Synthetic Ingenols Maximize Protein Kinase C-Induced HIV-1 Latency Reversal

Abstract

Antiretroviral therapy (ART) does not cure HIV-1 infection due to the persistence of proviruses in long-lived resting T cells. Strategies targeting these latently infected cells will be necessary to eradicate HIV-1 in infected individuals. Protein kinase C (PKC) activation is an effective mechanism to reactivate latent proviruses and allows for recognition and clearance of infected cells by the immune system. Several ingenol compounds, naturally occurring PKC agonists, have been described to have potent latency reversal activity. We sought to optimize this activity by synthesizing a library of novel ingenols via esterification of the C-3 hydroxyl group of the ingenol core, which itself is inactive for latency reversal. Newly synthesized ingenol derivatives were evaluated for latency reversal activity, cellular activation, and cytotoxicity alongside commercially available ingenols (ingenol-3,20-dibenzoate, ingenol 3-hexanoate, and ingenol-3-angelate) in HIV latency cell lines and resting CD4 T cells from aviremic participants. Among the synthetic ingenols that we produced, we identified several compounds that demonstrate high efficacy and represent promising leads as latency reversal agents for HIV-1 eradication.

Prodrugs of PKC modulators show enhanced HIV latency reversal and an expanded therapeutic window

“…We have previously shown that 4 is able to activate latent HIV both in vitro and ex vivo, demonstrating the value of 4 as an LRA candidate. Ingenol esters-esterified derivatives of the natural product ingenol (5)-which are finding clinical value in treating actinic keratosis and basal cell carcinoma, have also been shown to activate latent HIV reservoirs at a level that equals or exceeds the current best candidates, including prostratin (49)(50)(51)(52)(53)(54). The HIV latency reversal activity of extracts from Euphorbia kansui is also thought to arise from ingenol-derived constituents (55,56).…”

Structural anatomy of Protein Kinase C C1 domain interactions with diacylglycerol and other agonists

“…Shortly after their discovery, PKCs were identified as cellular receptors for tumor-promoting phorbol esters 10 that bind C1 domains in lieu of DAG. These observations, combined with the central roles executed by PKCs in intracellular signaling established their DAG-sensing function as an attractive target for therapeutic intervention, with considerable promise in the treatment of Alzheimer’s disease 11 , HIV/AIDS 12 , 13 , and cancer 14 , 15 . However, the structural basis of DAG recognition by the C1 domains has remained elusive, and the strategies for therapeutic agent design deployed to date all relied on modeling studies (reviewed in 16 ) based on the single available crystal structure of the C1 domain complexed to a ligand that does not activate PKC 17 .…”

Tracking HIV Rebound following Latency Reversal Using Barcoded HIV

“…One area in which humanized mice have been particularly useful is the exploration of “kick and kill” strategies to deplete latent HIV, 14 where non-expressing HIV proviruses are induced to express viral proteins with a latency-reversing agent (LRA) allowing the host cell to be killed by viral cytopathic effects, immune effector mechanisms, or other approaches targeting productively infected cells. Various LRAs that function through several different intracellular signaling pathways have been tested in different in vitro or in vivo models 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 and one of the most effective pathways for reversing HIV latency has proven to be via PKC (protein kinase C) modulation. 23 We have previously demonstrated that the latency-reversing capabilities of naturally occurring PKC modulators, including bryostatin 1 and prostratin, can be improved by designed synthetic analogs of these compounds.…”