2.1 Study Design
This was a phase 1, open-label, single-dose study conducted at four sites in the United States (US) (NCT03318809). The study consisted of a 28-day screening period followed by a 30-day treatment period. On day 1, enrolled participants received a single oral dose of AMG 986 200 mg on an empty stomach (no food or liquids, except water, for at least 8 h before dose administration) and remained in a fasted state (no food or liquids, except water) for at least 2 h after dose administration. Participants resided at the research facility until day 2 for safety assessments and collection of blood samples for PK assessments, after which they were discharged and followed through to day 30; participants returned to the research facility at specified time points between days 2 and 22 for the completion of study assessments. An end-of-study visit occurred on day 30.
2.2 Participants
Eligible participants were males or nonchildbearing females (permanently sterile or postmenopausal) aged 18–65 years with a body mass index of 18–38 kg/m2. Laboratory test values were within normal limits for participants with normal renal function or consistent with the underlying condition for participants with severe RI, or clinically acceptable to the investigator for both normal renal function and participants with severe RI. Participants were required to be non-hypertensive or have treated, stable hypertension (≤ 170/100 mmHg) during screening and day −1; for participants with severe RI, no change in dosage and medication was allowed for ≥ 4 weeks prior to screening, and participants were expected to remain on a stable dose and medication for the entire duration of the study. Exclusion criteria included the concurrent or prior use of strong CYP3A4 inhibitors or strong CYP3A4 inducers within 14 days and 30 days, respectively, of day 1.
Participants were assigned to one of two groups based on their eGFR, calculated with the Modification of Diet in Renal Disease equation [
13]: normal renal function (eGFR ≥ 90 mL/min/1.73 m
2) and severe RI (eGFR 15–29 mL/min/1.73 m
2). Participants in the severe RI group were not anticipated to require hemodialysis or renal transplantation and were anticipated to have renal function appropriate to severe RI for the duration of the study. Participants with normal renal function were matched to the severe RI group by age (± 5 years), body weight (± 10%), proportion of men and women, and race.
2.3 Pharmacokinetic Sampling and Outcomes
On day 1, blood samples for the PK analysis of AMG 986 were collected from each participant at pre-dose and 1, 2, 4, 6, 8, 12, 24, 48, 72, 96, and 120 h post-dose (day 6) using K2EDTA collection tubes. The PK parameters assessed were the maximum observed concentration (Cmax), time to Cmax (tmax), area under the curve (AUC) from time zero to the last quantifiable time point post-dose (AUClast), AUC from time zero to infinity (AUCinf), t½, and apparent drug clearance observed after extravascular administration (CL/F). All PK parameters were estimated using noncompartmental analysis by Phoenix® WinNonlin® version 6.4 (Certara, Princeton, NJ, US).
Plasma concentrations of AMG 986 in human plasma were determined using validated high-performance liquid chromatography (HPLC) mass spectrometry. The analyte AMG 986 and internal standard (IS) 13C6-AMG 986 were extracted from 0.050 mL of human plasma by a protein precipitation extraction procedure. The extraction began by adding 50.0 μL of calibration standards, quality control samples, and study samples to appropriate wells of a 96-well plate, with 50.0 μL of blank human plasma added to each blank well. The samples were diluted with 50 μL of methanol/water (50/50, volume per volume [v/v]). Following the addition of 150 μL of IS to all appropriate wells (or 150 μL of acetonitrile to blank wells), the plate was covered, vortexed, and centrifuged. A Tomtec Quadra4™ (Tomtec Inc., CT, US) 96-well pipettor system was used to transfer 100 μL of the supernatant to a new 96-well plate. After 400 μL of acetonitrile/water (80/20, v/v) was added to all wells, the plate was covered and vortexed. The extracts were chromatographed under reverse-phase conditions on a Kinetex® C8 (Phenomenex Inc., CA, US) HPLC column using a gradient system with 0.1% formic acid in water and 0.1% formic acid in acetonitrile. The compounds were detected and quantified by tandem mass spectrometry in positive ion mode on an API 4000™ (AB Sciex, MA, US) equipped with a Turbo IonSpray® interface. The m/z transition values for AMG 986 and IS were 524.3 → 312.2 and 530.3 → 318.2, respectively. The assay had a lower limit of quantitation (LLOQ) of 10.0 ng/mL. Calibration curves were obtained by performing a linear regression (weighted 1/x2) on the calibration standards.
2.4 Safety Outcomes
The safety and tolerability of AMG 986 was assessed and included the subject incidence of treatment-emergent adverse events (TEAEs), serious adverse events (SAEs), clinical laboratory tests, 12-lead electrocardiogram (ECG), and vital signs. All adverse events were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 4.0.
2.5 Statistical Analysis
Statistical analyses were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC, US). No formal statistical hypothesis testing was performed. The sample size of this study was based on practical considerations and is consistent with the number of participants enrolled in similar studies. The sample size was confirmed to provide a 90% confidence interval (CI) of 0.81–1.23 for the geometric least squares mean (GLSM) ratio of the PK parameters. Concentrations below the LLOQ (10.0 ng/mL) were set to 0 before data analysis. GLSMs and 90% CIs for the ratio of the GLSM (severe RI group/normal renal function group) were estimated using an analysis of variance model. The model used log-transformed PK parameters as the dependent variable and renal function group as the independent variable. The mean difference for the two groups was back-transformed to produce the GLSM ratio. Safety results were summarized using descriptive statistics.