Study Design
This was a phase I, single-dose, open-label, non-randomized, parallel-group study to evaluate the PK, safety, and tolerability of OM in individuals with normal renal function or varying degrees of renal impairment. The study consisted of a screening period lasting up to 21 days followed by a single 8-day treatment period (defined as check-in to discharge) for individuals with normal renal function or mild, moderate, or severe renal impairment (groups 1–4, defined below and in Table 1 of the Electronic Supplementary Material [ESM]) or two treatment periods (period 1, 2 days; period 2, 2 days) separated by a washout period of 7–14 days for individuals with ESRD (group 5; Fig. 1 of the ESM). An end-of-study visit occurred 12–16 days after the single OM dose for groups 1–4 and after the second OM dose (during treatment period 2) for group 5. Participants received a single oral dose of OM 50 mg on day 1 of each treatment period after fasting overnight for ≥ 10 h; fasting continued for ≥ 4 h post-dose. For participants in group 5, OM was administered 3 h before the start of dialysis in treatment period 1 and on a non-dialysis day in treatment period 2. The OM dose was administered as a film-coated oral tablet with a modified-release matrix formulation, which has been previously described [12].
Table 1 Baseline demographics The study was conducted in accordance with ethical guidelines from the Declaration of Helsinki and Council for International Organizations of Medical Sciences, applicable Good Clinical Practice guidelines of the International Council for Harmonization, and applicable local laws and regulations. An Advarra® (Columbia, MD, USA) institutional review board approved the research protocol and study conduct. All study participants provided written informed consent before enrollment in the study and could withdraw from the study at any time. Qualified researchers may request data from Amgen clinical studies; complete details are available at http://www.amgen.com/datasharing.
Study Participants
Eligibility was determined by medical history, physical examination, vital signs, laboratory values, and cardiac monitoring at screening and check-in. Eligible participants were male or female individuals aged 18–65 years (inclusive) for treatment groups 2 and 3 or aged 18–75 years (inclusive) for treatment groups 1, 4, and 5, with a body mass index between 18.0 and 38.0 kg/m2 (inclusive); only female individuals who were not of childbearing potential were eligible for the study. Non-hypertensive individuals or individuals with treated and stable hypertension were included in renal impairment groups (groups 2–5) if their systolic blood pressure did not exceed 170 mmHg and their diastolic blood pressure did not exceed 100 mm Hg at screening and check-in; individuals with renal impairment were eligible if the dosage and nature of their antihypertensive medication were stable for ≥ 4 weeks before screening and were expected to remain unchanged throughout the study duration.
Eligible participants were enrolled in one of five renal function groups on the basis of US Food and Drug Administration guidance for renal impairment studies [15] and as measured by eGFR and the need for renal replacement therapy (Table 1 of the ESM). The eGFR was calculated using serum creatinine levels and the Modification of Diet in Renal Disease (MDRD) formula [15]: MDRD formula (mL/min/1.73 m2) = 175 × (serum creatinine)−1.154 × (age)−0.203 × (0.742 if female) × (1.212 if African American). Participants in group 1 were considered to have normal renal function (eGFR, ≥ 90 mL/min/1.73 m2 and no history of renal disease); participants in group 2 had mild renal impairment (eGFR, 60–89 mL/min/1.73 m2); participants in group 3 had moderate renal impairment (eGFR, 30–59 mL/min/1.73 m2); participants in group 4 had severe renal impairment (eGFR, 15–29 mL/min/1.73 m2 without dialysis); and participants in group 5 had ESRD requiring dialysis and had been receiving hemodialysis for ≥ 1 month before screening or had an eGFR < 15 mL/min/1.73 m2. Participants in group 1 (normal renal function) were selected so that the mean and distribution of their age, sex, and body mass index matched those of the participants in the renal impairment groups.
Exclusion criteria were related to medical history (e.g., history of uncontrolled or unstable cardiovascular, respiratory, hepatic, gastrointestinal, endocrine, hematopoietic, psychiatric, or neurological disease within 6 months of screening) and laboratory screening tests, including aspartate aminotransferase or alanine aminotransferase levels more than two times the upper limit of normal, and clinically significant hyperkalemia (serum potassium level > 5 mmol/L for groups 1–3 and > 5.5 mmol/L at check-in or within 24 h of the last dialysis session for groups 4–5). Exclusion criteria also included elevated levels of biomarkers associated with coronary events: creatine kinase or creatine kinase muscle/brain levels greater than the upper limit of normal for group 1 or at levels inconsistent with chronic kidney disease (groups 2–5) in the opinion of the investigator at screening, and troponin I levels greater than the upper limit of normal for group 1 or at levels inconsistent with chronic kidney disease (groups 2–5) in the opinion of the investigator at screening or check-in. Participants were excluded if they had previous exposure to the study drug or if they had prior or concomitant use of over-the-counter or prescription drugs that could affect the PK of the study drug. Participants with renal impairment could continue receiving concomitant medication necessary for maintaining their clinical status during the study if they were taking the medication for ≥ 1 month before study drug administration.
Pharmacokinetic Sampling
Individuals in groups 1–4 remained at the study site and were supervised for approximately 9 days, beginning 2 days before dosing and lasting until collection of the last pharmacokinetic sample at 144 h post-dose. Pooled urine samples for measurement of OM concentrations were collected at 0–12, 12–24, 24–48, 48–72, 72–96, 96–120, and 120–144 h post-dose; urine samples for estimation of creatinine clearance were collected 24 h pre-dose (Table 2 of the ESM). Blood samples collected by venipuncture or cannulation for measurement of plasma OM concentrations were collected pre-dose and at 0.5, 1, 2, 3, 4, 6, 8, 12, 24, 48, 72, 96, 120, and 144 h post-dose. The lower limit of quantification for plasma samples was 1 ng/mL; the lower limit of quantification for urine samples was 50 ng/mL.
Individuals with ESRD (group 5) remained at the study site and were supervised for approximately 3 days in each treatment period, beginning 1 day before dosing and lasting until collection of the last pharmacokinetic samples at 24 h post-dose. Blood samples collected by venipuncture were collected for determining plasma OM concentrations pre-dose and at the same intervals as those used for groups 1–4 on the dialysis day in treatment period 1 and pre-dose and at 0.5, 1, 2, 3, 4, 6, 8, 12, and 24 h post-dose on day 1 in treatment period 2 (non-dialysis day; Table 2 of the ESM). During dialysis in treatment period 1, arterial (pre-dialysis) and venous (post-dialysis) plasma samples, as well as dialysate for measurement of OM concentration, were collected at 0.5, 1, 2, 3, and 4 h after the start of dialysis.
Study Assessments
The primary endpoints used to assess the effect of renal function on the PK of OM were maximum observed plasma concentration (Cmax), area under the plasma concentration–time curve from time zero to infinity (AUC∞), and fraction of dose excreted unchanged in urine (fe); the primary endpoints used to assess the effect of hemodialysis on the PK of OM in individuals with ESRD were Cmax and AUC from time zero to 24 h post-dose (AUC0–24). Additional endpoints included time to reach Cmax (tmax), AUC from time zero to time of last quantifiable concentration, apparent plasma terminal elimination half-life, apparent total body clearance, apparent renal clearance, and apparent volume of distribution.
Safety Evaluation
Secondary endpoints assessed the safety and tolerability of OM and included the monitoring of adverse events (AEs), clinical laboratory tests, 12-lead electrocardiograms, and vital signs. Monitoring of AEs occurred throughout the study. Clinical chemistry and hematology evaluations were conducted 24 h post-dose; in the case of a suspected coronary event, blood samples for troponin I and/or creatine kinase muscle/brain fraction could be collected at other times. Blood pressure and pulse rate, 12-lead electrocardiograms, and oral body temperature were recorded at screening, checking, scheduled timepoints post-dose, and at the end of the study visit (Table 2 of the ESM).
Statistical Analysis
The pharmacokinetic parameters Cmax, tmax, apparent plasma terminal elimination half-life, AUC∞ (for groups 1–4; for group 5, period 1 only), fe, and apparent renal clearance were determined using non-compartmental methods. Plasma pharmacokinetic parameter values including arithmetic mean, geometric mean, median, standard deviation, minimum, maximum, and coefficient of variation were calculated for each renal function group.
To determine the effect of renal impairment on the PK of OM, linear regression analyses were performed on the log-transformed Cmax and AUC values as a function of the eGFR and creatinine clearance from pre-dose (− 24 to 0 h); body weight, sex, and age were considered as possible covariates, as these were the characteristics used to match participants in group 1 with the participants in groups 2–5 with renal impairment. For group 5, to determine the effect of hemodialysis on the PK of OM, a repeated-measures analysis was performed.
Geometric least-squares mean ratios (GMRs) and 90% confidence intervals (CIs) were derived for comparisons of renal impairment (groups 2–5) vs normal renal function (group 1) and for the dialysis day (group 5, period 1) vs the non-dialysis day (group 5, period 2) for participants with ESRD. Safety outcomes were summarized using descriptive statistics. All statistical analyses were conducted by SAS Enterprise Guide, Version 7.13 (SAS Institute Inc., Cary, NC, USA).