New FDA approval process promotes development of rare disease gene therapies

Lexology September 5, 2025
Hogan Lovells

The U.S. Food and Drug Administration (FDA) announced a new process called “Rare Disease Evidence Principles” (RDEP), under which eligible drugs and biologics for ultra-rare diseases caused by known genetic defects will receive assurance of agency consideration of additional supportive data that may be used to meet regulatory approval standards. For programs meeting the eligibility requirements, FDA is offering an additional meeting with the appropriate agency review team. The meeting will help determine what data could be used to demonstrate “substantial evidence of effectiveness,” which FDA generally expects may be established based on one adequate and well-controlled clinical trial, including single arm trials, and qualifying confirmatory evidence.

Although FDA’s newly announced process does not alter the statutory “substantial evidence” standard...

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