According to a story from SMA News Today, a recent case study has reported instances in two spinal muscular atrophy (SMA) patients in which repeated administrations of the therapy nusinersen (marketed as Spinraza) were associated with the appearance of immune cells with unusual characteristics. The cells in question are macrophages, which play a role in cleaning up dead cells and getting rid of harmful microorganisms. These abnormal cells were found in the spinal fluid of patients.
About Spinal Muscular Atrophy
Spinal muscular atrophy is a type of neuromuscular disorder in which the motor neurons are destroyed, leading to muscle wasting. Without prompt treatment, the disease is lethal in many cases. This disorder is linked to genetic defects of the SMN1 gene. This gene encodes a protein called SMN, and when not present in certain amounts, neurons are unable to function. There are different kinds of spinal muscular atrophy that are categorized by when symptoms first appear. These symptoms may include loss of reflexes, muscle weakness and poor muscle tone, problems with feeding and swallowing, developmental delays, respiratory muscle weakness, tongue twitching, and a bell shaped torso. The most effective treatment currently available for the disease is called Zolgensma. To learn more about spinal muscular atrophy, click here.
The two patients in this study were infants, and the findings follow an earlier study which found a similar phenomenon in adult patients. The abnormalities found in the macrophages suggest the presence of a lysosomal storage disorder or fungal infection, but since no other symptoms of these disease states were present, the researchers concluded that treatment with nusinersen was the likely cause. The authors emphasize that physicians and patients should be aware of this effect to avoid potential concern or misdiagnosis.
About Nusinersen (Spinraza)
Nusinersen is classified as an antisense oligonucleotide and was developed by Biogen. It is the first disease modifying treatment that can work for all forms of spinal muscular atrophy. It boosts the production of a certain protein that is lacking in patients and plays a critical role in maintaining the health of muscles and motor neurons. The therapy is injected directly into the cerebrospinal fluid (CSF).
The first patient was a 24 day old boy who had CSF collected right before the second dose; they found high levels of macrophages with abnormal intracellular vesicles. By the time the patient had received their fourth dose, they had disappeared. The same thing was found in a 36 day old boy before his third dose, but once again, the macrophages were gone by dose four.
Thankfully, the appearance of these macrophages appears harmless, though the scientists aren’t exactly certain why the show up.
Check out the original study here.