Positive CHMP Opinion for Libmeldy™ for the Treatment of
Early-Onset Metachromatic Leukodystrophy (MLD)
The Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) has adopted a positive opinion recommending full, or standard, marketing authorization for Libmeldy® (cryopreserved autologous CD34+ cells encoding the arylsulfatase-A, or ARSA, gene), an investigational gene therapy for the treatment of metachromatic leukodystrophy (MLD), characterized by biallelic mutations in the ARSA gene leading to a reduction of the ARSA enzymatic activity in children with i) late infantile or early juvenile forms, without clinical manifestations of the disease, or ii) the early juvenile form, with early clinical manifestations of the disease, who still have the ability to walk independently and before the onset of cognitive decline. A final decision by the European Commission for Libmeldy® is anticipated before the end of 2020. If approved, Libmeldy would be the first commercial therapy and first gene therapy for eligible patients with early-onset MLD.
A gene therapy developed with SR-Tiget
Libmeldy® is designed as a one-time gene therapy, developed in partnership with the San Raffaele-Telethon Institute for Gene Therapy (SR-Tiget) in Milan, Italy, in which the patient’s own hematopoietic stem cells (HSCs) are selected, and functional copies of the ARSA gene are inserted into the genome of the HSCs using a lentiviral vector before these genetically modified cells are infused back into the patient. The ability of the gene-corrected HSCs to migrate across the blood-brain barrier into the brain, engraft, and express the functional enzyme has the potential to persistently correct the underlying genetic condition with a single treatment. “This is an important milestone toward making the availability of HSC gene therapy a reality for more patients, and it also is extremely rewarding for our multi-disciplinary team at SR-Tiget who has worked relentlessly along this 15-year journey to move the seminal proof of principle studies to the first in-human testing of this therapy,” said SR-Tiget director Luigi Naldini, M.D, Ph.D. “The robust and durable clinical benefits observed in early-onset MLD patients who received HSC gene therapy are compelling, especially when compared to the natural history of the disease. These results also further illustrate our view that the HSC gene therapy approach has the potential to deliver transformative effects in other storage diseases as well, especially when the cells are designed to overexpress the functional enzyme and provide an enhanced supply of it to the affected tissues.”
Data Supporting the Clinical Profile of Libmeldy®
The positive CHMP opinion is supported by clinical studies of Libmeldy® in both pre- and early- symptomatic, early-onset MLD patients. Early-onset MLD encompasses the disease variants traditionally referred to as late infantile (LI) and early juvenile (EJ). Clinical efficacy was based on the integrated analysis of results from 29 patients with early-onset MLD who were all treated with Libmeldy prepared as a fresh (non-cryopreserved) formulation:
• 20 patients were treated in a registrational study (median 4 years follow-up);
9 patients were treated in expanded access programs (median 1.5 years follow-up).
• 16 patients had a diagnosis of LI MLD; 13 had a diagnosis of EJ MLD.
• At the time of treatment, 20 patients were deemed pre-symptomatic;
9 were deemed early-symptomatic.
Clinical safety was evaluated in 35 patients with early-onset MLD (29 patients from integrated efficacy analysis (above), 6 patients treated with the cryopreserved formulation of Libmeldy®).
The co-primary endpoints of the integrated efficacy analysis were Gross Motor Function Measure (GMFM) total score and ARSA activity, both evaluated at 2 years post-treatment. Results of this analysis indicate that a single-dose intravenous administration of Libmeldy is effective in modifying the disease course of early-onset MLD in most patients.
Pre-symptomatic LI and EJ patients treated with Libmeldy® experienced significantly less deterioration in motor function at 2 years and 3 years post-treatment, as measured by GMFM total score, compared to age and disease subtype-matched untreated patients (p≤0.008). The mean difference between treated pre-symptomatic LI patients and age-matched untreated LI patients was 71.0% at year 2 and 79.8% at year 3. Similarly, the mean difference between treated pre-symptomatic EJ patients and age-matched untreated EJ patients was 52.4% at year 2 and 74.9% at year 3. Although not statistically significant, a clear difference in GMFM total score was also noted between treated early-symptomatic EJ patients and age-matched untreated EJ patients (28.7% at year 2; p=0.350 and 43.9% at year 3; p=0.054).
A statistically significant increase in ARSA activity in peripheral blood mononuclear cells was observed at 2 years post-treatment compared to pre-treatment in both pre-symptomatic patients (20.0-fold increase; p<0.001) and early-symptomatic patients (4.2-fold increase; p=0.004).
At the time of the integrated data analysis, all treated LI patients were alive with a follow-up post-treatment up to 7.5 years and 10 out of 13 treated EJ patients were alive with a follow-up post-treatment of up to 6.5 years. No treatment-related mortality has been reported in patients treated with Libmeldy.
Key secondary endpoints
For EJ patients who were early-symptomatic when treated with Libmeldy, meaningful effects on motor development were demonstrated when these patients were treated before entering the rapidly progressive phase of the disease (IQ≥85 and Gross Motor Function Classification (GMFC)≤1). By 4 years post-disease onset, an estimated 62.5% of treated, early-symptomatic EJ MLD patients survived and maintained locomotion and ability to sit without support compared with 26.3% of untreated early-symptomatic EJ MLD patients, representing a delay in disease progression following treatment with Libmeldy.
A secondary efficacy endpoint that measured cognitive and language abilities as quantified by Intelligence Quotient/Development Quotient (IQ/DQ) found:
• In the treated LI subgroup:
-12 out of 15 assessed patients had a fairly constant IQ/DQ, within the normal range (IQ/DQ score of 100 +/- SD of 15) throughout follow-up.
– All but 2 of these patients (1 pre-symptomatic and 1 early-symptomatic) remained above the threshold of severe mental disability (IQ/DQ>55) at chronological ages at which all 14 untreated comparator LI patients showed evidence of severe cognitive impairment
(i.e. IQ/DQ below 55 and close to 0).
• Of the 10 surviving EJ patients:
All 4 pre-symptomatic patients and 4 out of 6 early-symptomatic patients showed normal IQ/DQ throughout follow-up. In contrast, 11 out of 12 untreated EJ patients showed evidence of severe cognitive impairment during follow-up.
Safety data indicate that Libmeldy was generally well-tolerated. The most common adverse reaction attributed to treatment with Libmeldy was the occurrence of anti-ARSA antibodies (AAA) reported in 5 out of 35 patients. Antibody titers in all 5 patients were generally low and no negative effects were observed in post-treatment ARSA activity in the peripheral blood or bone marrow cellular subpopulations, nor in the ARSA activity within the cerebrospinal fluid. Treatment with Libmeldy is preceded by other medical interventions, namely bone marrow harvest or peripheral blood mobilization and apheresis, followed by myeloablative conditioning, which carry their own risks. During the clinical studies, the safety profiles of these interventions were consistent with their known safety and tolerability.
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