TB-500

Areas of active research — not promised effects

Each tag links to other compounds with research into that goal. Research use only: these are areas of study, not human-use claims.

Related by research scope · open each to compare

TB-500 is not an FDA-approved drug. It was placed on the FDA 503A bulk drug substances Category 2 list (significant safety risk designation) and subsequently removed from Category 2 effective approximately April 23, 2026, following HHS direction. Removal from Category 2 does NOT authorize compounding or human use; it means the substance exits the explicit prohibition tier and enters a formal evaluation process. The Pharmacy Compounding Advisory Committee (PCAC) is scheduled to review TB-500 (Thymosin Beta-4 Fragment, LKKTETQ) at its meeting of July 23–24, 2026, under docket FDA-2025-N-6895. Until a final FDA rulemaking places it on the 503A affirmative bulks list, compounding access remains unauthorized. Sale for human consumption remains unlawful.

Transparent blend · bci-1.0 · never paid-placement

Primary name

TB-500

Origin

TB-500 corresponds to the actin-binding domain of thymosin beta-4, an endogenous 43-amino-acid polypeptide found in virtually all nucleated mammalian cells. The fragment spanning residues 17–23 (Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln; CAS 885340-08-9; PubChem CID 62707662) was identified as the minimal sequence responsible for G-actin sequestration and cell-migration promotion. Unlike the full thymosin beta-4 protein, TB-500 is a synthetic, low-molecular-weight heptapeptide (~889 Da) that does not occur freely in nature at therapeutic concentrations.

Registry IDs

PubChem CID

62707662

CAS

885340-08-9

InChIKey

ADKDNDYYIZUVCZ-ZQNQAVPYSA-N

Molecular formula

C38H68N10O14

Molar mass

889.0 g/mol

Monoisotopic

888.49164688 Da

InChIKey

ADKDNDYYIZUVCZ-ZQNQAVPYSA-N

Appearance

White to off-white lyophilized powder

Solubility

Soluble in water and dilute aqueous buffers; reconstitution typically in sterile…

Sequence not available in current seed.

Stability: The heptapeptide is relatively stable as a lyophilized solid; susceptible to oxidation and enzymatic degradation in solution. pH stability optimal at approximat

Vial sizes

2 mg · 5 mg · 10 mg

Purity grades

research grade (>98% by HPLC)

Salt forms

Free base (primary)

• GHS hazard class on file
• PPE & spill response
• Disposal guidance
• Not-for-human-consumption posture

How much research exists, and of what maturity — never a verdict on whether it works.

Mechanism of action

• TB-500 binds monomeric G-actin through the same LKKT(X)E motif present in the full thymosin beta-4 protein, sequestering free actin monomers and preventing their incorporation into filamentous F-actin networks; this shifts the intracellular actin equilibrium in a manner that facilitates lamellipodia formation and directed cell migration
• Concurrently, the peptide activates integrin-linked kinase (ILK) signaling, promoting downstream phosphorylation events that stimulate keratinocyte and endothelial cell motility
• In rodent wound and ischemia models, these effects are accompanied by upregulation of vascular endothelial growth factor (VEGF) and accelerated capillary sprouting, suggesting a secondary pro-angiogenic axis
• NF-kB pathway modulation has also been reported in preclinical inflammation models, though the mechanistic hierarchy relative to actin sequestration remains unresolved

Pharmacokinetics (ADME)

Half-life

Approximately 1.5–3 hours plasma half-life (subcutaneous; rodent studies); formal human PK not published

Clearance

Presumed proteolytic degradation to constituent amino acids; route of elimination not formally characterized

PK–PD note: Rodent SC dosing at approximately 6 mg/kg produced Cmax of roughly 200–400 ng/mL at 0.5–1 h post-injection in preliminary reports. The plasma half-life is short, but tissue-level effects on actin remo…

Reading the evidence

• Evidence quality and gaps vary by application — see the cited grades above.
• Indexed-article counts span all evidence tiers, not only completed human trials.
• No first-party human-dosing, efficacy, or benefit claims are made here.

Key reviews & evidence-gap sources

• Thymosin Beta-4 and TB-500 in Tissue Healing, Regeneration, and Musculoskeletal Repair: A Scoping Review (MDPI Applied Sciences, 2026) — Anchoring scoping review; searched PubMed, Europe PMC, ClinicalTrials.gov through March 2026. Direct fetch blocked (HTTP 403); title/abstract confirmed via search snippet.
• Utilizing Developmentally Essential Secreted Peptides Such as Thymosin Beta-4 to Remind the Adult Organs of Their Embryonic State (PMC8228050)
• Thymosin β4: a multi-functional regenerative peptide. Basic Clin Pharmacol Toxicol. (PMID 22074294)

1 registered trial — 1 currently recruiting.

Phase 1
NCT07487363
TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD

RECRUITING

Summary (literature)

Formal toxicology studies specifically for the TB-500 fragment (CAS 885340-08-9) have not been published in the peer-reviewed literature as of 2026. Safety data for the parent molecule thymosin beta-4 from clinical development programs indicates a generally well-tolerated profile…

WADA status

Prohibited at all times under WADA 2026 Prohibited List: S0 (Non-Approved Substances) and S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics)…

Dominant research route: Subcutaneous (SC) is the dominant research-use route for the TB-500 fragment in preclinical and aggregate community protocols; intravenous (IV) is the route used in completed human Phase I RCTs of full-length thymosin beta-4 (NL005 / Ruff et al.), which is a distinct molecule from the 7-amino-acid TB-500 fragment

Full-length thymosin beta-4 (Tβ4, 43 aa) administered IV in healthy human volunteers in Phase I RCTs; TB-500 fragment (17-23) IV use described in equine doping-control detection models

Bioavailability: IV infusion delivers complete systemic exposure by definition; Phase I trials of recombinant human Tβ4 (NL005) at 0.05–25.0 μg/kg single dose and 0.5–5.0 μg/kg daily×10 showed dose-proportional Cmax and AUC with no obvious accumulation; terminal clearance consistent across dose groups

Human RCT evidence is for full-length Tβ4 (NL005 / Ruff et al.), NOT the 7-amino-acid TB-500 fragment. Ho et al. 2012 detected intact TB-500 and metabolites in equine urine and plasma after administration for doping-control purposes; no human detectability data available

Most commonly referenced route in published preclinical TB-500/Tβ4 literature and aggregate research-use protocols; rodent models report predictable systemic exposure

Bioavailability: Aggregator monographs cite SC bioavailability of ~60–80% with gradual absorption in animal models; plasma half-life of approximately 2–3 hours with detectable levels up to 24 h post-injection reported in animal PK studies (secondary citations; primary PK manuscript not retrieved)

SC is the dominant research-use route for the TB-500 fragment in community/aggregator protocols; no retrieved human RCT uses SC TB-500 fragment. Bioavailability figures are secondary aggregator claims, not independently verified primary sources

Described in some animal protocols and aggregate community protocols for site-specific research endpoints

Bioavailability: No retrieved primary PK study quantifying IM bioavailability of TB-500 fragment; full-length Tβ4 clinical trials used IV, not IM

IM appears in aggregator and community sources as an alternative to SC for localized-tissue research questions; no human RCT evidence for IM TB-500 fragment was retrieved

Used in rodent (mouse/rat) preclinical models of TB-500 and Tβ4

Bioavailability: No retrieved primary PK comparison of IP vs SC bioavailability; IP is a standard rodent laboratory route

IP is frequently cited alongside SC as a historical rodent administration route in TB-500 preclinical literature; Rahaman et al. 2024 quantified TB-500 and metabolites in rats (route not explicitly confirmed from abstract alone)

Emerging/exploratory; no retrieved controlled PK study of intranasal TB-500 in any species

Bioavailability: No established bioavailability data; aggregator sources note TB-500 (~4963 Da, 43 aa parent) is larger than BPC-157 and may achieve lower intranasal absorption; mucosal absorption described as uncertain

Intranasal TB-500 is a formulation trend in community/aggregator literature without published PK confirmation; cited as a practical needle-free research alternative only

Listed among preclinical administration routes in aggregator monographs; full-length Tβ4 topical wound-healing studies exist in animal models

Bioavailability: No retrieved primary PK study quantifying topical bioavailability of the TB-500 fragment

Topical route is mentioned in aggregator summaries of preclinical protocols; primary topical studies retrieved relate to full-length Tβ4 in dermal wound models, not the 17-23 fragment

Not studied as an active route; oral bioavailability of TB-500 not demonstrated

Bioavailability: TB-500 is not characterized as resistant to gastric proteolysis; oral bioavailability has not been demonstrated in retrieved literature

Oral route is not an established research route; capsule formulations are described only for studying peptide stability/degradation kinetics, not for systemic delivery

Animal & human figures are kept visibly separate so studied animal doses are never misread as human guidance.

Sorted A–Z by vendor — never by price

Weekly median $/mg from the live vendor crawl.

Researched storefront prices, bucketed

p25 $7.55 · median $9.93 · p75 $13.70 · 6 researched vendors

Legit, COA-backed band: $7.00–$14.50/mg.

Value rule: don't just buy the cheapest — a price under $3/mg is a red flag. Pair price with COA and independent-test grade.

Estimated cost of research (10 mg)

Vial (best researched price)

$54

Bacteriostatic water (generic estimate)

$6

Syringes / supplies (generic estimate)

$12

What each test proves — general guidance, plus this compound's researched purity data

Purity on the current market (researched)

Vendor labels typically claim ≥99% purity (HPLC). Independent aggregate testing by Janoshik Analytical (2024) found lower-tier gray-market peptide vendors delivering 71–91% purity despite claiming 99%+. No TB-500-specific lot-level purity distribution was identified in retrieved sources.

Independent labs cited for this compound

No FDA recall, market withdrawal, or safety alert specific to TB-500 was found in the FDA Recalls, Market Withdrawals & Safety Alerts database or in retrieved enforcement sources. TB-500 is not an FDA-approved drug, so it does not appear in drug-recall pathways; enforcement has instead taken the form of import detention (DWPE), compounding prohibitions (503A Category 2), and anti-doping sanctions.

Buyer red-flag checklist

• TB-500 is not FDA-approved for any indication; no regulatory oversight governs its manufacturing, purity, dosing accuracy, or contamination.
• Sold online as a 'research chemical' with 'Research Use Only' labels while frequently marketed/dosed for human use — a pattern FDA has cited as evidence of intended drug use in warning letters to peptide vendors.
• Prohibited at all times under WADA Prohibited List S2.3 since 2018; athlete use triggers anti-doping violations (e.g., 4-year CCES sanction).
• Classified as FDA 503A Category 2 bulk drug substance (Feb 2026 reclassification) — prohibited for compounding; cannot be legally dispensed by US pharmacies.
• No completed, published human RCTs for TB-500 (the 17-AA Ac-LKKTETQ fragment) for any indication as of April 2026.
• Gray-market quality inconsistency: independent testing shows ~43% of peptides fail label purity claims, with some lots at 71–91% purity.
• Originated in equine doping contexts; detection methods were developed for horse-racing anti-doping before human therapeutic development.

GMP vs research-grade: the chemistry (SPPS + HPLC + MS) is identical — the difference is the quality system.

Underdosing / mislabeling: Janoshik Analytical reported that 43% of peptides tested in 2024 failed to meet label purity claims, with lower-tier vendors showing purities of 71–91% despite claiming 99%+. This is an aggregate figure across gray-market peptides (not TB-500-specific) and is consistent with the absence of FDA manufacturing oversight for unapproved research chemicals.

• Detention Without Physical Examination of Unapproved New Drugs Promoted In The U.S. Revision dated 05/19/2026. Authorizes DWPE of unapproved new drug products from firms on the Red List. TB-500, as an unapproved new drug, falls within this alert's scope.66-41
• An RUO label is not an import exemption — CBP judges actual intended use.
• Lyophilized powder is ambient-stable in transit; temperature control needed for > 7-day transit.
• US-warehouse vendors dodge import scrutiny — they cost more but ship more reliably.

Every item dated & sourced

Prohibited at all times. Thymosin beta-4 and its derivatives/fragments (including TB-500) appear on the WADA Prohibited List; cited under S0 (Non-Approved Substances) and/or S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics). Classified as a non-Specified Substance per some sources.

No granted patents identified in current seed. Composition-of-matter coverage is limited given the peptide's synthetic origin.

• IACUC / IRB research context
• RUO buyer responsibilities & documentation
• Veterinary / alternative-use where lawful
• Jurisdiction-aware "who may lawfully obtain"

What people discuss

Reported concerns — discussion, not established effects

Reading caveats

• self-report anecdotes without controls
• vendor-affiliated promotion
• selection bias toward positive injury-recovery stories
• conflation of TB-500 fragment with full Thymosin Beta-4

Manually researched from reddit, youtube, x— theme weights are research estimates, not live counts; aggregated & de-identified. No individual posts, quotes, or usernames are ever shown.

Relative research / market volume — populated once the activity stream is wired

Inline tooltips for lyophilized, RUO, EU/mg, SPPS, 503A and more.

Toggle plain-language ↔ scientific in the header.

• How to read a COA
• Free base vs acetate
• Understanding evidence grades

Synthetic 9-amino-acid fragment (Ac-LKKTETQ) of thymosin beta-4 studied in animal models for tissue repair, cell migration, and angiogenesis. Approximately 16 articles are indexed (literature last scanned 2026-05-29). US regulatory status: Research use only; not approved; removed from FDA 503A Category 2 restriction list April 2026, PCAC review scheduled July 2026. Research use only.

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