A phase 3 randomized trial of mavorixafor, a CXCR4 antagonist, for WHIM syndrome

Abstract

AbstractWe investigated efficacy and safety of mavorixafor, an oral CXCR4 antagonist, for participants with warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome, a rare immunodeficiency caused by CXCR4 gain-of-function variants. This randomized (1:1), double-blind, placebo-controlled, phase 3 trial enrolled participants aged ≥12 years with WHIM syndrome and absolute neutrophil count (ANC) ≤400/μL. Participants received once-daily mavorixafor or placebo for 52 weeks. Primary end point was time (hours) above ANC threshold ≥500/μL (TATANC; over 24 hours). Secondary end points included TAT absolute lymphocyte count ≥1000/μL (TATALC; defined similar to TATANC); absolute changes in white blood cell (WBC), ANC, and absolute lymphocyte count (ALC) from baseline; annualized infection rate; infection duration; and total infection score (combined infection number/severity). In 31 participants (mavorixafor, n = 14; placebo, n = 17), mavorixafor least squares (LS) mean TATANC was 15.0 hours and that for placebo was 2.8 hours (P < .001). Mavorixafor LS mean TATALC was 15.8 hours and that for placebo 4.6 hours (P < .001). Higher absolute WBC, ANC, and ALC levels were seen with mavorixafor than placebo at each time point assessed. Annualized infection rates were 60% lower with mavorixafor vs placebo (LS mean 1.7 vs 4.2; nominal P = .007), and total infection scores were 40% lower (7.4 [95% confidence interval [CI], 1.6-13.2] vs 12.3 [95% CI, 7.2-17.3]). Treatment with mavorixafor reduced infection frequency, severity, duration, and antibiotic use. No discontinuations occurred because of treatment-emergent adverse events (TEAEs); no related serious TEAEs were observed. Overall, participants treated with mavorixafor showed significant increases in LS mean TATANC and TATALC, reduced infection frequency, severity/duration. Mavorixafor was well tolerated in participants with WHIM syndrome. The trial was registered at www.clinicaltrials.gov as #NCT03995108.