EX-10.21



 Exhibit 10.21 
  





 
  

			
		  	34175 Ardenwood Blvd
		  	Fremont, CA 94555
		  	(510) 745-1700 – Tele
		  	(510) 745-0493 – Fax
		  	www.ardelyx.com

 December 12, 2015 
 Paul
Korner, MD, MBA 
 809 Winnebago Drive 
 Franklin Lakes, NJ
07417 
 Dear Paul: 
 On behalf of Ardelyx (the
“Company”), I am pleased to offer you employment in the exempt position of Executive Vice President and Chief Medical Officer reporting to the Chief Executive Officer. This letter sets out the terms of Ardelyx’s offer of employment,
which is contingent upon the completion of reference checks to Ardelyx’s satisfaction. If you accept this offer, you will be required to execute the Company’s standard form of employee non-disclosure and assignment of inventions agreement.
In addition, you and the Company will enter into a Change in Control Severance Agreement that will further define some of the provisions set forth in this offer letter (the “Severance Agreement”). 

Your first day of full time employment with Ardelyx will be January 4, 2015. Your full time starting base salary will be $16,666.66 semi-monthly, which
is equivalent to $400,000.00 per year, less applicable tax and other withholdings in accordance with the Company’s normal payroll procedure. You will also be eligible to receive an annual bonus of up to forty percent (40%) of your base
salary, with the amount of the bonus determined by the Board of Directors based on your performance as well as the performance of the Company. You will first become eligible for consideration for an annual bonus based upon your performance and that
of the Company during calendar year 2016. 
 In addition, you will receive a signing bonus equal to $130,000 to be paid in full on or before your fifth day
of employment. This signing bonus will be subject to the terms and conditions of the Severance Agreement, which shall provide for your reimbursement of the applicable portion of the signing bonus to the Company in the event that you terminate your
employment with the Company without good reason or the Company terminates your employment for cause, in either case, on or before the first anniversary of your commencement of employment (one hundred percent (100%) to be reimbursed) or during
the period between the first and second anniversaries of the commencement of your employment (fifty percent (50%) to be reimbursed). Ardelyx will reimburse up to $150,000 in moving expenses, and such amount will be paid in a lump sum (grossed
up for applicable withholding) within thirty (30) days following notice by you to the Company that you have initiated your relocation to the Bay Area; which shall occur within two years of the commencement of your employment. 

On your first day of employment, you will be granted an option to purchase shares of Company common stock under the Company’s equity incentive plan which
stock option shall have an accounting grant date fair value of $1.5 million. Your option will be exercisable at per share exercise price equal to the fair market value of Ardelyx stock on your option grant date. Your option will vest over a period
of 4 years, with 25% of the shares vesting at the end of your first year of employment, and the remainder vesting monthly over the following three years, and will be subject to the terms and conditions of the Company’s equity incentive plan and
standard form of stock option agreement, which you will be required to sign as a condition of receiving the option. 







 In addition, on your first day of employment, you will be granted a Restricted Stock Unit (RSU) for such number
of shares as is equal to $1 million in full value on the date of grant. The RSU will vest over four years in four equal installments on the annual anniversary of the date of grant, and will be subject to the terms and conditions of the
Company’s equity incentive plan and standard form of full value award, which you will be required to sign as a condition of receiving the RSU. 
 You
will be eligible to participate in various Company equity and benefit plans, including group health insurance, 401(k), and the Employee Stock Purchase Plan. You will earn three weeks of vacation each year. 

If this offer of employment is accepted, your employment with the Company will be “at will.” This means it is for no specified term and may be
terminated by you or the Company at any time, with our without cause or advance notice. In addition, the Company reserves the right to modify your compensation, position, duties or reporting relationship to meet business needs and to decide on
appropriate discipline. The Severance Agreement will provide, subject to the terms and conditions thereof, for (i) nine month salary continuation and the payment of healthcare continuation costs for twelves months, if you terminate your
employment for good reason or you are terminated without cause, in either case, outside of a change of control period, and (ii) a lump sum payment equal to 100% of the sum of your base salary and your target annual bonus for the year of
termination; the payment of healthcare continuation costs for 12 months; and the vesting of 100% of your unvested stock options or RSUs, if you terminate your employment for good reason or you are terminated without cause, in either case during a
change of control period. 
 In the event of any dispute or claim relating to or arising out of your employment relationship with the Company, this
agreement, or the termination of your employment with the Company for any reason (including, but not limited to, any claims of breach of contract, defamation, wrongful termination or age, sex, sexual orientation, race, color, national origin,
ancestry, marital status, religious creed, physical or mental disability or medical condition or other discrimination, retaliation or harassment), you and the Company agree that all such disputes shall be fully resolved by confidential, binding
arbitration conducted by a single arbitrator through the American Arbitration Association (“AAA”) under the AAA’s National Rules for the Resolution of Employment Disputes then in effect, which are available online at the AAA’s
website at www.adr.org. You and the Company hereby waive your respective rights to have any such disputes or claims tried before a judge or jury. 
 Please
sign and date this letter on the spaces provided below to acknowledge your acceptance of the terms of this agreement and return it to me prior to or on 5:00pm EST, December 18, 2015, at which time this offer shall expire 

Paul, it has been a real pleasure meeting you and all of us here at Ardelyx concur that you are an excellent fit with our team, and we look forward to working
with you at Ardelyx. 
  

	
	 Sincerely,
  

Ardelyx, Inc.

	
	 By /s/ Michael Raab
  

    President and Chief Executive Officer










 I agree to and accept employment with Ardelyx on the terms and conditions set forth in this agreement. I
understand and agree that my employment with the Company is at-will. 
  

					
	Date: 12 Dec 2015	 		 	 /s/ Paul Korner

		 		 	Paul Korner, MD, MBA
			
	Tentative Start Date: 4 January 2016