Computational studies identifying entry inhibitor scaffolds targeting the Phe43 cavity of HIV-1 gp120

Targeting protein-protein interactions, such as the HIV-1 gp120-CD4 interface, has become a cutting-edge approach in the current drug discovery scenario. Many small molecules have been developed so far as inhibitors of the interaction between CD4 and HIV-1 gp120. However, due to a variety of reasons such as solubility, drug toxicity and drug resistance, these inhibitors have failed to prove clinically useful. As such, the identification of novel compounds that bind to protein-protein interactions is still a research area of considerable interest. Here, a structure-based virtual screening approach was successfully applied with the aim of identifying novel HIV-1 entry inhibitors targeting the Phe43 pocket of HIV-1 gp120. Several compounds able to inhibit viral replication in cell culture were identified, with the best agent endowed with an EC(50) value of 0.9 μM. Inactivity of all the identified hits toward a mutant (Met475Ile) strain strongly suggests that they interact in the Phe43 cavity of gp120, as intended. Remarkably, all of these small molecules have a chemical scaffold unrelated to any known class of entry inhibitors reported thus far. Overall, our strategy led to the identification of four novel chemical scaffolds that inhibit HIV-1 replication through the destabilization of the HIV-1 gp120-CD4 interface.