The Five Peptides Heading to PCAC Before February 2027 — and Why Analysts Consider Them a Harder Case Than July's Slate

Key takeaways

• The FDA has confirmed a second Pharmacy Compounding Advisory Committee (PCAC) meeting will take place before the end of February 2027 to review five additional peptides for the Section 503A Bulk Drug Substances List.
• The five compounds are: injectable GHK-Cu, Cathelicidin (LL-37), Dihexa acetate, Melanotan II, and Mechano Growth Factor, Pegylated (PEG-MGF).
• All five were removed from Category 2 in April 2026 when their original nominators withdrew their submissions, but none yet has a confirmed compounding pathway.
• Legal commentators and industry analysts regard this second slate as carrying a more contested evidentiary record than the seven peptides reviewed in July.
• Even a positive PCAC recommendation does not open a legal compounding pathway immediately — formal notice-and-comment rulemaking, which can exceed twelve months, is still required.
• UK research-use-only supply of these substances is unaffected by the US compounding timeline, provided standard RUO labelling and MHRA compliance obligations are observed.

Background: How the second wave was scheduled

The procedural sequence that placed these five peptides on the regulatory calendar began in September 2023, when the FDA placed more than a dozen peptides into Category 2 of the 503A Bulk Drug Substances List, a designation that effectively prohibited their use in licensed compounding pharmacies. The agency cited "significant safety concerns," including immunogenicity risks, impurity profiles, and limited human clinical data, according to McDermott Will & Emery.

On 27 February 2026, HHS Secretary Robert F. Kennedy Jr announced that many of the peptides on the FDA's Category 2 restricted list would be considered for reclassification to Category 1, and on 15 April 2026, Secretary Kennedy confirmed the removal of 12 peptides from Category 2 due to withdrawal of nominations by the nominators.

In April 2026, following guidance from HHS that the 2023 restrictions were unjustified, the FDA removed 12 peptides from Category 2, citing withdrawal of the original nominations, and simultaneously scheduled PCAC consultations for July 23–24, 2026 (seven peptides) and before February 2027 (the remaining substances) to consider adding the 12 products to the 503A Bulks List.

Together, the two meetings will address 12 of the 19 peptides placed in Category 2 in 2023. This phased approach — seven in July, five in February — suggests the FDA is moving methodically rather than issuing a blanket reversal.

The July meeting concluded on 24 July 2026. The PCAC voted by margins ranging from 7–4 to 8–6 to recommend the addition of BPC-157, KPV, TB-500, MOTS-c, Epitalon, and Semax to the Section 503A Bulk Drug Substances List, while voting against Emideltide (also known as delta sleep-inducing peptide).

The five peptides under review for February 2027

The FDA has announced that it will schedule a follow-on PCAC meeting before the end of February 2027 to review additional peptides — including GHK-Cu, Melanotan II, Cathelicidin (LL-37), Dihexa acetate, and Mechano Growth Factor, Pegylated (PEG-MGF) — which may provide further indication of how the Committee and the agency will approach peptide nominations going forward.

Injectable GHK-Cu. The copper-binding tripeptide (glycine–histidine–lysine) is already permitted in non-injectable routes under Category 1, so the February review is specifically concerned with its injectable form. Topical GHK-Cu preparations face vastly different FDA oversight compared to subcutaneous injectables; practitioners should remain cautious regarding injectable formulations until the February 2027 PCAC review. Injectable GHK-Cu was among the substances removed from Category 2 in April 2026, but its compounding status for parenteral administration remains unresolved pending the forthcoming review.

Cathelicidin (LL-37). LL-37 is the only human cathelicidin, a family of antimicrobial host-defence peptides. LL-37 has a narrow primary use case in antimicrobial and immune modulation research. The forthcoming PCAC review is notable because LL-37 was previously in a "withdrawn, no active review" state and is now being reconsidered. The human clinical evidence base for exogenous LL-37 administration remains limited, and the ECRI white paper published in April 2026 noted that human evidence for LL-37 ranges from sparse to absent in the peer-reviewed literature, according to ECRI.

Dihexa acetate. Dihexa (N-hexanoic-Tyr-Ile-(6) aminohexanoic amide) is a small peptide derived from angiotensin IV. Dihexa is investigated for cognitive support and neural connectivity, though its development remains at an early stage. Dihexa was previously in a withdrawn, no active review state, and is now being reconsidered. Preclinical data in rodent models have described potent effects on spatial memory; controlled human trials do not yet appear in the published literature, which is likely to be the principal point of contention at the February PCAC session.

Melanotan II. Melanotan II (a cyclic heptapeptide melanocortin receptor agonist) presents the most prominent safety signal of the five. The UK's Medicines and Healthcare products Regulatory Agency (MHRA) has logged adverse reactions to Melanotan II and warned the public of "serious health risks." The UK agency is also concerned that MT-II is increasingly being marketed to younger consumers and has been focused on removing UK-facing sales websites advertising MT-II since 2011. This pre-existing MHRA enforcement activity is relevant context for UK research-procurement teams: obtaining Melanotan II for research use requires careful documentation of purpose, and any RUO supplier should be in a position to demonstrate appropriate labelling and controls.

PEG-MGF (Pegylated Mechano Growth Factor). PEG-MGF is a modified IGF-1 splice variant with a polyethylene glycol moiety added to extend its half-life. PEG-MGF is investigated for muscle growth and recovery applications. Like Dihexa and LL-37, it was previously withdrawn from active FDA review and is now being formally reconsidered. The pegylation chemistry adds a manufacturing complexity dimension that the PCAC may examine alongside the underlying safety and efficacy evidence questions.

Why analysts regard this slate as harder to pass

Industry and legal commentary published since the July votes has consistently flagged the February 2027 slate as more contentious. One analyst commentary described the second slate as "materially riskier than this one," according to On Healthcare Tech. Several factors account for this assessment.

First, Melanotan II's established MHRA adverse-event record and its history of withdrawal from prior FDA review processes means agency scientists are likely to present a more detailed safety objection than they did for, say, BPC-157 or KPV.

Second, Dihexa and LL-37 lack even the modest clinical dataset that July's peptides could point to. For Epitalon, Semax, MOTS-c, KPV, DSIP, LL-37, Dihexa, and PEG-MGF, the ECRI assessment found that human evidence ranges from sparse to absent in the peer-reviewed literature. The July committee could at least cite some human exposure data for BPC-157 and TB-500; the February slate offers less of that foundation.

Third, the committee composition question — relevant to the July votes — is unlikely to be resolved before February. Three weeks before the July PCAC meeting, the Kennedy administration announced it had appointed eight new temporary voting panelists; on Day 1 of the July meeting, all eight yes votes came from those eight temporary members. Whether the same panel configuration applies in February 2027, and whether it withstands any legal challenge in the intervening period, remains to be seen.

What formal rulemaking still requires

A PCAC recommendation — whether positive or negative — is advisory only. Following the PCAC meetings, the FDA will initiate notice-and-comment rulemaking to officially add the peptides to the 503A Bulk Drug List, which could occur in 2027 or extend into a multi-year process.

Even if the agency follows the panel's advice, compounded peptides would not be immediately legal in the US. The agency would need to issue a rule to add them to the 503A bulk compounding list, which could take a year or more.

It is possible that HHS Secretary Kennedy will add peptides to Category 1 on an interim basis or otherwise promulgate statements signalling enforcement discretion pending final rulemaking. Legal practitioners at McDermott Will & Emery have noted, however, that until a rule is finalised, peptide marketers must be especially prudent in how any peptides are advertised, as violative promotion can trigger liability from the FDA, the Federal Trade Commission, litigants under the Lanham Act, and individual states.

Implications for UK research-procurement professionals

The 503A compounding framework is a US-specific statutory mechanism and has no direct parallel in UK or EU regulation. UK laboratories procuring any of the five February 2027 peptides for research purposes continue to do so under research-use-only (RUO) designation, unaffected by the US compounding timeline — provided appropriate labelling, chain-of-custody documentation, and MHRA compliance obligations are met.

The Melanotan II position warrants particular attention for UK procurement teams: given the MHRA's longstanding enforcement activity against MT-II sellers targeting UK consumers, any RUO supplier of this substance should be able to demonstrate that their stock is labelled, stored, and invoiced exclusively for laboratory research purposes, with no route-to-consumer sale pathway.

For research suppliers monitoring the US regulatory trajectory, the February 2027 PCAC session will be the next meaningful signal. A date within that window has not yet been published on the FDA advisory committee calendar, and stakeholders wishing to submit public comment or register as observers should monitor the FDA's Pharmacy Compounding Advisory Committee page for scheduling notices.