Category 1 vs Category 2 peptides

What do Category 1 and Category 2 actually mean?

They describe where a nominated substance stands while FDA builds the 503A bulks list. Category 1 substances were nominated with enough supporting information, may be eligible for the list, and FDA does not intend to act against a compounder using them if the guidance conditions are met [1]. Category 2 substances were nominated with enough information, but FDA identified significant safety risks in compounding them, and it publishes those concerns [1]. Category 3 substances lacked enough data to evaluate and need re-nomination [1].

Which peptides were Category 2?

FDA's page current as of April 22, 2026 lists BPC-157, TB-500 (thymosin beta-4 fragment) and thymosin alpha-1 as substances previously in Category 2 whose nominations were withdrawn, each flagged for possible immunogenicity, peptide-related impurities and little or no human safety data [2]. None has a USP monograph or is part of an approved drug, the other two routes that allow 503A compounding [3]. So a licensed pharmacy compounding them today is outside every route the law provides.

Are the categories going away?

Yes, slowly. FDA states it does not intend to place substances nominated on or after January 7, 2025 into these categories [1]. Existing categorizations stand until FDA finalizes each substance through rulemaking, which is why the July 2026 advisory votes on BPC-157 and TB-500 changed nothing on the ground yet.