Sec Form 4 Filing - Sanofi @ REGENERON PHARMACEUTICALS INC - 2015-10-06

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Sanofi 2. Issuer Name and Ticker or Trading Symbol REGENERON PHARMACEUTICALS INC [ REGN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 54, RUE LA BOETIE 3. Date of Earliest Transaction (MM/DD/YY) 10/06/2015 (Street) PARIS, I075008 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 10/06/2015 P 1,965 ( 1 ) ( 2 ) A $ 470.4102 ( 1 ) ( 3 ) 23,099,495 I See note ( 4 ) Common Stock 10/06/2015 P 3,625 ( 1 ) ( 2 ) A $ 471.6367 ( 5 ) ( 1 ) 23,103,120 I See note ( 4 ) Common Stock 10/06/2015 P 2,650 ( 1 ) ( 2 ) A $ 472.3657 ( 6 ) ( 1 ) 23,105,770 I See note ( 4 ) Common Stock 10/06/2015 P 1,000 ( 1 ) ( 2 ) A $ 473.3125 ( 7 ) ( 1 ) 23,106,770 I See note ( 4 ) Common Stock 10/06/2015 P 1,000 ( 1 ) ( 2 ) A $ 474.265 ( 8 ) ( 1 ) 23,107,770 I See note ( 4 ) Common Stock 10/06/2015 P 700 ( 1 ) ( 2 ) A $ 476.3543 ( 9 ) ( 1 ) 23,108,470 I See note ( 4 ) Common Stock 10/06/2015 P 100 ( 2 ) A $ 476.85 ( 10 ) 23,108,570 I See note ( 4 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Sanofi 54, RUE LA BOETIE PARIS, I075008 X Signatures /s/ John Felitti, Associate Vice President, Corporate Law, Financial & Securities Law 10/08/2015 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The number of securities reported represents an aggregate number of shares purchased in multiple market transactions over a range of purchase prices. The price reported represents the weighted average price per share. The Reporting Person undertakes to provide the staff of the SEC, the Issuer, or a stockholder of the Issuer, upon request, the number of shares purchased by the Reporting Person at each separate price within the range. ( 2 )Represents shares acquired directly by sanofi-aventis Amerique du Nord ("SAAN"). ( 3 )Purchase prices range from $470.00 to $470.99 per share, inclusive. ( 4 )Indirectly owned through (a) SAAN, a direct, wholly-owned subsidiary of Sanofi, and (b) Aventis Pharmaceuticals Inc. ("Aventis"), an indirect, wholly-owned subsidiary of SAAN. After giving effect to all acquisitions reported on this Form 4, the number of shares beneficially owned directly by SAAN and Aventis was 20,309,018 shares and 2,799,552 shares, respectively. Pursuant to the Amended and Restated Investor Agreement, dated as of January 11, 2014, by and among Sanofi, SAAN, sanofi-aventis US LLC, Aventis (collectively, the "Sanofi Parties") and the Issuer, the Sanofi Parties have agreed to vote their respective shares of the Issuer, subject to specified exceptions, in accordance with the recommendation of the Issuer's Board of Directors. ( 5 )Purchase prices range from $471.00 to $471.94 per share, inclusive. ( 6 )Purchase prices range from $472.00 to $472.96 per share, inclusive. ( 7 )Purchase prices range from $473.00 to $473.76 per share, inclusive. ( 8 )Purchase prices range from $474.01 to $474.45 per share, inclusive. ( 9 )Purchase prices range from $475.82 to $476.75 per share, inclusive. ( 10 )Purchase price was $476.85 per share.

Remarks: Due to technical limitation of the number of transactions reported, this report is 2 of 2.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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