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                                                                Exhibit 10.47



                               SEVERANCE AGREEMENT
                                (Mark Skaletsky)

     THIS SEVERANCE AGREEMENT (this "Agreement") is entered into as of July 27,
                                     ---------
2001, by and between Mark Skaletsky (the "Employee") and MICROCIDE
                                          --------
PHARMACEUTICALS, INC., a Delaware corporation (the "Company").
                                                    -------

     WHEREAS, the Employee has an employment agreement (the "Prior Agreement")
                                                             ----- ---------
with The Althexis Company, Inc., a Delaware corporation, pursuant to which he
has certain rights and obligations thereunder; and

     WHEREAS, simultaneously with and contingent upon the termination of the
Prior Agreement, this Agreement shall become effective.

     NOW, THEREFORE, the parties hereto hereby agree as follows:

     1. Term of Agreement.
        -----------------

     This Agreement shall remain in effect from the date of the termination of
the Prior Agreement until the earlier of:

          (a) The date when the Employee's employment with the Company
     terminates for any reason not described in Section 6; or

          (b) The date when the Company has met all of its obligations under
     this Agreement following a Termination Event, as defined in Section 6,
     below.

     2. Definition of Change in Control.
        -------------------------------

     For all purposes under this Agreement, "Change in Control" shall mean (i) a
                                             ------ -- -------
merger, reorganization or other transaction or series of related transactions
(other than financings) following which the shareholders of the Company do not
own a majority of the capital stock of the surviving corporation or (ii) the
sale of all or substantially all of the assets of the Company.

     3. Definition of Good Reason.
        -------------------------

     For all purposes under this Agreement, "Good Reason" shall mean that the
                                             ---- ------
Employee:

          (a) Has been demoted or has incurred a material reduction in his
     authority or responsibility as an employee of the Company, including
     (without limitation) a reduction or elimination of his authority to approve
     expenditures or to hire, promote, demote or terminate subordinates;

          (b) Has incurred a reduction in his total compensation (including
     benefits) as an employee of the Company, other than pursuant to a
     Company-wide reduction of total compensation (including benefits) for
     employees of the Company generally; or


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          (c) Has been notified that his principal place of work as an employee
     of the Company will be relocated by a distance of 50 miles or more.

     4. Definition of Cause.
        -------------------

     For all purposes under this Agreement, "Cause", shall mean:


          (a) A willful act by the Employee which constitutes misconduct or
     fraud and which is injurious to the Company; provided, however, that no
                                                  --------  -------
     act, or failure to act, by the Employee shall be considered "willful"
                                                                  -------
     unless committed without good faith and without a reasonable belief that
     the act or omission was in the Company's best interest; or

          (b) Conviction of, or a plea of "guilty" or "no contest" to, a felony.
                                           ------      -- -------

     The Board of Directors of the Company shall have sole discretion with
respect to whether any act or failure to act constitutes "Cause" for purposes of
this Agreement.

     5. Definition of Continuation Period.
        ---------------------------------

     For all purposes under this Agreement, "Continuation Period" shall mean the
                                             ------------ ------
period commencing on the date when the termination of the Employee's employment
under Section 6 is effective and ending on the earlier of:

          (a) The date twelve (12) months after the date when the employment
     termination was effective; or

          (b) The date of the Employee's death.

     6. Entitlement to Severance Pay and Benefits.
        -----------------------------------------

     The Employee shall be entitled to receive the severance pay described in
Section 7 (the "Severance Pay") and the benefits described in Section 8 from the
                --------- ---
Company if, and only if, one of the following events occurs (each a "Termination
                                                                     -----------
Event"):
-----

          (a) Within the first 12 month period after the occurrence of a Change
     in Control, the Employee voluntarily resigns his employment for Good
     Reason; or

          (b) Within the first 12 month period after the occurrence of a Change
     in Control, the Company terminates the Employee's employment for any reason
     other than Cause.


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     7. Amount of Severance Pay.
         -----------------------

     During the Continuation Period, the Company shall pay the Employee
Severance Pay at an annual rate equal to the Employee's base compensation at the
annual rate in effect on the date when the termination of his employment with
the Company is effective. Such amount shall be paid pro-rata at periodic
intervals in accordance with the Company's standard payroll procedures.

     8. Other Benefits.
        --------------

          (a) Stock Options and Restricted Stock. All unvested stock options and
              ----------------------------------
     shares of restricted stock granted to Employee by the Company shall vest
     immediately upon the occurrence of a Termination Event. The
     post-termination exercise grace period under the Employee's stock options
     shall commence at the end of the Continuation Period. The Employee
     represents that he has consulted or will consult a tax adviser regarding
     the impact of this Subsection (a) on the tax treatment of incentive stock
     options and shares of restricted stock.

          (b) Group Insurance. At the commencement of the Continuation Period,
              ---------------
     the Employee (and, where applicable, his dependents) shall be entitled to
     convert his key employee long-term disability policy and group life
     insurance policy into individual policies pursuant to the terms of such
     policies. Should the Employee elect to convert either or both of such
     policies, the Company will pay the premiums for such policy or policies
     during the Continuation Period. At the commencement of the Continuation
     Period, the Employee shall be eligible to continue his group health
     continuation coverage under the Consolidated Omnibus Budget Reconciliation
     Act of 1986, and the Company will pay the premiums for such coverage during
     the Continuation Period. The foregoing notwithstanding, in the event that
     the Employee becomes eligible for comparable group insurance coverage in
     connection with new employment, the premium payments by the Company under
     this Subsection (b) shall terminate immediately.

          (c) Outplacement Services. Upon the occurrence of a Termination Event,
              ---------------------
     the Employee shall be entitled to reasonable outplacement services at the
     Company's expense. Such services shall be provided by a firm selected by
     the Employee from a list compiled by the Company and shall be limited to a
     period of six consecutive months.

     9. Limitation on Payments.
        ----------------------

          (a) Basic Rule. Any other provision of this Agreement notwithstanding,
              ----------
     the Company shall not be required to make any payment or property transfer
     to, or for the benefit of, the Employee (under this Agreement or otherwise)
     that would be nondeductible by the Company by reason of Section 280G of the
     Internal Revenue Code of 1986, as amended (the "Code"), or that would
                                                     ----
     subject the Employee to the excise tax described in Section 4999 of the
     Code. All calculations required by this Section 9 shall be performed by the
     independent auditors retained by the Company most recently prior to the
     Change in Control (the "Auditors"), based on information supplied by the
                             --------
     Company and the Employee, and shall be binding on the Company and the
     Employee. All fees and expenses of the Auditors shall be paid by the
     Company.

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               (b) Reductions. If the amount of the aggregate payments or
                   ----------
          property transfers to the Employee must be reduced under this Section
          9, then the Employee shall direct in which order the payments or
          transfers are to be reduced, but no change in the timing of any
          payment or transfer shall be made without the Company's consent. As a
          result of uncertainty in the application of sections 280G and 4999 of
          the Code at the time of an initial determination by the Auditors
          hereunder, it is possible that a payment will have been made by the
          Company that should not have been made (an "Overpayment") or that an
                                                      -----------
          additional payment that will not have been made by the Company could
          have been made (an "Underpayment"). In the event that the Auditors,
                              ------------
          based upon the assertion of a deficiency by the Internal Revenue
          Service against the Company or the Employee that the Auditors believe
          has a high probability of success, determine that an Overpayment has
          been made, such Overpayment shall be treated for all purposes as a
          loan to the Employee that he shall repay to the Company, together with
          interest at the applicable federal rate specified in section
          7872(f)(2) of the Code; provided, however, that no amount shall be
                                  --------  -------
          payable by the Employee to the Company if and to the extent that such
          payment would not reduce the amount that is nondeductible under
          section 280G of the Code or is subject to an excise tax under section
          4999 of the Code. In the event that the Auditors determine that an
          Underpayment has occurred, such Underpayment shall promptly be paid or
          transferred by the Company to, or for the benefit of, the Employee,
          together with interest at the applicable federal rate specified in
          section 7872(f)(2) of the Code.

     10.  Non-Solicitation.
          ----------------

     After the occurrence of a Termination Event, the Employee agrees that for a
period of two years from the date of the Termination Event (the
"Non-Solicitation Term") he will not directly or indirectly solicit for
 ---------------- ----
employment any employee of the Company who was employed by the Company at the
time of the occurrence of the Termination Event and remains in the employment of
the Company during the Non-Solicitation Term.

     11. Successors.
         ----------

               (a) Company's Successors. The Company shall require any successor
                   --------------------
          (whether direct or indirect and whether by purchase, lease, merger,
          consolidation, liquidation or otherwise) to all or substantially all
          of the Company's business and/or assets, by an agreement in substance
          and form satisfactory to the Employee, to assume this Agreement and to
          agree expressly to perform this Agreement in the same manner and to
          the same extent as the Company would be required to perform it in the
          absence of a succession. For all purposes under this Agreement, the
          term "Company" shall include any successor to the Company's business
                -------
          and/or assets which executes and delivers the assumption agreement
          described in this Subsection (a) or which becomes bound by this
          Agreement by operation of law.

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                                      -5-


               (b) Employee's Successors. This Agreement and all rights of the
                   ----------------------
          Employee hereunder shall inure to the benefit of, and be enforceable
          by, the Employee's personal or legal representatives, executors,
          administrators, successors, heirs, distributees, devisees and
          legatees.

          12.  Miscellaneous Provisions.
               ------------------------

               (a) Notice. Notices and all other communications contemplated by
                   ------
          this Agreement shall be in writing and shall be deemed to have been
          duly given when personally delivered or when mailed by U.S. registered
          or certified mail, return receipt requested and postage prepaid. In
          the case of the Employee, mailed notices shall be addressed to him at
          the home address which he most recently communicated to the Company in
          writing. In the case of the Company, mailed notices shall be addressed
          to its corporate headquarters, and all notices shall be directed to
          the attention of its Secretary.

               (b) Waiver. No provision of this Agreement shall be modified,
                   ------
          waived or discharged unless the modification, waiver or discharge is
          agreed to in writing and signed by the Employee and by an authorized
          officer of the Company (other than the Employee). No waiver by either
          party of any breach of, or of compliance with, any condition or
          provision of this Agreement by the other party shall be considered a
          waiver of any other condition or provision or of the same condition or
          provision at another time.

               (c) Whole Agreement. No agreements, representations or
                   ---------------
          understandings (whether oral or written and whether express or
          implied) which are not expressly set forth in this Agreement have been
          made or entered into by either party with respect to the subject
          matter hereof.

               (d) No Setoff; Withholding Taxes. There shall be no right of
                   ----------------------------
          setoff or counterclaim, with respect to any claim, debt or obligation,
          against payments to the Employee under this Agreement. All payments
          made under this Agreement shall be subject to reduction to reflect
          taxes required to be withheld by law.

               (e) Choice of Law. The validity, interpretation, construction and
                   -------------
          performance of this Agreement shall be governed by the laws of the
          Commonwealth of Massachusetts.

               (f) Severability. The invalidity or unenforceability of any
                   ------------
          provision or provisions of this Agreement shall not affect the
          validity or enforceability of any other provision hereof, which shall
          remain in full force and effect.

               (g) Potential Pooling Transactions. In the event the Board
                   --------------------------------
          determines that the acceleration of options pursuant to Sections 8(a)
          above would preclude accounting for a proposed business transaction
          involving a Change in Control as a "Pooling of Interests," but the
          Board otherwise desires to approve and account for such transaction as
          a "Pooling of Interests," the acceleration of options described in
          Sections 8(a) above shall be null and void, and the Company shall
          enter into a consulting agreement with the employee covering services
          and compensation to be determined by the parties at that time. Such
          agreement shall be for a period of three years and shall not be
          subject to earlier termination unless by mutual consent of the
          parties.




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               (h) Arbitration. Except as otherwise provided in Section 9, any
                   -----------
          dispute or controversy arising under or in connection with this
          Agreement shall be settled exclusively by arbitration in Boston,
          Massachusetts, in accordance with the rules of the American
          Arbitration Association then in effect. Judgment may be entered on the
          arbitrator's award in any court having jurisdiction. Punitive damages
          shall not be awarded.

               (i) No Assignment of Benefits. The rights of any person to
                   -------------------------
          payments or benefits under this Agreement shall not be made subject to
          option or assignment, either by voluntary or involuntary assignment or
          by operation of law, including (without limitation) bankruptcy,
          garnishment, attachment, or other creditor's process, and any action
          in violation of this Subsection (i) shall be void.

               (j) Employment Taxes. All payments made pursuant to this
                   -----------------
          Agreement will be subject to withholding of applicable income and
          employment taxes.

               (k) Counterparts. This Agreement may be executed in counterparts,
                   ------------
          each of which shall be deemed an original, but all of which together
          will constitute one and the same instrument.


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                                 Microcide Pharmaceuticals, Inc.

                                 By:    /s/ James E. Rurka
                                    -------------------------------------------
                                    Name: James E. Rurka

                                    Title: President and Chief Executive Officer




                                        /s/ Mark Skaletsky
                                    --------------------------------------------
                                            Mark Skaletsky