Ardelyx Reports Fourth Quarter and Full Year 2020 Financial Results and Recent Highlights Company well positioned for PDUFA date of

Ardelyx Reports Fourth Quarter and Full Year 2020 Financial Results and Recent Highlights

Company well positioned for PDUFA date of April 29, 2021 and the potential launch of tenapanor

FREMONT, Calif./ WALTHAM, Mass., March 8, 2021 -- Ardelyx, Inc. (Nasdaq: ARDX), a biopharmaceutical company focused on developing innovative first-in-class medicines to improve treatment for people with kidney and cardiorenal diseases, today reported business highlights and financial results for the fourth quarter and full year ended December 31, 2020.

"The stage is set for an exciting year for Ardelyx in 2021" said Mike Raab, president and chief executive officer at Ardelyx. "With our PDUFA date of April 29 rapidly approaching, we are well positioned and well prepared to commercialize tenapanor upon potential FDA approval of the first and only phosphate absorption inhibitor for the control of serum phosphorus. In addition, we continue to make great progress in developing our pipeline of novel therapeutics and in building the organization for success. Our dedication and hard work over the years, particularly in 2020, have led to major advances in our development pipeline that we believe will offer differentiated benefits to patients."

Key Recent and 2020 Accomplishments:

decrease in mean pill burden while maintaining their serum phosphorus level. The results demonstrated that tenapanor enabled a significant reduction in overall pill burden (mean reduction in phosphate binder pill usage by 80%), while maintaining serum phosphorus levels (mean serum phosphorus levels 5.2 mg/dL at baseline and 4.7 mg/dL at week 26).

From November 2020 through February 2021, Ardelyx sold 8,198,217 shares of common stock under its At-the-Market Facility with Jefferies LLC for gross proceeds before commissions of $56.7 million, which includes approximately $21.7 million in gross proceeds in the fourth quarter 2020.

Full Year 2020 Financial Results

total revenues of $5.3 million and cost of revenues of $0.6 million for the year ended December 31, 2019.

R&D Expenses: Research and development expenses were $65.1 million for the year ended December 31, 2020, a decrease of $6.6 million, or 9%, compared to $71.7 million for the year ended December 31, 2019. The decrease in R&D expenses was primarily related to the winding down of expenses associated with our Phase 3 clinical program for tenapanor for the control of hyperphosphatemia, partially offset by higher expenses attributable to research expenses associated with our research collaboration and option agreement entered into with KKC in 2019.

G&A Expenses: General and administrative expenses were $33.2 million for the year ended December 31, 2020, an increase of $8.9 million, or 37%, compared to $24.3 million for the year ended December 31, 2019. The increase was primarily due to an increase in costs associated with building and staffing our commercial infrastructure and teams as we prepare for the anticipated U.S. launch of tenapanor for the control of serum phosphorus in CKD patients on dialysis. The increase consisted of headcount and related personnel costs and an increase in external spending for disease awareness initiatives, commercial infrastructure and strategy.

Ardelyx expects that its cash, cash equivalents and investments will be sufficient to fund the company's operations into the second half of 2022 based on its current operating plans.

Ardelyx is focused on discovering, developing and commercializing innovative first-in-class medicines to enhance the lives of patients with kidney and cardiorenal diseases. Ardelyx is advancing tenapanor, a novel product candidate to control serum phosphorus in adult patients with CKD on dialysis, for which the company's NDA is currently under review by the FDA, with a PDUFA date of April 29, 2021. Ardelyx is also advancing RDX013, a potassium secretagogue, for the potential treatment of elevated serum potassium, or hyperkalemia, a problem among certain patients with kidney and/or heart disease and has an early-stage program in metabolic acidosis, a serious electrolyte disorder in patients with CKD. In addition, Ardelyx received FDA approval of IBSRELA (tenapanor) on September 12, 2019. Ardelyx has established agreements with Kyowa Kirin in Japan, Fosun Pharma in China and Knight Therapeutics in Canada for the development and commercialization of tenapanor in their respective territories.

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 statements regarding the potential for tenapanor to be approved for marketing by the FDA for the control of serum phosphorus in chronic kidney disease patients on dialysis, the potential for the use of tenapanor as monotherapy and as part of a dual mechanism approach with tenapanor and phosphate binders for such indication, the potential for tenapanor alone or with small doses of phosphate binders to achieve normal serum phosphorus levels, Ardelyx's expected timing of the review of its NDA for tenapanor for the control of serum phosphorus, and Ardelyx's expectations regarding the exhaustion of its current capital resources. Such forward-looking statements involve substantial risks and uncertainties that could cause 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 associated with the regulatory approval process and uncertainties in the drug commercialization process. 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 Annual Report on Form 10-K to be filed with the Securities and Exchange Commission on March 8, 2021, and its future current and periodic reports to be filed with the Securities and Exchange Commission.

Investor and Media Contact:

Wheelhouse Life Science Advisors

Wheelhouse Life Science Advisors

Condensed Balance Sheets

Condensed Statements of Operations

(In thousands, except share and per share amounts)