DMPK perspective on quantitative model analysis for chimeric antigen receptor cell therapy: Advances and challenges.

Chimeric antigen receptor (CAR) cells are genetically engineered immune cells that specifically target tumor-associated antigens and have revolutionized cancer treatment, particularly in hematological malignancies, with ongoing investigations into their potential applications in solid tumors. This review provides a comprehensive overview of the current status and challenges in drug metabolism and pharmacokinetics (DMPK) for CAR cell therapy, specifically emphasizing on quantitative modeling and simulation (M&S). Furthermore, the recent advances in quantitative model analysis have been reviewed, ranging from clinical data characterization to mechanism-based modeling that connects in vitro and in vivo nonclinical and clinical study data. Additionally, the future perspectives and areas for improvement in CAR cell therapy translation have been reviewed. This includes using formulation quality considerations, characterization of appropriate animal models, refinement of in vitro models for bottom-up approaches, and enhancement of quantitative bioanalytical methodology. Addressing these challenges within a DMPK framework is pivotal in facilitating the translation of CAR cell therapy, ultimately enhancing the patients' lives through efficient CAR cell therapies.

Advanced translational PBPK model for transferrin receptor-mediated drug delivery to the brain.

Transferrin receptor (TfR)-mediated transcytosis is an attractive pathway for delivering large-molecule therapeutics to the central nervous system across the blood-brain barrier. Despite the clinical success of some drugs conjugated with TfR-binder, the desired drug profile for efficient TfR-mediated delivery to the targeted compartment within the brain, especially considering the species-related differences, has not been fully elucidated. To provide a prospective direction in the TfR-mediated drug delivery system, we developed an advanced physiologically based pharmacokinetic (PBPK) model. The model addresses TfR-mediated trans- and intracellular disposition of anti-TfR antibodies from brain capillary blood, endothelial cells, extracellular fluid (ECF), and eventually to brain parenchymal cells (BPCs), which correspond to pharmacological target sites of interest. The PBPK model is applicable in rats, monkeys, and human TfR knock-in (hTfR-KI) mice with satisfactory prediction accuracy through model calibration using the brain and plasma PK data of anti-TfR monoclonal antibodies, including their fused protein, with diverse binding affinity to TfR (TfR-Kd). The sensitivity analysis to determine drug properties required for the optimal brain delivery revealed 1) a bell-shaped relationship between TfR-Kd and brain exposure; 2) a minimum species difference between monkeys and hTfR-KI mice in the optimal TfR-Kd range, but not with rats; 3) a low TfR-Kd range to be preferably targeted for BPCs compared with ECF; and 4) an increase in brain exposure when using the pH-sensitive antibody. This may advance model-informed drug development, improve molecular design optimization, and provide precise human dose projection of drugs leveraging TfR-mediated shuttle technology into the brain.

Novel Cell Quantification Method Using a Single Surrogate Calibration Curve Across Various Biological Samples.

Quantitative polymerase chain reaction (qPCR) is generally used to quantify transplanted cell therapy products in biological samples. As the matrix effects on PCR amplification and variability in DNA recovery from biological samples are well-known limitations that hinder the assay's performance, a calibration curve is conventionally established for each matrix. Droplet digital PCR (ddPCR) is based on the endpoint assay and advantageous in avoiding matrix effects. Moreover, the use of an external control gene may correct assay fluctuations to minimize the effects caused by inconsistent DNA recovery. In this study, we aimed to establish a novel and robust ddPCR method capable of quantifying human cells across various mouse biological samples using a single surrogate calibration curve in combination with an external control gene and DNA recovery normalization. Acceptable accuracy and precision were observed for quality control samples from different tissues, indicating the excellent quantitative and versatile potential of the developed method. Furthermore, the established method enabled the evaluation of human CD8+ T cell biodistribution in immunodeficient mice. Our findings provide new insights into the use of ddPCR-based quantification methods in biodistribution studies of cell therapy products.

Preferential delivery of lipid-ligand conjugated DNA/RNA heteroduplex oligonucleotide to ischemic brain in hyperacute stage.

Antisense oligonucleotide (ASO) is a major tool used for silencing pathogenic genes. For stroke in the hyperacute stage, however, the ability of ASO to regulate genes is limited by its poor delivery to the ischemic brain owing to sudden occlusion of the supplying artery. Here we show that, in a mouse model of permanent ischemic stroke, lipid-ligand conjugated DNA/RNA heteroduplex oligonucleotide (lipid-HDO) was unexpectedly delivered 9.6 times more efficiently to the ischemic area of the brain than to the contralateral non-ischemic brain and achieved robust gene knockdown and change of stroke phenotype, despite a 90% decrease in cerebral blood flow in the 3 h after occlusion. This delivery to neurons was mediated via receptor-mediated transcytosis by lipoprotein receptors in brain endothelial cells, the expression of which was significantly upregulated after ischemia. This study provides proof-of-concept that lipid-HDO is a promising gene-silencing technology for stroke treatment in the hyperacute stage.

Quantitative Model Analysis and Simulation of Pharmacokinetics and Metastasis-Associated Lung Adenocarcinoma 1 RNA Knockdown Effect After Systemic Administration of Cholesterol-Conjugated DNA/RNA Heteroduplex Oligonucleotide Crossing Blood-Brain Barrier of Mice.

The cholesterol-conjugated heteroduplex oligonucleotide (Chol-HDO) is a double-stranded complex; it comprises an antisense oligonucleotide (ASO) and its complementary strand with a cholesterol ligand. Chol-HDO is a powerful tool for achieving target RNA knockdown in the brains of mice after systemic injection. Here, a quantitative model analysis was conducted to characterize the relationship between the pharmacokinetics (PK) and pharmacodynamics (PD), non-coding RNA metastasis-associated lung adenocarcinoma 1 (Malat1) RNA, of Chol-HDO, in a time-dependent manner. The established PK model could describe regional differences in the observed brain concentration-time profiles. Incorporating the PD model enabled the unique knockdown profiles in the brain to be explained in terms of the time delay after single dosing and enhancement following repeated dosing. Moreover, sensitivity analysis of PK exposure/persistency, target RNA turnover, and knockdown potency identified key factors for the efficient and sustained target RNA knockdown in the brain. The simulation of an adequate dosing regimen quantitatively supported the benefit of Chol-HDO in terms of achieving a suitable dosing interval. This was achieved via sufficient and sustained brain exposure and subsequent strong and sustained target RNA knockdown in the brain, even after systemic injection. The present study provides new insights into drug discoveries and development strategies for HDO in patients with neurogenic disorders. SIGNIFICANCE STATEMENT: The quantitative model analysis presented here characterized the PK/PD relationship of Chol-HDO, enabled its simulation under various conditions or assumptions, and identified key factors for efficient and sustained RNA knockdown, such as PK exposure and persistency. Chol-HDO appears to be an efficient drug delivery system for the systemic administration of desired drugs to brain targets.

Biodistribution and delivery of oligonucleotide therapeutics to the central nervous system: Advances, challenges, and future perspectives.

Considerable advances have been made in the research and development of oligonucleotide therapeutics (OTs) for treating central nervous system (CNS) diseases, such as psychiatric and neurodegenerative disorders, because of their promising mode of action. However, due to the tight barrier function and complex physiological structure of the CNS, the efficient delivery of OTs to target the brain has been a major challenge, and intensive efforts have been made to overcome this limitation. In this review, we summarize the representative methodologies and current knowledge of biodistribution, along with the pharmacokinetic/pharmacodynamic (PK/PD) relationship of OTs in the CNS, which are critical elements for the successful development of OTs for CNS diseases. First, quantitative bioanalysis methods and imaging-based approaches for the evaluation of OT biodistribution are summarized. Next, information available on the biodistribution profile, distribution pathways, quantitative PK/PD modeling, and simulation of OTs following intrathecal or intracerebroventricular administration are reviewed. Finally, the latest knowledge on the drug delivery systems to the brain via intranasal or systemic administration as noninvasive routes for improved patient quality of life is reviewed. The aim of this review is to enrich research on the successful development of OTs by clarifying OT distribution profiles and pathways to the target brain regions or cells, and by identifying points that need further investigation for a mechanistic approach to generate efficient OTs.

Brain microvascular endothelial cells derived from human induced pluripotent stem cells as in vitro model for assessing blood-brain barrier transferrin receptor-mediated transcytosis.

The blood-brain barrier (BBB), a selective barrier formed by brain microvascular endothelial cells (BMEC), represents a major challenge for the efficient accumulation of pharmaceutical drugs into the brain. The receptor-mediated transcytosis (RMT) has recently gained increasing interest for pharmaceutical industry as it shows a great potential to shuttle large-sized therapeutic cargos across the BBB. Confirming the presence of the RMT pathway by BMEC is therefore important for the screening of peptides or antibody libraries that bind RMT receptors. Herein, a comparative study was performed between a human cell line of BMEC (HBEC) and human induced pluripotent stem cells-derived BMEC-like cells (hiPS-BMEC). The significantly higher gene and protein expressions of transporters and tight junction proteins, excepting CD31 and VE-cadherin were exhibited by hiPS-BMEC than by HBEC, suggesting more biomimetic BBB features of hiPS-BMEC. The presence and functionality of transferrin receptor (TfR), known to use RMT pathway, were confirmed using hiPS-BMEC by competitive binding assays and confocal microscopy observations. Finally, cysteine-modified T7 and cysteine modified-Tfr-T12 peptides, previously reported to be ligands of TfR, were compared regarding their permeability using hiPS-BMEC. The hiPS-BMEC could be useful for the identification of therapeutics that can be transported across the BBB using RMT pathway.

Utility of Göttingen minipigs for the prediction of human pharmacokinetic profiles after intravenous drug administration.

Göttingen minipigs are increasingly used to evaluate the pharmacokinetic (PK) profiles of drug candidates. However, their accuracy in predicting human PK parameters is unclear. In this study, we investigated the utility of Göttingen minipigs for predicting human PK profiles. We evaluated the PK parameters of 30 compounds with diverse metabolic pathways after intravenous administration in minipigs. Human total clearance (CLtotal) was corrected using the blood to plasma ratio, and the volume of distribution at steady state (Vd(ss)) was corrected with plasma unbound fraction (fup). CLtotal and Vd(ss) were predicted using single-species allometric scaling using data from minipigs and other reported animal models (monkeys, human liver chimeric mice, and rats). The predicted values were compared with actual values reported in humans. Göttingen minipig were superior to rats because of their better predictability of Vd(ss) and CLtotal, as represented by lower absolute average fold error values. However, their predictability for Vd(ss) was inferior to monkey and human liver chimeric mice. Prediction of CLtotal from blood-based minipig data showed excellent correlation with human data, and comparable predictability with monkey and human liver chimeric mice. Thus, Göttingen minipigs can be used as an optional model for preclinical pharmaceutical research for predicting human CLtotal.

Cholesterol-functionalized DNA/RNA heteroduplexes cross the blood-brain barrier and knock down genes in the rodent CNS.

Achieving regulation of endogenous gene expression in the central nervous system (CNS) with antisense oligonucleotides (ASOs) administered systemically would facilitate the development of ASO-based therapies for neurological diseases. We demonstrate that DNA/RNA heteroduplex oligonucleotides (HDOs) conjugated to cholesterol or α-tocopherol at the 5' end of the RNA strand reach the CNS after subcutaneous or intravenous administration in mice and rats. The HDOs distribute throughout the brain, spinal cord and peripheral tissues and suppress the expression of four target genes by up to 90% in the CNS, whereas single-stranded ASOs conjugated to cholesterol have limited activity. Gene knockdown was observed in major CNS cell types and was greatest in neurons and microglial cells. Side effects, such as thrombocytopenia and focal brain necrosis, were limited by using subcutaneous delivery or by dividing intravenous injections. By crossing the blood-brain barrier more effectively, cholesterol-conjugated HDOs may overcome the limited efficacy of ASOs targeting the CNS without requiring intrathecal administration.

Biodistribution studies for cell therapy products: Current status and issues.

Information on the biodistribution (BD) of cell therapy products (CTPs) is essential for prediction and assessment of their efficacy and toxicity profiles in non-clinical and clinical studies. To conduct BD studies, it is necessary to understand regulatory requirements, implementation status, and analytical methods. This review aimed at surveying international and Japanese trends concerning the BD study for CTPs and the following subjects were investigated, which were considered particularly important: 1) comparison of guidelines to understand the regulatory status of BD studies in a global setting; 2) case studies of the BD study using databases to understand its current status in cell therapy; 3) case studies on quantitative polymerase chain reaction (qPCR) used primarily in non-clinical BD studies for CTPs; and 4) survey of imaging methods used for non-clinical and clinical BD studies. The results in this review will be a useful resource for implementing BD studies.

Highly specific, quantitative polymerase chain reaction probe for the quantification of human cells in cynomolgus monkeys.

Quantification of human cells may be performed using quantitative polymerase chain reaction (qPCR). In preclinical studies, the human Alu sequence is widely used as biomarker for human DNA. However, because the Alu gene is shared by primates, its use is limited to non-primate studies. The biodistribution of human cells in primates is also necessary for translational studies. Therefore, we aimed to design a novel, human-specific primer/probe that enables the quantification of human cells in primates and other animal models. A novel primer/probe set was successfully designed based on highly repetitive LINE1 sequences. qPCR efficiency (94.95-99.21%) and linearity of calibration curves (r2 = 0.996-0.999) were confirmed in tissue homogenates of cynomolgus monkey. The lower limit of detection was 10 cells per 15-mg tissue sample, a sensitivity that is equivalent to existing Alu primers/probes. The set was also effective in other animal models such as mice, rabbits, pigs, and common marmosets. To our knowledge, this is the first study describing the successful design of a human-specific qPCR primer/probe for human cell quantification in various animals, including non-human primates, using LINE1 sequence. The excellent selectivity, sensitivity, and versatility of the LINE1 primers/probes make it a promising quantification tool in preclinical biodistribution studies.

Quantitative PCR methodology with a volume-based unit for the sophisticated cellular kinetic evaluation of chimeric antigen receptor T cells.

Although the cellular kinetics of chimeric antigen receptor T (CAR T) cells are expressed in units of copies/µg gDNA, this notation carries the risk of misrepresentation owing to dramatic changes in blood gDNA levels after lymphocyte-depleting chemotherapy and rapid expansion of CAR T cells. Therefore, we aimed to establish a novel qPCR methodology incorporating a spike-in calibration curve that expresses cellular kinetics in units of copies/µL blood, as is the case for conventional pharmacokinetic studies of small molecules and other biologics. Dog gDNA was used as an external control gene. Our methodology enables more accurate evaluation of in vivo CAR T-cell expansion than the conventional approach; the unit "copies/µL blood" is therefore more appropriate for evaluating cellular kinetics than the unit "copies/µg gDNA." The results of the present study provide new insights into the relationship between cellular kinetics and treatment efficacy, thereby greatly benefiting patients undergoing CAR T-cell therapy.

Quantitative application of flow cytometry for the analysis of circulating human T cells: A preclinical pharmacokinetic study.

As the application of flow cytometry to a quantitative pharmacokinetic study with adoptive T cell therapy is new, we aimed to investigate the quantitativity of flow cytometry-based analysis for the pharmacokinetic assessment of circulating human T cells in a preclinical study. We evaluated the selectivity, linearity, accuracy, precision, and sensitivity of flow cytometry-based analysis for human CD8+ T cells in immunodeficient mouse blood. The CD3/8/45-positive cell population was successfully distinguished from the negative population. Linear regression analysis for the calibration curve showed good linearity and recovery was approximately 100%. Acceptable inter- and intra-day precision and accuracy were observed and the lower limit of quantification (30 cells/50 µL) was validated with acceptable precision and accuracy. Blood concentrations of human CD8+ T cells in immunodeficient mice were then evaluated after administration using this method and the time-concentration profile of human T cells in mice was successfully assessed. The present study is the first to clarify the quantitativity of flow cytometry-based analysis for circulating human T cells in animals. The concept of the present study would be applicable to quantitative pharmacokinetics/efficacy or safety analysis of adoptive T cell therapy.

Development of a bioanalytical method for circulating human T cells in animals using Arthrobacter luteus-based quantitative polymerase chain reaction and its application in preclinical biodistribution studies.

INTRODUCTION: In the development of cell therapy products for human use, studies on the biodistribution of transplanted cells in animals are important for assessing the safety and efficacy of these products. Although a few reports have described the biodistribution of human cells in animals using Arthrobacter luteus-based-polymerase chain reaction (Alu-PCR), most have used genomic DNA or synthetic oligonucleotide as calibrators, as opposed to actual cells. In addition, bioanalytical variability in the quantification of cells with respect to specificity, selectivity, accuracy, and precision, has not been evaluated. Accordingly, in this study, we validated the utility of this bioanalytical method for human T cells in mice to establish assay performance using cells as a calibrator. METHODS: A standard curve was constructed for the addition of cell lysates to mouse tissues and blood, and DNA was extracted. Alu-PCR was applied for the quantification of human peripheral blood CD8+ T cells in mice. To determine assay performance, we evaluated accuracy, precision, selectivity, specificity, and stability. In vivo cell kinetics and biodistribution were investigated based on intravenous administration of human T cells to mice. RESULTS: Alu-PCR enabled us to specifically detect human T cells in mouse blood and tissues. The lower detection limit of Alu-PCR was 10 cells/15 mg tissue (7.5 mg for spleen and lung) or cells/50 µL blood. Given that PCR threshold cycle (Cq) values among mouse samples (blood, liver spleen, lung, heart, and kidney) show slight variation, calibration curves should be generated using the same tissue as used for the assay. Most coefficients of variation in the assay were within 30%. The cell kinetics of administered human T cells in mice were successfully evaluated using the established Alu-qPCR. CONCLUSIONS: The Alu-PCR technique developed in this study showed sufficient specificity and sensitivity in detecting human peripheral blood CD8+ T cells in mice. This technique, which targets the primate-specific Alu gene, is applicable for quantifying transplanted human cells in animals without the necessity of cell labeling. The data presented herein will be useful for standardizing bioanalytical approaches in biodistribution studies of cell therapy products.

Anti-sortilin1 Antibody Up-Regulates Progranulin via Sortilin1 Down-Regulation.

Progranulin (PGRN) haploinsufficiency associated with loss-of-function mutations in the granulin gene causes frontotemporal dementia (FTD). This suggests that increasing PGRN levels could have promising therapeutic implications for patients carrying GRN mutations. In this study, we explored the therapeutic potential of sortilin1 (SORT1), a clearance receptor of PGRN, by generating and characterizing monoclonal antibodies against SORT1. Anti-SORT1 monoclonal antibodies were generated by immunizing Sort1 knockout mice with SORT1 protein. The antibodies were classified into 7 epitope bins based on their competitive binding to the SORT1 protein and further defined by epitope bin-dependent characteristics, including SORT1-PGRN blocking, SORT1 down-regulation, and binding to human and mouse SORT1. We identified a positive correlation between PGRN up-regulation and SORT1 down-regulation. Furthermore, we also characterized K1-67 antibody via SORT1 down-regulation and binding to mouse SORT1 in vivo and confirmed that K1-67 significantly up-regulated PGRN levels in plasma and brain interstitial fluid of mice. These data indicate that SORT1 down-regulation is a key mechanism in increasing PGRN levels via anti-SORT1 antibodies and suggest that SORT1 is a potential target to correct PGRN reduction, such as that in patients with FTD caused by GRN mutation.

Utility of hairless rats as a model for predicting transdermal pharmacokinetics in humans.

This study investigated the use of HWY hairless rats to predict human plasma concentrations of drugs following dermal application.Utilizing a deconvolution method, pharmacokinetic parameters (e.g. in vivo absorption rates) were determined for six transdermal drugs in hairless rats. Obtained data were used to simulate the human plasma concentration-time profiles of transdermal drugs, which were then compared with clinical data in humans. Because hairless rats have lower hair follicle density than do humans, the impact of hair follicle density on skin permeability to hydrophilic compounds was also evaluated.Pharmacokinetic parameters showed low intra-individual variability in hairless rats. Simulated concentration profiles for compounds with logarithm of the octanol-water partition coefficient exceeding two were comparable to clinical data, but simulated concentration profiles for hydrophilic compounds (i.e. bisoprolol and nicotine) at maximum concentration differed from clinical data by more than two-fold. Finally, in vitro permeability to bisoprolol and nicotine was higher in human skin than in hairless rat skin, but hair follicle plugging reduced human skin permeability.In vivo skin absorption data from HWY hairless rats help to predict human concentration profiles for lipophilic compounds. However, the data underestimate human absorption of hydrophilic compounds.

Direct Drug Delivery of Low-Permeable Compounds to the Central Nervous System Via Intranasal Administration in Rats and Monkeys.

PURPOSE: Intranasal administration enhances drug delivery to the brain by allowing targeted-drug delivery. Here, we investigated the properties that render a compound suitable for intranasal administration, and the differences between rodents and non-human primates in delivery to the brain. METHODS: The delivery of 10 low-permeable compounds to the brain, including substrates of efflux drug transporters expressed in the blood-brain barrier (didanosine, metformin, zolmitriptan, cimetidine, methotrexate, talinolol, ranitidine, atenolol, furosemide, and sulpiride) and two high-permeable compounds (ropinirole and midazolam) was evaluated following intranasal and intravenous administration in rats. Six of the 12 compounds (metformin, cimetidine, methotrexate, talinolol, sulpiride, and ropinirole) were also evaluated in monkeys, which have a similar nasal cavity anatomical structure to humans. RESULTS: In rats, most of the low-permeable compounds displayed an obvious increase in the brain/plasma concentration ratio (Kp) by intranasal administration (despite their substrate liability for efflux drug transporters); this was not observed with the high-permeable compounds. Similarly, intranasal administration increased Kp for all low-permeable compounds in monkeys. CONCLUSIONS: Compound permeability is a key determinant of Kp increase by intranasal administration. This route of administration is more beneficial for low-permeable compounds and enhances their delivery to the brain in rodents and non-human primates.

Midazolam suppresses the lipopolysaccharide-stimulated immune responses of human macrophages via translocator protein signaling.

BACKGROUND: Benzodiazepines are widely used for anesthesia and sedation and have immunomodulatory properties that may negatively influence clinical outcomes; however, the cellular targets and intermediary signaling pathways involved are unclear. We examined the immunomodulatory effects of the benzodiazepine midazolam on human macrophages and associated molecular mechanisms. METHODS: We analyzed effects of midazolam pretreatment on lipopolysaccharide (LPS)-induced upregulation of the costimulatory molecule CD80 and secretion of the pro-inflammatory factors interleukin-6 (IL-6), tumor necrosis factor-α, interleukin-10, and nitric oxide (NO) in the human monocyte-macrophage cell line THP-1 and in peripheral monocyte-derived macrophages (PMDMs). The effects of midazolam on NF-κB, IκBα protein, and mitogen-activated protein kinase (MAPK) activation were analyzed in THP-1 cells. We analyzed the involvement of translocator protein (TSPO) in the immunomodulatory effects of midazolam using TSPO ligands. The role of TSPO was investigated using THP-1 cells overexpressing TSPO and THP-1 cells with TSPO knockdown through transfection with small interfering RNA for TSPO. RESULTS: Midazolam suppressed LPS-induced upregulation of CD80 and release of IL-6 and NO in THP-1 cells and PMDMs. Additionally, midazolam suppressed the activation of NF-κB/AP-1 and MAPKs in human THP-1 cells. The assessed synthetic TSPO ligands showed the same inhibitory effects on macrophage activation as midazolam. Macrophages overexpressing TSPO exhibited enhanced susceptibility to immunosuppression by midazolam, and macrophages lacking TSPO expression exhibited reduced effects of midazolam. CONCLUSION: Midazolam inhibits LPS-stimulated immune responses in human macrophages by activating TSPO signaling. Suppression of macrophage activity may contribute to deleterious side effects of benzodiazepines reported in critically ill patients.

Impact of P-Glycoprotein on Intestinal Absorption of an Inhibitor of Apoptosis Protein Antagonist in Rats: Mechanisms of Nonlinear Pharmacokinetics and Food Effects.

PURPOSE: This study was designed to investigate the effects of P-glycoprotein (P-gp) expressed in the intestine on the nonlinear pharmacokinetics (PK) of T-3256336, an inhibitor of apoptosis protein inhibitor, and food effects on its bioavailability in rats. METHODS: To investigate the factors that contribute to nonlinear PK of T-3256336 in the intestine and liver, rats double-cannulated in the portal vein and femoral artery (PS rats) were used. FaFg (Fa, absorption ratio; Fg, intestinal availability) and hepatic availability (Fh) were simultaneously evaluated based on the difference between the portal and systemic blood area under the concentration-time curve (AUC). Elacridar was used as a P-gp inhibitor to assess the impact of P-gp on the intestinal absorption. RESULTS: After oral administration of T-3256336 to PS rats at 3 and 30 mg/kg, FaFg value increased with dose escalation, whereas Fh value was nearly constant. Moreover, co-administration of elacridar resulted in a 5-fold increase in the FaFg value at 3 mg/kg. The AUC value of T-3256336 under fed conditions was 3-fold lower than that under fasted conditions. This food effect on the oral bioavailability (BA) was reduced by concomitant administration of elacridar. CONCLUSION: P-gp expressed in the intestine would cause nonlinear PK and a food effect on BA of T-3256336 in rats.