• In a recently published study, 41 infants with type 1 spinal muscular atrophy (SMA) were treated with risdiplam, sold as Evrysdi.
• After 12 months, researchers measured several criteria related to motor function and motor development milestones.
• Compared with historical data from untreated infants with SMA, those treated with risdiplam were significantly more likely to meet key motor milestones and have improved motor function.
• Improvement continued over time, with even greater gains seen at 24 months.

On July 29, The New England Journal of Medicine published the results of a study led by Dr. Basil T. Darras, director of the Neuromuscular Center and Spinal Muscular Atrophy Program at Boston Children’s Hospital. The study compared motor function and motor milestones in infants with type 1 spinal muscular atrophy (SMA) who were treated with risdiplam — sold as Evrysdi — against the historical data of infants with SMA who had received no treatments.

The study results provide more data on risdiplam, which adds to the research that led to the U.S. Food and Drug Administration (FDA) approval of Evrysdi in August 2020. The first oral drug approved to treat SMA, Evrysdi is approved for use in people aged 2 months and older who have been diagnosed with SMA.

During the study, 41 infants between the ages of 1 and 7 months who had been diagnosed with type 1 SMA were treated with risdiplam for 12 months. Researchers monitored the following milestones:

• The ability to sit upright without support for at least five seconds
• Scores of 40 or higher on the Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), a measure of motor function
• An increase of four points or more on the CHOP-INTEND scale
• A motor milestone response, assessed using the Hammersmith Infant Neurological Examination (HINE-2)
• Survival without the need for permanent ventilator support

The results were then compared with the historical data of 40 infants with type 1 SMA who received no treatment. In comparison with untreated infants, researchers found that after 12 months of treatment with risdiplam:

• Twenty-nine percent of treated infants could sit unaided for five seconds — a goal never attained in untreated infants.
• Fifty-six percent of treated infants (compared with 17 percent of untreated infants) met CHOP-INTEND motor function criteria (scores of 40 or higher).
• Ninety percent of treated infants (compared with 17 percent of untreated infants) improved motor function by four points or more on the CHOP-INTEND scale.
• Seventy-eight percent of treated infants (compared with 12 percent of untreated infants) met HINE-2 motor milestone response criteria.
• Eighty-five percent of treated infants (compared with 42 percent of untreated infants) reached survival without permanent ventilation.

“The conclusion of this study was that risdiplam resulted in efficacy compared to the historical cohort, which far exceeds what you would expect without any intervention,” said Dr. Darras. “Historically, we did not see the ability to meet any major milestones for motor function in babies diagnosed with SMA type 1.”

It is also noteworthy that when treatment was extended to 24 months, 61 percent of infants were able to sit unaided for five seconds, and 44 percent were able to sit unsupported for at least 30 seconds. “It's important to emphasize that there continues to be improvement over time,” said Dr. Darras.

Dr. Darras also pointed out the study’s results regarding safety. “In terms of safety, there were no risdiplam-related adverse events,” he said. “This study supported the idea that risdiplam continued to be effective and safe in infants after 24 months of treatment.”

The study team called for larger and longer studies to learn more details about the safety and long-term effectiveness of risdiplam.

Read more about current treatments for SMA.