TB-500

§1 Definition

TB-500 is a synthetic seven-amino-acid peptide (Ac-LKKTETQ-OH) corresponding to the actin-binding fragment of thymosin beta-4, a naturally occurring 43-amino-acid protein — TB-500 is not the same molecule as full-length thymosin beta-4, and most published research covers the full-length protein rather than this fragment specifically. Not FDA-approved for any use; FDA reviewed and declined to add it to its list of substances eligible for pharmacy compounding in 2026, citing insufficient safety and effectiveness evidence.

§2 Evidence tier and regulatory status

Not FDA-approved for any use; sold only as a research chemical. In its own briefing materials for the July 23-24, 2026 Pharmacy Compounding Advisory Committee (PCAC) meeting, FDA staff recommended against adding TB-500 (both free base and acetate forms) to the 503A Positive Bulk Drug Substances list — citing no adequate effectiveness or safety evidence for wound-healing use, an immunogenicity concern specific to injectable routes with no human safety data to offset it, and inadequate physical/chemical characterization. The PCAC committee itself voted 8-6 in favor of listing TB-500 anyway, contrary to FDA staff's recommendation. No final rule has been issued as of this writing, and neither the committee vote nor FDA staff's position constitutes approval or confirms future compounding legality. This is the same PCAC review cycle that considered BPC-157, which followed the same pattern (staff against, committee in favor).

§3 Documented dosing

§4 Reconstitution math

No TB-500-specific published reconstitution protocol exists. General lyophilized-peptide reconstitution practice is commonly applied by research users, but this is not backed by a compound-specific clinical or regulatory source.

§5 What the research shows

Only two studies are tabulated above; a broader animal literature exists (e.g. a 1999 rat full-thickness wound study reporting accelerated reepithelialization with topical and intraperitoneal full-length thymosin beta-4) that this research pass could not confirm a precise sample size for and so did not include as a table row, consistent with not presenting an unverified number as fact. No human clinical trial has been identified for TB-500 (the fragment) itself — the one human trial listed above is for a different, related molecule (full-length thymosin beta-4) in a different formulation and indication.

§6 Safety and reported adverse effects

No published adverse-effect data located.

No systematic human adverse-effect data has been published for TB-500. Separately, several peer-reviewed studies report that overexpression of full-length thymosin beta-4 (not TB-500 specifically) correlates with more aggressive disease in some cancers (e.g. gastric gastrointestinal stromal tumors) — this is an observed association between the parent protein and existing tumor behavior in that research, not evidence that administering TB-500 causes cancer. It's noted here because the same cell-migration and angiogenesis mechanisms proposed for tissue healing are mechanistically the kind of activity that would raise theoretical concern in the presence of an existing malignancy, not because a causal link to cancer has been established.

§7 Storage and handling

Lyophilized

No published data located.

Reconstituted

No published data located.

§8 Sourcing considerations

• Since TB-500 is not FDA-approved for any use and is sold only as a research chemical, verify the seller provides a Certificate of Analysis from an independent, named third-party lab — not just in-house testing.
• Confirm which molecule is actually being sold — some listings blur the distinction between full-length thymosin beta-4 and the shorter TB-500 fragment, which are chemically different products.
• Check for batch-specific testing rather than a generic product-line certificate, since purity and identity can vary between batches.

§9 FAQ

§10 Sources