To further substantiate the specificity of [68Ga]Pentixafor binding to human CXCR4, we next performed competition studies where mice bearing MM xenograft tumors received the FDA-approved drug AMD3100 (Plerixafor) (Brave et al, 2010) before receiving the [68Ga]-labeled PET probe. This evidence concerns the gene CXCR4 and Miyoshi myopathy.