Dolutegravir Monotherapy of Simian Immunodeficiency Virus-Infected Macaques Selects for Several Patterns of Resistance Mutations with Variable Virological Outcomes.

Drug resistance remains a major concern for human immunodeficiency virus (HIV) treatment. To date, very few resistance mutations have emerged in first-line combination therapy that includes the integrase strand transfer inhibitor (INSTI) dolutegravir (DTG). In vitro, DTG selects for several primary mutations that induce low-level DTG resistance; secondary mutations, while increasing the level of resistance, however, further impair replication fitness, which raised the idea that DTG monotherapy may be feasible. The simian immunodeficiency virus (SIV) rhesus macaque model of HIV infection can be useful to explore this concept. Nine macaques were infected with virulent SIVmac251 and started on DTG monotherapy during either acute (n = 2) or chronic infection (n = 7). Within 4 weeks of treatment, all animals demonstrated a reduction in viremia of 0.8 to 3.5 log RNA copies/ml plasma. Continued treatment led to overall sustained benefits, but the outcome after 10 to 50 weeks of treatment was highly variable and ranged from viral rebound to near pretreatment levels to sustained suppression, with viremia being 0.5 to 5 logs lower than expected based on pretreatment viremia. A variety of mutations previously described to confer low-level resistance of HIV-1 to DTG or other INSTI were detected, and these were sometimes followed by mutations believed to be compensatory. Some mutations, such as G118R, previously shown to severely impair the replication capacity in vitro, were associated with more sustained virological and immunological benefits of continued DTG therapy, while other mutations, such as E92Q and G140A/Q148K, were associated with more variable outcomes. The observed variability of the outcomes in macaques warrants avoidance of DTG monotherapy in HIV-infected people.IMPORTANCE A growing number of anti-HIV drug combinations are effective in suppressing virus replication in HIV-infected persons. However, to reduce their cost and risk for toxicity, there is considerable interest in simplifying drug regimens. A major concern with single-drug regimens is the emergence of drug-resistant viral mutants. It has been speculated that DTG monotherapy may be a feasible option, because DTG may have a higher genetic barrier for the development of drug resistance than other commonly used antiretrovirals. To explore treatment initiation with DTG monotherapy, we started SIV-infected macaques on DTG during either acute or chronic infection. Although DTG initially reduced virus replication, continued treatment led to the emergence of a variety of viral mutations previously described to confer low-level resistance of HIV-1 to DTG, and this was associated with variable clinical outcomes. This unpredictability of mutational pathways and outcomes warns against using DTG monotherapy as initial treatment for HIV-infected people.

Durable suppression of HIV-1 with resistance mutations to integrase inhibitors by dolutegravir following drug washout.

OBJECTIVES: Dolutegravir (DTG) has achieved better long-term suppression of HIV-1 replication than other integrase strand transfer inhibitors (INSTIs), such as raltegravir (RAL) and elvitegravir (EVG). In in-vitro drug washout experiments, we previously showed that removal of DTG from pretreated MT-2 cells infected with wild-type HIV-1 showed slower rebound in viral replication as compared to removal of RAL. Now, we performed DTG, EVG and RAL washout experiments to compare the recovery of viral integration and production of 2-long terminal repeat (LTR) circles using wild-type HIV-1 clones, R263K viruses with low-level resistance to DTG and viruses with G140S/Q148H mutations showing cross-resistance against all currently approved INSTIs. DESIGN AND METHODS: MT-2 cells infected with wild-type, R263K or G140S/Q148H HIV-1 clones were treated with DTG, RAL or EVG for 3 days. Viral rebound following drug washout was assessed, monitoring viral integration and 2-LTR circle production by qPCR. RESULTS: Viral integration did not resume for up to 8 days after DTG washout from the wild-type or R263K infections but increased soon after washout of either RAL or EVG. With the G140S/Q148H virus, levels of integration were not significantly affected by the presence of either RAL or EVG. With DTG, integration was much lower at 3 days after infection than for the no-drug control. At 8 days after DTG washout, viral integration resumed but remained relatively low. CONCLUSION: DTG antiretroviral activity in tissue culture is more durable than that of either RAL or EVG after drug washout and this is true for both wild-type and drug-resistant viruses.

Prevalence of Rilpivirine and Etravirine Resistance Mutations in HIV-1 Subtype C-Infected Patients Failing Nevirapine or Efavirenz-Based Combination Antiretroviral Therapy in Botswana.

Rilpivirine (RPV) and Etravirine (ETR) are approved second-generation non-nucleoside reverse transcriptase inhibitors (NNRTIs) for HIV treatment. There is a cross-resistance HIV mutation profile between first- and second-generation NNRTI drugs. We determined the prevalence of HIV-1 drug resistance mutations (DRMs) to RPV and ETR in Botswana. A total of 168 HIV-1 polymerase gene sequences from participants failing nevirapine (NVP)- or efavirenz (EFV)-containing regimens were analyzed for DRMs using the Stanford University HIV drug resistance database. Forty-one sequences were from an adult antiretroviral therapy (ART) study, the Tshepo study, and 127 from a prevention of mother-to-child transmission (PMTCT) study, the Mashi study, all conducted in Botswana. Prevalence of RPV and ETR highest DRM in the adult ART study (n = 41) were K101E (26.2%), E138A (23.8%), and Y181C (26.2%). The PMTCT cohort's (n = 127) high prevalence mutations were Y181C (15.7%), E138A (15%), and K101E (11%). A total of 42.9% and 3.2% of patients in the adult ART study and PMTCT study, respectively, had three or more NNRTI mutations at virologic failure. We identified HIV-1 mutations conferring resistance to RPV and ETR even though they have not been used in Botswana. Of concern was the high proportion of sequences from the adult ART study that displayed multiple DRMs; as the number of NNRTI mutations increases, the level of cross-resistance increases. It is plausible that patients displaying such profiles maybe at increased risk of failing second-generation NNRTI drugs, hence, calls for genotyping in patients with prior NVP or efavirenz exposure before prescription of RPV- or ETR-containing cART.

The S230R Integrase Substitution Associated With Virus Load Rebound During Dolutegravir Monotherapy Confers Low-Level Resistance to Integrase Strand-Transfer Inhibitors.

Background: Dolutegravir (DTG) is an integrase strand-transfer inhibitor (INSTI) used for treatment of human immunodeficiency virus (HIV)-infected individuals. Owing to its high genetic barrier to resistance, DTG has been clinically investigated as maintenance monotherapy to maintain viral suppression and to reduce complication and healthcare costs. Our study aims to explain the underlying mechanism related to the emergence of a S230R substitution in patients who experienced virologic failure while using DTG monotherapy. Methods: We evaluated the effect of the S230R substitution in regard to integrase enzyme activity, viral infectivity, replicative capacity, and susceptibility to different INSTIs by biochemical and cell-based assays. Results: The S230R substitution conferred a 63% reduction in enzyme efficiency. S230R virus was 1.29-fold less infectious than wild-type virus but could replicate in PM1 cells without significant delay. Resistance levels against DTG, cabotegravir, raltegravir, and elvitegravir in tissue culture were 3.85-, 3.72-, 1.52-, and 1.21-fold, respectively, in virus with the S230R substitution. Conclusions: Our data indicate that the S230R substitution is comparable to the previously reported R263K substitution in some respects. Virologic failure during DTG monotherapy can occur through the development of the S230R or R263K mutation, without the need for high-level DTG resistance.

Inhibition of NF-κB-dependent HIV-1 replication by the marine natural product bengamide A.

HIV-1 inhibitors that act by mechanisms distinct from existing antiretrovirals can provide novel insights into viral replication and potentially inform development of new therapeutics. Using a multi-cycle HIV-1 replication assay, we screened 252 pure compounds derived from marine invertebrates and microorganisms and identified 6 (actinomycin Z2, bastadin 6, bengamide A, haliclonacyclamine A + B, keramamine C, neopetrosiamide B) that inhibited HIV-1 with 50% effective concentrations (EC50s) of 3.8 µM or less. The most potent inhibitor, bengamide A, blocked HIV-1 in a T cell line with an EC50 of 0.015 µM and in peripheral blood mononuclear cells with an EC50 of 0.032 µM. Bengamide A was previously described to inhibit NF-κB signaling. Consistent with this mechanism, bengamide A suppressed reporter expression from an NF-κB-driven minimal promoter and an HIV-1 long terminal repeat (LTR) with conserved NF-κB response elements, but lacked activity against an LTR construct with mutation of these elements. In single-cycle HIV-1 infection assays, bengamide A also suppressed viral protein expression when viruses encoded an intact LTR but exhibited minimal activity against those with mutated NF-κB elements. Finally, bengamide A did not inhibit viral DNA accumulation, indicating that it likely acts downstream of this step in HIV-1 replication. Our study identifies multiple new antiviral compounds including an unusually potent inhibitor of HIV-1 gene expression.

The antimalarial drug amodiaquine possesses anti-ZIKA virus activities.

Zika virus (ZIKV) outbreak has emerged as a global health threat, particularly in tropical areas, over the past few years. No antiviral therapy or vaccine is available at present. For these reasons, repurposing clinically approved drugs against ZIKV infection may provide rapid and cost-effective global health benefits. Here, we explored this strategy and screened eight FDA-approved drugs for antiviral activity against ZIKV using a cell-based assay. Our results show that the antimalarial drug amodiaquine has anti-ZIKV activity with EC50 at low micromolar concentrations in cell culture. We further characterized amodiaquine antiviral activity against ZIKV and found that it targets early events of the viral replication cycle. Altogether, our results suggest that amodiaquine may be efficacious for the treatment of ZIKV infection.

Cost-effectiveness of public-health policy options in the presence of pretreatment NNRTI drug resistance in sub-Saharan Africa: a modelling study.

BACKGROUND: There is concern over increasing prevalence of non-nucleoside reverse-transcriptase inhibitor (NNRTI) resistance in people initiating antiretroviral therapy (ART) in low-income and middle-income countries. We assessed the effectiveness and cost-effectiveness of alternative public health responses in countries in sub-Saharan Africa where the prevalence of pretreatment drug resistance to NNRTIs is high. METHODS: The HIV Synthesis Model is an individual-based simulation model of sexual HIV transmission, progression, and the effect of ART in adults, which is based on extensive published data sources and considers specific drugs and resistance mutations. We used this model to generate multiple setting scenarios mimicking those in sub-Saharan Africa and considered the prevalence of pretreatment NNRTI drug resistance in 2017. We then compared effectiveness and cost-effectiveness of alternative policy options. We took a 20 year time horizon, used a cost effectiveness threshold of US$500 per DALY averted, and discounted DALYs and costs at 3% per year. FINDINGS: A transition to use of a dolutegravir as a first-line regimen in all new ART initiators is the option predicted to produce the most health benefits, resulting in a reduction of about 1 death per year per 100 people on ART over the next 20 years in a situation in which more than 10% of ART initiators have NNRTI resistance. The negative effect on population health of postponing the transition to dolutegravir increases substantially with higher prevalence of HIV drug resistance to NNRTI in ART initiators. Because of the reduced risk of resistance acquisition with dolutegravir-based regimens and reduced use of expensive second-line boosted protease inhibitor regimens, this policy option is also predicted to lead to a reduction of overall programme cost. INTERPRETATION: A future transition from first-line regimens containing efavirenz to regimens containing dolutegravir formulations in adult ART initiators is predicted to be effective and cost-effective in low-income settings in sub-Saharan Africa at any prevalence of pre-ART NNRTI resistance. The urgency of the transition will depend largely on the country-specific prevalence of NNRTI resistance. FUNDING: Bill & Melinda Gates Foundation, World Health Organization.

Dolutegravir reshapes the genetic diversity of HIV-1 reservoirs.

Objectives: Better understanding of the dynamics of HIV reservoirs under ART is a critical step to achieve a functional HIV cure. Our objective was to assess the genetic diversity of archived HIV-1 DNA over 48 weeks in blood cells of individuals starting treatment with a dolutegravir-based regimen. Methods: Eighty blood samples were prospectively and longitudinally collected from 20 individuals (NCT02557997) including: acutely (n = 5) and chronically (n = 5) infected treatment-naive individuals, as well as treatment-experienced individuals who switched to a dolutegravir-based regimen and were either virologically suppressed (n = 5) or had experienced treatment failure (n = 5). The integrase and V3 loop regions of HIV-1 DNA isolated from PBMCs were analysed by pyrosequencing at baseline and weeks 4, 24 and 48. HIV-1 genetic diversity was calculated using Shannon entropy. Results: All individuals achieved or maintained viral suppression throughout the study. A low and stable genetic diversity of archived HIV quasispecies was observed in individuals starting treatment during acute infection. A dramatic reduction of the genetic diversity was observed at week 4 of treatment in the other individuals. In these patients and despite virological suppression, a recovery of the genetic diversity of the reservoirs was observed up to 48 weeks. Viral variants bearing dolutegravir resistance-associated substitutions at integrase position 50, 124, 230 or 263 were detected in five individuals (n = 5/20, 25%) from all groups except those who were ART-failing at baseline. None of these substitutions led to virological failure. Conclusions: These data demonstrate that the genetic diversity of the HIV-1 reservoir is reshaped following the initiation of a dolutegravir-based regimen and strongly suggest that HIV-1 can continue to replicate despite successful treatment.

Sophoraflavenone G Restricts Dengue and Zika Virus Infection via RNA Polymerase Interference.

Flaviviruses including Zika, Dengue and Hepatitis C virus cause debilitating diseases in humans, and the former are emerging as global health concerns with no antiviral treatments. We investigated Sophora Flavecens, used in Chinese medicine, as a source for antiviral compounds. We isolated Sophoraflavenone G and found that it inhibited Hepatitis C replication, but not Sendai or Vesicular Stomatitis Virus. Pre- and post-infection treatments demonstrated anti-flaviviral activity against Dengue and Zika virus, via viral RNA polymerase inhibition. These data suggest that Sophoraflavenone G represents a promising candidate regarding anti-Flaviviridae research.

Reduced antiretroviral drug efficacy and concentration in HIV-infected microglia contributes to viral persistence in brain.

BACKGROUND: In patients with HIV/AIDS receiving antiretroviral therapy (ART), HIV-1 persistence in brain tissue is a vital and unanswered question. HIV-1 infects and replicates in resident microglia and trafficking macrophages within the brain although the impact of individual ART drugs on viral infection within these brain myeloid cells is unknown. Herein, the effects of contemporary ART drugs were investigated using in vitro and in vivo models of HIV-1 brain infection. RESULTS: The EC50 values for specific ART drugs in HIV-infected human microglia were significantly higher compared to bone marrow-derived macrophages and peripheral blood mononuclear cells. Intracellular ART drug concentrations in microglia were significantly lower than in human lymphocytes. In vivo brain concentrations of ART drugs in mice were 10 to 100-fold less in brain tissues compared with plasma and liver levels. In brain tissues from untreated HIV-infected BLT mice, HIV-encoded RNA, DNA and p24 were present in human leukocytes while ART eradicated viral RNA and DNA in both brain and plasma. Interruption of ART resulted in detectable viral RNA and DNA and increased human CD68 expression in brains of HIV-infected BLT mice. In aviremic HIV/AIDS patients receiving effective ART, brain tissues that were collected within hours of last ART dosing showed HIV-encoded RNA and DNA with associated neuroinflammatory responses. CONCLUSIONS: ART drugs show variable concentrations and efficacies in brain myeloid cells and tissues in drug-specific manner. Despite low drug concentrations in brain, experimental ART suppressed HIV-1 infection in brain although HIV/AIDS patients receiving effective ART had detectable HIV-1 in brain. These findings suggest that viral suppression in brain is feasible but new approaches to enhancing ART efficacy and concentrations in brain are required for sustained HIV-1 eradication from brain.

Investigational HIV integrase inhibitors in phase I and phase II clinical trials.

INTRODUCTION: To date, three HIV integrase strand transfer inhibitors (INSTIs), i.e. raltegravir, elvitegravir and dolutegravir, have been approved for clinical use. Recent research has focused on new integrase inhibitors including those targeting non-catalytic sites of HIV integrase. Areas covered: This paper reviews two investigational INSTIs in phase I and II clinical trials, bictegravir (BIC) and cabotegravir (CAB), as well as an investigational noncatalytic integrase inhibitor (NCINI) termed BI 224436. Expert opinion: Data from phase I and II clinical trials demonstrate that CAB has good efficacy and is well-tolerated. CAB is promising because it can be formulated both orally and as a long-acting (LA) injectable for treatment and prevention of HIV infection. Since LA-CAB formulation offers the possibility of favourable dosing, it may help individuals who struggle with adherence issues. BIC also represents a promising safe, effective and well-tolerated drug that can be administered as a single once-daily regimen in coformulation with emtricitabine and tenofovir alafenamide (FTC/TAF). Ongoing phase III trials should clarify optimal doses and reveal the potential clinical advantages of these new drugs and formulations over other current regimens. Exploration of novel HIV integrase inhibitors acting through mechanisms different from those of INSTIs is still needed.

M184I/V substitutions and E138K/M184I/V double substitutions in HIV reverse transcriptase do not significantly affect the antiviral activity of EFdA.

BACKGROUND: 4'-Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) is a potent nucleoside analogue inhibitor of HIV that has an unusually long half-life. Cell culture selections with either EFdA or lamivudine using both subtype B and non-B clinical isolates selected the M184I/V substitutions in reverse transcriptase (RT). Unlike lamivudine, however, EFdA retained significant activity against viruses containing the M184I/V substitutions. In other clinical trials that evaluated rilpivirine together with emtricitabine in first-line therapy, the emergence of both the M184I/V and E138K mutations in RT was demonstrated. Moreover, the M184I/V and E138K substitutions were shown to be compensatory for each other with regard to both efficiency of RT activity and viral replicative capacity. This creates concern that E138K might emerge as a compensatory mutation for M184I/V in the aftermath of the use of EFdA. OBJECTIVES: We wished to determine whether the E138K mutation in HIV RT together with M184I/V would compromise the activity of EFdA. METHODS: Recombinant viruses containing the M184I/V and/or E138K substitutions were generated by site-directed mutagenesis and evaluated in tissue culture for susceptibility to various nucleoside compounds, including EFdA. RESULTS: Susceptibility to EFdA was retained in M184I/V viruses that also contained the E138K substitution. Moreover, the E138K substitution was not generated in these studies under selection pressure with EFdA. CONCLUSIONS: These findings help to alleviate concern that EFdA may not be active against viruses that contain both the M184I/V and E138K substitutions in RT.

Antiviral Activity of Bictegravir and Cabotegravir against Integrase Inhibitor-Resistant SIVmac239 and HIV-1.

Animal models are essential to study novel antiretroviral drugs, resistance-associated mutations (RAMs), and treatment strategies. Bictegravir (BIC) is a novel potent integrase strand transfer inhibitor (INSTI) that has shown promising results against HIV-1 infection in vitro and in vivo and against clinical isolates with resistance against INSTIs. BIC has a higher genetic barrier to the development of resistance than two clinically approved INSTIs, termed raltegravir and elvitegravir. Another clinically approved INSTI, dolutegravir (DTG) also possesses a high genetic barrier to resistance, while a fourth compound, termed cabotegravir (CAB), is currently in late phases of clinical development. Here we report the susceptibilities of simian immunodeficiency virus (SIV) and HIV-1 integrase (IN) mutants containing various RAMs to BIC, CAB, and DTG. BIC potently inhibited SIV and HIV-1 in single cycle infection with 50% effective concentrations (EC50s) in the low nM range. In single cycle SIV infections, none of the E92Q, T97A, Y143R, or N155H substitutions had a significant effect on susceptibility to BIC (≤4-fold increase in EC50), whereas G118R and R263K conferred ∼14-fold and ∼6-fold increases in EC50, respectively. In both single and multiple rounds of HIV-1 infections, BIC remained active against the Y143R, N155H, R263K, R263K/M50I, and R263K/E138K mutants (≤4-fold increase in EC50). In multiple rounds of infection, the G140S/Q148H combination of substitutions decreased HIV-1 susceptibility to BIC 4.8-fold compared to 16.8- and 7.4-fold for CAB and DTG, respectively. BIC possesses an excellent resistance profile in regard to HIV and SIV and could be useful in nonhuman primate models of HIV infection.

HIV-1 Resistance to Dolutegravir Is Affected by Cellular Histone Acetyltransferase Activity.

Integrase strand transfer inhibitors (INSTIs) are the newest class of antiretrovirals to be approved for the treatment of HIV infection. Canonical resistance to these competitive inhibitors develops through substitutions in the integrase active site that disrupt drug-protein interactions. However, resistance against the newest integrase inhibitor, dolutegravir (DTG), is associated with an R263K substitution at the C terminus of integrase that causes resistance through an unknown mechanism. The integrase C-terminal domain is involved in many processes over the course of infection and is posttranslationally modified via acetylation of three lysine residues that are important for enzyme activity, integrase multimerization, and protein-protein interactions. Here we report that regulation of the acetylation of integrase is integral to the replication of HIV in the presence of DTG and that the R263K mutation specifically disrupts this regulation, likely due to enhancement of interactions with the histone deacetylase I complex, as suggested by coimmunoprecipitation assays. Although no detectable differences in the levels of cell-free acetylation of the wild-type (WT) and mutated R263K enzymes were observed, the inhibition of cellular histone acetyltransferase enzymes sensitized the NL4.3WT virus to DTG, while NL4.3R263K was almost completely unaffected. When levels of endogenous acetylation were manipulated in virus-producing cells, inhibitors of acetylation enhanced the replication of NL4.3R263K, whereas inhibition of deacetylation greatly diminished the replication of NL4.3WT Taken together, these results point to a pivotal role of acetylation in the resistance mechanism of HIV to some second-generation integrase strand transfer inhibitors, such as DTG.IMPORTANCE This is, to our knowledge, the first report of the influence of posttranslational modifications on HIV drug resistance. Both viral replication and resistance to second-generation integrase strand transfer inhibitors of both WT and INSTI-resistant HIV strains were differentially affected by acetylation, likely as a result of altered interactions between integrase and the cellular deacetylation machinery. Many "shock and kill" strategies to eradicate HIV manipulate endogenous levels of acetylation in order to reactivate latent HIV. However, our results suggest that some drug-resistant viruses may differentially respond to such stimulation, which may complicate the attainment of this goal. Our future work will further illuminate the mechanisms involved.

Evaluation of Sofosbuvir (ß-D-2'-deoxy-2'-α-fluoro-2'-ß-C-methyluridine) as an inhibitor of Dengue virus replication.

We evaluated Sofosbuvir (SOF), the anti-hepatitis C virus prodrug of ß-d-2'-deoxy-2'-α-fluoro-2'-ß-C-methyluridine-5'-monophosphate, for potential inhibitory activity against DENV replication. Both cell-based and biochemical assays, based on use of purified DENV full-length NS5 enzyme, were studied. Cytopathic effect protection and virus yield reduction assays confirmed that SOF possessed anti-DENV activity in cell culture with a 50% effective concentration (EC50) of 4.9 µM and 1.4 µM respectively. Real-time RT-PCR verified that SOF inhibits generation of viral RNA with an EC50 of 9.9 µM. Purified DENV NS5 incorporated the active triphosphate form (SOF-TP) into nascent RNA, causing chain-termination. Relative to the natural UTP, the incorporation efficiency of SOF-TP was low (discrimination value = 327.5). In a primer extension assay, SOF-TP was active against DENV NS5 wild-type polymerase activity with an IC50 of 14.7 ± 2.5 µM. The S600T substitution in the B Motif of DENV polymerase conferred 4.3-fold resistance to SOF-TP; this was due to decreased incorporation efficiency rather than enhanced excision of the incorporated SOF nucleotide. SOF has antiviral activity against DENV replication. The high discrimination value in favor of UTP in enzyme assays may not necessarily preclude antiviral activity in cells. SOF may be worthy of evaluation against severe DENV infections in humans.

Efficacy, safety, and effect on sexual behaviour of on-demand pre-exposure prophylaxis for HIV in men who have sex with men: an observational cohort study.

BACKGROUND: Data for on-demand pre-exposure prophylaxis (PrEP) are scarce. We implemented a cohort study to assess its efficacy, safety, and effect on sexual behaviour. METHODS: We invited men and transgender women who have sex with men, previously enrolled in the randomised placebo-controlled ANRS IPERGAY trial at seven sites (six in France and one in Canada), to participate in an open-label extension with on-demand tenofovir disoproxil fumarate (300 mg) and emtricitabine (200 mg) to be taken before and after sexual intercourse. We assessed the incidence of HIV and other sexually transmitted infections (STIs), PrEP adherence, safety, and sexual behaviour. Statistical analyses included comparisons of proportions and incidence between the randomised phase of the ANRS IPERGAY trial and the open-label phase, and all participants were included in safety analyses. ANRS IPERGAY is registered with ClinicalTrials.gov, number NCT01473472. FINDINGS: Between Nov 4, 2014, and Jan 27, 2015, we enrolled 361 participants. Median follow-up was 18·4 months (IQR 17·7-19·1). One participant who discontinued PrEP acquired HIV infection. HIV incidence was 0·19 per 100 person-years (95% CI 0·01-1·08), compared with 6·60 per 100 person-years (3·60-11·05) in the placebo group of the randomised study, indicating a relative reduction of 97% (95% CI 81-100) in the incidence of HIV with on-demand PrEP. Participants used a median of 18 pills of study drugs per month (IQR 11-25), and at the 6 month visit 240 (71%) of 336 participants had tenofovir detected in plasma. Drug-related gastrointestinal events were reported in 49 participants (14%) but were self-limited. Only four participants (1%) discontinued PrEP, three because of an increase in plasma creatinine. The proportion of participants reporting condomless sex at their last receptive anal intercourse significantly increased from 77% (136 of 176 participants) at baseline to 86% (66 of 77 participants) at 18 months' follow-up (p for trend=0·0004). The incidence of a first bacterial STI during this open-label phase did not change significantly compared with the randomised phase (59·0 vs 49·1 per 100 person-years, respectively; p=0·11). INTERPRETATION: On-demand oral PrEP is highly effective at preventing HIV infection among high-risk men who have sex with men and therefore represents an alternative to daily PrEP, expanding choices for HIV prevention. High rates of STIs resulting from low condom use did not undermine PrEP efficacy, but warrant frequent testing. FUNDING: ANRS (France Recherche Nord and Sud Sida-HIV Hépatites), the Canadian HIV Trials Network, Fonds Pierre Bergé-Sidaction, Gilead Sciences, and the Bill & Melinda Gates Foundation.

Monotherapy with either dolutegravir or raltegravir fails to durably suppress HIV viraemia in humanized mice.

Objectives: To compare the effectiveness of HIV integrase inhibitor monotherapy between raltegravir and dolutegravir as an approach to simplify therapy. Methods: We evaluated and compared the efficacy of 20 week monotherapy with dolutegravir or raltegravir in humanized mice (HSC-NSG) infected with HIVBaL. Plasma HIV RNA was measured by quantitative RT-PCR (limit of detection of 150 copies/45 µL of plasma) and drug levels by LC-MS/MS. Escape viruses were genotyped and analysed for replication capacity and drug susceptibility in tissue culture. Results: Drug-untreated control mice maintained constant viraemia throughout the study. Virus isolates from these mice were susceptible to both raltegravir (EC50 of <8 nM) and dolutegravir (EC50 of <1 nM). Mice treated with raltegravir or dolutegravir had plasma drug levels comparable to those in humans. Monotherapy with raltegravir initially suppressed HIV viraemia, but failed to maintain suppression in 4/4 mice. Viruses from raltegravir failing mice developed mutations G140G/S and Q148H/K, and were resistant to both raltegravir (EC50 values of >100 nM) and dolutegravir (EC50 values ranging from 8.8 to 13.3 nM). Monotherapy with dolutegravir suppressed viraemia in 5/5 of mice, but viraemia rebounded in one animal. The virus from this mouse had mutations E138K, G140S, Q148H, N155H and S230R, was highly resistant to both raltegravir (EC50 of >1000 nM) and dolutegravir (EC50 of 550 nM), and replicated to levels similar to those of control viruses in PBMCs. Conclusions: Monotherapy with either raltegravir or dolutegravir does not consistently maintain HIV suppression, suggesting that dual therapy may be required in simplification strategies.