Species-Selective Targeting of Fungal Hsp90: Design, Synthesis, and Evaluation of Novel 4,5-Diarylisoxazole Derivatives for the Combination Treatment of Azole-Resistant Candidiasis.

Invasive fungal infections are emerging as serious infectious diseases worldwide. Because of the development of antifungal drug resistance, the limited efficacy of the existing drugs has led to high mortality in patients. The use of the essential eukaryotic chaperone Hsp90, which plays a multifaceted role in drug resistance across diverse pathogenic fungal species, is considered to be a new strategy to mitigate the resistance and counter the threat posed by drug-resistant fungi. Thus, a series of 4,5-diarylisoxazole analogues as fungal Hsp90 inhibitors were designed and synthesized that had potent synergistic effects with fluconazole in vitro and in vivo. In particular, compound A17 could avoid the potential mammalian toxicity of Hsp90 inhibitors based on key reside differences between humans and fungi. These data support the feasibility of targeting fungal Hsp90 as a promising antifungal strategy and further development of compound A17 as a valuable research probe for the investigation of fungal Hsp90.

Design, synthesis, and evaluation of novel 3-thiophene derivatives as potent fungistatic and fungicidal reagents based on a conformational restriction strategy.

Invasive fungal infections (IFIs) are emerging as serious infectious diseases worldwide, and due to the lack of effective antifungal agents and serious drug resistance, the limited efficacy of existing drugs has led to high morbidity and mortality in patients. We optimized the lead compound 7 by conformational restriction strategy to obtain a series of 3-thiophene phenyl compounds, of which compound 21b showed excellent inhibitory activity against pathogenic and drug-resistant fungi. In addition, the preferred compound 21b could prevent the formation of fungal biofilms and displayed satisfactory fungicidal activity. Furthermore, compound 21b was almost non-toxic to mammalian THLE2 and RAW264.7 cells and did not pose a risk of drug-drug interactions. These results strongly suggested that compound 21b is worthy of further study as a potential azole inhibitor.

Broadening antifungal spectrum and improving metabolic stablity based on a scaffold strategy: Design, synthesis, and evaluation of novel 4-phenyl-4,5-dihydrooxazole derivatives as potent fungistatic and fungicidal reagents.

5-phenylthiophene derivatives exhibited excellent antifungal activity against Candida albicans, Candida tropicalis and Cryptococcus neoformans. However, optimal compound 7 was inactive against Aspergillus fumigatus and unstable in human liver microsomes in vitro with a half-life of 18.6 min. To discover antifungal agents with a broad spectrum and improve the metabolic properties of the compounds, the scaffold hopping strategy was adopted and a series of 4-phenyl-4,5-dihydrooxazole derivatives were designed and synthesized. It was especially encouraging that compound 22a displayed significant antifungal activities against eight susceptible strains and seven FLC-resistant strains. Furthermore, the potent compound 22a could prevent the formation of fungalbiofilms and displayed satisfactory fungicidal activity. In addition, the metabolic stability of compound 22a was improved significantly, with the half-life of 70.5 min. Compound 22a was almost nontoxic to mammalian A549, MCF-7, HepG2, and 293T cells. Moreover, pharmacokinetic studies in SD rats showed that compound 22a exhibited pharmacokinetic properties with a bioavailability of 15.22% and a half-life of 4.44 h, indicating that compound 22a is worthy of further study.

Design, synthesis and evaluation of novel 5-phenylthiophene derivatives as potent fungicidal of Candida albicans and antifungal reagents of fluconazole-resistant fungi.

A series of 5-phenylthiophene derivatives with novel structures were designed and synthesized to combat the increasing incidence of susceptible and drug-resistant fungal infections. The antifungal activity of the synthesized compounds was assessed against seven susceptible strains and six fluconazole-resistant strains. It is especially encouraging that compounds 17b and 17f displayed significant antifungal activities against all tested strains. Furthermore, the potent compounds 17b and 17f could prevent the formation of fungi biofilms and 17f displayed satisfactory fungicidal activity. Preliminary mechanistic studies showed that the potent antifungal activity of compound 17f stemmed from inhibition of C. albicans CYP51. In addition, Compounds 17b and 17f were almost nontoxic to mammalian A549, MCF-7, and THLE-2 cells. These results strongly suggested that compounds 17b and 17f are promising as novel antifungal drugs.

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.