R1 Therapeutics launched with an oversubscribed $77.5 million Series A to advance AP‑306, an oral pan‑phosphate transporter inhibitor for hyperphosphatemia in chronic kidney disease (CKD). The financing will support a Phase IIb trial and global development planning. AP‑306, licensed from Alebund/Chugai, blocks active gastrointestinal phosphate transport and aims to reduce pill burden and improve tolerability versus existing binders. R1 said INDs are active in the US and China and plans global expansion. The round was co‑led by Abingworth, F‑Prime, and DaVita Venture Group, with strategic investors aligned to kidney care. Investors cited unmet needs in dialysis populations where uncontrolled phosphate drives morbidity. R1’s strategy centers on differentiated mechanism, clinical proof‑points, and partnerships to accelerate regional registrations and commercialization.