For Research Use Only. Not for human or animal consumption. This article summarizes publicly available FDA regulatory history for general informational purposes. It is not legal advice, does not describe or endorse any use of Ascenyx Bio products, and has no bearing on the research-use-only status of the products sold on this site.
If you follow peptide research at all, you’ve likely seen headlines about the FDA peptide Category 2 list — compounds like BPC-157 and TB-500 added, then removed, then a committee “recommending” them again. The terminology is confusing because it describes a narrow, specific regulatory lane — pharmacy compounding under a prescription — that has nothing to do with how research-use-only material like ours is sold or regulated. This timeline explains what actually happened, in order, and is explicit about what it does not mean.
What “Category 1” and “Category 2” Actually Are
Under Section 503A of the Food, Drug and Cosmetic Act, licensed pharmacies and physicians can compound a patient-specific prescription drug using a bulk substance only if that substance meets a USP/NF monograph, is a component of an FDA-approved drug, or appears on FDA’s 503A bulks list (FDA.gov). While FDA evaluates a nominated substance for that list, it places it into one of three interim categories (FDA.gov; Orrick):
| Category | What it means |
|---|---|
| Category 1 | Nominated with sufficient information, not flagged for significant safety risk. FDA generally does not intend to take enforcement action against compounding with these substances while evaluation continues. |
| Category 2 | Nominated with sufficient information, but FDA identified significant safety risks pending further evaluation. FDA does not extend the same enforcement discretion, and would consider action against a compounder using a Category 2 substance. |
| Category 3 | Inadequate supporting information to evaluate at all. |
This entire framework governs one thing: whether a licensed 503A or 503B pharmacy may compound a patient-specific prescription drug from that raw substance. It says nothing about, and has no legal connection to, the sale of research-use-only material to laboratories.
September 29, 2023 — Peptides Move Into Category 2
On September 29, 2023, FDA placed a group of peptides into Category 2, citing safety concerns that included immunogenicity risk from aggregation or peptide-related impurities, unnatural amino acids complicating characterization, and, for some substances, reports of serious adverse events in the available data (FDA.gov). Coverage of the episode identifies more than a dozen peptides affected by this and related actions, including BPC-157, TB-500, MOTS-C, GHK-Cu (injectable), Melanotan II, Semax, PEG-MGF, Emideltide (DSIP), Epitalon, KPV, Cathelicidin LL-37, and Dihexa acetate (McDermott Will & Emery). The practical effect was that 503A and 503B pharmacies lost the ability to compound patient-specific prescriptions using those substances without risking FDA enforcement.
April 15, 2026 — FDA Withdraws the Category 2 Designation for 12 Peptides
On April 15, 2026, HHS Secretary Robert F. Kennedy Jr. confirmed that FDA would remove 12 peptide bulk drug substances from Category 2, effective roughly seven days later, around April 22, 2026 (Orrick; McDermott). The stated reason was that the original nominations for these substances had been withdrawn by the nominators, not that FDA made an affirmative new safety finding in the peptides’ favor. Removal from Category 2 does not automatically place a substance in Category 1 — it simply takes it out of the “flagged as significant safety risk” bucket while its regulatory status is reconsidered from scratch (Orrick). FDA separately removed GHK-Cu from Category 1 in the same announcement, for the same nomination-withdrawal reason, with further PCAC consultation planned before the end of February 2027 (Orrick).
July 23–24, 2026 — The Pharmacy Compounding Advisory Committee Meets
FDA’s Pharmacy Compounding Advisory Committee (PCAC) held a two-day public meeting at its White Oak campus to formally discuss whether seven of those substances should be added to the 503A bulks list (FDA.gov meeting notice). For every single peptide discussed, FDA’s own scientific staff recommended against inclusion, citing insufficient safety data, insufficient efficacy data, and unresolved questions about how consistently the exact molecule (its “moiety”) is characterized across manufacturers (McDermott). The committee’s own vote came out differently:
| Peptide | Committee vote | Recommendation |
|---|---|---|
| BPC-157 | 8–6, 1 abstention | Recommended for inclusion |
| KPV | 8–6, 1 abstention | Recommended for inclusion |
| TB-500 | 8–6, 1 abstention | Recommended for inclusion |
| MOTS-C | 7–5, 2 abstentions | Recommended for inclusion |
| Epitalon | 7–4 | Recommended for inclusion |
| Semax | 8–5 | Recommended for inclusion |
| Emideltide (DSIP) | 6–7 | Not recommended |
Six of the seven substances received a majority committee vote in favor of eventual inclusion; Emideltide did not (McDermott; openloophealth).
What Happens Next
A PCAC vote is a recommendation, not a rule. FDA can accept, modify, or reject it, and by its own account rarely diverges from committee recommendations — but it still has to run the recommended substances through formal notice-and-comment rulemaking before any of them can lawfully return to the 503A bulks list (McDermott). Proposed rules may not appear until late 2026 or 2027, and the full process could extend for years. Even after a substance clears rulemaking, it would land in Category 1 — an interim enforcement posture, not an FDA approval or an efficacy finding — and compounding would still require a valid patient-specific prescription from a licensed 503A pharmacy, USP <797> sterile-compounding compliance, and FDA-registered, prescription-grade active ingredient sourcing (openloophealth).
What This Timeline Does Not Mean
This is the part that gets lost in headlines, so it’s worth stating directly:
- This entire process concerns prescription pharmacy compounding under Section 503A/503B — a licensed pharmacist preparing a patient-specific prescription drug for a named patient under a physician’s order. It has no legal connection to, and confers no legitimacy on, retail or direct-to-consumer sale of any substance for any use.
- A favorable PCAC vote is not FDA approval. No peptide discussed at the July 2026 meeting has been found safe or effective by FDA for any indication.
- None of this changes the regulatory status of research-use-only material. Ascenyx Bio is not a 503A or 503B compounding pharmacy, does not compound patient prescriptions, and does not sell drug products. Our peptides are laboratory research materials only, and this timeline is provided as regulatory context for researchers who follow the space — not as a signal that any product’s legal or commercial status has changed.
Sources: FDA — Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks; FDA — Bulk Drug Substances Used in Compounding Under Section 503A; FDA — July 23-24, 2026 PCAC Meeting Notice; Orrick, “FDA Announces Removal of 12 Peptides from Category 2 and Schedules PCAC Meetings”; McDermott Will & Emery, “Bulk List Bound: PCAC Backs Majority of Peptides in Two-Day Public Meeting”; NCPA, “FDA Advisory Committee Nominates Six Peptides for Pharmacies to Compound”; Open Loop Health, “What Happened at the July Peptide PCAC Meeting and What’s Next?”.