GENZYME CORPORATION DIRECTORS' DEFERRED COMPENSATION PLAN

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Exhibit 10.16

GENZYME CORPORATION DIRECTORS' DEFERRED
COMPENSATION PLAN

ARTICLE I

GENERAL

        1.1     Establishment of Plan.     Genzyme Corporation ("Genzyme") established the Genzyme Directors' Deferred Compensation Plan (the "plan"), effective as of May 16, 1996, to allow each member of the Genzyme Board of Directors who is not also an officer or employee of Genzyme or its subsidiaries (an "outside director") to defer receipt of all or a portion of the cash compensation payable to him or her as such a director of Genzyme until (i) with respect to compensation earned prior to January 1, 2005, the termination of his or her service as a director, or (ii) with respect to compensation earned on or after January 1, 2005, his or her Termination of Service as defined in Section 3.8, or (iii) with respect to compensation whenever earned, but subject to the requirements set forth in Section 3.1, such other date as may be specified by the director. The plan as set forth below was amended and restated effective December 1, 2008.

        1.2     No Right to Corporate Assets.     The plan is unfunded and Genzyme will not be required to set aside, segregate, or deposit any funds or assets of any kind to meet its obligations hereunder. Nothing in the plan will give a participant, a participant's beneficiary or any other person any equity or other interest in the assets of Genzyme, or create a trust of any kind or a fiduciary relationship of any kind between Genzyme and any such person. Any rights that a participant, beneficiary or other person may have under the plan will be solely those of a general unsecured creditor of Genzyme.

        1.3     Limitation on Rights Created by Plan.     Nothing in the plan will give a participant any right to continue as a director of Genzyme.

        1.4     Nonalienation of Benefits.     The rights and benefits of a participant in the plan are personal to the participant. No interest, right or claim under the plan and no distribution therefrom will be assignable, transferable or subject to sale, mortgage, pledge, hypothecation, anticipation, garnishment, attachment, execution or levy, except by designation of beneficiaries as provided in Section 3.5.

        1.5     Binding Effect of Plan.     The plan will be binding upon and inure to the benefit of participants and designated beneficiaries and their heirs, executors and administrators, and to the benefit of Genzyme and its assigns and successors in interest.

        1.6     Administration.     The plan will be administered by the Secretary of Genzyme, who will have sole responsibility for its interpretation.

        1.7     Interpretation.     The plan will be construed, enforced and administered according to the laws of the Commonwealth of Massachusetts.

ARTICLE II

DEFERRAL OF COMPENSATION

        2.1     Deferral Agreement.     Any active outside director (a "participant") is eligible to participate in the plan. For compensation earned on or after January 1, 2005, the following deferral election rules shall apply:

        (a)     Existing Outside Directors.     A participant may participate in the plan by executing an agreement before the first day of any calendar year (beginning on or after January 1, 2005) in which such agreement will take effect authorizing Genzyme to defer all or a portion of his or her compensation as director (the "deferral agreement"). A deferral agreement will become effective for compensation earned in the immediately following calendar year and remain in effect for

compensation earned in each succeeding calendar year unless the participant files a written revocation or superseding deferral agreement with the Secretary before the date that the deferral agreement is irrevocable. A deferral agreement for any particular year is irrevocable after the last day of the immediately preceding calendar year.

        (b)     New Outside Directors.     An individual who becomes a participant for the first time may participate in the plan by executing an agreement within 30 days after the date that his or her term as an outside director begins, authorizing Genzyme to defer all or a portion of his or eligible compensation during that calendar year as outside director (the "first-year deferral agreement"). A first-year deferral agreement will become effective for compensation earned beginning on the 31st day after becoming an outside director unless the participant files a written revocation or superseding deferral agreement with the Secretary before the date that the first-year deferral agreement is irrevocable. A first-year deferral agreement is irrevocable after 30 days following the date that an outside director's term begins. After a first-year deferral agreement is effective, Section 2.1(a) applies for compensation earned in each succeeding calendar year. Whether an individual is eligible for the first-year deferral rules of this Section 2.1(b) shall be determined in accordance with the regulations under Section 409A of the Internal Revenue Code of 1986, as amended (the "Code" and "Section 409A").

        2.2     Amount of Deferral.     Each participant may elect in his or her deferral agreement to defer 25 percent, 50 percent, 75 percent or 100 percent of the total cash compensation paid to the participant as an outside director of Genzyme.

        2.3     Deferral Account.     For bookkeeping purposes only, the Secretary will establish and maintain an account (the "deferral account") for each participant that documents the compensation deferred by the participant, earnings credited to the account and payments from the account. The deferral account will consist of a subaccount for amounts earning interest, which will be denominated on a dollar basis (the "cash account"), and a subaccount for amounts invested in hypothetical shares of Genzyme Common Stock, $0.01 par value ("Genzyme Stock") which will be denominated on a share basis (the "stock account"). Each participant will indicate in his or her deferral agreement the percentage of future deferrals to be invested in the cash account and the stock account. Amounts may not be transferred between the cash account and the stock account.

        2.4     Cash Account.     As of the first day of each calendar quarter, the Secretary will credit to the participant's cash account an amount equal to the amount of compensation otherwise payable to the participant in the preceding calendar quarter that the participant has elected to defer and invest in the cash account. As of the last day of each calendar quarter, the Secretary will credit interest on the balance in the cash account on that date at the rate paid on 90-day Treasury bills hypothetically purchased on the first day of such calendar quarter. For a participant receiving installment payments, interest will be credited on the balance from time to time remaining in the cash account until the account has been completely paid.

        2.5     Stock Account.     As of the first day of each calendar quarter, the Secretary will credit to the participant's stock account a number of shares of Genzyme Stock equal to the amount of compensation otherwise payable to the participant in the preceding calendar quarter that the participant has elected to defer and invest in Genzyme Stock divided by the stock price for Genzyme Stock. The stock price shall mean the average of the closing price of Genzyme Stock for all trading days during the preceding calendar quarter as reported by the NASDAQ National Market. As of the date of payment of any cash dividend on Genzyme Stock, the Secretary will credit to the stock account a number of shares of Genzyme Stock equal to (i) the cash dividend per share times the number of shares credited to the stock account as of the dividend record date divided by (ii) the closing price for Genzyme Stock on the date of payment of the dividend. As of the date of payment of any stock dividend on Genzyme Stock, the Secretary will credit to the stock account a number of shares equal to the per-share stock dividend declared times the number of shares of Genzyme Stock credited to the stock account as of the dividend record date. In the event of any stock dividend, recapitalization, reorganization, merger, consolidation, split-up, spin-off, exchange of shares or similar change affecting Genzyme Stock, appropriate

adjustment will be made in the number and/or kind of shares credited to the stock account. The stock account is maintained for bookkeeping purposes only, and shares credited to the stock account represent a notional investment only. Prior to distribution to a participant under Section 3.3 or 3.4, a participant will have no rights as a stockholder with respect to amounts credited to the stock account. Shares will include fractional shares computed to three decimal places.

        2.6     Shares Subject to the Plan.     The aggregate number of shares of Common Stock which may be issued under the plan is 105,962 shares of Genzyme Stock. In the event of any stock dividend, split-up, combination or reclassification of shares, recapitalization or similar capital change relating to the common stock, the maximum aggregate number and kind of shares or securities of Genzyme that may be issued under the plan shall be appropriately adjusted by the Genzyme Board of Directors (whose determination shall be conclusive).

ARTICLE III

PAYMENT OF DEFERRED COMPENSATION

        3.1     Commencement of Payment.     

        (a)     Compensation Earned Before January 1, 2005.     Each participant who participated in the plan with respect to compensation earned before January 1, 2005 elected in his or her deferral agreement a payment commencement year that was to be either (i) the calendar year following his or her termination of service as a director or (ii) another specified calendar year. If a participant elected a payment commencement year described in (ii) above, the earliest calendar year that a participant could elect was the second calendar year following the year in which the election was made. Elections were irrevocable.

        (b)     Compensation Earned On or After January 1, 2005.     With respect to compensation earned on or after January 1, 2005, a participant must elect in his or her deferral agreement a payment commencement year that is either (i) the calendar year following his or her Termination of Service or (ii) anothe