Document:

EX-10.50

Execution Version

AMENDED AND RESTATED EXECUTIVE EMPLOYMENT AGREEMENT

THIS AMENDED AND RESTATED EXECUTIVE EMPLOYMENT AGREEMENT (this “Agreement”), approved by Board
as of December 21, 2010 (the “Effective Date”), is between Inhibitex, Inc., a Delaware
corporation (the “Company”), and Geoff Henson (the “Executive”).

WHEREAS, the Company and the Executive are parties to an Executive Employment Agreement dated
as of September 20, 2007 (the “Prior Agreement”) and wish to amend and restate the Prior Agreement
in its entirety as provided herein;

WHEREAS, the Company desires to secure the Executive’s continued employment in an executive
capacity and to compensate him for such employment; and

WHEREAS, the Executive is willing to continue to be employed by the Company upon the terms and
subject to the conditions contained in this Agreement.

NOW THEREFORE, in consideration of the premises and mutual covenants contained herein and for
other good and valuable consideration, the adequacy and receipt of which are hereby acknowledged,
the parties hereto, intending to be legally bound, agree as follows:

Section 1. Position, Duties and Responsibilities.

(a) During the Term (as defined in Section 2), the Executive shall serve as the Senior Vice
President, Drug Development of the Company consistent with the by-laws of the Company, and shall be
responsible for the duties identified in the attached Appendix I, such other duties as are
attendant to such offices and such other managerial duties and responsibilities with the Company,
its affiliates, subsidiaries or divisions consistent with such position as may be assigned by the
Chief Executive Officer (“CEO”) or Board of Directors of the Company (the “Board”). The Executive
shall devote his full energies, interest, abilities and productive time to the business and affairs
of the Company and to promoting its best interests. The Executive acknowledges and agrees that
although his duties shall be performed from the Company’s offices in the Atlanta, Georgia
metropolitan area or at such other places as shall be necessary according to the needs, business
and opportunities of the Company, the performance by the Executive of his duties hereunder may
require substantial travel from time to time by the Executive. The Executive further agrees that,
during the Term, the Company shall be the Executive’s sole employer.

(b) Executive understands that the provisions of any employee handbooks, personnel manuals and
any and all other written statements of or regarding personnel policies, practices or procedures
that are or may be issued by the Company (the “Company Policies”) do not and shall not constitute a
contract of employment and do not and shall not create any vested rights; and that any such
provisions may be changed, revised, modified, suspended, canceled, or eliminated by the Company at
any time, in its sole discretion, with or without notice.

(c) Executive shall comply with all applicable Company Policies, which may be in effect from
time to time during the Term. Copies of all such Company Policies may be examined in the Human
Resource Department of the Company. If a provision in any Company Policy conflicts with this
Agreement, the terms of this Agreement shall prevail.

(d) For up to a one (1) year period following any termination of the Executive’s employment,
upon the request of the Company, the Executive shall reasonably cooperate with the Company in all
matters relating to the winding up of pending work on behalf of the Company and the orderly
transfer of work to other employees of the Company. The Executive shall also cooperate in the
defense of any action brought by any third party against the Company that relates in any way to the
Executive’s acts or omissions while employed by the Company. The Company shall reimburse the
Executive for his reasonable out-of-pocket costs incurred in connection with such cooperation.

Section 2. Term of Employment.

The term of the Executive’s employment under this Agreement shall continue through December
31, 2010, and thereafter shall be renewed automatically for successive one (1) year periods
(without any action by either party) effective as of each January 1st thereafter, unless
the Executive’s employment under this Agreement is earlier terminated in accordance with Section 4.
Executive may elect not to renew his employment under this Agreement for any reason upon sixty
(60) days prior written notice. For purposes of this Agreement, “Term” means the term of the
Executive’s employment under this Agreement.

Section 3. Compensation; Benefits; Expenses.

(a) Base Salary. For all services rendered by the Executive hereunder during the Term,
the Company shall pay the Executive an annual salary equal to Two Hundred Fifty Two Thousand
Dollars ($252,000), less standard deductions and withholdings, payable in equal installments at the
times and pursuant to the procedures regularly established for the payment of salaries generally to
employees, and as they may be amended by the Company during the Term. The Executive’s salary will
be reviewed from time to time by the CEO, the Board or a committee of the Board, or otherwise in
accordance with the Company’s established procedures for adjusting salaries, and will be subject to
increases (but not decreases, except pursuant to an across-the-board salary reduction as described
in Section 4(a)(iv)(B)) pursuant to such procedures.

(b) Incentive Compensation. The Executive shall be eligible to participate in such
bonus and incentive (including stock option and other equity-based) compensation plans of the
Company, if any, in which other executives of the Company are generally eligible to participate, as
the Board or a committee thereof shall determine from time to time in its sole discretion, subject
to and in accordance with the terms and provisions of such plans. Subject to the terms and
conditions of such bonus and incentive compensation plans, the Executive shall be eligible for
annual cash incentive compensation of up to 30% of his then annual salary. Any such cash incentive
compensation shall be paid to the Executive by no later than March 15th of the year
following the year in which such cash incentive compensation was earned.

(c) Benefits. The Company shall provide the Executive with the right to participate in
and to receive benefits from the group life, group disability and medical plans and all similar
benefits made generally available to similarly situated executives of the Company. The amount and
extent of benefits to which the Executive is entitled shall be governed by the specific benefit
plan or plans, as such may be amended from time to time.

(d) Equity Incentives. During the Term, the Executive shall be eligible to receive
equity-based incentive awards under the Inhibitex, Inc. Amended and Restated 2004 Stock Incentive
Plan, as amended, or any successor plan thereto.

(e) Reimbursement of Expenses. It is contemplated that in connection with the
Executive’s employment hereunder, he may be required to incur business, entertainment and travel
expenses. The Company agrees to promptly (twice monthly) reimburse the Executive in full for all
reasonable out-of-pocket business, entertainment and other related expenses (including all
reasonable expenses of travel and living expenses while away from home on business or at the
request of, and in service of, the Company) incurred or expended by him incident to the performance
of his duties hereunder, provided that the Executive properly accounts for such expenses in
accordance with the policies and procedures established by the Board and applicable to the
executives of the Company.

(f) Vacation; Personal Days. During the Term, the Executive shall be entitled to five
(5) weeks vacation with pay during each calendar year of his employment hereunder provided that the
vacation days taken do not materially interfere with the operations of the Company. Such vacation
may be taken, in the Executive’s discretion, at such time or times as are not inconsistent with the
reasonable business needs of the Company. The Executive shall also be entitled to all paid holidays
and personal days provided by the Company to its executives. Vacation, holiday and personal days
shall additionally be subject to applicable Company Policies.

Section 4. Termination.

(a) The Executive’s employment under this Agreement may be terminated under the following
circumstances:

(i) Death. The Executive’s employment shall immediately terminate upon his death.

(ii) Disability. In the event the Executive shall be unable to render services or
perform his duties hereunder by reason of “Disability,” as such term is defined in the Company’s
Long-Term Disability Plan, as the same shall be amended from time to time, the Company shall have
the right to terminate the Executive’s employment under this Agreement immediately upon notice to
the Executive.

(iii) Termination of Employment by the Company for Cause. The Company may terminate
the employment of the Executive immediately for Cause (as hereinafter defined). The term “Cause,”
as used herein, shall mean (1) the Executive’s willful misconduct, gross negligence, dishonesty or
fraud in the performance of his duties hereunder, (2) the material breach of this Agreement by the
Executive after notice of such breach and a reasonable opportunity to cure, (3) the Executive’s
willful refusal or failure to perform his duties hereunder or under any lawful directive of the
Board or his superior officer, as the case may be, which is consistent with his title and position
after notice of such failure and a reasonable opportunity to cure, or (4) the conviction, plea of
guilty or nolo contendere of the Executive in respect of any felony or other crime
involving moral turpitude, dishonesty, theft or unethical business conduct.

(iv) Termination of Employment by Executive for Good Reason. The Executive may resign
and terminate his employment hereunder for Good Reason (as defined below) by providing a written
notice thereof within sixty (60) days from the occurrence of the event that the Executive is
deeming Good Reason. For purposes of this Agreement, “Good Reason” shall mean there has occurred,
without the express written consent of the Executive:

(A) the assignment to the Executive of any duties materially inconsistent with his status as a
senior executive of the Company or a substantial diminution in the nature or status of his
responsibilities;

(B) a reduction by the Company in the Executive’s salary as in effect on the date hereof or as
the same may be increased from time to time, except for across-the-board salary reductions
similarly affecting all executives of the Company;

(C) (1) the relocation of the Company’s principal executive offices to a location outside the
Atlanta, Georgia metropolitan area or (2) the Company’s requiring the Executive to perform his
duties anywhere other than the Company’s principal executive offices; provided that, in any case,
required travel on the Company’s business to an extent substantially consistent with the
Executive’s responsibilities shall not constitute “Good Reason;”

(D) the failure by the Company to continue in effect any material cash, equity or incentive
compensation plan in which the Executive was participating or the failure by the Company to
continue the Executive’s participation therein, unless an equitable arrangement (embodied in an
ongoing substitute or alternative plan) has been made with respect to such plan or participation
(unless such change or discontinuation similarly affects all executives of the Company);

(E) the failure by the Company to continue to provide the Executive with benefits
substantially similar to those enjoyed by the Executive under the Company’s life insurance,
medical, health-and-accident, or disability plans in which the Executive was participating, the
taking of any action by the Company which would directly or indirectly materially reduce any of
such benefits or deprive the Executive of any other material fringe benefits enjoyed by the
Executive, or the failure by the Company to provide the Executive with the number of paid vacation
days to which the Executive is entitled on the basis of years of service with the Company in
accordance with the Company’s normal vacation policy, except for across-the-board changes in such
benefits similarly affecting all executives and/or employees of the Company; or

(F) the failure of the Company to obtain a satisfactory agreement from any successor to assume
and agree to perform this Agreement, as contemplated in Section 16 hereof.

(v) Terminations other than for Cause, Good Reason, Disability or upon Death. In
addition to the foregoing, either party may terminate the Executive’s employment under this
Agreement at any time, by providing thirty (30) days prior written notice of his or its desire to
terminate.

(b) Notice of Termination. Any termination of the Executive’s employment by the
Company or by the Executive (other than a termination pursuant to Section 4(a)(i) above) shall be
communicated by written notice of termination to the other party.

Section 5. Compensation Upon Termination.

(a) Compensation Upon Termination Due to Death. In the event of the death of the
Executive during the Term, the Executive’s designated beneficiary, or, in the absence of such
designation, the estate or other legal representative of the Executive (collectively, the “Estate”)
shall be paid, within thirty (30) days of the Executive’s death, an amount equal to the sum of the
Executive’s unpaid salary and any earned but unpaid bonuses through such termination;
provided, however, that any bonus compensation conditioned upon the satisfaction of
performance goals shall not be deemed earned or payable unless such performance goals have been
satisfied as of such termination. The Estate shall be entitled to other vested death benefits in
accordance with the terms of the Company’s benefit programs and plans.

(b) Compensation Upon Termination for Disability. If the Executive’s employment
hereunder is terminated for Disability, the Executive shall be entitled to receive (if entitled
thereto) disability compensation and benefits in accordance with the Company’s benefit programs and
plans. In addition, Executive shall be entitled to receive, within sixty (60) days after the date
of such termination, any unpaid salary and any earned but unpaid bonuses through such termination;
provided, however, that any bonus compensation conditioned upon the satisfaction of
performance goals shall not be deemed earned or payable unless such performance goals have been
satisfied as of such termination of employment.

(c) Compensation Upon Termination for Cause or Termination Without Good Reason. If the
Executive’s employment is terminated by the Company for Cause or by the Executive without Good
Reason, the Company shall pay the Executive his unpaid salary through such termination, and the
Company shall have no further obligations to the Executive under this Agreement. All amounts
payable under this Section 5(c) shall be paid within sixty (60) days after the date of such
termination.

(d) Compensation Upon Termination in Connection With a Change in Control (other than for
Cause, without Good Reason, Disability or upon Death).

(i) If the Executive’s employment is terminated by the Executive for Good Reason or by the
Company for any reason other than pursuant to Section 4(a)(i), 4(a)(ii) or 4(a)(iii) hereof, in
either case, within one (1) year after the consummation of a Change in Control (as hereafter
defined) (or in contemplation of a Change in Control that is reasonably likely to occur), the
Company shall pay to the Executive (or in the event of the Executive’s death, the Estate) a
lump-sum cash amount equal to the sum of (w) the Executive’s unpaid salary through such
termination; plus (x) any bonus compensation earned and unpaid through such termination;
provided, however, that any bonus compensation conditioned upon the satisfaction of
performance goals shall not be deemed earned or payable unless such performance goals have been
satisfied as of such termination; plus (y) the product of (A) a fraction, the numerator of
which is the number of months in the Change in Control Severance Period (as hereafter defined) and
the denominator of which is 12, and (B) the sum of (1) Executive’s annual base salary as then in
effect and (2) the bonus or incentive compensation paid to the Executive in respect of the most
recent fiscal year prior to the year in which the Change in Control occurs; plus (z) a payment
equal to the present value of the premium payments that would be made by the Company if Executive
were to continue to be covered under the Company’s group health, life and disability insurance for
the Change in Control Severance Period, which amount shall be determined by the Company in its sole
discretion. All amounts payable under clauses (w) and (x) of this Section 5(d)(i) shall be paid
within sixty (60) days after such termination of employment and all amounts payable under clauses
(y) and (z) of this Section 5(d)(i) shall be paid on the date that is six months plus one day after
such termination, or upon the Executive’s death, if earlier. The “Change in Control Severance
Period” shall be eighteen (18) months, commencing on the date of the Executive’s termination of
employment.

(ii) Notwithstanding any other provision herein to the contrary, in the event that the
Executive becomes entitled to any payments under Section 5(d)(i) (“Termination Payments”) and any
portion of such Termination Payments, when combined with any other payments or benefits provided to
the Executive (including, without limiting the generality of the foregoing, by reason of any stock
options), in the absence of this Section 5(d)(ii), would be subject to the tax (the “Excise Tax”)
imposed by Section 4999 of the Internal Revenue Code of 1986, as amended (the “Code”), then
(subject to Section 5(d)(iii) hereof) the amount payable to the Executive under Section 5(d)(i)
shall be reduced such that none of the amounts payable to the Executive under Section 5(d)(i) and
any other payments or benefits received or to be received by the Executive in connection with a
Change in Control or the termination of the Executive’s employment (whether pursuant to the terms
of this Agreement or any other plan, arrangement or agreement with the Company, any person whose
actions result in a Change in Control or any person having such a relationship with the Company or
such person as to require attribution of stock ownership between the parties under Section 318(a)
of the Code) shall be treated as “parachute payments” within the meaning of Section 280G(b)(2) of
the Code. For purposes of applying the foregoing sentence, if in the opinion of tax counsel
selected by the Company and reasonably acceptable to the Executive, such payments or benefits (in
whole or in part) represent reasonable compensation for services actually rendered within the
meaning of Section 280G(b)(4) of the Code, then such amounts shall be excluded from any such
calculation. Furthermore, in determining the maximum amount of the payments to the Executive which
would not constitute a parachute payment within the meaning of Sections 280G(b)(1) and (4) of the
Code, the value of any non-cash benefits or any deferred payment or benefit shall be determined by
the Company’s independent auditors in accordance with the principles of Sections 280G(d)(3) and
(4) of the Code or any applicable proposed or final Treasury Regulations promulgated under the
Code. Any reduction in Termination Payments under this Section 5(d)(ii) shall be done first by
reducing any cash payments with the last payment reduced first; next any equity or equity
derivatives that are included under Code Section 280G at full value rather than accelerated value,
with the highest value reduced first; next any non-cash, non-equity-based benefits, with the latest
scheduled benefit reduced first; finally any equity or equity derivatives based on accelerated
value shall be reduced with the highest value reduced first (with all equity and equity derivative
values to be determined under Treasury Regulation Section 1.280G-1, Q&A 24).

(iii) If the net after-tax amount of the Termination Payments which would be payable to the
Executive in the absence of the reduction described in Section 5(d)(ii) above exceeds the net
after-tax amount of the Termination Payments which would be payable to the Executive if the
reduction described in Section 5(d)(ii) above were applicable, then the reduction to the
Executive’s Termination Payments described in Section 5(d)(ii) above shall not be applicable. For
purposes of computing such net after-tax amounts, the Termination Payments shall be treated as
subject to Federal income tax and any state and local income taxes (based upon the residence of the
Executive at the time the first amount of Termination Payments is to be paid hereunder) at the
highest marginal rate of income tax imposed upon individuals (but without assuming any reduction in
Federal income taxes that could be obtained from the deduction of any such state or local taxes if
paid in such year), shall be subject only to the Medicare portion of the F.I.C.A tax and, in
calculating the net after-tax amount of the Termination Payments which would otherwise be payable
to the Executive if the reduction described in Section 5(d)(ii) above were not applicable, any
applicable Excise Tax, and all such taxes shall be computed based upon the tax rates in effect for
the calendar year in which the first amount of Termination Payments are to be paid hereunder. The
determination of the net after-tax amounts will be made by tax counsel selected by the Company and
reasonably acceptable to the Executive, whose determination will be binding on both the Executive
and the Company.

(iv) For purposes of this Agreement, a “Change in Control” of the Company shall mean (A) the
consummation of a merger or consolidation of the Company in which the stockholders of the Company
immediately prior to such merger or consolidation would not, immediately after the merger or
consolidation, beneficially own (as such term is defined in Rule 13d-3 under the Securities
Exchange Act of 1934, as amended (the “Exchange Act”)), directly or indirectly, shares representing
in the aggregate 45% or more of the combined voting power of the securities of the corporation
issuing cash or securities in the merger or consolidation (or of its ultimate parent corporation,
if any); (B) the stockholders of the Company approve a plan of complete liquidation or dissolution
of the Company, or there is consummated an agreement for the sale or disposition by the Company of
all or substantially all of the Company’s assets, other than a sale or disposition by the Company
of all or substantially all of the Company’s assets to an entity, at least 45% of the combined
voting power of the voting securities of which are owned by persons in substantially the same
proportion as their ownership of the Company immediately prior to such sale; (C) during any period
of two (2) consecutive years, individuals who at the beginning of such period constitute the Board,
including for this purpose any new director whose election or nomination for election by the
Company’s stockholders was approved by a vote of at least two-thirds of the directors then still in
office who were directors at the beginning of the period or whose election or nomination for
election was previously so approved but excluding for this purposes any such new director whose
initial assumption of office occurs as a result of either an actual or threatened election contest
(as such terms are used in Rule 14a-11 of Regulation 14A under the Exchange Act) or other actual or
threatened solicitation of proxies or consents by or on behalf of an individual, corporation,
partnership, group, association or other entity or Person (as such term is used in Sections 13(d)
and 14(d) of the Exchange Act) other than the Board, cease for any reason to constitute a majority
thereof; or (D) such other similar transaction not specifically identified above, which in the sole
discretion of the Board (or committee thereof) effectively constitutes a change in control of the
Company.

(e) Compensation Upon All Other Terminations. If the Company terminates the
Executive’s employment under this Agreement for any reason other than pursuant to Section 4(a)(i),
4(a)(ii), 4(a)(iii) or Section 5(d) or if Executive terminates his employment for Good Reason other
than pursuant to Section 5(d), then the Company shall pay Executive a lump sum equal to the sum of
(v) the Executive’s unpaid salary through such termination; plus (w) any bonus compensation
earned and unpaid through such termination; provided, however, that any bonus
compensation conditioned upon the satisfaction of performance goals shall not be deemed earned or
payable unless such performance goals have been satisfied as of such termination; plus
(x) the Executive’s salary for the Severance Period (as defined below); plus (y) the
product of (1) a fraction, the numerator of which is the number of months in the Severance Period
and the denominator of which is 12, and (2) the bonus or incentive compensation paid to the
Executive in respect of the most recent fiscal year prior to the year in which such termination
occurs; plus (z) an amount equal to the present value of the premium payments that would be made by
the Company if Executive were to continue to be covered under the Company’s group health, life and
disability insurance for the Severance Period, which amount shall be determined by the Company in
its sole discretion. All amounts payable under clauses (v) and (w) of this Section 5(e) shall be
paid within sixty (60) days after such termination of employment and all amounts payable under
clauses (x), (y) and (z) of this Section 5(e) shall be paid in cash in a lump-sum on the date that
is six months plus one day after such termination, or upon Executive’s death, if earlier. The
“Severance Period” shall be twelve (12) months, commencing on the date of the Executive’s
termination of employment.

(f) Notwithstanding anything else contained herein, the obligation of the Company to make any
severance payments to the Executive hereunder (other than accrued and unpaid salary, earned and
unpaid bonuses and other payments required under law) shall be conditioned upon the execution and
delivery by the Executive of a release from liability in favor of the Company in form and substance
reasonably satisfactory to the Company, such that such release is effective, with all revocation
periods having expired unexercised, within 60 days after the date of the Executive’s termination of
employment.

(g) The parties hereto agree that any termination of the Executive’s employment for Good
Reason or by the Company other than for Cause would be an “involuntary separation from service”
within the meaning of Treasury Regulation Section 1.409A-1(n). Therefore, notwithstanding the
severance payment schedules set forth in Sections 5(d) and 5(e) and provided that such action would
not result in the imposition of any taxes or penalties on the Executive under Code Section 409A,
any severance owed to the Executive under such Sections, to the extent such severance does not
exceed the limit set forth in Treasury Regulation Section 1.409A-1(b)(9)(iii)(A), shall be paid to
the Executive on the 60th day following his termination of employment, with any severance in excess
of such limit to be paid to the Executive at the time provided in Section 5(d) or Section 5(e), as
applicable.

Section 6. Confidentiality.

(a) Each Item, Trade Secret and piece of Confidential Information (in each case, as defined
below) that has come or comes into Executive’s possession by reason of his employment are the
property of the Company and shall not be used by Executive in any way except in the course of his
employment by, and for the benefit of, the Company. Executive will not remove any Items from
premises owned or leased by the Company except as his duties shall require, and upon termination of
his employment, all Items (including any copies or excerpts thereof) will be turned over to
Executive’s supervisor at the Company.

(b) Executive will preserve as confidential all Confidential Information that has been or may
be obtained by him. Executive will not, without written authority from the Company, use for his own
benefit or purposes, or disclose to others, either during his employment or for two (2) years
thereafter, any Confidential Information or any copy or notes made from any Item embodying
Confidential Information except as required by his employment with the Company or to the extent
disclosure is or may be required by a statute, by a court of law, by any governmental agency having
supervisory authority over the business of the Company or by any administrative or legislative body
(including a committee thereof) with jurisdiction to order him to divulge, disclose or make
accessible such information, provided, however, that the Executive shall give the Company notice of
any such request or demand for such information upon his receipt of same and the Executive shall
reasonably cooperate with the Company in any application the Company may make seeking a protective
order barring disclosure by the Executive. Executive understands that his obligations with respect
to Confidential Information shall continue for two years after termination of his employment with
the Company. These restrictions concerning use and disclosure of Confidential Information shall not
apply to information which is or becomes publicly known by lawful means, or comes into Executive’s
possession from sources not under an obligation of confidentiality to the Company.

(c) Executive agrees to hold in confidence all Trade Secrets of the Company that came into his
knowledge during or in connection with his employment by the Company and shall not disclose,
publish or make use of at any time after the date hereof such Trade Secrets without the prior
written consent of the Company for as long as the information remains a Trade Secret.

(d) Executive understands that any entrusting of Confidential Information or Trade Secrets to
him by the Company is done in reliance on a confidential relationship arising out of his employment
with the Company. Executive further understands that Confidential Information or Trade Secrets that
he may acquire or to which he may have access, especially with regard to research and development
projects and scientific findings, data, formulae, designs, formulation, processes, intellectual
property rights, know-how, the identity of suppliers, customers and patients, methods of
manufacture, and cost and pricing data is of great value to the Company.

(e) Executive agrees that following termination of his employment with the Company, Executive
will, if possible before answering but in any event as soon thereafter as practicable, make every
effort to contact the Company’s General Counsel if Executive is served with a subpoena or other
legal process asking for a deposition, testimony or other statement, or other potential evidence to
be used in connection with any lawsuit to which the Company is a party or involving Executive’s
employment with the Company or any Confidential Information or Trade Secret of the Company.

(f) For purposes of this Agreement: (i) “Confidential Information” means information relating
to the present or planned business of the Company which has not been released publicly by
authorized representatives of the Company. Executive understands that Confidential Information may
include, for example, discoveries, scientific data, inventions, know-how and products, customer,
patient, supplier and competitor information, sales, pricing, cost, and financial data, research,
development, marketing and sales programs and strategies, manufacturing, marketing and service
techniques, processes and practices, and regulatory strategies. Executive understands further that
Confidential Information also includes all information received by the Company under an obligation
of confidentially to a third party; (ii) “Items” include documents, reports, drawings, photographs,
designs, specifications, formulae, plans, samples, research or development information, prototypes,
tools, equipment, proposals, marketing or sales plans, customer information, customer lists,
patient lists, patient information, regulatory files, financial data, costs, pricing information,
supplier information, written, printed or graphic matter, or other information and materials that
concern the Company’s business that come into Executive’s possession or about which Executive has
knowledge by reason of his employment; and (iii) “Trade Secrets” include all information, including
a formula pattern, process, compilation, program, device, method, or technique that (A) derives
independent economic value, actual or potential, from not being generally known to, and not being
readily ascertainable by proper means by other persons who can obtain economic value from its
disclosure or use, (B) is the subject of efforts that are reasonable under the circumstances to
maintain its secrecy; and (C) otherwise satisfies the requirements of the Georgia Trade Secrets
Act.

Section 7. Proprietary Information.

(a) All Inventions (as defined below) related to the present or planned business of the
Company, which have been or are conceived or reduced to practice by Executive, either alone or with
others, during the period of his employment or during a period of one (1) year after termination of
such employment, whether or not done during his regular working hours, are the sole property of the
Company. The provisions of this paragraph shall not apply to an invention for which no equipment,
supplies, facilities or confidential or trade secret information of the Company was used and which
was developed entirely on Executive’s own time, unless (a) the invention relates to (i) the
business of the Company, or (ii) the Executive’s actual or demonstrably anticipated research or
development for the Company, or (b) the invention results from any work performed by Executive for
the Company.

(b) Executive will disclose promptly and in writing to the Company, through his supervisor,
all Inventions which are covered by this Agreement, and Executive agrees to assign to the Company
or its nominee all his right, title, and interest in and to such Inventions. Executive agrees not
to disclose any of these Inventions to others, without the express consent of the Company.
Executive will, at any time during or after his employment, on request of the Company, execute
specific assignments in favor of the Company or its nominee of his interest in and to any of the
Inventions covered by this Agreement, as well as execute all papers, render all assistance, and
perform all lawful acts which the Company considers necessary or advisable for the preparation,
filing, prosecution, issuance, procurement, maintenance or enforcement of patent applications and
patents of the United States and foreign countries for these Inventions, and for the transfer of
any interest Executive may have. Executive will execute any and all papers and documents required
to vest title in the Company or its nominee in the above Inventions, patent applications, patents,
and interests. Executive understands that if he is not employed by the Company at the time he is
requested to execute any document under this Section 7(b), Executive shall receive fifty dollars
($50.00) for the execution of each document, and one hundred fifty dollars ($150.00) per day for
each day or portion thereof spent at the request of the Company in the performance of acts pursuant
to this Section 7(b), plus reimbursement for any out-of-pocket expenses incurred by Executive at
the Company’s request in such performance. Executive further understands that the absence of a
request by the Company for information, or for the making of an oath, or for the execution of any
document, shall in no way be construed to constitute a waiver of the Company’s rights under this
Agreement. Should the Company be unable to secure the Executive’s signature on any document
necessary to apply for, prosecute, obtain, or enforce any patent, copyright, or other right or
protection relating to any Invention, whether due to the Executive’s mental or physical incapacity
or any other cause, the Executive hereby irrevocably designates and appoints the Company and each
of its duly authorized officers and agents as the Executive’s agent and attorney in fact, to act
for and in the Executive’s behalf and stead and to execute and file any such document, and to do
all other lawfully permitted acts to further the prosecution, issuance, and enforcement of patents,
copyrights, or other rights or protections with the same force and effect as if executed and
delivered by the Executive.

(c) Executive has disclosed to the Company all continuing obligations which he has with
respect to the assignment of Inventions to any previous employers, and Executive claims no previous
unpatented Inventions as his own, except for those which have been reduced to practice and which
are shown on a schedule, if any, attached to this agreement. Executive understands that the Company
does not seek any confidential or trade secret information which Executive may have acquired from a
previous employer, and Executive will not disclose to or utilize any such information on behalf of
the Company.

(d) All writings and other works which may be copyrighted (including computer programs) which
are related to the present or planned business of the Company and are prepared by Executive during
his employment by the Company shall be, to the extent permitted by law, works made for hire, and
the authorship and copyright of the work shall be in the Company’s name. To the extent that such
writings and works are not works for hire, Executive agrees to the wavier of “moral rights” in such
writings and works, and to assign to the Company all Executive’s right, title and interest in and
to such writings and works, including copyright.

(e) Executive will permit the Company and its agents to use and distribute any pictorial
images which are taken of him during his employment by the Company as often as desired for any
lawful purpose. Executive waives all rights of prior inspection or approval and releases the
Company and its agents from any and all claims or demands which Executive may have on account of
the lawful use of publication of such pictorial images.

(f) For purposes of this Agreement, “Invention” shall mean all ideas, potential marketing and
sales relationships, inventions, experiments, copyrightable expression, research, plans for
products or services, marketing plans, reports, strategies, processes, computer software
(including, without limitation, source code), computer programs, original works of authorship,
characters, know-how, trade secrets, information, data, developments, discoveries, improvements,
modifications, technology, algorithms, database schema, designs, and drawings, whether or not
subject to patent or copyright protection, made, conceived, expressed, developed, or actually or
constructively reduced to practice by the Executive solely or jointly with others prior to or
during the Term, which refer to, are suggested by, or result (i) from any work which the Executive
has performed prior to the Term of this Agreement, (ii) from any work which the Executive may
perform during his employment, or (iii) from any information obtained from the Company or any
affiliate of the Company, and shall not be limited to the meaning of “Invention” under the United
States patent laws.

Section 8. Agreement Not to Compete.

(a) While employed by the Company and thereafter for a period equal to the greater of (x) one
(1) year and (y) the Change in Control Severance Period in the event of a termination pursuant to
Section 5(d)(i), the Executive shall not, directly or indirectly, anywhere in the United States:

(i) render services which are substantially similar to the services performed by Executive for
the Company to any person, corporation, partnership or other entity which competes with the Company
(or any subsidiary) in the business of developing or manufacturing small molecule compounds
for the treatment of infections caused by varicella zoster virus or hepatitis C virus;
Executive agrees that this covenant is especially appropriate because, if he worked for a
competitor, he would inevitably make business decisions by relying on his knowledge of the
Company’s Confidential Information and Trade Secrets; thus, he would inevitably provide competitors
with the Company’s Confidential Information and Trade Secrets. The Company’s Confidential
Information and Trade Secrets are not generally known by others in the industry, and they would
provide an unfair advantage for competitors. Further, the Company recognizes that there are some
companies who provide many products and services, some of which may be competitive and some which
may not be. Accordingly, this covenant only prohibits Executive from performing the same or
substantially the same services for that section, division, group, subsidiary, affiliate or
operating unit of a competitor that actually develops or manufactures small molecule compounds
for the treatment of infections caused by varicella zoster virus or hepatitis C virus.
Further, the Company and Executive agree that the Company is engaged in the business of developing
or manufacturing small molecule compounds for the treatment of infections caused by
varicella zoster virus or hepatitis C virus throughout the United States and beyond; or

(ii) solicit for employment any person who was employed by the Company (or any subsidiary)
during the Executive’s employment with the Company and with whom the Executive had contact during
the last year of his employment with the Company.

(b) If any of the restrictions contained in this Section 8 shall be deemed by any court of
competent jurisdiction to be unenforceable by reason of the extent, duration or geographical scope
thereof, or otherwise, then the parties agree that such court shall modify such restriction, only
to the extent necessary to render it enforceable and, in its reduced form, such restriction shall
then be enforced, and in its reduced form this Section 8 shall be enforceable in the manner
contemplated hereby.

(c) The Executive and the Company agree to revise the specific description of the Company’s
line of business set forth in Section 8(a) as appropriate to reflect any material change in the
Company’s business due to an in-licensing, merger, acquisition or similar strategic transaction.

Section 9. Company Resources.

Executive may not use any of the Company’s (or any affiliate’s) equipment for personal
purposes without written permission from the Company. The Executive may not give access to the
Company’s (or any affiliate’s) offices or files to any person not in the employ of the Company
without written permission of the Company.

Section 10. Injunctive Relief.

Executive understands and agrees that the Company will suffer irreparable harm in the event
that the Executive breaches any of the Executive’s obligations under Sections 6, 7, 8 or 9 hereof
and that monetary damages will be inadequate to compensate the Company for such breach.
Accordingly, the Executive agrees that, in the event of a breach or threatened breach by the
Executive of any of the provisions of Sections 6, 7, 8 or 9 hereof, the Company shall be entitled
to appropriate injunctive relief, in addition to any other rights, remedies or damages available to
the Company at law or in equity.

Section 11. Severability.

In the event any of the provisions of this Agreement shall be held by a court or other
tribunal of competent jurisdiction to be unenforceable, the other provisions of this Agreement
shall remain in full force and effect.

Section 12. Survival.

Sections 1(d) and 4 through 16 shall survive the termination of this Agreement and the
Executive’s employment under this Agreement for any reason.

Section 13. Representations, Warranties, and Covenants.

Executive represents, warrants, and covenants that the Executive’s performance of all the
terms of this Agreement and any services to be rendered as an employee of the Company do not and
will not breach any fiduciary or other duty or any covenant, agreement or understanding (including,
without limitation, any agreement relating to any proprietary information, knowledge or data
acquired by the Executive in confidence, trust or otherwise prior to the Executive’s employment by
the Company) to which the Executive is a party or by the terms of which the Executive may be bound.
The Executive further covenants and agrees not to enter into any agreement or understanding, either
written or oral, in conflict with the provisions of this Agreement.

Section 14. Accounting for Profits; Indemnification.

Executive covenants and agrees that, if the Executive shall violate any of the Executive’s
covenants or agreements contained in Sections 6, 7, 8 or 9 hereof, the Company shall be entitled to
an accounting and repayment of all profits, compensation, royalties, commissions, remunerations or
benefits which the Executive directly or indirectly shall have realized or may realize relating to,
growing out of or in connection with any such violation; such remedy shall be in addition to and
not in limitation of any injunctive relief or other rights or remedies to which the Company is or
may be entitled at law or in equity or otherwise under this Agreement. The Executive hereby agrees
to defend, indemnify and hold harmless the Company against and in respect of: (a) any and all
losses and damages resulting from, relating or incident to, or arising out of any misrepresentation
or breach by the Executive of any of the Executive’s representations, warranties, covenants or
agreements made or contained in this Agreement; and (b) any and all actions, suits, proceedings,
claims, demands, judgments, costs and expenses (including reasonable attorneys’ fees) incident to
the foregoing.

Section 15. General.

This Agreement supersedes and replaces any existing agreement between the Executive and the
Company relating generally to the same subject matter (including, without limitation, the Prior
Agreement) and may be modified only in a writing signed by the parties hereto. Failure to enforce
any provision of the Agreement shall not constitute a waiver of any term herein. The Executive
agrees that he will not assign, transfer, or otherwise dispose of, whether voluntarily or
involuntarily, or by operation of law, any rights or obligations under this Agreement. Any
purported assignment, transfer, or disposition shall be null and void. Nothing in this Agreement
shall prevent the consolidation of the Company with, or its merger into, any other corporation, or
the sale by the Company of all or substantially all of its properties or assets, or the assignment
by the Company of this Agreement and the performance of its obligations hereunder. Subject to the
foregoing, this Agreement shall be binding upon and shall inure to the benefit of the parties and
their respective heirs, legal representatives, successors, and permitted assigns, and shall not
benefit any person or entity other than those enumerated above. The use of any gender herein shall
be applicable to all genders.

Section 16. Executive Acknowledgment.

Executive acknowledges (a) that he has consulted with, or has had the opportunity to consult
with, independent counsel of his own choice concerning this Agreement and has been advised to do so
by the Company, and (b) that he has read and understands the Agreement, is fully aware of its legal
effect, and has entered into it freely based on his own judgment.

Section 17. Section 409A.

This Agreement is intended to comply with Code Section 409A (to the extent applicable) and the
parties hereto agree to interpret, apply and administer this Agreement in the least restrictive
manner necessary to comply therewith and without resulting in any increase in the amounts owed
hereunder by the Company. Notwithstanding any other provision of this Agreement to the contrary,
if the Executive is a “specified employee” within the meaning of Code Section 409A and the
regulations issued thereunder, and a payment or benefit provided for in this Agreement would be
subject to additional tax under Code Section 409A if such payment or benefit is paid within six (6)
months after the Executive’s “separation from service” (within the meaning of Code Section 409A),
then such payment or benefit required under this Agreement shall not be paid (or commence) during
the six-month period immediately following the Executive’s separation from service except as
provided in the immediately following sentence. In such an event, any payments or benefits that
would otherwise have been made or provided during such six-month period and which would have
incurred such additional tax under Code Section 409A shall instead be paid to the Executive in a
lump-sum cash payment on the earlier of (i) the date that is six months and one day after such
separation from service or (ii) the 10th business day following the Executive’s death. If the
Executive’s termination of employment hereunder does not constitute a “separation from service”
within the meaning of Code Section 409A, then any amounts payable hereunder on account of a
termination of the Executive’s employment and which are subject to Code Section 409A shall not be
paid until the Executive has experienced a “separation from service” within the meaning of Code
Section 409A. In addition, no reimbursement or in-kind benefit shall be subject to liquidation or
exchange for another benefit and the amount available for reimbursement, or in-kind benefits
provided, during any calendar year shall not affect the amount available for reimbursement, or
in-kind benefits to be provided, in a subsequent calendar year. Any reimbursement to which the
Executive is entitled hereunder shall be made no later than the last day of the calendar year
following the calendar year in which such expenses were incurred.

[Signatures appear on the following page.] IN WITNESS WHEREOF, this Agreement has been
executed by the parties on the date first set forth above.

INHIBITEX, INC.

      

By: Russell H. Plumb

Title: President & CEO

EXECUTIVE

      

Geoff Henson

1

Job Description

Senior Vice President, Drug Development

The Senior Vice President, Drug Development has overall responsibility for activities related to
all drug development conducted by Inhibitex for the development of products with Regulatory
(Federal and International) requirements.

This position will be responsible for: management of project/project teams through the
developmental cycle; implementing and communicating the strategic and technical direction for the
product/project team; identifying the needs for specific projects and programs and managing their
development and execution; and working closely with the clinical development group and others for
the overall launch plan for new products.

RESPONSIBILITIES:

	 	•	 	Provide managerial oversight and leadership for the drug development team.

	 	•	 	Develop and implement the research, marketing, project development and operational
goals; provide integration and coordination of research and business development
activities.

	 	•	 	Provide management oversight to research programs consisting of multiple technologies
and capabilities that may be only broadly related.

	 	•	 	Provide administrative management by approving capital and major operating expenditures
consistent with operating plans; approve major proposals; allocate funding to business
development and other special purposes.

	 	•	 	Provide management oversight for the Company’s implementation of operational procedures
and practices.

	 	•	 	Propose, develop, and implement changes in practices and procedures in order to deliver
the highest quality research, products, and services.

	 	•	 	Manage staff by hiring, developing, appraising, and motivating division management and
technical staff. Approve new hires, terminations, disciplinary actions, promotions, and
salary adjustments for all staff.

	 	•	 	Perform investor relations and civic activities.

	 	•	 	Any other responsibilities assigned by the CEO.

REQUIREMENTS:

	 	•	 	MS or PhD in engineering or applied sciences, with significant experience in business
management, including full budget responsibilities.

	 	•	 	Strong knowledge of and contacts in the pharmaceutical industry.

	 	•	 	Possess sufficient experience in financial management to ensure that budgets are
realistically established and attained.

	 	•	 	Significant experience in development and/or Regulatory approval of new drugs or
biologic agents.

	 	•	 	Excellent communication skills, both written and verbal.

	 	•	 	Demonstrated leadership skills in managing teams.

	 	 	 
	INHIBITEX, INC.

	 	EXECUTIVE
	     

By: Russell H. Plumb

	 	     

Geoff Henson

Title: President & CEO

2EX-10.51

Execution Version

AMENDED AND RESTATED EXECUTIVE EMPLOYMENT AGREEMENT

THIS AMENDED AND RESTATED EXECUTIVE EMPLOYMENT AGREEMENT (this “Agreement”), approved by board
as of December 21, 2010 (the “Effective Date”), is between Inhibitex, Inc., a Delaware
corporation (the “Company”), and Joseph M. Patti (the “Executive”).

WHEREAS, the Company and the Executive are parties to an Executive Employment Agreement dated
as of February 26, 2007 (the “Prior Agreement”) and wish to amend and restate the Prior Agreement
in its entirety as provided herein;

WHEREAS, the Company desires to assure itself of the Executive’s continued employment in an
executive capacity and to compensate him for such employment; and

WHEREAS, the Executive is willing to continue to be employed by the Company upon the terms and
subject to the conditions contained in this Agreement.

NOW THEREFORE, in consideration of the premises and mutual covenants contained herein and for
other good and valuable consideration, the adequacy and receipt of which are hereby acknowledged,
the parties hereto, intending to be legally bound, agree as follows:

Section 1. Position, Duties and Responsibilities.

(a) During the Term (as defined in Section 2), the Executive shall serve as the Chief
Scientific Officer and Senior Vice President, Research & Development of the Company consistent with
the by-laws of the Company, and shall be responsible for the duties identified in the attached
Appendix I, such other duties as are attendant to such offices and such other managerial duties and
responsibilities with the Company, its affiliates, subsidiaries or divisions consistent with such
position as may be assigned by the Chief Executive Officer (“CEO”) or Board of Directors of the
Company (the “Board”). The Executive shall devote his full energies, interest, abilities and
productive time to the business and affairs of the Company and to promoting its best interests. The
Executive acknowledges and agrees that although his duties shall be performed from the Company’s
offices in the Atlanta, Georgia metropolitan area or at such other places as shall be necessary
according to the needs, business and opportunities of the Company, the performance by the Executive
of his duties hereunder may require substantial travel from time to time by the Executive. The
Executive further agrees that, during the Term, the Company shall be the Executive’s sole employer.

(b) Executive understands that the provisions of any employee handbooks, personnel manuals and
any and all other written statements of or regarding personnel policies, practices or procedures
that are or may be issued by the Company (the “Company Policies”) do not and shall not constitute a
contract of employment and do not and shall not create any vested rights; and that any such
provisions may be changed, revised, modified, suspended, canceled, or eliminated by the Company at
any time, in its sole discretion, with or without notice.

(c) Executive shall comply with all applicable Company Policies, which may be in effect from
time to time during the Term. Copies of all such Company Policies may be examined in the Human
Resource Department of the Company. If a provision in any Company Policy conflicts with this
Agreement, the terms of this Agreement shall prevail.

(d) For up to a one (1) year period following any termination of the Executive’s employment,
upon the request of the Company, the Executive shall reasonably cooperate with the Company in all
matters relating to the winding up of pending work on behalf of the Company and the orderly
transfer of work to other employees of the Company. The Executive shall also cooperate in the
defense of any action brought by any third party against the Company that relates in any way to the
Executive’s acts or omissions while employed by the Company. The Company shall reimburse the
Executive for his reasonable out-of-pocket costs incurred in connection with such cooperation.

Section 2. Term of Employment.

The term of the Executive’s employment under this Agreement shall continue through December
31, 2010, and thereafter shall be renewed automatically for successive one (1) year periods
(without any action by either party) effective as of each January 1st thereafter, unless
the Executive’s employment under this Agreement is earlier terminated in accordance with Section 4.
Executive may elect not to renew his employment under this Agreement for any reason upon sixty
(60) days prior written notice. For purposes of this Agreement, “Term” means the term of the
Executive’s employment under this Agreement.

Section 3. Compensation; Benefits; Expenses.

(a) Base Salary. For all services rendered by the Executive hereunder during the Term,
the Company shall pay the Executive an annual salary equal to Two Hundred Sixty Five Thousand
Dollars ($265,000), less standard deductions and withholdings, payable in equal installments at the
times and pursuant to the procedures regularly established for the payment of salaries generally to
employees, and as they may be amended by the Company during the Term. The Executive’s salary will
be reviewed from time to time by the CEO, the Board or a committee of the Board, or otherwise in
accordance with the Company’s established procedures for adjusting salaries, and will be subject to
increases (but not decreases, except pursuant to an across-the-board salary reduction as described
in Section 4(a)(iv)(B)) pursuant to such procedures.

(b) Incentive Compensation. The Executive shall be eligible to participate in such
bonus and incentive (including stock option and other equity-based) compensation plans of the
Company, if any, in which other executives of the Company are generally eligible to participate, as
the Board or a committee thereof shall determine from time to time in its sole discretion, subject
to and in accordance with the terms and provisions of such plans. Subject to the terms and
conditions of such bonus and incentive compensation plans, the Executive shall be eligible for
annual cash incentive compensation of up to 35% of his then annual salary. Any such cash incentive
compensation shall be paid to the Executive by no later than March 15th of the year
following the year in which such cash incentive compensation was earned.

(c) Benefits. The Company shall provide the Executive with the right to participate in
and to receive benefits from the group life, group disability and medical plans and all similar
benefits made generally available to similarly situated executives of the Company. The amount and
extent of benefits to which the Executive is entitled shall be governed by the specific benefit
plan or plans, as such may be amended from time to time.

(d) Equity Incentives. During the Term, the Executive shall be eligible to receive
equity-based incentive awards under the Inhibitex, Inc. Amended and Restated 2004 Stock Incentive
Plan, as amended, or any successor plan thereto.

(e) Reimbursement of Expenses. It is contemplated that in connection with the
Executive’s employment hereunder, he may be required to incur business, entertainment and travel
expenses. The Company agrees to promptly reimburse the Executive in full for all reasonable
out-of-pocket business, entertainment and other related expenses (including all reasonable expenses
of travel and living expenses while away from home on business or at the request of, and in service
of, the Company) incurred or expended by him incident to the performance of his duties hereunder,
provided that the Executive properly accounts for such expenses in accordance with the policies and
procedures established by the Board and applicable to the executives of the Company.

(f) Vacation; Personal Days. During the Term, the Executive shall be entitled to no
less than five (5) weeks vacation with pay during each calendar year of his employment hereunder
provided that the vacation days taken do not materially interfere with the operations of the
Company. Such vacation may be taken, in the Executive’s discretion, at such time or times as are
not inconsistent with the reasonable business needs of the Company. The Executive shall also be
entitled to all paid holidays and personal days given by the Company to its executives. Vacation,
holiday and personal days shall additionally be subject to applicable Company Policies.

Section 4. Termination.

(a) The Executive’s employment under this Agreement may be terminated under the following
circumstances:

(i) Death. The Executive’s employment shall immediately terminate upon his death.

(ii) Disability. In the event the Executive shall be unable to render services or
perform his duties hereunder by reason of “Disability,” as such term is defined in the Company’s
Long-Term Disability Plan, as the same shall be amended from time to time, the Company shall have
the right to terminate the Executive’s employment under this Agreement immediately upon notice to
the Executive.

(iii) Termination of Employment by the Company for Cause. The Company may terminate
the employment of the Executive immediately for Cause (as hereinafter defined). The term “Cause,”
as used herein, shall mean (1) the Executive’s willful misconduct, gross negligence, dishonesty or
fraud in the performance of his duties hereunder, (2) the material breach of this Agreement by the
Executive after notice of such breach and a reasonable opportunity to cure, (3) the Executive’s
willful refusal or failure to perform his duties hereunder or under any lawful directive of the
Board or his superior officer, as the case may be, which is consistent with his title and position
after notice of such failure and a reasonable opportunity to cure, or (4) the conviction, plea of
guilty or nolo contendere of the Executive in respect of any felony or other crime
involving moral turpitude, dishonesty, theft or unethical business conduct.

(iv) Termination of Employment by Executive for Good Reason. The Executive may resign
and terminate his employment hereunder for Good Reason (as defined below) by providing a written
notice thereof within sixty (60) days from the occurrence of the event that the Executive is
deeming Good Reason. For purposes of this Agreement, “Good Reason” shall mean there has occurred,
without the express written consent of the Executive:

(A) the assignment to the Executive of any duties materially inconsistent with his status as a
senior executive officer of the Company or a substantial diminution in the nature or status of his
responsibilities;

(B) a reduction by the Company in the Executive’s salary as in effect on the date hereof or as
the same may be increased from time to time, except for across-the-board salary reductions
similarly affecting all executives of the Company;

(C) (1) the relocation of the Company’s principal executive offices to a location outside the
Atlanta, Georgia metropolitan area or (2) the Company’s requiring the Executive to perform his
duties anywhere other than the Company’s principal executive offices; provided that, in any case,
required travel on the Company’s business to an extent substantially consistent with the
Executive’s responsibilities shall not constitute “Good Reason;”

(D) the failure by the Company to continue in effect without any material adverse change any
cash, equity or incentive compensation plan in which the Executive was participating or the failure
by the Company to continue the Executive’s participation therein, unless an equitable arrangement
(embodied in an ongoing substitute or alternative plan) has been made with respect to such plan or
participation;

(E) the failure by the Company to continue to provide the Executive with benefits
substantially similar to those enjoyed by the Executive under the Company’s life insurance,
medical, health-and-accident, or disability plans in which the Executive was participating, the
taking of any action by the Company which would directly or indirectly materially reduce any of
such benefits or deprive the Executive of any other material fringe benefits enjoyed by the
Executive, or the failure by the Company to provide the Executive with the number of paid vacation
days to which the Executive is entitled on the basis of years of service with the Company in
accordance with the Company’s normal vacation policy, except for across-the-board changes in such
benefits similarly affecting all executives of the Company; or

(F) the failure of the Company to obtain a satisfactory agreement from any successor to assume
and agree to perform this Agreement, as contemplated in Section 16 hereof.

(v) Terminations other than for Cause, Good Reason, Disability or upon Death. In
addition to the foregoing, either party may terminate the Executive’s employment under this
Agreement at any time, by providing thirty (30) days prior written notice of his or its desire to
terminate.

(b) Notice of Termination. Any termination of the Executive’s employment by the
Company or by the Executive (other than a termination pursuant to Section 4(a)(i) above) shall be
communicated by written notice of termination to the other party.

Section 5. Compensation Upon Termination.

(a) Compensation Upon Termination Due to Death. In the event of the death of the
Executive during the Term, the Executive’s designated beneficiary, or, in the absence of such
designation, the estate or other legal representative of the Executive (collectively, the “Estate”)
shall be paid, within thirty (30) days of the Executive’s death, an amount equal to the sum of the
Executive’s unpaid salary and any earned but unpaid bonuses through such termination;
provided, however, that any bonus compensation conditioned upon the satisfaction of
performance goals shall not be deemed earned or payable unless such performance goals have been
satisfied as of such termination. The Estate shall be entitled to other vested death benefits in
accordance with the terms of the Company’s benefit programs and plans.

(b) Compensation Upon Termination for Disability. If the Executive’s employment
hereunder is terminated for Disability, the Executive shall be entitled to receive (if entitled
thereto) disability compensation and benefits in accordance with the Company’s benefit programs and
plans. In addition, Executive shall be entitled to receive, within sixty (60) days after the date
of such termination, any unpaid salary and any earned but unpaid bonuses through such termination;
provided, however, that any bonus compensation conditioned upon the satisfaction of
performance goals shall not be deemed earned or payable unless such performance goals have been
satisfied as of such termination of employment.

(c) Compensation Upon Termination for Cause or Termination Without Good Reason. If the
Executive’s employment is terminated by the Company for Cause or by the Executive without Good
Reason, the Company shall pay the Executive his unpaid salary through such termination, and the
Company shall have no further obligations to the Executive under this Agreement. All amounts
payable under this Section 5(c) shall be paid within sixty (60) days after the date of such
termination.

(d) Compensation Upon Termination in Connection With a Change in Control (other than for
Cause, without Good Reason, Disability or upon Death).

(i) If the Executive’s employment is terminated by the Executive for Good Reason or by the
Company for any reason other than pursuant to Section 4(a)(i), 4(a)(ii) or 4(a)(iii) hereof, in
either case, within one (1) year after the consummation of a Change in Control (as hereafter
defined) (or in contemplation of a Change in Control that is reasonably likely to occur), the
Company shall pay to the Executive (or in the event of the Executive’s death, the Estate) a
lump-sum cash amount equal to the sum of (w) the Executive’s unpaid salary through such
termination; plus (x) any bonus compensation earned and unpaid through such termination;
provided, however, that any bonus compensation conditioned upon the satisfaction of
performance goals shall not be deemed earned or payable unless such performance goals have been
satisfied as of such termination; plus (y) the product of (A) a fraction, the numerator of
which is the number of months in the Change in Control Severance Period (as hereafter defined) and
the denominator of which is 12, and (B) the sum of (1) Executive’s annual base salary as then in
effect and (2) the bonus or incentive compensation paid to the Executive in respect of the most
recent fiscal year prior to the year in which the Change in Control occurs; plus (z) a payment
equal to the present value of the premium payments that would be made by the Company if Executive
were to continue to be covered under the Company’s group health, life and disability insurance for
the Change in Control Severance Period, which amount shall be determined by the Company in its sole
discretion. All amounts payable under clauses (w) and (x) of this Section 5(d)(i) shall be paid
within sixty (60) days after such termination of employment and all amounts payable under clauses
(y) and (z) of this Section 5(d)(i) shall be paid on the date that is six months plus one day after
such termination, or upon the Executive’s death, if earlier. The “Change in Control Severance
Period” shall be eighteen (18) months, commencing on the date of the Executive’s termination of
employment.

(ii) Notwithstanding any other provision herein to the contrary, in the event that the
Executive becomes entitled to any payments under Section 5(d)(i) (“Termination Payments”) and any
portion of such Termination Payments, when combined with any other payments or benefits provided to
the Executive (including, without limiting the generality of the foregoing, by reason of any stock
options), in the absence of this Section 5(d)(ii), would be subject to the tax (the “Excise Tax”)
imposed by Section 4999 of the Internal Revenue Code of 1986, as amended (the “Code”), then
(subject to Section 5(d)(iii) hereof) the amount payable to the Executive under Section 5(d)(i)
shall be reduced such that none of the amounts payable to the Executive under Section 5(d)(i) and
any other payments or benefits received or to be received by the Executive in connection with a
Change in Control or the termination of the Executive’s employment (whether pursuant to the terms
of this Agreement or any other plan, arrangement or agreement with the Company, any person whose
actions result in a Change in Control or any person having such a relationship with the Company or
such person as to require attribution of stock ownership between the parties under Section 318(a)
of the Code) shall be treated as “parachute payments” within the meaning of Section 280G(b)(2) of
the Code. For purposes of applying the foregoing sentence, if in the opinion of tax counsel
selected by the Company and reasonably acceptable to the Executive, such payments or benefits (in
whole or in part) represent reasonable compensation for services actually rendered within the
meaning of Section 280G(b)(4) of the Code, then such amounts shall be excluded from any such
calculation. Furthermore, in determining the maximum amount of the payments to the Executive which
would not constitute a parachute payment within the meaning of Sections 280G(b)(1) and (4) of the
Code, the value of any non-cash benefits or any deferred payment or benefit shall be determined by
the Company’s independent auditors in accordance with the principles of Sections 280G(d)(3) and
(4) of the Code or any applicable proposed or final Treasury Regulations promulgated under the
Code. Any reduction in Termination Payments under this Section 5(d)(ii) shall be done first by
reducing any cash payments with the last payment reduced first; next any equity or equity
derivatives that are included under Code Section 280G at full value rather than accelerated value,
with the highest value reduced first; next any non-cash, non-equity-based benefits, with the latest
scheduled benefit reduced first; finally any equity or equity derivatives based on accelerated
value shall be reduced with the highest value reduced first (with all equity and equity derivative
values to be determined under Treasury Regulation Section 1.280G-1, Q&A 24).

(iii) If the net after-tax amount of the Termination Payments which would be payable to the
Executive in the absence of the reduction described in Section 5(d)(ii) above exceeds the net
after-tax amount of the Termination Payments which would be payable to the Executive if the
reduction described in Section 5(d)(ii) above were applicable, then the reduction to the
Executive’s Termination Payments described in Section 5(d)(ii) above shall not be applicable. For
purposes of computing such net after-tax amounts, the Termination Payments shall be treated as
subject to Federal income tax and any state and local income taxes (based upon the residence of the
Executive at the time the first amount of Termination Payments is to be paid hereunder) at the
highest marginal rate of income tax imposed upon individuals (but without assuming any reduction in
Federal income taxes that could be obtained from the deduction of any such state or local taxes if
paid in such year), shall be subject only to the Medicare portion of the F.I.C.A tax and, in
calculating the net after-tax amount of the Termination Payments which would otherwise be payable
to the Executive if the reduction described in Section 5(d)(ii) above were not applicable, any
applicable Excise Tax, and all such taxes shall be computed based upon the tax rates in effect for
the calendar year in which the first amount of Termination Payments are to be paid hereunder. The
determination of the net after-tax amounts will be made by tax counsel selected by the Company and
reasonably acceptable to the Executive, whose determination will be binding on both the Executive
and the Company.

(iv) For purposes of this Agreement, a “Change in Control” of the Company shall mean (A) the
consummation of a merger or consolidation of the Company in which the stockholders of the Company
immediately prior to such merger or consolidation would not, immediately after the merger or
consolidation, beneficially own (as such term is defined in Rule 13d-3 under the Securities
Exchange Act of 1934, as amended (the “Exchange Act”)), directly or indirectly, shares representing
in the aggregate 45% or more of the combined voting power of the securities of the corporation
issuing cash or securities in the merger or consolidation (or of its ultimate parent corporation,
if any); (B) the stockholders of the Company approve a plan of complete liquidation or dissolution
of the Company, or there is consummated an agreement for the sale or disposition by the Company of
all or substantially all of the Company’s assets, other than a sale or disposition by the Company
of all or substantially all of the Company’s assets to an entity, at least 45% of the combined
voting power of the voting securities of which are owned by persons in substantially the same
proportion as their ownership of the Company immediately prior to such sale; (C) during any period
of two (2) consecutive years, individuals who at the beginning of such period constitute the Board,
including for this purpose any new director whose election or nomination for election by the
Company’s stockholders was approved by a vote of at least two-thirds of the directors then still in
office who were directors at the beginning of the period or whose election or nomination for
election was previously so approved but excluding for this purposes any such new director whose
initial assumption of office occurs as a result of either an actual or threatened election contest
(as such terms are used in Rule 14a-11 of Regulation 14A under the Exchange Act) or other actual or
threatened solicitation of proxies or consents by or on behalf of an individual, corporation,
partnership, group, association or other entity or Person (as such term is used in Sections 13(d)
and 14(d) of the Exchange Act) other than the Board, cease for any reason to constitute a majority
thereof; or (D) such other similar transaction not specifically identified above, which in the sole
discretion of the Board (or committee thereof) effectively constitutes a change in control of the
Company.

(e) Compensation Upon All Other Terminations. If the Company terminates the
Executive’s employment under this Agreement for any reason other than pursuant to Section 4(a)(i),
4(a)(ii), 4(a)(iii) or Section 5(d) or if Executive terminates his employment for Good Reason other
than pursuant to Section 5(d), then the Company shall pay Executive a lump sum equal to the sum of
(v) the Executive’s unpaid salary through such termination; plus (w) any bonus compensation
earned and unpaid through such termination; provided, however, that any bonus
compensation conditioned upon the satisfaction of performance goals shall not be deemed earned or
payable unless such performance goals have been satisfied as of such termination; plus
(x) the Executive’s salary for the Severance Period (as defined below); plus (y) the
product of (1) a fraction, the numerator of which is the number of months in the Severance Period
and the denominator of which is 12, and (2) the bonus or incentive compensation paid to the
Executive in respect of the most recent fiscal year prior to the year in which such termination
occurs; plus (z) an amount equal to the present value of the premium payments that would be made by
the Company if Executive were to continue to be covered under the Company’s group health, life and
disability insurance for the Severance Period, which amount shall be determined by the Company in
its sole discretion. All amounts payable under clauses (v) and (w) of this Section 5(e) shall be
paid within sixty (60) days after such termination of employment and all amounts payable under
clauses (x), (y) and (z) of this Section 5(e) shall be paid in cash in a lump-sum on the date that
is six months plus one day after such termination, or upon Executive’s death, if earlier. The
“Severance Period” shall be twelve (12) months, commencing on the date of the Executive’s
termination of employment.

(f) Notwithstanding anything else contained herein, the obligation of the Company to make any
severance payments to the Executive hereunder (other than accrued and unpaid salary, earned and
unpaid bonuses and other payments required under law) shall be conditioned upon the execution and
delivery by the Executive of a release from liability in favor of the Company in form and substance
reasonably satisfactory to the Company, such that such release is effective, with all revocation
periods having expired unexercised, within 60 days after the date of the Executive’s termination of
employment.

(g) The parties hereto agree that any termination of the Executive’s employment for Good
Reason or by the Company other than for Cause would be an “involuntary separation from service”
within the meaning of Treasury Regulation Section 1.409A-1(n). Therefore, notwithstanding the
severance payment schedules set forth in Sections 5(d) and 5(e) and provided that such action would
not result in the imposition of any taxes or penalties on the Executive under Code Section 409A,
any severance owed to the Executive under such Sections, to the extent such severance does not
exceed the limit set forth in Treasury Regulation Section 1.409A-1(b)(9)(iii)(A), shall be paid to
the Executive on the 60th day following his termination of employment, with any severance in excess
of such limit to be paid to the Executive at the time provided in Section 5(d) or Section 5(e), as
applicable.

Section 6. Confidentiality.

(a) Each Item, Trade Secret and piece of Confidential Information (in each case, as defined
below) that has come or comes into Executive’s possession by reason of his employment are the
property of the Company and shall not be used by Executive in any way except in the course of his
employment by, and for the benefit of, the Company. Executive will not remove any Items from
premises owned or leased by the Company except as his duties shall require, and upon termination of
his employment, all Items (including any copies or excerpts thereof) will be turned over to
Executive’s supervisor at the Company.

(b) Executive will preserve as confidential all Confidential Information that has been or may
be obtained by him. Executive will not, without written authority from the Company, use for his own
benefit or purposes, or disclose to others, either during his employment or for two (2) years
thereafter, any Confidential Information or any copy or notes made from any Item embodying
Confidential Information except as required by his employment with the Company or to the extent
disclosure is or may be required by a statute, by a court of law, by any governmental agency having
supervisory authority over the business of the Company or by any administrative or legislative body
(including a committee thereof) with jurisdiction to order him to divulge, disclose or make
accessible such information, provided, however, that the Executive shall give the Company notice of
any such request or demand for such information upon his receipt of same and the Executive shall
reasonably cooperate with the Company in any application the Company may make seeking a protective
order barring disclosure by the Executive. Executive understands that his obligations with respect
to Confidential Information shall continue for two years after termination of his employment with
the Company. These restrictions concerning use and disclosure of Confidential Information shall not
apply to information which is or becomes publicly known by lawful means, or comes into Executive’s
possession from sources not under an obligation of confidentiality to the Company.

(c) Executive agrees to hold in confidence all Trade Secrets of the Company that came into his
knowledge during or in connection with his employment by the Company and shall not disclose,
publish or make use of at any time after the date hereof such Trade Secrets without the prior
written consent of the Company for as long as the information remains a Trade Secret.

(d) Executive understands that any entrusting of Confidential Information or Trade Secrets to
him by the Company is done in reliance on a confidential relationship arising out of his employment
with the Company. Executive further understands that Confidential Information or Trade Secrets that
he may acquire or to which he may have access, especially with regard to research and development
projects and findings, formulae, designs, formulation, processes, the identity of suppliers,
customers and patients, methods of manufacture, and cost and pricing data is of great value to the
Company.

(e) Executive agrees that following termination of his employment with the Company, Executive
will, if at all possible before answering but in any event as soon thereafter as practicable, make
every effort to contact the Company’s General Counsel if Executive is served with a subpoena or
other legal process asking for a deposition, testimony or other statement, or other potential
evidence to be used in connection with any lawsuit to which the Company is a party or involving
Executive’s employment with the Company or any Confidential Information or Trade Secret of the
Company.

(f) For purposes of this Agreement: (i) “Confidential Information” means information relating
to the present or planned business of the Company which has not been released publicly by
authorized representatives of the Company. Executive understands that Confidential Information may
include, for example, discoveries, inventions, know-how and products, customer, patient, supplier
and competitor information, sales, pricing, cost, and financial data, research, development,
marketing and sales programs and strategies, manufacturing, marketing and service techniques,
processes and practices, and regulatory strategies. Executive understands further that Confidential
Information also includes all information received by the Company under an obligation of
confidentially to a third party; (ii) “Items” include documents, reports, drawings, photographs,
designs, specifications, formulae, plans, samples, research or development information, prototypes,
tools, equipment, proposals, marketing or sales plans, customer information, customer lists,
patient lists, patient information, regulatory files, financial data, costs, pricing information,
supplier information, written, printed or graphic matter, or other information and materials that
concern the Company’s business that come into Executive’s possession or about which Executive has
knowledge by reason of his employment; and (iii) “Trade Secrets” include all information, including
a formula pattern, process, compilation, program, device, method, or technique that (A) derives
independent economic value, actual or potential, from not being generally known to, and not being
readily ascertainable by proper means by other persons who can obtain economic value from its
disclosure or use, (B) is the subject of efforts that are reasonable under the circumstances to
maintain its secrecy; and (C) otherwise satisfies the requirements of the Georgia Trade Secrets
Act.

Section 7. Proprietary Information.

(a) All Inventions (as defined below) related to the present or planned business of the
Company, which have been or are conceived or reduced to practice by Executive, either alone or with
others, during the period of his employment or during a period of one (1) year after termination of
such employment, whether or not done during his regular working hours, are the sole property of the
Company. The provisions of this paragraph shall not apply to an invention for which no equipment,
supplies, facilities or confidential or trade secret information of the Company was used and which
was developed entirely on Executive’s own time, unless (a) the invention relates to (i) the
business of the Company, or (ii) the Executive’s actual or demonstrably anticipated research or
development for the Company, or (b) the invention results from any work performed by Executive for
the Company.

(b) Executive will disclose promptly and in writing to the Company, through his supervisor,
all Inventions which are covered by this Agreement, and Executive agrees to assign to the Company
or its nominee all his right, title, and interest in and to such Inventions. Executive agrees not
to disclose any of these Inventions to others, without the express consent of the Company.
Executive will, at any time during or after his employment, on request of the Company, execute
specific assignments in favor of the Company or its nominee of his interest in and to any of the
Inventions covered by this Agreement, as well as execute all papers, render all assistance, and
perform all lawful acts which the Company considers necessary or advisable for the preparation,
filing, prosecution, issuance, procurement, maintenance or enforcement of patent applications and
patents of the United States and foreign countries for these Inventions, and for the transfer of
any interest Executive may have. Executive will execute any and all papers and documents required
to vest title in the Company or its nominee in the above Inventions, patent applications, patents,
and interests. Executive understands that if he is not employed by the Company at the time he is
requested to execute any document under this Section 7(b), Executive shall receive fifty dollars
($50.00) for the execution of each document, and one hundred fifty dollars ($150.00) per day for
each day or portion thereof spent at the request of the Company in the performance of acts pursuant
to this Section 7(b), plus reimbursement for any out-of-pocket expenses incurred by Executive at
the Company’s request in such performance. Executive further understands that the absence of a
request by the Company for information, or for the making of an oath, or for the execution of any
document, shall in no way be construed to constitute a waiver of the Company’s rights under this
Agreement. Should the Company be unable to secure the Executive’s signature on any document
necessary to apply for, prosecute, obtain, or enforce any patent, copyright, or other right or
protection relating to any Invention, whether due to the Executive’s mental or physical incapacity
or any other cause, the Executive hereby irrevocably designates and appoints the Company and each
of its duly authorized officers and agents as the Executive’s agent and attorney in fact, to act
for and in the Executive’s behalf and stead and to execute and file any such document, and to do
all other lawfully permitted acts to further the prosecution, issuance, and enforcement of patents,
copyrights, or other rights or protections with the same force and effect as if executed and
delivered by the Executive.

(c) Executive has disclosed to the Company all continuing obligations which he has with
respect to the assignment of Inventions to any previous employers, and Executive claims no previous
unpatented Inventions as his own, except for those which have been reduced to practice and which
are shown on a schedule, if any, attached to this agreement. Executive understands that the Company
does not seek any confidential or trade secret information which Executive may have acquired from a
previous employer, and Executive will not disclose to or utilize any such information on behalf of
the Company.

(d) All writings and other works which may be copyrighted (including computer programs) which
are related to the present or planned business of the Company and are prepared by Executive during
his employment by the Company shall be, to the extent permitted by law, works made for hire, and
the authorship and copyright of the work shall be in the Company’s name. To the extent that such
writings and works are not works for hire, Executive agrees to the wavier of “moral rights” in such
writings and works, and to assign to the Company all Executive’s right, title and interest in and
to such writings and works, including copyright.

(e) Executive will permit the Company and its agents to use and distribute any pictorial
images which are taken of him during his employment by the Company as often as desired for any
lawful purpose. Executive waives all rights of prior inspection or approval and releases the
Company and its agents from any and all claims or demands which Executive may have on account of
the lawful use of publication of such pictorial images.

(f) For purposes of this Agreement, “Invention” shall mean all ideas, potential marketing and
sales relationships, inventions, experiments, copyrightable expression, research, plans for
products or services, marketing plans, reports, strategies, processes, computer software
(including, without limitation, source code), computer programs, original works of authorship,
characters, know-how, trade secrets, information, data, developments, discoveries, improvements,
modifications, technology, algorithms, database schema, designs, and drawings, whether or not
subject to patent or copyright protection, made, conceived, expressed, developed, or actually or
constructively reduced to practice by the Executive solely or jointly with others prior to or
during the Term, which refer to, are suggested by, or result (i) from any work which the Executive
has performed prior to the Term of this Agreement, (ii) from any work which the Executive may
perform during his employment, or (iii) from any information obtained from the Company or any
affiliate of the Company, and shall not be limited to the meaning of “Invention” under the United
States patent laws.

Section 8. Agreement Not to Compete.

(a) While employed by the Company and thereafter for a period equal to the greater of (x) one
(1) year and (y) the Change in Control Severance Period in the event of a termination pursuant to
Section 5(d)(i), the Executive shall not, directly or indirectly, anywhere in the United States:

(i) render services which are substantially similar to the services performed by Executive for
the Company to any person, corporation, partnership or other entity which competes with the Company
(or any subsidiary) in the business of developing or manufacturing small molecule compounds
for the treatment of infections caused by varicella zoster virus or hepatitis C virus;
Executive agrees that this covenant is especially appropriate because, if he worked for a
competitor, he would inevitably make business decisions by relying on his knowledge of the
Company’s Confidential Information and Trade Secrets; thus, he would inevitably provide competitors
with the Company’s Confidential Information and Trade Secrets. The Company’s Confidential
Information and Trade Secrets are not generally known by others in the industry, and they would
provide an unfair advantage for competitors. Further, the Company recognizes that there are some
companies who provide many products and services, some of which may be competitive and some which
may not be. Accordingly, this covenant only prohibits Executive from performing the same or
substantially the same services for that section, division, group, subsidiary, affiliate or
operating unit of a competitor that actually develops or manufactures small molecule compounds
for the treatment of infections caused by varicella zoster virus or hepatitis C virus.
Further, the Company and Executive agree that the Company is engaged in the business of developing
or manufacturing small molecule compounds for the treatment of infections caused by
varicella zoster virus or hepatitis C virus throughout the United States and beyond;

(ii) solicit for employment of any person who was employed by the Company (or any subsidiary)
during the Executive’s employment with the Company and with whom the Executive had contact during
the last year of his employment with the Company; or

(iii) call on or solicit, directly or indirectly for the purpose of providing services related
to the treatment of infections caused by varicella zoster virus or hepatitis C virus, any person or
entity known by the Executive to be a customer of the Company (or of any subsidiary), or with which
the Company (or any subsidiary) was in negotiations to become a customer of the Company (or such
subsidiary), as the case may be, during the Executive’s employment with the Company, and with whom
the Executive had direct contact. For purpose of this section, “contact” means interaction between
the Executive and the client within the last year of Executive’s employment to further the business
relationship or perform services for the client, and interaction between the Executive and
prospective client within the last year of Executive’s employment to develop a business
relationship.

(b) If any of the restrictions contained in this Section 8 shall be deemed by any court of
competent jurisdiction to be unenforceable by reason of the extent, duration or geographical scope
thereof, or otherwise, then the parties agree that such court shall modify such restriction, only
to the extent necessary to render it enforceable and, in its reduced form, such restriction shall
then be enforced, and in its reduced form this Section 8 shall be enforceable in the manner
contemplated hereby.

(c) The Executive and the Company agree to revise the specific description of the Company’s
line of business set forth in Section 8(a) as appropriate to reflect any material change in the
Company’s business due to an in-licensing, merger, acquisition or similar strategic transaction.

Section 9. Company Resources.

Executive may not use any of the Company’s (or any affiliate’s) equipment for personal
purposes without written permission from the Company. The Executive may not give access to the
Company’s (or any affiliate’s) offices or files to any person not in the employ of the Company
without written permission of the Company.

Section 10. Injunctive Relief.

Executive understands and agrees that the Company will suffer irreparable harm in the event
that the Executive breaches any of the Executive’s obligations under Sections 6, 7, 8 or 9 hereof
and that monetary damages will be inadequate to compensate the Company for such breach.
Accordingly, the Executive agrees that, in the event of a breach or threatened breach by the
Executive of any of the provisions of Sections 6, 7, 8 or 9 hereof, the Company shall be entitled
to appropriate injunctive relief, in addition to any other rights, remedies or damages available to
the Company at law or in equity.

Section 11. Severability.

In the event any of the provisions of this Agreement shall be held by a court or other
tribunal of competent jurisdiction to be unenforceable, the other provisions of this Agreement
shall remain in full force and effect.

Section 12. Survival.

Sections 1(d) and 4 through 16 shall survive the termination of this Agreement and the
Executive’s employment under this Agreement for any reason.

Section 13. Representations, Warranties, and Covenants.

Executive represents, warrants, and covenants that the Executive’s performance of all the
terms of this Agreement and any services to be rendered as an employee of the Company do not and
will not breach any fiduciary or other duty or any covenant, agreement or understanding (including,
without limitation, any agreement relating to any proprietary information, knowledge or data
acquired by the Executive in confidence, trust or otherwise prior to the Executive’s employment by
the Company) to which the Executive is a party or by the terms of which the Executive may be bound.
The Executive further covenants and agrees not to enter into any agreement or understanding, either
written or oral, in conflict with the provisions of this Agreement.

Section 14. Accounting for Profits; Indemnification.

Executive covenants and agrees that, if the Executive shall violate any of the Executive’s
covenants or agreements contained in Sections 6, 7, 8 or 9 hereof, the Company shall be entitled to
an accounting and repayment of all profits, compensation, royalties, commissions, remunerations or
benefits which the Executive directly or indirectly shall have realized or may realize relating to,
growing out of or in connection with any such violation; such remedy shall be in addition to and
not in limitation of any injunctive relief or other rights or remedies to which the Company is or
may be entitled at law or in equity or otherwise under this Agreement. The Executive hereby agrees
to defend, indemnify and hold harmless the Company against and in respect of: (a) any and all
losses and damages resulting from, relating or incident to, or arising out of any misrepresentation
or breach by the Executive of any of the Executive’s representations, warranties, covenants or
agreements made or contained in this Agreement; and (b) any and all actions, suits, proceedings,
claims, demands, judgments, costs and expenses (including reasonable attorneys’ fees) incident to
the foregoing.

Section 15. General.

This Agreement supersedes and replaces any existing agreement between the Executive and the
Company relating generally to the same subject matter (including, without limitation, the Prior
Agreement) and may be modified only in a writing signed by the parties hereto. Failure to enforce
any provision of the Agreement shall not constitute a waiver of any term herein. The Executive
agrees that he will not assign, transfer, or otherwise dispose of, whether voluntarily or
involuntarily, or by operation of law, any rights or obligations under this Agreement. Any
purported assignment, transfer, or disposition shall be null and void. Nothing in this Agreement
shall prevent the consolidation of the Company with, or its merger into, any other corporation, or
the sale by the Company of all or substantially all of its properties or assets, or the assignment
by the Company of this Agreement and the performance of its obligations hereunder. Subject to the
foregoing, this Agreement shall be binding upon and shall inure to the benefit of the parties and
their respective heirs, legal representatives, successors, and permitted assigns, and shall not
benefit any person or entity other than those enumerated above. The use of any gender herein shall
be applicable to all genders.

Section 16. Executive Acknowledgment.

Executive acknowledges (a) that he has consulted with, or has had the opportunity to consult
with, independent counsel of his own choice concerning this Agreement and has been advised to do so
by the Company, and (b) that he has read and understands the Agreement, is fully aware of its legal
effect, and has entered into it freely based on his own judgment.

Section 17. Section 409A.

This Agreement is intended to comply with Code Section 409A (to the extent applicable) and the
parties hereto agree to interpret, apply and administer this Agreement in the least restrictive
manner necessary to comply therewith and without resulting in any increase in the amounts owed
hereunder by the Company. Notwithstanding any other provision of this Agreement to the contrary,
if the Executive is a “specified employee” within the meaning of Code Section 409A and the
regulations issued thereunder, and a payment or benefit provided for in this Agreement would be
subject to additional tax under Code Section 409A if such payment or benefit is paid within six (6)
months after the Executive’s “separation from service” (within the meaning of Code Section 409A),
then such payment or benefit required under this Agreement shall not be paid (or commence) during
the six-month period immediately following the Executive’s separation from service except as
provided in the immediately following sentence. In such an event, any payments or benefits that
would otherwise have been made or provided during such six-month period and which would have
incurred such additional tax under Code Section 409A shall instead be paid to the Executive in a
lump-sum cash payment on the earlier of (i) the date that is six months and one day after such
separation from service or (ii) the 10th business day following the Executive’s death. If the
Executive’s termination of employment hereunder does not constitute a “separation from service”
within the meaning of Code Section 409A, then any amounts payable hereunder on account of a
termination of the Executive’s employment and which are subject to Code Section 409A shall not be
paid until the Executive has experienced a “separation from service” within the meaning of Code
Section 409A. In addition, no reimbursement or in-kind benefit shall be subject to liquidation or
exchange for another benefit and the amount available for reimbursement, or in-kind benefits
provided, during any calendar year shall not affect the amount available for reimbursement, or
in-kind benefits to be provided, in a subsequent calendar year. Any reimbursement to which the
Executive is entitled hereunder shall be made no later than the last day of the calendar year
following the calendar year in which such expenses were incurred.

[Signatures appear on the following page.] IN WITNESS WHEREOF, this Agreement has been
executed by the parties on the date first set forth above.

INHIBITEX, INC.

      

By: Russell H. Plumb

Title: President & CEO

EXECUTIVE

      

Joseph M. Patti

1

Appendix I

Job Description

The Chief Scientific Officer (CSO) will report to the President & CEO and will be responsible for
all research and development activities. He will serve as a business partner to the President & CEO
and other members of the executive team. Also, the CSO will provide leadership and direction to
ensure the development of relevant business information and continued research developments.

The CSO will be responsible for:

	 	•	 	Creating and communicating organization’s scientific vision and direction.

	 	•	 	Directing the activities of the scientific group in the research and/or development
relevant to long-term projects and programs.

	 	•	 	Writes and reviews manuscripts for publication.

	 	•	 	Develops strategies to ensure effective achievement of scientific objectives.

	 	•	 	Develops budgets for capital expenditures and labor for the scientific group.

	 	•	 	Prepare the appropriate R & D documents for reporting information and participate in
the “road show” and public offering of the company.

	 	•	 	Any other responsibilities assigned by the CEO.

	 	 	 
	INHIBITEX, INC.

	 	EXECUTIVE
	     

By: Russell H. Plumb

	 	     

Joseph M. Patti

Title: President & CEO

2

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