> CAT RESEARCH :: STATUS [NULL — NO HUMAN 7-MER DATA]

TB-500 research: the mechanism that holds, the studies that used the full protein, and the trial that does not exist.

The thymosin beta-4 literature is deep. The TB-500 heptapeptide literature, in completed human trials, reads zero. This page logs the difference.

See the references Read the dosage record

Thymosin Beta-4: The Parent Protein Behind TB-500

Thymosin beta-4 is a ubiquitous 43-amino-acid peptide and the body's principal G-actin-sequestering molecule. It is the parent protein from which TB-500 borrows its sequence — and it is the protein, not the fragment, that carries almost all of the data on this page. At roughly 4963 Da it is more than five times the mass of the ~889 Da TB-500 heptapeptide.

The structural basis is settled. X-ray crystallography of a gelsolin-domain-1–thymosin beta-4 hybrid bound to actin, resolved to 2 Å, established that thymosin beta-4 forms a 1:1 complex with globular actin and sequesters the monomer by capping both ends, preventing polymerization; the WH2 actin-interacting motif underlies the contact ^[1]. A 2012 review consolidated the downstream biology: thymosin beta-4 binds actin and promotes cell mobilization and migration, decreases myofibroblast number to reduce scarring, is released by platelets and macrophages after injury to limit apoptosis and inflammation, and promotes angiogenesis — the rationale that drove clinical development in dermal wounds, corneal injury, and heart and CNS repair ^[5].

The LKKTETQ segment in TB-500 is the actin-binding core of that protein. The marketing question — does the isolated core reproduce the whole protein's regenerative program — is precisely what the human trial record does not answer.

Are there any human clinical trials on TB-500?

No completed controlled trials of the TB-500 heptapeptide exist for any indication. Human data are limited to full-length thymosin beta-4: a randomized, placebo-controlled Phase 1 study gave intravenous synthetic thymosin beta-4 to 40 healthy volunteers at 42, 140, 420, or 1260 mg, finding it well tolerated with no dose-limiting toxicities and dose-proportional pharmacokinetics ^[6]. Topical ophthalmic thymosin beta-4 (RGN-259) has also been studied in dry-eye trials. The fragment itself has no completed human efficacy trial.

That single Phase 1 study is the closest thing to human evidence in the file, and it is a safety-and-pharmacokinetics study of the full protein, not an efficacy study of the fragment. Injectable thymosin beta-4 stroke and acute-MI trials were registered; the injectable acute-MI study completed and an early injectable trial was withdrawn ^[9]. A presumed clinical pipeline overstates the current evidence — much of the human-trial momentum stalled commercially.

Does TB-500 affect the heart?

In mice, thymosin beta-4 activated PINCH–ILK–Akt survival signaling, enhanced early cardiomyocyte survival, and improved cardiac function after coronary artery ligation ^[2]. Scaffold-delivered thymosin beta-4 — released from a functionalized self-assembling peptide — activated cardiac cells and promoted repair in a 2021 study ^[13]. But systemic thymosin beta-4 failed to attenuate myocardial ischemia-reperfusion injury in a porcine study, so the cardiac story is mixed, not settled.

The positive cardiac signal is real and mechanistically coherent: Bock-Marquette and colleagues traced it to a defined survival-kinase complex ^[2], and a separate rodent study reported cardioprotection with systemic dosing after ischemic injury ^[9]. The negative porcine result is the disciplined counterweight. Every result in this section used the full-length protein.

Does TB-500 promote angiogenesis and is that a safety concern?

Thymosin beta-4 is pro-angiogenic — it drives endothelial migration and differentiation, and a 2025 thymosin-beta-4-exosome-loaded hydrogel improved vascularized wound repair ^[14]. Because pro-angiogenic activity can also support tumor growth, the same property that aids repair is treated as a theoretical safety consideration alongside the benefit. It is a flagged caution in the record, not an established human risk for the fragment.

The mechanism cuts both ways, which is the honest framing. Angiogenesis is central to thymosin beta-4's wound-repair program ^[5]. It is also the reason the next section exists.

Does TB-500 cause cancer or promote tumor growth?

Thymosin beta-4 is overexpressed in several cancers — pancreatic and colorectal among them — and is implicated in metastasis and tumor angiogenesis. The same pro-migratory, pro-angiogenic properties that aid repair could theoretically support tumor progression. This is a recognized safety concern flagged in the literature, not an established human risk for the TB-500 fragment, for which no controlled human data exist ^[10].

The logic is mechanistic rather than clinical: a peptide that mobilizes cells, sequesters actin to enable migration, and promotes new vessel growth carries a plausible tumor-biology liability ^[5]. No human trial has tested whether the isolated fragment realizes that liability. The record marks it as a NULL-data caution and leaves it visible rather than dismissing it.

Does TB-500 have neuroprotective effects on the brain?

In rodent stroke models, intraperitoneal thymosin beta-4 improved neurological function. In male Wistar rats with embolic middle cerebral artery occlusion, doses of 2 and 12 mg/kg started 24 hours post-stroke produced significant improvement from day 14 through day 56, while 18 mg/kg gave no significant benefit — a modeled optimal dose of ~3.75 mg/kg was proposed ^[4]. In a 2024 zebrafish study, thymosin beta-4 promoted Mauthner-axon regeneration by facilitating actin dynamics ^[15].

The stroke result is one of the cleaner dose-response datasets in the file, and it carries a counterintuitive read: more was not better. The 18 mg/kg dose underperformed 12 mg/kg, a non-monotonic pattern that directly undercuts community "loading" rationales. The zebrafish finding is mechanistically tidy — it ties neuro-regeneration straight back to the actin mechanism.

Does TB-500 reduce inflammation?

Thymosin beta-4 suppressed corneal NF-κB as a potential anti-inflammatory pathway in the eye ^[8], and recent animal work extended the anti-inflammatory profile: a 2025 study reported thymosin beta-4 modulating the tissue inflammatory response in a mouse non-alcoholic fatty liver disease model ^[11], and a 2024 study found inhaled thymosin beta-4 suppressing bleomycin-induced pulmonary fibrosis ^[12]. These effects are described mechanistically in animals and in vitro, not proven for the fragment in humans.

The anti-inflammatory leg is broad — cornea, liver, lung — and consistent with the protein's role as a factor released at injury sites ^[5]. As with every section here, the species tag is the qualifier: these are animal and in-vitro findings on the full-length protein.

TB-500 Side Effects and Safety Signals in Research

What are the side effects of TB-500?

There is no controlled human side-effect profile for the TB-500 fragment. A 2026 Sports Medicine review notes that unapproved musculoskeletal peptides have scarce human safety data and potential for serious harm, and operate largely outside regulatory oversight ^[10]. The only human safety read in the file is the Phase 1 study of full-length thymosin beta-4, which was well tolerated to 1260 mg intravenously ^[6] — a different molecule from the 7-mer.

Is TB-500 safe for long-term use?

Long-term safety of the TB-500 fragment in humans is unknown; no controlled human trials exist ^[10]. The preclinical tumor-and-angiogenesis signal ^[5] and the scarce human safety data mean long-term use cannot be characterized as safe. A short acetylated peptide is more chemically robust than the full-length protein, but chemical stability is not a safety profile.

Does TB-500 work for muscle tears and recovery from exercise?

A 2026 Sports Medicine review lists TB-500 and thymosin beta-4 among unapproved musculoskeletal peptides with favorable tissue-repair signals in animal models but scarce human safety data ^[10]. Controlled human evidence for muscle recovery is lacking. A separate caution is concrete: in dystrophin-deficient (mdx) mice, chronic thymosin beta-4 increased regenerating fibers but did not improve muscle strength, cardiac function, or fibrosis.

The safety record, in short, is an absence flagged in plain sight — not a clean bill. The non-monotonic stroke dosing ^[4], the mixed cardiac results, and the tumor-biology caution are the signals the file actually contains; a reassuring human side-effect profile is not among them.

TB-500 and BPC-157 in the Musculoskeletal Peptide Literature

What is the difference between TB-500 and BPC-157?

They are distinct peptides studied for tissue repair. TB-500 is the Ac-LKKTETQ actin-binding fragment of thymosin beta-4; BPC-157 is a separate gastric-derived pentadecapeptide with an unrelated sequence and a different proposed mechanism. A 2026 Sports Medicine review lists both among unapproved musculoskeletal peptides that show favorable tissue-repair outcomes in animal models but lack rigorous human safety data ^[10].

The two are frequently named together because they occupy the same shelf: unapproved peptides marketed for recovery, each with an animal-model evidence base and a human-trial gap. That shared context does not make them interchangeable. TB-500's mechanism is actin sequestration via the thymosin beta-4 motif ^[1]; BPC-157's is its own. This page does not provide dosing or sourcing guidance for either — it logs what the review states about the class ^[10].

How long does it take for TB-500 to work for injury healing?

Timelines come from animal models, not humans. In a rat full-thickness wound study, topical or intraperitoneal thymosin beta-4 increased re-epithelialization by 42% at four days and up to 61% at seven days versus saline, with increased wound contraction and collagen deposition over the same window ^[3]. No human injury-healing timeline is established for the fragment ^[10].

Those figures are real and specific — and they are rat data on the full-length protein. Extrapolating a four-to-seven-day human timeline from them would be a fabrication the record does not support. The full wound-repair breakdown sits on the TB-500 tissue repair research page.