Risdiplam Granted Priority Review for Spinal Muscular Atrophy

Officials with the FDA have granted Priority Review for risdiplam (Genentech) for the treatment of spinal muscular atrophy (SMA), according to a press release.¹

SMA is a severe and progressive neuromuscular disease that causes devastating muscle atrophy and disease-related complications. Risdiplam, an investigational orally administered survival motor neuron-2 (SMN-2) splicing modifier, is designed to increase and sustain SMN protein levels throughout the central nervous system and peripheral tissues of the body. If approved, risdiplam would be the first at-home administered medicine for patients living with SMA, according to Genentech.¹

Risdiplam’s New Drug Application submission is supported by 12-month data from the dose-finding part 1 sections of the FIREFISH and SUNFISH clinical trials, as well as data from the confirmatory part 2 of SUNFISH.¹

The FIREFISH study evaluated risdiplam in infants with Type 1 SMA and consisted of 2 parts. In part 1, risdiplam was evaluated for efficacy in 21 infants ages 1 to 7 months, assessing the safety and dose for part 2. Part 2, a single-arm trial, evaluated risdiplam in 41 infants with Type 1 SMA for 24 months, followed by an open-label extension.¹

In the SUNFISH trial, risdiplam was evaluated in children and young adults ages 2 to 25 years old with Type 2 or 3 SMA. Part 1 of the trial determined the dose for the confirmatory part 2, which then evaluated the efficacy as an exploratory endpoint. SUNFISH part 2 recently met its primary endpoint of change from baseline in the Motor Function Measure 32 (MFM-32) scale.¹

Data from the dose-finding portion of the studies were previously presented at the American Academy of Neurology Annual Meeting.

In the FIREFISH trial, the median duration of treatment was 14.8 months, with 19 infants treated for more than 12 months, according to the findings.²

According to the data:²

• Among the 17 infants who received the dose selected for part 2 of the study, 41.2% were able to sit without support for at least 5 seconds, assessed by the Gross Motor Scale of the Bayley Scales of Infant and Toddler Development—Third Edition.
• 64.7% of infants were able to sit with or without support and 52.9% achieved upright head control after 12 months of treatment as assessed by the Hammersmith Infant Neurological Examination Module 2.
• 5.9% achieved the milestone of standing by the 12-month time point.
• 58.8% of infant in the therapeutically dosed group achieved a Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders total score of 40 points or more, with a median change of 17.5 points from baseline to month 12.

Data from part 1 of the SUNFISH trial showed that, among the 42 patients assessed at all visits up to month 12, 58% saw an improvement of at least 3 points on the scale from baseline. This included 71% among patients ages 2 to 11 years old and 42% ages 12 to 25 years old, according to the study.²

Overall, there were no treatment-related safety findings associated with risdiplam leading to study withdrawal.¹

“The FIREFISH and SUNFISH trials were designed to represent the real world spectrum of people living with SMA and include many people previously underrepresented in clinical trials,” Levi Garraway, MD, PhD, chief medical officer and head of Global Product Development, said in a statement.¹ “We look forward to working closely with the FDA to explore broad access to risdiplam for all individuals in the community who might benefit.”

Risdiplam is also being studied in the broad clinical trial program in SMA, with patients ranging from newborns to 60 years old, and including patients previously treated with SMA therapies, according to the release.¹

The FDA is expected to make a decision on approval by May 24, 2020, Genentech said.¹

Reference

• FDA Grants Priority Review to Genentech’s Risdiplam for Spinal Muscular Atrophy [news release]. Genentech’s website. https://www.gene.com/media/press-releases/14825/2019-11-24/fda-grants-priority-review-to-genentechs. Accessed November 25, 2019.
• Genentech Presents Data from the Risdiplam Pivotal FIREFISH and SUNFISH Studies in Spinal Muscular Atrophy at the 2019 AAN Annual Meeting [news release]. Genentech’s website. https://www.gene.com/media/press-releases/14787/2019-05-06/genentech-presents-data-from-the-risdipl. Accessed November 25, 2019.