IQP-0528 is a potent non-nucleoside reverse transcriptase inhibitor (NNRTI) that has potential for the treatment of HIV infection by blocking viral entry and shows antiviral activity as a microbicidal gel. . IQP-0528 showed inhibition of both HIV-1 and HIV-2, with an EC50 of 0.2 nM for HIV-1 and 100 nM for HIV-2.

HIV-1:0.2 nM(EC50), HIV-2:100 nM(EC50)

The in vitro safety evaluations showed no significant loss in cell viability or significant inflammatory response after treatment with a 3.0% HEC gel containing 0.25% IQP-0528. In an in vitro HIV-1 entry inhibition assay, the lead formulation showed an 50% effective concentration of 0.14 μg/ml for gel in culture media, which corresponds to ∼0.001 μM IQP-0528.[5]

we report the first-in-human evaluation of such a gel containing 1% IQP-0528, an investigational antiretroviral. Seven HIV-1-negative participants received one 10 mL rectal dose of radiolabeled 1% IQP-0528 gel. Median IQP-0528 concentrations in rectal tissue exceeded the in vitro EC95 against HIV-1 (0.07 ng/mg) by 3-5 h of dosing and remained above this concentration for at least 24 h, despite a 3-log reduction in concentration over this duration of time. Rectal tissue PD assessed by ex vivo HIV challenge-demonstrated significant p24 antigen reduction 3-5 h postdose compared with baseline , but not 24-26 h postdose. The IQP-0528 gel possesses desirable features for a topical microbicide including local safety with no systemic absorption, delivery of locally high IQP-0528 concentrations, and significant reductions in ex vivo HIV infectivity.[6]