HIV-1 Integrase Strand Transfer Research Articles

Placental transfer of elvitegravir and cobicistat in an ex-vivo human cotyledon double perfusion model.

To determine the transplacental pharmacokinetics of the HIV integrase strand transfer inhibitor elvitegravir and of cobicistat, a cytochrome P450 inhibitor used as a pharmacoenhancer in antiretroviral therapy. Maternal-to-fetal transfer across the term human placenta was investigated with the ex-vivo dually perfused cotyledon model, in seven open-circuit experiments and 10 closed-circuit (recirculating) experiments. Elvitegravir and cobicistat were added to a maternal perfusate containing 2 g/l of human serum albumin and antipyrine, as a marker to validate the cotyledon's viability. Elvitegravir and cobicistat concentrations were measured using ultraperformance liquid chromatography coupled with tandem mass spectrometry. For elvitegravir, in open-circuit experiments the mean (±SD) fetal transfer rate (FTR) (fetal/maternal concentration at steady state from 30 to 90 min) was 19 ± 13% and the mean clearance index was 0.46 ± 0.21; in the closed-circuit model, after 3 h of perfusion the FTR was 20 ± 10% and the mean accumulation index was 12.28 ± 5.57. For cobicistat, in the open perfusions the FTR was 23 ± 13% and the mean clearance index was 0.63 ± 0.34; in the closed perfusions after 3 h the fetal-to-maternal ratio of cobicistat was 21 ± 11%. The mean accumulation index was 3.46 ± 2.19 CONCLUSION:: The two models concurred to show moderate placental transfer of elvitegravir and cobicistat across the placenta as well as elvitegravir accumulation in the placenta tissue. Whether this may lead to toxicities and modifications in fetal or placental metabolism requires clinical studies.

Possible Role of Integrase Inhibitors in the Management of Untreated HIV-Infected Subjects in Intensive Care Units

The introduction HIV integrase strand transfer inhibitors may help reduce the risk of acquiring the infection by the operators as well of developing complications by the patients, in case of admission of untreated HIV-1-infected subjects with potentially dangerous viremia, suppressing plasma HIV RNA concentrations by 10 folds every 3 days.

Computational Studies of N-substituted Quinolinonyl Diketo Acid Derivatives as HIV Integrase Strand Transfer Inhibitors using 3D-QSAR, Pharmacophore Modeling and Molecular Docking

Computational Studies of N-substituted Quinolinonyl Diketo Acid Derivatives as HIV Integrase Strand Transfer Inhibitors using 3D-QSAR, Pharmacophore Modeling and Molecular Docking

Structure-Guided Optimization of HIV Integrase Strand Transfer Inhibitors.

Integrase mutations can reduce the effectiveness of the first-generation FDA-approved integrase strand transfer inhibitors (INSTIs), raltegravir (RAL) and elvitegravir (EVG). The second-generation agent, dolutegravir (DTG), has enjoyed considerable clinical success; however, resistance-causing mutations that diminish the efficacy of DTG have appeared. Our current findings support and extend the substrate envelope concept that broadly effective INSTIs can be designed by filling the envelope defined by the DNA substrates. Previously, we explored 1-hydroxy-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamides as an INSTI scaffold, making a limited set of derivatives, and concluded that broadly effective INSTIs can be developed using this scaffold. Herein, we report an extended investigation of 6-substituents as well the first examples of 7-substituted analogues of this scaffold. While 7-substituents are not well-tolerated, we have identified novel substituents at the 6-position that are highly effective, with the best compound (6p) retaining better efficacy against a broad panel of known INSTI resistant mutants than any analogues we have previously described.

P176 Clinical pharmacology of the HIV integrase strand transfer inhibitor bictegravir

IntroductionBictegravir(BIC), an investigational, once-daily, HIV integrase strand transfer inhibitor(INSTI) with potent in vitro activity against most INSTI-resistant variants, is currently in development as a single tablet regimen(STR) coformulated with FTC/TAF.MethodsBIC exposure was dose proportional following SD of 25–100mg. Steady-state accumulation was approximately 1.6x, consistent with the observed half-life of approximately 18 hours. Balanced glucuronidation and oxidation contributed to the major clearance pathways. The DDI study showed increased BIC AUC(61-74%) by CYP3A4 inhibitors voriconazole and DRV/COBI but showed a greater increase(~4x) by potent dual inhibitors of UGT1A1 and CYP3A4, ATV and ATV+COBI. Coadministration with a potent CYP3A4/UGT1A1/P–gp inducer, rifampin resulted in a 75% decrease of BIC AUC a lesser reduction(38%) was associated with the moderate CYP3A4/P–gp inducer, rifabutin. BIC was well tolerated at all doses studied.ResultsThe favourable BIC PK profile supports once daily dosing. DDI results are consistent with its ADME profile in which both CYP3A4 and UGT1A1contributed to BIC elimination. BIC was safe and well tolerated in healthy volunteers.DiscussionThe favourable BIC PK profile supports once daily dosing. DDI results are consistent with its ADME profile in which both CYP3A4 and UGT1A1contributed to BIC elimination. BIC was safe and well tolerated in healthy volunteers.

Discovery and optimization of 2-pyridinone aminal integrase strand transfer inhibitors for the treatment of HIV

HIV integrase strand transfer inhibitors (InSTIs) represent an important class of antiviral therapeutics with proven efficacy and excellent tolerability for the treatment of HIV infections. In 2007, Raltegravir became the first marketed strand transfer inhibitor pioneering the way to a first-line therapy for treatment-naïve patients. Challenges with this class of therapeutics remain, including frequency of the dosing regimen and the genetic barrier to resistance. To address these issues, research towards next-generation integrase inhibitors has focused on imparting potency against RAL-resistent mutants and improving pharmacokinetic profiles. Herein, we detail medicinal chemistry efforts on a novel class of 2-pyridinone aminal InSTIs, inpsired by MK-0536, which led to the discovery of important lead molecules for our program. Systematic optimization carried out at the amide and aminal positions on the periphery of the core provided the necessary balance of antiviral activity and physiochemical properties. These efforts led to a novel aminal lead compound with the desired virological profile and preclinical pharmacokinetic profile to support a once-daily human dose prediction.

Antiviral Activity, Safety, and Pharmacokinetics of Bictegravir as 10-Day Monotherapy in HIV-1–Infected Adults

Objective:To evaluate antiviral activity, safety, and pharmacokinetics of short-term monotherapy with bictegravir (BIC), a novel, potent HIV integrase strand transfer inhibitor (INSTI).Design:Phase 1b, randomized, double-blinded, adaptive, sequential cohort, placebo-controlled study.Methods:HIV-infected adults not taking antiretroviral therapy were randomized to receive BIC (5, 25, 50, or 100 mg) or placebo once daily for 10 days. Primary endpoint was time-weighted average change from baseline to day 11 (DAVG11) for plasma HIV-1 RNA. HIV-1 RNA, adverse events (AEs), and laboratory assessments were evaluated through day 17.Results:Twenty participants were enrolled (n = 4/group). Mean DAVG11 ranged from −0.92 to −1.61 across BIC doses versus −0.01 for placebo. Significant reductions in plasma HIV-1 RNA from baseline at day 11 were observed for all BIC doses compared with placebo (P < 0.001); mean decreases were 1.45–2.43 log10 copies/mL. Increased BIC exposures correlated with increased reduction in plasma HIV-1 RNA from baseline on day 11. Three participants on BIC (50 or 100 mg) achieved plasma HIV-1 RNA <50 copies/mL by end of study. Median Tmax ranged from 1.0 to 1.8 hours (day 1, postdose) and 1.3–2.7 hours (day 10), with median t1/2 ranging from 15.9 to 20.9 hours. No participant developed primary INSTI-R substitution through day 17. BIC was well tolerated, with no discontinuations because of adverse events.Conclusions:BIC is a novel, potent, unboosted INSTI that demonstrated rapid, dose-dependent declines in HIV-1 RNA after 10 days of monotherapy. BIC was well tolerated, and displayed rapid absorption and a half-life supportive of once-daily therapy in HIV-infected subjects.

Purification of Zika virus RNA-dependent RNA polymerase and its use to identify small-molecule Zika inhibitors.

The viral RNA-dependent RNA polymerase (RdRp) enzymes of the Flaviviridae family are essential for viral replication and are logically important targets for development of antiviral therapeutic agents. Zika virus (ZIKV) is a rapidly re-emerging human pathogen for which no vaccine or antiviral agent is currently available. To facilitate development of ZIKV RdRp inhibitors, we have established an RdRp assay using purified recombinant ZIKV NS5 polymerase. We have shown that both the hepatitis C virus (HCV) nucleoside inhibitor sofosbuvir triphosphate and a pyridoxine-derived non-nucleoside small-molecule inhibitor, DMB213, can act against ZIKV RdRp activity at IC 50 s of 7.3 and 5.2 μM, respectively, in RNA synthesis reactions catalysed by recombinant ZIKV NS5 polymerase. Cell-based assays confirmed the anti-ZIKV activity of sofosbuvir and DMB213 with 50% effective concentrations (EC 50 s) of 8.3 and 4.6 μM, respectively. Control studies showed that DMB213 did not inhibit recombinant HIV-1 reverse transcriptase and showed only very weak inhibition of HIV-1 integrase strand-transfer activity. The S604T substitution in motif B of the ZIKV RdRp, which corresponds to the S282T substitution in motif B of HCV RdRp, which confers resistance to nucleotide inhibitors, also conferred resistance to sofosbuvir triphosphate, but not to DMB213. Enzyme assays showed that DMB213 appears to be competitive with natural nucleoside triphosphate (NTP) substrates. Recombinant ZIKV RdRp assays can be useful tools for the screening of both nucleos(t)ide compounds and non-nucleotide metal ion-chelating agents that interfere with ZIKV replication.

No clinically significant pharmacokinetic interactions between dolutegravir and daclatasvir in healthy adult subjects.

BackgroundDaclatasvir (DCV) is an NS5A replication complex inhibitor recently approved for chronic hepatitis C virus treatment.MethodsTo assess drug interactions between the HIV integrase strand transfer inhibitor dolutegravir (DTG) and DCV, subjects were randomized into 1 of 2 sequences in an open-label, 3-period, crossover study. Subjects received either DTG 50 mg once daily or DCV 60 mg once daily for 5 days in periods 1 and 2 and DTG 50 mg plus DCV 60 mg once daily for 5 days in period 3, with no washout between periods 2 and 3. Between periods 1 and 2, there was a washout period of at least 7 days.ResultsThe geometric least-squares mean ratios (90 % confidence intervals) of DCV area under the concentration-time curve over a dosing interval (AUC0-τ), maximum observed concentration (Cmax), and concentration at the end of the dosing interval (Cτ) were 0.978 (0.831–1.15), 1.03 (0.843–1.25), and 1.06 (0.876–1.29), respectively, when DCV was administered with DTG compared with DCV alone. Compared with DTG alone, coadministration of DTG with DCV increased DTG AUC0-τ, Cmax, and Cτ by approximately 33, 29, and 45 %, respectively.ConclusionsDCV plasma exposure was not meaningfully affected by DTG. Coadministration of DTG with DCV resulted in slight increases in DTG AUC0-τ, Cmax, and Cτ. Accumulated safety and tolerability data in humans receiving DTG to date suggests this effect is not considered clinically significant. DTG and DCV can be coadministered without dose adjustment.Trial registrationRegistered on March 6, 2014 with ClinicalTrials.gov; registration number: NCT02082808 and as Study ID: 201102 on the ViiV Clinical Study Registry.

HIV-1 Integrase Strand Transfer Inhibitors with Reduced Susceptibility to Drug Resistant Mutant Integrases.

HIV integrase (IN) strand transfer inhibitors (INSTIs) are among the newest anti-AIDS drugs; however, mutant forms of IN can confer resistance. We developed noncytotoxic naphthyridine-containing INSTIs that retain low nanomolar IC50 values against HIV-1 variants harboring all of the major INSTI-resistant mutations. We found by analyzing crystal structures of inhibitors bound to the IN from the prototype foamy virus (PFV) that the most successful inhibitors show striking mimicry of the bound viral DNA prior to 3′-processing and the bound host DNA prior to strand transfer. Using this concept of “bi-substrate mimicry,” we developed a new broadly effective inhibitor that not only mimics aspects of both the bound target and viral DNA but also more completely fills the space they would normally occupy. Maximizing shape complementarity and recapitulating structural components encompassing both of the IN DNA substrates could serve as a guiding principle for the development of new INSTIs.

Novel HIV-1 Integrase Inhibitor Development by Virtual Screening Based on QSAR Models.

HIV-1 integrase (IN) plays an important role in the life cycle of HIV and is responsible for integration of the virus into the human genome. We present computational approaches used to design novel HIV-1 IN inhibitors. We created an IN inhibitor database by collecting experimental data from the literature. We developed quantitative structure-activity relationship (QSAR) models of HIV-1 IN strand transfer (ST) inhibitors using this database. The prediction accuracy of these models was estimated by external 5-fold cross-validation as well as with an additional validation set of 308 structurally distinct compounds from the publicly accessible BindingDB database. The validated models were used to screen a small combinatorial library of potential synthetic candidates to identify hits, with a subsequent docking approach applied to further filter out compounds to arrive at a small set of potential HIV-1 IN inhibitors. As result, 236 compounds with good druglikeness properties and with correct docking poses were identified as potential candidates for synthesis. One of the six compounds finally chosen for synthesis was experimentally confirmed to inhibit the ST reaction with an IC50(ST) of 37 µM. The IN inhibitor database is available for download from http://cactus.nci.nih.gov/download/iidb/.

Discovery of 2-Pyridinone Aminals: A Prodrug Strategy to Advance a Second Generation of HIV-1 Integrase Strand Transfer Inhibitors.

The search for new molecular constructs that resemble the critical two-metal binding pharmacophore required for HIV integrase strand transfer inhibition represents a vibrant area of research within drug discovery. Here we present the discovery of a new class of HIV integrase strand transfer inhibitors based on the 2-pyridinone core of MK-0536. These efforts led to the identification of two lead compounds with excellent antiviral activity and preclinical pharmacokinetic profiles to support a once-daily human dose prediction. Dose escalating PK studies in dog revealed significant issues with limited oral absorption and required an innovative prodrug strategy to enhance the high-dose plasma exposures of the parent molecules.

Dolutegravir maintains a durable effect against HIV replication in tissue culture even after drug washout.

Of the currently approved HIV integrase strand transfer inhibitors (INSTIs), dolutegravir has shown greater efficacy than raltegravir at suppressing HIV-1 replication in treatment-experienced individuals. Biochemical experiments have also shown that dolutegravir has a longer dissociative half-life when bound to HIV integrase than does raltegravir. In order to study the intracellular efficacy of various INSTIs, we asked whether drug removal from INSTI-treated HIV-1-infected cells would result in different times to viral rebound. In addition, we assessed the role of the R263K substitution within the integrase ORF that is associated with low-level resistance to dolutegravir. HIV-infected MT-2 cells were treated with dolutegravir, raltegravir or a third experimental INSTI (MK-2048) and the drugs were washed out after varying times. Viral replication was monitored by measuring reverse transcriptase (RT) activity in the culture fluids. We observed a significantly slower increase in RT activity after the removal of dolutegravir compared with raltegravir or MK-2048. The incubation time before the drug was removed also had an impact on the level of RT activity independently of the drug and virus used. The R263K substitution did not significantly impact on levels of RT activity after drug washout, suggesting that dolutegravir remained tightly bound to the integrase enzyme despite the presence of this mutation. These results suggest that the residency time of INSTIs on integrase is a key factor in the activity of these drugs and that the anti-HIV activity of dolutegravir persists more effectively than that of other INSTIs after drug washout.

N-Substituted Quinolinonyl Diketo Acid Derivatives as HIV Integrase Strand Transfer Inhibitors and Their Activity against RNase H Function of Reverse Transcriptase.

Bifunctional quinolinonyl DKA derivatives were first described as nonselective inhibitors of 3'-processing (3'-P) and strand transfer (ST) functions of HIV-1 integrase (IN), while 7-aminosubstituted quinolinonyl derivatives were proven IN strand transfer inhibitors (INSTIs) that also displayed activity against ribonuclease H (RNase H). In this study, we describe the design, synthesis, and biological evaluation of new quinolinonyl diketo acid (DKA) derivatives characterized by variously substituted alkylating groups on the nitrogen atom of the quinolinone ring. Removal of the second DKA branch of bifunctional DKAs, and the amino group in position 7 of quinolinone ring combined with a fine-tuning of the substituents on the benzyl group in position 1 of the quinolinone, increased selectivity for IN ST activity. In vitro, the most potent compound was 11j (IC50 = 10 nM), while the most active compounds against HIV infected cells were ester derivatives 10j and 10l. In general, the activity against RNase H was negligible, with only a few compounds active at concentrations higher than 10 μM. The binding mode of the most potent IN inhibitor 11j within the IN catalytic core domain (CCD) is described as well as its binding mode within the RNase H catalytic site to rationalize its selectivity.

Antiviral characteristics of GSK1265744, an HIV integrase inhibitor dosed orally or by long-acting injection.

GSK1265744 is a new HIV integrase strand transfer inhibitor (INSTI) engineered to deliver efficient antiviral activity with a once-daily, low-milligram dose that does not require a pharmacokinetic booster. The in vitro antiviral profile and mechanism of action of GSK1265744 were established through integrase enzyme assays, resistance passage experiments, and cellular assays with site-directed molecular (SDM) HIV clones resistant to other classes of anti-HIV-1 agents and earlier INSTIs. GSK1265744 inhibited HIV replication with low or subnanomolar efficacy and with a selectivity index of at least 22,000 under the same culture conditions. The protein-adjusted half-maximal inhibitory concentration (PA-EC50) extrapolated to 100% human serum was 102 nM. When the virus was passaged in the presence of GSK1265744, highly resistant mutants with more than a 10-fold change (FC) in EC50 relative to that of the wild-type were not observed for up to 112 days of culture. GSK1265744 demonstrated activity against SDM clones containing the raltegravir (RAL)-resistant Y143R, Q148K, N155H, and G140S/Q148H signature variants (FC less than 6.1), while these mutants had a high FC in the EC50 for RAL (11 to >130). Either additive or synergistic effects were observed when GSK1265744 was tested in combination with representative anti-HIV agents, and no antagonistic effects were seen. These findings demonstrate that, similar to dolutegravir, GSK1265744 is differentiated as a new INSTI, having a markedly distinct resistance profile compared with earlier INSTIs, RAL, and elvitegravir (EVG). The collective data set supports further clinical development of GSK1265744.

The effect of dolutegravir on the pharmacokinetics of metformin in healthy subjects.

Introduction Dolutegravir (DTG) is an HIV integrase strand transfer inhibitor approved for use in combination with other antiretrovirals for the treatment of HIV-infection in adults and adolescents. Metformin is a drug frequently used in diabetic HIV-infected patients, which requires titration to optimize dosing. In vitro, DTG inhibits organic cation transporter 2 (OCT2) and multidrug and toxin extrusion transporter 1 (MATE 1) which are known to be involved in the disposition of metformin. The objective of this study was to assess the drug interaction between DTG and metformin.Materials and Methods This was an open-label, parallel-group, three-period crossover study in healthy adult subjects. Eligible subjects were enrolled into one of the two treatment cohorts (15 subjects/cohort). Subjects received metformin 500 mg q12h for 5 days in Period 1; metformin 500 mg q12h plus DTG 50 mg q24h (Cohort 1) or 50 mg q12h (Cohort 2) for 7 days in Period 2; and metformin 500 mg q12h for 10 days in Period 3. There were no washout periods between treatments. All doses of study drug were taken with a moderate-fat meal. Serial plasma PK samples and safety assessments were obtained throughout the study. Non-compartmental PK analysis was performed and geometric least squares (GLS) mean ratios and 90% confidence intervals (CI) were generated by the mixed effect model for within-subject treatment comparisons for each cohort.Results Fourteen and thirteen subjects completed study in Cohort 1 and Cohort 2, respectively. Plasma exposures of metformin were significantly increased when co-administered with DTG (Table 1).There were no apparent changes in metformin half-life and tmax. Increased metformin plasma exposure returned to normal levels observed in Period 1 after DTG was discontinued in Period 3. No Grade 3 or 4 adverse events (AEs), deaths or serious AEs were reported during the study. Most frequently reported drug-related AEs were headache (9), loose stools (8), and nausea (7). All AEs were mild or Grade 1 with the exception of one Grade 2 headache.Conclusions Co-administration of DTG and metformin was well tolerated, yet significantly increased metformin plasma exposure; effects were DTG dose dependent. Though metformin has a wide therapeutic index and alone is not associated with hypoglycemia, close monitoring is recommended when co-administering metformin and DTG. Dose adjustments of metformin may be considered.

Dolutegravir: A New HIV Integrase Inhibitor for the Treatment of HIV Infection

ABSTRACT Dolutegravir is a second-generation HIV integrase strand transfer inhibitor (INSTI) and the most recent antiretroviral approved for treatment of HIV-1 infection. Dolutegravir in combination with two nucleoside reverse transcriptase inhibitors is one of the preferred regimens recommended by the Department of Health and Human Services HIV treatment guidelines for treatment-naive adults and adolescents. This recommendation is based on clinical trial data where dolutegravir demonstrated superiority compared with guideline preferred regimens containing efavirenz and ritonavir-boosted darunavir and noninferiority compared with first-generation INSTI, raltegravir. Dolutegravir also demonstrated superiority when compared with raltegravir in treatment-experienced, integrase-naive patients and clinical efficacy in patients with resistance to first-generation INSTIs. Overall, dolutegravir has demonstrated excellent tolerability, limited drug interactions, minimal drug resistance and once-daily dosing for treatment-naive patients.

Dolutegravir: An Integrase Strand Transfer Inhibitor for the Treatment of Human Immunodeficiency Virus 1 in Adults.

Objective: To review the efficacy, safety, pharmacokinetics, pharmacodynamics, administration, drug interactions, and cost of dolutegravir (Tivicay), a third in class integrase strand transfer inhibitor (INSTI), for the treatment of human immunodeficiency virus (HIV-1) in adults. Data Sources: MEDLINE, International Pharmaceutical Abstracts, ClinicalTrials.gov, and Google Scholar searches (January 2000 to May 2014) were conducted for articles published in English and limited to human subjects, using the key words antiretroviral drugs, HIV integrase strand transfer inhibitors, dolutegravir, DTG, and S/GSK1349572. Study Selection and Data Extraction: Following MEDLINE, International Pharmaceutical Abstracts, ClinicalTrials.gov, and Google Scholar searches, 6 clinical trials were identified and included in this review. Phase III/IV studies evaluating the safety and efficacy of dolutegravir in humans were selected and evaluated. Data Synthesis: In treatment naïve and experienced patients dolutegravir was noninferior to raltegravir at suppressing viral load when added to background therapy. Abacavir/lamivudine/dolutegravir was noninferior to efavirenz/emtricitabine/tenofovir disoproxil fumarate and darunavir/ritonavir plus background therapy at suppressing viral load. In patients with multiple-class antiretroviral resistance at baseline, dolutegravir decreased HIV RNA by 1.4 log10 copies/mL at day 8, 63% of patients had achieved virologic suppression at week 8, and retained potency in treatment-experienced INSTI-resistant patients up to week 48 or 96 of follow-up. Conclusion: Dolutegravir is a safe, effective, and well-tolerated treatment option for adults with HIV-1, even in the setting of resistance to other antiretrovirals.

Combined ligand and structure-based approaches on HIV-1 integrase strand transfer inhibitors

HIV-1 integrase (IN) is an essential enzyme in the viral replication cycle and represents a promising target for anti-HIV drug design. In the present study, pharmacophore modeling and atom-based 3D-QSAR studies were carried out on a series of compounds belonging to dihydroxy isoindole derivatives as HIV-1 IN strand transfer inhibitors. The best pharmacophore model generated consists of six features AADHRR: two hydrogen bond acceptors (A), a hydrogen bond donor (D), a hydrophobic group (H) and two aromatic rings (R). Based on the best pharmacophore model, a statistically valid atom-based 3D-QSAR model was developed. The obtained atom-based 3D-QSAR model has an excellent correlation coefficient value (R2=0.87) and also exhibited good predictive power (Q2=0.72). The best pharmacophore model was further validated through enrichment calculations and it shows strong predictive power with a high performance in identifying active ligands from the total hits (actives+decoys). QM-polarized ligand docking and molecular dynamics simulations of selected active compounds in the active site of prototype foamy virus intasome gave important insights into the chemical and structural basis involved in the molecular recognition process. The O,O,O donor atom triad of compounds show metal chelation with divalent Mg2+ ions bound to the three catalytic amino acids in the enzyme’s active site and π-stacking interaction with the viral DNA residue DA17. The results might have implications for rational design of specific HIV-1 integrase strand transfer inhibitors with improved affinity and selectivity.

Resistance to HIV Integrase Strand Transfer Inhibitors Among Clinical Specimens in the United States, 2009–2012

Resistance to HIV Integrase Strand Transfer Inhibitors Among Clinical Specimens in the United States, 2009–2012