Peptide & Experimental

TP508 (Rusalatide, Chrysalin)

Q: What is TP508?

TP508 is a laboratory-made peptide of 23 amino acids that mimics a section of the clotting enzyme thrombin. It was developed under the name Chrysalin as a treatment for wounds and bone fractures, but never approved.

Q: Does TP508 help wound healing?

A study with 60 people with diabetic foot ulcers points in that direction: with topically applied TP508, more than twice as many ulcers healed completely as with placebo. There is no larger confirmatory study.

Q: Does TP508 speed up the healing of bone fractures?

That is not established. The large study on wrist fractures with 274 participants was stopped because no benefit over placebo was seen. The developers report faster healing on X-ray and an effect in a subgroup, but TP508 missed the main endpoint.

Q: Is TP508 approved?

No, neither in Germany nor in the EU or the US. Since the fracture study was stopped in 2007, no further study in humans has been entered in the trial registry.

Q: Is TP508 allowed in sport?

No. As a non-approved substance, TP508 falls under S0 of the WADA 2026 Prohibited List and is prohibited both in and out of competition.

Q: How safe is TP508?

In the small studies, no more side effects occurred with TP508 than with placebo. However, the data come from a few hundred patients with topical or single administration; there are no human data on repeated injections or long-term use.

Synthetic thrombin fragment (23 amino acids, prothrombin 508–530), research substance, never approved · rusalatide acetate, rusalatide, Chrysalin, thrombin peptide TP508, TP-508

TP508 is a short piece of the clotting enzyme thrombin that was tested in humans in the 2000s as a treatment for wounds and bone fractures. A small study on diabetic foot ulcers was positive, the large study on wrist fractures was not. TP508 is not approved anywhere; today it is offered as a research peptide.

In short

TP508, also rusalatide acetate or Chrysalin, is a synthetic peptide of 23 amino acids that mimics a section of human prothrombin. In cell and animal experiments it promoted new blood vessel formation as well as wound and bone healing. In humans there is one published randomized trial with 60 patients in which topically applied TP508 led to complete healing of more diabetic foot ulcers than placebo. The large study on wrist fractures with 274 participants was stopped because no benefit over placebo was seen. There are no human data on repeated injections. In sport, TP508 is prohibited at all times.

What TP508 is and how it works

Thrombin is the key enzyme of blood clotting, but it also provides the impetus for tissue repair. TP508 mimics amino acids 508 to 530 of human prothrombin, sequence AGYKPDEGKRGDACEGDSGGPFV. According to the developer group, this is the site with which thrombin binds to a subgroup of receptors on fibroblasts; the fragment does not have the clotting-active cleavage function of the whole enzyme.

In human endothelial cells, the cells of the inner vessel wall, TP508 released nitric oxide within 5 minutes, two to four times as much as without the peptide and of a similar order of magnitude as the growth factor VEGF, but via a different signaling pathway. In animal models it accelerated the healing of skin and bone wounds; in rats, more large blood vessels were found in the fracture callus. In mice, a single injection 24 hours after lethal irradiation improved survival and protected the intestinal lining. Exactly which receptor is targeted has not been clearly established; in 2010 the developers themselves wrote that the molecular mechanisms were unclear.

What is well supported

One positive randomized finding on wounds. In a double-blind, placebo-controlled phase I/II trial with 60 people with diabetic foot ulcers, more than twice as many ulcers healed completely with topically applied TP508 as with placebo, and the median time to complete closure was about 40 percent shorter.
A described mode of action. The rapid release of nitric oxide in human endothelial cells and new blood vessel formation in wound and fracture models have been measured in cell culture and in animals.
Unremarkable tolerability in the wound study. Local reactions and side effects occurred equally often with TP508 and placebo; drug-related laboratory changes and serious side effects were not reported.

What the studies show

Diabetic foot ulcers, Fife 2007

60 participants were randomized double-blind to TP508 in saline or saline alone, applied to the ulcer twice a week, in addition to standard care and offloading. TP508 more than doubled the proportion of completely healed foot ulcers, accelerated the mean closure rate by about 80 percent and shortened the median time to complete closure by about 40 percent, each p<0.05. The authors report the dose-dependent effect for the per-protocol analysis, that is, only for the participants who completed the study as planned. For heel ulcers, 6 of 7 healed versus 0 of 5 on placebo.

Wrist fracture, phase 2b (NCT00131482)

274 adults with a fracture of the radius at the wrist received a single dose of TP508 at one of four dose levels or placebo at the fracture site during surgery. The primary endpoint was the time to removal of all rigid immobilization. The study was stopped in March 2007; as the reason, the registry states that TP508 showed no benefit over placebo. No results are posted in the registry.

The developers’ account, 2008

In a review, Carney and Olszewska-Pazdrak describe a phase III study on wrist fractures, one of the largest fracture studies of its time. On X-ray, the fractures healed significantly faster with TP508, but the agent missed the main clinical endpoint, the time to removal of immobilization, in the overall group. In a subgroup of women with osteopenia it was reached. Subgroup findings after a missed main endpoint generate hypotheses; they do not prove a benefit. Whether this study is identical to the registry entry is not clear from the sources; both name the same main endpoint.

Radiation damage in animals, Kantara 2015

The company Chrysalis BioTherapeutics provided TP508 for experiments as an agent against acute radiation damage. In mice that received a lethal radiation dose, a single injection 24 hours later improved survival, and the intestinal crypts were more likely to be preserved. This has not been studied in humans.

Where the data stop

A single published efficacy study. The positive finding comes from 60 patients with diabetic foot ulcers and was not confirmed in a larger study.
Bone fractures: null finding. The large fracture study was stopped without benefit over placebo; the favorable findings of the developers concern X-ray images and a subgroup.
No data on repeated injection. In humans, TP508 was applied topically to wounds or given once at a fracture site. For other forms of use there are only animal data.
No ongoing development in humans. Since the termination in 2007, no further study has been entered in the registry (query 2026-10-05). The research on radiation damage is animal research.
Gray-market products are not the study preparation. What is sold as a research peptide on the gray market is untested for purity, content and sterility.

Status, approval and legal

TP508 is not approved as a medicine in Germany, the EU or the US. It was developed as Chrysalin by OrthoLogic; the fracture study ran under Capstone Therapeutics and was stopped in 2007. Because it never became a medicine, it is also not on the list of prescription-only substances; it is offered as a research chemical. In sport, TP508 falls under S0 of the WADA 2026 list, non-approved substances, and is therefore prohibited at all times.

Safety

In the wound study with 60 participants, local wound reactions and side effects were equally frequent in both groups; drug-related laboratory changes and serious side effects were not reported. The developers also report no drug-related side effects for the fracture studies. This is a narrow basis: a few hundred patients, short follow-up, topical or single local administration. Long-term data and data on repeated injections are lacking, as are data on people with clotting disorders, vascular disease or tumors.

BK-Score Hype far ahead of evidence

Human evidence		3
Mechanism		4
Safety data		2
Hype gap		2
Track record of use		2

Evidence 3, because there is exactly one published randomized trial: 60 patients with diabetic foot ulcers, topical use, more than twice as many complete healings as with placebo (Fife 2007); the large fracture study with 274 participants was stopped, according to the registry, because TP508 showed no benefit over placebo (NCT00131482), and the developers report a missed primary goal for phase III (Carney 2008). Mechanism 4, because binding to thrombin receptors on fibroblasts, NO release in endothelial cells and new blood vessel formation have been shown in cell and animal models, but the receptor has not been clearly identified and the developers themselves described the molecular mechanisms as unclear in 2010. Safety 2, because tolerability data come only from a few hundred patients with topical or single local administration; there are no human data on repeated injections. Hype 2, because TP508 is traded as a healing peptide although the largest test in humans found no benefit. Use 2: few studies in the 2000s, no approval, no registered study since. Direction mixed: one small positive finding on wounds, one large null finding on bone fractures.

The score rates the state of knowledge, not the substance. “Safety data 9” means well studied – not harmless.
Subjective assessment by Biohacking Kompakt based on published scoring rules – not a scientific rating and not a medical recommendation. Rules and all ratings (German)

Frequently asked questions about TP508 (Rusalatide, Chrysalin)

What is TP508?