Side effects of TB-500: human studies, FDA review and vial tests
Side effects of TB-500 have not been quantified in a published human study of the exact fragment (searches checked 21 August 2026). No human treatment result for TB-500 appeared in searches checked 21 August 2026. A 2024 cell study reported no cytotoxicity for the parent peptide or tested metabolites (PMID 38382158; checked 21 August 2026). The United States FDA review found no human exposure data for TB-500 free base or acetate (FDA brief, 15 May 2026; checked 21 August 2026). A 2026 preprint reported 4 TB-500 identity failures and labelled the rate 10.0% (DOI 10.20944/preprints202604.1748.v1; checked 21 August 2026).
What is TB 500 peptide?
TB-500 is the seven-residue sequence Ac-LKKTETQ (PMID 22962027). It is the N-terminal acetylated 17-23 fragment of thymosin beta-4 (PMID 22962027). The detection paper found this sequence in a product called TB-500. The record was checked 21 August 2026.
Full-length thymosin beta-4 contains 43 amino-acid residues (American FDA briefing, 15 May 2026). TB-500 is not the full-length molecule. A human result for the parent peptide does not prove what TB-500 does.
The American FDA's May 2026 brief treats TB-500 free base and TB-500 acetate as different active ingredients. It says the name has been used for several salts and forms. The doubt is about which form a product contains. It does not change the sequence identified in PMID 22962027.
Are there published human TB-500 results?
No relevant published human result appeared in the opened evidence map or the fresh searches below.
| Source checked 21 August 2026 | Exact search or record | What it returned |
|---|---|---|
| PubMed | ("TB-500"[Title/Abstract] OR TB500[Title/Abstract]) AND (Clinical Trial[Publication Type] OR Randomized Controlled Trial[Publication Type]) | 1 result. PMID 33318598 is a tuberculosis study in which 500 participants had TB. It is not about the peptide. |
| Europe PMC | ("TB-500" OR "TB500") AND (PUB_TYPE:"Clinical Trial" OR PUB_TYPE:"Randomized Controlled Trial") | 3 results. They concern Terminalia bellerica, cocoa, and pulmonary tuberculosis. None concerns the peptide. |
| ClinicalTrials.gov | TB-500 | 1 record, NCT07487363. Its own summary begins, “This fictional study is an example of a ClinicalTrials.gov-style record.” It cannot establish that a trial is taking place. |
A 2026 scoping review searched PubMed, Europe PMC, and ClinicalTrials.gov through 26 March 2026. It screened 1,772 records and retained 80 studies (DOI 10.3390/app16126202). Only 1 of 80 directly studied TB-500. That item was the rat and fibroblast work in PMID 38382158. It was not a human result. The review's funding statement reports no external funding. Its authors declared no conflicts of interest. These details were checked 21 August 2026.
Two registry records that can look apt studied full-length thymosin beta-4. NCT00743769 was withdrawn. Its actual enrollment was zero. NCT01311518 was also withdrawn. Its actual enrollment was zero. Neither record has a result in people for TB-500 or its parent.
What TB-500 benefits have animal and laboratory studies found?
The newest direct study gives a positive tendon result in rats. It does not establish the same result in a person.
| Evidence | Population and design | Measured result | Limits, funding, and date |
|---|---|---|---|
Achilles-tendon study, PMID 42542926 | 32 male rats were randomized across control, BPC-157, TB-500, and combined groups. Each group contained 8 rats. Four tendons per group underwent mechanical testing. | Median maximum load to failure was 37.41 N for TB-500 and 26.91 N for controls. The adjusted comparison was p = 0.0406. Median total Bonar score was 4.0 for TB-500 and 9.5 for controls, with p = 0.016. | Treatment lasted four weeks after surgical tendon repair. The study measured rat tissue at one time point. The paper received no financial support. Checked 21 August 2026. |
Metabolism and cell study, PMID 38382158 | Researchers examined TB-500 in human serum, enzyme systems, rat urine, and fibroblast assays. This was not a human treatment study. | The assays found no cytotoxicity from the parent peptide or tested metabolites. Only the metabolite Ac-LKKTE showed significant wound-healing activity against the control. The abstract gives no effect size or interval. | The result belongs to cells and rat metabolism. The PubMed record lists no grant support. The authors declared no competing interests. Checked 21 August 2026. |
The scoping review concluded that direct TB-500 evidence was minimal. Its search predates the July 2026 rat tendon paper. The new paper adds a positive animal result. It does not fill the human-evidence gap.
What TB-500 side effects have human studies recorded?
No human study has produced a side-effect rate for the exact TB-500 fragment. The fresh literature search found no relevant clinical result. The American FDA review also found no data from use in people for TB-500 free base or acetate. These claims were checked 21 August 2026.
The 2024 laboratory study found no cytotoxicity in its cell assays (PMID 38382158). The 2026 rat paper was not a toxicology study (PMID 42542926). Neither finding provides a human safety rate.
The American FDA says clumps in an injected peptide may cause an immune response. It also cites related impurities. Its brief states that the potential human safety risks are unknown. This is the American agency's view of a gap in the data. It is not a recorded adverse event in a person.
What has testing found in products sold as TB-500?
A 2023 peer-reviewed paper analyzed three internet-sold products: TB500, TB1000, and SGF1000 (PMID 36482504). It found that the TB500 and TB1000 contents were not consistently aligned with past descriptions. PubMed lists two grants from the Institut francais du cheval et de l'equitation. The record was checked 21 August 2026.
A 2026 preprint reports a larger set of tests chosen by those who sent vials. It has not been peer-reviewed. People and peptide firms chose what to send. The dataset had 6,487 reports across 14 peptides (DOI 10.20944/preprints202604.1748.v1). Of those, 6,285 had full amount and purity data.
For TB-500, the preprint reports 4 identity failures and labels that result 10.0% (DOI 10.20944/preprints202604.1748.v1). Median purity was 97.29%. The middle half ran from 93.83% to 99.59%. The dual-pass rate was 22.5%. The opened text does not print the TB-500 sample count. We therefore keep the four failures with the paper's own rate.
The dataset was not a random market sample. Its rates do not describe all TB-500 vials. The preprint received no external funding. Its authors declared no conflict of interest.
Source, checked 21 August 2026: Mendias and Awan, DOI 10.20944/preprints202604.1748.v1.
The vial-testing guide explains what identity, amount, purity, sterility, and endotoxin tests answer separately.
What does EMA's central register show for TB-500?
Rules differ by country. EMA made its report on 22 August 2026. It held 2,731 medicine rows. No row matched TB-500, TB 500, Thymosin beta-4, or Thymosin beta 4.
The search covers only EMA's central EU route. It does not cover national registers. TB-500's status in Europe therefore stays unclear. Checked 22 August 2026.
What does the FDA say about TB-500 compounding in the US?
For pharmacy compounding in the US, the FDA reviewed TB-500 free base and TB-500 acetate for the 503A Bulks List. Its 15 May 2026 staff brief proposed not adding either form. The American agency based that view on identity, past use, evidence of effect, and known harm. It is not a human trial result.
The American FDA's meeting page placed both forms on the 23 July 2026 agenda. The American agency says the panel's advice does not bind it. The staff brief says the agency would not make a final decision until its review was done.
The American FDA's public safety-risk page places the earlier TB-500 nomination in its withdrawn-nominations table. TB-500 is not in the page's current Category 2 table. This US status was checked 21 August 2026.
Primary American sources: American FDA TB-500 briefing and American FDA bulk-substance safety-risk page.
How are TB-500 and thymosin beta-4 different?
TB-500 is the seven-residue acetylated fragment Ac-LKKTETQ (PMID 22962027). Its parent, thymosin beta-4, contains 43 amino-acid residues (American FDA briefing, 15 May 2026). Human trials of the parent molecule answer a different question.
A peer-reviewed narrative review makes the same distinction. It says TB-500 research has focused more on characterization than on safety and efficacy. The review is PMID 41966639, checked 21 August 2026. The accepted manuscript states that it received no external funding. PubMed lists an unrelated Arthrex consulting relationship for Tariq Awan.
See also
The training and recovery hub compares human and vial proof across compounds. The BPC-157 register article covers that peptide's three human reports. The TB-500 register record keeps proof and American FDA status apart. The COA guide shows what a certificate does not prove.