The fat mass and obesity-associated protein (FTO) catalytically demethylates RNA N6-methyl adenosine (m6A) modification, dynamically regulates gene expression in eukaryotes. Interestingly, FTO is highly expressed and functions as an oncogenic factor in a wide range of cancers. Therefore, using small-molecule inhibitors to target FTO has been established as a promising therapeutic strategy for combating cancers. Patent literature claiming novel chemical entities as FTO inhibitors disclosed from 2017 to present is available in Espacenet, including dozens of patent documents. The pivotal influence of FTO demethylase in a particular epigenetic layer of regulation of gene expression renders it promising for FTO to be a therapeutical target for many diseases, including malignant cancers. Several institutions were prompted and have patented chemical frameworks as FTO inhibitors. Remarkedly, the FTO inhibitor CS1 (Bisantrene) has advanced to clinical trials for treating acute myeloid leukemia (AML). The successful advancement of CS1 into clinical trials would continuingly stimulate researches on RNA epigenetic enzymes targeted first-in-class anticancer drug discovery.