Two-Year Risdiplam Data Show Continued Improvement in Motor Milestones in SMA

Newly released 2-year efficacy and safety data on risdiplam (Evrysdi) is showing that the treatment resulted in continued improvements and achievements in motor milestones among infants with spinal muscular atrophy (SMA).

The study results, coming from Part 1 of the FIREFISH study, revealed that at 2 years, 88% of the 17 infants who received the therapeutic dose of risdiplam were alive and did not require permanent ventilation, according to a statement from PTC Therapeutics.

Risdiplam, which was granted FDA approval in August for the treatment of patients with SMA who are 2 months and older, is a survival of motor neuron 2 splicing modifier designed to treat cases of SMA that are caused by mutations in chromosome 5q that lead to SMN protein deficiency.

“The results from the long-term FIREFISH trial demonstrate that SMA patients continue to improve in motor function and gain additional developmental milestones,” said Stuart W. Peltz, PhD, chief executive officer of PTC Therapeutics, in a statement. He said the results reinforce validate the drug’s “safety and durable efficacy profile.”He also touted the fact that as an oral therapy, it can be taken at home during the ongoing public health crisis.

Efficacy results showed that at 2 years:

• 59% (10/17) of infants were able to sit without support for at least 5 seconds compared with 41% at 1 year
• 65% (11/17) of infants had upright head control compared with 53% at 1 year
• 29% (5/17) of infants were able to turn over compared with 12% at 1 year
• 30% (5/17) of infants were able to stand supporting weight or with support compared with 6% at 1 year
• 71% (12/17) of infants had a Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders score of at least 40 points compared with 59% at 1 year

By 2 years, 2 of the 17 infants experienced fatal complications of their disease and 1 infant was withdrawn from the study and died 3.5 months later. According to the statement none of these were attributed to risdiplam by the investigator.

Among the 14 infants alive at the time of analysis, all maintained their ability to swallow and 93% were able to feed orally.

The data from the second year of the trial revealed no new safety signals and that the observed safety was consistent with the drug’s previously reported safety profile. The most commonly reported adverse events were fever, upper respiratory tract infection, cough, vomiting, diarrhea, and respiratory infection. Pneumonia was the most serious adverse event and occurred in 24% of the infants.

At enrollment, the median age of the infants was 6.3, and at the time of 2-year analysis, the youngest infant was 28.4 months and the oldest was 45.1 months.