COMP360 Psilocybin: The Phase 3 Results and Regulatory Path

**COMP360** is Compass Pathways' synthetic, pharmaceutical-grade formulation of psilocybin, developed for **treatment-resistant depression** and the furthest advanced classic psychedelic in the regulatory pipeline. It received FDA Breakthrough Therapy designation for TRD in 2018. ## The Phase 3 results **COMP005** (results announced 2025) met its primary endpoint. A single 25 mg dose produced a mean difference of **−3.6 points on the MADRS** depression scale versus placebo at the primary timepoint (p < 0.001). Participants achieving a clinically meaningful reduction maintained a durable effect through at least week 26 after one or two doses. **COMP006** (2026) also met its primary endpoint, with a mean difference of **−3.8 MADRS points**. An important design detail frequently dropped in summaries: the COMP006 comparison was **25 mg versus a 1 mg dose**, not versus inert placebo. That is a dose-comparison result. It reduces one problem — an inert placebo is trivially identifiable — while changing what the number means. Safety across both trials has been described as generally well tolerated, with treatment-emergent adverse events mild or moderate and mostly resolving within 24 hours. ## How to read the effect size A 3–4 point MADRS difference is **statistically strong and clinically modest**. MADRS runs 0–60, and the threshold usually cited for a clinically meaningful individual change is considerably larger. In COMP006, 39% of participants in the 25 mg arm showed a clinically meaningful reduction — which also means a majority did not. Two further qualifications: - **The blinding problem applies in full.** See Functional Unblinding: Why Psychedelic Trials Cannot Fully Blind. The measured difference includes an expectancy component of unknown size. - **Not every trial has been positive.** The EPISODE trial missed its primary endpoint of ≥50% symptom improvement, salvaging some secondary measures. ## Regulatory status As of mid-2026 the programme is heading toward an NDA submission, with reporting in April 2026 that the FDA granted national priority review vouchers to psilocybin programmes at Compass and Usona, and to a methylone programme for PTSD — a mechanism intended to compress review timelines substantially. On that trajectory a first approval of a classic psychedelic therapy would fall around late 2026 or 2027. **This section dates quickly.** Regulatory timelines slip, and voucher and review mechanisms change; treat specific dates as of mid-2026 and verify current status before relying on them. The larger point is that approval, if it comes, would be a genuine milestone in drug regulation — and would not by itself settle how much of the measured benefit is pharmacology. Compare Psilocybin: The Psychedelic Compound Reshaping Depression Treatment.