Spinraza treatment leads to gains in 1st year for most with SMA type 2
Most individuals with spinal muscular atrophy (SMA) type 2 experience improvements in physical abilities within a year after starting treatment with Spinraza (nusinersen). However, about 1 in 3 patients had some loss of function in the first year after beginning the approved SMA therapy.
That’s according to a new study, “Changes in abilities over the initial 12 months of nusinersen treatment for type II SMA,” which was published in Neuromuscular Disorders.
The results — which looked at improvements in individual measures rather than calculating total scores, as is typically done — showed that more than half of patients experienced gains in their abilities in at least one activity. About one-third, conversely, saw a loss of function in at least one measure.
SMA type 2 is defined by symptoms that appear between the ages of 6 months and 18 months. In the absence of treatment, children with SMA type 2 usually develop the ability to sit unassisted, but are never able to stand or walk.
Spinraza is the first disease-modifying therapy for SMA to become widely available. It works to boost levels of the SMN protein whose defect causes the disease, and has been proven in trials to slow or stop the progression of SMA.
Using a ‘shift analysis’ to assess impact of Spinraza treatment
Several previous studies have demonstrated that treatment with Spinraza tends to lead to improvements in motor function for people with SMA type 2. Generally, these benefits are more dramatic when Spinraza treatment is started as early as possible.
To measure patients’ motor function, studies often use a score called the Hammersmith Functional Motor Scale Expanded, or HFMSE. This score rates 33 activities, including standing, squatting, and moving one’s arms, on a three-point scale. A score of 0 means the patient cannot do the activity, while a 1 means it can be done with assistance or modification. Scoring a 2 means the activity can be done unassisted.
In SMA research, scientists usually track the total score on the HFMSE, with all 33 items added together for a total possible score of 66. However, according to the researchers, looking at the total score can miss nuanced changes in individual abilities. Thus, in this study, a team led by scientists in Italy conducted a different type of assessment known as a shift analysis.
Basically, rather than looking at whether total scores had changed, the researchers looked at how many patients experienced improvement in at least one of the 33 items on the HFMSE. Importantly, the team also similarly looked for how many patients experienced worsening on at least one item. This approach, the researchers wrote, “provides a more direct understanding of the implication of disease progression or improvement for affected individuals.”
“We felt that this method could also be used to assess treatment impact,” the team added.
The analysis included 104 people with SMA type 2. Most were children or adolescents, the youngest being about age 2.5, though the analysis also included adults as old as 49. The patients’ HFMSE scores were assessed at the time Spinraza was started, then again one year later.
Gains, some losses seen in individual functional abilities
More than half of patients (57.7%) had improvement in at least one item, with more than a third (36.5%) improving in two or more items, the results showed. On the other side of things, about 1 in 3 patients (34.6%) experienced a loss of function in at least one measure, with nearly 1 in 5 (18.3%) experiencing a loss in two or more.
The researchers noted that the specific items that showed improvement or loss varied widely, depending in large part on each individual’s functional abilities before starting treatment.
There was “no identifiable pattern of specific items being at higher risk of changes,” the team wrote.
Comparisons against historical data suggested that the chances of improvement were greater for patients treated with Spinraza than untreated SMA type 2 patients — and consistently, the chances of deterioration were lower for patients on Spinraza than among historical controls. The researchers noted, however, that these analyses could only be conducted for patients younger than 14, as there weren’t enough older teens or adults to perform statistically meaningful analyses.
[These] results confirm the efficacy of [Spinraza] treatment in type [2] patients, both in terms of increased number of activities gained and decreased loss of individual abilities that are known to be clinically meaningful to patients and carers.
Despite the limitations, the scientists concluded that these “results confirm the efficacy of [Spinraza] treatment in type [2] patients, both in terms of increased number of activities gained and decreased loss of individual abilities that are known to be clinically meaningful to patients and carers.”
Spinraza is sold by Biogen. This study was funded in part by the Italian Health Ministry, and it used data from an international registry that’s funded in part by Biogen as well as Novartis and Roche.
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