FDA CBER Issues Potency Assessment Guidance for Active Immunotherapy CGT Products

CMC and QA teams developing cellular and gene therapy products now have a formal FDA reference point for potency assessment: CBER's Office of Therapeutic Products has published guidance under docket FDA-2026-D-8561 addressing frequently asked questions on active immunotherapy product development, spanning regulatory review, CMC, pharmacology/toxicology, clinical, and clinical pharmacology disciplines.

The document is structured as an FAQ, reflecting questions the Agency has received directly from sponsors. That format signals where CBER sees recurring gaps in submissions, and for QA directors and regulatory leads, those gaps are worth mapping against internal development programs before the next IND or BLA interaction. Potency characterisation for CGT products remains one of the more contested CMC areas, given the complexity of defining a relevant biological activity for immune-mediated mechanisms of action.

The guidance does not carry legally enforceable weight. Per standard FDA framing, it represents the Agency's current thinking and should be read as recommendation rather than requirement, unless a specific regulatory or statutory citation is embedded in the text. Use of "should" throughout the document reflects that distinction. Teams treating FAQ-level guidance as binding risk over-engineering their programs; teams ignoring it risk misalignment with reviewer expectations at critical submission milestones.

For process development and analytical teams, the practical read is around potency assay design and qualification timelines. CBER has consistently signalled, across multiple CGT-related guidances, that potency methods should be sufficiently developed by Phase 3 to support licensure. This document extends that conversation into the immunotherapy space, where mechanism-based assays often lag behind manufacturing scale-up.

Comments on the guidance can be submitted at any time via the federal docket system, referencing FDA-2026-D-8561, or in writing to Dockets Management, FDA, 5630 Fishers Lane, Rm 1061, Rockville, MD 20852. Direct technical questions are routed through CBER's Office of Communication, Outreach and Development at [email protected] or (800) 835-4709.

The docket remains open for industry comment, making this an active window for sponsors to shape how the Agency refines its thinking on potency assessment as the CGT pipeline matures.

Source: FDA Center for Biologics Evaluation and Research via FDA Guidance Documents RSS Feed, 19 August 2026.