Discovery and Mechanistic Investigation of Piperazinone Phenylalanine Derivatives with Terminal Indole or Benzene Ring as Novel HIV-1 Capsid Modulators

HIV-1 capsid (CA) performs multiple roles in the viral life cycle and is a promising target for antiviral development. In this work, we describe the design, synthesis, assessment of antiviral activity, and mechanistic investigation of 20 piperazinone phenylalanine derivatives with a terminal indole or benzene ring. Among them, F(2)-7f exhibited moderate anti-HIV-1 activity with an EC(50) value of 5.89 μM, which was slightly weaker than the lead compound PF74 (EC(50) = 0.75 μM). Interestingly, several compounds showed a preference for HIV-2 inhibitory activity, represented by 7f with an HIV-2 EC(50) value of 4.52 μM and nearly 5-fold increased potency over anti-HIV-1 (EC(50) = 21.81 μM), equivalent to PF74 (EC(50) = 4.16 μM). Furthermore, F(2)-7f preferred to bind to the CA hexamer rather than to the monomer, similar to PF74, according to surface plasmon resonance results. Molecular dynamics simulation indicated that F(2)-7f and PF74 bound at the same site. Additionally, we computationally analyzed the ADMET properties for 7f and F(2)-7f. Based on this analysis, 7f and F(2)-7f were predicted to have improved drug-like properties and metabolic stability over PF74, and no toxicities were predicted based on the chemotype of 7f and F(2)-7f. Finally, the experimental metabolic stability results of F(2)-7f in human liver microsomes and human plasma moderately correlated with our computational prediction. Our findings show that F(2)-7f is a promising small molecule targeting the HIV-1 CA protein with considerable development potential.