This non-randomized, open-label, two-part Phase 1 trial, designed to compare the pharmacokinetics and safety of glepaglutide in adults with varying degrees of renal function, was conducted at two sites in Hungary (Pharmaceutical Research Associates Hungary Research and Development Ltd, Budapest and St. Imre Teaching Hospital, Budapest) and one site in Poland (SCM Spółka z o.o., Krakow) between 29 November 2019 and 14 July 2020.

The trial consisted of two parts. Part A had two groups: subjects with normal renal function and subjects with severe renal impairment or end stage renal disease (ESRD) not requiring dialysis. Based on the results from Part A, the trial was either terminated or progressed to Part B, consisting of 3 groups: subjects with normal renal function, mild renal impairment, and moderate renal impairment.

The trial protocol, consent form and other information provided to subjects were approved by independent ethics committees (Egészségügyi Tudományos Tanács Klinikai Farmakológiai Etikai Bizottsága, Budapest, Hungary, and Komisja Bioetyczna; przy Okręgowej Izbie Lekarskiej w Krakowie, Krakow, Poland) and by competent authorities. The trial was conducted according to the Declaration of Helsinki and Good Clinical Practice with written informed consent obtained from subjects before trial enrollment. The trial is registered at http://www.clinicaltrials.gov (NCT04178447) and has the EudraCT number: 2019-001466-15.

Eligible subjects were males or females aged between 18–70 years (both inclusive) with a body mass index (BMI) of 20–30 kg/m2. In line with guidance for studies in subjects with renal impairment [16, 17], subjects with renal impairment were recruited and then matched on a group level with subjects with normal renal function with comparable demographics (sex, age, and BMI). Subjects were categorized into a normal renal function group and renal impairment groups (mild, moderate, and severe/ESRD) according to their estimated glomerular filtration rate (eGFR) at screening, calculated using the Modification of Diet in Renal Disease (MDRD) equation [18]: normal renal function (eGFR ≥ 90 mL/min/1.73 m2), mild impairment (eGFR 60 to < 90 mL/min/1.73 m2), moderate impairment (eGFR 30 to < 60 mL/min/1.73 m2), severe impairment (eGFR 15 to < 30 mL/min/1.73 m2), and ESRD (eGFR < 15 mL/min/1.73 m2) not on dialysis.

Subjects with renal impairment were to have a stable disease, with no clinically significant changes in disease status (including disease(s) associated with renal impairment) within 3 months of screening. No changes in medications for the treatment of renal impairment were allowed in the 30 days prior to administration of the study drug.

Key exclusion criteria for all subjects included any clinically relevant medical history likely to interfere with the trial objectives or safety of the participant, uncontrolled hypertension, and current or documented history of repeated clinically significant hypotension or severe episodes of orthostatic hypotension. In addition, subjects with renal impairment were excluded if they had acute renal failure (as judged by the investigator), renal impairment requiring dialysis, a history of kidney transplant regardless of functionality, a serum albumin concentration < 25 g/L, a hemoglobin concentration < 100 g/L, or were taking medications within 60 days prior to study drug administration that were competitors of renal tubular secretion or known to affect the elimination of serum creatinine.

Eligible subjects were admitted to the trial site the day before dosing. On the dosing day (Day 1; morning), subjects received a single SC dose of glepaglutide 10 mg in the abdomen. Subjects stayed at the trial site for the first 3 days, after which they attended daily outpatient visits up to and including Day 8, and a follow-up visit on Day 11. Blood samples for determination of glepaglutide parent drug and the two main metabolites, M1 and M2, were drawn pre-dose and at 30 min and 1, 2, 4, 8, 12, 16, 20, 24, 36, 48, 60, 72, 96, 120, 144, 168 and 240 h post-dose. After Part A of the study, the pharmacokinetics of glepaglutide were compared between subjects with severe renal impairment/ESRD and those with normal renal function before a decision was made to proceed to Part B of the study. This decision was made by a pre-specified Data Review Board comprising the sponsor, the principal investigators, and representatives from the Contract Research Organization (PRA Health Services) that coordinated the trial on behalf of the sponsor. Since no clinically relevant difference in glepaglutide pharmacokinetics was found between the two renal function groups of Part A, the study was stopped according to the study protocol without progressing to Part B.

Venous blood samples were drawn in K2EDTA tubes and stored at − 80 °C until analyzed. Parent drug, M1 and M2 were quantified at the Charles River Laboratories Edinburgh Ltd (UK) using immunoaffinity extraction and subsequent analysis by liquid chromatography–tandem mass spectroscopy (LC–MS/MS); see electronic supplementary material for further details. The LC–MS/MS assay was validated according to current guidelines for bioanalysis of plasma samples and had a lower limit of quantification of 25.0 pmol/L (parent drug and M1) and 50.0 pmol/L (M2), and an upper limit of detection of 2500 pmol/L (parent drug and M1) and 5000 pmol/L (M2).

The objective of the trial was to compare the pharmacokinetic profile of glepaglutide in subjects with renal impairment relative to the corresponding pharmacokinetic profile obtained in subjects with normal renal function. The primary endpoints were maximum plasma concentration (Cmax) and area under the plasma concentration–time curve from time zero to 168 h (AUC0–168 h) for the constructed analyte (glepaglutide), which was calculated as the sum of parent drug, M1 and M2. Secondary pharmacokinetic endpoints included time to maximum concentration (Tmax), AUC from time zero to infinity (AUC0–∞) and AUC from time zero to time t (AUC0–t), where t is the last time point with concentrations above the lower limit of quantitation (LLOQ). No formal sample size calculations were performed because there was no prior information on the pharmacokinetic variability of glepaglutide in subjects with renal impairment. In line with guidance for the evaluation of the pharmacokinetics of medicinal products in patients with decreased renal function [16, 17], approximately 8 subjects were planned to be enrolled per renal function group to obtain at least 6 evaluable subjects for the primary analysis.

Analyses of pharmacokinetic endpoints were based on subjects who were exposed to trial product and had sufficient bioanalytical assessments to calculate reliable estimates of the pharmacokinetic parameters. Pharmacokinetic parameters were estimated via noncompartmental methods using Phoenix WinNonlin® Version 6.4 (Certara USA, Princeton, NJ, USA). Values below LLOQ were set to “missing” for endpoint derivations. Late positive concentration values were set to “missing” if following at least 2 consecutive values below LLOQ. Nominal times were used where actual times were missing.

The primary pharmacokinetic endpoints (Cmax and AUC0–168 h) were log-transformed and evaluated using an analysis of variance (ANOVA), with renal function as fixed effect; ratios of geometric least-squares means (impaired renal function/normal renal function) and corresponding 95% confidence intervals (CIs) were estimated from the model.

Safety and tolerability were assessed throughout the study by means of adverse event (AE) recording (MedDRA preferred terms are presented), vital signs measurements, 12-lead ECGs, clinical laboratory evaluations, physical examinations, and monitoring for injection site reactions.