HNHA is a cell-permeable inhibitor of histone deacetylase (HDAC) activity. HNHA induces histone hyperacetylation and p21 transcription with inhibition of cell cycle progression in human fibrosarcoma HT1080 cells. In in vivo murine xenographs, HNHA is equally as effective as SAHA in inhibiting tumor growth. HNHA inhibits HUVEC growth and prevents tube formation and migration in response to VEGF. Also HNHA blocks retinal neovascularization and choroidal angiogenesis in mice.