Ugi reaction-assisted assembly of covalent PROTACs against glutathione peroxidase 4

Design, synthesis, and biological evaluation of RSL3-based GPX4 degraders with hydrophobic tags

Ferroptosis is a new type of programmed cell death characterized by iron-dependent lipid peroxidation, during which glutathione peroxidase 4 (GPX4) plays an essential role and is well-recognized as a promising therapeutic target for cancer treatment. Although some GPX4 degradation molecules have been developed to induce ferroptosis, the discovery of GPX4 degraders with hydrophobic tagging (HyT) as an innovative approach is more challenging. Herein, we designed and synthesized a series of HyT degraders by linking the GPX4 inhibitor RSL3 with a hydrophobic and bulky group of adamantane. Among them, compound R8 is a potent degrader (DC50, 24h = 0.019 μM) which can effectively degrade GPX4 in a dose- and time-dependent manner. Furthermore, compound R8 exhibited superior in vitro antitumor potency against HT1080 and MDA-MB-231 cell lines with IC50 values of 24 nM and 32 nM respectively, which are 4 times more potent than parental compound RSL3. Mechanistic investigation evidenced that R8 consumes GPX4 protein mainly through the ubiquitin proteasome (UPS) and enables to induce the accumulation of LPO, thereby triggering ferroptosis. Our work presented the novel GPX4 degrader of R8 by HyT strategy, and provided a promising pathway of degradation agents for the treatment of ferroptosis relevant diseases.

Unveiling a new strategy for PDIA1 inhibition: Integration of activity-based probes profiling and targeted degradation

The overexpression of PDIA1 in cancer has spurred the quest for effective inhibitors. However, existing inhibitors often bind to only one active site, limiting their efficacy. In our study, we developed a PROTAC-mimetic probe dPA by combining PACMA31 (PA) analogs with cereblon-directed pomalidomide. Through protein profiling and analysis, we confirmed dPA's specific interaction with PDIA1's active site cysteines. We further synthesized PROTAC variants with a thiophene ring and various linkers to enhance degradation efficiency. Notably, H4, featuring a PEG linker, induced significant PDIA1 degradation and inhibited cancer cell proliferation similarly to PA. The biosafety profile of H4 is comparable to that of PA, highlighting its potential for further development in cancer therapy. Our findings highlight a novel strategy for PDIA1 inhibition via targeted degradation, offering promising prospects in cancer therapeutics. This approach may overcome limitations of conventional inhibitors, presenting new avenues for advancing anti-cancer interventions.

Research progress on GPX4 targeted compounds

Blocking the System Xc-_ GSH_GPX4 pathway to induce ferroptosis in tumor cells is a novel strategy for cancer treatment. GPX4 serves as the core of the System Xc-/GSH/GPX4 pathway and is a predominant target for inducing ferroptosis in tumor cells. This article summarizes compounds identified in current research that directly target the GPX4 protein, including inhibitors, activators, small molecule degraders, chimeric degraders, and the application of combination therapies with other drugs, aiming to promote further research on the target and related diseases.

Progress of proteolysis-targeting chimeras (PROTACs) delivery system in tumor treatment

Proteolysis targeting chimeras (PROTACs) can use the intrinsic protein degradation system in cells to degrade pathogenic target proteins, and are currently a revolutionary frontier of development strategy for tumor treatment with small molecules. However, the poor water solubility, low cellular permeability, and off-target side effects of most PROTACs have prevented them from passing the preclinical research stage of drug development. This requires the use of appropriate delivery systems to overcome these challenging hurdles and ensure precise delivery of PROTACs towards the tumor site. Therefore, the combination of PROTACs and multifunctional delivery systems will open up new research directions for targeted degradation of tumor proteins. In this review, we systematically reviewed the design principles and the most recent advances of various PROTACs delivery systems. Moreover, the constructive strategies for developing multifunctional PROTACs delivery systems were proposed comprehensively. This review aims to deepen the understanding of PROTACs drugs and promote the further development of PROTACs delivery system.

Ferroptosis in Cancer Therapy: Mechanisms, Small Molecule Inducers, and Novel Approaches

Ferroptosis, a unique form of programmed cell death, is initiated by an excess of iron accumulation and lipid peroxidation-induced damage. There is a growing body of evidence indicating that ferroptosis plays a critical role in the advancement of tumors. The increased metabolic activity and higher iron levels in tumor cells make them particularly vulnerable to ferroptosis. As a result, the targeted induction of ferroptosis is becoming an increasingly promising approach for cancer treatment. This review offers an overview of the regulatory mechanisms of ferroptosis, delves into the mechanism of action of traditional small molecule ferroptosis inducers and their effects on various tumors. In addition, the latest progress in inducing ferroptosis using new means such as proteolysis-targeting chimeras (PROTACs), photodynamic therapy (PDT), sonodynamic therapy (SDT) and nanomaterials is summarized. Finally, this review discusses the challenges and opportunities in the development of ferroptosis-inducing agents, focusing on discovering new targets, improving selectivity, and reducing toxic and side effects.

ZX703: A Small-Molecule Degrader of GPX4 Inducing Ferroptosis in Human Cancer Cells

Ferroptosis is a novel form of oxidative cell death triggered by iron-dependent lipid peroxidation. The induction of ferroptosis presents an attractive therapeutic strategy for human diseases, such as prostate cancer and breast cancer. Herein, we describe our design, synthesis, and biological evaluation of endogenous glutathione peroxidase 4 (GPX4) degraders using the proteolysis targeting chimera (PROTAC) approach with the aim of inducing ferroptosis in cancer cells. Our efforts led to the discovery of compound 5i (ZX703), which significantly degraded GPX4 through the ubiquitin-proteasome and the autophagy-lysosome pathways in a dose- and time-dependent manner. Moreover, 5i was found to induce the accumulation of lipid reactive oxygen species (ROS) in HT1080 cells, thereby inducing ferroptosis. This study provides an attractive intervention strategy for ferroptosis-related diseases.

Design, Synthesis, and Biological Evaluation of Hydrophobic-Tagged Glutathione Peroxidase 4 (GPX4) Degraders

Ferroptosis is an iron-dependent form of oxidative cell death induced by lipid peroxidation accumulation. Glutathione peroxidase 4 (GPX4) plays a key role in the regulation of ferroptosis and is considered to be a promising therapeutic target for cancer and other human diseases. Herein, we describe our design, synthesis, and biological evaluation of a series of HyT-based degraders of the GPX4. One of the most promising compounds, 7b (ZX782), effectively induces dose- and time-dependent degradation of GPX4 protein and potently suppresses the growth of human fibrosarcoma HT1080 cells, which are highly sensitive to ferroptosis and widely used for evaluating compound specificity in ferroptosis. Mechanism investigation indicated that 7b depletes GPX4 through both the ubiquitin-proteasome and the autophagy-lysosome. Furthermore, the degradation of GPX4 induced by 7b could significantly increase the accumulation of lipid reactive oxygen species (ROS) in HT1080 cells, ultimately leading to ferroptosis. Overall, compound 7b exhibits robust potency in depleting endogenous GPX4, thereby modulating ferroptosis in cancer cells.

Current advances and development strategies of orally bioavailable PROTACs

Proteolysis-targeting chimeras (PROTACs) have been an area of intensive research with the potential to extend drug space not target to traditional molecules. In the last half decade, we have witnessed several PROTACs initiated phase I/II/III clinical trials, which inspired us a lot. However, the structure of PROTACs beyond "rule of 5" resulted in developing PROTACs with acceptable oral pharmacokinetic (PK) properties remain one of the biggest bottleneck tasks. Many reports have demonstrated that it is possible to access orally bioavailable PROTACs through rational ligand and linker modifications. In this review, we systematically reviewed and highlighted the most recent advances in orally bioavailable PROTACs development, especially focused on the medicinal chemistry campaign of discovery process and in vivo oral PK properties. Moreover, the constructive strategies for developing oral PROTACs were proposed comprehensively. Collectively, we believe that the strategies summarized here may provide references for further development of oral PROTACs.