Search

Teriparatide is a potent therapeutic agent for the treatment of osteoporosis. One of the aims of this analysis was to develop a population pharmacokinetic (PPK) model to understand the pharmacokinetic characteristics of the once-weekly formulation of teriparatide. Another aim was to develop an exposure-response model to describe the relationship between change in bone mineral density (BMD) and teriparatide exposure after weekly subcutaneous administration. The PPK analysis showed that apparent total body clearance was significantly influenced by estimated creatinine clearance and the presence of osteoporosis. A data set consisting of lumbar spine BMD values for 513 osteoporosis patients whose area under the concentration-time curve (AUC) of teriparatide acetate was estimated by the developed PPK model was then compiled. Exposure-response analysis showed that the percentage change from baseline of BMD was well described by a function of the AUC of teriparatide acetate, time, and coadministration of alfacalcidol and a calcium preparation. The analysis indicated that AUC is an important parameter for predicting BMD response to once-weekly teriparatide in osteoporosis patients., (© 2017, The American College of Clinical Pharmacology.)

Teriparatide acetate, a synthetic polypeptide fragment consisting of human parathyroid hormone residues 1-34 [hPTH(1-34)], is a bone anabolic agent used to treat osteoporosis. The present study was conducted to characterise the pharmacokinetics of teriparatide acetate in rats after subcutaneous administration. Teriparatide was rapidly absorbed into the circulation and eliminated immediately. No intact teriparatide was detected in the urine. To elucidate the mechanism of teriparatide metabolism, we performed in vivo and in vitro studies using the radiolabelled bioactive analogue, [(125)I]-[Nle(8,18),Tyr(34)]-hPTH(1-34). After subcutaneous administration, the concentration of analogue metabolites increased in the plasma time-dependently. The concentration in the kidneys was more than 3-fold the concentration in the liver. In vitro analyses suggested that kidney radioactivity was associated with degraded bioactive analogue. In model rats, renal failure, but not hepatic failure, affected the pharmacokinetics of teriparatide acetate, which accounted for the decrease in the clearance of teriparatide. In conclusion, our results suggest that after subcutaneous administration of teriparatide acetate, teriparatide is rapidly absorbed and distributed to the liver or kidneys, where it is immediately degraded. The kidneys play a particularly important role in the distribution and metabolism of teriparatide, but not its excretion.

Thrombomodulin alfa is the recombinant extracellular domain of human thrombomodulin, which shows anticoagulation activity. To elucidate the pharmacokinetics of thrombomodulin alfa in patients with disseminated intravascular coagulation (DIC), population pharmacokinetic (PPK) analysis was performed using plasma concentration data obtained in phase 1 (20 patients, 348 time points) and phase 2 (116 patients, 305 time points) clinical trials. The actual and predicted plasma concentrations of thrombomodulin alfa based on the final PPK model showed a good linear correlation (R = 0.9504), and the pharmacokinetics of thrombomodulin alfa in DIC patients were affected by body weight, age, renal dysfunction, and hematocrit value. The distribution volume and clearance (CL) were proportional to body weight and were significantly increased in patients with lower hematocrit value (male <40%, female <35%). Furthermore, CL was decreased in patients with renal dysfunction and in elderly patients. Based on these results, the standard dose of thrombomodulin alfa is adjusted according to body weight. However, further dose adjustment is not needed based on age and hematocrit value, since these factors did not cause the large changes in plasma concentration that can affect the efficacy or safety.

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis in humans. EAE can be passively transferred into naive syngeneic animals by administration of MOG-specific T cell clones. Lymphocytes isolated from green fluorescent protein (GFP)-transgenic (Tg) mice can light up by emitting green fluorescence, thus making it feasible to use such animals in a passive transfer model for EAE. When MOG-sensitized splenic lymphocytes from GFP-Tg mice were adoptively transferred to irradiated, syngeneic C57BL/6 and RAG-1(-/-)mice, typical symptoms of EAE developed. Analysis of the reconstituted mice with EAE revealed prominent infiltration of fluorescing (GFP+), CD4+ T cells into the central nervous system (CNS). Real-time confocal imaging revealed these cells in the spinal cords and brains of recipient mice. This infiltration was also confirmed by anti-GFP monoclonal antibodies. Furthermore, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) evaluation indicated that the infiltrating GFP+, CD4+ T cells exclusively produced T helper type 1 (Th1) cytokines, especially interferon-gamma (IFN-gamma). These results clearly show that MOG-specific CD4+ T cells preferentially invade into the CNS and mediate the development of EAE by producing Th1-biased cytokines., (Copyright 2001 Academic Press.)

Multicellular spheroids of hepatocytes are known to maintain liver functions for a long period. Rat hepatocytes were isolated to form spheroids by rotation culture and immobilized within calcium alginate. Immobilized spheroids had a much higher extent of tyrosine aminotransferase induction, which is one of the liver-specific differentiated functions, than immobilized non-aggregated cells, while the spheroids secreted significantly less prothrombin than non-aggregated cells. Co-culture of hepatocytes and non-parenchymal liver cells in a monolayer enhanced tyrosine aminotransferase induction and suppressed prothrombin secretion, while conditioned medium prepared from non-parenchymal cells greatly stimulated tyrosine aminotransferase induction and suppressed the prothrombin secretion and DNA synthesis in monolayer-cultured hepatocytes. Prothrombin secretion in hepatocytes was subjected to cell-density-dependent regulation. In a similar manner to other growth-related functions, prothrombin secretion was stimulated at low cell density. It has been reported that thrombin activates the zymogen of hepatocyte growth factor activator [Shimomura, T., Kondo, J., Ochiai, M., Naka, D., Miyazawa, K., Morimoto, Y. & Kitamura, N. (1993) J. Biol. Chem. 268, 22,927-22,932]. Therefore, prothrombin secretion could be one of the growth-related functions and involved in wound healing and liver regeneration.

Tyrosine aminotransferase (TAT) induction and albumin secretion abilities were examined in rat hepatocytes immobilized within calcium alginate; the immobilized hepatocytes lost these abilities within a week. An attempt was then made to immobilize multicellular spheroids of hepatocytes for the purpose of stabilizing the liver functions. Although it takes at least 4 days to form spheroids in the conventional method using monolayer-cultured cells, in this study we developed a new method for rapid spheroid formation. Isolated hepatocytes were seeded into a polystyrene dish and incubated on a rotary shaker. Hepatocytes started to aggregate after 6 h of the rotation culture, and spheroids approximately 100 microns in diameter formed within 24 h. The immobilized spheroids had higher TAT induction and albumin secretion abilities, which were maintained for a longer time, than the immobilized nonaggregated cells. Further stabilization was observed in immobilized heterospheroids formed in the presence of nonparenchymal liver cells. This method for the rapid formation of spheroids consisting of hepatocytes and nonparenchymal liver cells could be utilized in the construction of a bioartificial liver support system.

Hepatocytes and non-parenchymal liver cells were isolated from adult rat liver and co-cultured for 48 hours as a monolayer on polystyrene culture dishes. The ability of tyrosine aminotransferase (TAT) induction in hepatocytes was examined in the presence of dexamethasone and dibutyryl cAMP. Non-parenchymal cells greatly enhance the ability of TAT induction of hepatocytes. A soluble factor with molecular weight of more than 10,000 is responsible for this enhancement, because conditioned medium prepared from non-parenchymal cells is also stimulatory. Non-parenchymal cells restored the ability in hepatocytes damaged with the addition of D-galactosamine. Conditioned medium prepared from non-parenchymal cells treated with D-galactosamine had higher activity of enhancement than the medium from normal cells. The soluble factor might be released in response to some signal of injury. Hepatocytes and non-parenchymal cells were immobilized within Ca-alginate, and although immobilized hepatocytes rapidly lost the ability to induce TAT, hepatocytes co-immobilized with non-parenchymal cells maintained the ability during 4 days of culture. These results indicated that non-parenchymal liver cells, as well as hepatocytes, could be used to construct a bioartificial liver support system.