R1 Therapeutics launches with $77.5M Series A to advance first-in-class kidney disease treatment AP306

For decades, hyperphosphatemia in chronic kidney disease has been treated with therapies that often fall short. Now, a new biotech startup, R1 Therapeutics, is aiming to change that with fresh funding and a different approach.

The company has launched from stealth with $77.5 million in oversubscribed Series A funding and a clear target: hyperphosphatemia, a common and dangerous condition affecting patients with chronic kidney disease. It is betting that its lead drug candidate, AP306, can succeed where decades of standard treatments have struggled.

The round was co-led by Abingworth, F-Prime, and DaVita Venture Group, with backing from Curie.Bio, SymBiosis, and U.S. Renal Care. Alongside the funding, R1 secured exclusive global rights outside Greater China to develop and commercialize AP306 through a partnership with Alebund Pharmaceuticals.

That combination of capital and licensing gives the company a running start. A Phase 2b trial is planned for later this year.

Hyperphosphatemia may not get the same attention as other conditions tied to chronic kidney disease, yet it sits at the center of patient outcomes. More than 500,000 people in the U.S. and millions globally rely on dialysis. A large share of them still fail to keep phosphate levels under control. The consequences are serious, ranging from bone damage to cardiovascular complications.

The standard treatments have barely changed in 60 years. Most rely on phosphate binders that bind phosphate in the digestive system. The approach comes with trade-offs: high pill burden, limited effectiveness, and side effects that make it hard for patients to stay on therapy.

R1 is taking a different path.

AP306 blocks active phosphate transport in the gastrointestinal tract by directly targeting three transporters. That sets it apart from existing therapies, which focus on passive binding. Early clinical data from a Phase 2a study published in Kidney International Reports showed meaningful reductions in serum phosphate levels along with a favorable safety profile.

The company believes that the mechanism could lead to better control with fewer pills, a shift that would matter for patients managing daily treatment routines.

“We are excited to be launching R1 Therapeutics in partnership with Alebund and with support from a strong, experienced syndicate, including DaVita and U.S. Renal Care, recognized global providers transforming kidney care. This backing, plus a differentiated clinical-stage asset, positions us to address one of the most persistent challenges in managing patients with chronic kidney disease,” said Krishna Polu, M.D., Co-Founder, President and CEO of R1 Therapeutics.

He added, “AP306 represents a fundamentally new approach to treating hyperphosphatemia. By blocking the active transport of phosphate through three different phosphate transporters in the GI tract, initial clinical studies suggest AP306 has the potential to deliver superior efficacy with substantially lower pill burden compared to current phosphate binder therapies. If successful, AP306 should redefine the class of phosphate lowering therapies and become the treatment of choice for the management of hyperphosphatemia.”

With $77.5M in funding, Biotech startup R1 Therapeutics targets hyperphosphatemia in chronic kidney disease

R1’s leadership team brings deep experience in nephrology and drug development. Polu, a nephrologist, has spent more than two decades in the biopharmaceutical industry building and advancing pipelines. He’s joined by L. Mary Smith, Ph.D., former Chief Development Officer at SpringWorks Therapeutics, who will lead development as Chief Operating Officer.

On the partner side, Alebund sees global potential in the program.

“R1 Therapeutics brings together an exceptional leadership team with deep nephrology expertise and a clear vision for advancing AP306,” said Gavin Xia, CEO of Alebund Pharmaceuticals. “This asset addresses a significant unmet need in a large, underserved patient population. We are delighted to partner with R1 Therapeutics to develop AP306 globally and improve outcomes for the millions of CKD patients struggling with inadequate phosphate control.”

AP306, previously known as EOS789, traces its origins to Chugai Pharmaceutical before being licensed to Alebund. Regulatory groundwork is already in place, with active investigational filings in both the United States and China.

For R1, the next stretch will test whether its approach can hold up in larger trials. If it does, the company may reshape a treatment category that has seen little real change for decades.