---
schema_version: "secwatch.filing_event.v1"
accession: "0001193805-25-001368"
form_type: "8-K"
ticker: "ARCT"
cik: "0001768224"
company_name: "Arcturus Therapeutics Holdings Inc."
filed_at: "2025-09-26T23:59:59+00:00"
generated_at: "2026-05-17T05:34:51.577950+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.55
calibrated_materiality_score: 0.55
confidence: "high"
source: SEC EDGAR
---

# Meiji Seika Pharma launches two-dose vial of KOSTAIVE (sa-mRNA COVID-19 vaccine) in Japan

## Summary
- New two-dose vial presentation of KOSTAIVE launched in Japan on September 26, 2025.
- Vaccine targets SARS-CoV-2 Omicron sublineage JN.1 variant XEC.
- Non-clinical studies show neutralizing antibodies against XEC, LP.8.1, XFG, NB.1.8.1 variants.
- Manufacturing and marketing approval granted August 28, 2025.

## SEC filing metadata
- accession: 0001193805-25-001368
- form_type: 8-K
- ticker: ARCT
- cik: 0001768224
- company_name: Arcturus Therapeutics Holdings Inc.
- filed_at: 2025-09-26T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.55
- calibrated_materiality_score: 0.55
- confidence: high
- sec_items: 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1768224/000119380525001368/0001193805-25-001368-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1768224/000119380525001368/e664858_8k-arct.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193805-25-001368
- JSON: https://secwatch.observer/filing/0001193805-25-001368.json
- Plain text: https://secwatch.observer/filing/0001193805-25-001368.txt

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.