R1 Therapeutics unveiled a $77.5 million Series A to develop AP306 (formerly EOS789), a pan‑phosphate transporter inhibitor targeting hyperphosphatemia in chronic kidney disease patients on dialysis. The financing is co‑led by Abingworth, F‑Prime and DaVita Venture Group and will fund a Phase IIb study and Phase III planning, according to CEO Krishna Polu. AP306 is positioned to block active intestinal phosphate transport rather than relying on phosphate binders; the company says this mechanism could reduce pill burden and improve tolerability compared with existing therapies. The drug was discovered at Chugai and licensed via Alebund, and INDs are active in the U.S. and China. One‑sentence clarification: hyperphosphatemia—elevated blood phosphate—is common in dialysis patients and contributes to bone and cardiovascular morbidity, so treatments that lower phosphate with fewer pills could shift standard care. Why it matters: the raise and licensing deal back AP306’s global development plan and highlight investor interest in differentiated oral approaches for chronic kidney disease complications.