Alexion, AstraZeneca Rare Disease and Merck (NYSE: MRK), known as MSD outside of the United States and Canada, announced positive topline results from the Phase 3 KOMET trial, which is the largest, global randomized double-blind placebo-controlled multicenter Phase 3 trial in adults with neurofibromatosis type 1 (NF1) who have symptomatic, inoperable plexiform neurofibromas (PN). Topline results showed that KOSELUGO, an oral, selective MEK inhibitor, demonstrated a statistically significant and clinically meaningful improvement in objective response rate (ORR), the study’s primary endpoint, versus placebo, in these adult patients.

Neurofibromatosis type 1 is a rare, progressive genetic condition affecting an estimated 1.7 million people worldwide, approximately 70% of whom are adults. In 30-50% of patients, tumors develop on the nerve sheaths and may cause debilitating symptoms. Neurofibromatosis type 1 is usually diagnosed in early childhood; however, NF1 often progresses into adulthood. There are no approved treatments for adults, leaving many to experience disfigurement, dysfunction, persistent pain or endure multiple surgeries.

Professor Ignacio Blanco Guillermo, M.D., Ph.D., chairman, genetic counseling and clinical genetics program at the Germans Trias i Pujol University Hospital, chairman, Spanish National Reference Center for Adult Patients with Neurofibromatosis and principal investigator of the KOMET trial, said, “With limited options to manage NF1 plexiform neurofibromas in adults, many patients experience functional impairment and symptoms, which can substantially impact their lives. These clinically meaningful data show KOSELUGO has the potential to make a positive impact in patient care by reducing the size of plexiform neurofibromas.”

Marc Dunoyer, chief executive officer, Alexion, said, “These promising results demonstrate that KOSELUGO, the first and only approved targeted therapy for certain children with NF1 plexiform neurofibromas, now has the potential to benefit adult patients for whom there are no approved targeted therapies. As the largest and only global placebo-controlled Phase 3 trial in adults with NF1 plexiform neurofibromas, KOMET reinforces our leadership in advancing potential treatment options for people living with this debilitating disease. We look forward to sharing these findings with regulatory authorities.”

Dr. Scot Ebbinghaus, vice president, global clinical development, Merck Research Laboratories, said, “Adults with NF1 are in critical need of treatment options to help manage symptomatic, inoperable plexiform neurofibromas. These positive results from the Phase 3 KOMET trial demonstrate the potential to expand the use of KOSELUGO beyond pediatric patients to also treat adult patients living with this rare and challenging genetic condition.”

In the trial, ORR was defined as the percentage of patients with confirmed complete response (disappearance of PNs) or partial response (at least 20% reduction in tumor volume) by cycle 16 (28 days per cycle) as determined by independent central review (ICR) per response evaluation in neurofibromatosis and schwannomatosis (REiNS) criteria.

The safety profile of KOSELUGO in this study was consistent with that observed in clinical trials among children and adolescents. No new safety signals were identified.

Alexion, AstraZeneca Rare Disease will share these data with regulatory authorities and present these data at a forthcoming medical meeting. AstraZeneca and Merck are jointly developing and commercializing KOSELUGO globally.