Prominent candidates are natalizumab targeting α-4 integrin and two “old” antibodies against lymphocyte surface markers, alemtuzumab (CD52) and rituximab (CD20), which have been repurposed for multiple sclerosis, and the recently from the U.S. Food and Drug Administration (FDA)-approved ocrelizumab, also targeting the B-cell antigen, CD20 and is the first for relapsing remitting (RRMS) and primary progressive forms of MS (PPMS) [1,2]. Here, MS4A1 is linked to primary progressive multiple sclerosis.