Evaluation of Ethnicity Effect on Intranasal Esketamine Pharmacokinetics by Population Pharmacokinetic Modeling Using Data From a Japanese Phase 2b Study.

Esketamine is used for the treatment of treatment-resistant depression in many countries. A population pharmacokinetic (popPK) model of esketamine and its metabolite (noresketamine) has been previously developed, which included Asian race and Japanese ethnicity as covariates on their exposures. The present study aimed to update the popPK model by adding new data from a phase 2b study in Japanese patients and reassess intrinsic and extrinsic factors on esketamine and noresketamine exposures. The updated model identified the effects of body weight on the fraction of the esketamine dose absorbed in the nasal cavity and elimination rate constant of esketamine, and Asian race on the apparent clearance of noresketamine. The model predicted that an increase of 30 kg of body weight would decrease esketamine exposures by ≈20%. Noresketamine exposures would be affected by Asian race and body weight. However, those newly identified covariates were not considered to have clinically relevant impacts, and therefore dose adjustments were not necessary. In conclusion, the popPK model of esketamine and noresketamine was successfully updated and suggested that interindividual variability of esketamine exposures can be better explained by body weight, rather than by race/ethnicity. The new findings obtained in this study should be useful information for the further development of esketamine and for clinical practice in the future.

Development of a New Conditionally Immortalized Human Liver Sinusoidal Endothelial Cells.

Liver sinusoidal endothelial cells (LSECs), which are specialized endothelial cells that line liver sinusoids, have been reported to participate in a variety of liver functions, such as blood macromolecule clearance and factor VIII production. In addition, LSECs play crucial roles in liver regeneration following acute liver injury, as well as the development and progression of liver diseases or drug-induced hepatotoxicity. However, the molecular mechanisms underlying their roles remain mostly unknown. Therefore, in order to contribute to the clarification of those mechanisms, herein we report on the development of a new immortalized human LSEC (HLSEC) line. To produce this cell line, two immortalized genes were introduced into the primary HLSECs, which eventually resulted in the establishment of the HLSEC/conditionally immortalized, clone-J (HLSEC/ciJ). Consistent with the two-immortalized gene expression, HLSEC/ciJ showed excellent proliferation activity. Additionally, the results of gene expression analyses showed that several LSEC (as well as pan-endothelial) marker mRNAs and proteins were clearly expressed in HLSEC/ciJ. Furthermore, we found that adherence junction proteins were localized at the cell border in the HLSEC/ciJ monolayer, and that the cells exhibited a tube-like structure formation property. Taken together, the results obtained thus far indicate that we have successfully immortalized HLSECs, resulting in creation of HLSEC/ciJ, a cell line that possesses infinite proliferation ability while retaining possession of at least some HLSEC features. We believe that the HLSEC/ciJ have the potential to provide a valuable and unlimited alternative source of HLSECs for use in liver/LSEC physiology/pathophysiology, pharmacology, and toxicology studies.

Mass balance and metabolism of Z-215, a novel proton pump inhibitor, in healthy volunteers.

The human mass balance of [14 C]Z-215, a novel proton pump inhibitor, was characterised in six healthy male volunteers following single oral administration of [14 C]Z-215 (20 mg, 3.7 MBq) to determine the elimination pathway of Z-215 and the distribution of its metabolites in plasma, urine, and faeces (NCT02618629). [14 C]Z-215 was rapidly absorbed, with a Cmax of 434 ng/mL at 0.38 h for Z-215 and 732 ng eq./mL at 0.5 h for total radioactivity. Means of 59.61% and 31.36% of the administered radioactive dose were excreted in urine and faeces, respectively, within 168 h post-dose. The majority of the dose was recovered within 24 h in urine and 96 h in faeces. Unchanged Z-215 was excreted in urine at trace levels but was not detected in faeces. The main components in plasma were Z-215 and Z-215 sulphone, accounting for 29.8% and 13.3% of the total circulating radioactivity, respectively. Additionally, Z-215 was metabolised through oxidation, reduction and conjugation. Our in vitro Z-215 metabolism study showed that the major isozyme contributing to the oxidation of Z-215, including the formation of Z-215 sulphone, was CYP3A4. In conclusion, Z-215 is well absorbed in humans and primarily eliminated via metabolism, where CYP3A4 plays an important role.

Characterization of release profile of ornithine carbamoyltransferase from primary rat hepatocytes treated with hepatotoxic drugs: Implications for its unique potential as a drug-induced liver injury biomarker.

Ornithine carbamoyltransferase (OCT) is a mitochondrial protein expressed primarily in the liver. It has been shown that, like alanine aminotransferase (ALT), OCT is released from damaged hepatocytes in rats and humans, which has given rise to the possibility that OCT might provide a diagnostic biomarker of various forms of liver damage, including drug-induced liver injury (DILI). However, OCT release characteristics in DILI, as well as their diagnostic advantages, remain elusive. Therefore, this study aimed at clarifying whether and how OCT is released from rat primary hepatocytes in vitro using seven potentially hepatotoxic drugs. The results showed that OCT releases from damaged hepatocytes were observed for all tested drugs, and that those releases were not associated with mitochondrial membrane proteins. It should be underscored that the release dynamics were significantly larger than those of ALT. Furthermore, unlike ALT, the maximum OCT release levels showed differences depending on the drug being tested, suggesting that OCT release was susceptible to toxicity mechanisms. Taken together, these unique release characteristics highlight the possibility that OCT could provide a promising DILI biomarker that might contribute not only to diagnostic accuracy improvements, but also to a better understanding of toxicity types in clinical and drug development settings.