Huntington’s Phase 2/3 Study Shows Promise for New Drug Therapy

Raptor Pharmaceutical Corp. has announced the efficacy and safety results from CYST-HD, a Phase 2/3 clinical trial conducted in collaboration with the Centre Hospitalier Universitaire d’Angers, evaluating the potential of RP103 as a Huntington’s disease therapy.

RP103 is an extended release oral drug candidate currently in clinical development for the treatment of Huntington’s disease and mitochondrial disorders, which has already demonstrated promise for its antioxidative protein stabilization properties in multiple animal models. The multicenter CYST-HD study enrolled 96 patients, who were randomly distributed between a drug group and a placebo group. After the first 18 months of the study, the patients in the placebo group were also treated with RP103 to assess the effect of a delayed treatment initiation (in an 18-month open label extension). The study’s primary endpoint was the change from baseline at 18 and 36 months in the Total Motor Score (TMS) component of the Unified Huntington’s Disease Rating Scale (UHDRS). Secondary endpoints included function evaluation through the Total Functional Capacity (TFC) and Independence Scale.

Data revealed that patients in the group treated initially the RP103 at 36 months showed a 25% slower disease progression compared to the placebo arm,  consistent with other study components, such as voluntary movements, favoring earlier treatment. Among this initial group of drgu patients, findings also showed a 23% slowing in the rate of decline in TFC, and a 46% slowing in the rate of deterioration on the Independence Scale. The most common observed adverse effects included nausea, vomiting, diarrhea, headache, and breath odor. The safety profile observed was consistent with previous studies.

“The 36-month efficacy results from the CYST-HD study are clinically meaningful and suggest that RP103 may play an important role in the treatment of Huntington’s disease. These data warrant further assessment as there remains a clear need for new, safe and tolerable therapies to treat this disease,” the principal investigator for CYST-HD, Dr. Dominique Bonneau, MD, professor of Medical Genetics at the CHU d’Angers, said in a press release.

“We are excited to be advancing a treatment that has the potential to slow the rate of motor and functional decline in Huntington’s disease patients. Such a therapy holds promise to be transformational for patients and is perfectly aligned with our strategic focus to develop and commercialize therapies that bring significant relief to patients and families living with life-threatening diseases. We look forward to discussing the 36-month data with the regulatory authorities and to advancing RP103 in a confirmatory study,” said Julie Anne Smith, Raptor’s president and CEO.