angiostatin

noun

an·​gio·​stat·​in ˈan-jē-ə-ˌsta-tᵊn 

: a naturally-occurring protein that is derived from the cleavage of plasminogen and that inhibits the formation and growth of blood vessels

… angiostatin shrinks blood vessel growth by binding to and shutting down ATP synthase, an enzyme on an endothelial cell's surface. It thereby cuts off the energy required for blood vessel growth.

—Gary Stix, Scientific American