Small-molecule anticancer drugs inhibited tumor growth based on targeted inhibition of specific proteins, while most of oncogenic proteins are "undruggable". Proteolysis targeting chimeras (PROTAC) is an attractive and general strategy for treating cancer based on targeted degradation of oncogenic proteins. This review briefly describes the peptide-based PTOTAC and small molecule-based PROTAC. Subsequently, we summarize the development of targeted delivery of PROTAC, such as targeting molecule-mediated targeted delivery of PROTAC, nanomaterial-mediated targeted delivery of PROTAC and controllable activation of small-molecular PROTAC prodrug. Such strategies show potential application in improving tumor selectivity, overcoming off-target effect and reducing biotoxicity. At the end, the druggability of PROTAC is prospected.
Humans ; Proteolysis Targeting Chimera ; Nanostructures ; Neoplasms/drug therapy* ; Proteolysis

Proteolysis targeting chimera (PROTAC) refers to heterobifunctional small molecules that can simultaneously bind an E3 ubiquitin ligase and a target protein, enabling specific degradation of the target protein with the aid of the ubiquitin proteasome system. At present, most PROTAC drugs are in the clinical trial stage, and the ligands are mainly non-covalent compounds. PROTAC drugs have the advantage of overcoming drug resistance and degrading "undruggable" target proteins, but non-covalent ligands could lead to the hook effect that undermines drug efficacy. With its own advantages, covalent ligands can avoid the occurrence of this phenomenon, which is of great help to the development of PROTAC. This review summarizes the progress in preclinical and clinical research and application of PROTAC molecules targeting three different classes of protein targets, including intranuclear, transmembrane, and cytosolic proteins. We also offer perspective discussions to provide research ideas and references for the future development of PROTAC.
Proteolysis ; Proteolysis Targeting Chimera ; Proteasome Endopeptidase Complex/metabolism* ; Ubiquitin-Protein Ligases/metabolism* ; Proteins/metabolism* ; Ligands

Proteolysis-targeting chimeras (PROTACs) are heterobifunctional small molecules by utilizing the ubiquitin proteasome system (UPS) to degrade proteins of interest. PROTACs have exhibited unprecedented efficacy and specificity in degrading various oncogenic proteins because of their unique mechanism of action, ability to target "undruggable" and mutant proteins. A series of PROTACs have been developed to degrade multiple key protein targets for the treatment of hematologic malignancy. Notably, PROTACs that target BCL-XL, IRAK4, STAT3 and BTK have entered clinical trials. The known PROTACs that have the potential to be used to treat various hematological malignancies are systematically summarized in this review.
Humans ; Hematologic Neoplasms/drug therapy* ; Proteasome Endopeptidase Complex/metabolism* ; Ubiquitin-Protein Ligases/metabolism* ; Proteolysis Targeting Chimera