SO859

SO859 (often written as S0859) is a small molecule inhibitor of sodium-dependent bicarbonate co-transporters (NCBTs), with high affinity for the electrogenic sodium bicarbonate cotransporter 1 (SLC4A4/NBCe1). Developed by Sanofi, it is widely utilized as a pharmacological tool in research to study pH regulation and bicarbonate transport in various tissues, including the heart and tumors. In the context of oncology, SO859 has been shown to disrupt intracellular pH homeostasis in hypoxic tumor cells, leading to intracellular acidification and reduced growth in 3D spheroid models. It is primarily used as a research reagent and has not progressed into clinical development.