Advances and prospects in targeted protein degradation / 药学实践杂志

Targeted protein degradation (TPD) techniques eliminate pathogenic proteins by hijacking the intracellular proteolysis machinery which includes the ubiquitin-proteasome system (UPS) and the lysosomal degradation pathway, holding promise to overcome the limitations of traditional inhibitors and further broaden the target space including many “undruggable” targets, and provide new targeted treatments for drug discovery. In this review, recent advances in a variety of promising TPD strategies were summarized, such as proteolysis targeting chimera (PROTAC), molecular glue, lysosome-targeting chimaera (LYTAC), autophagosome-tethering compound (ATTEC), autophagy-targeting chimera AUTAC and AUTOTAC, particularly. The representative case studies, potential applications and challenges were analyzed.

Emerging roles of Aurora-A kinase in cancer therapy resistance

Aurora kinase A (Aurora-A), a serine/threonine kinase, plays a pivotal role in various cellular processes, including mitotic entry, centrosome maturation and spindle formation. Overexpression or gene-amplification/mutation of Aurora-A kinase occurs in different types of cancer, including lung cancer, colorectal cancer, and breast cancer. Alteration of Aurora-A impacts multiple cancer hallmarks, especially, immortalization, energy metabolism, immune escape and cell death resistance which are involved in cancer progression and resistance. This review highlights the most recent advances in the oncogenic roles and related multiple cancer hallmarks of Aurora-A kinase-driving cancer therapy resistance, including chemoresistance (taxanes, cisplatin, cyclophosphamide), targeted therapy resistance (osimertinib, imatinib, sorafenib, etc.), endocrine therapy resistance (tamoxifen, fulvestrant) and radioresistance. Specifically, the mechanisms of Aurora-A kinase promote acquired resistance through modulating DNA damage repair, feedback activation bypass pathways, resistance to apoptosis, necroptosis and autophagy, metastasis, and stemness. Noticeably, our review also summarizes the promising synthetic lethality strategy for Aurora-A inhibitors in RB1, ARID1A and MYC gene mutation tumors, and potential synergistic strategy for mTOR, PAK1, MDM2, MEK inhibitors or PD-L1 antibodies combined with targeting Aurora-A kinase. In addition, we discuss the design and development of the novel class of Aurora-A inhibitors in precision medicine for cancer treatment.

Targeting histone deacetylases for cancer therapy: Trends and challenges

Dysregulation of histone deacetylases (HDACs) is closely related to tumor development and progression. As promising anticancer targets, HDACs have gained a great deal of research interests and two decades of effort has led to the approval of five HDAC inhibitors (HDACis). However, currently traditional HDACis, although effective in approved indications, exhibit severe off-target toxicities and low sensitivities against solid tumors, which have urged the development of next-generation of HDACi. This review investigates the biological functions of HDACs, the roles of HDACs in oncogenesis, the structural features of different HDAC isoforms, isoform-selective inhibitors, combination therapies, multitarget agents and HDAC PROTACs. We hope these data could inspire readers with new ideas to develop novel HDACi with good isoform selectivity, efficient anticancer effect, attenuated adverse effect and reduced drug resistance.

Click chemistry and drug delivery: A bird's-eye view

Click chemistry has been proven to be very useful in drug delivery. Due to the availability of a large number of click reactions with a various characteristics, selection of appropriate chemistry for a given application is often not a trivial task. This review is written for pharmaceutical researchers who are interested in click chemistry applications and yet may not be click chemistry experts. For this, the review gives an overview of available click reactions organized by application types. Further, the general understanding of click reactions being fast and high yielding sometimes overshadows the need to analyze reaction kinetics in assessing suitability of a given reaction for certain applications. For this, we highlight the need to analyze the relationship among reaction kinetics, concentration effects, and reaction time scales, knowing that lack of such analysis could easily lead to failures. Further, possible issues such as chemical stability with various click reagents are also discussed to aid experimental designs. Recent examples and extensive references are also provided to aid in-depth understanding of technical details. We hope this review will help those interested in using click chemistry in drug delivery to select the appropriate reactions/reagents and minimize the number of pitfalls.

On improving the activity and selectivity of small molecule drugs / 药学学报

Although small molecule drugs (SMD) are still mainstream for the treatment of diseases, large molecule biologicss of many advantages, pose a challenge to the further discovery and use of SMD. The advantages of SMD are the convenience of oral administration and good patient compliance. However, the challenge with SMD is to integrate the PD, PK, selectivity and safety into a chemical structure. Because of their small size and surface area they often bind to various proteins, and off-target actions can cause adverse reactions. In this sense, selectivity is critical. Based upon target as the core to construct a chemical structure, it is necessary to consider the requirements of all the attributes, but achievement of the full-dimensional optimization is difficult. Modern drug discovery has been greatly enhanced by molecular biology and structural biology, and new strategies and technologies have emerged, which have created many successful medicines. For example, under the guidance of structural biology, covalent binding drugs connect moderate "electrophilic warheads" to the appropriate positions of molecules, and upon binding to their targets the electrophiles are irreversibly linked to the target by covalent bonds. Molecular biology can be directly applied to the development of antibody-coupled drugs (ADC). The antibody (A) acts as a carrier and a guide (for PK), and carries toxic molecules (D) into cancer cells, thus playing a killing role (for PD). The separate pharmacodynamic and pharmacokinetic entities are coupled (C) by linkers. PROTACs are also bifunctional molecules, which recruit a target protein and ubiquitin ligase E3 to form a ternary complex, which then acts as a catalyst to ubiquitinate the target protein and lead to degradation by the proteasome. In addition, in recent years, the combination of two fixed-dose drugs has improved selectivity, safety, and long-term benefit with many severe diseases, and can be regarded as an innovative strategy of physical combination. This review discusses some successful examples to briefly present the principles from the perspective of medicinal chemistry and therapeutic application.

Synthesis, evaluation and proteomic analysis of PROTAC based on parthenolide / 药学学报

As a natural product with a long history of medicinal use, parthenolide has aroused great interest of chemists and biologists. Existing studies have shown that it has anti-inflammatory, antitumor and other pharmacological activities, and also revealed its action on NF-κB signaling pathway, DNMT1 enzyme and Wnt/β-catenin signaling pathway. But its biological targets remain to be elucidated systematically. Proteolysis Targeting Chimeras (PROTAC) provides a new strategy for target discovery of natural products, which can be used to explore the panorama of protein changes in cells through proteomic investigation, so as to analyze their potential targets. Based on this idea, current study designed and synthesized 20 parthenolide-derived degraders. After measured their antitumor activity in vitro, selected compounds were carried out the proteomic experiment. Finally, 139 down-regulated differentially expressed proteins were identified and the discovery of parthenolide interacting protein was preliminarily explored.

Construction of albumin nanoparticles loading PROTAC and its inhibition effect on NAD+ in glioma cells / 药学实践杂志

Objective To prepare and optimize the formulation of Albumin nanoparticles loading PROTAC molecule and observe the inhibition effect of nanoparticles on the proliferation and NAD+ metabolism of glioma cells. Methods Albumin nanoparticles loading NPT-B2 were prepared and characterized with a thermal driving method, and the prescription was optimized. An HPLC method was established to determine the content of NPT-B2. The proliferation inhibition of NPT-B2 and B2-BSA-NPs on U251 cells were investigated by the CCK8 method, and the degradation effects of NPT-B2 and B2-BSA-NPs on NAMPT in glioma cells were investigated by western blotting. Results The HPLC method was stable, with good linearity, precision, and recovery rate. The nanoparticles had a particle size of about 55.48 nm, a potential of about −12.9 mV, an encapsulation rate of about 94.74%, and a drug loading amount of about 8.61%. The IC50 of NPT-B2 on glioma cells was 61.16 nmol/L, which had a degradation effect on NAMPT. The IC50 of B2-BSA-NPs on glioma was 41.21 nmol/L, which had a very significant degradation effect on NAMPT. Conclusion Albumin nanoparticles loading PROTAC molecules were constructed. The prescription was optimized to improve the drug encapsulation rate, and the low water solubility of PROTAC molecule was improved, which had a significant inhibitory effect on the proliferation and NAD+ energy metabolism of glioma cells.

NAMPT-targeting PROTAC promotes antitumor immunity via suppressing myeloid-derived suppressor cell expansion

Nicotinamide phosphoribosyl transferase (NAMPT) is considered as a promising target for cancer therapy given its critical engagement in cancer metabolism and inflammation. However, therapeutic benefit of NAMPT enzymatic inhibitors appears very limited, likely due to the failure to intervene non-enzymatic functions of NAMPT. Herein, we show that NAMPT dampens antitumor immunity by promoting the expansion of tumor infiltrating myeloid derived suppressive cells (MDSCs) via a mechanism independent of its enzymatic activity. Using proteolysis-targeting chimera (PROTAC) technology, PROTAC A7 is identified as a potent and selective degrader of NAMPT, which degrades intracellular NAMPT (iNAMPT) via the ubiquitin-proteasome system, and in turn decreases the secretion of extracellular NAMPT (eNAMPT), the major player of the non-enzymatic activity of NAMPT. In vivo, PROTAC A7 efficiently degrades NAMPT, inhibits tumor infiltrating MDSCs, and boosts antitumor efficacy. Of note, the anticancer activity of PROTAC A7 is superior to NAMPT enzymatic inhibitors that fail to achieve the same impact on MDSCs. Together, our findings uncover the new role of enzymatically-independent function of NAMPT in remodeling the immunosuppressive tumor microenvironment, and reports the first NAMPT PROTAC A7 that is able to block the pro-tumor function of both iNAMPT and eNAMPT, pointing out a new direction for the development of NAMPT-targeted therapies.

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.

Homo-PROTAC mediated suicide of MDM2 to treat non-small cell lung cancer

The dose-related adverse effects of MDM2‒P53 inhibitors have caused significant concern in the development of clinical safe anticancer agents. Herein we report an unprecedented homo-PROTAC strategy for more effective disruption of MDM2‒P53 interaction. The design concept is inspired by the capacity of sub-stoichiometric catalytic PROTACs enabling to degrade an unwanted protein and the dual functions of MDM2 as an E3 ubiquitin ligase and a binding protein with tumor suppressor P53. The new homo-PROTACs are designed to induce self-degradation of MDM2. The results of the investigation have shown that PROTAC

Degradation of proteins by PROTACs and other strategies

Blocking the biological functions of scaffold proteins and aggregated proteins is a challenging goal. PROTAC proteolysis-targeting chimaera (PROTAC) technology may be the solution, considering its ability to selectively degrade target proteins. Recent progress in the PROTAC strategy include identification of the structure of the first ternary eutectic complex, extra-terminal domain-4-PROTAC-Von-Hippel-Lindau (BRD4-PROTAC-VHL), and PROTAC ARV-110 has entered clinical trials for the treatment of prostate cancer in 2019. These discoveries strongly proved the value of the PROTAC strategy. In this perspective, we summarized recent meaningful research of PROTAC, including the types of degradation proteins, preliminary biological data in vitro and in vivo, and new E3 ubiquitin ligases. Importantly, the molecular design, optimization strategy and clinical application of candidate molecules are highlighted in detail. Future perspectives for development of advanced PROTAC in medical fields have also been discussed systematically.

Small-molecule MDM2/X inhibitors and PROTAC degraders for cancer therapy: advances and perspectives

Blocking the MDM2/X-P53 protein-protein interaction has been widely recognized as an attractive therapeutic strategy for the treatment of cancers. Numerous small-molecule MDM2 inhibitors have been reported since the release of the structure of the MDM2-P53 interaction in 1996, SAR405838, NVP-CGM097, MK-8242, RG7112, RG7388, DS-3032b, and AMG232 currently undergo clinical evaluation for cancer therapy. This review is intended to provide a comprehensive and updated overview of MDM2 inhibitors and proteolysis targeting chimera (PROTAC) degraders with a particular focus on how these inhibitors or degraders are identified from starting points, strategies employed, structure-activity relationship (SAR) studies, binding modes or co-crystal structures, biochemical data, mechanistic studies, and preclinical/clinical studies. Moreover, we briefly discuss the challenges of designing MDM2/X inhibitors for cancer therapy such as dual MDM2/X inhibition, acquired resistance and toxicity of P53 activation as well as future directions.

The application of small molecule PROTAC in researches of different targets / 药学学报

The protein proteolysis-targeting chimeras (PROTAC) are a kind of bifunctional compound that can recruit target proteins and degrade the enzyme of target proteins. The mechanism of PROTAC is using the ubiquitin-proteasome pathway to degrade target protein specifically. Because of its potential to target non-proprietary proteins and to play roles in drug resistance, PROTAC has attracted wide attention. This review summarizes the application of small molecule PROTAC in previous studies of different targets, such as nuclear proteins, membrane proteins and cytoplasmic proteins.

A brief analysis of bifunctional molecules / 药学学报

Selectivity of drug action is a determinant for wide therapeutic window and less adverse response. From the viewpoint of molecular structure the conception and strategy of drug design are mainly embodied in raising selectivity. For the target-based drug discovery it is crucial to precisely obliterate detrimental targets in dimension of time and space, so as to efficaciously translate the in vitro active compounds into in vivo therapeutic medicines. To realize this translation drug molecules must be accurately transported to and destroy the harmful targets. To this end, chemical structures of drugs must be manipulated in multiple dimensions. This article attempts to concisely describe several kinds of bifunctional molecules for raising selectivity from the standpoint of medicinal chemistry. The bifunctionality of antibody-drug conjugates (ADCs) involves in the guidance and carrier of the antibody to guide ADC and reach to target cells, and simultaneously injury quality of the toxin moiety of ADC interacts with and destroys targets. Based upon target 3D structures design of irreversible inhibitors consist in connecting an appropriate electrophilic moiety to a well-defined ligand to endow the molecule with an additional ability to covalently bond to a specific amino acid residue. Hydrophobic tag (HyT), proteosis-targeting chimera (PROTAC), and degradation tag (dTAG) are new developed technologies, which are structurally characterized by bifunctionality, and mechanistically these compounds are capable of recruiting protein of interest (POI), inducing protein-protein interaction (PPI), and cleaving POI. In spite of large molecular size and the bottleneck of pharmacokinetic and physicochemical properties these technologies still have broad development prospect owing to high selectivity and wide adaptations.

Evaluation for endogenous anticoagulation potential of bone fracture patients with deep venous thrombosis formation / 临床检验杂志

Objective To evaluate the endogenous anticoagulation potential of bone fracture patients and its relationship with deep venous thrombosis formation (DVT).Methods A total of 95 DVT patients after bone fracture and 100 healthy subjects as control from Beijing Jishuitan Hospital were included in this study.On the third day after orthopedic surgery,the citrated anticoagulant plasma samples were collected and fibrin degradation products (FDP) and D-dimer (DD) were measured.Protac-induced coagulation inhibition percentage (PICI) was measured with ThromboPath (ThP) chromogenic assay as the marker of endogenous anticoagulation potential.The serum samples from patients were collected to measure the concentration of high-density lipoprotein cholesterol (HDL-C).Results Both FDP and DD values of DVT patient group were significantly higher than those of healthy control group (all P ＜ 0.01).The PICI (％) of DVT patients group was significantly lower than that of healthy control group (82.8 ± 7.2 vs 87.8 ± 3.6,P ＜ 0.01).The PICI of patients ≥65 years old was 4.8 percent lower than that of the patients ＜65 years old (P ＜0.05) in DVT group.When the cut-off value for PICI was set as 84.2％,a significant difference was showed between DVT and control group by Chi-Square test (P ＜0.0 1).PICI was negatively correlated with FDP and DD (r =-0.318,-0.336,both P ＜ 0.01),but positively correlated with HDLC (r =0.284,P ＜ 0.01).Logistic regression analysis suggested that PICI was a risk factor of DVT with odds ratio 1.243 (P ＜ 0.01).Conclusion The endogenous anticoagulation potential may be severely impaired in DVT patient after bone fracture.