

Balance Sheet Details - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accrued Liabilities Current [Abstract]
Accrued compensation	$ 3,099	$ 1,608
Cystic Fibrosis Foundation Liability	4,236	1,949
Singapore Economic Development Board Liability	2,106
Current portion of operating lease liability	1,198	827
Clinical accruals	1,352
Other accrued research and development expenses	3,847	2,750
Total	$ 15,838	$ 7,134

Subsequent Events (Details Textual) $ in Millions	Nov. 07, 2020 USD ($)
Subsequent Event [Member] \| Singapore Economic Development Board [Member] \| Maximum [Member]
Subsequent Event [Line Items]
Term loan	$ 45.0

Share-Based Compensation (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 1,988	$ 383	$ 3,938	$ 1,185
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	798	158	1,460	466
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 1,190	$ 225	$ 2,478	$ 719

Balance Sheet Details

9 Months Ended

Sep. 30, 2020

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Details

Note 4. Balance Sheet Details

Property and equipment, net consisted of the following:

(in thousands)	September 30, 2020			December 31, 2019
Research equipment	$	5,343		$	3,658
Computers and software		284			271
Office equipment and furniture		574			561
Leasehold improvements		44			40
Total		6,245			4,530
Less accumulated depreciation and amortization		(2,794	)		(2,181	)
Property and equipment, net	$	3,451		$	2,349

Depreciation and amortization expense was $0.2 million and $0.2 million for the three months ended September 30, 2020 and 2019, respectively, and $0.6 million and $0.5 million for the nine months ended September 30, 2020 and 2019, respectively.

Accrued liabilities consisted of the following as of September 30, 2020 and December 31, 2019:

(in thousands)	September 30, 2020		December 31, 2019
Accrued compensation	$	3,099	$	1,608
Cystic Fibrosis Foundation Liability		4,236		1,949
Singapore Economic Development Board Liability		2,106		—
Current portion of operating lease liability		1,198		827
Clinical accruals		1,352		—
Other accrued research and development expenses		3,847		2,750
Total	$	15,838	$	7,134

Income Taxes (Details Textual) - USD ($)	3 Months Ended	9 Months Ended
Income Taxes (Details Textual) - USD ($)	Sep. 30, 2020	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income tax expense	$ 0	$ 0

- Definition

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

+ References + Details

Balance Sheet Details - Summary of Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 6,245	$ 4,530
Less accumulated depreciation and amortization	(2,794)	(2,181)
Property and equipment, net	3,451	2,349
Research equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	5,343	3,658
Computer and software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	284	271
Office equipment and furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	574	561
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 44	$ 40

Stockholders' Equity

9 Months Ended

Sep. 30, 2020

Stockholders Equity Note [Abstract]

Stockholders' Equity

Note 6. Stockholders’ Equity

Common Stock

The Company is currently authorized to issue 30,000,000 shares of common stock under its Certificate of Incorporation. As of September 30, 2020, the Company has issued 24,473,002 shares of common stock and has approximately 5,526,998 shares of common stock reserved for issuance, resulting in no authorized shares of common stock available for issuance. As a result, the Company will hold a special meeting of stockholders on November 10, 2020 to vote to increase the number of shares of common stock it is authorized to issue from 30,000,000 shares to 60,000,000 shares.

Restricted Common Shares

In March 2013, the founders of the Company purchased 2,783,686 shares of common stock for $0.0068 per share. Of the shares purchased, 1,538,353 were subject to a repurchase option whereby the Company has an option for two months after date of termination of service to repurchase any or all of the unvested shares at the original purchase price per share. The repurchase option will be deemed to be automatically exercised by the Company as of the end of the two-month period unless the Company notifies the purchaser that it does not intend to exercise its option. The shares will be vested (1) 25% after obtaining suitable siRNA license; (2) 25% after in vivo proof-of-concept is achieved; (3) 25% after a regulatory agency new drug application (such as an IND application) is filed and accepted by the applicable regulatory agency; and (4) 25% after human biological proof-of-concept is achieved. The Company met the first two milestones during 2013 and 2014 leaving an unvested balance of 769,176 shares. In 2017, the stock purchase agreements were amended to clarify vesting conditions and also to accelerate the vesting of 146,510 shares resulting in a modification expense of $1,495,000. The third and fourth milestones were achieved during the second and third quarters of 2020, respectively, and therefore, as of September 30, 2020, all shares of common stock were fully vested.

Net Loss per Share

Dilutive securities that were not included in the calculation of diluted net loss per share for the three and nine months ended September 30, 2020 as they were anti-dilutive totaled 1,405,378 and 1,129,949, respectively, and 166,921 and 96,615 for the three and nine months ended September 30, 2019, respectively.