Isis Pharmaceuticals, Inc. (NASDAQ: ISIS) announced that it initiated a Phase 1 clinical study of ISIS-PKKRx. ISIS-PKKRx is an antisense drug in development to treat patients with hereditary angioedemia (HAE). HAE is a rare genetic disease that is characterized by rapid and painful attacks of inflammation in the hands, feet, limbs, face, abdomen, larynx and trachea. HAE affects approximately 20,000 patients in the United States and Europe and can be fatal if swelling occurs in the larynx. ISIS-PKKRx is designed to alter the course of HAE and therefore has the potential to be best-in-class for the treatment of HAE.