It's now available generically: Rituximab. There's another hack that Genentech was able to patent and approve for MS to produce Ocrelizumab, which does the same thing as Rituximab but costs an order of magnitude more. Because that's how the world of big pharma works.
In essence, wiping out your plasma cells (a.k.a. B cells or lymphocytes) seems to stop MS in its tracks. Where my neurologist would typically see 2 or 3 new lesions in any given patient per year, instead now my neurologist is seeing 2 or 3 new lesions per year in the population of all their RRMS patients who are on Rituximab (or Ocrelizumab). And it turns out the immune system can get along pretty well with all the other cells types it has, such as T cells.