New Gene Therapy for Pediatric Spinal Muscular Atrophy Approved by FDA

Zolgensma (onasemnogene abeparvovec-xioi, Novartis) has been approved as the first gene therapy to treat children under two years of age who have spinal muscular atrophy (SMA). 

Zolgensma is an adeno-associated virus vector-based gene therapy that delivers a fully functional copy of the human survival motor neuron gene (SMN) into target motor neuron cells. In SMA, this gene does not properly express the SMN protein. According to the FDA, a one-time intravenous administration of the treatment resulted in expression of SMN protein in a child’s motor neurons. This led to improved muscle movement and function and increased the likelihood of survival of children with SMA. 

The safety and effectiveness of repeat administrations of Zolgensma has not yet been evaluated. Furthermore, use of the treatment in patients with advanced SMA-complete paralysis of limbs, permanent ventilator dependence-has not been evaluated at this time. 

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Dosage of Zolgensma is 1.1 x 10¹⁴ vector genomes per kilogram of body weight, which is administered over 60 minutes via intravenous infusion. Prescribing information states that, starting one day prior to infusion, systemic corticosteroids equivalent to oral prednisolone at 1 mg/kg should be administered.

As yet, Zolgensma does not have any contraindications. The most common adverse events reported in clinical trials of Zolgensma infusion included elevated aminotransferases and vomiting. 

According to the FDA, pediatric SMA is the disease’s most severe form and a leading genetic cause of infant mortality. It is a rare genetic disease caused by a mutation in the SMN1 gene that prevents it from encoding the protein critical for the maintenance and function of motor neurons. SMA is generally classified into several subtypes, based on the age of onset and severity. Children with infantile-onset of SMA have problems holding their head up, swallowing, and breathing. These symptoms may present at birth or up to age 6 months.

“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” said Peter Marks, MD, PhD, director of the FDA’s Center for Biologics Evaluation and Research. “Patients with SMA now have another treatment option to minimize the progression of SMA and improve survival. This approval demonstrates the continued momentum of this promising new area of medicine and the FDA’s commitment to supporting and helping expedite the development of these products.”

News reports state that Novartis will price Zolgensma at more than $2 million. 

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