Preclinical Pharmacokinetic Data Research Articles

Liposome Formulation of Fullerene-Based Molecular Diagnostic and Therapeutic Agents

Fullerene medicine is a new but rapidly growing research subject. Fullerene has a number of desired structural, physical and chemical properties to be adapted for biological use including antioxidants, anti-aging, anti-inflammation, photodynamic therapy, drug delivery, and magnetic resonance imaging contrast agents. Chemical functionalization of fullerenes has led to several interesting compounds with very promising preclinical efficacy, pharmacokinetic and safety data. However, there is no clinical evaluation or human use except in fullerene-based cosmetic products for human skincare. This article summarizes recent advances in liposome formulation of fullerenes for the use in therapeutics and molecular imaging.

Sensitive liquid chromatography/mass spectrometry methods for quantification of pomalidomide in mouse plasma and brain tissue

Pomalidomide was recently approved by the United States Food and Drug Administration for the treatment of patients with relapsed or refractory multiple myeloma who have received at least two prior therapies. As pomalidomide is increasingly evaluated in other diseases and animal disease models, this paper presents development and validation of a sensitive liquid chromatography tandem mass spectrometry assay for quantification of pomalidomide in mouse plasma and brain tissue to fill a gap in published preclinical pharmacokinetic and analytical data with this agent. After acetonitrile protein precipitation, pomalidomide and internal standard, hesperitin, were separated with reverse phase chromatography on a C-18 column with a gradient mobile phase of water and acetonitrile with 0.1% fomic acid. Positive atmospheric pressure chemical ionization mass spectrometry with selected reaction monitoring mode was applied to achieve 0.3–3000nM (0.082–819.73ng/mL) linear range in mouse plasma and 0.6–6000pmol/g in brain tissue. The within- and between-batch accuracy and precision were less than 15% for both plasma and brain tissue. The method was applied to measure pomalidomide concentrations in plasma and brain tissue in a pilot mouse pharmacokinetic study with an intravenous dose of 0.5mg/kg. This assay can be applied for thorough characterization of pomalidomide pharmacokinetics and tissue distribution in mice.

Impaired Drug Absorption Due to High Stomach pH: A Review of Strategies for Mitigation of Such Effect To Enable Pharmaceutical Product Development

Published reports have clearly shown that weakly basic drugs which have low solubility at high pH could have impaired absorption in patients with high gastric pH thus leading to reduced and variable bioavailability. Since such reduction in exposure can lead to significant loss of efficacy, it is imperative to (1) understand the behavior of the compound as a function of stomach pH to inform of any risk of bioavailability loss in clinical studies and (2) develop a robust formulation which can provide adequate exposure in achlorhydric patients. In this review paper, we provide an overview of the factors that can cause high gastric pH in human, discuss clinical and preclinical pharmacokinetic data for weak bases under conditions of normal and high gastric pH, and give examples of formulation strategies to minimize or mitigate the reduced absorption of weakly basic drugs under high gastric pH conditions. It should be noted that the ability to overcome pH sensitivity issues is highly compound dependent and there are no obvious and general solutions to overcome such effect. Further, we discuss, along with several examples, the use of biopharmaceutical tools such as in vitro dissolution, absorption modeling, and gastric pH modified animal models to assess absorption risk of weak bases in high gastric pH and also the use of these tools to enable development of formulations to mitigate such effects.

Clinical pharmacokinetics (PK) and translational PK-pharmacodynamic (PD) modeling and simulation to predict antitumor response of various dosing schedules to guide the selection of a recommended phase II dose (RP2D) and schedule for the investigational agent MLN0128.

2567 Background: MLN0128 (INK128) is an investigational oral, potent, and highly selective inhibitor of mammalian target of rapamycin complex 1 and 2 (mTORC1/2) currently in clinical investigation. In the phase1 study INK128-001, MLN0128 was administered once daily (QD), once weekly (QW), QDx3D/week, and QDx5D/week, with respective MTDs of 6, 40, 16, and 10 mg. To guide selection of dose/schedule for further investigation, PD modulation in skin (pS6, p4EBP1, pNDRG1, pPRAS40) was put into context of clinical PK in INK128-001. A preclinical translational dynamic-PK efficacy model was used to describe the relationship and determine PK drivers of efficacy in tumor xenograft models. This model was implemented using human PK parameters to predict tumor volume-time curves, which was utilized to help determine the optimal MLN0128 dose/schedule. Methods: Phoenix NLME v1.1 was used for compartmental modeling of clinical and preclinical PK data, and modeling the preclinical PK-efficacy relationship of MLN0128. PD activity in skin was measured by immunohistochemistry, reported as H scores. Tumor growth curves were simulated using NONMEM v7.2; predicted tumor growth curves were plotted in S-Plus v8.1. Results: Clinical skin PD data suggests exposure dependent inhibition of pS6, and p4EBP1. A two compartment PK model adequately described the PK characteristics of MLN0128 [mean (%CV) ka: ~5.305 h-1 (114), k12: ~0.490 h-1(85), k21: ~0.67 h-1(69), V/F: ~180 L (44), Tlag: 0.317 h (73)]. Simulation of human tumor volume-time curves suggest efficacy is dependent on schedule and that MLN0128 administered in more frequent schedules (QD, QDx5D) provides stronger antitumor effect vs less frequent schedules (QW, QDx3D). Conclusions: The results indicate that per unit MLN0128 plasma exposure, QD and QDx5D may be optimal in comparison with QDx3D and QW dosing. However, these results will also need to be put into context with the overall safety profile and respective MTDs and RP2Ds for each schedule with their resultant achievable total cycle dose by schedule. Clinical trial information: NCT01058707.

Silibinin hemisuccinate binding to proteins in plasma and blood cell/plasma partitioning in mouse, rat, dog and man in vitro

The determination of plasma protein binding and blood cell/plasma partitioning is important when prescribing silibinin hemisuccinate to patients concomitantly receiving other drugs and to estimate the safety margins of exposure at the no observed adverse events levels determined from toxicity studies conducted in rats and dogs. Protein binding of [3'-14C]silibinin hemisuccinate (1, 10, 100, 1000 and 4000 μM) was evaluated in human, dog, rat and mouse plasma by ultrafiltration. Blood cell/plasma partitioning in all these species was also determined. Silibinin hemisuccinate is highly bound to plasma proteins with percentage binding ranging from 94.3% to 97.8%. Its association with blood cells was negligible (<7%) in all species. The degree of protein binding was concentration independent up to the pharmacologically effective concentration of 100 μM. The blood cell/plasma partitioning indicates that distribution into blood cells is not an important feature for the disposition of silibinin hemisuccinate. No corrections for fraction unbound are needed when comparing human and preclinical pharmacokinetic and pharmacodynamic data at pharmacological doses, and it is appropriate to analyze plasma as opposed to whole blood for the determination of silibinin hemisuccinate concentrations.

Application of In Silico, In Vitro and Preclinical Pharmacokinetic Data for the Effective and Efficient Prediction of Human Pharmacokinetics

In the present age of pharmaceutical research and development, focused delivery of decision making data is more imperative than ever before. Resulting from several years' success, failure and consequential learning, this article also proffers advice and guidance on which in vitro and in vivo experiments to perform to facilitate efficient and cost-effective pursuit of candidate drugs with acceptable human pharmacokinetic profiles. Predictive in silico models are important in directing design toward compounds with the highest probability of having suitable DMPK properties rather than in predicting human pharmacokinetics per se, and the value and utility of such approaches are reviewed with the intention of providing direction to DMPK scientists. Relating to absorption, distribution, elimination and effective half-life, strategies are described to provide direction in commonly encountered scenarios.

Accelerator mass spectrometry of ultra-small samples with applications in the biosciences

An overview is presented covering the biological accelerator mass spectrometry activities at Uppsala University. The research utilizes the Uppsala University Tandem laboratory facilities, including a 5MV Pelletron tandem accelerator and two stable isotope ratio mass spectrometers. In addition, a dedicated sample preparation laboratory for biological samples with natural activity is in use, as well as another laboratory specifically for 14C-labeled samples. A variety of ongoing projects are described and presented. Examples are: (1) Ultra-small sample AMS. We routinely analyze samples with masses in the 5–10μgC range. Data is presented regarding the sample preparation method, (2) bomb peak biological dating of ultra-small samples. A long term project is presented where purified and cell-specific DNA from various part of the human body including the heart and the brain are analyzed with the aim of extracting regeneration rate of the various human cells, (3) biological dating of various human biopsies, including atherosclerosis related plaques is presented. The average built up time of the surgically removed human carotid plaques have been measured and correlated to various data including the level of insulin in the human blood, and (4) In addition to standard microdosing type measurements using small pharmaceutical drugs, pre-clinical pharmacokinetic data from a macromolecular drug candidate are discussed.

Abstract A8: Combating adaptive ERBB3-mediated resistance to ERBB2 inhibitors: In Silico optimization of MM-111 and lapatinib dosing regimens

Abstract Upregulation of ErbB3 (HER3) signaling has been implicated as a resistance mechanism to targeted ErbB1 and ErbB2 (HER1/2) inhibitors, limiting the efficacy of drugs such as lapatinib (Tykerb®), gefitinib (Iressa©), cetuximab (Erbitux®), and trastuzumab (Herceptin©) through compensatory activation of downstream PI3K/AKT and MAPK/ERK cascades. Combining ErbB1/2 inhibitors with novel ERBB3 targeted agents could therefore combat, or preempt this adaptive resistance mechanism. Doing so in a rational manner however requires selecting appropriate drug combinations, and designing dosing regimens, which maximize therapeutic synergy. MM-111 is a novel bi-specific antibody against ErbB3, using an ErbB2 targeting arm to enhance avidity and inhibitor potency in HER2+ tumors. Pre-clinical data shows that combining MM-111 with the ErbB2 inhibitors lapatinib and/or trastuzumab results in synergistic tumor growth inhibition. We desired to leverage our preclinical signaling, pharmacokinetic (PK), pharmacodynamic (PD), and efficacy data to optimize dosing regimens of MM-111 combination therapies. To do so, we developed an integrated a mathematical model of MM-111′s mechanism of action, incorporating ErbB-family signal transduction, transcriptional regulation through FOXO, and resulting tumor proliferation, with pre-clinical PK information. This integrated model was trained using in vitro dose response data from BT-474-M3 and HER2 overexpressing MCF7 cells treated with the ErbB3 ligand heregulin, plus drug combinations. Levels of phospho- and total ErbB1, 2, 3, AKT, and ERK were quantified using ELISA, and cell growth effects quantified using the Cell Titer Glow assay. This was then integrated with a 2-compartment PK-model, to predict PD profiles and tumor growth effects in murine xenografts treated with the drug combinations. The model accurately predicted ERBB3 protein upregulation in response to ErbB2 inhibitor treatment (lapatinib and/or trastuzumab) in vivo, maintaining downstream AKT and ERK activity and supporting tumor growth. MM-111 inhibited compensatory signaling through phospho-ErbB3, thus blocking AKT and ERK re-activation, resulting in synergistic tumor growth inhibition. We are now using our computational model to screen alternate combination dosing regimens in silico with the goal of identifying theoretically optimal schedules that we will validate in vivo. In particular, we are investigating novel intermittent high-dose lapatinib treatment in combination with MM-111. These results will be used to design phase I/II clinical trials of MM-111 given with lapatinib. While this study design is focused on MM-111 combined with lapatinib, the strategy is generally applicable to molecular targeted therapeutics given alone or in combination. By integrating PK/PD with known molecular mechanisms of action, we are able to rationally design combination treatment strategies to combat adaptive resistance.

Abstract C118: Optimization of MM-111 and lapatinib dosing regimens using mathematical modeling and quantitative biology.

Abstract Designing therapeutically optimal dosing regimens for targeted biologic therapies is an open problem in translational oncology. There are at least two underlying reasons for this problem: First, biologics are generally well tolerated so it is not guaranteed that the maximum tolerated dose (MTD) will be observed in a Phase 1 dose escalation; and second, since targeted therapies work in only a subset of patients, there will be limited efficacy data available to determine a Phase 2 dose. This problem is further compounded by the use of combination drug treatments. MM-111 is a novel bispecific antibody against ErbB3 (HER3), using an ErbB2 (HER2) targeting arm to enhance avidity and inhibitor potency. Pre-clinical data shows that combining MM-111 with the ErbB2 inhibitor lapatinib (Tykerb®) results in synergistic tumor growth inhibition. We desired to leverage our pre-clinical modeling, signaling, pharmacokinetic (PK), pharmacodynamic (PD), and efficacy data to optimize dosing regimens of the combination therapy. While this study design is focused on MM-111 combined with lapatinib, this strategy is generally applicable to molecular targeted therapeutics given alone or in combination. Our approach was to integrate a mathematical model of the MM-111 and lapatinib's mechanism of action, incorporating ErbB-family signal transduction, transcriptional regulation, and resulting tumor proliferation, with pre-clinical PK models of the two drugs. This integrated model was trained using in vitro dose response data from BT-474-M3 cells treated with the ErbB3 ligand heregulin plus combinations of the two drugs. Levels of phospho- and total ErbB3, ERbB2, AKT, ERK, and p27 were quantified using ELISA, and cell growth effects quantified using the Cell Titer Glow assay. This was then integrated with a 2-compartment PK-model, to predict PD profiles and tumor growth effects in murine xenografts treated with the drug combinations. After validation of our model with these initial in vivo studies, we designed therapeutically optimal dosing schedules in silico. The novel dosing strategies are now being validated in xenografts, and will help inform future clinical studies. By integrating PK/PD with known molecular mechanisms of action, we are able to rationally design combination treatment strategies to maximize therapeutic synergy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C118.

Preclinical evaluation of drug in adhesive type ondansetron loaded transdermal therapeutic systems

The in vivo assessment of percutaneous absorption of molecules is a very important step in the evaluation of any transdermal drug delivery system and a key goal in the design and optimization of transdermal dosage forms lies in understanding the factors that determine a good in vivo performance. The objective of the present investigation is to assess the in vivo performance of an optimized transdermal system of ondansetron hydrochloride in rabbits and to generate preclinical pharmacokinetic data. The pharmacokinetic performance of ondansetron hydrochloride following intravenous and transdermal administration was studied in rabbits following non compartmental pharmacokinetic analysis. The pharmacokinetic parameters such as area under the curve, elimination rate constant, elimination half life and mean residence time, were significantly (P < 0.01) different following transdermal administration compared to intravenous administration. Absolute bioavailability of the transdermal film studied was estimated to be 0.37 ± 0.06 which is quite low because a very high drug loading in the transdermal system was essential to achieve sufficient thermodynamic activity for transdermal permeation. Though in vivo studies in rabbits are found promising, investigations in healthy human subjects are essential to confirm the performance of the developed transdermal films.

Paclitaxel poliglumex for ovarian cancer

Introduction: Despite an 80% initial response rate to the standard primary regimen of carboplatin and paclitaxel, most women with ovarian cancer will experience recurrence with incurable disease within five years and will be treated with several successive palliative regimens. Consequently, a significant need exists for chemotherapeutic agents, which are not only clinically efficacious, but have acceptable side-effect profiles. Paclitaxel poliglumex (PPX) is a recently developed taxane in which paclitaxel is conjugated to poly(l-glutamic acid), which renders it water soluble, reduces hypersensitivity reactions and preferentially targets it to the tumor.Areas covered: This review covers pre-clinical pharmacokinetic data and key Phase I and II clinical trial results in ovarian cancer.Expert opinion: While PPX is active in ovarian cancer, it is unclear at present whether it offers significant benefit in terms of its side-effect profile or outcomes over a standard taxane-based regimen as first-line therapy, or what role it will have in maintenance therapy as studies are ongoing.

Risk Assessment in Extrapolation of Pharmacokinetics from Preclinical Data to Humans

Prediction of pharmacokinetics in humans is essential for translating preclinical data to humans and planning safe and efficient clinical studies. The performance of various methods in extrapolation of preclinical pharmacokinetic data to humans is usually benchmarked by the fraction of predictions falling within a predefined interval that is centred on the value observed clinically. Recently, such an approach was used to compare physiologically based pharmacokinetic (PBPK) modelling and allometry in predicting the pharmacokinetics of a set of compounds in humans. Here, we present an analysis of the same dataset, focusing on predictions falling outside such a relatively narrow and centrally located interval. These are the main risk determinants in extrapolation of preclinical pharmacokinetic data to humans and should therefore be thoroughly understood in a risk mitigation approach to the design of early-phase human studies. Values that had been previously predicted by allometry and by PBPK modelling in terms of the apparent total clearance after oral administration, apparent volume of distribution, area under the plasma concentration-time curve, maximum plasma drug concentration, time to reach the maximum plasma concentration and terminal elimination half-life in humans were used to generate a log-transformed dataset of predicted/observed ratios. The probabilities of mispredicting the values of these pharmacokinetic parameters using PBPK modelling and allometry were estimated by a bootstrap procedure on this set of ratios. Our results, albeit from a limited dataset, indicated that although PBPK modelling yielded higher fractions of satisfactory predictions than allometry, both methodologies were associated with a significant and occasionally high probability of obtaining mispredictions of pharmacokinetic parameters by factors of >2, >3 and >10. In line with recent proposals to extend the goals of early-phase human studies beyond safety and tolerability, and considering the need to mitigate risks in studies dealing with novel and highly potent drug candidates, we discuss these results in a pharmacological context. Concise recommendations are given regarding the use of allometric and PBPK extrapolation methodologies in the translation process. The results presented here should alert clinical investigators to the limitations inherent in all approaches to prediction of human pharmacokinetics from preclinical data. We propose an adaptive approach to the design of early-phase clinical studies, particularly when dealing with compounds that are characterized by novel and only partially understood pharmacological profiles.

Radiation dose estimation using preclinical imaging with 124I-metaiodobenzylguanidine (MIBG) PET.

A pretherapy 124I-metaiodobenzylguanidine (MIBG) positron emission tomography (PET)/computed tomography (CT) provides a potential method to estimate radiation dose to normal organs, as well as tumors prior to 131I-MIBG treatment of neuroblastoma or pheochromocytoma. The aim of this work was to estimate human-equivalent internal radiation dose of 124I-MIBG using PET/CT data in a murine xenograft model. Athymic mice subcutaneously implanted with NB1691 cells that express high levels of human norepinephrine transporter (n = 4) were imaged using small animal microPET/CT over 96 h (approximate imaging time points: 0.5, 2, 24, 52, and 96 h) after intravenous administration of 3.07-4.84 MBq of 124I-MIBG via tail vein. The tumors did not accumulate 124I-MIBG to a detectable level. All four animals were considered as control and organ radiation dosimetry was performed. Volumes of interest were drawn on the coregistered CT images for thyroid, heart, lung, liver, kidney, and bladder, and transferred to PET images to obtain pharmacokinetic data. Based on tabulated organ mass distributions for both mice and adult male human, preclinical pharmacokinetic data were extrapolated to their human-equivalent values. Radiation dose estimations for different age groups were performed using the OLINDA/EXM software with modified tissue weighting factors in the recent International Commission on Radiological Protection (ICRP) Publication 103. The mean effective dose from 124I-MIBG using weighting factors from ICRP 103 to the adult male was estimated at 0.25 mSv/MBq. In different age groups, effective doses using values from ICRP 103 were estimated as follows: Adult female: 0.34, 15-yr-old: 0.39 mSv/MBq, 10-yr-old: 0.58 mSv/MBq, 5-yr-old: 1.03 mSv/MBq, 1-yr-old: 1.92 mSv/MBq, and newborn: 3.75 mSv/ MBq. For comparison, the reported effective dose equivalent of 124I-NaI for adult male (25% thyroid uptake, MIRD Dose Estimate Report No. 5) was 6.5 mSv/MBq. The authors estimated human-equivalent internal radiation dose of 124I-MIBG using preclinical imaging data. As a reference, the effective dose estimation showed that 124I-MIBG would deliver less radiation dose than 124I-NaI, a radiotracer already being used in patients with thyroid cancer.

The prediction of human response to ONO‐4641, a sphingosine 1‐phosphate receptor modulator, from preclinical data based on pharmacokinetic–pharmacodynamic modeling

The pharmacokinetic (PK) and pharmacodynamic (PD) parameters of ONO-4641 in humans were estimated using preclinical data in order to provide essential information to better design future clinical studies. The characterization of PK/PD was measured in terms of decreased lymphocyte counts in blood after administration of ONO-4641, a sphingosine 1-phosphate receptor modulator. Using a two-compartment model, human PK parameters were estimated from preclinical PK data of cynomolgus monkey and in vitro human metabolism data. To estimate human PD parameters, the relationship between lymphocyte counts and plasma concentrations of ONO-4641 in cynomolgus monkeys was determined. The relationship between lymphocyte counts and plasma concentrations of ONO-4641 was described by an indirect-response model. The indirect-response model had an I(max) value of 0.828 and an IC(50) value of 1.29 ng/ml based on the cynomolgus monkey data. These parameters were used to represent human PD parameters for the simulation of lymphocyte counts. Other human PD parameters such as input and output rate constants for lymphocytes were obtained from the literature. Based on these estimated human PK and PD parameters, human lymphocyte counts after administration of ONO-4641 were simulated. In conclusion, the simulation of human lymphocyte counts based on preclinical data led to the acquisition of useful information for designing future clinical studies.

Interspecies comparison of the pharmacokinetics and oral bioavailability of 99-357, a potent synthetic trioxane antimalarial compound

The pharmacokinetic data obtained in lower animals is of considerable importance in drug discovery and development. The objective of the present study was to generate in vitro and in vivo preclinical pharmacokinetic data of 99-357, a synthetic trioxane antimalarial, in rats and rabbits and to scale-up the data in order to apply for further studies. The pharmacokinetic profile of 99-357 was investigated after both intravenous and oral dose in rats and rabbits. Oral studies were carried out at three dose levels 6, 12 and 24 mg/kg in rats while in rabbit only one dose level was selected. Both compartmental and non-compartmental approaches were used to calculate the pharmacokinetic parameters following intravenous and oral doses in both the species. The clearance in rat and rabbit was 45–57% and 60–67% respectively of hepatic blood flow. The plasma protein binding in rats was ∼75%. In vitro studies showed high RBC partitioning and low to moderate hepatic clearance. Linearity was observed in terms of dose and AUCs suggesting linear pharmacokinetics at the dose levels studied in rats. The oral bioavailability of compound 99-357 in rat and rabbit at 12 mg/kg dose level was comparable and 39% and 41% respectively.

Abstract 2663: Preclinical pharmacokinetic characterizations and human pharmacokinetic prediction of AMG 900, an orally available small molecule inhibitor of aurora kinases

Abstract Introduction: AMG 900 is a small molecule being developed as an orally administered, highly potent and selective pan-aurora kinase inhibitor. AMG 900 is currently undergoing phase 1 clinical evaluation in patients with advanced solid tumors. The objectives of the studies were to characterize single dose pharmacokinetics (PK) of AMG 900 in preclinical species and use the preclinical PK data to predict its human PK. Methods: Following a single intravenous and oral administration of AMG 900 to mice, rats, dogs, and monkeys, blood samples were collected and processed for plasma by centrifugation. AMG 900 plasma concentrations were determined by LC-MS/MS. Non-compartmental analysis of the concentration - time data was performed to calculate PK parameters of AMG 900. Human PK were predicted based on data from preclinical species using the simple allometric scaling method assuming a human body weight of 60 kg. Results: AMG 900 exhibited low (mouse, monkey and dog) to moderate (rat) clearance in the species evaluated. The volume of distribution at steady state was less than 0.5 L/kg across species. Following intravenous administration, the compound had terminal elimination half-life ranging from 0.6 to 2.4 hours. AMG 900 was well absorbed in fasted animals across species with an oral bioavailability ranging from 31% to 104%. The clearance and volume of distribution at steady state in humans were predicted to be 0.03 L/hr/kg and 0.1 L/kg, respectively, with the predicted half-life to be approximately 2.3 hours. Bioavailability after oral administration of AMG 900 was predicted to be 75%, calculated from the mean values observed in non-clinical species. Conclusion: AMG 900 exhibits good PK properties in preclinical species and it was predicted to have low clearance and good oral bioavailability in human. Available PK results from the on-going phase 1 trial are consistent with the allometric scaling predictions. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2663.

Abstract B167: Identifying first in human (FIH) doses and schedule of U3-1287 (AMG 888), a fully human anti-HER3 mAb, based on preclinical pharmacokinetic (PK), pharmacodynamic (PD) and efficacy data

Abstract Background: HER3 is a member of the Human Epidermal Growth Factor Receptor (HER) family. Although HER3 lacks intrinsic kinase activity, it serves as a scaffold for PI3K/AKT signaling for the HER family via heterodimeric interactions. The goal of this study was to use preclinical modeling to predict a minimal effective dose regimen for objective response using preclinical PK and BxPC3 xenograft mice anti-tumor efficacy and PD data. Materials and Methods: U3-1287 (AMG 888) concentration-time data obtained from mice (0.025 to 2.5 mg/mouse), rats (1 to 100 mg/kg) and monkeys (1 to 200 mg/kg) were combined and analyzed using a target-mediated drug disposition model. Animal PK parameters were scaled based on body weight to predict human PK characteristics. An Emax model was used to relate drug concentration and inhibition of pHER (measure by ELISA) in BxPC3 xenograft tumors. A PK/PD/efficacy model (based on Simeoni et al 2004) was used to analyze tumor growth data from mice bearing BxPC3 pancreatic xenografts (∼200 mm3) treated twice per week at 25, 100, 200, or 500 g for a 1 month. The model was validated with tumor growth data following additional doses of 400 g biweekly and 200 g biweekly, weekly and twice a week. The relationship between drug concentration, the inhibition of pHER3 in animals and interspecies PK scaling was used to select the minimal effective dose for the first in human study. Results: U3-1287 (AMG 888) treatment of BxPC3 xenografts resulted in a statistically significant inhibition of tumor growth and pHER3 levels in a dose and schedule dependent manner (p&amp;lt;0.05). Treatment with U3-1287 (AMG 888) at 400 g/mouse biweekly and 200 g/mouse biweekly, weekly and twice a week resulted in a 50%, 33%, 74% and 70% inhibition of tumor growth (p&amp;lt;0.05), a 70%, 42%, 77% and 80% inhibition of pHER3 (measured by ELISA) versus the IgG control treated group, respectively. Serum concentrations of U3-1287 (AMG 888) at necropsy for the respective dose groups were (mean (SD)) of 2.07 (0.97), 0.45 (0.21), 3.08 (0.82) and 34.9 (9.1) g/mL, respectively. The estimated trough concentration needed to achieve 90% maximal pHER3 inhibition (IC90) was estimated to be ∼3 µg/mL. Based on interspecies scaling of PK parameters, a dose higher than 3 mg/kg given biweekly would achieve a steady-sate trough concentration that is above 3 µg/mL. Conclusion: The anti-tumor efficacy in the BxPC3 pancreatic xenograft model was correlated with an increased serum concentration of U3-1287 (AMG 888) and a decrease in pHER3 levels, allowing for the development of a PK/PD/Efficacy relationship. This relationship combined with interspecies PK scaling was used to determine a dose and schedule for U3-1287 (AMG 888) to investigate in a FIH study. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B167.

Disposition kinetics of a dipeptide ester prodrug of acyclovir and its metabolites following intravenous and oral administrations in rat

The objective of this work was to study the disposition kinetics of valine-valine-acyclovir (VVACV), a dipeptide ester prodrug of acyclovir following intravenous and oral administrations in rat. A validated LC-MS/MS analytical method was developed for the analysis VVACV, Valine-Acyclovir (VACV), and Acyclovir (ACV) using a linear Ion Trap Quadrupole. ACV was administered orally for comparison purpose. In the VVACV group, both blood and urine samples and in the ACV group only blood samples were collected. All the samples were analyzed using LC-MS/MS. The LLOQ for ACV, VACV, and VVACV were 10, 10, and 50 ng/ml, respectively. Relevant pharmacokinetic parameters were obtained by non-compartmental analyses of data with WinNonlin. Following i.v. administration of VVACV, AUC(0-inf) (min*µM) values for VVACV, VACV, and ACV were 55.06, 106, and 466.96, respectively. The AUC obtained after oral administration of ACV was 178.8. However, following oral administration of VVACV, AUC(0-inf) values for VACV and ACV were 89.28 and 810.77, respectively. Thus the exposure of ACV obtained following oral administration of VVACV was almost 6-fold higher than ACV. This preclinical pharmacokinetic data revealed that VVACV has certainly improved the oral bioavailability of ACV and is an effective prodrug for oral delivery of ACV.

Use of Pre-Clinical In Vitro and In Vivo Pharmacokinetics for the Selection of a Potent Hepatitis C Virus Protease Inhibitor, Boceprevir, for Clinical Development

Boceprevir is a novel hepatitis C virus (HCV) protease inhibitor undergoing clinical investigation for use in the treatment of human HCV infection. Preclinical in vivo pharmacokinetic studies have been performed in rat, dog, and/or monkey after single administration by oral and intravenous routes for about one thousand compounds prior to the selection of boceprevir as the development candidate. In vitro pharmacokinetic assessments of metabolic stability, cell permeability, and plasma protein binding have been performed. The compound has physicochemical properties (molecular weight of 519.7 and moderate lipophilicity and H-bonding functionalities) that are borderline for good pharmacokinetic behavior. Absorption in animals ranges from 12 to 37%, indicating incomplete absorption. Based on in vitro permeability studies in Caco-2 cells, boceprevir appears to be an efflux substrate displaying a saturable efflux profile at high dosing concentrations and a reversible efflux profile in the presence of P-glycoprotein (P-gp) inhibitors. Boceprevir displayed a rather high liver/plasma average ratio of 30 in rats, indicating good uptake by the target tissue. The rat liver/plasma ratio of boceprevir appeared to be higher than those for compounds that are under clinical evaluation. Based on the preclinical pharmacokinetic data, boceprevir appears to have limited absorption, but reasonable liver distribution which is a primary factor for selecting boceprevir as a development candidate. Recent clinical proof-of-concept study confirmed that boceprevir is efficacious in reducing the viral load in patients. Keywords: HCV protease inhibitor, In vivo pharmacokinetics, In vitro pharmacokinetics

Predictability of intranasal pharmacokinetics in man using pre-clinical pharmacokinetic data with a dopamine 3 receptor agonist, PF-219061

(R)-3-(4-propylmorpholin-2-yl) phenol (PF-219061) is a potent, selective agonist of the dopamine 3 receptor for the treatment of female sexual dysfunction.In vivo, PF-219061 exhibits liver blood flow clearance in both rat and dog. Oral bioavailability was 0.7% in dog and less than 5% in rat.Intranasal dosing was investigated to improve bioavailability. Pre-clinical assessments in rat and dog demonstrated intranasal bioavailabilities of 16–38% in rat and 54–61% in dog with very rapid absorption. It was predicted that an intranasal dose in man would give approximately 25–50% bioavailability.The clinical data verified the preclinical predictions demonstrating rapid absorption and approximately dose-proportional increases in exposure. The intranasal bioavailability in man was estimated to be 26–38%.These findings indicate the potential utility of intranasal dosing as a route that circumvents the first-pass effects for PF-219061 resulting in high exposures.