BPC-157 vs TB-500: how the two peptides differ in structure, evidence and regulatory status

BPC-157 and TB-500 are named together so often that they are easy to mistake for related molecules. They are not. One is a 15-residue sequence from a gastric juice protein, the other a seven-residue acetylated fragment of an actin-binding protein. What they share is a pattern: a large online reputation, a thin and mostly preclinical evidence base, no approval anywhere, and a ban in sport.

This comparison sets the two side by side on every point a researcher or quality team needs: origin, sequence and mass, proposed mechanisms, the size and type of the evidence, regulatory status, analytical identity checks and storage. Each molecule has its own detailed overview, BPC-157 and TB-500, and the figures here are the same verified figures. Nothing below is guidance on human or veterinary use.

BPC-157 vs TB-500 at a glance

	BPC-157	TB-500
Origin	Fragment of BPC, a protein described in human gastric juice [1]	N-acetylated residues 17-23 of thymosin beta-4 [2] [3]
Sequence	GEPPPGKPADDAGLV [4] [5]	Ac-LKKTETQ-OH [2]
Length	15 residues, free termini [4]	7 residues, acetylated N-terminus [2]
Molecular formula	C62H98N16O22 [5]	C38H68N10O14 (free base) [2] [6]
Average molecular weight	1419.5 g/mol [4]	889.01 g/mol free base; 949.1 g/mol acetate [2]
Monoisotopic mass	1418.70 Da [5]	888.49 Da [6]
CAS number	137525-51-0 [5]	885340-08-9 (free base) [2]
INN	None [4]	None; the parent protein’s INN is timbetasin [2] [7]
Receptor identified	None [4]	None for the fragment; the parent protein binds G-actin [2]
Human studies of the molecule itself	Three small uncontrolled reports [8]	None found by FDA [2]
FDA 2026 evaluation	Weighs against 503A listing [4]	Weighs against 503A listing [2]
WADA class	S0, non-approved substances [9]	S2 [9]

Origin: a gastric juice protein versus an actin-binding protein

BPC-157. In 1993 a University of Zagreb group described a gastric juice protein of about 40 kDa that they called BPC (body protection compound) and a 15-amino-acid fragment, BPC 157, which they considered essential for its activity [1]. The peptide also appears as PL 14736 and bepecin [5]. FDA notes that the naming used in compounding nominations did not follow USAN, INN or IUPAC conventions [4].

TB-500. TB-500 started as a product name rather than a molecule. In 2012, a Ghent anti-doping laboratory identified N-terminally acetylated LKKTETQ, the 17-23 fragment of human thymosin beta-4, in a TB-500 product by high-resolution mass spectrometry and synthesised it as a reference standard [3]. A Hong Kong equine laboratory described TB-500 as a veterinary preparation whose key ingredient is LKKTETQ with artificial N-terminal acetylation [10]. FDA’s 2026 review adopts that definition but warns that it has “encountered multiple salts, and derivatives, including different active moieties, sold commercially under the same common name” [2].

The parent of TB-500, thymosin beta-4, is a natural protein. UniProt records a 44-residue precursor whose initiator methionine is removed [11], and PubChem lists the mature protein (timbetasin) as C212H350N56O78S, about 4963 g/mol [7]. FDA states plainly that “thymosin beta-4 and TB-500 are not the same substance” [2]. Keeping that distinction is the single most important step in reading the TB-500 literature.

Sequence and structure compared

BPC-157 is linear, unmodified and all-L, with an unusual proline cluster (Pro3-Pro4-Pro5 plus Pro8) and a net acidic character from one glutamate and two aspartates against one lysine [4] [5]. TB-500 is shorter and basic: two adjacent lysines next to the N-terminal leucine, then Thr-Glu-Thr-Gln, with an acetyl cap that is part of its identity [2]. The unacetylated heptapeptide is a different compound.

Neither sequence contains cysteine, so there is no disulfide to form or mis-form. TB-500 also lacks methionine, whereas full-length thymosin beta-4 has one, which matters for oxidation impurities [11]. Neither has an internal sequence relationship to the other: they come from unrelated parent proteins [1] [2].

Proposed mechanisms of action

No receptor has been identified for either fragment. FDA writes that “the molecular targets for BPC-157 have not been identified” [4], and for TB-500 the mechanistic story is borrowed from the full-length protein [2].

Proposed mechanism	Molecule tested	Model	Evidence level	Ref
VEGFR2 up-regulation and VEGFR2-Akt-eNOS signalling, angiogenesis	BPC-157	Endothelial cells; chick chorioallantoic membrane; rat hind-limb ischaemia	In vitro and animal	[12]
FAK-paxillin activation, fibroblast outgrowth and migration	BPC-157	Rat tendon explants and fibroblasts	In vitro	[13]
G-actin sequestration (1:1 complex, inhibits polymerisation)	Full-length thymosin beta-4	Platelet and muscle actin	In vitro	[14]
Described as the actin-binding region of thymosin beta-4	TB-500	Description in doping-control literature	Not tested as a mechanism	[10]
Fibroblast wound closure by the metabolite Ac-LKKTE, not the parent	TB-500 and its metabolites	Fibroblast scratch assay	In vitro	[15]

The BPC-157 mechanisms come from experiments with the peptide itself, several of them by an independent group in Taiwan [12] [13]. For TB-500 the position is weaker. The 1991 work showing that thymosin beta-4 forms a 1:1 complex with G-actin and inhibits its polymerisation was done with the 43-residue protein [14]. When a Korean doping-control laboratory tested TB-500 and its metabolites in a fibroblast scratch assay, only the metabolite Ac-LKKTE showed significant wound-healing activity [15]. FDA’s reading is that TB-500 free base did not induce wound closure in that study and that its in vivo wound-healing properties remain unknown [2].

Evidence base: study counts and study types

The table below counts what exists, not what it shows. PubMed counts are title and abstract searches run on 26 October 2026; registry counts are ClinicalTrials.gov intervention searches on the same day.

Measure	BPC-157	TB-500	Ref
PubMed records (title or abstract)	230	39, of which 31 concern the peptide after title screening	[16] [17]
Share from one research group	174 of 230 (76%) list Predrag Sikirić as an author	No single dominant group; mostly doping-control laboratories	[16] [17]
Systematic review count of included studies	36 musculoskeletal studies: 35 preclinical, 1 clinical	No systematic review identified	[18]
Published human studies of the molecule	3 reports, 30 participants, no control groups	None found by FDA	[8] [2]
Certainty of human evidence	Very low (GRADE)	Not applicable	[8]
Registered trials of the molecule	None with posted results; includes a university phase 1 study, not yet recruiting	No valid registration identified	[19] [20]
Registered trials of the parent protein	Not applicable	17 records for full-length thymosin beta-4, including phase 3 eye-drop trials	[20]

What the BPC-157 evidence looks like

The BPC-157 literature is broad but concentrated. A 2025 systematic review screened 544 articles and included 36 studies, of which 35 were preclinical and one clinical; in preclinical models BPC-157 “improved functional, structural, and biomechanical outcomes in muscle, tendon, ligament, and bony injuries” [18]. The 2026 systematic review of human evidence found three studies with 30 participants in total, judged them to be of poor methodological quality and rated the overall certainty of evidence as very low “due to serious risk of bias, indirectness and imprecision” [8]. Three quarters of PubMed records share one author [16], so independent replication is the most obvious gap.

What the TB-500 evidence looks like

Of the 39 PubMed records retrieved for TB-500 or its sequence, eight are unrelated uses of the string “TB 500” (for example, tuberculosis and soil science), leaving 31 that concern the peptide [17]. Most of those are anti-doping analytical methods, metabolism studies and narrative reviews, such as the Ghent identification work [3], the Hong Kong equine method [10] and the Korean metabolite study [15]. FDA found no clinical studies of TB-500 in humans [2].

The human trial record that is often quoted for TB-500 belongs to full-length thymosin beta-4. ClinicalTrials.gov lists 17 studies of full-length thymosin beta-4 [20]. They include an intravenous phase 1 study in four cohorts of ten healthy volunteers that reported infrequent, mild or moderate adverse events [21], and the phase 3 ARISE-3 dry eye trial of a thymosin beta-4 eye drop, which enrolled 700 participants and reported primary-endpoint changes similar to placebo (inferior corneal staining −0.41 versus −0.46; ocular discomfort −0.4 versus −0.4) [22]. None of these trials tested the TB-500 fragment [2].

The only head-to-head study

One study has compared the two directly. In a 2026 rat study from Türkiye, 32 male Sprague-Dawley rats underwent Achilles tendon transection and repair and were randomised to control, BPC-157, TB-500 or the combination, eight per group, for four weeks [23]. Maximum load to failure was higher in both single-peptide groups than in controls but reached statistical significance only in the TB-500 group (p < 0.05). Total Bonar scores were significantly lower in the TB-500 group (p = 0.016), and total Movin scores in the TB-500 and combination groups (p = 0.017 and p = 0.040). The BPC-157 group showed numerically lower scores without reaching significance for total scores [23].

Three cautions apply. The groups were small, the follow-up was four weeks, and the paper does not report the sequence or molecular weight of the TB-500 it used, so it cannot be confirmed whether the fragment or full-length thymosin beta-4 was tested [23]. The authors themselves call the work exploratory. It is a single animal experiment, not evidence of a difference in people.

Registered trials, 2026

No controlled trial of either peptide has posted results. A University of Arkansas randomised, quadruple-masked phase 1 study of BPC-157 after arthroscopic rotator cuff repair, with an estimated 30 participants and a saline sham comparator, was first posted in September 2026 and is not yet recruiting [19]. The only registry entry naming TB-500 describes itself as “fictional” and “an example of a ClinicalTrials.gov-style record”, so it is not counted here [20]. Registration is not evidence; a record only shows where the first controlled data may come from.

Pharmacokinetics and metabolism

Parameter	BPC-157	TB-500	Ref
Species studied	Rats and beagle dogs	Horses, rats, human serum in vitro	[24] [10] [15]
Half-life or time course	Elimination half-life of intact peptide under 30 min	Horse plasma peak 60-120 min after subcutaneous dosing, unquantifiable by 6-10 h	[24] [2]
Main metabolites	Small fragments, then single amino acids	C-terminal truncations: Ac-LKKTET down to Ac-LK; Ac-LK main early rat metabolite; Ac-LKK detected up to 72 h	[24] [2] [15]
Excretion	Urine and bile	Detected in equine urine and plasma	[24] [10]
Human data	None	None	[4] [2]

Both are short-lived as intact peptides. For BPC-157, tritium-labelled studies showed rapid breakdown into small fragments and amino acids, with intramuscular bioavailability of about 14-19% in rats and 45-51% in dogs [24]. For TB-500, the metabolites are a ladder of C-terminal truncations [2], which is why doping laboratories target metabolites as well as the parent [15].

Safety findings reported in studies

• BPC-157. FDA’s summary of published nonclinical studies reports no acute toxicity or histopathological change 14 days after single intramuscular doses in rats and dogs and negative genotoxicity tests, but judged the studies “too limited in scope and duration” [4]. The three human reports did not describe treatment-related adverse events, which says little with 30 participants and no controls [8].
• TB-500. FDA identified no acute or repeat-dose toxicity studies of TB-500 free base or acetate and no human exposure data [2].
• Both. FDA raised immunogenicity concerns for injectable routes, linked to peptide-related impurities and aggregates, and noted that available certificates of analysis reported purity without impurity limits, aggregates, microbial quality or endotoxin [4] [2].

Regulatory status: FDA and WADA

Body	BPC-157	TB-500	Ref
FDA approval	None; no approved product in any country	None; not a component of an approved drug	[4] [2]
FDA 503A evaluation (May 2026)	Criteria weigh against listing (use evaluated: ulcerative colitis)	Criteria weigh against listing (use evaluated: wound healing)	[4] [2] [25]
Advisory committee, 23 July 2026	Reportedly voted 8 to 6, one abstention, in favour; non-binding	Reportedly voted 8 to 6, one abstention, in favour; non-binding	[26] [27]
Final FDA determination	Not issued; no minutes or vote posted by FDA	Not issued; no minutes or vote posted by FDA	[25]
WADA Prohibited List	S0, non-approved substances, prohibited at all times	S2; thymosin beta-4 also S2	[9] [2]

FDA evaluated both peptides for the 503A bulks list, which governs which bulk substances licensed pharmacies may compound. For BPC-157, it concluded that “a balancing of the criteria weighs against” listing, citing poor characterisation, insufficient safety and immunogenicity data and lack of effectiveness evidence [4]. For TB-500 it reached the same conclusion, citing poor characterisation, immunogenicity concerns for injectable routes and no clinical or adequate nonclinical evidence for wound healing [2].

The Pharmacy Compounding Advisory Committee discussed BPC-157, KPV, TB-500 and MOTS-c on 23 July 2026 [25]. ABC News reported an 8 to 6 vote with one abstention in favour of adding BPC-157 to the list, and that the vote is non-binding and needs FDA sign-off [26]. Pharmaceutical Executive reported the same 8 to 6 tally, with one abstention, for BPC-157, KPV and TB-500, and stated that the votes do not constitute FDA approval or demonstrated clinical benefit [27]. Both votes ran against FDA’s own evaluations [4] [2]. At the time of writing, FDA’s meeting page lists briefing documents and presentations but no minutes or voting results [25]. A compounding-list recommendation is not a drug approval and adds nothing to the clinical evidence above.

In sport, the US Anti-Doping Agency’s advisory on the 2027 list records “BPC-157 (Prohibited under S0)”, “TB-500 (Prohibited under S2)” and thymosin beta-4 under S2, and states that “S0 substances are prohibited at all times” [9]. FDA’s TB-500 review cites section S2.3 [2].

Analytical identity checks: telling them apart in the lab

The mass difference makes identity testing straightforward, provided the certificate of analysis states what it is measuring:

Check	BPC-157	TB-500 fragment	Full-length thymosin beta-4
Monoisotopic mass (free base)	1418.70 Da [5]	888.49 Da [6]	4960.49 Da [7]
Average molecular weight	1419.5 g/mol [4]	889.01 g/mol [2]	4963 g/mol [7]
Sequence confirmation	MS/MS across the Pro-Pro-Pro run	MS/MS plus acetyl group on Leu1 [3]	Peptide mapping; Met6 oxidation check [11]
Key related impurities	Deletion and truncation sequences, salt-form ambiguity [4]	Unacetylated heptapeptide; C-terminal truncations that mirror metabolites [2]	Methionine sulfoxide
Salt form to state	Free base or acetate; FDA treats them as different substances [4]	Free base or acetate (889.01 vs 949.1 g/mol) [2]	Not applicable here

Two practical points follow from FDA’s reviews. First, FDA found nominations and certificates in which the CAS number, salt form and molecular formula did not match each other [2] [4], so a certificate should report salt form, counter-ion and peptide content alongside purity. Second, because products sold as TB-500 may contain different active moieties [2], an intact-mass result is the minimum identity test: a vial near 889 Da contains the fragment, a vial near 4960 Da contains the full protein. Methods are covered in peptide purity testing by HPLC and MS and certificate review in how to read a peptide COA.

Synthesis and purity

Both are made by Fmoc solid-phase peptide synthesis. FDA’s summary of the original BPC-157 route describes stepwise Fmoc coupling, acid cleavage and HPLC purification to more than 95% [4]. The published TB-500 route builds the chain from glutamine on Wang resin, acetylates the N-terminal leucine on resin and cleaves with Reagent K [2]. At 15 and 7 residues, both are short enough that crude purity is usually high, but racemised residues and single deletions can sit close to the main peak, so a stability-indicating HPLC method and LC-MS identification of related substances matter more than a single purity figure. Route choices are compared in SPPS vs LPPS and specification setting in peptide API impurities and specifications.

Storage and stability of lyophilized material

	BPC-157	TB-500	Ref
Lyophilized powder	Free base expected stable below −18 °C, stored desiccated; acetate below −20 °C	Free base sealed, away from moisture and light, under nitrogen: −20 °C for 1 year or −80 °C for 2 years	[4] [2]
Main risks	Moisture uptake, which FDA says greatly decreases long-term stability of lyophilized peptides	Sensitivity to pH, temperature, concentration and excipients, driving aggregation and degradation	[4] [2]

In practice both are handled the same way in the laboratory: frozen, sealed and dry, equilibrated to room temperature before opening, with minimal freeze-thaw cycling of solutions. General principles are in lyophilised peptide stability and storage.

How Winhycare Pharma supplies BPC-157 and TB-500

Winhycare Pharma supplies BPC-157 as research-use-only material for laboratories and as an active pharmaceutical ingredient to licensed manufacturers, and TB-500 as research-use-only material. Both are supplied at a purity of at least 99%, as stated in our brochure, and custom synthesis is available. Because the name TB-500 covers more than one molecule, every TB-500 certificate of analysis states the sequence, molecular weight and salt form. Product details are on the BPC-157 page and the TB-500 page; to discuss supply, contact our pharma team about BPC-157 API or research material or TB-500 research material.

For laboratory research use only. Not for human or veterinary use.