PDE5A and rheumatoid arthritis: Other interesting genes without known genetic association with RA include 2 genes targeted by drugs in RA clinical trials (PDE5A: Dipyridamole, IMPDH1: Mizoribine), 1 additional gene targeted by drugs in clinical trials for other autoimmune diseases (ADRA1: Isoxsuprine for multiple sclerosis), 6 genes with known genetic association to autoimmune diseases but not RA (C1QTNF6, BCL2L11, KAZN, ETV3, MACROD2, PROK2, KCNE4), and 3 genes from pathways linked to IBD (PROK2, CYTH4, RAC2).