**Exhibit 31.3**

 

**CERTIFICATION OF CHIEF ACCOUNTING OFFICER**

 

(Pursuant to Rule 13a-14 of the Securities Exchange Act of 1934, asamended,as Adopted Pursuant to Section 302 of the Sarbanes-Oxley Act of 2002)

 

I,Brian M. Posner, certify that:

 

1.                                       I have reviewed this quarterly report on Form 10-Qof Pharmacopeia Drug Discovery, Inc.;

 

2.                                       Based on my knowledge, this report does notcontain any untrue statement of a material fact or omit to state a materialfact necessary to make the statements made, in light of the circumstances underwhich such statements were made, not misleading with respect to the periodcovered by this quarterly report;

 

3.                                       Based on my knowledge, the financialstatements, and other financial information included in this quarterly report,fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periodspresented in this quarterly report;

 

4.                                       The registrant’s other certifying officers andI are responsible for establishing and maintaining disclosure controls andprocedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))for the registrant and have:

 

a)                                      designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to be designedunder our supervision, to ensure that material information relating to theregistrant is made known to us by others within the entity, particularly duringthe period in which this quarterly report is being prepared;

 

b)                                     evaluated the effectiveness of the registrant’sdisclosure controls and procedures and presented in this report our conclusionsabout the effectiveness of the disclosure controls and procedures, as of theend of the period covered by this report based on such evaluation; and

 

c)                                      disclosed in this report any change in theregistrant’s internal control over financial reporting that occurred during theregistrant’s most recent fiscal quarter that has materially affected, or isreasonably likely to materially affect, the registrant’s internal control overfinancial reporting; and

 

5.                                       The registrant’s other certifying officers andI have disclosed, based on our most recent evaluation of internal control overfinancial reporting, to the registrant’s auditors and the audit committee of registrant’sboard of directors (or persons performing the equivalent functions):

 

a)                                      all significant deficiencies and materialweaknesses in the design or operation of internal control over financialreporting which are reasonably likely to adversely affect the registrant’sability to record, process, summarize and report financial information; and

 

b)                                     any fraud, whether or not material, thatinvolves management or other employees who have a significant role in theregistrant’s internal control over financial reporting.

 

Date:  August 5, 2005

 

 
|   | /s/ Brian  M. Posner   |   |
|--------|-----------------------------|--------|
|   | Brian  M. Posner            |
|   | Vice  President, Finance    |
|   | (Chief  Accounting Officer) |

 

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