Rankings / Sleep & Recovery

TB-500 (Thymosin beta-4 fragment)

Sleep & Recovery · Synthetic peptide

Tier D

High-risk evidence profile

Reviewed by Read Off Label · Last reviewed · How we grade

peptidebannedresearch-only
High-risk evidence profile
2.9 / 10
Tier D
Ev 2 Bn 5 Sf 3

Bottom line

Read Off Label grades TB-500 (Thymosin beta-4 fragment) as D (2.9/10) based on preclinical evidence, variable benefit magnitude, and a unknown-high-risk safety profile.

Its high-risk evidence profile reflects a Safety score of 3/10; reported benefits and harms can differ by indication, dose, route, duration, and population.

RegeneRx Biopharmaceuticals pursued clinical development; most programs stalled.

Studied, labeled, or reported-use context: 2-5 mg subQ weekly (anecdotal) — Not FDA-approved for any indication; Category 2 — compounding prohibited; WADA-banned; veterinary use common in horses; PCAC voted 8-6 (one abstention) in favour of adding TB-500 to the 503A bulks list (Jul 23-24, 2026) — advisory only, not an FDA approval or a final compounding decision; not individualized guidance.

Frontier potential — editorial judgment, not evidence

This is a separate axis from the grade above. It asks a different question: if this worked in humans, how much would it matter? It is our judgment, it is not part of the composite score, and it cannot raise a grade. A high number here is a statement about the idea, not about whether it works or whether anyone should take it.

4/10
Mechanistic story only Phase 2

What the ceiling rests on

Thymosin beta-4 is a real endogenous actin-sequestering protein with credible roles in cell migration and tissue repair, and RegeneRx carried it into Phase 2 trials for dry eye, stroke, and diabetic ulcers — further than most peptides in this category reach.

Why it may not get there

Those Phase 2 programmes were unconvincing and largely stalled, which is evidence against rather than pending. TB-500 is a fragment, and vendors frequently supply full TB-4 instead, so what people take is often not what was studied. No human data exist for the musculoskeletal-repair use the peptide is actually bought for.

What would change this A controlled trial in tendon or muscle injury, the indication it is used for.

What the evidence says

RegeneRx Biopharmaceuticals pursued clinical development; most programs stalled. Popular in horse racing (multiple high-profile positive tests) and bodybuilding peptide stacks. Vendors often sell full TB-4 rather than the fragment despite the name. Same FDA Jan 2025 compounding restriction as BPC-157; consumer supply is unverified research-peptide material. FDA briefing documents for the Jul 23-24, 2026 Pharmacy Compounding Advisory Committee hearing were posted ahead of the meeting: FDA's stated position is to recommend against adding this peptide to the 503A bulks list, citing poor characterization, weak human efficacy/safety evidence, and unassessed immunogenicity risk (same position taken on BPC-157, KPV, TB-500, and MOTS-c). PCAC is advisory only; no final decision yet. A Phase 1/2 RCT (Hudson Biotech, NCT07487363, n=80) evaluating TB-500 in adults with stable atherosclerotic cardiovascular disease began recruiting Feb 2026 -- the first registered human trial for this peptide; no results yet. The July 23-24, 2026 PCAC hearing convened as scheduled; outcome not yet published as of this sweep. The FDA Pharmacy Compounding Advisory Committee (PCAC) met Jul 23-24, 2026 and voted on seven peptides for the 503A bulk drug substances list. Committee votes are advisory: the FDA is not bound by them, adding a substance to the 503A list would follow notice-and-comment rulemaking, and inclusion would permit compounding — it would not constitute FDA approval, an efficacy finding, or a safety determination. FDA's own review staff had recommended against the four Jul 23 peptides, citing poor characterization, weak human efficacy and safety evidence, and unassessed immunogenicity; press coverage also noted committee members' financial ties to the peptide industry. The underlying human evidence base for these compounds is unchanged by the vote. On this compound the committee voted 8-6 (one abstention) in favour of adding TB-500 to the 503A bulks list.

Mechanism

Fragment (or sometimes full-length) of TB-4, an endogenous actin-sequestering peptide; proposed to promote cell migration, angiogenesis, and wound healing

Studied, labeled, or reported dose & route

2-5 mg subQ weekly (anecdotal)

This records doses and routes described in studies, approved labeling, clinical practice, or documented use. It is not individualized guidance and does not establish safety; context changes with indication, formulation, health history, monitoring, and other medicines.

Citations

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Common questions

What does the evidence show about TB-500 (Thymosin beta-4 fragment)'s effects?
Read Off Label rates the evidence for TB-500 (Thymosin beta-4 fragment) as Preclinical and the benefit magnitude as variable, producing an overall grade of D (2.9/10). RegeneRx Biopharmaceuticals pursued clinical development; most programs stalled.
What safety findings are reported for TB-500 (Thymosin beta-4 fragment)?
TB-500 (Thymosin beta-4 fragment) has a unknown-high risk profile in the database. Unknown-High (no established human safety; FDA flagged immunogenicity and peptide-impurity concerns for TB-4 fragment products) Legal status: Not FDA-approved for any indication; Category 2 — compounding prohibited; WADA-banned; veterinary use common in horses; PCAC voted 8-6 (one abstention) in favour of adding TB-500 to the 503A bulks list (Jul 23-24, 2026) — advisory only, not an FDA approval or a final compounding decision.
What does the low Safety score for TB-500 (Thymosin beta-4 fragment) represent?
The Safety score is 3/10. It records the substantial harms described for one or more use contexts; the Benefit score, indication, dose, route, duration, population, and legal status remain separate parts of the evidence profile.
What doses or routes are reported for TB-500 (Thymosin beta-4 fragment)?
2-5 mg subQ weekly (anecdotal) This is context from studies, approved labeling, clinical practice, or documented use; it is not individualized guidance and does not establish safety.
How does TB-500 (Thymosin beta-4 fragment) work?
Fragment (or sometimes full-length) of TB-4, an endogenous actin-sequestering peptide; proposed to promote cell migration, angiogenesis, and wound healing

This is an independent synthesis of published research by a non-clinician. Scores are opinions supported by citations, not prescriptions. See the full disclaimer and methodology for how this score was produced and what it does and doesn't mean.