Who is affected by the Category 1 vs 2 peptide framework

The FDA's peptide compounding classification system organizes bulk drug substances — the raw pharmaceutical ingredients used to make compounded preparations — into three categories. The category affects whether FDA's interim compounding policy applies to a substance. It affects patients, prescribers, pharmacies, and telehealth platforms in different ways.

What is the difference between Category 1 and Category 2 peptides

The FDA's 503A bulk drug substance framework divides substances into three evaluation buckets:

• Category 1 substances are under evaluation. They are not on the 503A Bulks List.
• Category 2 substances are ones FDA says raise significant safety risks. As of September 14, 2026, Category 2 lists six substances. The only peptides among them are ibutamoren (MK-677) and kisspeptin-10.
• Category 3 substances were nominated without adequate support.

The key practical distinction: FDA's interim policy of not taking action against compounding with a substance that is not yet on the 503A bulks list applies only to Category 1 substances, when other conditions are met. It does not cover Category 2 substances. Law firms that advise pharmacies say removal from Category 2 does not, by itself, put a substance on the bulks list or in Category 1.

Who does the peptide Category 2 classification affect

The classification affects four groups:

Patients who were prescribed or interested in a Category 2 peptide lose access through licensed 503A compounding pharmacies. They may have ongoing clinical relationships that need to be restructured around available alternatives.

Prescribing physicians must work within the available substance list. For substances on Category 2, prescribing compounded versions is not supported by standard pharmacy channels.

Compounding pharmacies cannot rely on FDA's interim non-enforcement policy for Category 2 substances. Use of those substances would expose them to regulatory and legal risk.

Telehealth platforms that had built protocols around Category 2 substances must revise their formularies or pause those protocols. In early March 2026, FDA announced 30 warning letters to telehealth companies over their marketing of compounded GLP-1 drugs.

Which peptides are Category 1 and available from compounding pharmacies

FDA updates its category list over time. It last updated the list on May 14, 2026. The PCAC — Pharmacy Compounding Advisory Committee — a federal advisory body — reviews nominated substances and recommends whether to add them to the 503A bulks list. Active clinical research is tracked at ClinicalTrials.gov.

FDA removed five peptides from Category 2 on September 27, 2024, and 12 more on April 22, 2026, after their nominations were withdrawn. Those peptides are not in any category and are not on the 503A bulks list. At its July 23–24, 2026 meeting, the PCAC voted to recommend adding six of them to the 503A bulks list: BPC-157, KPV, TB-500, MOTS-c, Semax, and Epitalon. It voted against recommending emideltide (DSIP). The committee is advisory. As of September 14, 2026, FDA has not made a final decision. Ibutamoren (MK-677) and kisspeptin-10 remain in Category 2. Non-injectable GHK-Cu is in Category 1; injectable GHK-Cu is in no category. The list is not static — it continues to evolve through the nomination and review process.

For more on what changed in 2026, see the April 2026 reclassification explained, which 12 peptides were removed from FDA restriction, and how the PCAC advisory committee works. The broader 2026 peptide regulatory landscape provides full context. For prescriber context, see what off-label prescribing means.

Frequently asked questions

What is the difference between Category 1 and Category 2 peptides? Category 1 substances are under FDA evaluation. FDA's interim policy of not taking action against compounding with a substance that is not yet on the 503A bulks list applies only to Category 1 substances, when other conditions are met. Category 2 substances are ones FDA says raise significant safety risks.

Who does the peptide Category 2 classification affect? Patients, prescribers, compounding pharmacies, and telehealth platforms are all affected. FDA's interim policy of not taking action against compounding with a substance that is not yet on the 503A bulks list does not cover Category 2 substances. As of September 14, 2026, the only peptides in Category 2 are ibutamoren (MK-677) and kisspeptin-10.

Which peptides are Category 1 and available from compounding pharmacies? FDA maintains the category list and last updated it on May 14, 2026. Category 1 means a substance is under evaluation; it is not the 503A bulks list. Non-injectable GHK-Cu is in Category 1. The peptides FDA removed from Category 2 in September 2024 and April 2026 are not in any category and are not on the 503A bulks list.

What is the PCAC? The PCAC — Pharmacy Compounding Advisory Committee — is the FDA's federal advisory body on compounding. It reviews nominated bulk drug substances and votes on whether to recommend adding them to the Section 503A bulks list. Its votes are advisory, and FDA makes the final decision. It met on July 23–24, 2026.

This article is educational and is not medical advice. Compounded medications are not FDA-approved. Clinical outcomes depend on individual factors and require physician evaluation. Results vary.