Research Progress in the Use of Small Molecule Smac Mimetics in Combination Therapy of Cancer.

Inhibitors of Apoptosis Proteins (IAP) are inhibitors that can block programmed cell death, are expressed at high levels in various cancers, and are recognized as a therapeutic target for cancer therapy. In the past few years, several small molecule IAP protein inhibitors have been designed to mimic the endogenous IAP antagonist, but no IAP inhibitors have been approved for marketing worldwide. Previously, xevinapant has been awarded a breakthrough therapy designation by the FDA. In addition, a combination of Smac-mimetics and chemotherapeutic compounds has been reported to improve anticancer efficacy. According to the phase II clinical data, xevinapant has the potential to significantly enhance the standard therapy for patients with head and neck cancer, which is expected to be approved as an innovative therapy for cancer patients. Therefore, this paper briefly describes the mechanism of IAPs (AT-406, APG-1387, GDC- 0152, TL32711, and LCL161) as single or in combination for cancer treatment, their application status as well as the synthetic pathway, and explores the research prospects and challenges of IAPs antagonists in the tumor combination therapy, with the hope of providing strong insights into the further development of Smac mimics in tumor therapy.

Current status of drugs targeting PDGF/PDGFR.

As an important proangiogenic factor, platelet-derived growth factor (PDGF) and its receptor PDGFR are highly expressed in a variety of tumors, fibrosis, cardiovascular and neurodegenerative diseases. Targeting the PDGF/PDGFR pathway is therefore a promising therapeutic strategy. At present, a variety of PDGF/PDGFR targeted drugs with potential therapeutic effects have been developed, mainly including PDGF agonists, inhibitors targeting PDGFR and proteolysis targeting chimera (PROTACs). This review clarifies the structure, biological function and disease correlation of PDGF and PDGFR, and it discusses the current status of PDGFR-targeted drugs, so as to provide a reference for subsequent research.

A New Dawn for Targeted Cancer Therapy: Small Molecule Covalent Binding Inhibitor Targeting K-Ras (G12C).

K-Ras is a frequently mutated oncogene in human malignancies, and the development of inhibitors targeting various oncogenic K-Ras mutant proteins is a major challenge in targeted cancer therapy, especially K-Ras(G12C) is the most common mutant, which occurs in pancreatic ductal adenocarcinoma (PDAC), non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and other highly prevalent malignancies. In recent years, significant progress has been made in developing small molecule covalent inhibitors targeting K-Ras(G12C), thanks to the production of nucleophilic cysteine by the G12C mutant, breaking the "spell" that K-Ras protein cannot be used as a drug target. With the successful launch of sotorasib and adagrasib, the development of small molecule inhibitors targeting various K-Ras mutants has continued to gain momentum. In recent years, with the popularization of highly sensitive surface plasmon resonance (SPR) technology, fragment-based drug design strategies have shown great potential in the development of small molecule inhibitors targeting K-Ras(G12C), but with the increasing number of clinically reported acquired drug resistance, addressing inhibitor resistance has gradually become the focus of this field, indirectly indicating that such small molecule inhibitors still the potential for the development of these small molecule inhibitors are also indirectly indicated. This paper traces the development of small molecule covalent inhibitors targeting K-Ras(G12C), highlighting and analyzing the structural evolution and optimization process of each series of inhibitors and the previous inhibitor design methods and strategies, as well as their common problems and general solutions, in order to provide inspiration and help to the subsequent researchers.

Protein Lysine Methyltransferases Inhibitors.

Protein lysine methylation is a significant protein post-translational modification (PTMs) and has a key function in epigenetic regulation. Protein lysine methyltransferase (PKMTs) mainly catalyzes the lysine methylation of various core histones and a few non-histone proteins. It has been observed that aberrant activity of PKMTs has been found in many cancers and other diseases, and some PKMT inhibitors have been discovered and progressed to clinical trials. This field developed rapidly and has aroused great interest. In this paper, we reviewed the biochemical and biological activities of PKMTs and their association with various cancers. Selective small-molecule inhibitors, including their chemical structure, structure-activity relationship, and in vitro/vivo studies, are also described to provide ideas for the discovery of highly potent, selective PKMT inhibitors.

Research Progress in Competitive Purine Antagonists.

Purine, one of the nucleotides, is an important substance for the metabolism and regulation of the body. Purine plays a key role not only in the composition of coenzymes but also in the supply of energy. Since purine was artificially synthesized, it has always been an important scaffold for respiratory diseases, cardiovascular diseases, and anti- tumor and anti-viral drugs. In addition to being widely used as competitive antagonists in the treatment of diseases, purines can be used in combination with other drugs and as precursors to benefit human life. Unfortunately, few new discoveries have been made in recent years. In this article, purine drugs in the market have been classified according to their different targets. In addition, their mechanism of action and structure-activity relationship have also been introduced. This paper provides details of the signaling pathways through which purine drugs can bind to the respective receptors on the surface of cells and cause consequent reactions within the cell, which finally affect the targeted diseases. The various receptors and biological reactions involved in the signaling for respective disease targets within the cells are discussed in detail.

Design, synthesis and biological characteristics of pyrazolo[3,4-d]pyrimidine derivatives as potential VEGFR-2 inhibitors.

Aim: Several VEGFR-2 inhibitors with the structure of [3,4-d]pyrimidine and based on sorafenib were designed and synthesized. Materials & methods: Cytotoxic activity was evaluated by MTT, wound healing and clone formation assays. Cell cycle and apoptosis were analyzed by flow cytometry. Molecular simulation and western blot were also applied. Results: Among them, II-1 significantly inhibited tumor cellular activity (IC50 = 5.90 ± 0.05 µM on HepG2 cells) compared with sorafenib (IC50 = 9.05 ± 0.54 µM on HepG2 cells). Molecular docking demonstrated that II-1 and sorafenib have the same hydrogen binding. Finally, the protein expression of phosphorylated VEGFR-2 was substantially reduced after II-1 treatment. Conclusion: Compound II-1 can inhibit VEFGR-2 activation and is an effective antitumor agent in liver cancer cells.

Protein Lysine Methyltransferase SMYD2: A Promising Small Molecule Target for Cancer Therapy.

In epigenetic research, the abnormality of protein methylation modification is closely related to the occurrence and development of tumors, which stimulates the interest of researchers in protein methyltransferase research and the efforts to develop corresponding specific small molecule inhibitors. Currently, the protein lysine methyltransferase SMYD2 has been identified as a promising new small molecule target for cancer therapy. But its biological functions have not been fully studied and relatively few inhibitors have been reported, thus this field needs to be further explored. This perspective provides a comprehensive and systematic review of the available resources in this field, including its research status, biological structure, related substrates and methylation mechanisms, and research status of inhibitors. In addition, this perspective elaborates in detail the current challenges in this field, our insights into what needs to be done next, rational drug design of novel SMYD2 inhibitors, and foreseeable development directions in the future.

New application of novel tetrazine derivatives as potent VEGFR-2 kinase inhibitors and anti-cancer agents.

Background: A novel series of s-tetrazine derivatives was designed as a new scaffold and synthesized efficiently as VEGFR-2 inhibitors for the first time. Methodology & results: The inhibitory activities of the new compounds were tested by MTT assay and enzyme assay, respectively. Western blot assay, cell apoptosis assay and cell migration assay were carried out to study the action mechanism of them. All the synthesized compounds showed evident VEGFR-2 inhibitory activities (IC50 in the range of 88.53-257.55 nM). Compounds 23h, 25d, 26e and 27c showed excellent anti-proliferative activities against the four tested cell lines and were better than sorafenib basically. Conclusion: Compounds with good activities based on this novel scaffold can be screened successfully.

Structure-Activity Relationships and Antileukemia Effects of the Tricyclic Benzoic Acid FTO Inhibitors.

The N6-methyladenosine (m6A) demethylase FTO is overexpressed in acute myeloid leukemia (AML) cells and promotes leukemogenesis. We previously developed tricyclic benzoic acid FB23 as a highly potent FTO inhibitor in vitro. However, it showed a moderate antiproliferative effect on AML cells. In this work, we performed a structure-activity relationship study of tricyclic benzoic acids as FTO inhibitors. The analog 13a exhibited excellent inhibitory effects on FTO similar to that of FB23 in vitro. In contrast to FB23, 13a exerted a strong antiproliferative effect on AML cells. Like FTO knock down, 13a upregulated ASB2 and RARA expression and increased the protein abundance while it downregulated MYC expression and decreased MYC protein abundance. These genes are key FTO targets in AML cells. Finally, 13a treatment improved the survival rate of MONOMAC6-transplanted NSG mice. Collectively, our data suggest that targeting FTO with tricyclic benzoic acid inhibitors may be a potential strategy for treating AML.

Targeting Janus Kinase (JAK) for Fighting Diseases: The Research of JAK Inhibitor Drugs.

Janus Kinase (JAK), a nonreceptor protein tyrosine kinase, has emerged as an excellent target through research and development since its discovery in the 1990s. As novel small-molecule targeted drugs, JAK inhibitor drugs have been successfully used in the treatment of rheumatoid arthritis (RA), myelofibrosis (MF), and ulcerative colitis (UC). With the gradual development of JAK targets in the market, JAK inhibitors have also received considerable feedback in the treatment of autoimmune diseases, such as atopic dermatitis (AD), Crohn's disease (CD), and graft-versus-host disease (GVHD). This article reviews the research progress of JAK inhibitor drugs, focusing on the existing JAK inhibitors in the market and some JAK inhibitors in clinical trials currently. In addition, the synthesis of various types of JAK inhibitors and the effects of different drug structures on drug inhibition and selectivity are summarized.

Molecules Containing Cyclobutyl Fragments as Therapeutic Tools: A Review on Cyclobutyl Drugs.

In recent years, cyclobutyl has become more influential in the field of drug design. Its unique four-membered ring structure is not only a useful intermediate for the synthesis of biomedical candidate materials but also an indispensable framework for drug design and application. According to the therapeutic field, cyclobutyl drugs are roughly divided into tumor and cancer drugs, nervous system drugs, analgesics, antiviral drugs, and gastrointestinal drugs. Among them, platinum-based anticancer drugs containing cyclobutyl fragments have achieved remarkable success in the treatment of cancer, bringing new hope for the development of more cyclobutyl drugs. This article provides details of the research progress of the structure types, structure-activity relationships, targets, and mechanisms of cyclobutyl drugs that have been on the market or are in the clinical stage and provides ideas for the discovery and synthesis of novel cyclobutyl-containing drugs.

Research Status, Synthesis and Clinical Application of Recently Marketed and Clinical BCR-ABL Inhibitors.

Tyrosine kinases expressed by BCR-ABL fusion genes can cause changes in cell proliferation, adhesion, and survival properties, which are the main causes of chronic myelogenous leukemia (CML). Inhibiting the activity of BCR-ABL tyrosine kinase has become one of the effective methods for the treatment of chronic myelogenous leukemia. Initially, imatinib was the first small molecule of BCR-ABL tyrosine kinases inhibitors (TKIs) for the effective treatment of chronic myelogenous leukemia. Later, due to the emergence of various BCR-ABL mutations, especially T315I mutation, imatinib developed strong resistance. The second-generation kinase inhibitors dasatinib and nilotinib were able to overcome most of the mutation resistance but not T315I mutations. Therefore, in order to further overcome the problem of drug resistance, new types of KTIs such as flumatinib and radotinib have been developed, providing more options for clinical treatment. Some new drugs have entered clinical trials. In this review, two new BCRABL inhibitors (flumatinib and radotinib) and five new BCR-ABL inhibitors have been introduced into the clinical market in recent years. We reviewed their research status, synthesis methods, and clinical applications.

Synthesis and Anti-Proliferation Activity Evaluation of Novel 2-Chloroquinazoline as Potential EGFR-TK Inhibitors.

A novel series of 2-chloroquinazoline derivatives had been synthesized and their anti-proliferation activities against the four EGFR high-expressing cells A549, NCI-H1975, AGS and HepG2 cell lines were evaluated. The preliminary SAR study of the scaffold of new compounds showed that the compounds with a chlorine substituent on R3 had a better anti-proliferation activity than those substituted by hydrogen atom or vinyl group. Among them, 2-chloro-N-[2-chloro-4-(3-chloro-4-fluoroanilino)quinazolin-6-yl]acetamide (10b) had the best activity, and the corresponding IC50 were 3.68, 10.06, 1.73 and 2.04 µM, respectively. And compound 10b had better or equivalent activity against four cell lines than Gefitinib. The activity of the compound 10b on the EGFR enzyme was subsequently tested. The Wound Healing of A549, AGS and HepG2 cells by this compound showed that the compound can inhibit the migration of cancer cells. Finally, the action channel of the compound 10b was supported by western blotting experiments. It provides useful information for the design of EGFR-TK inhibitors.

Design, synthesis, biological evaluation and docking study of novel quinazoline derivatives as EGFR-TK inhibitors.

Background: Quinazoline-based compounds have been proved effective in the treatment of cancers for years. Materials & methods: The structural features of several inhibitors of EGFR were integrated and quinazolines with a benzazepine moiety at the 4-position were constructed. Results: Most of the compounds exhibited excellent antitumor activities. Compound 33e showed excellent antitumor activities against the four tested cell lines (IC50: 1.06-3.55 µM). The enzymatic, signaling pathways and apoptosis assay of 33e were subsequently carried out to study the action of the mechanism. Conclusion: Compound 33e with a benzazepine moiety at the 4-position can be screened in this study and provides useful information for the design of EGFR-T790M inhibitors, which deserve additional research.

Anti-angiogenic Agents: A Review on Vascular Endothelial Growth Factor Receptor-2 (VEGFR-2) Inhibitors.

Tumor growth inhibition can be achieved by inhibiting angiogenesis, which has been a field of great concern in recent years. Important targets to inhibit angiogenesis include vascular endothelial growth factor receptor (VEGFR) and its homologous tyrosine kinase receptor. Anti-angiogenic therapy based on inhibition of VEGFR-2 is an effective clinical treatment strategy. The research progress of VEGFR-2 inhibitors is reviewed in this paper from the aspects of drug development and chemical synthesis.

A Review on Poly (ADP-ribose) Polymerase (PARP) Inhibitors and Synthetic Methodologies.

Poly (ADP-ribose) polymerase (PARP) acts as an essential DNA repair enzyme. PARP inhibitors are novel small molecule targeted drugs based on the principle of "Synthetic Lethality", which affect DNA repair process by competitively inhibiting the activity of PARP enzyme and thereby kill cancer cells. Currently, four PARP inhibitors including olaparib, rucaparib, niraparib, and talazoparib have been approved by FDA for cancer treatment and have achieved great success in the treatment of ovarian cancer, breast cancer, and pancreatic cancer, etc. This paper provides a general overview of the research progress of PARP inhibitors including the major structure types, structure-activity relationship (SAR), and synthetic routes, with the aim of providing ideas for the discovery and synthesis of novel PARP inhibitors.

Monoclonal Antibodies, Small Molecule Inhibitors and Antibody-drug Conjugates as HER2 Inhibitors.

Overexpression of human epidermal growth factor receptor (HER)-2 is found in a variety of cancers, often portending poor clinical outcomes. Therefore, HER2 is an attractive target for treatment. This review describes the research progress of HER2 targeted inhibitors in recent years. Excellent reviews are available, so we focus on the development, mechanisms of action, and structure-activity relationships of different types of inhibitors, including monoclonal antibodies, small molecule inhibitors, and antibody-drug conjugates (ADCs). In addition, the differences among them are compared.

Synthesis, structure analysis, antitumor evaluation and 3D-QSAR studies of 3,6-disubstituted-dihydro-1,2,4,5-tetrazine derivatives.

3,6-Diaryl-dihydro-1,2,4,5-tetrazine derivatives were synthesized and their structures were confirmed by single-crystal X-ray diffraction. Monosubstituted dihydrotetrazines are the 1,4-dihydro structure, but disubstituted dihydrotetrazines are the 1,2-dihydro structure. The results of further research indicated there may be a rearrangement during the synthesis process of disubstituted dihydrotetrazines. Their antitumor activities were evaluated against A-549 and P388 cells in vitro. The results showed several compounds to be endowed with cytotoxicity in the low micromolar range. Two compounds were highly effective against A-549 cell and IC50 values were 0.575 and 2.08 µM, respectively. Three-dimensional quantitative structure-activity relationship (3D-QSAR) studies of comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were carried out on 37 1,2,4,5-tetrazine derivatives with antitumor activity against A-549 cell. Models with good predictive abilities were generated with the cross validated q(2) values for CoMFA and CoMSIA being 0.744 and 0.757, respectively. Conventional r(2) values were 0.978 and 0.988, respectively, the predicted R(2) values were 0.916 and 0.898, respectively. The results provide the tool for guiding the design and synthesis of novel and more potent tetrazine derivatives.

Synthesis, antitumor evaluation and docking study of novel 4-anilinoquinazoline derivatives as potential epidermal growth factor receptor (EGFR) inhibitors.

Strike a pose! A series of 4-anilinoquinazolines were designed, synthesized and evaluated in vitro against lung and breast cancer cell lines. Several compounds were found to be endowed with cytotoxicity in the low micromolar range. Molecular docking suggests that these compounds bind to EGFR in a similar manner to known EGFR inhibitors.

Synthesis, structure analysis, and antitumor evaluation of 3,6-dimethyl-1,2,4,5-tetrazine-1,4-dicarboxamide derivatives.

3,6-Dimethyl-1,2,4,5-tetrazine-1,4-dicarboxamide derivatives were synthesized, and their structures were confirmed by single-crystal X-ray diffraction. This reaction yields the 1,4-dicarboxamide derivatives rather than the 1,2-dicarboxamide derivatives. Their in vitro antitumor activities were evaluated against SGC-7901, HO-8910, MCF-7, and A-549 cells. The results showed several compounds to be endowed with cytotoxicity in the low micromolar range. One compound (IC(50) =0.57 µM) was further evaluated in vivo against an A-549 xenograft in BALB/cA nude mice; it effected 76.4% inhibition of tumor weight through intraperitoneal (i.p.) administration of 40 mgkg(-1) body weight. Moreover, its acute toxicity was evaluated, and the i.p. LD(50) value was 325 mgkg(-1) in mice.