in a multicenter, phase 2, randomized trial, Kirstine Belongie, PhD, reported at the virtual annual meeting of the American Academy of Dermatology.
Based upon these favorable phase 2 results, a pivotal phase 3 clinical trial is now underway, added Dr. Belongie of Mitsubishi Tanabe Pharma Development America, in Jersey City, N.J., the study sponsor.
Erythropoietic protoporphyria (EPP) is the most common cutaneous porphyria as well as the most common porphyria of any type in children. It’s a rare but devastating disorder, with an incidence estimated at 1 in 75,000-200,000. It involves acute cutaneous photosensitivity to sunlight, which takes the form of incapacitating burning pain that lasts 3-7 days and is then followed by erythema and edema.
“These phototoxic reactions are extremely painful and cause the patients to have extreme fear of the sun. They do everything they can to avoid the sun. It leads to a highly impaired quality of life that’s restricted to the indoors,” she explained.
Current first-line therapy is sun avoidance, the use of zinc oxide sunblock, and protective clothing. It’s inadequate for most patients. “There is a tremendously high unmet medical need for treatment options, especially in the pediatric population,” Dr. Belongie observed.
Patients with EPP experience prodromal symptoms – tingling, itching, and burning – which serve as a signal to get out of the sun immediately. As demonstrated in the phase 2 trial, dersimelagon prolongs the time to onset of these prodromal symptoms by increasing melanin density in the skin in a dose-dependent fashion.
The phase 2 study included 102 EPP patients, with an average age 40 years, at 9 sites, who were randomized double blind to 16 weeks of dersimelagon at 100 mg or 300 mg once daily or placebo. The goal was to increase their pain-free sunlight exposure time.
The primary endpoint was change from baseline to week 16 in the average daily time to first prodromal symptoms. There was a 20-minute increase with placebo, a 74-minute gain with dersimelagon at 100 mg, and an 83-minute gain with dersimelagon at 300 mg. The difference between active medication and placebo became significant at week 6.
Treatment-emergent adverse events leading to study discontinuation occurred in one patient on dersimelagon at 100 mg/day, five patients on the higher dose, and none on placebo. Dr. Belangie said that the drug was well tolerated, with roughly 90% of adverse events being mild or moderate in severity. The frequency of adverse events was dose-related. The most common were headache, nausea, and diarrhea, occurring in 29%, 46%, and 23%, respectively, of patients on dersimelagon at 300 mg/day, compared with 18%, 12% and 12% of those on placebo.
Consistent with the drug’s mechanism of action, there was also a dose-related increase in hyperpigmentation side effects. New freckles were documented in 15% and 31% of patients on low- and high-dose dersimelagon, skin hyperpigmentation in 9% and 31%, and melanocytic nevi in 12% and 20%.
The ongoing double-blind, international, phase 3 trial includes not only patients with EPP, but also individuals with X-linked porphyria, which has similar clinical symptoms. The trial is double blind for the first 26 weeks, followed by another 26 weeks of open-label treatment.
EPP is an inherited metabolic disorder caused by a genetic mutation resulting in deficient activity of the enzyme ferrochelatase. This leads to accumulation of protoporphyrin IX in erythrocytes, skin, and the liver. The excess protoporphyrin is excreted in bile and can cause hepatobiliary disease. Indeed, up to 5% of patients with EPP develop liver failure.
In October 2019, the Food and Drug Administration approved afamelanotide (Scenesse), also a melanocortin-1 receptor agonist, to increase pain-free light exposure in adults with a history of phototoxic reactions EPP; this was the first FDA-approved treatment for helping EPP patients increase their exposure to light, according to the agency. It is administered as an implant every 2 months.
Dr. Belangie is employed by the study sponsor.