LSD1 and LSD2 histone demethylases are implicated in a number of physiological and pathological processes, ranging from tumorigenesis to herpes virus infection. A comprehensive structural, biochemical, and cellular study is presented here to probe the potential of these enzymes for epigenetic therapies. This approach employs tranylcypromine as a chemical scaffold for the design of novel demethylase inhibitors. This drug is a clinically validated antidepressant known to target monoamine oxidases A and B. These two flavoenzymes are structurally related to LSD1 and LSD2. Mechanistic and crystallographic studies of tranylcypromine inhibition reveal a lack of selectivity and differing covalent modifications of the FAD cofactor depending on the enantiomeric form. These findings are pharmacologically relevant, since tranylcypromine is currently administered as a racemic mixture. A large set of tranylcypromine analogues were synthesized and screened for inhibitory activities. We found that the common evolutionary origin of LSD and MAO enzymes, despite their unrelated functions and substrate specificities, is reflected in related ligand-binding properties. A few compounds with partial enzyme selectivity were identified. The biological activity of one of these new inhibitors was evaluated with a cellular model of acute promyelocytic leukemia chosen since its pathogenesis includes aberrant activities of several chromatin modifiers. Marked effects on cell differentiation and an unprecedented synergistic activity with antileukemia drugs were observed. These data demonstrate that these LSD1/2 inhibitors are of potential relevance for the treatment of promyelocytic leukemia and, more generally, as tools to alter chromatin state with promise of a block of tumor progression.

NAD(+)-dependent sirtuin deacetylases have emerged as potential therapeutic targets for treatment of human illnesses such as cancer, metabolic, cardiovascular, and neurodegenerative diseases. The benefits of sirtuin modulation by small molecules have been demonstrated for these diseases. In contrast to the discovery of inhibitors of SIRT1, -2, and -3, only activators for SIRT1 are known. Here, we rationalized the potential of the previously unexplored dihydropyridine scaffold in developing sirtuin ligands, thus we prepared a series of 1,4-dihydropyridine-based derivatives 1-3. Assessment of their SIRT1-3 deacetylase activities revealed the importance of the substituent at the N1 position of the dihydropyridine structure on sirtuin activity. Placement of cyclopropyl, phenyl, or phenylethyl groups at N1 conferred nonselective SIRT1 and SIRT2 inhibition activity, while a benzyl group at N1 conferred potent SIRT1, -2, and -3 activation. Senescence assays performed on hMSC and mitochondrial function studies conducted with murine C2C12 myoblasts confirmed the compounds' novel and unique SIRT-activating properties.