The FDA decision on Zolgensma, formerly known as AVXS-101, an investigational gene replacement therapy for the treatment of spinal muscular atrophy (SMA) Type 1, is expected to be announced in May.Spinal Muscular Atrophy, or SMA, is the number 1 genetic cause of infant death. Based on the age of the initial onset of muscle weakness and severity of the disease, spinal muscular atrophy is classified into four types: Type I (Infantile), Type II (Intermediate), Type III (Juvenile) and Type IV (Adult onset).Mutations in the human survival motor neuron 1 (SMN) gene are the primary cause of spinal muscular atrophy. Zolgensma is designed to replace the defective or lost SMN gene. Developed by AveXis Inc., Zolgensma came under Novartis’ fold, when the former was acquired by Novartis last April.If approved, Zolgensma could become the second therapy for SMA. This gene therapy is also under review in the European Union.Meanwhile, there have been two deaths in the European arm of the Zolgensma trial. While the first death was not related to the treatment, the second death involving a 6-month-old patient has been tied to the gene therapy.Spinraza, developed by Ionis and Biogen, which received approval in the U.S. in December 2016, and in the European Union in June 2017, is the first and only approved therapy for SMA. The total annual sales of Spinraza in 2018 were $1.72 billion compared to $883.7 million in 2017.NVS closed Thursday’s trading at $80.60, up 3.57%.