FDA's April 2026 503A update: what changed for compounded peptides

FDA published its quarterly update to the 503A bulks-list nominations document on April 22, 2026. Several peptides moved categories — but the reasons for those moves matter at least as much as the moves themselves. Removal from a Category does not mean approval, and inclusion in a Category does not mean a finding of safety.

What actually happened

Two peptides commonly tracked by readers were removed from Category 2: Melanotan II and BPC-157. In both cases, FDA’s stated reason was that the nominations were withdrawn — not that FDA concluded these peptides may safely be compounded. FDA further indicated that it intends to consult its Pharmacy Compounding Advisory Committee (PCAC) before the end of February 2027 on possible inclusion of Melanotan II on the 503A bulks list, with PCAC review of BPC-157 scheduled for July 23, 2026.

What “Category 2 removal” does and does not mean

Section 503A allows a state-licensed pharmacy to compound a drug from a bulk drug substance only if the substance has an applicable USP/NF monograph, is a component of an FDA-approved drug product, or appears on the FDA 503A bulks list. Removal from a nomination category is a procedural status change. It is not equivalent to placement on the bulks list, and it is not an FDA finding that the substance is appropriate for compounding under section 503A.

For readers tracking the regulatory ladder, the practical implication is narrow: as of the April 22, 2026 update, there is no compliant 503A pathway for routine compounding of Melanotan II or BPC-157, and there is no 503B pathway either, since neither substance appears on the 503B bulks list and there is no current shortage list entry that would create an enforcement-discretion period.

Where each peptide stands now

For Melanotan II, FDA’s safety-risk page continues to list the substance among withdrawn nominated substances and notes immunogenicity risks related to aggregation and peptide-related impurities, alongside published case reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome, and priapism. International regulators in Ireland (HPRA) and Australia (TGA) have issued public warnings against unauthorized Melanotan II tanning products.

For BPC-157, FDA states it has insufficient safety information to know whether compounded BPC-157 would harm humans for the proposed routes of administration. The substance remains prohibited under category S0 of the 2026 WADA Prohibited List for athletes, and USADA has stated that no clinical basis exists for a Therapeutic Use Exemption because BPC-157 is not an approved therapeutic agent in any country.

For Thymosin alpha-1, the December 2024 PCAC vote (4 yes / 17 no) against placement on the 503A bulks list remains the most recent substantive regulatory action; the April 2026 update did not change that. Thymosin alpha-1 is approved as a drug in over 30 jurisdictions under the brand name Zadaxin, but US regulatory status is unchanged.

What to watch next

The PCAC review of BPC-157 scheduled for July 23, 2026 is the next inflection point. PCAC recommendations are advisory, but they typically shape the timing of subsequent FDA action. The deadline for the parallel 503B proposed exclusion of semaglutide, tirzepatide, and liraglutide closes for public comment June 29, 2026, with an FDA final determination expected later in the year.

ProPeptideGuide tracks each of these regulatory inputs on the relevant peptide pages. The next 503A nomination update is expected in late July 2026.