CROI 2016 Abstract eBook

Abstract Listing

Poster Abstracts

466 Maturation Inhibitor BMS-955176: Integrated Model of Polymorphic Antiviral Responses Zeyu Lin; Joseph Cantone; Hao Lu; Beata Nowicka-Sans;Tricia Protack; Dieter Drexler; Mark Cockett; Mark Krystal; Alicia Regueiro-Ren; Ira Dicker Bristol-Myers Squibb, Wallingford, CT, USA

Background: HIV-1 maturation inhibitors (MIs) disrupt the final step in the HIV-1 protease-mediated cleavage of the Gag polyprotein, between capsid (CA) and spacer peptide 1 (SP1), leading to the production of non-infectious virus. BMS-955176 is a second generation MI with improved antiviral activity toward polymorphic Gag viruses. This study was conducted to understand the underlying mechanistic reasons for improvements to polymorphic coverage. Methods: Antiviral activities of wild type (wt) and Gag polymorphic viruses were studied using single and multiple cycle replication formats. Gag CA/SP1 cleavage kinetics of wt and polymorphic virus-like particles (VLP) were determined by a novel LC/MS assay. A radiolabel binding assay was used to determine VLP/MI affinities and off rates. The cleavage, binding and antiviral data was used to create a integrated model for calculating rates of CA/SP1 cleavage. Results: In antiviral assays, early generation MIs (EGMIs) do not achieve maximal percent inhibition (100%MPI) of certain Gag polymorphs, even at saturating concentrations, resulting in low levels of breakthrough virus (partial antagonism). BMS-955176 achieves higher MPIs of polymorphs, which is correlated with lower EC 50 values. Mechanistic studies show that more rapid CA/SP1 cleavage of polymorphs (2-10-fold vs. wt) is responsible for reduced viral sensitivity to EGMIs. Enzymatically, in vitro inhibition of wt CA/SP1 cleavage by the EGMI BVM is lost at longer times, while inhibition by BMS-955176 persists. The origin of antiviral and enzymatic improvements by BMS-955176 lies in its higher affinity to Gag polymorphs. Biochemical (CA/SP1 cleavage rates, MI-specific Gag affinities) and virological (MPI) data were combined to create an integrated kinetic model to calculate rate reductions of CA/SP1 cleavage by MIs. These predictions are in accord with both preclinical antiviral potency and clinical viral load reductions as a function of MI and Gag polymorph. Conclusions: The improved polymorphic antiviral activity and biochemical profile of BMS-955176 over EGMIs is a consequence of its higher affinity/slower rate of dissociation from its Gag target. Modeling calculates MI-induced reductions in the rates of CA/SP1 Gag cleavage that correlate well with preclinical antiviral potencies and MI monotherapy clinical response data. These findings offer new insights into MI activity and mechanism and may prove useful to a further understanding of clinical responses to MIs. 467 Reduction of SIV-Mediated Immune Activation by p38 MAPK In Vivo Inhibition Omkar Chaudhary 1 ;Vivek Narayan 1 ; RonaldVeazey 2 ; Anna Aldovini 1 1 Boston Children’s Hosp, Harvard Med Sch, Boston, MA, USA; 2 Tulane Natl Primate Rsr Cntr, Covington, LA, USA Background: Differences in immune activation have been identified as the most significant difference between AIDS-susceptible and resistant species. p38 MAPK, activated in HIV and SIV infection, is key to induction of Interferon-stimulated genes (ISG) and cytokine-mediated inflammation and is associated with some of the pathology produced by HIV and SIV infection in AIDS susceptible primates. As small molecule p38 MAPK inhibitors are currently tested in human trials for other inflammatory diseases, we evaluated the effects of treating SIV-infected macaques with a p38 inhibitor in conjunction with ART. Methods: Rhesus macaques were infected with SIV mac251 and after 6 weeks ART and p38 MAPK inhibitor treatment with compound PH-797804 was initiated in one group of animals. Additional groups included ART treatement alone, p38 inhibitor alone, and naive controls. As primary end points we evaluated differences in expression of surface and intracellular molecules linked to immune activation and intracellualr inflammatory cytokine expression in cell subpopulations of blood, lymph node and intestinal tissue, and plasma levels of inflammatory cytokines. As secondary end points, we evaluated the effects that treatments had on viral loads, preservation of central memory CD4+ T cells and anti-SIV immune responses. We also evaluate the treatment impact on protein levels of selected ISG. Results: ART reduced viremia to 70-80 copies /ml. The p38 inhibitor did not further reduced the viremia, did not affect negatively anti-SIV immune responses and had no side effects. The p38 inhibitor treatment by itself had no significant effect on immune activation. When combined with ART, numerous immune activation markers were significantly reduced compared to the ART alone group. CD38/HLA-DR an Ki67 percentages in blood, lymph node and rectal CD4+ and CD8+ T cells and percentages of IL-6, IL-8, IFN-g and IFN-a producing cells were all significantly reduced. IRF7, pSTAT1 and IP-10 protein accumulation was also reduced in APC. Significant preservation of CD4+/IL22+ and CD4+/ IL-17+ T-cells in PBMC, rectal and lymph node mononuclear cells and of central memory CD4+ T cells in blood was also observed in the ART+p38 inhibitor group compared to the ART group. Conclusions: The p38 MAPK inhibitor used in this studies, already in clinical trials for other inflammatory diseases, significantly reduced immune activation during ART treatment and could be a desirable addition to antiretroviral therapy. 468 PBMC From Patients on Chronic Treatment With Dasatinib Are Resistant to HIV Infection Mayte Coiras 1 ; Mercedes Bermejo 1 ; Javier Garcia-Perez 1 ; Benjamin Descours 2 ; Juan Ambrosioni 3 ; Nuria Climent 4 ; Monsef Benkirane 2 ; José M. Miro 3 ; Montserrat Plana 4 ; José Alcamí 1 1 Inst de Salud Carlos III, Madrid, Spain; 2 Inst de Genetique Humaine, Montpellier, France; 3 Hosp Clinic-IDIBAPS, Univ de Barcelona, Barcelona, Spain; 4 IDIBAPS, Barcelona, Spain Background: Inhibitors of tirosin kinases (ITKs) such as imatinib, nilotinib, dasatinib and bosutinib are currently used for the treatment of chronic myeloid leukemia (CML). Imatinib, nilotinib and dasatinib have also been described to control HIV-1 replication in vitro through their negative effect on viral fusion. However, we determined that dasatinib is not a fusion inhibitor but it can actually interfere with SAMHD1 phosphorylation, preserving the activity of this antiviral factor and consequently, avoiding viral retrotranscription and proviral integration. Our aims were to evaluate the antiviral activity of dasatinib and other ITKs in vitro and to determine whether in vivo treatment with ITKs such as dasatinib may preserve SAMHD1 function and interfere with HIV-1 replication. Methods: PBMCs from healthy donors were used to determine the effect of ITKs such as imatinib, nilotinib, dasatinib, bosutinib, saracatinib and KX2-391 on HIV-1 replication, SAMHD1 phosphorylation and HIV-1 fusion step. PBMCs from CML patients on treatment with ITKs such as Dasatinib were used to analyze SAMHD1 phosphorylation and susceptibility to HIV-1 infection ex vivo. Results: 1) All assayed ITKs interfered with HIV-1 infection of PBMCs in vitro. Dasatinib, saracatinib, and KX2-391 were the most potent (IC 50 =50.86nM, CC 50 >10.0uM; IC 50 =90.82nM, CC 50 >3.0uM and IC 50 =39.97nM, CC 50 >4.0uM, respectively). 2) PBMCs from five CML patients on chronic treatment with Dasatinib for more than two years were resistant to HIV-1 infection ex vivo, showing 119-fold less proviral integration. No patient presented serious adverse events or infectious complications related to the use of dasatinib. An appropriate cytotoxic activity was preserved in these patients. 3) PBMCs from CML patients showed 68% less SAMHD1 phosphorylation in response to activating stimuli ex vivo than untreated controls. This is the main mechanism of action of dasatinib to interfere with HIV-1 infection because in vitro infection of PBMCs with virions containing Vpx, which degrades SAMHD1, overcame the inhibitory effect of Dasatinib. 4) Fusion of BlaM-Vpr-containing HIV-1 viruses with activated PBMCs treated with Dasatinib showed that Dasatinib was not a fusion inhibitor. Conclusions: Dasatinib is the first compound currently used in clinic that was described to preserve the antiviral function of SAMHD1. ITKs such as Dasatinib in combination with antiretroviral therapy could make CD4 cells refractory to HIV-1 infection, thus reducing the size of the latent reservoir. 469LB Efficacy of an Engineered Bispecific Anti-HIV Antibody in Humanized Mice Anastasia Lanzi 1 ;Yaoxing Huang 1 ; JianYu 1 ; Chasity D. Andrews 1 ; XinYao 1 ; LilyTsai 1 ; Mili R. Gajjar 1 ; Michael Seaman 2 ; Neal N. Padte 1 ; David D. Ho 1 1 Aaron Diamond AIDS Rsr Cntr, New York, NY, USA; 2 Harvard Med School, Boston, MA, USA Background: While the search for an efficacious HIV vaccine remains elusive, the emergence of a new generation of virus-neutralizing monoclonal antibodies (Abs) has re-ignited the field of passive immunization as an alternative strategy for HIV prevention. However, the plasticity of HIV demands additional improvements to these Abs in order to better ensure their clinical utility. Here, we report the impressive in vitro and in vivo activity of an engineered bispecific Ab.

Poster Abstracts

180

CROI 2016