I discovered that there is a genetic test you can take to determine if you have the genes for Leflunomide to work as an immunosuppressive. However my Rheumatologist was very annoyed when I suggested that I would like to be tested before starting on it. She actually said to me " what difference would it make" (if it wasn't going to help with suppressing the immune system) "We only have a few options and Leflunomide was one of them". This was after trying Methotrexate and having a bad reaction. So she begrudgingly prescribed Hydroxychloroquine (Plaquinil) "because it is well tolerated in many patients but doesn't work". It has worked for me without side effects (so far). I started on a low dose and have increased slightly, haven't had to deal with the extreme infection risks of the stronger immunosuppressive drugs and it's definitely controlling the PMR inflammation (CPR results are confirming this) . There is a gene that strongly influences how you are able to metabolise some medications but Doctors generally refuse to acknowledge or test for it.