Gene Therapy for Wiskott-Aldrich Syndrome

The absence of prolonged aplasia (defined as ANC <0.5×10^9/L [<500/μL] at Day +60, with no evidence of BM recovery and requiring backup administration) was assumed as demonstrating the safety of the RIC regimen.

Safety and tolerability of lentiviral-transduced cell infusion. This will be evaluated on the basis of adverse events reporting and monitoring of the systemic reactions to cell infusion.

Engraftment is characterized by the presence of gene modified cells in the BM or PB compartments. The main indicator of gene correction is detection of the WAS LVV sequences in the HSPCs and their progeny.

The VCN, which is the mean number of integrated copies of the vector sequences per cell genome, was measured using PCR-based methods in DNA samples extracted from BM and PB cell populations at various timepoints post-treatment.

Adequate engraftment was defined as either ≥0.04 VCN/cell in BM CD34+ cells or ≥0.01 VCN/cell in PB CD3+ cells.

The percentage of subjects who present the proportion of PB cells expressing WASP was assessed by flow cytometry analysis.

Improvement in in vitro T-cell proliferation was assessed upon stimulation with 3 doses of anti-immobilized CD3 (CD3i) monoclonal antibodies ≥1 year after Telethon003 infusion (as compared with pre-GT values) in PBMC and/or T-cell lines. The degree of correction was evaluated with respect to healthy controls.

The ability to mount a protective humoral response to at least 4 out of 5 nominal antigens including antibodies to T-cell dependent antigens and conjugated or unconjugated polysaccharide antigens was measured after vaccination (planned >1 year after Telethon003 infusion). If results were available on n <5 antigens, the rule of at least n-1 applied to define success.

Sustained increase in platelet count compared to baseline, analyzing the individual longitudinal profile

Participant survival was monitored throughout the study.

Anti-WASP and anti-HIV-1 antibodies (anti-p24) were monitored to evaluate response to transgene and to vector, respectively.

Decrease in number of severe infections as evaluated in the second and third year after the treatment by clinical history, complete physical examinations, hematological and microbiological tests.

Reduction in bruising and/or bleeding manifestations when present, as assessed by clinical monitoring, compared to clinical history

Reduction in laboratory markers (number and titer of antibody when available) and/or clinical manifestations of autoimmunity, as evaluated by organ-specific and systemic autoantibodies, imaging and clinical follow-up, compared to clinical history. Reduction in eczema as evaluated by clinical score

Improved quality of life, measured after the first year of treatment by reduced hospitalization, reduced requirement of drugs, school attendance, social activities.

≥0.04 VCN/cell on all the available peripheral blood and/or bone marrow cell subpopulations (BM subpopulations: GlyA+, CD15+, CD61+, CD3+, CD19+, CD56+; PB subpopulations: CD15+, CD19+, CD56+)

Recording of AE, AR, SAE/SAR, UAR, SUSAR