Efavirenz is a nonnucleoside reverse transcriptase inhibitor (NNRTI) that in combination with two nucleoside/nucleotide [N(t)RTI] reverse transcriptase inhibitors is recommended as initial treatment of HIV-1 infection . Failure of efavirenz-containing regimens is often associated with the development of the K103N resistance mutation. The K103N mutation confers cross-resistance to nevirapine, but does not decrease by itself etravirine susceptibility .
Etravirine has been evaluated as part of a salvage regimen after multiple-antiretroviral failures. In this context, etravirine has demonstrated efficacy in the DUET and TRIO clinical trials, combined with other active drugs such as darunavir/ritonavir and raltegravir [3,4]. However efficacy data about the combination of two N(t)RTIs and etravirine in patients with prior NNRTI failures are scarce with one trial suggesting poor activity (TMC125-C227) . However, it should be noted that the 227 trial included patients with multiple N(t)RTI and NNRTI mutations and not only the K103N mutation. The objective of our study was to retrospectively report the efficacy of the etravirine and two N(t)RTIs in patients harboring HIV-1 isolates with only the K103N mutation.
In this study, we included HIV-1-infected patients, who showed an isolated K103N mutation in historical standard population genotypes and whose clinicians had decided to use an antiretroviral regimen consisting of two N(t)RTI and etravirine (without any other antiretroviral). For all patients, information on clinical variables, antirretroviral treatment, drug resistance mutations and laboratory parameters were obtained from clinical and laboratory databases. For patients, who at the time of inclusion remained virologically suppressed while receiving etravirine, we wished to demonstrate the persistence of archived K103N. To do so, total DNA was collected from whole blood, and the K103N mutation on cellular HIV-1 DNA was analyzed by single-genome pyrosequencing, a method based on the single-genome sequencing method , in which single genomes were obtained by serial dilutions and PCR detection, and sequencing was directed to codon 103 by a specific pyrosequencing assay . The local ethic committee approved the study.
Of the 1876 patients followed in our unit, we found six patients in whom standard genotypic resistance testing revealed K103N and who received treatment with two N(t)RTI along with etravirine. Two patients had K103N and other N(t)RTI mutations (M184V in both and H208Y, P236L in one and 69N, 70R in the other) and were excluded from this analysis. Four patients (two men) had K103N but no other major reverse transcriptase inhibitor resistance mutations. In all cases, the N(t)RTI combination was tenofovir/emtricitabine. Three patients (1, 2 and 4) had acquired K103N after virologic failure of an efavirenz-containing regimen. In the other patient, (3) the K103N mutation was transmitted. According to the Stanford HIV Database algorithm the tenofovir/emtricitabine combination was judged to be completely active in all four patients based on prior standard resistance genotyping (Table 1).
At the time of switching to tenofovir/emtricitabine and etravirine median age was 37 years, CD4 cell count was 547 (IQR: 537–597) cells/μl and duration of antiretroviral treatment was 5 years (IQR: 2–9). Two patients with acquired K103N (patients 1 and 2) and the patient with transmitted K103N (patient 3) were virologically suppressed before the switch to etravirine while receiving tenofovir/emtricitabine and lopinavir/ritonavir. The median period of suppressed viraemia was 8 months (IQR: 7–9). In these virologically suppressed patients, the main reason to change to etravirine was the presence of diarrhea due to lopinavir/ritonavir (patients 1 and 2). Substitution of lopinavir/ritonavir for etravirine resolved the diarrhea in both cases. One patient (patient 4) was experiencing virological failure when he switched to tenofovir/emtricitabine and etravirine.
After the switch to tenofovir/emtricitabine and etravirine all patients remained virologically suppressed for at least 2 years with a median exposure time to etravirine of 28 months (IQR: 27–31). No adverse event occurred during the etravirine treatment. By clonal analysis the K103N mutation was detected in cellular HIV-1 DNA in all the three patients (2, 3 and 4), who remained virologically suppressed while receiving etravirine at the time of entering the study (Table 1). One patient (patient 1) failed after 27 months of virological suppression because of an episode of very poor adherence and developed new N(t)RTI resistance mutations: K65R, K103N, Y181C, K219E (patient 1).
A prior study using ultradeep pyrosequencing  did not detect additional major NNRTI-resistance mutations in the plasma of patients with transmitted K103N but did so in NNRTI-experienced patients, suggesting that etravirine may not be fully active in patients with acquired K103N. In our study, the combination of etravirine and tenofovir/emtricitabine was efficacious despite infection with HIV-1 isolates showing acquired or transmitted K103N mutation in plasma and in cellular HIV-1 DNA. It is interesting that the patient with primary NNRTI resistance who had K103N detected in cellular HIV-1 DNA in 35/36 clones tested had remained suppressed during 35 months while receiving etravirine and tenofovir/emtricitabine.
In the TMC125-C227 clinical trial , etravirine in combination with two nucleoside reverse transcriptase inhibitors (NRTIs) was less effective than the control arm consisting of two NRTIs and a protease inhibitor (mainly boosted). The C227 study included treatment-experienced patients with high levels of NNRTIs and NRTIs resistance. In contrast, our four patients with isolated K103N received fully active etravirine and fully active tenofovir/emtricitabine.
There are no clinical trial data to support a preferred regimen in patients failing an efavirenz-containing regimen with isolated K103N. Conducting such a trial in the developed world has not been possible due to the low frequency of failure and because failure is due in general to poor adherence. Although more data are needed our small case series suggest that in selected patients in whom standard genotype detects only the K103N mutation, etravirine and two fully active N(t)RTIs might be efficacious.
J.M. was a recipient of a Ramón y Cajal fellowship financed by the European Social Fund and the Ministerio de Ciencia e Innovación. M.E., F.X.Z. and I.P.V. are supported by Río Hortega fellowships financed by Fondo de Investigaciones Sanitarias, Ministerio de Ciencia e Innovación. This work was supported by grants FIPSE 36749/08 and FIS08/0710.
Conflicts of interest
F.X.Z. has received advisory fees and speaker fees from BMS, Gilead, Abbot and ViiV. J.I.B. has received consulting and speaking fees from BMS, Gilead, Abbott, Janssen. I.P.-V. has received speaking fees from BMS, Gilead and Abbott and travel grants from Janssen. J.R.A. has received advisory fees, speaker fees and grant support from Viiv, Tibotec, Janssen, Abbott, BMS, Gilead, MSD.
1. Reiss P, Battegay M, Clumeck N, Mulcahy F, Arribas J, d’Arminio Monforte A et al. European AIDS Clinical Society Guidelines
. Version 6.0.October 2011.
2. Vingerhoets J, Tambuyzer L, Azijn H, Hoogstoel A, Nijs S, Peeters M, et al. Resistance profile of etravirine: combined analysis of baseline genotypic and phenotypic data from the randomized, controlled Phase III clinical studies
3. Katlama C, Clotet B, Mills A, Trottier B, Molina JM, Grinsztejn B, et al. Efficacy and safety of Etravirine at week 96 in reatment-experienced HIV type-1-infected patients in the DUET-1 and DUET-2 trials
. Antiviral Ther
4. Yazdanpanah Y, Fagard C, Descamps D, Taburet AM, Colin C, Roquebert B, et al. High rate of virologic suppression with raltegravir plus Etravirine and darunavir/ritonavir among treatment-experienced patients infected with multidrug-resistant HIV: results of the ANRS 139 TRIO trial
. Clin Infect Dis
5. Ruxrungtham K, Pedro RJ, Latiff GH, Conradie F, Domingo P, Lupo S, et al. TMC125-C227 study groupImpact of reverse transcriptase resistance on the efficacy of TMC125 (Etravirine) with two nucleoside reverse transcriptase inhibitors in protease inhibitor-naïve, nonnucleoside reverse transcriptase inhibitor-experienced patients: study TMC125-C227
. HIV Med
6. Palmer S, Kearney M, Maldarelli F, Halvas EK, Bixby CJ, Bazmi H, et al. Multiple, linked human immunodeficiency virus type 1 drug resistance mutations in treatment-experienced patients are missed by standard genotype analysis
. J Clin Microbiol
7. García-González C, García-Bujalance S, Ruiz-Carrascoso G, Arribas JR, González-García J, Bernardino JI, et al. Detection and quantification of the K103N mutation in HIV reverse transcriptase by pyrosequencing
. Diagn Microbiol Infect Dis
8. Varghese V, Shahriar R, Rhee S-Y, Liu T, Simen BB, Egholm M, Hanczaruk B, et al. Minority variants associated with transmitted and acquired HIV-1 nonnucleoside reverse transcriptase inhibitor resistance: implications for the use of second-generation nonnucleoside reverse transcriptase inhibitors
. J Acquir Immune Defic Syndr