An orally bioavailable SARS-CoV-2 main protease inhibitor exhibits improved affinity and reduced sensitivity to mutations.

Inhibitors of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) main protease (Mpro) such as nirmatrelvir (NTV) and ensitrelvir (ETV) have proven effective in reducing the severity of COVID-19, but the presence of resistance-conferring mutations in sequenced viral genomes raises concerns about future drug resistance. Second-generation oral drugs that retain function against these mutants are thus urgently needed. We hypothesized that the covalent hepatitis C virus protease inhibitor boceprevir (BPV) could serve as the basis for orally bioavailable drugs that inhibit SARS-CoV-2 Mpro more efficiently than existing drugs. Performing structure-guided modifications of BPV, we developed a picomolar-affinity inhibitor, ML2006a4, with antiviral activity, oral pharmacokinetics, and therapeutic efficacy similar or superior to those of NTV. A crucial feature of ML2006a4 is a derivatization of the ketoamide reactive group that improves cell permeability and oral bioavailability. Last, ML2006a4 was found to be less sensitive to several mutations that cause resistance to NTV or ETV and occur in the natural SARS-CoV-2 population. Thus, anticipatory design can preemptively address potential resistance mechanisms to expand future treatment options against coronavirus variants.

Optically activated MEK1/2 inhibitors (Opti-MEKi) as potential antimelanoma agents.

Mitogen-activated protein kinase kinases 1/2 (MEK1/2) play critical roles in the canonical RAS/RAF/MEK/ERK pathway. Highly selective and potent non-ATP-competitive allosteric MEK1/2 inhibitors have been developed, and three of them were clinically approved for the treatment of BRAFV600 -mutant melanoma. However, the accompanying side effects of the systemically administered MEK1/2 drugs largely constrain their tolerable doses and efficacy. In this study, a series of mirdametinib-based optically activatable MEK1/2 inhibitors (opti-MEKi) were designed and synthesized. A structural-based design led to the discovery of photocaged compounds with dramatically diminished efficacy in vitro, whose activities can be spatiotemporally induced by short durations of irradiation of ultraviolet (365 nm) light. We demonstrated the robust photoactivation of MEK1/2 inhibition and antimelanoma activity in cultured human cells, as well as in a xenograft zebrafish model. Taken together, the modular approach presented herein provides a method for the optical control of MEK1/2 inhibitor activity, and these data support the further development of optically activatable agents for light-mediated antimelanoma phototherapy.

Discovery of quinazoline derivatives CZw-124 as a pan-TRK inhibitor with potent anticancer effects in vitro and in vivo.

Herein, we report the discovery process and antitumor activity of the TRK inhibitor CZw-124 (8o), which is a quinazoline derivative. Starting from a PAK4 inhibitor, we used various drug design strategies, including pharmacophore feature supplementation, F-scanning, and blocking metabolic sites, and finally found a TRK inhibitor CZw-124 that is effective in vitro and in vivo. Docking studies and molecular dynamics simulations revealed a possible mode of binding of CZw-124 to TRKA. Biological activity evaluation showed that CZw-124 belongs to a class of pan-TRK inhibitors with moderate kinase selectivity. It inhibited the proliferation and induced the apoptosis of Km-12 cells in vitro by interfering with the phosphorylation of TRKA. Pharmacodynamic evaluation in vivo showed that CZw-124 had a tumor inhibition rate comparable to that of larotrectinib after oral administration of 40 mg/kg/d (tumor growth inhibiton = 71%).

Discovery of 7H-pyrrolo[2,3-d]pyridine derivatives as potent FAK inhibitors: Design, synthesis, biological evaluation and molecular docking study.

Focal adhesion kinase (FAK) is an intracellular non-receptor tyrosine kinase responsible for development of various tumor types. Aiming to explore new potent inhibitors, two series of 2,4-disubstituted-7H-pyrrolo[2,3-d]pyrimidine derivatives were designed and synthesized on the base of structure-based design strategy. Biological evaluation indicated that most of these new compounds could potently inhibit FAK kinase, leading to the promising inhibitors against the proliferation of U-87MG, A-549, and MDA-MB-231 cancer cell lines. Among them, the optimized compound 18h potently inhibited the enzyme (IC50 = 19.1 nM) and displayed stronger potency than TAE-226 in U-87MG, A-549 and MDA-MB-231 cells, with IC50 values of 0.35, 0.24, and 0.34 µM, respectively. Compound 18h is a multi-target kinase inhibitor. Furthermore, compound 18h also exhibited relatively less cytotoxicity (IC50 = 3.72 µM) toward a normal human cell line, HK2. According to the flow cytometry and wound healing assay results, compound 18h effectively induced apoptosis and G0/G1 phase arrest of MDA-MB-231 cells and suppressed the migration of U-87MG, A-549 and MDA-MB-231 cells. The docking study of compound 18h was performed to elucidate its possible binding modes and to provide a structural basis for the further structural guidance design of FAK inhibitors. Collectively, these data support the further development of compound 18h as a lead compound for FAK-targeted anticancer drug discovery.

Design, synthesis, biological evaluation and molecular docking study of novel thieno[3,2-d]pyrimidine derivatives as potent FAK inhibitors.

A series of 2,7-disubstituted-thieno[3,2-d]pyrimidine derivatives were designed, synthesized and evaluated as novel focal adhesion kinase (FAK) inhibitors. The novel 2,7-disubstituted-thieno[3,2-d]pyrimidine scaffold has been designed as a new kinase inhibitor platform that mimics the bioactive conformation of the well-known diaminopyrimidine motif. Most of the compounds potently suppressed the enzymatic activities of FAK and potently inhibited the proliferation of U-87MG, A-549 and MDA-MB-231 cancer cell lines. Among these derivatives, the optimized compound 26f potently inhibited the enzyme (IC50 = 28.2 nM) and displayed stronger potency than TAE-226 in U-87MG, A-549 and MDA-MB-231 cells, with IC50 values of 0.16, 0.27, and 0.19 µM, respectively. Compound 26f also exhibited relatively less cytotoxicity (IC50 = 3.32 µM) toward a normal human cell line, HK2. According to the flow cytometry results, compound 26f induced the apoptosis of MDA-MB-231 cells in a dose-dependent manner and effectively arrested MDA-MB-231 cells in G0/G1 phase. Further investigations revealed that compound 26f potently suppressed the migration of MDA-MB-231 cells. Collectively, these data support the further development of compound 26f as a lead compound for FAK-targeted anticancer drug discovery.

Design, synthesis, biological evaluation and molecular modeling of novel 1H-pyrrolo[2,3-b]pyridine derivatives as potential anti-tumor agents.

A class of 3-substituted 1H-pyrrolo[2,3-b]pyridine derivatives were designed, synthesized and evaluated for their in vitro biological activities against maternal embryonic leucine zipper kinase (MELK). Among these derivatives, the optimized compound 16h exhibited potent enzyme inhibition (IC50 = 32 nM) and excellent anti-proliferative effect with IC50 values from 0.109 µM to 0.245 µM on A549, MDA-MB-231 and MCF-7 cell lines. The results of flow cytometry indicated that 16h promoted apoptosis of A549 cells in a dose-dependent manner and effectively arrested A549 cells in the G0/G1 phase. Further investigation indicated that compound 16h potently suppressed the migration of A549 cells, had moderate stability in rat liver microsomes and showed moderate inhibitory activity against various subtypes of human cytochrome P450. However, compound 16h is a multi-target kinase inhibitor and recently several studies reported MELK expression is not required for cancer growth, suggesting that compound 16h suppressed the proliferation and migration of cancer cells should through an off-target mechanism. Collectively, compound 16h has the potential to serve as a new lead compound for further anticancer drug discovery.

Synthesis, bioconversion, pharmacokinetic and pharmacodynamic evaluation of N-isopropyl-oxy-carbonyloxymethyl prodrugs of CZh-226, a potent and selective PAK4 inhibitor.

We have previously disclosed compound 3 (CZh-226), a potent and selective PAK4 inhibitor, but its development was delayed due to poor oral pharmacokinetics. In an attempt to improve this issue, we synthesised a series of prodrugs by masking its terminal nitrogen of the piperazine moiety. Most synthesised prodrugs of 3 have low or no inhibition of PAK4 activity. The stability of synthetic prodrugs was evaluated in PBS, SGF, SIF, rat plasma and liver S9 fraction. Of these, prodrug 19 was not only stable under both acidic and neutral conditions but also could be quickly converted to parent drug 3 in rat plasma and liver S9 fraction. Such effective conversion into parent drug 3 was observed in rats, providing higher exposure of 3 compared to its direct administration. When given via oral route at daily doses of 25 and 50 mg/kg, the prodrug 19 was effective and well tolerated in mouse model of HCT-116 and B16F10.

Design, synthesis and biological evaluation of novel 7H-pyrrolo[2,3-d]pyrimidine derivatives as potential FAK inhibitors and anticancer agents.

A series of 7H-pyrrolo[2,3-d]pyrimidine derivatives possessing a dimethylphosphine oxide moiety were designed, synthesized and evaluated as novel Focal adhesion kinase (FAK) inhibitors. Most compounds potently suppressed the enzymatic activities of FAK, with IC50 values in the 10-8-10-9 M range, and potently inhibited the proliferation of breast (MDA-MB-231) and lung (A549) cancer cell lines. The representative compound 25b exhibited potent enzyme inhibition (IC50 = 5.4 nM) and good selectivity when tested on a panel of 26 kinases. 25b exhibited antiproliferative activity against A549 cells (IC50 = 3.2 µM) and relatively less cytotoxicity to a normal human cell line HK2. Compound 25b also induced apoptosis and suppressed the migration of A549 cells in a concentration-dependent manner. Further profiling of compound 25b revealed it had good metabolic stability in mouse, rat and human liver microsomes in vitro and showed weak inhibitory activity against various subtypes of human cytochrome P450. The docking study of compound 25b was performed to elucidate its possible binding modes and to provide a structural basis for further structure-guided design of FAK inhibitors.

Design, synthesis, structure-activity relationships study and X-ray crystallography of 3-substituted-indolin-2-one-5-carboxamide derivatives as PAK4 inhibitors.

We have previously described the identification of indolin-2-one-5-carboxamides as potent PAK4 inhibitors. This study expands the structure-activity relationships on our original series by presenting several modifications in the lead compounds, 2 and 3. A series of novel derivatives was designed, synthesized, and evaluated in biochemical and cellular assay. Most of this series displayed nanomolar biochemical activity and potent antiproliferative activity against A549 and HCT116 cells. The representative compound 10a exhibited excellent enzyme inhibition (PAK4 IC50 = 25 nM) and cellular potency (A549 IC50 = 0.58 µM, HCT116 IC50 = 0.095 µM). An X-ray structure of compound 10a bound to PAK4 was obtained. Crystallographic analysis confirmed predictions from molecular modeling and helped refine SAR results. In addition, Compound 10a displayed focused multi-targeted kinase inhibition, good calculated drug-likeness properties. Further profiling of compound 10a revealed it showed weak inhibitory activity against various isoforms of human cytochrome P450.

Design, synthesis and evaluation of benzoheterocycle analogues as potent antifungal agents targeting CYP51.

To further enhance the anti-Aspergillus efficacy of our previously discovered antifungal lead compound 1, a series of benzoheterocycle analogues were designed, synthesized and evaluated for their in vitro antifungal activity. The most promising compounds 13s and 14a exhibited excellent antifungal activity against C. albicans, C. neoformans, A. fumigatus and fluconazole-resistant C. albicans strains, that was superior or comparable to those of the reference drugs fluconazole and voriconazole. GC-MS analyses suggested that the novel compound 13s might have a similar mechanism to fluconazole by inhibiting fungal lanosterol 14α-demethylase (CYP51). Furthermore, compounds 13s and 14a exhibited low inhibition profiles for various human cytochrome P450 isoforms as well as excellent blood plasma stability.

The therapeutic potential of CETP inhibitors: a patent review.

INTRODUCTION: Epidemiological studies have identified that high levels of low-density lipoprotein-cholesterol (LDL-C) and low levels of high-density lipoprotein-cholesterol (HDL-C) are two independent causes of cardiovascular disease (CVD). Statins, niacin and fibrate are used for the treatment of CVD. However, some defects are shown in the treatment process. Thus, there is a demand for better treatment strategies that confer preferable efficacy with fewer side effects. Cholesteryl ester transfer protein (CETP) promotes the movement of CEs from HDL to LDL and VLDL in exchange for triglycerides (TGs). AREAS COVERED: In this review, we reviewed the development and therapeutic applications of CETP inhibitors. A comprehensive review of the patents and pharmaceutical applications between 2009 and 2017 has been highlighted. EXPERT OPINION: Recently, CETP inhibitors have attracted considerable interest in atherosclerosis-related disease. There are four drugs (torcetrapib, anacetrapib, evacetrapib and dalcetrapib) that have been clinically evaluated in phase III clinical trials and showed promising results in raising HDL-C levels, but there were suboptimal performances in reducing the risk of cardiovascular events with all the compounds. The correlation between plasma HDL-C levels and CVD incidence needs further verification. The timeline is still long for CETP inhibitors to emerge from the treatment of CVD.

Discovery of 2-(4-Substituted-piperidin/piperazine-1-yl)-N-(5-cyclopropyl-1H-pyrazol-3-yl)-quinazoline-2,4-diamines as PAK4 Inhibitors with Potent A549 Cell Proliferation, Migration, and Invasion Inhibition Activity.

A series of novel 2,4-diaminoquinazoline derivatives were designed, synthesized, and evaluated as p21-activated kinase 4 (PAK4) inhibitors. All compounds showed significant inhibitory activity against PAK4 (half-maximal inhibitory concentration IC50 < 1 µM). Among them, compounds 8d and 9c demonstrated the most potent inhibitory activity against PAK4 (IC50 = 0.060 µM and 0.068 µM, respectively). Furthermore, we observed that compounds 8d and 9c displayed potent antiproliferative activity against the A549 cell line and inhibited cell cycle distribution, migration, and invasion of this cell line. In addition, molecular docking analysis was performed to predict the possible binding mode of compound 8d. This series of compounds has the potential for further development as PAK4 inhibitors for anticancer activity.

Structure-Based Design of 6-Chloro-4-aminoquinazoline-2-carboxamide Derivatives as Potent and Selective p21-Activated Kinase 4 (PAK4) Inhibitors.

Herein, we report the discovery and characterization of a novel class of PAK4 inhibitors with a quinazoline scaffold. Based on the shape and chemical composition of the ATP-binding pocket of PAKs, we chose a 2,4-diaminoquinazoline series of inhibitors as a starting point. Guided by X-ray crystallography and a structure-based drug design (SBDD) approach, a series of novel 4-aminoquinazoline-2-carboxamide PAK4 inhibitors were designed and synthesized. The inhibitors' selectivity, therapeutic potency, and pharmaceutical properties were optimized. One of the best compounds, 31 (CZh226), showed remarkable PAK4 selectivity (346-fold vs PAK1) and favorable kinase selectivity profile. Moreover, this compound potently inhibited the migration and invasion of A549 tumor cells by regulating the PAK4-directed downstream signaling pathways in vitro. Taken together, these data support the further development of 31 as a lead compound for PAK4-targeted anticancer drug discovery and as a valuable research probe for the further biological investigation of group II PAKs.

LC-0882 targets PAK4 and inhibits PAK4-related signaling pathways to suppress the proliferation and invasion of gastric cancer cells.

Gastric cancer is the most common malignant tumor and globally the third leading cause of cancer-related deaths. Therefore, there exists an urgent need to identify new effective gastric cancer treatments. Given the important roles in tumorigenesis and progression, p21-activated kinase 4 (PAK4) has been regarded as an attractive high-value druggable target. In this study, we examined the effects and molecular mechanisms of action of the small molecular compound LC-0882 on gastric cancer cells in vitro. LC-0882 was found to significantly inhibit the proliferation of human gastric cancer cells by repressing phospho-PAK4/cyclin D1 and CDK4/6 expression. In addition, LC-0882 was found to attenuate cell invasion by blocking the PAK4/LIMK1/cofilin signaling pathway. Finally, analysis of immunofluorescence revealed that LC-0882 exposure decreased filopodia formation and induced cell elongation in BGC823 and SGC7901 gastric cancer cells. These findings suggest that targeting PAK4 with the novel compound LC-0882 may provide a new chemotherapeutic approach in gastric cancer treatment.

Design, synthesis and evaluation of aromatic heterocyclic derivatives as potent antifungal agents.

To further enhance the anti-Aspergillus efficacy of our previously discovered antifungal lead compounds (1), a series of aromatic heterocyclic derivatives were designed, synthesized and evaluated for in vitro antifungal activity. Many of the target compounds showed good inhibitory activity against Candida albicans and Cryptococcus neoformans. In particular, the isoxazole nuclei were more suited for improving the activity against Aspergillus spp. Among these compounds, 2-F substituted analogues 23g and 23h displayed the most remarkable in vitro activity against Candida spp., C. neoformans, A. fumigatus and fluconazole-resistant C.alb. strains, which is superior or comparable to the activity of the reference drugs fluconazole and voriconazole. Notably, the compounds 23g and 23h exhibited low inhibition profiles for various isoforms of human cytochrome P450 and excellent blood plasma stability.

Discovery of indolin-2-one derivatives as potent PAK4 inhibitors: Structure-activity relationship analysis, biological evaluation and molecular docking study.

Utilizing a pharmacophore hybridization approach, a novel series of substituted indolin-2-one derivatives were designed, synthesized and evaluated for their in vitro biological activities against p21-activated kinase 4. Compounds 11b, 12d and 12g exhibited the most potent inhibitory activity against PAK4 (IC50=22nM, 16nM and 27nM, respectively). Among them, compound 12g showed the highest antiproliferative activity against A549 cells (IC50=0.83µM). Apoptosis analysis in A549 cells suggested that compound 12g delayed cell cycle progression by arresting cells in the G2/M phase of the cell cycle, retarding cell growth. Further investigation demonstrated that compound 12g strongly inhibited migration and invasion of A549 cells. Western blot analysis indicated that compound 12g potently inhibited the PAK4/LIMK1/cofilin signalling pathways. Finally, the binding mode between compound 12g with PAK4 was proposed by molecular docking. A preliminary ADME profile of the compound 12g was also drawn on the basis of QikProp predictions.

Development of 2, 4-diaminoquinazoline derivatives as potent PAK4 inhibitors by the core refinement strategy.

Upon analysis of the reported crystal structure of PAK4 inhibitor KY04031 (PAK4 IC50 = 0.790 µM) in the active site of PAK4, we investigated the possibility of changing the triazine core of KY04031 to a quinazoline. Using KY04031 as a starting compound, a library of 2, 4-diaminoquinazoline derivatives were designed and synthesized. These compounds were evaluated for PAK4 inhibition, leading to the identification of compound 9d (PAK4 IC50 = 0.033 µM). Compound 9d significantly induced the cell cycle in the G1/S phase and inhibited migration and invasion of A549 cells that over-express PAK4 via regulation of the PAK4-LIMK1 signalling pathway. A docking study of compound 9d was performed to elucidate its possible binding modes and to provide a structural basis for further structure-guided design of PAK4 inhibitors. Compound 9d may serve as a lead compound for anticancer drug discovery and as a valuable research probe for further biological investigation of PAK4.

Discovery of biphenyl imidazole derivatives as potent antifungal agents: Design, synthesis, and structure-activity relationship studies.

Fungal infections have became a serious medical problem due to their high incidence and mortality. We describe the discovery and structure-activity relationships studies (SARs) of a series of novel biphenyl imidazole derivatives with excellent antifungal activities against Candida albicans and Cryptococcus neoformans. The most promising compounds 12f-g and 19a-b exhibited excellent activity with minimum inhibitory concentration (MIC) values in the range of 0.03125-2µg/mL. Preliminary mechanism studies showed that the potent antifungal activity of compound 12g stemed from inhibition of CYP51 in Candida albicans. Furthermore, compounds 12g and 19b exhibited low inhibition profiles for various human cytochrome P450 isoforms. The SARs and binding mode established in this study will be useful for further lead optimization.

Design, synthesis, and structure-activity relationship studies of benzothiazole derivatives as antifungal agents.

A series of compounds with benzothiazole and amide-imidazole scaffolds were designed and synthesized to combat the increasing incidence of drug-resistant fungal infections. The antifungal activity of these compounds was evaluated in vitro, and their structure-activity relationships (SARs) were evaluated. The synthesized compounds showed excellent inhibitory activity against Candida albicans and Cryptococcus neoformans. The most potent compounds 14o, 14p, and 14r exhibited potent activity, with minimum inhibitory concentration (MIC) values in the range of 0.125-2 µg/mL. Preliminary mechanism studies revealed that the compound 14p might act by inhibiting the CYP51 of Candida albicans. The SARs and binding mode established in this study are useful for further lead optimization.

Design, synthesis and biological evaluation of novel cholesteryl ester transfer protein inhibitors bearing a cycloalkene scaffold.

Cholesteryl ester transfer protein (CETP) is a potential target for cardiovascular disease therapy as inhibition of CETP leads to increased HDL-C in humans. Based on the structure of Merck's biphenyl CETP inhibitor, we designed novel N,N-substituted-cycloalkenyl-methylamine scaffold derivatives by utilizing core replacement and conformational restriction strategies. Consequently, twenty-eight compounds were synthesized and evaluated for their inhibitory activity against CETP. Their preliminary structure-activity relationships (SARs) studies indicate that polar substituents were tolerated in moiety A and hydrophobic alkyl groups at the 5-position of cyclohexene were critical for potency. Among them, compound 17a, bearing an N-(5-pyrazolyl-pyrimidin-2-yl)-cycloalkenyl- methylamine scaffold, exhibited excellent CETP inhibitory activity (IC50 = 0.07 µM) in vitro. Furthermore, it showed an acceptable pharmacokinetic profile in S-D rats and efficient HDL-C increase in high-fat fed hamsters.