While HIV/AIDS can be managed with antiretroviral drugs, these agents do not clear the virus and require life-long administration. Recently, we discovered a completely new class of compounds that interfere with the HIV-1 virulence factor called Nef. This viral protein is critical to HIV-1 replication in vivo, immune escape of HIV-infected cells, and AIDS progression. During the past year, we successfully completed Phase I of our STTR project aimed at development of Nef antagonists suitable for clinical testing. Working with the Fox Chase Chemical Diversity Center, we evaluated 50 analogs of our original diphenylpyrazolodiazene Nef inhibitor, some of which display tighter Nef binding while retaining potent antiretroviral activity and improved ADME properties. Several analogs prevent Nef-mediated downregulation of MHC-I on HIV-infected CD4+ T-cells, resulting in activation of autologous anti-HIV CD8+ CTLs. These data suggest that our Nef antagonists may restore recognition of HIV-infected cells by the patient's own immune system as a path to functional cure. In this Phase II application, we will expand our Nef drug development efforts with the following Specific Aims:
Aim 1 : Perform lead optimization medicinal chemistry. Based on SAR developed during Phase I, we propose to synthesize 100-150 new Nef inhibitor analogs to find suitable compounds for in vivo testing in Aim 3 using HIV-infected humanized mice. Our approach will employ structure-based design while considering analog ADMET and PK properties in parallel. All analogs will also be tested for Nef binding affinity, effects on Nef-mediated enhancement of HIV replication and reversal of CD4 and MHC-I downregulation by Nef in HIV-infected patient cells.
Aim 2 : Ensure suitable drug properties via in vitro and in vivo ADMET evaluation. Up to 15 compounds per year that meet Nef-binding and functional criteria (Aim 1) will be evaluated using in vitro ADMET assays including microsomal stability, CYP 3A4 inhibition, solubility and plasma protein binding. Three to six (IV) and 2-3 (PO) compounds will be evaluated in mouse PK studies, with the 2-3 most promising compounds advancing to in vitro non-GLP safety assays. These data are essential for choosing the best compounds for in vivo testing in humanized mouse models of HIV/AIDS (Aim 3).
Aim 3 : Test the hypothesis that Nef antagonists can suppress HIV replication and T-cell loss in a humanized mouse model of AIDS. Humanized mice infected with Nef-deleted HIV-1 exhibit dramatically lower viral loads and substantially less T cell depletion than those infected with wild-type virus. The most promising compounds identified in the first two Aims will therefore be administered to humanized mice to monitor effects on HIV replication, CD4+ T cell loss and immune system function. Successful completion of these goals will provide a comprehensive package to support advanced development, safety testing in large animals and advance the project further toward an IND submission for Phase I safety testing in normal volunteers.
The proposed studies are focused on new approaches to HIV/AIDS drug discovery targeting an HIV-1 accessory protein (Nef) essential for AIDS progression. Successful completion of the proposed work will identify small molecules for use as drug candidates that block Nef functions in HIV pathogenesis in animal models and ultimately in man. These Nef inhibitors represent lead compounds for future development as a new class of anti- HIV therapeutics with the potential to clear HIV-infected cells from patients.
| Emert-Sedlak, Lori A; Loughran, H Marie; Shi, Haibin et al. (2016) Synthesis and evaluation of orally active small molecule HIV-1 Nef antagonists. Bioorg Med Chem Lett 26:1480-1484 |
