Midazolam microdosing applied in early clinical development for drug-drug interaction assessment.

AIMS: We aimed to incorporate a pharmacologically inactive midazolam microdose into early clinical studies for the assessment of CYP3A drug-drug interaction liability. METHODS: Three early clinical studies were conducted with substances (Compounds A, B and C) which gave positive CYP3A perpetrator signals in vitro. A 75 µg dose of midazolam was administered alone (baseline CYP3A activity) followed by administration with the highest dose groups tested for each compound on Day 1/3 and Day 14 or Day 17. Midazolam exposure (AUC0-∞ , Cmax ) during administration with the test substances was compared to baseline data via an analysis of variance on log-transformed data. Partial AUC2-4 ratios were also compared to AUC0-∞ ratios using linear regression on log-transformed data. RESULTS: Test compound Cmax values exceeded relevant thresholds for drug-drug interaction liability. Midazolam concentrations were quantifiable over the full profiles for all subjects in all studies. Point estimates of the midazolam AUC0-∞ gMean ratios ranged from 108.3 to 127.1% for Compound A, from 93.3 to 114.5% for Compound B, and from 92.0 to 96.7% for the two highest dose groups of Compound C. Cmax gMean ratios were in the same range. Thus, no relevant drug-drug interactions were evident, based on the results of midazolam microdosing. AUC2-4 ratios from these studies were comparable to the AUC0-∞ ratios. CONCLUSION: Midazolam microdosing incorporated into early clinical studies is a feasible tool for reducing dedicated drug-drug interaction studies, meaning reduced subject burden. Limited sampling could further reduce subject burden, costs and needed resources.

Impact of baseline HIV-1 tropism on viral response and CD4 cell count gains in HIV-infected patients receiving first-line antiretroviral therapy.

BACKGROUND: Viral tropism influences the natural history of human immunodeficiency type 1 (HIV-1) disease: X4 viruses are associated with faster decreases in CD4 cell count. There is scarce information about the influence of viral tropism on treatment outcomes. METHODS: Baseline plasma samples from patients recruited to the ArTEN (Atazanavir/ritnoavir vs. Nevirapine on a background of Tenofovir and Emtricitabine) trial were retrospectively tested for HIV-1 tropism using the genotypic tool geno2pheno(FPR=5.75%). ArTEN compared nevirapine with atazanavir-ritonavir, both along with tenofovir-emtricitabine, in drug-naïve patients. RESULTS: Of 569 ArTEN patients, 428 completed 48 weeks of therapy; 282 of these received nevirapine and 146 of these received atazanavir-ritonavir. Overall, non-B subtypes of HIV-1 were recognized in 96 patients (22%) and X4 viruses were detected in 55 patients (14%). At baseline, patients with X4 viruses had higher plasma HIV RNA levels (5.4 vs 5.2 log copies/mL, respectively; P = .044) and lower CD4 cell counts (145 vs 188 cells/µL, respectively; P < .001) than those with R5 strains. At week 48, virologic responses were lower in patients with X4 viruses than in patients with R5 viruses (77% vs 92%, respectively; P = .009). Multivariate analysis confirmed HIV-1 tropism as an independent predictor of virologic response at week 24 (P = .012). This association was extended to week 48 (P = .007) in clade B viruses. Conversely, CD4 cell count recovery was not influenced by baseline HIV-1 tropism. CONCLUSIONS: HIV-1 tropism is an independent predictor of virologic response to first-line antiretroviral therapy. In contrast, it does not seem to influence CD4 cell count recovery. CLINICAL TRIALS REGISTRATION: NCT00389207.

Short article: Faldaprevir, deleobuvir and ribavirin in IL28B non-CC patients with HCV genotype-1a infection included in the SOUND-C3 phase 2b study.

BACKGROUND: SOUND-C3 was a multicentre, open-label, phase 2b study exploring the safety and efficacy of the interferon-free combination of faldaprevir (an NS3/A4 protease inhibitor), deleobuvir (BI 207127, a non-nucleoside polymerase inhibitor) and ribavirin in treatment-naive patients with chronic hepatitis C virus (HCV) genotype-1 infection. Results in patients with HCV genotype-1b and in IL28B CC genotype patients with HCV genotype-1a have been described previously. This report describes the results in IL28B non-CC genotype patients with HCV genotype-1a. METHODS: Patients were randomized to receive faldaprevir 120 mg once daily with deleobuvir at either 800 mg twice daily (b.i.d.; N=26) or 600 mg three times daily (t.i.d.; N=25), and weight-based ribavirin for 24 weeks. The primary endpoint was sustained virological response 12 weeks after treatment (SVR12). RESULTS: In each group, five patients completed 24 weeks of treatment. SVR12 rates were 19% (5/26) and 8% (2/25) in the b.i.d. and t.i.d. groups, respectively. On-treatment breakthrough [50% (13/26) and 68% (17/25) in the b.i.d. and t.i.d. groups, respectively] was the most frequent reason for not achieving SVR12. Adverse events led to premature treatment discontinuation in six (23%) patients in the b.i.d. group and in two patients (8%) in the t.i.d. group. The majority of adverse events were mild or moderate; the most frequently reported were nausea (67%), fatigue (35%) and diarrhoea (35%). CONCLUSION: In this small study, the interferon-free regimen of faldaprevir, deleobuvir and ribavirin resulted in high rates of virological breakthrough and low rates of SVR12 in IL28B non-CC genotype patients infected with genotype-1a HCV (http://www.clinicaltrials.gov NCT01132313).