Raptor Pharmaceuticals’ Experimental Therapy in Phase 2 / 3 Trial for Leigh Syndrome

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by Maureen Newman |

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Raptor Pharmaceuticals Inc. is looking to bring relief to a wide variety of young patients with inherited mitochondrial disease through its therapeutic called RP103 (cysteamine bitartrate delayed-release capsules). A Phase 2/3 clinical trial is currently recruiting and treating patients with diseases resulting from nuclear or mitochondrial DNA mutations, which include myoclonic epilepsy and ragged-red fibers, mitochondrial encephalomyopathy, Kearn-Sayre syndrome, and Leigh Syndrome, to name only a few.

“Patients with Leigh syndrome are expected to comprise two-thirds of the enrolled population in the study,” indicated “Development Status for RP103 for Leigh Syndrome,” on Raptor Pharmaceuticals’ website. Patients with Leigh syndrome are usually diagnosed in the first year of life and commonly lose their life by the age of ten, making treatment extremely necessary.

To investigate RP103, Raptor Pharmaceuticals is conducting the trial “Open-Label, Dose-Escalating Study to Assess Safety, Tolerability, Efficacy, PK and PD of RP103 in Children With Inherited Mitochondrial Disease (RP103-MITO-001).” As indicated by the title, efficacy is of primary concern, and change in Newcastle Paediatric Mitochondrial Disease Scale Score will be used as the primary outcome measure after patients receive 24 weeks of treatment using up to 1.3 g/square meter body area of RP103 per day. As a secondary measure, blood samples will be analyzed for the biomarkers glutathione, acetoacetate, beta-hydroxybutyrate, and lactate.

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RP103 is also in Phase 2/3 clinical trials for treating Huntington’s Disease. So far, data from 89 patients completing the initial 18 months of treatment demonstrate top line results from treatment. RP103 improved balance and gait in these patients and allowed better hand-eye coordination. “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,” said Patrice Rioux, MD, PhD, Chief Medical Officer at Raptor Pharmaceuticals, in a news release. “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 [non-alcoholic fatty liver disease], Leigh Syndrome and mitochondrial diseases.”

At the end of 2013, Raptor Pharmaceuticals submitted an investigation new drug (IND) application to the FDA to develop RP103 as a therapeutic option of Leigh syndrome and other mitochondrial myopathies. After the completion of this trial, Raptor Pharmaceuticals will know if RP103 is a suitable treatment option for individuals with these diseases, both in terms of safety and efficacy.