Different evolution of genotypic resistance profiles to emtricitabine versus lamivudine in tenofovir-containing regimens

Determinants of therapy failure among adults on first-line antiretroviral therapy in Asmara, Eritrea: a multicenter retrospective matched case-control study

BACKGROUND

Information on treatment failure (TF) in People living with HIV in a data-poor setting is necessary to counter the epidemic of TF with first-line combined antiretroviral therapies (cART) in sub-Saharan Africa (SSA). In this study, we examined the risk factors associated with TF in Asmara, Eritrea from 2001 to 2020.

METHODS

A multicenter, retrospective 1:2 matched (by age and gender) case-control study was conducted in four major hospitals in Asmara, Eritrea on adults aged ≥ 18 years who were on treatment for at least 6 months. Cases were patients who fulfills at least one of the WHO therapy failure criterion during the study period. Controls were randomly selected patients on first-line treatment and plasma viral load < 1000 copies/ml in their latest follow-up measurement. Multivariable logistic regression analysis was conducted to identify risk factors for TF. All P-values were 2-sided and the level of significance was set at P < 0.05 for all analyses.

RESULTS

Of the 1068 participants (356 cases; 712 controls), 585 (54.7%) were females. The median age at treatment initiation was 46 years [interquartile range (IQR): 39-51]. Median time to combined antiretroviral therapy (cART) failure was 37 months (IQR = 24-47). In the multivariate analysis, factors associated with increased likelihood of TF included initial nucleoside reverse transcriptase inhibitors (NRTI) backbone (Zidovudine + Lamivudine (AZT + 3TC): adjusted odds ratio (aOR) = 2.70, 95% Confidence interval (CI): 1.65-4.41, P-value < 0.001), (Abacavir + lamivudine (ABC + 3TC): aOR = 4.73, 95%CI: 1.18-18.92, P-value = 0.028], and (Stavudine + Lamivudine (D4T + 3TC): aOR = 5.00; 95% CI: 3.03-8.20, P-value < 0.001) in comparison to Emtricitabine and Tenofovir diproxil fumarate (FTC + TDF). Additional associations included prior exposure to cART (aOR = 2.28, 95%CI: 1.35-3.86; P- value = 0.002), record of sub-optimal drug adherence (aOR = 3.08, 95%CI: 2.22-4.28; P < 0.001), ambulatory/bedridden at presentation (aOR = 1.61, 95%CI: 1.12-4.28; P-value = 0.010), presence of comorbidities (aOR = 2.37; 95%CI: 1.36-4.10, P-value = 0.002), duration of cART (< 5 years: aOR: 5.90; 95% CI: 3.95-8.73, P-value < 0.001), and use of SMX-TMP prophylaxis (aOR = 2.00, 95%CI, 1.44-2.78, P-value < 0.001).

CONCLUSION

Our findings underscore the importance of optimizing cART adherence, diversification of cART regimens, and interventions directed at enhancing early HIV diagnosis, prompt initiations of treatment, and improved patient-focused monitoring of treatment response.

Transmitted drug resistance among HIV-1 drug-naïve patients in Greece

OBJECTIVES

Despite the success of antiretroviral treatment (ART), the persisting transmitted drug resistance (TDR) and HIV genetic heterogeneity affect the efficacy of treatment. This study explored the prevalence of TDR among ART-naïve HIV patients in Greece during the period 2016-2019.

METHODS

Genotypic resistance testing was available for 438 ART-naïve HIV patients. Multivariable Poisson regression models were fitted.

RESULTS

The majority of patients were male, and there was a slight predominance of Hellenic (26.5%) over non-Hellenic (21.9%) nationality. The prevalence of TDR was 7.8%. There was a predominance of mutations for non-nucleoside reverse-transcriptase inhibitors (5.7%) over nucleoside reverse-transcriptase inhibitors (0.2%). No mutations to protease inhibitors were detected. The prevalence of resistance was 22.1% based on all mutations identified through the HIVdb interpretation system. The most frequent resistance sites were E138A (9.6%), K103N (6.4%), and K101E (2.1%). The majority of detected mutations were confined to subtype A (52.6%), followed by B (19.6%). Non-Hellenic nationality was significantly associated with an increased risk of TDR (relative risk 1.32, 95% confidence interval 1.04-1.69).

CONCLUSIONS

Non-B HIV infections predominate in Greece, with an increasing trend in recent years. The prevalence of TDR remains stable. Ongoing surveillance of resistance testing is needed to secure the long-term success of ART.

Surveillance of transmitted HIV drug resistance among newly diagnosed, treatment-naive individuals at a county HIV clinic in Santa Clara County

Introduction

To our knowledge, HIV transmitted drug resistance (TDR) patterns have not been characterized specifically in Santa Clara County (SCC), California, one of the largest counties by population in the United States. Understanding TDR here will help improve antiretroviral therapy outcomes and prevent future transmission events.

Material and methods

This is a retrospective analysis of TDR among patients establishing care at a county HIV clinic at the Santa Clara Valley Health and Hospital System. We identified 206 treatment-naive individuals who were newly diagnosed with HIV between 2006-2013. Using these individuals, we assessed the prevalence and temporal trends of total TDR and TDR to nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), and integrase strand transfer inhibitors (INSTIs).

Results

We identified a total TDR prevalence of 17.5% during 2006–2013 (7.3% NNRTI, 6.8% NRTI, 2.4% PI, 2.9% INSTI) with 1.9% exhibiting dual-class resistance. Total TDR prevalence initially ranged between 19.0-22.7% during 2006–2008 and decreased to within 10.5–16.2% during 2011–2013, though this decrease was not significant (p = 0.42). NRTI TDR decreased from 22.7% in 2006 to 5.3% in 2013 (p = 0.02), and NNRTI TDR appeared to fluctuate between 2.7-13.5% (p = 0.96). PI and INSTI TDR remained low, with noted E138A prevalence of 2.9%.

Conclusions

The prevalence of TDR was substantial among newly diagnosed, treatment-naive individuals establishing care at a SCC-based county HIV clinic from 2006 to 2013. This, along with the presence of transmitted mutations associated with INSTI resistance, warrants continued surveillance of TDR in SCC and use of baseline genotyping prior to antiretroviral therapy initiation.

Substituting Generic Lamivudine for Emtricitabine in Virologically Suppressed HIV-Infected Patients

This study evaluated the effectiveness of formulary substitution from products or regimens containing name brand emtricitabine to alternative regimens containing generic lamivudine among virologically suppressed HIV-infected patients in a correctional managed health care system. Results of this retrospective cohort study showed that 94.9% of patients switched from emtricitabine to lamivudine ( n = 447) and 93.0% of emtricitabine control patients ( n = 449) had an undetectable viral load at last available test over a 2-year period. The two groups also showed similar values for CD4 counts, compliance, discontinuation, and M184V mutation; however, a slightly greater proportion of lamivudine patients experienced respiratory symptoms. Nonetheless, this study demonstrates that switching virologically suppressed HIV-infected patients from name brand emtricitabine-containing regimens to generic lamivudine-based regimens may reduce costs without compromising safety or effectiveness in correctional managed health care systems with directly observed therapy.

Virological responses to lamivudine or emtricitabine when combined with tenofovir and a protease inhibitor in treatment-naïve HIV-1-infected patients in the Dutch AIDS Therapy Evaluation in the Netherlands (ATHENA) cohort

OBJECTIVES

Lamivudine (3TC) and emtricitabine (FTC) are considered interchangeable in recommended tenofovir disoproxil-fumarate (TDF)-containing combination antiretroviral therapies (cARTs). This statement of equivalence has not been systematically studied. We compared the treatment responses to 3TC and FTC combined with TDF in boosted protease inhibitor (PI)-based cART for HIV-1-infected patients.

METHODS

An observational study in the AIDS Therapy Evaluation in the Netherlands (ATHENA) cohort was carried out between 2002 and 2013. Virological failure rates, time to HIV RNA suppression < 400 copies/mL, and time to treatment failure were analysed using multivariable logistic regression and Cox proportional hazard models. Sensitivity analyses included propensity score-adjusted models.

RESULTS

A total of 1582 ART-naïve HIV-1-infected patients initiated 3TC or FTC with TDF and ritonavir-boosted darunavir (29.6%), atazanavir (41.5%), lopinavir (27.1%) or another PI (1.8%). Week 48 virological failure rates on 3TC and FTC were comparable (8.9% and 5.6%, respectively; P = 0.208). The multivariable adjusted odds ratio of virological failure when using 3TC instead of FTC with TDF in PI-based cART was 0.75 [95% confidence interval (CI) 0.32-1.79; P = 0.51]. Propensity score-adjusted models showed comparable results. The adjusted hazard ratio (HR) for treatment failure of 3TC compared with FTC was 1.15 (95% CI 0.58-2.27) within 240 weeks after cART initiation. The time to two consecutive HIV RNA measurements < 400 copies/mL within 48 weeks (HR 0.94; 95% CI 0.78-1.16) and the time to treatment failure after suppression < 400 copies/mL (HR 0.94; 95% CI 0.36-2.50) were not significantly influenced by the use of 3TC in TDF/PI-containing cART.

CONCLUSIONS

The virological responses were not significantly different in treatment-naïve HIV-1-infected patients starting either 3TC/TDF or FTC/TDF and a ritonavir-boosted PI.

Effectiveness of a Treatment Switch to Nevirapine plus Tenofovir and Emtricitabine (or Lamivudine) in Adults with HIV-1 Suppressed Viremia

BACKGROUND

Switching subjects with persistently undetectable HIV-1 viremia under antiretroviral treatment (ART) to once-daily tenofovir/emtricitabine (or lamivudine) + nevirapine is a cost-effective and well-tolerated strategy. However, the effectiveness of this approach has not been established.

METHODS

We performed a retrospective study evaluating the rates of treatment failure, virological failure (VF), and variables associated, in all subjects initiating this switch combination in our clinic since 2001. Analyses were performed by a modified intention to treat, where switch due to toxicity equalled failure. The main endpoint was plasma HIV-RNA < 50 copies/mL.

RESULTS

341 patients were treated for a median of 176 (57; 308) weeks. At week 48, 306 (89.7%) subjects had HIV-1 RNA <50 copies/mL, 10 (2.9%) experienced VF, and 25 (7.4%) discontinued the treatment due to toxicity. During the whole follow-up 23 (6.7%) individuals (17 on lamivudine, 6 on emtricitabine; p = 0.034) developed VF and treatment modification due to toxicity occurred in 36 (10.7%). Factors independently associated with VF in a multivariate analysis were: intravenous drug use (HR 1.51; 95%CI 1.12, 2.04), time with undetectable viral load before the switch (HR 0.98; 0.97, 0.99), number of prior NRTIs (HR 1.49; 1.15, 1.93) or NNRTIs (HR 3.22; 1.64, 6.25), and previous NVP (HR 1.54; 1.10, 2.17) or efavirenz (HR 5.76; 1.11, 29.87) unscheduled interruptions. VF was associated with emergence of usual nevirapine mutations (Y181C/I/D, K103N and V106A/I), M184V (n = 16; 12 with lamivudine vs. 4 with emtricitabine, p = 0.04), and K65R (n = 7).

CONCLUSIONS

The rates of treatment failure at 48 weeks, or long-term toxicity or VF with this switch regimen are low and no unexpected mutations or patterns of mutations were selected in subjects with treatment failure.

Efficacy of tenofovir and efavirenz in combination with lamivudine or emtricitabine in antiretroviral-naive patients in Europe

BACKGROUND

The combination of tenofovir and efavirenz with either lamivudine or emtricitabine (TELE) has proved to be highly effective in clinical trials for first-line treatment of HIV-1 infection. However, limited data are available on its efficacy in routine clinical practice.

METHODS

A multicentre cohort study was performed in therapy-naive patients initiating ART with TELE before July 2009. Efficacy was studied using ITT (missing or switch = failure) and on-treatment (OT) analyses. Genotypic susceptibility scores (GSSs) were determined using the Stanford HIVdb algorithm.

RESULTS

Efficacy analysis of 1608 patients showed virological suppression to <50 copies/mL at 48 weeks in 91.5% (OT) and 70.6% (ITT). Almost a quarter of all patients (22.9%) had discontinued TELE at week 48, mainly due to CNS toxicity. Virological failure within 48 weeks was rarely observed (3.3%, n = 53). In multilevel, multivariate analysis, infection with subtype B (P = 0.011), baseline CD4 count <200 cells/mm³ (P < 0.001), GSS <3 (P = 0.002) and use of lamivudine (P < 0.001) were associated with a higher risk of virological failure. After exclusion of patients using co-formulated compounds, virological failure was still more often observed with lamivudine. Following virological failure, three-quarters of patients switched to a PI-based regimen with GSS <3. After 1 year of second-line therapy, viral load was suppressed to <50 copies/mL in 73.5% (OT).

CONCLUSIONS

In clinical practice, treatment failure on TELE regimens is relatively frequent due to toxicity. Virological failure is rare and more often observed with lamivudine than with emtricitabine. Following virological failure on TELE, PI-based second-line therapy was often successful despite GSS <3.

A significant reduction in the frequency of HIV-1 drug resistance in Québec from 2001 to 2011 is associated with a decrease in the monitored viral load

Background

HIV drug resistance represents a major threat for effective treatment. We assessed the trends in the frequency of drug resistance mutations and the monitored viral load (VL) in treatment-naïve (TN) and treatment-experienced (TE) individuals infected with HIV-1 in Québec, Canada, between 2001 and 2011.

Methods and Findings

Resistance data were obtained from 4,105 and 5,086 genotypic tests performed on TN and TE patients, respectively. Concomitantly, 274,161 VL tests were carried out in the Province. Changes over time in drug resistance frequency and in different categories of VL were assessed using univariate logistic regression. Multiple logistic regression was used to evaluate associations between the rates of certain mutations and antiretroviral prescriptions. From 2001 to 2011, the proportion of undetectable VL test results continually increased, from 42.1% to 75.9%, while a significant decrease in the frequency of resistance mutations associated with protease inhibitors [PI (from 54% to 16%)], nucleoside [NRTI (from 78% to 37%) and non-nucleoside reverse transcriptase inhibitors [NNRTI (from 44% to 31%)] was observed in TE patients. In TN individuals, the overall frequency of transmitted drug resistance was 13.1%. A multiple logistic regression analysis indicated that the introduction of co-formulated emtricitabine/tenofovir or emtricitabine/tenofovir/efavirenz was positively associated with the decrease of the frequency of the M184I/V mutations observed overtime (p = 0.0004).

Conclusions

We observed a significant decrease in the frequency of drug resistance mutations in TE patients, concomitant with a decrease in the proportion of patients with detectable viremia. These findings may be related to both the increased potencies and adherence to therapy associated with newer antiretroviral regimens. Nevertheless, our data demonstrate that broad use of antiretrovirals does not increase the level of circulating drug resistant variants.

Increased virological failure in naive HIV-1-infected patients taking lamivudine compared with emtricitabine in combination with tenofovir and efavirenz or nevirapine in the Dutch nationwide ATHENA cohort

BACKGROUND

Guidelines for treatment of human immunodeficiency virus type 1 (HIV-1) infection consider lamivudine and emtricitabine to be interchangeable components in first-line combination antiretroviral therapy (cART). The evidence for their clinical equivalence in cART is inconsistent. The primary aim of this study was to evaluate the virological responses to lamivudine and emtricitabine in recommended cART.

METHODS

This was an observational study using data from the AIDS Therapy Evaluation in the Netherlands (ATHENA) nationwide HIV cohort. The virological responses to lamivudine and emtricitabine were compared by multivariable adjusted logistic regression and Cox proportional hazard models. Sensitivity analyses included propensity score-adjusted models.

RESULTS

Therapy-naive HIV-1-infected patients without baseline resistance (N = 4740) initiated lamivudine or emtricitabine with efavirenz/tenofovir or nevirapine/tenofovir. The use of lamivudine was associated with more virological failure at week 48 compared to emtricitabine with efavirenz/tenofovir (10.8% vs 3.6%; adjusted odds ratio [AOR], 1.78; 95% confidence interval [CI], 1.11-2.84) and nevirapine/tenofovir (27% vs 11%; AOR, 2.09; 95% CI, 1.25-3.52) in on-treatment analysis. Propensity score-adjusted models and intent-to-treat sensitivity analyses gave comparable results. The adjusted hazard ratio of virological failure at week 240 using lamivudine instead of emtricitabine was 2.35 (95% CI, 1.61-3.42) with efavirenz and 2.01 (95% CI, 1.36-2.98) with nevirapine. The inclusion of lamivudine or emtricitabine in cART did not influence the time to virological suppression within 48 weeks or the probability of virological rebound after successful virological suppression.

CONCLUSIONS

The use of emtricitabine instead of lamivudine as part of cART was associated with better virological responses. These findings are relevant for settings with extensive use of lamivudine and for settings where generic lamivudine will be available.

Effectiveness of antiretroviral therapy in individuals who for economic reasons were switched from a once-daily single-tablet regimen to a triple-tablet regimen

BACKGROUND

To assess the impact on virological outcomes of a switch from branded single-tablet regimen (STR) including tenofovir, efavirenz, and emtricitabine (STR-TEE) to generic triple-tablet regimen (TTR), including tenofovir, efavirenz, and lamivudine (TTR-TEL), which was implemented on April 1, 2011 to obtain economic savings.

METHODS AND FINDINGS

From the Capital Region of Denmark (covering two-thirds of the Danish HIV patients), we included combination antiretroviral therapy (cART)-naive patients who administered STR-TEE from April 1, 2010 to March 31, 2011 (n = 111) or TTR-TEL from April 1, 2011 to March 31, 2012 (n = 56) and cART-experienced HIV patients who were on STR-TEE from April 1, 2010 (n = 356) or were switched from STR-TEE to TTR-TEL after April 1, 2011 (n = 512). We estimated the fraction with detectable HIV-RNA, development of the 184V/I resistance mutations, and time to switch of cART. Approximately 96.2% of cART-experienced patients on STR-TEE were shifted to TTR-TEL after April 1, 2011. For the naive STR-TEE and TTR-TEL patients, the fractions with detectable HIV-RNA at week 48 were 7.0% and 8.3% and for the cART experienced 4.0% and 4.4%, respectively. The 184V/I resistance mutation was detected in 1 cART-experienced patient on TTR-TEL with virological failure. The risk of switch to a new cART regimen was slightly increased in the cART-experienced population (difference in 1-year risk: 1.5%; 95% confidence interval: -2.4% to 5.4%).

CONCLUSIONS

In settings comparable with the Danish health care system, the estimated economic savings from a switch from STR-TEE to TTR-TEL can be realized with negligible short-term risk of adverse outcomes.

Antiretroviral treatment French guidelines 2013: economics influencing science

Guidelines for the preferred choice of initial combination antiretroviral therapy in those living with HIV are provided by several national and international committees. Following the recent presentation of the 2013 French guidelines on antiretroviral therapy, there has been a debate regarding whether and/or how economics should influence guideline decisions and to what extent this should counterbalance valid scientific evidence. We discuss here the reasons for the unique nature of some of the proposals made by the French guidelines panel. Indeed, some recommendations are debatable. In the new French guidelines, economic considerations significantly influence and, in some instances, take precedence over the scientific evidence, leading to guidelines that are significantly different from those of other national and international committees.

The emergence of drug resistant HIV variants at virological failure of HAART combinations containing efavirenz, tenofovir and lamivudine or emtricitabine within the UK Collaborative HIV Cohort

BACKGROUND

Lamivudine (3TC) and emtricitabine (FTC) are guideline choices for combination highly active antiretroviral therapy (HAART). 3TC has a shorter intracellular half life than FTC and may be more likely to lead to the development of drug resistant HIV variants.

METHODS

In this study we analysed linked data from the observational UK Collaborative HIV Cohort (CHIC) Study and UK HIV Drug Resistance Database (HDRD) to investigate the rate of development of K65R or M184V resistance mutations in patients failing on combinations containing tenofovir (TDF) and efavirenz (EFV) with either 3TC or FTC. Virological failure was defined as 1 viral load >400 copies/ml. Rates were stratified by demographic variables, baseline viral load, current CD4 count, current viral load and year of starting regimen. Significant associations were identified using Poisson regression models and multivariable analyses were performed adjusting for the variables above. Logistic regression was used to determine whether there were any significant associations between type of regimen and detection of resistance mutation.

RESULTS

5455 patients received either (or both) 3TC, TDF and EFV or FTC, TDF and EFV contributing 6465 treatment episodes over 9962 person-years follow up. 47 of these episodes were preceded by resistance tests showing development of K65R or M184V mutation and were hence excluded. The majority of treatment episodes consisted of FTC- (n = 5190) rather than 3TC- (n = 1228) based regimens. 21 cases of K65R were detected over the course of follow up, giving an overall event rate of 0.21 (95% CI: 0.12-0.31)/100 person years follow up (PYFU). The overall event rate for detection of M184V was 0.38 (95% CI: 0.26-0.5)/100 PYFU. 201 patients receiving either regimen for the first time experienced virological failure. Of those receiving 3TC (n = 53), 7 (13.2%), 12 (22.6%) and 15 (28.3%) developed K65R, M184V and either K65R or M184V respectively. Of those receiving FTC (n = 148), 13 (8.8%), 20 (13.5%) and 26 (17.6%) developed K65R, M184V and either K65R or M184V respectively. Although patients on 3TC were more likely to develop resistance, this was not statistically significant in univariable (OR 1.85 (95% CI: 0.89-3.85, p = 0.09)) or multivariable analyses (OR 1.89 (95% CI: 0.89-4.01, p = 0.1)).

CONCLUSIONS

We have not found evidence of an increased risk of development of M184V and K65R in patients exposed to 3TC.

Identification of a rare mutation at reverse transcriptase Lys65 (K65E) in HIV-1-infected patients failing on nucleos(t)ide reverse transcriptase inhibitors

OBJECTIVES

The HIV reverse transcriptase (RT) mutation K65R confers resistance to nucleos(t)ide reverse transcriptase inhibitors (NRTIs). Here, analysing a large database, we report the selection of another rare K65E mutation in patients failing on NRTI-containing regimens.

METHODS

Clinical and virological characteristics of patients harbouring the K65E mutation were analysed using a large RT sequence database from treatment-experienced individuals. Structural analysis of the K65E RT mutant complex was performed by means of docking simulations. The replication capacity was assessed using viruses harbouring the K65E mutation introduced by site-directed mutagenesis (SDM) in pNL 4-3.

RESULTS

Overall, in 23 530 sequences from patients failing on antiretroviral therapy, the prevalence of substitutions at position K65 in RT was 2.4%. In addition to K65R (n = 395) and K65N (n = 9), another mutation, K65E, was found in 15 patients. In 11 out of 15 cases, tenofovir, abacavir, didanosine or stavudine were present at the time of K65E selection. The molecular recognition of RT containing K65E supports evidence for the role of this mutation in resistance to tenofovir. The SDM pNL4-3 K65E variant harboured a very low replicative capacity (5% versus wild-type).

CONCLUSIONS

We investigated the role of a novel rare NRTI mutation located at position Lys65 of RT (K65E), found in drug-experienced patients failing on NRTIs. The low frequency of this mutation is probably related to the high impairment of replicative capacity induced by this mutation. This study should have significant clinical implications, as these findings warn clinicians that other minor substitutions at Lys65 (such as K65E) play a role in NRTI resistance.

Transmission patterns of HIV-subtypes A/AE versus B: inferring risk-behavior trends and treatment-efficacy limitations from viral genotypic data obtained prior to and during antiretroviral therapy

BACKGROUND

HIV subtypes A and CRF01_AE (A/AE) became prevalent in Israel, first through immigration of infected people, mostly intravenous-drug users (IVDU), from Former Soviet-Union (FSU) countries and then also by local spreading. We retrospectively studied virus-transmission patterns of these subtypes in comparison to the longer-established subtype B, evaluating in particular risk-group related differences. We also examined to what extent distinct drug-resistance patterns in subtypes A/AE versus B reflected differences in patient behavior and drug-treatment history.

METHODS

Reverse-transcriptase (RT) and protease sequences were retrospectively analyzed along with clinical and epidemiological data. MEGA, ClusalX, and Beast programs were used in a phylogenetic analysis to identify transmission networks.

RESULTS

318 drug-naive individuals with A/AE or patients failing combination antiretroviral therapy (cART) were identified. 61% were IVDU. Compared to infected homosexuals, IVDU transmitted HIV infrequently and, typically, only to a single partner. 6.8% of drug-naive patients had drug resistance. Treatment-failing, regimen-stratified subtype-A/AE- and B-patients differed from each other significantly in the frequencies of the major resistance-conferring mutations T215FY, K219QE and several secondary mutations. Notably, failing boosted protease-inhibitors (PI) treatment was not significantly associated with protease or RT mutations in either subtype.

CONCLUSIONS

While sizable transmission networks occur in infected homosexuals, continued HIV transmission among IVDU in Israel is largely sporadic and the rate is relatively modest, as is that of drug-resistance transmission. Deviation of drug-naive A/AE sequences from subtype-B consensus sequence, documented here, may subtly affect drug-resistance pathways. Conspicuous differences in overall drug-resistance that are manifest before regimen stratification can be largely explained in terms of treatment history, by the different efficacy/adherence limitations of older versus newer regimens. The phenomenon of treatment failure in boosted-PI-including regimens in the apparent absence of drug-resistance to any of the drugs, and its relation to adherence, require further investigation.

Economic savings versus health losses: the cost-effectiveness of generic antiretroviral therapy in the United States

BACKGROUND

U.S. HIV treatment guidelines recommend branded once-daily, 1-pill efavirenz-emtricitabine-tenofovir as first-line antiretroviral therapy (ART). With the anticipated approval of generic efavirenz in the United States, a once-daily, 3-pill alternative (generic efavirenz, generic lamivudine, and tenofovir) will decrease cost but may reduce adherence and virologic suppression.

OBJECTIVE

To assess the clinical effect, costs, and cost-effectiveness of a 3-pill, generic-based regimen compared with a branded, coformulated regimen and to project the potential national savings in the first year of a switch to generic-based ART.

DESIGN

Mathematical simulation of HIV disease.

SETTING

United States.

PATIENTS

HIV-infected persons.

INTERVENTION

No ART (for comparison); 3-pill, generic-based ART; and branded ART.

MEASUREMENTS

Quality-adjusted life expectancy, costs, and incremental cost-effectiveness ratios (ICERs) in dollars per quality-adjusted life-year (QALY).

RESULTS

Compared with no ART, generic-based ART has an ICER of $21,100/QALY. Compared with generic-based ART, branded ART increases lifetime costs by $42,500 and per-person survival gains by 0.37 QALYs for an ICER of $114,800/QALY. Estimated first-year savings, if all eligible U.S. patients start or switch to generic-based ART, are $920 million. Most plausible assumptions about generic-based ART efficacy and costs lead to branded ART ICERs greater than $100,000/QALY.

LIMITATION

The efficacy and price reduction associated with generic drugs are unknown, and estimates are intended to be conservative.

CONCLUSION

Compared with a slightly less effective generic-based regimen, the cost-effectiveness of first-line branded ART exceeds $100,000/QALY. Generic-based ART in the United States could yield substantial budgetary savings to HIV programs.

PRIMARY FUNDING SOURCE

National Institute of Allergy and Infectious Diseases.

Long-lasting protection of activity of nucleoside reverse transcriptase inhibitors and protease inhibitors (PIs) by boosted PI containing regimens

BACKGROUND

The accumulation of mutations after long-lasting exposure to a failing combination antiretroviral therapy (cART) is problematic and severely reduces the options for further successful treatments.

METHODS

We studied patients from the Swiss HIV Cohort Study who failed cART with nucleoside reverse transcriptase inhibitors (NRTIs) and either a ritonavir-boosted PI (PI/r) or a non-nucleoside reverse transcriptase inhibitor (NNRTI). The loss of genotypic activity <3, 3-6, >6 months after virological failure was analyzed with Stanford algorithm. Risk factors associated with early emergence of drug resistance mutations (<6 months after failure) were identified with multivariable logistic regression.

RESULTS

Ninety-nine genotypic resistance tests from PI/r-treated and 129 from NNRTI-treated patients were analyzed. The risk of losing the activity of ≥1 NRTIs was lower among PI/r- compared to NNRTI-treated individuals <3, 3-6, and >6 months after failure: 8.8% vs. 38.2% (p = 0.009), 7.1% vs. 46.9% (p<0.001) and 18.9% vs. 60.9% (p<0.001). The percentages of patients who have lost PI/r activity were 2.9%, 3.6% and 5.4% <3, 3-6, >6 months after failure compared to 41.2%, 49.0% and 63.0% of those who have lost NNRTI activity (all p<0.001). The risk to accumulate an early NRTI mutation was strongly associated with NNRTI-containing cART (adjusted odds ratio: 13.3 (95% CI: 4.1-42.8), p<0.001).

CONCLUSIONS

The loss of activity of PIs and NRTIs was low among patients treated with PI/r, even after long-lasting exposure to a failing cART. Thus, more options remain for second-line therapy. This finding is potentially of high relevance, in particular for settings with poor or lacking virological monitoring.

Emtricitabine/tenofovir in the treatment of HIV infection: current PK/PD evaluation

INTRODUCTION

Emtricitabine/tenofovir disoproxil fumarate fixed-dose combination (FTC/TDF FDC) is the co-formulation of a nucleoside and a nucleotide, respectively. After oral administration, both drugs exhibit plasma and intracellular half-lives suitable for once-daily dosing. Within the host cells, active metabolites FTC-TP and TFV-DP act as chain terminators to the newly synthesized proviral DNA, showing synergy at enzymatic level (viral reverse transcriptase). When given in HAART combinations, FTC/TDF FDC has a remarkable effectiveness in controlling HIV replication and securing a significant CD4(+) cell recovery. If patients treated with FTC/TDF FDC fail, a lower incidence of TDF-associated K65R resistance mutation seems to develop. Furthermore, cytidine analog-associated M184V is less likely to appear with FTC than with lamivudine when both are given with TDF. FTC and TFV are not metabolized by CYP450 enzymes and are eliminated by the renal route. TFV may accumulate in tubular cells and cause a decrease in GFR and a loss of phosphates. As a onsequence, patients treated with FTC/TDF FCD may experience varied degrees of renal impairment and osteopenia/osteoporosis.

AREAS COVERED

This paper has focused on the PK/PD features of FTC and TDF, when given as single agent or when administered as FDC. The interpretation of efficacy/toxicity was guided by PK/PD features. The review of the available literature included also conference presentations and recent guidelines (as of May 2012).

EXPERT OPINION

FTC/TDF FDC is a potent and reliable component of most HAART combinations due to its maintained activity across time, as demonstrated in many trials and studies. Toxicity issues (kidney, bone) are still to be entirely elucidated and the drug-induced component well separated from patient- and HIV-related ones. However, the clinical gain associated with the use of FTC/TDF FDC is fully acknowledged by its leading position in most current treatment guidelines.

Cost analysis of HIV treatment and drug-related adverse events when fixed-dose combinations of antiretrovirals (FDCs) were stopped, versus continuation with FDCs

BACKGROUND

The lower sales price of generic lamivudine has caused healthcare administrators to consider abolishing fixed-dose antiretroviral combinations (FDCs) that contain lamivudine and emtricitabine. The alternative is to administer the individual components of the FDCs separately, thus incorporating the new generic lamivudine medication.

METHODS

The Balearic Islands Health Service ordered the discontinuation of the treatment with FDCs in July 2010, but FDCs were reintroduced in August 2010. At that point, an independent, retrospective cost analysis was performed by Son Llàtzer Hospital. A total of 75 patients who were treated from July to August 2010 underwent replacement of their FDC treatment with the individual components. Additionally, 150 patients who continued using FDCs were randomly selected. For both patient groups, the antiretroviral therapy that was administered and the costs associated with management of adverse events were recorded. The study period used for the cost calculations was the average number of days that patients used separate components of FDCs (120 days). An alternative analysis was performed to consider the costs of the extra follow-up visit (consultation and clinical tests) that was required for patients who changed their antiretroviral therapy.

RESULTS

Considering antiretroviral therapies and adverse events, the administration of the separate components increased the total daily cost by 0.72 € per patient compared to treatment with FDCs. When the cost of an extra follow-up visit was considered, the daily cost increased by 3.61 € per patient.

CONCLUSIONS

Our study suggests that the discontinuation of FDC treatment and the replacement with the administration of separate antiretroviral agents could lead to an increase in healthcare costs due to the higher rate of adverse events that was observed with the discontinuation of FDCs.

Trends in HIV-1 reverse transcriptase resistance-associated mutations and antiretroviral prescription data from 2003-2010

BACKGROUND

The selection of antiretroviral (ARV) drugs for treatment of HIV-1 infection is based on several factors including potency, toxicity, resistance and ease of administration. Emtricitabine (FTC) or lamivudine (3TC), components of recommended initial ARV regimens, are structurally related and share the same resistance mutation (M184V/I). However they differ with respect to potency and incidence of M184V/I.

METHODS

Resistance-associated mutation (RAM) prevalence data were obtained from genotype test results performed in a large reference laboratory from 2003-2010; subsets of data were defined by mutation pattern to resemble those following failure of non-nucleoside reverse transcriptase inhibitor (NNRTI)-based combination therapy. Mutational trend data were compared to contemporaneous ARV prescription information.

RESULTS

In the unfiltered data set (n=107,231), the prevalence in 2010 decreased compared to 2003 for all nucleoside/nucleotide reverse transcriptase inhibitor (NRTI) RAMs, such as M184V/I (44.0% to 17.9%), T215Y (22.7% to 4.1%), and K65R (4.3% to 2.1%). Among samples resembling those typical of first-line NNRTI-based failures, prevalence of K103N increased slightly, but prevalence of M184V/I decreased (49.8% to 36.8%), as did other NRTI RAMs. These decreases were coincident with a shift in ARV prescriptions away from zidovudine and 3TC towards tenofovir and FTC, and an increase in use of fixed-dose combinations.

CONCLUSIONS

RAM prevalence decreased substantially since 2003 among samples submitted for resistance testing in the US. The causes of this decrease are multifactorial, but our results suggest a possible role of increased use of potent ARVs that are available as fixed-dose combinations or as single-tablet regimens.

Cytosine deoxyribonucleoside anti-HIV analogues: a small chemical substitution allows relevant activities

The search for new nucleoside analogue compounds targeting the virally encoded reverse transcriptase was developed by modifying the nucleoside structure to create inhibitor compounds. In this review, the structure-activity relationship of antiviral compounds synthesised from the naturally existing cytosine deoxyribonucleoside (dC) was evaluated. The line of research starting from dC led to the synthesis of 2',3'-dideoxycytidine (ddC; zalcitabine), 2',3'-dideoxy-3'-thiacytidine (3TC; lamivudine) and 2',3'-dideoxy-5-fluoro-3'-thiacytidine (FTC; emtricitabine) and looks very interesting because each product comes from a single small change in the chemical structure of the former compound, resulting in a progressive improvement in terms of activity, pharmacokinetics, tolerability and emergence of resistance.

Comparative outcomes of tenofovir-based and zidovudine-based antiretroviral therapy regimens in Lusaka, Zambia

BACKGROUND

Although tenofovir (TDF) is a common component of antiretroviral therapy (ART), recent evidence suggests inferior outcomes when it is combined with nevirapine (NVP).

METHODS

We compared outcomes among patients initiating TDF + emtricitabine or lamivudine (XTC) + NVP, TDF + XTC + efavirenz (EFV), zidovudine (ZDV) + lamuvidine (3TC) + NVP, and ZDV + 3TC + EFV. We categorized drug exposure by initial ART dispensation by a time-varying analysis that accounted for drug substitutions and by predominant exposure (>75% of drug dispensations) during an initial window period. Risks for death and program failure were estimated using Cox proportional hazard models. All regimens were compared with ZDV + 3TC + NVP.

RESULTS

Between July 2007 and November 2010, 18,866 treatment-naive adults initiated ART: 18.2% on ZDV + 3TC + NVP, 1.8% on ZDV + 3TC + EFV, 36.2% on TDF + XTC + NVP, and 43.8% on TDF + XTC + EFV. When exposure was categorized by initial prescription, patients on TDF + XTC + NVP [adjusted hazard ratio (AHR): 1.45; 95% confidence interval (CI): 1.03 to 2.06] had a higher post-90-day mortality. TDF + XTC + NVP was also associated with an elevated risk for mortality when exposure was categorized as time-varying (AHR: 1.51; 95% CI: 1.18 to 1.95) or by predominant exposure over the first 90 days (AHR: 1.91, 95% CI: 1.09 to 3.34). However, these findings were not consistently observed across sensitivity analyses or when program failure was used as a secondary outcome.

CONCLUSION

TDF + XTC + NVP was associated with higher mortality when compared with ZDV + 3TC + NVP but not consistently across sensitivity analyses. These findings may be explained in part by inherent limitations to our retrospective approach, including residual confounding. Further research is urgently needed to compare the effectiveness of ART regimens in use in resource-constrained settings.

Clinical implications of fixed-dose coformulations of antiretrovirals on the outcome of HIV-1 therapy

The substitution by generic equivalents of some of the drugs included in fixed-dose antiretroviral coformulations (FDACs) poses the potential risk of disrupting these combinations and administering the components separately in order to incorporate the new generic drug, which offers a more competitive sales price. This may represent a step backwards in the advances achieved in simplicity and adherence to therapy, posing an increased risk of selective noncompliance of some of the separately administered drug substances. Available antiretroviral drugs must be administered for life in the affected individuals - both children and adults. The FDACs represent a significant advance in the simplification of antiretroviral therapy, facilitating adherence to complex and chronic treatments, and contributing to a quantifiable improvement in patient quality of life. These drug coformulations reduce the risk of treatment error, are associated with a lower risk of hospitalization, and can lessen the possibility of covert monotherapy in situations of selective noncompliance. Thus, FDACs can reduce the risk of selection of HIV-1 resistances, which not only adversely affect the treatment options of the individual patient but also constitute a public health problem, and further increase the cost and complexity of therapy. With the exception of those cases requiring dose adjustments, the preferential use of FDACs should be recommended for the treatment of HIV-1 infection in those situations when the agents included in the coformulation are drugs of choice.