<unk>  is a purine antimetabolite that is FDA approved for the treatment of renal homotransplantation, rheumatoid arthritis. There is a Black Box Warning for this drug as shown here.  Common adverse reactions include nausea and vomiting.
Azathioprine
Hydroxychloroquine
Mycophenolate
Mycophenolate sodium
Cyclosporine 
Etanercept
Hydroxychloroquine sulfate
Tofacitinib