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                                                                     Exhibit 4.5



THE SECURITIES ISSUABLE UPON THE EXERCISE OF THIS OPTION HAVE NOT BEEN
REGISTERED UNDER THE SECURITIES ACT OF 1933 AS AMENDED (THE "ACT") OR ANY
APPLICABLE STATE SECURITIES LAWS, AND MAY NOT BE OFFERED, SOLD OR OTHERWISE
TRANSFERRED, PLEDGED OR HYPOTHECATED IN THE ABSENCE OF A REGISTRATION STATEMENT
IN EFFECT WITH RESPECT TO SUCH SECURITIES, OR DELIVERY OF AN OPINION OF COUNSEL
IN FORM AND SUBSTANCE REASONABLY SATISFACTORY TO THE COMPANY THAT SUCH OFFER,
SALE OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE WITH THE ACT OR
UNLESS SOLD IN FULL COMPLIANCE WITH RULE 144 UNDER THE ACT.

                                INHIBITEX, INC.

                               OPTION TO PURCHASE
                             SHARES OF COMMON STOCK

                                  May 7, 1999
                                  (Grant Date)

     THIS OPTION evidences that, for value received, Dr. Timothy J. Foster (the
"Optionee") is entitled to subscribe for and purchase from Inhibitex, Inc., a
Delaware corporation (the "Company"), subject to the terms set forth below (the
"Option"), seven thousand (7,000) shares (the "Shares") of the Company's Common
Stock (the "Common Stock") at a price per share of $0.15 (the "Exercise Price"),
upon surrender hereof, at the principal office of the Company referred to below,
with the Notice of Exercise attached hereto duly executed, and simultaneous
payment therefor in lawful money of the United States. The number, character and
Exercise Price of the Shares are subject to adjustment as provided below.

     1.         Grant and Exercise.  Optionee shall be entitled to purchase a
total of seven thousand (7,000) shares of Common Stock at the Exercise Price.
Optionee's right to exercise the Option depends upon the extent to which the
Option is vested. Optionee shall vest in the option as follows: 25% per year on
the date of the mailing of the completed annual report for the performance
period for the first four years after the date of the grant.  The Option shall
expire on the tenth anniversary of the Grant Date.

     2.         Method of Exercise; Payment. The Option may be exercised by the
Optionee, in accordance with Section 1 above, by the surrender of the notice of
exercise form attached hereto as Exhibit A, duly executed, at the principal
office of the Company and by the payment to the Company, by check or bank draft,
of an amount equal to the Exercise Price per share multiplied by the number of
Shares then being purchased. In the event of any exercise of the Option,
certificates representing the Shares shall be delivered to the Optionee as soon
as practicable thereafter.

     3.         Stock Fully Paid; Reservation of Shares. All Shares that may be
issued upon the exercise of the Option will, upon issuance, be fully paid and
nonassessable, and free from all taxes, liens and charges with respect to the
issue thereof. During the period within which
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the Option may be exercised, the Company will at all times have authorized and
reserved for the purpose of issuance upon exercise of the Option, a sufficient
number of shares of its Common Stock to provide for the exercise of the Option.

     4.         Adjustment of Exercise Price and Number of Shares. The number
and kind of securities purchasable upon the exercise of the Option and the
Exercise Price shall be subject to adjustment from time to time upon the
occurrence of certain events, as follows:

          a.    In case of (i) any reclassification of or similar change in the
Common Stock; (ii) any merger of the Company with or into another corporation
(other than a merger with another corporation in which the Company is a
continuing corporation and which does not result in any reclassification of or
similar change in the Common Stock); or (iii) any sale of all or substantially
all of the assets of the Company, the Company, or such successor or purchasing
corporation, as the case may be, shall execute a new Option having substantially
similar terms.

          b.    In case of (i) any subdivision or combination of the Common
Stock or (ii) at any time or from time to time after the Grant Date, any
declaration or payment, without consideration, any dividend on the Common Stock
payable in shares of its capital stock or in any right to acquire shares of its
capital stock without consideration, the number of shares of Common Stock or
other security issuable upon exercise hereof shall be proportionately increased
or decreased, as appropriate.

          c.    The Company will not, by amendment of its Certificate of
Incorporation or through any reorganization, recapitalization, transfer of
assets, consolidation, merger, dissolution, issue or sale of securities or any
other voluntary action, avoid or seek to avoid the observance or performance of
any of the terms to be observed or performed hereunder by the Company, but will
at all times in good faith assist in the carrying out of all the provisions of
this Paragraph 4 and in the taking of all such action as may be necessary or
appropriate in order to protect the rights of the Optionee against impairment.

     5.         Notice of Adjustments. Whenever the Exercise Price shall be
adjusted pursuant to the provisions hereof, the Company shall, within 30 days of
such adjustment, deliver a certificate signed by its chief financial officer to
the Optionee(s) setting forth, in reasonable detail, the event requiring the
adjustment, the amount of the adjustment, the method by which such adjustment
was calculated, and the Exercise Price after giving effect to such adjustment.

     6.         Transfers. This Option shall not be transferable by the Optionee
other than by will or the laws of descent and distribution.

     7.         Rights as Stockholders. No Optionee, as such, shall be entitled
to vote or receive dividends or be deemed the holder of Common Stock, nor shall
anything contained herein be construed to confer upon the Optionee, as such, any
of the rights of a stockholder of the Company or any right to vote for the
election of directors or upon any matter submitted to stockholders at any
meeting thereof, or to receive notice of meetings, or to receive dividends or
subscription rights or otherwise until all or a portion of this Option shall
have been exercised and the Shares shall have become deliverable, as provided
herein.


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     8.         Other Conditions. If so requested by the Company, Optionee shall
(as a condition to the exercise of the Option) enter into such additional
shareholder, buy-sell or other agreement or agreements prepared by the Company
as the Company deems appropriate, or make such representations requested by the
Company as the Company deems appropriate, which may restrict transfer of the
Shares. The certificate(s) evidencing the Stock shall include one or more
legends that reference or describe the conditions upon exercise.

     9.         Modification and Waiver. This Option and any provision hereof
may be changed, waived, discharged or terminated only by an instrument in
writing signed by the party against which enforcement of the same is sought.

     10.        Notices. Any notice, request or other document required or
permitted to be given or delivered to the Optionee or the Company shall be
delivered, or shall be sent by certified or registered mail, postage prepaid, to
each such Optionee at its address as shown on the books of the Company or to the
Company at the address indicated on Exhibit A.

     11.        Binding Effect on Successors. This Option shall be binding upon
any corporation succeeding the Company by merger, consolidation or acquisition
of all or substantially all of the Company's assets, and all of the obligations
of the Company relating to the Shares shall survive the exercise and termination
of this Option and all of the covenants and agreements of the Company shall
inure to the benefit of the successors and assigns of the Optionee. The Company
will, at the time of the exercise of this Option, in whole or in part, upon
request of the Optionee but at the Company's expense, acknowledge in writing its
continuing obligation to the Optionee hereof in respect of any rights to which
the Optionee shall continue to be entitled after such exercise in accordance
with this Option; provided, that the failure of the Optionee to make any such
request shall not affect the continuing obligation of the Company to the
Optionee in respect of such rights.

     12.        Lost Stock Certificates. The Company covenants to the Optionee
that upon receipt of evidence reasonably satisfactory to the Company of the
loss, theft, destruction, or mutilation of any stock certificate issued to the
Optionee pursuant to the exercise of this Option, and, in the case of any such
loss, theft or destruction, upon receipt of an indemnity reasonably satisfactory
to the Company, or in the case of any such mutilation upon surrender and
cancellation of such stock certificate, the Company will make and deliver a new
stock certificate, of like tenor, in lieu of the lost, stolen, destroyed or
mutilated stock certificate.

     13.        Governing Law. This Option shall be construed and enforced in
accordance with, and the rights of the parties shall be governed by, the laws of
the State of Delaware, without regard to such state's conflicts of laws
principles.


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     IN WITNESS WHEREOF, this Option to Purchase Common Stock is executed
effective as of the date first above written.

                             INHIBITEX, INC.



                             By: /s/ William D. Johnston
                                 -------------------------
                             Name: William D. Johnston
                             Title: President and Chief Executive Officer

                             OPTIONEE


                             /s/ Dr. Timothy J. Foster
                             -------------------------
                             Dr. Timothy J. Foster


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