Evaluation of the safety, pharmacokinetics and pharmacodynamic effects of subcutaneously administered PT-141, a melanocortin receptor agonist, in healthy male subjects and in patients with an inadequate response to Viagra

Summary

Phase 1/2 clinical trial report covering two studies of subcutaneously injected PT-141 (bremelanotide), a cyclic heptapeptide melanocortin analog: one in healthy male volunteers and one in men with erectile dysfunction (ED) who reported an inadequate response to Viagra. Erections were measured with RigiScan, without visual sexual stimulation in the healthy men and with visual sexual stimulation in the ED patients.

Key Findings

• Healthy men received doses ranging from 0.3 to 10 mg; the erectile response was statistically significant at doses greater than 1.0 mg
• ED patients received placebo, 4 mg or 6 mg PT-141 in a crossover design, and the erectile response was statistically significant at both doses
• PT-141 was safe and well tolerated in both studies
• The authors suggest PT-141 may be an alternative ED treatment with a potentially broad patient base, including men who do not respond adequately to a PDE5 inhibitor

Methodology

Two studies in men. Healthy subjects received subcutaneous PT-141 across a 0.3–10 mg dose range, with erectile activity recorded by RigiScan and no visual sexual stimulation. ED patients were enrolled if they reported that an erection suitable for vaginal penetration occurred 50% of the time or less while taking 100 mg Viagra; they received placebo, 4 mg and 6 mg PT-141 in a crossover design with visual sexual stimulation, again measured by RigiScan. PubMed indexes the paper as a phase 1/phase 2 randomized controlled trial. The abstract does not report participant numbers or pharmacokinetic values.

Limitations

• Lab-measured erectile response (RigiScan) rather than at-home sexual function outcomes
• Men only, subcutaneous route only
• Sample sizes and pharmacokinetic results are not given in the abstract
• Early-phase data; the abstract does not describe longer-term use or safety

Relevance to Content

Early human evidence that subcutaneous PT-141 produces erections in men, including men with ED who do not respond fully to Viagra. Useful for content on PT-141 in male sexual function, framed as early-phase, lab-setting data rather than a large efficacy trial.

See Also

• Parent compound: PT-141