TB-500

TB-500 is a synthetic heptapeptide (Ac-LKKTETQ), corresponding to residues 17–23 of thymosin beta-4 (Tβ4), the principal actin-sequestering molecule in eukaryotic cells. Its primary molecular action is high-affinity binding to G-actin (globular, monomeric actin), which modulates the equilibrium between monomeric and filamentous actin and thereby influences cytoskeletal dynamics and cell motility.

Philp et al. (FASEB J, 2003; PMID 14500546) demonstrated that this seven-amino-acid motif is essential for Tβ4's angiogenic activity, promoting endothelial cell migration, tubule formation, and aortic ring sprouting in vitro. Competitive inhibition by soluble actin confirmed that actin binding is the proximate mechanism.

Sosne et al. (FASEB J, 2010; PMID 20179146) mapped distinct active sites across full-length Tβ4: residues 1–4 (Ac-SDKP) mediate anti-inflammatory and antifibrotic effects; residues 1–15 inhibit apoptosis; and residues 17–23 drive angiogenesis and wound healing. Downstream signaling involves PI3K/Akt/eNOS, TGFβ/Smad, and Wnt pathways.

TB-500 contains only the angiogenic domain and lacks the anti-inflammatory Ac-SDKP sequence present in the full 43-residue parent protein. Whether the isolated fragment reproduces the complete biology of intact Tβ4 in human tissue has not been established in any controlled clinical trial.

The critical distinction for evaluating TB-500 is that all human clinical evidence was generated with full-length thymosin beta-4, not with the isolated heptapeptide fragment. No completed human efficacy or pharmacokinetic trials exist for TB-500 as a standalone compound.

In dermal wound healing, Phase 2 trials of topical Tβ4 showed accelerated repair versus placebo. A European randomized, double-blind, dose-escalation multicenter study (Guarnera et al., Ann NY Acad Sci, 2007; PMID 17495250) enrolled 73 patients with venous stasis ulcers and reported approximately 25% complete closure within 3 months and acceleration of healing by roughly one month in those who healed.

Ophthalmic application has generated the most rigorous human data. A Phase 3 randomized, placebo-controlled, double-masked trial of 0.1% Tβ4 ophthalmic solution (RGN-259; SEER-1; Sosne et al., Int J Mol Sci, 2022; PMID 36613994) enrolled 18 subjects with neurotrophic keratopathy; 6 of 10 treated subjects achieved complete corneal healing at day 29 versus 1 of 8 placebo subjects (p = 0.0656, narrowly missing prespecified significance). No serious adverse events were observed. A subsequent European Phase 3 trial (SEER-3) failed to meet its primary endpoint, representing a setback for the ophthalmic program.

For cardiac indications, a Phase 1 study in 54 healthy volunteers found no dose-limiting toxicities at intravenous Tβ4 doses of 0.05–25 μg/kg. A Phase 2 AMI trial (NCT01311518; RGN-352) enrolling approximately 75 patients was placed on clinical hold due to contract-manufacturer compliance issues, interrupting that development program.

In murine models, Tβ4 improved cardiomyocyte survival and cardiac function after coronary ligation through ILK/Akt signaling (Srivastava et al., 2007; PMID 17600280). These preclinical findings have not been replicated in completed human trials. No study to date has directly compared TB-500 to full-length Tβ4 in humans.

Typical dosage: 2-5 mg (weekly).

No regulatory authority has established dosing guidelines for TB-500. No human pharmacokinetic or dose-finding studies have been conducted for this fragment specifically.

In Phase 1 trials of full-length Tβ4 for cardiac indications, intravenous doses ranged from 0.05 to 25.0 μg/kg without dose-limiting toxicity (Xing et al., Front Endocrinol, 2021). A Phase 2 AMI trial (NCT01311518) employed doses of 450 mg and 1,200 mg IV daily for three consecutive days then weekly for four additional weeks.

Community and anecdotal use of TB-500 involves subcutaneous injection in the complete absence of a clinical evidence base. Commonly reported loading-phase protocols describe 2–5 mg per week, divided across two to three subcutaneous injections, sustained for four to six weeks. A maintenance phase of 2–2.5 mg per week or biweekly for a further four to twelve weeks is then frequently described. Reconstitution in bacteriostatic water and injection with a 29–31 gauge insulin needle, with rotation of abdominal injection sites, are typical practice among self-experimenters.

No data on oral bioavailability exist; subcutaneous injection is the only route reported in both veterinary and informal human use.

This information is educational only and reflects reported usage in uncontrolled, informal contexts. It does not constitute medical advice. TB-500 is not approved by the FDA or any major regulatory agency for human therapeutic use; as of February 2026, the FDA classified it as a Category 2 bulk drug substance prohibited for pharmaceutical compounding.

Lyophilized (before reconstitution)

Multiple vendor sources cite 18–24 months at either −20°C (freezer) or 2–8°C (refrigerator). Vendors additionally flag TB-500 as more light-sensitive than BPC-157 — amber or opaque vials and dark storage are specifically recommended. Keep dry and sealed; humidity is the primary threat to powder.

Reconstituted

Commonly cited at ~28 days refrigerated (2–8°C) in bacteriostatic water. Never freeze a reconstituted vial. Protect from light throughout the in-use period, which is more critical for TB-500 than for most other research peptides at this tier. This is a vendor-derived convention rather than a peptide-specific stability study — the 28-day window traces to the 0.9% benzyl alcohol preservative's validated antimicrobial window, not to a TB-500-specific chemical assay. See the Storage & handling primer for context.

For general storage chemistry (bacteriostatic vs sterile water, freeze-thaw, BUD framework), see Storage & handling.

Last reviewed: July 1, 2026

The most frequently described combination in performance-recovery communities is TB-500 paired with BPC-157 (Body Protection Compound-157), a pentadecapeptide fragment of human gastric juice protein. This pairing is colloquially called the "Wolverine Stack." The proposed rationale is mechanistic complementarity: BPC-157 is hypothesized to act locally at the injury site via nitric oxide synthase and growth hormone receptor pathways, while TB-500 purportedly promotes angiogenesis and cell migration through systemic actin dynamics. No published human clinical trial or controlled animal study has specifically investigated this combination; all claims of synergistic or additive healing effects are anecdotal.

Some users additionally pair TB-500 with growth hormone secretagogues such as ipamorelin or CJC-1295, positing complementary anabolic and regenerative signaling. This combination likewise has no clinical or formal preclinical evidence. Both TB-500 and BPC-157 are banned by WADA under S2 of the Prohibited List, and a Canadian athlete received a four-year ineligibility sanction for use of this exact combination.

TB-500 is not currently FDA-approved for any indication. Effective April 22, 2026, the FDA removed TB-500 from Category 2 of its Section 503A bulk drug substances list after the original nominators withdrew their nominations. This removal lifts the prior “significant safety risk” designation but does not place TB-500 on the 503A Bulks List. Compounding pharmacies may prepare it with a valid physician prescription and pharmaceutical-grade API from an FDA-registered manufacturer. The FDA’s Pharmacy Compounding Advisory Committee (PCAC) is scheduled to review this substance at its July 23–24, 2026 public meeting. Removed from FDA Category 2 effective April 22, 2026. Selected for PCAC review Day 1 — July 23, 2026. PCAC agenda: BPC-157, KPV, TB-500, MOTS-c. NOT currently on 503A Bulks List — requires physician Rx. Source: FDA Advisory Committee Calendar / Lengea Law, May 2026.

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Reported side effects: Minimal side effects. Rare: headache, nausea, injection site reactions

Clinical trials of full-length thymosin beta-4 demonstrated a consistently favorable safety profile. A Phase 1 study in 54 healthy volunteers found no dose-limiting toxicities and no serious adverse events across intravenous doses up to 25 μg/kg (Xing et al., 2021). In the Phase 3 SEER-1 ophthalmic trial (Sosne et al., 2022; PMID 36613994), 16 adverse events were recorded across 7 subjects, only one of which was deemed treatment-related; the investigators concluded the compound was safe in this population.

Extrapolating these findings to TB-500 specifically is not scientifically supported: no controlled human study has evaluated the isolated heptapeptide fragment. Community self-reports describe injection-site reactions (redness, localized swelling, transient pain), mild fatigue or lethargy during loading phases, and occasional headache. These reports cannot be systematically verified.

A theoretical concern applicable to angiogenic compounds is the potential for promoting vascularization of occult or established tumors. On this mechanistic basis, TB-500 is widely considered contraindicated in individuals with active malignancy or a strong personal cancer history, though no clinical observation directly confirms this risk. Pregnancy and breastfeeding are also commonly listed as contraindications.

Unregulated commercial TB-500 carries independent manufacturing risks: independent testing of peptide products sold outside pharmaceutical oversight has identified contamination with endotoxins, heavy metals, residual solvents, incomplete peptide sequences, and microbial agents, representing risks entirely separate from the pharmacology of the peptide itself.