TB-500
A synthetic version of the active region of thymosin beta-4, widely used for tissue repair, wound healing, and recovery from injuries.
What is TB-500?
TB-500 is a synthetic version of the active region of thymosin beta-4, a naturally occurring 43-amino acid peptide present in virtually all human cells. It promotes tissue repair by upregulating actin, a cell-building protein, and by promoting cell migration, blood vessel formation, and reducing inflammation. It is one of the most popular peptides for injury recovery.
What TB-500 Is Investigated For
TB-500 is investigated primarily for tissue repair through a mechanism distinct from BPC-157 — it regulates actin dynamics and cell migration rather than angiogenesis. The strongest preclinical signals are in wound healing, tendon/ligament repair, and cardiac tissue regeneration, where animal models consistently show accelerated recovery and reduced fibrosis. Hair regrowth and neuroprotection are interesting secondary signals emerging from broader thymosin beta-4 research. As with BPC-157, human clinical trials for the specific active fragment are essentially absent — most of the human data is for full-length recombinant thymosin beta-4, a related but larger molecule. The peptide is banned by WADA, a signal of perceived performance effects rather than proven efficacy.
History & Discovery
Thymosin beta-4, the parent 43-amino-acid peptide from which TB-500 is derived, was first isolated from bovine thymus in 1981 by Teresa L. K. Low and Allan L. Goldstein as part of NIH-funded work on thymosin peptide fractions. Over the following decade Hynda Kleinman's group at the National Institute of Dental and Craniofacial Research established much of the core biology — identifying thymosin beta-4 as a G-actin sequestering protein present in virtually every nucleated cell and showing that it accelerated wound healing in rodent models. This foundational work is the reason TB-4 is sometimes described as the prototypical 'regenerative' peptide. TB-500 itself is a synthetic peptide sold and researched as representing the active region of thymosin beta-4, though it is important to note that products sold under the TB-500 name are not always chemically identical to full-length recombinant TB-4 used in clinical trials. RegeneRx Biopharmaceuticals pursued thymosin beta-4 through Phase II human trials across multiple indications beginning in the 2000s, including dry eye (RGN-259), pressure ulcers and venous stasis ulcers (RGN-137), and cardiac ischemia — producing most of the human clinical data on the parent molecule. The peptide entered the sports and research-chemical market in the 2010s, where it is commonly stacked with BPC-157 for musculoskeletal repair despite the lack of human trials evaluating that specific combination.
How It Works
TB-500 helps your body repair itself faster by promoting the migration of repair cells to injury sites, growing new blood vessels to supply healing tissue, and reducing scar formation. It works on tendons, ligaments, muscles, skin, and even the heart.
TB-500 contains the actin-binding domain of thymosin beta-4, sequestering G-actin monomers and promoting F-actin polymerization for cell migration. It upregulates Akt/mTOR signaling for cell survival and proliferation. It promotes angiogenesis through VEGF upregulation, reduces inflammation via NF-kB modulation, and decreases fibrosis by inhibiting TGF-beta-driven collagen deposition. The Ac-SDKP tetrapeptide fragment specifically inhibits hematopoietic stem cell proliferation and has anti-fibrotic properties.
Evidence Snapshot
Human Clinical Evidence
Limited. Some clinical observations and small studies. Thymosin beta-4 has been in clinical trials for wound healing and dry eye.
Animal / Preclinical
Strong. Extensive data on wound healing, cardiac repair, and tissue regeneration in animal models.
Mechanistic Rationale
Strong. Actin biology and tissue repair mechanisms are well-characterized.
Research Gaps & Open Questions
What the current literature has not yet settled about TB-500:
- 01Human efficacy for the TB-500 fragment specifically — most human clinical data exists for full-length recombinant TB-4 (RegeneRx programs), not for the synthetic TB-500 fragment sold in the research-chemical market, and identity/purity of marketed TB-500 products is often not verified.
- 02Long-term safety and cancer risk — TB-4's documented role in tumor cell migration and metastasis in multiple cancer models has not been resolved through long-duration human safety data, leaving a meaningful oncology-signal question unanswered.
- 03Optimal human dosing — no human dose-ranging study has established minimum effective or maximum tolerated doses for musculoskeletal injury indications.
- 04Pharmacokinetics of subcutaneous and intramuscular administration in humans — bioavailability, tissue distribution, and effective half-life have not been rigorously characterized.
- 05TB-500 plus BPC-157 combination data — despite widespread anecdotal use of this stack, no controlled human study has evaluated additive or synergistic effects, adverse-event rates, or whether either peptide alone would achieve the same outcome.
- 06Differentiation between full-length TB-4 and synthetic fragment products — whether pharmacologic effects observed for recombinant TB-4 generalize to the shorter synthetic fragments commonly sold as TB-500 has not been established.
Forms & Administration
SC or IM injection. Loading phase: 2-2.5mg twice weekly for 4-6 weeks. Maintenance: 2mg every 2 weeks. Often combined with BPC-157 for synergistic healing. All injectable peptides should only be administered under the guidance of a qualified healthcare provider. Never self-administer without clinician oversight.
Dosing & Protocols
The ranges below reflect protocols commonly discussed in the literature and by clinicians — not a prescription. Actual dosing for any individual should be determined by a qualified healthcare provider who knows the patient.
Typical Range
Protocols discussed for injection typically use 2–2.5 mg per dose, with a front-loading phase of 2.5 mg twice weekly for 4–6 weeks followed by maintenance of 2 mg every 1–2 weeks. Some protocols use 5 mg once weekly during loading. These numbers come from community and clinician-reported protocols rather than human dose-ranging trials; the animal literature uses widely varying doses on a mg/kg basis that do not translate cleanly to human flat doses.
Frequency
During a loading phase, twice-weekly injection is the most commonly described cadence. After 4–6 weeks many protocols shift to once weekly or once every two weeks for maintenance. The rationale for infrequent dosing versus daily dosing is pharmacokinetic: thymosin beta-4's circulating half-life is short, but its effects on cell migration and actin remodeling are thought to persist beyond plasma clearance.
Timing Considerations
Time of day
No strict time of day — TB-500's long plasma persistence and typical twice-weekly or weekly dosing mean daily clock time is not meaningful.
Relative to meals
No meal timing required; inject at a consistent time rather than a specific meal window.
Relative to exercise
Not tied to training sessions. Some users align injections with rest days on the rationale that repair signaling proceeds during recovery periods, though this is convention rather than pharmacokinetic necessity.
Cycle Length
A typical discussed cycle is a 4–6 week loading phase followed by a lower-frequency maintenance phase or a washout. Some clinicians use 4–8 week courses tied to the healing timeline of a specific injury, then stop. Continuous long-term use has not been studied in humans.
Protocol Notes
TB-500 is typically supplied as a lyophilized powder requiring reconstitution in bacteriostatic water. A common reconstitution is 5 mg of peptide in 2–3 mL of bacteriostatic water; with 2 mL that yields 2,500 mcg/mL, meaning a 2 mg dose is 0.8 mL on an insulin syringe. Subcutaneous injection into the abdominal fat pad is the most common route; intramuscular injection near the affected tissue is also used in musculoskeletal protocols. One point of confusion worth flagging: the products sold as 'TB-500' on the research-chemical market may correspond to different synthetic fragments (commonly the N-acetylated 17-23 region of TB-4 identified in doping control literature) rather than the full 43-amino-acid thymosin beta-4 used in RegeneRx's clinical work. This means that dosing extrapolated from TB-4 clinical trials does not map cleanly to TB-500 products, and purity and identity should not be assumed. TB-500 is commonly stacked with BPC-157 in recovery protocols. There is no human trial evidence for the combination; the rationale is mechanistic complementarity (actin-driven cell migration plus angiogenesis and growth factor modulation) rather than demonstrated additive benefit.
These numbers are not a prescription. TB-500 is not FDA-approved for any medical condition, and products sold under this name vary in identity and purity. Any actual use should be under the direct supervision of a qualified healthcare provider.
Timeline of Effects
Onset
Anecdotal reports from injury-recovery use commonly describe initial subjective improvement (reduced pain or stiffness) within 1–2 weeks of starting a loading protocol. Tissue-level healing signals are inherently slower and are typically described over 3–4 weeks rather than days. Human trials of full-length TB-4 in dermal and corneal wound healing saw measurable endpoint changes on the order of several weeks.
Peak Effect
Peak effect is typically described in the 4–8 week window corresponding to the end of a standard loading phase. This aligns with the tissue-remodeling timelines observed in preclinical wound-healing models. Whether continued dosing beyond this window adds benefit or simply maintains a plateau is not established.
After Discontinuation
Thymosin beta-4's plasma half-life is short (minutes to a few hours), but its downstream effects on actin dynamics, cell migration, and tissue remodeling persist longer. Most users describe benefits that persist after cessation provided the underlying tissue has healed; ongoing anti-inflammatory effects tend to fade within weeks of discontinuation. Rebound effects have not been systematically described.
Monitoring & Measurement
Bloodwork & Labs
- •hs-CRP — systemic inflammation proxy; useful when the injury context is inflammatory
- •ESR — slower-moving inflammation marker, pairs with hs-CRP
- •CBC — tracks hematocrit, since TB-500 has documented angiogenic activity, and rules out confounding issues
- •Comprehensive metabolic panel — baseline only, for hepatic anchor
Functional & Performance Tests
- •Standardized pain score (VAS or NRS) on the target tissue, recorded daily
- •Goniometer-measured range of motion for the affected joint
- •Sport- or task-specific functional test (single-leg hop, grip strength, walking distance, throwing velocity — pick one your injury is actually limited by)
- •Diagnostic ultrasound or MRI at baseline and end-of-cycle for structural injuries
When to Test
Symptom and functional tracking daily. hs-CRP and CBC at baseline and 4–6 weeks. Imaging at baseline and end of a 4–6 week cycle if accessible.
Interpretation & Notes
As with BPC-157, TB-500's claimed effect is tissue-local and slow — the measurement job is functional documentation rather than a blood-marker chase. The credible at-home setup is a disciplined pain-and-function log paired with pre- and post-cycle imaging. hs-CRP moves when the injury context is systemically inflammatory and can stay flat in mechanical injuries where the peptide may still be helping. TB-500's theoretical angiogenesis signal is the reason the oncology-risk discussion exists — if you have a cancer history or active screening concern, this warrants a clinician conversation before use, not a post-hoc lab. There is no validated serum marker that tracks TB-500 activity. Basic panels via LabCorp, Quest, Marek Health, or Ulta Lab Tests; imaging typically needs a clinician order.
Common Questions
Who TB-500 Is NOT For
- •Pregnancy — no human pregnancy safety data exists; TB-4's broad effects on cell migration and angiogenesis raise theoretical fetal-development concerns that have not been studied.
- •Breastfeeding — no data on transfer into breast milk or effects on nursing infants.
- •Active or recent-history cancer — thymosin beta-4 has been implicated in tumor cell migration, invasion, and metastasis in several cancer types (including thyroid, hepatocellular, and colorectal), and several preclinical studies have shown that blocking TB-4 attenuates tumor progression. This is the most serious mechanistic concern for TB-500 and is reason for caution in anyone with an active or recent malignancy.
- •Pediatric use (under 18) — no studies in pediatric populations; developmental signaling effects are unknown.
- •Known hypersensitivity to peptide therapeutics or to excipients used in compounded preparations.
- •Concurrent anti-angiogenic oncology therapy — TB-500's promotion of angiogenesis and cell migration would be expected to oppose the intended effect of agents like bevacizumab or VEGF-targeted tyrosine kinase inhibitors.
Drug & Supplement Interactions
Documented human drug interactions for TB-500 are absent because human pharmacology studies are absent; what follows is theoretical and derived from mechanism. The most important theoretical interaction is with anti-angiogenic oncology and ophthalmology therapies (bevacizumab, aflibercept, VEGF-targeted kinase inhibitors): TB-500's upregulation of VEGF and cell migration opposes the intended effect of these agents, and co-administration should be avoided. Similar caution applies to patients receiving anti-VEGF intravitreal injections for wet macular degeneration or diabetic retinopathy. Because TB-4 modulates inflammatory signaling including NF-kB, theoretical interactions may exist with immunosuppressants used after transplant or for autoimmune disease, though direction and magnitude in humans are unknown. Patients on anticoagulants should be aware that the peptide's effects on vasculature and platelet behavior are not well characterized in humans. Absence of documented interactions is not the same as absence of interactions, and any concurrent medication use should be disclosed to the prescribing clinician.
Safety Profile
Common Side Effects
Cautions
- • Not FDA-approved
- • Theoretical concern about promoting growth of existing tumors
- • Banned by WADA in competitive sports
What We Don't Know
Long-term safety in humans is not well-established. Cancer risk with chronic use needs more study.
Legal Status
United States
TB-500 and thymosin beta-4 are not FDA-approved for any indication. Full-length recombinant TB-4 (RGN-259, RGN-137) has been studied in Phase II trials under RegeneRx and its partners but has not advanced to approval. TB-500 has historically been available through compounding pharmacies and research-chemical suppliers; following the FDA's 2023 review of peptides considered for 503A compounding, access has tightened, though enforcement varies. Research-chemical channel sales are not intended or authorized for human use.
International
No major regulator (EMA, MHRA, TGA, Health Canada) has authorized TB-500 or thymosin beta-4 as a medicine. Australia's TGA treats it as a Schedule 4 prescription-only substance and has taken enforcement action. Most other jurisdictions treat it as an unapproved investigational agent, and importation of personal-use quantities is restricted in several countries.
Sports & Competition
TB-500 is explicitly prohibited by WADA under S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics) at all times, in and out of competition. Multiple athletes — including high-profile cases in horse racing and human sport — have been sanctioned for TB-500 use. Doping-control laboratories have developed and validated assays specifically targeting the TB-500 synthetic fragment. Athletes subject to WADA code, USADA, UKAD, or equivalent bodies should treat TB-500 as unambiguously banned.
Regulatory status changes over time. Verify current local rules with a qualified professional.
Myths & Misconceptions
Myth
TB-500 is the same thing as thymosin beta-4.
Reality
TB-500 is typically a synthetic fragment marketed as representing the active region of thymosin beta-4, not full-length TB-4. The human clinical trial data (RegeneRx's Phase II programs in dry eye, wound healing, and cardiac ischemia) was largely performed with full-length recombinant TB-4, and products sold as TB-500 cannot be assumed to share identical pharmacology, purity, or efficacy.
Myth
TB-500 is FDA-approved for injury recovery.
Reality
It is not approved for any indication. No version of thymosin beta-4 — full-length or fragment — has received regulatory approval as a drug. Its availability has historically been through compounding pharmacies and research-chemical suppliers, not as an approved medicine.
Myth
TB-500 is safe from a sports-doping standpoint because it's 'just a healing peptide.'
Reality
TB-500 is explicitly prohibited by WADA under S2 at all times, and validated doping-control assays for the TB-500 fragment exist. Athletes have been sanctioned for its use. Treating it as outside the doping code because of its healing rationale is factually wrong and career-risking.
Myth
TB-500 and BPC-157 work better together than alone, based on the evidence.
Reality
There is no controlled human trial evaluating the TB-500 plus BPC-157 combination. The rationale for stacking them is mechanistic complementarity (actin/migration plus angiogenesis/growth factors), but 'makes sense mechanistically' is not the same as 'demonstrated additive benefit in humans.' The stack is ubiquitous in community protocols, but the evidentiary basis is thin.
Myth
Because TB-4 is present in nearly every human cell, exogenous TB-500 must be safe.
Reality
Endogenous presence of a signaling molecule does not imply that supraphysiologic exogenous dosing is safe. TB-4 has documented roles in tumor cell migration and metastasis across several cancer types in preclinical work, and long-term human safety data is absent. The 'naturally occurring' framing is misleading when applied to injectable dosing at research-chemical concentrations.
Published Research
39 studiesThymosin beta4-derived peptides alleviate neuroinflammation and neurite atrophy in both in vitro models and in vivo 5xFAD mice: A potential therapy for memory improvement in Alzheimer's disease.
Recombinant human thymosin beta 4 improves ischemic cardiac dysfunction in mice and patients with acute ST-segment elevation myocardial infarction after reperfusion
Thymosin beta 4 as an Alzheimer disease intervention target identified using human brain organoids
Thymosin Beta-4 Modulates Cardiac Remodeling by Regulating ROCK1 Expression in Adult Mammals
Enhancing fat graft survival: thymosin beta-4 facilitates mitochondrial transfer from ADSCs via tunneling nanotubes by upregulating the Rac/F-actin pathway
Thymosin β(4) and β(10) Expression in Human Organs during Development: A Review
Thymosin beta-4 - A potential tool in healing middle ear lesions in adult mammals
Thymosin beta-4 participate in antibacterial immunity and wound healing in black tiger shrimp, Penaeus monodon
Thymosin Beta 4 Protects Hippocampal Neuronal Cells against PrP (106-126) via Neurotrophic Factor Signaling
Thymosin beta 4: A potential novel adjunct treatment for bacterial keratitis
Thymosin beta 4 prevents systemic lipopolysaccharide-induced plaque load in middle-age APP/PS1 mice
Thymosin Beta 4 Inhibits LPS and ATP-Induced Hepatic Stellate Cells via the Regulation of Multiple Signaling Pathways
Thymosin beta-4 denotes new directions towards developing prosperous anti-aging regenerative therapies
Aberrant Expression of Thymosin Beta-4 Correlates With Advanced Disease and BRAF V600E Mutation in Thyroid Cancer
Thymosin beta-4 improves endothelial function and reparative potency of diabetic endothelial cells differentiated from patient induced pluripotent stem cells
Adjunctive Thymosin Beta-4 Treatment Influences PMN Effector Cell Function during Pseudomonas aeruginosa-Induced Corneal Infection
A first-in-human, randomized, double-blind, single- and multiple-dose, phase I study of recombinant human thymosin β4 in healthy Chinese volunteers
Utilizing Developmentally Essential Secreted Peptides Such as Thymosin Beta-4 to Remind the Adult Organs of Their Embryonic State-New Directions in Anti-Aging Regenerative Therapies
Thymosin beta 4 and the eye: the journey from bench to bedside
Thymosin beta 4 regulation of actin in sepsis
Sources of variability in quantifying circulating thymosin beta-4: literature review and recommendations
Potential role of thymosin beta 4 in the treatment of nonalcoholic fatty liver disease
Adsorption effects of the doping relevant peptides Insulin Lispro, Synachten, TB-500 and GHRP 5
Thymosin Beta 4: A Potential Novel Therapy for Neurotrophic Keratopathy, Dry Eye, and Ocular Surface Diseases
Thymosin β4 Promotes Dermal Healing
Cardioprotection by Thymosin Beta 4
Thymosin Beta 4 Is a Potential Regulator of Hepatic Stellate Cells
Potential role of thymosin Beta 4 in liver fibrosis
Doping control analysis of TB-500, a synthetic version of an active fragment of thymosin β₄.
Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500, a product suspected to possess doping potential
Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications
Thymosin beta-4 is essential for coronary vessel development and promotes neovascularization via adult epicardium
Thymosin beta-4 and the eye: I can see clearly now the pain is gone
Adhesive and proteolytic phenotype of migrating endothelial cells induced by thymosin beta-4
Thymosin beta4 promotes angiogenesis, wound healing, and hair follicle development.
Thymosin beta 4 interactions
Thymosin beta4 accelerates wound healing
Chemical characterization of thymosin beta 4
Thymosin beta 4: a ubiquitous peptide in rat and mouse tissues
Popular Stacks Including TB-500
Wolverine Peptide Stack (BPC-157 + TB-500)
The Wolverine Stack is the most popular peptide recovery combination — BPC-157 for localized tissue repair paired with TB-500 for systemic healing, cell migration, and anti-inflammatory support.
GLOW Peptide Stack (BPC-157 + TB-500 + GHK-Cu)
GLOW is a popular pre-mixed compounded peptide blend combining BPC-157 tissue repair, TB-500 cell migration, and GHK-Cu collagen remodeling in a single 70 mg vial. Also covers the two-peptide BPC-157 + GHK-Cu pairing for practitioners sourcing vials separately.
KLOW Peptide Stack (BPC-157 + TB-500 + GHK-Cu + KPV)
KLOW is a pre-mixed four-peptide compounded blend combining BPC-157 and TB-500 systemic repair, GHK-Cu collagen remodeling, and KPV anti-inflammatory coverage in a single 80 mg vial. It extends the popular GLOW formulation with an explicit anti-inflammatory layer.
Quick Facts
- Class
- Tissue Repair Peptide
- Tier
- C
- Evidence
- Emerging
- Safety
- Moderate Data
- Updated
- Apr 2026
- Citations
- 39PubMed
Also known as
Tags
Peptide Families
Related Goals
Conditions Discussed
Evidence Score
Clinical Trials
View Clinical TrialsLinks to ClinicalTrials.gov for reference. Listing does not imply endorsement.