On July 23 and 24, 2026, FDA's Pharmacy Compounding Advisory Committee (PCAC) met to consider seven peptides nominated for the 503A bulks list: BPC-157, KPV, TB-500, and MOTS-c on the first day, and Emideltide, Semax, and Epitalon on the second. Most coverage since has focused on the headline outcome, a committee recommendation that could open a legal compounding route for drugs that currently circulate almost entirely through unregulated online sale. The detail that matters more for anyone who reads a certificate of analysis is what several FDA scientists and panel members said on the record while casting that vote: they do not agree on a single accepted chemical definition for the substances in front of them.
What the committee actually voted on
Section 503A of the Federal Food, Drug, and Cosmetic Act sets out three, and only three, ways a bulk drug substance can legally be used by a compounding pharmacist. It must comply with an applicable United States Pharmacopeia (USP) or National Formulary (NF) monograph, or be a component of an FDA-approved drug product, or appear on the 503A bulks list that FDA develops through rulemaking. None of the seven peptides discussed at this meeting has a USP or NF monograph, and none is a component of a drug FDA has approved, so the bulks list is the only pathway available to them. The meeting itself was convened specifically to give the advisory committee's input on that nomination before FDA acts.
Committee votes are advisory. FDA is not bound to follow them, has departed from committee recommendations in past bulks-list decisions, and will only make a final determination once its own rulemaking process concludes, a step that historically takes months.
The four-factor test, and where it strains
FDA does not evaluate a bulks-list nomination on safety alone. A final rule published in the Federal Register on February 19, 2019 established four factors the agency weighs, on a balancing basis rather than as a checklist: the physical and chemical characterization of the substance, any safety issues raised by its use in compounded preparations, the available evidence of effectiveness (or lack of it), and the substance's historical use in compounded drug products.
The first factor is where trade-press coverage of this specific meeting got interesting. According to PharmExec's reporting on the July 23 session, an FDA scientist told the committee that "there is no universally accepted chemical formula for each compound" under discussion, adding, "we've never faced a problem of, 'What is it?'" One panelist put the resulting discomfort more bluntly: "I'm voting on something here, but I don't know what that something is. It's kind of like a black box to me." The committee voted anyway, recommending BPC-157, KPV, and TB-500 by an 8 to 6 margin with one abstention, and MOTS-c 7 to 5 with two abstentions, per the same reporting. On the second day, committee coverage indicates Semax and Epitalon were recommended while Emideltide was not.
Why this is a testing question, not only a legal one
A missing compendial monograph is not the same statement as an unknowable molecule. What the physical-and-chemical-characterization factor is actually asking is whether a nominated substance's identity can be established and confirmed by a defined analytical method, independent of whether that method has yet been codified into a USP chapter. That is the exact question the analytical side of peptide testing already answers for research material every day: mass spectrometry confirms molecular identity by matching observed to theoretical monoisotopic mass, and where mass alone cannot resolve an isomer, dedicated chiral analysis closes the gap, a distinction covered in more detail in synthetic peptide quality attributes under USP <1503> and <1504>. None of that requires a finished monograph to exist. It requires a laboratory to have actually run the method and reported the result, which is a different and narrower question than whether the compound is chemically well-defined in principle.
Framed that way, the committee's "black box" discomfort reads less like a statement that these peptides cannot be characterized, and more like a statement that no one has yet compiled a standardized reference characterization for them the way USP has for older compounds. Whether a specific batch has actually been confirmed by mass spectrometry, and whether the laboratory doing that confirmation is named or redacts a client's identity, are two separate questions; the second has no bearing on whether the first has been done.
If these peptides reach the bulks list
Should FDA ultimately add any of these substances to the 503A list, a compounding pharmacy preparing an injectable version would operate under USP General Chapter <797>, Pharmaceutical Compounding, Sterile Preparations, which sets minimum standards for sterile compounded preparations. Because none of these substances carries its own USP monograph, the burden of verifying the incoming bulk material's identity, strength, and purity would fall on the compounding pharmacy's own testing and documentation rather than on a pre-existing compendial specification. That is a heavier, not lighter, verification burden than a monographed drug substance carries, and it is the same category of question this site covers for any peptide vial: not whether the party supplying the material identifies itself, but whether a specific, checkable analytical method stands behind the identity and purity claims made about it.
What to watch next
FDA's rulemaking on this nomination has not concluded, and the agency's 2019 bulks-list rule shows it has excluded substances despite an advisory committee recommendation before. Whatever the eventual outcome, the characterization question raised inside this meeting will still apply to every vial of these peptides already circulating outside any compounding pathway: what test was run, by which method, and whether the result is documented well enough to check.
Further reading
How identity confirmation by mass spectrometry works, and its limits, is covered in mass spectrometry for peptide identity verification. The wider set of attributes a synthetic peptide should be characterized against beyond a single purity number, including chiral purity, is covered in USP <1503> and <1504> explained.