Lenmeldy (atidarsagene autotemcel)

The first FDA-approved treatment for MLD. It is meant for children treated before symptoms or very early in early juvenile disease, which makes early diagnosis important.

Children with MLD lack a working arylsulfatase A (ARSA) enzyme, so fatty substances called sulfatides build up and destroy myelin, the protective coating on nerves in the brain and body. To make Lenmeldy, doctors collect the child's own blood-forming stem cells, and a lab adds working copies of the ARSA gene using a lentiviral vector, a disabled virus that places the gene into the cells' DNA. After chemotherapy clears space in the bone marrow, the modified cells are infused back, settle in the marrow and multiply. The cells they produce make the ARSA enzyme, and some of them travel into the brain, where the enzyme can break down sulfatides or keep them from building up. Because the cells come from the child, no donor is needed.

Lenmeldy has no boxed warning and no contraindications. Its studies had no placebo group, and many side effects come from the busulfan chemotherapy given before the infusion. Among 39 treated children, the most common side effects in the first year were febrile neutropenia, a fever while infection-fighting white cells are very low (85%), mouth sores (77%), respiratory infections (54%), rash (33%), infections of the central IV line (31%), other viral infections (28%), fever (21%), stomach and gut infections (21%) and an enlarged liver (18%). Lab tests often showed a high D-dimer, a blood clotting marker (67%), low neutrophils (28%) and raised liver enzymes (23%)^[1]. The label warns about blood clots, because a child with early juvenile MLD died of a stroke caused by a clot about 1 year after treatment and a link to Lenmeldy could not be ruled out. It also warns about encephalitis, or brain inflammation, seen in 1 child; serious infections, with severe infections in 39% of children in the first year; veno-occlusive disease, a blockage of small liver blood vessels, in 3 children (8%); and slow platelet recovery after day 60 in 4 children (10%), which raises bleeding risk^[1]. Because the vector inserts into DNA, there is a potential risk of blood cancer (insertional oncogenesis). No cases were seen in the trials, and children need blood counts at least yearly for at least 15 years. Treated children can test falsely positive on PCR tests for HIV. Busulfan can affect fertility, and 7 girls, half of the girls treated, developed ovarian failure^[1].

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Approved for children with pre-symptomatic late infantile, pre-symptomatic early juvenile or early symptomatic early juvenile MLD. In the trials, late infantile meant expected onset by 30 months of age, early juvenile meant onset between 30 months and 7 years, and early symptomatic children could still walk independently and had an IQ of 85 or higher. Diagnosis required low ARSA enzyme activity and 2 disease-causing ARSA gene variants. Safety and effectiveness have not been established in late juvenile MLD, and doctors must first confirm that stem cell gene therapy is appropriate. Negative tests for HIV, hepatitis B and C, HTLV and mycoplasma are needed before cells are collected.

Source: Orchard Assist patient support

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Approval rested on 37 children treated in 2 single-arm, open-label studies at San Raffaele Hospital in Milan, Italy, Study 201222 (NCT01560182) and Study 205756 (NCT03392987), plus an expanded access program in Europe. Their results were compared with untreated children from a natural history study, 28 with late infantile and 21 with early juvenile MLD^[1][10][11]. In the 20 children treated before symptoms of late infantile MLD, the main measure was survival free of severe motor impairment, meaning losing the ability both to move around and to sit without support, or death. At age 5, all 17 treated children followed that long were event-free, against none of the untreated children, and 12 of those 17 could still walk on their own. At age 6, all 14 treated children with enough follow-up were alive, while 10 of 24 untreated children (42%) had died. Of the 20 treated children, 19 kept thinking and language scores above the range of severe impairment^[1]. Results in early juvenile MLD were fewer and more mixed. Of 7 children treated before symptoms, 1 died of a stroke and the 3 with enough follow-up kept walking normally or independently. In 10 children treated after early symptoms began, movement skills declined in most and 2 died of disease progression, although 4 kept stable thinking skills despite motor decline, which is not expected without treatment^[1]. Median safety follow-up was 6.8 years, and up to 12.2 years^[1].

Lenmeldy was developed at the San Raffaele Telethon Institute for Gene Therapy (SR-Tiget) in Milan and licensed to Orchard Therapeutics from GSK in 2018^[6]. The FDA granted it Orphan Drug designation on March 8, 2018, Rare Pediatric Disease designation on April 16, 2018 and Regenerative Medicine Advanced Therapy designation on January 13, 2021. Orchard's application was received on July 19, 2023, given priority review and approved on March 18, 2024, along with a rare pediatric disease priority review voucher^[3][2]. The FDA called it the first FDA-approved treatment option for children with MLD^[5]. The same therapy had been approved in the European Union in 2020 under the name Libmeldy^[3]. On March 20, 2024, Orchard, recently acquired by Kyowa Kirin, set the US wholesale acquisition cost at $4.25 million for the one-time treatment and said it would offer outcomes-based agreements to private and government insurers^[7]. A supplement approved May 30, 2025 let treatment centers use alternative mycoplasma tests when screening children before cell collection, along with a related label update^[4].