SIGNAL // FAQ READOUT
TB-500: Frequently Asked Questions, Answered From the Record
Direct answers about safety signals, comparisons, and evidence — each cited where it makes a quantitative claim.
Safety signals first
The TB-500 questions readers ask most are safety questions, so this FAQ leads with them. The honest summary up front, including on TB-500 side effects: there is no human side-effect profile for the Ac-LKKTETQ fragment, the closest human safety data come from intravenous full-length thymosin beta-4 [6], and the principal open concern is the tumor and angiogenesis signal. Each answer below states what is known and marks what is not.
What are the side effects of TB-500?
No human side-effect profile exists for the TB-500 fragment. The closest human safety data come from intravenous full-length thymosin beta-4, which was well tolerated to 1260 mg with no dose-limiting toxicities in a Phase 1 study [6]. The main theoretical concern is the tumor and angiogenesis signal, an unresolved issue rather than a documented fragment side effect.
Does TB-500 cause cancer or promote tumor growth?
thymosin beta-4 is overexpressed in several cancers and is implicated in metastasis and tumor angiogenesis; the same pro-migratory, pro-angiogenic properties that aid repair could theoretically support tumor progression [5]. This is an unresolved safety signal, not a demonstrated human effect of TB-500, and it is the reason the angiogenic activity is reported alongside its risk.
What is the difference between TB-500 and BPC-157?
TB-500 and BPC-157 are chemically unrelated peptides studied for overlapping tissue-repair interest. TB-500 is the Ac-LKKTETQ fragment of thymosin beta-4; BPC-157 is a separate 15-amino-acid sequence. A 2026 Sports Medicine review lists both among unapproved peptides with favorable animal-model outcomes but scarce human safety data and no regulatory approval [15].
Is TB-500 safe for long-term use?
There are no long-term human safety studies of the TB-500 fragment. Short-term intravenous full-length thymosin beta-4 was well tolerated over 14 days in a Phase 1 study [6], but that does not establish chronic safety of the heptapeptide, and the tumor and angiogenesis signal remains unresolved [5]. Long-term fragment safety is simply unknown.