Disclosed are cyclopentene compounds for use as inhibitors of aminotransferases such as gamma-aminobutyric acid (GABA) aminotransferase (AT) and/or ornithine aminotransferase (OAT). The disclosed cyclopentene compounds include 3-amino-4-halocyclopente carboxylic acid compounds which may be formulated in pharmaceutical composition for treating diseases and disorders associated with GABA-AT and/or OAT activity, including epilepsy, addiction, hepatocellular carcinoma (HCC), and non-small cell lung cancer (NSCLC).