Detection of BRAF mutations in the tumour and serum of patients enrolled in the AZD6244 (ARRY-142886) advanced melanoma phase II study.

BACKGROUND: This study investigated the potential clinical utility of circulating free DNA (cfDNA) as a source of BRAF mutation detection in patients enrolled into a phase II study of AZD6244, a specific MEK1/2 inhibitor, in patients with advanced melanoma. METHODS: BRAF mutations were detected using Amplification Refractory Mutation System allele-specific PCR. BRAF mutation status was assessed in serum-derived cfDNA from 126 patients enrolled into the study and from 94 matched tumour samples. RESULTS: Of 94 tumour samples, 45 (47.9%) were found to be BRAF mutation positive (BRAF+). Serum-derived cfDNA was BRAF+ in 33 of 126 (26.2%) samples, including in five samples for which tumour data were unavailable. Of BRAF+ tumours, 25 of 45 (55.6%) were BRAF+ in cfDNA. In three cases in which the tumour was negative, cfDNA was BRAF+. Progression-free survival (PFS) of patients with BRAF+ tumour and cfDNA was not significantly different compared with tumour BRAF+ but cfDNA BRAF-negative patients, indicating that cfDNA BRAF detection is not associated with poorer prognosis on PFS in stage III/IV advanced melanoma. CONCLUSIONS: These data demonstrate the feasibility of BRAF mutation detection in cfDNA of patients with advanced melanoma. Future studies should aim to incorporate BRAF mutation testing in cfDNA to further validate this biomarker for patient selection.

Do gastrointestinal transit parameters influence the pharmacokinetics of gefitinib?

The selective EGFR tyrosine kinase inhibitor, gefitinib has been shown to be active against certain human carcinomas. It had been noted that a proportion of volunteers consistently had lower gefitinib exposure following oral administration. The shape of the elimination profile in this subset was also different, showing a monophasic elimination pattern rather than the biphasic pattern observed in the majority of subjects. A gamma scintigraphic study was conducted to examine the relationship of gastrointestinal transit and drug absorption in a cohort of rapid clearance subjects (n=5) and normal profile volunteers (n=7). The fasted volunteer panel received a 250 mg gefitinib tablet labelled with [(111)In]-DTPA together with 240 mL [(99m)Tc]-labelled water. The rapid clearance cohorts were shown to have a faster mean gastric emptying T90 (37 min vs 74 min) and shorter small intestinal transit time (156 min vs 204 min), resulting in an earlier colonic arrival time (181 min vs 244 min). Mean plasma C(max) was lower (99.2 ng/mL vs 116 ng/mL) and AUC almost half in the rapid clearance group (2162+/-81 ngh/mL vs 4996+/-64 ngh/mL). These data suggest that gastrointestinal transit parameters play a role in the differences in the rapid clearance profile group, also contributing to the biphasic to monophasic switch. However, historical data show, at the recommended dose of 250 mg/day steady-state plasma concentrations adequate for clinical benefit are achieved in patients with non-small cell lung cancer.

An investigation of components of variance and tachyphylaxis in a placebo-controlled intravenous tyramine study.

AIMS: To explore inter- and intra-volunteer variability for the dose of intravenous tyramine eliciting a 20 mmHg increase in systolic blood pressure from baseline (TYR20) and to evaluate potential tachyphylaxis. METHODS: Twelve healthy volunteers received blinded placebo-controlled ascending and descending sequences of intravenous tyramine injections on two separate occasions. The TYR20 was derived by linear interpolation, using three interventions to deal with missing data. RESULTS: Analysis of covariance (ancova) demonstrated no significant difference in TYR20 between sequences, regardless of the missing data methodology applied. Inter-volunteer variability was 2.4-3.4 times larger than within-volunteer variability. No evidence of tachyphylaxis was seen using either the sign test or generalized additive models. CONCLUSIONS: Since inter-volunteer variability was greater than intra-volunteer variability, a crossover study design would be a more efficient study design, and the descending sequence of injections could be omitted since tachyphylaxis was not demonstrated.

The effect of fluconazole on the pharmacokinetics of rosuvastatin.

OBJECTIVE: To examine the effect of fluconazole, a potent inhibitor of CYP2C9 and CYP2C19, on the pharmacokinetics of rosuvastatin in healthy volunteers. Significantly increased plasma concentrations of fluvastatin have been observed following co-administration with fluconazole. METHODS: This was a randomised, double-blind, two-way crossover, placebo-controlled trial. Healthy male volunteers ( n=14) were given fluconazole 200 mg or matching placebo once daily for 11 days; rosuvastatin 80 mg was co-administered on day 8 of dosing. Plasma concentrations of rosuvastatin, N-desmethyl rosuvastatin, and active and total 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors were measured up to 96 h post-dose. RESULTS: Following co-administration with fluconazole, rosuvastatin geometric least-square mean area under the plasma concentration-time curve (AUC(0-t)) and peak plasma concentration (C(max)) were increased by 14% and 9%, respectively, compared with placebo (90% confidence intervals for the treatment ratios: 0.967 to 1.341 and 0.874 to 1.355, respectively). Individual treatment ratios for AUC(0-t) ranged from 0.59 to 2.23, and for C(max) ranged from 0.52 to 2.28. The limited data available for the N-desmethyl metabolite show that geometric mean C(max) was decreased by approximately 25% compared with placebo. Rosuvastatin accounted for essentially all of the circulating active HMG-CoA reductase inhibitors and most (>90%) of the total inhibitors. Fluconazole did not affect the proportion of circulating active or total inhibitors accounted for by circulating rosuvastatin. CONCLUSIONS: Fluconazole produced only small increases in rosuvastatin AUC(0-t) and C(max), which were not considered to be of clinical relevance. The results support previous in-vitro findings that CYP2C9 and CYP2C19 metabolism is not an important clearance mechanism for rosuvastatin.