Conventional small-molecule drugs (SMDs) are compounds characterized by low molecular weight, high cell permeability, and high selectivity. In clinical translation, SMDs are regarded as good candidates for oral drug formulation. SMD inhibitors play an important role in
cancer treatment; however, resistance and low effectiveness have been major bottlenecks in clinical application. Generally, only 20% of cell
proteins can potentially be targeted and have been developed as SMDs; thus, some types of
tumor targets are considered "undruggable." Among these are
transcription factors (TFs), an important class of
proteins that regulate the occurrence, formation, and development of
tumors. It is difficult for SMDs and macromolecular drugs to identify bioactive sites in TFs and hence for use as pharmacological inhibitors in targeting TF
proteins. For this reason, technologies that enable targeted protein degradation, such as
proteolysis-targeting chimera or molecular
glues, could serve as a potential tool to solve these conundrums.