<PAGE>   1
                                                                   EXHIBIT 10.24

                              EMPLOYMENT AGREEMENT


         This Agreement, entered into this 6th day of February, 1998,
by and between THERAPEUTIC ANTIBODIES INC., a Delaware corporation with
administrative offices in Nashville, Tennessee (the "Company") and ANDREW HEATH
(the "Employee").

                                   WITNESSETH:

1.       Employment. Company employs Employee and Employee hereby accepts
         employment under the terms and conditions hereinafter set forth.

2.       Duties. Employee is engaged as Vice Chairman and Chief Executive
         Officer of the Company. Employee shall perform faithfully and
         diligently the duties customarily performed by persons in the position
         for which Employee is engaged, together with such other duties assigned
         to him by the Board of Directors of the Company (the "Board"). Employee
         shall work at the Company's office in Nashville, Tennessee, and for
         reasonable temporary periods as agreed by the parties, at other
         locations. During the term of this Agreement, Employee shall serve
         without additional compensation in such other offices of the Company to
         which he may be elected or appointed by the Board.

3.       Payments.

         a.       Base Salary. Employee shall receive an annual base salary (the
                  "Annual Base Salary") at the rate of two hundred fifteen
                  thousand dollars (U.S. $215,000.00) (before all customary
                  payroll deductions), which shall be paid in arrears in equal
                  bi-weekly installments in accordance with the Company's normal
                  payroll practices. The Annual Base Salary shall be subject to
                  review by the Board from time to time and may be increased by
                  the Board during the term hereof.

         b.       Annual Bonus. In addition to the Annual Base Salary, Employee
                  shall be entitled to receive an annual bonus (the "Annual
                  Bonus"), the amount of which shall be determined by the
                  Compensation Committee of the Board at its sole discretion. If
                  certain milestones as set forth in Exhibit A attached hereto
                  are achieved by the Company in the first year of the term
                  hereof, Employee may receive a cash bonus of up to fifty
                  thousand dollars (U.S. $50,000.00) after his first year of
                  employment. Thereafter, Employee may receive a bonus in the
                  form of stock options, stock, or cash, the amount and timing
                  of which shall be determined in the sole discretion of the
                  Board. The Company reserves the right to change all such
                  plans, practices, policies and programs on 

<PAGE>   2

                  a prospective basis, at any time, effective upon delivery of
                  written notice to Employee. Employee shall not earn and
                  accumulate unused vacation and sick leave, or other benefits
                  in excess of an unused amount equal to the amount earned for
                  one year. Employee shall not be entitled to receive payments
                  in lieu of said benefits, other than for unused vacation leave
                  earned and accumulated at the time the employment relationship
                  terminates.

         c.       Stock Options. The Company shall grant Employee options to
                  purchase shares of the common stock of the Company on the
                  terms set forth in the option agreement attached as Exhibit B.

         d.       Benefit Plans. During the term hereof, Employee shall be
                  entitled to participate in all incentive, savings, retirement,
                  welfare, fringe benefit plans, practices, policies and
                  programs of the Company and agrees with their terms. Employee
                  shall be entitled to twenty-one (21) vacation days per year
                  plus public holidays recognized by the Company.

         e.       Employment Expenses. During the term hereof, Employee shall be
                  entitled to receive prompt reimbursement for all reasonable
                  and documented employment expenses incurred by the Employee in
                  accordance with the expense reimbursement policy of the
                  Company.

         f.       Relocation Expenses. Employee shall be entitled to be
                  reimbursed for all reasonable and documented closing expenses
                  for the sale of real property in California, personal moving
                  expenses, and incidental expenses related to his personal
                  relocation from California to Tennessee (the "Relocation
                  Expenses"); provided that the total reimbursement by the
                  Company of the Relocation Expenses shall not exceed one
                  hundred thousand dollars (U.S. $100,000.00).

4.       Extent of Service. Employee shall devote substantially his full
         business time, attention and energies to the business of the Company
         and the performance of his duties and shall not, during the term of
         this Agreement, provide consulting services or scientific services to
         any other business or enterprise without the prior written consent of
         the Company.

5.       Term and Termination.

         a.       Commencement of Employment. Employee's employment under this
                  Agreement shall begin on March 2, 1998 (the "Commencement
                  Date").

         b.       Termination by Employee. Employee may terminate this Agreement
                  at any time upon thirty (30) days prior written notice. If
                  Employee terminates this Agreement at any time prior to
                  eighteen (18) months 


                                       2
<PAGE>   3

                  after the Commencement Date, he shall reimburse the Company on
                  the last day worked for a portion of the Relocation Expenses.
                  The portion of the Relocation Expenses for which Employee must
                  reimburse the Company shall be the proportionate amount of
                  Relocation Expenses corresponding to the amount of time that
                  has not elapsed out of said eighteen-month (18-month) period
                  prior to termination by Employee. Reimbursement of Relocation
                  Expenses shall be payable in full upon the last day of
                  employment, and the Company reserves the right to offset or
                  withhold such amounts from monies due Employee. In the event
                  of termination by Employee, Employee shall not receive any
                  severance allowance. After providing notice of termination,
                  Employee shall continue to perform his duties diligently and
                  faithfully as requested by the Board until the termination
                  date.

         c.       Termination by Company Without Cause. The Company may
                  terminate this Agreement without "cause" (as defined herein)
                  at any time by giving thirty (30) days prior written notice to
                  Employee. Upon termination by the Company without "cause,"
                  Employee shall be entitled to compensation (the "Severance
                  Compensation") equal to the Annual Base Salary; provided that
                  on or after the third anniversary of the Commencement Date,
                  Severance Compensation may be calculated as an amount
                  different from Annual Base Salary if the Board authorizes a
                  new policy in regard to severance payments for the Employee.

         d.       Termination by Company With Cause. The Company may terminate
                  this Agreement at any time upon the occurrence of "cause"
                  hereunder and in such event all compensation and benefit
                  obligations of the Company hereunder shall terminate upon the
                  date of termination. For the purposes of this Agreement, the
                  Company shall have "cause" in the event any of the following
                  occurs:

                  (i)      Employee breaches a material term or condition of
                           this Agreement;

                  (ii)     Employee is convicted of any crime involving fraud,
                           dishonesty, or moral turpitude;

                  (iii)    Employee engages in theft or dishonesty in the
                           conduct of the Company business;

                  (iv)     Employee fails to adhere to any written policy of the
                           Company.

         e.       Termination by Death. This Agreement and the Company's
                  obligation to continue to pay salary to Employee shall
                  terminate upon (i) the 



                                       3
<PAGE>   4

                  death of Employee or (ii) an illness, injury or disability due
                  to which Employee is unable to perform substantially all of
                  his duties (a "Disability"); provided, however, that in the
                  event of the death or Disability of Employee, any and all
                  benefits vested in Employee shall remain in place in
                  accordance with the terms and conditions of the applicable
                  benefit plans.

6.       Restrictive Covenants.

         a.       Confidential Information. Employee agrees to comply with the
                  terms and conditions of the Confidentiality Agreement attached
                  hereto as Exhibit C and incorporated herein by reference as if
                  fully set forth herein.

         b.       Non-Compete. For a period determined as set forth below,
                  Employee agrees not to enter into or engage in the research,
                  development, and production of polyclonal antibodies and
                  polyclonal antibody-based products (the principal business
                  conducted by the Company) either as an individual for his own
                  account, as a partner for a joint venture, or as employee
                  agent, officer, director, or substantial shareholder in a
                  corporation or otherwise in the United States or the United
                  Kingdom. The term of this non-compete provision shall commence
                  on the date hereof. If the Employee voluntarily terminates his
                  employment, the term of the non-compete shall expire
                  twenty-four (24) months from the date of such termination. If
                  the Employee is terminated for "cause" as defined in Section
                  5, the term of the non-compete provision shall expire eighteen
                  (18) months from the date of such termination. If the Employee
                  is terminated without "cause," the term of the non-compete
                  provision shall expire on the date of such termination.

         c.       Non-Solicitation. Upon termination of his employment for any
                  reason, whether voluntary or involuntary, Employee agrees not
                  to directly or indirectly (i) offer employment to or procure
                  employment for any person who at any time during the twelve
                  (12) months immediately preceding such termination has been
                  employed by the Company or (ii) solicit business from any
                  entity, organization or person which has contracted with the
                  Company, which has been doing business with the Company, from
                  which the Company was soliciting business at the time of
                  Employee's termination, or from which the Employee knew or had
                  reason to know that the Company was going to solicit business
                  at the time of Employee's termination for a twelve-month
                  period from the date of termination of Employee's employment
                  with the Company.

         d.       Enforcement. Employee acknowledges that in the event of breach
                  of its covenants under this Section 6, the Company shall be
                  entitled, if it 



                                       4
<PAGE>   5

                  so elects, to institute and prosecute proceedings, either in
                  law or in equity, to enjoin Employee from violating any of the
                  terms of this Section 6, to enforce the specific performance
                  by Employee of any of the terms of this Section 6, and to
                  obtain damages for any of them, but nothing herein contained
                  shall be construed to prevent such remedy or combination of
                  remedies as the Company may elect to evoke. The failure of the
                  Company to promptly institute legal action upon any breach of
                  this Section 6 shall not constitute a waiver of that or any
                  other breach hereof.

         e.       Survival. Notwithstanding any provision to the contrary
                  otherwise contained in this Agreement, the agreements and
                  covenants contained in this Section 6 shall not terminate upon
                  Employee's termination of his employment with the Company or
                  upon the termination of this Agreement under any other
                  provision of this Agreement.

7.       Notices. Any notice required or permitted to be given under this
         Agreement shall be sufficient if in writing, and if sent by registered
         or certified mail to his residence on file with the Company in the case
         of Employee, or to its principal office in the case of the Company.

8.       Waiver of Breach. Either party's failure to enforce any provision of
         this Agreement shall not in any way be construed as a waiver of any
         such provision, or prevent that party thereafter from enforcing each
         and every other provision of this Agreement.

9.       Assignment. The rights and obligations of the Company under this
         Agreement shall inure to the benefit of and shall be binding upon the
         successors and assigns of the Company. Employee acknowledges that
         services to be rendered by him are unique and personal, and Employee
         may not assign any of his rights or allocate any of his duties or
         obligations under this Agreement.

10.      Entire Agreement. This instrument and the exhibits attached hereto
         comprise the entire agreement of the parties, and supersede all prior
         agreements. This Agreement may not be changed orally but only by an
         agreement in writing signed by the party against whom enforcement of
         any waiver, change, modification, extension or discharge is sought.

11.      Choice of Law and Forum. This Agreement shall be governed by the laws
         of the state of Tennessee. Any dispute arising out of this Agreement
         shall be resolved, at the Company's sole option, by federal or state
         courts sitting in Nashville, Tennessee, and Employee waives any
         objection to such venue.

12.      Severable Provisions. The provisions of this Agreement are severable,
         and if any one or more provisions may be determined to be judicially
         unenforceable, 



                                       5
<PAGE>   6

         in whole or in part, the remaining provisions shall nevertheless be
         binding and enforceable.

13.      Employee's Representation. Employee represents and warrants that
         Employee (i) is free to enter into this Agreement and to perform each
         of the terms and covenants contained herein, (ii) is not restricted or
         prohibited, contractually or otherwise, from entering into and
         performing this Agreement, and (iii) will not be in violation or breach
         of any other Agreement by reason of Employee's execution and
         performance of this Agreement.

14.      Headings. Headings in this Agreement are for convenience only and shall
         not be used to interpret or construe its provisions.

15.      Counterparts. This Agreement may be executed in two or more
         counterparts, each of which shall be deemed an original but all of
         which together shall constitute one and the same instrument.

         IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date set forth above.

                                                    EMPLOYEE

                                                    /s/ Andrew Heath
                                                    ---------------------------
                                                    Andrew Heath



                                                    THERAPEUTIC ANTIBODIES INC.


                                                    By: /s/ Martin S. Brown
                                                       ------------------------

                                                    Title:  Chairman
                                                          ---------------------

                                       6