We aimed to assess mavorixafor activity in R334X-expressing Jurkat cells, as this model allows us to compare the response to mavorixafor in cells endogenously expressing WT, R334X/WT or R334X/R334X CXCR4 at similar levels and, most importantly, in the R334X/WT cells that model the genotype of patients with WHIM syndrome. This evidence concerns the gene CXCR4 and WHIM syndrome.