Is TB-500 Legal in 2026? Current FDA Status Explained

TB-500 Current Legal Status

TB-500 (Thymosin Beta-4 fragment) is legal to purchase in the United States when sold for in vitro laboratory research use. It is not scheduled under the CSA, not an FDA-approved drug, and not federally banned.

TB-500 is a synthetic fragment of Thymosin Beta-4 — specifically the actin-binding domain of the 43-amino acid protein Tβ4. The full Tβ4 protein is naturally occurring in nearly every human cell and blood platelet. TB-500 is studied for cell migration, angiogenesis, soft tissue repair, and anti-inflammatory effects in preclinical models.

• Research compound purchases: Legal — no change from PCAC vote
• Controlled substance status: Not scheduled
• FDA-approved drug: No
• Category 2 (compounding prohibition): Removed April 23, 2026
• 503A bulks list: Not yet listed — PCAC vote July 23, 2026

The Evidence Challenge at PCAC

Of the seven compounds under PCAC review, TB-500 faces one of the steeper evidence challenges — and understanding why matters for interpreting the vote outcome.

TB-500 is a fragment of Thymosin Beta-4, not the full protein. This distinction matters for FDA review because the regulatory precedent involves the full protein — not the fragment. The full Tβ4 protein has undergone some clinical development, including a Phase 2 dry eye trial that did not hit its primary endpoints. TB-500-specific human clinical data is essentially zero: there are no completed randomized controlled trials of TB-500 specifically in humans.

FDA career scientists highlighted this in their June 30, 2026 briefing documents: the evidence base for TB-500 is almost entirely preclinical, with no completed human trials. The committee must evaluate whether existing preclinical data and the Tβ4 safety/efficacy background are sufficient to authorize pharmacy compounding.

Most analysts tracking this docket assign TB-500 lower probability of a positive PCAC recommendation than compounds like KPV (which has a more targeted indication in UC) or Semax (politically prioritized by the RFK Jr. administration for opioid applications). The honest expectation is a deferred or negative vote for TB-500, with research compound access completely unaffected.

Regulatory Timeline

TB-500's regulatory journey mirrors BPC-157's almost exactly — they were placed in Category 2 together in September 2023, removed together in April 2026, and are both on the Day 1 docket for July 23. The key difference is that BPC-157 has a much larger preclinical evidence base and a specific Phase 1/2 IBD program (LP17), while TB-500 has a smaller body of research and no clinical development program specific to the fragment.

For the full timeline, see the PCAC July 2026 Vote Results page which covers all seven compounds with the complete regulatory history.

What the PCAC Vote Means for TB-500

If the committee votes YES

FDA begins formal rulemaking to add TB-500 to the 503A bulks list. Licensed pharmacies could legally compound it with valid prescriptions after rulemaking completes (6–18 months). Research compound access is unchanged.

If the committee votes NO (more likely per analysts)

Compounding pharmacy pathway remains closed. Research compound vendors continue operating normally. TB-500 remains available for research purchase from Evo Peptides. This is the outcome most observers expect based on the clinical evidence gap.

In both scenarios, TB-500 availability for research purchase is completely unaffected.

TB-500 in the Context of the Wolverine Stack

TB-500 is most commonly discussed in research contexts alongside BPC-157 — the two form the Wolverine Stack, named for their complementary tissue repair mechanisms. BPC-157 addresses local vascular remodeling and fibroblast activity; TB-500 addresses systemic cell migration and ECM organization. For researchers studying these compounds in combination, both remain available as research compounds with independent regulatory status.

Evo Peptides' KLOW 80mg includes both BPC-157 and TB-500 alongside GHK-Cu and KPV in a single co-lyophilized vial.

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