Document:

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                                                                   EXHIBIT 10.33

November 5, 2001

Neil Kirby, PhD
7 Meeting House Square
Middleton, MA 01949

Dear Neil:

On behalf of TKT, I am pleased to extend the offer outlined below for you to
become the Vice President, Global Regulatory Affairs of Transkaryotic Therapies,
Inc. ("TKT"). It has been a pleasure introducing you to TKT, and I very much
appreciate your time and efforts during the recruitment process. I believe you
will have a critical role in the development of TKT's products and look forward
to the broad impact you will have on the Company.

The terms of this offer are as follows:

1.    Title of Position: Vice President, Global Regulatory Affairs reporting to
      the Senior Vice President, Administration and General Counsel.

2.    Gross Annual Base Salary: $200,000.00 to be paid semi-monthly at the rate
      of $8,333.33 gross per pay period. You will be eligible for an increase in
      your annual salary effective January 1, 2003.

3.    Annual Target Bonus: You will participate in the Management Incentive
      Bonus Program. Your annual bonus target will be 20% of you base
      compensation and will reflect your individual and departmental performance
      as well as TKT's overall performance.

4.    Stock Option Grant: You will receive an option to purchase 60,000 shares
      of TKT Common Stock (exercise price is the bid price of the stock as of
      the close of business on the last trading day before your official start
      date) which you will fully attain after a six year vesting provision,
      (10,000 shares will vest on your anniversary date each year for six
      consecutive years).

5.    Sign-on Bonus: You will receive a one-time, lump-sum payment of $20,000
      (less appropriate withholdings).

6.    Benefits: You will participate in those benefit programs which are in
      effect and for which you meet eligibility requirements during you
      employment with TKT, including a 401(k) company match of up to $5,250 per
      year, and Deferred Compensation company match of up to $10,000 per year.

7.    In the event of termination: Should your employment with TKT be terminated
      without cause after you have completed one year of service, you will be
      eligible for

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      severance pay for up to one (1) year at up to 100% of base pay (less
      appropriate withholdings and any income you earn from other sources during
      this period).

8.    You will be subject to a non-compete provision consistent with that of
      other TKT executives, calling for a non-compete term of two years in the
      field of niche proteins, non-viral gene therapy as it relates to products
      or processes directly competitive with TKT's, and gene activation. This
      non-compete will be revoked in the event of TKT's acquisition.

9.    As a condition of employment, you will be expected to sign an agreement of
      Confidentiality, Inventions and Noncompetition which is signed by all
      employees of Trankaryotic Therapies. Enclosed is this agreement for your
      review and signature.

10.   This off of employment is contingent upon your being legally able to work
      in the United States. Federal Law requires that you provide proof of
      employment eligibility within three days of your employment.

If you agree to the terms outlined in this offer, please sign and return one (1)
copy of this offer letter along with one (1) copy of the Confidentiality,
Inventions and Noncompetition Agreement. I anticipate that your start date will
be on or around January 2, 2002.

We have enjoyed our discussions with you and believe that your addition to TKT's
management team will have a profound impact on our ability to make TKT's vision
a reality. I look forward to a long, mutually beneficial, and enjoyable working
relationship.

Thank you for your time and consideration.

Sincerely,

/s/ Michael J. Astrue

Michael J. Astrue
Senior Vice President,
Administration and General Counsel

Agreed to and Accepted:  /s/ Neil Kirby
                        -------------------
                          Neil Kirby, PhD

                  Date:  November 14, 2001<PAGE>

                            TKT Management Bonus Plan

                                 2004 Plan Year

                             Name:
                             Title:

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                            TKT MANAGEMENT BONUS PLAN

PURPOSE

The purpose of the TKT Management Retention Bonus Plan (the "Plan") is to;

      >     Enable TKT to retain certain management employees from year to year
            and to provide such employees with incentive to remain with TKT
            after the conclusion of any given calendar year;

      >     Provide participating management employees with motivation and
            incentive to help drive TKT's and the individual's near and long
            term success;

      >     Align compensation with Company goals and the interests of the
            shareholders;

      >     Base variable compensation on individual and team performance;

PLAN DESIGN

Rewards under the Plan consist of cash and stock options. The cash component is
designed to provide near-term reward based on annual performance against goals
and foster continued retention. The stock component encourages continued
retention and longer- term achievement (through options and vesting periods).
Award amounts will be determined by TKT and will be consistent with industry
practices, internal equity and company resources.

Notwithstanding anything in this document to the contrary, the fully funded
bonus(es) provided pursuant to this Plan will only be made available if TKT
achieves the minimum financial performance threshold determined by the Company,
in its discretion.

PLAN DETAILS

Bonuses will be targeted as a percentage of annual base salary and Base Shares
Options for each Plan participant. "Base Share Options" shall be determined by
TKT in its discretion. Plan participants will be provided this information or
may contact the Human Resources Department with questions regarding the base
salary or Base Share Options applicable to him/herself.

Actual Bonus amounts will be determined in the Company's discretion and will be
calculated based on the achievement of Corporate Goals and Individual Goals, as
such terms are defined herein. Generally, half the actual bonus, if any, will be
determined based upon the achievement of Corporate Goals and the balance based
upon the achievement of Individual Goals.

                                                                               2
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"Corporate Goals" shall include those goals set forth for the Company as a whole
at the beginning of or during a given Plan Year. "Individual Goals" shall
include goals provided by an employee's supervisor to an employee at the
beginning of or during a given Plan Year.

The Company retains the right to weight each of the goals as it deems
appropriate and, thereby, determine what bonus, if any, is earned by each
participant in this Plan.

Participants who may be eligible for a bonus pursuant this Plan shall be
provided with information regarding their position classification ("Level").
Such Level will determine the Target Bonus for which the employee may be
eligible in a given year, upon achievement of all corporate and individual
goals. TKT reserves the right to determine the actual bonus to be provided, if
any to each participating employee.

        CASH TARGET BONUS

After meeting all eligibility requirements and after achieving of all corporate
and individual goals, you will be eligible for the following cash target bonus,
calculated as a percentage of the employee's base salary.

               Cash Target Bonus:_____________________

        STOCK OPTION TARGET

After meeting all eligibility requirements and after achieving all corporate and
individual goals, you will be eligible for the following stock option target
bonus.

               Stock Option Target Bonus:_______________

Based upon a participant and TKT's exceeding the goals, TKT reserves the right
to grant additional options in excess of the target stated above. Such
additional grant, if any, will range from 0 to 15% of the stock option target
bonus and are subject to the approval of TKT's Board of Directors.

Stock options granted pursuant to this Plan shall be granted with an exercise
price equal to the fair market value on the date of any such grant. In addition,
stock options shall be granted with such vesting schedule and other conditions
as TKT will determine in its discretion. All stock options granted under this
plan are subject to TKT Board of Directors approval. The stock options shall
also be subject to such option agreement(s) and/or plan(s) which are in effect
from time to time.

SUMMARY OF PROGRAM DETAILS

        PLAN YEAR

January 1 through December 31 annually

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        BONUS POOL DOLLARS

As stated above, the Plan will only be fully funded if TKT achieves the minimum
financial performance threshold determined by the Company, in its discretion.
The extent to which the Company does not meet, meets or exceeds such minimum
financial performance goals will vary TKT's contributions to the Plan and thus
the total bonus dollars available in the pool for distribution. The actual
amount contributed to the Plan shall be determined by TKT in the exercise of its
discretion.

        BONUS PAYMENT

If a cash bonus is to be paid out under the Plan, such bonus will be paid to
only those employees remaining employed by the Company on the date of such
payment. It is anticipated that bonus payments, if any, will be made at or
around the end of the first quarter of each calendar year.

        ELIGIBILITY

Certain management-level employees of TKT will be eligible pursuant to this
Plan. Employees are only eligible if they are provided with written Individual
Goals identified as correlating to this Plan.

Participants will only be eligible for bonus payments hereunder if they are in
good standing with the Company (employees who have been placed on a performance
improvement plan are not eligible) and if they remain employed with TKT on the
date the bonus payments are to be made.

Participants must be employed for at least 16 weeks of the Plan Year. Plan
participants who join TKT during the Plan Year period will be eligible to
receive a pro rata bonus based on their start date and December 31.

Eligible part time employees will receive pro rated bonuses based on their
number of scheduled work hours.

Employees who are eligible to receive incentive bonus(es) through an individual
or group plan of TKT (including sales incentive plans and individual employment
agreements) other than this Plan, will generally be ineligible under this Plan.
An employee who changes positions within a Plan Year can be eligible for a
prorated bonus pursuant to this Plan, if all other eligibility requirements are
met.

        HOW CASH BONUS PAY AFFECTS YOUR BENEFITS

The bonus amount, if any, will be taken into account when calculating
participation in the 401k plan. The elected contribution percentage will be
deducted from the lump sum bonus payment.

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OTHER PROVISIONS

Earnings from this Plan will be subject to applicable withholdings.

Subject to applicable law, TKT expressly reserves the right to deduct any
amounts or monies owed or due by a participating employee to TKT, for any
reason, from the payments provided hereunder. The employee specifically
authorizes such a deduction.

This Plan does not constitute a contract of employment or guarantee a bonus
award payment. Except as may be amended by a written agreement signed by the
President of TKT, each employee remains employed at-will and either the employee
or the Company may terminate the employment relationship at any time. The
Company does reserve that right to review, alter, amend or terminate this Plan
at anytime. The company also reserves the discretion to interpret the Plan as it
determined. This Plan and each employee's eligibility hereunder will be reviewed
on an annual basis.

----------------------------                --------------------------
Employee Name                               Plan Year

----------------------------                --------------------------
Employee Signature                          Date

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                                      2004

                            TKT MANAGEMENT BONUS PLAN

BONUSABLE TKT COMPANY GOALS                                                  50%
<TABLE>
<S>                                            <C>

REPLAGAL                                       HUNTER

GAUCHER                                        DYNEPO

RESEARCH                                       GENERAL CORPORATE GOALS

FINANCIAL                                      BUSINESS DEVELOPMENT GOALS
</TABLE>

BONUSABLE INDIVIDUAL GOALS                                                   50%
List 3-5 goals the individual will be evaluated against at the end of the plan
year.

<TABLE>
<S>                                                                             <C>
1.                                                                                       _____%

2.                                                                                       _____%

3.                                                                                       _____%

4.                                                                                       _____%

5.                                                                                       _____%
</TABLE>

<TABLE>
<S>                                                 <C>

Name:_________________________________________      Cash Target Bonus:_________________________

Title:__________________________________________       Stock Option Target: ___________________
</TABLE>

********************************************************************************

<TABLE>
<S>                                                       <C>
Employee signature:___________________________________    Date:________________________________

Supervisor's signature:________________________________   Date:________________________________
</TABLE>

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