PTC Therapeutics announced its joint development program in Spinal Muscular Atrophy (SMA) with Roche and the SMA Foundation (SMAF) transitioned into the pivotal part of the study evaluating the efficacy and safety of RG7916 in pediatric and adult Type 2/3 SMA patients. RG7916 is an oral survival motor neuron 2 (SMN2) splicing modifier. The study, named SUNFISH, consists of two parts, an exploratory dose finding part (Part 1) for 12-weeks which has been concluded - and a confirmatory part (Part 2) for 24-months. The initiation of Part 2 triggers a $20 million milestone payment to PTC from Roche. SMA is a rare genetic disorder that results in neuromuscular disability and is the leading genetic cause of mortality in infants and young children.
"We are excited to move RG7916 into the pivotal part of the SUNFISH trial," said Stuart W. Peltz, Ph.D., Chief Executive Officer of PTC Therapeutics. "RG7916 resulted in a substantial increase in SMN2 protein production in SMA patients. We believe that a major advantage of RG7916 is that it is an oral drug that distributes throughout the body. This is important because the SMN protein is critical both in the CNS and peripheral tissues."
The confirmatory part of SUNFISH is a randomized, double-blinded, placebo-controlled study. It will be conducted in approximately 168 Type 2 and Type 3 SMA patients for up to 24 months, followed by an open-label extension. The primary objective of the study is to evaluate the efficacy of RG7916 compared to placebo after 12 months of treatment.
The FDA granted orphan drug designation to RG7916 for the treatment of patients with SMA earlier this year. RG7916 directly targets the underlying molecular deficiency of SMA by modulating SMN2 splicing to increase expression of full-length SMN2 mRNA from the SMN2 gene. An interim analysis from the first part of SUNFISH of the five cohorts treated with RG7916 for 28 days or longer demonstrated an exposure-dependent increase in SMN protein. SMA is characterized by reduced levels of SMN protein, motor neuron loss, and muscle atrophy. To date, RG7916 remains well-tolerated in patients at all doses and there have been no drug-related safety findings leading to withdrawal.
The SMA program was initially developed by PTC Therapeutics in partnership with the SMA Foundation in 2006 to accelerate the development of a treatment for SMA. In November 2011, Roche gained an exclusive worldwide license to the PTC/SMA Foundation SMN2 alternative splicing program. The development of these compounds is being executed by Roche and overseen by a joint steering committee with members from PTC, Roche, and the SMA Foundation.