CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Cytotoxicity was evaluated using ViaCount (Millipore). WT NL4.3 was also passaged in the presence of SM111. Three independent drug-resistant strains were isolated, sequenced and assessed for their sensitivity to SM111. Vpu-mediated downregulation of CD4 and tetherin was monitored by flow cytometry. Results: SM111 inhibited NL4.3 in a dose-dependent manner between 10 m M and 100 m M, and was non-toxic at 100 m M concentration (viability >90%, similar to media control). Infected cells (%GFP+) were reduced >98% at 100 m M (56.7% [55.3-57.7] in absence vs. 0.89 % [0.76-0.99] in presence of SM111) at day 7. Similar activity was observed against RTI, PI and INI resistance strains (>95% reduction in all cases). All SM111-resistant viruses encoded mutations in the transmembrane of Vpu, including a 5AA deletion (clone A), a stop codon at highly conserved W22 (clone C) or a substitution (I17R) (clone H), which impaired Vpu-mediated downregulation of CD4 and Tetherin. Notably, SM111 was only partially active against NL4.3 Δ Vpu (46.5% [44-48.2] in absence vs. 22.4% [20.1-25.7] in presence of drug); and growth of resistant strains was inhibited to various degrees by SM111 (92%; 54%; and 16% reduction for clone A; C; and H respectively). Funded by CIHR & the Michael Smith Foundation for Health Research

SM111 chemical structure Conclusions: SM111 is a novel compound that inhibits replication of WT as well as RTI, PI and INI resistant HIV-1 strains. Passaging of NL4.3 with SM111 selected major mutations in Vpu. However, these mutants and a Δ Vpu strain remained partially sensitive to the drug, suggesting that Vpu may not be SM111’s primary target. Our results indicate that SM111’s mechanism of action is unique from current antiretroviral drugs, but more studies are necessary to explore this promising prototype. 537 4’-Ethynyl-2-Fluoro-2’-Deoxyadenosine (EFdA) Has an Extremely High Genetic Barrier, Persistently Exerting Highly Potent Activity Against a Variety of HIV-1 Isolates Including EFdA-Selected HIV-1 Variants Kenji Maeda 1 ;YukiTakamatsu 1 ; Satoru Kohgo 2 ; Nicole S. Delino 1 ; Simon B. Chang 1 ; Kazuhiro Haraguchi 3 ; Hiroaki Mitsuya 1 1 National Institutes of Health (NIH), Bethesda, MD, US; 2 National Center for Global Health and Medicine, Tokyo, Japan; 3 Nihon Pharmaceutical University, Saitama, Japan Background: 4’-Ethynyl-2-fluoro-2’-deoxyadenosine (EFdA), a nucleoside reverse transcriptase inhibitor (NRTI), exerts potent activity against a wide spectrum of HIV-1 variants, including multi-drug-resistant HIV-1 isolates. EFdA is currently under clinical trials in the US as a peroral QD-possible therapeutic against HIV-1 infection and AIDS. We have recently selected in vitro HIV-1 variants resistant against EFdA (HIV-1 EFdA-R ), carrying M41L/D67D/T69G/K70R/L74I/V75T/M184V/T215F/K219Q substitutions in reverse transcriptase (Maeda K et al. Antiviral Therapy 19:179-189, 2014). In the present study, we newly designed and synthesized a variety of novel 4’-modified NRTIs, which exert activity against various multi- drug-resistant-HIV-1 variants including HIV-1 EFdA-R . Methods: Anti-HIV-1 activity of EFdA and various newly synthesized EFdA-related NRTIs were examined using various cell-based assays including the MTT assay and p24 assay. Cytotoxicity of such NRTIs was also determined. Results: Multiple EFdA-related NRTIs were identified to be active against wild-type HIV-1 (HIV-1 WT ) with IC 50 values of 2 - 207 nM, most of which were also active against viruses carrying conventional multi-NRTI-resistance-associated amino acid substitutions such as K65R, K70R, and M184V (HIV-1 MDR s) with IC 50 values of 3 - 404 nM. However, most of such 4’-modified NRTIs failed to be active against HIV-1 EFdA-R (>1,000 nM): only two 4’-modified-pyrimidine-based NRTIs, YMS-99066 and YMS-03072, were identified to be active against HIV-1 EFdA-R with IC 50 values of 91 and 131 nM, respectively. Against HIV-1 WT and HIV-1 MDR s, EFdA exerted the most potent activity with IC 50 values of 0.1 - 2 nM. Against HIV- 1 EFdA-R , EFdA also exerted the most potent activity with IC 50 value of 44 nM. The CC 50 value of EFdA was 19.2 m M with a selectivity index of 64,000. Conclusions: We newly synthesized various 4’-modified NRTIs and tested their activity against HIV-1 WT , HIV-1 MDR s, and HIV-1 EFdA-R . The present data demonstrate that among a variety of 4’-modified purine- and pyrimidine-based NRTIs, EFdA persistently exerts the most potent activity against even EFdA-selected HIV-1 EFdA-R and warrant further clinical development as a novel QD-possible NRTI with an extremely high genetic barrier and potency against a variety of multi-drug-resistant HIV-1 variants. 538 GSK2838232, a Second Generation HIV-1 Maturation Inhibitor With an Optimized Virology Profile Jerry Jeffrey 1 ; PingWang 1 ; Charlene McDanal 1 ; Pauline J. Shipper 2 ; Kevin Brown 1 ; Cristin Galardi 1 ; JunTang 1 ; Monique Nijhuis 2 ; Brian Johns 1 1 GlaxoSmithKline, Research Triangle Park, NC, US; 2 University of Utrecht, Utrecht, Netherlands Background: The first generation HIV-1 maturation inhibitor bevirimat demonstrated clinical efficacy in infected subjects. However, gag polymorphisms in both capsid (p24) and Sp1 regions were liabilities for bevirimat potency against a broad range of HIV-1 isolates; therefore limiting the clinical utility of bevirimat to 40% of HIV patients without polymorphisms in the 369-370 region of gag. Methods: We aimed to improve the virology profile of an HIV-1 maturation inhibitor by combining a medicinal chemistry approach with a virology triage strategy focused on activity against gag polymorphisms. Initial anti-viral activity was assessed in an MT4 assay using NL4-3 with a consensus clade B capsid/Sp1 region and compared to a V370A mutant. Compounds with no loss of potency against V370A were progressed into mechanism of action studies and a panel of HIV-1 isolates in a PBMC anti-viral assay. Results: GSK2838232 was identified using this strategy with an NL4-3 IC 50 at 0.81nM and a similar IC 50 against V370A at 0.71nM. The effect of human serum addition was assessed on GSK2838232 potency and showed no effect with increasing serum concentrations up to 40%. When tested in a panel of 26 HIV-1 isolates covering a diversity of capsid/ Sp1 genotypes in clades A, AE, B, and C using a PBMC based assay, GSK2838232 had a mean IC 50 of 1.6nM (IC 50 range 0.8nM to 4.3nM). The broad spectrum isolate coverage was confirmed by an external contract research group in a panel of 60 isolates covering various clades with only 1 isolate (92BR014) not inhibited by GSK2838232. The external panel also included viruses with known resistance genotypes to show that GSK2838232 is not cross resistant with marketed anti-retroviral products. Based on previous observations of bevirimat potency and HIV protease inhibitor (PI) treatment, GSK2838232 was tested against a panel of viruses isolated from subjects prior to and post PI treatment and did not have a correlation in potency depending on PI experience. Conclusions: These data demonstrate the optimized anti-viral properties of GSK2838232 and support the further assessment of this compound as a second generation maturation inhibitor for the treatment HIV-1 infected subjects.

Poster Abstracts

349

CROI 2015