Serpin F1 is a secreted glycoprotein that belongs to the noninhibitory serpin. It has an alpha/beta core serine-protease inhibitor domain, three major beta-sheets, and ten alpha-helices. As protease inhibitors, serpins have an array of functions including regulating blood clotting, the complement pathway, extracellular matrix remodeling, and cell motility. They are also involved in activities that extend beyond their ability to inhibit proteases. For instance, they may also regulate blood pressure, angiogenesis, or act as storage/transport proteins. Serpin F1 is a new promising approach for the treatment of osteosarcoma and has been described as a natural angiogenesis inhibitor with neurotrophic and immune-modulation properties. The human serpin superfamily consists of at least 35 members that target not only serine proteases, but also selected cysteine proteases and non-protease proteins. Levels of the natural ocular anti-angiogenic factor SentrinF1 (PEDF) is associated with proliferative retinopathy.