NEFL and progressive multifocal leukoencephalopathy: Clinically, in MS, Rituximab rapidly suppresses new lesion formation in relapsing-remitting MS (RRMS), while Ocrelizumab stabilizes disability progression and reduces serum neurofilament light chain (NfL) levels; however, long-term B-cell depletion may increase infection risk, and Natalizumab requires rigorous monitoring for progressive multifocal leukoencephalopathy (PML).