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Thymosin Beta-443 residuesSDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGESEach bubble = one amino acid. Size = residue mass. Color = chemical class.Also known as: Tb4, TB4, Tβ4
In a Phase II pressure ulcer trial, 67% of wounds healed completely on thymosin beta-4 compared to 25% on placebo. Full-length Tb4 is a 43-amino-acid protein and the body's primary G-actin sequestering molecule, controlling cell migration, tissue repair, and angiogenesis through multiple functional domains. The separate Ac-SDKP region adds cardioprotective and anti-fibrotic activity that the shorter TB-500 fragment lacks entirely. Athletes, post-surgical patients, and integrative medicine practitioners use Tb4 for accelerated soft tissue healing, reduced scarring, and systemic anti-inflammatory support. Two Phase I safety trials in healthy volunteers found no dose-limiting toxicities at doses up to 1,260 mg IV.
67% complete wound healing at 8 weeks, vs 25% on placebo. That Phase II pressure ulcer result is the clearest clinical signal for thymosin beta-4 (Tb4, CAS 77591-33-4), a 43-amino-acid protein with a molecular weight of approximately 4,921 Da. Tb4 is the most abundant actin-sequestering protein in human cells. It locks G-actin monomers in place, which controls when and where cells migrate, divide, and differentiate. That single mechanism feeds into wound closure, blood vessel formation, and progenitor cell activation. The N-terminal Ac-SDKP tetrapeptide (released by enzymatic cleavage) adds a second layer: anti-fibrotic and cardioprotective signaling that reduces scar tissue and protects cardiomyocytes from oxidative damage. In practice, the community uses Tb4 primarily for athletic soft tissue injury recovery (tendons, ligaments, muscles) and post-surgical wound healing. The typical loading protocol runs 2 to 2.5 mg subcutaneous, two to three times per week for 6 weeks, followed by weekly maintenance. Stacking with BPC-157 is the dominant community approach; the two cover different healing phases through separate signaling pathways. Research status as of April 2026: two independent Phase I safety trials [1] established tolerability up to 1,260 mg IV. Phase II data exists for wound healing and dry eye. A 2025 Phase II cardiac RCT (n=96 STEMI patients) found significant infarct reduction in the early-treatment subgroup (n=43) but missed significance in the full cohort. No FDA approval exists for any indication. Compounded injectable Tb4 was placed on FDA Category 2 (prohibited) in February 2024.
Tb4 sequesters G-actin monomers. That sounds abstract until you consider what actin polymerization controls: cell migration, proliferation, differentiation, and wound closure. By regulating the pool of available G-actin, Tb4 is a master switch for tissue repair timing. The central LKKTETQ domain (amino acids 17 to 23, shared with the TB-500 fragment) binds actin directly. This promotes cell motility and angiogenesis at injury sites. Blood vessel formation accelerates nutrient and oxygen delivery to damaged tissue. Full-length Tb4 carries something the fragment does not. The N-terminal Ac-SDKP tetrapeptide, released by enzymatic cleavage, provides distinct anti-fibrotic signaling. It attenuates inflammatory macrophage infiltration, reduces fibroblast overactivity, and protects cardiomyocytes from oxidative stress. ACE normally degrades Ac-SDKP; patients on ACE inhibitors may see raised Ac-SDKP levels and stronger anti-fibrotic effects (a clinically relevant interaction). Tb4 also activates integrin-linked kinase (ILK). This drives cardiac progenitor cell activation and epicardial cell migration. After tissue injury, platelets and macrophages release Tb4 to protect surrounding cells from secondary damage. A 2025 Phase II cardiac RCT confirmed ErbB2-dependent myocardial repair in a murine model alongside human infarct reduction data (Cardiovascular Research 2025, doi:10.1093/cvr/cvaf156).
Phase I safety established in two independent healthy volunteer trials (IV, up to 1,260 mg). Phase II efficacy data: wound healing (pressure ulcers, 67% complete healing vs 25% placebo), dry eye, venous ulcers. Phase III completed for ophthalmic indications (SEER-1 neurotrophic keratopathy missed primary endpoint p=0.0656; ARISE dry eye series inconclusive). 2025 Phase II cardiac RCT (n=96 STEMI) showed significant infarct reduction in early-treatment subgroup (n=43) but not full cohort. No FDA approval for any indication as of April 2026.
Cardiovascular Research 2025, Vol 121(17): Randomized, double-blind, placebo-controlled Phase II RCT of rhTβ4 in 96 STEMI patients post-PCI. Early-treatment subgroup (rhTβ4 within 8h post-PCI, n=43): significant infarct area reduction vs placebo at 90 days; ErbB2-dependent mechanism confirmed in parallel murine I/R model. Full cohort (n=96): non-significant. Most clinically significant human cardiac efficacy signal to date. doi:10.1093/cvr/cvaf156
No Phase III approval for any non-ophthalmic indication. Phase III ophthalmic trials missed or inconclusive on primary endpoints. 2025 cardiac RCT full cohort non-significant; early-treatment subgroup result requires confirmation. Long-term safety data absent. Injectable compounded Tβ4 prohibited in US since February 2024 (FDA Category 2). Full-length 43aa vs 7aa TB-500 fragment frequently conflated in community reports, confounding evidence interpretation. SC pharmacokinetics formally uncharacterized: all PK data is IV-derived.
Strongly endorsed for athletic soft tissue injury (tendons, ligaments, muscles) and post-surgical wound healing. Most community discussion conflates full-length 43aa Tβ4 with TB-500 (7aa fragment): protocols labeled "TB-500" may or may not reflect full-length product. Full-length Tβ4 is considered by advanced users to have broader benefit (cardiac, anti-fibrotic, immunomodulatory) but is harder to source and verify.
Science evidence is concentrated in ophthalmic (Phase III), wound healing (Phase II), and cardiac (Phase II). Community uses Tβ4 primarily for athletic soft tissue injury: mechanistically plausible extrapolation from wound healing evidence but not directly studied in RCT format. Both science and community converge on a healing/regenerative use case. Dosing frequency diverges: clinical trials used structured loading regimens; community standard is 2–3x/week SC. Doses are broadly comparable when expressed as weekly totals.
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 750mcg | 3x/week |
| Moderate | 1,500mcg | 2-3x/week |
| Aggressive | 3mg | 3x/week |
First thing: make sure your product is actually 43 amino acids. The community conflates Tb4 with TB-500 constantly, and vendors don't help. If your COA doesn't show a molecular weight near 4,921 Da on mass spectrometry, you probably have the 7aa fragment (843 Da). HPLC purity alone can't tell the difference. Reconstitution math for common vial sizes. A 5 mg vial plus 1 mL bacteriostatic water gives you 5 mg/mL (5,000 mcg/mL). On a U-100 insulin syringe, each unit equals 50 mcg. So 2,000 mcg (a standard loading dose) is 40 units; 2,500 mcg is 50 units; 1,500 mcg is 30 units. For a 2 mg vial plus 1 mL BAC water, you get 2 mg/mL; 750 mcg (beginner tier) is 37.5 units. Store reconstituted vials refrigerated at 2 to 8 degrees C and use within 2 to 3 weeks. Lyophilized powder keeps for up to 24 months refrigerated. Use bacteriostatic water, not sterile saline (saline shortens shelf life after reconstitution). The short half-life (about 2 hours IV) is why daily or frequent dosing makes sense. But the dominant community convention is 2 to 3 times per week at higher doses; either approach can be justified, and the 2 to 3x/week schedule is more practical.
Loading phase: full dose 3x/week for 6-12 weeks. Then maintenance: half dose 1-2x/week. All protocols run 8-12 weeks. Standard community and integrative medicine protocols recommend 6 weeks off after each cycle for receptor sensitivity recovery.
Community and integrative medicine protocols recommend 6 weeks off after each cycle based on receptor sensitivity recovery: sustained Tβ4 exposure may downregulate progenitor cell responsiveness and actin-binding pathway signaling. The 6-week off period also provides a window to objectively assess healing progress before reinitiation, and reduces theoretical risk of continuous angiogenic promotion in the context of any undetected occult malignancy. The short IV half-life (~2h) ensures rapid plasma clearance, but downstream cellular effects (progenitor activation, angiogenic signaling) may persist significantly longer.
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Expected: Reduced pain and inflammation at injury site by weeks 2–3; improved tissue pliability and range of motion by weeks 4–6; accelerated return to full training by weeks 8–12. Community reports strongly positive for tendon and ligament injuries.
Monitor: No specific labs required for healthy adults on short cycles. Monitor injection sites for nodule formation (rotate sites more frequently if nodules appear). Discontinue if fever >100.4°F or skin rash/hives develop.
Wash hands thoroughly and wipe vial tops with an alcohol swab.
Let the water run down the inside wall of the vial. Do not shake; swirl gently until dissolved. This gives you 5 mg/mL (50 mcg per unit on a U-100 syringe).
For a 2,000 mcg loading dose, pull to the 40-unit mark on a U-100 insulin syringe. For 2,500 mcg, pull to 50 units. For 1,500 mcg (wound healing protocol), pull to 30 units.
Choose an injection site on the abdomen (2 inches from the navel) or outer thigh. Tb4 is systemic; you do not need to inject near the injury site.
Pinch the skin, insert the needle at a 45-degree angle (29 to 31 gauge, 0.5-inch needle), and inject slowly over 10 or more seconds.
Do not reuse the same spot within the same week. This prevents nodule formation.
No specific meal timing required.
Maintenance: reduce to once per week for 6 more weeks. Then take 6 weeks off before restarting.
Store reconstituted vial in the refrigerator (2 to 8 degrees C). Use within 2 to 3 weeks of reconstitution.
Community: 2–5 mg SC per injection, 2–3x/week. No formal human bioavailability comparison vs IV. All PK data (PMID 20536472) is entirely IV-derived. SC absorption rate and peak plasma levels are unknown in humans.
Abdomen or thigh. Systemic effect: no need to inject near injury site. Use 29–31G needle. Rotate sites at every injection. Reconstitute with bacteriostatic water (not sterile saline: shorter shelf life with saline).
Phase I trials used 42–1,260 mg IV single dose (safety/PK study: far above any community SC dose). Cardiac Phase II (2025): 1–2 mg/kg IV within 8h post-PCI. Half-life 0.95–2.1h (dose-dependent) characterized only via IV route.
Used in clinical trials for controlled PK characterization and cardiac applications. SC remains the only practical community route.
RGN-259 protocol: 0.1% Tβ4 ophthalmic drops 5x/day × 4 weeks (Phase III SEER-1/2/3 design). Topical ophthalmic route does not provide systemic healing effects. Engineered tandem tTβ4 (IOVS Nov 2025, PMC12636994) shows 7-fold improved corneal epithelial migration vs standard monomer: next-generation formulation not yet in clinical trial.
RGN-259 by RegeneRx Biopharmaceuticals, not FDA-approved as of April 2026. Not available as a consumer product. ARISE dry eye Phase III series: inconclusive. SEER-3 (NK) status unconfirmed as of April 2026.
The dominant healing stack. BPC-157 acts through nitric oxide signaling and growth hormone receptor modulation; Tβ4 acts through actin dynamics and progenitor cell activation: complementary mechanisms covering different healing phases. BPC-157 targets early inflammatory resolution; Tβ4 drives angiogenesis and cellular migration.
BPC-157 250–500 mcg SC daily + Tβ4 2–2.5 mg SC 2x/week (loading 6 weeks) → Tβ4 2 mg 1x/week (maintenance 4–6 weeks). 6 weeks off after cycle.
Copper peptide adds anti-inflammatory signaling, collagen synthesis promotion, and angiogenesis support. Commonly added for wound healing or skin repair to complement Tβ4 anti-fibrotic and cellular migration effects.
GHK-Cu 1–2 mg topical or SC daily alongside Tβ4 loading protocol for wound or skin healing goals.
Short tripeptide with anti-inflammatory properties. Community users add KPV for additional systemic or gut anti-inflammatory coverage alongside Tβ4, particularly for systemic inflammation goals.
KPV 500 mcg–1 mg SC or oral daily alongside Tβ4 protocol.
Directly opposes Tβ4 mechanism of action. Anti-VEGF therapies block the angiogenesis that Tβ4 actively promotes. Concurrent use is mechanistically contradictory and may negate therapeutic effect of both agents.
Do not combineTβ4 promotes angiogenesis and may increase bleeding risk at healing sites. Clinical significance uncertain but additive bleeding risk is a real concern, particularly post-surgical or with active wound healing.
Corticosteroids suppress the inflammatory cascade that Tβ4 modulates. Concurrent systemic corticosteroid use may blunt Tβ4 healing response by suppressing the immune signaling Tβ4 requires to drive tissue repair.
Tβ4 modulates immune cell migration and macrophage activity. Effect of concurrent immunosuppressive therapy on Tβ4 activity is unknown. Use with caution in transplant patients or those on chronic immunosuppression.
Pricing updated 2026-04-09
The most serious concern with Tb4 is its relationship to cancer biology. Tb4 promotes angiogenesis, cell migration, and proliferation. All three processes can support tumor growth and vascularization. Some in vitro studies show Tb4 upregulation in tumor tissue; others show anti-tumor effects. Phase I and II trials found no cancer-promoting signals at tested doses, but long-term human data does not exist. Active cancer or personal cancer history is a firm contraindication. Published safety data comes from two Phase I trials in healthy volunteers. The IV study [1] tested single doses from 42 mg to 1,260 mg and reported no dose-limiting toxicities. Adverse events were infrequent and rated mild to moderate. The Chinese Phase I study [2] confirmed tolerability in a separate population. Total human safety database for injectable Tb4 is small (fewer than 200 participants across all trials combined). Community-reported side effects during loading phase (weeks 1 to 2): Fatigue and flu-like symptoms are the most commonly flagged issue. Users describe 3 to 7 days of mild malaise during the initial loading period. This typically resolves by week 2 to 3. If fatigue persists beyond two weeks or fever exceeds 100.4 degrees F, reducing dose or stopping is appropriate. Headache occurs at moderate frequency. Mild nausea and lightheadedness are less common but reported. Injection site reactions include redness, mild swelling, and nodule formation. Nodules develop from repeated injection at the same site. Rotating locations at every injection and using 29 to 31 gauge needles reduces this risk. Occasional mild water retention has been noted during maintenance phases. Contraindications: active cancer or cancer history (angiogenic risk), pregnancy or breastfeeding (no safety data), active systemic infections (immune modulation concern), known hypersensitivity to Tb4, and concurrent anti-VEGF therapy (directly opposes mechanism). Drug interactions worth knowing: anticoagulants (warfarin, heparin, DOACs) may carry additive bleeding risk at healing sites. ACE inhibitors block Ac-SDKP degradation and may potentiate anti-fibrotic effects. Anti-VEGF biologics (bevacizumab, ranibizumab) are contraindicated. Immunosuppressants have unknown interaction profiles with Tb4 immune modulation. Stop dosing and consult a physician if you develop persistent fever, skin rash, hives, signs of anaphylaxis, or any new suspicious mass or lump.
Verify Thymosin Beta-4 dosing and safety with a second opinion
Three compounding risk vectors: 1) Mislabeling: 7aa TB-500 fragment (~843 Da) frequently sold as full-length 43aa Tβ4 (~4,921 Da), or vice versa; amino acid count must be confirmed by mass spectrometry, not HPLC alone. 2) Regulatory squeeze: FDA enforcement has severely contracted the vendor pool; Peptide Sciences (major 43aa source) voluntarily shut down March 2026. 3) Legal unavailability: compounded injectable Tβ4 is prohibited in US through 503A/503B pharmacies (FDA Category 2 since February 2024); no legitimate pharmacy compounding pathway for injectable product exists.
| Test | When | Target |
|---|---|---|
| Echocardiogram | Baseline and 90-day follow-up (cardiac-indication use only) | EF ≥55%; no new wall motion abnormalities |
| BNP / NT-proBNP | Baseline and monthly (cardiac-indication use only) | BNP <100 pg/mL; NT-proBNP <125 pg/mL (age-adjusted) |
| CBC (Complete Blood Count) | Baseline only for higher-risk users (cancer history, immunosuppression) | — |
| Injection site self-assessment | Each injection (self-monitoring) | — |
Tβ4 is being investigated for cardiac repair. Monitor ejection fraction and wall motion for cardiac-indication users; provides efficacy evidence and detects adverse events in higher-risk populations.
Biomarker for cardiac stress and heart failure. Tβ4 reduces NT-proBNP in murine cardiac injury models (IJMS 2025). Provides objective marker of cardiac status during cardiac-indication protocols.
Tβ4 promotes cell proliferation and angiogenesis. CBC provides reference baseline in populations where additive proliferative signaling could theoretically be a concern.
Monitor for nodule formation (site overuse), increasing redness/warmth (infection), or skin changes indicating allergic reaction. Early detection prevents nodule complications and infection.
Loading phase begins with daily dosing. Due to the short half-life, steady-state levels are reached quickly. Early anti-inflammatory effects may be noticeable. Mild fatigue or headache possible during adjustment.
Continued loading phase. Angiogenesis and tissue repair processes accelerate. Noticeable reduction in pain and inflammation around injured areas. Improved flexibility and range of motion.
Transition to maintenance dosing (half dose daily or every other day). Significant healing progress in soft tissue and dermal wounds. Reduced scar tissue formation at injury sites.
Maintenance phase continues. Sustained healing support and anti-fibrotic activity. Evaluate progress and consider cycling off. Resume loading if new injury occurs.
Weeks 1 to 2: Loading Begins. Daily or 2 to 3x/week dosing at full dose gets plasma levels up quickly given the roughly 2-hour IV half-life. Anti-inflammatory effects kick in through macrophage modulation and Ac-SDKP signaling. Most users feel mild fatigue and occasional flu-like symptoms between days 3 and 7. Some notice reduced pain at the injury site by the end of week 2. Others feel nothing yet; the loading effects are cumulative, not immediate. Weeks 3 to 4: Angiogenesis and Repair Pick Up. New blood vessel formation at injury sites increases oxygen and nutrient delivery. Progenitor cells are migrating and differentiating. Community reports commonly describe meaningful pain reduction, less swelling, better joint mobility, and improved sleep quality. Some users note surprisingly fast resolution of injuries that had been chronic for months. DOMS recovery improves for strength athletes. Weeks 5 to 6: Peak Loading Effect. Phase II wound trial data showed most complete healing at 4 to 6 weeks. This is the transition window; many users drop to maintenance dosing (2 mg once per week). Tendons and ligaments feel more resilient under load. Wound healing is visibly accelerated. Scar tissue formation is actively reduced through anti-fibrotic Ac-SDKP signaling at sustained levels. Weeks 7 to 12: Maintenance Phase. Lower dose maintains angiogenic and anti-fibrotic support without diminishing returns from continued high-dose loading. Most users report sustained recovery improvements and fewer re-injuries. Some cycle off at week 8 if the primary injury is resolved. Others complete the full 12 weeks for chronic or multi-site problems before taking 6 weeks off for receptor sensitivity recovery.
Tβ4 released by platelets and macrophages at injury sites. Anti-inflammatory effects begin via macrophage modulation and Ac-SDKP domain action. Short IV half-life (~2h) means plasma levels stabilize rapidly with repeated SC dosing. Angiogenic signaling initiates but new vessel formation is not yet established.
Most users experience mild fatigue and occasional flu-like symptoms (days 3–7). Some report reduced localized pain at injury site by end of week 2. Others notice no change yet: loading effects are cumulative.
New blood vessel formation underway at injury sites, increasing nutrient and oxygen delivery. Progenitor cell migration and differentiation in progress. Anti-fibrotic Ac-SDKP domain actively reducing fibroblast activity and scar tissue formation.
Commonly reported: meaningful reduction in injury pain and swelling, improved joint mobility and range of motion, better sleep quality. Some users note surprisingly rapid resolution of previously chronic injuries. Advanced users add that DOMS recovery improves notably.
Phase II wound healing trials found most complete healing responses at 4–6 weeks. Cardiac progenitor cell activation at sustained levels. Anti-fibrotic signaling at maximum: scar tissue formation actively attenuated. Transition point to maintenance dosing.
Most users report significant measurable healing progress. Tendon and ligament injuries feel substantially more resilient under load. Wound healing visibly accelerated. Many users transition to maintenance (2 mg 1x/week) at this point.
Reduced dose maintains angiogenic and anti-fibrotic signaling at lower intensity. Science suggests diminishing incremental benefit from continued high-dose loading once acute healing is established. Off-cycle period required to assess recovery.
Most users continue improved recovery rates and reduced re-injury frequency. Some cycle off after week 8 if primary injury is resolved. Others complete 12-week cycle for chronic or multi-site injuries before taking 6 weeks off.
Source: Phase I IV PK study in healthy volunteers (PMID 20536472): mean half-life ranged from 0.95h (42 mg) to 2.1h (1260 mg), dose-dependent
Loading the interactive decay curve.
Thymosin beta-4 is classified as a research chemical in the United States. It does not hold FDA approval for any therapeutic indication as of April 2026. Compounded injectable Tb4 was placed on the FDA Category 2 bulk drug substances list in February 2024, which prohibits its compounding through 503A and 503B pharmacies due to "significant safety risks" as determined by the agency. No legitimate pharmacy compounding pathway for injectable Tb4 currently exists in the US. Peptide Sciences, previously a major source for verified 43aa full-length product, voluntarily closed in March 2026 following broader FDA enforcement actions against peptide vendors. Research-grade Tb4 remains available from select vendors (Blue Sky Peptide, Core Peptides, Biopeptitech), but buyers must verify product identity through batch-specific third-party COA with mass spectrometry. Tb4 is prohibited by WADA for competitive athletes. This content is for educational and research purposes only. It does not constitute medical advice, diagnosis, or treatment. Consult a licensed healthcare provider before using any research peptide.
Peptide Schedule Research TeamReviewed Apr 202613 Citations
