TB4 and TB-500 Peptide Therapy | What to Know in 2026

Photo by Innerbody Research

If you’re reading this guide, chances are you’ve heard something about peptide therapy. Though a few FDA-approved options are already on the market — like semaglutide (Ozempic; for diabetes) and bremelanotide (Vyleesi; for hypoactive sexual desire disorder) — other peptides in various states of approval have been growing in popularity.1 2 Despite many of them still being in the preclinical phase of testing, some doctors have been prescribing these potentially beneficial peptides for years.

Two of those peptides, thymosin beta-4 (TB4) and TB-500, are touted as being able to promote a wide range of health benefits, some of which include faster injury recovery, lower inflammation, better heart health, and even increased hair growth. In this guide, we explore the legitimacy of these claims, address questions about safety, offer an inside look at the patient experience, and point you toward dependable sources of pharmaceutical-grade versions of these peptides.

To that last point, we can tell you right now that your options aren’t exactly vast, but we’ve explored the landscape extensively and have found one provider worthy of your consideration. It’s a concierge telehealth peptide clinic called Protocole. Read on to learn more.

Our Top Pick

Protocole offers pharmaceutical-grade forms of a wide range of therapeutic peptides, including relatively elusive ones like TB-500.

The options here aren’t limited to just a single treatment, either. Protocole’s TB-500 currently features in two recovery stacks — both with BPC-157, KPV, and GHK-Cu, and one with the addition of tesamorelin. Together, these peptides can help optimize your muscle-growth efforts. Additionally, Protocole’s clinicians can curate a suite of peptides tailored to your health history and goals, offering you a personalized therapeutic experience that few other telehealth providers can match.

Jump to

Jump to:

Why you should trust us

Over the past two decades, Innerbody Research has helped tens of millions of readers make more informed decisions about staying healthy and living healthier lifestyles.

Our team has dedicated more than 1,000 cumulative hours over the years researching various peptides, two of which are TB4 and one of its synthetic analogs, TB-500. Through lengthy research, communicating with credible doctors, and gaining firsthand knowledge from one of our own team members, we’ve learned key details about TB4’s and TB-500’s safety, potential benefits, bioavailability, efficacy, patient experience, and much more.

Additionally, like all health-related content on this website, this review was thoroughly vetted by one or more members of our Medical Review Board for accuracy. As the research on peptides evolves, so will the information in this guide.

What are TB4 and TB-500?

Thymosin beta-4 (often written as Tβ4 or TB4) is a naturally occurring peptide, and TB-500 (or fequesetide) is a synthetic peptide based on a segment of TB4.3 4 While TB4 is made up of 43 amino acids, TB-500 contains only seven.4 5 Sometimes, especially in earlier research, you may see TB-500 referred to by its amino acid sequence, Ac-LKKTETQ.6

Insider Tip: The “Ac-” before amino acid sequences, like those of peptides, means it’s been permanently modified with an added acetyl group — a process called N-terminal acetylation — to protect it from degradation.7 8 This can improve a peptide’s stability,9 bioavailability,10 and other properties.11 Though nearly all synthetic peptides are protected in one way or another during synthesis, this protection is usually reversible; not every synthetic peptide is permanently acetylated.12 13

Thymosins are a type of hormone-like polypeptide produced by the thymus,14 a small gland located behind your sternum that makes most of your body’s T lymphocytes (white blood cells that help your immune system function properly to destroy things like pathogens or even cancer cells).15 16 Though there are multiple distinct thymosins, TB4 is “the most abundant and biologically active member of the family in most mammalian cells,” according to researchers. In humans, TB4 is present in high concentrations in “all tissue types except red blood cells, with highest levels occurring in platelets, white blood cells, plasma, and wound fluid.”17

TB4 is an important actin-binding protein that helps actin perform various functions, such as muscular contraction and maintaining proper cell shape, movement, and division.18 19 These effects on cells are why some experts suggest supplemental TB4 can improve the repair and recovery of muscle and other soft tissues,20 21 promote wound healing,22 reduce inflammation, and more.23 Researchers also note that TB4 is critical for the repair and regeneration of eye, heart, skin, nerve, and brain tissue after injury.4

The derivative TB-500 is based on one of the “active sites” of TB4, specifically the peptide segment responsible for the compound’s actin-binding and cell migration abilities.4 Since most of TB4’s potential benefits are attributed to its actin-binding properties, it can be assumed that the same applies to TB-500. But that’s mainly an assumption at this time, as there isn’t very much research on TB-500 itself; most relevant studies focus on TB4.

Insider Tip: Peptides typically aren’t very bioavailable (even when administered intravenously or subcutaneously), but TB-500 may have improved bioavailability over TB4 due to its smaller size and stabilizing N-terminal acetylation.24 25

INNERBODY NEWSLETTER

Ready for the ultimate sleep upgrade?

Your privacy is important to us

What are TB4 and TB-500 peptides used for?

Though the current research suggests that TB4 and TB-500 may be able to support various aspects of your body’s general health and wellness, they’re most often promoted as ways to:

• Repair or regenerate tissue (e.g., heal injuries, boost muscle recovery)
• Lower inflammation
• Promote blood vessel formation
• Protect certain organs (e.g., heart, liver, and eyes)

These potential benefits also have some of the most promising research behind them, though it’s important to keep in mind that the majority of the data on TB4 (and TB-500) to date is from preclinical studies done on cells or animal subjects. Below, we break down the details from notable pieces of research, including the outcomes of a few completed clinical (human) trials.

February 2003 study

A 2003 mouse study found that TB4 in a solution or gel form promoted accelerated wound healing in healthy, diabetic, and aged mice. Researchers also point out that a “seven-amino acid synthetic peptide” based on the actin-binding part of TB4 was “able to promote repair in the aged animals comparable to that observed with the parent molecule.” The amino acid sequence noted was LKKTETQ — TB-500 without the N-terminal acetylation.26

November 2011 review

In a review of TB4’s basic properties and clinical applications, researchers dub it a “regenerative peptide” due to its role in repairing injured cells and tissues. After an injury, the body releases TB4, which works to reduce inflammation and “protect cells and tissues from further damage.” The authors go on to explain that TB4’s tissue regeneration ability is partially due to its promoting the formation of new blood vessels (angiogenesis). And since TB4 “decreases the number of myofibroblasts in wounds,” scarring after an injury is less likely to occur.27

July 2018 study

A 2018 study on mice found that TB4 — due to its apparent ability to reduce inflammation, oxidative stress, and the formation of fibrosis (scar tissue) — may be able to improve health outcomes in people with alcoholic liver injury.28

May 2021 review

In a 2021 review, researchers suggest that, since TB4 is “critical during embryonic development,” it may be a candidate for future therapies focused on reversing physical aging. This is because injections of TB4 into the hearts of mice (both injured and uninjured) basically kick-started repair processes and made the epicardium (the outermost layer of the heart) behave as it does in embryonic development. Thus, the authors state that TB4 may be “capable of re-activating embryonic processes.”29

December 2021 review

A 2021 review covers the results of a few human TB4 trials. One trial evaluated TB4 for heart health, finding that the peptide could “protect and repair” the heart in patients with acute myocardial infarction, and a separate trial found that TB4 improved outcomes during congenital heart surgery.21

The review also mentions a few clinical trials related to eye health, with results showing that TB4 can reduce eye dryness, relieve ocular discomfort, lower inflammation in the conjunctiva, and more. Finally, the review notes that a couple of clinical studies on TB4 for wound healing both resulted in the peptide accelerating the healing process.21

March 2024 study

Interestingly, in a 2024 study, researchers found that TB-500 (Ac-LKKTETQ) didn’t increase wound-healing activity, but one of its metabolites — Ac-LKKTE — did. The authors explain that the “reported wound-healing activity of TB-500 in literature may be due to its metabolite Ac-LKKTE rather than the parent form.”30

Additionally, there have been some positive preclinical research outcomes for the use of TB4 for hair growth,31 neuroprotection,32 tympanic membrane perforations,33 and decreasing mortality in sepsis, but more clinical research is needed before these potential benefits can be considered applicable to humans.5

Are TB4 and TB-500 safe?

Based on current research, TB4 appears to be generally safe for adults when used as directed under the supervision of a medical professional. It has been safely used in a number of preclinical and clinical trials. Some notable safety-related conclusions from scientific materials include:

• A 2016 review of TB4 for dermal healing: “The safety profile is excellent, and no preclinical toxicology has been found.”22
• A 2016 clinical trial on patients with STEMI: “Our pilot study suggested that Tβ4-optimized EPC transplantation appeared to be feasible and safe.”34
• A 2021 review of TB4 research: “It was well tolerated and safe in healthy people and suitable for use in a clinical study.”21

Though the compound itself may be generally safe for adults to use, some common side effects from TB4 injections reported by patients and doctors include:

• Injection site reactions (e.g., redness, mild swelling, or pain)
• Mild gastrointestinal symptoms
• Headaches and dizziness

Rare but more serious side effects can include fever, blistering at the injection site, muscle aches, skin rash, vomiting, severe itching, or hives. If these occur, it’s recommended to stop using the peptide and contact your doctor.

Insider Tip: While reputable clinics offer medical-grade TB4 and TB-500, some online outfits deal in research-grade peptides, instead. Research-grade peptides are not suitable for use in humans due to their lower purity standards. Only medical- or pharmaceutical-grade peptides prescribed by a qualified physician should be used for therapy.35

As for TB-500, there are unfortunately no studies on its safety. TB-500 is based on a part of TB4, so it should, in theory, have a similar safety profile, but studies specifically analyzing its safety still need to be conducted.

Also, it’s important to note that it’d be unsafe for certain groups of people to use either TB4 or TB-500, including those who are pregnant or breastfeeding and those who have suspected or active cancer. These peptides haven’t been evaluated in pregnant or breastfeeding individuals, so their safety hasn’t been established. And since TB4 and TB-500 can stimulate the growth of new blood vessels (angiogenesis), they may support the spread or growth of cancer.36

Who’s a candidate for TB-500 or TB4 peptide therapy?

Currently, it appears that TB4 and TB-500 are best suited for adults with:

• Troublesome injuries or wounds (including those that are slow to heal)
• Inflammation
• Chronic pain due to inflammation
• Health issues involving the heart, liver, or eyes

But it’s essential to remember that the research on these peptides is still in the early stages, and there have been only a handful of human trials. While those trials were largely successful, more research is needed to confirm the potential benefits of supplemental TB4 or TB-500.

Who should avoid TB4 and TB-500 peptides?

Research indicates that three groups that should avoid TB4 and TB-500 are:

• Those who are pregnant or breastfeeding: The safety of these peptides hasn’t been established in pregnant or nursing individuals.
• People with cancer (active or suspected): As mentioned previously, TB4 and TB-500 can promote the growth of new blood vessels, which could support the growth or spread of cancer.36
• Professional athletes: TB4 and TB-500 are banned by the World Anti-Doping Agency (WADA); the peptides fall under the ban on “Peptide Hormones, Growth Factors, Related Substances, and Mimetics.”37

Moreover, as with almost any drug, TB4 and TB-500 could potentially interact with certain medications or react with certain medical conditions, which is one reason why we recommend only using these peptides under the guidance of a doctor.

What’s it like to use TB4 or TB-500?

From our research — including speaking with knowledgeable health professionals and having a team member with firsthand experience — we can share a few insights into what it’s like to use TB4 or TB-500 peptide therapy.

Since peptides' oral bioavailability is usually limited, they are often administered by injection into subcutaneous fat (as around the belly, thighs, or upper arms).24 TB4 or TB-500 injections are typically administered once per day, at any time of day, five days per week. If you’re using them over the long term, you’ll likely cycle them, with one month off for every three months of use (or three cycles per year).

Insider Tip: Some reputable clinics offer a combination peptide therapy containing TB4/TB-500 and BPC-157, or body protection compound 157. These peptides can work well together to promote better healing and recovery. For example, while TB4/TB-500 boosts cellular migration to injuries, BPC-157 can protect and regenerate soft tissues.38 Similar synergistic properties are associated with the peptides KPV and GHK-Cu.

Initial improvements are often mild and include reduced inflammation and increased mobility in injured areas. After around a month or two, patients may notice more significant changes, such as faster healing and recovery times. With long-term use, scarring from injuries might decrease, cardiovascular improvements may be more noticeable, and sustained improvements in overall physical recovery may occur.

Insider Tip: Like many other prescription or supplemental products, peptides should generally be stored in a cool, dry, dark place to prevent degradation. Keeping them in the fridge may be an ideal solution. Consult with your prescribing doctor or any included materials for guidance on storage.

Common side effects from the injections may include injection site irritation, gastrointestinal discomfort, headaches, and dizziness, but they tend to be mild and transient. More rarely, a patient may experience severe symptoms such as a fever of 100.4°F (38°C) or higher, injection site blistering, muscle pain, skin rashes, hives, severe skin itching, or vomiting. In such cases, it’s best to discontinue using the peptide and reach out to your prescribing physician.

Some advice to reduce side effects from physicians well-versed in peptide therapy includes:

• Start with a lower dose and gradually increase to the prescribed dose.
• Rotate your injection sites to reduce irritation and prevent localized swelling.
• Try taking your peptides along with food if gastrointestinal symptoms occur.
• Maintain proper hydration to support your body throughout therapy.
• Keep in touch with your prescribing physician; they can make adjustments to your treatment and monitor your health status throughout.

Guidance on obtaining TB4 and TB-500 peptides

A quick search on the internet for TB4 or TB-500 will often present you with a host of online sellers, many of which aren’t exactly trustworthy and may try to sell customers research-grade peptides instead of pharmaceutical-grade ones. Only pharmaceutical-grade peptides are fit for human use, as the purity criteria for research-grade materials are “generally much less rigorous, partially incomplete, and/or poorly followed,” per one study. By using research-grade peptides, you may be injecting yourself with unknown contaminants.35

Therefore, it’s essential to get your TB4, TB-500, or other therapeutic peptides only through a reputable provider, whether in person or via telemed. If you pursue peptide therapies via an online clinic, make sure they're offering pharmaceutical-grade peptides. And if you feel that the initial consultation process is lacking the kind of substance that you typically associate with consultations as a new patient, we'd suggest you consider that a sign that you should seek additional medical advice elsewhere before proceeding.

At this time, the online clinic we recommend is Protocole, which currently offers TB-500 in two recovery stacks: both include BPC-157, KPV, and GHK-Cu, while the more advanced stack also includes tesamorelin.

Photo by Innerbody Research

In addition, Protocole’s clinicians will curate for you a suite of peptide treatments based on your health goals, and they’re on hand to help you select other treatments that may suit your needs. You can apply for a membership to see what options are available to you.

Innerbody uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

1. Wang, L., Wang, N., Zhang, W., Cheng, X., Yan, Z., Shao, G., Wang, X., Wang, R., & Fu, C. (2022). Therapeutic peptides: Current applications and future directions. Signal Transduction and Targeted Therapy, 7(1), 1-27.

2. Kingsberg, S. A., Clayton, A. H., Portman, D., Williams, L. A., Krop, J., Jordan, R., Lucas, J., & Simon, J. A. (2019). Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. Obstetrics and Gynecology, 134(5), 899.

3. National Center for Biotechnology Information. (2025). PubChem Compound Summary for CID 10169788, Fequesetide. National Library of Medicine.

4. Ho, E. N., Kwok, W., Lau, M., Wong, A. S., Wan, T. S., Lam, K. K., Schiff, P. J., & Stewart, B. D. (2012). Doping control analysis of TB-500, a synthetic version of an active region of thymosin β4, in equine urine and plasma by liquid chromatography–mass spectrometry. Journal of Chromatography A, 1265, 57-69.

5. Belsky, J. B., Rivers, E. P., Filbin, M. R., Lee, P. J., & Morris, D. C. (2018). Thymosin beta 4 regulation of actin in sepsis. Expert Opinion on Biological Therapy, 18(SUP1), 193.

6. The Global Substance Registration System (GSRS). (n.d.). TB-500. National Institutes of Health.

7. Ree, R., Varland, S., & Arnesen, T. (2018). Spotlight on protein N-terminal acetylation. Experimental & Molecular Medicine, 50(7), 1-13.

8. McTiernan, N., Kjosås, I., & Arnesen, T. (2025). Illuminating the impact of N-terminal acetylation: From protein to physiology. Nature Communications, 16(1), 1-15.

9. Li, D., Yang, Y., Li, R., Huang, L., Wang, Z., Deng, Q., & Dong, S. (2021). N-terminal acetylation of antimicrobial peptide L163 improves its stability against protease degradation. Journal of peptide science: an official publication of the European Peptide Society, 27(9), e3337.

10. John, H., Maronde, E., Forssmann, W. G., Meyer, M., & Adermann, K. (2008). N-terminal acetylation protects glucagon-like peptide GLP-1-(7-34)-amide from DPP-IV-mediated degradation retaining cAMP- and insulin-releasing capacity. European journal of medical research, 13(2), 73–78.

11. Marciano, Y., Nayeem, N., Dave, D., Ulijn, R. V., & Contel, M. (2023). N-Acetylation of Biodegradable Supramolecular Peptide Nanofilaments Selectively Enhances their Proteolytic Stability for Targeted Delivery of Gold-Based Anticancer Agents. ACS Biomaterials Science & Engineering, 9(6), 3379.

12. Stawikowski, M., & Fields, G. B. (2002). Introduction to Peptide Synthesis. Current Protocols in Protein Science / Editorial Board, John E. Coligan ... [et al.], CHAPTER, Unit.

13. Conda-Sheridan, M., & Krishnaiah, M. (2020). Protecting Groups in Peptide Synthesis. Methods in molecular biology (Clifton, N.J.), 2103, 111–128.

14. Severa, M., Zhang, J., Giacomini, E., Rizzo, F., Etna, M. P., Cruciani, M., Garaci, E., Chopp, M., & Coccia, E. M. (2019). Thymosins in multiple sclerosis and its experimental models: Moving from basic to clinical application. Multiple Sclerosis and Related Disorders, 27, 52-60.

15. Cleveland Clinic. (2022). Thymus. Cleveland Clinic.

16. Cleveland Clinic. (2023). T Cells. Cleveland Clinic.

17. Sosne, G., Rimmer, D., Kleinman, H., & Ousler, G. (2016). Thymosin Beta 4: A Potential Novel Therapy for Neurotrophic Keratopathy, Dry Eye, and Ocular Surface Diseases. Vitamins and Hormones, 102, 277-306.

18. National Cancer Institute. (n.d.). Recombinant thymosin. NIH.

19. Dominguez, R., & Holmes, K. C. (2011). Actin Structure and Function. Annual Review of Biophysics, 40, 169.

20. Spurney, C. F., Cha, J., Sali, A., Pandey, G. S., Pistilli, E., Guerron, A. D., Gordish-Dressman, H., Hoffman, E. P., & Nagaraju, K. (2010). Evaluation of Skeletal and Cardiac Muscle Function after Chronic Administration of Thymosin β-4 in the Dystrophin Deficient Mouse. PLoS ONE, 5(1), e8976.

21. Xing, Y., Ye, Y., Zuo, H., & Li, Y. (2021). Progress on the Function and Application of Thymosin β4. Frontiers in Endocrinology, 12, 767785.

22. Kleinman, H., & Sosne, G. (2016). Thymosin β4 Promotes Dermal Healing. Vitamins and Hormones, 102, 251-275.

23. Sosne, G., Qiu, P., & Kurpakus-Wheater, M. (2007). Thymosin beta 4: A novel corneal wound healing and anti-inflammatory agent. Clinical Ophthalmology (Auckland, N.Z.), 1(3), 201.

24. Bruno, B. J., Miller, G. D., & Lim, C. S. (2013). Basics and recent advances in peptide and protein drug delivery. Therapeutic Delivery, 4(11), 1443.

25. Lamers, C. (2022). Overcoming the Shortcomings of Peptide-Based Therapeutics. Future Drug Discovery, 4(2), FDD75.

26. Philp, D., Badamchian, M., Scheremeta, B., Nguyen, M., Goldstein, A. L., & Kleinman, H. K. (2003). Thymosin β4 and a synthetic peptide containing its actin-binding domain promote dermal wound repair in db/db diabetic mice and in aged mice. Wound Repair and Regeneration, 11(1), 19-24.

27. Goldstein, A. L., Hannappel, E., Sosne, G., & Kleinman, H. K. (2012). Thymosin β4: a multi-functional regenerative peptide. Basic properties and clinical applications. Expert opinion on biological therapy, 12(1), 37–51.

28. Shah, R., Reyes-Gordillo, K., Cheng, Y., Varatharajalu, R., Ibrahim, J., & Lakshman, M. R. (2018). Thymosin β4 Prevents Oxidative Stress, Inflammation, and Fibrosis in Ethanol- and LPS-Induced Liver Injury in Mice. Oxidative Medicine and Cellular Longevity, 2018(1), 9630175.

29. Maar, K., Hetenyi, R., Maar, S., Faskerti, G., Hanna, D., Lippai, B., Takatsy, A., & Bock-Marquette, I. (2021). 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. Cells, 10(6), 1343.

30. Rahaman, K. A., Muresan, A. R., Min, H., Son, J., Han, H., Kang, M., & Kwon, O. (2024). Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS and their screening by wound healing activities in-vitro. Journal of Chromatography B, 1235, 124033.

31. Gao, X., Liang, H., Hou, F., Zhang, Z., Nuo, M., Guo, X., & Liu, D. (2015). Thymosin Beta-4 Induces Mouse Hair Growth. PLoS ONE, 10(6), e0130040.

32. Song, K., Han, H., Kim, S., & Kwon, J. (2020). Thymosin beta 4 attenuates PrP(106-126)-induced human brain endothelial cells dysfunction. European Journal of Pharmacology, 869, 172891.

33. Bako, P., Lippai, B., Nagy, J., Kramer, S., Kaszas, B., Tornoczki, T., & Bock-Marquette, I. (2023). Thymosin beta-4 – A potential tool in healing middle ear lesions in adult mammals. International Immunopharmacology, 116, 109830.

34. Zhu, J., Song, J., Yu, L., Zheng, H., Zhou, B., Weng, S., & Fu, G. (2016). Safety and efficacy of autologous thymosin β4 pre-treated endothelial progenitor cell transplantation in patients with acute ST-segment elevation myocardial infarction: A pilot study. Cytotherapy, 18(8), 1037–1042.

35. Pauli, G. F., Chen, N., Simmler, C., Lankin, D. C., Gödecke, T., Jaki, B. U., Friesen, J. B., McAlpine, J. B., & Napolitano, J. G. (2014). Importance of Purity Evaluation and the Potential of Quantitative 1H NMR as a Purity Assay: Miniperspective. Journal of Medicinal Chemistry, 57(22), 9220.

36. Johns Hopkins. (n.d.). Angiogenesis Inhibitors. Johns Hopkins Medicine.

37. The World Anti-Doping Agency. (2024). 2025 World Anti-Doping Code International Standard Prohibited List. WADA.

38. Gwyer, D., Wragg, N. M., & Wilson, S. L. (2019). Gastric pentadecapeptide body protection compound BPC 157 and its role in accelerating musculoskeletal soft tissue healing. Cell and tissue research, 377(2), 153–159.