Treatment with Risdiplam Improves Motor Function in Spinal Muscular Atrophy

Risdiplam, an investigational drug for the treatment of spinal muscular atrophy (SMA), improved motor function in patients with the disease, according to new 1-year data from the SUNFISH clinical trial.

Risdiplam is a survival motor neuron-2 (SMN-2) splicing modifier for SMA designed to increase and sustain SMN protein levels throughout the central nervous system and in peripheral tissues of the body. The treatment is an orally administered liquid.

Part 2 of the SUNFISH study evaluated risdiplam in patients aged 2 to 25 years old with type 2 or 3 SMA. In this study, motor function was evaluated in 180 patients using total score of Motor Function Measure 32 (MFM-32) at 12 months. The MFM-32 scale is a validated scale used to evaluate fine and gross motor function in patients with neurologic disorders. The scale assesses 32 different motor function from standing and walking to the use of hands and fingers.

Part 1 of the study previously determined the dose for the confirmatory Part 2 phase of the trial.

Overall, the results showed that change from baseline in the MFM-32 scale was significantly greater in patients treated with risdiplam compared with placebo (1.55 point mean difference; p=0.0156). Additionally, there was also an improvement in the Revised Upper Limb Module (1.59 point difference; p=0.0028), a key secondary endpoint.

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According to exploratory subgroup analyses, the strongest responses in MFM-32 versus placebo were shown in the youngest age group of patients ages 2 to 5 years old (78.1% versus 52.9% achieving ≥3 point increase). The findings also showed that disease stabilization occurred in the 18-25 years age group (57.1% versus 37.5%, with stabilization defined as a ≥0 point increase), which is the goal of treatment for those with more established disease, according to Genentech.

Safety data were consistent with its known safety profile. The most common adverse events were upper respiratory tract infection, nasopharyngitis, pyrexia, headache, diarrhea, vomiting, and cough. The rate of lower respiratory tract infections was similar in both treatment arms; however, serious infections occurred more in the risdiplam group compared with placebo (10% versus 2%).

According to Genentech, more than 400 patients have been treated with risdiplam across all studies to date, with no treatment-related safety findings leading to study withdrawal.

“Risdiplam is the first potential treatment to have pivotal placebo-controlled data in a broad population of patients, including children, teenagers, and adults,” SUNFISH principal investigator Eugenio Mercuri, MD, PhD, Department of Pediatric Neurology, Catholic University, said in a statement. “The data suggest that risdiplam can preserve and potentially enable greater independence through improved motor function in people with Type 2 or non-ambulant Type 3 SMA.”

The FDA granted Priority Review to risdiplam in November 2019, with an expected decision on approval by May 24, 2020.

References:

• Genentech’s Risdiplam Showed Significant Improvement in Motor Function in People Aged 2-25 With Type 2 or 3 Spinal Muscular Atrophy [news release]. Genentech’s website. https://www.gene.com/media/press-releases/14836/2020-02-06/genentechs-risdiplam-showed-significant-. Accessed February 6, 2020.