Pharmacokinetics of NS-105, a novel cognition enhancer 1st communication:: Absorption, metabolism and excretion in rats, dogs and monkeys after single administration of 14C-NS-105

The absorption, metabolism and excretion of NS-105 ((+)-5-oxo-D-prolinepiperidinamide monohydrate, CAS 110958-19-5), a novel cognition enhancer, were studied in rats, dogs and monkeys after intravenous or oral administration of C-14-NS-105. The protein binding of this drug was also investigated in vivo and in vitro. After the intravenous and oral administrations of C-14-NS-105, the unchanged drug accounted for most of the plasma radioactivity in all the species tested. After the intravenous injection, the plasma concentration of NS-105 decreased monoexponentially with respective elimination half-lives of 0.67, 2.1 and 1.3 h for the rats, dogs and monkeys. After the oral administration, the plasma concentration of NS-105 reached a maximum within 1 h, then decreased as in intravenous administration in all the species tested. NS-105 was almost completely absorbed from the small intestine, and first-pass metabolism was very limited. As a result, its systemic availability was high; 97 % in the rats, 90 % in the dogs and 79 % in the monkeys. No significant sex-related differences in the plasma concentration profiles of radioactivity were observed in the rats after the oral administration of C-14-NS-105 (p > 0.05). Food affected the absorption of NS-105. The C-max and AUC(0-infinity) of radioactivity concentration were proportional to the dose for 1-100 mg/kg of C-14-NS-105. There were no marked differences between the intravenous and oral routes in the compositions of urinary radioactivity for any of the species tested. In the urine of dogs, LAM-162 (oxidative metabolite with C-N cleavage of the piperidine ring), LAM-79 (metabolite with 4-hydroxylated piperidine ring), LAM-163 (metabolite with 3-hydroxylated piperidine ring) and M1 (not identified) accounted for 20 %, 3 %, 6 % and 1 % of the urinary radioactivity, respectively. In the urine of rats and monkeys, LAM-162 and LAM-79 accounted for 1-6 % of the urinary radioactivity, but LAM-163 and M1 were not detected. After the intravenous and oral administrations, NS-105 was primarily eliminated by renal excretion in all the species tested, approximately 90 % of the dose being excreted unchanged in the urine for rats and monkeys and 60 % of it for dogs. Excretions of radioactivity in the bile and exhaled air in rats were less than 1.4 % of the dose, and lymphatic absorption of radioactivity was only 0.3 % of the dose. The percentage of C-14-NS-105 bound to serum proteins was less than 3.3 % in all the animal species tested, including humans.