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SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

SCHEDULE 13G
(Rule 13d-102)

INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
TO RULES 13d-1(b) (c) AND (d) AND AMENDMENTS THERETO FILED
PURSUANT TO 13d-2(b)
(Amendment No. 4)

    Repligen Corporation
(Name of Issuer)		    

 
 
 
 
 
    Common Stock
(Title of Class of Securities)		    

 
 
 
 
 
    759916 10 9
(CUSIP Number)		    

 
 
 
 
 
    May 22, 2003
(Date of Event Which Requires Filing of this Statement)		    

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

    o Rule 13d-1(b)
ý Rule 13d-1(c)
o Rule 13d-1(d)
     
CUSIP No. 759916 10 9   13G   Page 2 of 11 Pages
     
1   NAME OF REPORTING PERSON:
 Biotechnology Value Fund, L.P.
I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):		    
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*   (a)  ý
        (b)  o
         
3   SEC USE ONLY    

 
 
 
 
 
4   CITIZENSHIP OR PLACE OF ORGANIZATION

 
 
Delaware
 
 
    5   SOLE VOTING POWER
NUMBER OF       0
SHARES  
BENEFICIALLY   6   SHARED VOTING POWER
OWNED       743,063
BY  
EACH   7   SOLE DISPOSITIVE POWER
REPORTING       0
PERSON  
WITH:   8   SHARED DISPOSITIVE POWER
        743,063
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON    

 
 
743,063
 
 
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*   o

 
 
 
 
 
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)    

 
 
2.49%
 
 
12   TYPE OF REPORTING PERSON*    

 
 
PN
 
 

*SEE INSTRUCTIONS BEFORE FILLING OUT!

      
CUSIP No. 759916 10 9   13G   Page 3 of 11 Pages
     
1   NAME OF REPORTING PERSON:
 Biotechnology Value Fund II, L.P.
I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):		    
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*   (a)  ý
        (b)  o
         
3   SEC USE ONLY    

 
 
 
 
 
4   CITIZENSHIP OR PLACE OF ORGANIZATION    

 
 
Delaware
 
 
    7   SOLE VOTING POWER
NUMBER OF       0
SHARES  
BENEFICIALLY   6   SHARED VOTING POWER
OWNED       496,179
BY  
EACH   7   SOLE DISPOSITIVE POWER
REPORTING       0
PERSON  
WITH:   8   SHARED DISPOSITIVE POWER
        496,179
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON    

 
 
496,179
 
 
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*   o

 
 
 
 
 
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)    

 
 
1.66%
 
 
12   TYPE OF REPORTING PERSON*    

 
 
PN
 
 

*SEE INSTRUCTIONS BEFORE FILLING OUT!

      
CUSIP No. 759916 10 9   13G   Page 4 of 11 Pages
     
1   NAME OF REPORTING PERSON:
 BVF Investments, L.L.C.
I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):		    
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*   (a)  ý
        (b)  o
         
3   SEC USE ONLY    

 
 
 
 
 
4   CITIZENSHIP OR PLACE OF ORGANIZATION    

 
 
Delaware
 
 
    5   SOLE VOTING POWER
NUMBER OF       0
SHARES  
BENEFICIALLY   6   SHARED VOTING POWER
OWNED       1,005,221
BY  
EACH   7   SOLE DISPOSITIVE POWER
REPORTING       0
PERSON  
WITH:   8   SHARED DISPOSITIVE POWER
        1,005,221
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON    

 
 
1,005,221
 
 
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*   o

 
 
 
 
 
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)    

 
 
3.37%
 
 
12   TYPE OF REPORTING PERSON*    

 
 
OO
 
 

*SEE INSTRUCTIONS BEFORE FILLING OUT!

      
CUSIP No. 759916 10 9   13G   Page 5 of 11 Pages
     
1   NAME OF REPORTING PERSON:
 Investment 10, LLC
I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):		    
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*   (a)  ý
        (b)  o
         
3   SEC USE ONLY    

 
 
 
 
 
4   CITIZENSHIP OR PLACE OF ORGANIZATION    

 
 
Illinois
 
 
    5   SOLE VOTING POWER
NUMBER OF       0
SHARES  
BENEFICIALLY   6   SHARED VOTING POWER
OWNED       85,300
BY  
EACH   7   SOLE DISPOSITIVE POWER
REPORTING       0
PERSON  
WITH:   8   SHARED DISPOSITIVE POWER
        85,300
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON    

 
 
85,300
 
 
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*   o

 
 
 
 
 
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)    

 
 
0.29%
 
 
12   TYPE OF REPORTING PERSON*    

 
 
OO
 
 

*SEE INSTRUCTIONS BEFORE FILLING OUT!

      
CUSIP No. 759916 10 9   13G   Page 6 of 11 Pages
     
1   NAME OF REPORTING PERSON:
 BVF Partners L.P.
I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):		    
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*   (a)  ý
        (b)  o
         
3   SEC USE ONLY    

 
 
 
 
 
4   CITIZENSHIP OR PLACE OF ORGANIZATION    

 
 
Delaware
 
 
    5   SOLE VOTING POWER
NUMBER OF       0
SHARES  
BENEFICIALLY   6   SHARED VOTING POWER
OWNED       2,329,763
BY  
EACH   7   SOLE DISPOSITIVE POWER
REPORTING       0
PERSON  
WITH:   8   SHARED DISPOSITIVE POWER
        2,329,763
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON    

 
 
2,329,763
 
 
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*   o

 
 
 
 
 
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)    

 
 
7.81%
 
 
12   TYPE OF REPORTING PERSON*    

 
 
PN
 
 

*SEE INSTRUCTIONS BEFORE FILLING OUT!

      
CUSIP No. 759916 10 9   13G   Page 7 of 11 Pages
     
1   NAME OF REPORTING PERSON:
 BVF Inc.
I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES ONLY):		    
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP*   (a)  ý
        (b)  o
         
3   SEC USE ONLY    

 
 
 
 
 
4   CITIZENSHIP OR PLACE OF ORGANIZATION    

 
 
Delaware
 
 
    5   SOLE VOTING POWER
NUMBER OF       0
SHARES  
BENEFICIALLY   6   SHARED VOTING POWER
OWNED       2,329,763
BY  
EACH   7   SOLE DISPOSITIVE POWER
REPORTING       0
PERSON  
WITH:   8   SHARED DISPOSITIVE POWER
        2,329,763
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON    

 
 
2,329,763
 
 
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES*   o

 
 
 
 
 
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)    

 
 
7.81%
 
 
12   TYPE OF REPORTING PERSON*    

 
 
CO
 
 

*SEE INSTRUCTIONS BEFORE FILLING OUT!

      
CUSIP No. 759916 10 9   13G   Page 8 of 11 Pages
     

ITEM 1(a). NAME OF ISSUER:

        Repligen Corporation ("Repligen")

ITEM 1(b). ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES:

    41 Seyton Street
Building 1, Suite 100
Waltham, Massachusetts 02443

ITEM 2(a). NAME OF PERSON FILING:

        This Amendment to Schedule 13G is being filed on behalf of the following persons* (the "Reporting Persons"):

        *      Attached as Exhibit 1 is a copy of an agreement among the Reporting Persons that this Amendment to Schedule 13G is being filed on behalf of each of them.

ITEM 2(b). ADDRESS OF PRINCIPAL BUSINESS OFFICE:

        The principal business office of the Reporting Persons comprising the group filing this Amendment to Schedule 13G is located at 227 West Monroe Street, Suite 4800, Chicago, Illinois, 60606.

ITEM 2(c). CITIZENSHIP:

    BVF:   a Delaware limited partnership
    BVF2:   a Delaware limited partnership
    Investments:   a Delaware limited liability company
    Investment 10:   an Illinois limited liability company
    Partners:   a Delaware limited partnership
    BVF Inc.:   a Delaware corporation

ITEM 2(d). TITLE OF CLASS OF SECURITIES:

        This Amendment to Schedule 13G is being filed with respect to the common stock, par value $.01 per share (the 'Common Stock'), of Repligen. The Reporting Persons' percentage ownership of Common Stock is based on 29,838,973 shares of Common Stock being outstanding.

ITEM 2(e). CUSIP Number:

        759916 10 9

     
CUSIP No. 759916 10 9   13G   Page 9 of 11 Pages
     

ITEM 3. IF THIS STATEMENT IS FILED PURSUANT TO RULE 13d-1(b), or 13d-2(b) or (c) CHECK WHETHER THE PERSON FILING IS: One of the following

        Not applicable as this Amendment to Schedule 13G is filed pursuant to Rule 13d-1(c).

ITEM 4. OWNERSHIP:

        The information in items 1 and 5 through 11 on the cover pages (pp. 2 - 7) on this Amendment to Schedule 13G is hereby incorporated by reference.

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

        If this statement is being filed to report the fact that as of the date hereof the Reporting Persons have ceased to be the beneficial owner of more than five percent of the class of securities check the following. o

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

        Pursuant to the operating agreement of Investments, Partners is authorized, among other things, to invest the funds of Ziff Asset Management, L.P., the majority member of Investments, in shares of the Common Stock and to vote and exercise dispositive power over those shares of Common Stock. Partners and BVF Inc. share voting and dispositive power over the shares of Common Stock beneficially owned by BVF, BVF2, Investments and those owned by Investment 10, on whose behalf Partners acts as investment manager and, accordingly, Partners and BVF Inc. have beneficial ownership of all of the shares of Common Stock owned by such parties.

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 A GROUP:

        Not applicable.

ITEM 9. NOTICE OF DISSOLUTION OF GROUP:

        Not applicable.

     
CUSIP No. 759916 10 9   13G   Page 9 of 11 Pages
     

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.

        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:   May 28, 2003

 
 
BIOTECHNOLOGY VALUE FUND, L.P.

 
 
By:
 
BVF Partners L.P., its general partner

 
 
 
 
By:
 
BVF Inc., its general partner

 
 
 
 
 
 
By:
 
/s/  MARK N. LAMPERT      
               
Mark N. Lampert
President

 
 
BIOTECHNOLOGY VALUE FUND II, L.P.

 
 
By:
 
BVF Partners L.P., its general partner

 
 
 
 
By:
 
BVF Inc., its general partner

 
 
 
 
 
 
By:
 
/s/  MARK N. LAMPERT      
               
Mark N. Lampert
President

 
 
BVF INVESTMENTS, L.L.C.

 
 
By:
 
BVF Partners L.P., its manager

 
 
 
 
By:
 
BVF Inc., its general partner

 
 
 
 
 
 
By:
 
/s/  MARK N. LAMPERT      
               
Mark N. Lampert
President

 
 
INVESTMENT 10, L.L.C.

 
 
By:
 
BVF Partners L.P., its attorney-in-fact

 
 
 
 
By:
 
BVF Inc., its general partner

 
 
 
 
 
 
By:
 
/s/  MARK N. LAMPERT      
               
Mark N. Lampert
President

 
 
BVF PARTNERS L.P.

 
 
By:
 
BVF Inc., its general partner

 
 
 
 
 
 
By:
 
/s/  MARK N. LAMPERT      
               
Mark N. Lampert
President

 
 
BVF INC.

 
 
 
 
 
 
By:
 
/s/  MARK N. LAMPERT      
               
Mark N. Lampert
President


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SCHEDULE 13D