Arcturus Therapeutics Holdings Inc.

Our business is subject to various risks, including those described in Item 1A of our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, which we strongly encourage you to review. Except as disclosed below, there have been no material changes from the risk factors described in our Annual Report on Form 10-K for the year ended December 31, 2025 filed with the Commission on March 3, 2026.

The termination of our collaboration with CSL Seqirus requires us to advance, fund, and seek partners for our vaccine programs, and subjects us to additional risks and uncertainties.

On August 3, 2026, we entered into a Termination and Settlement Agreement with CSL Seqirus pursuant to which we mutually terminated the CSL Collaboration Agreement, effective as of such date (the “Termination Agreement”). The CSL Collaboration Agreement provided CSL Seqirus with exclusive global rights to research, develop, manufacture, and commercialize mRNA vaccines against COVID-19, influenza, and other infectious diseases using our STARR® and LUNAR® platform technologies. Under the CSL Collaboration Agreement, CSL Seqirus was responsible for leading development and commercialization of vaccines in the licensed fields, and collaboration revenue has historically been a significant component of our total revenue. We now bear sole responsibility for all decisions regarding the development, manufacturing, and commercialization of these vaccine products. We have limited experience commercializing vaccine products independently, and we may need to build internal commercial capabilities, enter into new partnerships, or engage distributors in order to maximize value of the assets, and there can be no assurance that we will be able to do so on favorable terms or at all. Several of the vaccine programs are in early-stage development, which will require substantial additional capital and resources to advance. We do not expect to receive any further milestone payments, research funding, or profit-sharing payments under the CSL Collaboration Agreement. Under the Termination Agreement, we are also obligated to pay CSL Seqirus royalties and revenue-sharing on our future commercialization of these vaccine products and successor products if such products are covered by CSL Seqirus royalty-bearing intellectual property, which could reduce the profitability of our vaccine programs and make such programs less attractive to potential partners.

During the Northern Hemisphere 2026-2027 season (expected to end June 30, 2027), CSL Seqirus and Meiji Seika Pharma (“Meiji”) will continue to be responsible for commercializing KOSTAIVE® in Japan, and for future seasons, we will need to establish direct or indirect commercial arrangements with Meiji or another distributor for the Japanese market, and any other markets. Any disruption in the transition of activities, supply, or regulatory responsibilities could adversely affect sales of KOSTAIVE® in Japan and damage our relationships with key counterparties and regulators. We have entered into a transition plan with CSL Seqirus for the orderly transfer of clinical trials, regulatory filings, intellectual property, and other materials, but there can be no assurance that such transition will be completed without delays or disruptions. We intend to evaluate strategic opportunities to maximize the value of the vaccine portfolio, including development, commercialization, and partnering opportunities, but there can be no assurance that we will identify suitable partners or enter into collaboration arrangements on favorable terms. The pursuit of multiple early-stage vaccine programs in parallel could strain our financial and operational resources and divert management attention from our rare disease therapeutic programs, which are our primary area of focus, and could have a material adverse impact on our business and results of operations.

We may not realize the anticipated benefits of our acquisition of myNEO, and the acquisition and integration of myNEO may disrupt our business.

On October 15, 2026, we completed our acquisition of myNEO, an artificial intelligence discovery company based in Belgium. The success of the acquisition will depend on our ability to integrate myNEO’s personnel, technology and operations, retain key myNEO personnel, several of whom have transitioned to consulting arrangements with us, and successfully apply myNEO’s computational engine to our mRNA design and target identification efforts. myNEO’s technology has not been validated in the development of an approved product, and there can be no assurance that it will improve the quality, speed or success of our research and development programs. The integration of myNEO may require significant management attention and resources, may involve unanticipated costs, liabilities or delays, and may expose us to risks associated with operating in a foreign jurisdiction, including compliance with data privacy, employment and tax laws. In addition, we issued unregistered shares of our common stock as part of the closing consideration and may issue additional shares in satisfaction of contingent milestone payments, which would result in dilution to our existing stockholders, and the sale of such shares into the public market following any applicable holding period could adversely affect the market price of our common stock. If we are unable to integrate myNEO successfully or realize the anticipated benefits of the acquisition, our business, financial condition and results of operations could be adversely affected.

Geopolitical risks associated with ongoing wars and armed conflicts could have an adverse impact on our business, financial condition and results of operations, including our clinical trials.

Geopolitical developments related to ongoing global conflicts and tensions are sources of uncertainty and risk, and may cause disruptions to global or regional markets, supply chains or operations in applicable regions, including those related to conflicts in the Middle East. We have and may continue to evaluate and engage in activities, including engagement of clinical sites, in the Middle East. Conflicts in the Middle East could disrupt operations of companies doing business in the region, including in Israel. Any significant changes in the political, economic, financial, competitive, legal and regulatory or reimbursement conditions where we conduct, or plan to expand, our international operations may have a material impact on our business, financial condition or results of operations.