Alterations in the activity or expression of proteins are associated with the pathology of many diseases, e.g., neurodegenerative diseases, and cancer, such as prostate cancer and breast cancer. Many proteins can be challenging targets for therapy with classical small molecules currently on the market. Therefore, new therapeutic modalities are being intensively developed, one example is the proteolysis targeting chimeras (PROTACs), which catalytically remove target proteins, allowing lower doses and broadening the spectrum of possible target proteins. During the master's thesis, we focused on monoamine oxidase A (MAO-A), which is responsible for the degradation of neurotransmitters in the central nervous system and thus plays a key role in the onset and development of mental disorders (depression) and neurodegenerative diseases. Studies have also confirmed its role in the development of prostate cancer. Based on the structure of harmine, a selective MAO-A inhibitor, we have developed chimeric degraders with pomalidomide, using various flexible and rigid linkers.
We began the synthesis with the preparation of linkers: on one side the amine was protected in the form of a tert-butyloxycarbonyl protecting group, and on the other side, an alkyl halide was prepared. The linker prepared was attached to the desmethylharmine in the O-alkylation reaction, followed by deprotection of the amine by acidolysis. Final heterobifunctional ligand was prepared by nucleophilic aromatic substitution with 4-fluorothalidomide. Isolation of the products was done by normal-phase and reverse-phase column chromatography. The identity of the intermediates and final ligands was confirmed by nuclear magnetic resonance and mass spectrometry, and the purity of the heterobifunctional ligands was determined by ultra-high-performance liquid chromatography. Two molecules with flexible spacers and four with rigid spacers were successfully synthesized, which inhibited the enzymatic activity of MAO-A as determined in a biochemical assay. The most potent inhibitor was a compound with an n-butyl linker – the inhibitory potency was comparable to that of harmine. Rigid spacers were weaker inhibitors of MAO-A, suggesting less favorable binding to the active site of MAO-A.
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