[23] used Ultrafast Shape Recognition (USR) [24] to search for compounds with similar shape to a previously reported inhibitor of protein arginine deiminase type 4 (PAD4), a new therapeutic target for the treatment of rheumatoid arthritis, and identified a novel compound that has a strikingly different structure from the template inhibitor yet showed significant inhibition on the enzymatic activity of PAD4. This evidence concerns the gene PADI4 and rheumatoid arthritis.