Darunavir Resistance Mutations Research Articles

HIV-1 protease with 10 lopinavir and darunavir resistance mutations exhibits altered inhibition, structural rearrangements and extreme dynamics

Antiretroviral drug resistance is a therapeutic obstacle for people with HIV. HIV protease inhibitors darunavir and lopinavir are recommended for resistant infections. We characterized a protease mutant (PR10x) derived from a highly resistant clinical isolate including 10 mutations associated with resistance to lopinavir and darunavir. Compared to the wild-type protease, PR10x exhibits ∼3-fold decrease in catalytic efficiency and Ki values of 2–3 orders of magnitude worse for darunavir, lopinavir, and potent investigational inhibitor GRL-519. Crystal structures of the mutant were solved in a ligand-free form and in complex with GRL-519. The structures show altered interactions in the active site, flap-core interface, hydrophobic core, hinge region, and 80s loop compared to the corresponding wild-type protease structures. The ligand-free crystal structure exhibits a highly curled flap conformation which may amplify drug resistance. Molecular dynamics simulations performed for 1 μs on ligand-free dimers showed extremely large fluctuations in the flaps for PR10x compared to equivalent simulations on PR with a single L76V mutation or wild-type protease. This analysis offers insight about the synergistic effects of mutations in highly resistant variants.

Temporal Trends in HIV-1 Mutations Used for the Surveillance of Transmitted Drug Resistance

In 2009, a list of nonpolymorphic HIV-1 drug resistance mutations (DRMs), called surveillance DRMs (SDRMs), was created to monitor transmitted drug resistance (TDR). Since 2009, TDR increased and antiretroviral therapy (ART) practices changed. We examined the changing prevalence of SDRMs and identified candidate SDRMs defined as nonpolymorphic DRMs present on ≥ 1 expert DRM list and in ≥0.1% of ART-experienced persons. Candidate DRMs were further characterized according to their association with antiretrovirals and changing prevalence. Among NRTI-SDRMs, tenofovir-associated mutations increased in prevalence while thymidine analog mutations decreased in prevalence. Among candidate NRTI-SDRMs, there were six tenofovir-associated mutations including three which increased in prevalence (K65N, T69deletion, K70G/N/Q/T). Among candidate NNRTI-SDRMs, six that increased in prevalence were associated with rilpivirine (E138K/Q, V179L, H221Y) or doravirine (F227C/L) resistance. With the notable exceptions of I47A and I50L, most PI-SDRMs decreased in prevalence. Three candidate PI-SDRMs were accessory darunavir-resistance mutations (L10F, T74P, L89V). Adding the candidate SDRMs listed above was estimated to increase NRTI, NNRTI, and PI TDR prevalence by 0.1%, 0.3%, and 0.3%, respectively. We describe trends in the prevalence of nonpolymorphic HIV-1 DRMs in ART-experienced persons. These data should be considered in decisions regarding SDRM list updates and TDR monitoring.

Low concordance and resistance mutation emergence in the HIV protease gene among circulating and cell-associated viruses at viral replication episodes during darunavir/ritonavir monotherapy.

To assess the changes on the HIV protease gene in plasma and peripheral blood mononuclear cell (PBMC) compartments during viral replication episodes in patients on boosted-darunavir monotherapy (mtDRV/rtv). A prospective study was carried out in which adult HIV-1-infected patients who started mtDRV/rtv after viral suppression for ≥ 6 months with no major darunavir-related resistance mutations were enrolled. Patients with two consecutive plasma HIV RNA measurements >200 HIV-1 RNA copies/mL were considered as having virological failure (VF), while patients with two consecutive plasma HIV RNA measurements >50 copies/mL without meeting the VF criteria were considered to have virological rebound (VR). HIV protease genotypic profiles from plasma and PBMCs were performed at baseline and at VF and VR episodes. One hundred and fifty patients were included in the study, with overall VF and VR rates of 14% (n=21) and 14.7% (n=22), respectively. No major darunavir resistance mutations were observed in the plasma or PBMC samples. Circulating and cell-associated viruses showed a wild-type protease gene sequence in 54% and 23% of patients, respectively while the remainder patients only harboured minor protease inhibitor-associated mutations. Full concordance between plasma RNA and PBMC DNA protease genotypes was found in 23% of the sequences. No darunavir-related mutations were found in patients with VF or VR, either in plasma or in PBMCs; thus, simplification to mtDRV/rtv does not comprise future antiretroviral treatment options.

Short Communication: Phenotypic Protease Inhibitor Resistance and Cross-Resistance in the Clinic from 2006 to 2008 and Mutational Prevalences in HIV from Patients with Discordant Tipranavir and Darunavir Susceptibility Phenotypes

To test tipranavir (TPV) or darunavir (DRV) as treatment options for patients with phenotypic resistance to protease inhibitors (PIs), including lopinavir, saquinavir, atazanavir, and fosamprenavir, the PhenoSense GT database was analyzed for susceptibility to DRV or TPV among PI-resistant isolates. The Monogram Biosciences HIV database (South San Francisco, CA) containing 7775 clinical isolates (2006-2008) not susceptible to at least one first-generation PI was analyzed. Phenotypic responses [resistant (R), partially susceptible (PS), or susceptible (S)] were defined by upper and lower clinical cut-offs to each PI. Genotypes were screened for amino acid substitutions associated with TPV-R/DRV-S and TPV-S/DRV-R phenotypes. In all, 4.9% (378) of isolates were resistant to all six PIs and 31.0% (2407) were resistant to none. Among isolates resistant to all four first-generation PIs, DRV resistance increased from 21.2% to 41.9% from 2006 to 2008, respectively, and resistance to TPV remained steady (53.9 to 57.3%, respectively). Higher prevalence substitutions in DRV-S/TPV-R isolates versus DRV-R/TPV-S isolates, respectively, were 82L/T (44.4% vs. 0%) and 83D (5.8% vs. 0%). Higher prevalence substitutions in DRV-R/TPV-S virus were 50V (0.0% vs. 28.9%), 54L (1.0% vs. 36.1%), and 76V (0.4% vs. 15.5%). Mutations to help predict discordant susceptibility to DRV and TPV in isolates with reduced susceptibility to other PIs were identified. DRV resistance mutations associated with improved virologic response to TPV were more prevalent in DRV-R/TPV-S isolates. TPV resistance mutations were more prevalent in TPV-R and DRV-S isolates. These results confirm the impact of genotype on phenotype, illustrating how HIV genotype and phenotype data assist regimen optimization.

Resistant minority species are rarely observed in patients on darunavir/ritonavir monotherapy

To analyse the emergence of resistant viruses in patients failing darunavir monotherapy, including minority species, and to investigate the impact of baseline reverse transcriptase (RT), protease (PR) and gag resistance mutations on virological failure (VF) occurrence. Nine of the 225 HIV-1-infected patients enrolled in the MONOI trial (darunavir/ritonavir monotherapy or darunavir/ritonavir + two nucleoside reverse transcriptase inhibitors in a switch strategy) experienced VF, defined as two plasma HIV-1 viral loads >400 copies/mL at least 2 weeks apart. Among these nine patients with VF, five were in the darunavir/ritonavir monotherapy arm and four were in the darunavir/ritonavir triple therapy arm. Bulk sequences of the PR, RT and gag genes at baseline (on DNA) and at the time of VF (on RNA) were determined for all patients with two viral loads >50 copies/mL at least 2 weeks apart (n = 47). PR and gag gene clonal analysis was performed on plasma samples of the nine patients with VF. There was no association between mutations in RT, PR and gag genes in DNA and VF occurrence. None of the patients demonstrated selection of darunavir resistance mutations among the 47 patients with a viral load >50 copies/mL at least 2 weeks apart. The virus of one of the nine patients with VF presented minority variants with darunavir resistance mutations at positions 32, 47 and 50. Clonal analysis of the gag region for the nine patients with VF did not show any selection of minority variants. In patients with failure on darunavir/ritonavir monotherapy we did not find any selection of darunavir resistance mutations using standard genotype testing. However, the virus of one patient among nine failures presented minority variants plus darunavir resistance mutations.

Prevalence and factors associated with darunavir resistance mutations in multi-experienced HIV-1-infected patients failing other protease inhibitors in a referral teaching center in Brazil

Information about resistance profile of darunavir (DRV) is scarce in Brazil. Our objectives were to estimate the prevalence of DRV resistance mutations in patients failing protease inhibitors (PI) and to identify factors associated with having more DRV resistance mutations. All HIV-infected patients failing PI-based regimens with genotyping performed between 2007 and 2008 in a referral teaching center in São Paulo, Brazil, were included. DRV-specific resistance mutations listed by December 2008 IAS-USA panel update were considered. Two Poisson regression models were constructed to assess factors related to the presence of more DRV resistance mutations. A total of 171 HIV-infected patients with available genotyping were included. The number of patients with lopinavir, saquinavir, and amprenavir used in previous regimen were 130 (76%), 83 (49%), and 35 (20%), respectively. The prevalence of major DRV resistance mutations was 50V: 5%; 54M: 1%; 76V: 4%; 84V: 15%. For minor mutations, the rates were 11I: 3%; 32I: 7%; 33F: 23%; 47V: 6%; 54L: 6%; 74P: 3%; 89V: 6%. Only 11 (6%) of the genotypes had > 3 DRV resistance mutations. In the clinical model, time of HIV infection of > 10 years and use of amprenavir were independently associated with having more DRV resistance mutations. In the genotyping-based model, only total number of PI resistance mutations was associated with our outcome. In conclusion, the prevalence of DRV mutations was low. Time of HIV infection, use of amprenavir and total number of PI resistance mutations were associated with having more DRV mutations.

Prevalence and factors associated with darunavir resistance mutations in multi-experienced HIV-1-infected patients failing other protease inhibitors in a referral teaching center in Brazil

Information about resistance profile of darunavir (DRV) is scarce in Brazil. Our objectives were to estimate the prevalence of DRV resistance mutations in patients failing protease inhibitors (PI) and to identify factors associated with having more DRV resistance mutations. All HIV-infected patients failing PI-based regimens with genotyping performed between 2007 and 2008 in a referral teaching center in São Paulo, Brazil, were included. DRV-specific resistance mutations listed by December 2008 IAS-USA panel update were considered. Two Poisson regression models were constructed to assess factors related to the presence of more DRV resistance mutations. A total of 171 HIV-infected patients with available genotyping were included. The number of patients with lopinavir, saquinavir, and amprenavir used in previous regimen were 130 (76%), 83 (49%), and 35 (20%), respectively. The prevalence of major DRV resistance mutations was 50V: 5%; 54M: 1%; 76V: 4%; 84V: 15%. For minor mutations, the rates were 11I: 3%; 32I: 7%; 33F: 23%; 47V: 6%; 54L: 6%; 74P: 3%; 89V: 6%. Only 11 (6%) of the genotypes had ≥ 3 DRV resistance mutations. In the clinical model, time of HIV infection of > 10 years and use of amprenavir were independently associated with having more DRV resistance mutations. In the genotyping-based model, only total number of PI resistance mutations was associated with our outcome. In conclusion, the prevalence of DRV mutations was low. Time of HIV infection, use of amprenavir and total number of PI resistance mutations were associated with having more DRV mutations.

Resistance analyses in highly experienced patients failing raltegravir, etravirine and darunavir/ritonavir regimen

ANRS 139 TRIO trial was a phase II noncomparative trial that evaluated in highly experienced patients, a combination of raltegravir, etravirine and darunavir boosted with ritonavir. We analyzed emergence of resistant viruses at the time of virological failure and investigated the impact of baseline integrase polymorphisms on virological failure occurrence. Bulk sequencing of protease, reverse transcriptase and integrase genes was performed for 103 patients at baseline and 14 patients at the time of virological failure. Additionally, integrase clonal analyses were performed at baseline and at virological failure in patients with successful integrase gene amplification. Impact of baseline integrase polymorphisms on virological failure occurrence was analyzed using Fisher exact and Wilcoxon tests. In the 14 failing patients median viral load at virological failure was 90 copies/ml (interquartile range = 60-783). Emergence of darunavir and etravirine resistance mutations was observed at virological failure in only one and three patients, respectively. Raltegravir resistance mutations were found neither at baseline nor at the time of virologic failure. Integrase clonal analyses showed neither the presence nor the selection of minority variants carrying raltegravir resistance mutations at baseline or at virological failure. No impact of baseline integrase polymorphisms was observed on virological failure either at week 24 or at week 48. Virological failure occurred in a small proportion of patients with low viral load. No raltegravir resistance mutations were observed using bulk sequencing or clonal analyses, and darunavir and etravirine resistance-associated mutations were detected in only one and three patients, respectively at virological failure. No impact of baseline integrase polymorphism was observed on virological failure occurrence.

Efficacy of darunavir/ritonavir maintenance monotherapy in patients with HIV-1 viral suppression: a randomized open-label, noninferiority trial, MONOI-ANRS 136

Darunavir/ritonavir (darunavir/r) maintenance strategy, in patients with suppressed HIV RNA viremia, is a potential long-term strategy to avoid nucleoside analogue toxicities and to reduce costs. MONOtherapy Inhibitor protease is a prospective, open-label, noninferiority, 96-week safety and efficacy trial in virologically suppressed patients on triple therapy who were randomized to a darunavir/r triple drug regimen or darunavir/r monotherapy. The primary endpoint was the proportion of patients with HIV RNA less than 400 copies/ml at week 48; treatment failure was defined as two consecutive HIV RNA more than 400 copies/ml (time to loss of virologic response) or any change in treatment. The trial had 80% power to show noninferiority for the monotherapy arm (delta =-10%, 90% confidence interval). A total of 242 patients were screened, 225 of whom were randomized. In the per protocol efficacy analysis, treatment success was 99% on darunavir/r triple drug versus 94% on darunavir/r monotherapy (delta = -4.9%, 90% confidence interval, from -9.1 to -0.8). Similar results were found in intent-to-treat population (92 versus 87.5%, delta = -4.5%, 90% confidence interval from -11.2 to 2.1). Three patients experienced virologic failure on darunavir/monotherapy and none on darunavir/r triple drug. No resistance to protease inhibitor emerged in patients with plasma viral load above 50 copies/ml. The two groups did not differ in the number of serious adverse events. Darunavir/r monotherapy exhibited efficacy rate over 85% with concordant results in the magnitude of difference with darunavir/r triple drug regimen in both intent-to-treat and per protocol analyses, but discordant conclusions with respect to the noninferiority margin. Patients failing on darunavir/r monotherapy had no emergence of new darunavir resistance mutations preserving future treatment options.

Factors predictive of successful darunavir/ritonavir-based therapy in highly antiretroviral-experienced HIV-1-infected patients (the DARWEST study)

Background Darunavir (DRV) is the latest protease inhibitor (PI) to be approved for antiretroviral-naive and -experienced HIV-infected patients. Objectives We examined virologic and immunologic outcomes of highly antiretroviral-experienced patients with triple-class drug resistance receiving DRV/r-based regimens, and attempted to identify factors predictive of virologic success. Study design We studied patients beginning a ritonavir-boosted DRV (DRV/r 600/100 mg twice daily)-containing regimen. Virologic success was defined as plasma viral load (pVL) < 50 copies/ml at week 36. Results We studied 62 patients with very severe immunodeficiency (CDC stage C in 69% of cases; median CD4 cell nadir 12/mm 3). They had previously received a median of four PI and had extensive PI resistance, with a median of three major PI and two DRV resistance mutations. The baseline median pVL and CD4 cell count values were 4.6 log 10 and 150/mm 3. At week 36, pVL had fallen by 2.6 log 10 and the CD4 cell count had risen by 123 cells/mm 3. The virologic success rate was 55% overall, and was improved by concomitant first use of enfuvirtide (67%), raltegravir (69%) or etravirine (75%). Virologic success was independently associated with fewer major PI mutations, previous tipranavir exposure, and concomitant first use of enfuvirtide or raltegravir. Conclusions In these highly antiretroviral-experienced patients with triple-class drug resistance, virologic success of DRV-containing regimens was mainly associated with the use of new drug classes and/or fully active drugs. Interestingly, previous tipranavir failure did not undermine the efficacy of DRV, confirming the low level of cross-resistance and, probably, distinct resistance profiles between DRV and tipranavir.

Managing treatment-experienced pediatric and adolescent HIV patients: role of darunavir

Darunavir is currently the most recently approved HIV-1 protease inhibitor. It is approved for twice-daily dosing with ritonavir in treatment-experienced patients as young as 6 years of age and is available in numerous pill strengths. Emergence of darunavir-specific mutations is generally slow; therefore it can retain activity against viral strains that are resistant to other protease inhibitors, including tipranavir. Darunavir pharmacokinetics, clinical efficacy, resistance mutations and pharmacodynamics, and adverse effects are reviewed here. Substantial data support its use as a potent, well-tolerated option for salvage therapy in highly treatment-experienced children and adolescents.

Darunavir Inhibitory Quotient Predicts the 48-Week Virological Response to Darunavir-Based Salvage Therapy in Human Immunodeficiency Virus-Infected Protease Inhibitor-Experienced Patients

The aim of this study was to evaluate the relationship between the virological response to darunavir-based salvage antiretroviral therapy and the darunavir genotypic and virtual inhibitory quotients (gIQ and vIQ, respectively). Thirty-seven HIV-infected patients failing protease inhibitor-based antiretroviral regimens who started salvage therapy containing darunavir-ritonavir were prospectively studied. The primary outcome of the study was a viral load (VL) of <50 copies/ml at week 48. The trough concentrations of darunavir in plasma, the number of darunavir resistance mutations, the change in the 50% inhibitory concentration (IC(50)) of darunavir in the virtual phenotype, and the darunavir gIQ and vIQ were correlated with the virological outcome in regression analyses adjusted by the number of active drugs in the background regimen. The VL was <50 copies/ml in 56.8% of patients at week 48. Changes in the VL were not significantly associated with the darunavir concentration (P = 0.304), the number of darunavir resistance mutations (P = 0.695), or the change in the IC(50) (P = 0.750). However, patients with darunavir vIQs of >or=1.5 had a 12-fold greater chance of achieving a >or=1 log(10) reduction in the VL (odds ratio [OR], 12.7; 95% confidence interval [95% CI], 1.9 to 81.6; P = 0.007), and a 5-fold greater chance of achieving a VL of <50 copies/ml (OR, 5.4; 95% CI, 1.2 to 24.5; P = 0.028), at week 48 than patients with darunavir vIQs of <1.5. The positive and negative predictive values of this darunavir vIQ cutoff for achieving a VL of <50 copies/ml at week 48 were 70% and 69%, respectively. The darunavir vIQ predicts virological response to darunavir-based salvage therapy better than the darunavir trough concentration or resistance mutations alone. We suggest targeting a darunavir vIQ of 1.5 for achieving long-term viral suppression.

Combating HIV resistance &amp;ndash; focus on darunavir

Darunavir is a second-generation protease inhibitor designed to have antiviral efficacy against HIV-1 isolates harboring multiple resistance mutations to protease inhibitors. Pivotal trials conducted in treatment-experienced HIV-infected individuals have demonstrated significantly greater virological suppression when darunavir was added to an optimized background treatment compared with a control protease inhibitor. This virological suppression was associated with an increase in CD4 counts and was sustained over time. Darunavir resistance-associated mutations have been defined as V11I, V32I, L33F, I47V, I50V, I54L/M, G73S, L76V, I84V, and L89V. In clinical trials, baseline darunavir susceptibility was a strong predictor of virological response. Prior use of fosamprenavir was associated with darunavir resistance mutations. Darunavir has a high genetic barrier and has a distinct resistance profile. Although some cross-resistance exists with other second-generation protease inhibitors such as tipranavir, different resistance mutation patterns have been observed upon failure to these regimens. It was found that mutations at 47V, 54M, 85V, and 73T were most prevalent in isolates resistant to both PIs. Mutations 48V, 50V, and 54L were associated with resistance to darunavir but not to tipranavir. 82S and 82T were associated with resistance to tipranavir but not to darunavir. Therefore, darunavir provides potent virological efficacy as well as high genetic barrier that can be useful to preserve treatment options in HIV-infected, treatment-experienced individuals.

Impact of gag mutations on selection of darunavir resistance mutations in HIV-1 protease

To search for genetic factors in the protease and gag regions (NC-p1/TFP-p6/p6pol) involved in selection of darunavir resistance mutations. We analysed 48 protease inhibitor (PI)-experienced HIV-infected patients experiencing darunavir treatment failure. Viral genotyping at baseline and months 3 and 6 was used to assess the selection of mutations in the protease and gag regions conferring resistance to PIs. There were no genotypic differences in the studied gag region between baseline and the latest available rebound isolates. There was an association between the presence of the mutation A431V in the gag sequence and the selection of the L76V mutation in the protease sequence in the latest available rebound. The I437T/V mutation in gag and the L76V mutation in the protease were associated with a lower risk of selecting darunavir resistance mutations. In these PI-treated patients experiencing treatment failure of a darunavir-containing regimen, we showed that mutations in the gag region NC-p1/TFP-p6/p6pol may influence the selection of darunavir resistance mutations; in particular, the I437T/V gag mutation that confers resistance to PIs reduces the selection of such mutations. Virus with L76V in protease or I437T/V in gag may be already resistant to darunavir and, therefore, no additional resistance mutations need to be selected.

Evidence for different susceptibility to tipranavir and darunavir in patients infected with distinct HIV-1 subtypes

Tipranavir (TPV) and darunavir (DRV) are potent against protease inhibitor (PI)-resistant viruses. Efficacy of these compounds when confronting distinct HIV subtypes is not known. All clinical specimens from HIV-positive patients sent to our institution for drug resistance testing between 1999 and 2006 were analysed. The prevalence of TPV and DRV resistance mutations was assessed based on the latest International AIDS Society-USA panel list. Phenotypic susceptibility to DRV and TPV was examined in a subset of these samples using the PhenoSense assay. A total of 1364 genotypes were analysed, including 1178 from individuals infected with clade B (285 drug naive) and 186 with non-B subtypes (137 drug naive). The mean number (+/-SD) of DRV resistance-associated mutations was higher in clade B than non-B (0.4 +/- 0.9 versus 0.06 +/- 0.3; P < 0.001), and more frequent among PI-experienced than drug-naive patients (0.6 +/- 1.02 versus 0.02 +/- 0.21; P < 0.001). In contrast, the mean number of TPV resistance-associated mutations was higher in non-B than B subtypes (2.7 +/- 1 versus 1.2 +/- 1.6; P < 0.001), regardless of PI experience. Susceptibility to TPV and DRV was examined in 29 drug-naive patients infected with non-B subtypes (1A, 3C, 2CRF01_AE, 9CRF02_AG, 1CRF12_BF, 3CRF14_BG, 3F and 7G). All showed susceptibility to DRV and 93% to TPV. Interestingly, two subtype F specimens showed reduced TPV susceptibility, with fold-changes of 2.7 and 2.1, respectively. Non-B subtypes show a greater number of TPV resistance-associated mutations than B viruses, regardless of PI exposure. While HIV clade has no influence on DRV susceptibility, some F subtypes may show reduced TPV susceptibility.

Factors Associated with the Selection of Mutations Conferring Resistance to Protease Inhibitors (PIs) in PI-Experienced Patients Displaying Treatment Failure on Darunavir

The objective of this study was to characterize the mutations selected by darunavir (DRV) use in protease inhibitor (PI)-experienced patients and the associated factors. We analyzed treatment failure in 54 PI-experienced human immunodeficiency virus (HIV)-infected patients on a DRV- and ritonavir-containing regimen. Viral genotyping was carried out at the baseline, at between 1 and 3 months of treatment, and at between 3 and 6 months of treatment to search for the selection of mutations conferring resistance to PIs. The median baseline HIV RNA level was 4.9 log(10) copies/ml, and the median CD4 count was 87 cells/mm(3). At the baseline, the median numbers of resistance mutations were as follows: 3 DRV resistance mutations, 4 major PI resistance mutations, and 10 minor PI resistance mutations. The most common mutations that emerged at rebound included V32I (44%), I54M/L (24%), L33F (25%), I84V (21%), and L89V (12%). Multivariate analysis showed that higher baseline HIV RNA levels and smaller numbers of nucleoside reverse transcriptase inhibitor simultaneously used with DRV were associated with a higher risk of DRV resistance mutation selection. By contrast, L76V, a known DRV resistance mutation, was found to decrease the risk of selection of another DRV resistance mutation. The occurrence of virological failure while a patient was on DRV was associated with the selection of mutations that increased the level of DRV resistance without affecting susceptibility to tipranavir (TPV). In these PI-treated patients who displayed treatment failure while they were on a DRV-containing regimen, we confirmed the set of emerging mutations associated with DRV failure and identified the factors associated with the selection of these mutations. TPV susceptibility does not seem to be affected by the selection of a DRV resistance mutation.

Impact of baseline protease genotype and phenotype on the response to darunavir outside clinical trials

Impact of baseline protease genotype and phenotype on the response to darunavir outside clinical trials

Prevalence of darunavir resistance mutations in HIV-1-infected patients failing other protease inhibitors

To estimate to what extent darunavir might be effective in patients failing distinct protease inhibitors (PIs), the genotypic resistance scores recently reported for the drug were examined in a large clinical HIV-1 drug resistance database. All clinical specimens from HIV-infected patients failing PI-based regimens referred for drug resistance testing between 1999 and 2007 to a reference centre in Madrid were analysed. Darunavir-specific resistance mutations listed by the September 2006 IAS-USA panel update were considered. A total of 1021 genotypes from patients failing lopinavir (39.2%), nelfinavir (28.1%), saquinavir (14.5%), indinavir (13.7%), atazanavir (6.6%), fosamprenavir (5.3%) and tipranavir (1.1%) were identified. The prevalence of major darunavir resistance mutations was I50V 2.1%, I54M 1.3%, L76V 2.7% and I84V 14.5%. For minor darunavir resistance mutations, the rates were V11I 3.3%, V32I 3.9%, L33F 11%, I47V 2.1%, I54L 2.3%, G73S 12.8% and L89V 2.4%. Overall, 6.7% (n = 68) of the genotypes had three or more darunavir resistance mutations, which corresponded to a mean total number of PI resistance mutations of 12.3 +/- 1.9. In the multivariate analysis, prior fosamprenavir failure, prior saquinavir failure, the total number of PI resistance mutations and the number of prior PIs used were all independently associated with having more darunavir resistance mutations. The prevalence of darunavir resistance mutations is low in patients failing other PI-based regimens, although prior failure to amprenavir and saquinavir might produce more cross-resistance to darunavir. Thus, darunavir may be a good option for patients who have failed other PI-based regimens.