Updated August 2026
TB-500 Dosage: Human Evidence, Research Protocol, and Reconstitution
Research status: TB-500 means the synthetic N-acetylated seven-amino-acid fragment Ac-LKKTETQ (thymosin-β4 residues 17–23) — not full-length 43-amino-acid thymosin-β4. FDA's 2026 review found no clinical study in which TB-500 free base or acetate was administered to humans. Direct dosing evidence is primarily analytical and metabolism work in horses, rats, and laboratory systems. Modern injection schedules are community protocols, not clinically validated doses. NCT07487363 is a fictional ClinicalTrials.gov example record — not human evidence.
There is no established human dosage for the TB-500 fragment. The most common online protocol — 2–2.5 mg subcutaneously twice weekly for 4–6 weeks, often followed by once-weekly use — is anecdotal and lacks a traceable clinical origin.
Direct animal exposure differs sharply: two thoroughbred geldings received a single 10 mg SC dose for doping-control analysis; six-week-old rats received 50 mg/kg IP once for metabolism research. Neither study tested injury healing. At 50 mcg/mL in vitro, parent TB-500 did not increase fibroblast scratch closure; the truncated metabolite Ac-LKKTE showed activity.
Full-length thymosin-β4 human studies (IV 42–1,260 mg, NL005 mcg/kg, topical wound formulations, RGN-259 eye drops) concern a different molecule and cannot validate TB-500 dosing. For a 10 mg vial at 2 mL, 2.5 mg = 0.5 mL = 50 U on a U-100 syringe — concentration arithmetic only, not a validated dose.
TB-500 dosage in 30 seconds
| Question | Evidence-based answer |
|---|---|
| Molecule covered | N-acetyl-LKKTETQ — Tβ4 residues 17–23 |
| Free-base mass | ~889.01 Da |
| Acetate representation | ~949.1 Da (FDA 1:1 acetate) |
| Published human TB-500 dose | None identified |
| Common anecdotal amount | 2–2.5 mg per administration |
| Common anecdotal frequency | Twice weekly × 4–6 weeks; then often weekly |
| Sport status | WADA S2 — prohibited at all times |
| Central dosing lesson | Do not transfer full-length Tβ4 evidence to TB-500 |
- No established human dosage for TB-500 free base or acetate by any route
- Common anecdotal protocol: 2–2.5 mg SC twice weekly × 4–6 weeks, then often once weekly
- Direct horse exposure: 10 mg SC once (analytical PK — not therapeutic)
- Direct rat exposure: 50 mg/kg IP once (metabolism — not efficacy)
- Direct cell concentration: 50 mcg/mL — parent inactive; Ac-LKKTE active in one assay
- Full-length Tβ4 doses cannot transfer to the seven-residue fragment
- NCT07487363 is fictional — not an actual trial or human dose evidence
- WADA S2: prohibited at all times as a thymosin-β4 derivative
What Is TB-500?
TB-500 is a nonstandardized commercial name most consistently associated with Ac-LKKTETQ, an N-terminally acetylated heptapeptide corresponding to amino acids 17–23 of human thymosin-β4. The fragment was identified in a seized or suspected doping product and chemically synthesized for confirmation.
Full-length thymosin-β4 is a 43-amino-acid intracellular peptide involved in actin regulation. A seven-residue fragment can have different binding, degradation, distribution, active metabolites, immunogenicity, and dose-response behavior than the parent peptide.
| Property | FDA-reviewed value |
|---|---|
| Chemical description | N-acetyl-L-leucyl-L-lysyl-L-lysyl-L-threonyl-L-alpha-glutamyl-L-threonyl-L-glutamine |
| Sequence shorthand | Ac-LKKTETQ |
| Relationship to Tβ4 | Residues 17–23 |
| CAS (free base) | 885340-08-9 |
| UNII (free base) | QHK6Z47GTG |
| Formula | C38H68N10O14 |
| Free-base mass | 889.01 g/mol |
| Acetate representation | C38H68N10O14·CH3COOH; 949.1 g/mol |
Naming is not reliably standardized. FDA found submitted documents mixed free base and acetate, used mismatched CAS numbers, and provided certificates for different forms from the nominated substance. A vial labeled only “TB-500” is not adequately identified without sequence, acetylation, salt, and assay confirmation.
Identity gate
Ac-LKKTETQ vs full Tβ4 vs salts, metabolites, and look-alikes
This page's subject — N-acetylated seven-residue Tβ4 fragment 17–23
Sequence: Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln-OH. Free-base formula C38H68N10O14; ~889.01 Da. Identified in seized doping products (Esposito et al., 2012).
- Length
- 7 amino acids
- Sequence / form
- Ac-LKKTETQ
- Studied routes
- SC in horses (10 mg once); IP in rats; in vitro
- Evidence types
- Analytical, metabolism, limited cell assays
- Human results
- No published human-administered dose identified
Findings do not transfer between molecules. Full-length Tβ4 human doses cannot validate TB-500 schedules.
Product, Salt, and Assay Checks
Before any controlled research use, document the exact test article. A “99% purity” chromatogram cannot establish vial content, sterility, activity, aggregation, or correct identity.
| Quality attribute | Question it answers |
|---|---|
| Intact-mass LC-MS | Main peak matches Ac-LKKTETQ — not full Tβ4, unacetylated LKKTETQ, or another fragment? |
| Sequence confirmation | All seven residues present in correct order? |
| N-terminal acetylation test | Product is actually Ac-LKKTETQ? |
| Quantitative peptide assay | Active peptide amount independent of HPLC area purity? |
| Acetate and water content | Label mass = free-base equivalent, acetate material, or hydrated gross mass? |
| Related-substance analysis | Truncations Ac-LKKTET, Ac-LKKTE, Ac-LKKT, Ac-LKK, Ac-LK quantified? |
| Aggregate test | Higher-order species present? |
| Sterility, endotoxin, bioburden | Acceptable for intended laboratory route? |
| Stability-indicating assay | Identity, assay, purity, aggregation within spec over use period? |
U.S. and International Status
There is no U.S. prescribing label or approved medicinal-product dosage for TB-500 free base or acetate. FDA's 2026 review reported no approved TB-500 products in the European Union, Canada, Australia, the United Kingdom, and other jurisdictions reviewed, and no recognition in the European or Japanese pharmacopoeias.
In July 2026, FDA staff recommended against placing TB-500 free base and acetate on the Section 503A Bulks List. The Pharmacy Compounding Advisory Committee subsequently recommended inclusion. Advisory-committee recommendations are nonbinding and separate from drug approval or proof of effectiveness.
| Regulatory question | Current answer |
|---|---|
| U.S. prescribing dose | None |
| Approved international dose | None identified in jurisdictions FDA reviewed |
| USP/NF monograph | None |
| FDA staff 2026 Bulks List recommendation | Do not include free base or acetate |
| Advisory committee role | Nonbinding recommendation to FDA |
| Does compounding status establish efficacy? | No |
Regulatory timeline
FDA 2026 staff vs PCAC · WADA S2 · no approved dose
2012
Ac-LKKTETQ identity in doping products
Analytical work identifies TB-500 active content as N-acetylated Tβ4 residues 17–23.
2026 WADA
S2 prohibition at all times
Thymosin-β4 and derivatives such as TB-500 prohibited under S2 — in and out of competition.
Jul 2026
FDA staff Bulks List recommendation
Staff recommended against placing TB-500 free base and acetate on the Section 503A Bulks List after reviewing identity, historical use, effectiveness, and safety.
Jul 23, 2026
PCAC advisory vote
Pharmacy Compounding Advisory Committee recommended inclusion despite staff recommendation. Nonbinding — separate from drug approval or proof of effectiveness.
Pending
Final FDA Bulks List action
Check FDA's final list action rather than inferring legal status from the advisory vote alone.
PCAC recommendation is nonbinding. Compounding-list inclusion ≠ approval. Check FDA's final Bulks List action. WADA S2 prohibits TB-500 at all times.
Dosage Used in Human Clinical Research
No published human-administered dose was identified. FDA searched PubMed, Embase, ClinicalTrials.gov, DailyMed, Drugs@FDA, and other sources and did not find clinical studies in which TB-500 free base or acetate was administered to patients. It also reported no human exposure data for drug products containing the fragment by any route.
Human evidence status
No published human TB-500 dose — fictional NCT is not evidence
Fictional registry record — do not cite as trial evidence
NCT07487363: TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD
“This fictional study is an example of a ClinicalTrials.gov-style record.”
The record displays Phase 1/2, recruiting, 80 participants, and dose cohorts — but its own brief summary states it is fictional, dose levels are not public, and it must not be counted as actual enrollment, human exposure, or established safe dose levels.
View record →| Human-evidence question | Finding |
|---|---|
| Published human TB-500 dose | None identified by FDA 2026 review |
| Human exposure data (any route) | None identified for TB-500 free base or acetate |
| Published Phase 1 safety/PK study | None identified |
| Published wound-healing trial | None identified |
| Published muscle/tendon/ligament trial | None identified |
| Verified interventional trial with usable dose | None verified |
| NCT07487363 registry record | Explicitly fictional example — not actual trial evidence |
| Full-length Tβ4 human dosing | Exists separately — cannot transfer to fragment |
| Common anecdotal amount | 2–2.5 mg per administration (unvalidated) |
| Common anecdotal frequency | Twice weekly × 4–6 weeks, then often once weekly |
| Human weight-based dose | None established |
| Human half-life | Unknown — horse parent unquantifiable ~6–10 h after 10 mg SC |
The ClinicalTrials.gov fictional study record
NCT07487363 is titled “TB-500 (Thymosin Beta 4 17-23 Fragment) for Cardiovascular Biomarkers in Stable ASCVD.” Its public modules display Phase 1/2, recruiting, 80 participants, and dose cohorts — but the record's own brief summary states: “This fictional study is an example of a ClinicalTrials.gov-style record.”
It should not be counted as an actual trial, proof of enrollment, human exposure, or evidence that a sponsor has established safe dose levels. Dose levels in the record are not public.
Related human dosing: full-length thymosin-β4
The studies below prevent evidence misattribution. They concern full-length 43-amino-acid Tβ4, not TB-500.
| Product / study | Dose | Route | Why not TB-500 dosing |
|---|---|---|---|
| Synthetic full-length Tβ4 Phase 1 | 42, 140, 420, or 1,260 mg | IV | Different 43-aa molecule and formulation |
| Recombinant Tβ4 / NL005 | 0.05–25 mcg/kg once; 0.5–5 mcg/kg × 10 days | IV | Recombinant full-length molecule; weight-based IV |
| Topical Tβ4 venous-ulcer study | Including 0.03% | Topical | Local wound formulation — not injected fragment |
| RGN-259 ocular | 0.1% ophthalmic | Eye drops | Local eye product — not systemic fragment |
TB-500 Research Dosage
The schedules below document what researchers encounter online. They are not established treatment directions.
Commonly reported anecdotal protocols
| Protocol | Amount | Frequency | Route | Duration | Evidence basis |
|---|---|---|---|---|---|
| Common loading | 2–2.5 mg | Twice weekly | Usually SC | 4–6 weeks | Repeated online — no matched human trial |
| Common maintenance | 2–2.5 mg | Once weekly | Usually SC | 4–8+ weeks | Anecdotal continuation |
| Broader range | 2–5 mg/week total | Once or divided | Usually SC | 4–12 weeks | Community/practitioner range |
| Higher loading variant | 5 mg | Twice weekly | Usually SC | 1–2 weeks | More aggressive community variant |
| Injury-site IM variant | 2–5 mg | 1–2× weekly | IM near injury | 4–6 weeks | No evidence local IM improves targeting |
Direct evidence supports only three clear exposure statements: (1) 10 mg SC once produced measurable parent peptide and metabolites in two thoroughbred geldings; (2) 50 mg/kg IP once produced urinary metabolites in rats; (3) 50 mcg/mL in vitro compared parent fragment and metabolites in a fibroblast scratch assay.
The evidence does not support a human loading phase, maintenance requirement, local injury targeting, four-to-six-week duration, tissue saturation, or combination with BPC-157. Horse plasma parent peptide became unquantifiable within approximately 6–10 hours after 10 mg SC — this does not prove a long human half-life or justify twice-weekly administration.
Evidence split
Direct experiments vs community anecdotal protocols
Direct TB-500 experiments
Single-dose analytical / metabolism studies
- Molecule
- Ac-LKKTETQ specified
- Amount
- Horse: 10 mg once; rat: 50 mg/kg once; cells: 50 mcg/mL
- Frequency
- Single exposure only
- Route
- SC (horse), IP (rat), cell culture
- Duration
- Hours to short analytical follow-up
- Purpose
- Detection, PK, metabolism, cell screening
- Efficacy evidence
- Parent inactive at 50 mcg/mL in one scratch assay
- Safety basis
- No fragment-specific toxicology program identified by FDA
Anecdotal human reports
Community convention — no clinical origin
- Molecule
- Often “TB-500” without sequence or salt verification
- Amount
- Commonly 2–2.5 mg; broader 2–5 mg; higher variants exist
- Frequency
- Twice weekly × 4–6 weeks, then often once weekly
- Route
- Usually SC; IM near injury also claimed
- Duration
- Commonly 4–12 weeks
- Purpose
- Recovery, wound, tendon, ligament, “systemic healing” claims
- Efficacy evidence
- Uncontrolled testimonials and commercial practice
- Safety basis
- No reliable denominator or standardized product
Reported Research Dosage Range
| Field | Evidence-based summary |
|---|---|
| Direct human range | None established |
| Common anecdotal amount | 2–2.5 mg per administration |
| Broader anecdotal amount | ~2–5 mg; higher variants exist |
| Common anecdotal frequency | Twice weekly during 4–6-week loading phase |
| Typical reported duration | 4–6 weeks loading; 4–8 weeks maintenance |
| Direct nonclinical overlap | None — single 10 mg horse or 50 mg/kg rat for analytical purposes |
| Evidence quality | Insufficient for a human regimen |
This table describes the online landscape. It should not be converted into “minimum,” “optimal,” or “maximum” human dosing.
Complete Evidence-Anchored Research Protocol
Single-dose equine pharmacokinetic and metabolite-characterization study of Ac-LKKTETQ. This is a controlled nonclinical analytical protocol, not an injury-treatment experiment. It preserves the only well-documented direct SC exposure — 10 mg once in thoroughbred geldings — while strengthening controls, blinding, product characterization, and sampling.
Research question: After one 10 mg SC dose of identity-confirmed TB-500 free base, what are the plasma concentration-time profile and plasma/urine metabolite patterns in adult thoroughbred geldings compared with vehicle controls?
Equine PK protocol
Single 10 mg SC dose — sampling timeline (nonclinical analytical)
Single SC administration
- Time
- Day 0
- Plasma
- —
- Urine
- —
- Note
- 10 mg active-peptide equivalent once — no loading, maintenance, or repeat dose
Nonclinical analytical protocol — not a human loading/maintenance healing cycle. No loading phase, maintenance, titration, or repeat dose.
Design summary
| Element | Prespecified protocol |
|---|---|
| Species / population | Healthy adult thoroughbred geldings |
| Suggested size | 8 animals: 6 TB-500 + 2 vehicle (analytical pilot) |
| Test dose | 10 mg active-peptide equivalent once |
| Route | Subcutaneous — single administration only |
| Comparator | Matched vehicle once |
| Primary endpoint | Plasma parent-peptide concentration-time profile and AUC0–t |
| Efficacy endpoints | None — no wound, tendon, performance, or healing claim |
A successful analytical replication does not justify a repeated equine cycle, a human dose, an injury-healing claim, or performance use. It supports only assay performance and fragment pharmacokinetics/metabolism in that model.
Animal and Laboratory TB-500 Doses
Direct TB-500 exposure evidence
Three direct exposures
- Horse: 10 mg SC once — PK/metabolism analytical study
- Rat: 50 mg/kg IP once — urinary metabolite identification
- Cells: 50 mcg/mL — parent inactive; Ac-LKKTE active in scratch assay
None of these establish a human healing dose or twice-weekly schedule.
| Model | Dose | Route | Purpose | Transfer boundary |
|---|---|---|---|---|
| Two thoroughbred geldings | 10 mg | SC once | Doping-control analytical method | Not therapeutic horse or human dose |
| Six-week-old SD rats | 50 mg/kg | IP once | In vivo metabolite identification | Not efficacy or HED |
| Fibroblast scratch assay | 50 mcg/mL | In vitro | Screen parent and metabolites | Cell concentration — not injection dosing |
| Human microsomes / serum | Study-specific | In vitro | Metabolic mapping | Ex vivo metabolism — not human exposure |
The horse study used a fixed 10 mg analytical exposure in a large animal; the rat study used 50 mg/kg IP — orders of magnitude apart on a body-weight basis. Neither established efficacy, a therapeutic window, repeat-dose safety, or route equivalence. No human-equivalent dose is calculated on this page.
Reconstitution and U-100 Syringe Math
Calculation boundary: These tables answer concentration search intent. They do not establish a human dose, validate the commonly reported protocol, prove sterility or stability, or show that a research vial should be administered. U-100 units describe liquid volume only — not milligrams or micrograms of peptide.
Core equations: Concentration (mg/mL) = vial mg ÷ final mL; Volume (mL) = target mg ÷ concentration; U-100 units = volume mL × 100.
Reconstitution math
5 mg @ 1/2 mL · 10 mg @ 1/2 mL — concentration arithmetic only
Vial preset
Target amount
10 mg · 2 mL (5 mg/mL) · concentration ≈ 5.00 mg/mL · ≈ 0.05 mg per U-100 unit
2.5 mg = 0.500 mL = 50.0 U-100 units
Highlighted: 10 mg/2 mL → 2.5 mg = 0.5 mL = 50 U (arithmetic only)
2.5 mg = 0.50 mL = 50 U — commonly cited community math
Calculation reference only — not a dose recommendation. Free base (~889 Da) vs acetate (~949 Da) mass basis must be confirmed before any concentration math.
5 mg vial · 1 mL final (5 mg/mL)
| Peptide amount | Volume | U-100 units |
|---|---|---|
| 1 mg | 0.20 mL | 20 U |
| 2 mg | 0.40 mL | 40 U |
| 2.5 mg | 0.50 mL | 50 U |
| 5 mg | 1.00 mL | 100 U |
5 mg vial · 2 mL final (2.5 mg/mL)
| Peptide amount | Volume | U-100 units |
|---|---|---|
| 1 mg | 0.40 mL | 40 U |
| 2 mg | 0.80 mL | 80 U |
| 2.5 mg | 1.00 mL | 100 U |
| 5 mg | 2.00 mL | 200 U (exceeds 1 mL syringe) |
10 mg vial · 2 mL final (5 mg/mL)
| Peptide amount | Volume | U-100 units |
|---|---|---|
| 1 mg | 0.20 mL | 20 U |
| 2 mg | 0.40 mL | 40 U |
| 2.5 mg | 0.50 mL | 50 U |
| 5 mg | 1.00 mL | 100 U |
| 10 mg | 2.00 mL | 200 U (exceeds 1 mL syringe) |
10 mg vial · 1 mL final (10 mg/mL)
| Peptide amount | Volume | U-100 units |
|---|---|---|
| 1 mg | 0.10 mL | 10 U |
| 2 mg | 0.20 mL | 20 U |
| 2.5 mg | 0.25 mL | 25 U |
| 5 mg | 0.50 mL | 50 U |
FDA lists 889.01 Da for TB-500 free base and 949.1 Da for the 1:1 acetate representation. Common errors include treating U-100 units as peptide-mass units, ignoring free-base vs acetate mass, and converting the 10 mg horse dose or 50 mg/kg rat dose into a human schedule.
Why Reported TB-500 Schedules Vary
Half-life: Horse data show parent peptide unquantifiable around 6–10 hours — not a human half-life and not support for twice-weekly dosing. Online claims of a multiday or ~7-day half-life lack direct human PK evidence.
Metabolites: Ac-LKKTETQ is progressively truncated at its C-terminus. In one cell assay, parent was inactive at 50 mcg/mL while Ac-LKKTE increased scratch closure — repeated parent dosing could create effects dependent on metabolite formation rather than parent concentration alone.
Route: Direct evidence includes SC (horse) and IP (rat). Community pages alternate SC and IM without human PK support for local injury targeting.
Loading/maintenance: No human trial shows tissue loading, a plateau, or that weekly maintenance preserves a measured effect.
Claim checker
Half-life, loading, local IM, Tβ4 transfer, fictional NCT, and stack claims
No direct human PK study exists. In two horses given 10 mg SC, parent peptide became unquantifiable around 6–10 hours. That is not a human half-life and does not justify multiday dosing intervals.
Storage and Handling
FDA summarized product-sheet storage for TB-500 free base as: powder −80°C for 2 years or −20°C for 1 year; in solvent −80°C for 6 months or −20°C for 1 month; sealed, protected from moisture and light, under nitrogen.
For TB-500 acetate, FDA found conflicting vendor information ranging from 2–8°C to below −15°C. These are bulk-reagent statements, not a universal beyond-use date for a sterile multidose preparation.
- Follow the exact lot certificate and a stability-indicating study.
- Do not infer a 28-day use period from bacteriostatic water alone.
- Inspect for haze, precipitate, particles, or unexplained volume loss before use.
Safety and Monitoring
Direct human adverse-event rates are unavailable because an adequate molecule-specific human dataset has not been identified. Full-length Tβ4 tolerability cannot establish TB-500 safety.
Safety summary
Human adverse-event rate
UnknownNo adequate molecule-specific human dataset identified by FDA
Acute / repeat-dose toxicology
Not identifiedFDA found no fragment-specific toxicology program
Identity and quality
Elevated concernConflicting naming, missing assay/aggregate/endotoxin controls in reviewed materials
Immunogenicity
Theoretical product-quality riskAggregates and impurities may provoke immune reactions by injectable routes
Full-length Tβ4 safety transfer
Not validParent-peptide tolerability cannot establish TB-500 fragment safety
Condition-specific concerns
Any human investigation would require specialist review for active malignancy, recent cancer treatment, autoimmune disease, immunodeficiency, transplant, bleeding disorder, anticoagulant use, serious infection, significant organ disease, pregnancy, breastfeeding, or prior severe peptide reaction.
Human cancer risk is unknown. Repair, cell-migration, and angiogenesis pathways create a theoretical concern, but evidence neither proves causation nor establishes long-term safety.
Mechanism: TB-500 vs Full-Length Tβ4
The scientifically accurate mechanism view treats three separate nodes — full-length thymosin-β4, parent TB-500/Ac-LKKTETQ, and TB-500 metabolites — rather than one continuous pathway from actin binding to healed tendon.
| Mechanism / claim | Full-length Tβ4 | TB-500 fragment |
|---|---|---|
| G-actin sequestration | Core well-characterized function | Contains part of binding region — equivalence not established |
| Cell migration | Demonstrated in parent systems | Parent failed one scratch assay at 50 mcg/mL |
| Wound closure | Parent has animal and topical human research | No direct human trial; no in vivo fragment wound-healing study identified |
| Tendon / ligament healing | Some related preclinical literature | No published human TB-500 trial |
| Active metabolites | Parent produces several relevant fragments | Ac-LKKTET → Ac-LK cascade; activity incompletely mapped |
TB-500 metabolism
Ac-LKKTETQ → C-terminal truncated metabolites
- Where detected
- Horse plasma/urine; rat; in-vitro systems
- Scratch / wound-closure note
- No increase in closure at 50 mcg/mL (FDA-reviewed assay)
Parent inactive at 50 mcg/mL in FDA-reviewed assay; Ac-LKKTE metabolite showed activity. Metabolite concentration is not parent-peptide dosing.
Dosage Evidence Ladder
How established is TB-500 dosing? Very poorly established. No verified human dose, pharmacokinetic target, therapeutic window, loading requirement, or maintenance schedule exists. The most repeated protocol is anecdotal; direct fragment research used single exposures for analytical and metabolism objectives.
Dosage evidence ladder
Very poorly established — anecdotal protocols dominate search results
| Evidence level | TB-500 evidence | Confidence |
|---|---|---|
| Approved medicinal-product dosing | None identified | None |
| Human TB-500 clinical-trial dosing | None verified — NCT07487363 is explicitly fictional | None |
| Published direct nonclinical dosing | Single-dose horse (10 mg SC) and rat (50 mg/kg IP) metabolism studies | Limited — analytical purpose only |
| Direct in vitro concentration | 50 mcg/mL scratch assay — parent inactive; metabolite active | Limited and mixed |
| Full-length Tβ4 human dosing | Substantial but separate molecule and routes | Cannot transfer to fragment |
| Anecdotal research protocols | 2–2.5 mg twice weekly commonly repeated online | Very low — no traceable clinical origin |
| Long-term / repeat-dose evidence | Absent | Fragment toxicology and human safety not established |
Anti-Doping Status
The 2026 WADA Prohibited List explicitly includes “Thymosin-β4 and its derivatives e.g. TB-500” under S2, Peptide Hormones, Growth Factors, Related Substances and Mimetics. It is prohibited at all times, in and out of competition.
Athletes remain responsible for what enters their bodies. A prescription, compounded label, “research use only” vial, or undisclosed blend does not remove anti-doping risk.
Frequently Asked Questions
What is the standard TB-500 dose?
There is no established human standard. The most common online claim is 2–2.5 mg SC twice weekly for 4–6 weeks, but no published human dose-ranging trial validates that schedule.
What is the TB-500 loading dose?
“Loading” commonly means 2–2.5 mg twice weekly, sometimes as high as 5 mg twice weekly. The phase is anecdotal; no study shows tissue loading occurs or improves outcomes.
What is the TB-500 maintenance dose?
Community pages often report 2–2.5 mg once weekly or 2–6 mg per month. No human PK or controlled trial shows maintenance is needed or effective.
How often is TB-500 used in research?
Direct published animal studies used a single administration. Repeated weekly protocols come from community practice, not direct therapeutic experiments with the fragment.
How long is a TB-500 cycle?
Online cycles commonly last 4–6 weeks, sometimes followed by 4–8 weeks of maintenance. There is no validated cycle length or automatic repeat schedule.
Does TB-500 need to be tapered?
No taper has been scientifically established. Direct animal studies used one dose; no human withdrawal dataset exists.
Is TB-500 dosed by body weight?
No human weight-based regimen exists. The 50 mg/kg rat dose was an IP metabolism experiment and should not be converted into human dosing.
Is TB-500 the same as thymosin beta-4?
No. TB-500 is usually a seven-residue N-acetylated fragment; full-length Tβ4 has 43 amino acids. Their human evidence and doses are not interchangeable.
Does TB-500 build muscle or heal tendons?
No controlled human study shows increased muscle mass, tendon/ligament healing, or muscle-tear recovery from verified Ac-LKKTETQ.
Does injection near an injury work better?
No human evidence shows local SC or IM placement targets the fragment to an injury or improves healing. Direct IM fragment PK data were not identified by FDA.
What is TB-500's half-life?
A human half-life is unknown. In two horses given 10 mg SC, parent peptide became unquantifiable around 6–10 hours. That cannot define a human dosing interval.
Why is TB-500 dosed twice weekly online?
The original basis is unclear — likely repeated copying, vial convenience, or extrapolation from unrelated research; not supported by direct human PK.
Did TB-500 work in a wound-healing cell study?
At 50 mcg/mL, parent Ac-LKKTETQ did not increase fibroblast scratch closure in the FDA-reviewed study. The Ac-LKKTE metabolite showed activity.
Is there a real TB-500 clinical trial?
No verified administered-human trial with usable dosing was identified. NCT07487363 explicitly says it is a fictional ClinicalTrials.gov-style example and must not be treated as evidence.
How many U-100 units is 2.5 mg from a 10 mg vial at 2 mL?
Concentration is 5 mg/mL. A 2.5 mg amount occupies 0.5 mL, which equals 50 U. This is arithmetic, not a dose recommendation.
How many units is 2 mg from a 5 mg vial at 2 mL?
Concentration is 2.5 mg/mL. Two milligrams occupies 0.8 mL, which equals 80 U.
Can reconstituted TB-500 be stored for 28 days?
Not on the basis of bacteriostatic water alone. A formulation-specific stability study is required.
Is TB-500 free base the same dose as TB-500 acetate?
Only if the label reports the same active-moiety equivalent and the assay confirms it. Gross acetate salt mass and free-base peptide mass are not automatically equal.
Can TB-500 be combined with BPC-157?
No controlled human study establishes a safe or effective ratio, schedule, or advantage for the “Wolverine stack.”
What are the side effects of TB-500?
A reliable human side-effect rate is unavailable. Plausible risks include hypersensitivity, anti-drug antibodies, impurities, aggregates, injection injury, infection, endotoxin, incorrect identity, and unknown organ or long-term effects.
Can TB-500 cause cancer?
Human cancer risk is unknown. Repair and angiogenesis pathways create a theoretical concern, but evidence neither proves causation nor establishes long-term safety.
Is TB-500 prohibited in sport?
Yes. WADA explicitly lists thymosin-β4 and derivatives such as TB-500 under S2, prohibited at all times.
Key References
FDA
2026 scientific review of TB-500 free base and acetateStaff scientific review.
FDA
July 23–24, 2026 Pharmacy Compounding Advisory Committee meetingMeeting materials.
Esposito S, et al.
Synthesis and characterization of Ac-LKKTETQ in TB-500Drug Test Anal. 2012.
Kwok KY, et al.
10 mg SC equine detection and metabolism studyRapid Commun Mass Spectrom. 2013.
Rahaman KA, et al.
TB-500 quantification, metabolites, and scratch-assay screeningJ Chromatogr B. 2024.
ClinicalTrials.gov
NCT07487363 — fictional example recordExplicitly not an actual trial.
Ruff D, et al.
IV full-length thymosin-β4 Phase 12010 — not TB-500.
WADA
2026 Prohibited ListS2 includes thymosin-β4 and derivatives such as TB-500.
Important Safety Information
TB-500 is usually the experimental 7-amino-acid fragment Ac-LKKTETQ. It is not full-length thymosin-β4, not FDA approved, and has no established human dosage.
Direct fragment research documents 10 mg SC once in horses, 50 mg/kg IP once in rats, and 50 mcg/mL in vitro — for detection, metabolism, and cell screening, not injury recovery. NCT07487363 is a fictional registry example, not human evidence.
This page is an evidence reference for educational purposes. It is not a dosing, injection, loading, or stack guide. WADA S2 prohibits TB-500 at all times in tested sport.