Document:

EX-10.1

 Exhibit 10.1 

IDENIX PHARMACEUTICALS, INC. 
 2012 STOCK INCENTIVE PLAN 
 1. Purpose 

The purpose of this 2012 Stock Incentive Plan (the “Plan”) of Idenix Pharmaceuticals, Inc. a Delaware corporation
(the “Company”), is to advance the interests of the Company’s stockholders by enhancing the Company’s ability to attract, retain and motivate persons who are expected to make important contributions to the Company
and by providing such persons with equity ownership opportunities and performance-based incentives that are intended to better align the interests of such persons with those of the Company’s stockholders. Except where the context otherwise
requires, the term “Company” shall include any of the Company’s present or future parent or subsidiary corporations as defined in Sections 424(e) or (f) of the Internal Revenue Code of 1986, as amended, and any
regulations thereunder (the “Code”) and any other business venture (including, without limitation, joint venture or limited liability company) in which the Company has a controlling interest, as determined by the Board of
Directors of the Company (the “Board”). 
 2. Eligibility 

All of the Company’s employees, officers, directors, consultants and advisors are eligible to be granted Awards under the Plan. Each
person who is granted an Award under the Plan is deemed a “Participant.” “Award” means Options (as defined in Section 5), SARs (as defined in Section 7), Restricted Stock (as defined in
Section 8), Restricted Stock Units (as defined in Section 8) and Other Stock-Based Awards (as defined in Section 9). 
 3.
Administration and Delegation 
 (a) Administration by Board of Directors. The Plan will be administered by the
Board. The Board shall have authority to grant Awards and to adopt, amend and repeal such administrative rules, guidelines and practices relating to the Plan as it shall deem advisable. The Board may construe and interpret the terms of the Plan and
any Award agreements entered into under the Plan. The Board may correct any defect, supply any omission or reconcile any inconsistency in the Plan or any Award in the manner and to the extent it shall deem expedient and it shall be the sole and
final judge of such expediency. All decisions by the Board shall be made in the Board’s sole discretion and shall be final and binding on all persons having or claiming any interest in the Plan or in any Award. No director or person acting
pursuant to the authority delegated by the Board shall be liable for any action or determination relating to or under this Plan made in good faith. 

 (b) Appointment of Committees. To the extent permitted by applicable law, the Board
may delegate any or all of its powers under the Plan to one or more committees or subcommittees of the Board (a “Committee”). All references in the Plan to the “Board” shall mean the Board or a
Committee of the Board or the officers referred to in Section 3(c) to the extent that the Board’s powers or authority under the Plan have been delegated to such Committee or officers. 

(c) Delegation to Officers. To the extent permitted by applicable law, the Board may delegate to one or more officers of the
Company the power to grant Options and other Awards that constitute rights under Delaware law (subject to any limitations under the Plan) to employees or officers of the Company and to exercise such other powers under the Plan as the Board may
determine, provided that the Board shall fix the terms of such Awards to be granted by such officers (including the exercise price of such Awards, which may include a formula by which the exercise price will be determined) and the maximum
number of shares subject to such Awards that the officers may grant; provided further, however, that no officer shall be authorized to grant such Awards to any “executive officer” of the Company (as defined by Rule 3b-7 under the
Securities Exchange Act of 1934, as amended (the “Exchange Act”)) or to any “officer” of the Company (as defined by Rule 16a-1 under the Exchange Act). The Board may not delegate authority under this
Section 3(c) to grant Restricted Stock, unless Delaware law then permits such delegation. 
 (d) Awards to Non-Employee
Directors. Discretionary Awards to non-employee directors may be granted and administered only by a Committee, all of the members of which are independent directors as defined by Section 5605(a)(2) of the NASDAQ Marketplace Rules.

 4. Stock Available for Awards 
 (a) Number of Shares; Share Counting. 
 (1) Authorized Number of
Shares. Subject to adjustment under Section 10, Awards may be made under the Plan for up to 10,000,000 shares of common stock, 0.001 par value per share, of the Company (the “Common Stock”), plus the number of shares
of Common Stock (up to 529,089) previously authorized for issuance under the Company’s 2005 Stock Incentive Plan, as amended, (i) which are not subject to outstanding awards on June 7, 2012 or (ii) which again become available
for the grant of future award as a result of the subsequent forfeiture, lapse or expiration of awards granted pursuant to the 2005 Stock Incentive Plan, as amended, and outstanding on June 7, 2012. Any or all Awards granted under the Plan may
be in the form of Incentive Stock Options (as defined in Section 5(b)). Shares issued under the Plan may consist in whole or in part of authorized but unissued shares or treasury shares. 

(2) Fungible Share Pool. Subject to adjustment under Section 10, any Award that is not a Full-Value Award shall be counted
against the share limits specified in Section 4(a)(1) as one share for each share of Common Stock subject to such Award and any Award that is a Full-Value Award shall be counted against the share limits specified in Section 4(a)(1) as 1.26
shares for each one share of Common Stock subject to such Full-Value Award. “Full-Value Award” means any Award (other than Options or SARs) with a per share price or per unit purchase price lower than 100% of Fair Market Value (as defined
below) on the date of grant. To the extent a share that was subject to an Award that counted as one share is returned to the Plan pursuant to Section 

  
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4(a)(3), each applicable share reserve will be credited with one share. To the extent that a share that was subject to an Award that counts as 1.26 shares is returned to the Plan pursuant to
Section 4(a)(3), each applicable share reserve will be credited with 1.26 shares 
 (3) Share Counting. For purposes
of counting the number of shares available for the grant of Awards under the Plan and under the sublimits contained in Sections 4(b)(2) and 4(b)(3): 
 (A) all shares of Common Stock covered by SARs shall be counted against the number of shares available for the grant of Awards under the Plan and against the sublimits listed in the first clause of this
Section 4(a)(3); provided, however, that if the Company grants an SAR in tandem with an Option for the same number of shares of Common Stock and provides that only one such Award may be exercised (a “Tandem SAR”),
only the shares covered by the Option, and not the shares covered by the Tandem SAR, shall be so counted, and the expiration of one in connection with the other’s exercise will not restore shares to the Plan; 

(B) if any Award (i) expires or is terminated, surrendered or canceled without having been fully exercised or is
forfeited in whole or in part (including as the result of shares of Common Stock subject to such Award being repurchased by the Company at the original issuance price pursuant to a contractual repurchase right) or (ii) results in any Common
Stock not being issued the unused Common Stock covered by such Award shall again be available for the grant of Awards; provided, however, that (1) in the case of Incentive Stock Options, the foregoing shall be subject to any limitations
under the Code, (2) in the case of the exercise of an SAR, the number of shares counted against the shares available under the Plan and against the sublimits listed in the first clause of this Section 4(a)(3) shall be the full number of
shares subject to the SAR multiplied by the percentage of the SAR actually exercised, regardless of the number of shares actually used to settle such SAR upon exercise and (3) the shares covered by a Tandem SAR shall not again become available
for grant upon the expiration or termination of such Tandem SAR; 
 (C) shares of Common Stock delivered (either
by actual delivery, attestation, or net exercise) to the Company by a Participant to (i) purchase shares of Common Stock upon the exercise of an Award or (ii) satisfy tax withholding obligations (including shares retained from the Award
creating the tax obligation) shall not be added back to the number of shares available for the future grant of Awards; and 
 (D) shares of Common Stock repurchased by the Company on the open market using the proceeds from the exercise of an Award shall not increase the number of shares available for future grant of Awards.

 (b) Sub-limits. Subject to adjustment under Section 10, the following sub-limits on the number of shares subject
to Awards shall apply: 
 (1) Section 162(m) Per-Participant Limit. The maximum number of shares of Common Stock with
respect to which Awards may be granted to any Participant under the Plan shall be 700,000 per calendar year. For purposes of the foregoing limit, the combination of an Option in tandem with an SAR shall be treated as a single Award. The per
Participant limit described in this Section 4(b)(1) shall be construed and applied consistently with Section 162(m) of the Code or any successor provision thereto, and the regulations thereunder (“Section 162(m)”).

  
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 (c) Substitute Awards. In connection with a merger or consolidation of an entity with
the Company or the acquisition by the Company of property or stock of an entity, the Board may grant Awards in substitution for any options or other stock or stock-based awards granted by such entity or an affiliate thereof. Substitute Awards may be
granted on such terms as the Board deems appropriate in the circumstances, notwithstanding any limitations on Awards contained in the Plan. Substitute Awards shall not count against the overall share limit set forth in Section 4(a)(1) or any
sublimits contained in the Plan, except as may be required by reason of Section 422 and related provisions of the Code. 
 5. Stock
Options 
 (a) General. The Board may grant options to purchase Common Stock (each, an
“Option”) and determine the number of shares of Common Stock to be covered by each Option, the exercise price of each Option and the conditions and limitations applicable to the exercise of each Option, including conditions
relating to applicable federal or state securities laws, as it considers necessary or advisable. 
 (b) Incentive Stock
Options. An Option that the Board intends to be an “incentive stock option” as defined in Section 422 of the Code (an “Incentive Stock Option”) shall only be granted to employees of Idenix Pharmaceuticals,
Inc., any of Idenix Pharmaceuticals, Inc.’s present or future parent or subsidiary corporations as defined in Sections 424(e) or (f) of the Code, and any other entities the employees of which are eligible to receive Incentive Stock Options
under the Code, and shall be subject to and shall be construed consistently with the requirements of Section 422 of the Code. An Option that is not intended to be an Incentive Stock Option shall be designated a “Nonstatutory Stock
Option.” The Company shall have no liability to a Participant, or any other party, if an Option (or any part thereof) that is intended to be an Incentive Stock Option is not an Incentive Stock Option or if the Company converts an
Incentive Stock Option to a Nonstatutory Stock Option. 
 (c) Exercise Price. The Board shall establish the exercise price
of each Option and specify the exercise price in the applicable Option agreement. The exercise price shall be not less than 100% of the fair market value per share of Common Stock as determined by (or in a manner approved by) the Board
(“Fair Market Value”) on the date the Option is granted; provided that if the Board approves the grant of an Option with an exercise price to be determined on a future date, the exercise price shall be not less than
100% of the Fair Market Value on such future date. 
 (d) Duration of Options. Each Option shall be exercisable at such
times and subject to such terms and conditions as the Board may specify in the applicable option agreement; provided, however, that no Option will be granted with a term in excess of 10 years. 

(e) Exercise of Options. Options may be exercised by delivery to the Company of a notice of exercise in a form (which may be
electronic) approved by the Company, together with payment in full (in the manner specified in Section 5(f)) of the exercise price for the number of shares for which the Option is exercised. Shares of Common Stock subject to the Option will be
delivered by the Company as soon as practicable following exercise. 

  
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 (f) Payment Upon Exercise. Common Stock purchased upon the exercise of an Option
granted under the Plan shall be paid for as follows: 
 (1) in cash or by check, payable to the order of the Company; 

(2) except as may otherwise be provided in the applicable Option agreement or approved by the Board, in its sole discretion, by
(i) delivery of an irrevocable and unconditional undertaking by a creditworthy broker to deliver promptly to the Company sufficient funds to pay the exercise price and any required tax withholding or (ii) delivery by the Participant to the
Company of a copy of irrevocable and unconditional instructions to a creditworthy broker to deliver promptly to the Company cash or a check sufficient to pay the exercise price and any required tax withholding; 

(3) to the extent provided for in the applicable Option agreement or approved by the Board, in its sole discretion, by delivery (either by
actual delivery or attestation) of shares of Common Stock owned by the Participant valued at their Fair Market Value, provided (i) such method of payment is then permitted under applicable law, (ii) such Common Stock, if acquired directly
from the Company, was owned by the Participant for such minimum period of time, if any, as may be established by the Board in its discretion and (iii) such Common Stock is not subject to any repurchase, forfeiture, unfulfilled vesting or other
similar requirements; 
 (4) to the extent provided for in the applicable Nonstatutory Option agreement or approved by the Board
in its sole discretion, by delivery of a notice of “net exercise” to the Company, as a result of which the Participant would receive (i) the number of shares underlying the portion of the Option being exercised, less (ii) such
number of shares as is equal to (A) the aggregate exercise price for the portion of the Option being exercised divided by (B) the Fair Market Value on the date of exercise. 

(5) to the extent permitted by applicable law and provided for in the applicable Option agreement or approved by the Board, in its sole
discretion, by payment of such other lawful consideration as the Board may determine; or 
 (6) by any combination of the above
permitted forms of payment. 
 (g) Limitation on Repricing. The Company may not (except as provided for under
Section 10): (1) amend any outstanding Option granted under the Plan to provide an exercise price per share that is lower than the then-current exercise price per share of such outstanding Option, (2) cancel any outstanding option
(whether or not granted under the Plan) and grant in substitution therefor new Awards under the Plan (other than Awards granted pursuant to Section 4(c)) covering the same or a different number of shares of Common Stock and having an exercise
price per share lower than the then-current exercise price per share of the cancelled option, (3) cancel in exchange for a cash payment any outstanding Option with an exercise price per share above the then-current Fair Market Value, other than
pursuant to Section 10, or (4) take any other action under the Plan that constitutes a “repricing” within the meaning of the rules of the NASDAQ Stock Market (“NASDAQ”). 

  
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 6. Intentionally Omitted 
 7. Stock Appreciation Rights 
 (a) General. The Board may grant
Awards consisting of stock appreciation rights (“SARs”) entitling the holder, upon exercise, to receive an amount of Common Stock determined by reference to appreciation, from and after the date of grant, in the Fair Market
Value of a share of Common Stock over the measurement price established pursuant to Section 7(b). The date as of which such appreciation is determined shall be the exercise date. 

(b) Measurement Price. The Board shall establish the measurement price of each SAR and specify it in the applicable SAR agreement.
The measurement price shall not be less than 100% of the Fair Market Value on the date the SAR is granted; provided that if the Board approves the grant of an SAR effective as of a future date, the measurement price shall be not less than
100% of the Fair Market Value on such future date. 
 (c) Duration of SARs. Each SAR shall be exercisable at such times
and subject to such terms and conditions as the Board may specify in the applicable SAR agreement; provided, however, that no SAR will be granted with a term in excess of 10 years. 

(d) Exercise of SARs. SARs may be exercised by delivery to the Company of a notice of exercise in a form (which may be electronic)
approved by the Company, together with any other documents required by the Board. 
 (e) Limitation on Repricing. The
Company may not (except as provided for under Section 10): (1) amend any outstanding SAR granted under the Plan to provide a measurement price per share that is lower than the then-current measurement price per share of such outstanding
SAR, (2) cancel any outstanding SAR (whether or not granted under the Plan) and grant in substitution therefor new Awards under the Plan (other than Awards granted pursuant to Section 4(c)) covering the same or a different number of shares
of Common Stock and having an exercise or measurement price per share lower than the then-current measurement price per share of the cancelled SAR, (3) cancel in exchange for a cash payment any outstanding SAR with a measurement price per share
above the then-current Fair Market Value, other than pursuant to Section 10, or (4) take any other action under the Plan that constitutes a “repricing” within the meaning of the rules of the NASDAQ. 

8. Restricted Stock; Restricted Stock Units 
 (a) General. The Board may grant Awards entitling recipients to acquire shares of Common Stock (“Restricted Stock”), subject to the right of the Company to repurchase all or
part of such shares at their issue price or other stated or formula price (or to require forfeiture of such shares if issued at no cost) from the recipient in the event that conditions specified by the Board in the applicable Award are not satisfied
prior to the end of the applicable restriction period or periods established by the Board for such Award. The Board may also grant Awards entitling the recipient to receive shares of Common Stock or cash to be delivered at the time such Award vests
(“Restricted Stock Units”) (Restricted Stock and Restricted Stock Units are each referred to herein as a “Restricted Stock Award”). 

  
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 (b) Terms and Conditions for All Restricted Stock Awards. The Board shall determine
the terms and conditions of a Restricted Stock Award, including the conditions for vesting and repurchase (or forfeiture) and the issue price, if any. 
 (c) Additional Provisions Relating to Restricted Stock. 
 (1)
Dividends. Unless otherwise provided in the applicable Award agreement, any dividends (whether paid in cash, stock or property) declared and paid by the Company with respect to shares of Restricted Stock (“Accrued
Dividends”) shall be paid to the Participant only if and when such shares become free from the restrictions on transferability and forfeitability that apply to such shares. Each payment of Accrued Dividends will be made no later than
the end of the calendar year in which the dividends are paid to stockholders of that class of stock or, if later, the 15th day of the third month following the lapsing of the restrictions on transferability and the forfeitability provisions
applicable to the underlying shares of Restricted Stock. 
 (2) Stock Certificates. The Company may require that any
stock certificates issued in respect of shares of Restricted Stock, as well as dividends or distributions paid on such Restricted Stock, shall be deposited in escrow by the Participant, together with a stock power endorsed in blank, with the Company
(or its designee). At the expiration of the applicable restriction periods, the Company (or such designee) shall deliver the certificates no longer subject to such restrictions to the Participant or if the Participant has died, to his or her
Designated Beneficiary. “Designated Beneficiary” means (i) the beneficiary designated, in a manner determined by the Board, by a Participant to receive amounts due or exercise rights of the Participant in the event of
the Participant’s death or (ii) in the absence of an effective designation by a Participant, the Participant’s estate. 
 (d) Additional Provisions Relating to Restricted Stock Units. 
 (1)
Settlement. Upon the vesting of and/or lapsing of any other restrictions (i.e., settlement) with respect to each Restricted Stock Unit, the Participant shall be entitled to receive from the Company one share of Common Stock or (if so provided
in the applicable Award agreement) an amount of cash equal to the Fair Market Value of one share of Common Stock. The Board may, in its discretion, provide that settlement of Restricted Stock Units shall be deferred, on a mandatory basis or at the
election of the Participant in a manner that complies with Section 409A of the Code. 
 (2) Voting Rights. A
Participant shall have no voting rights with respect to any Restricted Stock Units. 
 (3) Dividend Equivalents. The Award
agreement for Restricted Stock Units may provide Participants with the right to receive an amount equal to any dividends or other distributions declared and paid on an equal number of outstanding shares of Common Stock (“Dividend
Equivalents”). Dividend Equivalents may be paid currently or credited to an account for the Participant, may be settled in cash and/or shares of Common Stock and may be subject to the same restrictions on transfer and forfeitability as
the Restricted Stock Units with respect to which paid, in each case to the extent provided in the Award agreement. 

  
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 9. Other Stock-Based Awards 
 (a) General. Other Awards of shares of Common Stock, and other Awards that are valued in whole or in part by reference to, or are otherwise based on, shares of Common Stock or other property, may
be granted hereunder to Participants (“Other Stock-Based-Awards”). Such Other Stock-Based Awards shall also be available as a form of payment in the settlement of other Awards granted under the Plan or as payment in lieu of
compensation to which a Participant is otherwise entitled. Other Stock-Based Awards may be paid in shares of Common Stock or cash, as the Board shall determine. 
 (b) Terms and Conditions. Subject to the provisions of the Plan, the Board shall determine the terms and conditions of each Other Stock-Based Award, including any purchase price applicable thereto.

 10. Adjustments for Changes in Common Stock and Certain Other Events 

(a) Changes in Capitalization. In the event of any stock split, reverse stock split, stock dividend, recapitalization, combination
of shares, reclassification of shares, spin-off or other similar change in capitalization or event, or any dividend or distribution to holders of Common Stock other than an ordinary cash dividend, (i) the number and class of securities
available under the Plan, (ii) the share counting rules and sublimits set forth in Sections 4(a) and 4(b), (iii) the number and class of securities and exercise price per share of each outstanding Option, (iv) the share and per-share
provisions and the measurement price of each outstanding SAR, (v) the number of shares subject to and the repurchase price per share subject to each outstanding Restricted Stock Award and (vi) the share and per-share-related provisions and
the purchase price, if any, of each outstanding Other Stock-Based Award, shall be equitably adjusted by the Company (or substituted Awards may be made, if applicable) in the manner determined by the Board. Without limiting the generality of the
foregoing, in the event the Company effects a split of the Common Stock by means of a stock dividend and the exercise price of and the number of shares subject to an outstanding Option are adjusted as of the date of the distribution of the dividend
(rather than as of the record date for such dividend), then an optionee who exercises an Option between the record date and the distribution date for such stock dividend shall be entitled to receive, on the distribution date, the stock dividend with
respect to the shares of Common Stock acquired upon such Option exercise, notwithstanding the fact that such shares were not outstanding as of the close of business on the record date for such stock dividend. 

(b) Reorganization Events. 
 (1) Definition. A “Reorganization Event” shall mean: (a) any merger or consolidation of the Company with or into another entity as a result of which all of the Common
Stock of the Company is converted into or exchanged for the right to receive cash, securities or other property or is cancelled, (b) any transfer or disposition of all of the Common Stock of the Company for cash, securities or other property
pursuant to a share exchange or other transaction or (c) any liquidation or dissolution of the Company. 
 (2)
Consequences of a Reorganization Event on Awards Other than Restricted Stock. 

  
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 (A) In connection with a Reorganization Event, the Board may take any one
or more of the following actions as to all or any (or any portion of) outstanding Awards other than Restricted Stock on such terms as the Board determines (except to the extent specifically provided otherwise in an applicable Award agreement or
another agreement between the Company and the Participant): (i) provide that such Awards shall be assumed, or substantially equivalent Awards shall be substituted, by the acquiring or succeeding corporation (or an affiliate thereof),
(ii) upon written notice to a Participant, provide that all of the Participant’s unexercised Awards will terminate immediately prior to the consummation of such Reorganization Event unless exercised by the Participant (to the extent then
exercisable) within a specified period following the date of such notice, (iii) provide that outstanding Awards shall become exercisable, realizable, or deliverable, or restrictions applicable to an Award shall lapse, in whole or in part prior
to or upon such Reorganization Event, (iv) in the event of a Reorganization Event under the terms of which holders of Common Stock will receive upon consummation thereof a cash payment for each share surrendered in the Reorganization Event (the
“Acquisition Price”), make or provide for a cash payment to Participants with respect to each Award held by a Participant equal to (A) the number of shares of Common Stock subject to the vested portion of the Award
(after giving effect to any acceleration of vesting that occurs upon or immediately prior to such Reorganization Event) multiplied by (B) the excess, if any, of (I) the Acquisition Price over (II) the exercise, measurement or purchase
price of such Award and any applicable tax withholdings, in exchange for the termination of such Award, (v) provide that, in connection with a liquidation or dissolution of the Company, Awards shall convert into the right to receive liquidation
proceeds (if applicable, net of the exercise, measurement or purchase price thereof and any applicable tax withholdings) and (vi) any combination of the foregoing. In taking any of the actions permitted under this Section 10(b)(2), the
Board shall not be obligated by the Plan to treat all Awards, all Awards held by a Participant, or all Awards of the same type, identically. 
 (B) Notwithstanding the terms of Section 10(b)(2)(A), in the case of outstanding Restricted Stock Units that are subject to Section 409A of the Code: (i) if the applicable Restricted Stock
Unit agreement provides that the Restricted Stock Units shall be settled upon a “change in control event” within the meaning of Treasury Regulation Section 1.409A-3(i)(5)(i), and the Reorganization Event constitutes such a
“change in control event”, then no assumption or substitution shall be permitted pursuant to Section 10(b)(2)(A)(i) and the Restricted Stock Units shall instead be settled in accordance with the terms of the applicable Restricted
Stock Unit agreement; and (ii) the Board may only undertake the actions set forth in clauses (iii), (iv) or (v) of Section 10(b)(2)(A) if the Reorganization Event constitutes a “change in control event” as defined under
Treasury Regulation Section 1.409A-3(i)(5)(i) and such action is permitted or required by Section 409A of the Code; if the Reorganization Event is not a “change in control event” as so defined or such action is not permitted or
required by Section 409A of the Code, and the acquiring or succeeding corporation does not assume or substitute the Restricted Stock Units pursuant to clause (i) of Section 10(b)(2)(A), then the unvested Restricted Stock Units shall
terminate immediately prior to the consummation of the Reorganization Event without any payment in exchange therefor. 
 (C) For purposes of Section 10(b)(2)(A)(i), an Award (other than Restricted Stock) shall be considered assumed if, following consummation of the Reorganization Event, such Award confers the right to
purchase or receive pursuant to the terms of such Award, 

  
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for each share of Common Stock subject to the Award immediately prior to the consummation of the Reorganization Event, the consideration (whether cash, securities or other property) received as a
result of the Reorganization Event by holders of Common Stock for each share of Common Stock held immediately prior to the consummation of the Reorganization Event (and if holders were offered a choice of consideration, the type of consideration
chosen by the holders of a majority of the outstanding shares of Common Stock); provided, however, that if the consideration received as a result of the Reorganization Event is not solely common stock of the acquiring or succeeding
corporation (or an affiliate thereof), the Company may, with the consent of the acquiring or succeeding corporation, provide for the consideration to be received upon the exercise or settlement of the Award to consist solely of such number of shares
of common stock of the acquiring or succeeding corporation (or an affiliate thereof) that the Board determined to be equivalent in value (as of the date of such determination or another date specified by the Board) to the per share consideration
received by holders of outstanding shares of Common Stock as a result of the Reorganization Event. 
 (3) Consequences of a
Reorganization Event on Restricted Stock. Upon the occurrence of a Reorganization Event other than a liquidation or dissolution of the Company, the repurchase and other rights of the Company with respect to outstanding Restricted Stock shall
inure to the benefit of the Company’s successor and shall, unless the Board determines otherwise, apply to the cash, securities or other property which the Common Stock was converted into or exchanged for pursuant to such Reorganization Event
in the same manner and to the same extent as they applied to such Restricted Stock; provided, however, that the Board may provide for termination or deemed satisfaction of such repurchase or other rights under the instrument evidencing
any Restricted Stock or any other agreement between a Participant and the Company, either initially or by amendment. Upon the occurrence of a Reorganization Event involving the liquidation or dissolution of the Company, except to the extent
specifically provided to the contrary in the instrument evidencing any Restricted Stock or any other agreement between a Participant and the Company, all restrictions and conditions on all Restricted Stock then outstanding shall automatically be
deemed terminated or satisfied. 
 (c) Change in Control Events. 

(1) Definition. A “Change in Control Event” shall mean: 

(A) the acquisition by an individual, entity or group (within the meaning of Section 13(d)(3) or 14(d)(2) of the
Exchange Act) (a “Person”) of beneficial ownership of any capital stock of the Company if, after such acquisition, such Person beneficially owns (within the meaning of Rule 13d-3 under the Exchange Act) 50% or more of either
(x) the then-outstanding shares of common stock of the Company (the “Outstanding Company Common Stock”) or (y) the combined voting power of the then-outstanding securities of the Company entitled to vote generally
in the election of directors (the “Outstanding Company Voting Securities”); provided, however, that for purposes of this subsection (A), the following acquisitions shall not constitute a Change in Control Event:
(1) any acquisition directly from the Company or (2) any acquisition by any corporation pursuant to a Business Combination (as defined below) which complies with clauses (x) and (y) of subsection (C) of this definition; or

  
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 (B) a change in the composition of the Board that results in the Continuing
Directors (as defined below) no longer constituting a majority of the Board (or, if applicable, the Board of Directors of a successor corporation to the Company), where the term “Continuing Director” means at any date a
member of the Board (x) who was a member of the Board on the date of the initial adoption of the Plan by the Board or (y) who was nominated or elected subsequent to such date by at least a majority of the directors who were Continuing
Directors at the time of such nomination or election or whose election to the Board was recommended or endorsed by at least a majority of the directors who were Continuing Directors at the time of such nomination or election; provided,
however, that there shall be excluded from this clause (y) any individual whose initial assumption of office occurred as a result of an actual or threatened election contest with respect to the election or removal of directors or other
actual or threatened solicitation of proxies or consents, by or on behalf of a person other than the Board; or 

(C) the consummation of a merger, consolidation, reorganization, recapitalization or share exchange involving the Company
or a sale or other disposition of all or substantially all of the assets of the Company (a “Business Combination”), unless, immediately following such Business Combination, each of the following two conditions is satisfied:
(x) all or substantially all of the individuals and entities who were the beneficial owners of the Outstanding Company Common Stock and Outstanding Company Voting Securities immediately prior to such Business Combination beneficially own,
directly or indirectly, more than 50% of the then-outstanding shares of common stock and the combined voting power of the then-outstanding securities entitled to vote generally in the election of directors, respectively, of the resulting or
acquiring corporation in such Business Combination (which shall include, without limitation, a corporation which as a result of such transaction owns the Company or substantially all of the Company’s assets either directly or through one or
more subsidiaries) (such resulting or acquiring corporation is referred to herein as the “Acquiring Corporation”) in substantially the same proportions as their ownership of the Outstanding Company Common Stock and
Outstanding Company Voting Securities, respectively, immediately prior to such Business Combination and (y) no Person (excluding any employee benefit plan (or related trust) maintained or sponsored by the Company or by the Acquiring
Corporation) beneficially owns, directly or indirectly, 50% or more of the then-outstanding shares of common stock of the Acquiring Corporation, or of the combined voting power of the then-outstanding securities of such corporation entitled to vote
generally in the election of directors (except to the extent that such ownership existed prior to the Business Combination); or 
 (D) the liquidation or dissolution of the Company. 
 (2) Effect on Options and
SARs. Except to the extent specifically provided to the contrary in the instrument evidencing any Option or SAR or any other agreement between a Participant and the Company, all Options and SARs then outstanding shall automatically become
immediately exercisable in full in the instance where such Option or SAR is not assumed or substituted as set forth in Section 10(b) following a Change in Control Event where the Participant’s employment with the Company has been
terminated within one year of the Change in Control Event. 

  
 - 11 -

 (3) Effect on Restricted Stock. Except to the extent specifically provided to the
contrary in the instrument evidencing the Restricted Stock or any other agreement between a Participant and the Company, all restrictions and conditions on all Restricted Stock then-outstanding shall automatically be deemed terminated or satisfied
in the instance where such Award is not assumed or substituted as set forth in Section 10(b) following a Change in Control Event where the Participant’s employment with the Company has been terminated within one year of the Change in
Control Event. 
 (4) Effect on Restricted Stock Units. Effective immediately prior to a Change in Control Event, except
to the extent specifically provided to the contrary in the instrument evidencing any Restricted Stock Unit Award or any other agreement between a Participant and the Company, all restrictions and conditions on all Restricted Stock Units then
outstanding shall automatically be deemed terminated and satisfied in the instance where such Award is not assumed or substituted as set forth in Section 10(b); provided, however, that for any Restricted Stock Units that are not exempt from
Section 409A of the Code, if the Change in Control Event does not also constitute a “change in control event” within in the meaning of Treasury Regulation Section 1.409A-3(i)(5)(i), then the unvested Restricted Stock Units shall
terminate without any payment in exchange therefor. 
 (5) Effect on Other Stock-Based Awards. The Board may specify in an
Award agreement at the time of grant or otherwise the effect of a Change in Control on an Other Stock-Based Award. 
 (6)
Section 409A. The definition of Change in Control Event for purposes of the Plan is intended to conform to the description of “Change in Control Events” in Treasury Regulation Section 1.409A-3(i)(5), or in subsequent IRS
guidance describing what constitutes a change in control event for purposes of Section 409A of the Code when the Award is subject to Section 409A. Accordingly, no Change in Control Event will be deemed to provide for acceleration of
payment of Awards that are subject to Section 409A of the Code with respect to a transaction or event described in this Section 10(c) unless the transaction or event would constitute a “Change in Control Event” as described in
Treasury Regulation section 1.409A-3(i)(5), or in subsequent IRS guidance under Section 409A of the Code. 
 11. General Provisions
Applicable to Awards 
 (a) Transferability of Awards. Awards shall not be sold, assigned, transferred, pledged or
otherwise encumbered by the person to whom they are granted, either voluntarily or by operation of law, except by will or the laws of descent and distribution or, other than in the case of an Incentive Stock Option, pursuant to a qualified domestic
relations order, and, during the life of the Participant, shall be exercisable only by the Participant; provided, however, that, except with respect to Awards that are subject to Section 409A of the Code, the Board may permit or provide
in an Award for the transfer of the Award by the Participant to or for the benefit of any immediate family member, family trust or other entity established for the benefit of the Participant and/or an immediate family member thereof if the Company
would be eligible to use a Form S-8 under the Securities Act of 1933, as amended (the “Securities Act”) for the registration of the sale of the Common Stock subject to such Award to such proposed transferee; provided
further, that the Company shall not be required to recognize any such permitted transfer until such time as such 

  
 - 12 -

 
permitted transferee shall, as a condition to such transfer, deliver to the Company a written instrument in form and substance satisfactory to the Company confirming that such transferee shall be
bound by all of the terms and conditions of the Award. References to a Participant, to the extent relevant in the context, shall include references to authorized transferees. For the avoidance of doubt, nothing contained in this Section 11(a)
shall be deemed to restrict a transfer to the Company. 
 (b) Documentation. Each Award shall be evidenced in such form
(written, electronic or otherwise) as the Board shall determine. Each Award may contain terms and conditions in addition to those set forth in the Plan. 
 (c) Board Discretion. Except as otherwise provided by the Plan, each Award may be made alone or in addition or in relation to any other Award. The terms of each Award need not be identical, and the
Board need not treat Participants uniformly. 
 (d) Termination of Status. The Board shall determine the effect on an
Award of the disability, death, termination or other cessation of employment, authorized leave of absence or other change in the employment or other status of a Participant and the extent to which, and the period during which, the Participant, or
the Participant’s legal representative, conservator, guardian or Designated Beneficiary, may exercise rights under the Award. 
 (e) Withholding. The Participant must satisfy all applicable federal, state, and local or other income and employment tax withholding obligations before the Company will deliver stock certificates
or otherwise recognize ownership of Common Stock under an Award. The Company may decide to satisfy the withholding obligations through additional withholding on salary or wages. If the Company elects not to or cannot withhold from other
compensation, the Participant must pay the Company the full amount, if any, required for withholding or have a broker tender to the Company cash equal to the withholding obligations. Payment of withholding obligations is due before the Company will
issue any shares on exercise, vesting or release from forfeiture of an Award or at the same time as payment of the exercise or purchase price, unless the Company determines otherwise. If provided for in an Award or approved by the Board in its sole
discretion, a Participant may satisfy such tax obligations in whole or in part by delivery (either by actual delivery or attestation) of shares of Common Stock, including shares retained from the Award creating the tax obligation, valued at their
Fair Market Value; provided, however, except as otherwise provided by the Board, that the total tax withholding where stock is being used to satisfy such tax obligations cannot exceed the Company’s minimum statutory withholding
obligations (based on minimum statutory withholding rates for federal and state tax purposes, including payroll taxes, that are applicable to such supplemental taxable income). Shares used to satisfy tax withholding requirements cannot be subject to
any repurchase, forfeiture, unfulfilled vesting or other similar requirements. 
 (f) Amendment of Award. Except as
otherwise provided herein, the Board may amend, modify or terminate any outstanding Award. The Participant’s consent to such action shall be required unless (i) the Board determines that the action, taking into account any related action,
does not materially and adversely affect the Participant’s rights under the Plan or (ii) the change is permitted under Section 10. 

  
 - 13 -

 (g) Conditions on Delivery of Stock. The Company will not be obligated to deliver any
shares of Common Stock pursuant to the Plan or to remove restrictions from shares previously issued or delivered under the Plan until (i) all conditions of the Award have been met or removed to the satisfaction of the Company, (ii) in the
opinion of the Company’s counsel, all other legal matters in connection with the issuance and delivery of such shares have been satisfied, including any applicable securities laws and regulations and any applicable stock exchange or stock
market rules and regulations, and (iii) the Participant has executed and delivered to the Company such representations or agreements as the Company may consider appropriate to satisfy the requirements of any applicable laws, rules or
regulations. 
 (h) Acceleration. The Board may at any time provide that any Award shall become immediately exercisable in
whole or in part, free of some or all restrictions or conditions, or otherwise realizable in whole or in part, as the case may be. 
 (i) Performance Awards. 
 (1) Grants. Restricted Stock Awards and
Other Stock-Based Awards under the Plan may be made subject to the achievement of performance goals pursuant to this Section 11(i) (“Performance Awards”). No Performance Awards shall vest prior to the first anniversary
of the date of grant. 
 (2) Committee. Grants of Performance Awards to any Covered Employee (as defined below) intended
to qualify as “performance-based compensation” under Section 162(m) (“Performance-Based Compensation”) shall be made only by a Committee (or a subcommittee of a Committee) comprised solely of two or more
directors eligible to serve on a committee making Awards qualifying as “performance-based compensation” under Section 162(m). In the case of such Awards granted to Covered Employees, references to the Board or to a Committee shall be
treated as referring to such Committee (or subcommittee). “Covered Employee” shall mean any person who is, or whom the Committee, in its discretion, determines may be, a “covered employee” under
Section 162(m)(3) of the Code. 
 (3) Performance Measures. For any Award that is intended to qualify as
Performance-Based Compensation, the Committee shall specify that the degree of granting, vesting and/or payout shall be subject to the achievement of one or more objective performance measures established by the Committee, which shall be based on
the relative or absolute attainment of specified levels of one or any combination of the following, which may be determined pursuant to generally accepted accounting principles (“GAAP”) or on a non-GAAP basis, as determined
by the Committee: product sales, net income, earnings before or after discontinued operations, interest, taxes, depreciation and/or amortization, operating profit before or after discontinued operations and/or taxes, sales, sales growth, earnings
growth, cash flow or cash position, gross margins, stock price, market share, return on sales, assets, equity or investment, improvement of financial ratings; achievement of balance sheet or income statement objectives or total stockholder return,
entry into an arrangement or agreement with a third party for the development, commercialization, marketing or distribution of products, services or technologies, or for conducting a research program to discover and develop a product, service or
technology, and/or the achievement of milestones under such arrangement or agreement, including events that trigger an obligation or payment right; achievement of domestic and international regulatory milestones, including the submission of

  
 - 14 -

 
filings required to advance products, services and technologies in clinical development and the achievement of approvals by regulatory authorities relating to the commercialization of products,
services and technologies; the achievement of discovery, preclinical and clinical stage scientific objectives, discoveries or inventions for products, services and technologies under research and development; the entry into or completion of a phase
of clinical development for any product, service or technology, such as the entry into or completion of phase 1, 2 and/or 3 clinical trials; the consummation of debt or equity financing transactions, or acquisitions of businesses, technologies and
assets; or the achievement of qualitative or quantitative performance measures set forth in operating plans approved by our board of directors from time to time. Such goals may reflect absolute entity or business unit performance or a relative
comparison to the performance of a peer group of entities or other external measure of the selected performance criteria and may be absolute in their terms or measured against or in relationship to other companies comparably, similarly or otherwise
situated. The Committee may specify that such performance measures shall be adjusted to exclude any one or more of (i) extraordinary items, (ii) gains or losses on the dispositions of discontinued operations, (iii) the cumulative
effects of changes in accounting principles, (iv) the writedown of any asset, (vi) fluctuation in foreign currency exchange rates, and (vi) charges for restructuring and rationalization programs. Such performance measures:
(i) may vary by Participant and may be different for different Awards; (ii) may be particular to a Participant or the department, branch, line of business, subsidiary or other unit in which the Participant works and may cover such period
as may be specified by the Committee; and (iii) shall be set by the Committee within the time period prescribed by, and shall otherwise comply with the requirements of, Section 162(m). Awards that are not intended to qualify as
Performance-Based Compensation may be based on these or such other performance measures as the Board may determine. 
 (4)
Adjustments. Notwithstanding any provision of the Plan, with respect to any Performance Award that is intended to qualify as Performance-Based Compensation, the Committee may adjust downwards, but not upwards, the cash or number of shares
payable pursuant to such Award, and the Committee may not waive the achievement of the applicable performance measures except in the case of the death or disability of the Participant or a change in control of the Company. 

(5) Dividends. Unless otherwise provided in the applicable Award agreement, any dividends (whether paid in cash, stock or property)
declared and paid by the Company with respect to shares of Performance Awards shall be paid to the Participant only if and when shares become free from the restrictions on transferability or forfeitability that apply to such shares. 

(6) Other. The Committee shall have the power to impose such other restrictions on Performance Awards as it may deem necessary or
appropriate to ensure that such Awards satisfy all requirements for Performance-Based Compensation. 
 12. Miscellaneous 

(a) No Right To Employment or Other Status. No person shall have any claim or right to be granted an Award by virtue of the
adoption of the Plan, and the grant of an Award shall not be construed as giving a Participant the right to continued employment or any other relationship with the Company. The Company expressly reserves the right at any time to dismiss or otherwise
terminate its relationship with a Participant free from any liability or claim under the Plan, except as expressly provided in the applicable Award. 

  
 - 15 -

 (b) No Rights As Stockholder. Subject to the provisions of the applicable Award, no
Participant or Designated Beneficiary shall have any rights as a stockholder with respect to any shares of Common Stock to be distributed with respect to an Award until becoming the record holder of such shares. 

(c) Effective Date and Term of Plan. The Plan shall become effective on the date the Plan is approved by the Company’s
stockholders (the “Effective Date”). No Awards shall be granted under the Plan after the expiration of 10 years from the Effective Date, but Awards previously granted may extend beyond that date. 

(d) Amendment of Plan. The Board may amend, suspend or terminate the Plan or any portion thereof at any time provided that
(i) to the extent required by Section 162(m), no Award granted to a Participant that is intended to comply with Section 162(m) after the date of such amendment shall become exercisable, realizable or vested, as applicable to such
Award, unless and until the Company’s stockholders approve such amendment in the manner required by Section 162(m); (ii) no amendment that would require stockholder approval under the rules of NASDAQ may be made effective unless and
until the Company’s stockholders approve such amendment; and (iii) if the NASDAQ amends its corporate governance rules so that such rules no longer require stockholder approval of NASDAQ “material amendments” to equity
compensation plans, then, from and after the effective date of such amendment to the NASDAQ rules, no amendment to the Plan (A) materially increasing the number of shares authorized under the Plan (other than pursuant to Section 4(c) or
10), (B) expanding the types of Awards that may be granted under the Plan, or (C) materially expanding the class of participants eligible to participate in the Plan shall be effective unless and until the Company’s stockholders
approve such amendment. In addition, if at any time the approval of the Company’s stockholders is required as to any other modification or amendment under Section 422 of the Code or any successor provision with respect to Incentive Stock
Options, the Board may not effect such modification or amendment without such approval. Unless otherwise specified in the amendment, any amendment to the Plan adopted in accordance with this Section 12(d) shall apply to, and be binding on the
holders of, all Awards outstanding under the Plan at the time the amendment is adopted, provided the Board determines that such amendment, taking into account any related action, does not materially and adversely affect the rights of Participants
under the Plan. 
 (e) Authorization of Sub-Plans (including for Grants to non-U.S. Employees). The Board may from time to
time establish one or more sub-plans under the Plan for purposes of satisfying applicable securities, tax or other laws of various jurisdictions. The Board shall establish such sub-plans by adopting supplements to the Plan containing (i) such
limitations on the Board’s discretion under the Plan as the Board deems necessary or desirable or (ii) such additional terms and conditions not otherwise inconsistent with the Plan as the Board shall deem necessary or desirable. All
supplements adopted by the Board shall be deemed to be part of the Plan, but each supplement shall apply only to Participants within the affected jurisdiction and the Company shall not be required to provide copies of any supplement to Participants
in any jurisdiction which is not the subject of such supplement. 

  
 - 16 -

 (f) Compliance with Section 409A of the Code. Except as provided in individual
Award agreements initially or by amendment, if and to the extent (i) any portion of any payment, compensation or other benefit provided to a Participant pursuant to the Plan in connection with his or her employment termination constitutes
“nonqualified deferred compensation” within the meaning of Section 409A of the Code and (ii) the Participant is a specified employee as defined in Section 409A(a)(2)(B)(i) of the Code, in each case as determined by the
Company in accordance with its procedures, by which determinations the Participant (through accepting the Award) agrees that he or she is bound, such portion of the payment, compensation or other benefit shall not be paid before the day that is six
months plus one day after the date of “separation from service” (as determined under Section 409A of the Code) (the “New Payment Date”), except as Section 409A of the Code may then permit. The aggregate of
any payments that otherwise would have been paid to the Participant during the period between the date of separation from service and the New Payment Date shall be paid to the Participant in a lump sum on such New Payment Date, and any remaining
payments will be paid on their original schedule. 
 The Company makes no representations or warranty and shall have no liability to the
Participant or any other person if any provisions of or payments, compensation or other benefits under the Plan are determined to constitute nonqualified deferred compensation subject to Section 409A of the Code but do not to satisfy the
conditions of that section. 
 (g) Limitations on Liability. Notwithstanding any other provisions of the Plan, no
individual acting as a director, officer, employee or agent of the Company will be liable to any Participant, former Participant, spouse, beneficiary, or any other person for any claim, loss, liability, or expense incurred in connection with the
Plan, nor will such individual be personally liable with respect to the Plan because of any contract or other instrument he or she executes in his or her capacity as a director, officer, employee or agent of the Company. The Company will indemnify
and hold harmless each director, officer, employee or agent of the Company to whom any duty or power relating to the administration or interpretation of the Plan has been or will be delegated, against any cost or expense (including attorneys’
fees) or liability (including any sum paid in settlement of a claim with the Board’s approval) arising out of any act or omission to act concerning the Plan unless arising out of such person’s own fraud or bad faith. 

(h) Governing Law. The provisions of the Plan and all Awards made hereunder shall be governed by and interpreted in accordance with
the laws of the State of Delaware, excluding choice-of-law principles of the law of such state that would require the application of the laws of a jurisdiction other than the State of Delaware. 

Approved by the Board of Directors on March 1, 2012 
 Approved by the Stockholders on June 7, 2012 

  
 - 17 -EX-10.2

 Exhibit 10.2 
 Idenix Pharmaceuticals, Inc. 
 Incentive Stock Option Agreement 

Granted Under 2012 Stock Incentive Plan 
 1. Grant of Option. 
 This agreement evidences the grant by Idenix
Pharmaceuticals, Inc., a Delaware corporation (the “Company”), on              , 2012 (the “Grant Date”) to
[            ] (the “Participant”), of an option to purchase, in whole or in part, on the terms provided herein and in the Company’s 2012 Stock Incentive Plan
(the “Plan”), a total of [            ] shares (the “Shares”) of common stock, 0.001 par value per share, of the Company (“Common Stock”) at
$[            ] per Share. Unless earlier terminated, this option shall expire at 5:00 p.m., Eastern time, on [10years-1 day] (the “Final Exercise Date”).

 It is intended that the option evidenced by this agreement shall be an incentive stock option as defined in Section 422
of the Internal Revenue Code of 1986, as amended, and any regulations promulgated thereunder (the “Code”). Except as otherwise indicated by the context, the term “Participant”, as used in this option, shall be deemed to include
any person who acquires the right to exercise this option validly under its terms. 
 2. Vesting Schedule. 

This Option will become exercisable (“vest”) ratably on a monthly basis over a period of 48 months beginning of the last day of
the month in which the grant occurs and continuing thereafter on the last day of each of the next 47 successive months. 
 The
right of exercise shall be cumulative so that to the extent the option is not exercised in any period to the maximum extent permissible it shall continue to be exercisable, in whole or in part, with respect to all Shares for which it is vested until
the earlier of the Final Exercise Date or the termination of this option under Section 3 hereof or the Plan. 
 3. Exercise of
Option. 
 (a) Form of Exercise. Each election to exercise this option shall be in writing, signed by the Participant,
and received by the Company at its principal office, accompanied by this agreement, and payment in full in the manner provided in the Plan. The Participant may purchase less than the number of shares covered hereby, provided that no partial exercise
of this option may be for any fractional share or for fewer than ten whole shares. 
 (b) Continuous Relationship with the
Company Required. Except as otherwise provided in this Section 3, this option may not be exercised unless the Participant, at the time he or she exercises this option, is, and has been at all times since the Grant Date, an employee or
officer of, or consultant or advisor to, the Company or any parent or subsidiary of the Company as defined in Section 424(e) or (f) of the Code (an “Eligible Participant”). 

 (c) Termination of Relationship with the Company. If the Participant ceases to be an
Eligible Participant for any reason, then, except as provided in paragraphs (d) and (e) below, the right to exercise this option shall terminate 180 days after such cessation (but in no event after the Final Exercise Date), provided
that this option shall be exercisable only to the extent that the Participant was entitled to exercise this option on the date of such cessation. Notwithstanding the foregoing, if the Participant, prior to the Final Exercise Date, violates
the non-competition or confidentiality provisions of any employment contract, confidentiality and nondisclosure agreement or other agreement between the Participant and the Company, the right to exercise this option shall terminate immediately upon
occurrence of such violation. 
 (d) Exercise Period Upon Death or Disability. If the Participant dies or becomes disabled
(within the meaning of Section 22(e)(3) of the Code) prior to the Final Exercise Date while he or she is an Eligible Participant and the Company has not terminated such relationship for “cause” as specified in paragraph
(e) below, this option shall be exercisable, within the period of one year following the date of death or disability of the Participant, by the Participant (or in the case of death by an authorized transferee), provided that this
option shall be exercisable only to the extent that this option was exercisable by the Participant on the date of his or her death or disability, and further provided that this option shall not be exercisable after the Final Exercise Date.

 (e) Termination for Cause. If, prior to the Final Exercise Date, the Participant’s employment is terminated by the
Company for Cause (as defined below), the right to exercise this option shall terminate immediately upon the effective date of such termination of employment. If the Participant is party to an employment or severance agreement with the Company that
contains a definition of “cause” for termination of employment, “Cause” shall have the meaning ascribed to such term in such agreement. Otherwise, “Cause” shall mean willful misconduct by the Participant or willful
failure by the Participant to perform his or her responsibilities to the Company (including, without limitation, breach by the Participant of any provision of any employment, consulting, advisory, nondisclosure, non-competition or other similar
agreement between the Participant and the Company), as determined by the Company, which determination shall be conclusive. The Participant’s employment shall be considered to have been terminated for Cause if the Company determines, within 30
days after the Participant’s resignation, that termination for Cause was warranted. 
 4. Tax Matters. 

(a) Withholding. No Shares will be issued pursuant to the exercise of this option unless and until the Participant pays to the
Company, or makes provision satisfactory to the Company for payment of, any federal, state or local withholding taxes required by law to be withheld in respect of this option. 
 (b) Disqualifying Disposition. If the Participant disposes of Shares acquired upon exercise of this option within two years from the Grant Date or one year after such Shares were acquired pursuant
to exercise of this option, the Participant shall notify the Company in writing of such disposition. 

  
 - 2 -

 5. Transfer Restrictions. 
 This option may not be sold, assigned, transferred, pledged or otherwise encumbered by the Participant, either voluntarily or by operation of law, except by will or the laws of descent and distribution,
and, during the lifetime of the Participant, this option shall be exercisable only by the Participant. 
 6. Provisions of the Plan.

 This option is subject to the provisions of the Plan (including the provisions relating to amendments to the Plan), a copy of
which is furnished to the Participant with this option. 
 IN WITNESS WHEREOF, the Company has caused this option to be executed
under its corporate seal by its duly authorized officer. This option shall take effect as a sealed instrument. 
  

					
	Idenix Pharmaceuticals, Inc.
		
	By:	 	 
			
		 	Name:	 	 
			
		 	Title:	 	 

  
 - 3 -

 PARTICIPANT’S ACCEPTANCE 

The undersigned hereby accepts the foregoing option and agrees to the terms and conditions thereof. The undersigned hereby acknowledges
receipt of a copy of the Company’s 2012 Stock Incentive Plan. 
  

			
	PARTICIPANT:
	
	 
		
	Address:	 	 
		
		 	 

  
 - 4 -

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