MIRNA THERAPEUTICS LOGO]

Exhibit 10.22

[XXXXX THERAPEUTICS LOGO]

September 17, 2015

Xxxxxx X. Xxxxxxx, Ph.D.

Dear Xxxxxx:

On behalf of Xxxxx Therapeutics, Inc. (“Xxxxx”), a Delaware corporation, I am pleased to offer you the full-time position of Executive Vice President and Chief Scientific Officer.  We anticipate your start date to be September 28, 2015 (the “Start Date”).

Prior to your Start Date, you will be required to sign an Employment Agreement and a Confidentiality, Covenant Not To Compete, & Arbitration Agreement with Xxxxx.  These agreements are currently under negotiation.

Your base salary will be $13,461.54 per two week pay period.  You will be entitled to earn an annual bonus in the amount of up to 25% of your annual base salary upon your achievement of annual performance targets as determined by Xxxxx’s Board of Directors, as further described in the Employment Agreement.  Your annual bonus shall be pro-rated for the current fiscal year.

Xxxxx shall pay to you a signing bonus of $330,575, subject to applicable withholdings and deductions, by January 31, 2016.  You acknowledge and agree that your signing bonus will not be deemed earned until the first anniversary of your Start Date.  Should you voluntarily terminate your employment for any reason prior to the first anniversary of your Start Date, you will be required to reimburse Xxxxx for a pro-rata portion of your signing bonus; if Xxxxx terminates your employment prior to the first anniversary of the Start Date for cause (as such term is defined in the Employment Agreement), you will be required to reimburse Xxxxx for the full amount of your signing bonus.  For the avoidance of doubt, you may keep the signing bonus in the event that you are terminated by Xxxxx without cause prior to the first anniversary of your Start Date.  Your signature on this letter authorizes us to deduct the amount of your signing bonus from your final paycheck should this occur.  If there are any amounts not covered by your final paycheck you agree to repay them within 30 days of your separation.

Subject to approval by Xxxxx’s Board of Directors, and as further described in the Employment Agreement, upon the later of (i) your Start Date or (ii) the pricing of Xxxxx’s initial public offering, we anticipate granting you an option to purchase 284,206 shares of Xxxxx’s common stock (giving effect to a reverse split at the time of the initial public offering), which will represent approximately 1.7% of the outstanding shares of Mirna’s common stock immediately after the initial public offering, at an exercise price equal to the per share closing trading price of our common stock on the date of grant or, if the date of grant is prior to Xxxxx’s common stock becoming publicly traded, the price to the public agreed to with Xxxxx’s underwriters.  In the event that Xxxxx’s initial public offering is postponed to a date later than three months after your Start Date, we anticipate granting you an option to purchase common stock representing approximately 1.7% of the then outstanding shares of Xxxxx’s common stock, at a price per share equal to the fair market value of the common stock as determined in good faith by Xxxxx’s Board of Directors.

Xxxxx offers group insurance and time off benefits for which you are eligible for beginning on November 1, 2015.  You may choose insurance plans such as medical, dental, vision and supplemental life insurance (which is in addition to the amount Xxxxx provides for you).  Xxxxx pays 100% of the premiums for short and long-term disability, basic life, accidental death and dismemberment, and an employee assistance program.

Xxxxx Therapeutics, Inc. | 0000 Xxxxxxxx Xx., Xxxxx 000 x Xxxxxx, XX  00000 | 1.512.901.0900 | xxx.xxxxxxx.xxx

As of your Start Date, you will receive 15 days of vacation for your first year of employment, 7 days of sick time per calendar year and a total of 12 holidays (8 fixed date holidays and 4 flexible date or “flex” holidays) per calendar year.  Vacation, sick time and the flex holidays will be prorated if your start date is after January 1.

Once you have 90 days of continuous service at Xxxxx, you are eligible to participate in Mirna’s 401(k) Plan.  The 401(k) Plan has a matching component that is presently 50 cents per dollar up to 8% of your base compensation. The Board of Directors reserves the right to modify this matching percentage.

We expect you to relocate to Austin within five months of your Start Date.  As further described in the Employment Agreement, Xxxxx will reimburse you for reasonable and necessary documented relocation and moving expenses up to $45,000.

Your position is an “at will” position, which is the customary employment relationship in “at will” employment states such as Texas.  This simply means that the employment relationship between Xxxxx and you is based upon mutual consent and can be terminated at any time by either you or Xxxxx without advance notice and without any requirement for cause.  It also means that your job duties, title and responsibility and reporting level, work schedule, compensation and benefits, as well as the Company’s personnel policies and procedures, may be changed with prospective effect, with or without notice, at any time in the sole discretion of the Company.  This “at-will” nature of your employment shall remain unchanged during your tenure as an employee and may not be changed, except in an express writing signed by you and a duly authorized member of the Company.  If your employment terminates for any reason, you shall not be entitled to any payments, benefits, damages, awards or compensation other than as provided by your offer letter, Employment Agreement, and Confidentiality, Covenant Not To Compete, & Arbitration Agreement.  Your position is not governed by any other agreements, and you are not employed for any specific period of time.  No employee of Xxxxx has the authority to enter into any other agreement with you concerning your employment.

With the legal disclaimers out of the way, I am excited about your joining our Company and know that you can play a significant role in its continued growth.  Please do not hesitate to call me or Xxx Xxxxx if you have any questions. Please sign and return a copy of this letter by September 24, 2015 acknowledging your acceptance of this offer.  You may send a scanned copy of this letter to xxxxxx@xxxxxxx.xxx or fax a copy to our confidential facsimile at (000) 000-0000.

Sincerely,

/s/ Xxx X. Xxxxx

Xxx X. Xxxxx

Vice President - Finance

Accepted by:

/s/ Xxxxxx X. Xxxxxxx

9/17/15

Signature/Date