FDA Drops Another Cache of Heavily Redacted Rejection Letters, Promises Future 'Real-Time' Access

The FDA announced it will promptly release Complete Response Letters (CRLs) and published a new batch of 2024/2025 rejections, offering critical insights into regulatory hurdles. Most notably, Lykos Therapeutics' MDMA therapy for PTSD was rejected due to "substantial concerns about the reliability of safety data," including unreported events, potential for abuse, and study design flaws, with the FDA recommending new studies and an audit. Separately, Stealth BioTherapeutics' elamipretide for Barth syndrome was rejected as its proposed surrogate endpoints were deemed insufficient to establish effectiveness, despite regulatory flexibility for rare diseases. These detailed rejections underscore the FDA's rigorous scrutiny, particularly regarding data integrity and endpoint validation, impacting development pathways and investor confidence across the biopharma sector.

Analysis

The FDA's new policy of promptly releasing Complete Response Letters (CRLs) provides unprecedented insight into regulatory decision-making, with the latest batch highlighting critical hurdles for several biopharmaceutical firms. The rejection of Lykos Therapeutics' MDMA therapy for PTSD is particularly severe, stemming from "substantial concerns about the reliability of the safety data," including unreported events, potential for abuse, and flawed study design. The FDA's recommendation for a completely new study and an audit into patient abuse allegations suggests a prolonged and highly uncertain path to potential approval. In contrast, while Stealth BioTherapeutics' elamipretide for the ultra-rare Barth syndrome was also rejected, the CRL provides a more defined, albeit challenging, path forward. The FDA, despite exercising "regulatory flexibility," found the proposed surrogate endpoints insufficient but suggested resubmission for accelerated approval using a different endpoint, which the company has already pursued. Other rejections underscore different risk factors: Regeneron's odronextamab CRL was due to issues at a third-party manufacturing site operated by Catalent, a problem external to the drug's clinical profile, while Rocket Pharmaceuticals' rejection for Kresladi highlights chemistry, manufacturing, and controls (CMC) challenges common to complex gene therapies.

Key Decisions for Investors

• Investors should increase scrutiny on clinical trial data integrity and safety reporting, as the Lykos CRL demonstrates the FDA's willingness to reject high-profile therapies on these grounds, even with positive advisory committee aspects.
• For companies like Stealth BioTherapeutics that receive a CRL with specific guidance on an alternative regulatory pathway, the risk profile is altered but not eliminated; monitor the progress of the August resubmission for elamipretide as it represents a tangible route to potential value creation.
• Differentiate between rejections based on fundamental drug data versus manufacturing issues; a CRL for a company like Regeneron tied to a third-party site may represent a temporary setback and potential buying opportunity if the manufacturing issues are resolved in a timely manner.