Correction of Wiskott-Aldrich syndrome by hematopoietic stem cell gene therapy

K. BOZTUG; M. SCHMIDT; A. SCHWARZER; P. P. BANERJEE; M. BÖHM; R. BEIER; I. AVEDILLO DÍEZ; R. A. DEWEY; C. BALL; A. NOWROUZI; S. NAUNDORF; K. KUHLCKE; R. BLASCZYKS; M. ROSE; C. FRAZER; M. LIESL; R. FERRARI; M. ABBOUD; W. AL-HERZ; I. KONDRATENKO; L. MARODI; J.S. ORANGE; C. VON KALLE; C. KLEIN

Milan

Congreso; XVIIIth Annual Congress of the European Society of Gene and Cell Therapy (ESGCT),; 2010

Wiskott Aldrich Syndrome is a life-threatening immunedisordercharacterized by bleeding secondary to microthrombocytopenia,immunodeficiency, autoimmunity, andsusceptibility to lymphoma. A clinical gene therapy protocolusing transplantation of autologous hematopoietic stem cellstransduced with a GALV pseudotyped MLV-derived retroviralvector was developed at Hannover Medical School. Wehere present an analysis of ten patients treated in this trialbetween 2006 and 2009. Patients received 3 – 23 x 10e6=kggenetically modified hematopoietic progenitor cells uponpartial myeloablative conditioning using busulfan (8mg=kg).9=10 patients received more than 10e6=kg progenitor cellsand had evidence of sustained engraftment of WASP-positivehematopoietic progenitor cells. One patient received2.4x10e6=kg progenitor cells, failed to show sustained engraftmentand was eventually transplanted with haploidenticalhematopoietic stem cells. In the remaining patients,WASP expression was determined in myeloid and lymphoidcells as well as in CD34þ hematopoietic progenitor cells usingWestern Blot and FACS analysis, respectively. While thepercentage of WASP-positive myeloid cells was relativelystable over time (range 10 to 60%), a marked increase overtime in the percentage of WASP-positive T lymphocytes andNK cells was observed, resulting in more than 80% of WASPpositivelymphoid cells 12 months after gene therapy. Anincrease in platelet counts was observed in all patients. Furthermore,the majority of platelets showed evidence of WASPexpression, detectable as early as 3 months after gene therapy.Functional immune reconstitution was documented in dendriticcells (podosome formation), T cells (proliferation inresponse to CD3-signaling), and NK cells (formation of immunologicalsynapse and NK cell killing activity). TCR V?spectratyping analyses showed in improvement of receptorskewing upon gene therapy in some patients. A clinicalbenefit was notable in all 9 patients with sustained engraftment:eczema, bleeding diathesis and immunodeficiency resolved.Autoimmune phenomena such as autoimmunehemolytic anemia and colitis also resolved after gene therapy.Repetitive bone marrow examinations did not reveal morphologicalor cytogenetic alterations. Comprehensive insertionsite analysis using 454 pyrosequencing demonstratedvector integration that targeted multiple genes controllinggrowth, development and immunological responses in apersistently polyclonal hematopoiesis.In sum, hematopoietic stem cell gene therapy for Wiskott-Aldrich Syndrome is feasible and effective at correcting tovarious cellular defects implicated in this disease. Prospectivemonitoring will determine the long-term efficacy and safetyprofile of this experimental therapeutic approach in patientswith Wiskott-Aldrich syndrome.