A phase III randomized crossover trial of plerixafor versus G-CSF for treatment of WHIM syndrome

Warts, Hypogammaglobulinemia, Infections and Myelokathexis (WHIM) syndrome is a primary immunodeficiency disorder caused by heterozygous gain-of-function CXCR4 mutations. Myelokathexis is neutropenia from neutrophil retention in bone marrow and is associated with lymphopenia and monocytopenia. The CXCR4 antagonist plerixafor mobilizes leukocytes to the blood; however, safety and efficacy in WHIM syndrome are undefined. In this investigator-initiated, single-center, randomized, quadruple-masked phase 3 crossover trial, we compared the total infection severity score (TISS) as primary endpoint in an intent-to-treat manner in 19 WHIM patients for 12-months on plerixafor versus 12-months on G-CSF, the standard-of-care for severe congenital neutropenia. Plerixafor was non-superior to G-CSF for TISS (p=0.65). In exploratory endpoints, plerixafor was non-inferior to G-CSF for maintaining neutrophil counts >500 cells/microliter (p=0.023) and was superior to G-CSF for maintaining lymphocyte counts >1000 cells/microliter (p< 0.0001). Complete regression of a subset of large wart areas occurred on plerixafor in 5 of 7 patients with major wart burdens at baseline. Transient rash occurred on plerixafor, and bone pain was more common on G-CSF. There were no significant differences in drug preference or quality of life, or the incidence of drug failure or serious adverse events. Plerixafor was not superior in WHIM patients to G-CSF for TISS, the primary endpoint. Together with wart regression and hematologic improvement, the infection severity results support continued study of plerixafor as a potential treatment for WHIM syndrome.(Funded by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases; clinicaltrials.gov registration number, NCT02231879).

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