The world’s most expensive drug, which treats babies and young children with a rare and often fatal degenerative disorder, will be available this year for the first time on the NHS in England. Zolgensma, which costs £1.79m per dose, halts the progression of spinal muscular atrophy (SMA), which involves loss of movement, muscle weakness and paralysis, and is the leading genetic cause of death in infants. Up to 80 infants a year in England are expected to benefit from the drug, which is administered as a single dose and replaces the function of the faulty SMN1 gene. The active ingredient, onasemnogene abeparvovec, restores the gene and produces proteins essential for muscle movement and nerve function. Babies born with the most severe form of the muscle-wasting disease – SMA type 1 – have a life expectancy of two years. Zolgensma does not cure the disease but helps halt its progression, meaning babies breathe without a ventilator, sit up, crawl and even walk, with benefits lasting more than five years after treatment. For some babies diagnosed before developing symptoms it “might come close to being a cure”, said Meindert Boysen, the deputy chief executiveof the National Institute for Health and Care Excellence (Nice). “As is the case with many new treatments for very rare diseases, limited evidence means there are uncertainties about the long-term benefits,” he added. SMA affects one in every 10,000 live births. Each year 65 babies are born in England with the disease, 60% of whom are diagnosed with type 1. “This deal is a life-changer for youngsters with this cruel disease and for their families,” said Sir Simon Stevens, the chief executive of NHS England. “SMA is the leading genetic cause of death among babies and young children, which is why NHS England has moved mountains to make this treatment available, while successfully negotiating hard behind the scenes to ensure a price that is fair to taxpayers.” Zolgensma is produced by the Swiss company Novartis Gene Therapies, one of the world’s wealthiest drugmakers. The amount negotiated is confidential, but according to the NHS it has been obtained at a substantial discount. It is the most expensive treatment ever approved by Nice. The NHS is fast-tracking the drug and is looking to identify which specialist services would be able to administer the drug. Critics have previously criticised the staggering price of the drug, although the company says the cost is fair as it is a one-off treatment. “The cost of a single dose is much higher than the cost of a dose of a product that is used every day, every week or every month. But over a lifetime those products can cost million of pounds and Zolgensma is only needed once,” said Sally-Anne Tsangarides, the general manager of Novartis Gene Therapies in the UK. “The potential for one-time gene therapy in the future to treat genetic conditions with a single treatment is very exciting.” More than 60,000 children are diagnosed with the condition each year. Zolgensma has already been approved in more than 38 countries and more than 1,000 children have received treatment. Spinraza, the first drug to help infants with SMA, was made available on the NHS in May 2019. Future SMA drugs are being looked at by Nice. Prof Francesco Muntoni from Great Ormond Street hospital trust said: “Having seen first-hand the impact of severe SMA on infants and their families, this decision offers a glimpse of the potential of one-time gene therapy to replace the burden of years of repeated chronic treatments or palliative care.”