Thymosin Beta-4: An Actin-Sequestering Peptide for Wound Healing and Cardiac Regeneration

This content is provided by Superpower Health for educational and informational purposes only. Superpower Health facilitates access to thymosin beta-4 through licensed healthcare providers and compounding pharmacy partners. Thymosin beta-4 is a prescription compound available only by prescription through licensed compounding pharmacies. This page is not a substitute for medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider. For compound reference data, see the PubChem monograph (CID 16133418).

Every cell in your body contains thymosin beta-4. It is not a signaling molecule that arrives from somewhere else. It is already there, sequestering actin monomers, holding the cytoskeleton in a dynamic equilibrium that allows cells to move, divide, and respond to injury. When tissue is damaged, Tβ4 is released into the local environment. Cell migration accelerates. Blood vessels extend toward the wound. Inflammation begins to resolve. The scaffold of repair assembles.

That process is not hypothetical. It is the subject of two decades of preclinical research, multiple Phase I and Phase II human trials, and a Phase III randomized controlled trial in a rare corneal disease. Here is what thymosin beta-4 does, where the evidence currently stands, and how it differs from TB-500, the synthetic fragment that shares its mechanism but not its structure.

Key Takeaways

• Regulatory Status: As of April 2026, thymosin beta-4 is not FDA-approved for any indication. RGN-259 (0.1% Tβ4 ophthalmic solution, developed by RegeneRx) has completed Phase II and Phase III trials for dry eye and neurotrophic keratopathy and holds orphan drug designation; no FDA approval has been granted. Available only through licensed compounding pharmacies by prescription.
• Research Stage: Phase I safety data in healthy volunteers; Phase II and Phase III RCT data in ophthalmic disease; Phase I cardiac safety data; most recent human cardiac RCT published in 2025
• Availability: Not available through Superpower. Access, where available, is through licensed 503A compounding pharmacies under a patient-specific prescription and varies by state.
• Prescribing information: View compound reference data (PubChem CID 16133418)
• How it works: Sequesters G-actin monomers, promoting cell migration, angiogenesis, and anti-inflammatory signaling after tissue injury.
• What the research shows: In a 2022 Phase III randomized controlled trial published in International Journal of Molecular Sciences by Sosne and colleagues, RGN-259 significantly improved corneal healing and comfort in patients with neurotrophic keratopathy. A 2025 human RCT published in Cardiovascular Research by Zhang and colleagues evaluating recombinant human Tβ4 in 96 patients with acute ST-elevation myocardial infarction did not show a significant overall reduction in infarct size at 90 days, but identified a significant reduction in the subgroup treated within 8 hours of percutaneous coronary intervention.

What Is Thymosin Beta-4?

Thymosin beta-4 (Tβ4) is an endogenous 43-amino-acid actin-sequestering peptide found in virtually every nucleated mammalian cell. It is encoded by the TMSB4X gene and is the most abundant member of the beta-thymosin family. Tβ4 binds G-actin monomers with high affinity, regulating the availability of actin subunits for filament assembly and therefore controlling cytoskeletal dynamics, cell shape, and directed cell migration. It is not, as its name suggests, primarily a thymic hormone: it was initially isolated from thymosin fraction 5, but its biology extends to nearly every tissue type.

Safer, Elzinga, and Nachmias established in a 1991 landmark paper published in the Journal of Biological Chemistry that thymosin beta-4 is identical to "Fx," the actin-sequestering factor previously isolated from platelets, confirming that the full 43-amino-acid peptide is the primary G-actin buffer in most mammalian cells. In a 2005 review published in Trends in Molecular Medicine, Goldstein, Hannappel, and Kleinman described Tβ4 as an actin-sequestering protein that "moonlights" to repair injured tissues: the same intracellular cytoskeletal regulator becomes an extracellular repair signal when secreted after injury. A 2012 expanded review by Goldstein, Hannappel, Sosne, and Kleinman in Expert Opinion on Biological Therapy covered Tβ4's basic properties, structure, distribution, and clinical applications across ocular, dermal, cardiac, and neurological repair, establishing it as what the authors termed "a multi-functional regenerative peptide."

Thymosin beta-4 is distinct from TB-500, the synthetic 7-amino-acid fragment (Ac-LKKTETQ) corresponding to residues 17 through 23 of the full sequence, specifically the actin-binding domain. The fragment retains core pro-angiogenic and cell-migratory activity but lacks the full regulatory complexity of the intact peptide. That distinction, and its clinical implications, is addressed directly in a later section.

What Thymosin Beta-4 May Support

1. Wound healing and dermal repair

The wound-healing case for Tβ4 begins with a 1999 study published in the Journal of Investigative Dermatology by Malinda, Sidhu, Mani, Banaudha, Maheshwari, Goldstein, and Kleinman. In a rat full-thickness dermal wound model, topical or intraperitoneal Tβ4 increased reepithelialization by 42% over saline controls at day 4 and by up to 61% at day 7, with increased collagen deposition and angiogenesis in treated wounds. The mechanism involves Tβ4 stimulating directed migration of keratinocytes and dermal fibroblasts through G-actin sequestration and actin cytoskeletal reorganization, combined with pro-angiogenic signaling that extends the vascular supply to the healing wound edge. An earlier foundational study published in the FASEB Journal in 1997 by Malinda, Goldstein, and Kleinman first demonstrated that Tβ4 stimulates directional migration of human umbilical vein endothelial cells, establishing the cellular basis for the angiogenic component of wound healing that subsequent dermal repair studies built upon. These in vivo wound-healing findings remain the most cited preclinical basis for Tβ4's dermal applications; no large-scale human wound healing RCTs have been completed as of April 2026.

2. Corneal repair and dry eye disease

The strongest human clinical data for Tβ4 is in ophthalmic disease. A 2002 study in Experimental Eye Research by Sosne, Szliter, Barrett, Kernacki, Kleinman, and Hazlett first demonstrated that topical Tβ4 accelerates corneal wound healing and decreases inflammation after alkali injury in mice, establishing the foundation for the RegeneRx ophthalmic program. The mechanism in corneal tissue, reviewed by Sosne and Kleinman in a 2015 paper in Investigative Ophthalmology and Visual Science, involves G-actin sequestration facilitating corneal epithelial cell migration, anti-inflammatory effects via NF-κB suppression as established by Sosne in 2007 in Experimental Eye Research, and upregulation of laminin-5 at the basement membrane. A 2015 Phase II randomized placebo-controlled trial of 0.1% RGN-259 published in Cornea by Sosne, Dunn, and Kim enrolled 9 patients with severe dry eye (12 eyes active, 6 eyes vehicle) dosed six times daily for 28 days and reported at day 56 a 35.1% reduction in ocular discomfort (p = 0.0141) and a 59.1% reduction in corneal fluorescein staining (p = 0.0108) versus vehicle, with improvements also in tear film break-up time and tear volume; a companion 2015 Phase II double-masked placebo-controlled trial by Sosne and Ousler in Clinical Ophthalmology randomized 72 subjects 1:1 to 0.1% Tβ4 or placebo for 28 days in the controlled adverse environment dry eye model, with mixed results — the co-primary endpoints of ocular discomfort and inferior corneal staining did not reach significance, but secondary endpoints showed a 27% reduction in discomfort scores (p = 0.0244) and significant improvements in central and superior corneal staining (p = 0.0075 and p = 0.0210) favoring Tβ4; no adverse events were observed. The small sample sizes limit precision. A 2022 Phase III double-masked randomized placebo-controlled trial published in International Journal of Molecular Sciences by Sosne, Kleinman, Springs, Gross, Sung, and Kang evaluated 0.1% RGN-259 in 18 patients with Stage 2 or 3 neurotrophic keratopathy (10 active, 8 placebo) and reported complete healing of persistent epithelial defects in 6 of 10 RGN-259 subjects versus 1 of 8 placebo subjects at 4 weeks (p = 0.0656), with statistically significant healing at day 43 (p = 0.0359) and improvements in disease stage and ocular comfort; no significant adverse effects were observed. The small sample size, typical for rare-disease trials, limits the precision of the treatment effect estimate. A 2016 review of the RGN-259 program by Sosne, Rimmer, Kleinman, and Ousler in Vitamins and Hormones synthesizes the ophthalmic translation story across neurotrophic keratopathy, dry eye, and other ocular surface disease. Neurotrophic keratopathy is a rare, severe corneal disease with limited treatment options; RGN-259 holds orphan drug designation for this indication. As of April 2026, no FDA approval has been granted.

3. Cardiac repair and cardioprotection after myocardial injury

The cardiac case for Tβ4 rests on two landmark papers in Nature and a subsequent body of preclinical and clinical work. A 2004 paper by Bock-Marquette, Saxena, White, DiMaio, and Srivastava in Nature showed that Tβ4 activates integrin-linked kinase (ILK) and downstream Akt signaling, promotes cardiomyocyte survival and migration, and improves cardiac function after coronary artery ligation in mice. A 2007 companion paper in Nature by Smart, Risebro, Melville, Moses, Schwartz, Chien, and Riley demonstrated that Tβ4 mobilizes adult epicardial progenitor cells and induces neovascularization of the injured heart, identifying the epicardium as the source of Tβ4-responsive repair cells. A 2008 preclinical study in Circulation by Hinkel and colleagues identified Tβ4 as an essential paracrine factor in endothelial progenitor cell-mediated cardioprotection; retroinfusion of 15 mg Tβ4 at 55 minutes into a 60-minute coronary occlusion in pigs (n = 9 per arm) reduced infarct size from 54 ± 4% of the area at risk in controls to 37 ± 3% with Tβ4 (approximately 31% relative reduction, p < 0.01), providing large-animal preclinical support. Adverse events were not reported in the abstract. The cardiac review by Bollini, Riley, and Smart published in 2015 in Expert Opinion on Biological Therapy synthesized Tβ4's multiple cardiac functions, encompassing development, cardioprotection, epicardial activation, and vascular regeneration. A broader 2018 review by Dube and Smart in Expert Opinion on Biological Therapy extended the picture across vascular development, repair, and disease protection. The most recent human cardiac evidence was published in 2025 in Cardiovascular Research by Zhang, Dong, Bian, and colleagues, a randomized, double-blind, placebo-controlled trial of recombinant human Tβ4 (rhTβ4) in 96 patients with acute ST-segment elevation myocardial infarction after percutaneous coronary intervention (43 active, 53 placebo), with infarct area assessed at 90-day follow-up. The overall between-group difference in infarcted area did not reach statistical significance, but in the pre-specified subgroup of patients treated within 8 hours of PCI, rhTβ4 was associated with a significant reduction in infarct size versus placebo. This is the first human RCT of Tβ4 in STEMI, a successor to the RegeneRx RGN-352 intravenous program that was discontinued in earlier development, and the post-hoc nature of the time-window subgroup limits the strength of the benefit signal pending confirmation in a larger pre-specified trial.

4. Anti-inflammatory activity

Separate from its actin-sequestration function, Tβ4 has been studied for anti-inflammatory activity through suppression of NF-κB activation. Sosne established this axis in a 2007 paper in Experimental Eye Research, demonstrating that Tβ4 suppresses corneal NF-κB activation, reducing downstream expression of pro-inflammatory cytokines and enzymes. This anti-inflammatory activity is mechanistically distinct from actin sequestration and operates in parallel with the cell-migratory and angiogenic arms of Tβ4 biology. The implication suggested by this preclinical work is that in injured tissue, Tβ4 may simultaneously support repair and modulate the inflammatory response. Bock-Marquette and colleagues, in a review published in 2023 in International Immunopharmacology, positioned Tβ4 as a candidate for anti-aging regenerative therapeutics on the basis of this integrated cardiac, vascular, and anti-inflammatory literature.

5. Neurological repair

Preclinical data suggest Tβ4 may support neurological recovery after acute injury. A 2010 study in Neuroscience by Morris, Chopp, Zhang, Lu, and Zhang showed that Tβ4 improves functional neurological outcomes in a rat embolic stroke model when administered up to 24 hours post-stroke. A companion study in the Journal of Neurosurgery in 2011 by Xiong, Mahmood, Meng, Zhang, Zhang, Morris, and Chopp demonstrated Tβ4 promoted neurological recovery in rat traumatic brain injury via increased angiogenesis, neurogenesis, and oligodendrogenesis. A 2018 review by Morris, Zhang, and Chopp in Expert Opinion on Biological Therapy examined whether Tβ4 in acute stroke is neurorestorative versus neuroprotective, concluding that its primary mechanism in the CNS appears to be post-injury restorative rather than acutely protective. As of April 2026, no human RCTs of Tβ4 for any neurological indication have been completed.

6. Hair follicle activation

Two rodent studies support a role for Tβ4 in hair follicle stem cell activation. A 2004 paper in FASEB Journal by Philp, Nguyen, Scheremeta, St-Surin, Villa, Orgel, Kleinman, and Elkin was the first to show that Tβ4 activates hair follicle stem cells and increases hair growth in rodents. A 2015 replication study in PLoS ONE by Gao, Liang, Hou, Zhang, Nuo, Guo, and Liu independently confirmed that Tβ4 induces mouse hair growth and upregulates stem cell and angiogenesis-related pathways in follicular tissue. The proposed mechanism involves Tβ4's combined effect on progenitor cell migration and local vascular support to the follicle. As of April 2026, no human RCTs of Tβ4 for hair growth have been published.

Thymosin Beta-4 vs. TB-500: Key Differences

Thymosin beta-4 is a 43-amino-acid endogenous peptide. TB-500 is a synthetic 7-amino-acid acetylated fragment (Ac-LKKTETQ) corresponding specifically to the actin-binding domain (residues 17 through 23) of the full sequence. That structural difference has downstream implications for mechanism, the availability of human trial data, and what can be said with confidence about each compound.

The rationale for developing the fragment was straightforward: shorter peptides are simpler to synthesize, more stable, and easier to characterize pharmacologically. Crockford, Turjman, Allan, and Angel described the full 43-amino-acid sequence and the actin-binding motif in a 2010 review in the Annals of the New York Academy of Sciences, noting that the actin-binding sub-region was the mechanistic core of Tβ4's tissue repair activity. Philp and colleagues confirmed in a 2003 FASEB Journal paper that this same actin-binding domain drives angiogenesis in vitro and in vivo, which is precisely why TB-500, as the synthetic version of this domain, retains pro-angiogenic activity. The fragment captures the central mechanism but not the full structural complexity of the native peptide.

The practical consequence is that virtually all published clinical trial data — the Phase II and Phase III ophthalmic trials, the Phase I safety studies in healthy volunteers, the 2025 cardiac RCT — involve full-length Tβ4, not TB-500. The human evidence base belongs to the parent peptide. TB-500 data are primarily preclinical. The sister TB-500 article covers that compound in detail, including its research status and the distinction from the full-length clinical program.

From a regulatory perspective, the compounds are distinct. Full-length Tβ4 is the molecule in the RegeneRx clinical program and in the 2025 cardiac RCT. TB-500, as a synthetic fragment that has not been studied in the clinical trial pipeline, has a different regulatory characterization. Both are available only by prescription through compounding pharmacies in the United States as of April 2026.

Biomarkers to Monitor With Thymosin Beta-4

Because Tβ4 acts primarily through local tissue mechanisms rather than systemic endocrine pathways, there is no single serum biomarker that tracks its activity the way IGF-1 tracks growth hormone secretagogue response. Monitoring is organized around safety, inflammatory status, and the clinical indication for which the compound is being used.

• High-sensitivity C-reactive protein (hs-CRP): Tβ4's anti-inflammatory mechanism involves suppression of NF-κB, which drives CRP production during systemic inflammation. Baseline hs-CRP establishes the inflammatory starting point and allows providers to track whether systemic inflammatory tone changes during use. Relevant for anyone using Tβ4 in the context of tissue injury or repair where systemic inflammation may be a confounding factor.
• Complete blood count (CBC): Establishes baseline hematologic status. Relevant across all injectable peptide therapies to screen for pre-existing conditions and track hematologic safety. Monitor at baseline and periodically during systemic use. Hematocrit and hemoglobin are particularly relevant given Tβ4's pro-angiogenic mechanisms.
• Comprehensive metabolic panel: Covers hepatic and renal function. Relevant for safety monitoring of any systemically administered compounded compound. A Phase I study of intravenous Tβ4 in healthy volunteers published in 2010 in the Annals of the New York Academy of Sciences by Ruff, Crockford, Girardi, and Zhang, evaluating doses up to 1,260 mg, and an independent Phase I RCT of recombinant human Tβ4 published in 2021 in the Journal of Cellular and Molecular Medicine by Wang and colleagues both used comprehensive metabolic monitoring as part of their safety assessments. Establishing liver and kidney baselines before systemic use is standard practice.
• Insulin-like growth factor 1 (IGF-1): Tβ4 has indirect interactions with growth-related pathways through its effects on progenitor cell mobilization and angiogenesis. IGF-1 is worth establishing as a baseline when using Tβ4 alongside other regenerative peptides or in contexts where growth factor activity is clinically relevant, such as cardiac or musculoskeletal applications.
• Cardiac biomarkers (troponin I/T, BNP): Relevant specifically for systemic Tβ4 use in individuals with known or suspected cardiac disease, or when Tβ4 is used in a cardiac repair context as evaluated in clinical trials. A provider managing Tβ4 in a cardiac context will determine which specific cardiac markers are appropriate based on the clinical picture.
• Lipid panel: Tβ4's role in vascular remodeling and angiogenesis means that baseline cardiovascular biomarkers are worth establishing for individuals using it systemically, particularly those with cardiovascular risk factors. LDL, HDL, triglycerides, and apolipoprotein B provide a complete vascular baseline.

What Thymosin Beta-4 Is Typically Prescribed For

Providers who prescribe Tβ4 through compounding pharmacies most commonly consider it for individuals with significant tissue repair requirements where conventional approaches have been insufficient: refractory corneal surface disease, chronic wounds with impaired healing, or recovery contexts involving musculoskeletal or connective tissue injury. For ophthalmic indications, the clinical data from the RGN-259 program in dry eye and neurotrophic keratopathy provide the highest-quality basis for provider decision-making. For cardiac and neurological indications, the evidence is preclinical or early-phase; no approved indication exists and providers weigh the research context alongside individual clinical circumstance. Thymosin beta-4 requires a prescription from a licensed provider. Providers will evaluate baseline inflammatory status, the specific tissue injury or condition being addressed, and the appropriateness of a compounded formulation before prescribing. Use of compounded medications that are not FDA-approved represents the independent clinical judgment of the prescribing physician.

Who Should Not Use Thymosin Beta-4

A licensed provider will evaluate individual risk factors before prescribing. The following are generally considered contraindications or conditions requiring additional clinical scrutiny:

• Active or history of malignancy, particularly tumors with high angiogenic activity: Tβ4 promotes angiogenesis and may theoretically support tumor vascularization; providers assess oncological history before prescribing any pro-angiogenic compound
• Pregnancy or breastfeeding: safety in these populations has not been established through adequate clinical study
• Known hypersensitivity to thymosin beta-4 or to components used in its compounding formulation
• Severe hepatic or renal impairment: systemic clearance may be affected; compounded compounds require particular caution when metabolic function is compromised
• Individuals unwilling or unable to undergo baseline and follow-up monitoring: safe prescribing of systemic compounded compounds requires objective baseline data and provider-directed follow-up

This is not an exhaustive list. A licensed provider will conduct a full clinical evaluation before determining eligibility for any compounded peptide therapy.

Side Effects and Safety Considerations

The available human safety data for systemic Tβ4 comes primarily from two Phase I studies. Ruff, Crockford, Girardi, and Zhang's 2010 Phase I randomized placebo-controlled single- and multiple-dose study, published in the Annals of the New York Academy of Sciences, evaluated intravenous Tβ4 in 40 healthy volunteers (four cohorts of 10) at ascending single doses of 42, 140, 420, or 1,260 mg — followed by 14 days of daily dosing at the same level after safety review — and reported that adverse events were infrequent and mild to moderate in intensity, with no dose-limiting toxicities or serious adverse events. Wang, Liu, Qi, and colleagues published an independent first-in-human Phase I double-blind RCT of recombinant human Tβ4 in 84 healthy Chinese volunteers in 2021 in the Journal of Cellular and Molecular Medicine, using seven ascending single-dose cohorts (0.05–25.0 μg/kg) and three multiple-dose cohorts (0.5, 2.0, 5.0 μg/kg daily for 10 days); adverse events were mild to moderate with no dose-limiting toxicities or serious adverse events, and no dose-dependent accumulation after repeated dosing. For topical ophthalmic use, the Phase II and Phase III RGN-259 trials reported a safety profile consistent with ophthalmic vehicle controls.

Common (reported in clinical studies):

• Injection-site reactions with subcutaneous administration (typically transient redness or mild swelling)
• Mild transient discomfort with ophthalmic instillation (reported in the RGN-259 program)
• Headache (reported at low frequency in Phase I studies of intravenous Tβ4)

Less common or theoretical based on mechanism:

• Pro-angiogenic effects in tissue with active pathological vascularity: relevant in the context of malignancy; contact your provider promptly if unexpected tissue changes occur
• Immune modulation: Tβ4 has anti-inflammatory effects; theoretical interaction with immunomodulatory therapies is possible; providers should be informed of concurrent medications
• Long-term safety data for compounded subcutaneous Tβ4 in chronic use remain limited; no large-scale longitudinal safety studies have been completed as of April 2026

Is Thymosin Beta-4 Legal?

As of April 2026, thymosin beta-4 is not FDA-approved for any indication. No NDA or BLA for full-length Tβ4 has been approved by the FDA. RGN-259 (0.1% Tβ4 ophthalmic solution) completed Phase III clinical trials for neurotrophic keratopathy and holds orphan drug designation but has not received FDA marketing approval. In the United States, Tβ4 is available only through licensed compounding pharmacies by prescription from a licensed provider. All prescribing represents the independent clinical judgment of the provider. It is not available over the counter in any formulation.

For athletes, there is a separate regulatory consideration. As of the 2026 WADA Prohibited List, thymosin beta-4 is classified as a prohibited substance under Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics). This prohibition applies in competition and out of competition. Athletes subject to anti-doping rules should consult their sport's governing body before using any thymosin compound. TB-500 is equally prohibited under the same section.

Understanding Your Baseline Before Starting Thymosin Beta-4

Thymosin beta-4 does not produce a single trackable serum marker in the way that testosterone or IGF-1 does with their respective therapies. What baseline testing provides in this context is a starting reference point for safety and for understanding the inflammatory and tissue status you are working from. Inflammatory markers such as hs-CRP tell a provider how active systemic inflammation is before a compound with known anti-inflammatory effects is introduced. CBC and metabolic panels confirm that the organ systems responsible for compound processing and clearance are functioning appropriately. For cardiac or vascular applications, a complete lipid panel and relevant cardiac biomarkers establish the cardiovascular picture against which any changes should be interpreted. Without that baseline, a change during therapy has no reference. With it, a provider can make an informed judgment about whether a response is occurring as expected and whether any adjustment is warranted.

That principle, test first then decide, is central to Superpower's approach to preventive health: the belief that every clinical decision should be grounded in what your bloodwork actually shows.

IMPORTANT SAFETY INFORMATION

Thymosin beta-4 is not FDA-approved for any indication. As of April 2026, no NDA or BLA for thymosin beta-4 has been approved by the FDA. Superpower Health does not prescribe, sell, compound, or facilitate access to thymosin beta-4; this page is provided for educational and informational purposes only. Any access to thymosin beta-4 occurs through licensed compounding pharmacies pursuant to a patient-specific prescription from a licensed provider, and all prescribing represents the independent clinical judgment of the prescribing physician.

Contraindications: active or history of malignancy (particularly tumors with high angiogenic activity); pregnancy or breastfeeding (safety not established); known hypersensitivity to thymosin beta-4 or compounding excipients; severe hepatic or renal impairment. This list is not exhaustive.

Warnings: pro-angiogenic mechanism may be relevant in the context of active malignancy or pathological vascularity; anti-inflammatory effects may interact with concurrent immunomodulatory therapies; long-term safety data for chronic subcutaneous use are limited; contact your provider promptly if unexpected tissue changes or systemic symptoms develop.

Common side effects: injection-site reactions (transient redness or swelling), mild transient ocular discomfort with ophthalmic formulations, headache at low frequency in Phase I intravenous studies.

Sport prohibition: As of the 2026 WADA Prohibited List, thymosin beta-4 is prohibited in competition and out of competition under Section S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics). Athletes subject to anti-doping rules should not use this compound.

Long-term safety: No large-scale longitudinal safety studies for compounded subcutaneous thymosin beta-4 have been completed as of April 2026. The available Phase I safety data reflect intravenous administration in healthy volunteers and ophthalmic topical use; subcutaneous chronic dosing safety data are limited.

Full compound reference data available at PubChem CID 16133418.

Additional Questions

Are peptides legal in 2026?

Legality depends on the specific compound, its regulatory status, and the context of use. Thymosin beta-4 is legal in the United States when prescribed by a licensed provider and dispensed by an accredited compounding pharmacy, as a lawful pathway under Section 503A of the Federal Food, Drug, and Cosmetic Act. It is not approved for OTC sale. For athletes, Tβ4 is prohibited under the 2026 WADA Prohibited List (Section S2). The February 2026 FDA reclassification addressed certain peptides but does not directly affect the prescribing pathway for Tβ4 through licensed compounding as of April 2026; consult a qualified provider or regulatory expert for guidance specific to your situation.

What is the FDA peptide reclassification?

In February 2026, the FDA updated its classification of several peptide compounds affecting their availability through compounding pharmacies. Thymosin beta-4 is not directly affected by the primary reclassification that moved certain peptides to Category 1 or Category 3 status. As of April 2026, Tβ4 remains accessible through 503A compounding pharmacies by licensed provider prescription. Regulatory status for compounded peptides is subject to ongoing change; consult a qualified provider for current compounding pathway status for this compound.