Its best-supported claim is not speed but the quality of the tissue that grows back. Its weakest points are a figure taken on trust and a tumour association worth stating plainly.
Two claims about TB-500 travel further than the evidence behind them. One is a number everybody repeats. The other is a reassurance about cancer that, unlike the equivalent claim for BPC-157, the animal literature does not support.
Start with the number.
Search any forum and you will find it: TB-500 has a half-life of roughly ten days, which is why twice-weekly dosing works.
No published study produced that figure. There is no data on how the compound behaves after a subcutaneous injection at the doses people actually use. The number seems to have entered circulation by repetition alone.
What is known: the protein is small, around 5 kilodaltons, and it spreads through the body without anchoring to anything. Both facts argue for a longer working life than a peptide that clears in minutes. That is a fair inference. It is not a measurement. The dosing schedule built on top of it rests on a guess dressed up as a number.
Worth knowing before treating "twice weekly" as settled.
TB-500 is thymosin beta-4 made in a lab. The natural protein is 43 amino acids long, and your body already makes it and keeps almost everywhere — platelets, white blood cells, plasma, wound fluid, and nearly every tissue except red blood cells. It was found in the thymus in the 1960s during immune research. The WHO calls it timbetasin.
Different stretches of the chain do different jobs. That is unusual, and it explains how broad its effects are. Residues 1 to 4 handle the anti-inflammatory side. Residues 1 to 15 block programmed cell death. Residues 17 to 23 trigger blood vessel formation, and hair growth along with it.
Actin makes up roughly a tenth of all protein in your cells. It builds the cytoskeleton — the frame that gives a cell its shape and lets it move.
TB-500 binds single actin units one-to-one and keeps them from joining into filaments. That sounds backwards until you see what it is for. It holds a staged reserve of building material, ready to go. When a cell needs to move, TB-500 hands its actin to a protein called profilin. Profilin delivers it to the growing end of a filament, exactly where it is needed.
The handoff itself is neat. Profilin opens a pocket on the actin, which loosens TB-500's grip and lets the transfer happen. The result is controlled rebuilding of the cell frame, aimed at damaged tissue.
Now the part with a practical consequence. Most repair signals are tethered to the matrix around cells, which limits how far they reach. TB-500 is not. Low molecular weight, no matrix binding, so it moves freely through tissue.
That is why it does not need to be injected near the injury. It is the exact opposite of BPC-157, which clears in under 30 minutes and is argued to benefit from local placement. Two healing compounds, two completely different logistics.
Its potency at the cellular level is worth a line of its own: skin cell migration rose two- to threefold at concentrations as low as 10 picograms.
Most of the interest in this compound is about speed. The more interesting finding is about quality.
During metabolism, TB-500 sheds a four-residue fragment from its front end called Ac-SDKP. That fragment drives most of the anti-inflammatory and anti-scarring activity — it damps inflammatory cytokines and has shown antifibrotic effects across animal models of lung, liver, kidney and heart fibrosis.
This matters because excess scarring is one of the main reasons injuries heal badly. Scar tissue is weaker, stiffer and does not behave like the tissue it replaced.
Ehrlich and Hazard put numbers on it in 2010. Treated cuts in rats healed narrower, with few myofibroblasts — the cells that build scar. The collagen came out organised and mature, where controls showed random immature fibres. And this came without any loss of wound breaking strength. Faster and weaker would be a bad trade. Faster and better organised is a different claim.
The ligament work points the same way: treated tissue showed evenly spaced fibre bundles and thicker collagen fibrils, with better mechanical properties at four weeks.
One study belongs here precisely because it is inconvenient.
Spurney and colleagues, 2010, gave chronic thymosin beta-4 to mice bred without dystrophin. Regenerating muscle fibres increased significantly. Strength did not. Cardiac function did not. Fibrosis did not.
More regeneration, no measurable improvement in what regeneration is supposed to deliver. That gap sits between a marker moving and an outcome moving. It is the most common way healing compounds look better than they are, and it is worth carrying into every other result on this page.
There are more human subjects here than for most compounds in this category. They were studied for the wrong things.
Phase I safety, Ruff and colleagues, 2010. Randomised, placebo-controlled, escalating intravenous doses up to 1260 mg in healthy volunteers. Well tolerated, no dose-limiting toxicity, adverse events rare and mild to moderate.
Phase I safety, Wang and colleagues, 2021. 84 healthy volunteers, single and multiple intravenous doses of the recombinant protein. No dose-limiting toxicities, no serious adverse events, and no accumulation with repeat dosing.
Phase II, dry eye, Sosne and Ousler, 2015. 72 subjects, randomised and placebo-controlled. Discomfort scores fell 27% against placebo, with significant improvement in corneal staining and no adverse events.
Cardiac work has reached trials too. It follows a 2004 Nature paper showing thymosin beta-4 switching on integrin-linked kinase, and improving heart cell survival and movement in mice.
Not one published human trial covers tendon, ligament or muscle healing. That is the reason nearly everyone buys it. The safety record is genuinely encouraging as far as it goes. It says nothing about whether the compound does the job it is bought for.
This is where I want to be careful, because the answer differs from the one on the BPC-157 page and the difference is the point.
For BPC-157, the animal tumour work ran against the intuitive fear — it suppressed proliferation and downregulated VEGF in tumour models.
For TB-500, it does not. Thymosin beta-4 overexpression has been associated with greater metastatic potential and higher blood vessel counts in certain tumour types. Other cancers show reduced expression, so the relationship is not simple in either direction. But the mechanism is new blood vessels plus easier cell movement. That is a fair description of what a tumour needs to grow and spread.
To be exact about what is established: no study has shown that giving TB-500 causes cancer in a healthy body. The concern is different. In someone with an active cancer, or dormant cells nobody has found yet, those same two abilities are the wrong ones to amplify.
So the rule against use in active or recent cancer rests on mechanism plus an unhelpful association, not on observed harm. That is a slightly worse footing than the same rule on the BPC-157 page. Imaging clearance from an oncologist before starting, if there is any history, is not an over-cautious suggestion.
Human trials found a favourable profile, including no adverse events across 72 subjects in the dry eye study. Rodent toxicology found no significant adverse effects up to 100 mg/kg.
The honest caveat: there is no long-term human safety data. Short trials finding no harm is not the same as long use being safe. That work has not been done.
The most consistently reported effect in practice is not on any trial list. Fatigue, or a mild flu-like feeling, in the first one to three days. It clears within a day or two and fades with later doses. Nobody knows why. Shifts in immune and inflammatory signalling are the usual guess. Also reported: mild headache, a brief head rush right after injection, and injection site irritation.
Beyond active cancer or a cancer history, take care with pregnancy and breastfeeding (no data), severe immunodeficiency, and active autoimmune conditions. This compound shifts immune function, which is not a neutral thing to do to an immune system already misfiring. Heart conditions warrant monitoring, given how much of the research sits in cardiac tissue. Any unresolved mass or precancerous finding rules it out until settled.
No drug interactions are established, which reflects how little human research exists rather than an all-clear.
There is no blood test that tracks whether this is working. Assessment by whoever is treating the injury is the practical measure.
Not approved for human therapeutic use in any country. The FDA made it a Category 2 bulk drug substance in 2023, which shuts compounding pharmacies out of it. WADA prohibits it under S0, unapproved substances, and the UFC, NFL and NCAA ban it separately.
It has already sat at the centre of two large doping cases. One involved Essendon, an Australian rules club. The other involved the Cronulla-Sutherland Sharks in rugby league. Both ended in player suspensions.
For anyone who competes under a testing body, that history is the practical headline, well ahead of anything in the mechanism.
This article explains published research and the rules around it. It carries no dose, no protocol, and no claim that any compound treats, cures or prevents a condition in anyone. Where the evidence is thin we say so. See our editorial standards.
Research-grade material, sold for laboratory research use. We link to a single supplier rather than a list, so you know exactly where the recommendation goes. Check the certificate of analysis against what a COA can and cannot show before you buy anything.
Commercial link. Nothing on this page is a dose, a protocol, or a claim that this compound treats or prevents any condition.
KLOW is GLOW plus 10 mg of KPV — that part is simple. The more useful fact is that both are, by mass, mostly copper peptide, and that is the ingredient whose injected form has no human trials.
An open study found sleep normalised in six of seven patients. The controlled study by the same investigator found weak effects and said so. The difference between them is a placebo arm.
It does not raise dopamine — it magnifies what other things do to it. That one property explains why caffeine feels stronger on it, and why MAO inhibitors are a hard contraindication.
