X0202 4 2007-03-26 0 0000899866 ALEXION PHARMACEUTICALS INC alxn 0001231949 BELL LEONARD C/O ALEXION PHARMACEUTICALS INC 352 KNOTTER DRIVE CHESHIRE CT 06410 1 1 0 0 CEO Common Stock, par value $.0001 per share 2007-03-26 4 M 0 30000 10.38 A 403224 D common stock, par value $.0001 per share 2007-03-26 4 S 0 19580 44.26 D 383644 D Option to purchase Common Stock 10.38 2007-03-26 4 M 0 30000 0 A 2001-04-01 2007-04-01 Common Stock, par value $.0001 per share 30000 0 D The sales reported by this Form 4 are made pursuant to the terms of a Sales Plan designed to meet the requirements of Rule 10b5-1(c)(1) of the Securities Exchange Act. Dr. Leonard Bell 2007-03-28