The FDA's Pharmacy Compounding Advisory Committee (PCAC) voted on six peptides during its November 2024 meeting, recommending that five of them not be placed on the difficult-to-compound list. The sixth, AOD-9604, received a split vote, raising questions about how these decisions might ripple through the regulatory landscape for other peptides, including the investigational triple agonist retatrutide.
The committee's votes are advisory, but they signal the agency's thinking on compounding under sections 503A and 503B of the Federal Food, Drug, and Cosmetic Act. For retatrutide, which is not yet FDA-approved but is already appearing in compounding pharmacies, the PCAC's reasoning could preview future restrictions.
The PCAC Vote: What Happened
On November 20, 2024, the PCAC considered six bulk drug substances nominated for the 503A bulks list: oxytocin, vesugen, PT-141, AOD-9604, IGF-1 LR3, and retatrutide. The committee voted 13-0 against listing oxytocin. Vesugen and PT-141 each received unanimous no votes. IGF-1 LR3 was rejected 12-0. Retatrutide was voted down 12-1, with the sole yes vote coming from a patient representative.
AOD-9604 was the exception. The committee split 6-6 on whether it should be placed on the list, meaning the motion failed but the tie reflects ongoing debate. The FDA will now consider these recommendations before issuing a final rule.
Why the Votes Matter for Compounding
Under the Drug Quality and Security Act, a bulk drug substance must appear on the 503A bulks list for a pharmacy to compound it using that substance. If a substance is not listed, compounding it from bulk is generally prohibited. The PCAC evaluates nominations based on a risk-benefit framework that includes: 1) the clinical need for compounding, 2) the safety and efficacy evidence for the substance, and 3) the complexity of compounding it.
For retatrutide, the committee found insufficient evidence of safety and efficacy to justify compounding. This is a 2 of 3 on evidence quality, given the limited published data. The 2023 phase 2 trial (Jastreboff 2023) showed promising weight loss, but the FDA typically requires phase 3 data before considering a drug for widespread use. Compounding pharmacies have been offering retatrutide despite this, often citing patient demand during drug shortages. The PCAC vote signals that the agency views this practice skeptically.
Retatrutide's Unique Position
Retatrutide is a GLP-1/GIP/glucagon receptor triagonist, a novel mechanism not yet approved anywhere. Its regulatory path is distinct from the other peptides under review. Oxytocin and PT-141 are already FDA-approved as finished drug products, which automatically disqualifies their bulk forms from the 503A list. Vesugen and IGF-1 LR3 lack robust clinical data. AOD-9604, a fragment of human growth hormone, has some human studies but remains controversial.
Retatrutide's situation is complicated by its presence in compounding pharmacies before approval. The FDA has issued warning letters to compounders making retatrutide, as detailed in a recent analysis of FDA warning letters signaling a shift after GLP-1 quality concerns. These letters cite violations of current good manufacturing practices and the lack of a USP monograph for the peptide. The PCAC vote reinforces the message that retatrutide should not be compounded from bulk until more data are available.
AOD-9604: A Split Decision
The tie vote on AOD-9604 highlights the gray areas in compounding regulation. AOD-9604 is not an FDA-approved drug, but it has been studied in phase 2 trials for obesity and cartilage repair. The committee's split suggests that some members saw a clinical need, while others questioned the evidence. A 2019 trial (Stier 2019) showed modest weight loss effects, but the overall data are thin.
This outcome could influence how the FDA handles other peptides with limited human data. If the agency decides not to list AOD-9604, it may set a precedent that compounds with phase 2 data alone are insufficient for the bulks list. For retatrutide, which has only phase 2 data, this would be a negative signal. However, retatrutide's phase 3 trials are ongoing, and if those results are positive, the calculus could change.
What the Vote Means for Retatrutide's Regulatory Path
The PCAC vote does not directly block retatrutide compounding. The FDA must still issue a final rule, and the committee's recommendation is just one input. But the vote makes it more likely that the agency will formally prohibit compounding retatrutide from bulk. This would force compounders to either stop making it or source it from FDA-approved manufacturers, which do not yet exist.
There are three reasons this matters: 1) it could slow patient access to retatrutide before approval, 2) it may push some compounders into legal gray areas, and 3) it signals that the FDA is scrutinizing GLP-1-related compounding more closely. The agency's recent focus on quality concerns, as seen in a GLP-1 quality study that put retatrutide compounding under fire, suggests that enforcement could intensify.
For pharmacies operating under 503A, the vote is a warning. For 503B outsourcing facilities, the implications are similar, though they face additional FDA oversight. The key takeaway is that the FDA is unlikely to tolerate widespread compounding of an unapproved drug with a novel mechanism, especially when safety data are incomplete.
Who Is Affected
Compounding pharmacies are the most directly affected. Those that have built business models around retatrutide may need to pivot. Patients who rely on compounded retatrutide for weight loss could lose access, though some may turn to other sources. Physicians prescribing compounded retatrutide should be aware of the regulatory risk. The vote also affects investors and drug developers watching the GLP-1 space, as it could influence the competitive landscape.
Notably, the vote does not affect FDA-approved GLP-1 drugs like semaglutide or tirzepatide, which can be compounded during shortages under specific conditions. Retatrutide is different because it is not approved, so the shortage pathway does not apply. This distinction is critical for understanding the regulatory boundaries.
What to Watch Next
The FDA's final rule on the 503A bulks list is expected in 2025. Before then, the agency may issue additional guidance or warning letters. The phase 3 trials for retatrutide, including TRIUMPH-1 and TRIUMPH-2, are ongoing, with results anticipated in 2025 and 2026. Positive data could shift the regulatory conversation, but until approval, compounding remains risky.
Another factor is the potential for retatrutide to be placed on the FDA's drug shortage list once approved, which would temporarily allow compounding. However, this is speculative. The PCAC vote suggests that the agency will not preemptively facilitate compounding. For now, the regulatory path for retatrutide is narrowing, and stakeholders should monitor the FDA's enforcement actions closely. The recent analysis of retatrutide compounding risks amid FDA GLP-1 quality concerns provides further context on the quality issues driving this scrutiny.
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