Absorption, metabolism and excretion of once-weekly somapacitan, a long-acting growth hormone derivative, after single subcutaneous dosing in human subjects.

Somapacitan is a reversible albumin-binding growth hormone (GH) derivative in clinical development for once-weekly administration in patients with adult GH deficiency (AGHD) and children with GH deficiency (GHD). To date, the use of somapacitan in AGHD or severe AGHD has been approved in the USA and Japan, respectively. This study (ClinicalTrials.gov, NCT02962440) investigated the absorption, metabolism and excretion, as well as the pharmacokinetics (PK), of tritium-labelled somapacitan ([3H]-somapacitan). Seven healthy males received a single subcutaneous dose of 6 mg somapacitan containing [3H]-somapacitan 20 MBq. Blood, serum, plasma, urine, faeces, and expired air were collected for radioactivity assessment. Metabolites were identified and quantified in plasma and urine collected. The PK of plasma components were determined, and the radioactive peaks of the most abundant plasma metabolites and urine metabolites were selected for analysis. Twenty-eight days after dosing, 94.0% of the administered dose was recovered as [3H]-somapacitan-related material, most of which was excreted in urine (80.9%); 12.9% was excreted in faeces, and an insignificant amount (0.2%) was exhaled in expired air. PK properties of [3H]-somapacitan-related material appeared to be consistent across plasma, serum and blood. Three abundant plasma metabolites (P1, M1 and M1B) and two abundant urine metabolites (M4 and M5) were identified. The total exposure of intact somapacitan accounted for 59% of the total exposure of all somapacitan-related material, P1 accounted for 21% and M1 plus M1B accounted for 12%. M4 and M5 were the most abundant urine metabolites and accounted for 37% and 8% of the dosed [3H]-somapacitan radioactivity, respectively. No intact somapacitan was found in excreta. Two subjects had six adverse events (AEs); all were mild in severity and unlikely to be related to trial product. The majority of dosed [3H]-somapacitan (94%) was recovered as excreted metabolites. Urine was the major route for excretion of somapacitan metabolites, followed by faeces, and exhalation in expired air was negligible. The low molecular weights of identified urine metabolites demonstrate that somapacitan was extensively degraded to small residual fragments that were excreted (fully biodegradable). The extensive metabolic degradation and full elimination of metabolites in excreta were the major clearance pathways of somapacitan and the key elements in its biological fate. A single dose of 6 mg somapacitan (containing [3H]-somapacitan) in healthy male subjects was well tolerated with no unexpected safety issues identified.

Absorption, metabolism and excretion of the GLP-1 analogue semaglutide in humans and nonclinical species.

Semaglutide is a human glucagon-like peptide-1 analogue in clinical development for the treatment of type 2 diabetes. The absorption, metabolism and excretion of a single 0.5mg/450µCi [16.7MBq] subcutaneous dose of [3H]-radiolabelled semaglutide was investigated in healthy human subjects and compared with data from nonclinical studies. Radioactivity in blood, plasma, urine and faeces was determined in humans, rats and monkeys; radioactivity in expired air was determined in humans and rats. Metabolites in plasma, urine and faeces were quantified following profiling and radiodetection. The blood-to-plasma ratio and pharmacokinetics of both radiolabelled semaglutide-related material and of semaglutide (in humans only) were assessed. Intact semaglutide was the primary component circulating in plasma for humans and both nonclinical species, accounting for 69-83% of the total amount of semaglutide-related material, and was metabolised prior to excretion. Recovery of excreted radioactivity was 75.1% in humans, 72.1% in rats and 58.2% in monkeys. Urine and faeces were shown to be important routes of excretion, with urine as the primary route in both humans and animals. Semaglutide was metabolised through proteolytic cleavage of the peptide backbone and sequential beta-oxidation of the fatty acid sidechain, and metabolism was not confined to specific organs. Intact semaglutide in urine accounted for 3.1% of the administered dose in humans and less than 1% in rats; it was not detected in urine in monkeys. The metabolite profiles of semaglutide in humans appear to be similar to the profiles from the nonclinical species investigated.