Clinical Study On The Activation Of HIV-1 Latent Reservoir By Histone Deacetylase Inhibitor Chidamide And Its Mechanism

Background:Combination antiretroviral therapy(c ART)can repress HIV replication to undetectable level.However,in most cases,HIV replication will reignite in several weeks after cessation of c ART despite years of treatment.This viral rebound primarily comes from long-lived latently infected resting CD4~+T cells,whose genome incorporates transcriptionally silent but replication-competent HIV proviruses.A proposed strategy to purge the latent reservoir is to reactivate provirus expression with latency-reversing agents(LRAs),inducing viral antigen expression and allowing elimination of activated reservoir cells by viral cytopathic effects and immune-mediated mechanisms in the presence of c ART to prevent new infection.Early clinical trials have demonstrated that histone deacetylase inhibitors(HDACis)vorinostat,panobinostat and romidepsin can disrupt HIV latency in vivo.Chidamide is a new member of the benzamide class of HDACi,which inhibits HDAC1,2,3,and 10.Objective:To evaluate the safety and efficacy of chidamide on HIV latency reversal in vivo and to compare the in vitro effects of the four clinically tested HDACis on cytotoxicity,latency reversal and non-histone proteins necessary for HIV gene expression.Methods:The in vivo study was a two-step dose-escalation phase 1b/2a clinical trial.In step 1,seven c ART-suppressed aviremic patients were enrolled and administrated with 10mg of chidamide twice weekly for 4 consecutive weeks.After the dose was well tolerated and no safety concerns were noted in the 10 mg dose group,another six patients were enrolled and administrated with 30 mg of chidamide twice weekly for 4 weeks.All 13participants maintained their previous c ART regimen during the whole study.Primary outcome was plasma viral rebound during chidamide dosing and secondary outcomes were safety,pharmacokinetic and pharmacodynamic profiles,changes of cell-associated HIV-1RNA,HIV-1 DNA,and immune aspects.In vitro cytotoxicity of HDACis was determined by flow cytometry.Latency-reversing effect was evaluated on primary CD4~+T cells from aviremic HIV-infected patients.Western blot was used to compare their in vitro effects on HSP90,NF-κB and AP-1.Results:All 13 participants completed eight oral doses of chidamide.Chidamide was well tolerated and only grade 1 adverse events were presented in the 10 mg dose group.Hematological toxicity contributed to 58%(18/31)of the chidamide-related adverse events in the 30 mg dose group.Chidamide showed favorable pharmacokinetic and pharmacodynamic profiles without evident drug accumulation in both groups.Cyclic increases of histone acetylation were also observed in both groups.In the 10 mg dose group,all 7 participants showed robust and repeated plasma viral rebound(peak viremia 147-3850copies/m L)as well as increased cell-associated HIV-1 RNA during chidamide treatment.By contrast,participants in the 30 mg dose group experienced limited viral rebound.Furthermore,we discerned an enhanced HIV-1-specific T cell immune response and a modest 37.7%(p=0.028)reduction in cell-associated HIV-1 DNA in the 10 mg dose group,which was not seen in the 30 mg dose group.Compared with the other three HDACis,chidamide had minimal cytotoxicity in vitro at their clinically relevant concentrations,and showed a mechanistical superiority on non-histone proteins including HSP90,NF-κB and AP-1.Moreover,chidamide was the strongest LRA among the four HDACis in ex vivo CD4~+T cells from HIV-infected patients.Conclusion:Chidamide dosing by 10 mg twice weekly can safely and vigorously disrupt HIV latency in vivo.Chidamide shows a mechanistical superiority to other clinically tested HDACis in HIV latency reversal,which together makes it a more promising“shock”candidate in cure strategy.