Daily SMA treatment helps adults with severe disease, study shows

Daily treatment with Evrysdi (risdiplam) may help stabilize or improve motor function and improve well-being in adults with severe forms of spinal muscular atrophy (SMA), according to a real-world study from the Netherlands.

The study showed Evrysdi may benefit people with longstanding SMA type 1c or type 2. It also indicated that a broader motor assessment, the Adapted Test of Neuromuscular Disorders (ATEND), can capture treatment-related changes that a standard, arm-and-hand test may miss.

The study, “Motor function score changes in severe 5q spinal muscular atrophy during risdiplam treatment: an observational longitudinal nationwide cohort study,” was published in eClinicalMedicine.

SMA is caused by mutations in the SMN1 gene that result in a shortage of the survival motor neuron (SMN) protein. This leads to the progressive loss of motor neurons (specialized nerve cells that control movement), resulting in muscle weakness and wasting.

Evrysdi, marketed by Genentech, is designed to increase SMN production from the SMN2 gene, a backup to SMN1, and is approved in the U.S. for all types of SMA in children and adults. While post-approval studies have confirmed the treatment’s efficacy in patients not included in clinical trials, they have not evaluated severely affected adolescents and adults with SMA.

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Motor function maintained, improved

The researchers studied changes in motor function in 72 adolescents and adults with SMA type 1c (the mildest form of SMA type 1) or type 2 treated with Evrysdi. Participants’ median age was 29, and 61% were female.

In SMA types 1 and 2, symptoms usually emerge early in life: at three to six months for type 1, and six to 18 months for type 2.

All but one patient in the study started Evrysdi after age 18. Participants were treated for a median of 35 months, or almost three years. Motor function was evaluated using the Revised Upper Limb Module (RULM), which measures arm and hand function, and the ATEND scale.

Motor function was largely maintained over nearly three years of treatment, with some patients showing improvements. Upper limb function, in particular, showed early improvements on therapy and remained stable over time.

At study initiation (baseline), the median RULM score was 6 points out of a possible 37, indicating substantial impairment in arm and hand function. That score rose to 8 points after nine months of treatment and remained at a median of 6 points after three years. Overall, 43% of patients either improved or maintained their upper limb function.

“The observed stabilisation in RULM in our study cohort is different from the progressive deterioration shown in natural history studies of SMA type 1c and 2, which might suggest treatment effect of [Evrysdi],” the researchers wrote.

Scores on ATEND, which evaluates broader motor abilities such as head and trunk control and ease of performing daily activities, also rose. Median ATEND scores increased significantly from 24 at baseline to 27 during follow-up, and stabilized at 25 points over nearly three years. About 60% of patients achieved clinically meaningful improvements. Ten of 11 patients who maintained a RULM score of 0 showed benefits in ATEND.

Overall, RULM and ATEND scores were strongly associated at baseline and during treatment. “Reliance on RULM scores alone is insufficient in our population,” the scientists wrote. The two measures “strongly correlated,” they wrote, “and the ATEND was of added value by capturing motor function changes of patients whose RULM scores did not change.”

After more than three years, 89% of participants reported stability or improvement in overall well-being. This was assessed with a patient-reported outcome measure, a type of tool the researchers said provides “insight into the patients’ perspective, [captures changes] that may not be reflected by motor function scales and [allows] evaluation of clinical meaningfulness.”

Six patients discontinued therapy after a median of 23 months (almost two years) due to adverse events and/or the burden of hospital visits that they perceived as higher than the treatment’s benefit. One more stopped taking the drug because of perceived motor function deterioration. Five patients died from causes unrelated to the treatment.

The most common adverse events included respiratory tract infection, changes in stool, and skin issues, including rash or increased sun sensitivity.