The orally bioavailable CXCR4 antagonist mavorixafor has been shown to effect clinically meaningful improvements in peripheral blood neutrophil and lymphocyte counts, and reductions in infection rates among patients aged 12 and older with WHIM syndrome (32, 33), leading to the approval of Xolremdi® by the U.S. Food and Drug Administration. Here, CXCR4 is linked to WHIM syndrome.