Impact of model misspecification on model-based tests in PK studies with parallel design: real case and simulation studies

This article evaluates the performance of pharmacokinetic (PK) equivalence testing between two formulations of a drug through the Two-One Sided Tests (TOST) by a model-based approach (MB-TOST), as an alternative to the classical non-compartmental approach (NCA-TOST), for a sparse design with a few time points per subject. We focused on the impact of model misspecification and the relevance of model selection for the reference data. We first analysed PK data from phase I studies of gantenerumab, a monoclonal antibody for the treatment of Alzheimer’s disease. Using the original rich sample data, we compared MB-TOST to NCA-TOST for validation. Then, the analysis was repeated on a sparse subset of the original data with MB-TOST. This analysis inspired a simulation study with rich and sparse designs. With rich designs, we compared NCA-TOST and MB-TOST in terms of type I error and study power. With both designs, we explored the impact of misspecifying the model on the performance of MB-TOST and adding a model selection step. Using the observed data, the results of both approaches were in general concordance. MB-TOST results were robust with sparse designs when the underlying PK structural model was correctly specified. Using the simulated data with a rich design, the type I error of NCA-TOST was close to the nominal level. When using the simulated model, the type I error of MB-TOST was controlled on rich and sparse designs, but using a misspecified model led to inflated type I errors. Adding a model selection step on the reference data reduced the inflation. MB-TOST appears as a robust alternative to NCA-TOST, provided that the PK model is correctly specified and the test drug has the same PK structural model as the reference drug.

High-content phenotypic screening identifies novel chemistries that disrupt mosquito activity and development

New classes of chemistries are needed to control insecticide resistant populations of mosquitoes and prevent transmission of vector-borne diseases (VBDs). Organismal screens of chemical collections have played an important role in the search for new vector insecticides and the identification of active ingredients (AIs) that cause rapid mortality of mosquitoes. Advances in image-based screening offer an opportunity to identify chemistries that operate via novel biochemical modes and investigate the range of phenotypes exhibited by mosquitoes following exposure to lethal and sub-lethal chemical dose. An automated, high throughput phenotypic screen (HTS) employing high-content imaging of first instar (L1) Aedes aegypti larvae was developed to identify chemistries associated with mortality and atypical morphological phenotypes. A pilot screen of the Library of Pharmacologically Active Compounds (LOPAC₁₂₈₀) identified 92 chemistries that disrupted larval activity and development, including conventional insecticides and chemistries known to modulate G protein-coupled receptors (GPCRs) and other molecular targets in mammalian systems. Secondary assay series were used to evaluate a selection of chemistries for impacts on mosquito activity, survival and development. Ritodrine hydrochloride reduced mobility of larvae but had no observable effect on survival and development of mosquitoes. High doses of metergoline suppressed larval activity and sub-lethal dose resulted in pupal mortality. Assay data support the utility of phenotypic screening and diverse entomological end-points for discovery of novel insecticidal chemical scaffolds. The insecticide discovery process must consider how multi-modal efficacy spectra contribute to vector and VBD control.

Use of Partial Area Under the Curve in Bioavailability or Bioequivalence Assessments: A Regulatory Perspective

Peak drug concentration (C_max ) and total exposure, such as area under the concentration-time curve (AUC) from time zero to infinity may be insufficient for assessing relative bioavailability (BA) or bioequivalence (BE) among two products in cases where rapid onset of action or controlled duration of effect is needed to ensure similar drug efficacy. Regulatory agencies have recommended the use of partial AUC (pAUC) as an additional exposure measure for relative BA or BE assessments. The pAUC metric describes pharmacokinetic profiles with the focus on quantification of exposures over specific time intervals to support the determination of relative BA or BE for these drug products in relation to respective reference products. The principles and rationales for using pAUCs are included in the US Food and Drug Administration (FDA)'s general BA or BE guidances. Specific pAUC recommendations are also reflected in product-specific guidances for generic drug development published by the FDA. Rationales for the use of pAUCs in relative BA or BE assessments are based on drug-specific and product-specific considerations. This white paper introduces the general framework, including rationales for pAUC recommendations, and provides an overview of the current status, challenges, and the FDA considerations on the use of pAUC for relative BA or BE assessments in the United States.

CTNI-39. PHASE 1B CLINICAL TRIAL OF OKN-007 IN RECURRENT MALIGNANT GLIOMA

BACKGROUND

The nitrone compound OKN-007 is a novel anti-cancer agent. In glioblastoma xenografts, OKN-007 reduces cell proliferation and angiogenesis, and increases apoptosis. Here we report on the safety, efficacy, and pharmacokinetics (PK) of OKN-007 in adults with recurrent glioma.

METHODS

NCT01672463 is a phase 1b trial of OKN-007 in adults with recurrent gliomas previously treated with standard therapy. OKN-007 was administered by IV. The study comprised a 3 + 3 dose escalation design followed by an expansion cohort at the maximum tolerated dose (MTD). The dose escalation drug levels were 20 (n = 3), 40 (n = 3), and 60 mg/kg (n = 3), treating on a schedule of thrice weekly for 4 weeks, then twice weekly for 4 weeks, then once weekly until progression. Drug PK was determined in the dose escalation cohorts. The expansion cohort was treated with 60 mg/kg thrice weekly for 12 weeks, then twice weekly for 12 weeks, then once weekly until progression (n = 6). Kaplan-Meier analysis was used to determine progression-free (PFS) and overall survival (OS).

RESULTS

Median age was 51 years (range, 25–62). No dose-limiting toxicities were observed. The expansion dose was 60 mg/kg. Of 123 adverse events (AEs), 34 were deemed probably (1.6%) or possibly (26%) treatment-emergent (TEAE). The most commonly-occurring TEAEs were fatigue (4.1%) and headache (3.3%). Grade 3 TEAEs included headache, urinary tract infection, and increased prothrombin time (0.8% each). Two grade 1 AEs, hypokalemia and dizziness, were considered probably attributable to OKN-007. In patients receiving 60 mg OKN-007/kg, median PFS was 1.4 months and OS was 21 months (log rank p = 0.08 for comparison across doses). Systemic PK exposure was dose proportional. The average half-life of OKN-007 is 2.8 hours.

CONCLUSIONS

OKN-007 appears safe and, compared to standard therapy, may prolong OS in recurrent glioma.

Applications of Physiologically Based Biopharmaceutics Modeling (PBBM) to Support Drug Product Quality: A Workshop Summary Report

This report summarizes the proceedings for Day 3 of the workshop titled "Current State and Future Expectations of Translational Modeling Strategies toSupportDrug Product Development, Manufacturing Changes and Controls". From a drug product quality perspective, patient-centric product development necessitates the development of clinically relevant drug product specifications (CRDPS). In this regard, Physiologically Based Biopharmaceutics modeling (PBBM) is a viable tool to establish links between in-vitro to in-vivo data, and support with establishing CRDPS. The theme of day 3 was practical applications of PBBM to support drug product quality. In this manuscript, case studies from US FDA, EMA and pharmaceutical industry on applications of PBBM in drug product quality are summarized which include 1) regulatory agency's perspectives on establishing the safe space and achieving study waivers, 2) model-informed risk assessment on the effects of acid reducing agents, bridging of dissolution methods, food effect, and formulation selection, and 3) understanding clinical formulation performance. Breakout session discussions focused on four topics - 1) terminologies related to physiologically based modeling in support of drug product quality, 2) regulatory harmonization on evidentiary standards, 3) CRDPS approaches and 4) bridging between biorelevant and quality control (QC) dissolution methods.

New Model-Based Bioequivalence Statistical Approaches for Pharmacokinetic Studies with Sparse Sampling

In traditional pharmacokinetic (PK) bioequivalence analysis, two one-sided tests (TOST) are conducted on the area under the concentration-time curve and the maximal concentration derived using a non-compartmental approach. When rich sampling is unfeasible, a model-based (MB) approach, using nonlinear mixed effect models (NLMEM) is possible. However, MB-TOST using asymptotic standard errors (SE) presents increased type I error when asymptotic conditions do not hold. In this work, we propose three alternative calculations of the SE based on (i) an adaptation to NLMEM of the correction proposed by Gallant, (ii) the a posteriori distribution of the treatment coefficient using the Hamiltonian Monte Carlo algorithm, and (iii) parametric random effects and residual errors bootstrap. We evaluate these approaches by simulations, for two-arms parallel and two-period, two-sequence cross-over design with rich (n = 10) and sparse (n = 3) sampling under the null and the alternative hypotheses, with MB-TOST. All new approaches correct for the inflation of MB-TOST type I error in PK studies with sparse designs. The approach based on the a posteriori distribution appears to be the best compromise between controlled type I errors and computing times. MB-TOST using non-asymptotic SE controls type I error rate better than when using asymptotic SE estimates for bioequivalence on PK studies with sparse sampling.

Efficient model-based bioequivalence testing

The classical approach to analyze pharmacokinetic (PK) data in bioequivalence studies aiming to compare two different formulations is to perform noncompartmental analysis (NCA) followed by two one-sided tests (TOST). In this regard, the PK parameters area under the curve (AUC) and $C_{\max}$ are obtained for both treatment groups and their geometric mean ratios are considered. According to current guidelines by the U.S. Food and Drug Administration and the European Medicines Agency, the formulations are declared to be sufficiently similar if the $90\%$ confidence interval for these ratios falls between $0.8$ and $1.25 $. As NCA is not a reliable approach in case of sparse designs, a model-based alternative has already been proposed for the estimation of $\rm AUC$ and $C_{\max}$ using nonlinear mixed effects models. Here we propose another, more powerful test than the TOST and demonstrate its superiority through a simulation study both for NCA and model-based approaches. For products with high variability on PK parameters, this method appears to have closer type I errors to the conventionally accepted significance level of $0.05$, suggesting its potential use in situations where conventional bioequivalence analysis is not applicable.

Phase Ib clinical trial of OKN-007 in recurrent malignant glioma

2538

Background: Despite therapeutic advances, the median overall survival for patients with recurrent, high-grade gliomas remains poor. Thus, there is an urgent need for efficacious new therapies. The nitrone compound, OKN-007 (disodium 4-[(tert-butyl-imino) methyl] benzene-1,3-disulfonate N-oxide) is a promising novel anti-cancer agent. In orthotopic glioblastoma xenografts, OKN-007 reduces cell proliferation and angiogenesis, and increases apoptosis. Here we report on the safety, efficacy, and pharmacokinetics (PK) of OKN-007 in adults with recurrent glioma. Methods: NCT01672463 is a phase Ib trial of OKN-007 in adults with recurrent gliomas previously treated with standard therapy. Patients with recurrence, adequate performance status and organ function, receiving clinically appropriate doses of steroids, with a life expectancy greater than 8 weeks were eligible. OKN-007 was administered by IV. The study comprised a 3+3 dose escalation design followed by an expansion cohort at the maximum tolerated dose (MTD). The dose escalation drug levels were 20 (n = 3), 40 (n = 3), and 60 mg/kg (n = 3), treating on a schedule of thrice weekly for 4 weeks, then twice weekly for 4 weeks, then once weekly until progression. Drug PK was determined in the dose escalation cohorts. The expansion cohort was treated with 60 mg/kg thrice weekly for 12 weeks, then twice weekly for 12 weeks, then once weekly until recurrence (n = 6). Kaplan-Meier analysis was used to determine progression-free (PFS) and overall survival (OS). Results: Median age was 51 years (range, 25-62). No dose-limiting toxicities were observed and 60 mg/kg was chosen for the expansion dose. Of 123 adverse events (AE), 34 were deemed probably (1.6%) or possibly (26%) treatment-emergent (TEAE). The most commonly-occurring TEAE were fatigue (4.1%) and headache (3.3%). No drug-attributable grade 4 or 5 AE were observed. Grade 3 TEAE included headache, urinary tract infection, and increased prothrombin time (0.8% each). Only two grade 1 AE, hypokalemia and dizziness, were considered probably attributable to OKN-007. In patients receiving 60 mg OKN-007/kg, median PFS was 1.4 months and OS was 21 months (log rank p = 0.08 for comparison across doses). Systemic PK exposure was dose proportional. The average half-life of OKN-007 is 2.8 hours. Conclusions: OKN-007 appears safe for patients with recurrent glioma. The MTD was not reached. Our data suggest that, compared to standard therapy, OKN-007 may prolong OS in recurrent glioma. Based on new data, a trial of OKN-007 plus temozolomide is underway in patients with newly diagnosed glioblastoma (NCT03587038). Clinical trial information: NCT01672463 .

Physiologically Based Pharmacokinetic and Absorption Modeling for Osmotic Pump Products

Physiologically based pharmacokinetic (PBPK) and absorption modeling approaches were employed for oral extended-release (ER) drug products based on an osmotic drug delivery system (osmotic pumps). The purpose was to systemically evaluate the in vivo relevance of in vitro dissolution for this type of formulation. As expected, in vitro dissolution appeared to be generally predictive of in vivo PK profiles, because of the unique feature of this delivery system that the in vitro and in vivo release of osmotic pump drug products is less susceptible to surrounding environment in the gastrointestinal (GI) tract such as pH, hydrodynamic, and food effects. The present study considered BCS (Biopharmaceutics Classification System) class 1, 2, and 3 drug products with half-lives ranging from 2 to greater than 24 h. In some cases, the colonic absorption models needed to be adjusted to account for absorption in the colon. C _max (maximum plasma concentration) and AUCt (area under the concentration curve) of the studied drug products were sensitive to changes in colon permeability and segmental GI transit times in a drug product-dependent manner. While improvement of the methodology is still warranted for more precise prediction (e.g., colonic absorption and dynamic movement in the GI tract), the results from the present study further emphasized the advantage of using PBPK modeling in addressing product-specific questions arising from regulatory review and drug development.

"Target-Site" Drug Metabolism and Transport

The recent symposium on "Target-Site" Drug Metabolism and Transport that was sponsored by the American Society for Pharmacology and Experimental Therapeutics at the 2014 Experimental Biology meeting in San Diego is summarized in this report. Emerging evidence has demonstrated that drug-metabolizing enzyme and transporter activity at the site of therapeutic action can affect the efficacy, safety, and metabolic properties of a given drug, with potential outcomes including altered dosing regimens, stricter exclusion criteria, or even the failure of a new chemical entity in clinical trials. Drug metabolism within the brain, for example, can contribute to metabolic activation of therapeutic drugs such as codeine as well as the elimination of potential neurotoxins in the brain. Similarly, the activity of oxidative and conjugative drug-metabolizing enzymes in the lung can have an effect on the efficacy of compounds such as resveratrol. In addition to metabolism, the active transport of compounds into or away from the site of action can also influence the outcome of a given therapeutic regimen or disease progression. For example, organic anion transporter 3 is involved in the initiation of pancreatic β-cell dysfunction and may have a role in how uremic toxins enter pancreatic β-cells and ultimately contribute to the pathogenesis of gestational diabetes. Finally, it is likely that a combination of target-specific metabolism and cellular internalization may have a significant role in determining the pharmacokinetics and efficacy of antibody-drug conjugates, a finding which has resulted in the development of a host of new analytical methods that are now used for characterizing the metabolism and disposition of antibody-drug conjugates. Taken together, the research summarized herein can provide for an increased understanding of potential barriers to drug efficacy and allow for a more rational approach for developing safe and effective therapeutics.

Systems pharmacology approaches for optimization of antiangiogenic therapies: challenges and opportunities

Targeted therapies have become an important therapeutic paradigm for multiple malignancies. The rapid development of resistance to these therapies impedes the successful management of advanced cancer. Due to the redundancy in angiogenic signaling, alternative proangiogenic factors are activated upon treatment with anti-VEGF agents. Higher doses of the agents lead to greater stimulation of compensatory proangiogenic pathways that limit the therapeutic efficacy of VEGF-targeted drugs and produce escape mechanisms for tumor. Evidence suggests that dose intensity and schedules affect the dynamics of the development of this resistance. Thus, an optimal dosing regimen is crucial to maximizing the therapeutic benefit of antiangiogenic agents and limiting treatment resistance. A systems pharmacology approach using multiscale computational modeling can facilitate a mechanistic understanding of these dynamics of angiogenic biomarkers and their impacts on tumor reduction and resistance. Herein, we discuss a systems pharmacology approach integrating the biology of VEGF-targeted therapy resistance, including circulating biomarkers, and pharmacodynamics to enable the optimization of antiangiogenic therapy for therapeutic gains.

Quantitative insight in utilizing circulating angiogenic factors as biomarkers for antiangiogenic therapy: systems pharmacology approach

Circulating angiogenic factors (CAF) like vascular endothelial growth factor (VEGF), placental growth factor (PlGF), and sVEGFR2 have potential as biomarkers for antiangiogenic therapy. The interpretation of changes in CAF is complicated by the dynamic nature of the tumor and host cells emanating CAF in response to VEGF pathway inhibition. We developed a systems pharmacology model of anti-VEGF agents to investigate CAF modulation by tumor and host cells, and the relationship between overall CAF changes in response to sunitinib and antitumor efficacy. This model distinguishes between the tumor cells' contributions from tumor-independent response to therapy and total plasma CAF correlating with antitumor activity. Altered VEGF is more likely to serve as a useful biomarker reflecting tumor responses in cancer patients whose pretreatment VEGF is higher than baseline VEGF in healthy subjects. Our findings provide a mechanistic insight into tumor modulation of angiogenic molecules, and may explain the inconsistent results found in previous biomarker studies.

Pulmonary metabolism of resveratrol: in vitro and in vivo evidence

The role of pulmonary metabolism in trans-resveratrol (RES) pharmacokinetics was studied in a mouse model. Plasma concentrations of RES and its major metabolites trans-resveratrol-3-sulfate (R3S) and trans-resveratrol-3-glucuronide (R3G) were compared after administration of RES by intravenous (IV) and intra-arterial (IA) routes. Total area under the curve (AUC) of RES decreased by approximately 50% when RES was administered by the IV route compared with the IA route. The AUC of R3G was also significantly higher in mice administered RES by the IV route compared with the IA route. In vitro studies performed with mouse and human lung fractions confirmed pulmonary metabolism of RES. Interestingly, mouse-lung fractions gave rise to both R3S and R3G, whereas human lung fractions yielded R3S. This indicates marked interspecies variation in RES conjugation, especially in the context of extrapolating rodent data to humans. Taken together, the results presented here underline, for the first time, the impact of pulmonary metabolism on resveratrol pharmacokinetics and interspecies differences in RES pulmonary metabolism.

In vivo-formed versus preformed metabolite kinetics of trans-resveratrol-3-sulfate and trans-resveratrol-3-glucuronide

Metabolites in safety testing have gained a lot of attention recently. Regulatory agencies have suggested that the kinetics of preformed and in vivo-formed metabolites are comparable. This subject has been a topic of debate. We have compared the kinetics of in vivo-formed with preformed metabolites. trans-3,5,4'-Trihydroxystilbene [trans-resveratrol (RES)] and its two major metabolites, resveratrol-3-sulfate (R3S) and resveratrol-3-glucuronide (R3G) were used as model substrates. The pharmacokinetics (PK) of R3S and R3G were characterized under two situations. First, the pharmacokinetics of R3S and R3G were characterized (in vivo-formed metabolite) after administration of RES. Then, synthetic R3S and R3G were administered (preformed metabolite) and their pharmacokinetics were characterized. PK models were developed to describe the data. A three-compartment model for RES, a two-compartment model for R3S (preformed), and an enterohepatic cycling model for R3G (preformed) was found to describe the data well. These three models were further combined to build a comprehensive PK model, which was used to perform simulations to predict in vivo-formed metabolite kinetics. Comparisons were made between in vivo-formed and preformed metabolite kinetics. Marked differences were observed in the kinetics of preformed and in vivo-formed metabolites.

Low Temperature Laser Physical Vapor Deposition of Multilayered Thin Films

We have investigated the formation of various multilayer thin films by the laser physical vapor deposition technique. A multi stage target holder was constructed to perform all process steps in-situ; target/substrate cleaning, deposition, and annealing. The laser physical vapor deposition technique offers many advantages over conventional physical vapor techniques, such as, lower substrate temperature, microstructural control, and very low contamination levels. Film thickness can be controlled from near atomic to micron dimensions. A layer-by-layer (two dimensional) growth can be achieved, resulting in nonequilibrium structures. The films were analyzed using cross-section and high resolution transmission electron microscopy (TEM). The significant reduction in substrate temperature for the formation of high quality multilayer and epitaxial films opens up many new areas of applications requiring reduced thermal-budget processing.

Chebulagic acid, a COX-LOX dual inhibitor isolated from the fruits of Terminalia chebula Retz., induces apoptosis in COLO-205 cell line

ETHNOPHARMACOLOGICAL RELEVANCE

Terminalia chebula has an esteemed origin in Indian mythology; its fruits are used to treat many diseases such as digestive, diabetes, colic pain, chronic cough, sore throat, asthma, etc.

AIM OF THE STUDY

The water or ethanolic extracts of the fruits were reported to have anti-oxidant, anti-inflammatory, anti-cancer and radio-protector properties. The present study is to isolate and identify the compounds that inhibit COX and 5-LOX, the key enzymes involved in inflammation and carcinogenesis.

MATERIALS AND METHODS

The ethanolic extract of the fruits was fractionated by RP-HPLC and fractions were tested for enzyme inhibition activity against COX and 5-LOX. One of the fractionated compounds showed potent dual inhibition against COX and 5-LOX. It was identified as chebulagic acid by LC-MS, NMR and IR analyses. The chebulagic acid was also tested for anti-proliferative activity.

RESULTS

Chebulagic acid showed potent COX-LOX dual inhibition activity with IC(50) values of 15+/-0.288, 0.92+/-0.011 and 2.1+/-0.057 microM for COX-1, COX-2 and 5-LOX respectively. It also showed anti-proliferative activity against HCT-15, COLO-205, MDA-MB-231, DU-145 and K562 cell lines. Further mechanistic studies on COLO-205 cells revealed induction of apoptosis by chebulagic acid.

CONCLUSIONS

Chebulagic acid, a COX-2 and 5-LOX dual inhibitor isolated from the fruits of Terminalia chebula, induces apoptosis in COLO-205 cells.

Role of thyroid in tissue respiration of birds

Thyroidectomy after 1 week, 1 month, and 13 months significantly depressed and low level of L-T4 significantly elevated the oxygen uptake of the liver and skeletal muscle of spotted munia and common myna. A higher dose of L-T4 had no effect on the rate of respiration. A reexamination of the published results on submammalian vertebrates together with those presented here suggests that an uniform pattern of response of skeletal muscle emerges if the values from thyroidectomized animals are compared not only with the final controls but also with the initial controls. It is, therefore, suggested that all the earlier works be reexamined and reinterpreted.

In pursuit of the "spatial gene": a family study

Members of 192 families in the Tel Aviv area were given a battery of eight cognitive tests focusing on spatial measures but sampling verbal, numerical, and perceptual speed domains as well. The patterns of parent-child and sibling correlations gave very weak evidence, if any, for the operation of the X-linked recessive gene postulated by Stafford and others to affect performance on tasks involving spatial visualization. An analysis of male and female score distributions provided results more favorable to the X-linkage hypothesis, at least for the child generation, although suggesting that X linkage does not explain the whole male-female difference in performance on spatial tasks.

The relation of auditory, visual, and auditory-visual matching to reading performance of Israeli children

Six same-different matching tests, both verbal and nonverbal, in three modalities, along with a set of reading tests, were administered to 120 Israeli children in second, third, and fourth grade. The main effect of all S variables, except sex (grade, socioeconomic level, and ability) were significant, as were the test factors of modality (visual, auditory, cross-modal) and form (verbal-nonverbal), but interactions between S and test factors were small. Multiple regression analysis revealed that overall matching test scores accounted for 35% of the variance in reading scores, although the additional contribution of specific subtests was negligible. Performance on the visual-visual tests was virtually perfect. Auditory-auditory matches were more difficult than auditory-visual matches with nonverbal stimuli, while the reverse was true with verbal stimuli.