Can you use leflunomide and rituximab in a patient with both multiple sclerosis and rheumatoid arthritis?

It is rare for a patient to have both diseases, but immunosuppressive therapy can be used for the management of both conditions. A study published in 2021 investigated the use of a combination of rituximab and leflunomide in rheumatoid arthritis (Behrens et al., PMID 33738492). Rituximab has previously been utilized in clinical trials for multiple sclerosis, and the active metabolite of leflunomide (teriflunomide) is FDA-approved for the treatment of multiple sclerosis.

Leflunomide is an adjunct therapy for RA and the parent drug for teriflunomide. Teriflunomide was developed, in part, to reduce the potential for liver toxicity associated with leflunomide. The effect on WBC is minimal and manageable. In my experience, patients with both diseases have worse RA than MS, and I rely on my colleague rheumatologists to manage the RA. In this case, should they choose this combination, I would have no worries about the MS side - it will be well treated.

Although teriflunomide is not an immunosuppressant, I always worry about agents, that can alter white count, neutrophil count and lymphocyte count, and the potential risks of infection, not much of an answer, but again I am cautious about dual use with some of the newer therapies

Yes (in my limited experience), definitely! I’ve personally seen many patients with both a rheumatic disease and an autoimmune neurological disease since I previously had a multidisciplinary neuro-rheum clinic. We have done this combination many times (leflunomide-rituximab or MTX-rituximab or MTX-ocrelizumab) in various settings, including RA plus MS or Sjogren plus RA plus NMO and it seems to work!