Recent advances in epigenetic proteolysis targeting chimeras (Epi-PROTACs)

PROteolysis TArgeting Chimeras (PROTACs) are heterobifunctional molecules that trigger the poly-ubiquitination of the protein of interest (POI) inducing its degradation via the recruitment of the ubiquitin-proteasome system, thus suppressing the POI's intracellular levels and indirectly all its functions. Recently, one of the fields where the protein knockdown induced by PROTACs has demonstrated to serve as a promising biochemical tool and to provide new opportunities for drug discovery is the epigenetics (epi-PROTACs). A full inhibition of the functions of all domains of a specific epigenetic POI (e-POI), rather than just the block of its catalytic/single domain activity, is in fact a new more effective modality to hit an e-POI and, in principle, the complex it belongs to, and potentially to treat the related diseases, first cancer. In this review, we will present the most relevant progresses made, especially in the last two years, in the application of PROTACs technology to the three main classes of e-POIs: “writers”, “erasers” and “readers”. Emphasis will be devoted to the medicinal chemistry aspects of the epi-PROTACs design, preparation, and optimization and to the comparison with small molecule epi-drugs for both epi-targets functional annotation and potential anticancer therapy purposes.