Onset
Not established for the fragment; anecdotal same-week reports are not controlled findings.
Protocol / Research Dosing Guide
TB-500 Dosage Guide: Fragment vs Full Thymosin Beta-4 Evidence
An evidence-organized TB-500 reference that keeps the human evidence for full-length thymosin beta-4 formulations separate from the community schedules reported for the injectable Ac-LKKTETQ fragment.
Last reviewed September 16, 202618 minute readResearch information only
Level 2 — No human trial of the fragment itselfWADA prohibitedNot FDA approved
TB-500 Quick Start
TB-500 is a short synthetic fragment matching amino acids 17–23 of thymosin beta-4, keeping the actin-binding region but leaving out the rest of the parent molecule. Nearly all human safety and efficacy data in this space comes from full-length thymosin beta-4, given intravenously in a Phase 1 trial or formulated topically (RGN-137) or as eye drops (RGN-259), not from the injectable 7-amino-acid fragment sold as TB-500. No published human trial has tested TB-500 itself, and it is prohibited under the WADA Prohibited List.
Why researchers care
Actin-binding, tissue-repair and soft-tissue research interest
Class
Synthetic 7-amino-acid, N-acetylated fragment (Ac-LKKTETQ) of thymosin beta-4
Route reported
Subcutaneous injection in most research-use protocols; intramuscular or intraperitoneal in some animal work
Cycle length
4–12 weeks commonly referenced in community planning; not validated by a fragment-specific trial
Regulatory status
Not FDA approved; removed from FDA 503A Category 2 on April 15, 2026; on the WADA Prohibited List
Loading supplier information
TB-500 Dosing Protocol and Schedule
The supplied source reports community research-planning cycles of roughly 2–2.5 mg subcutaneously twice weekly for a 4–6 week loading phase, then 2–2.5 mg once weekly for maintenance, alongside a shorter acute-injury pattern of 2–2.5 mg every 2–3 days for two weeks followed by weekly tapering. It states these figures are community-derived research-planning references, not validated by a published human trial of the fragment.
| Phase or study | Amount | Frequency / evidence |
|---|---|---|
| Loading phase (community) | ~2–2.5 mg subcutaneous, twice weekly, Weeks 1–6 | Community reported |
| Maintenance phase (community) | ~2–2.5 mg subcutaneous, once weekly, Weeks 7–12 | Community reported |
| Acute-injury front-loading (community) | ~2–2.5 mg every 2–3 days, Weeks 1–2 | Community reported |
| Acute-injury taper (community) | ~2–2.5 mg once weekly, Weeks 3–8 | Community reported |
| Off period (community) | 4–8 weeks | Community reported |
| Full-length thymosin beta-4 Phase 1 | IV doses from 42 mg to 1,260 mg, then daily dosing for 14 days | Human trial (different molecule) |
The Phase 1 safety reference used the full 43-amino-acid parent peptide by intravenous infusion, not the 7-amino-acid subcutaneous fragment sold as TB-500. That trial reported no dose-limiting toxicities in that specific dosing pattern, but it does not establish that injectable TB-500 is safe over weeks or months, and the community load/maintenance figures have no fragment-specific trial behind them.
TB-500 Supplies Needed
Neutral research-material planning only. This does not establish an appropriate amount or route.
Research planning item
Exact labeled research vial
Research planning item
Bacteriostatic water at a measured volume
Research planning item
U-100 insulin syringes
Research planning item
Alcohol prep swabs
Research planning item
Sharps container
Research planning item
Refrigeration for the prepared vial
Research planning item
Written concentration label with the preparation date
TB-500 Reconstitution Calculator
Vial-format concentration math
Concentration
5 mg/mL
Draw volume
0.5 mL
U-100 units
50
Mathematical draws
4
Arithmetic only. The entered amount is not a recommendation and does not establish suitability.
Best Time to Take TB-500: Morning or Night?
Morning or evening?
Not established. No fragment-specific study compared times of day.
Twice weekly or weekly?
Community reports describe a twice-weekly loading phase transitioning to once-weekly maintenance; this pattern is not trial-validated.
With food?
Not applicable to an injected product.
Missed amount?
No validated replacement procedure exists for the fragment.
TB-500 Route Comparison
| Format | What is reported | Evidence limit |
|---|---|---|
| Subcutaneous injection | Most common research-use route for the fragment | No published human trial of the fragment by this route |
| Intramuscular/intraperitoneal | Used in some animal research | Animal-only; not a human dosing reference |
| Intravenous (full-length parent peptide) | 42–1,260 mg in a Phase 1 human safety study | Different molecule and route; not TB-500 |
| Topical/ophthalmic (full-length parent peptide) | RGN-137 and RGN-259 formulations | Different molecule and formulation; not TB-500 |
Routes and amounts are not interchangeable unless a verified study explicitly establishes a conversion.
TB-500 Half-Life and Dosing Frequency
| Measure | Finding | Evidence limit |
|---|---|---|
| Human half-life of TB-500 | Not established | No published human PK study of the fragment |
| Human half-life of full-length thymosin beta-4 | Not established in the sources reviewed as a specific figure | Different molecule; not directly transferable |
| Frequency logic | Twice-weekly then once-weekly is a community convention | Not derived from a fragment PK study |
| Solution stability | Not fragment-specific in the sources reviewed | Follow general peptide handling practice |
TB-500 Dosage Chart
| Route | Amount | Frequency | Source | Human validation |
|---|---|---|---|---|
| Subcutaneous | 2–2.5 mg | Twice weekly (loading) | Community report | No |
| Subcutaneous | 2–2.5 mg | Once weekly (maintenance) | Community report | No |
| Subcutaneous | 2–2.5 mg | Every 2–3 days (acute-injury front-load) | Community report | No |
| Intravenous (full-length peptide, not TB-500) | 42–1,260 mg then daily for 14 days | Phase 1 dose range | Human trial (different molecule) | No |
Published study values describe those studies. Community-reported values are not validated dosing recommendations.
TB-500 Reconstitution Guide
Concentration: 5 mg/mL
| Entered amount | Volume | U-100 units |
|---|---|---|
| 2.5 mg | 0.5 mL | 50 units |
| 5 mg | 1 mL | 100 units |
| 7.5 mg | 1.5 mL | 150 units |
- 1.Confirm the exact quantity printed on the vial label.
- 2.Choose and record the bacteriostatic water volume; 10 mg into 2 mL gives 5 mg/mL.
- 3.Clean the stopper with an alcohol swab.
- 4.Add the liquid slowly down the vial wall.
- 5.Swirl gently until clear; never shake.
- 6.Inspect for cloudiness, discoloration or particles and discard anything that is not clear.
- 7.Label the vial with the calculated concentration and preparation date.
- 8.Refrigerate the prepared vial and use only the calculated concentration for arithmetic.
Reconstitution does not establish identity, purity, sterility, stability, or an appropriate amount.
How TB-500 Works
Sequence
TB-500 is an N-acetylated synthetic fragment, Ac-LKKTETQ, matching residues 17–23 of thymosin beta-4.
TB-500 Human Trials and FDA Status
Current status · verified September 16, 2026
Not FDA approved; removed from FDA 503A Category 2 on April 15, 2026; on the WADA Prohibited List
- A Phase 1 study of full-length, intravenous thymosin beta-4 in healthy volunteers used doses from 42 mg to 1,260 mg, followed by daily dosing for 14 days, with no dose-limiting toxicities reported for that specific pattern.
- Topical (RGN-137) and ophthalmic (RGN-259) formulations of full-length thymosin beta-4 have been studied in human trials for wound and ocular surface conditions.
- No published human randomized controlled trial has tested the TB-500 fragment (Ac-LKKTETQ) itself.
- TB-500 is not FDA approved, was removed from the FDA 503A Category 2 list on April 15, 2026, and remains on the WADA Prohibited List.
Who Should Avoid TB-500?
This is an evidence-gap and precaution list, not an approved prescribing label.
Athletes subject to anti-doping testing
TB-500 is on the WADA Prohibited List
Pregnancy or breastfeeding
No safety data
History of cancer
Actin-binding and cell-migration mechanisms raise theoretical proliferation concerns that have not been studied for the fragment
Children or adolescents
No established protocol
Concurrent medicines without clinician review
No interaction studies for the fragment
Long-term unsupervised use
No fragment-specific long-term safety data
TB-500 Side Effects, Risks and Safety
Injection-site reactionsAnecdotal
Important limitation: No controlled incidence data for the fragment.
Fatigue or lethargyAnecdotal
Important limitation: Causality not established.
Effects on existing tumorsTheoretical
Important limitation: Based on actin-binding/cell-migration mechanism, not a fragment-specific finding.
Full-length IV peptide tolerabilityReported in Phase 1
Important limitation: Different molecule and route; not directly transferable to the fragment.
Long-term fragment safetyUnknown
Important limitation: No human safety database exists for injected TB-500.
Drug interactionsUnknown
Important limitation: No interaction studies.
TB-500 Timeline and Monitoring
Community loading window
4–6 weeks, then maintenance; a planning structure, not a measured clinical timeline.
Full-length peptide Phase 1 window
42 mg to 1,260 mg single doses, then 14 days of daily dosing; different molecule and route.
Monitoring
No validated fragment-specific monitoring schedule or stopping rule exists.
TB-500 Benefits and Results: What the Evidence Shows
| Claim | Evidence level | What research shows | Important limitation |
|---|---|---|---|
| Soft-tissue repair research interest | Not established for the fragment | Extrapolated from full-length peptide and animal actin-binding research | No human fragment trial |
| Wound healing | Established for full-length peptide formulations only | Human trials of RGN-137/RGN-259 | Different molecule/formulation than TB-500 |
| Athletic recovery | Not established | Community/anecdotal claim | No controlled human data; prohibited substance for tested athletes |
| Flexibility or range-of-motion changes | Not established | Anecdotal | No controlled data |
TB-500 Storage and Handling
Unreconstituted vial
No fragment-specific stability study was identified; follow the exact product label.
Prepared vial
Refrigerate; no validated fragment-specific storage duration was identified in the sources reviewed.
Appearance
A clear, colorless solution is expected; cloudiness or particles mean discard.
Light
Keep the vial out of light as a general peptide-handling practice.
TB-500 Troubleshooting
Solution appears cloudy
Stop and discard; do not use a non-clear solution.
Calculated units look wrong
Recheck vial quantity, diluent volume, target amount, and syringe conversion.
Confusing full-length thymosin beta-4 data with TB-500 data
These are different molecules studied in different routes; do not transfer findings between them.
Unexpected symptoms occur
No fragment-specific safety protocol exists; seek licensed clinical review.
A scheduled amount is missed
No validated missed-amount procedure exists for the fragment.
TB-500 Comparisons
| Compound | Class or mechanism | Evidence | FDA status |
|---|---|---|---|
| TB-500 (Ac-LKKTETQ) | 7-amino-acid fragment | No human fragment trial | WADA prohibited |
| Full-length thymosin beta-4 | 43-amino-acid parent peptide | Phase 1 IV safety data; topical/ophthalmic human trials | Not the same product as TB-500 |
| BPC-157 | Soft-tissue recovery research interest | Primarily preclinical | Not FDA approved |
| LL-37 | Wound and antimicrobial research interest | Topical human trials | Different mechanism and evidence base |
TB-500 Frequently Asked Questions
What is TB-500?
A synthetic 7-amino-acid, N-acetylated fragment (Ac-LKKTETQ) matching residues 17–23 of thymosin beta-4.
Is TB-500 the same as thymosin beta-4?
No. Most human research used the full 43-amino-acid peptide, not the TB-500 fragment.
Is TB-500 FDA approved?
No. It was removed from the FDA 503A Category 2 list on April 15, 2026.
Are there human trials of TB-500 itself?
No published human randomized controlled trial of the fragment was identified.
Is TB-500 banned in sport?
Yes, it is on the WADA Prohibited List.
What is its half-life?
Not established in the sources reviewed.
Does the Phase 1 full-length peptide safety data apply to TB-500?
Not directly. That trial used a different molecule and route (IV, full-length peptide) and does not establish injectable fragment safety over weeks or months.
Is the community load/maintenance schedule validated?
No. It is a community research-planning reference, not a trial-derived protocol.
Is there a validated cycle length?
No published human RCT of the fragment establishes an optimal cycle length.
What does the calculator do?
It converts entered vial and liquid values into concentration and syringe-volume arithmetic only.
Is long-term safety of the fragment known?
No.
Sources and Research
Coverage source
1. TB-500 protocol coverage source
Community loading/maintenance schedules and reconstitution math; not primary evidence.
Open direct sourceHuman research (different molecule)
2. Thymosin beta 4: a Phase 1 safety study in healthy volunteers
Intravenous full-length peptide dose-escalation and repeat-dosing safety data; different molecule and route than TB-500.
Open direct sourceLaboratory and animal research
3. Thymosin beta 4 promotes dermal healing
Preclinical actin-binding and wound-healing mechanism research on the full-length peptide.
Open direct sourceRegulatory
4. World Anti-Doping Agency Prohibited List
Lists TB-500/thymosin beta-4 fragments among prohibited substances.
Open direct sourceMissing information flagged for review
- Human trial of the TB-500 fragment itself: Not established
- Human pharmacokinetics and half-life of the fragment: Not established
- Validated cycle and rest period for the fragment: Not established
- Fragment-specific stability and long-term safety data: Not established
- Drug interaction data for the fragment: Not established