Personal and Social Functioning and Health-Related Quality of Life in Patients with Schizophrenia Treated with the Long-Acting Injectable Antipsychotic Risperidone ISM.

Objective: To analyze the effect of Risperidone ISM on social functioning and health-related quality of life (HR-QoL) in both short- and long-term treatment of patients with schizophrenia. Patients and Methods: This analysis was based on data from both phases of the PRISMA-3 study, including 433 relapsed patients from the double-blind (DB) phase of the PRISMA-3 trial who were treated for 12-weeks with once-monthly (every 28 days) intramuscular Risperidone ISM 75 mg or 100 mg (n = 288), or placebo (n = 145), as well as 174 patients transitioning from the DB to an open-label 52-week extension (OLE) phase, plus 41 de novo patients treated on a stable maintenance dose of oral risperidone. The clinician-administered Personal and Social Performance (PSP) scale and the patient-reported 20-item Subjective Well-being under Neuroleptics scale (SWN-20) were used to measure social functioning and HR-QoL outcomes, respectively. Results: Risperidone ISM significantly improved PSP total score from baseline to endpoint (Day 85) versus placebo in the DB phase with mean change total score (95% CI) of 10.7 (9; 12) compared to 4.8 (3; 7) for placebo (p < 0.0001). The statistically significant improvement was present from the first measurement time point (Day 29). SWN-20-measured HR-QoL increased on average in patients treated with Risperidone ISM in the DB phase. A significant improvement was also observed for PSP and SWN-20 scores from the OLE baseline to week 52 for patients transitioning from the DB phase. Stable de novo patients maintained similar PSP and SWN-20 scores during the whole OLE phase. Conclusion: Risperidone ISM provided a rapid and sustained improvement in personal and social functioning, and HR-QOL without need of oral risperidone supplementation or loading doses. These findings, along with a fast onset of efficacy, could contribute to reinforcing the therapeutic alliance and possibly an earlier discharge. Moreover, patient functioning continued improving or was maintained with long-term treatment.

Long-term efficacy and safety of once-monthly Risperidone ISM® in the treatment of schizophrenia: Results from a 12-month open-label extension study.

OBJECTIVE: To evaluate long-term efficacy, safety and tolerability of Risperidone ISM® in patients with schizophrenia, a multicenter, open-label extension of the PRISMA-3 study was conducted. METHODS: Eligible placebo (unstable) and Risperidone ISM® (stabilized) rollover patients from a previous 12-week double-blind phase and de novo stable patients received once-monthly intramuscular injections of Risperidone ISM® 75 or 100 mg for 12 months. The long term-efficacy assessment included the Positive and Negative Syndrome Scale (PANSS), Clinical Global Impression-Severity (CGI-S) and Clinical Global Impression-Improvement (CGI-I) scales. Safety evaluation included treatment-emergent adverse events (TEAEs), injection site reactions (ISR), laboratory tests and several safety scales. RESULTS: Altogether, 215 patients entered the study (55 unstable, 119 stabilized and 41 stable patients). Most patients (74.9%) completed, and discontinuation rates were broadly similar across the study subgroups, mainly due to withdrawal of consent (12.1%). PANSS total and subscales scores decreased from baseline to endpoint in all groups, with the largest decrease for unstable patients. Improvement from baseline to 12 months was also shown for CGI-S and CGI-I scores for both unstable and stabilized patients; the CGI-S and CGI-I scores remained almost unchanged for the stable group. At least one treatment-related TEAE was reported in 39.1% of patients; the most common were headache (12.1%), hyperprolactinemia (9.8%) and asthenia (5.1%). ISR were reported in 8 (0.3%) patients; injection site pain score was low across the 2355 doses assessed. CONCLUSION: Risperidone ISM® is an effective, safe, and well-tolerated long-term treatment of schizophrenia in adults, regardless of the initial disease severity or whether patients were previously treated with Risperidone ISM® during an acute exacerbation or switched from stable doses of oral risperidone.

The Steady-State Comparative Bioavailability of Intramuscular Risperidone ISM and Oral Risperidone: An Open-Label, One-Sequence Study.

INTRODUCTION: This open-label, one-sequence study evaluated the steady-state comparative bioavailability of risperidone in situ microimplants (ISM®) and oral risperidone in patients stabilized on oral risperidone treatment. METHODS: Repeat oral administration of once daily 4 mg risperidone for 7 days was followed by 4 monthly (once every four weeks) intramuscular (IM) doses of risperidone ISM 100 mg. Mean steady-state concentration versus time profiles for risperidone, 9-OH risperidone, and risperidone active moiety was characterized. RESULTS: A total of 104 subjects were enrolled, 81 were included in the safety population and 58 completed the study. Intersubject variability for the steady-state concentrations versus time profiles for risperidone active moiety presented a greater variability range for oral risperidone versus risperidone ISM (% coefficient of variation [CV] range: 40-65% and 38-52%, respectively). Minimum plasma concentration at steady-state (Cmin, ss) and fluctuation in plasma concentrations (Fluc) of risperidone active moiety after risperidone ISM administration met bioequivalence criteria compared to the reference oral risperidone (geometric mean ratio [GMR] = 1.09 and 0.96, respectively; both 90% CIs were within 0.80-1.25). Area under the curve during the dosing interval (AUCtau), maximum plasma concentration at steady-state (Cmax, ss) and average plasma concentration (Cave) were only slightly higher (GMR [90% CI] = 1.25 [1.16-1.34], 1.17 [1.08-1.27], and 1.25 [1.16-1.34], respectively). Overall, once daily oral risperidone 4 mg and once monthly IM risperidone ISM 100 mg were generally safe and well tolerated in the participating subjects with schizophrenia previously stabilized with oral risperidone. CONCLUSION: The rapid release of risperidone ISM allows the achievement of the desired levels similar to those observed at the steady-state after oral risperidone treatment. Therefore, direct switch after 24 hours from the last oral risperidone dose to risperidone ISM treatment can be done in schizophrenia patients with no time lag, maintaining steady-state levels of the active moiety throughout treatment and without the need for oral risperidone supplementation or loading doses.

A phase II study to evaluate the pharmacokinetics, safety, and tolerability of Risperidone ISM multiple intramuscular injections once every 4 weeks in patients with schizophrenia.

This study characterized the pharmacokinetics, safety, and tolerability of Risperidone ISM, a new long-acting intramuscular formulation, for monthly administration without oral supplementation. Patients with schizophrenia received multiple intramuscular injections of 75 mg in the gluteal or deltoid muscle at 28-day intervals. Of the 70 randomized patients, 67 received at least one dose of study medication. The mean Cmax of the active moiety was achieved 24-48 h (tmax) after each administration, regardless of injection site. They ranged over four consecutive doses from 39.6 to 53.2 and 54.1 to 61 ng/ml, when given in gluteal or deltoid muscle, respectively. Active moiety achieved therapeutic levels by 2 h after dose, and the levels were maintained throughout the 4-week dosing period. No significant changes across the study were observed on either Positive and Negative Syndrome Scale or Extrapyramidal Symptoms Scale. Overall, 63 (94%) patients experienced at least one treatment-emergent adverse event (TEAE). One serious TEAE (dystonia) was related to study treatment. The most frequently reported TEAEs were hyperprolactinaemia (57.7%) and injection site pain (32.8%). Risperidone ISM achieved therapeutic levels from the first hours after drug administration and provided a sustained release throughout the 4-week dosing period over multiple intramuscular injections and was found to be safe and well tolerated.

Phase I, open-label, randomized, parallel study to evaluate the pharmacokinetics, safety, and tolerability of one intramuscular injection of risperidone ISM at different dose strengths in patients with schizophrenia or schizoaffective disorder (PRISMA-1).

The aim of this study was to characterize the pharmacokinetics and to evaluate the safety of risperidone ISM in patients with schizophrenia or schizoaffective disorder after a single gluteal intramuscular injection at three different dose strengths (50, 75, and 100 mg). A total of 36 patients were randomized and blood samples were collected to measure the plasma concentrations. The pharmacokinetic of the active moiety was biphasic for all three dose groups, and the mean plasma concentration was 21.45, 24.60, and 29.68 ng/ml in the 50, 75, and 100 mg group, respectively, 24 h after dose administration; 22.81, 24.57, and 31.41 ng/ml in the 50, 75, and 100 mg group, respectively, 48 h after dose administration, and 12.26, 17.31, and 20.01 ng/ml in the 50, 75, and 100 mg group, respectively, 30 days after dose administration. Overall, 34 patients experienced at least one treatment-emergent adverse event (TEAE). Two patients experienced a serious TEAE and no deaths occurred. There were no extrapyramidal symptoms-related serious TEAEs and no significant changes in any Columbia Suicide Severity Rating Scale parameter were observed during the study. Risperidone ISM provided a sustained release of risperidone that achieved therapeutic plasma levels within the first day. Risperidone ISM was safe, well tolerated, and should be suitable for a 4-weekly administration without oral supplementation.

All-cause mortality in the cohorts of the Spanish AIDS Research Network (RIS) compared with the general population: 1997-2010.

BACKGROUND: Combination antiretroviral therapy (cART) has produced significant changes in mortality of HIV-infected persons. Our objective was to estimate mortality rates, standardized mortality ratios and excess mortality rates of cohorts of the AIDS Research Network (RIS) (CoRIS-MD and CoRIS) compared to the general population. METHODS: We analysed data of CoRIS-MD and CoRIS cohorts from 1997 to 2010. We calculated: (i) all-cause mortality rates, (ii) standardized mortality ratio (SMR) and (iii) excess mortality rates for both cohort for 100 person-years (py) of follow-up, comparing all-cause mortality with that of the general population of similar age and gender. RESULTS: Between 1997 and 2010, 8,214 HIV positive subjects were included, 2,453 (29.9%) in CoRIS-MD and 5,761 (70.1%) in CoRIS and 294 deaths were registered. All-cause mortality rate was 1.02 (95% CI 0.91-1.15) per 100 py, SMR was 6.8 (95% CI 5.9-7.9) and excess mortality rate was 0.8 (95% CI 0.7-0.9) per 100 py. Mortality was higher in patients with AIDS, hepatitis C virus (HCV) co-infection, and those from CoRIS-MD cohort (1997-2003). CONCLUSION: Mortality among HIV-positive persons remains higher than that of the general population of similar age and sex, with significant differences depending on the history of AIDS or HCV coinfection.

Resistance to the most recent protease and non-nucleoside reverse transcriptase inhibitors across HIV-1 non-B subtypes.

OBJECTIVES: Limited data are available on resistance to etravirine, rilpivirine, darunavir and tipranavir in patients infected with HIV-1 non-B subtypes, in which natural polymorphisms at certain positions could influence the barrier and/or pathways to drug resistance. METHODS: FASTA format sequences from the reverse transcriptase and protease genes recorded within the Spanish Drug Resistance database (ResRIS) were examined. RESULTS: From 8272 genotypes derived from 5930 different HIV-1 patients included in ResRIS, 5276 genotypes had complete treatment information. Overall, 85% were from antiretroviral-experienced subjects and 7.5% belonged to HIV-1 non-B subtypes: CRF02_AG, C, F and G being the most prevalent variants. For etravirine, only G190A was more prevalent in B than non-B subtypes, whereas V90I and V179E were more frequent in non-B than B subtypes. For rilpivirine, V108I and Y188I were more frequent in B than non-B subtypes, whereas V90I was more prevalent in non-B subtypes. Despite these differences, the overall prevalence of resistance did not differ significantly when comparing etravirine or rilpivirine in B versus non-B subtypes (11.3% versus 7.4%, P = 0.13, and 10.5% versus 7.4%, P = 0.23, respectively). Despite more frequent natural polymorphisms in non-B than B subtypes at tipranavir resistance positions, the prevalence of tipranavir resistance was greater in B than non-B subtypes (11% versus 4.3%, P = 0.004), reflecting a greater antiretroviral exposure in the former. Darunavir resistance did not differ significantly when comparing B and non-B subtypes (5.8% versus 5.5%, P = 0.998). CONCLUSIONS: The rate of resistance to the most recently approved protease and non-nucleoside reverse transcriptase inhibitors is low in antiretroviral-experienced patients, regardless of the HIV-1 subtype.

Rilpivirine resistance mutations in HIV patients failing non-nucleoside reverse transcriptase inhibitor-based therapies.

OBJECTIVE: Rilpivirine (RPV) is the latest approved nonnucleoside reverse transcriptase inhibitor (NNRTI). It displays in-vitro activity extending over other NNRTI-resistant HIV strains. There is scarce information about the rate of RPV resistance-associated mutations (RAMs) in patients failing other NNRTIs. METHODS: RPV RAMs were examined in plasma samples collected from HIV patients that had recently failed NNRTI-based regimens at 22 clinics in Spain. RESULTS: Resistance tests from a total of 1064 patients failing efavirenz (EFV) (54.5%), nevirapine (NVP) (40%) or etravirine (ETR) (5.5%) were examined. The prevalence of RPV RAMs was K101E (9.1%), K101P (1.4%), E138A (3.9%), E138G (0.3%), E138K (0.3%), E138Q (0.8%), V179L (0.2%), Y181C (21.8%), Y181I (0.5%), Y181V (0.2%), H221Y (8.3%), F227C (0.1%) and M230L (1.5%). K101E/M184I was seen in 1%. E138K/M184I were absent. Mutations L100I and V108I were significantly more frequent in patients failing EFV than NVP (7.9 vs. 0.2 and 12.2 vs. 7.3%, respectively). Conversely, Y181C, Y181I, V106A, H221Y and F227L were more prevalent following NVP than EFV failures. Using the Spanish resistance interpretation algorithm, 206 genotypes (19.3%) from patients failing NNRTI (NVP 52%, EFV 40.8% and ETR 7.8%) were considered as RPV resistant. In patients with ETR failure, cross-resistance to RPV was seen in 27.6%, mainly as result of Y181C (81.3%), V179I (43.8%), V90I (31.3%) and V108I (18.8%). CONCLUSION: RPV resistance is overall recognized in nearly 20% of patients failing other NNRTIs. It is more common following ETR (27.6%) or NVP (25%) failures than EFV (14.5%). E138 mutants are rarely seen in this context.

Clinical, virological and biochemical evidence supporting the association of HIV-1 reverse transcriptase polymorphism R284K and thymidine analogue resistance mutations M41L, L210W and T215Y in patients failing tenofovir/emtricitabine therapy.

BACKGROUND: Thymidine analogue resistance mutations (TAMs) selected under treatment with nucleoside analogues generate two distinct genotypic profiles in the HIV-1 reverse transcriptase (RT): (i) TAM1: M41L, L210W and T215Y, and (ii) TAM2: D67N, K70R and K219E/Q, and sometimes T215F. Secondary mutations, including thumb subdomain polymorphisms (e.g. R284K) have been identified in association with TAMs. We have identified mutational clusters associated with virological failure during salvage therapy with tenofovir/emtricitabine-based regimens. In this context, we have studied the role of R284K as a secondary mutation associated with mutations of the TAM1 complex. RESULTS: The cross-sectional study carried out with > 200 HIV-1 genotypes showed that virological failure to tenofovir/emtricitabine was strongly associated with the presence of M184V (P < 10-10) and TAMs (P < 10-3), while K65R was relatively uncommon in previously-treated patients failing antiretroviral therapy. Clusters of mutations were identified, and among them, the TAM1 complex showed the highest correlation coefficients. Covariation of TAM1 mutations and V118I, V179I, M184V and R284K was observed. Virological studies showed that the combination of R284K with TAM1 mutations confers a fitness advantage in the presence of zidovudine or tenofovir. Studies with recombinant HIV-1 RTs showed that when associated with TAM1 mutations, R284K had a minimal impact on zidovudine or tenofovir inhibition, and in their ability to excise the inhibitors from blocked DNA primers. However, the mutant RT M41L/L210W/T215Y/R284K showed an increased catalytic rate for nucleotide incorporation and a higher RNase H activity in comparison with WT and mutant M41L/L210W/T215Y RTs. These effects were consistent with its enhanced chain-terminated primer rescue on DNA/DNA template-primers, but not on RNA/DNA complexes, and can explain the higher fitness of HIV-1 having TAM1/R284K mutations. CONCLUSIONS: Our study shows the association of R284K and TAM1 mutations in individuals failing therapy with tenofovir/emtricitabine, and unveils a novel mechanism by which secondary mutations are selected in the context of drug-resistance mutations.

Rilpivirine: a next-generation non-nucleoside analogue for the treatment of HIV infection.

INTRODUCTION: HIV therapy has evolved rapidly since the 1990s; the arrival of more potent and safer antiretroviral drugs has transformed HIV infection into a chronic condition, which is rarely fatal. Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are frequently used as a third agent - as part of a triple-combination therapy. Side effects and low barriers to resistance have been the major drawbacks of NNRTIs. Rilpivirine (RPV) is a next-generation non-nucleoside analogue, the unique features of which might favor choosing this drug over other NNRTIs. RPV is the latest NNRTI approved for the treatment of HIV infection. Along with its high efficacy and good safety profile, data on pharmacokinetics and drug interactions make RPV particularly attractive. AREAS COVERED: This article aims to provide an in-depth analysis of the main features and data available from recent clinical trials that have tested the performance of RPV. EXPERT OPINION: RPV is a safe and efficacious antiretroviral drug with a better neuropsychiatric and metabolic profile than efavirenz, which is currently the most widely used NNRTI. The availability of a fixed-dose coformulation of RPV with tenofovir/emtricitabine makes the use of RPV even more attractive. The efficacy of RPV in patients with a high baseline viral load remains to be clarified in further trials.

Changing rate of non-B subtypes and coinfection with hepatitis B/C viruses in newly diagnosed HIV type 1 individuals in Spain.

Immigration from developing regions to Western countries has resulted in an increased rate of non-B subtypes in the HIV population. However, it is unclear whether these HIV variants remain confined to foreigners or are already spreading among natives. Since many immigrants come from regions in which hepatitis B virus (HBV) and hepatitis C virus (HCV) are endemic, HIV-hepatitis coinfection might be more frequent in newly diagnosed HIV persons. Herein, we report changes in the prevalence and distribution of HIV-1 subtypes in Madrid, Spain over the past 10 years as well as the rate of chronic HBV and HCV coinfection in 1854 newly diagnosed HIV-1 individuals. Overall 18.2% carried HIV-1 non-B subtypes, although the prevalence increased over time reaching a peak of 19.4% in the last period (2007-2010). The most common non-B variants were CRF02_AG (37%), G (12%), A (9.9%), and C (7.8%). In native Spaniards the rate of non-B subtypes increased from 1.5% in 2000-2002 to 7.2% in 2003-2006 and to 11.4% in 2007-2010 (p = 0.04). Chronic hepatitis B and C were found, respectively, in 4.2% and 8.3% of the study population. While the prevalence of chronic hepatitis B has remained fairly stable over time across distinct populations, the rate of chronic HCV infection has experienced a significant decline, mainly in native Spaniards as a result of a reduction in intravenous drug use. In summary, the prevalence of HIV-1 non-B subtypes is rising in newly diagnosed HIV-1 individuals in Spain, including the native population. In contrast, the rate of HBV coinfection remains unchanged and the rate of HCV coinfection has declined.

Drug resistance mutations in HIV-infected patients in the Spanish drug resistance database failing tipranavir and darunavir therapy.

The presence of resistance mutations in patients failing tipranavir or darunavir was examined at the national drug resistance database of the Spanish AIDS Research Network. Although mutations emerging during tipranavir and darunavir failures differed considerably, cross-resistance was found in up to half of the patients tested. Interestingly, mutation 54L, which is associated with tipranavir hypersusceptibility, was selected in half of the darunavir failures. Thus, resistance testing seems mandatory to ensure the benefit of the sequential use of these drugs.

Etravirine resistance associated mutations in HIV-infected patients failing efavirenz or nevirapine in the Spanish antiretroviral resistance database.

The prevalence of etravirine resistance mutations was examined in genotypes derived from 1343 HIV-infected patients failing nevirapine or efavirenz in the resistance database of the Spanish AIDS Research Network (ResRIS). Overall, etravirine-resistant genotypes were recognized in 18.7% of patients, with no significant differences between failures under nevirapine or efavirenz. Thus, more than 80% patients with prior failure to nonnucleoside reverse transcriptase inhibitors could potentially benefit from etravirine rescue therapy.

Changes in drug resistance patterns following the introduction of HIV type 1 non-B subtypes in Spain.

Natural genetic variability at the pol gene may account for differences in drug susceptibility and selection of resistance patterns across HIV-1 clades. Spread of non-B subtypes along with changes in antiretroviral drug use may have modified drug resistance patterns in recent years. All HIV-1 clinical samples sent to a reference laboratory located in Madrid for drug resistance testing since January 2000 were analyzed. The pol gene was sequenced and HIV-1 subtypes were assigned using the Stanford algorithm and phylogenetic analyses for non-B subtypes. Drug resistance mutations were recorded using the IAS-USA mutation list (April 2008). A total of 3034 specimens from 730 antiretroviral-naive individuals (92 with non-B subtypes) and 1569 antiretroviral-experienced patients (97 with non-B subtypes) were examined. The prevalence of HIV-1 non-B subtypes in the study period increased from 4.4% (2000-2003) to 10.1% (2004-2007) (p < 0.01). The most predominant variants were CRF02_AG (41.8%) and G (17.5%). Thymidine analogue mutations (TAMs) were more prevalent in B than non-B subtypes, in both drug-naive (6.2% vs. 1%; p < 0.01) and treatment-experienced patients (49% vs. 30%, p < 0.01). K103N was most frequent in B than non-B subtypes (34% vs. 21%; p < 0.01); conversely, 106A/M was more prevalent in non-B than B clades (11% vs. 5%). Codon 179 mutations associated with etravirine resistance were more frequent in non-B than B subtypes. Finally, secondary protease resistance mutations were more common in non-B than B clades, with a potentially significant impact at least on tipranavir. The prevalence of HIV-1 non-B subtypes has increased since the year 2000 in a large drug resistance database in Spain, determining changes in drug resistance patterns that may influence the susceptibility to new antiretroviral drugs and have an impact on genotypic drug resistance interpretation algorithms.

Use of different inhibitory quotients to predict early virological response to tipranavir in antiretroviral-experienced human immunodeficiency virus-infected patients.

Information about the relationship between pharmacological parameters and an early virological response to tipranavir (TPV) is scarce. Human immunodeficiency virus (HIV)-infected patients who had received TPV as part of a salvage regimen were analyzed retrospectively. A virological response was defined as a decline in the HIV RNA level of > or = 1 log unit or to <50 copies/ml between weeks 4 and 12 of therapy. The virtual inhibitory quotient (vIQ) was calculated as the ratio of the TPV plasma trough concentration (C(trough))/virtual change in the 50% inhibitory concentration. Three genotypic inhibitory quotients (gIQs) were calculated by using different TPV resistance mutation scores (from the International AIDS Society-USA [IAS-USA], Randomized Evaluation of Strategic Intervention in Multidrug-Resistant Patients with Tipranavir [RESIST], and Agence Nationale de Recherches sur le Sida et les Hépatites Virales [ANRS] trials). The sensitivities, specificities, positive predictive values (PPVs), negative predictive values (NPVs), and likelihood ratios for a positive result (LHR+) and a negative result (LHR-) [LHR+ = sensitivity/(1-specificity); LHR- = (1-sensitivity)/specificity] were calculated. A total of 57 HIV-infected patients were analyzed. A virological response was achieved by 77% of the patients. TPV resistance mutations, TPV C(trough), vIQs, and gIQs were all significantly associated with a virological response. The vIQ had the best PPV and NPV (97% and 78%, respectively). The values of the LHR+ were 7.8 for vIQ, 3.4 for the RESIST gIQ, 3.3 for the IAS-USA gIQ, 3.1 for the ANRS gIQ, 2.2 for TPV C(trough), and 1.3 for the IAS-USA and RESIST scores. The values of LHR- were 0 for the RESIST score, 0.07 for vIQ, 0.09 for the IAS-USA score, 0.27 for the RESIST gIQ, 0.32 for the IAS-USA gIQ, 0.37 for the ANRS gIQ, and 0.48 for TPV C(trough). HIV-infected patients who initiate a salvage regimen based on TPV may benefit from baseline drug resistance testing and TPV plasma concentration determination, as vIQ is the best predictor of a virological response.

HIV-1 genotypic drug resistance interpretation rules - 2009 Spanish guidelines.

Interpreting the results of drug resistance tests for HIV-1 is one of the most difficult tasks for both clinicians and virologists. There are many amino acid changes in viral proteins influencing the susceptibility to specific drugs, causing loss of activity or conversely hypersusceptibility. Moreover, the results of interactions derived from complex mutational patterns are difficult to predict. Different interpretation algorithms have been developed to facilitate the translation of information obtained in the genotypes to clinicians. Controversy exists, however, regarding the impact of genotypic changes over the activity of many antiretroviral drugs. Based on virologic outcomes, scientific literature, and expert opinion, the Drug Resistance Platform of the Spanish AIDS Research Network (RIS, Red de Investigación en SIDA) has developed over the last years its own interpretation system. Herein, we present the 2009 guidelines, in which special efforts have been made to standardize the criteria for interpreting resistance mutations for compounds within the same drug family and to facilitate the clinical interpretation of HIV-1 resistance genotypes.

Resistencia viral y barrera genética de atazanavir / Viral resistance and genetic barrier of atazanavir

La resistencia a los inhibidores de la proteasa (IP) generalmente es consecuencia de una mutación en el gen de la proteasa. Se han descrito distintos cambios para cada uno de los IP. La mutación I50L es la característica de resistencia al atazanavir (ATV). No produce resistencia cruzada con otros IP; por el contrario, aumenta la susceptibilidad a todos ellos (hipersusceptibilidad). Cuando los IP se administran conjuntamente con dosis bajas de ritonavir (r), la exposición a concentraciones más elevadas de IP hace necesaria la selección de múltiples mutaciones de resistencia en la proteasa para que haya una pérdida significativa de susceptibilidad. Para la mayoría de IP/r, incluido el ATV/r, se requieren >5 mutaciones en la proteasa para ocasionar un compromiso en la respuesta virológica. A pesar de tener una moderada barrera genética cuando no se potencia con ritonavir, la prolongada semivida del ATV minimiza el riesgo de resistencias en la práctica clínica

Resistance to protease inhibitors (PI) is generally due to a mutation in the protease gene. Different changes have been described for each PI. The I 50L mutation is characteristic of resistance to atazanavir (ATV). It does not produce cross resistance to other PI; but it does increase susceptibility to all of them (hypersusceptibility). When PI are given concomitantly with low doses of ritonavir, the exposure to higher levels of PI requires that multiple resistance mutations have to be selected in the protease so that there is a significant loss of susceptibility. For the majority of PI/r, including ATV/r, >5 mutations in the protease are required to produce a compromise in the virological response. Despite having a moderate genetic barrier when not boosted with ritonavir, the prolonged half-life of ATV minimises the risk of resistance in clinical practice