| SC 13G/A | 2007-02-13 | PRICE T ROWE ASSOCIATES INC /MD/ | ALEXION PHARMACEUTICALS INC | 2,896,750 | 8.3% | EDGAR |
| SC 13G/A | 2007-02-13 | CITADEL L P | ALEXION PHARMACEUTICALS INC | 1,874,402 | - | EDGAR |
| SC 13G | 2007-02-13 | BlackRock Inc. | ALEXION PHARMACEUTICALS INC | 1,799,104 | 5.2% | EDGAR |
| SC 13G/A | 2007-02-09 | SECTORAL ASSET MANAGEMENT INC | ALEXION PHARMACEUTICALS INC | 2,667,134 | 7.7% | EDGAR |
| SC 13G/A | 2007-02-08 | BALYASNY ASSET MANAGEMENT LLC | ALEXION PHARMACEUTICALS INC | 89,878 | 0.3% | EDGAR |
| SC 13G/A | 2007-02-01 | JANUS CAPITAL MANAGEMENT LLC | ALEXION PHARMACEUTICALS INC | 1,395,071 | 4.0% | EDGAR |
| SC 13G | 2006-10-12 | CITADEL L P | ALEXION PHARMACEUTICALS INC | 1,653,406 | - | EDGAR |
| SC 13G | 2006-03-06 | D. E. Shaw Valence Portfolios, L.L.C. | ALEXION PHARMACEUTICALS INC | 1,771,517 | 5.7% | EDGAR |
| SC 13G | 2006-03-06 | BROOKSIDE CAPITAL PARTNERS FUND LP | ALEXION PHARMACEUTICALS INC | 1,921,500 | 6.2% | EDGAR |
| SC 13G | 2006-02-17 | BALYASNY ASSET MANAGEMENT LLC | ALEXION PHARMACEUTICALS INC | 1,613,761 | 5.2% | EDGAR |
| SC 13G/A | 2006-02-14 | FMR CORP | ALEXION PHARMACEUTICALS INC | 3,282,290 | 10.6% | EDGAR |
| SC 13G/A | 2006-02-14 | SECTORAL ASSET MANAGEMENT INC | ALEXION PHARMACEUTICALS INC | 2,624,552 | 8.5% | EDGAR |
| SC 13G/A | 2006-02-14 | SAC CAPITAL ADVISORS LLC | ALEXION PHARMACEUTICALS INC | 3,000 | 0.0% | EDGAR |
| SC 13G/A | 2006-02-14 | BAKER FELIX | ALEXION PHARMACEUTICALS INC | 1,360,667 | 4.2% | EDGAR |
| SC 13G | 2006-02-14 | JANUS CAPITAL MANAGEMENT LLC | ALEXION PHARMACEUTICALS INC | 3,026,858 | 9.8% | EDGAR |
| SC 13G/A | 2006-02-13 | PRICE T ROWE ASSOCIATES INC /MD/ | ALEXION PHARMACEUTICALS INC | 1,824,150 | 5.9% | EDGAR |
| SC 13G/A | 2006-02-13 | ZIFF ASSET MANAGEMENT LP | ALEXION PHARMACEUTICALS INC | 1,208,321 | 3.9% | EDGAR |
| SC 13G/A | 2006-02-13 | CITADEL L P | ALEXION PHARMACEUTICALS INC | 1,799,531 | - | EDGAR |
| SC 13G | 2006-02-13 | WESTFIELD CAPITAL MANAGEMENT CO LLC | ALEXION PHARMACEUTICALS INC | 1,868,550 | 6.0% | EDGAR |
| SC 13G/A | 2006-02-10 | RS INVESTMENT MANAGEMENT CO LLC | ALEXION PHARMACEUTICALS INC | - | 0.0% | EDGAR |