Healing & Repair

TB-500 (Ac-LKKTETQ)

Dosing evidence

Dose at a glance

FDA nomination concentration

FDA's 2026 briefing describes a proposed compounded TB-500 injectable product at 3 mg/mL for SC or IM administration. 3 mg/mL is a concentration. It is not an FDA-approved dose, proof that 3 mg should be given, a validated frequency, a validated wound protocol or an approved SC regimen.

Community protocol examples

Current community protocol pages are highly inconsistent. Examples include:

• approximately 500 mcg to 1 mg daily on one protocol site
• historically common schedules around 2 mg twice weekly for 4 to 6 weeks, then lower-frequency maintenance, on another site that itself describes these schedules as community-derived
• 1 to 1.25 mg weekly
• 1 to 2.5 mg several times weekly
• 2 to 2.5 mg twice weekly
• higher multi-milligram loading schedules

Taken together, community protocols are highly variable, roughly 0.5 to 2.5 mg per administration, with schedules from daily to 2 to 3 times weekly. There is no stable community consensus and no clinically established dose. These protocols have not been validated in human trials.

Historical 2 to 4 mg protocol

A multi-milligram intermittent protocol has circulated for years in peptide communities, usually described as about 2 to 4 mg per administration, given one or more times weekly during a loading phase (often 2 to 4 mg twice weekly). Its historical origin is unclear: TB-500, LKKTETQ and full-length Tβ4 have repeatedly been conflated in commercial and secondary literature, and no clear source chain links it to a specific human or animal Tβ4 study. Classification: historical community protocol with unclear molecular provenance; not a human TB-500 research dose.

Frequency

Human Ac-LKKTETQ frequency is unknown. No human trial establishes once daily, twice weekly, three times weekly or once weekly as the optimal schedule. Full-length Tβ4 human research schedules depend on route and product (daily IV administration in Phase 1 studies, topical wound-treatment schedules, ophthalmic dosing schedules), and these cannot be converted into a fragment frequency.

Timing

No human evidence establishes that TB-500 should be given in the morning or evening, fasted or fed, before or after exercise, or on training or rest days. There is no evidence-based timing requirement.

Local injection near an injury

Community protocols often describe injecting TB-500 near an injured tendon, ligament, muscle or joint. There is no human evidence for this: no controlled human Ac-LKKTETQ study shows that SC placement close to an injury improves tissue exposure, healing, pain, biomechanics or recovery speed. Local SC administration is community practice; local superiority is not established.

Duration and cycle

No human TB-500 fragment cycle has been established. Community material commonly describes 4 weeks, 4 to 6 weeks or 6 to 8 weeks, with maintenance periods afterward. No evidence shows that week 4 or week 6 is optimal, that week 8 is a biological stop point, or that maintenance or a washout is required. These durations are community convention.

Receptor reset

No established requirement. Tβ4 biology is closely tied to actin dynamics, cytoskeletal organization, cell migration and tissue signaling. There is no established TB-500 receptor with a clinically defined desensitization and reset schedule, and no evidence for a two-week washout, a four-week break, receptor resensitization or a periodic reset.

Expected results timeline

Protocol logic check

Medical literature and study context

What is TB-500?

On this page, TB-500 means the molecule FDA currently defines as TB-500, which is not just another name for full-length thymosin β4. FDA defines TB-500 free base as a synthetic seven-amino-acid fragment corresponding to residues 17 to 23 of full-length thymosin β4, with an acetyl group attached to the N-terminal leucine.

FDA-defined sequence: Ac-LKKTETQ (N-acetyl-Leu-Lys-Lys-Thr-Glu-Thr-Gln). FDA reports a molecular weight of approximately 889.01 g/mol for TB-500 free base, and evaluates TB-500 free base and TB-500 acetate as different bulk drug substances.

Three molecules to keep separate

1. FDA-defined TB-500 (Ac-LKKTETQ): seven amino acids, N-terminally acetylated, corresponding to thymosin β4 residues 17 to 23.
2. Non-acetylated LKKTETQ: also seven amino acids, but with no N-terminal acetyl group. FDA warns that acetylation can change a peptide's charge, hydrophobicity, size, lifespan, folding and binding properties, so pharmacology seen with plain LKKTETQ does not automatically transfer to Ac-LKKTETQ.
3. Full-length thymosin β4 (Tβ4): a naturally occurring 43-amino-acid peptide with a substantially larger mechanistic, animal and human research program than either short fragment. FDA's review also distinguishes it from the seven-amino-acid TB-500 fragment.

Ac-LKKTETQ, LKKTETQ and full-length Tβ4 are related but not interchangeable.

Why the naming problem matters

The term TB-500 has been used inconsistently by peptide vendors, anti-doping literature, research summaries, community protocol sites, clinic websites and scientific papers. FDA found identity problems even within the formal nomination package it reviewed: the nomination referred to TB-500 free base, while the accompanying certificate of analysis appeared to describe TB-500 acetate. FDA also found inconsistencies in CAS numbers, molecular formula information and chemical identification.

A vial labeled only "TB-500" does not reliably identify the exact molecule. Details that identify it:

• exact peptide
• sequence
• length: 7 or 43 amino acids
• N-terminal acetylation: yes or no
• form: free base, acetate or other
• molecular weight

A product containing the complete 43-amino-acid molecule is full-length thymosin β4, even if a vendor markets it as TB-500.

What may FDA-defined TB-500 help with?

Human evidence: not established. FDA did not identify clinical evidence that Ac-LKKTETQ TB-500 treats any disease or wound condition in humans.

Ac-LKKTETQ TB-500 has not been clinically established in humans to:

• heal tendon tears
• heal ligament injuries
• accelerate muscle recovery
• regenerate cartilage
• repair joints
• improve flexibility
• reduce scar tissue
• accelerate return to sport
• improve wound healing
• treat chronic inflammation
• regenerate nerves
• prevent surgery

Exact Ac-LKKTETQ laboratory evidence

The direct fragment data are weaker than the broad thymosin literature makes them appear. FDA reviewed a 2024 fibroblast scratch-wound experiment using TB-500 free base (Ac-LKKTETQ) at 50 µg/mL. After eight hours, wound closure was not significantly different from vehicle.

Under the same conditions, the TB-500 metabolite N-acetylated LKKTE at 50 µg/mL produced a small but statistically significant increase in wound closure. This raises an open question: some effects attributed to TB-500 could depend partly on metabolism into shorter peptides rather than on the intact Ac-LKKTETQ molecule. FDA states that this remains unknown. Classification: direct N-acetylated TB-500 pharmacology is very limited and mixed.

Non-acetylated LKKTETQ wound research

The classic positive fragment study used plain LKKTETQ, not Ac-LKKTETQ. In aged mice with experimental skin wounds, topical 0.01% non-acetylated LKKTETQ was associated with greater epidermal closure and collagen content by day 7 compared with vehicle. Because acetylation changes molecular properties, FDA warns that this finding cannot be transferred to the acetylated TB-500 molecule. Classification: related-fragment evidence; not direct TB-500 proof.

2026 rat Achilles-tendon study

An animal study published in July 2026 evaluated a product identified by the investigators as TB-500 in a rat Achilles rupture-and-repair model. Thirty-two rats were assigned to control, BPC-157, TB-500, or BPC-157 + TB-500. Doses were BPC-157 10 µg/kg/day and TB-500 60 µg/kg/day, given intraperitoneally for approximately 30 days.

The TB-500 group showed significantly greater maximum load to failure versus controls, improved total Bonar histopathology and Movin scores, improved collagen organization, and evidence consistent with more advanced matrix remodeling. The authors described the findings as preliminary evidence supporting further study. Classification: positive exploratory rat tendon evidence.

Identity limitation. The paper identifies its product as TB-500, product 27-155-PS from a commercial peptide supplier, but does not report enough independent analytical information to confirm the amino-acid sequence, N-terminal acetylation, molecular weight or free-base versus salt status. The authors also chose the 60 µg/kg/day dose from biologically active full-length Tβ4 preclinical dose ranges, not from TB-500 tendon dose-optimization studies. The paper therefore does not establish whether the tested material was FDA-defined Ac-LKKTETQ, non-acetylated LKKTETQ or another thymosin-related commercial preparation. The result is TB-500-labeled animal evidence with an identity limitation, not definitive Ac-LKKTETQ evidence.

Combination result. The study also directly tested BPC-157 + TB-500. The combination gave no additional biomechanical or histopathologic benefit over the individual treatments. This does not prove the combination can never be additive in humans: the study was animal, small, limited to one tendon model, one dose combination and one main time point, and affected by the TB-500 identity uncertainty. It does directly contradict claims that BPC-157 + TB-500 has already been experimentally proven superior to either peptide alone. Classification: no additive benefit in this specific rat study; not proof of a lack of human synergy.

What may full-length thymosin β4 help with?

Human evidence exists in several route-specific areas: short-term IV safety and pharmacokinetics, topical chronic-wound research, ophthalmic corneal research and cardiovascular research. Full-length Tβ4 has not been clinically established as a systemic SC sports-recovery treatment for tendon tears, ligament injuries, muscle injuries, joint repair, cartilage regeneration or athletic recovery.

Most of the human evidence that is attributed online to "TB-500" belongs to full-length thymosin β4, not the seven-amino-acid fragment. Full-length thymosin β4 has human Phase 1 safety and pharmacokinetic research; FDA-defined Ac-LKKTETQ TB-500 does not have verified human administration data.

Human full-length Tβ4 evidence

1. IV healthy-volunteer study (2010). A randomized placebo-controlled study gave synthetic full-length Tβ4 intravenously to healthy volunteers. Single-dose cohorts received 42 mg, 140 mg, 420 mg or 1,260 mg, then the same study-specific dose daily for 14 days after safety review. Treatment was reported as generally well tolerated over the short trial. This supports genuine systemic human exposure to full-length Tβ4 and short-term IV tolerability research. It does not support Ac-LKKTETQ safety, 2 mg or 4 mg TB-500 SC, twice-weekly community use or sports-injury treatment.

2. Recombinant full-length Tβ4 Phase 1 (2021). A randomized double-blind Phase 1 program evaluated recombinant full-length human Tβ4 (NL005) in 84 healthy volunteers. In single-dose cohorts, 54 participants received 0.05 to 25 µg/kg IV. In multiple-dose cohorts, 30 participants received 0.5, 2 or 5 µg/kg once daily for 10 days. Adverse events were generally mild to moderate, with no serious adverse events or dose-limiting toxicity reported. This supports human full-length Tβ4 pharmacokinetics, repeated systemic IV exposure and short-term safety information. It does not support fragment safety, SC fragment dosing, community loading schedules or local musculoskeletal injection.

The two Phase 1 programs used dramatically different dose scales. Clinical exposure has to be read within the exact molecule, investigational product, formulation, manufacturing system, route and study design, and cannot be converted into a community fragment protocol.

3. Venous-ulcer research. A randomized Phase 2 study enrolled 73 patients with venous stasis ulcers and evaluated topical full-length thymosin β4. It reported a wound-healing signal, with 0.03% Tβ4 identified as a potentially useful concentration. Classification: human topical full-length Tβ4 evidence; not TB-500 fragment evidence.

4. Pressure-ulcer research. Full-length Tβ4 has also been studied topically in controlled pressure-ulcer programs. ClinicalTrials.gov records a double-blind placebo-controlled study designed to assess safety, tolerability and wound-healing efficacy. Topical full-length Tβ4 wound research does not establish a systemic SC TB-500 protocol.

5. Ophthalmic research. Full-length Tβ4 has progressed into Phase 3 ophthalmic development as RGN-259, a 0.1% Tβ4 ophthalmic solution. In the small SEER-1 neurotrophic-keratopathy trial, 6 of 10 RGN-259-treated participants achieved complete healing at about four weeks, compared with 1 of 8 on placebo. This strong numerical corneal-healing signal narrowly missed conventional statistical significance on the prespecified four-week primary comparison; later healing and symptom outcomes favored RGN-259. It does not show that Phase 3 proved Tβ4 heals corneas.

6. STEMI trial (2025). A randomized, double-blind, placebo-controlled trial tested recombinant human full-length Tβ4 in 96 patients with ST-elevation myocardial infarction after PCI. Across the full randomized population, the infarct-area difference versus placebo was not statistically significant. In a reported early-treatment subgroup that received the first dose within about 8 hours after PCI, the rhTβ4 group had a significantly smaller infarct area at 90 days. Classification: encouraging but not unequivocally positive systemic human Tβ4 efficacy evidence. This is not TB-500 fragment evidence.

Mechanism

Full-length Tβ4 and actin. Full-length thymosin β4 is a major actin-regulating peptide. It binds globular G-actin and helps regulate the pool of actin monomers involved in cytoskeletal remodeling, cell migration, cell shape, intracellular transport and tissue repair. FDA identifies the LKKTET sequence within the 17 to 23 region as the classic actin-binding segment of full-length Tβ4.

Does TB-500 have the same actin function? Possibly, as a hypothesis. FDA states it has been hypothesized that the LKKTETQ fragment may bind G-actin and provide some of the G-actin-buffering activity of full-length thymosin β4, and that it remains uncertain whether actin binding explains the reported angiogenesis, mast-cell effects, wound healing or other fragment activity. The TB-500/LKKTETQ region overlaps the classic actin-binding region of full-length Tβ4, but how far the isolated fragment reproduces full-length Tβ4 biology is uncertain.

The "active region" oversimplification. The claim that TB-500 is just the active part of Tβ4 and therefore does everything Tβ4 does is not supported. Full-length Tβ4 contains multiple regions that can generate distinct biological effects and fragments, and the 17 to 23 region does not represent the whole peptide's biology.

Ac-SDKP and other full-length functions. Full-length Tβ4 can also act as a precursor for other active sequences, including Ac-SDKP from its N-terminal region, which has been studied separately for anti-inflammatory and anti-fibrotic biology. TB-500 (residues 17 to 23) does not contain this N-terminal sequence. Even if TB-500 retains some actin-related biology, it cannot automatically reproduce every full-length Tβ4 pathway.

Metabolism. Animal and in vitro research reviewed by FDA shows that Ac-LKKTETQ is shortened from the C-terminal end. Identified metabolites include Ac-LKKTET, Ac-LKKTE, Ac-LKKT, Ac-LKK and Ac-LK. The Ac-LKKTE metabolite is of particular interest because it showed a small wound-closure signal in the fibroblast assay where intact TB-500 did not. Whether some effects of administered TB-500 depend on metabolite formation rather than the intact parent peptide is unknown.

Half-life and pharmacokinetics

Ac-LKKTETQ TB-500 in humans: not established. FDA identified no human administration or human PK study for the fragment.

Animal SC pharmacokinetics: FDA reviewed a study in thoroughbred horses given 10 mg TB-500 free base SC. Plasma levels peaked at about 60 to 120 minutes and became unquantifiable roughly 6 to 10 hours after administration, with measurable systemic exposure and metabolites. This is equine SC pharmacokinetics and is not a human TB-500 half-life; it does not establish a human injection interval.

Full-length Tβ4: human IV pharmacokinetic research exists, but full-length Tβ4 PK cannot be substituted for fragment PK.

Accumulation: unknown for exact TB-500 in humans. The 2021 recombinant full-length Tβ4 IV trial did not show obvious accumulation over its short repeated-dose regimen; that is a full-length finding, not a fragment finding.

ClinicalTrials.gov record NCT07487363

ClinicalTrials.gov contains a record titled as a Phase 1/2 TB-500 cardiovascular study that looks like legitimate recruiting human TB-500 research. The record itself states that it is a fictional example of a ClinicalTrials.gov-style record. It is not human TB-500 exposure, an active clinical program, Phase 1 or Phase 2 human evidence, or proof that TB-500 is being tested clinically. Some secondary databases already present the entry as though it were genuine.

Independent evidence

How well studied is FDA-defined Ac-LKKTETQ TB-500?

FDA's May 2026 evaluation states it did not identify human administration data for TB-500 free base or TB-500 acetate by any route, and found major gaps in acute toxicity, repeat-dose toxicity, genotoxicity, reproductive toxicity and carcinogenicity data. Overall evidence strength: very limited.

Non-acetylated LKKTETQ

Full-length thymosin β4

Evidence hierarchy

Research at a glance

Evidence strength

FDA-defined Ac-LKKTETQ: very weak direct efficacy evidence.

• Stronger evidence for: molecular identification, animal PK and metabolism, relation to the Tβ4 17 to 23 region
• Weak or mixed evidence for: direct wound-healing pharmacology
• Unestablished: human safety, human efficacy, human dose, human PK, human results timeline, chronic safety

Non-acetylated LKKTETQ: limited positive preclinical evidence, but chemically different from TB-500.

Full-length Tβ4: meaningful preclinical evidence with real human clinical research.

• Human areas: IV safety, PK, wounds, ophthalmology, cardiovascular disease
• Still unestablished: a systemic musculoskeletal recovery protocol, equivalence of the TB-500 fragment, community SC sports-recovery dosing

Summary

Bottom line

TB-500 shows why molecular identity has to be settled before evidence can be interpreted. There are at least three distinct categories: FDA-defined Ac-LKKTETQ, plain LKKTETQ and full-length 43-amino-acid thymosin β4. FDA reports no human administration data for TB-500 free base or acetate, so claims that "TB-500 has Phase 1 human safety data" refer to studies of full-length thymosin β4, not Ac-LKKTETQ.

Full-length Tβ4 has a legitimate human research program (systemic IV exposure, pharmacokinetics, topical chronic-wound research, ophthalmic trials and randomized cardiovascular research), and even that evidence needs careful reading. The 2025 STEMI trial showed no statistically significant overall infarct-area difference, with a favorable signal in patients treated within about eight hours after PCI. SEER-1 showed a strong numerical corneal-healing signal, but its four-week primary comparison narrowly missed conventional statistical significance. These studies are meaningful but are not fragment dosing studies.

Plain LKKTETQ showed positive wound-healing findings in aged mice, but acetylation changes peptide properties. Exact N-acetylated TB-500 at 50 µg/mL did not significantly improve fibroblast scratch closure, while the shorter metabolite Ac-LKKTE showed a small positive effect. The July 2026 Achilles study found that a product called TB-500 improved several rat tendon-healing outcomes, including maximum load to failure, but did not independently confirm the product's sequence or acetylation, and its dose came from full-length Tβ4 literature. In the same study, BPC-157 plus TB-500 did not outperform the individual compounds.

Community dosing ranges from daily 500 mcg to 1 mg, to intermittent 1 to 2.5 mg, to older 2 to 4 mg multi-milligram schedules, with no stable consensus and unclear provenance. There is no established human SC dose, IM dose, maximum dose, half-life, optimal frequency, local-injection advantage, 4 to 6 week clinical cycle, maintenance schedule or receptor-reset requirement.

Full-length thymosin β4 has legitimate and growing human research. FDA-defined Ac-LKKTETQ TB-500 does not have an established human treatment evidence base, and plain LKKTETQ is another related but chemically distinct fragment.

Storage

Formulation, stability and sterility

There is no FDA-approved TB-500 injectable product providing a universal validated:

• vial strength
• reconstitution volume
• diluent
• final concentration
• pH
• refrigerated shelf life
• 14-day rule
• 28-day rule
• multidose beyond-use period

FDA notes that peptide stability and immunogenicity can be strongly affected by manufacturing, formulation, impurities, aggregation and storage conditions.

Bulk API storage is not reconstituted-vial stability

FDA cites source information reporting that dry TB-500 free-base material may be stored below approximately -20°C under specified protected conditions. That does not establish how long a reconstituted vial stays stable after water is added. A statement such as "all TB-500 lasts 28 days refrigerated after reconstitution" is unsupported unless the exact formulation has validated data behind it.

Contraindications & cautions

Formal contraindications

FDA-labeled contraindications: none, because there is no FDA-approved TB-500 prescribing label. The cautions below are theoretical or practical and are not official contraindications.

Pregnancy and breastfeeding

Human TB-500 safety is not established, and reproductive and developmental toxicology is inadequate. Classification: safety unknown.

Children and adolescents

Human pediatric dosing and safety are not established. Classification: safety and dose unknown.

Active malignancy or recent cancer treatment

Full-length Tβ4 has experimental roles in angiogenesis, cell migration and tissue remodeling, which creates a biologically understandable concern in active malignancy. Human TB-500 cancer risk has not been established, and FDA found no adequate carcinogenicity studies for TB-500 free base or acetate. Neither "TB-500 causes cancer" nor "TB-500 is proven safe in cancer" is established. Classification: unresolved, mechanism-based precaution; not a formal FDA contraindication.

Unverified injectable product

One of the strongest practical cautions: the exact molecule may be unclear, impurity testing may be incomplete, and aggregation, sterility and endotoxin all matter. Classification: product-quality concern.

Product identity is a safety issue

Even formal documentation reviewed by FDA did not consistently distinguish TB-500 free base from TB-500 acetate. Community products add further possibilities: full-length Tβ4 sold as "TB-500," non-acetylated fragments, or incompletely characterized peptide material. The label alone is not enough to identify the product.

FDA and regulatory status

FDA-approved: no. Neither TB-500 free base nor TB-500 acetate is a component of an FDA-approved drug.

FDA May 2026 scientific evaluation. FDA's detailed TB-500 evaluation, dated May 15, 2026, assessed TB-500 free base and TB-500 acetate for possible inclusion on the Section 503A Bulks List. FDA staff concluded the evidence weighed against inclusion because of inadequate characterization, inconsistent molecular identification, unclear historical compounding use, absence of human exposure, lack of demonstrated clinical effectiveness, inadequate safety data and potential injectable immunogenicity risk.

Effectiveness conclusion. FDA concluded there was insufficient evidence to evaluate TB-500 for wound healing. At the time of the May review, FDA found no human TB-500 trials, no in vivo wound-healing study using confirmed TB-500 free base or acetate, a negative direct fibroblast scratch assay for TB-500 free base, and a small positive signal from the Ac-LKKTE metabolite. The July 2026 Achilles rat paper adds new TB-500-labeled animal evidence, but because exact molecular confirmation in that paper is inadequate, it does not fully resolve FDA's exact-molecule concern.

July 23, 2026 PCAC recommendation. The Pharmacy Compounding Advisory Committee then voted to recommend inclusion of TB-500-related substances on the 503A Bulks List, by a reported 8 in favor, 6 against and 1 abstention. FDA advisory committees give non-binding recommendations, and FDA states it is not legally bound to follow them. The vote is not FDA drug approval, a prescribing label, proof of efficacy, proof of safety, an approved protocol or automatic final Bulks List inclusion. FDA has not approved TB-500 for compounding.

Final FDA action. As of August 19, 2026, no final FDA action adding TB-500 free base or TB-500 acetate to the final Section 503A Bulks List had been identified. FDA's posted materials still distinguish the staff recommendation from the advisory process, and FDA's briefing stated that a final determination would follow only after advisory input and remaining reviews were considered.

Current FDA safety position. FDA's safety-risk page continues to list thymosin β4 fragment / TB-500 among substances with significant unresolved safety issues. FDA states that compounded products containing the fragment may pose immunogenicity risk because of aggregation and peptide-related impurities, and that it has not identified human exposure data for products containing the fragment.

WADA status

The 2026 WADA Prohibited List explicitly includes "thymosin-β4 and its derivatives, e.g. TB-500" among prohibited substances. In competitive sport, thymosin β4 and derivatives such as TB-500 are prohibited.

Possible side effects

Exact TB-500 fragment

Human safety profile: not established. FDA did not identify human administration data for TB-500 free base or acetate, so there is no adequate human dataset from which to estimate common adverse-effect rates.

Community reports often mention injection-site discomfort, redness, headache, fatigue and transient systemic symptoms. Classification: community-reported, causality uncertain; not established clinical adverse effects.

Missing toxicology

At the time of FDA's evaluation, the agency did not identify adequate acute toxicity, repeat-dose toxicity, genotoxicity, reproductive and developmental toxicity, or carcinogenicity studies for TB-500 free base or acetate. The absence of a known toxicity signal is not evidence that long-term use is safe.

Full-length thymosin β4

Short-term human safety information is much better for the full-length molecule. The 2010 and 2021 IV programs found short-term administration generally tolerated in healthy volunteers. This does not validate TB-500 fragment safety, community vials, SC community protocols or multi-month gray-market use.

FDA safety and quality concerns

For injectable TB-500-related substances, FDA identifies concerns involving incomplete molecular characterization, inconsistent naming, peptide-related impurities, aggregation, microbial quality, bacterial endotoxin information, immunogenicity and manufacturing quality. FDA notes that injectable peptides can present greater immunogenicity concerns when aggregation or peptide impurities are present.

Compatibility

The compounds below are commonly paired with TB-500. Commonly paired does not mean synergistic; no controlled combination evidence exists.

BPC-157

The most common TB-500 community pairing, often called the "Wolverine Stack," with numerous combination schedules published on community sites. Human combination evidence is not established. The 2026 rat Achilles study directly compared BPC-157, TB-500 and BPC-157 + TB-500 and found no additive benefit from the combination over either peptide alone. That animal finding has a significant TB-500 product-identity limitation and cannot establish human synergy or its absence, but it directly contradicts claims that the combination has already been experimentally proven superior.

GHK-Cu

Often combined in repair-oriented peptide stacks. Classification: community combination. No controlled human study establishes a superior GHK-Cu + TB-500 repair protocol.

KPV

Often included in inflammation and recovery combinations. Classification: community combination. There are no validated human synergy data.

Premixed blends

TB-500 or thymosin-related peptides appear in vendor-defined products such as Wolverine, GLOW, KLOW and other repair blends. A label may not show whether the product contains Ac-LKKTETQ, LKKTETQ or full-length Tβ4, so the thymosin molecule in the product has to be known before any amount can be interpreted. Ingredient identity comes before dose interpretation.

Same-vial compatibility

Community co-use does not establish pharmaceutical compatibility. For BPC-157 + TB-500 or other blends, none of the following is validated unless the exact finished formulation has been tested:

• pH compatibility
• chemical stability
• solubility
• aggregation behavior
• potency retention
• degradation rate
• sterility duration

Sources

1. U.S. Food and Drug Administration. Scientific evaluation of TB-500 free base and TB-500 acetate for the Section 503A Bulks List. May 15, 2026.
2. U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks: thymosin β4 fragment (TB-500).
3. U.S. Food and Drug Administration. Pharmacy Compounding Advisory Committee meeting, July 23, 2026: TB-500-related substances, including FDA briefing materials.
4. World Anti-Doping Agency. 2026 Prohibited List: thymosin-β4 and its derivatives, e.g. TB-500.
5. Fibroblast scratch-wound assay of TB-500 free base (Ac-LKKTETQ) and the Ac-LKKTE metabolite at 50 µg/mL. 2024. As reviewed by FDA.
6. Aged-mouse skin-wound study of topical 0.01% non-acetylated LKKTETQ.
7. Rat Achilles rupture-and-repair study of BPC-157, TB-500 and BPC-157 + TB-500 (32 rats). July 2026.
8. Equine pharmacokinetic and metabolism study of 10 mg TB-500 free base SC in thoroughbred horses. As reviewed by FDA.
9. Randomized placebo-controlled IV study of synthetic full-length thymosin β4 in healthy volunteers. 2010.
10. Randomized double-blind Phase 1 study of recombinant full-length human thymosin β4 (NL005) in 84 healthy volunteers. 2021.
11. Randomized Phase 2 study of topical full-length thymosin β4 in 73 patients with venous stasis ulcers.
12. ClinicalTrials.gov. Double-blind placebo-controlled study of topical thymosin β4 in pressure ulcers.
13. SEER-1 Phase 3 trial of RGN-259 (0.1% thymosin β4 ophthalmic solution) in neurotrophic keratopathy.
14. Randomized, double-blind, placebo-controlled trial of recombinant human thymosin β4 in 96 patients with ST-elevation myocardial infarction after PCI. 2025.
15. ClinicalTrials.gov. NCT07487363 (fictional example record; not human research). clinicaltrials.gov/study/NCT07487363