CROI 2019 Abstract eBook

Abstract eBook

Poster Abstracts

and PIs, the rates were highest for Y188C/H/L (63.6%) and L90M (65.9%) and lowest for V108I (33.3%) and I54L/M (29.0%). Re-detection rates showed no association with length of ART or of VS, current antiretroviral regimens or other factors such as current or nadir CD4 cells. Conclusion: In this large cohort study of pts with multidrug resistant HIV infection, DS of proviral DNA regained more than half of the DRMs that had emerged during previous virologic failures. Almost 10%were newly detected and a lower cut-off of 2% yielded almost 15% additional DRMs. However, detection consistency between DS and historical testings was low for specific mutations. Re-detection rates were not associated with any factor analysed, including length of viral suppression or current ART regimen.

and is the main RAM to emerge during in vitro selection studies with tenofovir. Here, we evaluated the in vitro activity of TAF at physiological concentration in a large set of K65R-containing HIV-1, with or without M184V/I. Methods: HIV primary isolates (n=42) with K65R ±M184V/I spanning 5 different subtypes were selected. Samples with mutation mixtures at RT residues K65 and/or M184 were not included. The PR-RT region was amplified and cloned into the pXXLAI proviral DNA vector and transfected into virus producing cell lines; viral isolates were harvested after 48 h. Antiviral drug susceptibilities (EC50 fold change [FC] relative to wild-type) were determined in MT-2 cells using a 5-day Multi-Cycle HIV assay. Comparison of TAF and TDF resistance barriers were further assessed in viral breakthrough assay performed at clinically relevant drug concentrations. Results: TAF mean FC for all tested viruses was 4.0 (n=42; range: 1.0-27.4). The TAF FC of the viruses harboring K65R with M184V/I (average FC of 3.3; n = 28) was numerically lower than the TAF FC of the viruses without M184V (average FC of 5.4; n = 14). All 42 mutant isolates were subsequently assayed at TAF or TDF physiological concentration in viral breakthrough assay (28 days), resulting in 4/42 mutants breaking through under TAF treatment (average FC of 12.2 for viruses breaking through; range 6.1-27.4), and 18/42 mutants breaking through under TDF treatment (average FC of 6.1 for viruses breaking through; range 3.2-27.4). Conclusion: In a viral breakthrough assay mimicking the 4-fold higher intracellular levels of TFV-DP delivered by TAF compared to TDF in vivo, TAF inhibited breakthrough of the majority of K65R-containing HIV-1 evaluated compared to TDF, emphasizing the higher resistance barrier provided by TAF vs TDF. These differences were observed for HIV isolates regardless of their subtypes or genetic diversity around the K65 position. 547 GSS OF NRTI-BACKBONE PREDICTS TIME TO VIROLOGICAL FAILURE OF INI-BASED REGIMENS Alberto Borghetti 1 , Arturo Ciccullo 1 , Francesca Lombardi 1 , Gianmaria Baldin 1 , Simone Belmonti 1 , Mattia Prosperi 2 , Francesca Incardona 3 , Eva Heger 4 , Vanni Borghi 5 , Anders Sönnerborg 6 , Simona Di Giambenedetto 1 , for the INTEGRATE - EuResist Group 1 Catholic University of the Sacred Heart, Rome, Italy, 2 University of Florida, Gainesville, FL, USA, 3 EuResist Network, Rome, Italy, 4 Cologne University Hospital, Cologne, Germany, 5 Azienda Ospedaliera Universitaria Policlinico di Modena, Modena, Italy, 6 Karolinska Institute, Stockholm, Sweden Background: INI-based regimens are the mainstay of antiretroviral therapy (ART). We evaluated the impact of NRTIs backbone-associated drug resistance mutations (DRM) at the start of a INI-based regimen on the onset of virological failure (VF). Methods: The sum of genotypic susceptibility scores (GSS) obtained by Stanford HIVdb algorithm version 8.6.1 (classified as: 0 for high-level resistance, 0.5 for low or intermediate-level resistance, 1 for potential low-level resistance or susceptible) for each NRTI was calculated for patients starting 2 NRTIs (3TC/FTC, ABC or TDF/TAF) plus RAL, EVG/c or DTG or 1 NRTI plus DTG in the INTEGRATE - EuResist cohort. Probability of VF (defined as the criterion for regimen discontinuation) after 1 year was estimated for each regimen, and the association of GSS with VF was evaluated by Cox regression. Results: From 1998 to 2017, 7,972 pts were eligible for the study (44%men, 47 yrs median age): 26.9% of them started 2NRTIs+RAL, 10.5% 2NRTIs+EVG, 56.3% 2NRTIs+DTG, 6.3% 1NRTI+DTG. Median time since HIV diagnosis and ART initiation were 8 and 5 yrs, respectively; zenith HIV-RNA was >100k cp/ mL in 51.4% of pts and nadir CD4 count was <200 cells/µL in 47.1%; at baseline (BL) HIV-RNA was <50 cp/mL in 62.9% of pts and CD4 count was >500 cells/ µL in 49.0%. Pts mainly switched from a 3-drug regimen (60.7%), mostly for simplification (28.2%) and toxicity (6.8%); 1,420 (17.8%) pts were naive to ART. Historical genotype was available for 4,265 pts: 105 (2.5%) had DRM for at least 1 NRTI included in the backbone. Over 10,485.5 pt-yrs of follow-up (1 yr median follow-up time) 108 VF were detected (1.03 per 100 pt-yrs). Probability of VF after 1 yr was 2.1% (95% CI 1.3-2.9) with 2NRTIs+RAL, 1.2% (95% CI 0.2-2.2) with NRTIs+EVG/c, 0.2% (95% CI 0.0-0.4) with 2NRTIs+DTG, 2.1% (95% CI 0.5-3.7) with 1NRTI+DTG (p<0.001). Higher GSS (per 1 unit increase, aHR 0.12, p<0.001) and the use of 2NRTIs+DTG (vs 2NRTI+RAL, aHR 0.11, p=0.002) were associated with reduced risk of VF. Viral subtype G (vs B, aHR 8.51, p=0.016), zenith HIV-RNA>500k cp/mL (vs <100k cp/mL, aHR 6.36, p=0.005), and continent of infection (Africa vs Europe, aHR 107.82, p<0.001) predicted VF independently from HIV risk factor and gender, BL HIV-RNA, previous VF with

545LB LTR TRANSLOCATION MUTATIONS UNDER HIGH-LEVEL CABOTEGRAVIR MAINTAIN HIV REPLICATION Xierong Wei 1 , Jonathan T. Lipscomb 1 , Ariana P. Santos 2 , Mian-er Cong 1 , Susan Ruone 1 , Gerardo Garcia-Lerma 1 , Jeffrey A. Johnson 1 1 CDC, Atlanta, GA, USA, 2 Anyar, Inc., Fort Walton Beach, FL, USA Background: Recent reports have described HIV replication under high levels of the integrase (IN) inhibitor, dolutegravir (DTG), was associated with mutations in the 3’PPT with no resistance mutations observed in the integrase gene (int). Cabotegravir (CAB), a longer-acting analogue of DTG, has a high genetic barrier to resistance emergence. We examined for int drug resistance mutations in vitro both with increasing concentrations of CAB and under continuous high concentration. We also looked for changes in IN-binding regions in the long terminal repeats (LTR). Methods: For dose escalation, CEMx174 cells were infected with wild-type HIV- 1IIIB (5.0X10^8 cp/1M cells) beginning with 0.1nM CAB. After visualization of cytopathology (CPE), CAB concentration was doubled for 12 culture passages up to 205nM. In a second experiment, 300nM CAB (~350-times EC90) was added to cultures 24h after infection with wild-type HIV-1IIIB. Int sequences in viral RNA (vRNA) and DNA were analyzed weekly by both Sanger and deep sequencing. vRNA LTR 5’R-U5 and 3’U3-R, proviral U3-U5 LTR and 2-LTR DNA junction regions were also sequenced. Results: Increasing CAB concentrations over a year generated no int mutations despite continued, albeit prolonged, appearance of CPE. Initiating cultures with 300nM CAB quickly yielded vRNA LTR mutations by day 7 at a 1% frequency (f) (VL=3x10^7cp/ml) and 48% at day 105 (VL=3x10^9). Proviral LTR mutations were first detected (f =14%) at day 14, with 98% of amplified proviral LTRs mutated at day 105. These mutations were in the LTR U3 and are similar to previously described DTG-associated 3’PPT mutations. We have identified the mutations as translocated copies of the LTR U5 IN cleavage site, which introduced adjacent to the U3 cut site another IN binding/cleavage site but in complementary orientation. Deletions in U3 were also observed. 2-LTR circles accumulated rapidly and had majority wild-type junction sequences; also present were circles with tandem repeats in U3 3’-flanking the junction. Conclusion: We propose that replacing sequences adjacent to the U3 IN cleavage site with a U5 cleavage motif is a functional mutation that permits HIV integration in the presence of high-level IN inhibitor, possibly by an altered IN complex conformation. These variant proviruses may form by erroneous IN processing of preintegration LTRs. The nearly ubiquitous presence of the U5 site in U3 proviral LTRs after 100 days in culture supports this as a mechanism for HIV persistence in vitro under CAB. 546 ANTIVIRAL ACTIVITY OF TENOFOVIR ALAFENAMIDE AGAINST HIV-1 HARBORING K65R Stephanie W. Cox , Nicolas A. Margot, Renee R. Ram, Christian Callebaut Gilead Sciences, Inc, Foster City, CA, USA Background: Tenofovir alafenamide (TAF) and tenofovir disoproxil fumarate (TDF) and are prodrugs of the HIV-1 nucleotide reverse transcriptase (RT) inhibitor tenofovir (TFV). In vivo, TAF achieves ~4-fold higher intracellular levels of TFV diphosphate (TFV-DP) in PBMCs, compared to TDF. Although rare, K65R is a resistance associated mutation (RAM) for several NRTIs, including TAF and TDF,

Poster Abstracts

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