Document:

Form of Incentive Stock Option Agreement under the 1998 Stock Option Plan

 EXHIBIT 10.19 
  
 ACHILLION PHARMACEUTICALS, INC 
  
 Incentive Stock Option Agreement 
 Granted Under 1998 Stock Option Plan 
  

	1.	Grant of Option. 

  
 This agreement evidences the grant by Achillion Pharmaceuticals, Inc., a Delaware corporation (the “Company”), on
                    , 2003 (the “Grant Date”) to
                    , an employee of the Company (the “Participant”), of an option to purchase, in whole or in part, on the terms
provided herein and in the Company’s 1998 Stock Option Plan (the “Plan”), a total of              shares (the “Shares”) of common stock, $.001 par value per
share, of the Company (“Common Stock”) at $             per Share. Unless earlier terminated, this option shall expire on
                    , 2013 (the “Final Exercise Date”). For purposes of this Agreement, the “Vesting Commencement Date”
shall be September 10, 2003. 
  
 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. 

  
 (a) This option will become exercisable (“vest”) as to 25% of the original number of Shares on the first anniversary of the Vesting Commencement
Date and as to an additional 6.25% of the original number of Shares at the end of each successive three-month period following the first anniversary of the Vesting Commencement Date until the fourth anniversary of the Vesting Commencement Date.

  
 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. 
  
 (b) Notwithstanding the exercisability schedule set forth in paragraph 2(a), the Participant may elect to exercise this option as to the unvested Shares (in addition to the vested Shares) if simultaneously with such exercise the Participant
enters into a Stock Restriction Agreement with the Company in the form attached hereto as Exhibit A (the “Stock Restriction Agreement”. The Stock Restriction Agreement provides that the unvested Shares shall be subject to a right of
repurchase in favor of the Company in the event that the Participant ceases to be employed by the Company. 
  
 (c) Upon the occurrence of a Corporate Transaction (as defined below) that is not a Private Transaction (as defined below), the vesting schedule of this
option shall be accelerated in part so that the option shall become exercisable for an additional number of shares equal to 25% of the Shares subject to this option. The remaining number of shares shall continue to vest in accordance with the
original vesting schedule set forth in this option. 

 (d) Upon the occurrence of a Corporate Transaction, and if, within twelve months following the Corporate
Transaction, the Participant’s employment with the Company or the acquiring or succeeding corporation is terminated for Good Reason (as defined below) by the Participant or is terminated without Cause (as defined below) by the Company or the
acquiring or succeeding corporation, the vesting schedule of this option shall become exercisable for an additional number of shares equal to 50% of the Shares subject to this option. 
  
 (e) For purposes of this Agreement, the following terms shall have the following meanings: 
  
 (1) “Cause” shall mean (a) a good faith finding by the
Company that (i) the Participant has failed to substantially perform his or her reasonably assigned duties for the Company, or (ii) the Participant has engaged in dishonesty, gross negligence or misconduct, which dishonesty, gross
negligence or misconduct has had a material adverse effect on the Company, (b) the conviction of the Participant of, or the entry of a pleading of guilty or nolo contendere by the Participant to, any crime involving moral turpitude or any
felony or (c) breach by the Participant of any material provision of the Amended and Restated Employment Agreement between the Company and the Participant, or any invention and non-disclosure agreement, non-competition and non-solicitation
agreement or other agreement with the Company, which breach is not cured within thirty days written notice thereof. 
  
 (2) “Corporate Transaction” shall mean the sale of all or substantially all of the capital stock (other than the sale of capital stock to
one or more venture capitalists or other institutional investors pursuant to an equity financing (including a debt financing that is convertible into equity) of the Company approved by a majority of the Board of Directors of the Company), assets or
business of the Company, by merger, consolidation, sale of assets or otherwise (other than a merger or consolidation in which all or substantially all of the individuals and entities who were beneficial owners of the Common Stock immediately prior
to such transaction beneficially own, directly or indirectly, more than 50% of the outstanding securities entitled to vote generally in the election of directors of the resulting, surviving or acquiring corporation in such transaction). 

 
 (3) “Good Reason” shall mean (i) mutual written
agreement by the Participant and the Board of Directors of the Company that Good Reason exists; (ii) the Participant being required by the Company to relocate such that such Participant’s daily commute is increased by at least 60 miles
without the written consent of the Participant; (iii) any material breach by the Company or any successor thereto of any agreement to which the Participant and the Company are parties, which breach is not cured within thirty days of written
notice thereof; or (iv) demotion of the Participant to a position with responsibilities substantially less than such Employee’s current position without the prior consent of the Employee; provided, however, that nothing shall require the
Participant to hold the same title or same functional role within an entity resulting from a Corporate Transaction so long as the Participant’s responsibilities are not substantially diminished. 
  

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 (4) “Private Transaction” shall mean any Corporate Transaction where the consideration
received or retained by the holders of the then outstanding capital stock of the Company does not consist of (i) cash or cash equivalent consideration, (ii) securities which are registered under the Securities Act of 1933, as amended, or
any successor statute (the “Securities Act”) and/or (iii) securities for which the Company or any other issuer thereof has agreed to file a registration statement within ninety (90) days of completion of the transaction for
resale to the public pursuant to the Securities Act. 
  

	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, officer or director 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 three months 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 written notice to the Participant from the Company describing 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, 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) Discharge for Cause. If the Participant, prior to the Final Exercise Date, is discharged by the Company for “Cause,” as determined by
the Board of Directors, or is otherwise attributable to a breach, as determined by the Board, by the Participant of an employment agreement with the Company, the right to exercise this option shall terminate immediately upon the effective date of
such discharge. For purposes of this Agreement “Cause” 

  

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shall include 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 shall be considered to have been discharged for “Cause” if the Company determines, within 30 days after the Participant’s resignation, that discharge for cause was warranted.

  

	4.	Right of First Refusal. 

  
 (a) If the Participant proposes to sell, assign, transfer, pledge, hypothecate or otherwise dispose of, by operation of law or otherwise (collectively,
“transfer”) any Shares acquired upon exercise of this option, then the Participant shall first give written notice of the proposed transfer (the “Transfer Notice”) to the Company. The Transfer Notice shall name the proposed
transferee and state the number of such Shares the Participant proposes to transfer (the “Offered Shares”), the price per share and all other material terms and conditions of the transfer. 
  
 (b) For 30 days following its receipt of such Transfer Notice, the Company
shall have the option to purchase all (or any portion) of the Offered Shares at the price and upon the terms set forth in the Transfer Notice. In the event the Company elects to purchase all (or any portion) of the Offered Shares, it shall give
written notice of such election to the Participant within such 30-day period. Within 10 days after his receipt of such notice, the Participant shall tender to the Company at its principal offices the certificate or certificates representing the
Offered Shares, duly endorsed in blank by the Participant or with duly endorsed stock powers attached thereto, all in a form suitable for transfer of the Offered Shares to the Company. Promptly following receipt of such certificate or certificates,
the Company shall deliver or mail to the Participant a check in payment of the purchase price for the Offered Shares; provided that if the terms of payment set forth in the Transfer Notice were other than cash against delivery, the
Company may pay for the Offered Shares on the same terms and conditions as were set forth in the Transfer Notice; and provided further that any delay in making such payment shall not invalidate the Company’s exercise of its option
to purchase the Offered Shares. 
  
 (c) If the Company does not
elect to acquire all of the Offered Shares, the Participant may, within the 30-day period following the expiration of the option granted to the Company under subsection (b) above, transfer any remaining Offered Shares to the proposed
transferee, provided that such transfer shall not be on terms and conditions more favorable to the transferee than those contained in the Transfer Notice. Notwithstanding any of the above, all Offered Shares transferred pursuant to
this Section 4 shall remain subject to the right of first refusal set forth in this Section 4 and such transferee shall, as a condition to such transfer, deliver to the Company a written instrument confirming that such transferee shall be
bound by all of the terms and conditions of this Section 4. 
  
 (d) After the time at which the Offered Shares are required to be delivered to the Company for transfer to the Company pursuant to subsection (b) above, the Company shall not pay any dividend to the Participant on account of such
Offered Shares or permit the Participant to exercise any of the privileges or rights of a stockholder with respect to such Offered Shares, but shall, in so far as permitted by law, treat the Company as the owner of such Offered Shares. 

 

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 (e) The following transactions shall be exempt from the provisions of this Section 4: 
  
 (1) any transfer of Shares to or for the benefit of any spouse, child or
grandchild of the Participant, or to a trust for their benefit; 
  
 (2) any transfer pursuant to an effective registration statement filed by the Company under the Securities Act; and 
  
 (3) the sale of all or substantially all of the shares of capital stock of the Company (including pursuant to a merger or consolidation); 
  
 provided, however, that in the case of a transfer pursuant to clause
(1) above, such Shares shall remain subject to the right of first refusal set forth in this Section 4 and such transferee shall, as a condition to such transfer, deliver to the Company a written instrument confirming that such transferee
shall be bound by all of the terms and conditions of this Section 4. 
  
 (f) The Company may assign its rights to purchase Offered Shares in any particular transaction under this Section 4 to one or more persons or entities. 
  
 (g) The provisions of this Section 4 shall terminate upon the earlier of
the following events: 
  
 (1) the closing of the sale of shares
of Common Stock in an underwritten public offering pursuant to an effective registration statement filed by the Company under the Securities Act; or 
  
 (2) the consummation of a Corporate Transaction. 
  
 (h) The Company shall not be required (a) to transfer on its books any of the Shares which shall have been sold or transferred in violation of any of
the provisions set forth in this Section 4, or (b) to treat as owner of such Shares or to pay dividends to any transferee to whom any such Shares shall have been so sold or transferred. 
  

	5.	Agreements in Connection with a Public Offering or Acquisition. 

  
 (a) The Participant agrees, in connection with the initial underwritten public offering of the Company’s securities pursuant to a registration
statement under the Securities Act, (i) not to sell, make short sale of, loan, grant any options for the purchase of, or otherwise dispose of any shares of Common Stock held by the Participant (other than those shares included in the offering)
without the prior written consent of the Company or the underwriters managing such initial underwritten public offering of the Company’s securities for a period of 180 days from the effective date of such registration statement, and
(ii) to execute any agreement reflecting clause (i) above as may be requested by the Company or the managing underwriters at the time of such offering. 
  
 (b) The Participant agrees that, in the event of a Corporate Transaction, if holders of at least [30%] of the outstanding
shares of capital stock of the Company agree, in connection with such Corporate Transaction, not to sell, make short sale of, loan, grant any options for the 

  

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purchase of, or otherwise dispose of any shares of capital stock of the acquiring entity received in such change of Control Transaction (a “Lock-Up
Agreement”); then the Participant agrees, if requested by the Company or the acquiring entity, to execute a Lock-Up Agreement; provided, however, that such lock-up period shall extend for no more than the three months following the date of the
consummation of the Corporate Transaction. 
  

	6.	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. 
  

	7.	Nontransferability of Option. 

  
 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. 
  

	8.	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. 
  

	9.	Provisions of the Plan. 

  
 This option is subject to the provisions of the Plan, a copy of which is furnished to the Participant with this option. 
  
 [Remainder of page intentionally left blank] 
  

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 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. 
  

					
	 	 	ACHILLION PHARMACEUTICALS, INC.
			
	Dated:
                                        
            	 	By:	 	  

	 	 	Name:	 	  

	 	 	Title:	 	  

  

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 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 1998 Stock Option Plan. 
  

			
	PARTICIPANT:
	
	  

	Mary Kay Fenton
		
	Address:	 	  

	 	 	  

  

 8Form of Incentive Stock Option Agreement, Non-Executives under the 1998 Plan

 Exhibit 10.20 
  
 ACHILLION PHARMACEUTICALS, INC 
  
 Incentive Stock Option Agreement 
 Granted Under 1998 Stock Option Plan 
  

	1.	Grant of Option. 

  
 This agreement evidences the grant by Achillion Pharmaceuticals, Inc., a Delaware corporation (the “Company”), on August 1, 2005 (the
“Grant Date”) to Ronald Gugliotti, an employee of the Company (the “Participant”), of an option to purchase, in whole or in part, on the terms provided herein and in the Company’s 1998 Stock Option Plan (the
“Plan”), a total of 15,000 shares (the “Shares”) of common stock, $.001 par value per share, of the Company (“Common Stock”) at $0.20 per Share. Unless earlier terminated, this option shall expire on August 1, 2015
(the “Final Exercise Date”). For purposes of this Agreement, the “Vesting Commencement Date” shall be August 1, 2005. 
  
 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. 

  
 (a) Option Exercise Schedule. This option will become exercisable (“vest”) as to 25% of the original number of Shares on the first
anniversary of the Grant Date and as to an additional 6.25% of the original number of Shares at the end of each successive three-month period until the fourth anniversary of the Grant Date. 
  
 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. 
  
 (b) Early Exercise
Alternative. Notwithstanding the exercisability schedule set forth in paragraph 2(a), the Participant may elect to exercise this option as to the unvested Shares (in addition to the vested Shares) if simultaneously with such exercise the
Participant enters into a Stock Restriction Agreement with the Company (the “Stock Restriction Agreement”). The Stock Restriction Agreement provides that the unvested Shares shall be subject to a right of repurchase in favor of the Company
in the event that the Participant ceases to be employed by the Company. 
  

	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, officer or director 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 three months 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 written notice to the Participant from the Company
describing 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, 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) Discharge for Cause. If the Participant, prior to the Final
Exercise Date, is discharged by the Company for “Cause,” as determined by the Board of Directors, or is otherwise attributable to a breach, as determined by the Board, by the Participant of an employment agreement with the Company, the
right to exercise this option shall terminate immediately upon the effective date of such discharge. For purposes of this Agreement “Cause” shall include 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 shall be considered to have been discharged for “Cause” if the Company determines, within 30 days after the Participant’s
resignation, that discharge for cause was warranted. 
  

	4.	Right of First Refusal. 

  
 (a) If the Participant proposes to sell, assign, transfer, pledge, hypothecate or otherwise dispose of, by operation of law or otherwise (collectively,
“transfer”) any Shares acquired upon exercise of this option, then the Participant shall first give written notice of the 
  

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 proposed transfer (the “Transfer Notice”) to the Company. The Transfer Notice shall name the proposed
transferee and state the number of such Shares the Participant proposes to transfer (the “Offered Shares”), the price per share and all other material terms and conditions of the transfer. 
  
 (b) For 30 days following its receipt of such Transfer Notice, the Company
shall have the option to purchase all (or any portion) of the Offered Shares at the price and upon the terms set forth in the Transfer Notice. In the event the Company elects to purchase all (or any portion) of the Offered Shares, it shall give
written notice of such election to the Participant within such 30-day period. Within 10 days after his receipt of such notice, the Participant shall tender to the Company at its principal offices the certificate or certificates representing the
Offered Shares, duly endorsed in blank by the Participant or with duly endorsed stock powers attached thereto, all in a form suitable for transfer of the Offered Shares to the Company. Promptly following receipt of such certificate or certificates,
the Company shall deliver or mail to the Participant a check in payment of the purchase price for the Offered Shares; provided that if the terms of payment set forth in the Transfer Notice were other than cash against delivery, the Company
may pay for the Offered Shares on the same terms and conditions as were set forth in the Transfer Notice; and provided further that any delay in making such payment shall not invalidate the Company’s exercise of its option to purchase
the Offered Shares. 
  
 (c) If the Company does not elect to
acquire all of the Offered Shares, the Participant may, within the 30-day period following the expiration of the option granted to the Company under subsection (b) above, transfer any remaining Offered Shares to the proposed transferee,
provided that such transfer shall not be on terms and conditions more favorable to the transferee than those contained in the Transfer Notice. Notwithstanding any of the above, all Offered Shares transferred pursuant to this Section 4
shall remain subject to the right of first refusal set forth in this Section 4 and such transferee shall, as a condition to such transfer, deliver to the Company a written instrument confirming that such transferee shall be bound by all of the
terms and conditions of this Section 4. 
  
 (d) After the
time at which the Offered Shares are required to be delivered to the Company for transfer to the Company pursuant to subsection (b) above, the Company shall not pay any dividend to the Participant on account of such Offered Shares or permit the
Participant to exercise any of the privileges or rights of a stockholder with respect to such Offered Shares, but shall, in so far as permitted by law, treat the Company as the owner of such Offered Shares. 
  
 (e) The following transactions shall be exempt from the provisions of this
Section 4: 
  
 (1) any transfer of Shares to or for the
benefit of any spouse, child or grandchild of the Participant, or to a trust for their benefit; 
  
 (2) any transfer pursuant to an effective registration statement filed by the Company under the Securities Act of 1933, as amended (the “Securities
Act”); and 
  
 (3) the sale of all or substantially all of
the shares of capital stock of the Company (including pursuant to a merger or consolidation); 
  
 provided, however, that in the case of a transfer pursuant to clause (1) above, such Shares shall remain subject to the right of first refusal set forth in this Section 4 and such transferee
shall, as a condition to such transfer, deliver to the Company a written instrument confirming that such transferee shall be bound by all of the terms and conditions of this Section 4. 
  

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 (f) The Company may assign its rights to purchase Offered Shares in any particular transaction under this
Section 4 to one or more persons or entities. 
  
 (g) The
provisions of this Section 4 shall terminate upon the earlier of the following events: 
  
 (1) the closing of the sale of shares of Common Stock in an underwritten public offering pursuant to an effective registration statement filed by the Company under the Securities Act; or 
  
 (2) the sale of all or substantially all of the capital stock, assets or
business of the Company, by merger, consolidation, sale of assets or otherwise (other than a merger or consolidation in which all or substantially all of the individuals and entities who were beneficial owners of the Common Stock immediately prior
to such transaction beneficially own, directly or indirectly, more than 75% of the outstanding securities entitled to vote generally in the election of directors of the resulting, surviving or acquiring corporation in such transaction). 

 
 (h) The Company shall not be required (a) to transfer on its books
any of the Shares which shall have been sold or transferred in violation of any of the provisions set forth in this Section 4, or (b) to treat as owner of such Shares or to pay dividends to any transferee to whom any such Shares shall have
been so sold or transferred. 
  

	5.	Agreement in Connection with Public Offering. 

  
 The Participant agrees, in connection with the initial underwritten public offering of the Company’s securities pursuant to a registration statement
under the Securities Act, (i) not to sell, make short sale of, loan, grant any options for the purchase of, or otherwise dispose of any shares of Common Stock held by the Participant (other than those shares included in the offering) without
the prior written consent of the Company or the underwriters managing such initial underwritten public offering of the Company’s securities for a period of 180 days from the effective date of such registration statement, and (ii) to
execute any agreement reflecting clause (i) above as may be requested by the Company or the managing underwriters at the time of such offering. 
  

	6.	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. 
  

	7.	Nontransferability of Option. 

  
 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. 
  

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	8.	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. 
  

	9.	Provisions of the Plan. 

  
 This option is subject to the provisions of 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. 
  

			
	 ACHILLION PHARMACEUTICALS, INC.

		
	 By:
	 	  

	 Name:
	 	 Michael D. Kishbauch

	 Title:
	 	 Chief Executive Officer

  

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 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 1998 Stock Option Plan. 
  

			
	 PARTICIPANT:

	

		
	 Address:
	 	  

	 	 	  

  

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