plate v - the questions
TB-500 questions, answered with the caveats up front.
The safety signal, the legal standing, and the comparisons people actually search for — each answer leads with the honest part.
Reading these answers
Two rules govern every answer below. The first is the identity rule: where a finding comes from full-length thymosin beta-4 rather than the TB-500 fragment, the answer says so, because most of the evidence is on the 4,963 Da protein, not the 889 Da heptapeptide [5]. The second is the honesty rule: where the data to answer a question does not exist — and for the fragment's human safety it largely does not — the answer says that plainly rather than filling the gap with reassurance [11].
The questions are grouped into safety and side effects, comparisons and definitions, and — on the dedicated TB-500 legal status page — the regulatory and access questions. Every quantitative claim links to a numbered source on the references page. None of this is medical advice, and none of it is a recommendation to use the compound.
Safety and side effects
What are the side effects of TB-500?
No controlled human safety data exist for the TB-500 fragment, so TB-500 side effects in humans are, strictly speaking, uncharacterized. Intravenous full-length thymosin beta-4 was well tolerated to 1,260 mg in a Phase 1 study [6], but the chief documented concern is the theoretical tumor and angiogenesis risk [5], compounded by unreliable research-grade purity [5]. The absence of an adverse-event profile is itself the finding here.
Does TB-500 cause cancer or promote tumor growth?
Thymosin beta-4 is overexpressed in several cancers and implicated in metastasis and tumor angiogenesis; the same pro-migratory, pro-angiogenic properties that aid repair could theoretically support tumor progression [5]. This is a recognized safety concern, not a settled human finding — but it is the single most cited caution in the literature.
Is TB-500 safe for long-term use?
Long-term human safety is unknown. There are no completed controlled clinical trials of the TB-500 fragment for any indication [11]. Combined with the tumor and angiogenesis signal [5] and the absence of any long-term data, long-term use cannot be characterized as safe. The honest answer is that the data to answer this does not exist.
Comparisons and definitions
What is the difference between TB-500 and BPC-157?
They are unrelated peptides studied for tissue repair. TB-500 is the Ac-LKKTETQ actin-binding fragment of thymosin beta-4; BPC-157 is a separate gastric-derived peptide with a different sequence and origin [5]. A 2026 Sports Medicine review lists both as unapproved peptides with favorable animal repair data but scarce human safety data and potential for serious harm [14].
What does TB-500 stand for and what does TB stand for in TB-500?
TB refers to thymosin beta (β). TB-500 is a research and veterinary designation for the synthetic Ac-LKKTETQ fragment of thymosin beta-4; it is not an abbreviation with an official chemical expansion beyond that thymosin-beta-4 origin [5]. The related veterinary designation TB1000 refers to the same peptide.
Is TB-500 FDA approved?
No. TB-500 has no FDA-approved therapeutic indication. It is a research-chemical and veterinary-context substance; FDA placed 'Thymosin beta-4, fragment (LKKTETQ), also known as TB-500' in 503A Category 2, flagging significant safety concerns for compounding [18]. See the TB-500 legal status page for the full regulatory picture.