PROTAC-mediated Degradation of HIV-1 Nef Efficiently Restores Cell-surface CD4 and MHC-I Expression and Blocks HIV-1 Replication

Abstract

The HIV-1 Nef accessory factor is critical to the viral life cycle in vivo where it promotes immune escape of HIV-infected cells and viral persistence. While these features identify Nef as an attractive antiretroviral drug target, Nef lacks enzymatic activity and an active site, complicating development of occupancy-based drugs. Here we describe the development of proteolysis targeting chimeras (PROTACs) for the targeted degradation of Nef. Nef-binding compounds, based on a previously reported hydroxypyrazole core, were coupled to ligands for ubiquitin E3 ligases via flexible linkers. The resulting bivalent PROTACs induced formation of a ternary complex between Nef and the Cereblon E3 ubiquitin ligase, resulting in ubiquitylation of Nef and proteolytic degradation. Nef-directed PROTACs efficiently rescued Nef-mediated MHC-I and CD4 downregulation in T cells and suppressed HIV-1 replication in donor PBMCs. Targeted degradation of Nef is anticipated to reverse all HIV-1 Nef functions and may help restore adaptive immune responses against HIV-1 reservoir cells in vivo.