Drs Mary Schroth and Jill Jarecki Discuss Treatments for All SMA Types

Current treatment options spinal muscular atrophy (SMA) are available for all types of the disease regardless of motor strength, explained Jill Jarecki, PhD, chief scientific officer at Cure SMA, and Mary Schroth, MD, FAAP, FCCP, chief medical officer at Cure SMA.

Transcript

What do treatment or management options look like for people with milder subtypes of SMA?

Schroth: Treatment and management options for people with milder subtypes of SMA really are the same. SMA's a progressive neurodegenerative disease, meaning that any person living with SMA will experience progressive loss of function over time. SMA is caused by deletion or mutation of the survivor motor neuron gene 1 [SMN1].

In a healthy person, this gene produces a protein that is critical to the function of nerves that control our muscles. Without it, those nerves cannot properly function and eventually die leading to debilitating and often fatal weakness of the muscles. When that happens is determined by the number of backup genes known as SMN2 genes a person has. So, it is not a matter of if symptoms start or progress, but rather when they do.

There are treatments approved for all types of SMA and 2 of these medications have age eligibility criteria, however, the available treatments are the same regardless of motor strength.

Jarecki: Just to elaborate a little bit on what Dr. Schroth said, we have a traditionally 4 types of SMA. We have Type 1 SMA, which is the most severe form of SMA, which typically correlates to 2 copies of SMN2, the backup gene she mentioned. Type 2 SMA, which typically correlates to 3 copies of SMN2. And then, Type 3 SMA is where you have a 50/50 split of patients with 3 and 4 copies of SMN2. And then Type 4, which is a very rare adult onset of SMA where you could have even more than 4 copies of SMN2.

Each of these types traditionally is defined by maximal motor function. So, Type 1 children would be considered nonsitters. Type 2 children would be sitters. Type 3 patients would walk, but lose the ability to walk. And then, Type 4 patients would be the mildest form of the disease. But we're excited because those labels are becoming obsolete with the ability of these SMN upregulating approved drugs to improve the phenotype.

For example, in our patient reported database, we now have 37% of people who self-identify, having Type 1 SMA being able to sit. So, we really are seeing a dramatic change in our landscape with these SMN enhancing drugs like Spinraza [nusinersen], Zolgensma [onasemnogene abeparvovec-xioi], Evrysdi [risdiplam].