EPAS1 and anemia (phenotype): On the other hand, belzutifan was reported by Jonasch et al. to have better tolerability, with most patients having grade 1-2 adverse reactions in anemia, headache, fatigue, and dizziness [12]. The increased risk of anemia was expected because of the HIF-2α inhibitory effect on erythropoietin [21,28,29].