Arcturus Therapeutics Stock Plummets 55% on Mixed Clinical Trial Results
Arcturus Therapeutics (ARCT) shares collapsed after interim Phase 2 data showed its cystic fibrosis treatment failed to demonstrate meaningful lung function improvement. The inhaled mRNA therapy ARCT-032 showed biological activity in reducing mucus plugs—a key pathology of the disease—but lacked immediate efficacy in standard respiratory metrics.
Researchers observed delayed effects post-treatment, prompting plans for a 12-week study in 2026. "Mucus plug reduction after 28 days suggests we're addressing the underlying mechanism," said Erasmus Medical Center's Dr. Harm Tiddens. The market's violent reaction reflects investor impatience with prolonged biotech development timelines despite potential long-term therapeutic promise.