Major Holders

The names of our directors and executive officers, and certain additional information with respect to each of them, are set forth below.

Position Held* Position Held Percent of Outstanding Shares
Efficacy Capital Ltd. 2,580,013 20.2
Visium Asset Management LLC 1,180,687 9.24
Promed Management, Inc. 663,144 5.19
Franklin Advisors, Inc. 637,000 4.99
RA Capital Management LLC 579,806 4.54
Seneca Capital Advisors LLC 450,300 3.53
Vermillion Asset Management LLC 435,000 3.44
Great Point Partners LLC 280,940 2.2
Wall Street Associates LLC 275,000 2.15
Dimensional Fund Advisors, Inc. 263,243 2.06
Barclays Global Investors NA (CA) 217,697 1.7
Joseph S. Podolski 110,881 0.87
DWS Investment GmbH 106,400 0.83

* Data as reported by NASDAQ on May 16, 2008

2408 Timberloch Place, B-7
The Woodlands, Texas 77380
281-719-3400
281-719-3446 fax