Mavorixafor, another small molecule CXCR4 antagonist, has gained FDA approval for the treatment of WHIM syndrome.674 WHIM syndrome typically results from an autosomal dominant pathogenic variant in the C-terminal end of the CXCR4 gene, resulting in reduced internalization of CXCR4 and hyperactive downstream signaling. Here, CXCR4 is linked to WHIM syndrome.