CCR4 and T-cell leukemia: Until now, only two therapeutic monoclonal antibodies that recognize extracellular regions of GPCRs are on the market: mogamulizumab, an anti-neoplasic Ig directed against C-C chemokine receptor type 4 (CCR4) in T cell leukemia (11) and erenumAb, an antagonist of the Calcitonin gene-related peptide type 1 receptor (CALCRL) used to treat migraine (12).