Improved outcome of HSCT in STAT1 gain-of-function disease following JAK inhibition bridging.

Germline gain-of-function (GOF) mutations in signal transducer and activator of transcription 1 (STAT1) are associated with infections, including chronic mucocutaneous candidiasis and autoimmunity. Morbidity is high, and disease manifestations can be life-threatening. Curative allogeneic hematopoietic stem cell transplantation (HSCT) historically has had poor outcomes. We identified 36 patients with STAT1 GOF disease, receiving 40 HSCT procedures in 2010-2023, in a combined effort of the EBMT-IEWP and the PIDTC. Median age at first transplant was 11 years (range 1 - 33). Indications for HSCT were combined immunodeficiency, severe and/or refractory infections, and autoimmunity. Acute GvHD occurred in 22/40 HSCT procedures; 5 patients suffered from grade III/IV acute GvHD. One patient had chronic GvHD. Overall survival was 72.2%, and event-free survival was 55.6%, markedly improved from an earlier report on HSCT for STAT1 GOF disease. Patients with an HCT-CI score of 1 or higher had worse outcome. Pre-treatment with Janus kinase (JAK) inhibitors was associated with better event-free survival.