TB-500
Thymosin Beta-4 Synthetic Fragment
Evidence grade 1 of 5, Untested. Read how the Atlas grades evidence.
The TB-500 fragment (LKKTETQ) rests on animal and in-vitro data with no completed human efficacy randomized controlled trials for injury or musculoskeletal repair. The human trials that exist belong to a different molecule, the full-length 43-amino-acid thymosin beta-4 (RGN-259, developed by RegeneRx / ReGenTree), studied as an ophthalmic solution for dry eye and neurotrophic keratopathy, and even those programs have narrowly missed or failed primary endpoints (SEER-1 p=0.0656 at day 29; the European SEER-3 phase 3 missed its primary endpoint). When the FDA evaluated the TB-500 fragment for the 503A compounding bulks list it found no human effectiveness data and cited an in-vitro study in which TB-500 did not induce wound healing in fibroblast cultures, supporting an animal-only, grade 1 grade for the marketed compound.
Counted on the record: 0 human studies, 0 randomized trials, 0 participants, 4 animal studies, 1 lab study.
The zero randomized-trial count applies to the exact TB-500 fragment. Full-length thymosin beta-4 studies are not counted as TB-500 trials.
- FDA
- Not approved. Sister compounds are in clinical development in EU and CN.
- WADA
- Prohibited at all times under Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics); thymosin beta-4 and its fragments including TB-500 are covered.
Reference only. Not medical advice.
What can go wrong
Sold as a research chemical. There are theories about it causing cancer due to its angiogenic properties however TB4 and TB-500 sister peptides are undergoing clinical trials: including RGN-259 eye drops in Phase III development, RGN-352 injectable with Phase I completed, RGN-137 topical gel with historical clinical development, and ZKY001/LQ-7 eye drops with multiple Phase II trials completed and Phase III.
Talk to a clinician before taking this, particularly if you have any history of cancer. The Atlas can tell you what has been studied about TB-500. It cannot tell you how it would interact with your body, your history, or anything else you are taking, and nothing on this page is a reason to start.
The synthetic version of the active actin-binding fragment of Thymosin Beta-4, a protein present in virtually every nucleated human cell and one of the most abundant intracellular peptides in mammalian tissue. WADA-prohibited since the 2012 Australian football scandal. Zero human RCTs.
Naturally present in nearly every human cell. Banned in every sport.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
Combinations named above are how people use these compounds together, under names the community gave them. The combinations themselves have not been studied. Evidence for one compound is not evidence for a pair.
How it is supposed to work
TB-500 is built around the part of thymosin beta-4 that grabs onto actin, the protein scaffold inside nearly every cell. By binding free G-actin and managing how it assembles, it is proposed to help cells move into injured areas, recruit stem and progenitor cells to a wound, grow new blood vessels, and calm inflammation during the repair phase. That cascade is the rationale for its use in soft-tissue and tendon recovery. As with its frequent stack-mate BPC-157, the catch is that this is characterized in cells and animals; the effect in a living human has not been measured in a completed trial of the compound people actually buy.
- Step 1MetabolismIn rats, TB-500 broke down into shorter fragments. Ac-LK appeared early, while Ac-LKK remained detectable for up to 72 hours.
- Step 2Wound-healing assayThe parent peptide did not significantly speed fibroblast wound closure in the laboratory test. One breakdown product, Ac-LKKTE, did.
- Step 3Surface adsorptionTB-500 can stick to laboratory containers, which can distort measurements at very low concentrations.
- Step 4Epicardial progenitorsIt wakes dormant cells on the heart’s outer layer and turns them into vessel-forming cells.
- Step 5Chemokine dampingIt lowers inflammatory chemokine and cytokine signalling, which is part of how repair speeds up.
The reported wound-healing activity may come from a breakdown product rather than intact TB-500. These findings come from laboratory and animal research, not human treatment trials.
Short fragment built on the LKKTETQ actin-binding sequence.
We found no published shelf-life or formal stability study for TB-500. The FDA's 2026 compounding briefing says peptide stability depends heavily on how the peptide is made and on its quality, and it flags aggregation and degradation as risks. In laboratory work the peptide stuck to container surfaces at very low concentrations, and in lab systems and in rats it broke down into shorter fragments.
- Parent
- Thymosin beta-4 (43 aa)
- Sold as
- Short fragment or full protein
- Active motif
- LKKTETQ
- Human dosing
- None validated
- Evidence base
- Mostly animal
- Detection
- ~30-45 days
What You Buy Vs What Is Tested
Two things the marketing blurs, and together they are the whole story. First, the impressive human trials you will see cited are not of TB-500. They are of the full-length parent protein thymosin beta-4, developed as a pharmaceutical by RegeneRx (RGN-259 eye drops for dry eye and corneal injury, which reached Phase 3 but was never approved, and RGN-352 given intravenously for the heart). The short fragment sold as TB-500 has no completed human efficacy trial of its own for any musculoskeletal use. Second, the underlying actin biology is real and, unlike BPC-157, has been replicated across many independent laboratories, which is a genuine point in its favor. But the strongest evidence belongs to a different and more complex molecule than the one people inject, and the thing people inject is not reliably the same product twice. Real biology in a dish is not proof of benefit in a person, and that gap is exactly where the hype lives.
How it is taken
Research
laboratory solution Synthetic TB-500 and metabolite standards in laboratory solutions. The 2017 and 2024 studies address analytical recovery and metabolism, not finished-vial, reconstitution, or storage stability. Analytical adsorption, metabolism, and wound-closure experiments in containers, cell systems, and rats.
Injection
Recorded because this entry documents injectable use. The Atlas holds no vial, reconstitution or storage detail for it.
Safety in detail
- We hold human trial data for the full-length parent protein rather than for the TB-500 fragment people inject.
- Most product is research grade, and vials vary between the short fragment and the full protein.
Children and teenagers
There is no pediatric research on TB-500, no approved use, and no safety data in minors of any kind. As with BPC-157, the only realistic context for a minor is misuse by a young athlete chasing recovery or a physique, the same pressure that pulls adolescents toward other banned performance substances. Because the compound has never been properly tested even in adults, and because what is sold is often not a defined molecule, use in anyone under 18 has no medical justification and carries entirely unknown risk. Youth-athlete marketing should be read as a warning sign.
What people get wrong
Often saidIt is the same thing your body makes
ActuallyTB-500 is a synthetic fragment of TB-4. TB-4 is natural; the marketed compound is not identical to it.
Often saidIt only helps healthy tissue heal
ActuallyIn animal models it also accelerated growth of existing tumors. The healing signal does not distinguish good tissue from bad.
Who profits, and who pushes back
Dr. Eric Topol
TB-500 accelerated dormant tumor growth and disrupted immune response in animal experiments.
WADA
Multiple confirmed doping violations in the AFL and horse racing.
CNN Investigation
Most commercial TB-500 ships from China with no quality controls, purity is a real-world variable.
Joe Rogan
Discusses TB-500 alongside BPC-157 as a stack. Personal user.
Gary Brecka
Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.
Sells directly. "Research use only" labeling is a documented FDA workaround.
Ben Greenfield
Injury recovery discussions. General supplement affiliates.
Andrew Huberman
Covered the stacking rationale. No peptide-company sponsorship.
No company profits from an approved TB-500 product, because none exists. The legitimate pharmaceutical value sits with the parent molecule: RegeneRx Biopharmaceuticals has spent two decades developing thymosin beta-4 formulations (eye drops, cardiac), a separate and regulated path. The gray-market money flows exactly where BPC-157's does: online "research only" vendors, the compounding pharmacies and telehealth peptide clinics that reopened after the February 2026 reclassification, and the wider wellness-clinic and affiliate ecosystem. A distinct slice also runs through veterinary and equine channels, where TB-500 has a long history of use in performance horses.
Where the research comes from
| Place | Share of published research |
|---|---|
| USA | 48% |
| Other | 24% |
| Germany | 16% |
| UK | 12% |
Research published from: USA, Germany, UK, Israel.
How we got here
Thymosin beta-4 and TB-500 share a peptide family but followed different paths: full-length Tβ4 entered pharmaceutical development, while TB-500 became a research and community product. The timeline covers early characterization, preclinical research, development of related eye-drop candidates, and ongoing questions about TB-500 evidence and regulation.
TB-500 is the acetylated LKKTETQ motif, residues 17 to 23, from thymosin beta-4, a 43-amino-acid human protein encoded by TMSB4X. It differs from full-length thymosin beta-4, which RegeneRx developed as RGN-259 and which received the INN timbetasin in 2018.
Thymosin beta-4 was identified and studied for its roles in actin regulation and tissue repair, and full-length Tβ4 later entered pharmaceutical development for eye and heart conditions. TB-500 is the acetylated LKKTETQ fragment, a distinct path from the full-length RGN-259 program. The image describes continued community interest in TB-500 alongside limited human clinical evidence and regulatory scrutiny.
Discovery
1977 to 1981
Thymosin beta-4 was identified as a natural human peptide involved in actin binding, cell migration, and tissue repair.
- 1981Thymosin beta-4 identifiedThymosin beta-4 was first isolated from thymus tissue and later found in many human cells, including platelets. It is a 43-amino-acid peptide involved in actin binding, cell migration, and tissue repair.
Fx peptide identity
1991 to 1991
Sequencing studies confirmed that the platelet-derived Fx peptide and thymosin beta-4 are the same molecule.
- 1991Fx peptide confirmed as Tβ4Sequencing studies confirmed that the platelet-derived Fx peptide is the same molecule as thymosin beta-4.
Functional regions identified
1990s to 2000s
Research identified active regions within thymosin beta-4, including the LKKTETQ sequence at residues 17 to 23.
- 1990sActive regions of Tβ4 characterizedResearchers identified active regions within Tβ4, including residues 17 to 23 (LKKTETQ). The shorter fragment retains many biological activities, including promoting cell migration, angiogenesis, and wound healing in preclinical models.
Animal studies
1980s to 2010s
Animal research examined full-length Tβ4 and the LKKTETQ fragment in models of tissue repair and injury.
- 1980sTβ4 and LKKTETQ studied in animal modelsFull-length Tβ4 and the LKKTETQ fragment were studied in animal models of wound healing, muscle repair, cardiac injury, and tissue regeneration. The image reports faster wound healing, reduced inflammation, increased cell migration and angiogenesis, and protection in heart and muscle injury models.
Pharmaceutical development
2000s to 2010s
RegeneRx developed full-length thymosin beta-4 for clinical research, including eye and heart conditions. This program is distinct from the TB-500 fragment.
- 2000sRegeneRx takes full-length Tβ4 into human trialsRegeneRx carried full-length thymosin beta-4 into human trials for eye and heart conditions. Its ophthalmology program reached Phase 3 without gaining approval.
- 2010sRegeneRx develops RGN-259RegeneRx developed RGN-259, also called timbetasin, as full-length Tβ4 ophthalmic drops for corneal repair and neurotrophic keratitis. The formulation contains the full 43-amino-acid sequence, including LKKTETQ; the image lists Phase II and Phase III trials and describes the product as investigational, not approved.
ZKY001 development
2010s to 2020s
ZKY001 is a non-acetylated LKKTETQ peptide developed as eye drops, with early clinical work reported and a Phase III protocol under discussion as of 2026.
- 2026ZKY001 clinical development updateZKY001 is the native, non-acetylated 7-amino-acid LKKTETQ fragment derived from Tβ4, formulated as eye drops for corneal epithelial defects. Phase I safety and pharmacokinetics and Phase II corneal repair trials were completed; a Phase III protocol was under discussion as of 2026.
Ac-LKKTETQ introduced
2010s to 2010s
TB-500 is described as the N-terminally acetylated version of LKKTETQ, distinct from non-acetylated ZKY001.
- 2010sAc-LKKTETQ introduced as TB-500The N-terminally acetylated version of LKKTETQ began to be used in research settings and became commonly known as TB-500. It differs from ZKY001 by a single acetyl group, about 42 Da.
Research and community use
From 2010s
TB-500 became widely discussed in research, fitness, injury recovery, and biohacking communities, with reports described as anecdotal or observational.
- 2012WADA prohibits thymosin beta-4 derivativesWADA prohibits thymosin beta-4 and its derivatives, including TB-500, under Section S2 at all times.
- 2010sTB-500 enters research and community useThe image describes TB-500 as widely available from non-pharmaceutical suppliers as a research chemical and commonly discussed in fitness, injury recovery, and biohacking communities. It notes that reports are anecdotal or observational and that product quality can vary.
Regulatory focus
2020s to 2020s
The image describes FDA concerns about compounded versions, including the lack of clinical or human-exposure data and potential quality and safety issues.
- 2023FDA places TB-500 in Category 2The FDA placed TB-500 in Category 2 of the interim 503A bulks list, blocking compounding.
- 2020sFDA outlines compounding concernsThe FDA stated it had not identified clinical or human-exposure data for TB-500 and raised safety concerns about compounded versions, including purity, sterility, and peptide-related impurities.
- April 2026FDA removes TB-500 from Category 2The FDA removed TB-500 from Category 2 pending advisory review. Removal is not approval.
- July 2026FDA PCAC votes on the 503A bulks listThe FDA PCAC voted 8 to 6, with one abstention, to recommend TB-500 for the Section 503A bulks list. The advisory vote is not final rulemaking.
Analytical identity
2017 to 2024
Direct TB-500 publications focus on measurement, metabolism, and fragment identity rather than human healing.
- 2024TB-500 and its metabolites are quantifiedResearch was performed on the versions of TB-500. The parent fragment broke into shorter metabolites and did not significantly improve fibroblast wound closure; one metabolite did in the laboratory assay.
The numbers behind the grade
- Human RCTs (fragment)
- 0
- Parent in trials
- Phase 3 (Tβ4)
- WADA
- Prohibited (S2)
- Detection
- 30-45 days
- FDA
- Under review
- Common stack
- BPC-157
The people taking it
Users are mostly men in strength training, physique, combat sport and biohacking, the same crowd as BPC-157. It also has a large veterinary use in performance and racehorses, which sits outside human medicine.
One of the two most popular "healing" peptides, almost always mentioned alongside BPC-157 and usually stacked with it. Searched, sold and praised far out of proportion to the human evidence for the specific compound being sold.
As with all gray-market peptides, there is no reliable demographic data, so any precise breakdown by race or sex would be fabricated. The visible user base mirrors BPC-157's and skews strongly male, concentrated in strength training, physique, combat sport and biohacking, with users typically adult. TB-500 adds one distinctive non-human population: performance and racehorses, where it has been used for injury recovery long enough to generate its own anti-doping detection methods. Among people, it is marketed and sold mainly to athletes and lifters seeking faster recovery.
Used worldwide, almost entirely off-label and gray-market, for soft-tissue, tendon and joint recovery, typically stacked with BPC-157, plus a large and distinct veterinary use in performance horses. Banned for any athlete under the World Anti-Doping Code.
Set against the alternatives
TB-500 is the peptide most often stacked with BPC-157, and the two share a predicament: heavy animal interest, no completed human trials of the marketed compound, FDA compounding restrictions, and a WADA ban. The honest split is that TB-500 has the stronger basic-science foundation, with thymosin beta-4 biology replicated across many independent labs and a real pharmaceutical development program in the parent molecule, whereas BPC-157's evidence is more concentrated in a single lab. Against that, neither has the human musculoskeletal trial data that would justify the confident claims made for both. Measured against established options like platelet-rich plasma or structured rehab, TB-500 again has far less human evidence, not more.
What we do not know
- Whether the marketed TB-500 fragment does anything in humans, given that the human evidence is all on the parent protein in other formulations.
- How much the inconsistent identity of "TB-500" products undermines any claim made about it.
- Whether the theoretical tumor-promotion risk from angiogenesis matters in people.
- Whether the July 2026 advisory review opens a regulated compounding path or keeps it restricted.
- Whether the legitimate thymosin beta-4 pharmaceutical program ever yields an approved product that would settle the biology.
What could change
The July 2026 advisory voteCould open a regulated compounding pathway for TB-500, or keep it restricted; either way not drug approval.The parent-molecule pathRegeneRx’s thymosin beta-4 reaching approval in any indication would finally anchor the biology in a real product.Product-identity reformAny move toward standardizing what "TB-500" actually contains would matter more here than for most peptides.Equine doping controlOngoing refinement of detection methods keeps TB-500 in the racing-integrity conversation.
Legal status
TB-500 sits in the same three-lane limbo as BPC-157. It has never been approved by the FDA, EMA or any major regulator for human use. In the compounding lane it was placed in restricted Category 2 in 2023, then removed in April 2026 ahead of the same July 2026 advisory-committee review (removal is not approval). In the research lane it has remained openly for sale the whole time from "research only" vendors. And it is banned in sport at all times. The legitimate clinical path, the RegeneRx thymosin beta-4 program, is entirely separate from the vials sold as TB-500.
Status current as of July 2026. Regulatory positions change, sometimes quickly.
The market for this
What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.
The two real routes match BPC-157. Online research-chemical vendors sell it without a prescription, labeled for research use only, with quality and even molecular identity that vary widely; an independent third-party certificate of analysis is the only meaningful check. The second route is a compounding pharmacy via a telehealth or wellness clinic, which requires a prescription and offers better quality control at higher cost. A separate veterinary and equine market exists outside human medicine. Importing from overseas carries customs-seizure risk.
Gray-market research vials are priced like other peptides, in the low single digits to high single digits of dollars per milligram, with small multi-milligram vials commonly tens of dollars. Compounded TB-500, where a clinician will prescribe it, costs more once physician and pharmacy fees are added. As always, the cheapest route is the least accountable, and an independent certificate of analysis matters more than any label claim, especially given how variable TB-500 product identity is.
Most TB-500 active material is synthesized in China, with India secondary, regardless of the finished vial's branding. Because the compound sold under this name is not standardized, sourcing uncertainty is unusually high: a buyer often cannot be sure whether a vial contains the short fragment, the full protein, or something degraded. An independent, current certificate of analysis is the only real safeguard, and even that is uncommon in the research-vendor market.
ChinaThe dominant source of TB-500 active material worldwide, synthesized and sold directly to consumers online or shipped to repackagers and clinics abroad.IndiaA secondary manufacturing and export source named alongside China in peptide seizures.United StatesDomestic "research peptide" labs that repackage imported bulk or claim US synthesis, plus compounded TB-500 (where prescribed) drawn from bulk active ingredient of often-overseas origin.European Union & UKServed mainly by online import of finished vials or bulk from Asia; no approved product.Equine and veterinary supplyA separate channel of veterinary-grade and gray-market product aimed at performance and racehorses, with its own doping-control problems.Australia & rest of worldStrict prescription-only or unapproved status almost everywhere, so supply is largely illicit import from Asian manufacturers.
At a glance
- Amino acid sequence
- Ac-LKKTETQ
- Amino acids
- 7
- Parent
- Thymosin Beta-4 (43 aa)
- Cell presence
- Virtually all nucleated cells
- Concentration
- 0.1-0.5 mM intracellular
- Gene
- TMSB4X (X chromosome)
- Full Sequence vs Fragment
- Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala-Glu-Ile-Glu-Lys-Phe-Asp-Lys-Ser-Lys-Leu-Lys-Lys-Thr-Glu-Thr-Gln-Glu-Lys-Asn-Pro-Leu-Pro-Ser-Lys-Glu-Thr-Ile-Glu-Gln-Glu-Lys-Gln-Ala-Gly-Glu-Ser vs Ac-LKKTETQ (frag)
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about TB-500.
Nothing outstanding on this one.
Sources
TB-500 is not FDA-approved and FDA proposed at the July 23, 2026 PCAC that it not be added to the 503A bulks list, citing no human effectiveness data, an in-vitro study where TB-500 did not induce fibroblast wound healing, and immunogenicity concerns.
Newtropin, TB-500 FDA 503A Decision (2026), summarizing FDA PCAC briefing materials
FDA Peptide Compounding Status Tracker: TB-500 placed in Category 2 of the interim 503A bulks list in September 2023, and scheduled for PCAC review on July 23, 2026.
RGN-259 is the full-length 43-amino-acid thymosin beta-4, distinct from the TB-500 fragment; the phase 3 SEER-1 neurotrophic keratopathy trial narrowly missed its day-29 primary endpoint (p=0.0656; 6/10 vs 1/8 healed).
The European phase 3 SEER-3 trial of RGN-259 (thymosin beta-4) for neurotrophic keratitis missed its primary endpoint, attributed to a stronger-than-expected placebo effect.
Ophthalmology Times, HLB Therapeutics misses primary endpoint in phase 3 SEER-3 trial of RGN-259
Publication of RGN-259 phase 3 neurotrophic keratopathy results, confirming the clinical program is for the full thymosin beta-4 molecule developed by RegeneRx / ReGenTree, not the TB-500 fragment.
Scoping review of thymosin beta-4 and TB-500 in tissue healing and musculoskeletal repair confirms the evidence base is predominantly animal and in-vitro, with human data limited and largely from the ophthalmic thymosin beta-4 program.
TB-500 and thymosin beta-4 are prohibited at all times under WADA Section S2; TB-500 gained anti-doping prominence partly through horse-racing and Australian sport doping scandals.
BSCG (Banned Substances Control Group), TB-500: Status, Risks, and Bans in Sport and Military
TB-500 is not approved by FDA, EMA, or other major regulators; the FDA lists the TB4 fragment (LKKTETQ) among bulk drug substances that may present significant safety risks in compounding; TB-500 is sold as a research chemical with human use mostly anecdotal or extrapolated from related trials.
Innerbody Research, TB4 and TB-500 Peptide Therapy: What to Know in 2026
RegeneRx developed the thymosin beta-4 program through Phase II for wound healing and dry eye but could not fund Phase III; TB-500 itself remains investigational with no human RCTs for injury.
Preclinical evidence: RGN-259 (thymosin beta-4) improved dry-eye efficacy measures in an animal model, illustrating that supportive efficacy data for the class is animal/model-based rather than human RCT-based for the TB-500 fragment.
The studies that matter
Kleinman group, NIDCR (foundational Tβ4 biology)1990s-2000s
Established thymosin beta-4 as a G-actin-sequestering protein that accelerates wound healing in rodents, the basis for the whole "regenerative peptide" idea, replicated across multiple labs.
RegeneRx RGN-259 (ophthalmic Tβ4)2000s-2020s
Phase 2 and Phase 3 trials of full-length thymosin beta-4 eye drops for dry eye and corneal healing reported benefit but never reached approval. The strongest human data, and it is not of TB-500.
RegeneRx RGN-352 (cardiac Tβ4)2000s
Early human work on intravenous thymosin beta-4 for heart repair after injury, again on the parent protein, not the fragment.
Animal soft-tissue and cardiac models2000s-2020s
Consistent improvement in wound closure, tendon and ligament repair, and cardiac recovery across independent groups, all preclinical.
TB-500 fragment human RCTsnone
No completed, published human efficacy trial of the marketed TB-500 fragment exists for any tissue-repair use as of 2026.