FDA OKs Gene Therapy for Pediatric Spinal Muscular Atrophy

On May 24, 2019, FDA approved the first gene therapy to treat pediatric spinal muscular atrophy (SMA), Zolgensma (onasemnogene abeparvovec-xioi). The approval was granted to AveXis, a US biotechnology company specializing in gene therapies. The therapy is indicated for children less than two years of age with SMA, which is the most severe form of the disorder and a leading genetic cause of infant mortality.

SMA is a rare genetic disease caused by a mutation in the survival motor neuron 1 (SMN1) gene, which encodes the survival motor neuron (SMN) protein. The SMN protein is found throughout the body and is critical for the maintenance and function of motor neurons, which control muscle movement throughout the body. Insufficient functional SMN protein leads to the death of the motor neurons, which results in debilitating and often fatal muscle weakness.

SMA caused by mutations in the SMN1 gene is generally classified into several subtypes, based on the age of onset and severity; infantile-onset SMA is the most severe and most common subtype. Children with this condition have problems holding their head up, swallowing and breathing. These symptoms may be present at birth or may present by the age of 6 months.

Zolgensma is an adeno-associated virus vector-based gene therapy that targets the cause of SMA. It delivers a fully functional copy of human SMN gene into the target motor neuron cells via a one-time intravenous administration, which results in expression of the SMN protein in a child’s motor neurons, improving muscle movement, function, and survival. Dosing is determined based on the weight of the patient.

“Today’s approval marks another milestone in the transformational power of gene and cell therapies to treat a wide range of diseases,” said Acting FDA Commissioner Ned Sharpless, MD, in an agency press release. “With each new approval, we see this exciting area of science continue to move beyond the concept phase into reality. The potential for gene therapy products to change the lives of those patients who may have faced a terminal condition, or worse, death, provides hope for the future. [FDA] will continue to support the progress in this field by helping to expedite the development of products for unmet medical needs through the use of review pathways designed to advance innovative, safe, and effective treatment options.”

“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 FDA’s Center for Biologics Evaluation and Research, in the press release. “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 [FDA’s] commitment to supporting and helping expedite the development of these products.”

Zolgensma received fast track, breakthrough therapy, priority review, and orphan drug designations from FDA.

Source: FDA