TB-500
| Category | Healing & Recovery |
| Goals | Joint & Tendon Repair · Recovery |
| Evidence level | Preclinical (mostly animal/in-vitro; parent protein has limited human trials) |
| Legal status | Research-only — not approved for human use; banned in sport (WADA) |
| FDA status | Not FDA-approved; on PCAC 503A agenda Jul 23, 2026 (use evaluated: wound healing) |
| Half-life | Not well established in humans; short–moderate, route-dependent |
| Routes | Subcutaneous · Intramuscular |
| CAS / MW / Sequence | 885340-08-9 (fragment) · 877.99 g/mol · Ac-LKKTETQ (Tβ4 17–23) |
| Last reviewed | 2026-06-07 |
In one line
A synthetic peptide marketed as a Thymosin Beta-4 (Tβ4) fragment, studied mainly in animals and cells for cell migration and tissue repair; the classic partner to BPC-157.
Evidence at a glance
What is sold as “TB-500” is usually the short Ac-LKKTETQ (Tβ4 17–23) actin-binding fragment, not the full 43-amino-acid Thymosin Beta-4 protein that was studied in clinical trials. Most repair-related human-use claims are extrapolated from animal data and from the parent protein. See Evidence Grading Explained and the Disclaimer.
Key Takeaways
- “TB-500” most commonly refers to the synthetic Ac-LKKTETQ fragment of Thymosin Beta-4 — a small actin-binding sequence, not the full protein.
- Best known for soft-tissue and systemic repair / cell migration — but strong evidence is preclinical (animal/in-vitro).
- The parent protein (Tβ4) reached Phase I/II human trials (e.g. RGN-259 eye drops, RGN-352 cardiac/neuro) with a favorable safety signal; these do not validate the bodybuilding fragment or its uses.
- Not FDA-approved; sold as a research chemical and explicitly banned by WADA (Prohibited List, S2) since 2012.
- Most commonly paired with BPC-157 (see the Wolverine Stack).
What Is It
Thymosin Beta-4 (Tβ4) is a naturally occurring 43-amino-acid protein that regulates actin, the cytoskeletal protein involved in cell movement, division, and migration. “TB-500” is the trade name used by research-chemical vendors; in practice the marketed product is usually a short synthetic fragment (Ac-LKKTETQ, residues 17–23) that contains the actin-binding domain, sometimes acetylated for stability. Because of this, TB-500 and full-length Tβ4 are related but not identical, a distinction often blurred in marketing.
Mechanism of Action
Mechanisms are largely from animal and cell models:
- Actin sequestration / regulation (in-vitro) — Tβ4 binds G-actin and modulates cytoskeletal dynamics, proposed to enable cell migration during repair.
- Cell migration & angiogenesis (animal evidence) — promotes endothelial and other cell migration and new blood-vessel formation in wound models.
- Anti-inflammatory / anti-fibrotic signaling (animal/in-vitro) — reduces inflammation and scarring in some injury models.
- Tissue regeneration (animal evidence) — studied in cardiac, corneal, and dermal injury in animals.
Limitations
The molecular activity of the short fragment in humans is not well characterized, and most regeneration data comes from the full protein or animal models — not from controlled human studies of injectable TB-500.
Evidence by Outcome
| Outcome | Evidence | Notes |
|---|---|---|
| Tendon / ligament / muscle repair | Preclinical | Animal and in-vitro data; no human RCTs of TB-500 |
| Wound healing (skin, cornea) | Preclinical / Clinical (parent Tβ4) | Tβ4 eye drops (RGN-259) reached Phase II for dry eye |
| Cardiac / neuro repair | Preclinical / Clinical (parent Tβ4) | Tβ4 (RGN-352) studied in Phase I/II; not the fragment |
| General “everything heals faster” | Anecdotal | Widely reported; no controlled human data |
| Hair growth | Preclinical / Anecdotal | Early animal signals; no robust human evidence |
Reported Dosing
Not medical advice
Protocols as reported in community sources and non-clinical literature. There is no established human therapeutic dose. See Reconstitution & Dosing Math.
| Route | Dose (reported) | Frequency | Cycle |
|---|---|---|---|
| Subcutaneous | ~2–2.5 mg, “loading” | 2× weekly | ~4–6 weeks |
| Subcutaneous | ~2 mg, “maintenance” | 1× weekly | After loading phase |
| Intramuscular | Similar, sometimes near injury site | 1–2× weekly | Variable |
Pharmacokinetics
Human PK of the marketed fragment is not well established. The full protein has been reported with a half-life on the order of hours and broad tissue distribution in animal/early human work; the short fragment may differ. Dosing is described weekly (less frequent than BPC-157), reflecting anecdotal practice rather than validated PK. See Half-Life & Pharmacokinetics.
Side Effects & Risks
- Human safety data for injectable TB-500 is minimal; “well tolerated” largely reflects a lack of studies, not proven safety.
- Anecdotal reports: injection-site reactions, fatigue, head-rush/lightheadedness, transient flu-like feelings — not systematically documented.
- Theoretical concern: pro-angiogenic and pro-migratory activity raises speculative concern about effects on tumor growth; not adequately studied in humans.
- Banned in sport — athletes risk sanctions; long detection windows are reported.
- Sourcing risk: identity (full protein vs. fragment) and purity vary widely — see Sourcing and Red Flags & Scams.
- See Side Effects & Risk Management.
Cycling
Anecdotal protocols use a loading phase (twice weekly, ~4–6 weeks) followed by weekly maintenance or a break. No evidence-based cycling standard exists. See Cycling.
Stacks It Appears In
- Wolverine Stack — TB-500 + BPC-157 (the most-searched repair blend)
- Occasionally alongside healing blends such as GLOW / KLOW
Comparisons
- BPC-157 vs TB-500
- vs BPC-157 — BPC-157 is dosed more frequently (short half-life) and is acid-stable/oral-capable; TB-500 is dosed weekly and injection-only.
Sourcing & Quality
Sold as a lyophilized “research chemical,” so identity and purity are not guaranteed — and the full protein vs. 17–23 fragment ambiguity is a common point of confusion. Verify before trusting a product: How to Read a CoA, HPLC vs Mass Spec, Third-Party Testing, Red Flags & Scams. Reconstitution and storage: Reconstitution & Dosing Math, Storage & Handling. No vendors are endorsed here.
Legal & Regulatory Status
(As of 2026-06-07.) Not FDA-approved for human use. TB-500-related bulk drug substances (TB-500 free base / acetate) are on the agenda of the FDA’s Pharmacy Compounding Advisory Committee (PCAC) meeting on July 23, 2026, being considered for inclusion on the 503A Bulks List; the use FDA evaluated is wound healing. Public docket FDA-2025-N-6895 (closes July 22, 2026; comments by July 9, 2026 go to the Committee). Inclusion is not approval as a drug — it would only determine eligibility for traditional (503A) pharmacy compounding. WADA prohibits thymosin beta-4 in sport (Prohibited List, S2) — effective since 2012. Status varies by country. See Regulatory & Legal Status.
FAQ
Is TB-500 the same as Thymosin Beta-4? Not exactly. TB-500 usually denotes the short Ac-LKKTETQ (17–23) fragment, while Tβ4 is the full 43-amino-acid protein. They are related but should not be treated as identical.
Is TB-500 FDA-approved? No. It is not approved for human use; the parent protein is under compounding review.
Does TB-500 work in humans? Repair claims are mostly extrapolated from animal data and from the parent protein. Controlled human trials of injectable TB-500 are lacking.
Can athletes use it? No — it is banned by WADA; use risks sanctions.
What is it usually stacked with? Most often BPC-157 — see the Wolverine Stack.
References
- Goldstein A.L., Hannappel E., Kleinman H.K. (2005). “Thymosin β4: actin-sequestering protein moonlights to repair injured tissues.” Trends in Molecular Medicine.
- Crockford D. et al. (2010). “Thymosin beta4: structure, function, and biological properties supporting current and future clinical applications.” Annals of the New York Academy of Sciences.
- RegeneRx Biopharmaceuticals — Tβ4 clinical programs (RGN-259 dry eye; RGN-352 systemic), Phase I/II safety data.
- World Anti-Doping Agency (WADA). Prohibited List — thymosin beta-4 (S2), in force since 2012; current 2026 list.
- U.S. FDA (2026). “July 23–24, 2026: Meeting of the Pharmacy Compounding Advisory Committee” — TB-500 (free base/acetate), use evaluated: wound healing; Docket FDA-2025-N-6895. fda.gov
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