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Stefano Bonora

Publications and source records attributed to Stefano Bonora.

At least 19 recordsLinked to original sources
PubMed2006

A simple and sensitive assay for determining plasma tipranavir concentration in the clinical setting by new HPLC method.

A simple method for the quantification of tipranavir, the first non-peptidic HIV protease inhibitor, was developed and validated. Quinoxaline, as internal standard, was added to 50 microl of plasma before a liquid-liquid extraction by 600 microl of protein precipitation solution. The extracts were diluted before being injected in the chromatographic system. Chromatographic separation was made on a C18 column using potassium phosphate buffer (pH 3.2) and acetonitrile with gradient. Detection was performed by an UV detector at 260 nm. Relative error at three control quality concentrations ranged from -1.81 to 1.72%. Intra-day (CV%) and inter-day (CV%) precision ranged from 0.94 to 2.55% and from 3.07 to 4.24%, respectively. LOQ and LOD were 0.090 microg/ml and 0.035 microg/ml, respectively. Mean recovery was 87.1%+/-2.4%. Calibration curve was linear up to 180 microg/ml. Concentration range when optimized (0.703-180 microg/ml) proved to be adequate to measure tipranavir concentration in HIV-1-positive patients, therefore this method could be suitable for therapeutic drug monitoring of this drug.

Anti-HIV Agents↗
PubMed2006

Unexpected drug-drug interaction between tipranavir/ritonavir and enfuvirtide.

Fifty-five patients placed on tipranavir/ritonavir 500/200 mg twice a day (27 with enfuvirtide and 28 without) underwent tipranavir and ritonavir plasma concentration measurements by high-pressure liquid chromatography. Markedly higher tipranavir and ritonavir trough concentrations were observed in enfuvirtide recipients. The modelling of sparse plasma samples using a first order absorption and elimination monocompartmental model without time lag predicted higher tipranavir elimination half-life and volume of distribution in enfuvirtide takers. This unexpected drug-drug interaction warrants further investigation.

Anti-HIV Agents↗
PubMed2006

Specific mutations in HIV-1 gp41 are associated with immunological success in HIV-1-infected patients receiving enfuvirtide treatment.

OBJECTIVES: To investigate gp41 variability and correlation with viro-immunological parameters in 54 HIV-1-infected patients receiving enfuvirtide added as single active drug to a failing regimen. METHODS: One hundred and two HIV-1 gp41 sequences and clinical follow-up from 54 enfuvirtide-treated patients were analysed from baseline to week 36 of treatment. The association of mutations with viraemia/CD4 count was assessed by Mann-Whitney test. RESULTS: The addition of enfuvirtide to the failing regimen induced at week 4 a viraemia decrease from 5.1 to 4.3 log(10)/mL (P = 0.0002) and a CD4 increase from 48 to 106 cells/mm(3) (P = 0.008). While viraemia rebounded to 4.8 and 4.6 log(10)/mL at week 12 and 36, respectively, CD4 continued to increase to 136 cells/mm(3) at week 36. Enfuvirtide resistance mutations, rarely found at baseline, occurred in 45/54 (83.3%) enfuvirtide-treated patients. V38A/E were the most represented mutations at all time-points. The presence of V38A/E was significantly associated with a 4.5-fold CD4 increase from baseline to week 24 and with a 6-fold increase at week 36 (P = 0.004 and 0.02 compared without V38A/E, respectively), without significant correlation with viraemia. In contrast, Q40H + L45M (present in six enfuvirtide-treated patients at week 36) correlated with CD4 loss from baseline to week 36 (P = 0.02), without significant correlation with viraemia. Mutation N126K (observed in six enfuvirtide-treated patients, never found at baseline) abrogates the fourth gp41 glycosylation site and correlates with a 2.1-fold CD4 increase at week 24. CONCLUSIONS: Specific enfuvirtide resistance mutations (V38A/E) are associated with a sustained CD4 increase, without remarkable effects upon viraemia. This CD4 recovery, due to virus- and immune-mediated mechanisms most probably not applicable to protease/reverse transcriptase inhibitors, is important for innovative therapeutic strategies.

Adult↗
PubMed2006

Validation of liquid/liquid extraction method coupled with HPLC-UV for measurement of ribavirin plasma levels in HCV-positive patients.

Measurement of ribavirin plasma levels in HCV-positive patients have been shown to be useful in order to optimise individual ribavirin exposure. Efficacy and toxicity of this drug are shown to be concentration-dependant. A simple HPLC-UV method was developed and validated, which has an easy liquid/liquid extraction, sensitive limit of detection, without any interference peaks, reproducible and linear over the range of clinical relevant concentrations. The assay warrants further evaluation as a tool for ribavirin therapeutic drug monitoring in HCV-positive patients.

Chemical Fractionation↗
PubMed2006

Influence of genotype 3 hepatitis C coinfection on liver enzyme elevation in HIV-1-positive patients after commencement of a new highly active antiretroviral regimen: results from the EPOKA-MASTER Cohort.

BACKGROUND: The independent role of hepatitis C virus (HCV) genotype 3 in liver transaminase elevation following highly active antiretroviral regimens is still controversial. METHODS: Analysis of data from a cohort of 492 HIV/HCV-coinfected patients was conducted using an intention-to-treat approach. Incidence of grade > or = III liver transaminase elevation was estimated per 100 patient-years of follow-up. Univariate and multiple proportional hazards regression analysis of factors that may predict liver enzyme elevation was performed. RESULTS: The incidence of grade > or = III hepatotoxicity was 25 per 100 patient-years among patients coinfected with HCV genotype 3 and 11 per 100 patient-years among those with other genotypes. On multiple proportional hazard regression analysis, time-to-grade > or = III liver enzyme elevation was directly correlated with HCV genotype 3 (hazards ratio [HR]: 2.0, 95% CI: 1.3 to 2.9; P = 0.001), male gender (HR: 2.7; 95% CI: 1.3 to 5.7; P = 0.007), chronic hepatitis B virus infection (HR: 2.9, 95% CI: 1.5 to 5.9; P = 0.002), and alanine aminotransferase level at baseline (per 10 IU/L HR: 1.10; 95% CI: 1.06 to 1.15; P < 0.001). In the same model, higher CD4 T-cell counts at baseline were inversely correlated with risk of hepatotoxicity (HR: 0.998; 95% CI: 0.997 to 0.999; P = 0.036). Moreover, among patients experienced to antiretroviral drugs, previous grade > or = III hepatotoxicity (HR: 2.8; 95% CI: 1.8 to 4.3; P < 0.001) was an adjunctive independent risk factor. CONCLUSIONS: HIV-positive patients coinfected with HCV genotype 3 displayed a higher risk of relevant hepatotoxicity, independently from other clinical variables. The impact of HCV genotype outweighed the role of drugs in determining hepatotoxicity.

Adult↗
PubMed2006

Enfurvitide prevents vertical transmission of multidrug-resistant HIV-1 in pregnancy but does not cross the placenta.

The use of previously successful antiretroviral regimens in mother-to-child transmission (MTCT) prevention will be increasingly challenged by the rising prevalence of multidrug-resistant (MDR) HIV. We used enfurvitide together with an optimized antiretroviral backbone to prevent the MTCT prevention of MDR HIV in two pregnant women. The measurement of maternal and foetal peripheral blood levels of enfurvitide showed no evidence of transplacental transfer.

Adult↗
PubMed2006

An improved HPLC fluorimetric method for the determination of enfuvirtide plasma levels in HIV-infected patients.

An improved HPLC fluorimetric method for the quantification of enfuvirtide in plasma of HIV-infected subjects was described and validated. The use of an internal standard improved the reproducibility and precision of the analysis. Our method showed lower limits of detection and quantification (LOD = 32 ng/mL, LOQ = 78 ng/mL), lower intraday (RSD% 1.25-2.95) and interday (RSD% 1.75-4.69) coefficients of variation, greater recovery (>100%), lower duration (16 minutes) and lower cost than previously described fluorimetric methods. Therefore, this method can be used as a reliable tool for pharmacokinetic studies of enfuvirtide.

Chromatography, High Pressure Liquid↗
PubMed2006

Antiviral efficacy and genotypic resistance patterns of combination therapy with stavudine/tenofovir in highly active antiretroviral therapy experienced patients.

OBJECTIVES: To evaluate antiviral efficacy of stavudine/tenofovir (d4T/TDF) backbone combination in late-line antiretroviral therapy, and to assess clinical and virological determinants of treatment success. DESIGN: Multicentric retrospective analysis on patients starting d4T/TDF after highly active antiretroviral therapy (HAART) failure. METHODS: The primary endpoint was the change in plasma HIV-1 RNA from the baseline (time of d4T/TDF initiation) to 6 months of therapy; secondary endpoint was the risk of virological failure. RESULTS: Among 172 patients included, a mean change in HIV-1 RNA of -1.69 (+1.23) and -1.53 (+1.43) log10 cp/ml was observed respectively at weeks 24 and 48 after starting d4T/TDF combination. Any single type-1 thymidine analogue mutation (TAM; M41L, L210W, T215Y) had a negative effort on the change in HIV RNA at 6 months, whereas among type-2 TAMs (D67N, K70R, K219Q), only D67N showed a trend for a negative effect. Presence of M184V mutation was related with a greater reduction in HIV RNA during d4T/TDF exposure. The risk of virological failure at 6 months after d4T/TDF starting was 22%. Type-1 TAMs were associated with a greater risk of failure (adjusted hazard ratio [HR]=1.65; 95% confidence interval [CI] 1.19-2.29). Conversely, M184V showed a protective effect. In 17 genotypic tests available at failure, no K65R mutation was detected, whereas a trend for an increasing prevalence of d4T-associated mutations was found. CONCLUSIONS: Combining TDF with a thymidine analogue as d4T may be effective as component of antiretroviral rescue regimens in HIV-infected patients with previous exposure to nucleoside analogue reverse transcriptase inhibitor. Previous selection of type-1 TAMs induces a detrimental effect over virological response.

Adenine↗
PubMed2005

Drug-drug interactions and tolerance in combining antituberculosis and antiretroviral therapy.

Worldwide, tuberculosis (TB) is one of the most important infectious diseases in subjects with HIV infection. Although effective therapy is available for both conditions, there are major problems in the concurrent treatment of HIV and TB co-infection. In this article the knowledge available on drug-drug interactions between anti-HIV and anti-TB compounds is analysed, particularly with regard to pharmacological interactions secondary to interference with cytochrome P450 enzymes. Within the same setting, facts and possible interpretations of the problems encountered in terms of tolerance and safety of the concurrent treatment of TB and HIV are also reviewed. Current guidelines, as well as additional possible strategies to be adopted in this particular co-morbidity setting are discussed.

Anti-Retroviral Agents↗
PubMed2004

Which agents should we use for the treatment of multidrug-resistant Mycobacterium tuberculosis?

The inappropriate treatment of drug-susceptible tuberculosis can lead to the selection and transmission of multidrug-resistant tuberculosis (MDR-TB), indicating resistance to at least isoniazid and rifampicin. In the treatment of MDR-TB, residual first-line drugs, such as ethambutol, pyrazinamide and streptomycin must be appropriately combined with additional second-line drugs, guided by individual susceptibility patterns. The clinical pharmacology of these second-line antituberculous drugs is reviewed. Fluoroquinolones represent the only substantial therapeutic advance in the last 20 years. Many factors potentially affect the outcome of MDR-TB. Treatment adherence, prior exposure to antituberculous drugs, the number of drugs to which the infection is still susceptible and the time since the first diagnosis of tuberculosis are the most relevant. The management of MDR-TB requires considerable expertise. When initiating or revising therapy for MDR-TB, the process of selecting drugs should rely on prior treatment history, results of susceptibility testing and an evaluation of the patient's adherence. In making drug selection, we propose to follow a hierarchy based on the intrinsic activity against Mycobacterium tuberculosis and the clinical evidence of efficacy of the available active compounds.

Antitubercular Agents↗
PubMed2004

The relationship between nevirapine plasma concentrations and abnormal liver function tests.

Abnormal liver function tests are frequently observed in HIV-infected individuals receiving nevirapine (NVP). Here we investigate the relationship between total and unbound plasma concentrations of NVP and the liver enzymes alanine aminotransferase (ALT) and gamma-glutamyl transferase (gammaGT). HIV-infected individuals [n = 85, 22 female, 34 hepatitis C or B virus (HCV or HBV(+))] receiving NVP (200 mg bd; median duration 66 weeks, range 3-189) and two nucleoside reverse transcriptase inhibitors (NRTIs) were enrolled into this study. Blood samples were taken at C(trough) (12 hr postdose) for measurement of NVP and liver function tests (ALT and gammaGT). Plasma protein bound and unbound drug was separated using ultrafiltration and NVP concentrations quantified using HPLC-MS/MS. A linear relationship was observed between total and unbound NVP C(trough) (r(2) = 0.77, p < 0.0001). Patients with elevated ALT (>37 IU/liter; n = 31) had higher NVP unbound C(trough) than those with ALT within the normal range (median 2268 vs. 1694 ng/ml, p = 0.04) but there was no difference in total C(trough). Logistic regression revealed no association between higher NVP C(trough) and ALT elevations. Significantly higher NVP total and unbound C(trough) were observed in patients with increased gammaGT (>40 IU/liter; n = 63; total 6747 vs. 4530 ng/ml, p = 0.001; unbound 2113 vs. 1557 ng/ml, p = 0.03). Significantly higher unbound NVP C(trough) was observed in HCV/HBV(+) (median 2275 vs. 1726 ng/ml, p = 0.02) and on bivariate analysis, higher NVP C(trough) was associated with HCV/HBV coinfection (chi(2) = 4.228; p = 0.04). Overall we found no strong association between NVP concentrations and hepatotoxicity. Although in this study NVP was well tolerated in HCV/HBV coinfected patients, higher plasma concentrations were observed.

Alanine Transaminase↗
PubMed2004

Lopinavir protein binding in vivo through the 12-hour dosing interval.

Most protease inhibitors available for the treatment of human immunodeficiency virus (HIV) infection are highly bound to plasma proteins, mainly alpha-1 acid glycoprotein. Therapeutic drug monitoring (TDM) of total protease inhibitor (PI) concentrations has been increasing in the past few years; however, the pharmacological activity of the PIs is dependent on unbound drug entering cells harboring HIV. There is little information available on unbound drug concentrations of these drugs in vivo. The aim of the study was to measure unbound plasma concentrations of lopinavir (LPV) and to relate them to the total plasma concentrations to establish the unbound percentage in vivo during a full dosage interval. A pharmacokinetic study was performed in HIV-infected subjects (n = 23; median CD4 cell count = 290 x 10(6) cells x L(-1); viral load < 50 copies x mL(-1)) treated with a LPV/ritonavir (RTV)-containing regimen. Ultrafiltration was used to separate unbound LPV in all plasma samples (n = 115). Equilibrium dialysis was also used to compare with ultrafiltration measurements in 10/23 patients at baseline and 2 hours after drug intake. Total and unbound LPV concentrations were measured by a fully validated method using high-performance liquid chromatography-mass spectometry (HPLC-MS/MS). Based on a comparison of AUC(unbound)AUC(total), the mean (+/- SD) unbound percentage of LPV from all the samples studied (n = 115) was 0.92% (+/- 0.22) when measured with ultrafiltration and 1.32% (+/- 0.44) when equilibrium dialysis was used (n = 20), showing a higher drug recovery (P = 0.048). The unbound percentage of LPV was found to be significantly higher after 2 h than at baseline (P < 0.05 with both methods), suggesting a concentration-dependent binding of LPV that has not been observed in vitro. However, the clinical significance of such phenomena is still unclear.

Adult↗
PubMed2003

HIV-1 phenotypic susceptibility to lopinavir (LPV) and genotypic analysis in LPV/r-naive subjects with prior protease inhibitor experience.

The relationship between phenotypic susceptibility to lopinavir (LPV) and genotypic pattern was investigated in LPV-naive, protease inhibitor (PI)-experienced subjects. Protease sequences of 100 HIV isolates with ascertained susceptibility (determined by Antivirogram) to LPV were analyzed (VircoGen). Two different thresholds (2.5- and 10-fold) were used for defining reduced susceptibility. Mutations were classified as LPV/r (the actual formulation of LPV that combines LPV with low-dose ritonavir) mutations according to the International AIDS Society-USA. Thirty-four isolates showed reduced LPV susceptibility (2.6- to 75.9-fold). Fold resistance to LPV correlated with the number of total and LPV/r mutations (Spearman coefficient = 0.62 and 0.74, respectively; P < 0.001). Current PI therapy (P = 0.002) and indinavir administration (P < 0.001), >5 LPV/r mutations (P < 0.0012), and detection of L10FIRV, K20MR, M46IL, I54VL, A71VT, G73SA, V82AFTS, I84V, and M90L were associated with LPV resistance in univariate analysis. Factors independently associated with LPV resistance were K20MR (odds ratio [OR], 13.9; 95% confidence interval [CI], 1.3-145.1; P = 0.028), I54VL (OR, 131.7; 95% CI, 10.5-1654.7; P < 0.001), G73SA (OR, 19.2; 95% CI, 1.4-273.7; P = 0.029), and I84V (OR, 177.5; 95% CI, 6.0-5232.5; P = 0.003) mutations and >9 protease mutations (OR, 18.6; 95% CI, 1.6-213.0; P = 0.019). Sixteen of 34 and 18 of 34 isolates with reduced LPV susceptibility showed >10-fold or <10-fold LPV resistance, respectively. Linear regression analysis demonstrated that each additional LPV mutation and I54VL accounted for much of the fold resistance to LPV (adjusted R2 = 0.70). In conclusion, for PI-experienced patients requiring salvage therapy, switching to LPV should be based on the number of baseline mutations and the presence of mutation 54.

Adult↗