I used to take Imuran before taking Cellcept. I cannot tolerate the drug and I got serious reaction. I lost all my hair, had horrible mouth ulcer, dropped WBC, dropped platelet, higher fever due to extremely low WBC (close to zero). I was hospitalized for ten days, and I looked exactly like a person who has chemo. Then few years later another rhumty starts me on Cellcept and it works extremely well on me.
If you are stable and no flares, better to stay on the same drug you are taking (in your case is Cellcept). That's what my rhumty always tells me, because I tried to ask if I should try those new Lupie drugs.