Induction effect of antiretroviral bictegravir on the expression of Abcb1, Abcg2 and Abcc1 genes associated with P-gp, BCRP and MRP1 transporters present in rat peripheral blood mononuclear cells

BACKGROUND

Antiretrovirals have the potential to cause drug interactions leading to inefficacy or toxicity via induction of efflux transporters through nuclear receptors, altering drug concentrations at their target sites.

RESEARCH DESIGN AND METHODS

This study used molecular dynamic simulations and qRT-PCR to investigate bictegravir's interactions with nuclear receptors PXR and CAR, and its effects on efflux transporters (P-gp, BCRP, MRP1) in rat PBMCs. PBMC/plasma drug concentrations were measured using LC-MS/MS to assess the functional impact of transporter expression.

RESULTS

Bictegravir significantly increased the expression of ABC transporters, with Car identified as a key mediator. This suggests that bictegravir's influence on nuclear receptors could affect drug transport and efficacy at the cellular level.

CONCLUSIONS

Bictegravir activates nuclear receptors enhancing efflux transporter expression. Understanding these interactions is crucial for preventing drug-drug interactions and reducing toxicity in clinical use. Combining CAR antagonists with bictegravir may prevent drug resistance and toxicity. However, these findings are based on preclinical data and necessitate further clinical trials to confirm their applicability in clinical settings.

Bictegravir/emtricitabine/tenofovir alafenamide as first-line treatment in naïve HIV patients in a rapid-initiation model of care: BIC-NOW clinical trial

OBJECTIVE

Multiple strategies have been utilised to reduce the incidence of HIV, including PrEP and rapid antiretroviral therapy initiation. The study objectives were to evaluate the efficacy, safety, satisfaction, treatment adherence, and system retention obtained with rapid initiation of bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) in naïve patients.

METHODS

This phase IV, multicenter, open-label, single-arm, 48-week clinical trial enrolled patients between January 2020 and June 2022. Adherence to treatment was evaluated with the SMAQ questionnaire and patient satisfaction with the EQ-5D.

RESULTS

Two hundred eight participants were enrolled with mean age of 35.6 years; 87.6% were males; mean CD4 count was 393.5 cells/uL (<200 cells/uL in 22.1%); viral load log was 5.6 (VL>100 000 cop/mL in 43.3%); 22.6% had AIDS, and 4.3% were coinfected with HBV. BIC/FTC/TAF was initiated on the day of their first visit to the HIV specialist in 98.6% of participants, and 9.6% were lost to follow-up. The efficacy at week 48 was 84.1 % by intention-to- treat (ITT), 94.6% by modified ITT, and 98.3% by per protocol analysis. The regimen was discontinued in two subjects (0.9%) during week 1 for grade 3 adverse events. Treatment adherence (weeks 4 [90%, IQR: 80-99%] vs. 48 [90%, IQR: 80-95%; P = 0.49]) and patient satisfaction (weeks 4 [90%, IQR: 80-99%] vs. 48 [90%, IQR: 80-95 P = 0.49]) rates were very high over the 48- week study period.

CONCLUSIONS

BIC/FTC/TAF is an appropriate option for rapid ART initiation in naïve HIV patients, offering high efficacy, safety, durability, treatment adherence, retention in the healthcare system, and patient satisfaction. Number Clinical Trial registration: NCT06177574.

Real-world persistence with dolutegravir/lamivudine versus bictegravir/emtricitabina/tenofovir-alafenamide among people with HIV

OBJETIVES

The main objective was to compare the persistence between dolutegravir/lamivudine (DTG/3TC) and bictegravir/emtricitabine/tenofovir-alafenamide (BIC/FTC/TAF) and to analyze reasons for discontinuation.

METHODS

We conducted a retrospective, non-interventional, descriptive and longitudinal study. All human immunodeficiency virus (HIV) patients over 18 years treated with DTG/3TC or BIC/FTC/TAF in our center were included. Persistence after first year was compared using the χ2 test. Kaplan-Meier survival analysis was performed.

RESULTS

Three hundred fifty-eight patients were included. 99.5% versus 90.99% of patients were persistent after the first year for DTG/3TC and BIC/FTC/TAF respectively (p = 0.001). Persistence with DGT/3TC was 1,237 days (IC95% 1,216-1,258) and persistence with BIC/FTC/TAF was 986 days ([IC95% 950-1,021]; p < 0.001). The difference was remained after adjusting for covariates with the cox regression model (HR= 8.2 [IC95% 1.03-64.9], p = 0.047). The main reasons for discontinuation for BIC/FTC/TAF were toxicity/tolerability.

CONCLUSION

In our study patients had a high persistence. Patients on DTG/3TC treatment were more persistent compared to BIC/FTC/TAF, although BIC/FTC/TAF have worse baseline characteristics. The main reason for discontinuation of BIC/FTC/TAF was tolerability/toxicity.

Study on the hydrolytic degradation behaviour of bictegravir by LC-PDA-Q/TOF-MS/MS NMR and in silico toxicity assessment

Forced degradation studies provide rapid access to degradation products (DPs), where structural characterization and assessment of their potential toxicity are vital for pharmaceutical safety and regulatory compliance. As per the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use (ICH) Q1A R(2) guidelines, a forced degradation study of Bictegravir (BIC), a USFDA-approved drug for HIV wild type, in hydrolytic conditions (acid, base, and neutral) revealed the formation of six DPs in RP-HPLC (Reverse Phase- High-Performance Liquid Chromatography) gradient elution program using a C18 (4.6 × 250 mm, 5 µm) column. DP-1, 2, and 3 were characterized using liquid chromatography-tandem mass spectrometry (LC-MS/MS), whereas DP-4, 5, and 6 posed difficulties in characterization due to their isomeric nature. Using characteristic NOEs (Nuclear Overhauser Effect) from 2D ROESY NMR (Nuclear Magnetic Resonance) studies, we have elucidated diastereomeric DP-4/5 and isomeric DP-6/BIC configurational structures. Furthermore, in silico toxicity studies for the six degradation products were predicted for toxicity endpoints by employing DEREK, SARAH, and Pro Tox-II application tools. The DP-1 (methanamine) and DP-3 (carboxylic acid) resulting from acid-catalyzed hydrolysis, were predicted to have potential carcinogenic and mutagenic properties. These findings contribute significantly to our understanding of BIC's stability and safety profile in pharmaceutical development and underscore the rigorous characterization of stereoisomers by NMR that were further utilized for toxicity prediction.

Comparing the efficacy and safety of a first-line regimen with emtricitabine/tenofovir alafenamide fumarate plus either bictegravir or dolutegravir: Results from clinical practice

BACKGROUND

First-line integrase strand transfer inhibitor-based regimens have become commonly used in clinical practice over the last decade. This study aimed to analyse and compare the efficacy and safety of bictegravir (BIC) and dolutegravir (DTG) when prescribed in association with emtricitabine/tenofovir alafenamide (FTC/TAF) as part of a first-line regimen for the treatment of human immunodeficiency-1 (HIV-1) infection.

METHODS

Treatment-naïve people living with HIV (PLWHIV) starting a first-line regimen with either BIC/FTC/TAF (BIC group) or FTC/TAF+DTG (DTG group) were analysed. Snapshot analyses were performed after 24 and 48 weeks to evaluate virological efficacy. In addition, differences in the rate of treatment discontinuation (TD) between the two groups were evaluated using the Kaplan-Meier method and the log rank test.

RESULTS

Data from 327 PLWHIV were analysed: 140 in the DTG group and 187 in the BIC group. At 48 weeks, 90.0% of individuals in the DTG group and 86.7% of those in the BIC group achieved HIV-RNA <50 copies/mL. In total, 88 and 38 cases of TD were observed in the DTG group and BIC group, respectively. The estimated probability of maintaining the study regimen at week 48 was 59.5% in the DTG group and 84.2% in the BIC group. Analysing changes in immunological parameters after 48 weeks, median improvements of +169 cell/mm3 (P<0.001) and +233 cell/mm3 (P<0.001) were observed in the DTG group and the BIC group, respectively.

CONCLUSIONS

Both BIC and DTG, in combination with FTC/TAF, show promising efficacy and safety as first-line strategies in clinical practice, with favourable immunological recovery even in the short term.

Application to patients with HIV

BACKGROUND

Fixed-dose combinations of antiretroviral drugs are commonly used to treat HIV infection and therapeutic monitoring is not part of routine clinical practice. However, drug concentrations monitoring might have role in different clinical scenarios as well as for research purposes. This study aimed to develop and validate UHPLC-MS/MS procedures for measuring total and unbound concentrations of bictegravir, dolutegravir, darunavir and doravirine in human plasma.

MATERIAL AND METHODS

Equilibrium dialysis preceded sample preparation (based on protein precipitation) for measuring unbound antiretroviral concentrations. Chromatographic separations were achieved on an Acquity®-UPLC® HSS™-T3 column (50 mm × 2.1 mm; 1.8 µm) using a non-linear water/acetonitrile gradient containing 0.1 % formic acid at a 0.5 mL/min flow rate. Antiretrovirals were detected by tandem mass spectrometry in positive electrospray ionisation and multiple reaction monitoring modes.

RESULTS

No significant interferences or carry-over were observed. Imprecisions, absolute relative biases, normalised matrix effects and recoveries were ≤15.0 %, ≤11.1 %, (94.7-104.1)% and (96.7-105.5)%, respectively. Non-linear measuring intervals were observed between (25-10,000) µg/L for total/plasma dialysate concentrations and linearity schemes (1.00-100) µg/L for buffer dialysate concentrations.

CONCLUSIONS

The UHPLC-MS/MS procedures developed could be used for research purposes and therapeutic drug monitoring of antiretrovirals in routine clinical practice.

Effectiveness of second-generation integrase strand-transfer inhibitor-based regimens for antiretroviral-experienced people with HIV who had viral rebound

BACKGROUND

Antiretroviral regimens containing a second-generation integrase strand-transfer inhibitor (INSTI) plus 2 nucleos(t)ide reverse-transcriptase inhibitors (NRTIs) are the recommended therapy for people with HIV (PWH) who are antiretroviral-naïve or on stable antiretroviral therapy (ART) with viral suppression. Real-world data on the virologic effectiveness of co-formulated bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) among PWH with virologic failure while receiving other ART remain sparse.

METHODS

We retrospectively reviewed the medical records of PWH who had viral rebound with plasma HIV RNA >1000 copies/mL and were switched to either dolutegravir combined with 2 NRTIs or BIC/FTC/TAF. The primary end point was re-achieving viral suppression within the first 48 weeks of switch. The association between NRTI-related resistance-associated mutations (RAMs) and virologic effectiveness was examined.

RESULTS

Seventy-nine PWH with viral rebound while receiving other antiretroviral regimens were included. Within the first 48 weeks of switch, the overall probability of re-achieving viral suppression was 79.7% (82.5% [33/40] and 76.9% [30/39] for BIC/FTC/TAF and dolutegravir-based regimens, respectively, p = 0.78). PWH with a higher CD4 lymphocyte count (adjusted odds ratio, per 100-cell/mm3 increase, 1.41; 95% confidence interval, 1.02-1.95) were more likely to re-achieve viral suppression. Among PWH switching to BIC/FTC/TAF who had pre-existing RAMs to NRTIs before switch, 14 of 15 (93.3%) successfully achieved viral suppression.

CONCLUSIONS

Switching to BIC/FTC/TAF and dolutegravir-based regimens could re-achieve viral suppression in four-fifth of the PWH who experienced viral rebound during treatment with other antiretroviral regimens. Pre-existing NRTI-related RAMs did not have adverse impact on the effectiveness of dolutegravir combined with 2 NRTIs or BIC/FTC/TAF.

Therapy initiation and rapid start with Bictegravir/Emtricitabine/Tenofovir Alafenamide in PLWH

Advanced HIV naive represents an unfavorable prognostic condition due to a persistent high risk of death, increased probability of virological failure, immunologic impairment, clinical progression, and immune reconstitution inflammatory syndrome (IRIS), cumulative adverse drug events, drug-drug interactions and increased healthcare costs. Currently, all international guidelines recommend the rapid initiation of ART, especially in late-stage naive patients. Bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF), due to its efficacy high genetic barrier, good safety profile, and low DDI potential, is one of the regimens recommended for overall rapid initiation by international guidelines. B/F/TAF has been tested in observational or uncontrolled pilot studies (OPERA, RAINBOW), while a large randomized controlled trial is currently ongoing (LAPTOP). In conclusion, B/F/TAF is an ideal combination for the initiation of antiretroviral therapy, particularly in the HIV late presenter or advanced HIV disease patient, even in the context of rapid start or same-day treatment regimens, where the initiation of treatment usually occurs in the absence of information on viral load, CD4 count, biochemical profile and HIV transmitted resistance.

Clinical pharmacology of the SingleTablet Regimen (STR) Bictegravir/Emtricitabine/Tenofovir Alafenamide (BIC/FTC/TAF)

In Italy a proportion of HIV patients exceeding 50% are diagnosed at advanced stages of disease. A sizeable proportion of patients under chronic HIV treatment has a story of poor adherence with archived resistance associated mutations, a condition implying some risks in case of treatment with dual regimens. Conventional three-drug regimens will remain necessary in the short-mid term, in order to avoid treatment failure and selection of drug resistance. Efficacy, tolerability, safety, genetic barrier, forgiveness and a good compatibility with concurrent medications are all features that describe the overall quality of BIC/FTC/TAF, a combination whose robustness will remain a point of reference for the next years.

[Sleep disorders related to HIV treatment.]

OBJECTIVE

HIV Clinical Guidelines have positioned integrase inhibitors recently as first-line treatment. However, two of these drugs have also been associated with adverse side effects on the central nervous system, especially with sleep disturbances. The objective was to analyse the influence of bictegravir and dolutegravir on the sleep quality in HIV patients.

METHODS

An observational, cross-sectional study was carried out between December 2020 and January 2021 in HIV patients attended in a pharmacy care clinic. Demographic and adherence variables were collected. Sleep quality was measured using the Pittsburgh questionnaire or PSQI. We classified patients into two groups: patients with bictegravir or dolutegravir in their treatment (study group) and the rest (control group). The influence of the variables collected on the PSQI result was analysed using the Chi-Square test for categorical variables and the student t-test or Mann-Whitney U test for continuous variables.

RESULTS

One hundred and nineteen patients were included. 64% in the study group and 67% in the control group suffered from sleep disorders according to the PSQI questionnaire (p=0.788). Neither were statistical differences found when the different components of sleep were analysed between the two groups.

CONCLUSIONS

A high percentage of patients, regardless of whether their treatment includes bictegravir or dolutegravir, have problems with their sleep quality. We didn't find a correlation between sleep quality and treatment with bictegravir or dolutegravir compared to the other treatments.

LC-QQQ-MS based intracellular quantification of bictegravir in peripheral blood mononuclear cells and plasma

Most antiretrovirals (ARVs) have intracellular therapeutic target sites and therefore, their plasma concentration may be misleading when relating to their efficacy or toxicity. A bioanalytical method for quantification of the ARV drug bictegravir (BTG) in its target site peripheral blood mononuclear cells (PBMCs) is not available till date. This is the first time to establish a sufficiently sensitive mass spectrometry-based bioanalytical method to quantify BTG in both rat PBMCs and plasma. The developed method was validated over the range of 1 ng/ml to 100 ng/ml and 0.005 ng-10ng/sample for plasma and PBMCs, respectively. For PBMCs, average accuracy and precision at four quality control levels were found to be 93.30%-110.00% and 6.52%-8.25%, respectively. Plasma and intracellular pharmacokinetics of BTG was evaluated by the developed method in rats and a lack of accumulation of BTG in the PBMCs was observed. Pearson correlation coefficient data analysis indicated a moderated correlation between plasma and PBMC concentration of BTG. Therefore, it will be beneficial to include a quantification plan for BTG in its actual therapeutic target site during all its future research and development work. This reported method can be useful for site-specific monitoring of BTG in research laboratories and pharmaceutical industries.

An indirect comparison of 144-week efficacy, safety, and tolerability of dolutegravir plus lamivudine and second-generation integrase inhibitor-based, 3-drug, single-tablet regimens in therapy-naive people with HIV-1

BACKGROUND

The long-term efficacy and safety of the 2-drug regimen dolutegravir (DTG) + lamivudine (3TC) and 3-drug single-tablet regimens recommended for antiretroviral therapy (ART)-naive people with HIV-1 (PWH) have yet to be compared directly in clinical trials. This indirect treatment comparison (ITC) was conducted to compare the durability of efficacy and long-term safety of DTG + 3TC vs second-generation, integrase strand transfer inhibitor (INSTI)-based, 3-drug, single-tablet regimens bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) and DTG/abacavir/3TC (DTG/ABC/3TC) at Week 144 after treatment initiation.

METHODS

A systematic literature review identified 4 trials evaluating the treatment regimens of interest in ART-naive PWH (GEMINI-1, GEMINI-2, GS-US-380-1489, and GS-US-380-1490). Safety, efficacy, and tolerability results were compared using fixed-effects Bucher ITC methodology to calculate relative outcomes.

RESULTS

Rates of virologic suppression (HIV-1 RNA < 50 copies/mL, US Food and Drug Administration Snapshot analysis) and virologic failure (HIV-1 RNA ≥ 50 copies/mL) as well as mean change in CD4 + cell count were similar with DTG + 3TC, BIC/FTC/TAF, and DTG/ABC/3TC at Week 144. Serious adverse events occurred less frequently with DTG + 3TC compared with both BIC/FTC/TAF (odds ratio [OR], 0.51; 95% CI 0.29-0.87; P = 0.014) and DTG/ABC/3TC (OR, 0.38; 95% CI 0.19-0.75; P = 0.006). Discontinuations and overall adverse events were similar across all 3 regimens.

CONCLUSIONS

These results suggest that the 2-drug regimen DTG + 3TC offers comparable and durable efficacy with fewer serious adverse events vs BIC/FTC/TAF and DTG/ABC/3TC through 144 weeks of treatment in ART-naive PWH. These long-term comparative data support the therapeutic value of DTG + 3TC for PWH.

Efficacy and safety of switching to bictegravir, emtricitabine, and tenofovir alafenamide in virologically suppressed Asian adults living with HIV: A pooled analysis from three international phase III randomized trials

OBJECTIVES

Data on switching to bictegravir, emtricitabine, and tenofovir alafenamide (B/F/TAF) in virologically suppressed Asian people living with HIV are limited. We performed a pooled analysis of virologically suppressed Asian participants from three international phase III trials to evaluate the efficacy and safety of switching to B/F/TAF.

METHODS

Virologically suppressed people living with HIV were randomized to switch to B/F/TAF or to stay on baseline regimens. The primary endpoint was the proportion of participants with plasma HIV-1 RNA ≥50 copies/ml at week 48. We analysed the incidence of adverse events (AEs), laboratory abnormalities, and changes in relevant tolerability parameters through 48 weeks.

RESULTS

Overall, 136 Asian participants were included. The proportions of participants with plasma HIV-1 RNA ≥50 copies/ml at week 48 were low in both arms (0% for B/F/TAF vs 1.4% for those who stayed on baseline regimens). Those who switched to B/F/TAF had virological suppression rates similar to those who stayed on baseline regimens (100% vs 95.9%, p = 0.2485), with no treatment-emergent resistance. Drug-related AEs occurred in three participants in each arm; none were serious. No participants discontinued the study drug because of AEs, and no deaths were observed. No significant differences were observed between the arms in the median changes in estimated glomerular filtration rate, body weight, and most lipid parameters. Switching from tenofovir disoproxil fumarate-containing regimens to B/F/TAF resulted in a significant decrease in tubular proteinuria compared with those who stayed on baseline regimens (p < 0.01).

CONCLUSIONS

Virologically suppressed Asian people living with HIV who switched to B/F/TAF maintained 100% virological suppression at week 48, with no treatment-emergent drug resistance and safety profiles comparable to those seen in people who stayed on baseline regimens.

CLINICAL TRIAL NUMBER

ClinicalTrials.gov (NCT02603120, NCT02652624, and NCT02603107).

A possible case of bictegravir-associated severe unconjugated hyperbilirubinemia

BACKGROUND

Bictegravir (BIC) co-formulated with emtricitabine (FTC) and tenofovir alafenamide (TAF) is approved by Federal Food and Drug Administration in 2018 for both treatment-naïve and experienced persons living with HIV (PLWH).

CASE PRESENTATION

A young man with recently diagnosed human immunodeficiency virus (HIV) infection presented with jaundice. Blood work was significant for mild anemia and grade 4 unconjugated hyperbilirubinemia. A comprehensive evaluation for hemolytic anemia failed to reveal any etiology. Other causes of hyperbilirubinemia were negative. Four months prior, patient was started on antiretroviral therapy with a single tablet regimen containing bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF), brand name Biktarvy®, and the medication was suspected to be the cause. The medication was held, and the hyperbilirubinemia improved.

CONCLUSION

Severe hyperbilirubinemia can be found in the patient using BIC/FTC/TAF. The data for this adverse reaction is scarce, and more studies are needed on this possible side effect. The mechanism of unconjugated hyperbilirubinemia by INSTI remains undefined.

Efficacy and Safety of Bictegravir-Based Regimen in Pregnant Women Living with HIV: A Case Report

Bictegravir (BIC) is included in international guidelines as the first line of therapy for patients living with Human Immunodeficiency Virus (HIV), either as initial therapy or as a replacement for patients with prior antiretroviral therapy (ART). Due to limited efficacy and safety data, BIC is currently not recommended during pregnancy. Data on the safety and efficacy of BIC during pregnancy were unavailable at the time of drug approval. In our case, BIC/TAF/FTC was effective in suppressing viral load (VL) in pregnancy, and there were no reported safety issues for the mother or the baby.

Human pharmacokinetics prediction with an in vitro-in vivo correction factor approach and in vitro drug-drug interaction profile of bictegravir, a potent integrase-strand transfer inhibitor component in approved biktarvy® for the treatment of HIV-1 infection

Bictegravir (BIC) is a potent small-molecule integrase strand-transfer inhibitor (INSTI) and a component of Biktarvy^®, a single-tablet combination regimen that is currently approved for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. The in vitro properties, pharmacokinetics (PK), and drug-drug interaction (DDI) profile of BIC were characterised in vitro and in vivo.BIC is a weakly acidic, ionisable, lipophilic, highly plasma protein-bound BCS class 2 molecule, which makes it difficult to predict human PK using standard methods. Its systemic plasma clearance is low, and the volume of distribution is approximately the volume of extracellular water in nonclinical species. BIC metabolism is predominantly mediated by cytochrome P450 enzyme (CYP) 3A and UDP-glucuronosyltransferase 1A1. BIC shows a low potential to perpetrate clinically meaningful DDIs via known drug metabolising enzymes or transporters.The human PK of BIC was predicted using a combination of bioavailability and volume of distribution scaled from nonclinical species and a modified in vitro-in vivo correlation (IVIVC) correction for clearance. Phase 1 studies in healthy subjects largely bore out the prediction and supported the methods used. The approach presented herein could be useful for other drug molecules where standard projections are not sufficiently accurate. .

The effect of changing to Bictegravir on lipids using real world data: A brief report

WHAT IS KNOWN AND OBJECTIVE

Cardiovascular disease is of increasing concern in patients living with HIV. The significant advancement in antiretroviral treatment has ensured that patients are now succumbing to traditional diseases of ageing. First generation antiretroviral therapy caused multiple side effects including significant dyslipidaemia. Despite the advancement and improving safety profile of treatment concerns remain about antiretroviral induced dyslipidaemia. We sought to investigate the real-world effect on lipids in patients switching to a Bictegravir based regime.

METHODS

We conducted a retrospective analysis in patients switching therapy to Biktarvy at the Royal Liverpool University Hospital. Data was collected from the HIV database that is established for clinical use, as an electronic patient record, and audit purposes. Lipid data was cross checked with the Trust electronic reporting system. Participants were included if they were HIV-positive, >18 years and had switched to Biktarvy Patients were also required to have a lipid profile available 52 weeks prior to switching and 100 weeks post switching. Summary statistic were calculated and multiple regressions models were constructed to assess the independent predictors of lipid change. We also performed one way analysis of covariance (ANCOVA) to assess the impact of switching therapy on each quartile of the baseline lipid panel.

RESULTS AND DISCUSSION

There were 135 patients included in the analysis with a mean age of 47. The majority of the population were male (80%). At a mean follow up of 42 weeks post switch there was no significant difference in total cholesterol (p = 0.64), triglyceride (p = 0.64) or high density lipoprotein (HDL) cholesterol (p = 0.08). In the regression analysis the highest quartile of baseline total cholesterol and triglyceride were independently associated with improvement in lipid markers. Switching from protease inhibitor therapy was also significantly associated with improvement in triglyceride. In addition, the ANCVOA demonstrated that the highest quartiles of total cholesterol, triglyceride and the lowest quartile of HDL were associated with significant improvement in lipid markers after switching to Bictegravir.

WHAT IS NEW AND CONCLUSION

We demonstrated that patients with the most adverse lipid profiles at baseline had significant improvements in lipid profiles. In addition, patient switching away from protease inhibitor therapy also had significant improvements in triglyceride.

A clinical review of HIV integrase strand transfer inhibitors (INSTIs) for the prevention and treatment of HIV-1 infection

Integrase strand transfer inhibitors (INSTIs) have improved the treatment of human immunodeficiency virus (HIV). There are currently four approved for use in treatment-naïve individuals living with HIV; these include first generation raltegravir, elvitegravir, and second generation dolutegravir and bictegravir. The most recent INSTI, cabotegravir, is approved for (1) treatment of HIV infection in adults to replace current antiretroviral therapy in individuals who maintain virologic suppression on a stable antiretroviral regimen without history of treatment failure and no known resistance to its components and (2) pre-exposure prophylaxis in individuals at risk of acquiring HIV-1 infection. Cabotegravir can be administered intramuscularly as a monthly or bi-monthly injection depending on the indication. This long-acting combination has been associated with treatment satisfaction in clinical studies and may be helpful for individuals who have difficulty taking daily oral medications. Worldwide, second generation INSTIs are preferred for treatment-naïve individuals. Advantages of these INSTIs include their high genetic barrier to resistance, limited drug-drug interactions, excellent rates of virologic suppression, and favorable tolerability. Few INSTI resistance-associated mutations have been reported in clinical trials involving dolutegravir, bictegravir and cabotegravir. Other advantages of specific INSTIs include their use in various populations such as infants and children, acute HIV infection, and individuals of childbearing potential. The most common adverse events observed in clinical studies involving INSTIs included diarrhea, nausea, insomnia, fatigue, and headache, with very low rates of treatment discontinuation versus comparator groups. The long-term clinical implications of weight gain associated with second generation INSTIs dolutegravir and bictegravir warrants further study. This review summarizes key clinical considerations of INSTIs in terms of clinical pharmacology, drug-drug interactions, resistance, and provides perspective on clinical decision-making. Additionally, we summarize major clinical trials evaluating the efficacy and safety of INSTIs in treatment-naïve patients living with HIV as well as individuals at risk of acquiring HIV infection.

Bictegravir nanomicelles and anionic pullulan loaded vaginal film: Dual mechanistic pre-exposure prophylaxis (PrEP) for HIV

Locally delivered pre-exposure prophylaxis (PrEP) has proven to be a promising strategy to combat Human immunodeficiency virus (HIV) transmission but several findings encountered toxicities or proved to be marginally effective in clinical settings. Therefore, innovative, multifunctional, and safer alternatives are being progressively investigated. Herein, we explored negatively charged carbohydrate, anionic pullulan (AP) as a rapidly soluble film-former and novel anti-HIV agent. Additionally, Bictegravir (BCT), an HIV integrase inhibitor was co-delivered in the form of nanomicelles for sustained antiviral activity. BCT-loaded PLGA-PEG polymeric nanomicelles (BN) were incorporated into PVA/pullulan-based film matrix comprising of 2 % w/v AP (BN-AP film). In cell-based assays, biocompatibility and TEER values for BN-AP films were similar to control while the commercial vaginal contraceptive film (VCF®) showed severe cytotoxicity and drastically reduced the tight junction integrity. Rapid disintegration of BN-AP film with >85 % drug release was observed in simulated vaginal and seminal fluid. Most importantly, AP and BN-AP film significantly inhibited HIV-1 replication with IC₅₀ at as low as 91 μg/mL and 0.708 nM, respectively. Therefore, this study entails successful development of BN-AP film that functioned as an effective, biocompatible dual-acting PrEP formulation.

Human and nonclinical disposition of [14C]bictegravir, a potent integrase strand-transfer inhibitor for the treatment of HIV-1 infection

Bictegravir (BIC) is a potent small-molecule integrase strand-transfer inhibitor (INSTI) and a component of Biktarvy®, a single-tablet combination regimen that is currently approved for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. The absorption, metabolism, distribution, and elimination (ADME) characteristics of BIC were determined through in vivo nonclinical and clinical studies (IND 121318).[¹⁴C]BIC was rapidly absorbed orally in mice, rats, monkeys and human. The cumulative dose recovery was high in nonclinical species (>80%) and humans (95.3%), with most of the excreted dose recovered in faeces. Quantifiable radioactivity with declining concentration was observed in rat tissues suggesting reversible binding. Unchanged BIC was the most abundant circulating component in all species along with two notable metabolites M20 (a sulphate conjugate of hydroxylated BIC) and M15 (a glucuronide conjugate of BIC). BIC was primarily eliminated by hepatic metabolism followed by excretion of the biotransformed products into faeces. In vitro drug-drug interaction (DDI) studies with M15 and M20 demonstrated that no clinically relevant interactions were expected.Overall, BIC is a novel and potent INSTI with a favourable resistance, PK, and ADME profile that provides important improvements over other currently available INSTIs for the treatment of HIV-1.

Validation of an LC-MS/MS assay for the simultaneous determination of bictegravir, doravirine, and raltegravir in human plasma

Bictegravir (BIC), an integrase inhibitor, and doravirine (DOR), a non-nucleoside reverse transcriptase inhibitor, were recently approved by the US FDA for HIV treatment and are recommended first line treatment options. Because certain clinical scenarios warrant using them in combination, we developed a fully validated LC-MS/MS method for simultaneous measurement of BIC and DOR, along with a legacy integrase inhibitor, raltegravir (RAL), in human plasma over a clinically relevant 1000-fold range for each analyte. These analytes were extracted from the plasma by protein precipitation with their stable, isotopically labeled internal standards (BIC-d₅, ¹³C₆-DOR, and RAL-d₆). Following extraction, samples were analyzed by reverse phase chromatography on a Waters Atlantis T3 C18 (50 ×2.1 mm, 3 µm particle size) column with subsequent detection by electrospray ionization in positive ion mode on an AB Sciex API-5000 triple quadrupole mass spectrometer. The assay was linear (R² >0.994) over the selected calibration ranges (20.0-20,000 ng/mL (BIC), 3.00-3000 ng/mL (DOR), and 10.0-10,000 (RAL)). The assay was accurate (inter-assay %Bias ≤ ± 8.5) and precise (inter-assay %CV ≤11.4). This method was validated according to FDA guidance for industry and can be used to assess the pharmacokinetics of two newly approved antiretrovirals, or to support therapeutic drug monitoring for modern antiretroviral therapy.

Comprehensive Review on Different Analytical Techniques for HIV 1- Integrase Inhibitors: Raltegravir, Dolutegravir, Elvitegravir and Bictegravir

The advent of HIV-Integrase inhibitors (IN) has marked a significant impact on the lives of HIV patients. Since the launch of the first anti retro-viral drug "Azidothymidine" to the recent advances of IN inhibitors, about 27.4 million people benefit by antiretroviral therapy (ART). The path had been challenging due to many crossroads, leading to the discovery of newer targets. One such recent ART target is Integrase. Use of Integrase inhibitors has surpassed the usage of all other ART owing to a strong barrier to resistance and have been reported to be the first-line therapy. Raltegravir, Elvitegravir, Dolutegravir and Bictegravir are US FDA approved IN inhibitors. The high usage of ART created an opportunity to study various analytical techniques for IN inhibitors. Hitherto, no review encompassing all IN inhibitors is presented. Herein, this review describes the analytical techniques employed for IN inhibitors estimation and quantification reported in the literature and official compendia. Literature suggests that most studies focus on LC-MS/MS and HPLC methods for drug estimation, and few reports suggest spectrophotometric, spectrofluorimetric and electrochemical methods. Furthermore, the review presents the techniques that describe the quantification of integrase drugs in various matrices. Although, antiretroviral drugs are extensively used but data suggests that limited studies have been conducted for determination of impurity profile and stability. This therefore, presents a scope to detect and validate impurities in order to meet ICH guidelines for their limits and further to improve the quality and safety of antiretroviral drugs.

Development and Validation of a Stability-Indicating RP-HPLC Method for the Simultaneous Estimation of Bictegravir, Emtricitabine, and Tenofovir Alafenamide Fumarate

Objectives

The focal intent of the current research work is to develop and validate a novel and reliable stability-indicating reverse-phase high performance liquid chromatographic method for the simultaneous estimation of a few anti-retrovirals, i.e., bictegravir, emtricitabine, and tenofovir alafenamide fumarate (AF).

Materials and Methods

The novel method employs inertsil octyldecylsilyl C18 (4.6×250 mm, 5 mm) using 0.2% triethylamine buffer and methanol in a ratio of 40:60% (v/v) as the mobile phase to attain optimal elution. The detection wavelength was 260 nm with a 1.2 mL/min flow rate and a 20 μL injection volume.

Results

The linearity ranges for bictegravir, emtricitabine and tenofovir AF were 25-125 μg/mL, 100-500 μg/mL, and 12.5-62.5 μg/mL, respectively. The retention times for bictegravir, emtricitabine, and tenofovir AF were found to be 5.998 min, 2.805 min, and 4.537, min respectively. The percent recoveries of bictegravir, emtricitabine, and tenofovir AF were within the range of 98-102% w/w.

Conclusion

The novel method was successfully validated as per International Conference on Harmonization guidelines. In forced degradation studies, emtricitabine was found to be sensitive to thermal conditions; bictegravir and tenofovir AF, to oxidative conditions. The developed method is economical and reliable for routine analysis concerning all validated parameters.

Bictegravir/Emtricitabine/Tenofovir Alafenamide in Virologically Suppressed People with HIV Aged ≥ 65 Years: Week 48 Results of a Phase 3b, Open-Label Trial

Introduction

We report the 48-week results of an ongoing study to assess the efficacy and safety of switching older people with HIV to bictegravir/emtricitabine/tenofovir alafenamide (B/F/TAF).

Methods

This was a 96-week, phase 3b, open-label, single-arm study (GS-US-380-4449; NCT03405935). Virologically suppressed individuals aged ≥ 65 years receiving elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide or a tenofovir disoproxil fumarate-based regimen were switched to B/F/TAF. Primary endpoint was the percentage of participants with HIV-1 RNA < 50 copies/ml at week 24.

Results

Eighty-six participants (median age 69 [range 65–80] years; 87% male; 95% white) were enrolled and treated in five European countries. Rates of virologic suppression were 97.7% at week 24 and 90.7% at week 48; none had HIV-1 RNA ≥ 50 copies/ml, and 100% had virologic suppression by missing = excluded analysis at both time points. No treatment-emergent resistance was observed. There were no grade 3–4 study drug-related adverse events (AEs) or study drug-related serious AEs or deaths. Three AEs led to premature discontinuation; one (moderate abdominal discomfort) was attributed to the study drug by the investigator. At week 48, median changes from baseline in weight and estimated glomerular filtration rate were + 0.1 kg (interquartile range [IQR] − 1.0, 2.3) and − 6.0 ml/min (IQR − 10.2, 0.0), respectively. There were no clinically relevant changes from baseline to week 48 in fasting lipid parameters. Treatment satisfaction improved, and health-related quality of life was maintained from baseline through week 48. Median adherence to the study drug was 98.6% (IQR 96.0, 100).

Conclusions

Switching to B/F/TAF was effective and well tolerated through 48 weeks in virologically suppressed adults aged ≥ 65 years.

Trial Registration

ClinicalTrials.gov identifier, NCT03405935.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00419-5.

Development of gynecomastia following initiation of bictegravir/emtricitabine/tenofovir alafenamide

Bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) is a recently approved single-tablet antiretroviral regimen and is recommended as a first-line agent. No cases of gynecomastia were reported in clinical trials. We report development of ultrasound-confirmed gynecomastia in a previously antiretroviral-naïve patient approximately two months after starting BIC/FTC/TAF, which resolved ten weeks after discontinuing bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF) based therapy.

Failure to bictegravir and development of resistance mutations in an antiretroviral-experienced patient

We present here one of the first cases of virological failure during treatment with bictegravir/emtricitabine/tenofovir alafenamide (BIC/FTC/TAF). On March 2019, an antiretroviral-experienced HIV-infected patient was admitted to hospital because of cerebral toxoplasmosis. After undergoing treatment with sulfadiazine-pyrimethamine for two weeks, the patient initiated a BIC/FTC/TAF treatment, with 6.01 HIV RNA Log copies/mL, and 37 CD4 cells/μL. After two months under antiretroviral therapy (ART), acute neurologic deterioration with epilepsy, right hemiparesis and dysphagia occurred, leading to nasogastric nutrition and treatment. After several weeks, virological failure was confirmed with 4.01 HIV RNA Log copies/mL and R263K and M184V resistance mutations were detected.

Bictegravir, a novel integrase inhibitor for the treatment of HIV infection

Bictegravir (BIC), a second-generation integrase strand transfer inhibitor (INSTI) approved for HIV treatment in fixed-dose combination with emtricitabine and tenofovir alafenamide, has potent antiviral activity in vitro to wild-type virus and strains with resistance to first-generation INSTIs. As part of combination therapy, BIC's virologic suppression rates in clinical trials are comparable to those of first-line combination antiretroviral drug regimens. BIC has demonstrated a high genetic barrier to resistance development in vitro, can be administered with or without food, and has a bioavailability of > 70%. A median plasma half-life of 18 hours allows once-daily dosing. Clearance is primarily hepatic through cytochrome P450 3A4 (CYP3A4) oxidation and UDP-glucuronosyltransferase 1A1 (UGT1A1) glucuronidation. Thus, potent inducers of UGT1A1 and CYP3A4 (e.g., rifamycins/anticonvulsants) should be avoided due to significantly decreased BIC serum exposure. Chelation with polyvalent cations can decrease absorption; otherwise, drug-drug interactions are few. BIC is well tolerated; diarrhea, nausea and headache are the main adverse effects associated with its use.

Update on Adverse Effects of HIV Integrase Inhibitors

PURPOSE OF REVIEW

The goal of this paper is to provide an up-to-date review of adverse events related to the class of integrase strand transfer inhibitors (INSTIs), which became the class of choice in few years. We sought answers specifically to issues pertaining to neuropsychiatric adverse events, as well as weight gain, which were the two most important categories of adverse events raised in recent studies based on real-life experience. The primary focus of this paper is on adults with a brief summary on pregnant women and children/adolescents.

RECENT FINDINGS

Dolutegravir (DTG) bears the heaviest burden of neuropsychiatric side effects. Weight gain was reported with all INSTIs, although there are methodological caveats in the analyses and the findings need to be interpreted with caution.Moreover, due to recent findings on neural tube defects in infants exposed to dolutegravir during their peri-conception period, its use is not recommended for women of childbearing age without proper birth control method, while raltegravir remains the only drug which may be prescribed without caution. Given the importance of cognitive and metabolic co-morbidities in people living with HIV in regard to their quality of life, future research needs to focus on long-term effects of INSTIs in relation to these adverse events. Pharmacogenetics seems to be a promising tool. Safety during pregnancy is also another important issue to further clarify.

SUMMARY

INSTIs are a generally well-tolerated class of antiretrovirals (ARV), and has a higher antiviral potency compared to other classes of ARV.Clinicians and patients need however to be aware of some red flags when starting with and monitoring patients on INSTIs.All INSTIs can lead to mild increases in creatinine levels, usually without clinical significance, but caution is needed in patients with low eGFR (<30ml/min), when using other nephrotoxic drugs, such as as tenofovir disoproxil.Neuro-psychiatric (NP) effects are to be monitored with INSTIs, especially with DTG (though reports are at times contradictory); clinicians might want to avoid DTG for patients with history of severe NP symptoms, until clarity is provided.Weight gain was reported with all INSTIs, especially with DTG, with possible differential effects according to sex and ethnicity (female and non-white patients being at increased risk). This is worrying since patients from African descent are at higher risk of cardio-vascular events and increased body mass index (BMI) can cause further increase metabolic risk. There is possibly an additional effect of tenofovir alafenamide (TAF) on weight increase.Discrepancies between clinical trials - with low rates of adverse events - and reports from real-life settings might be due partly to under-representation of some groups of patients in clinical trials, and/or the short duration of follow-up, since some adverse effects may only occur after prolonged exposure.Preliminary data on safety of bictegravir (BIC), from clinical trials and non-trial settings, are very reassuring and seem to show lower rates of adverse events compared to DTG.Elvitegravir/cobicistat (EVG/cobi) need to be used with caution in patients with other co-morbidities given potential for polypharmacy, as it is the case for aging patients, because of the high potential of drug-drug interactions due to effects of the cobicistat booster.We are awaiting the release of cabotegravir (CAB), which could represent a good option for patients struggling with adherence, despite injection site reactions.Pharmacogenetics is a promising way to explore adverse effects occurrence in the INSTI class.

Neuropsychiatric Adverse Events with Dolutegravir and Other Integrase Strand Transfer Inhibitors

Neuropsychiatric adverse events (NPAEs) observed with the integrase strand transfer inhibitor (INSTI) dolutegravir (DTG) are usually mild to moderate. The most prevalent symptoms are insomnia and sleep disorders, but the spectrum also includes dizziness, anxiety, depression, headache, paraesthesia, muscle-skeletal pain, poor concentration, and slow thinking. In recent cohort studies involving >6400 patients in different countries, discontinuation rates due to NPAEs were observed in around 3.5% (range, 1.4-7.2%) of subjects treated with DTG. These rates have been higher than those seen in randomized clinical trials and were also higher than with other INSTIs such as elvitegravir or raltegravir. Elderly, female patients and those who initiate abacavir simultaneously appear to be more vulnerable in some cohorts. It remains unclear if NPAEs are driven by an increased DTG exposure. With heightened awareness of health-care providers and patients, reports of NPAEs will probably increase in the future.

Initial Antiretroviral Therapy in an Integrase Inhibitor Era: Can We Do Better?

With the second-generation integrase inhibitors (dolutegravir and bictegravir) extending the attributes of earlier integrase inhibitors, three-drug regimens containing integrase inhibitors plus two nucleos(t)ide reverse transcriptase inhibitors are now widely recommended for first-line (initial) treatment of human immunodeficiency virus-1 infection. Led by dolutegravir plus lamivudine, two-drug therapy is emerging as a way to reduce antiretroviral therapy cost and adverse effects without compromising treatment options should virologic failure occur. Initial two-drug therapy has limitations, including the relative incompatibility with the coemerging concept of same-day antiretroviral therapy initiation.

A potential long-acting bictegravir loaded nano-drug delivery system for HIV-1 infection: A proof-of-concept study

Bictegravir (BIC), a newly FDA-approved integrase strand transfer inhibitor (INSTI), as a single tablet regimen has proven efficacious in treating HIV-1 and SIV viruses, with reduced resistance. BIC clinical trials have not investigated its prophylaxis potency. This study investigates the HIV prevention potency of a novel long-acting BIC nano-formulation aimed to improve adherence. Poly (lactic-co-glycolic acid) loaded BIC nanoparticles (BIC NPs) were formulated using an oil-in-water emulsion methodology. BIC NPs were <200 nm in size, with 47.9 ± 6.9% encapsulation efficiency. A novel, sensitive and high throughput LC-MS/MS method was used to estimate intracellular pharmacokinetics (PK) of BIC NPs and compared to BIC solution demonstrated prolonged intracellular BIC retention. BIC NPs safety was assessed based on cytotoxicity. Further, in-vitro prevention study of BIC NPs vs BIC solution was assessed against HIV-1_NLX and HIV-1_ADA on TZM-bl cell line and PBMCs, respectively. BIC nanoencapsulation demonstrated elevated cellular cytotoxicity concentration (CC₅₀: 2.25 μM (BIC solution) to 820.4 μM (BIC NPs)] and lowers HIV-1 inhibitory concentration [EC₅₀: 0.604 μM (BIC solution) to 0.0038 μM (BIC NPs)) thereby improving selectivity index (SI) from 3.7 (BIC solution) to 215,789 (BIC NP) for TZM-bl cells. Comparable results in PBMCs were obtained where BIC NPs improved SI from 0.29 (BIC solution) to 523.33 (BIC NPs). This demonstrates long-acting BIC nano-formulation with sustained drug-release potency, improved BIC cytotoxicity and enhanced HIV-1 protection compared to BIC in solution.

Tolerability of Current Antiretroviral Single-Tablet Regimens

The advent of protease inhibitors (PI) in the mid-nineties and its use as part of triple combinations revolutionized the management of HIV infection. Since then, progression to AIDS and AIDS-related deaths can be prevented. However, antiretroviral therapy based on PI has been discouraged for a while given its lower tolerability compared to alternative options; and only recent improvements in pharmacotherapy have renewed the interest for the newest agents within this class. First, the tolerability of the latest PI darunavir (DRV) and atazanavir is much better than for older PI, such as indinavir or lopinavir. Second, metabolic abnormalities and/or drug interactions associated to ritonavir boosting have been ameliorated using cobicistat. Third, adding safer accompanying nucleos(t)ides, such as tenofovir alafenamide (TAF), have minimized further toxicity concerns of PI. Finally, the unique barrier to resistance and new single-tablet regimen (STR) presentation makes DRV, especially attractive for long-term therapy. The recent coformulation of DRV, cobicistat, TAF, and emtricitabine (DRV/c/TAF/FTC) within a single pill to be given once daily (Symtuza^®) has positioned PI again at the frontline of HIV therapeutics. In this review, we discuss the results of studies that have assessed the efficacy and safety of the newest STR. In view of the current data, it seems worthy expanding the consideration of Symtuza® for a wider range of clinical scenarios, beyond the treatment of antiretroviral failures including first-line therapy and switching of otherwise virologically suppressed patients. The good tolerability and robust resistance profile should reward Symtuza^® and position it among the preferred contemporary STRs.

Bictegravir in a fixed-dose tablet with emtricitabine and tenofovir alafenamide for the treatment of HIV infection: pharmacology and clinical implications

INTRODUCTION

Current antiretroviral therapy is more effective and simpler than in previous times due to the development of new drugs with improved pharmacokinetic and pharmacodynamic profiles and the advent of single pill regimens with low toxicity that facilitate long-term adherence. The recent approval of the novel potent integrase strand-transfer inhibitor bictegravir (BIC) co-formulated with emtricitabine (FTC) and tenofovir alafenamide (TAF) in a fixed daily dose pill, B/F/TAF, adds to the list of single-tablet regimens available to treat HIV infection. Areas covered: This review provides an overview of the pharmacological and clinical information obtained from MEDLINE/PubMed publications and the latest international conferences. Expert opinion: BIC is a potent antiretroviral with an improved resistance profile over previous integrase inhibitors. Its combination with the new tenofovir prodrug TAF and FTC creates an effective regimen B/F/TAF for treatment-naïve patients and for those switching from another successful combination. B/F/TAF's favorable pharmacokinetic profile, simple dose, low pill burden, and few drug-drug interactions or treatment-related adverse events, will make it one of the preferred regimens in the future.

HIV drug resistance against strand transfer integrase inhibitors

Integrase strand transfer inhibitors (INSTIs) are the newest class of antiretroviral drugs to be approved for treatment and act by inhibiting the essential HIV protein integrase from inserting the viral DNA genome into the host cell’s chromatin. Three drugs of this class are currently approved for use in HIV-positive individuals: raltegravir (RAL), elvitegravir (EVG), and dolutegravir (DTG), while cabotegravir (CAB) and bictegravir (BIC) are currently in clinical trials. RAL and EVG have been successful in clinical settings but have relatively low genetic barriers to resistance. Furthermore, they share a high degree of cross-resistance, which necessitated the development of so-called second-generation drugs of this class (DTG, CAB, and BIC) that could retain activity against these resistant variants. In vitro selection experiments have been instrumental to the clinical development of INSTIs, however they cannot completely recapitulate the situation in an HIV-positive individual. This review summarizes and compares all the currently available information as it pertains to both in vitro and in vivo selections with all five INSTIs, and the measured fold-changes in resistance of resistant variants in in vitro assays. While the selection of resistance substitutions in response to RAL and EVG bears high similarity in patients as compared to laboratory studies, there is less concurrence regarding the “second-generation” drugs of this class. This highlights the unpredictability of HIV resistance to these inhibitors, which is of concern as CAB and BIC proceed in their clinical development.