US-based R1 Therapeutics has expanded its Series A financing to $80.5m to advance its lead asset, AP306, in a Phase IIb trial for hyperphosphatemia in dialysis-dependent chronic kidney disease patients.
The financing includes investment from Samsara BioCapital. R1 Therapeutics anticipates reporting top-line results from the trial in the first half of 2027.
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The expanded funding builds on an oversubscribed $77.5m Series A round originally announced in March 2026.
Samsara BioCapital joins an investor syndicate comprising Abingworth, Curie.Bio, DaVita Venture Group, F-Prime, SNMA Capital (formerly Symbiosis Capital Management), and US Renal Care.
R1 Therapeutics co-founder, president and CEO Krishna Polu said: “Samsara brings a rare combination of scientific depth and a track record of investing in kidney companies across the private and public markets.
“Their decision to join ahead of the Phase IIb readout is a strong endorsement of our novel approach to addressing hyperphosphatemia.
“With our global trial underway, their support, alongside that of our existing syndicate, further strengthens our ability to generate the clinical data needed to bring AP306 to patients.”
AP306 is a first-in-class pan-phosphate active transport inhibitor designed to block three key phosphate transporters in the gut.
The randomised, multi-centre, placebo-controlled, double-blind Phase IIb study is evaluating the monotherapy across clinical sites in China and the US through a global collaboration with Alebund Pharmaceuticals (Jiangsu).
Initially discovered by Chugai Pharmaceutical, AP306 was licensed to Alebund Pharmaceuticals in 2021, with R1 Therapeutics subsequently acquiring exclusive global development and commercialisation rights, excluding Greater China.
The clinical programme targets hyperphosphatemia, a condition linked to cardiovascular complications, bone disease, and higher mortality rates when phosphate remains poorly controlled.
