AP-306

AP306 is a first-in-class pan phosphate transporter inhibitor in development as a monotherapy for hyperphosphatemia, a near-universal and serious complication in chronic kidney disease patients Study underway with first patient randomized in the global Phase 2b trial of AP306 conducted in partnership with Alebund in the US and China Study builds on positive Phase 2a data and is designed to evaluate AP306's activity and tolerability across a range of doses to guide Phase 3 development REDWOOD CITY, Calif., July 21, 2026 (GLOBE NEWSWIRE) -- R1 Therapeutics, Inc (“R1”), a clinical-stage biopharmaceutical company developing first-in-class therapies for patients with kidney disease, today announced that the first patient has been randomized in its global Phase 2b trial of AP306, a first-in-class pan phosphate transporter inhibitor in development as a monotherapy for the treatment of hyperphosphatemia in patients with chronic kidney disease (CKD) on dialysis. The multi-center, randomized, double-blind, placebo-controlled study ( NCT06712654 ) is evaluating the safety, tolerability, and serum phosphate lowering effect of AP306 at fixed doses in patients receiving maintenance hemodialysis. The study plans to enroll approximately 168 patients, randomized across six fixed-dose AP306 regimens and placebo, over an eight-week treatment period. The primary endpoint is the change in serum phosphate from baseline to the end of treatment, with secondary endpoints including the proportion of patients reaching the target phosphate range and the time to phosphate control. It is being conducted at multiple clinical sites across the US and in China through R1's global partnership with Alebund Pharmaceuticals (Jiangsu) Limited (HKEX: 09637) ("Alebund"). Hyperphosphatemia is one of the most common complications of advanced CKD and is almost universal in patients on dialysis. It is an independent risk factor for cardiovascular disease, bone disease, and mortality, 1 yet more than 70% of US dialysis patients fail to achieve normal phosphate levels. 2 Phosphate binders, the standard of care for 60 years, are limited by high pill burden and suboptimal gastrointestinal tolerance, contributing to poor adherence. 3 “Randomizing the first patient is a significant milestone for R1 and reflects the rapid pace at which our team and partners are moving,” said L. Mary Smith, Ph.D., Co-Founder and Chief Operating Officer of R1 Therapeutics. “We founded R1 to address a problem that has lacked therapeutic innovation for decades. Patients on dialysis face a heavy daily pill burden yet still struggle to keep their phosphate in range, and AP306 was designed to change that. Advancing it into Phase 2b alongside our partner Alebund is a meaningful step forward, and we're focused on generating the data needed to bring AP306 to patients.” ezstandalone.cmd.push(function () { ezstandalone.showAds(131); }); AP306 is the only agent that blocks the “active” transport of phosphate, targeting three key transporters in the gut, with the potential for rapid, effective phosphate lowering at a substantially reduced treatment burden. The Phase 2b study builds on positive Phase 2a data published in Kidney International Reports , 4 which showed significant reductions in serum phosphate with good safety and tolerability. It is designed to expand the understanding of AP306's activity and tolerability across a range of doses and dosing intervals, and to inform Phase 3 development and regulatory discussions. Topline results are expected in the first half of 2027. Glenn M. Chertow, M.D., M.P.H., Chair of R1's Scientific Advisory Board added: “Hyperphosphatemia is among the most stubborn challenges we face in the day-to-day management of patients receiving maintenance dialysis, and is associated with mortality, cardiovascular events, and fracture. AP306 targets the absorption of phosphate through inhibition of three active transporters in the gut, providing a unique mechanism of action that could complement or potentially replace the use of commonly prescribed phosphate binders, agents that have been used for decades with only modest success. It is exciting to see this study begin, and I look forward to the insights it will provide on AP306's potential to lower serum phosphate across a range of doses.” AP306 was originally discovered by Chugai Pharmaceutical Co., Ltd. and subsequently licensed to Alebund Pharmaceuticals in 2021. For further information: Optimum Strategic Communications Mary Clark, Isabelle Abdou, Eleanor Cooper Tel: +44 20 3922 0900 Email: r1therapeutics@optimumcomms.com About R1 Therapeutics R1 Therapeutics is a clinical-stage biopharmaceutical company focusing on the development of first-in-class therapies for patients with kidney disease. Its lead program, AP306, targets hyperphosphatemia in patients with chronic kidney disease on dialysis, a condition associated with serious bone and cardiovascular complications and poorer outcomes when phosphate remains uncontrolled. AP306 is a first-in-class pan phosphate active transport inhibitor designed to block three key phosphate transporters in the gut, with the potential to deliver rapid and effective phosphate lowering with a significantly reduced treatment burden. R1 has licensed exclusive global rights outside of Greater China to AP306 from Alebund Pharmaceuticals and is advancing a global Phase 2b development program. AP306 was originally discovered by Chugai Pharmaceutical Co., Ltd. and subsequently licensed to Alebund Pharmaceuticals in 2021. R1 launched in March 2026 with an oversubscribed $77.5 million Series A financing co-led by Abingworth, DaVita Venture Group, and F-Prime, with participation from Curie.Bio, SymBiosis, and U.S. Renal Care. For more information, visit and follow R1 on LinkedIn . References Ketteler M, Block GA, Evenepoel P, et al. 2017 Executive summary of the 2017 KDIGO Chronic Kidney Disease–Mineral and Bone Disorder (CKD-MBD) Guideline Update: what's changed and why it matters. Kidney Int . 2017;92:26–36 United States Renal Data System. 2024. USRDS 2024 Annual Data Report. National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases. Fissel R et al. 2016 Phosphate binder pill burden, patient-reported non-adherence, and mineral bone disorder markers: Findings from the DOPPS. Hemodial Int . 2016 January; 20(1): 38–49. doi:10.1111/hdi.12315 Wang L, Zuo L, Shi M, et al. 2025 A pan-inhibitor of phosphate transporters AP306 in hemodialysis patients. Kidney Int Rep . 2025;10(4):1143–1151. doi:10.1016/S2468-0249(25)00063-4