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Abstract Co‐administration of clesacostat (acetyl‐CoA carboxylase inhibitor, PF‐05221304) and ervogastat (diacylglycerol O‐acyltransferase inhibitor, PF‐06865571) in laboratory models improved non‐alcoholic fatty liver disease (NAFLD)/non‐alcoholic steatohepatitis (NASH) end points and mitigated clesacostat‐induced elevations in circulating triglycerides. Clesacostat is cleared via organic anion‐transporting polypeptide‐mediated hepatic uptake and cytochrome P450 family 3A (CYP3A); in vitro clesacostat is identified as a potential CYP3A time‐dependent inactivator. In vitro ervogastat is identified as a substrate and potential inducer of CYP3A. Prior to longer‐term efficacy trials in participants with NAFLD, safety and pharmacokinetics (PK) were evaluated in a phase I, non‐randomized, open‐label, fixed‐sequence trial in healthy participants. In Cohort 1, participants (n = 7) received clesacostat 15 mg twice daily (b.i.d.) alone (Days 1–7) and co‐administered with ervogastat 300 mg b.i.d. (Days 8–14). Mean systemic clesacostat exposures, when co‐administered with ervogastat, decreased by 12% and 19%, based on maximum plasma drug concentration and area under the plasma drug concentration–time curve during the dosing interval, respectively. In Cohort 2, participants (n = 9) received ervogastat 300 mg b.i.d. alone (Days 1–7) and co‐administered with clesacostat 15 mg b.i.d. (Days 8–14). There were no meaningful differences in systemic ervogastat exposures when administered alone or with clesacostat. Clesacostat 15 mg b.i.d. and ervogastat 300 mg b.i.d. co‐administration was overall safe and well tolerated in healthy participants. Cumulative safety and no clinically meaningful PK drug interactions observed in this study supported co‐administration of these two novel agents in additional studies exploring efficacy and safety in the management of NAFLD.

Abstract PF‐05251749 is a dual inhibitor of casein kinase 1 δ/ε under clinical development to treat disruption of circadian rhythm in Alzheimer's and Parkinson's diseases. In vitro, PF‐05251749 (0.3–100 μM) induced CYP3A in cryopreserved human hepatocytes, demonstrating non‐saturable, dose–dependent CYP3A mRNA increases, with induction slopes in the range 0.036–0.39 μM−1. In a multiple‐dose study (B8001002) in healthy participants, CYP3A activity was explored by measuring changes in 4β‐hydroxycholesterol/cholesterol ratio. Following repeated oral administration of PF‐05251749, up to 400 mg q.d., no significant changes were observed in 4β‐hydroxycholesterol/cholesterol ratio; this ratio increased significantly (~1.5‐fold) following administration of PF‐05251749 at 750 mg q.d., suggesting potential CYP3A induction at this dose. Physiologically based pharmacokinetic (PBPK) models were developed to characterize the observed clinical pharmacokinetics (PK) of PF‐05251749 at 400 and 750 mg q.d.; the PBPK induction model was calibrated using the in vitro linear fit induction slope, with rifampin as reference compound (Indmax = 8, EC50 = 0.32 μM). Clinical trial simulation following co‐administration of PF‐05251749, 400 mg q.d. with oral midazolam 2 mg, predicted no significant drug interaction risk. PBPK model predicted weak drug interaction following co‐administration of PF‐05251749, 750 mg q.d. with midazolam 2 mg. In conclusion, good agreement was obtained between CYP3A drug interaction risk predicted using linear‐slope PBPK model and exploratory biomarker trends. This agreement between two orthogonal approaches enabled assessment of drug interaction risks of PF‐05251749 in early clinical development, in the absence of a clinical drug–drug interaction study.

The 2022 United States Food and Drug Administration (US FDA) draft guidance on diversity plan (DP), which will be implemented through the Diversity Action Plans by December 2025, under the 21st Century Cures Act, marks a pivotal effort by the FDA to ensure that registrational studies adequately reflect the target patient populations based on diversity in demographics and baseline characteristics. This white paper represents the culminated efforts of the International Consortium of Quality and Innovation (IQ) Diversity and Inclusion (D&I) Working Group (WG) to assess the implementation of the draft FDA guidance by members of the IQ consortium in the discipline of clinical pharmacology (CP). This article describes current practices in the industry and emphasizes the tools and techniques of quantitative pharmacology that can be applied to support the inclusion of a diverse population during global drug development, to support diversity and inclusion of underrepresented patient populations, in multiregional clinical trials (MRCTs). It outlines strategic and technical recommendations to integrate demographics, including age, sex/gender, race/ethnicity, and comorbidities, in multiregional phase III registrational studies, through the application of quantitative pharmacology. Finally, this article discusses the challenges faced during global drug development, which may otherwise limit the enrollment of a broader, potentially diverse population in registrational trials. Based on the outcomes of the IQ survey that provided the current awareness of diversity planning, it is envisioned that in the future, industry efforts in the inclusion of previously underrepresented populations during global drug development will culminate in drug labels that apply to the intended patient populations at the time of new drug application or biologics license application rather than through post‐marketing requirements. [ABSTRACT FROM AUTHOR]

The article focuses on advocating for the nationwide authorization of licensed US pharmacists to prescribe oral contraceptives (OCs) based on their safety and efficacy. Topics include the endorsement of pharmacist-prescribed OCs by the American College of Clinical Pharmacology (ACCP), the evolution of OC formulations, and the training recommendations for pharmacists regarding OC prescription based on US Medical Eligibility Criteria (US MEC) for contraceptive use.

Co‐administration of clesacostat (acetyl‐CoA carboxylase inhibitor, PF‐05221304) and ervogastat (diacylglycerol O‐acyltransferase inhibitor, PF‐06865571) in laboratory models improved non‐alcoholic fatty liver disease (NAFLD)/non‐alcoholic steatohepatitis (NASH) end points and mitigated clesacostat‐induced elevations in circulating triglycerides. Clesacostat is cleared via organic anion‐transporting polypeptide‐mediated hepatic uptake and cytochrome P450 family 3A (CYP3A); in vitro clesacostat is identified as a potential CYP3A time‐dependent inactivator. In vitro ervogastat is identified as a substrate and potential inducer of CYP3A. Prior to longer‐term efficacy trials in participants with NAFLD, safety and pharmacokinetics (PK) were evaluated in a phase I, non‐randomized, open‐label, fixed‐sequence trial in healthy participants. In Cohort 1, participants (n = 7) received clesacostat 15 mg twice daily (b.i.d.) alone (Days 1–7) and co‐administered with ervogastat 300 mg b.i.d. (Days 8–14). Mean systemic clesacostat exposures, when co‐administered with ervogastat, decreased by 12% and 19%, based on maximum plasma drug concentration and area under the plasma drug concentration–time curve during the dosing interval, respectively. In Cohort 2, participants (n = 9) received ervogastat 300 mg b.i.d. alone (Days 1–7) and co‐administered with clesacostat 15 mg b.i.d. (Days 8–14). There were no meaningful differences in systemic ervogastat exposures when administered alone or with clesacostat. Clesacostat 15 mg b.i.d. and ervogastat 300 mg b.i.d. co‐administration was overall safe and well tolerated in healthy participants. Cumulative safety and no clinically meaningful PK drug interactions observed in this study supported co‐administration of these two novel agents in additional studies exploring efficacy and safety in the management of NAFLD. [ABSTRACT FROM AUTHOR]

PF‐05212377 (SAM760) is a potent and selective 5‐HT6 antagonist, previously under development for the treatment of Alzheimer's disease. In vitro, PF‐05212377 was determined to be a P‐gp/non‐BCRP human transporter substrate. Species differences were observed in the in vivo brain penetration of PF‐05212377 with a ratio of the unbound concentration in brain/unbound concentration in plasma (Cbu/Cpu) of 0.05 in rat and 0.64 in non‐human primates (NHP). Based on pre‐clinical evidence, brain penetration and target engagement of PF‐05212377 was confirmed in NHP using positron emission tomography (PET) measured 5‐HT6 receptor occupancy (%RO). The NHP Cpu EC50 of PF‐05212377 was 0.31 nM (consistent with the in vitro human 5HT6 Ki: 0.32 nM). P‐gp has been reported to be expressed in higher abundance at the rat BBB and in similar abundance at the BBB of non‐human primates and human; brain penetration of PF‐05212377 in humans was postulated to be similar to that in non‐human primates. In humans, PF‐05212377 demonstrated dose and concentration dependent increases in 5‐HT6 RO; maximal 5‐HT6 RO of ∼80% was measured in humans at doses of ≥15 mg with an estimated unbound plasma EC50 of 0.37 nM (which was similar to the in vitro human 5HT6 binding Ki 0.32 nM). In conclusion, cumulative evidence from NHP and human PET RO assessments confirmed that NHP is more appropriate than the rat for the prediction of human brain penetration of PF‐05212377, a P‐gp/non‐BCRP substrate. Clinical trial number: NCT01258751. [ABSTRACT FROM AUTHOR]

PF‐05251749 is a dual inhibitor of casein kinase 1 δ/ε under clinical development to treat disruption of circadian rhythm in Alzheimer's and Parkinson's diseases. In vitro, PF‐05251749 (0.3–100 μM) induced CYP3A in cryopreserved human hepatocytes, demonstrating non‐saturable, dose–dependent CYP3A mRNA increases, with induction slopes in the range 0.036–0.39 μM−1. In a multiple‐dose study (B8001002) in healthy participants, CYP3A activity was explored by measuring changes in 4β‐hydroxycholesterol/cholesterol ratio. Following repeated oral administration of PF‐05251749, up to 400 mg q.d., no significant changes were observed in 4β‐hydroxycholesterol/cholesterol ratio; this ratio increased significantly (~1.5‐fold) following administration of PF‐05251749 at 750 mg q.d., suggesting potential CYP3A induction at this dose. Physiologically based pharmacokinetic (PBPK) models were developed to characterize the observed clinical pharmacokinetics (PK) of PF‐05251749 at 400 and 750 mg q.d.; the PBPK induction model was calibrated using the in vitro linear fit induction slope, with rifampin as reference compound (Indmax = 8, EC50 = 0.32 μM). Clinical trial simulation following co‐administration of PF‐05251749, 400 mg q.d. with oral midazolam 2 mg, predicted no significant drug interaction risk. PBPK model predicted weak drug interaction following co‐administration of PF‐05251749, 750 mg q.d. with midazolam 2 mg. In conclusion, good agreement was obtained between CYP3A drug interaction risk predicted using linear‐slope PBPK model and exploratory biomarker trends. This agreement between two orthogonal approaches enabled assessment of drug interaction risks of PF‐05251749 in early clinical development, in the absence of a clinical drug–drug interaction study. [ABSTRACT FROM AUTHOR]

Measurements of drug occupancies using positron emission tomography (PET) can be biased if the radioligand concentration exceeds “tracer” levels. Negative bias would also arise in successive PET scans if clearance of the radioligand is slow, resulting in a carryover effect. We developed a method to (1) estimate the in vivo dissociation constant Kd of a radioligand from PET studies displaying a non-tracer carryover (NTCO) effect and (2) correct the NTCO bias in occupancy studies taking into account the plasma concentration of the radioligand and its in vivo Kd. This method was applied in a study of healthy human subjects with the histamine H3 receptor radioligand [11C]GSK189254 to measure the PK-occupancy relationship of the H3 antagonist PF-03654746. From three test/retest studies, [11C]GSK189254 Kd was estimated to be 9.5 ± 5.9 pM. Oral administration of 0.1 to 4 mg of PF-03654746 resulted in occupancy estimates of 71%–97% and 30%–93% at 3 and 24 h post-drug, respectively. NTCO correction adjusted the occupancy estimates by 0%–15%. Analysis of the relationship between corrected occupancies and PF-03654746 plasma levels indicated that PF-03654746 can fully occupy H3 binding sites (ROmax = 100%), and its IC50 was estimated to be 0.144 ± 0.010 ng/mL. The uncorrected IC50 was 26% higher. [ABSTRACT FROM AUTHOR]

1. Unbound brain drug concentration (Cb,u), a valid surrogate of interstitial fluid drug concentration (CISF), cannot be directly determined in humans, which limits accurately defining the humanCb,u:Cp,uof investigational molecules. 2. For the H3R antagonist (1R,3R)-N-ethyl-3-fluoro-3-[3-fluoro-4-(pyrrolidin-1-lmethyl)phenyl]cyclobutane-1-carboxamide (PF-03654746), we interrogatedCb,u:Cp,uin humans and nonhuman primate (NHP). 3. In rat,PF-03654746achieved net blood–brain barrier (BBB) equilibrium (Cb,u:Cp,uof 2.11). 4. In NHP and humans, the PET receptor occupancy-basedCp,uIC50ofPF-03654746was 0.99 nM and 0.31 nM, respectively, which were 2.1- and 7.4-fold lower than itsin vitrohuman H3Ki(2.3 nM). 5. In an attempt to understand this higher-than-expected potency in humans and NHP, rat-derivedCb,u:Cp,uofPF-03654746was integrated withCp,uIC50to identify unbound (neuro) potency ofPF-03654746,nIC50. 6. ThenIC50ofPF-03654746was 2.1 nM in NHP and 0.66 nM in human which better correlated (1.1- and 3.49-fold lower) within vitrohuman H3Ki(2.3 nM). 7. This correlation of thenIC50andin vitro hH3Kisuggested the translation of net BBB equilibrium ofPF-03654746from rat to NHP and humans, and confirmed the use ofCp,uas a reliable surrogate ofCb,u. 8. Thus,nIC50quantitatively informed the humanCb,u:Cp,uofPF-03654746. [ABSTRACT FROM PUBLISHER]

1.The first generation 5HT-4 partial agonist, 4-{4-[4-Tetrahydrofuran-3-yloxy)-benzo[d]isoxazol-3-yloxymethyl]-piperidin-1-ylmethyl}-tetrahydropyran-4-ol, PF-4995274 (TBPT), was metabolized to N-dealkylated (M1) and an unusual, cyclized oxazolidine (M2) metabolites.M1andM2demonstrated pharmacological activity at 5HT receptor subtypes warranting further investigation into their dispositional properties in humans;M2was a minor component in vitro but was the pre-dominant metabolite identified in human plasma. 2.To shift metabolism away from the piperidine ring ofTBPT, a series of heterocyclic replacements were designed, synthesized, and profiled. Groups including azetidines, pyrrolidines, as well as functionalized piperidines were evaluated with the goal of identifying an alternative group that maintained the desired potency, functional activity, and reduced turnover in human hepatocytes. 3.Activities of 4-substituted piperidines or pyrrolidine analogs at the pharmacological target were not significantly altered, but the same metabolic pathways of N-dealkylation and oxazolidine formation were still observed. Altering these to bridged ring systems lowered oxazolidine metabolite formation, but not N-dealkylation. 4.The effort concluded with identification of azetidines as second-generation 5HT4partial agonists. These were neither metabolized via N-dealkylation nor converted to cyclized oxazolidine metabolites rather oxidized on the isoxazole ring. The use of azetidine as a replacement for aliphatic aza-heterocyclic rings in drug design to alter drug metabolism and pharmacology is discussed. [ABSTRACT FROM PUBLISHER]

1. In early discovery stages, 2-methyl- N-(2′-(pyrrolidinyl-1-ylsulfonyl)-[1,1′-biphenyl]-4-yl)propan-1-amine (PBPA ) demonstrated monoamine oxidase A (MAO-A) and cytochrome P450 (CYP)-mediated clearance. While human liver microsomes predicted low CLb PBPA demonstrated a moderate CLp/ F in humans. The plasma pharmacokinetic (PK) of PBPA was characterized by unexpected high inter-individual variability. Hence, a retrospective analysis was undertaken to understand the disposition processes of PBPA, by applying in vitro mechanistic tools. 2. The in vitro-to- in vivo of rat CLb of PBPA was calculated as similar to that of human, suggesting rat to be a better predictor of a MAO-A/CYP substrate, but not dog or monkey; this is consistent with differences in expression of MAO-A in rat, dog, monkey and human. Fraction metabolized ( fm) of human MAO A ( hMAO-A) (50%), CYP3A4 (8%), CYP3A5 (16%) and CYP2D6 (29%) was determined, in vitro. 3. While the fm of CYP3A5 was <50%, Michaelis-Menten kinetics demonstrated that it was a higher capacity pathway compared with MAO-A, 2D6 and 3A4. This was consistent with strong association of dose-normalized plasma Cmax and area under the plasma concentration time curve (AUC0-tlast) of PBPA with CYP3A5 genotype, but not with genotype of CYP2D6. 4. This investigation demonstrates the value of integrating in vitro mechanistic tools to gain comprehensive understanding of disposition properties of drug candidates, in a discovery paradigm and prior to the investment in clinical trials. [ABSTRACT FROM AUTHOR]

By use of parallel chemistry coupled with physicochemical property design, a series of selective κ opioid antagonists have been discovered. The parallel chemistry strategy utilized key monomer building blocks to rapidly expand the desired SAR space. The potency and selectivity of the in vitro κ antagonism were confirmed in the tail-flick analgesia model. This model was used to build an exposure–response relationship between the κ Kiand the free brain drug levels. This strategy identified 2-methyl-N-((2′-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine, PF-4455242, which entered phase 1 clinical testing and has demonstrated target engagement in healthy volunteers. [ABSTRACT FROM AUTHOR]

Background There are no effective treatments available or on the horizon for cognitive impairments associated with schizophrenia (CIAS) and primary negative symptoms. Cholinergic and glutamatergic systems, alpha-7 nicotinic acetylcholine receptor (alpha-7nAChR), and N-methyl-D-aspartate receptor (NMDA-R) have been implicated in the pathophysiology of CIAS and primary negative symptoms. Seven studies in animals showed that the galantamine-memantine combination was effective for cognition—synergistic benefits were also seen. The galantamine-memantine combination was significantly better for cognition than the donepezil-memantine combination in patients with Alzheimer's disease. There is evidence that kynurenine pathway (KP) metabolites are associated with CIAS and deficit syndrome. Kynurenic acid (KYNA) is elevated in schizophrenia and is an antagonist of the alpha-7nAChR and NMDA-R. The aim of this study was to examine whether the galantamine-memantine combination is effective for CIAS. Methods In this 6-week open-label clinical trial, three participants with schizophrenia were enrolled; two completed the study. Participants received galantamine ER 24 mg and memantine XR 21 mg for four weeks. Plasma was analyzed for KP metabolites. Results In a 36-year-old man with schizophrenia, scores improved in five of seven MATRICS Consensus Cognitive Battery (MCCB) domains; the exceptions were working memory and verbal learning. Also, the Scale for the Assessment of Negative Symptoms total score decreased from five to zero. This finding is suggestive of primary negative symptoms because the Brief Psychiatric Rating Scale, Simpson Angus Scale, and Calgary Depression Scale for Schizophrenia scores were minimal, and the urinary drug screen was negative at baseline and endpoint. In a 45-year-old man with schizoaffective disorder, there were improvements in speed of processing and working memory. Picolinic acid (PIC) concentration decreased in both participants. KYNA concentration decreased in both participants, and kynurenine concentration decreased in one participant. Discussion This is the first study that is suggestive of the association of MCCB and KP metabolites in schizophrenia. The decrease in PIC concentration with the treatment is a promising finding because high concentrations of PIC are toxic to the brain. Although this pilot study is not powered, the data are promising. RCTs are warranted to validate the findings. "Repurposing" of approved medications such as galantamine and memantine could lead to rapid clinical implementation if the results of RCTs are positive. This study is the first in which the nicotinic-cholinergic and glutamatergic systems were simultaneously targeted in people with schizophrenia. In addition, the galantamine-memantine combination (unique and novel) has synergistic effects of α7nAChR and NMDA-R. The galantamine-memantine combination targeting both receptors concurrently is a paradigm shift in schizophrenia because until now only one receptor (NMDA or nicotinic with partial treatment response) has been targeted at a time. This combination may broaden the number of cognitive domains that may significantly improve compared to placebo and potentially increase the composite score. The pathophysiological mechanism of mismatch negativity may occur via interactive effects of alpha7nACh and NMDA receptors. This combination targets the quintuple hypotheses (dopamine, nicotinic-cholinergic, glutamatergic/NMDA, GABA, and KYNA) concurrently and has the potential to treat positive, cognitive, and primary negative symptoms. The galantamine-memantine combination has the potential to become the first anti-schizophrenia treatment. [ABSTRACT FROM AUTHOR]

The regulation of drug-metabolizing enzymes and transporters by cytokines has been extensively studied in vitro and in clinic. Cytokine-mediated suppression of cytochrome P450 (CYP) or drug transporters may increase or decrease the systemic clearance of drug substrates that are primarily cleared via these pathways; neutralization of cytokines by therapeutic proteins may thereby alter systemic exposures of such drug substrates. The Food and Drug Administration recommends evaluating such clinical drug interactions during clinical development and has provided labeling recommendations for therapeutic proteins. To determine the clinical relevance of these drug interactions to dose adjustments, trends in steady-state exposures of CYP-sensitive substrates coadministered with cytokine modulators as reported in the University of Washington Drug Interaction Database were extracted and examined for each of the CYPs. Coadministration of cytochrome P450 family 3 subfamily A (CYP3A) (midazolam/simvastatin), cytochrome P450 subfamily 2C19 (omeprazole), or cytochrome P450 subfamily 1A2 (caffeine/tizanidine) substrates with anti-interleukin-6 and with anti-interleukin-23 therapeutics led to changes in systemic exposures of CYP substrates ranging from ∼ -58% to ∼35%; no significant trends were observed for cytochrome P450 subfamily 2D6 (dextromethorphan) and cytochrome P450 subfamily 2C9 (warfarin) substrates. Although none of these changes in systemic exposures have been reported as clinically meaningful, dose adjustment of midazolam for optimal sedation in acute care settings has been reported. Simulated concentration-time profiles of midazolam under conditions of elevated cytokine levels when coadministered with tocilizumab, suggest a ∼six- to sevenfold increase in midazolam clearance, suggesting potential implications of cytokine-CYP drug interactions on dose adjustments of sensitive CYP3A substrates in acute care settings. Additionally, this article also provides a brief overview of nonclinical and clinical assessments of cytokine-CYP drug interactions in drug discovery and development. SIGNIFICANCE STATEMENT: There has been significant progress in understanding cytokine-mediated drug interactions for CYP-sensitive substrates. This article provides an overview of the progress in this field, including a trend analysis of systemic exposures of CYP-sensitive substrates coadministered with anti-interleukin therapeutics. In addition, the review also provides a perspective of current methods used to assess these drug interactions during drug development and a focus on individualized medicine, particularly in acute care settings., (Copyright © 2024 by The Author(s).)

PF-05212377 (SAM760) is a potent and selective 5-HT 6 antagonist, previously under development for the treatment of Alzheimer's disease. In vitro, PF-05212377 was determined to be a P-gp/non-BCRP human transporter substrate. Species differences were observed in the in vivo brain penetration of PF-05212377 with a ratio of the unbound concentration in brain/unbound concentration in plasma (C bu /C pu ) of 0.05 in rat and 0.64 in non-human primates (NHP). Based on pre-clinical evidence, brain penetration and target engagement of PF-05212377 was confirmed in NHP using positron emission tomography (PET) measured 5-HT 6 receptor occupancy (%RO). The NHP C pu EC 50 of PF-05212377 was 0.31 nM (consistent with the in vitro human 5HT6 K i : 0.32 nM). P-gp has been reported to be expressed in higher abundance at the rat BBB and in similar abundance at the BBB of non-human primates and human; brain penetration of PF-05212377 in humans was postulated to be similar to that in non-human primates. In humans, PF-05212377 demonstrated dose and concentration dependent increases in 5-HT 6 RO; maximal 5-HT6 RO of ∼80% was measured in humans at doses of ≥15 mg with an estimated unbound plasma EC 50 of 0.37 nM (which was similar to the in vitro human 5HT6 binding K i 0.32 nM). In conclusion, cumulative evidence from NHP and human PET RO assessments confirmed that NHP is more appropriate than the rat for the prediction of human brain penetration of PF-05212377, a P-gp/non-BCRP substrate. Clinical trial number: NCT01258751., (© 2023 John Wiley & Sons Ltd.)

PF-05251749 is a dual inhibitor of casein kinase 1 δ/ε under clinical development to treat disruption of circadian rhythm in Alzheimer's and Parkinson's diseases. In vitro, PF-05251749 (0.3-100 μM) induced CYP3A in cryopreserved human hepatocytes, demonstrating non-saturable, dose-dependent CYP3A mRNA increases, with induction slopes in the range 0.036-0.39 μM -1 . In a multiple-dose study (B8001002) in healthy participants, CYP3A activity was explored by measuring changes in 4β-hydroxycholesterol/cholesterol ratio. Following repeated oral administration of PF-05251749, up to 400 mg q.d., no significant changes were observed in 4β-hydroxycholesterol/cholesterol ratio; this ratio increased significantly (~1.5-fold) following administration of PF-05251749 at 750 mg q.d., suggesting potential CYP3A induction at this dose. Physiologically based pharmacokinetic (PBPK) models were developed to characterize the observed clinical pharmacokinetics (PK) of PF-05251749 at 400 and 750 mg q.d.; the PBPK induction model was calibrated using the in vitro linear fit induction slope, with rifampin as reference compound (Ind max  = 8, EC 50  = 0.32 μM). Clinical trial simulation following co-administration of PF-05251749, 400 mg q.d. with oral midazolam 2 mg, predicted no significant drug interaction risk. PBPK model predicted weak drug interaction following co-administration of PF-05251749, 750 mg q.d. with midazolam 2 mg. In conclusion, good agreement was obtained between CYP3A drug interaction risk predicted using linear-slope PBPK model and exploratory biomarker trends. This agreement between two orthogonal approaches enabled assessment of drug interaction risks of PF-05251749 in early clinical development, in the absence of a clinical drug-drug interaction study., (© 2022 The Authors. Clinical and Translational Science published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.)

This commentary summarizes expert mini-reviews and original research articles that have been assembled in a special issue on novel models of drug metabolism and disposition. The special issue consists of research articles or reviews on novel static or micro-flow based models of the intestine, liver, eye, and kidney. This issue reviews static intestinal systems like mucosal scrapings and cryopreserved intestinal enterocytes, as well as novel bioengineered or chemically engineered intestinal models derived from primary human tissue, iPSCs, enteroids, and crypts. Experts have reviewed hepatic systems like cryopermeabilized Metmax hepatocytes and longer term, hepatocyte coculture system from H µ REL, yielding in vivo-like primary and secondary drug metabolite profiles. Additional liver models, including micropattern hepatocyte coculture, 3D liver spheroids, and microflow systems, applicable to the study of drug disposition and toxicology have also been reviewed. In this commentary, we have outlined expert opinions and current efforts on hepatic- and nephrotoxicity models. Ocular disposition models including corneal permeability models have been included within this special issue. This commentary provides a summary of in vivo mini-reviews of the issue, which have discussed the applications and drawbacks of pig and humanized mice models of P450, UGT, and rat organic anionic transporting polypeptide 1a4. While not extensively reviewed, novel positron emissions tomography imaging-based approaches to study the distribution of xenobiotics have been highlighted. This commentary also outlines in vitro and in vivo models of drug metabolism derived from breakthrough genetic, chromosomal, and tissue engineering techniques. The commentary concludes by providing a futuristic view of the novel models discussed in this issue., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

Intestinal disposition of small molecules involves interplay of drug metabolizing enzymes (DMEs), transporters, and host-microbiome interactions, which has spurred the development of in vitro intestinal models derived from primary tissue sources. Such models have been bioengineered from intestinal crypts, mucosal extracts, induced pluripotent stem cell (iPSC)-derived organoids, and human intestinal tissue. This minireview discusses the utility and limitations of these human-derived models in support of small molecule drug metabolism and disposition. Enteroids from human intestinal crypts, organoids derived from iPSCs using growth factors or small molecule compounds, and enterocytes extracted from mucosal scrapings show key absorptive cell morphology while are limited in quantitative applications due to the lack of accessibility to the apical compartment, the lack of monolayers, or low expression of key DMEs, transporters, and nuclear hormone receptors. Despite morphogenesis to epithelial cells, similar challenges have been reported by more advanced technologies that have explored the impact of flow and mechanical stretch on proliferation and differentiation of Caco-2 cells. Most recently, bioengineered human intestinal epithelial or ileal cells have overcome many of the challenges, as the DME and transporter expression pattern resembles that of native intestinal tissue. Engineering advances may improve such models to support longer-term applications and meet end-user needs. Biochemical characterization and transcriptomic, proteomic, and functional endpoints of emerging novel intestinal models, when referenced to native human tissue, can provide greater confidence and increased utility in drug discovery and development., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

Kynurenic acid (KYNA) plays a significant role in maintaining normal brain function, and abnormalities in KYNA levels have been associated with various central nervous system disorders. Confirmation of its causality in human diseases requires safe and effective modulation of central KYNA levels in the clinic. The kynurenine aminotransferases (KAT) II enzyme represents an attractive target for pharmacologic modulation of central KYNA levels; however, KAT II and KYNA turnover kinetics, which could contribute to the duration of pharmacologic effect, have not been reported. In this study, the kinetics of central KYNA-lowering effect in rats and nonhuman primates (NHPs, Cynomolgus macaques ) was investigated using multiple KAT II irreversible inhibitors as pharmacologic probes. Mechanistic pharmacokinetic-pharmacodynamic analysis of in vivo responses to irreversible inhibition quantitatively revealed that 1) KAT II turnover is relatively slow [16-76 hours' half-life ( t 1/2 )], whereas KYNA is cleared more rapidly from the brain (<1 hour t 1/2 ) in both rats and NHPs, 2) KAT II turnover is slower in NHPs than in rats (76 hours vs. 16 hours t 1/2 , respectively), and 3) the percent contribution of KAT II to KYNA formation is constant (∼80%) across rats and NHPs. Additionally, modeling results enabled establishment of in vitro-in vivo correlation for both enzyme turnover rates and drug potencies. In summary, quantitative translational analysis confirmed the feasibility of central KYNA modulation in humans. Model-based analysis, where system-specific properties and drug-specific properties are mechanistically separated from in vivo responses, enabled quantitative understanding of the KAT II-KYNA pathway, as well as assisted development of promising candidates to test KYNA hypothesis in humans., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

SAM-760 [(2-methyl-1-(phenylsulfonyl)-4-(piperazin-1-yl)-1H-benzo[d]imidazole)], a 5HT 6 antagonist, was investigated in humans for the treatment of Alzheimer's disease. In liver microsomes and recombinant cytochrome P450 (P450) isozymes, SAM-760 was predominantly metabolized by CYP3A (∼85%). Based on these observations and an expectation of a 5-fold magnitude of interaction with moderate to strong CYP3A inhibitors, a clinical DDI study was performed. In the presence of ketoconazole, the mean C and area under the plasma concentration-time curve from time zero extrapolated to infinite time values of SAM-760 showed only a modest increase by 30% and 38%, respectively. In vitro investigation of this unexpectedly low interaction was undertaken using [ max C]SAM-760. Radiometric profiling in human hepatocytes confirmed all oxidative metabolites previously observed with unlabeled SAM-760; however, the predominant radiometric peak was an unexpected polar metabolite that was insensitive to the pan-P450 inhibitor 1-aminobenzotriazole. In human hepatocytes, radiometric integration attributed 43% of the total metabolism of SAM-760 to this non-P450 pathway. Using an authentic standard, this predominant metabolite was confirmed as benzenesulfinic acid. Additional investigation revealed that the benzenesulfinic acid metabolite may be a novel, nonenzymatic, thiol-mediated reductive cleavage of an aryl sulfonamide group of SAM-760. We also determined the relative contribution of P450 to the metabolism of SAM-760 in human hepatocytes by following the rate of formation of oxidative metabolites in the presence and absence of P450 isoform-specific inhibitors. The P450-mediated oxidative metabolism of SAM-760 was still primarily attributed to CYP3A (33%), with minor contributions from P450 isoforms CYP2C19 and CYP2D6. Thus, the disposition of [ 14 C]SAM-760. Radiometric profiling in human hepatocytes confirmed all oxidative metabolites previously observed with unlabeled SAM-760; however, the predominant radiometric peak was an unexpected polar metabolite that was insensitive to the pan-P450 inhibitor 1-aminobenzotriazole. In human hepatocytes, radiometric integration attributed 43% of the total metabolism of SAM-760 to this non-P450 pathway. Using an authentic standard, this predominant metabolite was confirmed as benzenesulfinic acid. Additional investigation revealed that the benzenesulfinic acid metabolite may be a novel, nonenzymatic, thiol-mediated reductive cleavage of an aryl sulfonamide group of SAM-760. We also determined the relative contribution of P450 to the metabolism of SAM-760 in human hepatocytes by following the rate of formation of oxidative metabolites in the presence and absence of P450 isoform-specific inhibitors. The P450-mediated oxidative metabolism of SAM-760 was still primarily attributed to CYP3A (33%), with minor contributions from P450 isoforms CYP2C19 and CYP2D6. Thus, the disposition of [ 14 C]SAM-760 in human hepatocytes via novel sulfonamide metabolism and CYP3A verified the lower than expected clinical DDI when SAM-760 was coadministered with ketoconazole., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

( R )-4-((4-(((4-((tetrahydrofuran-3-yl)oxy)benzo[d]isoxazol-3-yl)oxy)methyl)piperidin-1-yl)methyl)tetrahydro-2H-pyran-4-ol (TBPT), a serotonin-4 receptor partial agonist, is metabolized to two metabolites: an N -dealkylation product [( R )-3-(piperidin-4-ylmethoxy)-4-((tetrahydrofuran-3-yl)oxy)benzo[d]isoxazole (M1)] and a cyclized oxazolidine structure [7-(((4-((( R )-tetrahydrofuran-3-yl)oxy)benzo[d]isoxazol-3-yl)oxy)methyl)octahydro-3H (M2)]. After administration of TBPT to humans the exposure to M1 was low and the exposure to M2 was high, relative to the parent drug, despite this being the opposite in vitro. In this study, projection of the plasma metabolite/parent (M/P) ratios for M1 and M2 was attempted using in vitro metabolism, binding, and permeability data in static and dynamic physiologically based pharmacokinetic (PBPK) models. In the static model, the fraction of parent clearance yielding the metabolite (which also required taking into account secondary metabolites of M1 and M2), the clearance of the metabolites and parent, and an estimate of the availability of the metabolites from the liver were combined to yield estimated parent/metabolite ratios of 0.32 and 23 for M1 and M2, respectively. PBPK modeling that used in vitro and physicochemical data input yielded estimates of 0.26 and 20, respectively. The actual values were 0.12 for M1/TBPT and 58 for M2/TBPT. Thus, the ratio for M1 was overpredicted, albeit at values less than unity. The ratio for M2/TBPT was underpredicted, and the high ratio of 58 may exceed a limiting ceiling of the approach. Nevertheless, when considered in the context of determining whether a potential circulating metabolite may be quantitatively important prior to administration of a drug for the first time to humans, the approaches succeeded in highlighting the importance of M2 (M/P ratio >> 1) relative to M1, despite M1 being much greater than M2 in vitro., (Copyright © 2018 by The American Society for Pharmacology and Experimental Therapeutics.)

Measurements of drug occupancies using positron emission tomography (PET) can be biased if the radioligand concentration exceeds "tracer" levels. Negative bias would also arise in successive PET scans if clearance of the radioligand is slow, resulting in a carryover effect. We developed a method to (1) estimate the in vivo dissociation constant K d of a radioligand from PET studies displaying a non-tracer carryover (NTCO) effect and (2) correct the NTCO bias in occupancy studies taking into account the plasma concentration of the radioligand and its in vivo K d . This method was applied in a study of healthy human subjects with the histamine H 3 receptor radioligand [ 11 C]GSK189254 to measure the PK-occupancy relationship of the H 3 antagonist PF-03654746. From three test/retest studies, [ 11 C]GSK189254 K d was estimated to be 9.5 ± 5.9 pM. Oral administration of 0.1 to 4 mg of PF-03654746 resulted in occupancy estimates of 71%-97% and 30%-93% at 3 and 24 h post-drug, respectively. NTCO correction adjusted the occupancy estimates by 0%-15%. Analysis of the relationship between corrected occupancies and PF-03654746 plasma levels indicated that PF-03654746 can fully occupy H 3 binding sites ( RO max  = 100%), and its IC 50 was estimated to be 0.144 ± 0.010 ng/mL. The uncorrected IC 50 was 26% higher.

Dopamine receptor antagonism is a compelling molecular target for the treatment of a range of psychiatric disorders, including substance use disorders. From our corporate compound file, we identified a structurally unique D3 receptor (D3R) antagonist scaffold, 1. Through a hybrid approach, we merged key pharmacophore elements from 1 and D3 agonist 2 to yield the novel D3R/D2R antagonist PF-4363467 (3). Compound 3 was designed to possess CNS drug-like properties as defined by its CNS MPO desirability score (≥4/6). In addition to good physicochemical properties, 3 exhibited low nanomolar affinity for the D3R (D3 K i = 3.1 nM), good subtype selectivity over D2R (D2 K i = 692 nM), and high selectivity for D3R versus other biogenic amine receptors. In vivo, 3 dose-dependently attenuated opioid self-administration and opioid drug-seeking behavior in a rat operant reinstatement model using animals trained to self-administer fentanyl. Further, traditional extrapyramidal symptoms (EPS), adverse side effects arising from D2R antagonism, were not observed despite high D2 receptor occupancy (RO) in rodents, suggesting that compound 3 has a unique in vivo profile. Collectively, our data support further investigation of dual D3R and D2R antagonists for the treatment of drug addiction.

The cognitive impairments observed in Alzheimer's disease (AD) are in part a consequence of reduced acetylcholine (ACh) levels resulting from a loss of cholinergic neurons. Preclinically, serotonin 4 receptor (5-HT(4)) agonists are reported to modulate cholinergic function and therefore may provide a new mechanistic approach for treating cognitive deficits associated with AD. Herein we communicate the design and synthesis of potent, selective, and brain penetrant 5-HT(4) agonists. The overall goal of the medicinal chemistry strategy was identification of structurally diverse clinical candidates with varying intrinsic activities. The exposure-response relationships between binding affinity, intrinsic activity, receptor occupancy, drug exposure, and pharmacodynamic activity in relevant preclinical models of AD were utilized as key selection criteria for advancing compounds. On the basis of their excellent balance of pharmacokinetic attributes and safety, two lead 5-HT(4) partial agonist candidates 2d and 3 were chosen for clinical development.

5-Hydroxytryptamine (5-HT)(4) receptor agonists reportedly stimulate brain acetylcholine (ACh) release, a property that might provide a new pharmacological approach for treating cognitive deficits associated with Alzheimer's disease. The purpose of this study was to compare the binding affinities, functional activities, and effects on neuropharmacological responses associated with cognition of two highly selective 5-HT(4) receptor agonists, prucalopride and 6,7-dihydro-4-hydroxy-7-isopropyl-6-oxo-N-[3-(piperidin-1-yl)propyl]thieno[2,3-b]pyridine-5-carboxamide (PRX-03140). In vitro, prucalopride and PRX-03140 bound to native rat brain 5-HT(4) receptors with K(i) values of 30 nM and 110 nM, respectively, and increased cAMP production in human embryonic kidney-293 cells expressing recombinant rat 5-HT(4) receptors. In vivo receptor occupancy studies established that prucalopride and PRX-03140 were able to penetrate the brain and bound to 5-HT(4) receptors in rat brain, achieving 50% receptor occupancy at free brain exposures of 330 nM and 130 nM, respectively. Rat microdialysis studies revealed that prucalopride maximally increased ACh and histamine levels in the prefrontal cortex at 5 and 10 mg/kg, whereas PRX-03140 significantly increased cortical histamine levels at 50 mg/kg, failing to affect ACh release at doses lower than 150 mg/kg. In combination studies, donepezil-induced increases in cortical ACh levels were potentiated by prucalopride and PRX-03140. Electrophysiological studies in rats demonstrated that both compounds increased the power of brainstem-stimulated hippocampal θ oscillations at 5.6 mg/kg. These findings show for the first time that the 5-HT(4) receptor agonists prucalopride and PRX-03140 can increase cortical ACh and histamine levels, augment donepezil-induced ACh increases, and increase stimulated-hippocampal θ power, all neuropharmacological parameters consistent with potential positive effects on cognitive processes.

2-Methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine (PF-04455242) is a novel κ-opioid receptor (KOR) antagonist with high affinity for human (3 nM), rat (21 nM), and mouse (22 nM) KOR, a ∼ 20-fold reduced affinity for human μ-opioid receptors (MORs; K(i) = 64 nM), and negligible affinity for δ-opioid receptors (K(i) > 4 μM). PF-04455242 also showed selectivity for KORs in vivo. In rats, PF-04455242 blocked KOR and MOR agonist-induced analgesia with ID(50) values of 1.5 and 9.8 mg/kg, respectively, and inhibited ex vivo [(3)H](2-(benzofuran-4-yl)-N-methyl-N-((5S,7R,8R)-7-(pyrrolidin-1-yl)-1-oxaspiro[4.5]decan-8-yl)acetamide ([(3)H]CI977) and [(3)H](2S)-2-[[2-[[(2R)-2-[[(2S)-2-amino-3-(4-hydroxyphenyl) propanoyl]amino]propanoyl]amino]acetyl]-methylamino]-N-(2-hydroxyethyl)-3-phenylpropanamide ([(3)H]DAMGO) binding to KOR and MOR receptors with ID(50) values of 2.0 and 8.6 mg/kg, respectively. An in vivo binding assay was developed using (-)-4-[(3)H]methoxycarbonyl-2-[(1-pyrrolidinylmethyl]-1-[(3,4-dichlorophenyl)acetyl]-piperidine ([(3)H]PF-04767135), a tritiated version of the KOR positron emission tomography ligand (-)-4-[(11)C]methoxycarbonyl-2-[(1-pyrrolidinylmethyl]-1-[(3,4-dichlorophenyl)acetyl]-piperidine ([(11)C]GR103545) in which PF-04455242 had an ID(50) of 5.2 mg/kg. PF-04455242 demonstrated antidepressant-like efficacy (mouse forced-swim test), attenuated the behavioral effects of stress (mouse social defeat stress assay), and showed therapeutic potential in treating reinstatement of extinguished cocaine-seeking behavior (mouse conditioned place preference). KOR agonist-induced plasma prolactin was investigated as a translatable mechanism biomarker. Spiradoline (0.32 mg/kg) significantly increased rat plasma prolactin levels from 1.9 ± 0.4 to 41.9 ± 4.9 ng/ml. PF-04455242 dose-dependently reduced the elevation of spiradoline-induced plasma prolactin with an ID(50) of 2.3 ± 0.1 mg/kg, which aligned well with the ED(50) values obtained from the rat in vivo binding and efficacy assays. These data provide further evidence that KOR antagonists have potential for the treatment of depression and addiction disorders.