The U.S. Food and Drug Administration (FDA) has approved Novartis’ Zolgensma (onasemnogene abeparvovec-xioi) at a cost of $2.1 milllion per treatment.

The drug is the first gene therapy approved to treat children less than two years of age with spinal muscular atrophy (SMA), which is the most severe form of SMA and a leading genetic cause of infant mortality.

The price tag has garnered substantial criticism, as even the split payment structure adds up to $425,000 per year over five years. Novartis has announced that it will give ‘partial rebates’ if the treatment doesn't work.

The approval marks a “milestone in the transformational power of gene and cell therapies to treat a wide range of diseases,” said acting FDA commissioner Ned Sharpless.

He continued, “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.

“The 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.”

The indication is for the treatment of children less than two years of age with SMA, which is caused by a mutation in the survival motor neuron 1 (SMN1) gene. The gene encodes the survival motor neuron (SMN) protein – a protein found throughout the body, which is critical for the maintenance and function of specialised nerve cells, called motor neurons. Motor neurons in the brain and spinal cord control muscle movement throughout the body. If there is not enough functional SMN protein, then the motor neurons die, leading to debilitating and often fatal muscle weakness that can lead to the child eventually not being able to eat or breathe.