Pegaptanib is a selective vascular endothelial growth factor (VEGF) antagonist indicated for the treatment of neovascular (wet) age-related macular degeneration. Pegaptanib is an aptamer, a pegylated modified single-stranded oligonucleotide, which adopts a threedimensional conformation that enables it to bind to extracellular VEGF. Pegaptanib specifically binds to the 165 isoform of VEGF, a protein that plays a critical role in angiogenesis (the formation of new blood vessels) and increased permeability (leakage from blood vessels), two of the primary pathological processes responsible for the vision loss associated with neovascular age-related macular degeneration. Pegaptanib is administered in a 0.3 mg dose once every six weeks by intravitreal injection. An intravitreal injection is one that is administered directly into the eye, more specifically, into the vitreous humour, or the jelly-like fluid within the eye.