Blockade of the endothelin receptor B resulted in decreased expression of VEGF and other angiogenic mediators, and in a reduction of pathological vascular development in the retina.11 Although we did not measure MR-proANP or CT-proET1 at the time when the ROP progressed in phase 2, it is conceivable that elevations of these two biomarkers at any time point of retinal development might disturb the delicate balance of vasoactive substances in the immature retina and promote the development of ROP. The gene discussed is NPPA; the disease is retinopathy of prematurity.