TB-500 in Humans: What Studies Actually Exist

Short answer

Direct human TB-500 evidence: none identified by FDA in its review. The Agency stated that it did not identify clinical studies or human exposure data using TB-500. The sentence is dated to the 2026 evaluation.¹

Direct TB-500 studies

No clinical trial identified on that record administers TB-500 to people. There is, in that review, no human-exposure study with an Ac-LKKTETQ identity. Esposito 2012 does not fill the gap: it characterizes a material, not a clinical outcome.^1,5

Philp 2003 does not enter here either. It is a mouse study of non-acetylated LKKTETQ and of full-length Tβ4.⁶

Full-length thymosin β4 — dry eye

Sosne and Ousler published a randomized, placebo-controlled Phase II trial of a thymosin β4 ophthalmic solution in dry eye. Seventy-two participants were randomized.²

The primary endpoints were ocular discomfort and inferior corneal staining. At the specified primary evaluation there were no statistically significant differences. Some secondary endpoints were significant. That combination is not summarized as “Phase II proved thymosin β4 effective.” Still less is it a TB-500 result.²

The route is ophthalmic. The object is the 43-amino-acid peptide. Neither fact transfers to a seven-residue fragment. An advertisement that takes a secondary from that trial and places it under the name TB-500 makes two shifts at once: from primary to secondary, and from Tβ4 to fragment.

Full-length thymosin β4 — venous ulcers

Guarnera, DeRosa, and Camerini described a randomized, placebo-controlled Phase II trial of topical thymosin β4 in venous ulcers. Seventy-three patients were randomized across eight European sites.³

Registry NCT00832091 matches that program. The registry reports 72 participants as the enrollment figure; the paper reports 73 randomized. We use 73 for the published trial and leave the registry as a design document. Neither figure is a TB-500 trial.^4,3

The authors describe an acceptable safety profile and suggest that one of the studied concentrations might speed closure in a subset. That reading belongs to topical Tβ4. It is not turned into a regimen and it is not copied onto Ac-LKKTETQ.³

Why these are not TB-500 trials

The distinction is molecular. A trial names the substance that was administered. If it administered 43-amino-acid thymosin β4, the result stays in that column. FDA said as much when it reviewed the nomination: the cited references were thymosin β4 studies, not TB-500 studies in humans.¹

What evidence would be needed

• A human study that administers TB-500, not Tβ4 and not non-acetylated LKKTETQ.
• Clear substance identity: sequence, acetylation, and salt form.
• A defined formulation, not a catalog name.
• Prospective registration.
• Safety monitoring.
• Controlled outcomes, with primaries declared in advance.

This list is not a protocol and does not include amounts. It describes the kind of record that was missing from the 2026 review. A forum, a lot certificate, or a trial of another molecule does not replace those elements.¹

A thymosin β4 registry is not enough either. NCT00832091 documents a completed topical Tβ4 program. It is not an active TB-500 registry and is not presented here as if it were.⁴

The useful sentence for a reader arriving from an advertisement is this: if the advertisement says TB-500 “has Phase II,” ask which molecule was administered. If the answer is thymosin β4, the advertisement transferred evidence. If the answer is TB-500 and a trial can be cited, that trial was not in the record FDA said it searched in 2026.¹

• Why Tβ4 is not the same evidence
• What FDA concluded and what PCAC voted
• TB-500 research hub