The interest in developing inhibitors of DNA methyltransferases (IDNMT) as modifiers of epigenetic features for the treatment of several chronic diseases is rapidly increasing. Herein, we present insights of a chemoinformatic characterization of IDNMT focused on the analysis of the chemical space and structure-activity relationships (SAR) using activity landscape modeling (ALM). Analysis of the chemical space revealed two main groups of compounds whose chemical structures are associated with either cofactor analogs or non-nucleoside compounds. The ALM showed that non-nucleoside compounds have a continuous SAR while cofactor analogs have a rough SAR with several deep activity cliffs. Molecular modeling helped to explain the structural basis of the activity cliffs. The significance of the results is threefold: 1) the combined analysis of chemical space with activity landscape gave rise to a novel 'activity landscape sweeping' strategy that enabled a better structurebased interpretation of the SAR; 2) it is feasible -and advisable-to develop predictive models for nonnucleoside IDNMT studied in this work, and 3) structure-based interpretation of the SAR gave clear insights into the molecular mechanism of inhibition of novel IDNMT suggesting specific strategies to optimize the activity of leads compounds. structure-activity relationships; SAS maps, structure-activity-similarity maps.of cytosine, preferably within CpG dinucleotides. Also, as a product of the methylation mechanism, S-Adenosyl-L-homocysteine (SAH) is generated. 4 In mammals, four DNMT enzymes have been identified: DNMT1 (the most abundant, it is a maintenance methyltransferase that acts on hemimethylated DNA); DNMT3A and DNMT3B (de novo methyltransferases that are capable of generating new methylation patterns in DNA), and DNMT3L that is associated with DNMT3A and DNMT3B, enhancing their activity.