UK Regulatory Approval for Costave
MHRA granted approval in January 2026 for Costave (self-amplifying mRNA COVID-19 vaccine) for individuals aged 18+, validating commercial/regulatory potential for the sa-mRNA platform.
ARCT-2304 (A/H5N1) Phase I Durable Immune Response
BARDA-funded ARCT-2304 completed Phase I in 212 younger adults and 80 older adults; 8-month follow-up showed durable immune responses across 1.5, 5 and 12 µg doses, with no safety concerns—supporting the STARR® sa-mRNA platform and cell-mediated immunity signal.
ARCT-032 (CF) Advancement to 12-Week Phase II
ARCT-032 progressed from 4-week dosing into a planned 12-week Phase II (initiating dosing H1 2026) enrolling up to ~20 Class I CF patients across U.S. and international sites; 15 mg dosing (4 patients) showed no safety concerns and 10 mg earlier cohort had early signals (4 of 6 subjects had reduced mucus plugs after 28 days).
ARCT-810 (OTC) Moving Toward Pivotal Development
ARCT-810 advancing toward pivotal development with intent to serve both late-onset adult OTC patients and young children with severe disease; Type C regulatory meetings scheduled H1 2026 to clarify paths for adult and pediatric indications.
Cost and Dose Flexibility / Manufacturing Headroom
Company retains dosing flexibility (10 mg chosen for upcoming cohort with ability to dose to 15 mg and historical dosing up to 27 mg) which allows balancing efficacy testing and cost-of-goods considerations (lower dose reduces manufacturing expense).
Operating Expense Reductions and Extended Runway
Annual R&D decreased by $83.0M and annual G&A decreased by $6.7M (quarterly R&D down $19.3M); disciplined refocus extended cash runway into Q2 2028, supporting near-term program milestones.