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Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2019	Mar. 01, 2020	Jun. 28, 2019
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Trading Symbol	ARCT
Entity Registrant Name	ARCTURUS THERAPEUTICS HOLDINGS INC.
Entity Central Index Key	0001768224
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Interactive Data Current	Yes
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		15,137,964
Entity Public Float			$ 76.4
Document Transition Report	false
Document Annual Report	true

CONSOLIDATED BALANCE SHEETS - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 71,353,000	$ 36,709,000
Accounts receivable	2,179,000	4,481,000
Prepaid expenses and other current assets	758,000	638,000
Total current assets	74,290,000	41,828,000
Property and equipment, net	2,349,000	1,975,000
Operating lease right-of-use asset, net	5,134,000
Equity-method investment	263,000	288,000
Non-current restricted cash	107,000	107,000
Total assets	82,143,000	44,198,000
Current liabilities:
Accounts payable	5,793,000	2,398,000
Accrued liabilities	7,134,000	3,907,000
Deferred revenue	8,397,000	6,272,000
Total current liabilities	21,324,000	12,577,000
Deferred revenue, net of current portion	15,182,000	7,534,000
Long-term debt	14,995,000	9,911,000
Operating lease liability, net of current portion	4,850,000
Deferred rent		534,000
Total liabilities	56,351,000	30,556,000
Commitments and contingencies (Note 11)
Stockholders’ equity:
Common stock: $0.001 par value; 30,000 shares authorized; 15,138 issued and outstanding at December 31, 2019; NIS 0.07 par value; 30,000 shares authorized, 10,762 issued, 10,719 outstanding and 43 held in treasury at December 31, 2018;	15,000	214,000
Additional paid-in capital	97,445,000	58,302,000
Accumulated deficit	(71,668,000)	(44,874,000)
Total stockholders’ equity	25,792,000	13,642,000
Total liabilities and stockholders’ equity	$ 82,143,000	$ 44,198,000

CONSOLIDATED BALANCE SHEETS (Parenthetical)	Dec. 31, 2019 $ / shares shares	Dec. 31, 2018 ₪ / shares shares
Statement Of Financial Position [Abstract]
Common stock, par value \| (per share)	$ 0.001	₪ 0.07
Common stock, shares authorized	30,000,000	30,000,000
Treasury shares		43,000
Common stock, shares issued	15,138,000	10,762,000
Common stock, shares outstanding	15,138,000	10,719,000

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Collaboration revenue	$ 20,789	$ 15,753
Operating expenses:
Research and development, net	33,640	16,982
General and administrative	12,662	20,582
Total operating expenses	46,302	37,564
Loss from operations	(25,513)	(21,811)
Loss from equity-method investment	(32)	(302)
Finance (expense) income, net	(446)	328
Net loss	$ (25,991)	$ (21,785)
Net loss per share, basic and diluted	$ (2.15)	$ (2.16)
Weighted-average shares outstanding, basic and diluted	12,069	10,069
Comprehensive loss:
Net loss	$ (25,991)	$ (21,785)
Unrealized gain on short-term investments		3
Comprehensive loss	$ (25,991)	$ (21,782)

STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2017	$ 33,794	$ 212	$ 56,674	$ (3)	$ (23,089)
Balance (in shares) at Dec. 31, 2017		10,699,000
Net loss	(21,785)				(21,785)
Unrealized gain on short-term investments	3			$ 3
Share-based compensation	1,259		1,259
Issuance of common stock upon exercise of stock options	371	$ 2	369
Issuance of common stock upon exercise of stock options (in shares)		63,000
Balance at Dec. 31, 2018	13,642	$ 214	58,302		(44,874)
Balance (in shares) at Dec. 31, 2018		10,762,000
Net loss	(25,991)				(25,991)
Share-based compensation	1,982		1,982
Redomiciliation share exchange		$ (203)	203
Redomiciliation share exchange (in shares)		(43,000)
Issuance of restricted common stock and option, net of issuance costs	15,545	$ 2	15,543
Issuance of restricted common stock and option, net of issuance costs (in shares)		2,400,000
Issuance of common stock, net of issuance costs	21,278	$ 2	21,276
Issuance of common stock, net of issuance costs (in shares)		1,995,000
Issuance of common stock upon exercise of stock options	$ 139		139
Issuance of common stock upon exercise of stock options (in shares)	24,290	24,000
Effect of adoption of ASU 2014-09	$ (803)				(803)
Balance at Dec. 31, 2019	$ 25,792	$ 15	$ 97,445		$ (71,668)
Balance (in shares) at Dec. 31, 2019		15,138,000

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
OPERATING ACTIVITIES:
Net loss	$ (25,991)	$ (21,785)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	684	582
Share-based compensation expense	1,982	1,259
Loss from equity-method investment	25	302
Other non-cash expenses	873	38
Changes in operating assets and liabilities:
Accounts receivable	2,302	(4,001)
Prepaid expenses and other assets	(120)	421
Accounts payable	3,155	578
Accrued liabilities	1,675	1,687
Deferred revenue	8,970	159
Net cash used in operating activities	(6,445)	(20,760)
INVESTING ACTIVITIES:
Acquisition of property and equipment	(818)	(1,478)
Purchases of short-term investments		(6,594)
Proceeds from maturities of short-term investments		30,206
Net cash (used in) provided by investing activities	(818)	22,134
FINANCING ACTIVITIES:
Proceeds from long-term debt, net of lender fees	4,945	9,872
Proceeds from exercise of stock options	139	332
Proceeds from issuance of restricted common stock and option, net of issuance costs	15,545
Proceeds from issuance of common stock, net of issuance costs	21,278
Net cash provided by financing activities	41,907	10,204
NET INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	34,644	11,578
Cash, cash equivalents and restricted cash at beginning of year	36,816	25,238
Cash, cash equivalents and restricted cash at end of year	71,460	36,816
Supplemental disclosure of cash flow information:
Cash paid for interest	691	146
Non-cash investing activities
Right-of-use asset obtained in exchange for lease liabilities	5,868
Sale of intangible assets for equity method investment		590
Purchase of property and equipment in accounts payable	$ 240	30
Release of repurchase liability for restricted shares		$ 39

Organization

12 Months Ended

Dec. 31, 2019

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization

Note 1. Organization

Description of Business

Arcturus Therapeutics Holdings Inc. (the “Company”) is a messenger RNA medicines company focused on significant opportunities within liver and respiratory rare diseases, and the development of infectious disease vaccines utilizing our 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, enables multiple nucleic acid medicines.

The financial statements for periods prior to June 17, 2019, the effective date of the Redomiciliation (as described below), relate to Arcturus Therapeutics Ltd. and for the period from and after June 17, 2019 relate to Arcturus Therapeutics Holdings Inc.

Recent Developments

In May 2019, shareholders of Arcturus Therapeutics Ltd. (“Arcturus Israel”) approved the Redomiciliation to the United States (the “Redomiciliation”). In connection therewith, in February 2019, Arcturus Israel entered into a share exchange agreement (the “Exchange Agreement”) with Arcturus Therapeutics Holdings Inc., a newly established Delaware corporation. In June 2019, pursuant to the terms of the Exchange Agreement, all issued ordinary shares and options to purchase ordinary shares of Arcturus Israel were exchanged on a one-for-one basis for newly issued shares of common stock and options to purchase common stock, respectively, of the Company, resulting in Arcturus Israel becoming a subsidiary of the Company.

In June 2019, Arcturus Israel’s ordinary shares were delisted from trading on Nasdaq and the Company’s shares commenced trading on Nasdaq under the symbol “ARCT.” Arcturus Israel is now a wholly-owned subsidiary of the Company, which is the successor to Arcturus Israel. Proceedings to liquidate Arcturus Israel are now pending in Israeli court.

On October 30, 2019, the Company amended its loan agreement with Western Alliance Bank (the “Bank”). See “Note 7. Long-term debt with Western Alliance Bank” for further information.

See “Note 8 Stockholders’ Equity – Registered Direct Offerings” for further information on the Company’s recent registered direct offerings.

See “Note 14 Subsequent Events” for further information on the Duke-NUS Medical School Agreement.

Going Concern

The Company’s activities since inception have consisted principally of performing research and development 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 preclinical bioscience company that is dependent on obtaining external equity and debt financings to fund its operations. Historically, the Company’s primary source of financing has been through the sale of its securities, through issuance of debt and through collaboration agreements. On June 18, 2019, the Company entered into a Third Amendment to the Research Collaboration and License Agreement with Ultragenyx Pharmaceutical Inc. (“Ultragenyx”), from which the Company received $24.0 million from Ultragenyx’s purchase of common stock and a $6.0 million upfront payment. Furthermore, in separate offerings, the Company raised total net proceeds of $21.4 million during the third quarter of 2019 through the sale of equity securities. Research and development activities have required significant capital investment since the Company’s inception.

The Company expects its operations to continue to require cash investment to pursue the Company’s research and development activities, including preclinical studies, formulation development, clinical trials and related drug manufacturing. The Company has experienced net losses since its inception and as of December 31, 2019 has an accumulated deficit of $71.7 million. The Company expects to continue to incur additional losses for the foreseeable future, and the Company will need to raise additional debt or equity financing or enter into additional collaborations to fund its development. The ability of the Company to transition to profitability is dependent on identifying and developing successful mRNA drug candidates. In the near future, if the Company is not able to achieve planned milestones, incurs costs in excess of its forecasts, or does not meet covenant or other requirements of its debt (Note 7), it will need to reduce discretionary spending, discontinue the development of some or all of its products, which will delay part of its development programs, all of which would have a material adverse effect on the Company’s ability to achieve its intended business objectives. There can be no assurances that additional financing will be secured or, if secured, will be on favorable terms. Management has prepared cash flow forecasts which indicate that based on the Company’s expected operating losses and negative cash flows, there is substantial doubt about the Company’s ability to continue as a going concern within twelve months after the date that the financial statements for the year ended December 31, 2019, are issued. The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and the settlement of liabilities and commitments in the normal course of business. The consolidated financial statements do not reflect any adjustments related to the recoverability and classification of assets or the amounts and classification of liabilities that might be necessary if the Company is unable to continue as a going concern.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Note 2. Summary of Significant Accounting Policies

Basis of Presentation and Principles of Consolidation

The accompanying consolidated financial statements include the accounts of Arcturus Therapeutics Holdings Inc. and its subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation. These consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States (U.S. GAAP), which requires management to make estimates and assumptions regarding the valuation of certain debt and equity instruments, the equity method investment, share-based compensation, accruals for liabilities, income taxes, revenue and deferred revenue, leases, expense accruals, 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 period. Although these estimates are based on management’s knowledge of current events and actions the Company may undertake in the future, actual results could materially differ from those estimates.

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.

Cash and Cash Equivalents

Cash equivalents are short-term highly liquid investments that are readily convertible to cash with original maturities of three months or less at the date of purchase.

Restricted cash

Restricted cash represents cash required to be set aside as security for lease payments and to maintain a letter of credit for the benefit of the landlord for the Company’s offices. At December 31, 2019 and 2018, the Company had restricted cash of $107,000 in conjunction with property leases in San Diego, California, and such restriction is expected to be removed at the end of the lease term in 2025.

Fair Value Measurements

Fair value is defined as the exit price, or the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants as of the measurement date. A hierarchy has been established for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available (Note 4).

Observable inputs are inputs that market participants would use in valuing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the factors market participants would use in valuing the asset or liability developed based upon the best information available under the circumstances. The hierarchy consists of three levels. Level 1 inputs are quoted prices (unadjusted) in active markets for identical assets or liabilities. Level 2 inputs include quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, and inputs (other than quoted prices) that are observable for the asset or liability, either directly or indirectly. Level 3 inputs are unobservable inputs for the asset or liability. Categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.

Accounts Receivable

Accounts receivable are recorded at the net invoice value and are non-interest bearing. The Company considers receivables past due based on the contractual payment terms. The Company reserves for specific receivables if collectability is no longer reasonably assured. Estimates for allowances for doubtful accounts are determined based on existing contractual obligations, historical payment patterns, and individual customer circumstances. The Company reevaluates such reserves on a regular basis and adjusts its reserves as needed. Once a receivable is deemed to be uncollectible, such balance is charged against the reserve. No reserves have been recorded as of December 31, 2019 or 2018.

Concentration of Credit Risk and Significant Customers

Financial instruments, which potentially subject the Company to concentrations of credit risk, consist of cash and cash equivalents. The Company limits its exposure to credit loss by placing its cash and cash equivalents with high credit quality financial institutions in instruments with short maturities.

There was one customer that comprised 98% of the total accounts receivable balance at December 31, 2019 and one customer that comprised 96% of the total accounts receivable balance at December 31, 2018.

For the year ended December 31, 2019, the Company’s top four customers collectively represented 91% of the Company’s total revenue. For the year ended December 31, 2018, there were three customers that collectively represented 80% of the Company’s total revenue.

Intangible Assets Held for Sale and Equity Method Investment

At the end of the second quarter of 2018, the Company completed the sale of its intangible assets related to the ADAIR technology. Pursuant to the asset purchase agreement for ADAIR, the Company received a 30% ownership interest in the common stock of a privately held company in consideration for the sale of the ADAIR technology. As this ownership interest is greater than 20% and one executive of the Company holds a seat on the investee’s board of directors, the Company has the ability to exercise significant influence over the operating and financial policies of this investee; therefore, the Company accounts for this investment as an equity-method investment.

The Company accounts for its share of the earnings or losses of the investee with a reporting lag of three months, as the financial statements of the investee are not completed on a basis that is sufficient for the Company to apply the equity method on a current basis.

Property and Equipment, net

Property and equipment are stated at cost, net of accumulated depreciation and amortization. The cost of property and equipment is depreciated or amortized using the straight-line method over the respective useful lives of the assets, ranging from three to five years. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful life of the asset or the lease term. Long-lived assets, including property and equipment are reviewed for impairment whenever events or circumstances indicate that the carrying amount of these assets may not be recoverable. The determinants used for this evaluation include management’s estimate of an asset’s ability to generate positive income from operations and positive cash flow in future periods, as well as the strategic significance of the assets to the Company’s business objectives. The Company did not recognize any impairment losses for the years ended December 31, 2019 and 2018.

Comprehensive Income/Loss

Comprehensive income/loss is defined as the change in stockholders’ equity during a period from transactions and other events and circumstances from non-owner sources. Other comprehensive loss represents unrealized losses on the Company’s marketable securities. The was no income tax effect related to unrealized losses for the years ended December 31, 2019 or 2018.

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 obligations under these arrangements. The event-based milestone payments represent variable consideration, and the Company uses the most likely amount method to estimate this variable consideration because the Company will either receive the milestone payment or will not, which makes the potential milestone payment a binary event. The most likely amount method requires the Company to determine the likelihood of earning the milestone payment. Given the high degree of uncertainty around achievement of these milestones, the Company determines the milestone amounts to be fully constrained and does not recognize revenue until the uncertainty associated with these payments is resolved. The Company will recognize revenue from sales-based royalty payments when or as the sales occur. The Company will re-evaluate the transaction price in each reporting period as uncertain events are resolved and other changes in circumstances occur.

A performance obligation is a promise in a contract to transfer a distinct good or service to the collaborative partner and is the unit of account in Topic 606. A contract’s transaction price is allocated to each distinct performance obligation based on relative standalone selling price and recognized as revenue when, or as, the performance obligation is satisfied.

See “Note 3, Collaboration Revenue” for specific details surrounding the Company’s collaboration arrangements.

Research and Development Costs, 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 and other external costs are shown net of any grants.

Share-Based Compensation

The Company recognizes share-based compensation for equity awards granted to employees, officers, and directors as an expense on the statements of operations. Share-based compensation is recognized over the requisite service period of the individual awards using the straight-line attribution method, which generally equals the vesting period. Employees and officers’ share options have a ten-year life and generally vest 25% on the first anniversary of the grant and in 1/36^th equal installments on each monthly anniversary thereafter, such that options are fully vested on the four-year anniversary of the date of grant.

The fair value of share options is estimated using a Black-Scholes valuation model on the date of grant. This method requires certain assumptions be used as inputs, such as the fair value of the underlying common shares, expected term of the option before exercise, expected volatility of the Company’s common stock, expected dividend yield, and a risk-free interest rate. The Company has limited historical share option activity and therefore estimates the expected term of share options granted using the simplified method, which represents the average of the contractual term of the share option and its weighted-average vesting period. The expected volatility of share options is based upon the historical volatility of a peer group of publicly traded companies. The Company has not declared or paid any dividends and does not currently expect to do so in the foreseeable future. The risk-free interest rates used are based on the implied yield currently available in United States Treasury securities at maturity with a term equivalent to the expected term of the share options. The effect of forfeited awards is recorded when the forfeiture occurs.

Statement of cash flows

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

	As of December 31,
(in thousands)	2019		2018
Cash and cash equivalents	$	71,353	$	36,709
Non-current Restricted cash		107		107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$	71,460	$	36,816

Income Tax Expense

Income taxes are accounted for using an asset and liability approach that requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities at the applicable tax rates, along with net operating loss and tax credit carryovers. The Company records a valuation allowance against its deferred tax assets to reduce the net carrying value to an amount that it believes is more likely than not to be realized. Management has considered estimated taxable income and ongoing prudent and feasible tax planning strategies in assessing the amount of the valuation allowance. Based upon the weight of available evidence, which includes the Company’s historical operating performance and limited potential to utilize tax credit carryforwards, the Company has determined that total deferred tax assets should be fully offset by a valuation allowance. When the Company establishes or reduces the valuation allowance against its deferred tax assets, its provision for income taxes will increase or decrease, respectively, in the period such determination is made.

The Company is required to file federal and state income tax returns in the United States and various other state jurisdictions. The Company also files income tax returns in the foreign countries in which it operates. The preparation of these income tax returns requires the Company to interpret the applicable tax laws and regulations in effect in such jurisdictions, which could affect the amount of tax paid by the Company.

Additionally, the Company follows an accounting standard addressing the accounting for uncertainty in income taxes that prescribes rules for recognition, measurement, and classification in the consolidated financial statements of tax positions taken or expected to be taken in a tax return.

Net Loss per Share

Basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding for the period determined using the treasury-stock method. Dilutive shares of common stock for the years ended December 31, 2019 and 2018 are comprised of stock options.

No dividends were declared or paid during the reporting periods.

Recently Adopted Accounting Pronouncements

Revenue from Contracts with Customers

In May 2014, the Financial Accounting Standards Board (FASB) issued Topic 606, which supersedes nearly all existing revenue recognition guidance under GAAP. The FASB subsequently issued amendments to Topic 606 that have the same effective date and transition date.

The Company adopted this new guidance, effective January 1, 2019, using the modified retrospective transition method, in which the standard is applied as of the date of initial adoption. The Company recorded the cumulative effect of initially applying the standard as an adjustment to the opening balance of accumulated deficit. The adoption of the new revenue recognition guidance resulted in an increase of $0.8 million to deferred revenue and an increase of $0.8 million to accumulated deficit as of January 1, 2019. The change in revenue was due to a change in how the Company accounts for changes in the measure of progress and changes to the transaction price and for the recognition of revenue. Under Topic 605, the Company accounted for changes to the measure of progress and changes to the transaction price prospectively. Topic 606 requires companies to account for a change to the measure of progress or a change to the transaction price as a cumulative catch-up in the period of change. There were no other impacts upon the adoption of Topic 606. The Company will apply the standard to all new contracts initiated on or after the effective date.

Leases

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous GAAP. ASU 2016-02 requires a lessee to recognize a liability for lease payments (the lease liability) and a right-of-use asset (representing its right to use the underlying asset for the lease term) on the balance sheet. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 (including interim periods within those periods) using a modified retrospective approach.

In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements, which provides entities an optional transition method to apply the new guidance as of the adoption date, rather than as of the earliest period presented. In transition, entities may also elect a package of practical expedients that must be applied in its entirety to all leases commencing before the effective date, unless the lease was modified, to not reassess (a) the existence of a lease, (b) lease classification or (c) determination of initial direct costs, which effectively allows entities to carryforward accounting conclusions under previous U.S. GAAP.

The Company adopted ASU 2016-02, using the optional transition method and electing the package of practical expedients described above on January 1, 2019. Due to the adoption, the Company recognized a new lease liability on the Company’s consolidated balance sheet for its operating lease of office and lab space of $6.4 million on January 1, 2019, with a corresponding right-of-use asset of $5.9 million based on the present value of the remaining minimum lease payments. See Note 11 for further discussion.

Collaboration Revenue

12 Months Ended

Dec. 31, 2019

Collaboration Agreements [Abstract]

Collaboration Revenue

NOTE 3. Collaboration Revenue

The Company has entered into license agreements and collaborative research and development arrangements with pharmaceutical and biotechnology companies. Under these arrangements, the Company is entitled to receive license fees, upfront payments, milestone payments if and when certain research and development milestones or technology transfer milestones are achieved, royalties on approved product sales and reimbursement for research and development activities. The Company’s costs of performing these services are included within research and development expenses. The Company’s milestone payments are typically defined by achievement of certain preclinical, clinical, and commercial success criteria. Preclinical milestones may include in vivo proof of concept in disease animal models, lead candidate identification, and completion of IND-enabling toxicology studies. Clinical milestones may, for example, include successful enrollment of the first patient in or completion of Phase I, II, and III clinical trials, and commercial milestones are often tiered based on net or aggregate sale amounts. The Company cannot guarantee the achievement of these milestones due to risks associated with preclinical and clinical activities required for development of nucleic acid medicine-based therapeutics.

The following table presents changes during the year ended December 31, 2019 in the balances of contract assets, including receivables from collaborative partners, and contract liabilities, including deferred revenue.

(in thousands)	Contract Assets
BALANCE - December 31, 2018	$	4,480
Additions for revenue recognized		17,523
Deductions for cash collections		(19,824	)
BALANCE - December 31, 2019	$	2,179

(in thousands)	Contract Liabilities
BALANCE - December 31, 2018	$	13,806
Additions for advanced billings		30,134
Additions resulting from adoption of Topic 606		803
Deductions for promised goods/services provided in current period		(21,164	)
BALANCE – December 31, 2019	$	23,579

The following table summarizes the Company’s collaboration revenues for the periods indicated (in thousands). Approximately $7.0 million and $5.0 million of total collaboration revenue represents revenue derived from foreign countries for the years ended December 31, 2019 and 2018, respectively.

	For the Year Ended December 31,
(Dollars in thousands)	2019		2018
Collaboration Partner – Janssen	$	2,912	$	1,232
Collaboration Partner – Ultragenyx		5,862		6,794
Collaboration Partner – CureVac		6,611		4,427
Collaboration Partner – SGI		3,518		1,402
Other		1,886		1,898
Total collaboration revenue	$	20,789	$	15,753

The following paragraphs provide information on the nature and purpose of these collaboration arrangements.

Collaboration Partner – Janssen

Janssen 2017 Agreement

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

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

As of December 31, 2019, 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 33 months. None of the development and commercialization milestones were included in the transaction price as they are outside the control of the Company and contingent upon success in future clinical trials and the collaborator’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur, provided that the reported sales are reliably measurable, and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to Janssen and therefore have also been excluded from the transaction price.

Total deferred revenue as of December 31, 2019 and December 31, 2018 for Janssen was $5.9 million and $6.5 million, respectively. No transition adjustment was necessary upon adoption of Topic 606.

Collaboration Partner – Ultragenyx

In October 2015 the Company entered into a research collaboration and license agreement with Ultragenyx (the “Ultragenyx Agreement”), whereby Arcturus granted to Ultragenyx a co-exclusive license under Arcturus technology 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 (as further described below) during the second quarter of 2019. During the initial phase of the collaboration, the Company will design and optimize therapeutics for certain rare disease targets. Ultragenyx has the option under the Ultragenyx Agreement to add additional rare disease targets during the collaborative development period. Additionally, during the collaborative development period, the Company will participate with Ultragenyx in a joint steering committee. The Ultragenyx Agreement also includes an initial exclusivity period with an option to extend this period.

As part of the Ultragenyx Agreement and related amendments, Ultragenyx has paid $27.9 million in upfront fees, exclusivity extension fees and additional consideration. Ultragenyx also reimburses the Company for internal and external development costs incurred pursuant to the Ultragenyx Agreement, and 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. Upon certain net annual commercial sales thresholds, 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 from $0.5 million to $1.5 million.

The current potential development, regulatory and commercial milestone payments for the existing development targets as of December 31, 2019 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 December 31, 2019, the Company has not yet reached the clinical phase of the contract.

On June 18, 2019, Arcturus and Ultragenyx amended the collaboration agreement for a third time (“Amendment 3”). As part of Amendment 3, the total number of targets was increased from 10 to 12, and reserve targets will be exclusively reserved for Ultragenyx with no fees for four years after execution of the amendment. An equity component was also added as part of Amendment 3 wherein Ultragenyx purchased 2.4 million shares of common stock at a premium price. Along with the equity purchase, Ultragenyx received the option to purchase 0.6 million additional shares of common stock at $16 per share within two years of executing the amendment (Note 8).

The consideration received from Ultragenyx as a result of Amendment 3 was equal to $30.0 million and was comprised of a $24.0 million common stock purchase and a $6.0 million upfront payment. Specifically for Amendment 3, management determined the transaction price to be $14.4 million. See further discussion below regarding determining the transaction price. Management determined the fair value of the premium received by using the opening stock price subsequent to execution of Amendment 3 and applying a lack of marketability discount as the shares received by Ultragenyx are restricted for two years.

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

At December 31, 2019, 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 milestone consideration is outside the control of the Company and contingent upon success in future clinical trials, approval from the Food and Drug Administration and the collaborator’s efforts. Any consideration related to sales-based royalties will be recognized when the related sales occur as they are constrained, provided that the reported sales are reliably measurable and the Company has no remaining promised goods/services, as such sales were determined to relate predominantly to the license granted to Ultragenyx and therefore have also been excluded from the transaction price.

Amendment 3 was deemed a contract modification and accounted for as part of the original Ultragenyx Agreement and the Company recorded a cumulative catch-up adjustment of $1.1 million on the modification date. The transaction price will be recognized to revenue on a straight-line basis using an input method over the 4-year reserve target exclusivity period. The reserve target exclusivity period represents the timing over which promised goods/services will be provided. Total deferred revenue as of December 31, 2019 and December 31, 2018 from Ultragenyx was $12.7 million and $2.7 million, respectively.

Upon adoption of Topic 606, the Company reversed $0.8 million of previously recorded revenue related to Ultragenyx through an increase to deferred revenue and a decrease to beginning accumulated deficit. The adjustment was due to a change in the way the Company accounts for updates to the period over which revenue is recognized as well as accounting for adjustments to the transaction price. Under Topic 605, the Company accounted for these changes prospectively and under Topic 606 the Company accounts for the changes as a change in estimate recorded as a cumulative catch-up in the period in which the change occurred.

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

Prior to expiration of the initial term of 8 years (which was subsequently amended, as discussed below), the Agreement also includes an option to extend the term on an annual basis for up to 3 years and subject to payment by CureVac to Arcturus of a non-refundable annual extension fee. The agreement included potential milestone payments for selected targets from CureVac to the Company. The current potential milestone payment for the remaining targets as of December 31, 2019 is $14.0 million for rare disease targets and $23.0 million for non-rare disease targets. CureVac will pay royalties as a percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term in the low single-digit range. As of December 31, 2019, the Company has not yet reached the clinical phase of the contract. Pursuant to a May 2018 amendment to the Development and Option Agreement (as amended and restated on September 28, 2018), the Company increased the number of targets available to CureVac under the Development and Option Agreement and agreed upon the license forms to be executed upon selection of the targets by CureVac.

Concurrently with the Development and Option Agreement, the Company entered into a Co-Development and Co-Commercialization Agreement (the “Co-Development Agreement”) which the Company considered a combined contract with the Development and Option Agreement for purposes of revenue recognition. However, on February 11, 2019, the Company announced the termination of the obligations of CureVac for the preclinical development of ARCT-810, effective 180 days from February 5, 2019 and the re-assumption by the Company of the worldwide rights thereto. As a result, Arcturus will reassume 100% of the global rights for its flagship asset, clinical development candidate ARCT-810, a messenger RNA (mRNA) drug to treat ornithine transcarbamylase deficiency.

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

In connection with the CureVac Amendment, the Company and CureVac also entered into a Termination Agreement (the “Termination Agreement”) terminating the Co-Development Agreement between the Company and CureVac dated as of January 1, 2018. The Termination Agreement is effective as of July 26, 2019. Pursuant to the Termination Agreement, CureVac agreed to make a settlement payment to Arcturus in the amount of $4.0 million. The payment was made in July 2019 and was recognized as revenue during the period in which the related expenses were incurred.

In evaluating the CureVac Development and Option Agreement and Co-Development Agreement in accordance with ASC Topic 606, the Company concluded that the contract counterparty, CureVac, is a customer. The Company has identified the following promised goods/services as part of the initial agreement with CureVac and subsequent amendments: (i) research services, (ii) license to use Arcturus technology, (iii) exclusivity and (iv) participation in the Joint Steering Committee. The Company concluded that the promised goods/services are incapable of being distinct 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.

At December 31, 2019, 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. During the year ended December 31, 2019, no adjustments were made to the transaction price.

The transaction price of $5.0 million was recorded as deferred revenue in the Company’s balance sheet upon receipt and is currently being recognized as revenue on a straight-line basis using an input method over the amended forty-six-month contractual term as of December 31, 2019. As a result of CureVac Amendment, the Company recorded a cumulative catch up adjustment of $0.4 million on the modification date, July 26, 2019. Total deferred revenue as of December 31, 2019 and December 31, 2018 for CureVac was $3.2 million and $4.4 million, respectively. No adjustment was necessary upon adoption of Topic 606.

Collaboration Partner – Synthetic Genomics

The Company entered into a Research and Exclusive License Agreement with Synthetic Genomics, Inc. (“SGI”) during the fourth quarter of 2017. Under the agreement, the Company granted SGI an exclusive license certain of our technology to research, develop and sell products for diseases excluding all respiratory disease viruses other than influenza. Revenue related to this agreement is made up of labor reimbursements and sublicense revenue. The sublicense revenue is calculated as a percentage of all cash payments received by SGI from any sublicense for a LUNAR product, in the mid 10% to 20% range, less payments made to third parties to obtain the right to practice intellectual property used to develop or necessary to make, use, or sell all or part of licensed LUNAR product. Under certain circumstances, the Company will be owed a percentage ranging from 5% to 10% of amounts received by SGI should they enter into agreements. As part of the agreement, SGI paid an upfront fee of $0.2 million upon contract execution which is creditable against any payments to Arcturus. Therefore, the upfront fee was fully deferred upon the receipt of funds.

As of December 31, 2019, there is no consideration included in the transaction price as all forms of consideration included in the agreement are fully constrained. As it relates to FTE reimbursements, the Company will recognize revenue as the services are performed and recognized $0.2 million and $1.2 million for the years ended December 31, 2019 and 2018, respectively. Additionally, sublicensee consideration is fully constrained until the subsequent sublicence by SGI occurs. The Company recognized a sublicense revenue amount of $3.3 million for year ended December 31, 2019 as SGI sublicensed the technology to multiple parties.

Other Collaboration Agreements

The remaining revenue from smaller collaboration agreements relates to the agreements with Millennium Pharmaceuticals, Inc., a wholly owned subsidiary of Takeda Pharmaceutical Company Limited (“Takeda”) and Providence Therapeutics, Inc. (“Providence”). Under the agreement with Takeda, the Company recognized $1.3 million related to amortization of an upfront payment during FY 2019 related to research and development activities. The current agreement was entered into on March 18, 2019 and is expected to be completed during the first half of 2020.

Under the agreement with Providence, the Company recognized revenue of $0.4 million from labor reimbursements and out-of-pocket cost reimbursements during FY 2019.

Fair Value Measurements

12 Months Ended

Dec. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

NOTE 4. Fair Value Measurements

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

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

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

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

Level 3: Unobservable inputs in which little or no market data exists and are therefore determined using estimates and assumptions developed by the Company, which reflect those that a market participant would use.

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

As of December 31, 2019 and 2018, all assets measured at fair value on a recurring basis consisted of cash equivalents, 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

Balance Sheet Details

12 Months Ended

Dec. 31, 2019

Balance Sheet Related Disclosures [Abstract]

Balance Sheet Details

NOTE 5. Balance sheet details

Accrued liabilities consisted of the following as of December 31, 2019 and December 31, 2018.

	December 31,
(in thousands)	2019		2018
Accrued compensation	$	1,608	$	974
Cystic Fibrosis Foundation Liability (Note 11)		1,949		—
Refundable fees received		—		2,259
Current portion of operating lease liability		827		—
Other accrued research and development expenses		2,750		674
Total	$	7,134	$	3,907

Property and Equipment, Net

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Property and Equipment, Net

NOTE 6. Property and Equipment, Net

Property and equipment, net consisted of the following:

	December 31,
(in thousands)	2019			2018
Research equipment	$	3,658		$	2,711
Computers and software		271			200
Office equipment and furniture		561			527
Leasehold improvements		40			34
Total	$	4,530		$	3,472
Less accumulated depreciation and amortization		(2,181	)		(1,497	)
Property and equipment, net	$	2,349		$	1,975

Depreciation and amortization expense was $684,000 and $582,000 for the years ended December 31, 2019 and 2018, respectively.

Debt

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Debt

NOTE 7. Debt

Long-term debt with Western Alliance Bank

On October 12, 2018, the Company entered into a Loan and Security Agreement with the Bank whereby the Company received gross proceeds of $10.0 million under a long-term debt agreement (the “Loan”).

The Loan is collateralized by all of the assets of the Company, excluding intellectual property, which is subject to a negative pledge. The Loan contains customary conditions of borrowing, events of default and covenants, including covenants that restrict the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. In addition, the Company is required to maintain at least 100% of its consolidated, unrestricted cash, or $15 million, whichever is lower, with the Bank.

On October 30, 2019, the Company and the Bank entered into a Third Amendment (the “Third Amendment”) to the Loan and Security Agreement dated as of October 12, 2018 (as amended, the “Loan Agreement”).

Pursuant to the amendment, the Bank agreed to make a term loan to the Company on October 30, 2019, in the amount of $15 million (the “Term Loan”). The resulting net increase in the indebtedness of the Company was $5.0 million. The Term Loan bears interest at a floating rate ranging from 1.25% to 2.75% above the prime rate. The amendment further provides that the Term Loan has a maturity date of October 30, 2023. The Company shall make monthly payments of interest only until the interest-only end date of April 1, 2021, which is subject to extension to October 1, 2021 upon the occurrence of an equity or expansion event and the absence of an event of default, and thereafter shall make monthly payments of principal and interest during a 30-month amortization period.

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

The Term Loan may be prepaid in full at any time, provided that a prepayment fee is required to be paid by the Company upon prepayment. The prepayment fee ranges from 0.50% to 2.00% of the prepaid principal amount depending upon the date on which the prepayment is made. In connection with the Third Amendment, the Company guaranteed the obligations under the Loan Agreement and pledged substantially all of its assets as security under the Loan Agreement.

The Term Loan also includes covenants which includes the Company’s submission of a clinical candidate for IND application made to the U.S. Food and Drug Administration by May 31, 2020 and have it accepted by June 30, 2020.

Upon maturity or prepayment, the Company will be required to pay a 3% fee, or a 2% fee if the U.S. Food and Drug Administration accepts certain Investigational New Drug (“IND”) applications prior to maturity. Because acceptance of an IND is outside of the Company’s control, management estimated that the Company will be liable for a fee of 3% of the principal balance, or $450,000 upon repayment or maturity, and such fee is accreted to the debt balance using the effective interest method over the term of the Loan Agreement.

Should an event of default occur, including the occurrence of a material adverse effect, the Company could be liable for immediate repayment of all obligations under the Loan Agreement. As of December 31, 2019, the Company was in compliance with all covenants under the Loan Agreement.

Principal payments, including the final payment due at repayment, on the long-term debt are as follows as of December 31, 2019:

Year Ending December 31,
2020	$	—
2021		4,000,000
2022		6,000,000
2023		5,450,000
Total		15,450,000

The Company recognized interest expense related to its long-term debt of $0.9 million and $0.2 million during the years ended December 31, 2019 and 2018, respectively.

Shareholders' Equity

12 Months Ended

Dec. 31, 2019

Stockholders Equity Note [Abstract]

Stockholders' Equity

NOTE 8. Stockholders’ Equity

Common Stock

Registered Direct Offerings

In July and September of 2019, the Company entered into engagement letters with H.C. Wainwright & Co., LLC (the “Placement Agent”) relating to registered direct offerings of common stock to certain institutional investors. Pursuant to each letter agreement, the Company agreed to pay the Placement Agent a cash fee of 6.0% of the gross proceeds from each offering and reimburse the cost of expenses.

In connection therewith, on August 1, 2019, August 2, 2019 and September 26, 2019, the Company and certain investors entered into securities purchase agreements relating to the issuance and sale of shares of common stock. The purchase price per share for each share offered in the offerings was $11.50. The aggregate gross proceeds of the offerings were $23.0 million for an aggregate of 1,995,653 shares of common stock.

The net proceeds to the Company from the offerings, after deducting Placement Agent fees and the Company’s estimated offering expenses, were approximately $21.3 million.

Equity Purchase Agreement

On June 18, 2019, the Company entered into an Equity Purchase Agreement (the “Expanded Ultragenyx Agreement”) with Ultragenyx. Pursuant to the terms of the Expanded Ultragenyx Agreement, the Company sold an aggregate of 2,400,000 shares of common stock, par value $0.001 per share (“Common Stock”) at a price of $10.00 per share to Ultragenyx on June 19, 2019. Ultragenyx is restricted from selling the shares of common stock for two years subsequent to the issuance date. Pursuant to the Expanded 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 Option to purchase additional shares of Common Stock may not be exercised if Ultragenyx’s ownership of the Company’s common stock would exceed 19.99% of the Company’s total shares outstanding following such exercise. The option was recorded as a component of stockholders’ equity within additional paid-in capital.

Pursuant to the terms of the Expanded Ultragenyx Agreement, until the later of (i) the first anniversary of the closing date or (ii) the date on which Ultragenyx beneficially owns less than 8.0% of the total voting power of the Company, at each annual shareholders’ meeting or any shareholders’ meeting at which members of the board of directors (the “Board”) are to be elected, the Company must nominate one director designated by Ultragenyx (the “Ultragenyx Designee”). Additionally, the Ultragenyx Designee has the contractual right to be appointed to all Board committees (subject to applicable Nasdaq rules). Ultragenyx also has the right to have a designee attend Board meetings as a non-voting observer.

In connection with the Expanded Ultragenyx Agreement, the Company and Ultragenyx entered into a Registration Rights Agreement (the “Registration Rights Agreement”). The Registration Rights Agreement required the Company to file a registration statement providing for the resale of the shares within 180 days of June 18, 2019 and provided Ultragenyx with certain “piggy-back” registration rights with respect to registration statements that the Company may file. The registration statement was filed by the Company on December 12, 2019.

Restricted Common Stock

In March 2013, the founders of the Company purchased 2,783,686 common stock of stock for $0.0068 per share. Of the shares purchased, 1,538,353 were subject to a repurchase option whereby the Company has an option for two months after date of termination of service to repurchase any or all of the unvested shares at the original purchase price per share. The repurchase option shall be deemed to be automatically exercised by the Company as of the end of the two-month period unless the Company notifies the purchaser that it does not intend to exercise its option. The shares will be vested (1) 25% after obtaining suitable siRNA license; (2) 25% after in vivo proof-of-concept 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 Common stock. In 2017, the common stock purchase agreements were amended to clarify vesting conditions and also to accelerate the vesting of 146,510 common stock resulting in a modification expense of $1,495,000 as of December 31, 2017. As of December 31, 2019 and 2018, there were 622,667 common stock unvested and subject to the repurchase option.

Net Loss per Share

Dilutive securities at December 31, 2019 and 2018 that were not included in the calculation of diluted net loss per share for the years ended December 31, 2019 and 2018 as they were anti-dilutive totaled 138,377 and 94,000, respectively.

For the years ended December 31, 2019 and 2018, the calculation of the weighted-average number of shares outstanding excludes unvested restricted common stock of 622,667.

Share-Based Compensation

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Share-Based Compensation

NOTE 9. Share-Based Compensation

In August 2018, the Company adopted the 2018 Omnibus Equity Incentive Plan (“2018 Plan”). Under the 2018 Plan, the Company is authorized to issue up to a maximum of 1,100,000 shares of common stock pursuant to the exercise of incentive stock options or other awards provided for therein. Outstanding options as shown in the table in this Note 9 represent a portion of authorized shares from the 2018 Plan along with previous option plans for all periods presented in the balance sheet. In June 2019, the Company adopted the 2019 Omnibus Equity Incentive Plan (“2019 Plan”), which was ratified by the shareholders at the Company’s annual meeting on October 25, 2019. 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 connection with the Redomiciliation, all outstanding options to purchase shares in Arcturus Israel were exchanged for an option to purchase the same number of shares of the Company’s common stock under the 2019 Plan. Accordingly, as of December 31, 2019, a total of 927,457 shares remain available for future issuance under the 2019 Plan.

Share Options

The following table presents the weighted-average assumptions used in the Black-Scholes valuation model by the Company in calculating the fair value of stock options granted:

	For the Year Ended December 31,
	2019			2018
Expected life (in years)		5.92			6.07
Expected volatility		73.9	%		73.3	%
Expected dividend yield		—	%		—	%
Risk-free interest rate		1.82	%		2.77	%
Grant date weighted average fair value	$	6.39		$	5.38

The following table summarizes the Company’s stock option activity for the year ended December 31, 2019:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding – December 31, 2018		1,184,433		$	7.41
Granted		590,115		$	7.81
Exercised		(24,290	)	$	5.72
Forfeited/cancelled		(101,182	)	$	8.01
Outstanding – December 31, 2019		1,649,076		$	7.54		8.59	$	5,498
Exercisable – December 31, 2019		581,135		$	7.03		7.68	$	2,236
Exercisable and expected to vest – December 31, 2019		1,649,076		$	7.54		8.59	$	5,498

At December 31, 2019, the total unrecognized compensation cost of $5.8 million will be recognized over the weighted-average remaining service period of approximately 2.7 years. The fair value of the options vested during the years ended December 31, 2019 and 2018 was $1.9 million and $1.0 million, respectively.

Share-based compensation expenses included in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019 and 2018 were:

	For the Year Ended December 31,
(in thousands)	2019		2018
Research and development	$	654	$	566
General and administrative		1,328		693
Total	$	1,982	$	1,259

Income Taxes

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Income Taxes

NOTE 10. Income Taxes

A reconciliation of loss before income taxes for domestic and foreign locations for the years ended December 31, 2019 and 2018 is as follows:

	For the Year Ended December 31,
(In thousands)	2019			2018
United States	$	(25,922	)	$	(21,604	)
Foreign		(69	)		(181	)
Total loss before income taxes	$	(25,991	)	$	(21,785	)

The Company accounts for income taxes in accordance with ASC 740-10, Accounting for Uncertainty in Income Taxes. The impact of an uncertain income tax position on the income tax return must be recognized at the largest amount that is more likely than not to be sustained upon audit by the relevant taxing authority. An uncertain tax position will not be recognized if it has less than 50% likelihood of being sustained.

A reconciliation of income tax expense for the years ended December 31, 2019 and 2018 is as follows (in millions):

	December 31,
	2019		2018
Beginning balance of unrecognized tax benefits	$	0.4	$	0.4
Settlement of prior period tax positions		—		—
Increase for prior period tax positions		—		—
Increase for current period tax positions		—		—
Ending balance of unrecognized tax benefits	$	0.4	$	0.4

Included in the balance of unrecognized tax benefits at both December 31, 2019 and 2018 is $0.4 million that could impact the Company’s effective tax rate, if recognized, subject to a valuation allowance. None of the unrecognized tax benefits currently impact the Company’s effective tax rate due to the full valuation allowance the Company has recorded against its deferred tax assets.

The Company is subject to taxation and files income tax returns in the United States, California and Israel. The Company’s tax years 2018 and 2019 are under examination in Israel. The Company’s tax years from 2013 to date are subject to examination by the Israeli, U.S. and state taxing authorities due to the carryforward of unutilized net operating losses and research and development credits. The Company’s policy is to recognize interest expense and penalties related to income tax matters as income tax expense. As of December 31, 2019, there are unrecognized tax benefits of $0.2 million and $0.2 million for the United States and California, respectively. There was no tax related interest or penalties recognized for the years ended December 31, 2019 and 2018.

The Company does not anticipate any material changes to its unrecognized tax benefits within the next twelve months.

The significant components of deferred income taxes at December 31, 2019 and 2018:

	December 31,
(in thousands)	2019			2018
Deferred tax assets:
Net operating loss	$	15,078		$	8,399
Tax credits		28			35
Accrued liabilities		410			261
Deferred revenue		1,248			1,713
Lease liability		1,466			—
Depreciation and amortization		—			46
Share-based compensation		339			85
Total gross deferred tax assets		18,569			10,539
Deferred tax liabilities:
Depreciation and amortization		(11	)		—
Right-of-use asset		(1,326	)		—
Valuation allowance		(17,232	)		(10,539	)
Net deferred tax asset	$	—		$	—

The Company has established a valuation allowance against net deferred tax assets due to the uncertainty that such assets will be realized. The Company periodically evaluates the recoverability of the deferred tax assets. At such time as it is determined that it is more likely than not that deferred tax assets will be realizable, the valuation allowance will be reduced.

At December 31, 2019, the Company had federal and state net operating losses (“NOL”) carryforwards of approximately $59.0 million and $42.8 million, respectively. The federal NOL carryforwards begin to expire in 2034, and the state NOL carryforwards begin to expire in 2034. The federal net operating loss carryover includes $43.2 million of net operating losses generated in 2018 and after. Federal net operating losses generated in 2018 and afterwards carryover indefinitely and may generally be used to offset up to 80% of future taxable income. The Company has foreign NOL carryforwards of approximately $89.3 million that do not expire and can be carried forward indefinitely. Due to the Company’s recent Redomiciliation and planned liquidation of the Israel entity, it is more likely than not that the foreign NOL will not be realized. As a result, the Company has removed the foreign NOL carryforwards from its deferred tax asset schedule and recorded a corresponding decrease to its valuation allowance beginning January 1, 2018.

Excluded from the deferred tax assets for the net operating losses are pre-acquisition Alcobra Inc. and Alcobra Ltd. federal and foreign losses of $0.3 million and $20.5 million, respectively. The Company does not believe these losses will be available to use in the future due to limitations under IRC Section 382 and contemplated restructuring as well as restructuring and planned liquidation of Arcturus Therapeutics Ltd.

At December 31, 2019, the Company had federal and state research and development credit carryforwards of approximately $0.2 million and $0.2 million, respectively. The federal credit carryforwards begin to expire in 2033, and the state credits carry forward indefinitely.

The Company has also incurred research and development expenses of $33.6 million and $17.0 million for the years ended December 31, 2019 and 2018, respectively. The Company believes that a portion of these expenditures will yield additional federal and California tax credits; however, the potential credits under the tax laws have not yet been calculated.

Pursuant to Internal Revenue Code of 1986, as amended (the “Code”) Sections 382 and 383, annual use of the Company’s federal and California net operating loss and research and development credit carryforwards may be limited in the event a cumulative change in ownership of more than 50% occurs within a three-year period. The Company has not completed a Code Section 382 analysis regarding the limitation of net operating loss carryforwards and other tax attributes. There is a risk that changes in ownership have occurred since Company’s formation. If a change in ownership were to have occurred, the NOL carryforwards and other tax attributes could be limited or restricted. If limited, the related asset would be removed from the deferred tax asset schedule with a corresponding reduction in the valuation allowance. Due to the existence of the valuation allowance, limitations created by future ownership changes, if any, related to the Company’s operations in the U.S. will not impact the Company’s effective tax rate.

A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows:

	For the Year Ended December 31,
	2019			2018
Federal statutory income tax rate		21.0	%		21.0	%
State income taxes, net of federal benefit		4.6	%		5.3	%
Foreign rate differential		0.3	%		(1.3	%)
Share-based compensation		(0.1	%)		(0.2	%)
Change in tax rate		(0.1	%)		—	%
Change in valuation allowance		(25.1	%)		(20.7	%)
Other		0.1	%		(3.0	%)
Permanent differences		(0.7	%)		(1.1	%)
Provision for income taxes		—	%		—	%

ASC Topic 606

The Company adopted Accounting Standards Codification (“ASC”) Topic 606 - Revenue from Contracts with Customers (the new revenue guidance), on January 1, 2018. Under Topic 606, the Company recognizes revenue when its customers obtain control of promised goods or services, in an amount that reflects the consideration which the Company expects to be entitled in exchange for those goods or services. Upon adoption, no change in retained earnings was recorded related to income taxes as the Company maintains a full valuation allowance. An adjustment of $0.2 million was recorded as a deferred tax asset and a corresponding increase to the valuation allowance. See above for more information about the non-income tax impact of adoption of the new revenue guidance.

ASC Topic 842

The Company adopted Accounting Standards Codification (“ASC”) Topic 842 - Leases, on January 1, 2019. Under Topic 842, the Company is required to recognize the assets and liabilities that arise from most operating leases on the balance sheet. Upon adoption, no change in retained earnings was recorded related to income taxes as the Company maintains a full valuation allowance. As of the implementation date, an adjustment of $1.7 million was recorded as a deferred tax liability and an adjustment of $1.7 million was recorded as a deferred tax asset. See above for more information about the non-income tax impact of adoption of the new leasing standard.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

NOTE 11. Commitments and Contingencies

Cystic Fibrosis Foundation Therapeutics Funding 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 will increase 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, (iii) the related disbursement schedule from CFF to Arcturus will be modified such that (a) $4.0 million will be disbursed upon execution of the CFF Amendment, (b) $2.0 million will be disbursed within 30 days of the first day of each of January, April, July and October 2020 upon Arcturus invoicing CFF to meet project goals, and (c) the last payment of $3.0 million less the prior award previously paid out, equaling approximately $2.3 million, will be disbursed upon Arcturus Sub invoicing CFF to meet good manufacturing practices and opening an Investigational New Drug (“IND”) application. The funds received from CFF will be recognized as contra research and development expense in proportion to the percentage covered by CFF of the overall budget. For the year ended December 31, 2019, the Company recognized $2.0 million of contra expense with $1.9 million remaining in accrued expenses.

Leases

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

Operating lease right-of-use asset and liability on the consolidated balance sheets represent the present value of remaining lease payments over the remaining lease terms. The Company does not allocate lease payments to non-lease components; therefore, payments for common-area-maintenance and administrative services are not included in the operating lease right-of-use asset and liability. The Company uses its incremental borrowing rate to calculate the present value of the lease payments, as the implicit rate in the lease is not readily determinable.

As of December 31, 2019, the payments of the operating lease liability were as follows:

(in thousands)	Remaining Lease Payments
2020	$	1,272
2021		1,310
2022		1,349
2023		1,390
2024		1,432
Thereafter		314
Total remaining lease payments		7,067
Less: imputed interest		(1,390	)
Total operating lease liabilities	$	5,677
Weighted-average remaining lease term	5.25 years
Weighted-average discount rate		8.4	%

Operating lease costs consist of the fixed lease payments included in operating lease liability and are recorded on a straight-line basis over the lease terms. Operating lease costs were $1.2 million and $1.1 million for the years ended December 31, 2019 and 2018, respectively.

Related Party Transactions

12 Months Ended

Dec. 31, 2019

Related Party Transactions

Note 12. Related Party Transactions

Ultragenyx

On June 17, 2019, Arcturus and Ultragenyx executed Amendment 3. In addition, as a result of the Expanded Ultragenyx Agreement, Ultragenyx owns 15.9% of the outstanding common stock of the Company as of December 31, 2019. For the year ended December 31, 2019, the Company has recognized revenue of $5.9 million and for the year ended December 31, 2018, the Company recognized revenue of $6.8 million. As of December 31, 2019 and 2018, the Company holds accounts receivable balances of negligible amounts.

Equity-Method Investment

As noted above at Note 2, the Company completed the sale of its intangible asset related to the ADAIR technology. Pursuant to the asset purchase agreement for ADAIR, the Company received a 30% ownership interest in the common stock of a privately held company in consideration for the sale of the ADAIR technology. The Company has no requirement to invest further in this private company. During the third quarter of 2019, the equity-method investee issued shares of its common stock at a share price greater than the initial investment which resulted in the Company recording a gain in its equity-method investment. The gain, partly offset by additional losses incurred by the equity-method investee and calculated on a lag, resulted in a net gain of a negligible amount for the year ended December 31, 2019. Subsequent to the equity-method investee issuing shares of its common stock, the Company’s ownership was reduced to 19%. As the Company continues to have the ability to exercise significant influence over the operating and financial policies of the investee, the Company will continue to account for the investment as an equity-method investment.

Litigation

12 Months Ended

Dec. 31, 2019

Loss Contingency Information About Litigation Matters [Abstract]

Litigation

Note 13. Litigation

On December 13, 2019, a former employee of the Company filed a complaint in San Diego County Superior Court, captioned Adonary Munoz v. Arcturus Therapeutics, Inc., et al, Case No. 37-2019-00066358-CU-PO-CTL. The lawsuit alleges sexual assault by an acquaintance of one of our employees and seeks to hold the Company liable on a number of causes of action. On January 17, 2020, a second amended complaint (“SAC”) was filed seeking $30 million in damages, including punitive damages and damages for emotional distress. The Company is required to file a response to the SAC by March 20, 2020. The Company believes the allegations of Ms. Munoz in her complaint are without merit, and intends to vigorously defend itself in the foregoing action. However, in light of the preliminary stage of the litigation, the Company is unable to estimate a potential loss or range of losses relating to this matter.

Subsequent Events

12 Months Ended

Dec. 31, 2019

Subsequent Events [Abstract]

Subsequent Events

Note 14. Subsequent Events

On March 4, 2020, the Company was awarded a grant (the “Grant”) from the Singapore Economic Development Board (“EDB”) to support the co-development of a COVID-19 vaccine with the Duke-NUS Medical School. The grant provides for up to S$14.0 million (approximately US$10.0 million using the March 4, 2020 exchange rate) in grants to support the development of the vaccine. A portion of the Grant will be paid by the EDB in advance and the remainder of the Grant will be paid to the Company upon the achievement of certain milestones related to the progress of the development of the vaccine, as set forth in the award agreement. The Company has agreed to pay Duke-NUS Medical School a royalty based on annual net sales of the vaccine in markets or jurisdictions outside of Singapore.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Basis of Presentation and Principles of Consolidation

Segment Information

Cash and Cash Equivalents

Cash equivalents are short-term highly liquid investments that are readily convertible to cash with original maturities of three months or less at the date of purchase.

Restricted Cash

Restricted cash

Fair Value Measurements

Accounts Receivable

Concentration of Credit Risk and Significant Customers

Intangible Assets Held for Sale and Equity Method Investment

Property and Equipment, net

Comprehensive Income/Loss

Revenue Recognition

See “Note 3, Collaboration Revenue” for specific details surrounding the Company’s collaboration arrangements.

Research and Development Costs, net

Share-Based Compensation

Statement of Cash Flows

Statement of cash flows

	As of December 31,
(in thousands)	2019		2018
Cash and cash equivalents	$	71,353	$	36,709
Non-current Restricted cash		107		107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$	71,460	$	36,816

Income Tax Expense

Net Loss per Share

No dividends were declared or paid during the reporting periods.

Recently Issued Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Revenue from Contracts with Customers

Leases

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2019

Accounting Policies [Abstract]

Schedule of Cash and Cash Equivalents and Restricted Cash

	As of December 31,
(in thousands)	2019		2018
Cash and cash equivalents	$	71,353	$	36,709
Non-current Restricted cash		107		107
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$	71,460	$	36,816

Collaboration Revenue (Tables)

12 Months Ended

Dec. 31, 2019

Collaboration Agreements [Abstract]

Summary of Changes in Balances of Contract Assets and Contract Liability

(in thousands)	Contract Assets
BALANCE - December 31, 2018	$	4,480
Additions for revenue recognized		17,523
Deductions for cash collections		(19,824	)
BALANCE - December 31, 2019	$	2,179

(in thousands)	Contract Liabilities
BALANCE - December 31, 2018	$	13,806
Additions for advanced billings		30,134
Additions resulting from adoption of Topic 606		803
Deductions for promised goods/services provided in current period		(21,164	)
BALANCE – December 31, 2019	$	23,579

Summary of Collaboration Revenue

	For the Year Ended December 31,
(Dollars in thousands)	2019		2018
Collaboration Partner – Janssen	$	2,912	$	1,232
Collaboration Partner – Ultragenyx		5,862		6,794
Collaboration Partner – CureVac		6,611		4,427
Collaboration Partner – SGI		3,518		1,402
Other		1,886		1,898
Total collaboration revenue	$	20,789	$	15,753

Balance Sheet Details (Tables)

12 Months Ended

Dec. 31, 2019

Balance Sheet Related Disclosures [Abstract]

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following as of December 31, 2019 and December 31, 2018.

	December 31,
(in thousands)	2019		2018
Accrued compensation	$	1,608	$	974
Cystic Fibrosis Foundation Liability (Note 11)		1,949		—
Refundable fees received		—		2,259
Current portion of operating lease liability		827		—
Other accrued research and development expenses		2,750		674
Total	$	7,134	$	3,907

Property and Equipment, Net (Tables)

12 Months Ended

Dec. 31, 2019

Property Plant And Equipment [Abstract]

Summary of Components of Property and Equipment

Property and equipment, net consisted of the following:

	December 31,
(in thousands)	2019			2018
Research equipment	$	3,658		$	2,711
Computers and software		271			200
Office equipment and furniture		561			527
Leasehold improvements		40			34
Total	$	4,530		$	3,472
Less accumulated depreciation and amortization		(2,181	)		(1,497	)
Property and equipment, net	$	2,349		$	1,975

Debt (Tables)

12 Months Ended

Dec. 31, 2019

Debt Disclosure [Abstract]

Schedule of Maturities of Long-term Debt

Principal payments, including the final payment due at repayment, on the long-term debt are as follows as of December 31, 2019:

Year Ending December 31,
2020	$	—
2021		4,000,000
2022		6,000,000
2023		5,450,000
Total		15,450,000

Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Schedule of Weighted Average Assumptions Used in Black -Scholes Valuation Model

The following table presents the weighted-average assumptions used in the Black-Scholes valuation model by the Company in calculating the fair value of stock options granted:

	For the Year Ended December 31,
	2019			2018
Expected life (in years)		5.92			6.07
Expected volatility		73.9	%		73.3	%
Expected dividend yield		—	%		—	%
Risk-free interest rate		1.82	%		2.77	%
Grant date weighted average fair value	$	6.39		$	5.38

Summary of Share Option Activity

The following table summarizes the Company’s stock option activity for the year ended December 31, 2019:

	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding – December 31, 2018		1,184,433		$	7.41
Granted		590,115		$	7.81
Exercised		(24,290	)	$	5.72
Forfeited/cancelled		(101,182	)	$	8.01
Outstanding – December 31, 2019		1,649,076		$	7.54		8.59	$	5,498
Exercisable – December 31, 2019		581,135		$	7.03		7.68	$	2,236
Exercisable and expected to vest – December 31, 2019		1,649,076		$	7.54		8.59	$	5,498

Schedule of Share-based Compensation Expenses

Share-based compensation expenses included in the Company’s statements of operations and comprehensive loss for the years ended December 31, 2019 and 2018 were:

	For the Year Ended December 31,
(in thousands)	2019		2018
Research and development	$	654	$	566
General and administrative		1,328		693
Total	$	1,982	$	1,259

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2019

Income Tax Disclosure [Abstract]

Summary of Reconciliation of Loss Before Income Taxes for Domestic and Foreign Locations

A reconciliation of loss before income taxes for domestic and foreign locations for the years ended December 31, 2019 and 2018 is as follows:

	For the Year Ended December 31,
(In thousands)	2019			2018
United States	$	(25,922	)	$	(21,604	)
Foreign		(69	)		(181	)
Total loss before income taxes	$	(25,991	)	$	(21,785	)

Summary of Reconciliation of Income Tax Expense

A reconciliation of income tax expense for the years ended December 31, 2019 and 2018 is as follows (in millions):

	December 31,
	2019		2018
Beginning balance of unrecognized tax benefits	$	0.4	$	0.4
Settlement of prior period tax positions		—		—
Increase for prior period tax positions		—		—
Increase for current period tax positions		—		—
Ending balance of unrecognized tax benefits	$	0.4	$	0.4

Significant Components of Deferred Income Taxes

The significant components of deferred income taxes at December 31, 2019 and 2018:

	December 31,
(in thousands)	2019			2018
Deferred tax assets:
Net operating loss	$	15,078		$	8,399
Tax credits		28			35
Accrued liabilities		410			261
Deferred revenue		1,248			1,713
Lease liability		1,466			—
Depreciation and amortization		—			46
Share-based compensation		339			85
Total gross deferred tax assets		18,569			10,539
Deferred tax liabilities:
Depreciation and amortization		(11	)		—
Right-of-use asset		(1,326	)		—
Valuation allowance		(17,232	)		(10,539	)
Net deferred tax asset	$	—		$	—

Reconciliation of Federal Statutory Income Tax Rate to Company's Effective Income Tax Rate

A reconciliation of the federal statutory income tax rate to the Company’s effective income tax rate is as follows:

	For the Year Ended December 31,
	2019			2018
Federal statutory income tax rate		21.0	%		21.0	%
State income taxes, net of federal benefit		4.6	%		5.3	%
Foreign rate differential		0.3	%		(1.3	%)
Share-based compensation		(0.1	%)		(0.2	%)
Change in tax rate		(0.1	%)		—	%
Change in valuation allowance		(25.1	%)		(20.7	%)
Other		0.1	%		(3.0	%)
Permanent differences		(0.7	%)		(1.1	%)
Provision for income taxes		—	%		—	%

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2019

Commitments And Contingencies Disclosure [Abstract]

Payments of Operating Lease Liability

As of December 31, 2019, the payments of the operating lease liability were as follows:

(in thousands)	Remaining Lease Payments
2020	$	1,272
2021		1,310
2022		1,349
2023		1,390
2024		1,432
Thereafter		314
Total remaining lease payments		7,067
Less: imputed interest		(1,390	)
Total operating lease liabilities	$	5,677
Weighted-average remaining lease term	5.25 years
Weighted-average discount rate		8.4	%

Organization (Details Textual) $ in Thousands			3 Months Ended	12 Months Ended
Organization (Details Textual) $ in Thousands	Jun. 18, 2019 USD ($)	Jun. 12, 2019	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Organization And Significant Accounting Policies [Line Items]
Issued ordinary shares and options to purchase ordinary shares, conversion description				one-for-one
Stock, conversion ratio		1
Accumulated deficit				$ (71,668)	$ (44,874)
Total net proceeds through sale of equity securities			$ 21,400
Research Collaboration and License Agreement [Member] \| Ultragenyx [Member]
Organization And Significant Accounting Policies [Line Items]
Third amendment fee received	$ 24,000
Upfront payment received	$ 6,000

Summary of Significant Accounting Policies (Details Textual)		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2019 USD ($) Segment Customer	Dec. 31, 2018 USD ($) Customer
Summary Of Significant Accounting Policy [Line Items]
Number of Operating Segments \| Segment		1
Non-current restricted cash		$ 107,000	$ 107,000
Lease expiration year		2025
Allowance for Doubtful Accounts Receivable		$ 0	0
Equity method ownership percentage		30.00%
Impairment losses		$ 0	0
Income tax effect related to unrealized losses on marketable securities		0	0
Dividends declared or paid		0	0
Increase in deferred revenue due to adoption of new revenue recognition		8,970,000	$ 159,000
Operating lease liability		5,677,000
Operating lease right-of-use asset		$ 5,134,000
Office and Lab Space [Member]
Summary Of Significant Accounting Policy [Line Items]
Operating lease liability	$ 6,400,000
Operating lease right-of-use asset	5,900,000
ASC 606 [Member]
Summary Of Significant Accounting Policy [Line Items]
Increase in deferred revenue due to adoption of new revenue recognition	800,000
Increase in accumulated deficit	$ 800,000
Employees and Officers [Member]
Summary Of Significant Accounting Policy [Line Items]
Share options expiration period		10 years
Vesting period		4 years
Vesting description		Share-based compensation is recognized over the requisite service period of the individual awards using the straight-line attribution method, which generally equals the vesting period. Employees and officers’ share options have a ten-year life and generally vest 25% on the first anniversary of the grant and in 1/36th equal installments on each monthly anniversary thereafter, such that options are fully vested on the four-year anniversary of the date of grant.
First Year Anniversary of the Grant [Member] \| Employees and Officers [Member]
Summary Of Significant Accounting Policy [Line Items]
Vesting percentage		25.00%
Minimum [Member]
Summary Of Significant Accounting Policy [Line Items]
Equity method ownership percentage		20.00%
Property and equipment, useful lives		3 years
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Property and equipment, useful lives		5 years
Credit Risk [Member] \| Accounts Receivable [Member]
Summary Of Significant Accounting Policy [Line Items]
Number of customers \| Customer		1	1
Concentration risk, percentage		98.00%	96.00%
Credit Risk [Member] \| Revenue [Member]
Summary Of Significant Accounting Policy [Line Items]
Number of customers \| Customer		4	3
Concentration risk, percentage		91.00%	80.00%

Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 71,353,000	$ 36,709,000
Non-current Restricted cash	107,000	107,000
Total cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 71,460,000	$ 36,816,000	$ 25,238,000

Collaboration Revenue - Summary of Changes in Balances of Contract Assets and Contract Liability (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Collaboration Agreements [Abstract]
Contract Assets, Balance	$ 4,480
Contract Assets, Additions for revenue recognized	17,523
Contract Assets, Deductions for cash collections	(19,824)
Contract Assets, Balance	2,179
Contract Liabilities, Balance	13,806
Contract Liabilities, Additions for advanced billings	30,134
Contract Liabilities, Additions resulting from adoption of Topic 606	803
Contract Liabilities, Deductions for promised goods/services provided in current period	(21,164)
Contract Liabilities, Balance	$ 23,579

Collaboration Revenue (Details Textual)					12 Months Ended
Collaboration Revenue (Details Textual)	Jul. 26, 2019 USD ($)	Feb. 11, 2019	Jan. 01, 2019 USD ($)	Jun. 18, 2018 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($)	Jun. 18, 2019 Target	Jun. 16, 2019 Target
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					$ 20,789,000	$ 15,753,000
Deferred revenue					$ 23,579,000	$ 13,806,000
Purchase of common stock, shares \| shares					15,138,000	10,762,000
Increase in deferred revenue due to adoption of new revenue recognition					$ 8,970,000	$ 159,000
ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase in deferred revenue due to adoption of new revenue recognition			$ 800,000
Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					2,912,000	1,232,000
Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					5,862,000	6,794,000
Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					6,611,000	4,427,000
Minimum [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	4 years
Maximum [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential target license term	8 years
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received					7,700,000
Revenue recognition potential milestone revenue recognized					56,500,000
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member] \| ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation					0
Deferred revenue					5,900,000	6,500,000
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					5,900,000	6,800,000
Upfront payment received				$ 6,000,000	27,900,000
Revenue recognition potential milestone revenue recognized					$ 138,000,000
Royalty payment term description					Ultragenyx will pay royalties as a single-digit percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term.
Number of targets \| Target								12	10
Purchase of common stock, shares \| shares				2,400,000
Purchase of additional shares of common stock \| shares				600,000
Purchase of additional shares of common stock price per share \| $ / shares				$ 16
Consideration received				$ 30,000,000
Consideration received for common stock purchase				24,000,000
Transaction price				$ 14,400,000
Lack of marketability discount restricted period				2 years
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member] \| ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation					$ 0
Deferred revenue					$ 12,700,000	2,700,000
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. As part of its evaluation of the constraint
Cumulative catch up adjustment					$ 1,100,000
Revenue recognition, reserve target exclusivity period					4 years
Increase in deferred revenue due to adoption of new revenue recognition					$ 800,000
Decrease in accumulated deficit due to adoption of new revenue recognition					800,000
Research Collaboration And Exclusive License Agreement [Member] \| Minimum [Member] \| Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target							$ 1,000,000
Research Collaboration And Exclusive License Agreement [Member] \| Minimum [Member] \| Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target					500,000
Research Collaboration And Exclusive License Agreement [Member] \| Maximum [Member] \| Collaboration Partner Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target							$ 5,000,000
Research Collaboration And Exclusive License Agreement [Member] \| Maximum [Member] \| Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Option exercise revenue range per target					1,500,000
Research Collaboration And Exclusive License Agreement [Member] \| Foreign Countries [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					$ 7,000,000	5,000,000
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Royalty payment term description					CureVac will pay royalties as a percentage of net sales on a product-by-product and country-by-country basis during the applicable royalty term in the low single-digit range
Development and option agreement date					Jan. 31, 2018
Expiration of initial term					8 years
Option to extend initial term on an annual basis					3 years
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member] \| Rare Disease Targets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized					$ 14,000,000
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member] \| Non-Rare Disease Targets [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognition potential milestone revenue recognized					23,000,000
mRNA Technology [Member] \| Collaboration Partner - CureVac [Member] \| ASC 606 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Remaining performance obligation	$ 0
Deferred revenue					3,200,000	4,400,000
Transaction price					$ 5,000,000
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
Contractual term					46 months
Cumulative catch up adjustment					$ 400,000
mRNA Technology [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement termination date		Feb. 11, 2019
Percentage of global rights reassumed		100.00%
Termination Agreement [Member] \| Collaboration Partner CureVac Entered Into Co Development Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement settlement obligation settled amount	$ 4,000,000
Research And Exclusive License Agreement \| Synthetic Genomics, Inc [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					200,000	$ 1,200,000
Upfront fee received					200,000
Sublicense revenue recognized					$ 3,300,000
Research And Exclusive License Agreement \| Minimum [Member] \| Synthetic Genomics, Inc [Member] \| LUNAR Product [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of all cash payments received					10.00%
Research And Exclusive License Agreement \| Minimum [Member] \| Synthetic Genomics, Inc [Member] \| Non-LUNAR Product [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of consideration received					5.00%
Research And Exclusive License Agreement \| Maximum [Member] \| Synthetic Genomics, Inc [Member] \| LUNAR Product [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of all cash payments received					20.00%
Research And Exclusive License Agreement \| Maximum [Member] \| Synthetic Genomics, Inc [Member] \| Non-LUNAR Product [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of consideration received					10.00%
Other Collaboration Agreements [Member] \| Takeda Pharmaceutical Company Limited and Providence Therapeutics Incorporation [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue related to amortization of upfront payment					$ 1,300,000
Labor reimbursement and out-of pocket revenue recognized					$ 400,000

Collaboration Revenue - Summary of Collaboration Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 20,789	$ 15,753
Collaboration Partner - Janssen [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	2,912	1,232
Collaboration Partner - Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	5,862	6,794
Collaboration Partner - CureVac [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	6,611	4,427
Collaboration Partner - SGI [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	3,518	1,402
Other Collaboration [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total collaboration revenue	$ 1,886	$ 1,898

Collaboration Revenue (Details Textual 1)	Dec. 31, 2019
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner Janssen [Member] \| ASC 606 [Member] \| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-01-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Remaining research period	33 months

Balance Sheet Details - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Accrued compensation	$ 1,608	$ 974
Cystic Fibrosis Foundation Liability (Note 11)	1,949
Refundable fees received		2,259
Current portion of operating lease liability	827
Other accrued research and development expenses	2,750	674
Total	$ 7,134	$ 3,907

Property and Equipment, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 4,530	$ 3,472
Less accumulated depreciation and amortization	(2,181)	(1,497)
Property and equipment, net	2,349	1,975
Research equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,658	2,711
Computer and software [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	271	200
Office equipment and furniture [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	561	527
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 40	$ 34

Property and Equipment, Net (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Abstract]
Depreciation and amortization	$ 684	$ 582

Debt (Details Textual) - USD ($)			12 Months Ended
Debt (Details Textual) - USD ($)	Oct. 30, 2019	Oct. 12, 2018	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Interest expense related to long-term debt			$ 900,000	$ 200,000
Loan and Security Agreement [Member] \| Western Alliance Bank [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Gross proceeds from long-term debt agreement		$ 10,000,000
Debt instrument, collateral			The Loan is collateralized by all of the assets of the Company, excluding intellectual property, which is subject to a negative pledge. The Loan contains customary conditions of borrowing, events of default and covenants, including covenants that restrict the Company’s ability to dispose of assets, merge with or acquire other entities, incur indebtedness and make distributions to holders of the Company’s capital stock. In addition, the Company is required to maintain at least 100% of its consolidated, unrestricted cash, or $15 million, whichever is lower, with the Bank.
Debt instrument, collateral amount		15,000,000
Term loan	$ 15,000,000
Net increase in indebtedness	$ 5,000,000
Loan maturity date	Oct. 30, 2023
Loan interest-only payment extended maturity date	Oct. 01, 2021
Loan interest-only payment maturity date	Apr. 01, 2021
Debt Instrument, amortization period	30 months
Loan origination fee paid		54,000
Warrant fee payable		$ 525,000
Prepayment fee percentage		3.00%
Prepayment fee percentage		2.00%
Percentage of fee liable on principal balance		3.00%
Fee payable upon repayment		$ 450,000
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%

Debt - Summary of Final Payment Due at Repayment (Details)	Dec. 31, 2019 USD ($)
Debt Disclosure [Abstract]
2021	$ 4,000,000
2022	6,000,000
2023	5,450,000
Total	$ 15,450,000

Stockholders' Equity (Details Textual)				1 Months Ended	12 Months Ended
Stockholders' Equity (Details Textual)	Sep. 26, 2019 USD ($) $ / shares shares	Jun. 19, 2019 $ / shares shares	Jun. 18, 2019	Mar. 31, 2013 $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 ₪ / shares shares	Dec. 31, 2017 USD ($) Milestone shares	Dec. 31, 2016 Milestone	Dec. 31, 2014 shares
Class Of Stock [Line Items]
Gross proceeds from offering \| $					$ 21,278,000
Common stock, shares issued					15,138,000	10,762,000
Common stock, par value \| (per share)					$ 0.001	₪ 0.07
Antidilutive securities excluded from computation of earnings per share					138,377	94,000
Unvested Restricted Ordinary Shares [Member]
Class Of Stock [Line Items]
Antidilutive securities excluded from computation of earnings per share					622,667	622,667
Restricted Common Stock [Member]
Class Of Stock [Line Items]
Stock issued during period				2,783,686
Share price of stock issued \| $ / shares				$ 0.0068
Shares subject to repurchase option				1,538,353
Share based compensation arrangement by share based payment award period from termination date of employee or consultant for repurchase of shares				2 months
Number of milestones achieved \| Milestone							2	2
Common shares, unvested					622,667,000	622,667,000			769,176,000
Accelerated ordinary shares vested							146,510,000
Modification expense resulting from accelerated vesting of ordinary shares \| $							$ 1,495,000
Vested After Obtaining Suitable siRNA License [Member] \| Restricted Common Stock [Member]
Class Of Stock [Line Items]
Shares vesting percentage				25.00%
Vested After in Vivo Proof-of-concept Achieved [Member] \| Restricted Common Stock [Member]
Class Of Stock [Line Items]
Shares vesting percentage				25.00%
Vested After IND Application Completed [Member] \| Restricted Common Stock [Member]
Class Of Stock [Line Items]
Shares vesting percentage				25.00%
Vested After in Human Efficacy Achieved [Member] \| Restricted Common Stock [Member]
Class Of Stock [Line Items]
Shares vesting percentage				25.00%
Equity Purchase Agreement [Member] \| Collaboration Partner - Expanded Ultragenyx [Member]
Class Of Stock [Line Items]
Common stock purchase price per share \| $ / shares		$ 10.00
Common stock, shares issued		2,400,000
Common stock, par value \| $ / shares		$ 0.001
Common stock shares restricted from selling period subsequent to issuance date		2 years
Purchase of additional shares of common stock		600,000
Purchase of additional shares of common stock price per share \| $ / shares		$ 16.00
Equity Purchase Agreement [Member] \| Collaboration Partner - Ultragenyx [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Ownership interest of common stock		8.00%
Registration Rights Agreement \| Collaboration Partner - Ultragenyx [Member]
Class Of Stock [Line Items]
Percentage of minimum common stock may not exercised total shares outstanding			19.99%
Registration Rights Agreement \| Collaboration Partner - Ultragenyx [Member] \| Maximum [Member]
Class Of Stock [Line Items]
Period to register sale of shares			180 days
H.C. Wainwright & Co., LLC [Member] \| Securities Purchase Agreement [Member]
Class Of Stock [Line Items]
Net proceeds from offerings after deducting placement agent fees and offering expenses \| $	$ 21,300,000
Common Stock [Member]
Class Of Stock [Line Items]
Stock issued during period					1,995,000
Common Stock [Member] \| H.C. Wainwright & Co., LLC [Member] \| Letter Agreement [Member]
Class Of Stock [Line Items]
Percentage of cash fee on gross proceeds from offering					6.00%
Common Stock [Member] \| H.C. Wainwright & Co., LLC [Member] \| Securities Purchase Agreement [Member] \| Investor
Class Of Stock [Line Items]
Common stock purchase price per share \| $ / shares	$ 11.50
Gross proceeds from offering \| $	$ 23,000,000
Common stock, shares issued	1,995,653

Share-Based Compensation (Details Textual) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jun. 30, 2019	Aug. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost not yet recognized	$ 5.8
Weighted-average remaining service period	2 years 8 months 12 days
Fair value of options vested	$ 1.9	$ 1.0
2018 Omnibus Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized				1,100,000
2019 Omnibus Equity Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation number of shares authorized			2,600,000
Common stock reserved for future issuance	927,457

Share-Based Compensation (Details) - Stock Option [Member] - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected life (in years)	5 years 11 months 1 day	6 years 25 days
Expected volatility	73.90%	73.30%
Risk-free interest rate	1.82%	2.77%
Grant date weighted average fair value	$ 6.39	$ 5.38

Share-Based Compensation (Details 1) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding \| shares	1,184,433
Number of Shares, Granted \| shares	590,115
Number of Shares, Exercised \| shares	(24,290)
Number of Shares, Forfeited/cancelled \| shares	(101,182)
Number of Shares, Outstanding \| shares	1,649,076
Number of Shares, Exercisable – December 31, 2019 \| shares	581,135
Number of Shares, Exercisable and expected to vest – December 31, 2019 \| shares	1,649,076
Weighted-Average Exercise Price, Outstanding \| $ / shares	$ 7.41
Weighted-Average Exercise Price, Granted \| $ / shares	7.81
Weighted-Average Exercise Price, Exercised \| $ / shares	5.72
Weighted-Average Exercise Price, Forfeited/cancelled \| $ / shares	8.01
Weighted-Average Exercise Price, Outstanding – December 31, 2019 \| $ / shares	7.54
Weighted-Average Exercise Price, Exercisable - December 31, 2019 \| $ / shares	7.03
Weighted-Average Exercise Price, Exercisable and expected to vest -December 31, 2019 \| $ / shares	$ 7.54
Weighted-Average Remaining Contractual Term (Years), Outstanding - December 31, 2019	8 years 7 months 2 days
Weighted-Average Remaining Contractual Term (Years), Exercisable - December 31, 2019	7 years 8 months 4 days
Weighted-Average Remaining Contractual Term (Years), Exercisable and expected to vest - December 31, 2019	8 years 7 months 2 days
Aggregate Intrinsic Value, Outstanding - December 31, 2019 \| $	$ 5,498
Aggregate Intrinsic Value, Exercisable - December 31, 2019 \| $	2,236
Aggregate Intrinsic Value, Exercisable and expected to vest - December 31, 2019 \| $	$ 5,498

Share-Based Compensation (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 1,982	$ 1,259
Research and Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	654	566
General and Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation expenses	$ 1,328	$ 693

Income Taxes (Details 1) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details 1) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
United States	$ (25,922)	$ (21,604)
Foreign	(69)	(181)
Total loss before income taxes	$ (25,991)	$ (21,785)

Income Taxes (Details Textual) - USD ($)			12 Months Ended
Income Taxes (Details Textual) - USD ($)	Jan. 01, 2019	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Maximum percentage of likelihood of uncertain tax position recognized to be sustained			50.00%
Unrecognized Tax Benefits			$ 400,000	$ 400,000	$ 400,000
Unrecognized tax benefits impacting effective tax rate			0	0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense			0	0
Research and Development Expenses			$ 33,640,000	16,982,000
Net Operating Loss and Research and Development Credit Carryforwards Limitations On Cumulative Change In Ownership Minimum Percentage			50.00%
Net Operating Loss and Research and Development Credit Carryforwards Limitations on Cumulative Change In Ownership Period			3 years
ASC Topic 606 [Member]
Income Taxes [Line Items]
Deferred tax asset, increase in valuation allowance		$ 200,000
ASC Topic 842 [Member]
Income Taxes [Line Items]
Adjustment to deferred tax liability	$ 1,700,000
Adjustment to deferred tax assets	$ 1,700,000
Federal [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards			$ 59,000,000	$ 43,200,000
Operating Loss Carryforwards Expiration Year			2034
Federal [Member] \| Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Credit Carryforward Amount			$ 200,000
Credit Carryforward Expiration Year			2033
Federal [Member] \| Alcobra Inc. and Alcobra Ltd. [Member]
Income Taxes [Line Items]
Net operating loss amount excluded from deferred tax assets			$ 300,000
State [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards			$ 42,800,000
Operating Loss Carryforwards Expiration Year			2034
State [Member] \| Research Tax Credit Carryforward [Member]
Income Taxes [Line Items]
Credit Carryforward Amount			$ 200,000
Credit Carryforward Expiration Year			2033
Foreign [Member]
Income Taxes [Line Items]
Operating Loss Carryforwards			$ 89,300,000
Foreign [Member] \| Alcobra Inc. and Alcobra Ltd. [Member]
Income Taxes [Line Items]
Net operating loss amount excluded from deferred tax assets			20,500,000
United States [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits			200,000
California [Member]
Income Taxes [Line Items]
Unrecognized Tax Benefits			$ 200,000
Israel [Member]
Income Taxes [Line Items]
Tax years under examination			2018 2019

Income Taxes (Details 2) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Reconciliation Of Unrecognized Tax Benefits Excluding Amounts Pertaining To Examined Tax Returns Roll Forward
Beginning balance of unrecognized tax benefits	$ 0.4	$ 0.4
Ending balance of unrecognized tax benefits	$ 0.4	$ 0.4

Income Taxes (Details 3) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deferred tax assets:
Net operating loss	$ 15,078	$ 8,399
Tax credits	28	35
Accrued liabilities	410	261
Deferred revenue	1,248	1,713
Lease liability	1,466
Depreciation and amortization		46
Share-based compensation	339	85
Total gross deferred tax assets	18,569	10,539
Deferred tax liabilities:
Depreciation and amortization	(11)	0
Right-of-use asset	(1,326)	0
Valuation allowance	$ (17,232)	(10,539)
Net deferred tax asset		$ 0

Income Taxes (Details 4)	12 Months Ended
Income Taxes (Details 4)	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal statutory income tax rate	21.00%	21.00%
State income taxes, net of federal benefit	4.60%	5.30%
Foreign rate differential	0.30%	(1.30%)
Share-based compensation	(0.10%)	(0.20%)
Change in tax rate	(0.10%)
Change in valuation allowance	(25.10%)	(20.70%)
Other	0.10%	(3.00%)
Permanent differences	(0.70%)	(1.10%)

Commitments and Contingencies (Details Textual) - USD ($)			1 Months Ended	12 Months Ended
	Jul. 13, 2019	Jul. 12, 2019	Oct. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Commitment And Contingencies [Line Items]
Operating lease costs				$ 1,200,000	$ 1,100,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Payments for matching funds for remaining budgeted costs	$ 5,000,000
Disbursed amount upon execution of amendment	4,000,000
Final payment of disbursement amount	3,000,000
Disbursement payment upon achievement of required manufacturing practices and IND application	2,300,000
Contra expense included in research and development expense				2,000,000
Contra expense remaining amount included in accrued expenses				$ 1,900,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due January 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due April 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due July 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member] \| Disbursement Due October 2020 [Member]
Commitment And Contingencies [Line Items]
Disbursement amount payable upon achievement of project goal	2,000,000
October 2017 Lease Amendment [Member]
Commitment And Contingencies [Line Items]
Operating lease extended additional term			84 months
Lessor, 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
LUNAR-CF [Member] \| Underlying Agreement [Member] \| Cystic Fibrosis Foundation [Member]
Commitment And Contingencies [Line Items]
Payments for advance	$ 15,000,000	$ 3,200,000

Commitments and Contingencies - Payments of Operating Lease Liability (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Leases [Abstract]
2020	$ 1,272
2021	1,310
2022	1,349
2023	1,390
2024	1,432
Thereafter	314
Total remaining lease payments	7,067
Less: imputed interest	(1,390)
Total operating lease liabilities	$ 5,677
Weighted-average remaining lease term	5 years 3 months
Weighted-average discount rate	8.40%

Related Party Transactions - Ultragenyx (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Related Party Transaction [Line Items]
Collaboration revenue	$ 20,789	$ 15,753
Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Collaboration revenue	$ 5,862	6,794
Research Collaboration And Exclusive License Agreement [Member] \| Collaboration Partner - Ultragenyx [Member]
Related Party Transaction [Line Items]
Ownership interest of common stock	15.90%
Collaboration revenue	$ 5,900	$ 6,800

Related Party Transactions - Equity-Method Investment (Details Textual)	Dec. 31, 2019
Related Party Transaction [Line Items]
Equity method ownership percentage	30.00%
Minimum [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage	20.00%
ADAIR Technology [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage	30.00%
ADAIR Technology [Member] \| Minimum [Member]
Related Party Transaction [Line Items]
Equity method ownership percentage	19.00%

Litigation (Details Textual) $ in Millions	Jan. 17, 2020 USD ($)
Subsequent Event [Member]
Loss Contingencies [Line Items]
Loss contingency, damage sought, value	$ 30

Subsequent Events (Details Textual) - Mar. 04, 2020	USD ($)	SGD ($)
Subsequent Event [Member] \| Maximum [Member] \| Singapore Economic Development Board [Member]
Subsequent Event [Line Items]
Grant awarded	$ 10,000,000	$ 14,000,000