GS-9822, a Preclinical LEDGIN Candidate, Displays a Block-and-Lock Phenotype in Cell Culture

Abstract

The ability of HIV to integrate into the host genome and establish latent reservoirs is the main hurdle preventing an HIV cure. LEDGINs are small-molecule integrase inhibitors that target the binding pocket of LEDGF/p75, a cellular cofactor that substantially contributes to HIV integration site selection. They are potent antivirals that inhibit HIV integration and maturation. In addition, they retarget residual integrants away from transcription units and towards a more repressive chromatin environment. As a result, treatment with the LEDGIN CX14442 yielded residual provirus that proved more latent and more refractory to reactivation, supporting the use of LEDGINs as research tools to study HIV latency and a functional cure strategy. In this study we compared GS-9822, a potent, pre-clinical lead compound, with CX14442 with respect to antiviral potency, integration site selection, latency and reactivation. GS-9822 was more potent than CX14442 in most assays. For the first time, the combined effects on viral replication, integrase-LEDGF/p75 interaction, integration sites, epigenetic landscape, immediate latency and latency reversal was demonstrated at nanomolar concentrations achievable in the clinic. GS-9822 profiles as a preclinical candidate for future functional cure research.

Single-Cell Imaging Shows That the Transcriptional State of the HIV-1 Provirus and Its Reactivation Potential Depend on the Integration Site

“…After LEDGIN-mediated retargeting, the residual HIV-1 reservoir was shown to be more latent and less prone to reactivation ( 21 ). This result was corroborated recently using the LEDGIN GS-9822 ( 34 ), displaying activity in the low-nanomolar range, which increased immediate latency and reduced provirus reactivation at nanomolar concentrations in in vitro -infected T cell lines. Immediate latency refers to early silencing of HIV-1 expression, usually within 24 h prior to initiation of Tat-dependent HIV-1 transcription ( 35 , 36 ).…”

Toward a Functional Cure for HIV-1 Infection: The Block and Lock Therapeutic Approach

“…Specifically, proviruses were integrating into less-genedense regions with a more repressive epigenetic environment, and were shifted away from H3K36me3, which lowered HIV-1 transcription. Similar results were noted with GS-9822, also an ALLINI, in that residual provirus was both more latent and refractory to reactivation, and were integrated away from genes and gene-dense chromatin, resulting in a more repressive heterochromatin environment (33). Collectively, these studies suggest that if HIV-1-infected individuals are treated early with ART regimens that include an ALLINI, the replication-competent viral reservoir in resting CD4+ T cells will be transcriptionally impaired, thus mimicking a "locked" phenotype.…”

Multimodal Functionalities of HIV-1 Integrase

“…The δ-retroviral human T lymphotropic virus 1 transcriptional activator Tax protein can also significantly enhance HIV-1 transcription from unintegrated vDNA [ 136 , 137 ]. Research that aims to inform the roles of IN residues or IN inhibitors on HIV-1′s ability to replicate under physiologically relevant conditions might appropriately avoid Tax-expressing cell lines such as MT-4 and C8166-45 [ 40 , 138 , 139 , 140 , 141 , 142 , 143 , 144 ] moving forward.…”

“…Prototypical quinoline and pyridine compounds are shown in Figure 6 A. Recent studies have characterized several highly potent compounds based on expanded chemical scaffolds that inhibit HIV-1 replication in cell culture at effective concentration 50% (EC 50 ) values of ~0.4–2.5 nM [ 143 , 215 , 216 , 217 ].…”