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                                                                   EXHIBIT 10.33


                              EMPLOYMENT AGREEMENT


     AGREEMENT, dated as of February 4, 2000, between Transkaryotic Therapies,
Inc., a Delaware corporation (the "Company"), and Joseph G. Habarta, Ph.D. (the
"Executive").

     1. EMPLOYMENT. The Company hereby employs the Executive and the Executive
hereby accepts employment with the Company upon the terms and conditions herein
set forth.

     2. DUTIES. The Executive shall be engaged as a full-time employee to act as
the Company's Vice President, Quality and shall report to the Company's Founder
and Chief Executive Officer. The Executive shall perform the duties consistent
with such position as the Founder and Chief Executive Officer shall from time to
time reasonably designate. The Executive shall devote his entire time, attention
and energies to the business of the Company and shall not engage in any other
business activity or activities, whether or not such business activity is
pursued for gain, profit or other pecuniary advantage that, in the judgment of
the Company, may conflict with the proper performance of the Executive's duties
under this Agreement. Notwithstanding the foregoing, (a) with respect to
businesses which do not compete with the Company, the Executive may invest his
personal or family assets in such form or manner as will not require any
services on the part of the Executive in the operation of the affairs of the
companies in which such investments are made and in which his participation is
solely that of an investor, and (b) the Executive may purchase securities in any
corporation whose securities are regularly traded in recognized securities
markets, provided that such investments shall not result in his collectively
owning beneficially at any time one percent (1%) or more of the equity
securities of any corporation engaged in a business competitive to that of the
Company.

     3. COMPENSATION.

     (a) BASE SALARY. For services rendered under this Agreement, the Company
     shall pay the Executive an annual salary of $200,000 (the "Base Salary"),
     payable (after deduction of applicable withholding for Federal and state
     income and payroll taxes) in equal semi-monthly installments. The Company
     may review the Executive's compensation annually and make such increases to
     the Base Salary as the Company determines are merited, based upon the
     Executive's performance and consistent with the



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     Company's compensation policies as established by the Compensation
     Committee of the Company's Board of Directors. Any such increase in annual
     Base Salary shall be communicated to the Executive shortly after the
     January meeting of the Board of Directors and shall be made effective on
     the first day of January each year.

     (b) BONUS. At least thirty (30) days prior to each calendar year under this
     Agreement, the Company shall establish objective performance goals for the
     Executive for such calendar year. Upon the attainment of such performance
     goals, but subject to the overall performance of the Company during such
     year, the Executive may be entitled to a bonus, as determined by the
     Compensation Committee of the Company's Board of Directors. Within thirty
     (30) days after the close of each such calendar year, the Company shall
     evaluate the attainment of the performance goals for such calendar year and
     determine the amount of any performance bonus payable hereunder. Any such
     performance bonus shall be payable within ninety (90) days after the
     calendar year to which it relates.

     (c) FRINGE BENEFITS. In addition to Base Salary and Bonus payments under
     Sections 3(a), (b), and (c) above, the Executive shall be eligible for and
     participate in such fringe benefits, in accordance with the terms of each
     such benefit, as shall be generally provided to executives of the Company,
     including incentive compensation, the Company's 401(k) Plan, health and
     dental insurance, and any retirement programs, stock options plans or
     employee stock purchase plans which may be adopted from time to time during
     the term hereof by the Company. Nothing herein contained shall be deemed to
     preclude the Company from granting such additional compensation or benefits
     to the Executive as it shall in its sole discretion determine.

     (d) STOCK OPTIONS. Upon authorization by the Company's Board of Directors
     or Compensation Committee, the Company will promptly grant the Executive
     under the Company's 1993 Long-Term Incentive Plan (the "Plan") a stock
     option to purchase an aggregate of seventy-five thousand (75,000) shares of
     the Common Stock of the Company, par value $.01 per share, at a purchase
     price of forty-six and 50/100 dollars ($46.50) per share. The stock options
     will vest annually for a period of six (6) years on the anniversary date of
     employment in installments of 12,500 options each. Such option shall be
     exercisable during the ten (10) year period following its date of vesting
     and shall be subject to all the terms and conditions of the Plan and the
     Company's standard form of Stock Option Agreement, copies of which have
     been delivered to the Executive separately.


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     4. VACATION. During the term of this Agreement, the Executive shall be
entitled to fifteen (15) annual vacation days accrued at the rate of 1.25 days
per month.

     5. SICK LEAVE. During the term of this Agreement, the Executive shall be
entitled to sick leave consistent with the Company's customary sick leave
policy.

     6. EXPENSES. During the term of this Agreement, the Company shall reimburse
the Executive in accordance with the Company's customary policies for all
reasonable out-of-pocket expenses incurred by the Executive in connection with
the business of the Company and in performance of his duties under this
Agreement upon the Executive's presentation to the Company of an itemized
accounting of such expenses with reasonable supporting data.

     7. TERM.

     (a) The Executive's employment under this Agreement shall commence on
     November 1, 1999 (the "Commencement Date") and shall continue until
     terminated by the Company as provided in this Section 7(a) or by the
     Executive as provided in Section 7(c) below. The Company may, at its
     election, terminate the obligations of the Company under this Agreement as
     follows:

          (i) Upon at least sixty (60) days' prior written notice if the
          Executive becomes physically or mentally incapacitated or is injured
          so that he is unable to perform the services required of him hereunder
          and such inability to perform continues for a period in excess of six
          (6) months and is continuing at the time of such notice; or

          (ii) For "Cause" upon prior written notice of such termination to the
          Executive. For purposes of this Agreement, the Company shall have
          "Cause" to terminate its obligations hereunder upon (a) the Company's
          determination that the Executive has ceased or failed to substantially
          perform his duties hereunder (other than as a result of his incapacity
          due to physical or mental illness or injury), and at least thirty (30)
          days' prior written notice to the Executive, (b) the Executive's
          death, (c) the Company's determination that the Executive has engaged
          or is about to engage in conduct materially injurious to the Company,
          (d) the Executive's having been convicted of a felony, or (e) the
          Executive's participation in


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          activities proscribed by the provisions of Sections 2, 9, or 11 hereof
          or material breach of any of the other covenants herein; or

          (iii) Without Cause upon at least sixty (60) days' prior written
          notice of such termination to the Executive.

     (b) If, subsequent to six (6) months of the date the Executive's employment
     hereunder commences, this Agreement is terminated pursuant to Section
     7(a)(i) above, subject to Section 11(d) below, the Executive shall receive
     severance pay until the fourth anniversary of the date hereof at the rate
     of one hundred percent (100%) of Base Salary, reduced by applicable payroll
     taxes and further reduced by the amount received by the Executive during
     such period under any Company maintained disability insurance policy or
     plan or under Social Security or similar laws. Such severance payments
     shall be paid periodically to the Executive as provided in Section 3(a) for
     the payment of Base Salary. If this Agreement is terminated at any time
     pursuant to Section 7(a)(ii) above, the Executive shall receive no
     severance pay. If this Agreement is terminated pursuant to Section
     7(a)(iii) above, the Executive shall receive severance pay, for a period of
     twelve (12) months from and after such termination, equal to the Base
     Salary less the amount, if any, earned by the Executive during such twelve
     (12) month period, whether as salary, consulting fees, deferred payments or
     other direct or indirect compensation. Such severance payments (less
     applicable withholding and payroll taxes) shall be paid periodically to the
     Executive as provided in Section 3(a) for the payment of Base Salary.

     (c) The Executive may terminate his employment under this Agreement upon
     breach by the Company or for Good Reason. Termination of the Executive's
     employment for "breach" shall mean in the event that the Company fails to
     perform, in any material respect, its obligations under this Agreement,
     after written notice to the Company setting forth in reasonable detail the
     nature of such breach, if such breach remains uncured for a period of 90
     days following such notice to the Company. Termination of the Executive's
     employment for "Good Reason" shall only mean termination based on (i) a
     substantial diminution in the responsibilities, duties, and powers of the
     Executive including, without limitation, the Executive ceasing to be the
     Vice President, Quality of the Company; and/or (ii) the relocation of the
     Executive's present office location to an area more than 100 miles from the
     metropolitan Boston area. In the event of termination of employment
     pursuant to this paragraph (c), the Company shall pay to the Executive
     severance pay for a period of twelve (12) months in an amount equal to
     (x) 100% of the


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     Executive's Base Salary immediately prior to such termination; plus,
     (y) any bonus payment for the fiscal year preceding the year in which such
     termination occurs that was earned but not paid at the date of such
     termination. The Executive shall not be required to mitigate the amount of
     any payment provided for in this paragraph (c) by seeking other employment
     or otherwise, but the amount of any payment or benefit provided for in this
     paragraph (c) shall be reduced by an amount equal to any compensation
     earned by the Executive as a result of employment with another employer
     after termination of employment with the Company, or otherwise.

     (d) The Executive may terminate his employment under this Agreement for any
     reason upon at least sixty (60) days' prior written notice. In the event of
     any such termination of employment pursuant to this paragraph (d)
     (excluding any termination of employment paragraph (c) above), the
     Executive shall not be entitled to any severance payments.

     8. REPRESENTATIONS. The Executive hereby represents to the Company that
(a) he is legally entitled to enter into this Agreement and to perform the
services and other obligations contemplated herein; (b) he has, and throughout
the term of this Agreement will continue to have, the full right, power and
authority, subject to no rights of third parties, to grant to the Company the
rights contemplated by Section 10 hereof; and (c) he is not subject to any
agreement, rule, regulation or policy of any university, research institution or
other third party inconsistent with the foregoing representations.

     9. DISCLOSURE OF INFORMATION.

     (a) The Executive recognizes and acknowledges that the Company's trade
     secrets, know-how and proprietary processes as they may exist from time to
     time (including, without limitation, information regarding methods,
     cultures, vectors, plasmids, synthesis techniques, nucleic acid sequences,
     purification techniques, and assay procedures) as well as the Company's
     confidential business plans, and financial data are valuable, special, and
     unique assets of the Company's business, access to and knowledge of which
     are essential to the performance of the Executive's duties hereunder. The
     Executive shall not, during or after the term of his employment by the
     Company, in whole or in part, disclose such secrets, know-how, processes,
     business plans, or financial data to any person, firm, corporation,
     association, or other entity for any reason or purpose whatsoever, nor
     shall the Executive make use of any such property for his own purposes or
     for the benefit of any person, firm, corporation, or other entity (except
     the Company) under any circumstances during or after the


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     term of his employment, provided that after the term of his employment,
     these restrictions shall not apply to such secrets, know-how, and processes
     which the Executive can establish by competent proof:

          (i) were known, other than under binder of secrecy, to the Executive
          prior to his employment by the Company;

          (ii) were passed into the public domain prior to or after their
          development by or for the Company, other than through acts or
          omissions attributable to the Executive; or

          (iii) were subsequently obtained, other than under binder of secrecy,
          from a third party not acquiring the information under an obligation
          of confidentiality from the disclosing party.

          (b) Upon termination of his employment hereunder, the Executive shall
          promptly turn over to the Company all originals and copies which he
          may have of any of the Company's confidential information described in
          this Section 9.

     10. INTELLECTUAL PROPERTY. The Executive hereby sells, transfers, and
assigns to the Company, or to any person or entity designated by the Company,
the entire right, title, and interest of the Executive in and to all inventions,
ideas, discoveries, and improvements (including, without limitation, all
microorganisms, strains, or cultures) whether patented or unpatented, and
copyrightable material made or conceived by the Executive, solely or jointly,
during the term hereof, which arise out of research or other activities
conducted by, for, or under the direction of the Company, whether or not
conducted at the Company's facilities, or which relate to methods, apparatus,
designs, products, processes, or devices, sold, leased, used, or under
consideration or development by the Company. The Executive acknowledges that all
copyrightable materials developed or produced by the Executive within the scope
of his employment constitute works made for hire. The Executive shall
communicate promptly and disclose to the Company, in such form as the Company
may reasonably request, all information, details, and data pertaining to any
such inventions, ideas, discoveries, and improvements; and the Executive shall
execute and deliver to the Company such formal transfers and assignments and
such other papers and documents and shall give such testimony as may be
necessary or required of the Executive to permit the Company or any person or
entity designated by the Company to file and prosecute patent applications and,
as to copyrightable material, to obtain copyrights thereof. Any such invention,
idea, discovery, or improvement disclosed by the Executive within one (1) year
following the termination of this Agreement shall be deemed to fall within the


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provisions of this Section 10 unless proved to have been first conceived and
made following such termination.

     11. COVENANTS NOT TO COMPETE OR INTERFERE.

     (a) Subject to Section 11(b) below, during the term of this Agreement and
     the period ending twenty-four (24) months from and after the termination of
     the Executive's employment hereunder, the Executive shall not engage in any
     business (whether as an officer, director, owner, employee, partner,
     consultant, advisor, or other direct or indirect participant) engaged in
     the development of EX VIVO gene therapy and/or gene targeting and/or gene
     activation methods and/or niche proteins and/or the sale of products or
     rendering of services related to EX VIVO gene therapy and/or gene targeting
     and/or gene activation and/or niche proteins and/or to any other activities
     which directly compete with the Company's business activities. This
     Agreement shall not be construed to restrict the Executive's right to be
     employed as a faculty member of any university or employee of any nonprofit
     agency or foundation after any termination of this Agreement where this
     covenant not to compete shall continue to be in effect. During the period
     in which this covenant not to compete is in effect the Executive also shall
     not interfere with, disrupt, or attempt to disrupt the relationship,
     contractual or otherwise, between the Company and any customer, supplier,
     lessor, lessee, employee, consultant, research partner, or investor of the
     Company.

     (b) If this Agreement is terminated by the Company pursuant to Section
     7(a)(iii) above, the provisions of the first sentence of Section 11(a)
     shall apply until twelve (12) months from and after such termination.

     (c) It is the desire and intent of the parties that the provisions of this
     Section 11 shall be enforced to the fullest extent permissible under the
     laws and public policies applied in each jurisdiction in which enforcement
     is sought. Accordingly, if any particular Subsection or portion of this
     Section 11 shall be adjudicated to be invalid or unenforceable, this
     Section 11 shall be deemed amended to delete therefrom the portion thus
     adjudicated to be invalid or unenforceable, such deletion to apply only
     with respect to the operation of this Section in the particular
     jurisdiction in which such adjudication is made.

     (d) In the event of any breach of the provisions of this Section 11 by the
     Executive, any and all rights of the Executive to receive severance
     payments under Section 7(b) above shall automatically terminate.


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     12. INJUNCTIVE RELIEF. If there is a breach or threatened breach of the
provisions of Section 9, 10, or 11 of this Agreement, the Company shall be
entitled to an injunction, without bond, restraining the Executive from such
breach. Nothing herein shall be construed as prohibiting the Company from
pursuing any other remedies for such breach or threatened breach.

     13. INSURANCE. The Company may, at its election and for its benefit, insure
the Executive against accidental loss or death, and the Executive shall submit
to such physical examinations and supply such information as may be required in
connection therewith.

     14. NOTICES. Any notice required or permitted to be given under this
Agreement to the Executive shall be sufficient if in writing and if sent by
certified or registered mail to his residence, or in the case of the Company, to
Transkaryotic Therapies, Inc., 195 Albany Street, Cambridge, MA 02139,
Attention: Chief Executive Officer, or to such other offices or addresses as the
Company shall designate from time to time in writing to the Executive. Any such
notice shall be effective on the earlier of (a) the date on which it is
personally delivered or (b) three (3) days after it is deposited in the United
States mails, postage prepaid.

     15. WAIVER OF BREACH. A waiver by the Company or the Executive of a breach
of any provision of this Agreement by the other party shall not operate or be
construed as a waiver of any subsequent breach by the other party.

     16. GOVERNING LAW. This Agreement shall be governed by and construed and
enforced in accordance with the internal laws of the Commonwealth of
Massachusetts.

     17. ASSIGNMENT. This Agreement may be assigned, without the consent of the
Executive, by the Company to any person, partnership, corporation or other
entity which succeeds to the business of the Company or which has purchased
substantially all the assets of the Company, provided such assignee assumes all
the liabilities of the Company hereunder.

     18. ENTIRE AGREEMENT. This Agreement contains the entire agreement of the
parties and supersedes any prior understandings or agreements between the
Executive and the Company. This Agreement may be changed only by an agreement in
writing signed by the party against whom enforcement of any waiver, change,
modification, extension, or discharge is sought.


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     IN WITNESS WHEREOF, the parties have executed this Employment Agreement as
of the date first above written.

                                       TRANSKARYOTIC THERAPIES, INC.



                                        By:   /s/ Richard F Selden
                                             -------------------------------
                                              Richard F Selden, M.D., Ph.D.
                                              Founder and Chief Executive
                                              Officer


                                              /s/ Joseph G. Habarta
                                             -------------------------------
                                             Joseph G. Habarta, Ph.D.




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