Ardenwood Blvd Fremont, CA 94555 (510) 745-1700 Tele (510) 745-0493 Fax www.ardelyx.com Ardelyx Reports Second Quarter 2016 Financial Results Results from the First Phase 3 trial for Tenapanor for the Treatment of Hyperp

Ardelyx Reports Second Quarter 2016 Financial Results

Results from the First Phase 3 trial for Tenapanor for the Treatment of Hyperphosphatemia in

Patients with ESRD Expected Q1 2017

Ardelyx s Proprietary Potassium Binder, RDX227675, Obtains Notification of Allowance for

Composition of Matter Claims

Conference Call and Webcast Today at 4:30 p.m. ET

FREMONT, Calif., August 8, 2016 /PRNewswire/ Ardelyx, Inc. (NASDAQ: ARDX), a clinical-stage biopharmaceutical company focused on

gastrointestinal and cardio-renal diseases, today announced financial results for the second quarter ended June 30, 2016.

2016 continues to be

a momentous year, said Mike Raab, President and Chief Executive Officer of Ardelyx. With the completion of our recently announced $110 million private placement, we have raised net proceeds of over $190 million in 2016. Now that we have

strengthened our balance sheet with sufficient capital to support the company through our receipt of critical clinical milestones in 2017, our primary focus is the execution of our late-stage clinical programs and advancement of the company towards

commercialization. During 2017, all three of our late-stage programs will generate important clinical data. This includes currently expected results in the first quarter of next year from our first Phase 3 trial of tenapanor for the treatment of

hyperphosphatemia in ESRD patients on dialysis. We believe that tenapanor has the potential to be a truly important development for the treatment of hyperphosphatemia in these patients. We also currently expect results in the first half of 2017 from

our onset-of-action trial for RDX227675 in patients with hyperkalemia. Finally, we currently expect results from both Phase 3 clinical trials of tenapanor for IBS-C, with T3MPO-1 mid-year and T3MPO-2 by the end of 2017.

Upcoming Clinical Milestones

Second Quarter Ended June 30, 2016 Financial Results

Net loss for the second quarter of 2016 was $28.6 million, or $0.83 per basic and diluted share, compared to a net income of $9.0 million, or $0.43 per basic

and $0.42 diluted share for the second quarter of 2015.

Total revenue is comprised of licensing revenue and collaborative development revenue. Licensing

revenue for the second quarter of 2016 decreased to zero from $17.7 million for the second quarter of 2015. Licensing revenue for the three months ended June 30, 2015 was related to the recognition of revenue from upfront and milestone payments

received from AstraZeneca. As the Company s collaboration agreement with AstraZeneca was terminated in June 2015, there was no further recognition of revenue related to the upfront and milestone payments after the six-month period ended

Collaborative development revenue is comprised of development expenses that were reimbursable to Ardelyx by AstraZeneca.

Collaborative development revenue for the second quarter of 2016 decreased to zero from $0.4 million for the second quarter of 2015. The decrease was due to the termination of the AstraZeneca agreement in June 2015 and related cessation of

reimbursement of research and development expenses.

Research and development expense for the second quarter of 2016 increased to $23.8 million from $6.2

million for the second quarter of 2015. The increase was due to expenses incurred primarily for clinical development activities as well as clinical manufacturing and process development activities associated with tenapanor, RDX227675 and RDX98940.

General and administrative expense was $4.9 million for the second quarter of 2016 as compared to $2.9 million

for second quarter of 2015. The increase was primarily due to an increase in professional services fees including fees for market research and pre-commercialization activities, systems implementation and intellectual property management, as well as

an increase in personnel-related expenses and facility costs.

Accounting for the net proceeds from the Company s private placement in July

2016, the Company s pro forma cash and cash equivalents as of June 30, 2016 were approximately $257 million including $146.7 million in cash and cash equivalents as of June 30, 2016 plus gross proceeds from the

private placement completed in July 2016 of approximately $110 million. Cash and cash equivalents were $146.7 million as of June 30, 2016 compared with $107.0 million as of December 31, 2015 primarily as a result of the completion of an

underwritten public offering of common stock in January 2016 that yielded approximately $80.8 million in net proceeds, offset by $41.1 million in cash required for operating and other activities for the period of December 31, 2015 through

Conference Call & Webcast Information

Ardelyx management will host a live conference call and webcast today at 4:30 p.m. Eastern Time to discuss the second quarter financial results. The live

webcast and a replay may be accessed by visiting the investor relations section of the Ardelyx website at ir.ardelyx.com.

Please connect to the

Company s website at least 15 minutes prior to the live webcast to ensure adequate time for any software download that may be needed to access the webcast. Alternatively, please call 1-855-296-9612 (US) or 920-663-6277 (International) to listen

to the live conference call. The conference ID number for the live call is 56269341. Please dial in approximately 10 minutes prior to the call. An archived webcast replay will be available on the Company s website until August 22, 2016.

Ardelyx is a clinical-stage

biopharmaceutical company focused on the discovery, development and commercialization of innovative, minimally-systemic, small molecule therapeutics that work exclusively in the gastrointestinal (GI) tract to treat GI and cardio-renal diseases.

Ardelyx has developed a proprietary drug discovery and design platform enabling it, in a rapid and cost-efficient manner, to discover and design novel drug candidates. Utilizing this platform, Ardelyx has discovered and designed tenapanor, which it

is evaluating for the treatment of irritable bowel syndrome with constipation (IBS-C) and for the treatment of hyperphosphatemia in patients with end-stage renal disease (ESRD) on dialysis. In addition to tenapanor, Ardelyx is developing RDX227675,

a non-absorbed polymer for the treatment of hyperkalemia, or high potassium, a problem prevalent in patients with kidney and heart disease. Ardelyx is also advancing several research programs focused in GI and cardio-renal diseases. Ardelyx is

located in Fremont, California. For more information, please visit Ardelyx s website at www.ardelyx.com.

Forward Looking Statements

To the extent that statements contained in this press release are not descriptions of historical facts regarding Ardelyx, they are forward-looking statements

reflecting the current beliefs and

expectations of management made pursuant to the safe harbor of the Private Securities Reform Act of 1995,

including the potential of tenapanor in the treatment of IBS-C, the expected timing for the receipt of the results from Ardelyx s two on-going Phase 3 clinical trials evaluating tenapanor for the treatment of IBS-C, the potential for tenapanor

in treating hyperphosphatemia in ESRD patients on dialysis, the expected timing of the results of the ongoing Phase 3 clinical trial evaluating tenapanor for the treatment of hyperphosphatemia in ESRD patients on dialysis, the expected timing of the

initiation of the second Phase 3 clinical trial evaluating tenapanor for the treatment of hyperphosphatemia, the potential for RDX227675 in treating hyperkalemia in CKD patients, the expected timing of the initiation of the onset-of-action and Phase

3 clinical trials evaluating RDX227675 in treating hyperkalemia in CKD patients and the expected timing of the results of the onset-of-action clinical trial, the expected timing for the filing of an investigational new drug (IND) application for

RDX98940 and the potential of Ardelyx s drug discovery and design platform. Such forward-looking statements involve substantial risks and uncertainties that could cause the development of tenapanor, RDX227675, or Ardelyx s future results,

performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainties inherent in research and the clinical development process

and the uncertainties in the manufacture of clinical trial material, including process development, and scale up. Ardelyx undertakes no obligation to update or revise any forward-looking statements. For a further description of the risks and

uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to Ardelyx s business in general, please refer to Ardelyx s Quarterly Report on Form 10-Q filed

with the Securities and Exchange Commission on August 8, 2016, and its future current and periodic reports to be filed with the Securities and Exchange Commission.

Condensed Balance Sheets

Condensed Statements of Operations and Comprehensive (Loss) Income

(In thousands, except share and per share amounts)

Investor and Media Contact:

McClellan on behalf of Ardelyx Inc.