PIK3CA and hereditary hemorrhagic telangiectasia: We show that targeting Vegfr2 prevents angiogenesis in Alk1iΔEC mice but does not rescue normal vascular patterning and AVM formation, whereas PI3K inhibition rescues vascular malformations in BMP signalling-deficient retinas and GI tract, identifying PI3K pathway inhibition as a novel putative treatment approach for HHT patients.