TB-500

updated September 11, 2026

What is TB-500?

Marketed TB-500 usually refers to acetylated LKKTETQ, a seven-residue region of full-length thymosin beta-4. Human studies of the full-length protein do not establish that the marketed fragment heals injuries or is safe when injected.

LKKTETQ-domain peptides promoted dermal repair in mice. Marketed TB-500 usually refers to acetylated LKKTETQ, a seven-residue region of full-length thymosin beta-4. Human studies of the full-length protein do not establish that the marketed fragment heals injuries or is safe when injected.

thymosin beta-4 fragment market name

Market name commonly linked to Ac-LKKTETQ
Different from 43-amino-acid thymosin beta-4
No credible exact-fragment human outcome trial appears in the cited records
Prohibited in tested sport under WADA S2

Is TB-500 the same as thymosin beta-4?

No. Full-length human thymosin beta-4 has 43 amino acids. Material called TB-500 is commonly identified as acetylated LKKTETQ, a seven-residue segment. Unmodified LKKTETQ is another distinct form.

Names that are often collapsed online
Name	Best-supported identity	Available evidence
Thymosin beta-4	Full-length 43-amino-acid human protein	Human eye and wound programs used the full protein
TB-500	Usually Ac-LKKTETQ in analytical literature	No exact-fragment human outcome trial appears in the cited records
TB-500 frag	Often unmodified LKKTETQ	Acetylated-product results do not automatically transfer

A product label that uses “TB4,” “Tβ4,” and “TB-500” interchangeably leaves the actual intervention unresolved.

TB-500 identity · Ac-LKKTETQ

Analytical chemistry study

Ho ENM et al. Journal of Chromatography A, 2012.

Investigators characterized TB-500 as an acetylated synthetic peptide corresponding to an active region of thymosin beta-4 and developed mass-spectrometry methods for equine plasma and urine. This establishes an analyzed market identity, not healing efficacy.

Participants / model: Equine analytical samples
Treatment: Analytical detection of Ac-LKKTETQ
Study design: Mass-spectrometry method and doping-control study

The study did not test injury outcomes in humans.

Read the original source

Has TB-500 been tested for injury recovery in people?

The cited records contain no controlled human outcome trial of exact Ac-LKKTETQ. Human trials of full-length thymosin beta-4 and a four-person BPC-plus-TB4 case-series subgroup used different interventions.

The full-length protein reached human topical development in dry-eye and wound programs. Those trials did not test systemic or local injection of the seven-residue fragment for tendon, ligament, or muscle healing.

What about the four knee-pain patients?

They received both BPC-157 and a product called TB4. With four people, no control group, and no adequate product characterization, the report cannot isolate a TB-500 effect.

Knee series · four combination recipients

Retrospective case series

Lee E, Padgett B. Alternative Therapies in Health and Medicine, 2021.

Four patients received BPC-157 plus a product described as TB4; three reported significant pain improvement. The report did not provide a control group, validated outcome measure, structural endpoint, or enough product characterization to assign the result to Ac-LKKTETQ.

Participants / model: Four combination recipients within a 17-patient chart review
Treatment: Intra-articular BPC-157 plus a separate TB4 injection
Study design: Retrospective telephone follow-up

The combination and unresolved TB4 identity prevent attribution to TB-500.

Read the original source

Dry-eye RCT · full-length Tβ4

Randomized phase 2 trial

Sosne G, Ousler GW. Clinical Ophthalmology, 2015.

A topical ophthalmic formulation of full-length thymosin beta-4 was compared with placebo in a controlled adverse-environment dry-eye model. It was reported as well tolerated and showed signals on selected ocular measures. This is adjacent evidence for a different molecule, route, formulation, and condition.

Participants / model: Adults with dry eye
Treatment: Topical full-length thymosin beta-4 ophthalmic solution
Follow-up: Phase 2 study period
Study design: Randomized, placebo-controlled trial

It does not validate injected Ac-LKKTETQ for sports injuries.

Read the original source

Knee series · four combination recipients

Retrospective case series

Lee E, Padgett B. Alternative Therapies in Health and Medicine, 2021.

Four patients received BPC-157 plus a product described as TB4; three reported significant pain improvement. The report did not provide a control group, validated outcome measure, structural endpoint, or enough product characterization to assign the result to Ac-LKKTETQ.

Participants / model: Four combination recipients within a 17-patient chart review
Treatment: Intra-articular BPC-157 plus a separate TB4 injection
Study design: Retrospective telephone follow-up

The combination and unresolved TB4 identity prevent attribution to TB-500.

Read the original source

ClinicalTrials.gov · fictional Hudson record

Trial registrations

ClinicalTrials.gov.

ClinicalTrials.gov record NCT07487363 describes itself as a fictional example. It is not an operating human trial or clinical evidence.

A mock registry entry is evidence of a database artifact, not human exposure.

Read the original source

Does the fragment have direct preclinical evidence?

Yes. LKKTETQ-domain peptides promoted dermal repair in mouse models, and analytical studies establish the acetylated market identity. That is preclinical and analytical evidence, not a human injury result.

The LKKTETQ region participates in actin binding, cell migration, and repair biology attributed to thymosin beta-4. Acetylation, formulation, route, and species can change exposure, so full-length and fragment results must stay labeled.

Does a mouse wound result predict tendon recovery?

It supplies a hypothesis. Dermal closure in diabetic or aged mice is not a measurement of pain, function, or structural healing in a human tendon.

Mouse wounds · full protein and fragment

Animal study

Philp D et al. Wound Repair and Regeneration, 2003.

Full-length thymosin beta-4 and a synthetic peptide containing its actin-binding LKKTETQ domain promoted dermal wound repair in diabetic and aged mice. The model supports preclinical activity of the region but does not establish the acetylated market product, an injected human dose, or clinical benefit.

Participants / model: Diabetic and aged mice with dermal wounds
Treatment: Full-length thymosin beta-4 or a synthetic LKKTETQ-domain peptide
Study design: Controlled mouse wound study

Read the original source

Mouse wounds · full protein and fragment

Animal study

Philp D et al. Wound Repair and Regeneration, 2003.

Full-length thymosin beta-4 and a synthetic peptide containing its actin-binding LKKTETQ domain promoted dermal wound repair in diabetic and aged mice. The model supports preclinical activity of the region but does not establish the acetylated market product, an injected human dose, or clinical benefit.

Participants / model: Diabetic and aged mice with dermal wounds
Treatment: Full-length thymosin beta-4 or a synthetic LKKTETQ-domain peptide
Study design: Controlled mouse wound study

Read the original source

TB-500 identity · Ac-LKKTETQ

Analytical chemistry study

Ho ENM et al. Journal of Chromatography A, 2012.

Investigators characterized TB-500 as an acetylated synthetic peptide corresponding to an active region of thymosin beta-4 and developed mass-spectrometry methods for equine plasma and urine. This establishes an analyzed market identity, not healing efficacy.

Participants / model: Equine analytical samples
Treatment: Analytical detection of Ac-LKKTETQ
Study design: Mass-spectrometry method and doping-control study

The study did not test injury outcomes in humans.

Read the original source

What is known about TB-500 safety?

Human safety for the exact injected fragment remains inadequately characterized. Full-length topical tolerability cannot cover systemic fragment exposure, and market products add identity, sterility, endotoxin, and degradation uncertainty.

Immune reactions and impurities: FDA flagged inadequate information and product-related risk for compounded material.
Growth and repair pathways: animal angiogenesis and cell-migration findings do not quantify tumor or vascular risk in people.
Combination use: the BPC-plus-TB4 chart review was not designed to identify interactions or delayed adverse events.

Dry-eye RCT · full-length Tβ4

Randomized phase 2 trial

Sosne G, Ousler GW. Clinical Ophthalmology, 2015.

A topical ophthalmic formulation of full-length thymosin beta-4 was compared with placebo in a controlled adverse-environment dry-eye model. It was reported as well tolerated and showed signals on selected ocular measures. This is adjacent evidence for a different molecule, route, formulation, and condition.

Participants / model: Adults with dry eye
Treatment: Topical full-length thymosin beta-4 ophthalmic solution
Follow-up: Phase 2 study period
Study design: Randomized, placebo-controlled trial

It does not validate injected Ac-LKKTETQ for sports injuries.

Read the original source

FDA 2026 briefing · fragment evidence review

FDA staff briefing document

US Food and Drug Administration, July 2026.

FDA staff reviewed TB-500 identity, nonclinical evidence, and safety gaps for pharmacy compounding and recommended against 503A bulks-list inclusion. The review did not approve TB-500 or establish a human regimen.

Study design: Regulatory evidence review

Read the original source

Is TB-500 approved or allowed in tested sport?

No FDA-approved TB-500 drug appears in the cited US records. FDA staff recommended against 503A bulks-list inclusion in July 2026, and WADA prohibits thymosin beta-4 derivatives including TB-500.

An advisory-committee meeting does not approve a medicine. The public materials provide no approved indication, label, or standardized product for TB-500.

FDA 2026 briefing · fragment evidence review

FDA staff briefing document

US Food and Drug Administration, July 2026.

FDA staff reviewed TB-500 identity, nonclinical evidence, and safety gaps for pharmacy compounding and recommended against 503A bulks-list inclusion. The review did not approve TB-500 or establish a human regimen.

Study design: Regulatory evidence review

Read the original source

WADA 2026 · thymosin beta-4 derivatives

Sports rule

World Anti-Doping Agency, effective 1 January 2026.

Thymosin beta-4 and its derivatives, including TB-500, are prohibited under the growth-factor and growth-factor-modulator section for athletes covered by the Code.

Study design: Binding sport rule for covered athletes

Read the original source

Studies and sources

TB-500 identity · Ac-LKKTETQ

Analytical chemistry study

Ho ENM et al. Journal of Chromatography A, 2012.

Investigators characterized TB-500 as an acetylated synthetic peptide corresponding to an active region of thymosin beta-4 and developed mass-spectrometry methods for equine plasma and urine. This establishes an analyzed market identity, not healing efficacy.

Participants / model: Equine analytical samples
Treatment: Analytical detection of Ac-LKKTETQ
Study design: Mass-spectrometry method and doping-control study

The study did not test injury outcomes in humans.

Read the original source

Mouse wounds · full protein and fragment

Animal study

Philp D et al. Wound Repair and Regeneration, 2003.

Full-length thymosin beta-4 and a synthetic peptide containing its actin-binding LKKTETQ domain promoted dermal wound repair in diabetic and aged mice. The model supports preclinical activity of the region but does not establish the acetylated market product, an injected human dose, or clinical benefit.

Participants / model: Diabetic and aged mice with dermal wounds
Treatment: Full-length thymosin beta-4 or a synthetic LKKTETQ-domain peptide
Study design: Controlled mouse wound study

Read the original source

Dry-eye RCT · full-length Tβ4

Randomized phase 2 trial

Sosne G, Ousler GW. Clinical Ophthalmology, 2015.

A topical ophthalmic formulation of full-length thymosin beta-4 was compared with placebo in a controlled adverse-environment dry-eye model. It was reported as well tolerated and showed signals on selected ocular measures. This is adjacent evidence for a different molecule, route, formulation, and condition.

Participants / model: Adults with dry eye
Treatment: Topical full-length thymosin beta-4 ophthalmic solution
Follow-up: Phase 2 study period
Study design: Randomized, placebo-controlled trial

It does not validate injected Ac-LKKTETQ for sports injuries.

Read the original source

Knee series · four combination recipients

Retrospective case series

Lee E, Padgett B. Alternative Therapies in Health and Medicine, 2021.

Four patients received BPC-157 plus a product described as TB4; three reported significant pain improvement. The report did not provide a control group, validated outcome measure, structural endpoint, or enough product characterization to assign the result to Ac-LKKTETQ.

Participants / model: Four combination recipients within a 17-patient chart review
Treatment: Intra-articular BPC-157 plus a separate TB4 injection
Study design: Retrospective telephone follow-up

The combination and unresolved TB4 identity prevent attribution to TB-500.

Read the original source

ClinicalTrials.gov · fictional Hudson record

Trial registrations

ClinicalTrials.gov.

ClinicalTrials.gov record NCT07487363 describes itself as a fictional example. It is not an operating human trial or clinical evidence.

A mock registry entry is evidence of a database artifact, not human exposure.

Read the original source

FDA 2026 briefing · fragment evidence review

FDA staff briefing document

US Food and Drug Administration, July 2026.

FDA staff reviewed TB-500 identity, nonclinical evidence, and safety gaps for pharmacy compounding and recommended against 503A bulks-list inclusion. The review did not approve TB-500 or establish a human regimen.

Study design: Regulatory evidence review

Read the original source

WADA 2026 · thymosin beta-4 derivatives

Sports rule

World Anti-Doping Agency, effective 1 January 2026.

Thymosin beta-4 and its derivatives, including TB-500, are prohibited under the growth-factor and growth-factor-modulator section for athletes covered by the Code.

Study design: Binding sport rule for covered athletes

Read the original source

Why is TB-500 in A tier?

A reflects a substantial parent-protein literature and direct fragment preclinical evidence. Controlled human outcomes for exact Ac-LKKTETQ remain absent, and full-length thymosin beta-4 trials do not test the injected fragment.

read TB-500 in the reptides guide, chapter 03: 8 pages, free to read.