Shares fell 3.0% as investors appeared unsettled by a cautious outlook and the early-stage nature of clinical progress, with no new commercial or financial guidance provided to offset ongoing development risks.

• ARCT-032 CF program advanced into a 12-week Phase II open-label study, focusing on safety, tolerability, and early lung function endpoints in Class I CF patients.
• The repeated dosing beyond one month, a historic challenge for inhaled mRNA therapies, is underway but remains exploratory without efficacy data presented.
• ARCT-810 OTC deficiency program received FDA feedback outlining a pediatric pivotal trial pathway, with additional exploratory data being collected ahead of an End of Phase II meeting later this year.
• Commercial guidance for KOSTAIVE COVID vaccine in Japan remains delegated to partner Meiji, with no updated financial targets disclosed by Arcturus.
• Leadership additions in finance and medical roles signal internal strengthening but do not mitigate uncertainties around clinical or commercial milestones.