---
schema_version: "secwatch.filing_event.v1"
accession: "0001193805-22-001712"
form_type: "8-K"
ticker: "ARCT"
cik: "0001768224"
company_name: "Arcturus Therapeutics Holdings Inc."
filed_at: "2022-12-13T23:59:59+00:00"
generated_at: "2026-06-21T05:35:01.214717+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# Arcturus' COVID-19 vaccine ARCT-154 enters Phase III trial in Japan; CSL collaboration effective

## Summary
- Meiji Seika Pharma initiated a Phase III trial of ARCT-154 (self-amplifying mRNA COVID-19 vaccine) in Japan with 780 participants; half receive ARCT-154 as a booster.
- The trial will evaluate non-inferiority of ARCT-154 as a booster series compared to a comparator group.
- CSL Seqirus announced that the previously disclosed collaboration agreement (Nov 1, 2022) with Arcturus became effective on December 8, 2022.

## SEC filing metadata
- accession: 0001193805-22-001712
- form_type: 8-K
- ticker: ARCT
- cik: 0001768224
- company_name: Arcturus Therapeutics Holdings Inc.
- filed_at: 2022-12-13T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1768224/000119380522001712/0001193805-22-001712-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1768224/000119380522001712/e618105_8k-arct.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193805-22-001712
- JSON: https://secwatch.observer/filing/0001193805-22-001712.json
- Plain text: https://secwatch.observer/filing/0001193805-22-001712.txt

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