Wiskott-Aldrich Syndrome

BackgroundWiskott-Aldrich syndrome is a rare, life-threatening, X-linked primary immunodeficiency characterised by microthrombocytopenia, infections, eczema, autoimmunity, and malignant disease. Lentiviral vector-mediated haemopoietic stem/progenitor cell (HSPC) gene therapy is a potentially curative treatment that represents an alternative to allogeneic HSPC transplantation. Here, we report safety and efficacy data from an interim analysis of patients with severe Wiskott-Aldrich syndrome who received lentiviral vector-derived gene therapy.MethodsWe did a non-randomised, open-label, phase 1/2 clinical study in paediatric patients with severe Wiskott-Aldrich syndrome, defined by either WAS gene mutation or absent Wiskott-Aldrich syndrome protein (WASP) expression or a Zhu clinical score of 3 or higher. We included patients who had no HLA-identical sibling donor available or, for children younger than 5 years of age, no suitable 10/10 matched unrelated donor or 6/6 unrelated cord blood donor. After treatment with rituximab and a reduced-intensity conditioning regimen of busulfan and fludarabine, patients received one intravenous infusion of autologous CD34+ cells genetically modified with a lentiviral vector encoding for human WAS cDNA. The primary safety endpoints were safety of the conditioning regimen and safety of lentiviral gene transfer into HSPCs. The primary efficacy endpoints were overall survival, sustained engraftment of genetically corrected HSPCs, expression of vector-derived WASP, improved T-cell function, antigen-specific responses to vaccinations, and improved platelet count and mean platelet volume normalisation. This interim analysis was done when the first six patients treated had completed at least 3 years of follow-up. The planned analyses are presented for the intention-to-treat population. This trial is registered with ClinicalTrials.gov (number NCT01515462) and EudraCT (number 2009-017346-32).FindingsBetween April 20, 2010, and Feb 26, 2015, nine patients (all male) were enrolled of whom one was excluded after screening; the age range of the eight treated children was 1·1-12·4 years. At the time of the interim analysis (data cutoff April 29, 2016), median follow-up was 3·6 years (range 0·5-5·6). Overall survival was 100%. Engraftment of genetically corrected HSPCs was successful and sustained in all patients. The fraction of WASP-positive lymphocytes increased from a median of 3·9% (range 1·8-35·6) before gene therapy to 66·7% (55·7-98·6) at 12 months after gene therapy, whereas WASP-positive platelets increased from 19·1% (range 4·1-31·0) to 76·6% (53·1-98·4). Improvement of immune function was shown by normalisation of in-vitro T-cell function and successful discontinuation of immunoglobulin supplementation in seven patients with follow-up longer than 1 year, followed by positive antigen-specific response to vaccination. Severe infections fell from 2·38 (95% CI 1·44-3·72) per patient-year of observation (PYO) in the year before gene therapy to 0·31 (0·04-1·11) per PYO in the second year after gene therapy and 0·17 (0·00-0·93) per PYO in the third year after gene therapy. Before gene therapy, platelet counts were lower than 20 × 109 per L in seven of eight patients. At the last follow-up visit, the platelet count had increased to 20-50 × 109 per L in one patient, 50-100 × 109 per L in five patients, and more than 100 × 109 per L in two patients, which resulted in independence from platelet transfusions and absence of severe bleeding events. 27 serious adverse events in six patients occurred after gene therapy, 23 (85%) of which were infectious (pyrexia [five events in three patients], device-related infections, including one case of sepsis [four events in three patients], and gastroenteritis, including one case due to rotavirus [three events in two patients]); these occurred mainly in the first 6 months of follow-up. No adverse reactions to the investigational drug product and no abnormal clonal proliferation or leukaemia were reported after gene therapy.InterpretationData from this study show that gene therapy provides a valuable treatment option for patients with severe Wiskott-Aldrich syndrome, particularly for those who do not have a suitable HSPC donor available.FundingItalian Telethon Foundation, GlaxoSmithKline, and Orchard Therapeutics.

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immunodeficiency with severe platelet abnormalities and complex immunodeficiency. Although clinical gene therapy approaches using lentiviral vectors have produced encouraging results, full immune and platelet reconstitution is not always achieved. Here we show that a CRISPR/Cas9-based genome editing strategy allows the precise correction of WAS mutations in up to 60% of human hematopoietic stem and progenitor cells (HSPCs), without impairing cell viability and differentiation potential. Delivery of the editing reagents to WAS HSPCs led to full rescue of WASp expression and correction of functional defects in myeloid and lymphoid cells. Primary and secondary transplantation of corrected WAS HSPCs into immunodeficient mice showed persistence of edited cells for up to 26 weeks and efficient targeting of long-term repopulating stem cells. Finally, no major genotoxicity was associated with the gene editing process, paving the way for an alternative, yet highly efficient and safe therapy.

Patients with Wiskott-Aldrich syndrome (WAS) lacking a human leukocyte antigen-matched donor may benefit from gene therapy through the provision of gene-corrected, autologous hematopoietic stem/progenitor cells. Here, we present comprehensive, long-term follow-up results (median follow-up, 7.6 years) (phase I/II trial no. NCT02333760 ) for eight patients with WAS having undergone phase I/II lentiviral vector-based gene therapy trials (nos. NCT01347346 and NCT01347242 ), with a focus on thrombocytopenia and autoimmunity. Primary outcomes of the long-term study were to establish clinical and biological safety, efficacy and tolerability by evaluating the incidence and type of serious adverse events and clinical status and biological parameters including lentiviral genomic integration sites in different cell subpopulations from 3 years to 15 years after gene therapy. Secondary outcomes included monitoring the need for additional treatment and T cell repertoire diversity. An interim analysis shows that the study meets the primary outcome criteria tested given that the gene-corrected cells engrafted stably, and no serious treatment-associated adverse events occurred. Overall, severe infections and eczema resolved. Autoimmune disorders and bleeding episodes were significantly less frequent, despite only partial correction of the platelet compartment. The results suggest that lentiviral gene therapy provides sustained clinical benefits for patients with WAS.

IntroductionNeurological involvement in Wiskott-Aldrich syndrome (WAS) - an inborn error of immunity caused by mutations in the WAS gene - is primarily documented through isolated case reports, limiting systematic synthesis and clear characterization of clinical patterns. We conducted a systematic review to characterize central and peripheral nervous system involvement in patients with confirmed WAS.MethodsA systematic search was conducted in PubMed, Embase, Scopus, and Web of Science following the PRISMA 2020 guidelines. Studies reporting neurological manifestations in WAS were eligible. Extracted variables included neurological diagnosis, age at WAS diagnosis, age at neurological onset, hematopoietic stem cell transplantation (HSCT) status, viral associations, and outcomes. Methodological quality was assessed using the Newcastle-Ottawa Scale and Joanna Briggs Institute tools. Analyses were descriptive at the patient level.ResultsTwenty-six studies describing 32 patients were included. Most patients were pediatric (78.1%), with a median age at WAS diagnosis of 0.4 years; neurological manifestations occurred a median of 3.0 years later. Manifestations were classified as brain hemorrhagic (8/32), immune-mediated (6/32), infectious (6/32), or neoplastic (12/32). Median age at neurological onset differed across categories (p = 0.018): brain hemorrhagic events occurred earliest (1.2 years), immune-mediated events in childhood (3.8 years), infectious events later (14.5 years), and neoplastic events across a broad age range (5.0 years). Infectious cases were predominantly John Cunningham virus-positive progressive multifocal leukoencephalopathy; neoplastic cases involved central nervous system lymphoma or post-transplant lymphoproliferative disorder. Case-fatality varied by phenotype (p = 0.002), reaching 100% in infectious, 75% in neoplastic, 62.5% in hemorrhagic, and 0% in immune-mediated cases. Overall, neurological event-attributed case-fatality was 59.4%. Events occurred both before and after HSCT, with numerically higher mortality among non-transplant patients (63.6% vs 50.0%).DiscussionNeurological involvement in WAS exhibits age-dependent phenotypic patterns, with substantial case-fatality particularly in infectious and neoplastic presentations. Although derived from case-based evidence, these findings support heightened neurological vigilance across the disease course and the need for systematic neurological reporting in future registries.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/display_record.php?RecordID=1141002, identifier CRD420251141002.