Fimepinostat, a novel dual inhibitor of HDAC and PI3K, effectively reverses HIV-1 latency ex vivo without T cell activation

Abstract

Objectives: To test the potential of fimepinostat (CUDC-907), a dual inhibitor of histone deacetylases (HDAC) and phosphatidylinositol-3-kinases (PI3K), to reverse human immunodeficiency virus type 1 (HIV-1) latency in infected cell lines and in CD4+ T cells from HIV-1-infected donors on long-term combination antiretroviral therapy (cART).

Methods: Latently HIV-1-infected J-lat Tat-GFP and ACH-2 cell lines were stimulated with clinically relevant concentrations of fimepinostat using the HDAC inhibitors (HDACi) panobinostat and romidepsin for comparison. Next, CD4+ T cells from donors living with HIV-1 on long-term cART were stimulated ex vivo and cell-associated unspliced HIV-1 RNA was measured to quantify changes in HIV-1 transcription. Finally, the impact of fimepinostat on T cell activation (CD69 expression) and proliferation (Ki67 expression) was determined using peripheral blood mononuclear cells from uninfected donors.

Results: We found fimepinostat to be a potent latency-reversing agent. This was true in two latently infected cell lines as well as ex vivo in CD4+ T cells isolated from donors living with HIV-1. Relative to therapeutic dosing levels, fimepinostat showed latency-reversing potential comparable to romidepsin, which is the most potent HDACi tested in HIV-1 cure-related trials. Interestingly, in contrast to romidepsin, fimepinostat stimulation resulted in decreased T cell activation and had no negative impact on T cell proliferation.

Conclusions: At therapeutic concentration, the dual HDAC and PI3K inhibitor fimepinostat was a potent HIV-1 latency-reversing agent and it did not induce T cell activation and proliferation. The potential of fimepinostat as a latency-reversing agent warrants further investigation.

Keywords: HDACi; HIV; PI3Ki; T cell activation; fimepinostat; latency-reversal agent.

Figure 1.

Fimepinostat induced HIV-1 reactivation in latently infected J-lat Tat-GFP cells. (a) HIV-1 reactivation in J-lat Tat-GFP cells at the indicated concentrations in nanomoles of fimepinostat, panobinostat and romidepsin. (b) Effects on the viability of indicated concentrations in nanomoles. Viability was higher in cells treated with fimepinostat than in cells treated with panobinostat and romidepsin. Shaded areas indicate CC50, the cytotoxic concentrations where >50% of the cells were dead. (c) MFI with indicated concentrations in nanomoles. Data are presented as mean ± SD of five (a,c) and two (b) independent experiments. Dotted lines indicate positive and negative controls with PMA at 25 nM and DMSO at 0.01%. DMSO: dimethylsulphoxide; HIV, HIV type 1; MFI: median fluorescence intensity; PMA:, phorbol 12-myristate 13-acetate

Figure 2.

Fimepinostat induced p24 production in latently infected ACH-2 cells. (a) HIV type 1 p24 production in ACH-2 cells in picograms per millilitre with indicated concentrations of fimepinostat, panobinostat and romidepsin in nanomoles. (b) Cells alive after exposure of indicated concentrations in nanomoles. Shaded areas indicate concentrations where >50% of the cells were dead after exposure. Data are presented as mean ± SD of four (a) and three (b) independent experiments. Dotted lines indicate positive and negative controls with PMA at 25 nM and DMSO at 0.01%. DMSO: dimethylsulphoxide; PMA: phorbol 12-myristate 13-acetate

Figure 3.

Fimepinostat induced HIV-1 transcription in CD4+ T cells from donors on long-term cART. (a) Absolute quantification of CA usHIV-1 RNA in CD4+ T cells from donors on long-term cART. (b) Fold change of CA usHIV-1 RNA in CD4+ T cells from donors on long-term cART relative to negative control (DMSO). Columns represent the mean. Individual donors, n = 10 with fimepinostat and n = 6 with romidepsin; CA usHIV-1: cell-associated unspliced HIV-1; DMSO: dimethylsulphoxide

Figure 4.

Fimepinostat showed no T cell activation in PBMCs from HIV-1-negative donors. Expression of activation marker CD69 (a) and proliferation marker Ki67 (b) on PBMCs from HIV-1-negative donors after 48-hour incubation with indicated concentrations of fimepinostat, romidepsin and negative control (DMSO at 0.01%) on the percentages of central memory (TCM) and effector memory (TEM) CD4+ T cells, respectively. Columns represent the mean. DMSO: dimethylsulphoxide; PBMC: peripheral blood mononuclear cell; TCM: central memory T cell; TEM: effector memory T cell