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FDA reviewer outlines IND expectations for phage therapy: sequencing, host controls and phased CMC data
Summary
At an FDA workshop, Dr. Susan Leman said phage therapy products are regulated as investigational biologics and stressed sponsors should provide full phage sequencing, host‑strain characterization, validated purification and phase‑appropriate CMC to manage safety and support INDs or expanded‑access use.
Dr. Susan Leman, a product reviewer in FDA’s Office of Vaccines, told attendees that bacteria‑targeting phage products must be treated as investigational biologics when intended to treat humans and reviewed under IND pathways. “At the moment in the US, there are no phage products that are licensed to treat human infections,” Leman said, and FDA’s evaluation centers on safety derived from chemistry, manufacturing and controls (CMC).
Leman said early‑stage INDs should include fully sequenced obligately lytic phages that are non‑transducing and lack recognizable virulence or antibiotic‑resistance genes. She advised sponsors to document why each phage is included in any cocktail and to provide wet‑lab and bioinformatic evidence of activity and absence of problematic genes. ‘‘For early stage studies, we expect that phages will be fully sequenced,’’ she said.
The reviewer described four core CMC areas FDA examines: the phages themselves, the bacterial production host, production and purification processes, and testing (potency, identity, purity and stability). She highlighted the production host as a particular safety focal point because host genomes and impurities influence final product safety. If a host encodes toxin genes, sponsors should either show the phage cannot transduce that gene or provide testing demonstrating the toxin is absent in the final product, Leman said.
Leman explained the agency’s pragmatic approach to manufacturing expectations across development: phase‑appropriate GMP for investigational phases, increasing demands for process robustness, validated assays and stability data as products move from phase 1 toward a potential BLA. She recommended pre‑IND meetings so sponsors can get multidisciplinary feedback on CMC and clinical plans before submission.
During audience Q&A, she said expanded‑access INDs (single‑patient/compassionate use) are evaluated with more flexible CMC expectations when the potential benefit justifies the risk and clinical investigations would not be compromised. She urged sponsors uncertain about classification (drug, biologic, supplement, or food use) to contact the appropriate FDA center for guidance.
The FDA presentation underscores that sponsors seeking to develop phage therapy in the U.S. should prepare rigorous molecular characterization data for phages and hosts, robust purification and impurity control strategies, and early regulatory engagement to align IND packages with FDA expectations. The agency’s team will review INDs within the standard review clock and can place studies on hold if CMC is insufficient.
