The present invention relates generally to compositions and methods for treating cancer and neoplastic disease. Provided herein are substituted pyrido[3,4-d]pyrimidin-4-one derivative compounds and pharmaceutical compositions comprising said compounds. The subject compounds and compositions are useful for inhibition of histone demethylase. Furthermore, the subject compounds and compositions are useful for the treatment of cancer, such as prostate cancer, breast cancer, bladder cancer, lung cancer, melanoma, and the like.