UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

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Rule 13d-1(b)

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Rule 13d-1(c)

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Rule 13d-1(d)

CUSIP No.  75886F 10 7

1.

Names of Reporting Persons. I.R.S. Identification Nos. of above persons (entities only)
Sanofi-Aventis

Not applicable

2.

Check the Appropriate Box if a Member of a Group (See Instructions)

(a)

o

(b)

o

3.

SEC Use Only

4.

Citizenship or Place of Organization
The Republic of France

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5.

Sole Voting Power
2,799,552 shares

6.

Shared Voting Power 
0 shares

7.

Sole Dispositive Power 
0 shares

8.

Shared Dispositive Power
2,799,552 shares

9.

Aggregate Amount Beneficially Owned by Each Reporting Person
2,799,552 shares

10.

Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions)  o

11.

Percent of Class Represented by Amount in Row (9)
5.2%

12.

Type of Reporting Person (See Instructions)
CO

Item 1.

(a)

Name of Issuer
Regeneron Pharmaceuticals Incorporated

(b)

Address of Issuer’s Principal Executive Offices
777 Old Saw Mill River Road, Tarrytown, New York, 10591-6707

Item 2.

(a)

Name of Person Filing
(i)            Sanofi-Aventis

(ii)           Aventis Pharmaceuticals Inc

(iii)          Aventis Holdings Inc.

(iv)          Aventis Inc.

(b)

Address of Principal Business Office or, if none, Residence
(i)            174 avenue de France, 75013 ParisFrance

(ii)           300 Somerset Corporate Boulevard, Bridgewater, New Jersey  08807

(iii)          3711 Kenneth Pike, Suite 200 Greenville, Delaware 19807

(iv)          300 Somerset Corporate Boulevard, Bridgewater, New Jersey  08807

(c)

Citizenship
(i)            Sanofi-Aventis : France

(ii)           Aventis Pharmaceuticals Inc : Delaware

(iii)          Aventis Holdings Inc.: Delaware

(iv)          Aventis Inc.: Pennsylvania

(d)

Title of Class of Securities
COMMON STOCK, $.001 PAR VALUE

(e)

CUSIP Number
75886F107

Item 3.

If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

o

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b)

o

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c)

o

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d)

o

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C 80a-8).

(e)

o

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

(f)

o

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

(g)

o

A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h)

o

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

o

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

o

Group, in accordance with §240.13d-1(b)(1)(ii)(J).

Item 3 is not applicable.

Item 4.

Ownership

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

(a)

Amount beneficially owned:   

(i) Sanofi-Aventis : 2,799,552

(ii) Aventis Pharmaceuticals Inc : 2,799,552

(iii) Aventis Holdings Inc.: 2,799,552

(iv) Aventis Inc. : 2,799,552

(b)

Percent of class:   

(i) Sanofi-Aventis : 5.2%

(ii) Aventis Pharmaceuticals Inc : 5.2%

(iii) Aventis Holdings Inc.: 5.2%

(iv) Aventis Inc. : 5.2%

(c)

Number of shares as to which the person has:

(i)

Sole power to vote or to direct the vote

(i) Sanofi-Aventis : 2,799,552

(ii) Aventis Pharmaceuticals Inc : 2,799,552

(iii) Aventis Holdings Inc.: 2,799,552

(iv) Aventis Inc. : 2,799,552

(ii)

Shared power to vote or to direct the vote    

None

(iii)

Sole power to dispose or to direct the disposition of   

None

(iv)

Shared power to dispose or to direct the disposition of   

(i) Sanofi-Aventis : 2,799,552

(ii) Aventis Pharmaceuticals Inc : 2,799,552

(iii) Aventis Holdings Inc.: 2,799,552

(iv) Aventis Inc. : 2,799,552

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 person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following   o.

Item 5 is not applicable.

Item 6.

Ownership of More than Five Percent on Behalf of Another Person

Item 6 is not applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person

Item 7 is not applicable.

Item 8.

Identification and Classification of Members of the Group

Item 8 is not applicable.

Item 9.

Notice of Dissolution of Group

Item 9 is not applicable.

Item 10.

Certification

Item 10 is not applicable.