Spinraza led to motor gains for 3 SMA adults in small Japanese study
Other 3 patients did not see significant improvement in motor function
Other aspects, including respiratory and swallowing function, did not change considerably.
“The distinct efficacy of [Spinraza] requires further investigation using a large number of cases and a long follow-up period,” researchers wrote.
Spinraza designed to boost production of SMN protein
Spinraza is an approved disease-modifying therapy which aims to boost production of the SMN protein that patients lack, helping to slow the progressive muscle weakness and wasting that characterize all types of SMA.
Spinraza’s benefits on motor function in infants and children have been well described. Reports have indicated the therapy is also safe, feasible, and beneficial for adult patients, but the evidence related to its long-term effects in adults is limited, according to the researchers.
In the study, they report outcomes from six adult patients with SMA types 2 or 3 who were treated with Spinraza at the Nagara Medical Center, in Gifu, Japan. This included two women and four men, who started Spinraza at a median age of 51.5 and were treated for a median of 50.5 months, or a little more than four years.
All patients were given Spinraza as described on its prescribing label in Japan. This involves injections directly into the spinal canal once every six months after loading doses on day 1, and after 1, 3, and 6 months.
Motor function was monitored using the Hammersmith Functional Motor Scale – Expanded (HFMSE). A clinically meaningful improvement was defined as an increase of at least three points on this scale.
3 of 6 patients exhibited meaningful improvements with Spinraza
Overall, three of the six patients exhibited meaningful improvements with Spinraza treatment, emerging a median of 633 days (about 1.7 years) after treatment initiation.
One of these patients, a 33-year-old man with SMA type 3, had been living in a wheelchair since about age 20, and was able to maintain a stable sitting position without support. About a year and nine months after starting Spinraza, he could roll from a laying to a sitting position without needing his hands.
A 48-year-old woman with SMA type 2 and scoliosis, which is a sideways curvature of the spine, had also been wheelchair-bound since childhood and had very low respiratory function. A little more than two years after starting treatment, she could maintain a stable sitting position without support, but these gains were not considered “fully satisfactory” in terms of making daily life easier.
The final case where motor improvement was observed involved a 49-year-old man with SMA type 3. He had scoliosis and eye degeneration, and was in a wheelchair. He gained the ability to maintain a stable sitting position with his legs extended and without support, with his hands above his head, after about a year and three months on Spinraza.
The remaining three patients did not see meaningful motor improvements. This included a 54-year-old man with SMA type 2 who saw no change with treatment after about three years and eventually discontinued Spinraza, as well as a 56-year-old man with SMA type 3 who did not see any benefit after three years. He also discontinued Spinraza due to the emergence of cheek cancer.
Woman, 59, saw no change in motor function but reported strength in arms
Finally, a 59-year-old woman with SMA type 2 saw no change in motor function after about four years, but she reported that she felt strength in both arms immediately after receiving treatment.
Activities of daily living, respiratory function, and swallowing function, among others, generally did not meaningfully change with treatment.
Significant side effects were observed in three patients, including a subdural hematoma, where blood pools on the brain, a bone fracture, and skin cancer on the cheek. Scientists noted it was difficult to determine whether Spinraza was the cause of the cancer case due to lack of information.
“Further research on the molecular mechanism and a long follow-up period are required to determine the carcinogenicity of [Spinraza] in patients with SMA,” the researchers wrote.
Overall, the analysis was limited by the few included patients and lack of other methods for evaluating motor function.
“The long-term efficacy of [Spinraza], particularly in adult patients, needs to be further investigated by the accumulation of several cases treated with [Spinraza] and by a multiplicity of evaluation methods … which will lead to improved management, including rehabilitation and other medical therapies,” the researchers wrote.