A small number of pheochromocytoma tumors in that clinical trial meant that the critical requirement of HIF2α signaling for VHL disease-associated pheochromocytoma could not be assessed, but a single-patient clinical trial of a patient with Pacak-Zhuang syndrome (another name for Class 1a/b HIF2-driven disease) revealed that Belzutifan treatment can result in the shrinkage of paraganglioma tumors and the resolution of polycythemia (Kamihara et al., 2021). Here, EPAS1 is linked to polycythemia.