Dual Raltegravir-Etravirine Combination as Maintenance Regimen in Virologically Suppressed HIV-1-Infected Patients

Abstract

Nucleoside reverse transcriptase inhibitor (NRTI)- and protease inhibitor (PI)-sparing antiretroviral regimens may be useful in selected human immune deficiency virus (HIV)-infected patients with resistance or intolerance to these drug classes. This was an observational prospective study of patients on suppressive antiretroviral therapy containing two NRTIs plus one ritonavir-boosted PI who switched to a dual regimen containing raltegravir plus etravirine. Patients were required not to have prior virological failure to raltegravir and to have efficacy of etravirine shown through the genotypic resistance assay in case of prior non-nucleoside reverse transcriptase inhibitor (NNRTI) virological failure. As a whole, 38 patients were enrolled. The mean duration of current regimen was 4.3 years, and the reason for simplification was toxicity in 29 patients and resistance to NRTIs in 9 patients. After switching, the percentage of patients with HIV RNA <20 copies/ml at week 48 was 81.6% in the intent-to-treat-exposed analysis. The switch led to a significant reduction in the mean serum triglyceride levels (−81.2 mg/dl), in the mean total cholesterol levels (−44.3 mg/dl), and in the prevalence of tubular proteinuria (−30.2%), with a significant increase in the mean phosphoremia (+0.52 mg/dl) and in both mean lumbar and femoral neck bone mineral density (+6.5% and +4.7%, respectively). Two patients (5.2%) had virological failure due to suboptimal adherence, and five subjects (13.1%) discontinued treatment due to adverse events. In our study, simplification to the dual-therapy raltegravir plus etravirine was associated with a good efficacy and tolerability, in addition to a favorable effect on kidney, bone, and serum lipids.

Introduction

Combination antiretroviral therapy (cART) has drastically reduced the mortality associated with human immune deficiency virus (HIV) infection and considerably prolonged the life expectancy of the HIV-infected people.^1,2 So, antiretroviral treatment should be maintained for long time and can lead to some potential long-term problems, including toxicity, drug-drug interactions, and increasing costs.

A prolonged treatment, including two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) and one ritonavir-boosted protease inhibitor (PI), has been associated with a not negligible risk of metabolic abnormalities (mostly dyslipidemia and insulin resistance), renal function alteration, and reduced bone mineral density (BMD).^3

–8

Moreover, the aging of HIV-positive people has been associated with an increased risk of several comorbidities (such as myocardial infarction, renal disease, and osteoporosis), and the concomitant use of several nonantiretroviral medications leads to a significant risk of pharmacokinetic interactions (particularly with PIs).⁹ So, it seems crucial today to optimize the cART in patients with persistently suppressed viral replication to minimize the long-term risk of comorbidities and drug-drug interactions.

Among the most recent antiretroviral agents, the integrase strand transfer inhibitor (INSTI) raltegravir and the non-nucleoside reverse transcriptase inhibitor (NNRTI) etravirine proved to be also effective in patients with prior resistance to NRTIs and PIs and were associated with a negligible incidence of metabolic disturbances, renal dysfunction, and bone disease.^10
–12 Moreover, the risk of clinically significant pharmacokinetic interactions is very low for raltegravir and limited for etravirine too, in comparison with boosted PIs.^13,14

The 48-week efficacy and safety results of the dual-regimen raltegravir plus etravirine as a simplification strategy in HIV-infected patients on PI-based cART and with persistently undetectable HIV RNA were reported in the present study.

Methods

We performed an observational prospective analysis of HIV-1-infected adult patients referring to our Clinics of Infectious Diseases from January 2011 through December 2014 receiving a stable antiretroviral regimen for at least 12 months, including a ritonavir-boosted PI plus two NRTIs and with persistently undetectable plasma HIV viral load (HIV RNA <50 copies/ml) for at least 12 months. All patients who switched to a dual antiretroviral regimen constituted by raltegravir (400 mg twice daily) and etravirine (200 mg twice daily) were enrolled in the study and followed up for 48 weeks.

Exclusion criteria were previous virological failure to raltegravir or etravirine, previous virological failure to other NNRTIs without genotypic testing or with genotypic testing showing reduced sensitivity to etravirine, previous genotypic testing (including integrase inhibitor-resistance mutations) showing reduced sensitivity to raltegravir and/or etravirine, no regular clinical or laboratory data of follow-up for at least 48 weeks, active opportunistic diseases or severe infectious diseases, acute or chronic inflammatory diseases, alcohol or drug abuse, hypothyroidism, Cushing's syndrome, acute or chronic kidney diseases, acute hepatitis, chronic hepatitis B virus (HBV) infection, liver cirrhosis, myopathy, alanine aminotransferase (ALT) or aspartate aminotransferase (AST) >80 U/liter, creatinine >1.2 mg/dl, creatine kinase (CK) >170 U/liter, pregnancy, an underlying treatment with corticosteroids, nonsteroidal anti-inflammatory drugs (NSAIDs), immune-modulatory agents, lipid-lowering drugs, or a concomitant administration of medications or herbal supplements known to affect the raltegravir or etravirine pharmacokinetics (such as the St. John's Wort).

Current alcohol use and intravenous drug dependence were defined as a daily alcohol consumption >30 g and ≥1 intravenous drug use within 6 months before starting the dual regimen, respectively. Liver cirrhosis was excluded by liver biopsy or elastometry. The HBV and hepatitis C virus (HCV) coinfections were diagnosed by the persistent positivity of hepatitis Bs antigen or HCV serum antibodies associated with HCV-RNA positivity.

The following demographic, clinical, and laboratory data were recorded at the start of therapy and at 12-week intervals during the 48-week follow-up: sex, age, race, physical examination, body mass index, arterial pressure, clinical manifestations, and current and past medications; spot urinalysis, estimated glomerular filtration rate (eGFR), and serum levels of triglycerides, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, glucose, complete liver and kidney function tests, CK, aldolase, CD4+ and CD8+ T lymphocyte count, and HIV viral load. Patients with proteinuria on spot urines underwent proteinuria and albuminuria (by protein electrophoresis) on 24-h collected urines. The eGFR was calculated by using the four-variable Modification of Diet in Renal Disease (MDRD) formula.¹⁵

All the plasma samples were analyzed for HIV-RNA level by using the automated COBAS AmpliPrep Instrument for specimen processing and the COBAS TaqMan Analyzer for amplification and detection (Roche CobasAmpliPrep/Cobas TaqMan HIV-1 tests version 2.0; Roche Diagnostics, Mannheim, Germany). Besides gag primers and an FAM-labeled gag probe, additional LTR primers and an FAM-labeled LTR probe were included in the assay. The two targets, gag and LTR, are amplified with the same efficiency and the limit of quantification, as defined by the manufacturer, was reduced to 20 copies/ml. Viral blip was defined as an isolated plasma HIV RNA ≥20 and ≤400 copies/ml followed by a return to virological suppression (<20 copies/ml). Virological failure was defined by a confirmed plasma HIV RNA ≥20 copies/ml.

The bone health was assessed by a whole-body DXA scanning (Hologic, QDR 4500A) performed at baseline and at week 48 to evaluate lumbar spine, total hip, and femoral neck BMD.

Raltegravir was swallowed by tablets at the standard dose of 400 mg twice daily at breakfast time and at suppertime. Etravirine was administered by tablets at the standard dose of 200 mg twice daily at breakfast time and at suppertime after a meal. We have assessed the trough plasma concentration (C_trough) of raltegravir and etravirine, which is the standard parameter used to define the therapeutic range of these drugs. The C_trough of raltegravir and etravirine was assessed at steady state (>4 weeks after treatment initiation), with blood samples obtained before the morning dose and 11–13 h after the previous evening dose. The exact times of the predose sample and of the previous morning and evening intake were recorded, to ensure accurately timed blood sampling. C_trough was considered to be within an acceptable sampling timeframe if it felt within a defined time range for both drugs every 12 h within 11–13 h after the previous dose.

The procedures regarding the C_trough determination and the pharmacokinetic analyses were described in Appendix 1.

Treatment failure was defined by virological failure or permanent discontinuation of either one of the two antiretroviral drugs. Genotypic testing was performed in case of virological failure. Virological success was defined as an HIV RNA <20 copies/ml on the study dual regimen at the end of the 48-week follow-up with no more than one viral blip. Results were evaluated in both intention-to-treat (ITT) and per-protocol (PP) analyses. The ITT analysis included all subjects who switched to the dual-regimen raltegravir plus etravirine and were enrolled into the study, whereas the PP analysis included all the ITT patients except those who discontinued the dual regimen for reasons other than a virological failure. Missing data were considered failures. The dual regimen is considered virologically effective if the percentage of patients with HIV RNA <20 copies/ml 48 weeks after the switch is ≥80% in the ITT analysis.

Data were presented as mean ± standard deviation for descriptive data, whereas comparisons between groups were performed by Student's t-test or Fisher exact test (where appropriate). The significance of changes in all the considered variables were assessed by using the paired Student's t-test. The post hoc sample size calculation showed that 25 patients were needed to achieve 80% power with a 5% significance level. The primary outcome of this study was the evaluation of both efficacy and safety of this dual antiretroviral regimen, whereas the secondary endpoints were changes in serum lipid parameters, glucose, renal function parameters, BMD, and the pharmacokinetic evaluation.

The adherence to the current therapy was carefully checked on the outpatient visits by self-reported questionnaires. The study was approved by the Ethic Committee of the S. Orsola-Malpighi Hospital, and all participants signed an informed consent after receiving information about the purpose of the study.

Results

Study inclusion criteria were met by 38 patients who were enrolled in the study. The mean age was 46.4 years, 27 patients (71%) were men, the mean current CD4+ lymphocyte count was 489 cells/mm³, the mean duration of current antiretroviral treatment was 4.3 years, and the mean duration of plasma HIV RNA <50 copies/ml was 45.4 months. The lipid parameters were generally abnormal: 28 subjects (73.7%) had serum triglyceride levels >200 mg/dl, and 21 (55%) had total cholesterol levels >200 mg/dl. A significant percentage of patients showed abnormal proteinuria (55.3%), represented mostly by tubular proteinuria (44.7%). Demographic, clinical, and laboratory characteristics of study patients are summarized in Table 1.

Table 1.

Baseline Characteristics of the 38 Patients Enrolled in the Study

No. of patients	38
Males, n (%)	27 (71)
White subjects, n (%)	35 (92.1)
Age (years), mean (SD)	46.4 (19.7)
HIV transmission risk category, n (%)
IDU	9 (23.7)
MSM	17 (44.7)
Heterosexual	12 (31.6)
CD4+ cell count nadir (cells/mm³), mean (SD)	197 (87)
Current CD4+ lymphocyte count (cells/mm³), mean (SD)	489 (188)
Duration of HIV infection (years), mean (SD)	10.4 (4.9)
Duration of current ARV therapy (years), mean (SD)	4.3 (2.4)
Cumulative exposure to ARV therapy (years), mean (SD)	8.9 (3.5)
Duration of plasma HIV RNA <50 copies/ml with current ARV therapy (months), mean (SD)	45.4 (17.6)
Patients with hypertension, n (%)	8 (21)
Patients with diabetes mellitus, n (%)	3 (7.9)
Patients with chronic hepatitis C, n (%)	6 (15.8)
Total cholesterol levels (mg/dl), mean (SD)	249 (51)
LDL cholesterol levels (mg/dl), mean (SD)	154 (32)
HDL cholesterol levels (mg/dl), mean (SD)	46 (13)
Triglyceride levels (mg/dl), mean (SD)	292 (84)
Creatinine (mg/dl), mean (SD)	1.04 (0.49)
eGFR (ml/min/1.73 m²), mean (SD)	82.1 (13.2)
Phosphorus (mg/dl), mean (SD)	2.47 (0.55)
Patients with proteinuria >30 mg/dl, n (%)	21 (55.3)
Patients with tubular proteinuria, n (%)	17 (44.7)

ARV, antiretroviral; eGFR, estimated glomerular filtration rate; HDL, high-density lipoprotein; HIV, human immune deficiency virus; IDU, intravenous drug users; LDL, low-density lipoprotein; MSM, males who have sex with males; SD, standard deviation.

Current antiretroviral therapy included tenofovir/emtricitabine, abacavir/lamivudine, or zidovudine/lamivudine plus darunavir/ritonavir, atazanavir/ritonavir, or lopinavir/ritonavir. All subjects on darunavir/ritonavir treatment were taking the dosage of 800/100 mg daily. The reasons for switch to raltegravir plus etravirine were renal toxicity (increased creatinine, hypophosphoremia, or tubular proteinuria), reduced BMD, hyperlipidemia, gastrointestinal symptoms, or resistance to nucleoside/nucleotide analogues. Current antiretroviral regimens and reasons for switching treatment are presented in Table 2. The baseline genotypic resistance testing of the nine subjects with NRTI resistance showed the following mutations: M184V in 8 cases, M41L in 6, K70R in 6, K65R in 5, L210W in 4, L74V in 2, and T215Y in 2 subjects.

Table 2.

Current Antiretroviral Treatment at the Moment of the Switch and Reasons for Switching Treatment to Raltegravir Plus Etravirine

Current NRTIs, n (%)
Tenofovir+emtricitabine	25 (65.8)
Abacavir+lamivudine	12 (31.6)
Zidovudine+lamivudine	1 (2.6)
Current PIs, n (%)
Darunavir/ritonavir	16 (42.1)
Atazanavir/ritonavir	11 (28.9)
Lopinavir/ritonavir	11 (28.9)
Reasons for discontinuation
Increased creatinine, n (%)	9 (23.7)
Hypophosphoremia, n (%)	12 (31.6)
Tubular proteinuria, n (%)	17 (44.7)
Reduced BMD, n (%)	7 (18.4)
Hyperlipidemia, n (%)	29 (76.3)
Gastrointestinal symptoms, n (%)	17 (44.7)
Resistance to NRTIs, n (%)	9 (23.7)

BMD, bone mineral density; NRTIs, nucleoside reverse transcriptase inhibitor; PIs, protease inhibitors.

After 48 weeks from the switch to raltegravir plus etravirine, seven discontinuations were observed: two discontinuations due to virological failure and five discontinuations due to nonserious adverse events. Overall, virological success at week 48 was 81.6% in the intent-to-treat analysis and 94.7% in the PP analysis (Table 3).

Table 3.

Immunological, Virological, and Biological Results After the Switch to Raltegravir Plus Etravirine

	Week 24	p	Week 48	p
Treatment failures, n (%)
Discontinuations to AE	3 (7.9)	.491	5 (13.1)	.722
Virological failures	1 (2.6)	.667	2 (5.2)	.518
Loss to follow-up or missing data or withdrew consent	0		0
Virological successes, n (%)
HIV RNA <20 copies/ml (ITT analysis)	34 (89.5)	.431	31 (81.6)	.387
HIV RNA <20 copies/ml (PP analysis)	37 (97.4)	.802	36 (94.7)	.672
Median change from baseline in CD4+ lymphocyte count (cells/mm³) (95% CI)	+36 (−9 to +83)	.281	+48 (+2 to +95)	.307
Median change from baseline in serum lipids (mg/dl), (95% CI)
Total cholesterol levels	−49.5 (−16.5 to −77.9)	.034	−44.3 (−13.6 to −65.4)	.041
LDL cholesterol levels	−31.2 (−15.1 to −62.1)	.044	−30.6 (−17.2 to −64.5)	.039
HDL cholesterol levels	+3.5 (+0.7 to +5.2)	.518	+3.8 (+0.5 to +4.8)	.109
Triglyceride levels	−85.6 (−40.2 to −141.4)	.029	−81.2 (−44.2 to −121.5)	.023
Median change from baseline in serum glucose (mg/dl), (95% CI)	−6.7 (+1.5 to −11.4)	.079	−5.9 (+2.3 to −9.8)	.288
Median change from baseline in creatinine (mg/dl), (95% CI)	−0.05 (+0.01 to −0.13)	.088	−0.04 (+0.01 to −0.11)	.147
Median change from baseline in eGFR (ml/min/1.73 m²), (95% CI)	+2.1 (+0.9 to +2.9)	.093	+1.8 (+0.3 to +2.7)	.115
Median change from baseline in phosphorus (mg/dl), (95% CI)	+0.61 (+0.19 to +0.85)	.021	+0.52 (+0.17 to +0.91)	.016
Patients with tubular proteinuria, n (%)	10 (29.4)		6 (14.5)
Change in prevalence of tubular proteinuria (%)	−15.3	.032	−30.2	.008

AE, adverse events; CI, confidence interval; ITT, intention-to-treat; PP, per-protocol.

The first case of virological failure was observed at week 24 (HIV RNA rebound to 2,715 copies/ml) in a patient who had been virologically suppressed for 32 months with a regimen including abacavir/lamivudine plus darunavir/ritonavir. The second case of virological failure was observed at week 36 (HIV RNA rebound to 4,120 copies/ml) in a patient who had been virologically suppressed for 27 months with a regimen including tenofovir/emtricitabine plus atazanavir/ritonavir. In both cases, the patient's adherence to cART was lower than 95% (ranging from 80% to 95%), and genotypic analysis at the start of cART and at the time of virological failure demonstrated no resistance mutations. The five discontinuations for nonserious adverse events were due to diarrhea with abdominal discomfort in three cases, nausea with lack of appetite in one case, and headache with sleeping disturbances in one case.

All the immunological, virological, and biological results at week 24 and at week 48 after the switch are summarized in Table 3. After 48 weeks, there was a statistically significant reduction in the mean serum concentration of triglycerides, total cholesterol, and LDL cholesterol. Variations in the mean values of glucose, serum creatinine, and eGFR were not statistically significant, whereas there was a significant increase in the mean serum phosphorus concentration and a significant decrease in the prevalence of tubular proteinuria.

With regard to the bone safety, 48 weeks after the switch, a significant increase in mean BMD, T-score, and Z-score was registered in all the evaluated sites (lumbar spine, total hip, and femoral neck). Moreover, the mean fracture risk over 10 years significantly decreased for both major osteoporotic fractures and hip fractures (Table 4).

Table 4.

Changes in Bone Mineral Density and Osteoporotic Fracture Risk

	Baseline	Week 48	Week 48% change	p
Mean BMD (g/cm²), (95% CI)
Lumbar spine	0.85 (0.78 to 0.91)	0.91 (0.87 to 0.96)	+6.5 (+2.9 to +9.3)	.011
Total hip	0.78 (0.74 to 0.85)	0.82 (0.77 to 0.88)	+5.2 (+1.6 to +8.5)	.022
Femoral neck	0.81 (0.77 to 0.89)	0.85 (0.79 to 0.93)	+4.7 (+1.4 to +7.9)	.019
Mean T-score (95% CI)
Lumbar spine	−0.67 (−0.57 to −0.75)	−0.61 (−0.53 to −0.69)	+8.7 (+4.1 to +11.8)	.004
Total hip	−0.72 (−0.64 to −0.81)	−0.64 (−0.55 to −0.73)	+10.4 (+5.2 to +13.8)	<.001
Femoral neck	−0.75 (−0.61 to −0.86)	−0.67 (−0.51 to −0.78)	+9.8 (+4.7 to +12.6)	<.001
Mean Z-score (95% CI)
Lumbar spine	−0.58 (−0.51 to −0.69)	−0.52 (−0.46 to −0.62)	+9.4 (+5.2 to +13.2)	<.001
Total hip	−0.62 (−0.55 to −0.71)	−0.57 (−0.47 to −0.64)	+8.2 (+4.8 to +12.2)	.016
Femoral neck	−0.65 (−0.57 to −0.78)	−0.6 (−0.54 to −0.68)	+7.8 (+4.1 to +11.8)	.004
Mean fracture risk over 10 years (%), (95% CI)^a
Major osteoporotic fracture	3.17 (2.91 to 3.39)	2.63 (2.54 to 2.77)	−18.5 (−24.2 to −11.6)	<.001
Hip fracture	0.46 (0.35 to 0.54)	0.37 (0.26 to 0.48)	−19.6 (−28.2 to −10.4)	<.001

Fracture risk over 10 years calculated by the World Health Organization (WHO) FRAX^® algorithm.²⁰

No serious adverse events were reported during the 48-week follow-up. No grade 3 or 4 clinical events or laboratory abnormalities were recorded during the study. The most common adverse events reported during the follow-up were diarrhea with abdominal discomfort (5 patients; 13.1%), nausea and loss of appetite (2; 5.3%), headache (2; 5.3%), asthenia (2; 5.3%), sleeping disturbances (2; 5.3%), myalgias (1; 2.6%), and a slight increase (<400 U/liter) in the CK level (1; 2.6%).

The pharmacokinetic evaluation by the C_trough assessment was performed in all the 38 enrolled subjects. The mean C_trough of raltegravir was 87 ng/ml [confidence interval (95% CI), 49–144], and the median value (and range) for raltegravir C_trough was 95 (35–188) ng/ml. Between and within variability of the raltegravir plasma C_trough were 85% and 114%, respectively. The mean C_trough of etravirine was 488 ng/ml (95% CI, 266–717), and the median value (and range) for etravirine C_trough was 556 (137, 905) ng/ml. Between and within variability of the etravirine plasma C_trough were 41% and 59%, respectively. Between and within variability of the raltegravir C_trough were higher than those of the etravirine C_trough, but the raltegravir concentration was above the recommended minimum effective concentration (15 ng/ml) in all the evaluated subjects.

Overall, the adherence to the antiretroviral treatment was ≥95% in 30 out of 38 (78.9%) enrolled patients and in 27 out of 31 (87.1%) patients who completed the study. All the remaining patients had a treatment adherence ≥80%.

Discussion

The efficacy of the dual raltegravir/etravirine combination in virologically suppressed patients was previously evaluated in some observational studies as a potential option of NRTI- and PI-sparing antiretroviral strategies.

A retrospective study assessed 18 patients who were switched from different antiretroviral regimens to raltegravir plus etravirine and having plasma HIV RNA <200 copies/ml at the moment of switch. The median age was 48 years, and the median duration of viral suppression was 6 years. After 12 months, the efficacy (percentage of patients with HIV RNA <50 copies/ml) was 100% in the PP analysis and 83.3% in the intent-to-treat analysis, and no tolerability-related treatment discontinuations were reported.²¹

The efficacy and the potential drug-drug interactions of this dual combination were evaluated in an observational, cohort study including 25 subjects. The mean age of the enrolled patients was 46 years, 21 subjects (84%) had plasma HIV RNA <50 copies/ml at the moment of switch, and 20 patients (80%) had a chronic hepatitis C infection. The reason for the switch was cART-related toxicity in 19 cases and drug-drug interactions in 9 cases. After a median follow-up of 24 months, there were no cases of virological failure and there were six cases (24%) of treatment discontinuations (four cases due to lost follow-up and two cases due to a treatment simplification). There were no cases of liver toxicity grade 3–4, whereas the dual combination was associated with a significant decrease in triglycerides and total cholesterol levels. No clinically significant pharmacokinetic interactions between both drugs were registered.^22,23

A prospective, cohort study enrolled 25 patients on PI- or NRTI-based cART, with persistent virological suppression and who were switched to raltegravir plus etravirine because of concomitant toxicities or drug-drug interactions. Patients with prior virological failure to raltegravir or reduced sensitivity to etravirine in case of virological failure to NNRTIs were excluded. The median age was 54 years, and the median total duration of cART was 16 years. After 48 weeks, the percentage of patients with HIV RNA <50 copies/ml was 84% by the intent-to-treat analysis and 91.3% by the PP analysis, whereas the median increase in the CD4+ T cell count was 114 cells/mm³. Virological failure was reported in only one patient (4%), and resistance genotype testing showed a high-level resistance to etravirine (103N, 179F, 179I, 181C, and 225H mutations) without resistance to raltegravir. This patient was previously exposed to nevirapine and efavirenz without a documented virological failure. Moreover, there were two discontinuations (8%) due to gastrointestinal symptoms and one death due to biliary sepsis. The switch led to a significant decrease in serum triglycerides, glucose, and total cholesterol/HDL cholesterol ratio, with a significant increase in the HDL cholesterol levels.²⁴

Our study is currently the largest published work assessing efficacy and tolerability of the dual-regimen raltegravir (400 mg twice daily) plus etravirine (200 mg twice daily) as a simplification strategy in patients treated with two NRTIs plus one PI and with persistently suppressed HIV viral load. The results of our study are comparable to those of the previously published studies assessing efficacy and safety of this switching regimen in virologically suppressed patients.

As in previous reports, in our study too, this dual combination maintained the viral suppression in the large majority of patients in association with a good tolerability. After a 48-week follow-up, the dual regimen proved effective: The 94.7% of patients maintained the virological suppression by the PP analysis, and virological failure was reported in only two cases. Moreover, the dual combination showed an acceptable tolerability profile, with only five discontinuations (13.1%) due to adverse events, but no serious adverse events were described. The switch led to a significant improvement in some toxicities that were associated with tenofovir disoproxil fumarate or PIs, such as decreased tubular proteinuria prevalence, increased phosphoremia, reduced serum levels of triglycerides and total cholesterol, and increased BMD. The patients' adherence to the dual regimen was very elevated in spite of a daily dosage, including four tablets.

The evaluation of the raltegravir and etravirine serum concentrations showed that mean, median, and range values of the C_trough for each drug were within the therapeutic range established in previous studies and international guidelines. Therefore, no unfavorable pharmacokinetic interactions between raltegravir and etravirine were observed in our study.

Our work clearly presents several limitations. First, it was an observational study with a limited sample size. Second, the effectiveness of dual regimen was not compared with the standard NRTI-based triple regimen. In spite of this, the rate of virological suppression was high and similar to that observed among subjects receiving triple antiretroviral therapy in randomized clinical studies assessing other strategies of simplification to a dual regimen.^25

–28 Third, the heterogeneity of the triple regimens switched to the raltegravir/etravirine combination, which made it impossible to assess the improvement after the switch in some toxic effects associated with specific kinds of NRTIs and boosted PIs. Fourth, some aspects, such as the control of viral replication in the central nervous system or other reservoirs, and the effect on the immune activation markers or peripheral fat were not evaluated.

Finally, the attractiveness of a dual regimen, including raltegravir plus etravirine, might seem to be scarce in light of the availability of the newest once-daily and single-tablet regimens or the less toxic tenofovir alafenamide. However, this dual antiretroviral combination could be useful in subjects with intolerance or contraindication to other simplified and most recent regimens.

Despite these limitations, in our study, the dual raltegravir/etravirine combination was effective and well tolerated after a 48-week follow-up as a simplification strategy in persistently suppressed HIV-infected patients on stable triple therapy containing two NRTIs and one boosted PI. Moreover, this simplification regimen was associated with a favorable metabolic, renal, and bone safety profile. Larger and properly designed randomized studies are certainly requested to better evaluate the effectiveness and the safety of this strategy, as well as to better define the selected patients in whom this option is applicable.

Footnotes

Author Disclosure Statement

L.C. has received research grants from ViiV and Gilead, and has received honoraria for consulting (as advisory board member) and speaking from Janssen, Merck, and Bristol-Myers Squibb. The other authors have no conflicts of interest to declare.

Appendix 1

Blood samples were collected in 3.0 ml Vacuette EDTA-containing tubes and were centrifuged (600 g for 10 min) to obtain plasma samples within 2 h of collection. The plasma samples were frozen at −20°C and were sent on dry ice to the Central Laboratory of the S. Orsola-Malpighi Hospital to assess the antiretroviral drugs' C_trough. After thawing, HIV was inactivated at 56°C for 30 min; then, the plasma samples were extracted and subjected to a validated high-performance liquid chromatography (HPLC)-tandem mass spectrometry method, as deviations from the method described by Dickinson et al. ¹⁶ Internal standard (cimetidine) and acetonitrile (400 μl) were added to aliquots (100 μl) of calibrators, quality controls (QCs), and patient ultrafiltrate. After mixing, centrifugation, and addition of ammonium formate buffer (100 μl; 20 mM), samples were analyzed by HPLC-tandem mass spectrometry (10 μl). Fragmentation of parent molecules into daughter ions occurred by electrospray ionization; ions were separated according to their m/z ratio and quantified by the intensity of their respective daughter ions. The standard curves for raltegravir and etravirine were linear within the ranges of 40 ng/ml to 1,190 ng/ml in plasma, with a lower limit of detection of 20 ng/ml for all drugs. Intra-assay coefficients of variation for etravirine and raltegravir QC concentrations were 9.7% and 9.3%, respectively, for the low QC concentration (40 ng/ml), and 8.4% and 8.8%, respectively, for the high QC concentration (1,190 ng/ml). Inter-assay coefficients of variation were 9.2% and 9.6% for etravirine and raltegravir, respectively, for the low QC concentration, and 8.2% and 8.7%, respectively, for the high QC concentration. The corresponding accuracy ranged between 91% and 104% for etravirine, and between 94% and 108% for raltegravir.

The median value (range) of C_trough from clinical studies was 275 (81–2980) ng/ml for etravirine and 72 (29–118) ng/ml for raltegravir.^17

–20 These concentrations have been used as a guideline for analyzing the data.

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