**Exhibit**
**      31.1**

**CERTIFICATION**

**PURSUANT      TO RULE 13a-14(a) AND RULE 15d-14(a) UNDER THE**

**SECURITIES      EXCHANGE ACT OF 1934, AS AMENDED**

|   | a) | designed                such disclosure controls and procedures, or caused such disclosure                controls and procedures to be designed under our supervision, to                ensure                that material information relating to the registrant is made known                to us                by others within the registrant, particularly during the period in                which                this report is being prepared; |
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|   | b) | designed                such internal control over financial reporting, or caused such internal                control over financial reporting to be designed under our supervision,                to                provide reasonable assurance regarding the reliability of financial                reporting and the preparation of financial statements for external                purposes in accordance with generally accepted accounting                principles; |
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|   | c) | evaluated                the effectiveness of the registrant’s disclosure controls and procedures                and presented in this report our conclusions about the effectiveness                of                the disclosure controls and procedures, as of the end of the period                covered by this report based on such evaluation; |
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|   | d) | disclosed                in this report any change in the registrant’s internal control over                financial reporting that occurred during the registrant’s most recent                fiscal quarter (the registrant’s fourth fiscal quarter in the case of an                annual report) that has materially affected, or is reasonably likely                to                materially affect, the registrant’s internal control over financial                reporting; and |
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|   | a) | all                significant deficiencies and material weaknesses in the design or                operation of internal control over financial reporting which are                reasonably likely to adversely affect the registrant’s ability to record,                process, summarize and report financial information;                and |
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|   | b) | any                fraud, whether or not material, that involves management or other                employees who have a significant role in the registrant’s internal control                over financial reporting. |
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| Date:                August 8, 2006 |  **/s/                Paul J. Maddon, M.D., Ph.D.**                         |
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|                                | Paul                J. Maddon, M.D., Ph.D.Chief                Executive Officer |