SEC Filing | Arcturus Therapeutics, Inc.

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Filed Pursuant to Rule 424(b)(5)

Registration No. 333-251175

The information in this preliminary prospectus supplement is not complete and may be changed. A registration statement relating to these securities has been filed with the Securities and Exchange Commission and is effective. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and we are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to Completion, dated December 7, 2020

PRELIMINARY PROSPECTUS SUPPLEMENT

(To prospectus dated December 7, 2020)

Shares

Common Stock

We are offering an aggregate of shares of our common stock pursuant to this prospectus supplement and accompanying prospectus.

Our common stock is listed on the Nasdaq Global Market under the symbol “ARCT.” The last reported sale price of our common stock on the Nasdaq Global Market on December 7, 2020 was $123.66 per share.

An investment in our common stock involves a high degree of risk. Please read “Risk Factors” on page S-8 of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement before investing in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

	Per Share	Total
Public offering price	$	$
Underwriting discounts and commissions⁽¹⁾	$	$
Proceeds, before expenses, to us	$	$

___________________

(1)	We refer you to “Underwriting” beginning on page S-21 of this prospectus supplement for information regarding underwriting compensation.

We have granted the underwriters an option to purchase up to an additional shares of our common stock from us at the public offering price, less the underwriting discounts and commissions, within 30 days from the date of this prospectus supplement.

The underwriters expect to deliver the shares against payment on or about , 2020.

Joint Book-Running Managers

Piper Sandler

Guggenheim Securities

Wells Fargo Securities

The date of this prospectus supplement is , 2020.

TABLE OF CONTENTS

Prospectus Supplement

Page

About This Prospectus Supplement	S-1
Prospectus Supplement Summary	S-2
The Offering	S-7
Risk Factors	S-8
Cautionary Note Regarding Forward-Looking Statements	S-13
Use Of Proceeds	S-15
Dividend Policy	S-15
Dilution	S-16
Material U.S. Federal Income Tax Consequences For Non-U.S. Holders Of Our Common Stock	S-17
Underwriting	S-21
Legal Matters	S-26
Experts	S-26
Where You Can Find Additional Information	S-26
Incorporation Of Certain Information By Reference	S-26

Prospectus

Page

About This Prospectus	1
Where You Can Find More Information	1
Incorporation of Certain Documents by Reference	2
Cautionary Note Regarding Forward-Looking Statements	3
Prospectus Summary	5
Risk Factors	6
Use of Proceeds	6
Description of Capital Stock We May Offer	6
Description of Debt Securities We May Offer	9
Description of Warrants We May Offer	16
Description of Units We May Offer	18
Plan of Distribution	20
Legal Matters	22
Experts	22

ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is the prospectus supplement, including the documents incorporated by reference herein, which describes the specific terms of this offering and also adds to and updates the information contained in the accompanying prospectus and the documents incorporated by reference therein. The second part, the accompanying prospectus, including the documents incorporated by reference therein, provides more general information, some of which may not apply to this offering. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. Before you invest, you should carefully read this prospectus supplement, the accompanying prospectus and the information incorporated by reference herein and therein, as well as the additional information described in this prospectus supplement under “Where You Can Find Additional Information.” This prospectus supplement may add, update or change information contained in the accompanying prospectus. To the extent that any statement we make in this prospectus supplement is inconsistent with statements made in the accompanying prospectus or any documents incorporated by reference therein, the statements made in this prospectus supplement will be deemed to modify or supersede those made in the accompanying prospectus and such documents incorporated by reference therein. However, if any statement in one of these documents is inconsistent with a statement in another document with a later date that is incorporated by reference herein, the statement in the document having the later date modifies and supersedes the earlier statement. Before buying any of the shares of common stock that we are offering, we urge you to carefully read this prospectus supplement, the accompanying prospectus and any related free writing prospectus and all of the information incorporated by reference herein and therein, as well as the additional information described under the headings “Where You Can Find Additional Information” and “Incorporation of Certain Information by Reference.” These documents contain important information that you should consider when making your investment decision.

You should rely only on the information contained in or incorporated by reference in this prospectus supplement, the accompanying prospectus, and any related free writing prospectus filed by us with the Securities and Exchange Commission, or SEC. Neither we nor the underwriters have authorized any other person to provide you with any information that is different. If anyone provides you with different or inconsistent information, you should not rely on it.

This prospectus supplement does not constitute an offer to sell or the solicitation of an offer to buy any securities other than the shares of common stock described in this prospectus supplement or an offer to sell or the solicitation of an offer to buy such securities in any circumstances in which such offer or solicitation is unlawful. Persons outside the United States who come into possession of this prospectus supplement must inform themselves about, and observe any restrictions relating to, the offering of the shares of common stock and the distribution of this prospectus supplement outside the United States.

You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference herein and therein and any related free writing prospectus is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed materially since those dates.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference in this prospectus supplement or the accompanying prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

In this prospectus supplement, the terms “Arcturus Therapeutics,” “we,” “us,” “our” and the “Company” refer to Arcturus Therapeutics Holdings Inc. and its predecessors and consolidated subsidiaries unless otherwise stated or the context otherwise requires.

The Arcturus logo and other trademarks of Arcturus are some of our trademarks and registered marks used in this prospectus supplement and the documents incorporated by reference herein. This prospectus supplement and the documents incorporated by reference herein also include trademarks, tradenames and service marks that are the property of other organizations. Solely for convenience, our trademarks and tradenames appear without the ^® and ^™ symbol, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights, or the right of the applicable licensor to these trademarks and tradenames.

S-1

PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights information contained in other parts of this prospectus supplement or incorporated by reference from our Annual Report on Form 10-K for the year ended December 31, 2019 and our other filings with the SEC listed under the section of the prospectus titled “Incorporation of Certain Information by Reference” contained in this prospectus supplement. This summary does not contain all of the information you should consider in making your investment decision. Before deciding to invest in our common stock, you should read this prospectus supplement, the accompanying prospectus, any related free writing prospectus and the information incorporated by reference herein and therein in their entirety. You should carefully consider, among other things, the matters discussed under the section titled “Risk Factors” contained in this prospectus supplement and any related free writing prospectus, and under similar headings in the other documents that are incorporated by reference in this prospectus supplement and the accompanying prospectus. Some of the statements in this prospectus supplement constitute forward-looking statements that involve risks and uncertainties. See the section titled “Cautionary Note Regarding Forward-Looking Statements.”

Company Overview

We are a clinical-stage messenger RNA medicines company focused on the development of infectious disease vaccines and significant opportunities within liver and respiratory rare diseases utilizing our Self-Transcribing and Replicating RNA (“STARR”) technology. In addition to our internal messenger RNA (“mRNA”) platform, our proprietary lipid mediated delivery system, LUNAR, has the potential to enable multiple nucleic acid medicines.

Our key proprietary technology has the potential to address the major hurdles in RNA development, namely the effective and safe delivery of RNA therapeutics to disease-relevant target tissues. We believe the versatility of our platform to target multiple tissues, its compatibility with various nucleic acid therapeutics, and our expertise in developing scalable manufacturing processes puts us in a good position to deliver on the next generation of nucleic medicines.

We have deep expertise in the discovery and development of RNA medicines, including key experience in the production of RNA drug substance and nanoparticle-formulated drug product.

We have a pipeline of eleven drug candidates in late-stage discovery and early-stage development, five of which are wholly-owned and six of which involve partnered programs

We have developed and continue to develop LUNAR, a novel lipid-mediated delivery technology platform, which draws from a growing library of over 200 lipids that were designed at Arcturus and many of which are claimed in issued patents. Other lipids in this growing library are undergoing extensive research to test for desirable properties, and we continue to seek patent protection for newly designed lipids. Our lipid library is intended to enable safer and more efficient delivery than lipids commonly used in the industry.

We have developed the STARR technology platform which combines self-replicating RNA with LUNAR into a single solution for partners.

Our wholly-owned, LUNAR and nucleic acid technologies are covered by a patent portfolio of 200 patents and patent applications, issued in the United States, China, Europe, Japan and other countries. This patent portfolio covers our proprietary mRNA and STARR chemistry, design, modifications and manufacturing process as well as our LUNAR chemistry, design and drug product manufacturing.

We believe that we can use our proprietary technologies to develop RNA medicines in multiple therapeutic approaches: (1) mRNA, DNA, and replicon protein replacement for therapeutics and antigen expression for vaccines; (2) siRNA, microRNA, and antisense oligonucleotides - knockdown of genes overexpressed in disease; and (3) CRISPR, TALEN, zinc finger proteins, megaTALs and meganucleases - gene editing of errant genes.

S-2

Recent Developments

LUNAR-COV19 Vaccine Candidate

Coronaviruses are a family of viruses that can lead to respiratory illness, including Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV). Coronaviruses are transmitted between animals and people and can evolve into strains not previously identified in humans. On January 7, 2020, a novel coronavirus was identified as the cause of pneumonia cases in Wuhan City, Hubei Province of China. On February 11, 2020 the World Health Organization announced the official name for the disease that caused the 2019 novel coronavirus outbreak as coronavirus disease 2019, commonly abbreviated as COVID-19. The spread of COVID-19 has resulted in the current global coronavirus pandemic.

In response to this pandemic, in March of 2020 we partnered with Duke-NUS Medical School to develop a COVID-19 vaccine for the Singapore Economic Development Board, or EDB, based on the Company’s STARR™ Technology and designated the vaccine candidate LUNAR-COV19. Duke-NUS Medical School is a graduate entry medical school in Singapore, established in 2005 through a partnership between Duke University School of Medicine and the National University of Singapore (NUS).

On March 4, 2020, we were awarded a grant from the EDB to support the co-development of LUNAR-COV19 with Duke-NUS Medical School. In exchange for the grant, we agreed to supply LUNAR-COV19 to the EDB for use within Singapore and we retained the right to sell and market LUNAR-COV19 outside of Singapore. We have agreed to pay Duke-NUS Medical School a low single digit royalty based on annual net sales of the vaccine in markets or jurisdictions outside of Singapore.

On April 27, 2020, we released positive immunogenicity data from our preclinical study in rodents for LUNAR-COV19, as measured by investigators at the Duke-NUS Medical School. Seroconversion, using an industry standard virus neutralization assay (Vero-E6 cells with a SARS-CoV-2 Singapore Clinical Isolate), and IgG/IgM antibody titers were assessed at day 10 and day 19. Rodents were immunized with a single dose (0.2, 2, and 10 µg, i.m.) of LUNAR-COV19 vaccine. The study results showed self-transcribing and replicating (STARR™) mRNA induced higher seroconversion relative to conventional mRNA at equivalent doses. In conjunction, anti-SARS-CoV-2 IgG and IgM antibody titers were also higher.

On May 4, 2020, we entered into an agreement with Catalent, Inc. to manufacture LUNAR-COV19 at Catalent’s cGMP drug substance biomanufacturing facility in Madison, Wisconsin, for human clinical studies.

On May 8, 2020, we disclosed new supportive preclinical data, providing evidence for an adaptive cellular (CD8+ cells) and balanced (Th1/Th2) immune response data from LUNAR-COV19, providing strong support for human vaccine clinical trials. The preclinical data was measured by investigators at the Duke-NUS Medical School.

On June 30, 2020, we submitted a Clinical Trial Application (CTA) for LUNAR-COV19 to the Singapore Health Sciences Authority (HSA). On July 20, 2020, the HSA notified us that LUNAR-COV19 was approved to proceed into clinical trials. We commenced a Phase 1/2 clinical trial in Singapore in August 2020 to test several dose levels of LUNAR-COV19 in up to 108 adults, including older adults, to evaluate safety, tolerability and the extent and duration of the humoral and cellular immune response.

On August 17, 2020, our wholly owned subsidiary entered into a definitive Supply Agreement (the “Supply Agreement”) with the Israeli Ministry of Health (“MOH”) which provides for the supply of LUNAR-COV19 to the MOH. The MOH has elected to reserve delivery by us of doses of LUNAR-COV19 for an initial 500,000 vaccinations (the “Initial Reserve Doses”). The Supply Agreement also provides the MOH with the right to elect, in its discretion, to purchase additional doses of LUNAR-COV19 upon notice to us prior to specified dates at specified purchase prices. If the MOH elects to purchase the maximum number of doses currently subject to reservations or rights to reserve under the Supply Agreement, the total purchase price will range between $212.5 million and $225 million, with the exact price tied to when we obtain the required regulatory approvals. As a result of the entry into the Supply Agreement, the MOH has secured the right to receive the doses subject to reservation or rights to reserve before any third party other than Singapore, subject to certain terms and conditions. On October 14, 2020, we received a non-refundable first reserve payment of US$12.5 million from the MOH. This first reserve payment of US$12.5 million is associated with a specified clinical trial milestone, and was provided after a data review process during which the MOH had access to material preclinical and clinical data for our LUNAR-COV19 vaccine candidate. This payment serves as partial payment for the Initial Reserve Doses.

S-3

On October 2, 2020, our wholly-owned subsidiary was awarded a grant (the “Grant”) from the Singapore Economic Development Board (the “EDB”) to support the further development of our LUNAR-COV19 vaccine candidate. The Grant provides for up to S$9.3 million (approximately US$6.7 million) to support the development of the vaccine candidate. The Grant will be paid in two installments upon the achievement of certain milestones related to the progress of the development of the vaccine candidate.

In November 2020, we announced interim Phase 1/2 data suggesting favorable immunogenicity and safety results for both single-dose and prime-boost regimens. Such data also observed 100% seroconversion for IgG binding antibodies in younger adults; 1 out of 5 older adult participants has not yet seroconverted; observed geometric mean titer (GMT)> 2300 in all cohorts. In addition, in November 2020, we secured manufacturing slots with Recipharm to support cGMP manufacture, and completed the transfer of our lyophilization technology. In November 2020, we also announced a manufacturing support agreement with Singapore’s EDB that includes a limited recourse loan of $45 million and terms for LUNAR-COV19 vaccine purchase of up to $175 million, with shipments to Singapore of LUNAR-COV19 for stockpiling purposes expected to begin as early as the first quarter of 2021.

We intend to utilize a portion of the proceeds of this offering to fund clinical trials and manufacturing of LUNAR-COV19.

We also expect to seek additional funding to continue development and scaling up of LUNAR-COV19 from securities offerings in the future and from additional contracts with foreign governmental authorities in addition to those of Singapore and Israel.

S-4

ARCT-810 mRNA-based therapeutic candidate for OTC deficiency

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

The Phase 1b study and Phase 1 study are focused on an mRNA-based therapeutic candidate for OTC deficiency named ARCT-810. ARCT-810 utilizes our LUNAR® lipid-mediated delivery platform to deliver OTC messenger RNA to liver cells. The ARCT-810 program is supported by preclinical data in OTC deficiency murine models demonstrating that dosing of LUNAR-OTC results in robust OTC protein expression and activity resulting in improvements in ureagenesis and plasma ammonia, and increased survival. Worldwide development and commercialization rights to ARCT-810 are entirely held by Arcturus.

On June 5, 2020, we announced that we dosed the first healthy volunteer in a Phase 1 study of ARCT-810 in a double blind, placebo-controlled, dose-escalation trial in healthy adult volunteers. The study evaluated four cohorts in total; three cohorts with six subjects each and one cohort (the top dose of 0.4 mg/kg) with 12 subjects. In each cohort, four (or eight) subjects are expected to received ARCT-810 and two (or four) have received a placebo. The study is intended to evaluate safety and tolerability, pharmacokinetics, and exploratory pharmacodynamic biomarkers.

In November 2020, we announced that we completed dose escalation for ARCT-810 of all cohorts (0.1, 0.2, 0.3, 0.4 mg/kg) in our Phase 1 Study, and that the Phase 1b study in OTC-deficient patients in the United States was open for enrollment. We intend to commence a Phase 2 multiple does study for ARCT-810 in mid-2021.

On December 7, 2020, we announced that we initiated dosing in the United States in our Phase 1b trial of ARCT-810 in patients with OTC deficiency. The trial will enroll approximately 12 patients and is designed to assess safety, tolerability and pharmacokinetics, as well as various exploratory biomarkers of drug activity.

LUNAR-FLU Vaccine

Flu season is an annually recurring time period characterized by the prevalence of outbreaks of influenza (flu). The season occurs during the cold half of the year in each hemisphere. Influenza activity can usually be predicted and even tracked geographically.

Arcturus is initiating a pipeline program to develop a vaccine against seasonal flu. The program builds on the STARR/LUNAR platform and the learnings from our COVID-19 vaccine program. The vaccine will be quadrivalent and target hemagglutinin antigens from two strains of Influenza/A and two strains of Influenza/B. The intended product will mediate serological conversion of antibody-mediated immunity following a single intramuscular injection.

LUNAR-CV Targeted mRNA Therapeutic

We are developing a mRNA replacement therapy targeting Low-Density Lipoprotein (LDL) Receptor (LDLR) for the treatment of homozygous familial hypercholesterolemia (HoFH), a severe genetic disease characterized by premature and aggressive plaque buildup, life threatening coronary artery disease and aortic valve disease predominantly due to abnormalities in the function or expression of LDLR. Present therapies do not sufficiently lower the plasma LDL-cholesterol (LDL-C) that lead to cardiovascular disease. Our preliminary studies in an LDLR knock out mouse model have demonstrated restoration of normal LDL plasma levels following a single intravenous administration of a LUNAR-mRNA encoding the LDLR. This normalization returned to baseline as the drug was metabolized.

Ultragenyx Option Exercise

On June 18, 2019, we entered into an Equity Purchase Agreement with Ultragenyx Pharmaceutical Inc. (“Ultragenyx”). Pursuant to this agreement, we granted Ultragenyx a two-year option to purchase up to 600,000 additional shares of our common stock at a price of $16.00 per share. On May 20, 2020, Ultragenyx completed the exercise of this option to purchase an additional 600,000 shares of Common Stock in accordance with the terms of the agreement. The issuance of the additional 600,000 shares closed on May 20, 2020.

S-5

Corporate Information

Our company was founded in 2013 as Arcturus Therapeutics, Inc., and we have maintained our principal executive offices in San Diego, California since that time. In November 2017, Alcobra Ltd., an Israeli limited company, merged with our company, changed its name to Arcturus Therapeutics Ltd. (“Arcturus Israel”), and commenced trading on Nasdaq under the symbol “ARCT.” On June 17, 2019, we redomiciled to the United States (the “Redomiciliation”) and changed our name to Arcturus Therapeutics Holdings Inc., as described more fully below.

Redomiciliation

In May 2019, shareholders of Arcturus Israel approved 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.

S-6

THE OFFERING

Common stock offered by us	shares of our common stock

Option to purchase additional shares	We have granted the underwriters an option to purchase up to an additional shares of our common stock for a period of 30 days from the date of this prospectus supplement.

Use of proceeds	We intend to use the net proceeds from this offering to conduct clinical trials and to commence manufacturing our LUNAR-COV19 vaccine candidate for stockpiling purposes. See “Use of Proceeds” on page S-15 for additional information.

Risk factors	You should read the “Risk Factors” section of this prospectus supplement and in the documents incorporated by reference in this prospectus supplement for a discussion of factors that you should read and consider before investing in our common stock.

Nasdaq Global Market symbol	ARCT

The number of shares of our common stock to be outstanding immediately following this offering as shown above is based on 24,473,002 shares of our common stock outstanding on September 30, 2020 and excludes:

•

2,342,225 shares of our common stock reserved for issuance under stock option agreements issued pursuant to our 2019 Omnibus Equity Incentive Plan at a weighted average exercise price of $16.57 per share;

•

2,388,340 shares of our common stock reserved for future issuance under our Amended and Restated 2019 Omnibus Equity Incentive Plan; and

•

600,000 shares of our common stock reserved for future issuance under our 2020 Employee Stock Purchase Plan.

Except as otherwise noted, all information in this prospectus supplement assumes no exercise by the underwriters of their option to purchase additional shares of common stock.

S-7

RISK FACTORS

You should carefully consider the following risk factors and the risk factors discussed under “Item 1A—Risk Factors” contained in our Annual Report on Form 10-K for the fiscal year ended December 31, 2019 and in Part II, Item 1A, Risk Factors of our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2020, June 30, 2020 and September 30, 2020 and of any subsequently filed Annual Reports on Form 10-K and Quarterly Reports on Form 10-Q, which are incorporated by reference in this prospectus supplement in their entirety, together with all of the other information contained in this prospectus supplement and the accompanying prospectus or incorporated by reference in this prospectus supplement and the accompanying prospectus. The risks described in any document incorporated by reference are not the only ones we have, but are considered to be the most material. Additional risks of which we are not presently aware or that we currently believe are immaterial may also harm our business and results of operations. If any of these risks actually occur, our business, financial condition and results of operations would likely suffer. In that case, the market price of the common stock could decline, and you may lose part or all of your investment in our company.

Risks Related to the Discovery and Development of Product Candidates

We expect to announce data from the Phase 1/2 trial of our COVID-19 vaccine candidate in December 2020 and if positive commence a Phase 2 trial shortly thereafter. If we are unable to generate successful results, or experience significant delays in doing so, we may be unable to market and sell a COVID-19 vaccine.

We have completed dosing all subjects in our initial Phase 1/2 trial with several dose levels of LUNAR-COV19 and we are continuing to monitor and will release further data from this study. Based on the strength of the data already generated from the Phase 1/2 trial, we expect to commence a Phase 2 trial, of LUNAR-COV19 in the first quarter of 2021 in order to identify the optimal regimens. We also expect to commence our Phase 3 LUNAR-COV19 trial in the second quarter of 2021,and anticipate that it will continue through 2021. We plan to continue to monitor subjects in the Phase 3 trial into 2022 (whether or not we receive emergency use authorization for LUNAR-COV19 during 2021). We will need to identify additional funding sources to continue the Phase 3 trial. The data received to date, although providing sufficient information to allow us to proceed further is not complete enough to provide conclusive evidence with respect to conclusive safety and potential efficacy of LUNAR COV19. We have submitted a CTA and an IND application, respectively, to the HSA and the FDA to allow us to proceed with our Phase 2 clinical study. We are positioned to manufacture finished doses of LUNAR-COV19 in the first quarter of 2021 for stockpiling purposes. Clinical trial results are inherently uncertain, and a significant portion of our success and business prospects depend on the progress of this program. Our failure to demonstrate safety or obtain positive clinical trial results, or our inability to meet the expected timeline for release of data for this trial, could have an adverse effect on our business operations and financial condition. Furthermore, although we may receive preliminary efficacy data from the Phase 2 trials, we will not have a more detailed understanding of the efficacy of LUNAR-COV19 until a sufficient number of subjects in the placebo group of a Phase 3 clinical trial have been infected. If our data is not positive or inconclusive, we may not be able to continue our studies or identify additional funding to continue the studies. No assurance can be given that the results of the trials will produce adequate results to allow us to commence or continue expected trials or that that adequate efficacy will be demonstrated such that LUNAR-COV19 will be a viable commercial product. Finally, we cannot assure that either the HSA or FDA will approve our CTA or IND on a timely basis or at all.

There is significant competition in the development of a vaccine against COVID-19, and many of our competitors have substantially greater financial, scientific and other resources than us.

A large number of vaccine manufacturers, academic institutions and other organizations currently have programs to develop COVID-19 vaccine candidates. While we are not aware of all of our competitors’ efforts, there are reports that Johnson & Johnson/Janssen, Pfizer, GlaxoSmithKline, Moderna, Sanofi, Inovio, AstraZeneca and many other companies are all in various stages of developing vaccine candidates against COVID-19. In particular, both Pfizer and Moderna have reported that their COVID-19 vaccine candidates showed a high degree of efficacy in initial trials and are further along in clinical trials than we are, and it appears they will be able commercialize their vaccines before us.

Despite funding provided to us to date, many of our competitors pursuing vaccine candidates have significantly greater product candidate development, manufacturing and marketing resources than we do. Larger pharmaceutical and biotechnology companies have extensive experience in clinical testing and obtaining regulatory approval for their products, and may have the resources to heavily invest to accelerate discovery and development of their vaccine candidates. Our business could be materially and adversely affected if competitors develop and commercialize one or more COVID-19 vaccines before we can complete development and seek approval for our vaccine candidate, or if they develop and commercialize one or more COVID-19 vaccines that are safer, more effective, have fewer or less severe side effects, have broader market acceptance, are more convenient or are less expensive than any vaccine candidate that we may develop. Furthermore, if any competitors are successful in producing a more efficacious vaccine or other treatment for COVID-19, or if any competitors are able to manufacture and distribute any such vaccines or treatments with greater efficiency, there may be a diversion of potential governmental and other funding away from us and toward such other parties.

S-8

If we are unable to manufacture our vaccines in sufficient quantities, at sufficient yields or are unable to obtain regulatory approvals for a manufacturing facility for our LUNAR-COV19 vaccine, we may experience delays in product development, clinical trials, regulatory approval and commercial distribution.

Completion of our clinical trials and commercialization of our vaccine candidates require access to, or development of, facilities to manufacture our LUNAR-COV19 vaccine candidate at sufficient yields and at commercial-scale. We have limited experience manufacturing our LUNAR-COV19 vaccine candidate in the volumes that will be necessary to support large-scale clinical trials or commercial sales. Efforts to establish these capabilities may not meet initial expectations as to scheduling, scale-up, reproducibility, yield, purity, cost, stability, potency or quality. In addition, other companies, many with substantial resources, may compete with us for access to materials needed to manufacture our vaccines.

Manufacturing our LUNAR-COV19 vaccine candidate involves a complicated process with which we have limited experience. We are dependent on third-party organizations to conduct a portion of our vaccine manufacturing activities. If third-party manufacturing organizations are unable to manufacture our vaccine candidates in clinical quantities or, when necessary, in commercial quantities and at sufficient yields, then we will need to identify and reach supply arrangements with additional third parties. Third-party manufacturers must also be inspected by the FDA as part of the FDA’s review of our marketing application. Our LUNAR-COV19 vaccine may be in competition with other products for access to these facilities and may be subject to delays in manufacture if third parties give other products higher priority. We may not be able to enter into any necessary additional third-party manufacturing arrangements on acceptable terms, or on a timely basis. In addition, we have to enter into technical transfer agreements and share our know-how with the third-party manufacturers, which can be time-consuming and may result in delays. Any delay in the manufacture or delivery of a vaccine could adversely affect our ability to sell the LUNAR-COV19 vaccine, if approved.

Our reliance on third-party manufacturers may adversely affect our operations or result in unforeseen delays or other problems beyond our control. Because of contractual restraints and the limited number of third-party manufacturers with the expertise, required regulatory approvals and facilities to manufacture our bulk vaccines on a commercial scale, replacement of a manufacturer may be expensive and time-consuming and may cause interruptions in the production of our vaccine. A third-party manufacturer may also encounter difficulties in production. These problems may include:

	•	difficulties with production costs, scale up and yields;
	•	challenges in developing a lyophilized formula of, or validating a lyophilization process for, LUNAR-COV19;
	•	challenges in storage and cold chain distribution of LUNAR-COV19 (even with lyophilization);
	•	availability of raw materials and supplies;
	•	quality control and assurance;
	•	shortages of qualified personnel;
	•	compliance with strictly enforced federal, state and foreign regulations that vary in each country where products might be sold; and
	•	lack of capital funding.

As a result, any delay or interruption could have a material adverse effect on our business, financial condition, and results of operations.

The recent coronavirus outbreak has caused interruptions or delays of our business plan and may have a significant adverse effect on our business.

In December 2019, a strain of coronavirus, COVID-19, was reported to have surfaced in Wuhan, China, and on March 12, 2020, the World Health Organization declared COVID-19 to be a pandemic. In an effort to contain and mitigate the spread of COVID-19, many countries, including the United States, Canada and China, have imposed unprecedented restrictions on travel, quarantines, and other public health safety measures. The extent to which the pandemic may impact our business will depend on future developments, which are highly uncertain and cannot be predicted, but the development of clinical supply materials could be delayed and enrollment of patients in our study for LUNAR-OTC and LUNAR-COV19 may be delayed or suspended, as hospitals and clinics in areas where we are conducting trials shift resources to cope with the COVID-19 pandemic and may limit access or close clinical facilities due to the COVID-19 pandemic. Additionally, if our trial participants are unable to travel to our clinical study sites as a result of quarantines or other restrictions resulting from the COVID-19 pandemic, we may experience higher drop-out rates or delays in our clinical studies.

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Government-imposed quarantines and restrictions may also require us to temporarily suspend or terminate activity at our clinical sites. Furthermore, if we determine that our trial participants may suffer from exposure to COVID-19 as a result of their participation in our clinical trials, we may voluntarily terminate certain clinical sites as a safety measure until we reasonably believe that the likelihood of exposure has subsided. As a result, our expected development timelines for our product candidates may be negatively impacted. We cannot predict the ultimate impact of the COVID-19 pandemic as consequences of such an event are highly uncertain and subject to change. We do not yet know the full extent of potential delays or impacts on our business, our clinical studies or as a whole; however, the COVID-19 outbreak may materially disrupt or delay our business operations, further divert the attention and efforts of the medical community to coping with COVID-19, disrupt the marketplace in which we operate, and/or have a material adverse effect on our operations.

Moreover, the various precautionary measures taken by many governmental authorities around the world in order to limit the spread of the coronavirus has had and may continue to have an adverse effect on the global markets and global economy generally, including on the availability and pricing of employees, resources, materials, manufacturing and delivery efforts and other aspects of the global economy. There have been business closures and a substantial reduction in economic activity in countries that have had significant outbreaks of COVID-19. Significant uncertainty remains as to the potential impact of the COVID-19 pandemic on the global economy as a whole. It is currently not possible to predict how long the pandemic will last or the time that it will take for economic activity to return to prior levels. The COVID-19 pandemic could materially disrupt our business and operations, interrupt our sources of supply, hamper our ability to raise additional funds or sell or securities, continue to slow down the overall economy or curtail consumer spending.

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Risks Related to this Offering of Our Common Stock

You will suffer immediate dilution in the net tangible book value per share of the common stock that you purchase in this offering.

The public offering price of our common stock is substantially higher than the as-adjusted net tangible book value per share of our common stock. Therefore, investors purchasing shares of our common stock in this offering will pay a price per share that substantially exceeds the as-adjusted net tangible book value per share after this offering. For more information, see “Dilution.”

We will require additional capital funding, the receipt of which may impair the value of our common stock.

Our future capital requirements depend on many factors, including our research, development, sales and marketing activities. We will need to raise additional capital through public or private equity or debt offerings or through arrangements with strategic partners or other sources in order to continue to develop our drug candidates. There can be no assurance that additional capital will be available when needed or on terms satisfactory to us, if at all. To the extent we raise additional capital by issuing equity securities, our stockholders may experience substantial dilution and the new equity securities may have greater rights, preferences or privileges than our existing common stock.

Our management will have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

Our management will have broad discretion in the application of the net proceeds from this offering and our stockholders will not have the opportunity as part of their investment decisions to assess whether the net proceeds are being used appropriately. You may not agree with our decisions, and our use of the proceeds may not yield any return on your investment. Because of the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently intended use. Our failure to apply the net proceeds of this offering effectively could compromise our ability to pursue our growth strategy and we might not be able to yield a significant return, if any, in our investment of these net proceeds. You will not have the opportunity to influence our decisions on how to use our net proceeds from this offering.

The market price of our common stock has been, and may continue to be, volatile which could reduce the market price of our common stock.

The publicly traded shares of our common stock have experienced, and may experience in the future, significant price and volume fluctuations. This market volatility could reduce the market price of our common stock without regard to our operating performance. In addition, the trading price of our common stock could change significantly in response to actual or anticipated variations in our quarterly operating results, announcements by us or our competitors, factors affecting the medical imaging industry generally, changes in national or regional economic conditions, changes in securities analysts’ estimates for us or our competitors’ or industry’s future performance or general market conditions, making it more difficult for shares of our common stock to be sold at a favorable price or at all. The market price of our common stock could also be reduced by general market price declines or market volatility in the future or future declines or volatility in the prices of stocks for companies in our industry. The COVID-19 pandemic has resulted in significant financial market volatility and uncertainty in recent weeks. A continuation or worsening of the levels of market disruption and volatility seen in the recent past could have an adverse effect on our ability to access capital, on our business, results of operations and financial condition, and on the market price of our common stock.

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A substantial number of shares of our common stock are eligible for future sale, and the sale of shares of common stock into the market, or the perception that such sales may occur, may depress our stock price.

Sales of substantial additional shares of our common stock in the public market, or the perception that these sales may occur, may significantly lower the market price of our common stock. We are unable to estimate the amount, timing or nature of future sales of shares of our common stock. We have previously issued a substantial number of shares of common stock, which are eligible for resale under Rule 144 of the Securities Act of 1933, as amended, or the Securities Act, and may become freely tradable. We have also registered shares that are issuable upon the exercise of options and warrants. If holders of options or warrants choose to exercise their securities and sell shares of common stock issued upon the exercise in the public market, or if holders of currently restricted common stock choose to sell such shares of common stock in the public market under Rule 144 or otherwise, or attempt to publicly sell such shares all at once or in a short time period, the prevailing market price for our common stock may decline.

Future issuances of shares of our common stock may cause significant dilution of equity interests of existing holders of common stock and decrease the market price of shares of our common stock.

We have previously issued options that are exercisable into a significant number of shares of our common stock and may issue additional options and warrants in the future. Should holders of options or warrants exercise their securities into shares of our common stock, it may cause significant dilution of equity interests of existing holders of our common stock and reduce the market price of shares of our common stock.

We are not currently paying dividends and will likely not pay dividends for the foreseeable future.

We have never paid or declared any cash dividends on our common stock. We currently intend to retain all available funds and any future earnings to fund the development and expansion of our business, and we do not anticipate paying any cash dividends in the foreseeable future. Any future determination to pay cash dividends will be at the discretion of our board of directors and will depend on our financial condition, results of operations, capital requirements, contractual restrictions and other factors that our board of directors deems relevant.

If securities or industry analysts issue an adverse opinion regarding our stock, our stock price and trading volume could decline.

The trading market for our common stock is influenced by the research and reports that securities or industry analysts may publish about us, our business, our market or our competitors. If any of the analysts who may cover us adversely change their recommendation regarding our common stock, or provide more favorable relative recommendations about our competitors, the trading price of our common stock could decline. If any analyst who may cover us were to cease coverage of our company or fail to regularly publish reports on us, we could lose visibility in the financial markets, which in turn could cause the trading price of our common stock or trading volume to decline.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus, the documents incorporated by reference and any free writing prospectus that we have authorized for use in connection with this offering contain certain forward-looking statements within the meaning of Section 27A of the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act, in reliance upon the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include, without limitation, statements regarding the success, safety and efficacy of our drug products, product approvals, product sales, revenues, development timelines, product acquisitions, liquidity and capital resources and trends, and other statements containing forward-looking words, such as, “believes,” “may,” “could,” “would,” “will,” “expects,” “intends,” “estimates,” “anticipates,” “plans,” “seeks,” or “continues” or the negative thereof or variation thereon or similar terminology (although not all forward-looking statements contain these words). Such forward-looking statements are based on the beliefs of our management as well as assumptions made by and information currently available to our management. Readers should not put undue reliance on these forward-looking statements because they involve known and unknown risks, uncertainties and other factors, some of which are beyond our control. These risks, uncertainties and other factors may cause our actual results, performance or achievements to be materially different from the anticipated future results, performance or achievements expressed or implied by the forward-looking statements.

Factors that might cause these differences include the following:

•

the initiation, cost, timing, progress and results of, and our expected ability to undertake certain activities and accomplish certain goals with respect to, our research and development activities, preclinical studies and clinical trials;

•

our ability to obtain and maintain regulatory approval of our product candidates, and any related restrictions, limitations, and/or warnings in the label of an approved product candidate;

•

our ability to obtain and deploy funding for our operations;

•

our ability to continue as a going concern;

•

our plans to research, develop and commercialize our product candidates;

•

our strategic alliance partners’ election to pursue development and commercialization of any programs or product candidates that are subject to our collaboration and license agreements with such partners;

•

our ability to attract collaborators with relevant development, regulatory and commercialization expertise;

•

future activities to be undertaken by our strategic alliance partners, collaborators and other third parties;

•

our ability to avoid, settle or be victorious at costly litigation with shareholders, former executives or others;

•

our ability to obtain and maintain intellectual property protection for our product candidates;

•

the size and growth potential of the markets for our product candidates, and our ability to serve those markets;

•

our ability to successfully commercialize, and our expectations regarding future therapeutic and commercial potential with respect to, our product candidates;

•

the rate and degree of market acceptance of our product candidates;

•

our ability to develop sales and marketing capabilities, whether alone or with potential future collaborators;

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•

regulatory developments in the United States and foreign countries;

•

our ability to attract and retain experienced and seasoned scientific and management professionals to lead the Company;

•

the performance of our third-party suppliers and manufacturers;

•

the success of competing therapies that are or may become available;

•

the accuracy of our estimates regarding future expenses, future revenues, capital requirements and need for additional financing;

•

the use of proceeds from this offering; and

•

the other risks and uncertainties described in “Risk Factors” beginning on page S-8 of this prospectus supplement and in Part I, Item 1A, Risk Factors of our Annual Report on Form 10-K for the fiscal year ended December 31, 2019 and in Part II, Item 1A, Risk Factors of our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2020, June 30, 2020 and September 30, 2020 and any subsequently filed Quarterly Reports on Form 10-Q, which are incorporated by reference in this prospectus supplement and the accompanying prospectus.

We urge you to consider these factors carefully in evaluating the forward-looking statements contained in this prospectus supplement, the accompanying prospectus or the documents incorporated by reference herein. All subsequent written or oral forward-looking statements attributable to our company or persons acting on our behalf are expressly qualified in their entirety by these cautionary statements. The forward-looking statements included in this prospectus supplement are made only as of the date of this prospectus supplement. We undertake no obligation to update publicly any forward-looking statements, whether as a result of new information, future events or otherwise, except to the extent that we are required to do so by law.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $ million (or $ million if the underwriters exercise their option to purchase additional shares in full), after deducting the underwriting discounts and commissions and estimated offering expenses payable by us.

We intend to use the net proceeds from this offering to conduct clinical trials and to commence manufacturing our LUNAR-COV19 vaccine candidate for stockpiling purposes. The amounts and timing of our actual use of the net proceeds from this offering will vary depending on numerous factors, including the factors described under “Risk Factors” located elsewhere in this prospectus supplement, the accompanying prospectus or in the information incorporated by reference herein or therein. As a result, management will have broad discretion in the application of the net proceeds, and investors will be relying on our judgment regarding the application of the net proceeds from this offering.

Pending application of the net proceeds as discussed above, we plan to invest any remaining proceeds from this offering in a variety of capital preservation instruments, including short-term, interest-bearing obligations, investment-grade instruments, or direct or guaranteed obligations of the U.S. government.

DIVIDEND POLICY

We have not declared any cash dividends on our common stock since inception and we do not anticipate paying any cash dividends on our common stock in the foreseeable future.

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DILUTION

If you purchase shares of common stock in this offering, you will experience dilution to the extent of the difference between the public offering price per share in this offering and our as adjusted net tangible book value per share after this offering.

Net tangible book value per share represents total tangible assets less total liabilities, divided by the number of shares of common stock outstanding. Our historical net tangible book value as of September 30, 2020 was $261.6 million, or $10.69 per share of common stock. After giving effect to our sale of shares of common stock at a public offering price of $ per share, and after deducting commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of September 30, 2020 would have been approximately $ million, or approximately $ per share. This represents an immediate increase in net tangible book value of approximately $ per share to existing stockholders and an immediate dilution in as adjusted net tangible book value of approximately $ per share to new investors in this offering.

Public offering price per share			$
Net tangible book value per share as of September 30, 2020	$	10.69
Increase in net tangible book value per share attributable to this offering	$
As adjusted net tangible book value per share, after giving effect to this offering			$
Dilution per share to new investors in this offering			$

If the underwriters fully exercise their option to purchase additional shares of common stock, our as adjusted net tangible book value after this offering would increase to $ per share, and there would be an immediate dilution of $ per share to new investors in this offering.

The above discussion and tables are based on 24,473,002 shares of common stock outstanding as of September 30, 2020 and excludes the following:

•

2,342,255 shares of our common stock reserved for issuance under stock option agreements issued pursuant to our 2019 Omnibus Equity Incentive Plan at a weighted average exercise price of $16.57 per share;

•

2,388,340 shares of our common stock reserved for future issuance under our Amended and Restated 2019 Omnibus Equity Incentive Plan; and

•

600,000 shares of our common stock reserved for future issuance under our 2020 Employee Stock Purchase Plan.

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MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES

FOR NON-U.S. HOLDERS OF OUR COMMON STOCK

The following is a general discussion of material U.S. federal income tax considerations and certain U.S. federal estate tax considerations relating to the ownership and disposition of our common stock applicable to non-U.S. holders. For purposes of this discussion, a “non-U.S. holder” means a beneficial owner of our common stock (other than an entity or arrangement that is treated as a partnership for U.S. federal income tax purposes) that is not, for U.S. federal income tax purposes, any of the following:

•

an individual who is a citizen or resident of the United States;

•

a corporation (or other entity treated as a corporation for U.S. federal income tax purposes) created or organized in the United States or under the laws of the United States, any state thereof or the District of Columbia;

•

an estate, the income of which is includable in gross income for U.S. federal income tax purposes regardless of its source; or

•

a trust if (i) a court within the United States is able to exercise primary supervision over the administration of the trust and one or more “U.S. persons,” as defined under the U.S. Internal Revenue Code of 1986, as amended (which we refer to as the Code), have the authority to control all substantial decisions of the trust or (ii) such trust has made a valid election to be treated as a U.S. person for U.S. federal income tax purposes.

If a partnership (or other entity or arrangement treated as a partnership for U.S. federal income tax purposes) holds our common stock, the tax treatment of a partner therein will generally depend on the status of the partner and the activities of the partnership. Partners of a partnership holding our common stock should consult their tax advisors as to the particular U.S. federal income tax consequences applicable to them.

This discussion is based on current provisions of the Code, final, temporary and proposed Treasury regulations promulgated thereunder (which we refer to as the Treasury Regulations), judicial decisions, published rulings and administrative pronouncements of the U.S. Internal Revenue Service, or IRS, all in effect as of the date of this prospectus supplement and all of which are subject to change or to differing interpretation, possibly with retroactive effect. Any change could alter the tax consequences to non-U.S. holders described herein. There can be no assurance that the IRS will not challenge one or more of the tax consequences described herein.

This discussion is limited to non-U.S. holders that hold our common stock as a “capital asset” within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion does not address all aspects of U.S. federal income and estate taxation that may be relevant to a particular non-U.S. holder in light of that non-U.S. holder’s individual circumstances nor does it address any aspects of U.S. state, local or non-U.S. taxes, the alternative minimum tax, or the unearned income Medicare contribution tax on net investment income. This discussion also does not consider any specific facts or circumstances that may apply to a non-U.S. holder and does not address the special tax rules applicable to particular non-U.S. holders, such as:

•

banks, insurance companies and other financial institutions;

•

brokers or dealers or traders in securities;

•

tax-exempt organizations;

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•

pension plans, including “qualified foreign pension funds” as defined in Section 897(l)(2) of the Code and entities, all of the interests of which are held by qualified foreign pension funds;

•

persons who hold our common stock as part of a straddle, hedge, conversion transaction, synthetic security or other integrated investment or who have elected to mark securities to market;

•

“controlled foreign corporations,” “passive foreign investment companies,” and corporations that accumulate earnings to avoid U.S. federal income tax;

	•		persons who hold or receive our common stock pursuant to the exercise of any employee stock option or otherwise as compensation;

	•		persons subject to special tax accounting rules as a result of any item of gross income with respect to our common stock being taken into account in an applicable financial statement;

•

non-U.S. governments; and

•

U.S. expatriates and former citizens or long-term residents of the United States.

THIS SUMMARY IS NOT INTENDED TO CONSTITUTE A COMPLETE DESCRIPTION OF ALL TAX CONSEQUENCES FOR NON-U.S. HOLDERS RELATING TO THE OWNERSHIP AND DISPOSITION OF OUR COMMON STOCK. PROSPECTIVE HOLDERS OF OUR COMMON STOCK SHOULD CONSULT WITH THEIR TAX ADVISORS REGARDING THE TAX CONSEQUENCES TO THEM (INCLUDING THE APPLICATION AND EFFECT OF ANY STATE, LOCAL, NON-U.S. INCOME AND OTHER TAX LAWS) OF THE OWNERSHIP AND DISPOSITION OF OUR COMMON STOCK.

Distributions

As discussed under “Dividend Policy” above, we do not expect to make distributions on our common stock in the foreseeable future. However, if we do make distributions of cash or property on our common stock, such distributions will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. Amounts of distributions not treated as dividends for U.S. federal income tax purposes will first constitute a tax-free return of capital of the non-U.S. holder’s investment and be applied against and reduce a non-U.S. holder’s adjusted tax basis in its common stock, but not below zero. Any remaining excess will be treated as capital gain and will be treated as described below under “Gain on Sale or Other Disposition of Common Stock.” Because we may not know the extent to which a distribution is a dividend for U.S. federal income tax purposes at the time it is made, for purposes of the withholding rules discussed below we or the applicable withholding agent may treat the entire distribution as a dividend. Any such distributions will also be subject to the discussions below under the headings “FATCA” and “Backup Withholding, Information Reporting and Other Reporting Requirements.”

Subject to the discussion in the next two paragraphs, dividends paid to a non-U.S. holder generally will be subject to withholding of U.S. federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder’s country of residence.

Dividends we pay to a non-U.S. holder that are effectively connected with such non-U.S. holder’s conduct of a trade or business within the United States (and, if required by an applicable tax treaty, are attributable to a U.S. permanent establishment or a fixed base maintained by such non-U.S. holder) will generally be exempt from the U.S. federal withholding tax described above, if the non-U.S. holder complies with applicable certification and disclosure requirements (generally including provision of a valid IRS Form W-8ECI (or applicable successor form) certifying that the dividends are effectively connected with the non-U.S. holder’s conduct of a trade or business within the United States). Instead, such dividends generally will be subject to U.S. federal income tax on a net income basis, at regular U.S. federal income tax rates as would apply if such holder were a U.S. person (as defined in the Code). Any U.S. effectively connected income received by a non-U.S. holder that is classified as a corporation for U.S. federal income tax purposes may also be subject to an additional “branch profits tax” at a rate of 30% (or such lower rate as may be specified by an applicable income tax treaty).

A non-U.S. holder of our common stock who claims the benefit of an applicable income tax treaty between the United States and such holder’s country of residence generally will be required to provide a properly executed IRS Form W-8BEN or W-8BEN-E (or successor form) and satisfy applicable certification and other requirements. Non-U.S. holders are urged to consult their tax advisors regarding their entitlement to benefits under a relevant income tax treaty and the specific methods available to them to satisfy these requirements.

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Gain on Sale or Other Disposition of Common Stock

Subject to the discussion below under the headings “FATCA” and “Backup Withholding, Information Reporting and Other Reporting Requirements,” a non-U.S. holder generally will not be subject to U.S. federal income tax on any gain realized upon the sale or other disposition of the non-U.S. holder’s shares of our common stock unless:

•

the gain is effectively connected with a trade or business carried on by the non-U.S. holder within the United States (and, if required by an applicable income tax treaty, is attributable to a U.S. permanent establishment or fixed base maintained by such non-U.S. holder);

•

the non-U.S. holder is an individual and is present in the United States for 183 days or more in the taxable year of disposition and certain other conditions are met; or

•

we are or have been a “U.S. real property holding corporation” for U.S. federal income tax purposes at any time within the shorter of the five-year period preceding such disposition or such non-U.S. holder’s holding period of our common stock, and, provided that our common stock is regularly traded in an established securities market within the meaning of applicable Treasury Regulations, the non-U.S. holder has held, directly or constructively, at any time during said period, more than 5% of our common stock.

Gain that is effectively connected with the conduct of a trade or business in the United States generally will be subject to U.S. federal income tax on a net income tax basis, at regular U.S. federal income tax rates. If the non-U.S. holder is a non-U.S. corporation, the branch profits tax described above also may apply to such effectively connected gain. An individual non-U.S. holder who is subject to U.S. federal income tax because the non-U.S. holder was present in the United States for 183 days or more during the year of sale or other disposition of our common stock will be subject to a flat 30% tax (or such lower rate as may be specified by an applicable income tax treaty) on the gain derived from such sale or other disposition, which may be offset by certain U.S. source capital losses, if any. We believe that we are not and we do not anticipate becoming a U.S. real property holding corporation for U.S. federal income tax purposes. Non-U.S. holders should consult their tax advisors regarding potentially applicable income tax treaties that may provide for different rules.

FATCA

Withholding taxes may be imposed under the Foreign Account Tax Compliance Act, or FATCA, on certain types of payments made to non-U.S. financial institutions and certain other non-U.S. entities. Specifically, a 30% withholding tax may be imposed on dividends (including deemed dividends) paid on our common stock, to a “foreign financial institution” or a “non-financial foreign entity” (each as defined in the Code), unless (1) the foreign financial institution undertakes certain diligence and reporting obligations, (2) the non-financial foreign entity either certifies it does not have any “substantial United States owners” (as defined in the Code) or furnishes identifying information regarding each substantial U.S. owner, or (3) the foreign financial institution or non-financial foreign entity otherwise qualifies for an exemption from these rules. Foreign financial institutions located in jurisdictions that have an intergovernmental agreement with the U.S. governing FATCA may be subject to the reporting rules of that intergovernmental agreement. Because we may not know the extent to which a distribution is a dividend for U.S. federal income tax purposes at the time it is made, for purposes of these withholding rules we or the applicable withholding agent may treat the entire distribution as a dividend. Although withholding under FATCA would have applied also to payments of gross proceeds from the sale or other disposition of stock on or after January 1, 2019, proposed Treasury Regulations would eliminate FATCA withholding on payments of gross proceeds entirely. Taxpayers generally may rely on these proposed Treasury Regulations until final Treasury Regulations are issued. Prospective investors should consult their tax advisors regarding the potential application of these withholding provisions.

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Backup Withholding, Information Reporting and Other Reporting Requirements

We must report annually to the IRS and to each non-U.S. holder the amount of any distributions paid to, and the tax withheld with respect to, each non-U.S. holder. These reporting requirements apply regardless of whether withholding was reduced or eliminated by an applicable income tax treaty. Copies of this information reporting may also be made available under the provisions of a specific income tax treaty or agreement with the tax authorities in the country in which the non-U.S. holder resides or is established.

A non-U.S. holder will generally be subject to backup withholding for dividends on our common stock paid to such holder unless such holder certifies under penalties of perjury that, among other things, it is a non-U.S.

holder (provided that the payor does not have actual knowledge or reason to know that such holder is a U.S. person) or otherwise establishes an exemption.

Information reporting and backup withholding generally will apply to the proceeds of a disposition of our common stock by a non-U.S. holder effected by or through the U.S. office of any broker, U.S. or non-U.S., unless the holder certifies its status as a non-U.S. holder and satisfies certain other requirements, or otherwise establishes an exemption. Generally, information reporting and backup withholding will not apply to a payment of disposition proceeds to a non-U.S. holder where the transaction is effected outside the United States through a non-U.S. office of a broker. However, for information reporting purposes, dispositions effected through a non-U.S. office of a broker with substantial U.S. ownership or operations generally will be treated in a manner similar to dispositions effected through a U.S. office of a broker. Non-U.S. holders should consult their tax advisors regarding the application of the information reporting and backup withholding rules to them.

Backup withholding is not an additional income tax. Any amounts withheld under the backup withholding rules from a payment to a non-U.S. holder generally can be credited against the non-U.S. holder’s U.S. federal income tax liability, if any, or refunded, provided that the required information is furnished to the IRS in a timely manner. Non-U.S. holders should consult their tax advisors regarding the application of the information reporting and backup withholding rules to them.

U.S. Federal Estate Tax

Shares of our common stock that are owned or treated as owned by an individual who is not a citizen or resident of the United States (as specially defined for U.S. federal estate tax purposes) at the time of death are considered U.S. situs assets and will be included in the individual’s gross estate for U.S. federal estate tax purposes. Such shares, therefore, may be subject to U.S. federal estate tax, unless an applicable estate tax or other treaty provides otherwise.

The preceding discussion of material U.S. federal income tax considerations and certain U.S. federal estate tax considerations is for information only. It is not legal or tax advice. Prospective investors should consult their tax advisors regarding the particular U.S. federal, state, local and non-U.S. tax consequences of owning and disposing of our common stock, including the consequences of any proposed changes in applicable laws.

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UNDERWRITING

We are offering the shares of common stock described in this prospectus supplement through Piper Sandler & Co., Guggenheim Securities, LLC and Wells Fargo Securities, LLC as the joint book running managers, We have entered into an underwriting agreement with Piper Sandler & Co., Guggenheim Securities, LLC and Wells Fargo Securities, LLC as representatives of the several underwriters named below.

The underwriting agreement provides that the obligations of the underwriters are subject to certain conditions precedent, including approval of legal matters by their counsel. The underwriters have the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part. Subject to the terms and conditions set forth in the underwriting agreement, we have agreed to sell to the underwriters, and each of the underwriters has agreed, severally and not jointly, to purchase from us, the number of shares of our common stock listed opposite its name below.

Underwriters		Number of Shares
Piper Sandler & Co.
Guggenheim Securities, LLC
Wells Fargo Securities, LLC

Total

Option to Purchase Additional Shares

We have granted the underwriters an option to buy up to additional shares of common stock from us. The underwriters may exercise this option at any time and from time to time during the 30-day period from the date of this prospectus supplement. If any additional shares of common stock are purchased, the underwriters will offer the additional shares on the same terms as those on which the shares are being offered.

Discounts and Commissions

The underwriters have advised us that they propose to offer the common stock directly to the public at the offering price set forth on the cover page of this prospectus supplement. The underwriters propose to offer the shares to certain dealers at the same price less a concession of not more than $ per share. After the offering, these figures may be changed by the underwriters.

The underwriting fee is equal to the public offering price per share of common stock less the amount paid by the underwriters to us per share of common stock. The following table shows the per share and total underwriting discount to be paid by the underwriters in connection with this offering, assuming either no exercise and full exercise of the option to purchase additional shares:

Total

Per Share

Without Option

With Option

Public offering price

Underwriting discounts and commissions

Proceeds, before expenses, to us

We estimate that the total fees and expenses payable by us, excluding underwriting discount, will be approximately $ , which includes $ that we have agreed to reimburse the underwriters for the fees incurred by them in connection with the offering.

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No Sales of Similar Securities

We and each of our directors and executive officers are subject to lock-up agreements that prohibit us and them from offering, selling, contracting to sell, granting any option or contract to purchase, purchasing any option or contract to sell, granting any option, right or warrant to purchase, lending or otherwise transferring or disposing of any shares of our common stock or any securities convertible into or exercisable or exchangeable for shares of our common stock or other capital stock for a period of at least 60 days with respect to us, and 90 days with respect to such director and executive officers. following the date of this prospectus supplement without the prior written consent of Piper Sandler & Co. and Guggenheim Securities, LLC, subject to specified limited exceptions. Piper Sandler & Co. and Guggenheim Securities, LLC, in their sole discretion may release any of the securities subject to these lock-up agreements at any time without notice.

The lock-up agreements do not prohibit our directors and executive officers from transferring shares of our common stock for bona fide gifts or by will, or for estate or tax planning purposes, subject to certain requirements, including that the transferee be subject to the same lock-up terms. The lock-up provisions do not prohibit us from issuing shares upon the exercise or conversion of securities outstanding on the date of this prospectus supplement. The lock-up provisions do not prevent us from selling shares to the underwriters pursuant to the underwriting agreement, or from granting options to acquire securities under our existing stock option plans or issuing shares upon the exercise or conversion of securities outstanding on the date of this prospectus supplement. We may also enter into an at-the-market facility with one or more sales agents during the lock-up period provided that no sales can be made under such facility during the lock-up period.

Listing

Our common stock is listed on The Nasdaq Global Market under the symbol “ARCT.”

Price Stabilization, Short Positions and Penalty Bids

To facilitate the offering, the underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of our common stock during and after the offering. Specifically, the underwriters may over-allot or otherwise create a short position in the common stock for their own account by selling more shares of common stock than we have sold to them. Short sales involve the sale by the underwriters of a greater number of shares than the underwriters are required to purchase in the offering. The underwriters may close out any short position by either exercising their option to purchase additional shares or purchasing shares in the open market.

In addition, the underwriters may stabilize or maintain the price of the common stock by bidding for or purchasing shares of common stock in the open market and may impose penalty bids. If penalty bids are imposed, selling concessions allowed to syndicate members or other broker-dealers participating in the offering are reclaimed if shares of common stock previously distributed in the offering are repurchased, whether in connection with stabilization transactions or otherwise. The effect of these transactions may be to stabilize or maintain the market price of the common stock at a level above that which might otherwise prevail in the open market. The imposition of a penalty bid may also affect the price of the common stock to the extent that it discourages resales of the common stock. The magnitude or effect of any stabilization or other transactions is uncertain. These transactions may be effected on The Nasdaq Global Market or otherwise and, if commenced, may be discontinued at any time. The underwriters may also engage in passive market making transactions in our common stock. Passive market making consists of displaying bids on The Nasdaq Global Market is limited by the prices of independent market makers and effecting purchases limited by those prices in response to order flow. Rule 103 of Regulation M promulgated by the SEC limits the amount of net purchases that each passive market maker may make and the displayed size of each bid. Passive market making may stabilize the market price of the common stock at a level above that which might otherwise prevail in the open market and, if commenced, may be discontinued at any time.

Electronic Distribution

This prospectus supplement and the accompanying base prospectus in electronic format may be made available on the web sites maintained by one or more of the underwriters and the underwriters may distribute prospectuses and prospectus supplements electronically.

Affiliations

From time to time in the ordinary course of its businesses, the underwriters and certain of their affiliates have engaged, and may in the future engage, in commercial banking or investment banking transactions with us and our affiliates.

S-22

Selling Restrictions

European Economic Area

In relation to each Member State of the European Economic Area which has implemented the Prospectus Directive (each, a “Relevant Member State”) an offer to the public of any shares of our common stock may not be made in that Relevant Member State, except that an offer to the public in that Relevant Member State of any shares of our common stock may be made at any time under the following exemptions under the Prospectus Directive, if they have been implemented in that Relevant Member State:

(a)	to any legal entity which is a qualified investor as defined in the Prospectus Directive;

(b)

to fewer than 100 or, if the Relevant Member State has implemented the relevant provision of the 2010 PD Amending Directive, 150, natural or legal persons (other than qualified investors as defined in the Prospectus Directive), as permitted under the Prospectus Directive, subject to obtaining the prior consent of the representatives for any such offer; or

(c)	in any other circumstances falling within Article 3(2) of the Prospectus Directive, provided that no such offer of shares of our common stock shall result in a requirement for the publication by us or any underwriter of a prospectus pursuant to Article 3 of the Prospectus Directive.

For the purposes of this provision, the expression an “offer to the public” in relation to any shares of our common stock in any Relevant Member State means the communication in any form and by any means of sufficient information on the terms of the offer and any shares of our common stock to be offered so as to enable an investor to decide to purchase any shares of our common stock, as the same may be varied in that Member State by any measure implementing the Prospectus Directive in that Member State, the expression “Prospectus Directive” means Directive 2003/71/EC (and amendments thereto, including the 2010 PD Amending Directive, to the extent implemented in the Relevant Member State), and includes any relevant implementing measure in the Relevant Member State, and the expression “2010 PD Amending Directive” means Directive 2010/73/EU.

United Kingdom

Each underwriter has represented and agreed that:

(a)

it has only communicated or caused to be communicated and will only communicate or cause to be communicated an invitation or inducement to engage in investment activity (within the meaning of Section 21 of the Financial Services and Markets Act 2000 (the “FSMA”)) received by it in connection with the issue or sale of the shares of our common stock in circumstances in which Section 21(1) of the FSMA does not apply to us; and

(b)	it has complied and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the shares of our common stock in, from or otherwise involving the United Kingdom.

Canada

The common shares may be sold only to purchasers purchasing as principal that are both “accredited investors” as defined in National Instrument 45-106 Prospectus and Registration Exemptions and “permitted clients” as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the common shares must be made in accordance with an exemption from the prospectus requirements and in compliance with the registration requirements of applicable securities laws.

Germany

Each person who is in possession of this prospectus is aware of the fact that no German securities prospectus (wertpapierprospekt) within the meaning of the German Securities Prospectus Act (Wertpapier-prospektgesetz, or the Act) of the Federal Republic of Germany has been or will be published with respect to the shares of our common stock. In particular, each underwriter has represented that it has not engaged and has agreed that it will not engage in a public offering in the Federal Republic of Germany within the meaning of the Act with respect to any of the shares of our common stock otherwise than in accordance with the Act and all other applicable legal and regulatory requirements.

S-23

Hong Kong

The common shares may not be offered or sold in Hong Kong by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong), or (ii) to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a “prospectus” within the meaning of the Companies Ordinance (Cap. 32, Laws of Hong Kong) and no advertisement, invitation or document relating to the shares may be issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to common shares which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Singapore

This prospectus has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the common shares may not be circulated or distributed, nor may the common shares be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (the “SFA”), (ii) to a relevant person pursuant to Section 275(1), or any person pursuant to Section 275(1A), and in accordance with the conditions specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA, in each case subject to compliance with conditions set forth in the SFA.

Where the common shares are subscribed or purchased under Section 275 of the SFA by a relevant person which is:

(a)	a corporation (which is not an accredited investor (as defined in Section 4A of the SFA)) the sole business of which is to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or

(b)	a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary of the trust is an individual who is an accredited investor,

shares, debentures and units of shares and debentures of that corporation or the beneficiaries’ rights and interest (howsoever described) in that trust shall not be transferred within six months after that corporation or that trust has acquired the common shares pursuant to an offer made under Section 275 of the SFA except:

(a)

to an institutional investor (for corporations, under Section 274 of the SFA) or to a relevant person defined in Section 275(2) of the SFA, or to any person pursuant to an offer that is made on terms that such shares, debentures and units of shares and debentures of that corporation or such rights and interest in that trust are acquired at a consideration of not less than $200,000 (or its equivalent in a foreign currency) for each transaction, whether such amount is to be paid for in cash or by exchange of securities or other assets, and further for corporations, in accordance with the conditions specified in Section 275 of the SFA;

(b)	where no consideration is or will be given for the transfer; or

(c)	where the transfer is by operation of law.

Switzerland

The common shares may not be publicly offered in Switzerland and will not be listed on the SIX Swiss Exchange (the “SIX”) or on any other stock exchange or regulated trading facility in Switzerland. This document has been prepared without regard to the disclosure standards for issuance prospectuses under art. 652a or art. 1156 of the Swiss Code of Obligations or the disclosure standards for listing prospectuses under art. 27 ff. of the SIX Listing Rules or the listing rules of any other stock exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the common shares or the offering may be publicly distributed or otherwise made publicly available in Switzerland.

Neither this document nor any other offering or marketing material relating to the offering, or the common shares have been or will be filed with or approved by any Swiss regulatory authority. In particular, this document will not be filed with, and the offer of common shares will not be supervised by, the Swiss Financial Market Supervisory Authority FINMA, and the offer of common shares has not been and will not be authorized under the Swiss Federal Act on Collective Investment Schemes (“CISA”). Accordingly, no public distribution, offering or advertising, as defined in CISA, its implementing ordinances and notices, and no distribution to any non-qualified investor, as defined in CISA, its implementing ordinances and notices, shall be undertaken in or from Switzerland, and the investor protection afforded to acquirers of interests in collective investment schemes under CISA does not extend to acquirers of common shares.

S-24

United Arab Emirates

This offering has not been approved or licensed by the Central Bank of the United Arab Emirates (the “UAE”), Securities and Commodities Authority of the UAE and/or any other relevant licensing authority in the UAE including any licensing authority incorporated under the laws and regulations of any of the free zones established and operating in the territory of the UAE, in particular the Dubai Financial

Services Authority (“DFSA”), a regulatory authority of the Dubai International Financial Centre (“DIFC”). The offering does not constitute a public offer of securities in the UAE, DIFC and/or any other free zone in accordance with the Commercial Companies Law, Federal Law No 8 of 1984 (as amended), DFSA Offered Securities Rules and NASDAQ Dubai Listing Rules, accordingly, or otherwise. The common shares may not be offered to the public in the UAE and/or any of the free zones.

The common shares may be offered and issued only to a limited number of investors in the UAE or any of its free zones who qualify as sophisticated investors under the relevant laws and regulations of the UAE or the free zone concerned.

France

This prospectus (including any amendment, supplement or replacement thereto) is not being distributed in the context of a public offering in France within the meaning of Article L. 411-1 of the French Monetary and Financial Code (Code monétaire et financier).

This prospectus has not been and will not be submitted to the French Autorité des marchés financiers (the “AMF”) for approval in France and accordingly may not and will not be distributed to the public in France.

Pursuant to Article 211-3 of the AMF General Regulation, French residents are hereby informed that:

1. the transaction does not require a prospectus to be submitted for approval to the AMF;

2. persons or entities referred to in Point 2°, Section II of Article L.411-2 of the Monetary and Financial Code may take part in the transaction solely for their own account, as provided in Articles D. 411-1, D. 734-1, D. 744-1, D. 754-1 and D. 764-1 of the Monetary and Financial Code; and

3. the financial instruments thus acquired cannot be distributed directly or indirectly to the public otherwise than in accordance with Articles L. 411-1, L. 411-2, L. 412-1 and L. 621-8 to L. 621-8-3 of the Monetary and Financial Code.

This prospectus is not to be further distributed or reproduced (in whole or in part) in France by the recipients of this prospectus. This prospectus has been distributed on the understanding that such recipients will only participate in the issue or sale of our common stock for their own account and undertake not to transfer, directly or indirectly, our common stock to the public in France, other than in compliance with all applicable laws and regulations and in particular with Articles L. 411-1 and L. 411-2 of the French Monetary and Financial Code.

S-25

LEGAL MATTERS

Dentons US LLP, New York, New York, will pass upon the validity of the shares of common stock offered by this prospectus supplement. The underwriters are being represented in connection with this offering by Goodwin Procter LLP, New York, New York.

EXPERTS

The consolidated financial statements of Arcturus Therapeutics Holdings, Inc. and its Subsidiaries appearing in Arcturus Therapeutics Holdings, Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2019, and the effectiveness of Arcturus Therapeutics Holdings Inc. and its Subsidiaries’ internal control over financial reporting as of December 31, 2019 have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their reports thereon (which contains an explanatory paragraph describing conditions that raise substantial doubt about the Company’s ability to continue as a going concern as described in Note 1 to the consolidated financial statements), included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND ADDITIONAL INFORMATION

We file annual reports, quarterly reports, current reports, proxy statements and other information with the SEC. Our SEC filings are and will become available to the public over the Internet at the SEC’s website at www.sec.gov. You can also find our public filings on our website at www.arcturusrx.com. Our website and the information contained therein or connected thereto are not part of this prospectus supplement or the accompanying prospectus.

We have filed with the SEC a registration statement on Form S-3 under the Securities Act with respect to the shares of common stock being offered by this prospectus supplement. This prospectus supplement and the accompanying prospectus are a part of that registration statement but do not contain all of the information set forth in the registration statement or the exhibits to the registration statement. For further information with respect to us and the shares we are offering pursuant to this prospectus supplement, you should refer to the registration statement and its exhibits. Statements contained in this prospectus supplement as to the contents of any contract, agreement or other document referred to are not necessarily complete, and you should refer to the copy of that contract or other documents filed as an exhibit to the registration statement. You may read or obtain a copy of the registration statement at the SEC’s website referred to above.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to “incorporate by reference” information from other documents that we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus supplement and the accompanying prospectus. Information in this prospectus supplement supersedes information incorporated by reference that we filed with the SEC prior to the date of this prospectus supplement.

We incorporate by reference the information or documents listed below that we have filed with the SEC:

	—	our Annual Report on Form 10-K for the year ended December 31, 2019 filed with the SEC on March 16, 2020;

	—	The information specifically incorporated by reference into our Annual Report on Form 10-K for the year ended December 31, 2019 from our definitive proxy statement on Schedule 14A (other than information furnished rather than filed), which was filed with the SEC on April 29, 2020;

	—	our Quarterly Reports on Form 10-Q for the periods ended March 31, 2020, June 30, 2020 and September 30, 2020 filed with the SEC on May 8, 2020, August 10, 2020 and November 9, 2020, respectively;

	—	our Current Reports on Form 8-K filed with the SEC on March 4, 2020, March 27, 2020, April 17, 2020, April 21, 2020, May 21, 2020, June 9, 2020; July 24, 2020; July 29, 2020; August 10, 2020; August 18, 2020; September 11, 2020, October 2, 2020; October 15, 2020; November 9, 2020; November 13, 2020; November 25, 2020 and December 7, 2020 (in each case, except for information contained therein which is furnished rather than filed); and

	—	the description of our common stock set forth in the Form 8-K12B filed on June 18, 2019.

S-26

All documents we file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, except as to any portion of any report or documents that is not deemed filed under such provisions, on or after the date of this prospectus supplement until the termination of this offering shall be deemed incorporated by reference in this prospectus supplement and the accompanying prospectus and to be a part of this prospectus supplement from the date of filing of those documents.

Documents incorporated by reference are available from us, without charge. You may obtain documents incorporated by reference in this prospectus supplement and accompanying prospectus by requesting them in writing or by telephone at the following address:

Arcturus Therapeutics Holdings Inc.

10628 Science Center Drive, Suite 250

San Diego, California 92121

Telephone: (858) 900-2660

Attention: Investor Relations

You also may access these filings on our Internet site at www.arcturusrx.com. Our web site and the information contained on that site, or connected to that site, are not incorporated into this prospectus supplement, the accompanying prospectus or the registration statement of which this prospectus supplement and accompanying prospectus is a part.

We have authorized no one to provide you with any information that differs from that contained in this prospectus supplement, the accompanying prospectus or incorporated by reference herein or therein. Accordingly, you should not rely on any information that is not contained in this prospectus supplement or the accompanying prospectus or incorporated by reference herein or therein. You should not assume that the information in this prospectus supplement is accurate as of any date other than the date of the front cover of this prospectus supplement.

Any statement contained in a document incorporated or deemed to be incorporated by reference in this prospectus supplement will be deemed modified, superseded or replaced for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or any other subsequently filed document that is deemed to be incorporated by reference into this prospectus supplement modifies, supersedes or replaces such statement

S-27

PROSPECTUS

Common Stock

Preferred Stock
Debt Securities

Warrants
Units

____________________________

This prospectus relates to common stock, preferred stock, debt securities, warrants for debt or equity securities and units consisting of the foregoing that we may sell from time to time in one or more transactions. We will provide the specific terms and conditions of these transactions and the securities we may sell in supplements to this prospectus prepared in connection with each transaction. The applicable prospectus supplement will contain information, where applicable, as to other listings, if any, on The Nasdaq Global Market, or the NASDAQ, or any securities exchange of the securities covered by the prospectus supplement. Any such prospectus supplement may also add, update or change information in this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. You should carefully read this prospectus, any applicable prospectus supplement and any related free writing prospectuses, as well as the documents incorporated by reference or deemed to be incorporated by reference into this prospectus, carefully before you invest. This prospectus may not be used to offer or sell securities unless accompanied by a prospectus supplement.

Our common stock is traded on the NASDAQ under the symbol “ARCT.”

_______________________________________

Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties referenced under the heading “Risk Factors” on page 6 of this prospectus and contained in our filings made with the Securities and Exchange Commission and the applicable prospectus supplement.

The securities may be sold directly by us to investors, through agents designated from time to time or to or through underwriters or dealers. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution” in this prospectus. If any underwriters are involved in the sale of these securities with respect to which this prospectus is being delivered, the names of such underwriters and any applicable commissions or discounts and over-allotment options will be set forth in a prospectus supplement. The price to the public of such securities and the net proceeds that we expect to receive from such sale will also be set forth in a prospectus supplement. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

This prospectus may not be used to offer or sell any securities unless accompanied by a prospectus supplement.

_______________________________________

The date of this prospectus is December 7, 2020.

TABLE OF CONTENTS

Page

ABOUT THIS PROSPECTUS	1
WHERE YOU CAN FIND MORE INFORMATION	1
INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE	2
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS	3
PROSPECTUS SUMMARY	5
RISK FACTORS	6
USE OF PROCEEDS	6
DESCRIPTION OF CAPITAL STOCK WE MAY OFFER	6
DESCRIPTION OF DEBT SECURITIES WE MAY OFFER	9
DESCRIPTION OF WARRANTS WE MAY OFFER	16
DESCRIPTION OF UNITS WE MAY OFFER	18
PLAN OF DISTRIBUTION	20
LEGAL MATTERS	22
EXPERTS	22

ABOUT THIS PROSPECTUS

This prospectus is part of an automatic shelf registration statement on Form S-3 that we filed with the Securities and Exchange Commission, or the SEC, as a “well-known seasoned issuer” as defined in Rule 405 under the Securities Act of 1933, as amended, or the Securities Act, utilizing a “shelf” registration process. Under this shelf registration process, we may, from time to time, offer and sell common stock, preferred stock, debt securities, warrants for debt and equity securities and units consisting of the foregoing in one or more transactions.

This prospectus only provides you with a general description of the securities we may sell in these transactions. Each time we sell any securities under this prospectus, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement also may add, update or change information contained in this prospectus. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. This prospectus does not contain all of the information included in the registration statement we filed with the SEC. For further information about us or the securities offered hereby, you should carefully read this prospectus, any applicable prospectus supplement, any related free writing prospectuses, the information and documents incorporated herein by reference and the additional information under the heading “Where You Can Find Additional Information” before making an investment decision.

You should rely only on the information contained or incorporated by reference in this prospectus, any applicable prospectus supplement and any related free writing prospectuses that we may authorize to be provided to you. We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. This prospectus and the accompanying supplement to this prospectus are not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted. You should assume that the information appearing in this prospectus, any applicable prospectus supplement or any related free writing prospectuses, as well as information we have previously filed with the SEC and incorporated by reference, is accurate only as of the date on the cover of those documents. If any statement in one of these documents is inconsistent with a statement in another document having a later date-for example, a document incorporated by reference in this prospectus-the statement in the document having the later date modifies or supersedes the earlier statement as our business, financial condition, results of operations and prospects may have changed since the earlier dates.

This prospectus may not be used to consummate sales of any of these securities unless it is accompanied by a prospectus supplement. To the extent there are inconsistencies between any prospectus supplement, this prospectus and/or any documents incorporated by reference, the document with the most recent date will control.

WHERE YOU CAN FIND MORE INFORMATION

We are a reporting company and file annual, quarterly and current reports, proxy and information statements and other information with the SEC. This prospectus is part of a registration statement that we have filed with the SEC relating to the securities to be offered under this prospectus. This prospectus does not contain all of the information set forth in the registration statement and the exhibits to the registration statement. For further information with respect to us and the securities to be offered under this prospectus, we refer you to the registration statement and the exhibits and schedules filed as a part of the registration statement.

The SEC maintains an internet site that contains reports, proxy and information statements, and other information regarding issuers that file electronically with the SEC, where you may read and copy the registration statement, as well as our reports, proxy and information statements and other information. The address of the SEC’s web site is http://www.sec.gov.

Copies of certain information filed by us with the SEC are also available on our website at https://arcturusrx.com. Information contained in or accessible through our website does not constitute a part of this prospectus and is not incorporated by reference in this prospectus.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

The SEC allows us to “incorporate by reference” information into this prospectus. This means that we can disclose important information about us and our financial condition to you by referring you to another document filed separately with the SEC. The information incorporated by reference is considered to be part of this prospectus. This prospectus incorporates by reference the documents listed below that we have previously filed with the SEC:

Our Annual Report on Form 10-K for the fiscal year ended December 31, 2019, as filed with the SEC on March 16, 2020, including the information specifically incorporated by reference into the Annual Report on Form 10-K from our definitive proxy statement on Schedule 14A, filed with the SEC on April 29, 2020;

Our Quarterly Reports on Form 10-Q for the periods ended March 31, 2020, as filed with the SEC on May 8, 2020, June 30, 2020, as filed with the SEC on August 10, 2020, and September 30, 2020, as filed with the SEC on November 9, 2020.

Our Current Reports on Form 8-K, as filed with the SEC on March 4, 2020, March 27, 2020, April 17, 2020, April 21, 2020, May 21, 2020, June 9, 2020, July 24, 2020, July 29, 2020, August 18, 2020, October 2, 2020, October 15, 2020, November 13, 2020, November 25, 2020 and December 7, 2020 (in each case, except for information contained therein which is furnished rather than filed); and

the description of our common stock set forth in the Form 8-K12B filed on June 18, 2019.

We also incorporate by reference into this prospectus all documents filed by us with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the termination of any offering of securities made by this prospectus. Nothing in this prospectus shall be deemed to incorporate information furnished but not filed with the SEC (including without limitation, information furnished under Item 2.02 or Item 7.01 of Form 8-K, and any exhibits relating to such information).

Any statement contained in this prospectus or in a document incorporated or deemed to be incorporated by reference in this prospectus shall be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained herein or in the applicable prospectus supplement or in any other subsequently filed document which also is or is deemed to be incorporated by reference modifies or supersedes the statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

You may request a copy of the filings incorporated herein by reference, including exhibits to such documents that are specifically incorporated by reference, at no cost, by writing or calling us at the following address or telephone number:

Arcturus Therapeutics Holdings Inc.

10628 Science Center Drive, Suite 250

San Diego, California 92121

Telephone: (858) 900-2660

Attention: Investor Relations

Statements contained in this prospectus as to the contents of any contract or other documents are not necessarily complete, and in each instance investors are referred to the copy of the contract or other document filed as an exhibit to the registration statement, each such statement being qualified in all respects by such reference and the exhibits and schedules thereto.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the documents incorporated by reference into this prospectus contain certain forward-looking statements within the meaning of Section 27A of the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act, in reliance upon the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include, without limitation, statements regarding the success, safety and efficacy of our drug products, product approvals, product sales, revenues, development timelines, product acquisitions, liquidity and capital resources and trends, and other statements containing forward-looking words, such as, “believes,” “may,” “could,” “would,” “will,” “expects,” “intends,” “estimates,” “anticipates,” “plans,” “seeks,” or “continues” or the negative thereof or variation thereon or similar terminology (although not all forward-looking statements contain these words). Such forward-looking statements are based on the beliefs of our management as well as assumptions made by and information currently available to our management. Readers should not put undue reliance on these forward-looking statements because they involve known and unknown risks, uncertainties and other factors, some of which are beyond our control. These risks, uncertainties and other factors may cause our actual results, performance or achievements to be materially different from the anticipated future results, performance or achievements expressed or implied by the forward-looking statements.