The FDA has cleared the most expensive drug yet, Novartis’ gene therapy drug Zolgensma, for introduction to the market. Zolgensma, which could save the lives of young children with spinal muscular atrophy (SMA) with bi-allelic mutations in the survival motor neuron 1 (SMN1) gene, has been priced at $2.125 million, or $425,000 annually over five years.

SMA is caused by the SMN1 gene either missing or becoming defective. Infants with the disease lose the ability to control vital functions such as breathing, swallowing or walking.

Zolgensma is currently the only gene therapy approved by the FDA to treat SMA. It was approved due to ongoing data from Novartis’ Phase 3 trial, that analysed the efficacy and safety of the drug in patients under six months old with SMA type 1. The drug provided unprecedented survival rates, Novartis said, with patients’ motor functions rapidly improving.

Zolgensma has “Priority Medicines” designation in Europe, and is being reviewed under Accelerated Assessment Procedure.