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**UNITED STATES  SECURITIES AND EXCHANGE COMMISSION  WASHINGTON, D.C. 20549**

**SCHEDULE 13G**

**UNDER THE SECURITIES EXCHANGE ACT OF 1934  (Amendment No. )***

**ICAGEN, INC.**  (Name of Issuer)

 Common Stock, par value $0.001  (Title of Class of Securities)

 45104P104  (CUSIP Number)

  8/20/2007  (Date of Event Which Requires Filing of this Statement)

  Check the appropriate box to designate the rule pursuant to which this Schedule  is filed:

 |_| Rule 13d-1(b)  |X| Rule 13d-1(c)  |_| Rule 13d-1(d)

 *The remainder of this cover page shall be filled out for a reporting  person's initial filing on this form with respect to the subject class of  securities, and for any subsequent amendment containing information which would  alter disclosures provided in a prior cover page.

 The information required on the remainder of this cover page shall not be  deemed to be "filed" for the purpose of Section 18 of the Securities  Exchange  Act of 1934 ("Act") or otherwise subject to the liabilities of that  section of  the Act but shall be subject to all other provisions of the Act (however, see  the Notes).

 

CUSIP No.  45104P104  --------------------------------------------------------------------------------

1) Names of Reporting Persons. PFIZER INC.  I.R.S. Identification Nos. of Above Persons (entities only) 13-5315170

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2) Check the Appropriate Box if a Member of a Group (See Instructions)  (a) |_|  (b) |_|

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3) SEC Use Only

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4) Citizenship or Place of Organization  Delaware

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| NUMBER OF          SHARES           BENEFICIALLY 

OWNED BY EACH REPORTING

 PERSON WITH: | 5. Sole Voting Power   2,688,172 |
|-------------------------------------------------------------------------------------------|--------------------------------------------|
| 6. Shared Voting Power 0                                                                  |
| 7. Sole Dispositive Power  2,688,172                                                 |
| 8. Shared Dispositive Power 0                                                             |

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9) Aggregate Amount Beneficially Owned by Each Reporting Person  2,688,172

10) Check if the Aggregate Amount in Row (9) Excludes Certain Shares  (See Instructions) |_|

11) Percent of Class Represented by Amount in Item 9     6.6%

12) Type of Reporting Person (See Instructions)   CO

 

  ITEM 1.

(A) NAME OF ISSUER: ICAGEN, INC.

(B) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICE:

4222 Emperor Boulevard, Suite 350, Durham, North Carolina 27703 

ITEM 2.

(A) NAME OF PERSONS FILING: PFIZER INC.

(B) ADDRESS OF PRINCIPAL BUSINESS OFFICE OR IF NONE, RESIDENCE:  235 E. 42nd Street, New York, N.Y. 10017

(C) CITIZENSHIP: DELAWARE, U.S.A.

(D) TITLE OF CLASS OF SECURITIES: COMMON STOCK

(E) CUSIP NUMBER: 45104P104

ITEM 3. STATEMENT FILED PURSUANT TO RULE 13D-1(B) OR 13D-2(B) OR (C)

Not applicable. 

ITEM 4. OWNERSHIP.

 (a) Amount beneficially owned: 2,688,172

 (b) Percent of class: 6.6%

 (c) Number of shares as to which the person has: 

 (i) Sole power to vote or to direct the vote: 2,688,172

 (ii) Shared power to vote or to direct the vote: 0

 (iii) Sole power to dispose or to direct the disposition of:  2,688,172

 (iv) Shared power to dispose or to direct the disposition of:     0

  ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS

Not applicable.

ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON

Not applicable.

ITEM 7.  IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED  THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY

Not applicable.

ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP

Not applicable.

ITEM 9. NOTICE OF DISSOLUTION OF GROUP

Not applicable.

ITEM 10. CERTIFICATION.

By signing below I certify that, to the best of my knowledge and belief, the  securities referred to above were not acquired and are not held for the purpose  of or with the effect of changing or influencing the control of the issuer of  the securities and were not acquired and are not held in connection with or  as a  participant in any transaction having that purpose or effect.

 

**Signature**

  After reasonable inquiry and to the best of my knowledge and belief, I certify  that the information set forth in this statement is true, complete and correct.

Dated: August 28, 2007

 PFIZER INC. 

 By: /s/ Lawrence A. Fox  Name: Lawrence A. Fox  Title: Vice President, Assistant General Counsel and  Assistant Secretary