Guoqiang Dong

Three-Dimensional Model of Lanosterol 14α-Demethylase from Cryptococcus neoformans: Active-Site Characterization and Insights into Azole Binding

ABSTRACT Cryptococcus neoformans is one of the most important causes of life-threatening fungal infections in immunocompromised patients. Lanosterol 14α-demethylase (CYP51) is the target of azole antifungal agents. This study describes, for the first time, the 3-dimensional model of CYP51 from Cryptococcus neoformans (CnCYP51). The model was further refined by energy minimization and molecular-dynamics simulations. The active site of CnCYP51 was well characterized by multiple-copy simultaneous-search calculations, and four functional regions important for rational drug design were identified. The mode of binding of the natural substrate and azole antifungal agents with CnCYP51 was identified by flexible molecular docking. A G484S substitution mechanism for azole resistance in CnCYP51, which might be important for the conformation of the heme environment, is suggested.

New tricks for an old natural product: discovery of highly potent evodiamine derivatives as novel antitumor agents by systemic structure-activity relationship analysis and biological evaluations.

Evodiamine is a quinazolinocarboline alkaloid isolated from the fruits of traditional Chinese herb Evodiae fructus . Previously, we identified N13-substituted evodiamine derivatives as potent topoisomerase I inhibitors by structure-based virtual screening and lead optimization. Herein, a library of novel evodiamine derivatives bearing various substitutions or modified scaffold were synthesized. Among them, a number of evodiamine derivatives showed substantial increase of the antitumor activity, with GI(50) values lower than 3 nM. Moreover, these highly potent compounds can effectively induce the apoptosis of A549 cells. Interestingly, further computational target prediction calculations in combination with biological assays confirmed that the evodiamine derivatives acted by dual inhibition of topoisomerases I and II. Moreover, several hydroxyl derivatives, such as 10-hydroxyl evodiamine (10j) and 3-amino-10-hydroxyl evodiamine (18g), also showed good in vivo antitumor efficacy and low toxicity at the dose of 1 mg/kg or 2 mg/kg. They represent promising candidates for the development of novel antitumor agents.

Discovery, synthesis, and biological evaluation of orally active pyrrolidone derivatives as novel inhibitors of p53-MDM2 protein-protein interaction.

The p53-MDM2 interaction has been proved to be a valuable target to develop effective antitumor agents. Novel p53-MDM2 inhibitors bearing pyrrolidone scaffolds were successfully identified by structure-based design. The nanomolar inhibitor 5 possessed good p53-MDM2 inhibitory activity (K(i) = 780 nM) due to its hydrophobic and hydrogen bonding interactions with MDM2. Further hit optimization led to the discovery of a number of highly potent pyrrolidone derivatives with improved p53-MDM2 inhibitory activity and in vitro antiproliferative potency. Compounds 41 (K(i) = 260.0 nM) and 60a (K(i) = 150.0 nM) showed good and selective activity against tumor cells with deleted p53. In addition, these two compounds also effectively inhibited the tumor growth in the A549 xenograft model. Interestingly, compound 41 was proved to be a potent MDM2/MDMX dual inhibitor. The novel pyrrolidone p53-MDM2 inhibitors represent promising lead structures for the development of novel antitumor agents.

Selection of evodiamine as a novel topoisomerase I inhibitor by structure-based virtual screening and hit optimization of evodiamine derivatives as antitumor agents.

Human topoisomerase I (TopoI) is recognized as a valuable target for the development of effective antitumor agents. Structure-based virtual screening was applied to the discovery of structurally diverse TopoI inhibitors. From 23 compounds selected by virtual screening, a total of 14 compounds were found to be TopoI inhibitors. Five hits (compounds 1, 14, 20, 21, and 23) also showed moderate to good in vitro antitumor activity. These novel structures can be considered as good starting points for the development of new antitumor lead compounds. Hit 20 (evodiamine) was chosen for preliminary structure-activity relationship studies. Various groups, including alkyl, benzoyl, benzyl and ester, were introduced to the indole nitrogen atom of evodiamine. The substituted benzoyl groups were found to be favorable for the antitumor activity and spectrum. The 4-Cl benzoyl derivative, compound 29u, was the most active one with IC(50) values in the range 0.049-2.6 μM.

New azoles with potent antifungal activity: Design, synthesis and molecular docking

In response to the urgent need for novel antifungal agents with improved activity and broader spectrum, computer modeling was used to rational design novel antifungal azoles. On the basis of the active site of lanosterol 14alpha-demethylase from Candida albicans (CACYP51), a series of new azoles with substituted-phenoxypropyl piperazine side chains were rational designed and synthesized. In vitro antifungal activity assay indicates that the new azoles show good activity against most of the tested pathogenic fungi. Interestingly, the designed compounds are also active against an azole-resistant clinical strain. Compared to fluconazole and itraconazole, several compounds (such as 12i, 12j and 12n) show higher antifungal activity and broader spectrum, which are promising leads for the development of novel antifungal agents.

Scaffold Diversity Inspired by the Natural Product Evodiamine: Discovery of Highly Potent and Multitargeting Antitumor Agents

A critical question in natural product-based drug discovery is how to translate the product into drug-like molecules with optimal pharmacological properties. The generation of natural product-inspired scaffold diversity is an effective but challenging strategy to investigate the broader chemical space and identify promising drug leads. Extending our efforts to the natural product evodiamine, a diverse library containing 11 evodiamine-inspired novel scaffolds and their derivatives were designed and synthesized. Most of them showed good to excellent antitumor activity against various human cancer cell lines. In particular, 3-chloro-10-hydroxyl thio-evodiamine (66c) showed excellent in vitro and in vivo antitumor efficacy with good tolerability and low toxicity. Antitumor mechanism and target profiling studies indicate that compound 66c is the first-in-class triple topoisomerase I/topoisomerase II/tubulin inhibitor. Overall, this study provided an effective strategy for natural product-based drug discovery.

Design, synthesis and antifungal activity of isosteric analogues of benzoheterocyclic N-myristoyltransferase inhibitors

N-myristoyltransferase (NMT) has been a promising new target for the design of novel antifungal agents with new mode of action. A series of benzoxazole and indole derivatives were designed and synthesized as isosteric analogues of benzoheterocyclic NMT Inhibitors. In vitro antifungal assay indicated that the benzoxazole derivatives were far more potent than the indoles. Molecular docking studies revealed that the hydrogen bonding interaction between the benzoheterocyclic core and NMT might be essential in the orientation of the inhibitor to a proper position. The antifungal activity of benzoxazole derivative 8f was comparable or superior to that of fluconazole, which can serve as a good starting point for further studies of structural diversity of the benzoheterocyclic NMT inhibitors.

Meeting Organocatalysis with Drug Discovery: Asymmetric Synthesis of 3,3′-Spirooxindoles Fused with Tetrahydrothiopyrans as Novel p53-MDM2 Inhibitors

An organocatalytic enantioselective Michael-Michael cascade reaction is developed for the synthesis of chiral spirotetrahydrothiopyrans. This highly functionalized scaffold was assembled in moderate to good yield (55-74%) and excellent diastereo- and enantioselectivities (>30:1 dr, ≥ 99% ee) with the creation of four consecutive stereogenic centers. The novel spiro-oxindole scaffold is validated as a new class of p53-MDM2 protein-protein interaction inhibitors with good antitumor activity.

Design, synthesis and antifungal activity of novel triazole derivatives containing substituted 1,2,3-triazole-piperdine side chains.

Due to increasing incidence of invasive fungal infections and severe drug resistance to triazole antifungal agents, a series of novel antifungal triazoles with substituted triazole-piperidine side chains were designed and synthesized. Most of the target compounds showed good inhibitory activity against a variety of clinically important fungal pathogens. In particular, compounds 8t and 8v were highly active against Candida albicans and Cryptococcus neoformans with MIC values in the range of 0.125 μg/mL to 0.0125 μg/mL. They represent promising leads for the development of new generation of triazole antifungal agents. Molecular docking studies revealed that the target compounds interacted with CACYP51 mainly through hydrophobic and Van der Waals interactions.

Discovery of highly potent triazole antifungal derivatives by heterocycle-benzene bioisosteric replacement

On the basis of our previously discovered triazole antifungal lead compounds, heterocycle-benzene bioisosteric replacement was used to improve their pharmacokinetic profile. The designed new triazole derivatives have good antifungal activity toward a wide range of pathogenic fungi. Their binding mode with the target enzyme was clarified by molecular docking. The MIC value of the highly potent compound 8f against Candida albicans, Candida tropicalis, and Cryptococcus neoformans is 0.016 μg/mL, 0.004 μg/mL, and 0.016 μg/mL, respectively. Moreover, preliminary pharmacokinetic studies revealed that it showed improved oral absorption as compared to the lead compound iodiconazole and deserved for further evaluations.