Arcturus released interim Phase 2 data for ARCT-032, an inhaled mRNA therapy for Class I cystic fibrosis, showing no meaningful improvement in FEV1 over 28 days in the first cohort. The company reported safety signals consistent with prior cohorts but fell short on the key respiratory function measure investors were watching. Arcturus outlined next dose-escalation cohorts and a longer-duration safety/efficacy study while its stock reacted sharply to the interim readout.