TB-500: molecular identity, eye-drop research and report limits

Sources checked: 22 October 2026.

TB-500 is a name used for chemically different research materials. Before comparing study results, establish whether a source means full-length thymosin β4 or its acetylated seven-amino-acid fragment. An analytical identification, a cell experiment and a clinical trial each answer a different question. They cannot be combined into a general claim that a commercial vial repairs injuries.

Why the name needs clarification

Full-length thymosin β4 contains 43 amino acids. The acetylated 17–23 fragment, Ac-LKKTETQ, contains seven. In 2012, Esposito and colleagues identified the latter in a preparation labelled TB-500 using chromatography and mass spectrometry. They also synthesised the fragment and proposed a detection strategy for plasma and urine. This was a chemical identification study, not a treatment trial. Primary study

What the human eye-drop study tested

Sosne and colleagues reported a small, randomised, double-masked phase-2 study of thymosin β4 eye drops in nine patients with severe dry eye. Treatment lasted 28 days, followed by another 28 days of observation. The comparator was the eye-drop vehicle. The outcomes included ocular discomfort and corneal fluorescein staining; the preparation was RGN-259, not a commercial TB-500 research vial. Primary study

Patients, eyes and percentages

At day 56 the paper reported a 35.1% reduction in discomfort and a 59.1% reduction in total staining relative to the vehicle group. The groups were described as 12 treated eyes and six control eyes. Those 18 eyes came from nine people, so they must not be described as 18 independent patients. The small sample and eye-specific outcomes limit generalisation.

What this does not establish

The trial does not test tendon healing, athletic recovery, muscle growth or systemic administration of a research vial. The analytical fragment study does not establish any of those benefits either. Even a positive clinical result depends on the molecule, formulation, route, population and measured endpoint. Changing several of those conditions creates a new research question.

Reading the PP laboratory report

The catalogue format is TB-500 10 mg. Janoshik report 222317 identifies the tested sample as TB-500 (TB-4), reporting 11.48 mg measured content and 99.028% purity. These are sample results, not a guarantee for every vial. Purity and content are separate measurements, and neither number demonstrates clinical effectiveness or replaces an identity assessment.

A practical evidence checklist

Check the sequence or molecular identity first, then the exact preparation and comparator. Record whether the endpoint is a laboratory signal, a symptom score or an injury outcome. Finally, match the report to the tested sample and its date. PP supplies laboratory research material, not material for human or veterinary use. This is a selected-source guide, not a systematic review.