Supplement: TB-500

What It Is

Sellers market TB-500 online, mostly as a powder for injection, to speed recovery from tendon, muscle, and joint injuries. They sell it under the name of thymosin beta-4, written Tβ4. The marketing borrows the reputation of that natural repair peptide.

The product is not the whole peptide. A TB-500 sample analyzed in a doping-control laboratory contained a synthetic fragment: residues 17 to 23 of thymosin beta-4, seven amino acids, with an acetyl group on one end. That short piece includes the part of the peptide believed to do the actin-binding and healing. Because it is a different molecule from the full protein, most human research on the whole peptide does not directly test the fragment people inject.

Anatomy

1The natural peptide

The body makes thymosin beta-4 in most tissues and in platelets. Almost all of the healing research studied this full peptide, in animals and cell cultures.

2The marketed fragment

What people inject is the short fragment of thymosin beta-4, produced synthetically on its own. It carries an acetyl cap on one end that slows how fast enzymes break it down.

3How it reaches people

TB-500 is sold as a research chemical, a label that sidesteps the approval a medicine needs. It ships as a freeze-dried powder to be mixed and injected under the skin. No approved medical use for injury recovery exists.

What It Does

The findings behind TB-500 come from animals and cultured cells; no one has been studied injecting it for an injury. In a rat full-thickness wound, thymosin beta-4 sped skin closure by about 42% at four days over saline, and by as much as 61% at seven days. The treated wounds also showed more contraction, more new collagen, and more blood-vessel growth. After a heart attack was induced in mice by tying off a coronary artery, the peptide improved heart-muscle-cell survival and heart function. It worked by switching on a molecular pathway that keeps heart-muscle cells alive.

The only human trials of the natural peptide used an eye drop applied to the eye surface. In a 72-person randomized trial for dry eye, the thymosin beta-4 drop missed both primary endpoints. It still improved some secondary measures: ocular discomfort fell 27% and corneal staining eased. In a nine-person trial in severe dry eye, the drop cut ocular discomfort by about 35% and corneal staining by about 59% against placebo. That evidence is for the eye surface, and it says nothing about recovery from a torn tendon or a strained muscle.

None of these studies tests the product people inject. No completed human trial has injected TB-500, or the full peptide, to heal a tendon, a muscle, or a joint. A promising result in animals is a reason to test a compound in people. It does not show the fragment repairs a human tendon.

No completed human trial has injected TB-500, or the full peptide, to heal a tendon, a muscle, or a joint. A promising result in animals is a reason to test a compound in people. It does not show the fragment repairs a human tendon.

The Research & Studies

Everything here is based on the research we have collected and checked, sorted into groups and ordered with the strongest evidence first. Click any claim to open the studies behind it.

How it works

Thymosin beta-4 accelerated skin wound healing in ratsPreliminary

In plain terms

In rats, the natural peptide thymosin beta-4 made skin wounds close faster and grow more new tissue and blood vessels. TB-500 is sold on the strength of this kind of repair biology, but the healing was shown in animals, not in people.

In detail

Malinda and colleagues (1999) applied thymosin beta-4 topically or by injection into the abdomen in a rat full-thickness wound model and found reepithelialization increased about 42% at day 4 and as much as 61% at day 7 versus saline controls, with wounds contracting at least 11% more by day 7 and showing increased collagen deposition and angiogenesis. The peptide also stimulated keratinocyte migration in a Boyden chamber assay. The work is in rats, so it demonstrates the effect in an animal model and not in people, and it uses the whole peptide, not the TB-500 fragment.

Who this may not transfer to:Shown in a rat wound model using the full thymosin beta-4 peptide; there is no completed human trial and no test of the marketed TB-500 fragment to transfer from.

How to use it

Animal wound-healing data is a reason to study a compound, not evidence that injecting the TB-500 fragment repairs a tendon, muscle, or joint in a person.

The study · 1

Malinda et al., Thymosin beta4 accelerates wound healing · J Invest Dermatol 1999;113(3):364-368

Thymosin beta-4 drives endothelial cell migration and blood-vessel growth in cell and in vivo assaysPreliminary

In plain terms

In cell cultures, thymosin beta-4 pulls the cells that line blood vessels to move and multiply, which builds new blood vessels. This is the mechanism proposed for its healing effects, shown in a dish and in gel implants, not a health outcome in a person.

In detail

Malinda and colleagues (1997) reported that thymosin beta-4 acts as a chemoattractant for human umbilical vein endothelial cells, stimulating migration in Boyden chambers four- to sixfold over media alone, accelerating migration into a scratch-wounded monolayer, increasing matrix metalloproteinase production, and promoting cell migration in subcutaneously implanted Matrigel. This was the first direct evidence that the peptide promotes angiogenesis by moving endothelial cells. The work is cell-based and in vivo animal gel assays, so it characterizes a mechanism, not a clinical benefit, and it does not test the marketed TB-500 fragment in people.

Who this may not transfer to:Shown in human endothelial cell cultures and animal gel implants; a mechanism, not a clinical result, and no human outcome trial exists.

How to use it

A mechanism in cell culture explains why the peptide could aid repair, but a moved cell in a dish is not a healed injury in a person.

The study · 1

Malinda et al., Thymosin beta 4 stimulates directional migration of human umbilical vein endothelial cells · FASEB J 1997;11(6):474-481

Thymosin beta-4 eye drops improved some dry-eye signs and symptoms in two small human trialsPreliminary

In plain terms

The one place the natural peptide reached human trials is the eye. As an eye drop it eased some dry-eye signs in two small studies, though the larger one missed its main goals. This is human evidence for a topical eye treatment, not for injecting TB-500 to heal an injury.

In detail

Sosne and Ousler (2015) randomized 72 subjects with moderate to severe dry eye to 0.1% thymosin beta-4 (RGN-259) or placebo for 28 days using a controlled adverse environment model; neither primary endpoint reached significance, but secondary measures improved, including a 27% reduction in ocular discomfort on day 28 (P=0.0244) and reduced central and superior corneal staining, with no adverse events. Sosne, Dunn and Kim (2015) treated 9 patients with severe dry eye in a randomized, double-masked, placebo-controlled phase 2 trial, reporting a 35.1% reduction in ocular discomfort (P=0.0141) and a 59.1% reduction in total corneal fluorescein staining (P=0.0108) at day 56. Both are small topical eye-drop studies of the whole peptide; neither tests the injected TB-500 fragment or any musculoskeletal recovery outcome.

Who this may not transfer to:Studied as a topical eye drop in adults with dry eye; the effect is specific to the ocular surface and the whole peptide, and does not transfer to injected TB-500 for injury.

How to use it

This is the strongest human evidence for thymosin beta-4, and it is for an eye drop. It does not establish that injecting TB-500 helps a tendon, muscle, or joint.

The studies · 2

Sosne and Ousler, Thymosin beta 4 ophthalmic solution for dry eye: a randomized, placebo-controlled, Phase II clinical trial (CAE model) · Clin Ophthalmol 2015;9:877-884

Sosne et al., Thymosin beta4 significantly improves signs and symptoms of severe dry eye in a phase 2 randomized trial · Cornea 2015;34(5):491-496

A marketed TB-500 product was a short synthetic fragment of thymosin beta-4, not the whole peptidePreliminary · mixed

In plain terms

When a TB-500 product was analyzed in the lab, its ingredient was a short synthetic piece of thymosin beta-4, the stretch at residues 17 to 23, not the whole peptide. So the animal and human research on the full protein does not directly test the fragment that people inject.

In detail

Esposito and colleagues (2012) detected and identified the N-terminal acetylated 17-23 fragment of human thymosin beta-4 (Ac-LKKTETQ) as the ingredient in the formulation TB-500 using high-resolution mass spectrometry, then synthesized the fragment and developed a detection strategy for plasma and urine. A doping-control method paper (Ho and colleagues, 2012) likewise describes the key ingredient of TB-500 as the acetylated peptide LKKTETQ, the residue 17-23 active site of thymosin beta-4. The marketed product is therefore a short synthetic fragment, which is a different molecule from the full peptide most healing research studied.

Who this may not transfer to:An analytical chemistry finding about what a marketed product contains, not a human or animal outcome.

How to use it

Read claims about TB-500 with the substitution in mind: research on the whole peptide is being used to sell a small fragment of it.

The study · 1

Esposito et al., Synthesis and characterization of the N-terminal acetylated 17-23 fragment of thymosin beta 4 identified in TB-500 · Drug Test Anal 2012;4(9):733-738

Heart And Vascular

Thymosin beta-4 improved heart-cell survival and cardiac function after induced heart attack in micePreliminary

In plain terms

After an induced heart attack in mice, thymosin beta-4 helped heart-muscle cells survive and improved how the heart pumped. This is animal evidence about the natural peptide, not a test of injected TB-500 in people.

In detail

Bock-Marquette and colleagues (2004) showed that thymosin beta-4 promotes migration and survival of embryonic and postnatal cardiomyocytes and forms a complex with PINCH and integrin-linked kinase that activates Akt. After coronary artery ligation in mice, treatment upregulated integrin-linked kinase and Akt activity in the heart, enhanced early myocyte survival, and improved cardiac function. The findings are in a mouse model of acute myocardial damage and describe the full peptide, so they do not establish a cardiac or recovery benefit of the injected TB-500 fragment in humans.

Who this may not transfer to:Shown in a mouse model of acute heart injury using the full thymosin beta-4 peptide; no human trial exists to transfer from.

How to use it

This mouse cardiac-repair result explains the healing mechanism the marketing invokes, but it is preclinical and does not support injecting TB-500 for injury or heart health in people.

The study · 1

Bock-Marquette et al., Thymosin beta4 activates integrin-linked kinase and promotes cardiac cell migration, survival and cardiac repair · Nature 2004;432(7016):466-472

How It Works

Thymosin beta-4 binds more actin than any other peptide inside cells. Actin gives a cell its shape and lets it crawl. The peptide keeps a reserve of loose actin on hand, and cells draw on that reserve to build the scaffolding they need to move into a wound. Cell migration into the wound is the first step of tissue repair; nothing happens until cells reach it.

The peptide also draws endothelial cells, the cells lining blood vessels, toward it. In culture they moved four to six times faster than cells with nothing added to pull them, then gathered to form new vessels, a process called angiogenesis. It dampens some inflammatory signaling at the same time. Faster cell migration, more new blood vessels, and less inflammation are the ordinary steps of healing. The fragment sold as TB-500 covers only part of the full peptide. No one has shown that it does the same job in a living person that the whole peptide does.

How to Think About It

How to Think About It

The healing research on thymosin beta-4 is animal and cell work, and the injury-recovery use of TB-500 has no human trial behind it. The treatments with human evidence that rebuild tendon and muscle cost nothing.

1

Separate the fragment from the full peptideFreeEasy

The healing research is on thymosin beta-4, the full peptide, done in rats, mice, and cell cultures. The product injected as TB-500 is a short synthetic fragment of it. A result for the whole peptide in an animal does not carry automatically to the fragment in a person.

2

The injury-recovery use is untested in peopleFreeEasy

No injury-recovery trial in people has finished. Every claim made for TB-500 online traces back to rodent and cell studies.

3

Weigh the grey-market and legal factsFreeEasy

No regulator has approved TB-500 for anything. It is marketed as a research chemical and sits on the World Anti-Doping Agency prohibited list. An athlete who competes under testing can be sanctioned for using it.

4

Do the free thing with human evidence firstFreeModerate

Progressive resistance training and a graded physical-therapy plan repair tendon and muscle, with human trials behind them. Load the injured tissue in steps, and eat enough protein to supply the building blocks. Start here.

Go Deeper

• BPC-157: a related repair peptide sold the same way, with the same shape of evidence: rodent research and no finished human trial.
• Peptides: the wider category TB-500 belongs to, and how to keep the few approved peptide drugs apart from the many unregulated ones.
• Copper peptides (GHK-Cu): another repair peptide sold for healing, studied mostly on skin and in cells.
• Resistance training: the graded loading that repairs and strengthens tendon and muscle, with human evidence behind it.
• Protein and muscle: the food-first building blocks that recovery needs.

Cautions

Everything to be aware of is here, in one place. This practice suits most healthy people; a few situations call for real care.

Illegally sold injectable peptides analyzed in the lab have shown identity and quality problems

Janvier and colleagues (2017) developed and validated a chromatography-mass spectrometry method to identify and quantify the illegal peptides most often encountered on the European market, noting that these lyophilized peptides under 5 kDa are meant for subcutaneous injection and are easily bought online. Analyses in this literature have repeatedly found falsified injectable peptide products with incorrect identity, wrong or missing active ingredient, and impurities. TB-500 is sold in exactly this grey market, so the composition, dose, sterility, and purity of a given product are not assured.Janvier et al., Analysis of illegal peptide drugs via HILIC-DAD-MS

TB-500 is treated as a doping agent and can be detected by anti-doping laboratories

Ho and colleagues (2012) developed a method to detect the acetylated LKKTETQ ingredient of TB-500 and its metabolites in urine and plasma, confirming it at 0.02 ng/mL in plasma and 0.01 ng/mL in urine after a single 10 mg dose, as part of controlling misuse of the peptide in sport. Thymosin beta-4 and its synthetic fragments fall under the World Anti-Doping Agency prohibited list, and the detection work reflects that TB-500 is treated as a doping agent, not an approved therapy.Ho et al., Doping control analysis of TB-500, a synthetic version of an active region of thymosin beta 4, in equine urine and plasma

What is in the vial is unverified

TB-500 is made and sold outside pharmaceutical controls, labeled for research use. Analyses of illegally sold injectable peptides have found wrong doses, missing ingredients, and impurities. What a given vial holds is unknown before it enters the syringe.

Injecting a grey-market product carries its own risks

Whether or not the peptide does anything, self-injecting a non-sterile or mislabeled product can cause infection, abscesses, and injection-site reactions, at a dose no one has verified. No human trial has tested TB-500 for safe self-administration. The circulating doses come from online forums; no trial has set a dose.

Long-term human safety is unknown

No finished human trial of injected TB-500 or thymosin beta-4 for injury exists, so its safety over weeks, months, or years is unknown. The peptide promotes blood-vessel growth and cell migration. Tumors use those same processes, so driving them with an unstudied injected compound is an open concern.

No regulator has cleared it, and no maker stands behind it

No regulator has judged TB-500 safe or effective for the recovery uses it is sold for. No manufacturer is accountable for what a batch contains.

See a clinician before acting on animal data

For an injury you are trying to heal, a doctor or physical therapist can tell you what the evidence supports and whether the problem needs imaging. An injury that is not improving, a joint that locks or gives way, or pain that wakes you at night deserves a professional look.

Start slow, be smart, read the research, and consult a professional if you have any concerns. This is here to inform your choice, not make it for you.

Common Questions

Does TB-500 heal tendons and injuries?

In rats and mice, thymosin beta-4 sped wound closure and heart-tissue repair and grew new blood vessels, and those results held across studies. Nobody has run a finished trial putting injected TB-500 into an injured person. Every injury-recovery claim for it rests on animal and cell work. A result in a rat is a reason to run a human trial; it does not tell you the fragment repairs a person.

Is TB-500 safe?

Its safety in people is unknown, because it has barely been studied. No finished trial has measured what injected TB-500 does over months or years. As a research chemical, a vial's real contents and dose often go unverified before injection.

Is TB-500 legal, or banned in sport?

TB-500 has no approval as a medicine. The World Anti-Doping Agency bans it in sport, along with thymosin beta-4 and its fragments. Anti-doping laboratories can detect those peptides in urine and blood, so an athlete subject to testing who uses it can fail a drug test, whatever the route. Free sale online does not make it legal to use as a medicine or permitted in competition.

Can you take TB-500 as a pill?

Peptides like this are digested in the gut. A pill would be broken apart before it could act, which is why TB-500 is sold as a powder to inject. Gut enzymes take the peptide, or its fragment, apart the same way they break down the protein in food. Swallowing it would not make it safer; it would mostly destroy it.