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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