R1 Therapeutics has emerged with a substantial Series A round, securing $77.5 million to push forward AP306, a phosphate-lowering candidate for chronic kidney disease.
The California-based startup says AP306 is designed as a pan phosphate transporter inhibitor, a mechanism the company describes as distinct from existing phosphate binders because it targets active phosphate transport. According to R1, that could translate into stronger control of serum phosphate with a lower pill burden for patients.
The financing was co-led by Abingworth, F-Prime, and DaVita Venture Group. R1 plans to use the capital to support global development of the asset and to prepare a Phase 2b study with partner Alebund Pharmaceuticals later this year.
AP306 already has Phase 2a data from China, where treatment was associated with a meaningful reduction in serum phosphate levels. In that study, a greater share of patients reached guideline-recommended phosphate ranges compared with Sanofi’s Renvela.
The program has an interesting origin story as well. AP306 was initially developed by Chugai and later licensed to Alebund, which granted R1 an exclusive worldwide sublicense outside Greater China. Financial details of that arrangement were not disclosed.
“AP306 has the potential to deliver superior efficacy with substantially lower pill burden compared to current phosphate binder therapies,” R1 CEO Krishna Polu said in the company announcement.
The same fundraising day also saw new capital for other biotech programs, including Mestag Therapeutics and iDEL Therapeutics, underscoring continued investor interest in oncology and platform-driven drug development.
