Roche announced Monday that the second part of a pivotal study of risdiplam in patients aged two to 25 years with type 2 or 3 spinal muscular atrophy (SMA) met its primary endpoint, demonstrating significant improvements in motor function versus placebo. The Swiss drugmaker is leading development of the experimental SMN2 splicing modifier, also known as RG7916, as part of a collaboration  with PTC Therapeutics and the SMA Foundation.
The first part of the SUNFISH trial determined the dose of risdiplam to be used in the second confirmatory part of the study, which investigated the oral drug in 180 non‐ambulant patients aged two to 25 years with type 2 or 3 SMA. The main goal of the second part of the trial was the evaluation of motor function using total score of Motor Function Measure 32 (MFM-32) at 12 months.
Commenting on the findings, Stuart Peltz, chief executive of PTC Therapeutics, said "the results from the study will be shared first with regulators globally and then will be presented at an SMA conference early next year." Roche added that no treatment-related safety findings leading to study withdrawal have been seen in any risdiplam trial to date.
Along with the SUNFISH study, risdiplam is being investigated in a broad clinical trial programme in SMA, including the FIREFISH trial in infants with type 1 SMA and the JEWELFISH study in patients with SMA aged six months to 60 years who have been previously treated with SMA-directed therapies.
In 2016, the FDA approved  Biogen and Ionis Pharmaceuticals' Spinraza (nusinersen) for use in children and adults with SMA, making the drug the first treatment approved in the US in this indication. The therapy, administered via intrathecal injection, costs $750,000 per patient in the first year of treatment, and $375,000 per patient in subsequent years.
Meanwhile, in May this year, the FDA authorised  Novartis' gene therapy Zolgensma (onasemnogene abeparvovac-xioi) for the treatment of patients under two years of age with SMA with bi-allelic mutations in the SMN1 gene. However, the product, which costs around $2.1 million for a single intravenous infusion, has since met with controversy  surrounding data manipulation. More recently, the FDA placed  a partial hold on trials investigating intrathecal administration of the gene therapy due to safety issues identified in preclinical animal studies.
For related analysis, see ViewPoints: PTC, Roche plan to take no prisoners in SMA battle .