RG7916 is an investigational oral therapeutic which is in two clinical studies: SUNFISH, a trial in childhood onset (Type II/III) SMA patients, and FIREFISH, a trial in infant onset (Type I) SMA patients. SMA is a genetic disorder caused by the mutation or deletion of the survival of motor neuron (SMN1) gene. It affects one in approximately 10,000 live births and in the most severe forms is associated with a high rate of childhood mortality. SMA is characterized by progressive loss of motor neurons, muscle weakness and atrophy. The disorder affects mainly proximal muscles, including intercostal muscles (chest muscles), and patients often die due to respiratory complications. We believe RG7916 may have the potential to target the underlying cause of the disorder by increasing SMN protein levels in the nervous system, muscles, and other tissues by modifying the splicing of the SMN2 gene to generate more full-length SMN mRNA in SMA patients.
The SUNFISH clinical study is a Phase 2 study in adult and pediatric patients with Type II and Type III SMA. It is a placebo-controlled, randomized, ascending dose study and will enroll approximately 36 patients for a minimum of 12 weeks to investigate the safety and tolerability of RG7196 and determine the dose for the second part of the study. The second part of SUNFISH will be a double-blinded, placebo-controlled, randomized, confirmatory study in approximately 150 Type II and Type III SMA patients for up to 24 months, followed by an open-label extension. The primary objective of the pivotal second part of the study is to evaluate the efficacy of RG7916 compared to placebo.
The FIREFISH clinical study is a study in infant patients with Type I SMA. It is an open-label, ascending dose study and will enroll approximately 8 patients for a minimum of four weeks to assess the safety profile of RG7916 in infants and determine the dose for the second part of the study. The second part of FIREFISH will be to be an open-label, single-arm study in approximately 40 infants with Type I SMA for 24 months, followed by an open-label extension. The primary objective of the second part of the study will be to assess the efficacy of RG7916 at the selected dose after 12 months of treatment.
The recently completed Phase 1 single-ascending dose study in healthy volunteers demonstrated that all doses studied were safe, well tolerated and demonstrated a dose-dependent effect on SMN2 splicing as shown by a change in the ratio of full-length SMN2 mRNA to SMN2 mRNA without exon 7 (SMND7), which is interpreted as proof of mechanism in terms of the expected pharmacodynamic effect.
The SMA program was initially developed by PTC Therapeutics in partnership with the SMA Foundation (SMAF) to utilize PTC's Alternative Splicing technology platform to identify and develop new small-molecule therapeutics for use in the treatment or prevention of SMA. In November 2011, Roche gained an exclusive worldwide license to the PTC/ SMAF SMA program. Clinical development of RG7916 is being led by Roche and overseen by a joint steering committee with members from Roche, PTC and the SMA Foundation.