World’s priciest drug treats MLD

The US Food and Drug Administration has approved the first therapy for metachromatic leukodystrophy (MLD), a rare fatal genetic disorder. The lysosomal storage disease affects about 40

children each year in the USA. It is caused by a mutation in the gene encoding the arylsulfatase enzyme that leads to progressive demyelination and progressive loss of motor and cognitive

functions. There were previously no treatments. The new gene therapy, Orchard Therapeutics’ Lenmeldy (atidarsagene autotemcel), has a price tag of $4.25 million, making it the world’s most

expensive drug. It inserts functional copies of the arylsulfatase A (ARSA) gene into the patient’s own hematopoietic stem ex vivo with a lentiviral vector. The repaired stem cells are

re-infused, correcting the enzyme deficiency and preventing the harmful buildup of sulfatide fats that cause nerve cell demyelination.

The approval is based on results from 37 pediatric patients showing that Lenmeldy improved motor impairment and survival compared with the natural history of MLD. All presymptomatic patients

treated with Lenmeldy who had the late infantile form of MLD were alive at age 6 years, compared with just over half of the natural history group. Treated patients could walk and had normal

language and cognitive skills. In patients with pre- or early symptomatic juvenile forms of MLD, the gene therapy also slowed motor and cognitive decline.

Lenmeldy was developed by Italy’s San Raffaele Telethon Institute for Gene Therapy in partnership with GlaxoSmithKline, which sold the asset to Orchard, now part of Japanese pharma group

Kyowa Kirin. The gene therapy received European Commission approval as Libmeldy in 2020. Lenmeldy carries warnings for the risk of infections, blood clots and brain swelling, among others.

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