BPC-157 vs TB-500: How the Two Peptides Differ

BPC-157 and TB-500 are unrelated synthetic peptides that are often discussed together. BPC-157 is a 15-residue peptide (about 1419.5 g/mol) described in 1993 as a fragment of a gastric juice protein, with no identified receptor. TB-500 is a 7-residue acetylated peptide (about 889.0 g/mol) copied from the actin-binding region of thymosin beta-4, a well-characterized intracellular protein. Neither is an approved drug, and both are prohibited in sport.

They share almost nothing at the level of sequence, origin or proposed mechanism. What they do share is a regulatory history: both were in FDA's Category 2 for compounding, both were presented to FDA's compounding advisory committee on the same day in July 2026, and both are sold as research chemicals, individually and pre-combined in one vial. This comparison puts the verified facts for each side by side. The full profiles are in what is BPC-157 and what is TB-500.

Side-by-side comparison

Identity values are from PubChem (CID 9941957 and CID 62707662); regulatory entries are from FDA and World Anti-Doping Agency documents listed in the references.

Origin: an orphan fragment and a mapped motif

The two peptides reached the research catalog by different routes, and that difference shapes how confidently anything can be said about them.

BPC-157 was described by Sikirić's group in Zagreb as a 15-amino-acid fragment of BPC, a protein of roughly 40,000 Da they reported in human gastric juice, and the fragment they considered essential for its activity. A 2025 review by Józwiak and colleagues notes that the sequence shows no homology with known intestinal peptides. In other words, BPC-157 is not a recognized piece of a characterized human protein with a known function, and its "parent" is known mainly from the originating group's own reports.

TB-500 has a well-documented parent. Thymosin beta-4 was sequenced in 1981 from calf thymus, and in 1991 it was shown to be identical to Fx, the peptide that holds actin monomers in an unpolymerized state in human platelets. Mapping work in 1996 located its actin-binding site, including the motif at residues 17 to 22. TB-500 itself entered the scientific literature in 2012, when anti-doping chemists (Esposito and colleagues) identified Ac-LKKTETQ as the peptide in a product sold under that name.

Mechanism: downstream signals versus a structural motif

BPC-157. No receptor has been identified. The mechanistic literature reports changes in signaling pathways, mostly in cultured cells:

• activation of the VEGFR2–Akt–eNOS pathway and VEGFR2 internalization in vascular endothelial cells (Hsieh and colleagues, 2017);
• phosphorylation of focal adhesion kinase and paxillin, with increased spreading and migration, in rat tendon fibroblasts (Chang and colleagues, 2011);
• increased growth hormone receptor expression, and JAK2 activation on growth hormone exposure, in the same fibroblasts (Chang and colleagues, 2014).

Reviews also list effects on nitric oxide signaling, early growth response-1 expression and neurotransmitter systems in rodents. What binds first is unknown.

TB-500. The rationale is structural. In the intact protein, Van Troys and colleagues found that actin binding needs both an N-terminal helical region (residues 1 to 16) and the motif at residues 17 to 22, with lysine 18 making a key electrostatic contact. Philp and colleagues (2003) then tested the seven-residue motif directly and found near-identical activity to full-length thymosin beta-4 at about 50 nM in endothelial cell migration and aortic ring sprouting assays, while peptides lacking part of the motif were inactive. The caveat is that the short fragment lacks the N-terminal region, and most of the biology attributed to "TB-500" online was measured with the full-length protein.

So the contrast is this: BPC-157 has a set of observed signaling changes and no known target, while TB-500 has a known structural origin but a thin literature of its own.

Evidence base

BPC-157 has the larger body of published work, but it is concentrated. The Józwiak review catalogs rat studies (Sprague-Dawley and Wistar), plus mice, beagle dogs and broiler chicks, across gastrointestinal, musculoskeletal, skin and neurological models, and in-vitro work in endothelial cells, Caco-2 cells, HEK 293 cells and tendon fibroblasts. A large share of it comes from a small number of groups.

TB-500's own literature is small. Beyond the endothelial assays with the motif and the analytical papers that define and detect it, most of what is described for it was measured with full-length thymosin beta-4. FDA's Category 2 entry states that the agency had not identified any human exposure data for the fragment.

For BPC-157, one Phase 1 safety and pharmacokinetics study of an oral product (PCO-02) was registered on ClinicalTrials.gov in 2015 with an estimated 42 participants; its status is listed as unknown, and no outcome data have been posted. Neither peptide has published, controlled human trial data.

Regulatory status, side by side

FDA. Both peptides sat in Category 2 of FDA's interim compounding policy, the group of nominated bulk substances with significant safety concerns. FDA's page, updated April 22, 2026, lists both nominations as withdrawn by the nominators. For BPC-157, FDA recorded concerns about possible immunogenicity for certain routes and about peptide-related impurities and characterization of the active ingredient. For TB-500, it cited immunogenicity risk from potential aggregation and impurities, and the absence of human exposure data. FDA then presented both to its compounding advisory committee (PCAC) on July 23, 2026, BPC-157 in the morning and TB-500 in the afternoon. The briefing document states that FDA proposed that neither the free base nor the acetate form of either peptide be included on the 503A bulks list, and that it will not issue a final determination until the advisory process and its reviews are complete.

WADA. The 2026 Prohibited List places them in different classes. BPC-157 is named under S0, non-approved substances, which it has been since 2022. TB-500 is named under S2.3 as a derivative of thymosin beta-4 ("Thymosin-ß4 and its derivatives e.g. TB-500"). Both classes are prohibited at all times.

In the lab: two peptides, one vial or two

Anhydrolabs supplies BPC-157 and TB-500 as separate lyophilized powders in vacuum-sealed vials, and pre-combined as BPC-157 / TB-500 at 10 mg of each. All three are also available as 10-vial kits. They are supplied for in-vitro research only, under the terms on the research-use page.

Some points that matter when choosing between them:

Equal mass is not equal moles. Because TB-500 is the smaller molecule, 10 mg of it is about 11.25 µmol, while 10 mg of BPC-157 is about 7.04 µmol. A 10 mg / 10 mg vial therefore holds the two peptides at a molar ratio of roughly 1 : 1.6 (BPC-157 : TB-500). Experiments designed around molar concentrations need to account for that.

Controls need single-compound material. A combined vial fixes the ratio and removes a weighing step, which is useful for experiments that always use both at that ratio. It cannot provide the single-peptide arms of an experiment. A design that asks what each peptide contributes on its own needs the separate vials alongside the combination.

Analytics are straightforward, because the two are easy to tell apart. Both are hydrophilic (PubChem's computed XLogP is about −9.0 for BPC-157 and −8.6 for TB-500), but they differ in size, charge and composition, so a reversed-phase HPLC method can be set up to separate them as distinct components. Mass spectrometry separates them unambiguously: 1418.70 Da against 888.49 Da. A certificate for a combined vial should report identity and purity for each component, not a single figure for the mixture. How to read a peptide certificate of analysis covers what to look for.

Handling is the same. Both are short, unmodified peptides without cysteine or methionine. Store sealed powder frozen, dry and protected from light, let the vial warm before opening, dissolve in sterile water or an aqueous buffer for in-vitro stocks, and aliquot rather than refreezing one tube. The method is in how to reconstitute lyophilized peptides, and storage temperatures are in the storage and handling guide.

Summary