UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D

                   Under the Securities Exchange Act of 1934*
                                (Amendment No. 4)

                         Regeneron Pharmaceuticals, Inc.
- -------------------------------------------------------------------------------
                              (Name of The Company)

                   Common Stock (Par Value $ 0.001 Per Share)
- -------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                   75886F 10 7
- -------------------------------------------------------------------------------
                                 (CUSIP Number)

                                Terry L. Overbey
- -------------------------------------------------------------------------------
                          The Procter & Gamble Company
                           One Procter & Gamble Plaza
                            Cincinnati, OH 45202-3315
                                 (513) 983-4463
            (Name, Address and Telephone Number of Persons Authorized
                     to Receive Notices and Communications)

                                  March 9, 2000
- -------------------------------------------------------------------------------
             (Date of Event which Requires Filing of this Statement)


If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  which is the subject of this  Schedule 13D, and is filing this
schedule because of Rule 13d-1(e), 13d-1(f) or 13d-1(g), check the following box
|_|.

*The  remainder  of this cover page will 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 will 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 will be subject to all other provisions of the Act (however, see the Notes).





                                  SCHEDULE 13D
- -------------------------
CUSIP No.   75886F 10 7
- -------------------------

- ---------- --------------------------------------------------------------------
1          NAME OF REPORTING PERSON
           S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

                    The Procter & Gamble Company
                    Identification Number 31-0411980

- ---------- --------------------------------------------------------------------
2          CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP            (a) |_|
                                                                       (b) |_|

- ---------- --------------------------------------------------------------------
3          SEC USE ONLY


- ---------- --------------------------------------------------------------------
4          SOURCE OF FUNDS

           WC

- ---------- --------------------------------------------------------------------
5          CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
           TO ITEMS 2(d) or 2(e)                                           |_|


- ---------- --------------------------------------------------------------------
6          CITIZENSHIP OR PLACE OF ORGANIZATION

                    Ohio

- ------------------------- -------- --------------------------------------------
                          7        SOLE VOTING POWER

       NUMBER OF
                                            0
         SHARES
                          -------- --------------------------------------------
      BENEFICIALLY        8        SHARED VOTING POWER

        OWNED BY                            5,662,505

                          -------- --------------------------------------------
                          9        SOLE DISPOSITIVE POWER
          EACH
                                            0
       REPORTING

                          -------- --------------------------------------------
         PERSON           10       SHARED DISPOSITIVE POWER

          WITH                              5,662,505

- ------------------------- -------- --------------------------------------------
- ---------- --------------------------------------------------------------------
11         AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                    5,662,505

- ---------- --------------------------------------------------------------------
12         CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

                                                                            |-|


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

                    ------%

- ---------- --------------------------------------------------------------------
14         TYPE OF REPORTING PERSON

                    CO

- ---------- --------------------------------------------------------------------



                                  SCHEDULE 13D
- -------------------------
CUSIP No.   75886F 10 7
- -------------------------

- ---------- --------------------------------------------------------------------
1          NAME OF REPORTING PERSON
           S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

                    Procter & Gamble Pharmaceuticals, Inc.
                    Identification Number  31-1209457

- ---------- --------------------------------------------------------------------
2          CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP            (a) |_|
                                                                       (b) |_|

- ---------- --------------------------------------------------------------------
3          SEC USE ONLY


- ---------- --------------------------------------------------------------------
4          SOURCE OF FUNDS

           WC

- ---------- --------------------------------------------------------------------
5          CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT
           TO ITEMS 2(d) or 2(e)                                           |_|


- ---------- --------------------------------------------------------------------
6          CITIZENSHIP OR PLACE OF ORGANIZATION

                    Ohio

- ------------------------- -------- --------------------------------------------
                          7        SOLE VOTING POWER

       NUMBER OF
                                            0
         SHARES
                          -------- --------------------------------------------
      BENEFICIALLY        8        SHARED VOTING POWER

        OWNED BY                            5,662,505

                          -------- --------------------------------------------
                          9        SOLE DISPOSITIVE POWER
          EACH
                                            0
       REPORTING

                          -------- --------------------------------------------
         PERSON           10       SHARED DISPOSITIVE POWER

          WITH                              5,662,505

- ------------------------- -------- --------------------------------------------
- ---------- --------------------------------------------------------------------
11         AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                    5,662,505

- ---------- --------------------------------------------------------------------
12         CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

                                                                            |-|


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

                    16.54%

- ---------- --------------------------------------------------------------------
14         TYPE OF REPORTING PERSON

                    CO

- ---------- --------------------------------------------------------------------




ITEM 1.    SECURITY AND ISSUER.
           --------------------

           This  Amendment  No. 4 (the  "Amendment  No. 4") to the  Statement on
Schedule 13D  (the  Statement  as so amended,  the  "Statement")  relates to the
Common  Stock,  par value  $.001 per share (the  "Common  Stock)  of  Regeneron
Pharmaceuticals,  Inc., a New York corporation  (the  "Company").  The principal
executive  offices of the  Company are at 777 Old Saw Mill Road,  Tarrytown,  NY
10591.


ITEM 2.    IDENTITY AND BACKGROUND.
           ------------------------

           (a) Name:  The Procter & Gamble Company
               State of Incorporation:  Ohio
               Principal Business:  Manufacture and marketing of consumer
                                    products
               Address of Principal Business:  One Procter & Gamble Plaza
                                               Cincinnati, Ohio 45202

               Name:  Procter & Gamble Pharmaceuticals, Inc.
               State of Incorporation:  Ohio
               Principal Business:  Manufacture and marketing of pharmaceutical
                                    products
               Address of Principal Business:  same

           (b) Not applicable

           (c) Not applicable

           (d) Not applicable

           (e) Not applicable

           (f) Not applicable

ITEM 3.    SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.
           --------------------------------------------------

           Not applicable

ITEM 4.    PURPOSE OF TRANSACTION.
           -----------------------

           (a)  Item 4(a) of the Statement is hereby amended as follows:

           On March  9,  2001,  Procter  & Gamble  Pharmaceuticals,  Inc.  ("P&G
Pharmaceuticals")  entered  into an  agreement  to sell (the  "Sale")  1,000,000
shares  of  Common  Stock  owned  by  P&G  Pharmaceuticals  to  four  affiliated
institutional investors at a cash price of $20.00 per share and for an aggregate
purchase price of $20 million.  The Sale is scheduled to be consummated on March
14,  2001.  Following  the Sale,  the  Reporting  Person will  beneficially  own
5,662,505 the shares of Common Stock. In connection with the Sale, the Reporting
Person, on March 9, 2001, entered into an agreement with the Company pursuant to
which the Reporting  Person agreed not to,  directly or  indirectly,  effect any
sale,  pledge or other  disposition  to any third  party of any other  shares of
Common  Stock  owned by the  Reporting  Person for a period of one year from the
date of such agreement,  except that the Reporting  Person may tender all or any
shares of Common Stock owned by it into any tender or exchange  offer for shares
representing  more than 20% of the  Company's  voting power that is supported by
the Company's  Board or for shares  representing  more than 50% of the Company's
voting power as to which the Company's rights plan is rendered inapplicable as a
result of Company action or final court order.

           (b) None
           (c) None
           (d) None
           (e) None
           (f) None
           (g) None
           (h) None
           (i) None
           (j) None

ITEM 5.    INTERESTS IN SECURITIES OF THE COMPANY.
           ---------------------------------------

           (a)  After  giving  effect  to  the  Sale,   the   Reporting   Person
beneficially owns 5,662,505 shares of Common Stock,  representing  16.54% of the
total shares of Common Stock.

           (b) The  Reporting  Person has sole  voting  power over all shares of
Common  Stock so  beneficially  owned by it and does not share voting power over
any such shares. The Reporting Person has sole dispositive power over all shares
of Common Stock so beneficially owned by it and does not share dispositive power
over any such shares.

           (c) See Item 4(a) for information responsive to this item.

           (d) Not applicable.

           (e) Not applicable.

ITEM 6.    CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS
           WITH RESPECT TO SECURITIES OF THE COMPANY.
           --------------------------------------------------------

           Not applicable

ITEM 7.    MATERIAL TO BE FILED AS EXHIBITS.
           ---------------------------------

           The following documents are filed as Exhibit:

Exhibit 1  Form of Sale Agreement
Exhibit 2  Letter Agreement  between the Company and the Reporting Person with
           respect to the disposition of shares of Common Stock.




                                    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.


March 12, 2001
                                         THE PROCTER & GAMBLE COMPANY




                                         By:    /s/GRETCHEN W. PRICE
                                                -------------------------------
                                         Name:  Gretchen W. Price
                                         Title: Vice President and Treasurer



           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.

March 12, 2001
                                         PROCTER & GAMBLE PHARMACEUTICALS, INC.




                                         By:    /s/GRETCHEN W. PRICE
                                                -------------------------------
                                         Name:  Gretchen W. Price
                                         Title: Vice President and Treasurer



                                    EXHIBIT 1

          PROCTER & GAMBLE  PHARMACEUTICALS,  INC.  ("Seller")  hereby agrees to
sell to [BUYER'S NAME] ("Buyer"),  and Buyer agrees to buy from Seller,  [number
of  shares]  shares of Common  Stock of  REGENERON  PHARMACEUTICALS,  INC.  (the
"Issuer") at $20 per share, or [dollar  amount] in the aggregate.  Seller agrees
that on March 16, 2001, Seller will deliver or cause to be delivered to Buyer at
[Buyer's Address],  a certificate or certificates for such shares, duly endorsed
for transfer to Buyer or with an accompanying stock power or powers in customary
form,  against  payment by Buyer of the purchase price therefor by wire transfer
in  immediately  available  funds to Seller at [bank account] for the account of
The Procter & Gamble Company on March 16, 2001.

          Seller  represents  that  Seller is not,  and has not been  during the
preceding three months, an "affiliate" of the Issuer, as such term is defined in
Rule 144 under the  Securities  Act of 1933, and that such shares may be sold at
this time by Seller  under  such Rule 144  without  limitation  on the amount of
securities sold or the manner of sale.

          IN WITNESS  WHEREOF,  Buyer and Seller have signed this  Agreement  on
March 9, 2001.


                                          PROCTER & GAMBLE PHARMACEUTICALS, INC.



                                          By_________________________

                                          [BUYER]



                                          By_________________________



                                   Exhibit II



                                          March 9, 2001



Regeneron Pharmaceuticals, Inc.
777 Old Saw Mill River Road
Tarrytown, NY  10591-6707

     Re: Lock-Up

Dear Sirs:

     The undersigned,  a stockholder of Regeneron  Pharmaceuticals,  Inc., a New
York  corporation  (the  "Company"),  understands  that the  Company is making a
public  offering of its common  stock,  par value  $0.001 per share (the "Common
Stock").  In  recognition  of the benefit that such an offering will confer upon
the undersigned as a stockholder of the Company, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
undersigned  agrees with the Company  that,  from March 12, 2001 until March 31,
2002,  the  undersigned  will not,  without  the prior  written  consent  of the
Company, directly or indirectly, (i) offer, pledge, sell, contract to sell, sell
any option or contract  to  purchase,  purchase  any option or contract to sell,
grant any option,  right or warrant for the sale of, or otherwise  dispose of or
transfer any shares of the Common Stock or any  securities  convertible  into or
exchangeable  or  exercisable  for Common Stock,  whether now owned or hereafter
acquired by the  undersigned  or with  respect to which the  undersigned  has or
hereafter acquires the power of disposition,  or file any registration statement
under  the  Securities  Act of 1933,  as  amended,  with  respect  to any of the
foregoing or (ii) enter into any swap or any other  agreement or any transaction
that  transfers,  in whole or in part,  directly  or  indirectly,  the  economic
consequence  of  ownership  of the  Common  Stock,  whether  any  such  swap  or
transaction is to be settled by delivery of Common Stock or other securities, in
cash or  otherwise;  provided the  foregoing  will not  prohibit  any  Permitted
Transfers (as defined below). For purposes hereof, a "Permitted  Transfer" shall
mean  (i)  transfers  between  The  Procter  &  Gamble  Company  and  any of its
wholly-owned  subsidiaries,  so long as the  transferee in any case described in
this  clause (i) agrees to be bound by the  restrictions  of this letter and the
undersigned remains responsible for the performance of the transferee,  and (ii)
dispositions  made  pursuant to bona fide  tender or  exchange  offers made by a
third party or the Company for shares of capital  stock of the Company,  so long
as either (x) such offer is for capital  stock  representing  20% or more of the
Company's  voting  power  and  such  offer is  supported  by a  majority  of the
Company's Board of Directors or (y) such offer is for capital stock representing
50% or more of the Company's voting power and the Company's  shareholders rights
plan is  rendered  inapplicable  to such offer by Company  action or final court
order.

                                          Very truly yours,

                                          THE PROCTER & GAMBLE COMPANY



                                          By: /s/MARK A. COLLAR
                                              -----------------------------
                                              Mark A. Collar
                                              Vice President






                                          March 9, 2001



Regeneron Pharmaceuticals, Inc.
777 Old Saw Mill River Road
Tarrytown, NY  10591-6707

     Re: Lock-Up

Dear Sirs:

     The undersigned,  a stockholder of Regeneron  Pharmaceuticals,  Inc., a New
York  corporation  (the  "Company"),  understands  that the  Company is making a
public  offering of its common  stock,  par value  $0.001 per share (the "Common
Stock").  In  recognition  of the benefit that such an offering will confer upon
the undersigned as a stockholder of the Company, and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged, the
undersigned  agrees with the Company  that,  from March 12, 2001 until March 31,
2002,  the  undersigned  will not,  without  the prior  written  consent  of the
Company, directly or indirectly, (i) offer, pledge, sell, contract to sell, sell
any option or contract  to  purchase,  purchase  any option or contract to sell,
grant any option,  right or warrant for the sale of, or otherwise  dispose of or
transfer any shares of the Common Stock or any  securities  convertible  into or
exchangeable  or  exercisable  for Common Stock,  whether now owned or hereafter
acquired by the  undersigned  or with  respect to which the  undersigned  has or
hereafter acquires the power of disposition,  or file any registration statement
under  the  Securities  Act of 1933,  as  amended,  with  respect  to any of the
foregoing or (ii) enter into any swap or any other  agreement or any transaction
that  transfers,  in whole or in part,  directly  or  indirectly,  the  economic
consequence  of  ownership  of the  Common  Stock,  whether  any  such  swap  or
transaction is to be settled by delivery of Common Stock or other securities, in
cash or  otherwise;  provided the  foregoing  will not  prohibit  any  Permitted
Transfers (as defined below). For purposes hereof, a "Permitted  Transfer" shall
mean  (i)  transfers  between  The  Procter  &  Gamble  Company  and  any of its
wholly-owned  subsidiaries,  so long as the  transferee in any case described in
this  clause (i) agrees to be bound by the  restrictions  of this letter and the
undersigned remains responsible for the performance of the transferee,  and (ii)
dispositions  made  pursuant to bona fide  tender or  exchange  offers made by a
third party or the Company for shares of capital  stock of the Company,  so long
as either (x) such offer is for capital  stock  representing  20% or more of the
Company's  voting  power  and  such  offer is  supported  by a  majority  of the
Company's Board of Directors or (y) such offer is for capital stock representing
50% or more of the Company's voting power and the Company's  shareholders rights
plan is  rendered  inapplicable  to such offer by Company  action or final court
order. Very truly yours,

                                          PROCTER & GAMBLE PHARMACEUTICALS, INC.



                                          By: /s/MARK A. COLLAR
                                              ----------------------------------
                                              Mark A. Collar
                                              President