In mouse tests, a super‑potent melanin‑boosting peptide (NDP‑MSH) showed no major organ damage or hormone changes even at high doses for up to three months, though a small rise in blood fats and platelets was seen with weekly dosing. Skin‑based delivery worked, but only a tiny fraction of the drug actually passed through the skin, meaning injections are far more effective. The data suggest the compound is likely safe enough to move into early human trials, but users should watch blood lipids and platelets if they plan long‑term use.

A toxicology study was performed in mice given a superpotent alpha melanocyte stimulating hormone (MSH) analog. This 13 amino acid derivative, [Nle4, D-Phe7]alpha-MSH or NDP-MSH, is a melanotropin which is very slowly biodegraded in vivo and is active at 1/1,000 the concentration of natural alpha-MSH. Mice were administered up to 2 mg/kg of the analog daily and weekly over 4 or 12 weeks by both topical application (in 90% DMSO) or by IP injections (in physiologic saline). At the end of this period, no toxic effects were observed in various organs, on hematologic indices, or on weight gain. A slight increase in triglyceride and platelet levels were noted in mice given the analog weekly for 12 weeks. There was no evidence of an effect on behavior nor ACTH-like endocrine actions such as elevated serum cortisol levels. Transdermal drug delivery studies performed in vitro showed reproducible diffusion of the NDP-MSH analog through full-thickness mouse skin. Approximately 0.002% to 0.05% of a 10(-4) M preparation was transdermally delivered using a DMSO/water solution or a PEG/alcohol cream base, respectively. This superpotent analog is now entering a Phase I clinical trial with possible therapeutic applications for the treatment of hypomelanotic disorders such as vitiligo and for pharmacologic tanning without the need for sunlight exposure.