NRP1 and neoplasm: Small-molecule inhibitors directed against NRP1 are currently under development and we hope that these can soon be tested alongside existing or new αvβ3-integrin antagonists, with the caveat that both molecules are expressed by multiple cell types that contribute to tumour growth and angiogenesis, including platelets, and off-target (i.e. non-EC) effects will have to be examined carefully; although we can rule out their contribution to the EC-double-KO intervention studies (Fig. 6), these other cells types might be contributing to β3-HET angiogenic responses.