8-K: Arcturus Partner Launches New COVID Vaccine in Japan

Meiji Seika Pharma, a partner of Arcturus Therapeutics, has launched a new two-dose vial presentation of KOSTAIVE, a self-amplifying mRNA COVID-19 vaccine targeting the Omicron JN.1 variant XEC, in Japan.

Summary

• Meiji Seika Pharma Co., Ltd., a subsidiary of Meiji Holdings Co., Ltd., launched a new presentation of KOSTAIVE, a self-amplifying mRNA vaccine against COVID-19, in Japan.
• The new formulation of KOSTAIVE is supplied as a two-dose vial, with one vial per carton.
• KOSTAIVE targets the SARS-CoV-2 Omicron sublineage JN.1 variant XEC.
• Non-clinical studies demonstrated that KOSTAIVE induced neutralizing antibodies against Omicron JN.1 and XEC, as well as against LP.8.1 and the currently circulating variants XFG and NB.1.8.1.
• Meiji Seika Pharma entered into a distribution agreement with Seqirus, Inc. (CSL Seqirus), a part of CSL Limited, for the distribution and sales of Arcturus Therapeutics Holdings Inc.'s self-amplifying mRNA vaccine candidate against COVID-19 in Japan, as previously announced on April 11, 2023.
• The manufacturing and marketing approval for KOSTAIVE was granted on August 28, 2025, and the product was launched in Japan on September 26, 2025.
• The vaccine is administered as a single 0.5 mL intramuscular dose after dissolving in 1.5 mL of Japanese Pharmacopoeia physiological saline solution.

Sentiment

Score: 8

Explanation: The launch of a new vaccine presentation in a major market like Japan, targeting current variants, is a significant positive development for Arcturus and its partners. It represents successful product development, regulatory approval, and market entry, indicating potential for future revenue and market share.

Positives

• Successful launch of a new presentation of KOSTAIVE, a self-amplifying mRNA COVID-19 vaccine, in Japan, indicating market entry and potential revenue generation.
• The vaccine targets the prevalent SARS-CoV-2 Omicron sublineage JN.1 variant XEC, addressing current public health needs.
• Non-clinical studies showed broad neutralizing antibody induction against multiple Omicron variants (JN.1, XEC, LP.8.1, XFG, NB.1.8.1), suggesting potential efficacy against evolving strains.
• The partnership with Meiji Seika Pharma and CSL Seqirus provides a robust distribution network in Japan, leveraging CSL Seqirus's expertise as a leading influenza vaccine provider.

Risks

• Actual results may differ materially from forward-looking statements due to known and unknown risks, uncertainties, and other factors.
• The likelihood that non-clinical data will be predictive of future clinical results or real-world effectiveness is uncertain.
• Potential supply of KOSTAIVE in 2025 and its timing are subject to risks.
• General business and economic conditions could impact the company's performance.
• Risks discussed under the 'Risk Factors' heading in Arcturus's most recent Annual Report on Form 10-K and subsequent SEC filings could affect outcomes.

Future Outlook

Arcturus's forward-looking statements include expectations regarding partnered programs, the potential for non-clinical data to predict future results, the potential supply of KOSTAIVE in 2025 and its timing, and the impact of general business and economic conditions. However, actual results may vary due to substantial risks and uncertainties.

Management Comments

• Meiji Seika Pharma remains committed to contributing to the prevention of COVID-19.

Industry Context

The launch of KOSTAIVE's new presentation by Meiji Seika Pharma, leveraging Arcturus's self-amplifying mRNA technology, signifies continued innovation in the global COVID-19 vaccine market. This development addresses the ongoing need for vaccines targeting evolving SARS-CoV-2 variants, particularly Omicron sublineages. The partnership with CSL Seqirus, a major influenza vaccine provider, highlights the strategic importance of established distribution networks in the competitive vaccine landscape.

Stakeholder Impact

• Shareholders: Potential positive impact due to new product revenue streams and market expansion.
• Patients in Japan: Access to a new self-amplifying mRNA COVID-19 vaccine targeting current Omicron variants.
• Arcturus Therapeutics: Validation of its self-amplifying mRNA platform and potential for royalty or milestone payments from the partnership.
• Meiji Seika Pharma and CSL Seqirus: Expansion of their product portfolios and strengthening their position in the vaccine market.

Next Steps

• Continued distribution and sales of KOSTAIVE in Japan by Meiji Seika Pharma and CSL Seqirus.
• Monitoring of real-world effectiveness and safety of KOSTAIVE.
• Potential future development or adaptation of the vaccine to address new SARS-CoV-2 variants.

Key Dates

Recommendation

The successful launch of a new, variant-targeting COVID-19 vaccine in Japan by a key partner represents a significant positive milestone for Arcturus Therapeutics. This event validates the company's mRNA technology, opens a new revenue stream through its distribution agreement, and addresses an ongoing public health need. While specific financial metrics are not provided, market entry and product commercialization are generally strong indicators of future growth potential for a biotech company, suggesting a 'buy' recommendation for investors looking for growth opportunities in the vaccine sector.

Keywords

COVID-19 vaccine, mRNA vaccine, self-amplifying mRNA, KOSTAIVE, Arcturus Therapeutics, Meiji Seika Pharma, Japan, Omicron JN.1, XEC variant, vaccine launch, biotechnology, pharmaceuticals