Advances in targeted delivery of proteolysis targeting chimeras in cancer therapy / 生物工程学报

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.

Research progress in controllable proteolysis targeting chimeras / 药学学报

Proteolysis targeting chimeras (PROTACs) is an innovative technique in targeted protein degradation. PROTACs is a heterobifunctional molecule which can bind to the E3 ligase and target protein to form a ubiquitination complex, resulting in the ubiquitin-proteasome system dependent degradation of target protein. PROTACs has been regarded as the promising method in drug discovery campaign, for its high commonality, potent degradation activity and unique selectivity profile. However, the catalytic mechanism also induces the uncontrollable protein degradation risk. Controllable PROTACs contain the responsive element in the molecular entity. In certain conditions, the element can be triggered to activate or terminate the degradation event. In this review, we will briefly summarize the strategies in controllable PROTACs and describe the representative examples according to the responsive mechanism. We hope this review could provide some insight into the further development of controllable PROTACs.

Discovery of novel exceptionally potent and orally active c-MET PROTACs for the treatment of tumors with MET alterations

Various c-mesenchymal-to-epithelial transition (c-MET) inhibitors are effective in the treatment of non-small cell lung cancer; however, the inevitable drug resistance remains a challenge, limiting their clinical efficacy. Therefore, novel strategies targeting c-MET are urgently required. Herein, through rational structure optimization, we obtained novel exceptionally potent and orally active c-MET proteolysis targeting chimeras (PROTACs) namely D10 and D15 based on thalidomide and tepotinib. D10 and D15 inhibited cell growth with low nanomolar IC50 values and achieved picomolar DC50 values and >99% of maximum degradation (Dmax) in EBC-1 and Hs746T cells. Mechanistically, D10 and D15 dramatically induced cell apoptosis, G1 cell cycle arrest and inhibited cell migration and invasion. Notably, intraperitoneal administration of D10 and D15 significantly inhibited tumor growth in the EBC-1 xenograft model and oral administration of D15 induced approximately complete tumor suppression in the Hs746T xenograft model with well-tolerated dose-schedules. Furthermore, D10 and D15 exerted significant anti-tumor effect in cells with c-METY1230H and c-METD1228N mutations, which are resistant to tepotinib in clinic. These findings demonstrated that D10 and D15 could serve as candidates for the treatment of tumors with MET alterations.

Recent advancement in targeting the KRAS-G12C mutant for cancer therapy / 药学学报

RAS, as a well-known proto-oncogene, is the most frequently mutated oncogene in human cancers, yet tremendous efforts over the past 30 years have failed to develop effective therapies for RAS-mutant cancer. Recently, specifically targeting the KRAS-G12C mutant, a frequently occurring KRAS mutation in human cancers, has shown promise in conquering KRAS-mutant cancers, and has inspired interest in this direction. We herein review the very recent progress achieved in the development of covalent inhibitors towards KRAS-G12C mutant, in combinational therapies and in proteolysis-targeting chimeras (PROTACs)-based approaches to disrupt KRAS-G12C protein. We provide insights for drug discovery against KRAS-G12C-mutated tumors and discuss the potential challenges in this field.

Advances in the optimization of the linker in proteolysis-targeting chimeras (PROTAC) / 药学学报

With high selectivity and potency, target protein degradation technology has recently emerged as a strategy for drug discovery and design. Proteolysis-targeting chimeras (PROTAC) function as inducers for the degradation of target proteins and are a research focus in drug development. Current research on PROTAC mainly revolves around the rational design of PROTAC molecules, the discovery of new E3 ubiquitin ligase ligands and improvement in drug targeting. In this review, we focus on the PROTAC linker and its effects on the generation of the E3 enzyme-PROTAC-target protein ternary complex from three standpoints: length, binding site and chemical properties. We discuss the influences of the linker on the efficacy and the selectivity of PROTAC molecules.

Advances of targeted protein degradation technology and its applications in diseases therapy / 生物工程学报

Targeted protein degradation (TPD) technology facilitates specific and efficient degradation of disease-related proteins through hijacking the two major protein degradation systems in mammalian cells: ubiquitin-proteasome system and lysosome pathway. Compared with traditional small molecule-inhibitors, TPD-based drugs exhibit the characteristics of a broader target spectrum. Compared with techniques interfere with protein expression on the gene and mRNA level, TPD-based drugs are target-specific, efficaciously rapid, and not constrained by post-translational modification of proteins. In the past 20 years, various TPD-based technologies have been developed. Most excitingly, two TPD-based therapeutic drugs have been approved by FDA for phase Ⅰ clinical trials in 2019. Despite of the early stage characteristics and various obstructions of the TPD technology, it could serve as a powerful tool for the development of novel drugs. This review summarizes the advances of different degradation systems based on TPD technologies and their applications in disease therapy. Moreover, the advantages and challenges of various technologies were discussed systematically, with the aim to provide theoretical guidance for further application of TPD technologies in scientific research and drug development.

Advances in the treatment of cancer by PROTACs / 药学学报

Proteolysis-targeting chimeras (PROTACs) are small-molecule protein degraders based on the ubiquitin-proteasome system. Recently, the development of specific small-molecule ligands for several E3 ligases (CRL4CRBN, CRL2VHL and cIAP) have significantly advanced the PROTACs technology. Several PROTACs against various oncogenic proteins including bromodomain-containing protein 4 (BRD4), estrogen receptor (ER) and androgen receptor (AR) have been developed and considered a novel approach for therapy of cancers. There are advantages of the new technology over the traditional small-molecule strategies. This review article provides a summary on the recent progress in the small-molecule-based PROTACs as antitumor drugs, and the challenges of this technology.

Protein degradation as an innovative strategy in drug discovery / 药学学报

The success rate of mechanism-based drug discovery depends on the drug targets. With the rapid development of genomics and proteomics, a lot of nonenzymic proteins have been identified as potential drug targets. However, these nonenzymic proteins cannot be regulated by occupying the active site, which were recognized as undruggable targets. Direct regulation of the concentration of these proteins in cells by the innate ubiquitin-proteasome is a potential approach to target these proteins. The ubiquitination of target protein by E3 ligase is the key step for ubiquitin-proteasome mediated protein degradation. Proteolysis targeting chimeras (PROTACs) can facilitate the assembly of complex that consists of the target protein and E3 ligase. The target protein will be ubiquitinated, leading to the degradation by proteasome. This type of regulation mechanism can expand the scope of potential drug targets, and the development of PROTACs may be an innovative strategy in drug discovery.