On Friday, the Food and Drug Administration approved the first gene therapy for spinal muscular atrophy, designed specifically for children under the age of two.
Developed by AveXis, a subsidiary of Novartis, Zolgensma is a one-time infusion that works by providing a functional copy of the gene that makes SMN. Zolgensma was submitted for FDA-approval in October 2018. The FDA granted the drug Fast Track, Breakthrough Therapy and Priority Review designations, speeding up the approval process.
SMA is typically caused by mutations in the SMN1 gene. SMN1 provides the blueprint for SMN, a protein that helps maintain the health of motor neurons in the spinal cord and brainstem. There are four primary types of SMA — types 1 through 4 — each varying in severity and life-expectancy. About 95% of people with SMA have mutations that delete a piece of the SMN1 gene in both copies of the gene in each cell, according to the National Institutes of Health. Zolgensma can be used in any child with SMA under the age of two, regardless of which type or gene mutation they have.
Those treated with Zolgensma during the clinical trial saw an improvement in developmental milestones such as head control and sitting without support as well as breathing without support.
“Children with SMA experience difficulty performing essential functions of life. Most children with this disease do not survive past early childhood due to respiratory failure,” Peter Marks, M.D., Ph.D., director of the FDA’s Center for Biologics Evaluation and Research, said in a statement. “Patients with SMA now have another treatment option to minimize the progression of SMA and improve survival.”
Zolgensma is one of two FDA-approved treatments for SMA. The other, Spinraza, requires regular spinal infusions and treats both milder and severe forms of SMA. A third therapy, an oral medication called risdiplam, is currently in development.
“This is an important day for the SMA community. Clinical data shows that a one-time infusion of Zolgensma can change the course of SMA,” Kenneth Hobby, president of Cure SMA, said in a statement.
Though the community welcomes these drugs, the price tag for Zolgensma has many concerned about the affordability of drugs for rare disease. Zolgensma’s one-time infusion costs $2.1 million, making it the most expensive drug on the market worldwide. Spinraza costs less at first, though its cost over time exceeds that of Zolgensma. According to STAT, Spinraza costs $750,000 in the first year and $375,000 annually for life.
Drugs for rare diseases often come with a hefty price tag due to a lack of market competition. Costs are usually brought down by the addition of generic drugs. When a drug’s patent expires, competitor drug companies can release its version of the drug, typically lowering the cost of all drugs with that formulary. Since rare and orphan diseases affect fewer people, there is less of a financial incentive for drug companies to create generic versions.
It’s unclear how much of Zolgensma’s cost insurance — government-subsidized or private — will cover.