TB-500

TB-500 is a synthetic peptide fragment of thymosin beta-4 (Tβ4), a naturally-occurring protein involved in actin sequestration, cell migration, tissue repair, and cardiovascular remodeling. TB-500 is sold as 'thymosin beta-4 fragment' by research-peptide vendors and has become the other half of the 'Wolverine Stack' alongside BPC-157 in injury-recovery biohacker protocols. It is not FDA approved for any human indication. It was placed on the FDA's Category 2 list in 2023 alongside other peptides, with a February 2026 HHS proposal to remove it.

Thymosin beta-4, the parent protein, is an abundant intracellular G-actin sequestering molecule that regulates actin polymerization and cell motility. Extracellular Tβ4 has been studied for angiogenesis, wound healing, cardiomyocyte regeneration, and anti-inflammatory effects. TB-500 is a shorter peptide (variably described as the Tβ4 17-23 amino acid fragment or similar) that reportedly retains some of these effects in preclinical models, though exact mechanism at the cellular level is not fully characterized.

Tβ4 itself has reasonable clinical research — trials in epidermolysis bullosa, corneal ulcer, dry eye disease (RegeneRx), and cardiac repair. TB-500 as a discrete fragment is less-studied; most of the preclinical evidence is in animal models for injury repair and wound healing, with the caveat that different 'TB-500' preparations sold under that name may have varying sequence purity. Human clinical data specifically for TB-500 is sparse. The World Anti-Doping Agency banned Tβ4 peptide analogs across competitive sport on suspected performance-enhancing use.

No Phase 3 trials for TB-500 specifically. RegeneRx advanced Tβ4 through several Phase 2 trials but without clear Phase 3 progression. No on-market human therapeutic use.

Not FDA approved. Category 2 as of September 2023; Feb 2026 HHS proposed removal. WADA-prohibited in competitive sport. Research-peptide vendors selling TB-500 have been subjects of FDA warning letters. Full regulatory timeline →

Several. First, the 'TB-500' sold commercially is inconsistently characterized — some vendor products are the canonical Tβ4 fragment, others are full Tβ4, others are different sequences marketed under the TB-500 brand. Purity and identity vary by source. Second, the peer-reviewed human evidence is essentially absent despite widespread biohacker use. Third, the 'Wolverine Stack' (BPC-157 + TB-500) has no RCT-level human evidence for the stacked approach at all.

• Thymosin beta-4 Nature review →
• WADA prohibited list (peptide hormones) →
• FDA Category 2 bulk substances →