Design, synthesis and evaluation of heteroaryldihydropyrimidine analogues bearing spiro ring as hepatitis B virus capsid protein inhibitors.

GLS4, a potent antiviral drug candidate, has been widely studied and entered into phase II clinical trials. Nevertheless, the therapeutic application of GLS4 is limited due to poor water solubility, short half-life, and low bioavailability. In order to improve the hydrophilicity and pharmacokinetic (PK) properties of GLS4, herein, we retained the dominant fragments, and used a scaffold hopping strategy to replace the easily metabolized morpholine ring of GLS4 with diverse sizes of spiro rings consisting of hydrogen bond donor and acceptor substituents. Potent in vitroanti-HBV activity and low cytotoxicity were observed for compound 4r (EC ₅₀  = 0.20 ± 0.00 μM, CC ₅₀  > 87.03 μM), which was more potent than the positive control lamivudine (EC ₅₀  = 0.37 ± 0.04 μM, CC ₅₀  > 100.00 μM) in this assay and was about a quarter as effective as GLS4 (EC ₅₀  = 0.045 ± 0.01 μM, CC ₅₀  > 99.20 μM). Preliminary structure-activity relationship (SAR) analysis and molecular docking studies were carried out to explore potential interactions and binding mode between compounds and target protein. In terms of the physicochemical properties, 4r was predicted to be consistent with the rule-of-five, which means 4r may have favourable absorption and permeation. Finally, ADMET and PK characteristics of 4r and GLS4 were predicted to be comparable in most aspects, implying that the two compounds may have similar profiles in vivo.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. The authors declare no conflict of interest.
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