Data from Initial Patient Cohorts of Phase 2 AFFINITY Study Expected to be Reported in 2022 SEATTLE, April 07, 2021 (GLOBE NEWSWIRE) — Chinook Therapeutics, Inc. (NASDAQ: KDNY), a biopharmaceutical company focused on the discovery, development and commercialization of precision medicines for kidney diseases, today announced that the first patient has been dosed in the AFFINITY Study, a phase 2 clinical trial evaluating the efficacy and safety of atrasentan, a potent and selective inhibitor of the endothelin A receptor, in patients with proteinuric glomerular disease who are at risk of progressive loss of renal function. “Initiation of the phase 2 AFFINITY Study is an important step in evaluating atrasentan across multiple proteinuric glomerular diseases for which there are currently limited treatment options,” said Alan Glicklich, M.D., chief medical officer of Chinook. “Atrasentan’s proteinuria-lowering, anti-fibrotic and anti-inflammatory properties have the potential to provide therapeutic benefit in a variety of chronic kidney diseases. Data generated in the AFFINITY Study will help inform the development strategy for atrasentan in these additional indications in parallel to our phase 3 ALIGN Study in IgA nephropathy.” About the AFFINITY Study The AFFINITY Study (see www.clinicaltrials.gov, identifier NCT04573920) is a phase 2, open-label, basket study to evaluate the efficacy and safety of atrasentan in patients with proteinuric glomerular disease who are at risk of progressive loss of renal function. Four initial cohorts will consist of patients with: IgA nephropathy (IgAN) with urine protein to creatinine ratio (UPCR) of 0.5 to less than 1.0 g/g, focal segmental glomerulosclerosis (FSGS), Alport syndrome and diabetic kidney disease (DKD) in combination with an SGLT2 inhibitor. Additional cohorts may be added to the study over time. Approximately 20 patients will be enrolled in each cohort to receive 0.75 mg atrasentan for 52 weeks. Patients in all cohorts will continue receiving a maximally tolerated and stable dose of a RAS inhibitor as standard of care. The AFFINITY Study will enroll patients in the United States, Australia, South Korea, the United Kingdom, Italy and Spain. The primary efficacy endpoint of the AFFINITY Study is the effect on proteinuria as measured by urine protein to creatinine ratio (UPCR) in patients with IgAN, FSGS and Alport syndrome and the change in albuminuria as measured by urine albumin to creatinine (UACR) in patients with DKD, from baseline to 12 weeks. Chinook expects to report data from initial cohorts of patients in the AFFINITY Study during 2022. About Chinook Therapeutics, Inc.Chinook Therapeutics, Inc. is a clinical-stage biotechnology company developing precision medicines for kidney diseases. Chinook’s product candidates are being investigated in rare, severe chronic kidney disorders with opportunities for well-defined clinical pathways. Chinook’s lead program is atrasentan, a phase 3 endothelin receptor antagonist for the treatment of IgA nephropathy and other proteinuric glomerular diseases. BION-1301, an anti-APRIL monoclonal antibody is being evaluated in a phase 1b trial for IgA nephropathy. In addition, Chinook is advancing CHK-336, an oral small molecule LDHA inhibitor for the treatment of primary hyperoxaluria, as well as research programs for other rare, severe chronic kidney diseases. Chinook is building its pipeline by leveraging insights in kidney single cell RNA sequencing, human-derived organoids and new translational models, to discover and develop therapeutics with differentiating mechanisms of action against key kidney disease pathways. To learn more, visit www.chinooktx.com. Cautionary Note on Forward-Looking Statements Certain of the statements made in this press release are forward looking, including those relating to Chinook’s business, future operations, advancement of its product candidates and product pipeline, clinical development of its product candidates, including expectations regarding timing of initiation and results of clinical trials. In some cases, you can identify these statements by forward-looking words such as “may,” “will,” “continue,” “anticipate,” “intend,” “could,” “project,” “expect” or the negative or plural of these words or similar expressions. Forward-looking statements are not guarantees of future performance and are subject to risks and uncertainties that could cause actual results and events to differ materially from those anticipated, including, but not limited to, our ability to develop and commercialize our product candidates, including initiation of clinical trials, whether results of early clinical trials or preclinical studies will be indicative of the results of future trials, our ability to obtain and maintain regulatory approval of our product candidates, our ability to operate in a competitive industry and compete successfully against competitors that may be more advanced or have greater resources than we do, our ability to obtain and adequately protect intellectual property rights for our product candidates and the effects of COVID-19 on our clinical programs and business operations. Many of these risks are described in greater detail in our filings with the SEC. Any forward-looking statements in this press release speak only as of the date of this press release. Chinook assumes no obligation to update forward-looking statements whether as a result of new information, future events or otherwise, after the date of this press release. Contact:Noopur LiffickVice President, Investor Relations & Corporate Communicationsinvestors@chinooktx.com media@chinooktx.com