Severe B cell-mediated disease activation despite two cycles of alemtuzumab in a patient with multiple sclerosis.

Alemtuzumab is a potent monoclonal CD52 antibody used to treat patients with multiple sclerosis (MS). However, recent literature reports have described paradoxical activation of B cell-mediated disease within 1 year of the first cycle of alemtuzumab. We raise awareness that severe B cell-mediated disease activation could develop, even after two cycles of alemtuzumab, in some vulnerable MS patients; therefore, individualized therapeutic strategies should be considered in clinical practice. We also propose that a novel regulatory B-cell subset may be a candidate for a predictive biomarker of disease activation in MS patients treated with alemtuzumab.