What to Know About TB4 and TB-500 Peptide Therapy

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’ll explore the legitimacy of these claims, address questions about safety, and offer an inside look at the patient experience.

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 hundreds of 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 and TB-500’s safety, potential benefits, bioavailability, efficacy, patient use 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.

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

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 (thymosin beta-4) is, according to researchers, “the most abundant and biologically active member of the family in most mammalian cells…” 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

Pivoting to TB-500, it’s based on a single one of the “active sites” of TB4 — 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. However, that is mainly an assumption at this point in time, as there isn’t very much research on TB-500 itself; most of it focuses on TB4.

Though these peptides may be able to support various aspects of your body’s general health and wellness based on current research, 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)

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

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

Based on current research, TB4 appears to be generally safe for adults when used as directed under the supervision of a medical professional. Unfortunately, however, there aren’t any studies on the safety of TB-500, its synthetic analog. Even though TB-500 is based on a part of TB4, its safety can’t necessarily be assumed; studies analyzing the safety of the peptide still need to be conducted.

With that being said, TB4 has been safely used in a number of preclinical and clinical trials. Some notable safety-related quotes 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.

Finally, it’s important to note that it’d be unsafe for certain groups of people to use 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 A physician can order any and all necessary pre-treatment tests as a prerequisite for prescribing peptide therapy.

Currently, it seems like TB4 and TB-500 could be best suited for adults with troublesome injuries or wounds (including those that are slow to heal), inflammation, chronic pain due to inflammation, or 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 only been 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?

Until more research is conducted, we don’t know all of the populations that should avoid TB4 and TB-500. There could be undiscovered medication interactions or reactions with certain medical conditions (which is one of many reasons why we highly recommend only using these peptides under the guidance of a doctor).

From what we do know, the three groups that should avoid TB4 and TB-500 include:

• 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

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 particularly limited, they are often administered by injection into subcutaneous fat (stomach, thighs, or upper arms).24 The TB4 or TB-500 injections can be used at any time of day, once per day, for five days per week followed by two days off. If using these peptides long term, you’ll likely cycle them, with one month off for every three months of use (or three cycles per year).

Initial improvements are often mild and include things like lower inflammation or 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 can be more noticeable, and sustained improvements in overall physical recovery may occur.

Common side effects from the injections may include symptoms like injection site irritation, gastrointestinal discomfort, headaches, and dizziness, but they tend to be mild and transient. More rarely, a patient may experience severe symptoms like a fever of 100.4°F (38°C) or higher, injection site blistering, muscle pain, skin rashes, hives, severe skin itching, or vomiting. In those 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 include:

• Start off with a lower dose and increase to the prescribed dose gradually
• Change up 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

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- or medical-grade ones. Though both research- and medical/pharmaceutical-grade peptides are on the market, only the latter would be suitable for humans; research-grade peptides are not safe for human use. As noted in one study, the purity criteria for research-grade materials are “generally much less rigorous, partially incomplete, and/or poorly followed.” This could mean injecting yourself with unknown contaminants.35

The above information is one of the many reasons why it’s essential to only get your peptides through a qualified medical doctor, either through a reputable in-person clinic or telehealth service.