TB-500 Safety Profile — Preclinical Research Reference

*Preclinical safety record of thymosin β4 fragment TB-500: organ toxicity, acute and repeat-dose exposure data, angiogenesis-related cautions, and the absence of long-term human safety studies.*

Research Use Only. All material on this page is provided strictly for in vitro and in vivo laboratory research purposes. It is not medical advice and is not intended for human or veterinary therapeutic use. Researchers are responsible for compliance with all applicable laws, IRB/IACUC oversight and institutional biosafety policy.

Overview

TB-500 is the synthetic active-region fragment of thymosin β4 (Tβ4). Preclinical safety data exist for the full-length Tβ4 (RegeneRx clinical program) and limited preclinical work on the TB-500 fragment specifically. No long-term human safety package has been published for the fragment.

Preclinical & Limited Clinical Findings

• Acute toxicity: no LD50 reached in published rodent studies up to 50 mg/kg for full-length Tβ4
• RegeneRx Phase 1 (RGN-352, IV Tβ4): single doses to 1,260 mg in healthy adults were well-tolerated with no SAEs; mild headache and transient flushing reported
• RegeneRx Phase 2 ophthalmic (RGN-259): topical Tβ4 well-tolerated through 28-day dosing
• Hematology, LFTs, renal: no significant deviations in published Phase 1 panels

Mechanistic Safety Considerations

Tβ4 promotes angiogenesis (via VEGF / HIF-1α / KLF2 pathways) and accelerates extracellular matrix remodelling. As with BPC-157, the angiogenic activity raises a theoretical concern in occult-tumor settings, although no preclinical model has demonstrated tumor promotion.

Gaps In The TB-500 Fragment Record

• Most published safety data are for the full 43-amino-acid peptide, not the TB-500 fragment
• No long-term repeat-dose human studies of the fragment
• No standardised pharmacokinetic comparison between TB-500 and full-length Tβ4

Practical Research Considerations

Investigators should clearly specify whether the test article is full-length thymosin β4 or the TB-500 active region; the safety datasets are not interchangeable. Pre-specify hematology, CMP and (in tumor-bearing models) tumor growth tracking.

Frequently Asked Research Questions

Is TB-500 the same as thymosin β4?

TB-500 is a synthetic peptide corresponding to the active region of thymosin β4 (Tβ4). It is structurally similar but not identical to the full-length 43-amino-acid Tβ4 used in the RegeneRx clinical program.

Has TB-500 been tested in humans?

The TB-500 active-region fragment itself has no published Phase 1 dose-escalation in humans. Safety inferences are typically drawn from RegeneRx's full-length Tβ4 program (RGN-352, RGN-259), which is a related but distinct molecule.

What is the angiogenesis concern?

Tβ4 is a potent pro-angiogenic peptide. While no preclinical model has shown tumor promotion, researchers working in oncology-adjacent models should pre-specify tumor monitoring.

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