Frequently asked questions
TB-500 FAQ: The Questions, Answered and Cited
Twenty-four questions on the cardiac record, the actin mechanism, the safety signal, dose context, and the FDA and WADA standing — each answered from the studies, with the fragment kept apart from the parent protein.
Definitions
What is TB-500?
TB-500 is a synthetic, N-acetylated heptapeptide (Ac-LKKTETQ) corresponding to residues 17–23 of thymosin beta-4, the actin-binding motif of the body's main G-actin-sequestering peptide [5]. It is sold for research and veterinary use and is not approved for humans.
What does TB-500 stand for and what does TB stand for in TB-500?
TB refers to thymosin beta-4, the parent protein; TB-500 is a research and veterinary designation for the synthetic Ac-LKKTETQ fragment of that protein, not an official chemical name [5].
What is TB-500 used for in research?
Thymosin beta-4 and its actin-binding region have been studied in animal and topical-human models for wound and corneal healing, cardiac and neurological repair, angiogenesis, and anti-fibrotic effects [5][3]; human efficacy of the seven-mer is unproven.
How does TB-500 work?
TB-500 carries thymosin beta-4's actin-binding LKKTETQ motif; the parent protein binds monomeric G-actin 1:1 and caps both ends to buffer the unpolymerized actin pool, regulating cytoskeletal dynamics, cell migration, angiogenesis, and survival signaling [1][5].
Cardiac
Does TB-500 affect the heart?
In animal models, full-length thymosin beta-4 activated the PINCH-ILK-Akt survival pathway and, after coronary artery ligation in mice, enhanced early cardiomyocyte survival and improved cardiac function [2]; whether the isolated TB-500 fragment reproduces this in humans is unproven.
Is TB-500 cardioprotective after a heart attack?
Thymosin beta-4 was reported cardioprotective after myocardial infarction in rodent models [8] and with systemic dosing after ischemia [9], but a porcine ischemia-reperfusion study found no attenuation of injury [4], so the cardiac evidence is mixed and animal-based.
Did thymosin beta-4 improve outcomes in cardiac clinical trials?
A human acute-myocardial-infarction trial of thymosin beta-4 (NCT05984134) was completed and a Phase 1 IV safety study in healthy volunteers was well tolerated to 1260 mg [6]; no completed controlled efficacy trial exists for the TB-500 heptapeptide specifically.
Efficacy and mechanism
Does TB-500 help wound healing?
Thymosin beta-4 accelerated re-epithelialization, contraction, collagen deposition, and angiogenesis in animal wound models [3], and recent delivery-system studies (exosome hydrogels, cutaneous-flap models) report improved vascularized healing in animals [14][15].
How long does it take for TB-500 to work for injury healing?
No human timeline is established. In a rat full-thickness wound model, topical or intraperitoneal thymosin beta-4 increased re-epithelialization by about 42% at 4 days and up to 61% at 7 days versus saline [3], but those are animal endpoints, not human guidance.
Can TB-500 help with tendon injuries and ligament repair?
Thymosin beta-4 has been studied in animal soft-tissue injury models, and a 2026 review groups TB-500 among unapproved peptides studied for musculoskeletal injury [16]; controlled human tendon and ligament efficacy data are lacking.
Does TB-500 work for muscle tears and recovery from exercise?
A 2026 Sports Medicine review lists TB-500/thymosin beta-4 among unapproved musculoskeletal peptides with favorable tissue-repair signals in animal models but scarce human safety data [16]; a chronic mdx-mouse study increased regenerating fibers without improving strength [4].
Does TB-500 have neuroprotective effects on the brain?
In a rat embolic-stroke dose-response study, intraperitoneal thymosin beta-4 improved neurological function at 2 and 12 mg/kg (a modeled optimal near 3.75 mg/kg) but not at 18 mg/kg [13] — an animal, non-monotonic result rather than human evidence.
Does TB-500 reduce inflammation?
Thymosin beta-4 has been reported to suppress NF-κB signaling and reduce myofibroblast number in animal and in-vitro models [5], and 2024 work links its effects to pro-resolving inflammation pathways [12]; these are preclinical findings.
Does TB-500 promote angiogenesis and is that a safety concern?
Thymosin beta-4 promotes endothelial migration and new-vessel formation, acting as a paracrine factor for endothelial progenitors [7], which aids repair but is also why its pro-angiogenic activity is flagged as a theoretical tumor-progression concern [5].
Safety
What are the side effects of TB-500?
Controlled human safety data for the TB-500 fragment do not exist; full-length thymosin beta-4 was well tolerated to 1260 mg IV in a Phase 1 study [6], while the main theoretical concern is the tumor/angiogenesis safety signal [5] alongside unregulated material quality.
Does TB-500 cause cancer or promote tumor growth?
Thymosin beta-4 is overexpressed in several cancers and implicated in metastasis and tumor angiogenesis; the same pro-migratory, pro-angiogenic properties that aid repair could theoretically support tumor progression, which is a recognized safety concern [5].
Is TB-500 safe for long-term use?
Long-term human safety of the TB-500 fragment is unknown; there are no chronic human trials, the longest preclinical dosing (6 months in mdx mice) showed no functional benefit [4], and the tumor/angiogenesis signal makes prolonged exposure a recognized concern [5].
Are there any human clinical trials on TB-500?
Human data exist only for full-length thymosin beta-4: a randomized placebo-controlled Phase 1 IV safety study [6] and topical ophthalmic dry-eye RCTs, plus a completed acute-MI trial (NCT05984134); there are no completed controlled trials of the TB-500 heptapeptide itself.
Comparison and regulatory
What is the difference between TB-500 and BPC-157?
TB-500 is the Ac-LKKTETQ fragment of thymosin beta-4 acting through actin/cytoskeletal biology, whereas BPC-157 is a distinct gastric-pentadecapeptide derivative; a 2026 review lists both as unapproved peptides studied for musculoskeletal repair with scarce human safety data [16].
Is TB-500 banned by WADA and in competitive sports?
Yes. TB-500 and thymosin beta-4 fall under WADA-prohibited peptide, growth-factor, and tissue-repair categories and are banned in and out of competition; anti-doping LC-MS assays detect it in equine and human samples [16].
Is TB-500 FDA approved?
No. TB-500 has no FDA-approved therapeutic indication; the FDA lists it as "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" and placed it in 503A Category 2 — bulk substances that may present significant safety risks — effective with the September 29, 2023 update [17].
Is TB-500 legal?
TB-500 has no FDA-approved human indication and is in FDA 503A Category 2, outside the enforcement-discretion policy for compounding [17], and is WADA-prohibited [16]; legal standing varies by jurisdiction and use context, and this is general information rather than legal advice.
Can you get TB-500 from a compounding pharmacy?
Compounding access turns on ingredient eligibility under the 503A/503B framework; because the FDA placed TB-500 in Category 2 (outside enforcement discretion), it is not eligible for routine 503A compounding while that status stands [17][18], and legally compounded medications otherwise require a licensed-prescriber evaluation and a valid, patient-specific prescription.
What is the FDA 503A status of TB-500?
The FDA placed "Thymosin beta-4, fragment (LKKTETQ), also known as TB-500" in 503A Category 2 — bulk substances that may present significant safety risks — effective with its September 29, 2023 update, so it is not covered by the enforcement-discretion policy for 503A compounding [17]; "TB-500 (free base)" and "TB-500 acetate" are on the July 23–24, 2026 PCAC agenda as candidates for the 503A bulks list, a scheduled discussion rather than a decision [19].