NATURE OF OPERATIONS	6 Months Ended
Jun. 30, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
NATURE OF OPERATIONS	NATURE OF OPERATIONS We are a commercial-stage biopharmaceutical company focused on the development and commercialization of innovative medicines that meet significant unmet medical needs. We currently market two therapies from the active ingredient tenapanor, a sodium/hydrogen exchanger (NHE3) inhibitor that was discovered and developed by Ardelyx. NHE3 is an antiporter expressed on the apical surface of the small and large intestines. Tenapanor is a minimally absorbed, small molecule therapy. In addition, we are building a pipeline which is currently focused on expanding the commercial footprint of tenapanor. Tenapanor, branded as IBSRELA®, is approved in the U.S. for the treatment of adults with irritable bowel syndrome with constipation (IBS-C). We are seeking to further expand the IBSRELA eligible patient population to include patients with chronic idiopathic constipation (CIC), and have initiated a Phase 3 clinical trial evaluating tenapanor in adults with CIC. Tenapanor, branded as XPHOZAH®, is approved in the U.S. to reduce serum phosphorus in adults with chronic kidney disease (CKD) on dialysis as add-on therapy in patients who have an inadequate response to phosphate binders or who are intolerant of any dose of phosphate binder therapy. We are also developing a next-generation NHE3 inhibitor, RDX10531, which is currently in IND-enabling studies and has demonstrated in preclinical models to have improved solubility and potency compared to tenapanor. We believe that RDX10531 can have application across multiple therapeutic areas. We operate in one business segment, which is the development and commercialization of biopharmaceutical products. Refer to Note 12. Segment Reporting for further segment reporting information. Basis of Presentation These condensed financial statements have been prepared in accordance with U.S. GAAP and pursuant to the requirements of the SEC for interim reporting. As permitted under those rules and regulations, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted. These condensed financial statements have been prepared on the same basis as our most recent annual financial statements and, in the opinion of management, reflect all normal and recurring adjustments necessary to present fairly our financial position, results of operations, changes in stockholders’ equity and cash flows for the interim periods presented. Certain prior year amounts have been reclassified to conform to the current year presentation on the condensed statements of operations and comprehensive loss to include the “cost of product sales” and the “other cost of revenue” captions within the “cost of sales” caption. Certain prior year amounts have also been reclassified to conform to the current year presentation in Note 12. Segment Reporting. These reclassifications had no effect on the previously reported results of operations. The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in our 2025 Form 10-K. The results for the three and six months ended June 30, 2026 are not necessarily indicative of results to be expected for the entire year ending December 31, 2026, or for any other interim period or future year. Refer to the Summary of Abbreviated Terms at the end of this Quarterly Report on Form 10-Q for definitions of terms used throughout the document. Use of Estimates The preparation of financial statements requires management to make estimates, judgments and assumptions. The most significant assumptions are estimates used in our revenue gross-to-net accruals. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could materially differ from those estimates. Concentration of Credit Risk Financial instruments that potentially subject us to significant concentrations of credit risk consist primarily of cash, cash equivalents, short-term investments and accounts receivable. We are exposed to credit risks in the event of default by the counterparties to the extent of the amount recorded in our condensed balance sheets. Cash, cash equivalents and short-term investments are invested through banks and other financial institutions in the U.S. Recent Accounting Pronouncements Recent Accounting Pronouncement Not Yet Adopted In November 2024, the FASB issued ASU No. 2024-03, Income Statement (Topic 220) - Reporting Comprehensive Income - Expense Disaggregation Disclosures, Disaggregation of Income Statement Expenses, which requires public companies to disclose, in interim and annual reporting periods, additional information about certain expenses in the financial statements. The new disclosure requirements are effective for the Company’s annual periods beginning January 1, 2027, and interim periods beginning January 1, 2028, with early adoption permitted, and may be applied either prospectively or retrospectively. The Company is in the process of evaluating the impact of this new guidance on its disclosures.

We are a commercial-stage biopharmaceutical company focused on the development and commercialization of innovative medicines that meet significant unmet medical needs. We currently market two therapies from the active ingredient tenapanor, a sodium/hydrogen exchanger (NHE3) inhibitor that was discovered and developed by Ardelyx. NHE3 is an antiporter expressed on the apical surface of the small and large intestines. Tenapanor is a minimally absorbed, small molecule therapy. In addition, we are building a pipeline which is currently focused on expanding the commercial footprint of tenapanor.

Tenapanor, branded as IBSRELA®, is approved in the U.S. for the treatment of adults with irritable bowel syndrome with constipation (IBS-C). We are seeking to further expand the IBSRELA eligible patient population to include patients with chronic idiopathic constipation (CIC), and have initiated a Phase 3 clinical trial evaluating tenapanor in adults with CIC.

Tenapanor, branded as XPHOZAH®, is approved in the U.S. to reduce serum phosphorus in adults with chronic kidney disease (CKD) on dialysis as add-on therapy in patients who have an inadequate response to phosphate binders or who are intolerant of any dose of phosphate binder therapy.

We are also developing a next-generation NHE3 inhibitor, RDX10531, which is currently in IND-enabling studies and has demonstrated in preclinical models to have improved solubility and potency compared to tenapanor. We believe that RDX10531 can have application across multiple therapeutic areas.

We operate in one business segment, which is the development and commercialization of biopharmaceutical products. Refer to Note 12. Segment Reporting for further segment reporting information.

These condensed financial statements have been prepared in accordance with U.S. GAAP and pursuant to the requirements of the SEC for interim reporting. As permitted under those rules and regulations, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted. These condensed financial statements have been prepared on the same basis as our most recent annual financial statements and, in the opinion of management, reflect all normal and recurring adjustments necessary to present fairly our financial position, results of operations, changes in stockholders’ equity and cash flows for the interim periods presented.

Certain prior year amounts have been reclassified to conform to the current year presentation on the condensed statements of operations and comprehensive loss to include the “cost of product sales” and the “other cost of revenue” captions within the “cost of sales” caption. Certain prior year amounts have also been reclassified to conform to the current year presentation in Note 12. Segment Reporting. These reclassifications had no effect on the previously reported results of operations.

The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in our 2025 Form 10-K. The results for the three and six months ended June 30, 2026 are not necessarily indicative of results to be expected for the entire year ending December 31, 2026, or for any other interim period or future year.

Refer to the Summary of Abbreviated Terms at the end of this Quarterly Report on Form 10-Q for definitions of terms used throughout the document.

The preparation of financial statements requires management to make estimates, judgments and assumptions. The most significant assumptions are estimates used in our revenue gross-to-net accruals. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could materially differ from those estimates.

Financial instruments that potentially subject us to significant concentrations of credit risk consist primarily of cash, cash equivalents, short-term investments and accounts receivable. We are exposed to credit risks in the event of default by the counterparties to the extent of the amount recorded in our condensed balance sheets. Cash, cash equivalents and short-term investments are invested through banks and other financial institutions in the U.S.

In November 2024, the FASB issued ASU No. 2024-03, Income Statement (Topic 220) - Reporting Comprehensive Income - Expense Disaggregation Disclosures, Disaggregation of Income Statement Expenses, which requires public companies to disclose, in interim and annual reporting periods, additional information about certain expenses in the financial statements. The new disclosure requirements are effective for the Company’s annual periods beginning January 1, 2027, and interim periods beginning January 1, 2028, with early adoption permitted, and may be applied either prospectively or retrospectively. The Company is in the process of evaluating the impact of this new guidance on its disclosures.