Analysis of PK11195 concentrations in rodent whole blood and tissue samples by rapid and reproducible chromatographic method to support target-occupancy PET studies

Abstract

In Positron Emission Tomography (PET) research, it is important to assess not only pharmacokinetics of a radiotracer in vivo , but also of the drugs used in blocking/displacement PET studies. Typically, pharmacokinetic/pharmacodynamic (PK/PD) analyses of drugs used in rodent PET studies are based on population average pharmacokinetic profiles of the drugs due to limited blood volume withdrawal while simultaneously maintaining physiological homeostasis. This likely results in bias of PET data quantification, including unknown bias of target occupancy (TO) measurements. This study aimed to develop a High Performance Liquid Chromatography (HPLC) method for PK/PD quantification of drugs used in preclinical rodent PET research, specifically the translocator 18 kDa protein (TSPO) selective drug, PK11195, that used sub-millilitre blood volumes. The lowest detection limit for the proposed HPLC method ranged between 7.5 and 10 ng/mL depending on the method used to calculate the limit of detection, and the measured average relative standard deviation for intermediate precision was equal to 17.2%. Most importantly, we were able to demonstrate a significant difference between calculated PK11195 concentrations at 0.5, 1, 2, 3, 5, 15 and 30 min post-administration and individually measured whole blood levels (significance level range from p < 0.05 to p < 0.001; one-way ANOVA, Dunnet's post hoc test, p < 0.05). The HPLC method developed here uses sub-millilitre sample volumes to reproducibly assess PK/PD of PK11195 in rodent blood. This study highlights the importance of individually measured PK/PD drug concentrations when quantifying the TO from blocking/displacement rodent PET experiments.

PK11195 Protects From Cell Death Only When Applied During Reperfusion: Succinate-Mediated Mechanism of Action

“…Therefore, further validation in in vivo and large animal studies is required to account for the extent and substrate utilization changes in the working heart. A single concentration of PK11195 was employed based on prior studies (Stadulyte et al, 2019) and thus it is unknown whether different concentrations would have greater or lesser effects. Several reports indicate that PK11195 can affect lipid fluidity of mitochondrial outer membrane, and, therefore, can potentially affect the function of other proteins in OMM (Miccoli et al, 1999;Hatty et al, 2014) or even directly inhibit the OSCP subunit of F 0 F 1 -ATP synthase (Cleary et al, 2007;Krestinina et al, 2009) which is reported to form mPTP (Alavian et al, 2014;Mnatsakanyan et al, 2019;Bernardi, 2020).…”