Safety, Tolerability, and Pharmacokinetic Evaluation of Single and Multiple Doses of the Dipeptidyl Peptidase 1 Inhibitor Brensocatib in Healthy Japanese and White Adults.

Brensocatib, an investigational first-in-class, small-molecule, orally bioavailable, selective, and reversible dipeptidyl peptidase 1 inhibitor that blocks activation of neutrophil serine proteases, is currently under clinical development for the treatment of bronchiectasis and other chronic inflammatory diseases. In a 2-part phase 1 study, the safety, tolerability, and pharmacokinetics of brensocatib were evaluated in healthy Japanese and White adults. In part A, participants received single and multiple once-daily doses of brensocatib (10, 25, or 40 mg) or placebo after an overnight fast. In part B, participants received a single oral dose of brensocatib 40 mg on days 1 and 8, with or without food in a crossover fashion. Following a single dose and at steady state, brensocatib exposure was dose dependent, with low to moderate interindividual variability; systemic exposure between Japanese and White participants was similar. Elimination half-life of brensocatib ranged from 22 to 28 hours, resulting in ≈2-fold accumulation in maximum plasma concentration and area under the plasma concentration-time curve at steady state. In both ethnic groups, the presence of food slightly delayed brensocatib absorption with time to maximum plasma concentration increased by 0.7 to 1.7 hours, but it had no significant effect on brensocatib exposure (maximum plasma concentration and area under the plasma concentration-time curve). Brensocatib was well tolerated in Japanese and White participants. The most frequently reported treatment-emergent adverse events were headache and skin exfoliation. No clinically significant vital signs, laboratory abnormalities, or evidence of renal toxicity were observed. The results from this study demonstrate that brensocatib can be administered with or without food and that dose adjustment is unnecessary for Japanese patients when receiving brensocatib treatment.

Discovery of 3,4-Dihydrobenzo[f][1,4]oxazepin-5(2H)-one Derivatives as a New Class of Selective TNIK Inhibitors and Evaluation of Their Anti-Colorectal Cancer Effects.

The Traf2- and Nck-interacting protein kinase (TNIK) is a downstream signal protein of the Wnt/ß-catenin pathway and has been thought of as a potential target for the treatment of colorectal cancer (CRC) that is often associated with dysregulation of Wnt/ß-catenin signaling pathway. Herein, we report the discovery of a series of 3,4-dihydrobenzo[f][1,4]oxazepin-5(2H)-one derivatives as a new class of TNIK inhibitors. Structure-activity relationship (SAR) analyses led to the identification of a number of potent TNIK inhibitors with compound 21k being the most active one (IC50: 0.026 ± 0.008 µM). This compound also displayed excellent selectivity for TNIK against 406 other kinases. Compound 21k could efficiently suppress CRC cell proliferation and migration in in vitro assays and exhibited considerable antitumor activity in the HCT116 xenograft mouse model. It also showed favorable pharmacokinetic properties. Overall, 21k could be a promising lead compound for drug discovery targeting TNIK and deserves further studies.

Development of a Once-Daily Modified-Release Formulation for the Short Half-Life RIPK1 Inhibitor GSK2982772 using DiffCORE Technology.

PURPOSE: GSK2982772 is a selective inhibitor of receptor-interacting protein kinase-1 (RIPK1) with a short 2- to 3-h half-life. In a previous modified-release (MR) study, a matrix monolithic formulation (80% GSK2982772 released over 12 h) provided a once-daily (QD) pharmacokinetic (PK) profile in the fasted state; however, it was susceptible to food effects. The current study evaluated the safety and PK of MR formulations using GSK proprietary DiffCORE™ technology. METHODS: Part A evaluated PK following single-dose (240 mg) fasted and fed (high-fat meal) administration of three DiffCORE MR formulations within pre-defined in vitro extremes of 80% GSK2982772 released over 12 h (MR-12 h) to 80% GSK2982772 released over 18 h (MR-18 h) versus an immediate-release formulation. Part B evaluated MR-16 h (120-960 mg) in different prandial states. RESULTS: Pharmacokinetic profiles for all MR formulations and doses tested in the fasted and fed states were consistent with QD dosing. CONCLUSIONS: The DiffCORE technology overcame the food effect vulnerability observed with the matrix monolithic formulation. The MR-16 h formulation was selected for further clinical development as a QD dosing regimen (NCT03649412 September 26, 2018).

Development of a Prototype, Once-Daily, Modified-Release Formulation for the Short Half-Life RIPK1 Inhibitor GSK2982772.

PURPOSE: GSK2982772 is a selective inhibitor of receptor-interacting protein kinase-1, with a 2-3 h half-life. This study evaluated if a once-daily modified-release formulation of GSK2982772 could be developed with no significant food effect. METHODS: Part A evaluated the pharmacokinetics of GSK2982772 following fasted single-dose (120 mg) administration of two matrix minitab formulations (MT-8 h and MT-12 h) vs 120 mg immediate release (IR) and MT-12 h with a high-fat meal. Part B evaluated once-daily MT-12 h for 3 days at three dose levels. Part C evaluated a matrix monolithic (MM-12 h) formulation at two dose levels in different prandial states. RESULTS: All modified-release formulations dosed in the fasted state reduced maximum plasma concentration (Cmax), delayed time to Cmax, and decreased area under the curve (AUC) vs IR. When MT-12 h or MM-12 h were co-administered with a meal (standard or high-fat) Cmax and AUC increased. Dosing MM-12 h 1 h before a standard or high-fat meal had minimal impact on exposure vs fasted. CONCLUSIONS: MT-12 h and MM-12 h provided a QD pharmacokinetic profile in the fasted state, however when MT-12 h was dosed with a high-fat meal a QD profile was not maintained. ( ClinicalTrials.gov Identifier: NCT03266172).

Comparison of the Pharmacokinetics of RIPK1 Inhibitor GSK2982772 in Healthy Western and Japanese Subjects.

BACKGROUND AND OBJECTIVES: GSK2982772 is an oral small-molecule RIPK1 inhibitor with potential therapeutic efficacy in immune-mediated inflammatory diseases (IMIDs). An inter-ethnic comparison of GSK2982772 pharmacokinetics was conducted based on data from Western (Study 1) and Japanese subjects (Study 2). METHODS: Both studies were single-centre, randomised, double-blind, placebo-controlled studies with objectives to assess the safety and characterise the pharmacokinetics of GSK2982772. Western subjects in Study 1 (NCT03305419), Part A (N = 15), were randomly assigned to receive 120 mg three times daily (TID), 240 mg TID, or 360 mg twice daily (BID) doses of GSK2982772, or placebo (TID or BID) for 1 day. Part B subjects (N = 47) received GSK2982772 120 mg TID, 240 mg TID, or placebo TID for 14 days. Japanese subjects in Study 2 (N = 13) (NCT03590613) were randomly assigned to receive TID doses of GSK2982772 60, 120, 240 mg TID or placebo TID for 1 day. RESULTS: GSK2982772 was well tolerated and adverse events were generally mild. Maximum observed plasma drug concentration (Cmax), time to reach Cmax (Tmax), area under the plasma drug concentration versus time curve after the first GSK2982772 dose (AUC(0-7)) of 120 and 240 mg, and (AUC(0-24)) values for the 120 and 240 mg TID doses over a single day were similar in Japanese and Western subjects. CONCLUSIONS: The pharmacokinetics and tolerability of GSK2982772 were similar between Western and Japanese subjects, justifying inclusion of Japanese subjects in future global clinical studies to assess the therapeutic potential of RIPK1 inhibition for the treatment of IMIDs. Clinical Trials: NCT03305419 and NCT03590613 available from http://www.clinicaltrials.gov .

Hit-to-Lead Optimization of Benzoxazepinoindazoles As Human African Trypanosomiasis Therapeutics.

Human African trypanosomiasis (HAT) is a neglected tropical disease caused by infection with either of two subspecies of the parasite Trypanosoma brucei. Due to a lack of economic incentive to develop new drugs, current treatments have severe limitations in terms of safety, efficacy, and ease of administration. In an effort to develop new HAT therapeutics, we report the structure-activity relationships around T. brucei for a series of benzoxazepinoindazoles previously identified through a high-throughput screen of human kinase inhibitors, and the subsequent in vivo experiments for HAT. We identified compound 18, which showed an improved kinase selectivity profile and acceptable pharmacokinetic parameters, as a promising lead. Although treatment with 18 cured 60% of mice in a systemic model of HAT, the compound was unable to clear parasitemia in a CNS model of the disease. We also report the results of cross-screening these compounds against T. cruzi, L. donovani, and S. mansoni.

POSEIDON Trial Phase 1b Results: Safety, Efficacy and Circulating Tumor DNA Response of the Beta Isoform-Sparing PI3K Inhibitor Taselisib (GDC-0032) Combined with Tamoxifen in Hormone Receptor Positive Metastatic Breast Cancer Patients.

PURPOSE: The strategy of combining endocrine therapy with PI3K-mTOR inhibition has shown promise in estrogen receptor (ER)-positive breast cancer, but new agents and combinations with a better therapeutic index are urgently needed. Taselisib is a potent, selective, beta-isoform-sparing PI3 kinase inhibitor. PATIENTS AND METHODS: 30 patients with ER-positive, metastatic breast cancer who had failed prior endocrine therapy were treated with escalating doses of taselisib (2 or 4 mg in an intermittent or continuous schedule) combined with tamoxifen 20 mg once daily in this phase 1b study using a "rolling six" design. RESULTS: Taselisib combined with tamoxifen was generally well tolerated, with treatment-emergent adverse events as expected for this class of drugs, including diarrhea (13 patients, 43%), mucositis (10 patients, 33%), and hyperglycemia (8 patients, 27%). No dose-limiting toxicities were observed. Objective responses were seen in 6 of 25 patients with RECIST-measurable disease (ORR 24%). Median time to disease progression was 3.7 months. Twelve of 30 patients (40%) had disease control for 6 months or more. Circulating tumor (ct)DNA studies using next-generation tagged amplicon sequencing identified early indications of treatment response and mechanistically relevant correlates of clinical drug resistance (e.g., mutations in KRAS, ERBB2) in some patients. CONCLUSIONS: Taselisib can be safely combined with tamoxifen at the recommended phase 2 dose of 4 mg given once daily on a continuous schedule. Preliminary evidence of antitumor activity was seen in both PIK3CA mutant and wild-type cancers. The randomized phase 2 part of POSEIDON (testing tamoxifen plus taselisib or placebo) is currently recruiting.

A phase Ib, open-label, dose-escalation study of the safety and pharmacology of taselisib (GDC-0032) in combination with either docetaxel or paclitaxel in patients with HER2-negative, locally advanced, or metastatic breast cancer.

PURPOSE: This open-label, phase Ib, dose-escalation, and dose-expansion study (NCT01862081) evaluated taselisib with a taxane in locally advanced or metastatic breast cancer (BC) and/or non-small cell lung cancer (NSCLC). METHODS: Patients received taselisib (2-6 mg tablet or 3-6 mg capsule) plus docetaxel or paclitaxel. Primary endpoints were safety, dose-limiting toxicities, maximum tolerated dose, and identification of a recommended phase II dose. Secondary endpoints included pharmacokinetics and antitumor activity assessment. RESULTS: Eighty patients (BC: 72; NSCLC: 7; BC/NSCLC: 1) were enrolled (docetaxel-receiving arms: 21; paclitaxel-receiving arms: 59). Grade ≥ 3 adverse events (AEs), serious AEs, and AEs leading to death were reported in 90.5%, 42.9%, and 14.3% of patients, respectively (docetaxel-receiving arms), and 78.9%, 40.4%, and 3.5% of patients, respectively (paclitaxel-receiving arms). Eight patients experienced dose-limiting toxicities. The maximum tolerated dose was exceeded with 3 mg taselisib (capsule) for 21 consecutive days plus 75 mg/m2 docetaxel and not exceeded with 6 mg taselisib (tablet) for 5 days on/2 days off plus 80 mg/m2 paclitaxel. Objective response rates and clinical benefit rates were 35.0% and 45.0%, respectively (docetaxel-receiving arms), and 20.4% and 27.8%, respectively (paclitaxel-receiving arms). Exposure for paclitaxel or docetaxel plus taselisib was consistent with the single agents. CONCLUSIONS: Taselisib in combination with a taxane has a challenging safety profile. Despite evidence of antitumor activity, the benefit-risk profile was deemed not advantageous. Further development is not planned.

Development and validation of a simple and sensitive high-resolution LC/MS method for determination of PF-04620110 in dog plasma: Application to a pharmacokinetic study.

In this study, a more sensitive and reliable quantitative method based on ultra-high performance liquid chromatography coupled with Q-Exactive-Orbitrap-MS in full-mass scan was developed and validated for the determination of PF-04620110 in dog plasma. After protein precipitation with acetonitrile, the sample separations were carried out on an Acquity BEH C18 column with 1 mm ammonium acetate in water and acetonitrile containing 0.1% acetic acid as mobile phase, at a flow rate of 0.4 mL/min. The assay showed excellent linearity over the concentration range of 1-2000 ng/mL with correlation coefficient >0.9980 (r > 0.9980). The LLOQ was 1 ng/mL. The inter- and intra-day precision (RSD, %) was within 9.69% while the accuracy (RE, %) was in the range of -8.59-11.24%. The extraction recovery was >85.37% and the assay was free of matrix effects. PF-04620110 was demonstrated to be stable under various processing and handing conditions. The validated method was successfully applied to the pharmacokinetic study of PF-04620110 in dogs and the results revealed that PF-04620110 was slowly eliminated from plasma with a clearance of 60.81 ± 7.11 mL/h/kg for intravenous administration and 81.44 ± 25.79 mL/h/kg for oral administration. The oral bioavailability was determined to be 77.89% in dogs.

Model-based pharmacokinetic and pharmacodynamic analysis for acute effects of a small molecule inhibitor of diacylglycerol acyltransferase-1 in the TallyHo/JngJ polygenic mouse.

The purpose of this study was to evaluate the acute effect of a small molecule inhibitor of DGAT-1 on triglycerides (TG) and cholesterol in polygenic type 2 diabetic TallyHo/JngJ (TH) mice. PF-04620110, a potent and selective DGAT-1 inhibitor, was used as a model compound in this study and which was administered to TH and ICR mice. The concentration of the model compound that produced 50% of maximum lowering of TG level (IC50) in TH mice was not significantly different from that in ICR mice, when estimated using the model-based pharmacokinetic and pharmacodynamic assay, a two-compartmental model and an indirect response model. The clearance of the inhibitor in TH mice was fivefold higher than that in ICR mice, suggesting significantly altered pharmacokinetics. Moreover, the in vitro metabolic elimination kinetic parameters (ke,met), determined using liver microsomes from TH and ICR mice were 1.24 ± 0.14 and 0.174 ± 0.116 min-1, respectively. Thus, we report that the differences in the acute effects of the small molecule DAGT-1 inhibitor between TH mice and ICR mice can be attributed to altered pharmacokinetics caused by an altered metabolic rate for the compound in TH mice.

Phase I study of taselisib in Japanese patients with advanced solid tumors or hormone receptor-positive advanced breast cancer.

Taselisib is a potent and selective phosphatidylinositide 3-kinase (PI3K) inhibitor. The present article reports the first study of taselisib administration in Japanese patients. The aim of this 2-stage, phase I, multicenter, open-label, dose-escalation study was to evaluate the safety, pharmacokinetics, and preliminary efficacy of taselisib as monotherapy in Japanese patients with advanced solid tumors (stage 1), and as part of combination therapy in Japanese patients with hormone receptor (HR)-positive locally advanced or recurrent breast cancer (stage 2). In stage 1, oral taselisib tablets 2, 4, and 6 mg/d were given in 28-day cycles. In stage 2, successive cohorts of patients received oral taselisib tablets (2 or 4 mg/d) with i.m. fulvestrant 500 mg. Nine and 6 patients were enrolled in stage 1 and stage 2, respectively. Taselisib was well tolerated. No dose-limiting toxicities were experienced in any cohort of patients and no deaths were observed. The most common treatment-related adverse events in stage 1 and stage 2, respectively, were rash (55.6%, 66.7%), diarrhea (44.4%, 66.7%), and stomatitis (44.4%, 66.7%). Taselisib was rapidly absorbed after dosage; its half-life was 12.9-32.0 hours in stage 1 and 16.1-26.5 hours in stage 2. Two patients achieved partial response (PR), 5 patients had stable disease (SD) and 2 patients had progressive disease (PD) in stage 1, and 1 patient had PR and 3 patients had SD in stage 2. All patients with PR were positive for PIK3CA gene mutations. These preliminary data suggest that taselisib may be effective in patients with PIK3CA-mutated solid tumors or HR-positive advanced breast cancer.

Dipeptidyl Peptidase 1 Inhibitor AZD7986 Induces a Sustained, Exposure-Dependent Reduction in Neutrophil Elastase Activity in Healthy Subjects.

Neutrophil serine proteases (NSPs), such as neutrophil elastase (NE), are activated by dipeptidyl peptidase 1 (DPP1) during neutrophil maturation. High NSP levels can be detrimental, particularly in lung tissue, and inhibition of NSPs is therefore an interesting therapeutic opportunity in multiple lung diseases, including chronic obstructive pulmonary disease (COPD) and bronchiectasis. We conducted a randomized, placebo-controlled, first-in-human study to assess the safety, tolerability, pharmacokinetics, and pharmacodynamics of single and multiple oral doses of the DPP1 inhibitor AZD7986 in healthy subjects. Pharmacokinetic and pharmacodynamic data were analyzed using nonlinear mixed effects modeling and showed that AZD7986 inhibits whole blood NE activity in an exposure-dependent, indirect manner-consistent with in vitro and preclinical predictions. Several dose-dependent, possibly DPP1-related, nonserious skin findings were observed, but these were not considered to prevent further clinical development. Overall, the study results provided confidence to progress AZD7986 to phase II and supported selection of a clinically relevant dose.

Pharmacokinetics of TAK-475, a Squalene Synthase Inhibitor, in Rats and Dogs.

The pharmacokinetics of TAK-475 (lapaquistat acetate), a squalene synthase inhibitor, was investigated in rats and dogs. After oral administration of (14)C-labeled TAK-475 ([(14)C]TAK-475) to rats and dogs at a dose of 10 mg/kg, the bioavailability (BA) was relatively low at 3.5 and 8.2%, respectively. The main component of the radioactivity in the plasma was M-I, which has a comparable pharmacological activity to TAK-475 in vitro. The radioactivity in the portal plasma after intraduodenal administration of [(14)C]TAK-475 to portal vein-cannulated rat was also mainly M-I, suggesting that most of the TAK-475 was hydrolyzed to M-I during the permeable process in the intestine. The concentrations of M-I in the liver, the main organ of cholesterol biosynthesis, were much higher than those in the plasma after oral administration of [(14)C]TAK-475 to rats. The main elimination route of the radioactivity was fecal excretion after oral administration of [(14)C]TAK-475 to rats and dogs, and the absorbed radioactivity was mainly excreted via the bile as M-I in rats. M-I excreted into the bile was partially subjected to enterohepatic circulation. These results suggest that although the BA values of TAK-475 are low, M-I can exert compensatory pharmacological effects in the animals. These pharmacokinetic characteristics in animals were also confirmed in the clinical studies. The evaluation of M-I disposition is important for the pharmacokinetics, pharmacodynamics and toxicity of TAK-475 in animals and humans.

A selective prostaglandin E2 receptor subtype 2 (EP2) antagonist increases the macrophage-mediated clearance of amyloid-beta plaques.

A high-throughput screen resulted in the discovery of benzoxazepine 1, an EP2 antagonist possessing low microsomal stability and potent CYP3A4 inhibition. Modular optimization of lead compound 1 resulted in the discovery of benzoxazepine 52, a molecule with single-digit nM binding affinity for the EP2 receptor and significantly improved microsomal stability. It was devoid of CYP inhibition and was ∼4000-fold selective against the other EP receptors. Compound 52 was shown to have good PK properties in CD-1 mice and high CNS permeability in C57Bl/6s mice and Sprague-Dawley rats. In an ex vivo assay, it demonstrated the ability to increase the macrophage-mediated clearance of amyloid-beta plaques from brain slices in a dose-dependent manner.

Benzazepinones and benzoxazepinones as antagonists of inhibitor of apoptosis proteins (IAPs) selective for the second baculovirus IAP repeat (BIR2) domain.

XIAP is a key regulator of apoptosis, and its overexpression in cancer cells may contribute to their survival. The antiapoptotic function of XIAP derives from its BIR domains, which bind to and inhibit pro-apoptotic caspases. Most known IAP inhibitors are selective for the BIR3 domain and bind to cIAP1 and cIAP2 as well as XIAP. Pathways activated upon cIAP binding contribute to the function of these compounds. Inhibitors selective for XIAP should exert pro-apoptotic effects through competition with the terminal caspases. This paper details our synthetic explorations of a novel XIAP BIR2-selective benzazepinone screening hit with a focus on increasing BIR2 potency and overcoming high in vivo clearance. These efforts led to the discovery of benzoxazepinone 40, a potent BIR2-selective inhibitor with good in vivo pharmacokinetic properties which potentiates apoptotic signaling in a manner mechanistically distinct from that of known pan-IAP inhibitors.

Defining the key pharmacophore elements of PF-04620110: discovery of a potent, orally-active, neutral DGAT-1 inhibitor.

DGAT-1 is an enzyme that catalyzes the final step in triglyceride synthesis. mRNA knockout experiments in rodent models suggest that inhibitors of this enzyme could be of value in the treatment of obesity and type II diabetes. The carboxylic acid-based DGAT-1 inhibitor 1 was advanced to clinical trials for the treatment of type 2 diabetes, despite of the low passive permeability of 1. Because of questions relating to the potential attenuation of distribution and efficacy of a poorly permeable agent, efforts were initiated to identify compounds with improved permeability. Replacement of the acid moiety in 1 with an oxadiazole led to the discovery of 52, which possesses substantially improved passive permeability. The resulting pharmacodynamic profile of this neutral DGAT-1 inhibitor was found to be similar to 1 at comparable plasma exposures.

Discovery of 2-{3-[2-(1-isopropyl-3-methyl-1H-1,2-4-triazol-5-yl)-5,6-dihydrobenzo[f]imidazo[1,2-d][1,4]oxazepin-9-yl]-1H-pyrazol-1-yl}-2-methylpropanamide (GDC-0032): a ß-sparing phosphoinositide 3-kinase inhibitor with high unbound exposure and robust in vivo antitumor activity.

Dysfunctional signaling through the phosphoinositide 3-kinase (PI3K)/AKT/mTOR pathway leads to uncontrolled tumor proliferation. In the course of the discovery of novel benzoxepin PI3K inhibitors, we observed a strong dependency of in vivo antitumor activity on the free-drug exposure. By lowering the intrinsic clearance, we derived a set of imidazobenzoxazepin compounds that showed improved unbound drug exposure and effectively suppressed growth of tumors in a mouse xenograft model at low drug dose levels. One of these compounds, GDC-0032 (11l), was progressed to clinical trials and is currently under phase I evaluation as a potential treatment for human malignancies.

Pharmacological inhibition to examine the role of DGAT1 in dietary lipid absorption in rodents and humans.

Alterations in fat metabolism, in particular elevated plasma concentrations of free fatty acids and triglycerides (TG), have been implicated in the pathogenesis of Type 2 diabetes, obesity, and cardiovascular disease. Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1), a member of the large family of membrane-bound O-acyltransferases, catalyzes the final step in triacylglycerol formation. In the intestine, DGAT1 is one of the acyltransferases responsible for the reesterficiation of dietary TG. Following a single dose of a selective pharmacological inhibitor of DGAT1, PF-04620110, a dose-dependent inhibition of TG and vitamin A absorption postprandially was demonstrated in rodents and human subjects. In C57/BL6J mice, acute DGAT1 inhibition alters the temporal and spatial pattern of dietary lipid absorption. To understand the impact of DGAT1 inhibition on enterocyte lipid metabolism, lipomic profiling was performed in rat intestine and plasma as well as human plasma. DGAT1 inhibition causes an enrichment of polyunsaturated fatty acids within the TG class of lipids. This pharmacological intervention gives us insight as to the role of DGAT1 in human dietary lipid absorption.

Determination of PF-04620110, a novel inhibitor of diacylglycerol acyltransferase-1, in rat plasma using liquid chromatography-tandem mass spectrometry and its application in pharmacokinetic studies.

In this study, we developed a method for the determination of PF-04620110 (2-{(1r,4r)-4-[4-(4-amino-5-oxo-7,8-dihydropyrimido[5,4-f][1,4]oxazepin-6(5H)-yl)phenyl]cyclohexyl}acetic acid), a novel diacylglycerol acyltransferase 1 (DGAT-1) inhibitor, in rat plasma and validated it using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Rat plasma samples were processed following a protein precipitation method by using acetonitrile and were then injected into an LC-MS/MS system for quantification. PF-04620110 and imipramine (internal standard) were separated using a Hypersil Gold C18 column, with a mixture of acetonitrile and 10 mm ammonium formate (90:10, v/v) as the mobile phase. The ion transitions monitored in positive-ion mode [M + H](+) of multiple-reaction monitoring were m/z 397.0 → 260.2 for PF-04620110 and m/z 280.8 → 86.0 for imipramine. The detector response was specific and linear for PF-04620110 at concentrations within the range 0.05-50 µg/mL and the signal-to-noise ratios for the samples were ≥10. The intra- and inter-day precision and accuracy of the method matched the acceptance criteria for assay validation. PF-04620110 was stable under various processing and/or handling conditions. PF-04620110 concentrations in the rat plasma samples could be measured up to 24 h after intravenous or oral administration of PF-04620110, suggesting that the assay is useful for pharmacokinetic studies in rats.

Population pharmacokinetics of the selective serotonin 5-HT1A receptor partial agonist piclozotan.

BACKGROUND/AIMS: Serotonin (5-HT) and its receptors are known to play important roles in various physiological and pathophysiological processes. The 5-HT1A receptor subtype is thought to be involved in psychiatric disorders, immunomodulation, and in cerebral ischemic conditions. Piclozotan, a selective and potent partial agonist of 5-HT1A, has been shown to be neuroprotective against ischemic neuronal damage in animal models. Its pharmacokinetics (PK), tolerability, and safety have been evaluated in patients with acute ischemic stroke. The aim of the study was to describe piclozotan PK, using population PK modeling. METHODS: A total of 1308 plasma piclozotan concentration measurements from 84 healthy subjects and 412 plasma piclozotan measurements from 74 stroke patients were included in the analysis. Covariates considered during the model building process included disease status, age, weight, sex, smoking status, and alcohol consumption. Data were analyzed using nonlinear mixed-effects modeling with the NONMEM software system. The final model was qualified via predictive check and nonparametric bootstrap procedures. RESULTS: Piclozotan PK was well described using a 3-compartment model with first-order elimination. Parameter estimates (intersubject variability) were V1, central volume: 64.0 L (66.5%) and CL, systemic clearance: 18.0 L/h (31.4%). Peripheral volumes (V2, V3) were related to total body weight, whereas CL was related to ideal body weight. Clearance decreased with advancing age, yielding a decrease of 35%-65% in patients aged 70-90. There was no discernable difference in PK between healthy subjects and stroke patients. CONCLUSIONS: Piclozotan disposition was well described by the population model, and the intersubject variability around the estimated parameters was moderate in magnitude (<60%). The population PK analysis of piclozotan allows for characterization of piclozotan exposure in individual subjects based on their age and body weight. The availability of a population PK model will facilitate dose optimization and further clinical development of piclozotan.