Medicines work by correcting the effects of a genetic mutation. In patients with metachromatic leukodystrophy due to a mutated gene of the ARSA enzyme, sulfatides accumulate in the cells, which especially damage the nervous system. This leads to impaired motor and cognitive functions, as a result of which half of the patients die in early childhood, and the rest acquire severe disabilities. "Lenmeldi" changes the stem cells of the patient's bone marrow in such a way that they begin to produce a working version of ARSA, capable of effectively breaking down toxic sulfatides.

Treatment of cells with drugs is carried out in the laboratory, so stem cells are previously selected from the patient. Also, after selection, the patient must undergo high-dose chemotherapy to kill the remaining stem cells in the bone marrow with the mutated ARSA gene. Therefore, the modified cells are returned to the bone marrow. In experiments on 37 children with an asymptomatic phase of the disease, the approach showed that at the age of five, it was able to provide 85 percent of patients with the opportunity to communicate normally and develop mentally, which was not observed in untreated children. Also, at the age of five, 71 percent of the children after "Lenmeldi" could walk without assistance, and at the age of six, all the treated children were alive, in contrast to only 58 percent of the untreated ones.

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