This study was conducted at 1 clinical study center in the United Kingdom. The protocol was approved by the Independent Ethics Committee Plymouth, UK, and was conducted in accordance with the 1975 Declaration of Helsinki, as revised in 2000 , and the European Commission's directive on clinical research (2001/20/CE) . Before enrollment, all subjects provided written informed consent. Subjects were required to be taking an OC prior to study entry and be healthy pre-menopausal females, 18 to 45 years old, with a BMI between 19 to 35 kg/m2. Subjects were excluded from the study if they had diabetes mellitus or had received implanted contraceptives for 6 months or injectable contraceptives for 12 months prior to the study. Grapefruit was restricted within 7 days and concomitant drug therapies that could induce or inhibit CYP3A were not permitted within 14 days before the first drug administration. In case of mild intercurrent illness during the study, ibuprofen and/or anti-emetic medications that would not affect gastrointestinal motility were allowed at the discretion of the investigator. Lifestyle habits of eligible subjects, such as smoking, alcohol consumption, diet, and exercise, were not altered during the study.
This was an open-label, 3-period, 3-sequence, randomised crossover study in healthy female subjects who were using OCs prior to study entry (clinicaltrials.gov registration: NCT00254800). The primary objective was to evaluate the effect of exenatide on the multiple-dose PK of a combination oral contraceptive (EE and LV) administered 1 hour before and 30 minutes after the exenatide dose. Up to 40 subjects were to be enrolled to ensure that approximately 18 subjects completed the study. Comparing OC alone and OC administered 1 hour before exenatide, a sample size of 18 subjects was estimated to provide approximately 90% power to demonstrate that the 90% CI of the ratio of geometric means for AUC (EE or LV) would be contained within the interval (0.80, 1.25). This sample size estimate was based on an intra-subject coefficient of variation of 15%.
The OC combination product (Microgynon 30®) consisted of EE, 30 μg and LV, 150 μg. Prior to starting the active dosing period, screening was conducted over 2 visits. The purpose of the first screening visit, approximately 2 months prior to admission, was to initiate a run-in period either to convert to the study OC or to synchronise the OC cycle within a cohort of subjects. The second screening visit occurred approximately 21 days prior to the first day of dosing to confirm study eligibility.
Each subject participated in 3 treatment periods, each of 28 days duration: OC alone, OC 1 hour before exenatide, and OC approximately 30 minutes after exenatide. Exenatide was self-administered 15 minutes prior to the morning and evening meals at 5 μg BID on Days 1 through 4 and increased to 10 μg BID on Days 5 through 22. Subjects received a single dose of OC on Day 8 of each treatment period; dosing was omitted on Day 9 to allow for single-dose PK sampling. Subsequently, once-daily doses of OC were resumed on Days 10 through 28. Given that exenatide was administered 15 minutes before meals, OC was administered either 75 minutes before the meal (ie, 1 hour before exenatide) or 15 minutes after the meal (ie, 30 minutes after exenatide), depending on the treatment period. In the OC alone arm, all multiple OC doses and the majority of the single OC doses were given approximately 75 minutes before the meal.
During each treatment period after the first dose of the OC (Day 8), venous blood samples (4 mL each) were taken pre-dose, and at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 8, 10, 12, 16, 24 and 48 hours post-dose. Blood samples were also taken following multiple doses of the OC (Day 22) pre-dose, and at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 8, 10, 12, 16 and 24 hours post-dose. At a minimum, subjects were admitted to the Clinical Research Unit (CRU) on Day 7, resident on Day 8, and discharged on Day 9, then admitted again on Day 21, resident on Day 22, and discharged on Day 23. Subjects were required to attend the CRU on Days 10 and 28 as outpatients. At the investigator's discretion, subjects could be resident in the CRU or attend as outpatients after the first exenatide dose (Day 1) and upon dose increases to 10 μg (Day 5).
Human plasma PK samples obtained during this study were analysed at PPD, Richmond, VA, USA. The samples were analysed for EE and LV using validated liquid chromatography with tandem mass spectrometric methods . The lower limit of quantification was 2.00 pg/mL for EE and 50.0 pg/mL for LV; the upper limit of quantification was 200 pg/mL for EE and 12500 pg/mL for LV and. The intra-assay accuracy (% relative error) during partial validation ranged from -4.24% to 0.992% for LV and from 0.233% to 2.96% for EE. The intra-assay precision (% relative standard deviation) during partial validation ranged from 6.30% to 8.67% for LV and from 4.63% to 12.1% for EE.
Plasma EE and LV pharmacokinetics were characterised by noncompartmental methods of analysis using WinNonLin Professional Version 5.0.1 (Pharsight, Cary, NC). Plasma concentrations for each OC component were plotted semi-logarithmically against time following single (Day 8) or multiple doses (Day 22). The maximum concentration after single or multiple doses (Cmax or Cmax, ss) and the corresponding time of maximum concentration (Tmax or Tmax, ss) were identified from the observed data. After a single dose, the area under the concentration-time curve up to the last sampling time point (AUC0-t, last) was calculated and extrapolated to infinity (AUC0-∞) using the log-linear trapezoidal rule. Following multiple-dose administration of the OC, the area under the curve over the 24-hour post-dose interval (AUC0-τ, ss) was calculated on Day 22. Additionally, concentrations were tabulated at the 24-hour post-dose scheduled time points following single and multiple doses. These 24-hour post-dose concentrations are referred to as daily trough concentrations in the remainder of the document.
The statistical analysis included all data from subjects who received at least 1 dose of drug, and who had evaluable PK data. The primary PK parameters analysed statistically for EE and LV were AUC0-∞ and Cmax following single-dose administration (Day 8) and AUC0-τ, ss and Cmax, ss following multiple-dose administration (Day 22). In addition, OC trough concentrations on Day 8 and Day 22 were analysed. PK parameters were log-transformed (base e) prior to analysis. Single- (Day 8) and multiple-dose (Day 22) PK profiles of EE and LV were assessed separately. A linear mixed-effects model was applied that included subject as a random effect, and treatment, period, and sequence as fixed effects. The differences between treatments and the control (OC alone) were back-transformed to yield the ratio of the LS geometric mean for each PK parameter relative to the control treatment, and the corresponding 90% CI. An interaction was concluded when the 90% CI for the ratio of the LS geometric mean was not contained within the pre-specified interval (0.80, 1.25). Inter-and intra-subject variability estimates were derived from the mixed-effects model. Tmax was analysed separately for Day 8 and Day 22 using the nonparametric Wilcoxon rank sum test.
Safety was assessed by recording spontaneously reported adverse events and was evaluated at scheduled intervals by physical examination, vital sign measurement (including sitting blood pressure and heart rate), body weight assessments, clinical laboratory tests (including serum biochemistry, hematology, and urinalysis), and 12-lead electrocardiogram recordings.