nerve and tendon repair

why it works

All four are peptides, all four are injected or applied locally in the literature, and none is an approved drug for this purpose. That shared shape is worth stating once at the top rather than four times below.

ARA-290, or cibinetide, is the best-evidenced item here by a distance. It reached real clinical trials in small-fibre neuropathy, including in sarcoidosis, with results on corneal nerve fibre measures and on symptom scores. It is also the most mechanistically interesting: the innate repair receptor is a distinct complex from the classical EPO receptor, which is why the tissue protection can be had without the red-cell effect.

TP-508, or chrysalin, is a twenty-three amino acid fragment of thrombin. It went through genuine company-run clinical trials in fracture and diabetic ulcer healing, which is unusual for this roster and worth crediting even where the programmes did not continue.

BPC-157 is the most popular and the most poorly evidenced of the four in humans: a pentadecapeptide from gastric juice, with a large and remarkably consistent rodent literature across tendon, ligament, gut and nerve, and essentially no controlled human data. Both halves of that are true and both belong.

TB-500 is a synthetic fragment of thymosin beta-4. Again, strong animal work, thin human evidence.

⚠️ BPC-157 AND TB-500 ARE BOTH ON WADA'S PROHIBITED LIST, which matters for anyone who competes at a tested level.

how they work together

The roster splits cleanly in two, and that split is the argument for running four peptides rather than one.

TP-508 and TB-500 are aimed at tissue. TP-508 is a fragment of human thrombin's receptor-binding domain and its literature is about revascularisation, fracture healing and wound repair; TB-500 is a thymosin beta-4 fragment that sequesters actin, promoting angiogenesis and cell migration. Both are about getting blood supply and cells into a repairing site, which is the rate-limiting problem in tendon and ligament specifically, since those tissues are poorly vascularised to begin with.

ARA-290 is aimed at nerve, and its design is the most elegant thing in this roster. It is an eleven-amino-acid peptide taken from erythropoietin's helix B that binds the innate repair receptor without any erythropoietic effect, which separates EPO's tissue-protective signalling from its haematocrit-raising one. That separation is the entire point of the molecule and it has genuine human trial data in small-fibre neuropathy behind it.

BPC-157 spans both halves in its animal literature, which is part of why it is the most popular and the hardest to characterise.

what it feels like

ARA-290 has the clearest reported profile because it has the clearest evidence: reduced neuropathic pain over weeks in the populations studied.

BPC-157 and TB-500 are almost entirely anecdotal in humans and the reports are correspondingly varied. What people describe most consistently is faster resolution of a specific soft-tissue injury, which is exactly the kind of claim that is hardest to distinguish from ordinary healing.

None of these should be expected to work on a timescale shorter than the tissue's own repair timescale, which for tendon is months rather than weeks.