Tanabe’s MC1R Agonist Dersimelagon Clears Primary Endpoint in Phase 3 EPP/XLP Trial

Edited by Robert McTiernan··2 min read

Tanabe Pharma America reported positive topline results from the global Phase 3 INSPIRE study of dersimelagon (MT-7117) in adult and adolescent patients with erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), two ultra-rare genetic phototoxic disorders. The study met its primary endpoint of delaying the time to first prodromal symptom associated with sunlight exposure and showed a favorable safety and tolerability profile.

Dersimelagon is a novel, orally administered small molecule that acts as a selective melanocortin-1 receptor (MC1R) agonist, a mechanism intended to increase melanin production and improve light tolerance in patients with EPP and XLP. The program received US FDA Fast Track and Orphan Drug Designations, but remains unapproved globally.

In the INSPIRE trial, patients randomized to dersimelagon 200mg once daily demonstrated a statistically significant increase in the duration of pain-free sunlight exposure before prodromal symptoms such as burning, tingling, itching, or stinging occurred, compared with placebo during the 16-week double-blind period. Most adverse events were mild or moderate, and the open-label extension portion of the study is ongoing.

The AllSci BriefSystematic R&D and deal news. Daily.

Clinical and Competitive Context

EPP and XLP are caused by disruptions in heme biosynthesis that result in protoporphyrin IX accumulation in blood and tissues, leading to severe photosensitivity and debilitating pain within minutes of sunlight exposure. Management historically focused on sun avoidance and protective measures, with only a few pharmacologic options available that address photosensitivity directly.

The melanocortin-1 receptor (MC1R) is a G protein-coupled receptor primarily expressed in melanocytes, where it regulates melanin synthesis and skin pigmentation. MC1R activation by its natural ligand, alpha-melanocyte-stimulating hormone (α-MSH), increases eumelanin production, which provides photoprotection against ultraviolet (UV) radiation and oxidative stress. This photoprotective effect underpins the rationale for targeting MC1R in drug development, especially for conditions involving photosensitivity or pigmentary disorders.

Of note, Clinuvel Pharmaceuticals’ afamelanotide (Scenesse) is a synthetic α-MSH analogue and potent MC1R agonist that was first approved for EPP in the EU in 2014 and the US in 2019. However, that drug is administered via a small implant inserted under the skin, with Tanabe’s oral dersimelagon on course to offer a more convenient option for EPP/XLP patients.