Library Volume 2, Issue 2: Resistance Reporter© 6th European HIV Drug Resistance Workshop


Selections from the 6th European HIV Drug Resistance Workshop (EHDRW); 26-28 March, 2008; Budapest, Hungary.

  • Section 1: Select presentations concerning resistance to antiretroviral drugs and clinical implications
  • Section 2: Select presentations concerning integrase inhibitor resistance and resistance testing

Section 1 (Section 2 Also Available)

Select presentations concerning resistance to antiretroviral drugs and clinical implications


Combined PI and NNRTI Resistance Analysis of the Pooled DUET Trial: Towards a Regimen-Based Resistance Interpretation

EHDRW Abstract 46, Schapiro J et al.

Assessing drug resistance in relation to an entire antiretroviral regimen may be a better predictor of virologic response than assessing resistance to individual regimen components. This concept was explored using pooled data from the DUET studies, parallel randomized phase 3 trials which compared the safety and efficacy of etravirine with that of placebo, each combined with a darunavir/ritonavir-containing optimized background regimen (OBR), in a total of 1,203 treatment-experienced patients with resistance to NNRTIs and PIs, and HIV-1 RNA > 5,000 copies/mL at baseline. The proportion of patients with HIV-1 RNA < 50 copies/mL at     Week 48 was higher in the etravirine arm in an intent-to-treat time-to-loss-of-virologic-response (ITT-TLOVR) analysis (61% versus 40%, P < .0001). Schapiro and colleagues conducted a subanalysis designed to evaluate the combined effect of 13 predefined etravirine resistance-associated mutations (RAMs) and 11 predefined darunavir RAMs on virologic response. Patients were ineligible if their OBR included de novo enfuvirtide or they had stopped treatment for causes excluding virologic failure. Data from 406 individuals were included. Patients with HIV-1 RNA < 50 copies/mL at Week 24 were considered to be virologic responders. Response rates decreased in line with an increasing number of combined baseline RAMs. Among patients with an absence of baseline RAMs, 77.8% had HIV-1 RNA < 50 copies/mL at Week 24, compared with 14.3% of patients with > 7 baseline RAMs. Response rates among patients with no more than 1 RAM to each drug ranged between 66.7% and 81.8%. For those patients with no more than 2 RAMs to each drug, response rates ranged from 56.3% to 100.0%. Rates of response fell below 60% in patients with 2 or more RAMs to each drug.


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Emerging Mutations in Patients with Virological Failure on Etravirine (ETR; TMC125) in the DUET-1 and DUET-2 Clinical Trials

EHDRW Abstract 47, Tambuyzer L et al.

The efficacy of etravirine following failure of a prior NNRTI-based regimen has been demonstrated in DUET-1 and -2, parallel randomized phase 3 trials that compared etravirine with placebo, each combined with a darunavir/ritonavir-containing OBR, in a total of 1,203 viremic patients with resistance to NNRTIs and PIs at baseline. At Week 48, 61% of patients receiving etravirine had HIV-1 RNA < 50 copies/mL compared with 40% of placebo-treated patients by ITT-TLOVR analysis (P < .0001). Tambuyzer and colleagues performed a subanalysis of these DUET studies in order to identify RAMs that emerge following virologic failure on etravirine. Virologic failure, defined as confirmed HIV-1 RNA increase ≥ 0.5 log10 copies/mL from nadir following a confirmed decrease ≥ 1.0 log10 copies/mL from baseline, occurred in 91 of 599 (15%) etravirine-treated DUET patients by Week 48, compared with 28% of placebo-treated patients. Among the 91 etravirine failures, 75 individuals had genotypic and phenotypic data available from baseline and at endpoint, defined as the last on-study visit. Patients who experienced virologic failure on etravirine exhibited greater phenotypic resistance to etravirine and darunavir at baseline than etravirine-treated patients who remained virologic responders. Median baseline fold change (FC) in failures versus responders was 3.3 versus 1.6 for etravirine, and 14.0 versus 5.3 for darunavir, respectively. Virologic failure was associated with increased phenotypic resistance to etravirine and darunavir. Median FC at failure rose to 34.2 (from 3.3) for etravirine, and to 70.6 (from 14.0) for darunavir, respectively. Four NNRTI RAMs emerged in ≥ 10% of patients failing etravirine: V179F in 17%, V179I in 17%, Y181C in 12%, and V108I in 11%. In most cases, these mutations emerged alongside other NNRTI RAMs. Y181C and V179F are known etravirine RAMs. By site-directed mutagenesis, Y181C produced an increase in etravirine phenotypic resistance (FC = 3.9). V179F was detected only in the presence of Y181C, and the combined impact of these two mutations increased etravirine FC to 187.0. V179I and V108I had no discernible impact on virologic response or etravirine FC, and were not therefore considered to be etravirine RAMs.


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Characterization of Maraviroc Resistance in Patients Failing Treatment With CCR5-Tropic Virus in MOTIVATE 1 and MOTIVATE 2 (24-Week Analysis)

EHDRW Abstract 51, Mori J et al.

MOTIVATE 1 and 2 were parallel randomized phase 3 studies that demonstrated the efficacy of the CCR5 antagonist maraviroc in treatment-experienced patients with CCR5- HIV-1, who received a concomitant optimized background regimen (OBR). Failure of maraviroc in the MOTIVATE studies has been associated either with emergence of CXCR4-using variants (undetected at screening due to assay insensitivity) or with evolution of CCR5-using variants that exhibit maraviroc resistance. Phenotypic resistance to maraviroc is evidenced by a plateauing in maximal percentage inhibition (MPI) at < 95%, whereas genotypic markers of maraviroc resistance have yet to be clearly identified. To this end, Mori and colleagues selected patients who experienced virologic failure on maraviroc with CCR5-using virus by Week 24 in the MOTIVATE studies. Among the 36 patients identified, 15 displayed phenotypic maraviroc resistance at failure. Most individuals (9 of 15) who failed with maraviroc-resistant virus were receiving an OBR that contained no active agents. Failure without maraviroc-resistant virus was associated with suboptimal maraviroc exposure. Among the 21 patients with maraviroc-sensitive virus at failure, 15 were observed to have undetectable or low maraviroc levels in plasma, indicative of nonadherence. Sequencing of env clones from patients with maraviroc-resistant virus identified various amino acid changes within the V3 loop. No clear pattern of mutations emerged, although mutations occurred largely within the stem and tip of the V3 loop, with the base region generally remaining conserved. Mutations in gp120 were found outside the V3 loop, but with no recognizable pattern.


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Detection of CXCR4-Using HIV by the TrofileTM and MT2 Assays and Clinical Samples

EHDRW Abstract 81, Coakley E et al.

Optimal use of CCR5 antagonists is dependent on the availability of screening tools able to identify patients with non-R5-utilizing variants, as these strains are not susceptible to agents from this drug class. Coakley and colleagues compared the performance of two tropism detection techniques, the plasma-based TrofileTM assay (Monogram Biosciences, California) and the peripheral blood mononuclear cell (PBMC)-based MT-2 assay (Academic Medical Center, Amsterdam, Netherlands) using a panel of clinical HIV-1 isolates obtained from the Amsterdam HIV/AIDS Cohort. Tropism data were collected for a subset of HAART-naïve cohort members every 3 months using the MT-2 assay: The current analysis included tropism data recorded at 5 or 6 time points per patient close to the time of conversion to syncytium-inducing (SI) virus (CXCR4-using virus) as determined by the MT2 assay. For 21 biological HIV-1 clones derived from 2 patients the two assays reported concordant results for 20 of 21 clones (95%). For 42 MT-2 cell culture derived supernatants obtained from 4 patients, assay results were concordant in 39 of 42 samples (93%). For 20 MT-2 cell culture derived cells from 4 patients, the assays provided concordant results in 19 of 20 (95%). Finally, in 67 consecutive plasma samples obtained from 10 patients (with corresponding PBMC samples available), TrofileTM detected a switch to non-R5-utilizing virus at the same time or before SI detection by the MT-2 assay in 5 of 10 patients (50%). The time lapse between SI detection and subsequent detection of non-R5-utilizing virus by TrofileTM for the remaining 5 patients was 3, 3, 6, 6, and 15 months, respectively. When this last analysis was repeated using a novel TrofileTM assay with enhanced sensitivity, non-R5-utilizing virus was detected at or before the detection of SI virus by the MT-2 assay in 9 of 10 patients (90%).


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Section 2 (Section 1 Also Available)

Select presentations concerning integrase inhibitor resistance and resistance testing


Identification of Residues in HIV-1 Integrase RNAseH and the RT Connection Domain Associated With the Presence of Thymidine Analogue-Associated Resistance

EHDRW Abstract 53, van Eygen V et al.

Assays currently used to monitor antiretroviral resistance in clinical settings do not assess resistance to integrase inhibitors. With the approval of the first agent from this class, raltegravir, modification of current assays to include the integrase region of the HIV-1 genome is required. Van Eygen and colleagues used a genotyping technique to assess sequence variability within the reverse transcriptase (RT) connection domain, RNAseH, and integrase (IN) gene regions in 220 clinical HIV-1 isolates derived from integrase inhibitor-naive individuals. The study aimed to draw associations between thymidine analogues mutations (TAMs) and other amino acid changes. The following RT mutations were defined as TAMs: M41L, D67N, K70R, L210W, T215Y/F, and K219Q/E. Samples were classified as either TAM-containing (n = 95), TAM-negative but other RAMs detected (n = 29), or RAM-negative (n = 96). In addition, samples were subtyped and found to be predominantly subtype B (65.5%), with 11.8% of samples subtype C, 6.8% subtype A, 5.5% subtype CRF02-AG, and 10.5% other subtypes. The dataset did not include variants in which major IN mutations were present. Several secondary IN mutations were detected, and their presence was correlated with the presence of TAMs. The IN mutations M154I, M154L, and K156N were detected in 7.4%, 4.3% and 16.0% of TAM-positive samples, compared with 1.0%, 1.0% and 4.2% of RAM-negative samples, respectively. In samples containing other RAMs but no TAMs, M154I also occurred at a higher frequency (6.5%) than in the RAM-negative group. Two mutations found in RNAseH from TAM-positive variants, T57S (8.6%) and Q72T (5.4%) were not detected in samples from either TAM-negative subgroup. In addition, two further mutations found in RT from TAM-positive variants, R284K (10.8%) and N348I (10.8%) were either absent or present at lower frequency in the TAM-negative groups. A few things to note:
(1) R248K is in the tail end of the polymerase domain of RT, and N348I is in the connection domain (the part between the polymerase and RNaseH domains),
(2) these mutations have nothing to do with integrase,
(3) the clinical significance of these mutations is uncertain.


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Development of a Commercial Assay for Genotyping HIV-1 Integrase

EHDRW Abstract 79, Marlowe N et al.

Marlowe and colleagues reported data on a prototype IN genotyping assay designed to enhance the scope of the ViroSeq HIV-1 Genotyping System (Celera Diagnostics, California). A panel of 84 HIV-1 isolates were obtained from donors in Cameroon, Brazil, Thailand and the United Kingdom. Samples were taken between 2001 and 2006. Samples were categorized by HIV-1 subtype as either subtype A (n = 10), subtype B (n = 24), subtype C (n = 10), subtype D (n = 6), subtype F (n = 6), subtype G (n = 6), subtype CRF01_AE (n = 10), or CRF02_AG (n = 12). Using the prototype technique, the IN region was amplified effectively, and the complete
IN gene (aa 1-288) sequenced, in 83 of 84 (98.8%) samples. A bidirectional sequence of the key catalytic core domain (aa 50-240) in the IN gene that is the site of known integrase inhibitor RAMs was obtained for 82 samples (98.8%). Polymorphisms associated with resistance to the FDA-approved integrase inhibitor, raltegravir, were detected at L74I (9.6%), L74M (4.8%), T97A (3.6%), V151I (2.4%), I203M (1.2%), S230R (1.2%), and N232D (97.6%). Polymorphisms associated with resistance to, elvitegravir, another integrase inhibitor in development, were detected at Q95K (2.4%), E157Q (4.8%), and N232D (97.6%). Several integrase inhibitor mutations were not found within this dataset: H51Y, T66I, L74A, E92Q, F121Y, E138A/K, G140A/S, Y143C/H/R, Q146P, S147G, Q148H/K/R, S153Y, N155H, G163R, H183P, Y226D/F/H, and R263K. The author noted that this prototype assay provides the foundation for the development of a commercial assay for IN genotyping.


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