TB-500
Evidence: ERepair / Tissue Healing
Evidence Snapshot
What this grade covers
E: No direct human exposure, efficacy, pharmacokinetic, or safety evidence was identified for the exact TB-500/LKKTETQ fragment. Human evidence involving full-length thymosin beta-4, recombinant or synthetic Tβ4, and RGN-259 is molecule-, formulation-, route-, and indication-specific contextual evidence only. Regulatory records establish identity, absence-of-data, compounding-safety, advisory-process, and anti-doping context but do not establish clinical benefit.
Regulatory Context
No FDA-approved TB-500 fragment drug product was identified. FDA reports no identified human exposure data for the exact LKKTETQ fragment and has published compounding-safety concerns involving aggregation, peptide impurities, immunogenicity, and product characterization. FDA staff proposed against adding TB-500 free base and acetate to the 503A Bulks List during the July 2026 review; the advisory process did not itself create FDA approval, an approved indication, or an approved dosing regimen. TB-500 is prohibited under applicable WADA rules.
Research Takeaway
TB-500 is represented on this page as the short LKKTETQ thymosin-beta-4-derived fragment, not full-length thymosin beta-4.
See all 10 evidence claims →Quick Summary
TB-500 is marketed as the short thymosin-beta-4 fragment LKKTETQ and is not the same molecule as full-length 43-amino-acid thymosin beta-4. FDA reports no identified human exposure data for drug products containing the exact fragment. Human studies of full-length thymosin beta-4 and RGN-259 are related biological context only and do not establish TB-500 efficacy, safety, pharmacokinetics, or dosing.
Mechanism & Research Overview
The LKKTETQ sequence is discussed in relation to actin binding, cell migration, angiogenesis, and tissue-remodeling biology associated with thymosin-beta-4 research. However, the marketed TB-500 fragment is molecularly distinct from full-length thymosin beta-4, and findings from full-length, recombinant, synthetic, or ophthalmic thymosin-beta-4 products cannot be transferred directly to TB-500.
Evidence Grade Breakdown
A single letter grade can't capture how evidence quality differs across approved use, off-label use, and unsupported claims. The categories below break that down -- none of them grade this compound "overall."
Overall Research Grade
TB-500 has no identified direct human exposure, efficacy, pharmacokinetic, or safety evidence for the exact LKKTETQ fragment. The available human studies involve molecule-distinct full-length thymosin beta-4 or RGN-259 products and are retained only as related biological context. FDA and WADA records provide identity, absence-of-data, compounding-safety, advisory-process, and anti-doping information but do not establish clinical effectiveness.
CCompound Identity
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Compound Identity
FDA materials identify the reviewed TB-500 substance as the LKKTETQ fragment and distinguish it from full-length thymosin beta-4. Commercial product identity, acetylation state, purity, and formulation may still vary.
EDirect Human TB-500 Evidence
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Direct Human TB-500 Evidence
No direct human exposure, efficacy, pharmacokinetic, or safety evidence was identified for the exact TB-500 fragment.
DRelated Full-Length Tβ4 Evidence
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Related Full-Length Tβ4 Evidence
Human studies exist for full-length, recombinant, or synthetic thymosin beta-4 and RGN-259, but these are molecule-, route-, formulation-, and indication-specific and cannot be counted as direct TB-500 evidence.
ESafety Evidence
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Safety Evidence
Fragment-specific human safety, long-term safety, reproductive safety, pediatric safety, pharmacokinetics, and immunogenicity remain inadequately characterized. FDA identifies additional aggregation, impurity, and product-characterization concerns.
CRegulatory and Anti-Doping Context
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Regulatory and Anti-Doping Context
FDA records document the fragment identity, absence of identified human exposure data, compounding-safety concerns, and the nonbinding 503A advisory process. WADA materials prohibit TB-500 for covered athletes. These records do not establish clinical approval or efficacy.
ERepair, Recovery, and Performance Claims
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Repair, Recovery, and Performance Claims
Controlled human evidence does not establish that the exact fragment improves tendon, ligament, muscle, wound-healing, recovery, bodybuilding, anti-aging, or athletic-performance outcomes.
Evidence reviewed
Covers the final TB-500 source graph: regulatory records directly addressing the LKKTETQ fragment, compounding-safety and 503A review, WADA status, human studies of molecule-distinct full-length thymosin beta-4 or RGN-259, related trial registries, one animal study, 2 direct analytical-identity studies for the exact fragment, and contextual full-length-Tβ4 reviews. No source provides direct human efficacy, pharmacokinetic, or safety evidence for the exact TB-500 fragment.
- Randomized human trials
- 3
- Observational human studies
- 2
- Regulatory documents
- 4
- Preclinical studies
- 2
- Primary sources reviewed
- 15 of 18
Study counts describe the reviewed evidence base. They do not independently determine evidence quality.
How MitoCore grades evidence
Grade definitions
- A
- Strong and directly applicable evidence, generally including regulatory support or multiple high-quality replicated human trials for the exact claim and population.
- A-
- Strong human evidence with limited uncertainty, narrower applicability, or incomplete replication.
- B+
- Moderately strong evidence with meaningful human support but important scope, duration, safety, or generalizability limitations.
- B
- Credible evidence with notable uncertainty, limited replication, or mixed results.
- C
- Preliminary or inconsistent evidence, usually limited human data or strong indirect evidence.
- D
- Weak, indirect, population-limited, or largely unsupported evidence for the specific use being graded.
- F
- No credible supporting evidence, evidence contradicting the claim, or claims based primarily on speculation or marketing.
Confidence definitions
- High
- The evidence classification is unlikely to change substantially with ordinary additional research.
- Moderate
- The classification is reasonably supported but could change with additional high-quality evidence.
- Low
- The evidence base is sparse, indirect, inconsistent, or dependent on uncertain assumptions.
- Very Low
- The evidence base is extremely limited, speculative, or unsuitable for firm conclusions.
Scope
The grade evaluates the evidence supporting the specific category or claim. A grade does not evaluate product purity, supplier quality, personal suitability, treatment appropriateness, individual outcomes, legality, or medical safety for a specific person.
These grades and confidence levels describe the research evidence itself. They are not medical recommendations, and they do not evaluate any specific product, supplier, or individual's situation.
Evidence Claims
Individual scientific statements drawn from the sources cited below, each shown with the specific evidence boundary that statement does not establish.
Supported
TB-500 is represented on this page as the short LKKTETQ thymosin-beta-4-derived fragment, not full-length thymosin beta-4.
Sources: Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks
Supported
FDA reports that it has not identified human exposure data for drug products containing the exact thymosin-beta-4 LKKTETQ fragment.
Sources: Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks
Supported
Human studies of full-length, recombinant, or synthetic thymosin beta-4 do not establish the efficacy, safety, pharmacokinetics, or dosing of the shorter TB-500 fragment.
Sources: A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers; A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers
Supported
RGN-259 ophthalmic studies are formulation-, route-, indication-, and molecule-specific contextual evidence and cannot be treated as direct evidence for TB-500.
Supported
FDA identifies potential aggregation, peptide-impurity, immunogenicity, and characterization concerns for compounded products containing the fragment.
Sources: Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks
Supported
FDA's PCAC evaluation did not create approval, an approved indication, or an approved dosing regimen for TB-500.
Sources: FDA Briefing Document — Pharmacy Compounding Advisory Committee Meeting, July 23–24, 2026; FDA Advisory Panel Vote on Unapproved Peptides
Supported
The 2026 WADA Prohibited List includes thymosin-beta-4 and derivatives such as TB-500.
Sources: The 2026 Prohibited List
Supported
Analytical and anti-doping studies can identify TB-500/Ac-LKKTETQ and its metabolites but do not establish therapeutic benefit.
Sources: Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential; Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro
Supported
Preclinical findings involving LKKTETQ or full-length Tβ4 must remain separated by exact molecular identity and model.
Sources: FDA Evaluation of TB-500-Related Bulk Drug Substances; Thymosin beta4 accelerates wound healing
Supported
No direct human efficacy claim for tissue healing, recovery, performance, or injury treatment is supported for the exact TB-500 fragment.
Sources: Thymosin Beta-4 and Venous Ulcers; RGN-259 Dry Eye Trial; Thymosin Beta-4 in Pressure Ulcers; Recombinant Thymosin Beta-4 in Acute Myocardial Infarction
Safety & Evidence Limitations
Considerations reported in the sources cited on this page — not a complete list of every possible risk, and not medical advice.
Higher-Priority Safety Consideration
FDA reports no identified human exposure data for drug products containing the TB-500/LKKTETQ fragment. Human exposure, pharmacokinetics, efficacy, and safety therefore remain unestablished for the exact fragment.Higher-Priority Safety Consideration
Human trials involving full-length, recombinant, or synthetic thymosin beta-4 and RGN-259 study molecule-distinct products. Their efficacy and safety findings cannot be transferred directly to the shorter TB-500 fragment.Higher-Priority Safety Consideration
FDA identifies aggregation, peptide impurities, immunogenicity, acetylation state, molecular identity, and product characterization as material concerns for compounded TB-500 fragment products.Higher-Priority Safety Consideration
Unapproved injectable products may carry sterility, contamination, concentration, formulation, storage, and labeling risks that are not resolved by biological research involving thymosin beta-4.Higher-Priority Safety Consideration
Long-term human safety has not been established for the exact TB-500 fragment. Short-duration or molecule-distinct thymosin-beta-4 studies cannot resolve chronic fragment-specific risks.Higher-Priority Safety Consideration
Adequate pregnancy, reproductive, developmental, and pediatric safety data were not identified for the exact TB-500 fragment.Higher-Priority Safety Consideration
TB-500 is prohibited for athletes subject to applicable World Anti-Doping Code rules.Safety Consideration
Thymosin-beta-4 biology is associated with angiogenesis and cell migration. These mechanisms create context-dependent theoretical cancer-related concerns, but the reviewed evidence does not establish that the TB-500 fragment causes or accelerates cancer in humans.Safety Consideration
The July 2026 Pharmacy Compounding Advisory Committee process was advisory and nonbinding. It did not create FDA approval, an approved indication, or an approved dosing regimen for TB-500.
Research Areas Being Studied
Research areas discussed on this page reflect the Repair / Tissue Healing category and the sources cited below.
Findings Reported in Studies
Educational summary only — reported in cited studies, not a claim of proven benefit.
- 0.1% RGN-259 (Thymosin ß4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial (2023): 0.1% ophthalmic full-length thymosin beta-4 formulation.
- A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers (2021): Single and multiple intravenous doses of recombinant full-length thymosin beta-4.
- A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers (2010): Single and multiple intravenous doses of full-length thymosin beta-4.
- RGN-259 Dry Eye Trial ():
- Thymosin Beta-4 and Venous Ulcers ():
Study Tables by Evidence Type
Human Studies & Clinical Data
| Title | Year | Population / Model | Dose / Duration / Finding | Safety Notes | Source |
|---|---|---|---|---|---|
| 0.1% RGN-259 (Thymosin ß4) Ophthalmic Solution Promotes Healing and Improves Comfort in Neurotrophic Keratopathy Patients in a Randomized, Placebo-Controlled, Double-Masked Phase III Clinical Trial | 2023 | Patients with neurotrophic keratopathy | 0.1% ophthalmic full-length thymosin beta-4 formulation. | Related-identity and indication-specific evidence only. | |
| A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers | 2021 | Healthy Chinese volunteers | Single and multiple intravenous doses of recombinant full-length thymosin beta-4. | Related-identity evidence only. | |
| A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin beta4 in healthy volunteers | 2010 | Healthy volunteers | Single and multiple intravenous doses of full-length thymosin beta-4. | Related-identity evidence only; do not transfer directly to TB-500 fragment products. | |
| RGN-259 Dry Eye Trial | An ophthalmic dry-eye trial of RGN-259, a full-length-thymosin-beta-4-based investigational formulation. Route-, formulation-, indication-, and molecule-specific -- does not validate injectable TB-500 for tendon, ligament, muscle, or systemic repair. | ||||
| Thymosin Beta-4 and Venous Ulcers | A human study of full-length 43-amino-acid thymosin beta-4 in venous ulcers. This concerns a different molecule and formulation than the marketed TB-500 fragment and does not validate TB-500 efficacy, safety, or dosing. |
Animal / Cell / Preclinical Data
| Title | Year | Population / Model | Dose / Duration / Finding | Safety Notes | Source |
|---|---|---|---|---|---|
| Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro | 2024 | Developed and applied a UHPLC-Q-Exactive orbitrap MS/MS method to simultaneously quantify TB-500 and its metabolites in in-vitro experiments and rats, with in-vitro wound-healing activity screening. | |||
| Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential | 2012 | Synthesized and characterized the N-terminal acetylated LKKTETQ (Ac-LKKTETQ) fragment identified in TB-500, establishing direct analytical/molecular identity for anti-doping detection purposes. | |||
| Thymosin beta4 accelerates wound healing | 1999 | Rat wound model | Topical/intraperitoneal Tβ4 — Increased re-epithelialization and wound contraction in rat model. | Preclinical only; animal/cell findings do not establish human safety or efficacy. |
Regulatory Documents & Official Trial Registries
| Title | Year | Population / Model | Dose / Duration / Finding | Safety Notes | Source |
|---|---|---|---|---|---|
| Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks | 2026 | FDA safety and compounding review | Exact-fragment identity and current human-data/safety statement. | Applies to the TB-500 fragment, not full-length thymosin beta-4. | |
| FDA Advisory Panel Vote on Unapproved Peptides | 2026 | On July 23, 2026, the FDA Pharmacy Compounding Advisory Committee voted 8-6 with one abstention to recommend possible 503A-list inclusion for TB-500, KPV, and BPC-157. The vote was advisory and nonbinding and did not create FDA approval or an approved indication for any of the substances. | |||
| FDA Briefing Document — Pharmacy Compounding Advisory Committee Meeting, July 23–24, 2026 | 2026 | FDA advisory-committee review | Staff proposal pending advisory process. | The meeting remained upcoming on the research-review date. | |
| FDA Evaluation of TB-500-Related Bulk Drug Substances | 2026 | FDA's May 2026 evaluation of TB-500 free base and acetate for the 503A Bulks List found inconsistent identity and naming, inadequate physicochemical/quality characterization, no identified human administration data, no identified in-vivo pharmacologic wound-healing study, an in-vitro fibroblast scratch assay in which TB-500 did not significantly improve wound closure at the tested concentration, no adequate nonclinical toxicology, and immunogenicity/aggregation/impurity/sterility/endotoxin concerns. | |||
| The 2026 Prohibited List | 2026 | Anti-doping regulatory list | TB-500 is prohibited for athletes subject to the World Anti-Doping Code. | Anti-doping status is separate from clinical safety or efficacy. | |
| Recombinant Thymosin Beta-4 in Acute Myocardial Infarction | A registered trial of recombinant full-length thymosin beta-4 in acute myocardial infarction. Molecule-specific -- not TB-500 fragment evidence. | ||||
| Thymosin Beta-4 in Pressure Ulcers | A registered trial of full-length thymosin beta-4 in pressure ulcers. Molecule-specific -- not TB-500 fragment evidence. |
Review Articles / Secondary Sources
| Title | Year | Population / Model | Dose / Duration / Finding | Safety Notes | Source |
|---|---|---|---|---|---|
| The regenerative peptide thymosin β4 accelerates the rate of dermal healing in preclinical animal models and in patients | 2012 | Review | Wound repair mechanisms — Discusses migration, stem-cell mobilization, and anti-inflammatory mechanisms. | Secondary source; useful for context but not a substitute for primary study review. | |
| Thymosin beta-4 regenerative peptide review | 2011 | Review | Basic science and clinical applications — Reviews repair/regeneration roles in injured tissues. | Secondary source; useful for context but not a substitute for primary study review. | |
| Thymosin beta 4: A novel corneal wound healing and anti-inflammatory agent | 2009 | Review | Corneal injury/inflammation — Summarizes corneal wound-healing and anti-inflammatory effects. | Secondary source; useful for context but not a substitute for primary study review. |
Anecdotal Reported Patterns — Not Medical Advice
Anecdotal Reported Patterns — Not Medical Advice
Reported dosing patterns are included for educational context only. They are self-reported, unverified, not medical advice, and not instructions for human use. Community-submitted patterns are not yet available in this Phase 1 prototype; this section is a placeholder reserved for moderated, aggregated community data.
Lab Markers to Discuss With a Clinician
Educational topics only — not self-monitoring instructions.
FAQ
Disclaimer
Evidence involving full-length thymosin beta-4, recombinant thymosin beta-4, synthetic thymosin beta-4, RGN-259, or other molecule-distinct products is presented only as related biological context. It does not establish the efficacy, safety, pharmacokinetics, or dosing of the shorter marketed TB-500/LKKTETQ fragment. This page does not provide treatment, repair, recovery, injection, or dosing recommendations.
Educational use only. This content is provided for informational and research-summary purposes only. It is not medical advice, not a treatment recommendation, not a dosing guide, and not a substitute for care from a licensed medical professional. Nothing here is intended to diagnose, treat, cure, prevent, or mitigate disease. Reported dosing patterns, when shown elsewhere on the site, must be labeled either as Study / Trial Dosing or Anecdotal Reported Patterns — Not Medical Advice. Community reports are self-reported, unverified, and not scientific proof.
Community-reported experiences, once enabled, must be displayed only as moderated, anonymized, or aggregated data. They are anecdotal, self-reported, unverified, and should never be presented as proof of safety, efficacy, or expected results.
Content status: Website/CMS content draft; source verification and legal/privacy review required before public launch. Last updated 2026-08-09.
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