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Raptor Announces Clinical Results With RP103 in Huntington’s Disease Phase 2/3 Trial

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Raptor Pharmaceutical Corp. today announced top line results from a planned 18 month analysis of an ongoing 3 year Phase 2/3 clinical trial of RP103 (delayed-release cysteamine) for the potential treatment of Huntington's disease (HD) in collaboration with the Centre Hospitalier Universitaire d'Angers (CHU d'Angers). A total of 96 patients with HD were randomized to treatment with RP103 or placebo.

February 20, 2014

Raptor Pharmaceutical Corp. today announced top line results from a planned 18 month analysis of an ongoing 3 year Phase 2/3 clinical trial of RP103 (delayed-release cysteamine) for the potential treatment of Huntington’s disease (HD) in collaboration with the Centre Hospitalier Universitaire d’Angers (CHU d’Angers). A total of 96 patients with HD were randomized to treatment with RP103 or placebo. Eighty nine patients completed the initial 18 month phase. Analysis of all 96 patients enrolled in the trial showed a positive trend towards slower progression of Total Motor Score (TMS) in patients treated with RP103 vs. those patients on placebo, the primary endpoint of the study. TMS progression was 32% slower in patients treated with RP103 vs. those treated with placebo after 18 months treatment (4.51 vs. 6.68 respectively, p=0.19). In 66 patients not taking concurrent tetrabenazine, RP103 treatment resulted in a statistically significant slower progression in TMS vs. the placebo group (2.84 points vs. 6.78 respectively, p=0.03).

Due to the 36 month duration of the study, patients were allowed to continue their baseline medication regime, including antidepressants and tetrabenazine, the latter being an approved medication to treat chorea associated with HD. Patients were not randomized in the study based on concomitant medications. To confirm that the TMS results were not influenced by a potential treatment effect of tetrabenazine on chorea (a sub-score of TMS) the subset of patients not receiving tetrabenazine were analyzed for TMS. In these 66 patients (32 under placebo and 34 under RP103), RP103 treatment caused a statistically significant 58% slower progression in TMS of 2.84 points compared to 6.78 points for placebo (p=0.03) at 18 months. Slower progression was seen across all TMS sub-score measurements including eye and hand movements, balance and gait, as well as maximal dystonia and maximal chorea. Adverse events were similar in the two groups and were comparable to what has been observed in other studies in this patient population.

“We are very encouraged by these trial results and we believe that the significant slowdown of loss of muscle control in these early stage patients indicates that RP103 is potentially effective at slowing the progression of Huntington’s disease,” said Dr. Christophe Verny, Lead Investigator for the Phase 2/3 clinical trial and Chief of Neurology Department at CHU d’Angers. “We look forward to working with Raptor to develop and implement a continuing access program so that we can continue to provide RP103 to the patients who participated in the study initiated by CHU d’Angers, and avoid any treatment interruption after they finish the study.”

“We are very grateful to the patients who participated in the study and the French clinical network of physicians, led by Drs. Christophe Verny and Dominique Bonneau in Angers,” said Patrice Rioux, M.D., Ph.D., Chief Medical Officer at Raptor. “We are thrilled to build on these results and will engage regulatory agencies to discuss the most efficient means to advance this program to potential approval. These results not only support the safety and efficacy of Raptor’s RP103 in Huntington’s disease, but also the rationale for testing the use of RP103 in other indications such as NAFLD, Leigh Syndrome and mitochondrial diseases.”

RP103 was well tolerated with 48/52 patients experiencing at least one adverse event (AE) during the 18 month study vs. 38/44 under placebo. There were slightly more patients under RP103 than under placebo reporting at least one gastrointestinal AE (61.5% RP103 vs. 45.5% placebo), mostly nausea, vomiting, abdominal pain, constipation and breath odor. There were also slightly more headache AEs on RP103 than on placebo. There were 5 patients treated with RP103 who experienced serious adverse events (SAEs) compared with 4 patients treated with placebo.

See the full press release here.

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