Document:

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                                                                     EXHIBIT 4.6

                 INTERNATIONAL LANGUAGE ENGINEERING CORPORATION

                   AMENDED AND RESTATED 1997 STOCK OPTION PLAN

                  ADOPTED MARCH 31, 1997; AMENDED JUNE 22, 1997

                     APPROVED BY SHAREHOLDERS JUNE 22, 1997

1.    PURPOSES.

      (a) The purpose of the Plan is to provide a means by which selected
Employees and Directors of the Company, and its Subsidiaries, may be given an
opportunity to purchase stock of the Company.

      (b) The Company, by means of the Plan, seeks to retain the services of
persons who are now Employees or Directors of the Company or its Subsidiaries,
to secure and retain the services of new Employees and Directors, and to provide
incentives for such persons to exert maximum efforts for the success of the
Company and its Subsidiaries.

      (c) The Company intends that the Options issued under the Plan shall, in
the discretion of the Board or any Committee to which responsibility for
administration of the Plan has been delegated pursuant to subsection 3(c), be
either Incentive Stock Options or Nonstatutory Stock Options. All Options shall
be separately designated Incentive Stock Options or Nonstatutory Stock Options
at the time of grant, and in such form as issued pursuant to Section 6, and a
separate certificate or certificates will be issued for shares purchased on
exercise of each type of Option.

2.    DEFINITIONS.

      (a) "Board" means the Board of Directors of the Company.

      (b) "Code" means the Internal Revenue Code of 1986, as amended.

                                       1.
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      (c) "Committee" means a Committee appointed by the Board in accordance
with subsection 3(c) of the Plan.

      (d) "Company" means International Language Engineering Corporation, a
Colorado corporation.

      (e) "Consultant" means any person, including an advisor, engaged by the
Company or an Affiliate to render consulting services and who is compensated for
such services, provided that the term "Consultant" shall not include Directors
who are paid only a director's fee by the Company or who are not compensated by
the Company for their services as Directors,

      (f) "Continuous Status as an Employee, Director or Consultant" means that
the service of an individual to the Company, whether as an Employee, Director or
Consultant, is not interrupted or terminated. The Board, in its sole discretion,
may determine whether Continuous Status as an Employee, Director or Consultant
shall be considered interrupted in the case of: (i) any leave of absence
approved by the Board, including sick leave, military leave, or any other
personal leave; or (ii) transfers between the Company, Subsidiaries or their
successors.

      (g) "Director" means a member of the Board.

      (h) "Employee" means any person, including Officers and Directors,
employed by the Company or any Affiliate of the Company. Neither service as a
Director nor payment of a director's fee by the Company shall be sufficient to
constitute "employment" by the Company.

      (i) "Exchange Act" means the Securities Exchange Act of 1934, as amended.

      (j) "Fair Market Value" means, as of any date, the price per share as
quoted on any public exchange, or if the common stock of the Company is not
publicly treaded the value of the common stock of the Company determined in good
faith by the Board.

                                       2.
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      (k) "Incentive Stock Option" means an Option intended to qualify as an
incentive stock option within the meaning of Section 422 of the Code and the
regulations promulgated thereunder.

      (l) "Nonstatutory Stock Option" means an Option not intended to qualify as
an Incentive Stock Option.

      (m) "Option" means a stock option granted pursuant to the Plan.

      (n) "Option Agreement" means a written agreement between the Company and
an Optionee evidencing the terms and conditions of an individual Option grant.
Each Option Agreement shall be subject to the terms and conditions of the Plan.

      (o) "Optionee" means an Employee or Director who holds an outstanding
Option.

      (p) "Plan" means this 1997 Stock Option Plan.

      (q) "Subsidiary" means any subsidiary corporation, whether now or
hereafter existing, as such term is defined in Section 424 of the Code.

3.    ADMINISTRATION.

      (a) The Plan shall be administered by the Board unless and until the Board
delegates administration to a Committee, as provided in subsection 3(c).

      (b) The Board shall have the power, subject to, and within the limitations
of, the express provisions of the Plan:

            (1) To determine from time to time which of the persons eligible
under the Plan shall be granted Options; when and how each Option shall be
granted; whether an Option will be an Incentive Stock Option or a Nonstatutory
Stock Option; the provisions of each Option granted, including the time or times
such Option may be exercised in whole or in part; and the number of shares for
which an Option shall be granted to each such person.

            (2) To construe and interpret the Plan and Options granted under it,
and to establish, amend and revoke rules and regulations for its administration.
The Board, in the exercise of this power, may correct any defect, omission or
inconsistency in the Plan or in any Option

                                       3.
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Agreement, in a manner and to the extent it shall deem necessary or expedient to
make the Plan fully effective.

            (3) To amend the Plan or an Option as provided in Section 11.

            (4) Generally, to exercise such powers and to perform such acts as
the Board deems necessary or expedient to promote the best interests of the
Company which are not in conflict with the provisions of the Plan.

      (c) The Board may delegate administration of the Plan to any person or
persons (the "Committee"). If administration is delegated to a Committee, the
Committee shall have, in connection with the administration of the Plan, the
powers theretofore possessed by Board (and references in this Plan to the Board
shall thereafter be to the Committee), subject, however, to such resolutions,
not inconsistent with the provisions of the Plan, as may be adopted from time to
time by the Board. The Board may abolish the Committee at any time and revest in
the Board the administration of the Plan.

4.    SHARES SUBJECT TO THE PLAN.

      (a) Subject to the provisions of Section 10 relating to adjustments upon
changes in stock, the stock that may be sold pursuant to Options shall not
exceed in the aggregate eight hundred forty thousand six hundred seventy eight
(840,678) shares of the Company's common stock. If any Option shall for any
reason expire or otherwise terminate, in whole or in part, without having been
exercised in full, the stock not purchased under such Option shall revert to and
again become available for issuance under the Plan.

      (b) The stock subject to the Plan may be unissued shares or reacquired
shares, bought on the market or otherwise.

                                       4.
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5.    ELIGIBILITY.

      (a) Incentive Stock Options may be granted only to Employees. Nonstatutory
Stock Options may be granted only to Employees or Directors.

      (b) No person shall be eligible for the grant of an Incentive Stock Option
if, at the time of grant, such person owns (or is deemed to own pursuant to
Section 424(d) of the Code) stock possessing more than ten percent (10%) of the
total combined voting power of all classes of stock of the Company or of any of
its Subsidiaries unless the exercise price of such Incentive Stock Option is at
least one hundred ten percent (110%) of the Fair Market Value of such stock at
the date of grant and the Incentive Stock Option is not exercisable after the
expiration of five (5) years from the date of grant.

6.    OPTION PROVISIONS.

      Each Option shall be in such form and shall contain such terms and
conditions as the Board shall deem appropriate. The provisions of separate
Options need not be identical, but each Option shall include (through
incorporation of provisions hereof by reference in the Option or otherwise) the
substance of each of the following provisions:

      (a) Term. No Option shall be exercisable after the expiration often (10)
years from the date it was granted.

      (b) Price. The exercise price of each Incentive Stock Option shall be not
less than one hundred percent (100%) of the Fair Market Value of the stock
subject to the Incentive Stock Option on the date the Incentive Stock Option is
granted. The exercise price of each Nonstatutory Stock Option shall be
determined by the Board. Notwithstanding the foregoing, the Board may grant an
Option with an exercise price lower than that set forth above if such Option is
granted as part of a transaction to which section 424(a) of the Code applies.

                                       5.
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      (c) Consideration. The purchase price of stock acquired pursuant to an
Option shall be paid to the extent permitted by applicable statutes and
regulations, either (i) in cash at the time the Option is exercised, or (ii) at
the discretion of the Board or the Committee, at the time of the grant of the
Option, by delivery to the Company of other common stock of the Company or in
any other form of legal consideration that may be acceptable to the Board.

      In the case of any deferred payment arrangement, interest shall be payable
at least annually and shall be charged at the minimum rate of interest necessary
to avoid the treatment as interest, under any applicable provisions of the Code,
of any amounts other than amounts stated to be interest under the deferred
payment arrangement.

      (d) Transferability. An Option shall not be transferable except by will or
by the laws of descent and distribution, and shall be exercisable during the
lifetime of the person to whom the Option is granted only by such person. The
person to whom the Option is granted may, by delivering written notice to the
Company, in a form satisfactory to the Company, designate a third party who, in
the event of the death of the Optionee, shall thereafter be entitled to exercise
the Option.

      (e) Vesting. The total number of shares of stock subject to an Option may,
but need not be allocated in periodic installments (which may, but need not, be
equal). The Option Agreement may provide that from time to time during each of
such installment periods, the Option may become exercisable ("vest") with
respect to some or all of the shares allotted to that period, and may be
exercised with respect to some or all of the shares allotted to such period
and/or any prior period as to which the Option became vested but was not fully
exercised. The Option may be subject to such other terms and conditions on the
time or times when it may be exercised (which may be based on performance or
other criteria) as the Board may deem appropriate. The provisions

                                       6.
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of this subsection 6(e) are subject to any Option provisions governing the
minimum number of shares as to which an Option may be exercised.

      (f) Securities Law Compliance. The Company may require any Optionee, or
any person to whom an Option is transferred under subsection 6(d), as a
condition of exercising any such Option, (1) to give written assurances
satisfactory to the Company as to the Optionee's knowledge and experience in
financial and business matters and/or to employ a purchaser representative
reasonably satisfactory to the Company who is knowledgeable and experienced in
financial and business matters, and that he or she is capable of evaluating,
alone or together with the purchaser representative, the merits and risks of
exercising the Option; and (2) to give written assurances satisfactory to the
Company stating that such person is acquiring the stock subject to the Option
for such person's own account and not with any present intention of selling or
otherwise distributing the stock. The foregoing requirements, and any assurances
given pursuant to such requirements, shall be inoperative if (i) the issuance of
the shares upon the exercise of the Option has been registered under a then
currently effective registration statement under the Securities Act of 1933, as
amended (the "Securities Act"), or (ii) as to any particular requirement, a
determination is made by counsel for the Company that such requirement need not
be met in the circumstances under the then applicable securities laws. The
Company may require the Optionee to provide such other representations, written
assurances or information which the Company shall determine is necessary,
desirable or appropriate to comply with applicable securities and other laws as
a condition of granting an Option to such Optionee or permitting the Optionee to
exercise such Option. The Company may, upon advice of counsel to the Company,
place legends on stock certificates issued under the Plan as such counsel deems
necessary or appropriate in order to comply with applicable securities laws,
including, but not limited to, legends restricting the transfer

                                       7.
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of the stock.

      (g) Termination of Employment or Relationship as a Director or Consultant.
Subject to the terms of any Option Grant Agreement, in the event an Optionee's
Continuous Status as an Employee, Director or Consultant terminates (other than
upon the Optionee's death or disability), the Optionee may exercise his or her
Option (to the extent that the Optionee was entitled to exercise it as of the
date of termination) but only within such period of time ending on (i) in the
case of Incentive Stock Options, the date three (3) months after the termination
of the Optionee's Continuous Status as an Employee, Director or Consultant, or
such longer or shorter period specified in the Option Agreement, or (ii) in the
case of Nonstatutory Stock Options, the expiration date of such Option. If,
after termination, the Optionee does not exercise his or her Option within the
time specified above, the Option shall terminate, and the shares covered by such
Option shall revert to and again become available for issuance under the Plan.
Finally, an Optionee's Option Agreement may also provide that if the exercise of
the Option following the termination of the Optionee's Continuous Status as an
Employee, Director or Consultant (other than upon the Optionee's death or
disability) would be prohibited at any time solely because the issuance of share
would violate the registration requirements under the Securities Act, then the
Option shall terminate on the earlier of (i) the expiration of the term of the
Option set forth in the first paragraph of this Section 7, or (ii) the
expiration of a period of three (3) months after the termination of the
Optionee's Continuous Status as an Employee, Director or Consultant during which
the exercise of the Option would not be in violation of such registration
requirements.

      (h) Disability of Optionee. In the event an Optionee's Continuous Status
as an Employee, Director or Consultant terminates as a result of the Optionee's
disability, the Optionee may exercise his or her Option (to the extent that the
Optionee was entitled to exercise it as of the

                                       8.
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date of termination), but only within such period of time ending on the earlier
of (i) in the case of Incentive Stock Options the date three (3) months
following such termination (or such longer or shorter period specified in the
Option Agreement), or (ii) in the case of Nonstatutory Stock Options the
expiration of the term of the Option as set forth in the Option Agreement. If,
at the date of termination, the Optionee is not entitled to exercise his or her
entire Option, the shares covered by the unexercisable portion of the Option
shall revert to and again become available for issuance under the Plan. If,
after termination, the Optionee does not exercise his or her Option within the
time specified herein, the Option shall terminate, and the shares covered by
such Option shall revert to and again become available for issuance under the
Plan.

      (i) Death of Optionee. In the event of the death of an Optionee during, or
within a period specified in the Option Agreement after the termination of, the
Optionee's Continuous Status as an Employee, Director or Consultant, the Option
may be exercised (to the extent the Optionee was entitled to exercise the Option
as of the date of death) by the Optionee's estate, by a person who acquired the
right to exercise the Option by bequest or inheritance or by a person designated
to exercise the option upon the Optionee's death pursuant to subsection 6(d), at
any time before the expiration of the term of such Option as set forth in the
Option Agreement. If, at the time of death, the Optionee was not entitled to
exercise his or her entire Option, the shares covered by the unexercisable
portion of the Option shall revert to and again become available for issuance
under the Plan. If, after death, the Option is not exercised within the time
specified herein, the Option shall terminate, and the shares covered by such
Option shall revert to and again become available for issuance under the Plan.

      (j) Early Exercise. The Option may, but need not, include a provision
whereby the Optionee may elect at any time while an Employee, Director or
Consultant to exercise the Option

                                       9.
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as to any part or all of the shares subject to the Option prior to the full
vesting of the Option. Any unvested shares so purchased may be subject to a
repurchase right in favor of the Company or to any other restriction the Board
determines to be appropriate.

      (k) Right of Repurchase. The Option may, but need not, include a provision
whereby the Company may elect, prior to the date of the first registration of an
equity security of the Company under Section 12 of the Exchange Act, to
repurchase all or any part of the vested shares exercised pursuant to the
Option.

      (l) Right of First Refusal. The Option may, but need not, include a
provision whereby the Company may elect, prior to the date of the first
registration of an equity security of the Company under Section 12 of the
Exchange Act, to exercise a right of first refusal following receipt, of notice
from the Optionee of the intent to transfer all or any part of the shares
exercised pursuant to the Option.

      (m) Withholding. To the extent provided by the terms of an Option
Agreement, the Optionee may satisfy any federal, state or local tax withholding
obligation relating to the exercise of such Option by any of the following means
or by a combination of such means: (1) tendering a cash payment; (2) authorizing
the Company to withhold shares from the shares of the common stock otherwise
issuable to the Optionee as a result of the exercise of the Option; or (3)
delivering to the Company owned and unencumbered shares of the common stock of
the Company.

7.    COVENANTS OF THE COMPANY.

      (a) During the terms of the Options, the Company shall keep available at
all times the number of shares of stock required to satisfy such Options.

      (b) The Company shall seek to obtain from each regulatory commission or
agency having jurisdiction over the Plan such authority as may be required to
issue and sell shares of stock

                                      10.
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upon exercise of the Options; provided, however, that this undertaking shall not
require the Company to register under the Securities Act either the Plan, any
Option or any stock issued or issuable pursuant to any such Option. If, after
reasonable efforts, the Company is unable to obtain from any such regulatory
commission or agency the authority which counsel for the Company deems necessary
for the lawful issuance and sale of stock under the Plan, the Company shall be
relieved from any liability for failure to issue and sell stock upon exercise of
such Options unless and until such authority is obtained.

8.    USE OF PROCEEDS FROM STOCK.

      Proceeds from the sale of stock pursuant to Options shall constitute
general funds of the Company.

9.    MISCELLANEOUS.

      (a) The Board shall have the power to accelerate the time at which an
Option may first be exercised or the time during which an Option or any part
thereof will vest pursuant to subsection 6(e), notwithstanding the provisions in
the Option stating the time at which it may first be exercised or the time
during which it will vest.

      (b) Neither an Optionee nor any person to whom an Option is transferred
under subsection 6(d) shall be deemed to be the holder of, or to have any of the
rights of a holder with respect to, any shares subject to such Option unless and
until such person has satisfied all requirements for exercise of the Option
pursuant to its terms.

      (c) Nothing in the Plan or any instrument executed or Option granted
pursuant thereto shall confer upon any Employee, Director, Consultant or
Optionee any right to continue in the employ of the Company or any Affiliate (or
to continue acting as a Director or Consultant) or shall affect the right of the
Company or any Affiliate to terminate the employment of any Employee with

                                      11.
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or without cause, the right of the Company's Board of Directors and/or the
Company's shareholders to remove any Director pursuant to the terms of the
Company's shareholders to remove any Director pursuant to the terms of the
Company's By-Laws and applicable law, or the right to terminate the relationship
of any Consultant pursuant to the terms of such Consultant's agreement with the
Company or Affiliate.

      (d) To the extent that the aggregate Fair Market Value (determined at the
time of grant) of stock with respect to which Incentive Stock Options are
exercisable for the first time by any Optionee during any calendar year under
all plans of the Company and its Subsidiaries exceeds one hundred thousand
dollars ($100,000), the Options or portions thereof which exceed such limit
(according to the order in which they were granted) shall be treated as
Nonstatutory Stock Options.

      (e) The Board or the Committee shall have the authority to effect, at any
time and from time to time (i) the repricing of any outstanding Options under
the Plan and/or (ii) with the consent of the affected holders of Options, the
cancellation of any outstanding Options and the grant in substitution therefor
of new Options under the Plan covering the same or different numbers of shares
of common stock, but having an exercise price per share not less than one
hundred percent (100%) of the Fair Market Value in the case of an Incentive
Stock Option or, in the case of a ten percent (10%) shareholder (as defined in
subsection 5(c)), not less than one hundred and ten percent (110%) of the Fair
Market Value per share of Common Stock on the new grant date. Notwithstanding
the foregoing, the Board may grant an Option with an exercise price lower than
that set forth above if such Option is granted as part of a transaction to which
section 424(c) of the Code applies.

                                      12.
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10.   ADJUSTMENTS UPON CHANGES IN STOCK.

      (a) If any change is made in the stock subject to the Plan, or subject to
any Option (through merger, consolidation, reorganization, reincorporation,
recapitalization, stock dividend, dividend in property other than cash, stock
split, liquidating dividend, combination of shares, exchange of shares, change
in corporate structure or other transaction not involving the receipt of
consideration by the Company), the Plan will be appropriately adjusted in the
class(es) and maximum number of shares subject to the Plan pursuant to
subsection 4(a), and the outstanding Options will be appropriately adjusted in
the class(es) and number of shares and price per share of stock subject to such
outstanding Options. Such adjustments shall be made by the Board or Committee,
the determination of which shall be final, binding and conclusive. (The
conversion of any convertible securities of the Company shall not be treated as
a "transaction not involving the receipt of consideration by the Company.")

      (b) In the event of the proposed dissolution or liquidation of the
Company, each outstanding Option shall terminate immediately prior to the
consummation of such proposed action, unless otherwise provided by the Board.

11.   AMENDMENT OF THE PLAN AND OPTIONS.

      (a) The Board at any time, and from time to time, may amend the Plan.
However, except as provided in Section 10 relating to adjustments upon changes
in stock, no amendment shall be effective unless approved by the shareholders of
the Company within twelve (12) months

                                      13.
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before or after the adoption of the amendment, where the amendment will modify
the Plan in any other way if such modification requires shareholder approval in
order for the Plan to satisfy the requirement of Section 422 of the Code
(including an increase in the number of shares reserved for issuance under the
Plan).

      (b) The Board may in its sole discretion submit any other amendment to the
Plan for shareholder approval.

      (c) It is expressly contemplated that the Board may amend the Plan in any
respect the Board deems necessary or advisable to provide Optionees with the
maximum benefits provided or to be provided under the provisions of the Code and
the regulations promulgated thereunder relating to Incentive Stock Options
and/or to bring the Plan and/or Incentive Stock Options granted under it into
compliance therewith.

      (d) Rights and obligations under any Option granted before amendment of
the Plan shall not be impaired by any amendment of the Plan unless (i) the
Company requests the consent of the person to whom the Option was granted and
(ii) such person consents in writing.

      (e) The Board at any time, and from time to time, may amend the terms of
any one or more Options; provided, however, that the rights and obligations
under any Option shall not he impaired by any such amendment unless (i) the
Company requests the consent of the person to whom the Option was granted and
(ii) such person consents in writing.

12.   TERMINATION OR SUSPENSION OF THE PLAN.

      (a) The Board may suspend or terminate the Plan at any time. Unless sooner
terminated, the Plan shall terminate ten (10) years from the date the Plan is
adopted by the Board or approved by the shareholders of the Company, whichever
is earlier. No Options may be granted under the Plan while the Plan is suspended
or after it is terminated.

                                      14.
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      (b) Rights and obligations under any Option granted while the Plan is in
effect shall not be impaired by suspension or termination of the Plan, except
with the written consent of the person to whom the Option was granted.

13.   EFFECTIVE DATE OF PLAN.

      The Plan shall become effective as determined by the Board, but no Options
granted under the Plan shall be exercised unless and until the Plan has been
approved by the shareholders of the Company, which approval shall be within
twelve (12) months before or after the date the Plan is adopted by the Board.

                                      15.<PAGE>

  THIS WARRANT AND THE SHARES OF COMMON STOCK ISSUED UPON ITS EXERCISE ARE
                         SUBJECT TO THE RESTRICTIONS ON

                 TRANSFER SET FORTH IN SECTION 4 OF THIS WARRANT
            ----------------------------------------------------------

Warrant No. 1                                       Number of Shares: 400,000
                                                    (subject to adjustment)
Date of Issuance: March 10, 1997

                                  VERSICOR INC.

                          COMMON STOCK PURCHASE WARRANT

                           (Void after March 10, 2002)

      Versicor Inc., a Delaware corporation (the "Company"), for value received,
hereby certifies that Genome Therapeutics Corporation, or its registered assigns
(the "Registered Holder"), is entitled, subject to the terms set forth below, to
purchase from the Company, at any time or from time to time on or after the date
of issuance and on or before March 10, 2002 at not later than 5:00 p.m. (Boston,
Massachusetts time), 400,000 shares of Common Stock, $.01 par value per share,
of the Company, at a purchase price of $.50 per share. The shares purchasable
upon exercise of this Warrant, and the purchase price per share, each as
adjusted from time to time pursuant to the provisions of this Warrant, are
hereinafter referred to as the "Warrant Shares" and the "Purchase Price,"
respectively.

      1.    EXERCISE.

            (a) This Warrant may be exercised by the Registered Holder on not
more than one occasion, in whole or in part, by surrendering this Warrant, with
the purchase form appended hereto as APPENDIX I duly executed by such Registered
Holder or by such Registered Holder's duly authorized attorney, at the principal
office of the Company, or at such other office or agency as the Company may
designate, accompanied by payment in full, in lawful money of the United States,
of the Purchase Price payable in respect of the number of Warrant Shares
purchased upon such exercise.

            (b) The exercise of this Warrant shall be deemed to have been
effected immediately prior to the close of business on the day on which this
Warrant shall have been surrendered to the Company as provided in subsection
l(a) above. At such time, the person or persons in whose name or names any
certificates for Warrant Shares shall be issuable upon such exercise as provided
in subsection l(c) below shall be deemed to

<PAGE>

have become the holder or holders of record of the Warrant Shares represented by
such certificates.

            (c) As soon as practicable after the exercise of this Warrant in
full or in part, and in any event within 10 days thereafter, the Company, at its
expense, will cause to be issued in the name of, and delivered to, the
Registered Holder, or as such Holder (upon payment by such Holder of any
applicable transfer taxes) may direct:

      (i) a certificate or certificates for the number of full Warrant Shares to
which such Registered Holder shall be entitled upon such exercise plus, in lieu
of any fractional share to which such Registered Holder would otherwise be
entitled, cash in an amount determined pursuant to Section 3 hereof; and

      (ii) in case such exercise is in part only, a new warrant or warrants
(dated the date hereof) of like tenor, calling in the aggregate on the face or
faces thereof for the number of Warrant Shares equal (without giving effect to
any adjustment therein) to the number of such shares called for on the face of
this Warrant minus the number of such shares purchased by the Registered Holder
upon such exercise.

      2.    ADJUSTMENTS.
            -----------

            (a) RECAPITALIZATIONS. If outstanding shares of the Company's Common
Stock shall be subdivided into a greater number of shares or a dividend in
Common Stock shall be paid in respect of Common Stock, the Purchase Price in
effect immediately prior to such subdivision or at the record date of such
dividend shall simultaneously with the effectiveness of such subdivision or
immediately after the record date of such dividend be proportionately reduced.
If outstanding shares of Common Stock shall be combined into a smaller number of
shares, the Purchase Price in effect immediately prior to such combination
shall, simultaneously with the effectiveness of such combination, be
proportionately increased.

            (b) MERGERS, ETC. If there shall occur any capital reorganization or
reclassification of the Company's Common Stock (other than a change in par value
or a subdivision or combination as provided for in subsection 2(a) above), or
any consolidation or merger of the Company with or into another corporation, or
a transfer of all or substantially all of the assets of the Company, then, as
part of any such reorganization, reclassification, consolidation, merger or
sale, as the case may be, lawful provision shall be made so that the Registered
Holder of this Warrant shall have the right thereafter to receive upon the
exercise hereof the kind and amount of shares of stock or other securities or
property which such Registered Holder would have been entitled to receive if,
immediately prior to any such reorganization, reclassification, consolidation,
merger or sale, as the case may be, such Registered Holder had held the

                                      -2-
<PAGE>

number of shares of Common Stock which were then purchasable upon the exercise
of this Warrant. In any such case, appropriate adjustment (as reasonably
determined in good faith by the Board of Directors of the Company) shall be made
in the application of the provisions set forth herein with respect to the rights
and interests thereafter of the Registered Holder of this Warrant, such that the
provisions set forth in this Section 2 (including provisions with respect to
adjustment of the Purchase Price) shall thereafter be applicable, as nearly as
is reasonably practicable, in relation to any shares of stock or other
securities or property thereafter deliverable upon the exercise of this Warrant.

            (c) ADJUSTMENT IN NUMBER OF WARRANT SHARES. When any adjustment is
required to be made in the Purchase Price, the number of Warrant Shares
purchasable upon the exercise of this Warrant shall be changed to the number
determined by dividing (i) an amount equal to the number of shares issuable upon
the exercise of this Warrant immediately prior to such adjustment, multiplied by
the Purchase Price in effect immediately prior to such adjustment, by (ii) the
Purchase Price in effect immediately after such adjustment.

            (d) CERTIFICATE OF ADJUSTMENT. When any adjustment is required to be
made pursuant to this Section 2, the Company shall promptly mail to the
Registered Holder a certificate setting forth the Purchase Price after such
adjustment and setting forth a brief statement of the facts requiring such
adjustment. Such certificate shall also set forth the kind and amount of stock
or other securities or property into which this Warrant shall be exercisable
following such adjustment.

      3. FRACTIONAL SHARES. The Company shall not be required upon the exercise
of this Warrant to issue any fractional shares, but shall make an adjustment
therefor in cash on the basis of the fair market value per share of Common
Stock, as reasonably determined by the Board of Directors of the Company.

      4.    REQUIREMENTS FOR TRANSFER.
            -------------------------

            (a) This Warrant and the Warrant Shares shall not be sold or
transferred unless either (i) they first shall have been registered under the
Securities Act of 1933, as amended (the "Act"), or (ii) the Company first shall
have been furnished with an opinion of legal counsel, reasonably satisfactory to
the Company, to the effect that such sale or transfer is exempt from the
registration requirements of the Act.

            (b) Notwithstanding the foregoing, no registration or opinion of
counsel shall be required for (i) a transfer by a Registered Holder which is a
partnership to a partner of such partnership or a retired partner of such
partnership who retires after the date hereof, or to the estate of any such
partner or retired partner, if the transferee

                                      -3-
<PAGE>

agrees in writing to be subject to the terms of this Section 4, or (ii) a
transfer made in accordance with Rule 144 under the Act.

            (c) Each certificate representing Warrant Shares shall bear a legend
substantially in the following form:

      "The securities represented by this certificate have not been registered
      under the Securities Act of 1933, as amended, and may not be offered, sold
      or otherwise transferred, pledged or hypothecated unless and until such
      securities are registered under such Act or an opinion of counsel
      satisfactory to the Company is obtained to the effect that such
      registration is not required."

The foregoing legend shall be removed from the certificates representing any
Warrant Shares, at the request of the holder thereof, at such time as they
become eligible for resale pursuant to Rule 144(k) under the Act.

      5. NO IMPAIRMENT. The Company will not, by amendment of its charter or
through reorganization, consolidation, merger, dissolution, sale of assets or
any other voluntary action, avoid or seek to avoid the observance or performance
of any of the terms of this Warrant, but will at all times in good faith assist
in the carrying out of all such terms and in the taking of all such action as
may be necessary or appropriate in order to protect the rights of the holder of
this Warrant against impairment.

      6. LIQUIDATING DIVIDENDS. If the Company pays a dividend or makes a
distribution on the Common Stock payable otherwise than in cash out of earnings
or earned surplus (determined in accordance with generally accepted accounting
principles) except for a stock dividend payable in shares of Common Stock (a
"Liquidating Dividend"), then the Company will pay or distribute to the
Registered Holder of this Warrant, upon the exercise hereof, in addition to the
Warrant Shares purchased upon such exercise, the Liquidating Dividend which
would have been paid to such Registered Holder if he had been the owner of
record of such Warrant Shares immediately prior to the date on which a record is
taken for such Liquidating Dividend or, if no record is taken, the date as of
which the record holders of Common Stock entitled to such dividends or
distribution are to be determined.

      7.    NOTICES OF RECORD DATE, ETC. In case:

            (a) the Company shall take a record of the holders of its Common
Stock (or other stock or securities at the time deliverable upon the exercise of
this Warrant) for the purpose of entitling or enabling them to receive any
dividend or other distribution,

                                      -4-
<PAGE>

or to receive any right to subscribe for or purchase any shares of stock of any
class or any other securities, or to receive any other right; or

            (b) of any capital reorganization of the Company, any
reclassification of the capital stock of the Company, any consolidation or
merger of the Company with or into another corporation (other than a
consolidation or merger in which the Company is the surviving entity), or any
transfer of all or substantially all of the assets of the Company; or

            (c) of the voluntary or involuntary dissolution, liquidation or
winding-up of the Company, then, and in each such case, the Company will mail or
cause to be mailed to the Registered Holder of this Warrant a notice specifying,
as the case may be, (i) the date on which a record is to be taken for the
purpose of such dividend, distribution or right, and stating the amount and
character of such dividend, distribution or right, or (ii) the effective date on
which such reorganization, reclassification, consolidation, merger, transfer,
dissolution, liquidation or winding-up is to take place, and the time, if any is
to be fixed, as of which the holders of record of Common Stock (or such other
stock or securities at the time deliverable upon the exercise of this Warrant)
shall be entitled to exchange their shares of Common Stock (or such other stock
or securities) for securities or other property deliverable upon such
reorganization, reclassification, consolidation, merger, transfer, dissolution,
liquidation or winding-up. Such notice shall be mailed at least ten (10) days
prior to the record date or effective date for the event specified in such
notice.

      8. RESERVATION OF STOCK. The Company will at all times reserve and keep
available, solely for issuance and delivery upon the exercise of this Warrant,
such number of Warrant Shares and other stock, securities and property, as from
time to time shall be issuable upon the exercise of this Warrant.

      9. EXCHANGE OF WARRANTS. Upon the surrender by the Registered Holder of
any Warrant or Warrants, properly endorsed, to the Company at the principal
office of the Company, the Company will, subject to the provisions of Section 4
hereof, issue and deliver to or upon the order of such Holder, at the Company's
expense, a new Warrant or Warrants of like tenor, in the name of such Registered
Holder or as such Registered Holder (upon payment by such Registered Holder of
any applicable transfer taxes) may direct, calling in the aggregate on the face
or faces thereof for the number of shares of Common Stock called for on the face
or faces of the Warrant or Warrants so surrendered.

      10.   REPLACEMENT  OF WARRANTS.  Upon  receipt of evidence  reasonably
satisfactory  to the Company of the loss,  theft,  destruction or mutilation
of this  Warrant  and (in the  case of  loss,  theft  or  destruction)  upon
delivery of an indemnity agreement (with surety

                                      -5-
<PAGE>

      if reasonably required) in an amount reasonably satisfactory to the
Company, or (in the case of mutilation) upon surrender and cancellation of this
Warrant, the Company will issue, in lieu thereof, a new Warrant of like tenor.

      11.   TRANSFERS, ETC.

            (a) The Company will maintain a register containing the names and
addresses of the Registered Holders of this Warrant. Any Registered Holder may
change its or his address as shown on the warrant register by written notice to
the Company requesting such change.

            (b) Subject to the provisions of Section 4 hereof, this Warrant and
all rights hereunder are transferable, in whole or in part, upon surrender of
this Warrant with a properly executed assignment (in the form of APPENDIX II
hereto) at the principal office of the Company.

            (c) Until any transfer of this Warrant is made in the warrant
register, the Company may treat the Registered Holder of this Warrant as the
absolute owner hereof for all purposes; PROVIDED, HOWEVER, that if and when this
Warrant is properly assigned in blank, the Company may (but shall not be
obligated to) treat the bearer hereof as the absolute owner hereof for all
purposes, notwithstanding any notice to the contrary.

      12. MAILING OF NOTICES. ETC. All notices and other communications from the
Company to the Registered Holder of this Warrant shall be mailed by first-class
certified or registered mail, postage prepaid, to the address furnished to the
Company in writing by the last Registered Holder of this Warrant who shall have
furnished an address to the Company in writing. All notices and other
communications from the Registered Holder of this Warrant or in connection
herewith to the Company shall be mailed by first-class certified or registered
mail, postage prepaid, to the Company at its principal office set forth below.
If the Company should at any time change the location of its principal office to
a place other than as set forth below, it shall give prompt written notice to
the Registered Holder of this Warrant and thereafter all references in this
Warrant to the location of its principal office at the particular time shall be
as so specified in such notice.

      13.   NO RIGHTS AS  STOCKHOLDER.  Until the exercise of this  Warrant,
the  Registered  Holder  of this  Warrant  shall  not have or  exercise  any
rights by virtue hereof as a stockholder of the Company.

                                      -6-
<PAGE>

      14.   INCIDENTAL REGISTRATION.

            (a) Whenever the Company proposes to file a registration statement
as provided in Section 15 it will, prior to such filing, give written notice to
the Registered Holder of its intention to do so and, upon the written request of
the Registered Holder given within 20 days after the Company provides such
notice, use its best efforts to cause all Warrant Shares which the Company has
been requested by the Registered Holder to register to be registered under the
Securities Act to the extent necessary to permit their sale or other disposition
in accordance with the intended methods of distribution specified in the request
of the Registered Holder; provided that the Company shall have the right to
postpone or withdraw any registration effected pursuant to this Section 14
without obligation to the Registered Holder.

            (b) In connection with any registration under this Section 14
involving an underwriting, the Company shall not be required to include any
Warrant Shares in such registration unless the holders thereof accept the terms
of the underwriting as agreed upon between the Company and the underwriters
selected by it (provided that such terms must be consistent with this
Agreement). If in the opinion of the managing underwriter it is appropriate
because of marketing factors to limit the number of Warrant Shares to be
included in the offering, then the Company. shall be required to include in the
registration only that number of Warrant Shares, if any, which the managing
underwriter believes should be included therein. If the number of Warrant Shares
to be included in the offering in accordance with the foregoing is less than the
total number of shares which the holders of Warrant Shares have requested to be
included in the offering, then the holders of Warrant Shares who have requested
registration and all other holders of securities with incidental registration
rights entitled to include such securities in such registration shall
participate in the offering pro rata, based upon their total ownership of shares
of Common Stock of the Company (giving effect to the conversion into Common
Stock of all convertible securities). If any holder would thus be entitled to
include more securities than such holder requested to be registered, the excess
shall be allocated among other requesting holders pro rata in the manner
described in the preceding sentence. Notwithstanding the foregoing, the Company
shall not limit the number of Warrant Shares to be included in a registration
pursuant to this Section 14 in order to include shares held by stockholder with
no registration rights or to include any shares of stock issued to employees,
officers, directors or consultants pursuant to the Company's stock option plan.

            (c) All expenses of registration (excluding underwriting discounts,
selling commissions and the fees and expenses of Registered Holders' counsel
(other than the counsel selected to represent all selling stockholders) incurred
in connection with any registration pursuant to Section 14 shall be borne solely
by the Company.

                                      -7-
<PAGE>

      15. "STAND-OFF" AGREEMENT. The Registered Holder, if requested by the
Company and the managing underwriter of an offering by the Company of Common
Stock or other securities of the Company pursuant to a registration statement
filed by the Company with the Securities and Exchange Commission for a public
offering and sale of Common Stock (other than a registration statement on Form
S-8 or Form S-4, or their successors, or any other form for a similar limited
purpose, or any registration statement covering only securities proposed to be
issued in exchange for securities or assets of another corporation), shall agree
not to sell publicly or otherwise transfer or dispose of any Warrant Shares or
other securities of the Company held by such Registered Holder for a specified
period of time (not to exceed 180 days) following the effective date of such
registration statement; PROVIDED, that such agreement shall only apply to the
first such registration statement covering Common Stock to be sold on the
Company's behalf to the public in an underwritten offering.

      16.   CHANCE OR  WAIVER.  Any term of this  Warrant  may be changed or
waived only by an  instrument  in writing  signed by the party against which
enforcement of the change or waiver is sought.

      17.   HEADINGS.  The  headings  in this  Warrant  are for  purposes of
reference  only and shall not limit or  otherwise  affect the meaning of any
provision of this Warrant.

      18.   GOVERNING  LAW.  This Warrant will be governed by and  construed
in accordance with the laws of the State of Delaware.

                                       VERSICOR INC.

                                       By:
                                          ------------------------------------
                                           George F. Horner, III

[Corporate Seal]                       Title:  Chief Executive Officer and
                                               Director

ATTEST:

-----------------------

                                      -8-
<PAGE>

                                                                      APPENDIX I

                                  PURCHASE FORM

To:                                                   Dated:
   ---------------                                               ---------------

      The undersigned, pursuant to the provisions set forth in the attached
Warrant (No. ), hereby irrevocably elects to purchase shares of the Common Stock
covered by such Warrant. The undersigned herewith makes payment of $ in lawful
money of the United States, representing the full purchase price for such shares
at the price per share provided for in such Warrant.

                                    Signature:
                                               -----------------
                                    Address:
                                               -----------------

                                               -----------------

                                      -1-
<PAGE>

                                                                     APPENDIX II

                                 ASSIGNMENT FORM

      FOR VALUE RECEIVED, hereby sells, assigns and transfers all of the rights
of the undersigned under the attached Warrant (No. ) with respect to the number
of shares of Common Stock covered thereby set forth below, unto:

NAME OF ASSIGNEE              ADDRESS                 NO. OF SHARES

Dated:                        Signature:
      ------------------                  -------------------

Dated:                        Signature:
      ------------------                  -------------------

                                      -2-

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