# TB-500 (thymosin beta-4)

Rating: Early — Mostly animal or cell studies; few or uncontrolled human data
Type: Compound
Updated: 2026-10-14
Canonical: https://heretic.bio/articles/tb-500-thymosin-beta-4.html

> TB-500 is the research-market name for an active fragment (amino acids 17-23) of thymosin beta-4, a natural actin-binding peptide involved in cell migration and wound repair. Full-length T-beta-4 has real human data, including phase II/III trials in dry eye and dermal wounds and a phase II cardiac RCT reporting ejection-fraction improvement, but the TB-500 fragment itself has no published human studies. A 2026 scoping review of 80 papers makes this distinction explicit. It is also flagged as unsafe in active malignancy because it promotes migration and angiogenesis.

> **Aliases:** Thymosin β4, Tβ4, TB4, TB-500 **Sequence:** Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala-Glu-Ile-Glu-Lys-Phe-Asp-Lys-Ser-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 (43 amino acids) **Molecular Weight:** 4963.5 Da **Origin:** Naturally occurring actin-sequestering protein found in virtually all human cells

## Overview

TB-500 is a synthetic version of **Thymosin Beta-4 (Tβ4)** , a naturally occurring 43-amino-acid peptide that is one of the most abundant peptides in the human body. Tβ4 accounts for ~70–80% of total β-thymosin in humans, is present in virtually all cells (except red blood cells), and plays a fundamental role in **actin regulation** — the protein responsible for cell shape, movement, and division.

The Tβ4 molecule is functionally partitioned into discrete active fragments (Xing et al., _Front Endocrinol_ 2021, PMID [34992578](https://pubmed.ncbi.nlm.nih.gov/34992578/)): \- **aa 1–4:** anti-inflammatory and anti-fibrotic activity \- **aa 1–15:** anti-apoptotic / cell-survival effects \- **aa 17–23 (LKKTET motif):** principal actin-binding domain; drives angiogenesis and hair-follicle growth — this is the minimal "TB-500 fragment" commonly referenced in research contexts.

> **Regulatory note:** Full-length Tβ4 is the molecule investigated in the RegeneRx clinical program and the 2025–26 cardiac RCT. TB-500 (the synthetic 17–23 or active-region analogue) has no comparable human trial program as of mid-2026 (McGuire et al., _Appl Sci_ 2026, DOI [10.3390/app16126202](https://doi.org/10.3390/app16126202)).

**Evidence Level:** Moderate — Phase II/III human trials in dry eye and dermal wounds; Phase II cardiac RCT ongoing. Extensive preclinical data.

## Mechanism of Action

### Primary: Actin Regulation

  * **G-actin sequestration** — Binds globular actin (G-actin) at 1:1 stoichiometry, preventing polymerization into F-actin filaments (Hannappel & Horecker; classical)
  * The **LKKTET motif** (aa 17–23) is the main electrostatic contact site with actin; the C-terminus binds actin His-40, shifting monomer conformation
  * Regulates **cell motility** and **cell shape** — essential for wound healing and tissue repair
  * Profilin-dependent dissociation of the G-actin–Tβ4 complex liberates actin for filament assembly when polymerization is needed



### Signaling Pathways

  * **Integrin-linked kinase (ILK) activation** → promotes cardiac cell migration, survival, and repair (Bock-Marquette et al., _Nature_ 2004, [PMC3548046](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548046/))
  * **Akt2 / PKB pathway** — downstream of ILK in lamellipodia; increases metalloproteinase production
  * **PKC (Protein Kinase C) activation** — initiates embryonic coronary developmental program and epicardial progenitor cell activation
  * **VEGF and angiopoietin-1 / vWF upregulation** — promotes angiogenesis via paracrine and endothelial-progenitor recruitment (Xing 2021, PMID [34992578](https://pubmed.ncbi.nlm.nih.gov/34992578/))
  * **Heat-shock protein 70 (HSP70) elevation** — linked to F-actin regulation during burn-wound healing



### Additional Pathways (Srinivasan 2025 — Discov Biotechnol, comprehensive review of Tβ4 in diabetic ulcers, DOI [10.1007/s44340-025-00015-0](https://doi.org/10.1007/s44340-025-00015-0))

  * **NF-κB suppression** — Tβ4 prevents NF-κB nuclear translocation, reducing IL-8, TNF-α, IL-6; first-four-aa fragment is the principal anti-inflammatory determinant
  * **Nrf2 antioxidant axis** — Tβ4 upregulates superoxide dismutase (SOD) and catalase via Nrf2; suppresses NADPH-oxidase-driven ROS — distinct from canonical G-actin role
  * **Angiopoietin-1 / Tie-2** — Tβ4 increases Ang-1, reduces VCAM-1; restores intraepidermal nerve-fiber density in diabetic neuropathy models
  * **Wnt/β-catenin** — stabilizes β-catenin, promotes nuclear translocation, drives VEGF + keratinocyte/fibroblast ECM remodelling
  * **PI3K/Akt → eNOS** — Tβ4 phosphorylates PI3K/Akt → endothelial nitric oxide synthase → vasodilation + blood-flow to healing tissue; also modulates autophagy via downstream mTOR inhibition
  * **miR-146a / TLR4** — Tβ4 induces miR-146a in oligodendrocyte precursors (targeting IRAK1, TRAF6), promoting myelin basic protein expression; concurrently activates IκBα to block TLR4-driven inflammation
  * **High-glucose protection** — in HUVECs under hyperglycemia, Tβ4 pretreatment reduces ROS, restores VEGF expression, activates IGF-1 signaling cascade (Wang et al. _Discov Biotechnol_ 2025)
  * **Lipid metabolism** — Tβ4 lowers total cholesterol, triglycerides, LDL-C, raises HDL-C; lowers IL-2/IL-6/TNF-α; protects hepatocytes from palmitic-acid apoptosis via ferroptosis-gene regulation
  * **Autophagy / DAPK1** — in chronic granulomatous disease (CGD) macrophages, Tβ4 restores autophagy and DAPK1 expression, enhancing phagocytosis against _Aspergillus_ spp.



### Downstream Effects

  1. **Cellular migration** — Enhanced movement of keratinocytes, endothelial cells, EPCs to injury sites
  2. **Angiogenesis** — Capillary formation, endothelial tube formation, EPC recruitment (often via VEGF-independent cytoskeletal route distinct from BPC-157/VEGFR2 mechanism)
  3. **Anti-inflammatory** — Reduces inflammatory cytokines; first-four-aa fragment is the principal anti-inflammatory determinant
  4. **Anti-fibrotic** — Reduces scar tissue formation
  5. **Anti-apoptotic** — aa 1–15 segment reduces cytotoxicity
  6. **Myoblast migration** — Muscle stem cell recruitment to injury sites
  7. **Neuromuscular junction regeneration**
  8. **Laminin-332 synthesis** ↑ — migration factor for keratinocytes and endothelial cells



## Primary Uses & Applications

Application | Evidence Level | Notes  
---|---|---  
**Dermal wound healing** | Phase II human (pressure ulcers, stasis ulcers, epidermolysis bullosa) | Tβ4 accelerates wound closure; safe and well-tolerated  
**Dry-eye disease / corneal wounds** | Phase II/III human | RGN-259 (ophthalmic Tβ4) reduced ocular discomfort, conjunctival inflammation  
**Cardiac repair (post-MI)** | Phase II RCT (2025–26) | Tβ4 + EPC transplantation pilot; ejection-fraction gains reported  
**Diabetic foot ulcer (adjunct with selenium)** | Mechanistic review 2025 (PMID [40401023](https://pubmed.ncbi.nlm.nih.gov/40401023/)) | Combined Tβ4 + selenium reduces oxidative stress, accelerates angiogenesis  
**Muscle/tendon repair** | Preclinical + anecdotal | Widely used in sports medicine; "Wolverine stack"  
**Stroke / neuroprotection** | Preclinical dose-finding | —  
**Hair growth** | Preclinical | Drives follicle development  
**Liver / renal fibrosis** | Preclinical | Anti-fibrotic effect documented  
**Ulcerative colitis / colon cancer biology** | Preclinical | Dual role — therapeutic in UC, oncogenic in CRC  
  
## Clinical Evidence

### Human Clinical Trials

  * **Dry-eye disease (Phase II/III, RGN-259):** Tβ4 ophthalmic solution reduced ocular discomfort, lowered conjunctival inflammation, improved tear-film metrics. Phase I safety studies in healthy volunteers well-tolerated even at higher doses with no dose-limiting toxicities.
  * **Wound healing (Phase II dermal):** Accelerates wound closure in pressure ulcers, stasis ulcers, and epidermolysis bullosa. Conclusions from pooled Phase II data: Tβ4 is safe, well-tolerated, with additional application to skin regeneration ([PMC8228050](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8228050/)).
  * **Cardiac repair — STEMI pilot (Phase II, 2016):** Tβ4-primed endothelial progenitor cell (EPC) transplantation — pilot suggested feasibility and safety in patients with ST-elevation MI.
  * **Cardiac RCT (2025–26):** New Phase II human data reports measurable ejection-fraction improvement in post-MI recovery; Phase 2b extension registered with longer follow-up, multi-center replication underway.
  * **Dose-response stroke study ([PMC4177939](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4177939/)):** Tβ4 significantly improved long-term neurological functional recovery at day 56 after MCAo; **optimal dose 3.75 mg/kg** in rodent model.
  * **NL005 — first-in-human Phase I SAD/MAD in healthy Chinese volunteers (Wang X, Liu L, Qi L et al. 2021):** Recombinant human Tβ4 (Beijing Northland Biotech) evaluated in single-ascending-dose and multiple-ascending-dose arms. Adverse events were mild-to-moderate with no serious toxicities; plasma concentrations increased proportionally with dose (predictable linear PK). Establishes the most rigorous contemporary human safety/PK baseline for full-length rhTβ4. _J Cell Mol Med_ 25(17):8222–8228. DOI [10.1111/jcmm.16693](https://onlinelibrary.wiley.com/doi/10.1111/jcmm.16693) — _cited in Srinivasan 2025_ (DOI [10.1007/s44340-025-00015-0](https://doi.org/10.1007/s44340-025-00015-0)).
  * **Venous stasis ulcer — topical Tβ4 (RegeneRx Phase II):** 0.03% concentration was the optimal dose — highest healing rate and significantly reduced median healing time vs. placebo and other doses; larger baseline ulcers had lower healing rates. Cited in Srinivasan 2025.



### Key Preclinical Studies

  * **Bock-Marquette I. et al. (2004).** "Thymosin beta 4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair." _Nature_ 432:466–472. [PMC3548046](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548046/).
  * **Smart N. et al. (2007).** "Thymosin beta-4 Is Essential for Coronary Vessel Development and Promotes Neovascularization via Adult Epicardium." _Ann N.Y. Acad. Sci._ 1112:171–188. PMID [17632766](https://pubmed.ncbi.nlm.nih.gov/17632766/).
  * **Smart N. et al. (2012).** "De novo cardiomyocytes from within the activated adult epicardium." _Dev Cell_.
  * **Peng H. et al. (2014).** "Thymosin-β4 prevents cardiac rupture and improves cardiac function in mice with myocardial infarction." _Am J Physiol_ 307:H741–H751.
  * **Goldstein AL, Hannappel E, Kleinman HK. (2005).** "Thymosin β4: Actin-sequestering protein moonlights to repair injured tissues." _Trends Mol Med_.
  * **Xing Y, Ye Y, Zuo H, Li Y. (2021).** "Progress on the Function and Application of Thymosin β4." _Front Endocrinol_ 12:767785. PMID [34992578](https://pubmed.ncbi.nlm.nih.gov/34992578/) — fragment-function mapping; EPC + VEGF mechanism; fibrosis and oncogenesis review.
  * **Srinivasan K, Sureshkumar R, Nellore J et al. (2025).** "The combined impact of thymosin beta 4 and selenium on diabetic ulcers: a comprehensive review." _Discov Biotechnol_ 2:11. DOI [10.1007/s44340-025-00015-0](https://doi.org/10.1007/s44340-025-00015-0) — combines Tβ4 mechanisms with selenium antioxidant/anti-inflammatory activity.
  * **McGuire F, Hughes E, Maak T, Cushman DM. (2026).** "Thymosin Beta-4 and TB-500 in Tissue Healing, Regeneration, and Musculoskeletal Repair: A Scoping Review." _Appl Sci_ 16(12):6202. DOI [10.3390/app16126202](https://doi.org/10.3390/app16126202) — 80-study scoping review with explicit TB4 vs TB-500 delineation; mechanism/outcome taxonomy (cell migration 12.5%, angiogenesis 23.8%, functional outcomes largely preclinical).
  * **Stadelmann N. et al. (2025).** "Growth Factors IGF-1 and KGF and Adipose-Derived Stem Cells Promote Migration and Viability of Primary Human Keratinocytes in an In Vitro Wound Model." _Front Med_ 12:1516116.
  * **Hao Q. et al. (2018).** "A dimeric thymosin beta 4 with novel bio-activity protects…" — engineered Tβ4 variants.



## Recent Developments (2024–2026)

Year | Development | Source  
---|---|---  
2024 | Selenium + Tβ4 mechanistic evidence mounts for diabetic ulcer synergy | Srinivasan 2025 review  
2025 | Phase II cardiac RCT reports ejection-fraction improvement post-MI | PeptIQ Research Team blog 2026 (industry summary)  
2025 | "Stable vasculature" models confirm Tβ4's non-VEGFR2 angiogenic axis | Multiple  
2026 | First formal scoping review (Appl Sci) delineates TB4 (clinical-grade) from TB-500 (research fragment) | McGuire 2026  
2026 | 16 new primary studies catalogued on musculoskeletal applications | McGuire 2026  
  
## Uses

> ⚠️ **Disclaimer:** Research protocols, not medical recommendations.

Purpose | Notes  
---|---  
Tissue repair (general) | Often split into 2 doses/week  
Acute injury | Loading phase, then taper  
Maintenance/chronic |   
Stroke recovery (research) | From animal dose-response study  
  
## Safety Profile

Aspect | Assessment  
---|---  
**Overall safety** | Excellent in clinical trials; "no preclinical toxicology has been found" (2016 dermal review)  
**Cancer concerns** | **Theoretical — promotes cell migration and angiogenesis.** Tβ4 has been implicated in NSCLC progression and colon-cancer biology; the peptide is _not_ safe in active malignancy  
**Immunogenicity** | Low risk — naturally occurring human peptide  
**Drug interactions** | Not well characterized  
  
## Source & Origin

  * **Natural source:** Present in virtually all mammalian cells; first isolated from thymus gland
  * **Discovery:** Tβ4 identified in the early 1980s by Hannappel E. and Horecker BL
  * **Key researchers:** Alpha and beta thymosins first characterized at the Roche Institute of Molecular Biology (Goldstein, White)
  * **Clinical development:** RegeneRx Biopharmaceuticals (RGN-352 for cardiac; RGN-259 for ophthalmic)



## Diabetic Ulcer & Tβ4 + Selenium Synergy (Srinivasan 2025)

The 2025 review by Srinivasan et al. (DOI [10.1007/s44340-025-00015-0](https://doi.org/10.1007/s44340-025-00015-0)) consolidates evidence for combined Tβ4 + selenium in diabetic ulcer management — a major unmet need (15–30% of diabetics develop ulcers; mortality 40–80% within 6 years post-amputation).

### Why synergy is plausible (mechanistic integration)

Pathway | Tβ4 contribution | Selenium contribution | Combined effect  
---|---|---|---  
**PI3K/Akt** | Activates PI3K/Akt → anti-apoptotic, pro-migration | Selenoprotein-mediated redox regulation enhances Akt phosphorylation | Amplified pro-survival signaling  
**NF-κB** | Suppresses nuclear translocation, ↓IL-8/TNF-α/IL-6 | Seleno-GPx modulates NF-κB → ↓inflammation | Dual inhibition → stronger anti-inflammatory tone  
**JAK2/STAT3** | Modulates STAT3 → proliferation, migration | Redox-sensitive JAK2/STAT3 modulation | Optimized STAT3-mediated tissue repair  
**Wnt/β-catenin** | Stabilizes β-catenin → nuclear translocation | Regulates β-catenin via oxidative-stress axis | Enhanced stem-cell activation, re-epithelialization  
**Nrf2 / oxidative stress** | ↑ SOD, catalase; ↓ NADPH-oxidase ROS | Direct GPx/TrxR selenoenzyme antioxidant activity | Complementary ROS control; selenium protects Tβ4-induced new vasculature  
**MMP / ECM remodelling** | Actin-cytoskeleton reorganization | Modulates MMP2 via TGFβ1/Smad | Better wound contraction + ECM remodelling  
  
### Benchmarks from the review (animal/preclinical unless noted)

  * **SeNPs + PRP (Karas 2024,_Sci Rep_):** SeNPs + platelet-rich plasma in diabetic mice — additive wound healing activity
  * **Selenium-chitosan-mupirocin nanohybrid:** >90% antibacterial, 35–50% faster wound closure in 10 days, ~80% wound-size reduction
  * **SeNPs-decorated bacterial cellulose/gelatin hydrogel:** >95% antibacterial, ~60% ↓ oxidative-stress markers, 40–60% ↑ cell proliferation
  * **Selenium-stimulated exosomes:** 2–3× ↑ VEGF, 30% reduction in healing time, 50% ↓ TNF-α/IL-6
  * **Fungal-extract SeNPs:** 30–40% faster closure, ~80% wound-size reduction by day 10, >90% antibacterial against _E. coli/S. aureus_
  * **SeNPs + T2DM metabolic effects:** 15–25% ↑ insulin sensitivity, 30–40% ↓ oxidative stress, 20% ↓ triglycerides
  * **SeNPs in pregnancy (rat model):** 30–50% ↓ serum creatinine, 40–60% ↓ oxidative-stress markers in renal tissue



### Open questions

  * **No direct empirical combined-treatment study exists yet** — the synergy is theoretical/mechanistic. No Tβ4 + selenium co-administration clinical trial has been registered.
  * Optimal Tβ4:Se ratio undefined.
  * Selenium toxicity (esp. SeNPs) — narrow therapeutic window.
  * Need for delivery systems that maintain stability/bioavailability of both at wound site (scaffolds, hydrogels, nanofibers all proposed).



### Adjacent context

Diabetic foot ulcer standard care remains inadequate: hyperbaric O₂ closes ~33% of wounds in 8 weeks; EGF injection → 70–85% closure in 6–8 weeks; adipose MSC exosomes → 40–60% angiogenesis improvement. A combined Tβ4 + selenium strategy has potential to outperform these — but only controlled trials will tell.

## Peptide Combinations

  * **TB-500 + BPC-157:** Most popular combination for tissue repair — TB-500 drives cellular migration / actin remodeling, BPC-157 drives NO/angiogenic signaling via VEGFR2 (distinct mechanisms)
  * **TB-500 + BPC-157 + GHK-Cu:** "Holy trinity" for wound and tissue healing (migration + signaling + ECM)
  * **TB-500 / Tβ4 + selenium:** Combined angiogenic + antioxidant strategy for diabetic ulcers (Srinivasan 2025)
  * **Tβ4 + EPC transplantation:** Cardiac regeneration protocol investigated in STEMI pilot and 2025 RCT

## Sources

1. Xing Y, Ye Y, Zuo H, Li Y. (2021). "Progress on the Function and Application of Thymosin β4." Front Endocrinol 12:767785. PMID 34992578 . (PubMed 34992578)
2. McGuire F, Hughes E, Maak T, Cushman DM. (2026). "Thymosin Beta-4 and TB-500 in Tissue Healing, Regeneration, and Musculoskeletal Repair: A Scoping Review." Appl Sci 16(12):6202. DOI 10.3390/app16126202 . (DOI 10.3390/app16126202)
3. Bock-Marquette I. et al. (2004). Nature 432:466–472. PMC3548046 . (PMC3548046)
4. DOI 10.1007/s44340-025-00015-0 (DOI 10.1007/s44340-025-00015-0)
5. PubMed 40401023 (PubMed 40401023)
6. PMC8228050 (PMC8228050)
7. Morris DC et al. (2014). "A Dose Response Study of Thymosin β4 for the Treatment of Acute Stroke." PMC4177939 . (PMC4177939)
8. Smart N. et al. (2007). Ann N.Y. Acad. Sci. 1112:171–188. PMID 17632766 . (PubMed 17632766)
9. Karas RA, Alexeree S, Elsayed H, Attia YA. (2024). "Assessment of wound healing activity in diabetic mice treated with a novel therapeutic combination of selenium nanoparticles and platelets rich plasma." Sci Rep . DOI 10.1038/s41598-024-54064-2 . (DOI 10.1038/s41598-024-54064-2)