Sanofi — Director's Dealing 2011

Apr 8, 2011

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: GENZYME CORP (GENZ)
CIK: 0000732485
Period of Report: 2011-04-06

Reporting Person: SANOFI-AVENTIS (10% Owner)
Reporting Person: GC Merger Corp. (10% Owner)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2011-04-06	Common Stock, $0.01 par value	P	3947680	—	Acquired	187986225	Indirect
2011-04-07	Common Stock, $0.01 par value	P	44891208	—	Acquired	232877433	Indirect
2011-04-08	Common Stock, $0.01 par value	P	4435393	—	Acquired	237312826	Indirect
2011-04-08	Common Stock, $0.01 par value	P	16245894	$76.33	Acquired	253558720	Indirect

Footnotes

F1: Reflects shares purchased in an exchange offer.

F2: On April 6, 2011, these shares of Genzyme Corporation ("Genzyme") common stock were exchanged for cash and a contingent value right (each, a "CVR") pursuant to GC Merger Corp.'s ("Purchaser") offer to exchange each issued and outstanding share of Genzyme common stock for $74.00 in cash and one CVR. The closing price of Genzyme common stock on April 5, 2011 was $76.33.

F3: The shares are held by Purchaser. The Purchaser is a direct, wholly-owned subsidiary of sanofi-aventis ("Parent"). The shares may also be deemed to be indirectly beneficially owned by Parent.

F4: On April 7, 2011, these shares of Genzyme common stock were exchanged for cash and one CVR pursuant to Purchaser's offer to exchange each issued and outstanding share of Genzyme common stock for $74.00 in cash and one CVR. The closing price of Genzyme common stock on April 6, 2011 was 76.38.

F5: On April 8, 2011, these shares of Genzyme common stock were exchanged for cash and one CVR pursuant to Purchaser's offer to exchange each issued and outstanding share of Genzyme common stock for $74.00 in cash and one CVR. The closing price of Genzyme common stock on April 7, 2011 was 76.33.

F6: Reflects shares acquired by Purchaser pursuant to the exercise of the "top-up" option provided for in the Agreement and Plan of Merger, dated as of February 16, 2011 among Parent, Purchaser and Genzyme.