Compass Pathways reported positive outcomes from the largest-ever trial of psilocybin for treatment-resistant depression, meeting its primary endpoint of a significant reduction in depression severity compared to placebo. Despite the clinical success, the drug's effect size was modest, leading to a 36% pre-market drop in its stock price. The trial demonstrated no meaningful imbalance in suicidal ideation between treatment groups. Compass noted this milestone is critical toward FDA approval, fulfilling a requirement for placebo-controlled data despite challenges posed by functional unblinding inherent with psychedelic therapies.