2-Aminothiazolones as anti-HIV agents that act as gp120-CD4 inhibitors

Abstract

We report here the synthesis of 2-aminothiazolones along with their biological properties as novel anti-HIV agents. Such compounds have proven to act through the inhibition of the gp120-CD4 protein-protein interaction that occurs at the very early stage of the HIV-1 entry process. No cytotoxicity was found for these compounds, and broad antiviral activities against laboratory strains and pseudotyped viruses were documented. Docking simulations have also been applied to predict the mechanism, at the molecular level, by which the inhibitors were able to interact within the Phe43 cavity of HIV-1 gp120. Furthermore, a preliminary absorption, distribution, metabolism, and excretion (ADME) evaluation was performed. Overall, this study led the basis for the development of more potent HIV entry inhibitors.

FIG 1

(A) Synthesis of aminothiazolones 16a to 16l. Step i, Pd(PPh₃)₂Cl₂, Na₂CO₃, dimethylformamide (DMF)-EtOH, occurring at room temperature for 1 h; step ii, 1 N NaOH and MeOH-THF, with reflux, overnight; step iii, EtOH at 150°C in microwave (MW), 20 min. (B) Synthesis of the aminothiazolone 16m. Step i, Pd(PPh₃)₂Cl₂, Na₂CO₃, DMF-EtOH at room temperature for 1 h; ii, EtOH at 150°C, MW, 20 min.

FIG 2

Time-of-addition assay. The target of the antiviral compound 16l was identified by comparing its activity in the time scale to those of reference drugs. In the assay, a panel of reference drugs sequentially targeting distinct replication steps of HIV-1 from entry to the integration into cell chromosome was used (shown as bars at the bottom): IgGb12 (an anti-gp120 antibody that binds the CD4-binding site), maraviroc (a CCR5 coreceptor inhibitor), enfuvirtide (T20, a fusion inhibitor), azidothymidine (AZT) (a reverse transcriptase inhibitor), and dolutegravir (DTG) (an integrase inhibitor). For compound 16l, the efficacy was at its maximum only when the virus was pretreated as for IgGb12, and it was ineffective once the virus attached the CD4 cell surface receptor.

FIG 3

gp120-CD4-His tag binding assay. Two representative 2-aminothiazolone derivative molecules, 16h and 16l, were tested in a competitive ELISA to demonstrate that gp120 binding to CD4 was the target of this class of compounds. Both compounds were able to displace soluble CD4 from a dual tropic gp120 in a dose-dependent manner (IC₅₀ for both compounds, 20 μM). DMSO was also tested at the same concentrations present at each compound dilution. The experiments were repeated twice in triplicate.

FIG 4

(A) Binding mode of compound 16h (blue) as predicted by computational studies. (B) Phe43 cavity occupied at the same time by 16h (blue) and DMJ-II-121 (green) (PDB code 4I54).

FIG 5

Time evolution of root mean square deviation (RMSD) (Å) calculated on heavy atoms of ligand 16f in AD8 (blue lines) and NL4.3 (red lines).