Discovery of quinolinonyl derivatives as anti-HIV-1 inhibitors endowed with an innovative mechanism of action.

HIV integrase (IN) is a pivotal antiretroviral drug target. In this regard, IN strand transfer inhibitors (INSTIs), binding to the IN active site, have proven to be highly effective, becoming a potent first-line therapy to treat infected patients. However, despite their effectiveness as therapeutic options and the high barriers with the second-generation FDA-approved INSTIs, drug therapy selects for drug resistance and mutations responsible for multiple INSTIs resistance, underscoring the need for the development of more effective antiretroviral compounds. The development of small molecule protein-protein interaction inhibitors is a new attractive strategy for discovering anti-HIV agents. In this field of research, allosteric IN inhibitors (ALLINIs), are a promising new class of antiretroviral agents. These inhibitors act differently in respect to INSTIs, in fact, they alter the functional IN multimerization. Recently, it was unraveled that aberrant IN multimerization underlies the inhibition of IN-vRNA interactions by ALLINIs. In doing so, ALLINIs indirectly disrupt the IN-vRNA binding, leading to the formation of defective viral particles with greatly reduced infective potential with mis-localization of the vRNA outside the viral capsid. While the indirect disruption of IN-vRNA binding (caused by the impairment of functional IN multimerization) has been described with the treatment of virus-producing cells with ALLINIs, the direct disruption of this binding (without affecting IN multimerization properties) by small molecules has not been reported so far. We describe a series of compounds identified as inhibitors of the IN-vRNA binding via a direct mechanism. In particular, we deepened the mechanism of action of some compounds previously described by us as INSTIs. Indeed, we speculated that these quinolinonyl derivatives, being endowed with two DKA chains, could also act as protein-nucleic acid interaction inhibitors. To verify our hypothesis, we decided to test a set of derivatives and their analogues endowed with a variable “base-like” functional group. We assessed the capability of our derivatives of inhibiting at low micromolar concentrations both IN 3’-processing and strand transfer reactions in a LEDGF/p75 independent assay. In addition, we performed in vitro binding assays, and we found that our quinolinonyl derivatives are able to disrupt the IN-vRNA interaction, that is vital for a correct generation of a functional infective virion. The data coming from the biological assays will be shown and discussed.