EX-10.6





 Exhibit 10.6 

SYNTHORX, INC. 

NON-EMPLOYEE DIRECTOR COMPENSATION
POLICY 
 Each member of the Board of Directors (the “Board”) who is not also serving as an
employee of or consultant to Synthorx, Inc. (the “Company”) or any of its subsidiaries (each such member, an “Eligible Director”) will receive the compensation described in this Non-Employee Director Compensation Policy for his or her Board service upon and following the date of the underwriting agreement between the Company and the underwriters managing the initial public offering of the
Company’s common stock (the “Common Stock”), pursuant to which the Common Stock is priced in such initial public offering (the “Effective Date”). An Eligible Director may decline all or any
portion of his or her compensation by giving notice to the Company prior to the date cash may be paid or equity awards are to be granted, as the case may be. This policy is effective as of the Effective Date and may be amended at any time in the
sole discretion of the Board. 
 Annual Cash Compensation 

The annual cash compensation amount set forth below is payable to Eligible Directors in equal quarterly installments, payable in arrears on
the last day of each fiscal quarter in which the service occurred. If an Eligible Director joins the Board or a committee of the Board at a time other than effective as of the first day of a fiscal quarter, each annual retainer set forth below will
be pro-rated based on days served in the applicable fiscal year, with the pro-rated amount paid for the first fiscal quarter in which the Eligible Director provides the
service and regular full quarterly payments thereafter. All annual cash fees are vested upon payment. 
  

	1.	 Annual Board Service Retainer: 



	 	a.	 All Eligible Directors: $35,000 



	 	b.	 Chairman of the Board Service Retainer (in addition to Eligible Director Service Retainer): $30,000



  

	2.	 Annual Committee Chair Service Retainer: 



	 	a.	 Chairman of the Audit Committee: $15,000 



	 	b.	 Chairman of the Compensation Committee: $10,000 



	 	c.	 Chairman of the Nominating and Corporate Governance Committee: $8,000 



 

	3.	 Annual Committee Member Service Retainer (not applicable to Committee Chairs): 




	 	a.	 Member of the Audit Committee: $7,500 



	 	b.	 Member of the Compensation Committee: $5,000 



	 	c.	 Member of the Nominating and Corporate Governance Committee: $4,000 



Equity Compensation 
 The equity
compensation set forth below will be granted under the Company’s 2018 Equity Incentive Plan (the “Plan”), subject to the approval of the Plan by the Company’s stockholders. All stock options granted under this
policy will be nonstatutory stock options, with an exercise price per share equal to 100% of the Fair Market Value (as defined in the Plan) of the underlying 

  
 1. 













 
Common Stock on the date of grant, and a term of ten years from the date of grant (subject to earlier termination in connection with a termination of service as provided in the Plan, provided
that upon a termination of service other than for death, disability or cause, the post-termination exercise period will be three months from the date of termination). 

1.        Initial Grant: For each Eligible Director who is first elected or appointed to the
Board following the Effective Date, on the date of such Eligible Director’s initial election or appointment to the Board (or, if such date is not a market trading day, the first market trading day thereafter), the Eligible Director will be
automatically, and without further action by the Board, granted a stock option to purchase Common Stock with an aggregate Black-Scholes option value of $240,350 (the “Initial Grant”). Each person who, after the Effective
Date, served as an employee of, or consultant to, the Company and as a member of the Board, but who later ceases to provide such employment or consulting services shall not be entitled to an Initial Grant. The shares subject to each Initial Grant
will vest in equal monthly installments over a three year period such that the option is fully vested on the third anniversary of the date of grant, subject to the Eligible Director’s Continuous Service (as defined in the Plan) through each
such vesting date and will vest in full upon a Change in Control (as defined in the Plan). 

2.        Annual Grant: On the date of each annual stockholder meeting of the Company held
after the Effective Date, each Eligible Director who continues to serve as a non-employee member of the Board following such stockholder meeting will be automatically, and without further action by the Board,
granted a stock option to purchase Common Stock with an aggregate Black-Scholes option value of $120,175 (the “Annual Grant”); provided, however, that if the Eligible Director has not served as member of the Board for
12 months prior to the applicable annual stockholder meeting, the number of shares subject to such individual’s Annual Grant will be pro-rated based on the number of full months served on the Board,
rounded to the nearest whole share. The shares subject to the Annual Grant will vest in equal monthly installments over the 12 months following the date of grant, provided that the Annual Grant will in any case be fully vested on the date of
Company’s next annual stockholder meeting, subject to the Eligible Director’s Continuous Service (as defined in the Plan) through such vesting date and will vest in full upon a Change in Control (as defined in the Plan). 

  
 2.