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                                                                   Exhibit 10.19

                               GENZYME CORPORATION

                        1999 EMPLOYEE STOCK PURCHASE PLAN

1.   PURPOSE.

     The purpose of this 1999 Employee Stock Purchase Plan (the "Plan") is to
provide employees of Genzyme Corporation (the "Company") and its subsidiaries
who wish to become shareholders of the Company an opportunity to purchase shares
of the Company's common stock, $0.01 par value (the "Shares"). The Plan is
intended to qualify as an "employee stock purchase plan" within the meaning of
Section 423 of the Internal Revenue Code of 1986, as amended (the "Code").

     The Plan constitutes an amendment and restatement of the Company's 1990
Employee Stock Purchase Plan (the "1990 Plan"), which is hereby merged with and
into the Plan, and the separate existence of the 1990 Plan shall terminate on
the effective date of the Plan. The rights and privileges of the holders of
outstanding rights under the 1990 Plan shall not be adversely affected by the
foregoing action.

2.   ELIGIBLE EMPLOYEES.

     Subject to the provisions of Sections 7, 8 and 9 below, any individual who
is in the full-time employment (as defined below) of the Company, or any of its
subsidiaries (as defined in Section 425(f) of the Code), the employees of which
are designated by the Board of Directors as eligible to participate in the Plan,
is eligible to participate in any Offering of Shares (as defined in Section 3
below) made by the Company hereunder. Full-time employment shall include all
employees whose customary employment is:

     (a)  20 hours or more per week; and

     (b)  more than five months

in the calendar year during which said Offering Date (as defined in Section 3
below) occurs or in the calendar year immediately preceding such year.

3.   OFFERING DATES.

     From time to time, the Company, by action of the Board of Directors, will
grant rights to purchase the Shares to employees eligible to participate in the
Plan pursuant to one or more offerings (each of which is an "Offering") on a
date or series of dates (each of which is an "Offering Date") designated for
this purpose by the Board of Directors.

4.   PRICES.

     The price per share for each grant of rights hereunder shall be the lesser
of:

     (a)  eighty-five percent (85%) of the fair market value of a Share on the
Offering Date on which such right was granted; or

     (b)  eighty-five percent (85%) of the fair market value of a Share on the
date such right is exercised. At its discretion, the Board of Directors may
determine a higher price for a grant of rights.

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5.   EXERCISE OF RIGHTS AND METHOD OF PAYMENT.

     (a)  Rights granted under the Plan will be exercisable periodically on
specified dates as determined by the Board of Directors.

     (b)  The method of payment for Shares purchased upon exercise of rights
granted shall be through regular payroll deductions or by lump sum cash payment
or both, as determined by the Board of Directors. No interest shall be paid upon
payroll deductions unless specifically provided for by the Board of Directors.

     (c)  Any payments received by the Company from a participating employee and
not utilized for the purchase of Shares upon exercise of a right granted
hereunder shall be promptly returned to such employee by the Company after
termination of the right to which the payment relates.

6.   TERM OF RIGHTS.

     The total period from an Offering Date to the last date on which rights
granted on that Offering Date are exercisable (the "Offering Period") shall in
no event be longer than twenty-seven (27) months. The Board of Directors when it
authorizes an Offering may designate one or more exercise periods during the
Offering Period. Rights granted on an Offering Date shall be exercisable in full
on the Offering Date or in such proportion on the last day of each exercise
period as the Board of Directors determines.

7.   SHARES SUBJECT TO THE PLAN.

     The aggregate number of shares that may be issued upon exercise of options
granted under this Plan is 4,829,391. Appropriate adjustments in the number of
Shares subject to the Plan, in the number of Shares covered by outstanding
rights granted hereunder, in the exercise price of the rights and in the maximum
number of Shares which an employee may purchase (pursuant to Section 8 below)
shall be made to give effect to any mergers, consolidations, reorganizations,
recapitalizations, stock splits, stock dividends or other relevant changes in
the capitalization of the Company occurring after the effective date of the
Plan, provided that no fractional Shares shall be subject to a right and each
right shall be adjusted downward to the nearest full Share. Any agreement of
merger or consolidation shall include provisions for protection of the then
existing rights of participating employees under the Plan. Either authorized and
unissued Shares or issued Shares heretofore or hereafter reacquired by the
Company may be subject to rights under the Plan. If for any reason any right
under the Plan terminates in whole or in part, Shares subject to such terminated
right may be subject to a right under the Plan.

8.   LIMITATIONS ON GRANTS.

     (a)  No employee shall be granted a right hereunder if such employee,
immediately after the right is granted would own stock or rights to purchase
stock possessing five percent (5%) or more of the total combined voting power or
value of all series of common stock of the Company, or of any subsidiary,
computed in accordance with Section 423(b)(3) of the Code.

     (b)  No employee shall be granted a right which permits the employee's
rights to purchase shares under all employee stock purchase plans of the Company
and its subsidiaries to accrue at a rate which exceeds twenty-five thousand
dollars ($25,000) (or such other maximum as may be prescribed from time to time
by the Code) of the fair market value of such shares (determined at the time
such right is granted) for each calendar year in which such right is outstanding
at any time in accordance with the provisions of Section 423(b)(8) of the Code.

     (c)  No right granted to any participating employee under an Offering, when
aggregated with rights granted under any other Offering still exercisable by the
participating employee, shall cover more shares than may be purchased at an
exercise price not to exceed fifteen percent (15%) of the employee's

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annual rate of compensation on the date the employee elects to participate in
the Offering or such lesser percentage as the Board of Directors may determine.

9.   LIMIT ON PARTICIPATION.

     Participation in an Offering shall be limited to eligible employees who
elect to participate in such Offering in the manner, and within the time
limitations, established by the Board of Directors when it authorizes the
Offering.

10.  CANCELLATION OF ELECTION TO PARTICIPATE.

     An employee who has elected to participate in an Offering may cancel such
election as to all (but not part) of the unexercised rights granted under such
Offering by giving written notice of such cancellation to the Company before the
expiration of any exercise period. Any amounts paid by the employee for the
Shares or withheld for the purchase of Shares from the employee's compensation
through payroll deductions shall be paid to the employee, without interest
unless otherwise determined by the Board of Directors, upon such cancellation.

11.  TERMINATION OF EMPLOYMENT.

     Upon the termination of employment for any reason, including the death of
the employee, before the date on which any rights granted under the Plan are
exercisable, all such rights shall immediately terminate and amounts paid by the
employee for the Shares or withheld for the purchase of Shares from the
employee's compensation through payroll deductions shall be paid to the employee
or to the employee's estate, without interest unless otherwise determined by the
Board of Directors.

12.  EMPLOYEE'S RIGHTS AS SHAREHOLDER.

     No participating employee shall have any rights as a shareholder in the
Shares covered by a right granted hereunder until such right has been exercised,
full payment has been made for the corresponding Share and the Share certificate
is actually issued.

13.  RIGHTS NOT TRANSFERABLE.

     Rights under the Plan are not assignable or transferable by a participating
employee and are exercisable only by the employee.

14.  AMENDMENTS TO OR DISCONTINUATION OF THE PLAN.

     The Board of Directors of the Company shall have the right to amend, modify
or terminate the Plan at any time without notice; provided, however, that the
then existing rights of all participating employees shall not be adversely
affected thereby, and provided further that, subject to the provisions of
Section 7 above, no such amendment to the Plan shall, without the approval of
the shareholders of the Company, increase the total number of Shares which may
be offered under the Plan.

15.  EFFECTIVE DATE AND APPROVALS.

     Subject to the approval of the shareholders of the Company, this Plan shall
be effective on March 24, 1999, the date it was adopted by the Board of
Directors.

     The Company's obligation to offer, sell and deliver its Shares under the
Plan is subject to (i) the approval of any governmental authority required in
connection with the authorization, issuance or sale of such Shares, (ii)
satisfaction of the listing requirements of any national securities exchange on
which the

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Shares are then listed and (iii) compliance, in the opinion of the Company's
counsel, with all applicable federal and state securities and other laws.

16.  TERM OF PLAN.

     No rights shall be granted under the Plan after March 24, 2009.

17.  ADMINISTRATION OF THE PLAN.

     The Board of Directors or any committee or person(s) to whom it delegates
its authority (the "Administrator") shall administer, interpret and apply all
provisions of the Plan as it deems necessary. Nothing contained in this Section
shall be deemed to authorize the Administrator to alter or administer the
provisions of the Plan in a manner inconsistent with the provisions of Section
423 of the Code.

18.  RIGHTS LIMITED.

     In no event shall the Plan form a part of an employee's contract of
employment or service, if any. The Plan shall not confer upon any employee of
the Company or its subsidiaries any right with respect to the continuance of his
or her employment by, or other service with, the Company or its subsidiary, nor
shall it limit the right of the Company or its subsidiaries to terminate the
employee or otherwise change the terms of employment. The loss of existing or
potential profit in any Offering of Shares shall not constitute an element of
damages in the event of termination of employment for any reason, even if the
termination is in violation of an obligation of the Company or its subsidiary to
the employee.

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                                                                 Exhibit 10.20

                     GENZYME CORPORATION DIRECTORS' DEFERRED
                                COMPENSATION PLAN

                                    ARTICLE I

                                     GENERAL

         1.1 ESTABLISHMENT OF PLAN. Genzyme Corporation ("Genzyme") hereby
establishes 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 to defer receipt of
all or a portion of the cash compensation payable to him or her as a director of
Genzyme until his or her termination of service as a director or, subject to
requirements set forth in Section 3.1, such other date as may be specified by
him or her.

         1.2 NO RIGHT TO CORPORATE ASSETS. This 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 this 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 this plan will be solely
those of a general unsecured creditor of Genzyme.

         1.3 LIMITATION ON RIGHTS CREATED BY PLAN. Nothing in this 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 this plan are personal to the participant. No interest, right or claim under
this 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 3.6.

         1.5 BINDING EFFECT OF PLAN. This 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. This plan will be administered by the Clerk of
Genzyme who will have sole responsibility for its interpretation.

         1.7 INTERPRETATION. This 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 member of the Board of Directors of
Genzyme who is not an officer or employee of Genzyme or its subsidiaries (an
"outside director") is eligible to participate in this plan. An outside director
may participate in the plan by executing an agreement before the first day of
any calendar quarter 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 remain in effect for each
succeeding calendar quarter unless the participant files a written revocation or
superseding deferral agreement with the Clerk. A deferral agreement for any
particular quarter is irrevocable after the last day of the immediately
preceding calendar quarter.

         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 Clerk will
establish and maintain an account (the "deferral account") for each participant
which 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
Clerk 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 which the participant has elected to defer and invest in the
cash account. As of the last day of each calendar quarter, the Clerk 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
Clerk 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 which 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 applicable calendar quarter as reported by
the Nasdaq National Market. As of the date of payment of any cash dividend on
Genzyme Stock, the Clerk will credit to the stock account a number of shares of
Genzyme Stock upon which such dividend was declared 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 Clerk will credit to the stock account a number
of shares equal to the stock dividend declared times the number of shares of
Genzyme Stock upon which such dividend was declared 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.
Prior to distribution to a participant under Section 3.3 or 3.4, shares credited
to the stock account are not considered actual shares of common stock of Genzyme
for any purpose and a participant will have no rights as a stockholder with
respect to such shares. Shares will include fractional shares computed to three
decimal places.

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         2.6 SHARES SUBJECT TO THE PLAN. The aggregate number of shares of
Common Stock which may be optioned under this 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. Each participant will elect in his or her
deferral agreement to have payments commence in the calendar year following his
or her termination of service as a director or such other calendar year as may
be specified; provided, however, that if a participant elects to have payments
commence in a calendar year other than the calendar year following his or her
termination of service as a director, the earliest calendar year that a
participant may elect to have payments commence shall be the second calendar
year following the date of such election. For example, a deferral agreement
executed in 1996 may not specify a payment commencement date earlier than 1998.
Such election will be irrevocable.

         3.2 ELECTION OF FORM OF PAYMENT. Each participant will elect in his or
her deferral agreement to have his or her deferral account paid in either a lump
sum or in annual installments for a period specified by the participant, which
period may not exceed five years.

         3.3 LUMP SUM PAYMENTS. A participant who elects to have his or her
deferral account paid in a lump sum will receive the lump sum payment on or
before March 1 of the year specified in the deferral agreement for commencement
of payment. The lump sum payment will consist of (a) cash in the amount credited
to his or her cash account, and (b) subject to Section 3.5, the number of shares
of Genzyme Stock credited to his or her stock account; provided, however, that
no fractional shares will be issued under the plan and the number of shares
issued will be rounded down to the nearest full share.

         3.4 INSTALLMENT PAYMENTS. A participant who elects to have his or her
deferral account paid in annual installments will receive an installment payment
on or before March 1 of each year that installments are due commencing with the
year specified in his or her deferral agreement. Each installment payment will
consist of (a) cash in the amount credited to his or her cash account on the
date of payment divided by the number of annual installments remaining to be
paid, and (b) subject to Section 3.5, the number of shares of Genzyme Stock
credited to his or her stock account divided by the number of annual
installments remaining to be paid; provided, however, that no fractional shares
will be issued under the plan and the number of shares issued will be rounded
down to the nearest full share.

         3.5 LIMITATION ON STOCK DISTRIBUTIONS. If a participant would receive
any payment from his or her stock account before the end of the period during
which his or her transactions in Genzyme's equity securities are subject to
reporting under Section 16 of the Securities Act of 1933, such payments shall be
made in accordance with Section 3.3 or 3.4, as applicable, except that in lieu
of shares, the participant shall receive cash in an amount equal to the number
of shares of Genzyme Stock in his or her stock account times the closing price
for Genzyme Stock as of the trading day preceding the date of distribution.

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         3.6 BENEFICIARIES. A participant may designate in his or her deferral
agreement a beneficiary or beneficiaries (which may be an entity other than a
natural person) to receive any payments to be made upon his or her death. A
participant may elect to have payments to beneficiaries paid in a lump sum or in
annual installments for a period not to exceed five years. At any time, and from
time to time, a participant may change or revoke his or her designation of
beneficiary or form of payment without the consent of any beneficiary. Any such
designation, change or revocation must be made in writing and filed with the
Clerk. If the participant designates more than one beneficiary, any payments to
beneficiaries will be made in equal percentages unless the participant
designates otherwise. Any portion of a participant's deferral account that is
not disposed of by designation of beneficiary upon the participant's death will
be paid to his or her estate.

         3.7 PAYMENTS ON DEATH. If a participant dies before full payment of his
or her deferral account, Genzyme will make payments to the participant's
designated beneficiary or beneficiaries, or to his or her estate, of the amount
remaining in the deceased participant's deferral account. Such payments will be
in the form designated by the participant and will commence on the first day of
the calendar quarter following the death of the participant (or as soon
thereafter as practicable) and, in the case of annual installments, will be paid
on or before March 1 of each succeeding year.

         3.8 HARDSHIP DISTRIBUTIONS FROM ACCOUNTS. The Clerk may, in his
discretion, distribute a portion or all of a participant's cash account in case
of the participant's financial hardship. The Clerk will determine the date of
payment of the distribution. Hardship distributions are not permitted from a
participant's stock account.

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                                   ARTICLE IV

                            AMENDMENT AND TERMINATION

         4.1 AMENDMENT. Genzyme may, without the consent of any participant,
beneficiary or other person, amend the plan at any time and from time to time;
provided, however, that no amendment will reduce the amount credited to the
deferral account of any participant.

         4.2 TERMINATION. Genzyme may terminate the plan at any time. Upon
termination of the plan, payments from a participant's deferral account shall be
made in the manner and at the time prescribed in Article III; provided, however,
that Genzyme may, in its discretion, distribute a participant's deferral account
in a lump sum as soon as practicable after the date the plan is terminated.

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