Known as Zolgensma, the gene therapy treats children under 2 years of age with spinal muscular atrophy, an inherited neuromuscular disease that causes progressive loss of muscle function. The most severe form of SMA causes infants to die or rely on permanent breathing support by the age of 2. The disease is caused by a defect in a gene that makes SMN, a protein necessary for the survival of motor neurons. Zolgensma uses a re-engineered virus to deliver a functional copy of the defective gene so that SMN protein can be produced.

Novartis is pricing Zolgensma at $2.125 million, or an annualized cost of $425,000 per year for five years, the company said.

Launching Zolgensma will be a big test for Novartis and CEO Vas Narasimhan, now two years on the job. Shareholders expect the gene therapy to deliver blockbuster sales to justify the $8.7 billion that Novartis spent to acquire it last year.