Thursday, March 21, 2024

Atidarsagene autotemcel for metachromatic leukodystrophy

The Food and Drug Administration (FDA) granted approval for Lenmeldy (atidarsagene autotemcel, Orchard Therapeutics, London, UK), the first gene therapy for children with pre-symptomatic late infantile, pre-symptomatic early juvenile, or early symptomatic early juvenile metachromatic leukodystrophy (MLD). MLD is a rare genetic disorder affecting the brain and nervous system caused by a deficiency of the enzyme arylsulfatase A (ARSA), leading to sulfatide accumulation and severe neurological damage. The therapy involves a one-time infusion of genetically modified hematopoietic stem cells (HSCs) containing functional ARSA genes, aiming to halt disease progression.

Lenmeldy's approval was based on data from clinical trials showing improved motor function and survival rates in treated children compared to untreated individuals. Notably, treated children exhibited enhanced motor skills, cognitive function, and survival rates, highlighting the therapy's potential to alter disease outcomes positively.

According to a statement from Nicole Verdun, MD, Director of the Office of Therapeutic Products at the FDA’s Center for Biologics Evaluation and Research (CBER), “MLD is a devastating disease that profoundly affects the quality of life of patients and their families. “This approval represents important progress in the advancement and availability of effective treatments, including gene therapies, for rare diseases.”

Treatment with Lenmeldy requires preconditioning. The safety profile of Lenmeldy includes common side effects like fever and infections, necessitating close monitoring post-treatment for potential complications such as blood clots or encephalitis. Patients are advised to undergo lifelong monitoring for blood-related issues due to a potential risk of blood cancer associated with the therapy.

Horgan C, Watts K, Ram D, Rust S, Hutton R, Jones S, Wynn R. A retrospective cohort study of Libmeldy (atidarsagene autotemcel) for MLD: What we have accomplished and what opportunities lie ahead. JIMD Rep. 2023 Jun 22;64(5):346-352. doi: 10.1002/jmd2.12378. PMID: 37701322; PMCID: PMC10494509.


Metachromatic leukodystrophy (MLD) results from ARSA gene mutations. Affected individuals meet early milestones before neurological deterioration and early death. Atidarsagene autotemcel (arsa-cel), an autologous haematopoietic stem cell gene therapy (HSC-GT) product, has demonstrated sustained clinical benefits in MLD. Arsa-cel was approved for NHS treatment in February 2022 for asymptomatic late infantile or early juvenile disease, or early symptomatic early juvenile MLD. We evaluate the impact of this approval in the largest real-world dataset of MLD HSC-GT. Hospital records were reviewed for all patients referred for NHS treatment following arsa-cel approval. Information was gathered about disease phenotype, presentation, eligibility, and affected siblings. In the year following NHS approval, 17 UK MLD patients were referred for treatment. Four patients met eligibility criteria and have been treated, including 1 infant who weighed 5 kg at leukapheresis. Eleven patients failed screening: 10 symptomatic patients with late infantile disease and 1 with early juvenile disease and cognitive decline. Two further patients with later onset subtypes did not meet the approval criteria. Three out of four treated patients were diagnosed by screening after MLD was diagnosed in a symptomatic older sibling. The success of HSC-GT for MLD has heralded a new era of hope for families affected by this devastating disease, yet currently, most patients are ineligible for treatment at diagnosis. The feasibility of apheresis in infants and the availability of a licenced, effective HSC-GT product highlights the urgent need for newborn screening to ensure that patients can be diagnosed and treated before symptom onset.

Messina M, Gissen P. Atidarsagene autotemcel for metachromatic leukodystrophy. Drugs Today (Barc). 2023 Feb;59(2):63-70. doi: 10.1358/dot.2023.59.2.3461911. PMID: 36811406.


Metachromatic leukodystrophy (MLD) is a rare autosomal recessive disorder of sphingolipid metabolism, due to a deficiency of the enzyme arylsulfatase A (ARSA). The main clinical signs of the disease are secondary to central and peripheral nervous system demyelination. MLD is subdivided into early- and late-onset subtypes based upon the onset of neurological disease. The early-onset subtype is associated with a more rapid progression of the disease that leads to death within the first decade of life. Until recently, no effective treatment was available for MLD. The blood-brain barrier (BBB) prevents systemically administered enzyme replacement therapy from reaching target cells in MLD. The evidence for the efficacy of hematopoietic stem cell transplantation is limited to the late-onset MLD subtype. Here, we review the preclinical and clinical studies that facilitated the approval of the ex vivo gene therapy atidarsagene autotemcel for early-onset MLD by the European Medicines Agency (EMA) in December 2020. This approach was studied in an animal model first and then in a clinical trial, eventually proving its efficacy in preventing disease manifestations in presymptomatic patients and stabilizing its progression in paucisymptomatic subjects. This new therapeutic consists of patients' CD34+ hematopoietic stem/progenitor cells (HSPCs) transduced with a lentiviral vector encoding functional ARSA cDNA. The gene-corrected cells get reinfused into the patients after a cycle of chemotherapy conditioning.

Fumagalli F, Calbi V, Natali Sora MG, Sessa M, Baldoli C, Rancoita PMV, Ciotti F, Sarzana M, Fraschini M, Zambon AA, Acquati S, Redaelli D, Attanasio V, Miglietta S, De Mattia F, Barzaghi F, Ferrua F, Migliavacca M, Tucci F, Gallo V, Del Carro U, Canale S, Spiga I, Lorioli L, Recupero S, Fratini ES, Morena F, Silvani P, Calvi MR, Facchini M, Locatelli S, Corti A, Zancan S, Antonioli G, Farinelli G, Gabaldo M, Garcia-Segovia J, Schwab LC, Downey GF, Filippi M, Cicalese MP, Martino S, Di Serio C, Ciceri F, Bernardo ME, Naldini L, Biffi A, Aiuti A. Lentiviral haematopoietic stem-cell gene therapy for early-onset metachromatic leukodystrophy: long-term results from a non-randomised, open-label, phase 1/2 trial and expanded access. Lancet. 2022 Jan 22;399(10322):372-383. doi: 10.1016/S0140-6736(21)02017-1. PMID: 35065785; PMCID: PMC8795071.


Background: Effective treatment for metachromatic leukodystrophy (MLD) remains a substantial unmet medical need. In this study we investigated the safety and efficacy of atidarsagene autotemcel (arsa-cel) in patients with MLD.

Methods: This study is an integrated analysis of results from a prospective, non-randomised, phase 1/2 clinical study and expanded-access frameworks. 29 paediatric patients with pre-symptomatic or early-symptomatic early-onset MLD with biochemical and molecular confirmation of diagnosis were treated with arsa-cel, a gene therapy containing an autologous haematopoietic stem and progenitor cell (HSPC) population transduced ex vivo with a lentiviral vector encoding human arylsulfatase A (ARSA) cDNA, and compared with an untreated natural history (NHx) cohort of 31 patients with early-onset MLD, matched by age and disease subtype. Patients were treated and followed up at Ospedale San Raffaele, Milan, Italy. The coprimary efficacy endpoints were an improvement of more than 10% in total gross motor function measure score at 2 years after treatment in treated patients compared with controls, and change from baseline of total peripheral blood mononuclear cell (PBMC) ARSA activity at 2 years after treatment compared with values before treatment. This phase 1/2 study is registered with, NCT01560182.

Findings: At the time of analyses, 26 patients treated with arsa-cel were alive with median follow-up of 3·16 years (range 0·64-7·51). Two patients died due to disease progression and one due to a sudden event deemed unlikely to be related to treatment. After busulfan conditioning, all arsa-cel treated patients showed sustained multilineage engraftment of genetically modified HSPCs. ARSA activity in PBMCs was significantly increased above baseline 2 years after treatment by a mean 18·7-fold (95% CI 8·3-42·2; p<0·0001) in patients with the late-infantile variant and 5·7-fold (2·6-12·4; p<0·0001) in patients with the early-juvenile variant. Mean differences in total scores for gross motor function measure between treated patients and age-matched and disease subtype-matched NHx patients 2 years after treatment were significant for both patients with late-infantile MLD (66% [95% CI 48·9-82·3]) and early-juvenile MLD (42% [12·3-71·8]). Most treated patients progressively acquired motor skills within the predicted range of healthy children or had stabilised motor performance (maintaining the ability to walk). Further, most displayed normal cognitive development and prevention or delay of central and peripheral demyelination and brain atrophy throughout follow-up; treatment benefits were particularly apparent in patients treated before symptom onset. The infusion was well tolerated and there was no evidence of abnormal clonal proliferation or replication-competent lentivirus. All patients had at least one grade 3 or higher adverse event; most were related to conditioning or to background disease. The only adverse event related to arsa-cel was the transient development of anti-ARSA antibodies in four patients, which did not affect clinical outcomes.

Interpretation: Treatment with arsa-cel resulted in sustained, clinically relevant benefits in children with early-onset MLD by preserving cognitive function and motor development in most patients, and slowing demyelination and brain atrophy.

Faccioli S, Sassi S, Pandarese D, Borghi C, Montemaggiori V, Sarzana M, Scarparo S, Butera C, Calbi V, Aiuti A, Fumagalli F. Preserving Ambulation in a Gene Therapy-Treated Girl Affected by Metachromatic Leukodystrophy: A Case Report. J Pers Med. 2023 Apr 6;13(4):637. doi: 10.3390/jpm13040637. PMID: 37109023; PMCID: PMC10144348.


(1) Background: Atidarsagene autotemcel is a hematopoietic stem and progenitor cell gene therapy (HSPC-GT) approved to treat early-onset metachromatic leukodystrophy (MLD). The purpose of this case report is to describe the long-term management of residual gait impairment of a child with late infantile MLD treated with HSPC-GT. (2) Methods: Assessment included Gross Motor Function Measure-88, nerve conduction study, body mass index (BMI), Modified Tardieu Scale, passive range of motion, modified Medical Research Council scale, and gait analysis. Interventions included orthoses, a walker, orthopedic surgery, physiotherapy, and botulinum. (3) Results: Orthoses and a walker were fundamental to maintaining ambulation. Orthopedic surgery positively influenced gait by reducing equinovarus. Nonetheless, unilateral recurrence of varo-supination was observed, attributable to spasticity and muscle imbalance. Botulinum improved foot alignment but induced transient overall weakness. A significant increase in BMI occurred. Finally, a shift to bilateral valgopronation was observed, more easily managed with orthoses. (4) Conclusions: HSPC-GT preserved survival and locomotor abilities. Rehabilitation was then considered fundamental as a complementary treatment. Muscle imbalance and increased BMI contributed to gait deterioration in the growing phase. Caution is recommended when considering botulinum in similar subjects, as the risk of inducing overall weakness can outweigh the benefits of spasticity reduction.

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