Tanabe’s oral MC1R agonist dersimelagon extends pain-free light exposure in Phase III EPP/XLP trial

Tanabe Pharma Corporation reported that dersimelagon, an investigational oral melanocortin 1 receptor (MC1R) agonist, significantly extended pain-free sunlight exposure in patients with erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) in the Phase III setting, a result that could position the drug as the first oral option for these rare phototoxic disorders. The placebo-adjusted improvement in light tolerance addresses a core functional limitation for patients, where treatment options remain limited, particularly in adolescents.

In the Phase III INSPIRE study, a randomized, double-blind, placebo-controlled global trial, Tanabe evaluated dersimelagon in adolescents and adults with EPP or XLP over a 16-week treatment period.

The primary endpoint—change in daily sunlight exposure time to first prodromal symptom during Weeks 12–16—showed a placebo-adjusted increase of approximately 23 minutes (p=0.004), with the effect reaching nearly 30 minutes by Week 16 in supplementary analysis. On secondary measures, patients reported improvements in global disease status and fewer pain episodes, with total pain events reduced by about 39% versus placebo, supporting that the extended exposure translated into clinically meaningful benefit.

Safety was generally consistent with the drug’s mechanism, with adverse events including hyperpigmentation and benign nevi, alongside headache and gastrointestinal effects, and no unexpected signals reported.

Dersimelagon is a small-molecule MC1R agonist designed to increase eumelanin production and improve tolerance to light exposure, differentiating it from existing options such as afamelanotide, an implantable therapy that also targets the melanocortin pathway. Cross-trial comparisons are limited, but an oral therapy could offer a more convenient alternative if efficacy and tolerability are sustained, particularly in younger patients where no approved therapies exist.

Tanabe said it is preparing a rolling New Drug Application submission to the US FDA following the Phase III results.