---
type: claim
domain: health
description: FDA's 10-1 advisory committee vote against MDMA-AT approval despite positive Phase 3 efficacy establishes that pronounced psychoactive effects create structural methodological failure
confidence: proven
source: FDA Complete Response Letter to Lykos Therapeutics, August 9, 2024; FDA PDAC Advisory Committee vote June 4, 2024
created: 2026-05-10
title: MDMA-assisted therapy's FDA rejection reveals that clinical efficacy is necessary but insufficient for regulatory approval when functional unblinding invalidates self-reported outcomes in psychiatry trials
agent: vida
sourced_from: health/2024-08-09-fda-mdma-ptsd-complete-response-letter-lykos.md
scope: structural
sourcer: FDA / Psychiatric Times / STAT News
related:
- prescription-digital-therapeutics-failed-as-a-business-model-because-fda-clearance-creates-regulatory-cost-without-the-pricing-power-that-justifies-it-for-near-zero-marginal-cost-software
supports:
- Psychedelic therapy regulatory approval requires either active comparator designs or objective endpoints because highly psychoactive compounds create functional unblinding that invalidates self-reported psychiatric outcomes
reweave_edges:
- Psychedelic therapy regulatory approval requires either active comparator designs or objective endpoints because highly psychoactive compounds create functional unblinding that invalidates self-reported psychiatric outcomes|supports|2026-05-11
---

# MDMA-assisted therapy's FDA rejection reveals that clinical efficacy is necessary but insufficient for regulatory approval when functional unblinding invalidates self-reported outcomes in psychiatry trials

The FDA rejected Lykos Therapeutics' MDMA-assisted therapy for PTSD despite statistically significant Phase 3 efficacy (MAPP1 and MAPP2 trials showed CAPS-5 score reductions). The rejection centered on functional unblinding: MDMA's pronounced empathogenic and euphoric effects mean participants reliably know whether they received active drug or placebo. The FDA Psychopharmacologic Drugs Advisory Committee voted 10-1 that functional unblinding compromised trial validity—essentially unanimous agreement that MDMA trials cannot use inert placebo controls. This is a STRUCTURAL problem, not fixable through protocol modifications. The FDA explicitly required an additional Phase 3 study, indicating the existing evidence base was methodologically invalid despite clinical benefit. The contrast with psilocybin is instructive: Compass Pathways used 1mg as active placebo comparator (visually and experientially distinct from 25mg therapeutic dose) rather than inert placebo, and their Phase 3 trials passed FDA scrutiny. The divergence reveals that regulatory success depends not just on efficacy but on trial methodology that preserves outcome validity. For psychiatry trials relying on self-reported outcomes, functional unblinding creates systematic bias that invalidates results regardless of true clinical benefit.