An ATP-competitive, serine/arginine-rich protein kinase (SRPK)-specific inhibitor (Ki = 0.89 µM for SRPK1). SRPIN 340 does not inhibit other classes of Serine-Arginine-Rich Protein Kinases (SRPKs) significantly, including Clk1 and Clk4 and >140 other SR kinases. SRPIN340 also suppresses VEGF expression and attenuates choroidal neovascularization (CNV).