Paul A. Dickinson

AZD9291 in EGFR inhibitor-resistant non-small-cell lung cancer.

BACKGROUND The EGFR T790M mutation is the most common mechanism of drug resistance to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in patients who have lung cancer with an EGFR mutation (EGFR-mutated lung cancer). In preclinical models, the EGFR inhibitor AZD9291 has been shown to be effective against both EGFR tyrosine kinase inhibitor-sensitizing and T790M resistance mutations. METHODS We administered AZD9291 at doses of 20 to 240 mg once daily in patients with advanced lung cancer who had radiologically documented disease progression after previous treatment with EGFR tyrosine kinase inhibitors. The study included dose-escalation cohorts and dose-expansion cohorts. In the expansion cohorts, prestudy tumor biopsies were required for central determination of EGFR T790M status. Patients were assessed for safety, pharmacokinetics, and efficacy. RESULTS A total of 253 patients were treated. Among 31 patients enrolled in the dose-escalation cohorts, no dose-limiting toxic effects occurred at the doses evaluated. An additional 222 patients were treated in five expansion cohorts. The most common all-cause adverse events were diarrhea, rash, nausea, and decreased appetite. The overall objective tumor response rate was 51% (95% confidence interval [CI], 45 to 58). Among 127 patients with centrally confirmed EGFR T790M who could be evaluated for response, the response rate was 61% (95% CI, 52 to 70). In contrast, among 61 patients without centrally detectable EGFR T790M who could be evaluated for response, the response rate was 21% (95% CI, 12 to 34). The median progression-free survival was 9.6 months (95% CI, 8.3 to not reached) in EGFR T790M-positive patients and 2.8 months (95% CI, 2.1 to 4.3) in EGFR T790M-negative patients. CONCLUSIONS AZD9291 was highly active in patients with lung cancer with the EGFR T790M mutation who had had disease progression during prior therapy with EGFR tyrosine kinase inhibitors. (Funded by AstraZeneca; ClinicalTrials.gov number, NCT01802632.).

In vitro models for the prediction of in vivo performance of oral dosage forms.

Accurate prediction of the in vivo biopharmaceutical performance of oral drug formulations is critical to efficient drug development. Traditionally, in vitro evaluation of oral drug formulations has focused on disintegration and dissolution testing for quality control (QC) purposes. The connection with in vivo biopharmaceutical performance has often been ignored. More recently, the switch to assessing drug products in a more biorelevant and mechanistic manner has advanced the understanding of drug formulation behavior. Notwithstanding this evolution, predicting the in vivo biopharmaceutical performance of formulations that rely on complex intraluminal processes (e.g. solubilization, supersaturation, precipitation…) remains extremely challenging. Concomitantly, the increasing demand for complex formulations to overcome low drug solubility or to control drug release rates urges the development of new in vitro tools. Development and optimizing innovative, predictive Oral Biopharmaceutical Tools is the main target of the OrBiTo project within the Innovative Medicines Initiative (IMI) framework. A combination of physico-chemical measurements, in vitro tests, in vivo methods, and physiology-based pharmacokinetic modeling is expected to create a unique knowledge platform, enabling the bottlenecks in drug development to be removed and the whole process of drug development to become more efficient. As part of the basis for the OrBiTo project, this review summarizes the current status of predictive in vitro assessment tools for formulation behavior. Both pharmacopoeia-listed apparatus and more advanced tools are discussed. Special attention is paid to major issues limiting the predictive power of traditional tools, including the simulation of dynamic changes in gastrointestinal conditions, the adequate reproduction of gastrointestinal motility, the simulation of supersaturation and precipitation, and the implementation of the solubility-permeability interplay. It is anticipated that the innovative in vitro biopharmaceutical tools arising from the OrBiTo project will lead to improved predictions for in vivo behavior of drug formulations in the GI tract.

Clinical relevance of dissolution testing in quality by design.

Quality by design (QbD) has recently been introduced in pharmaceutical product development in a regulatory context and the process of implementing such concepts in the drug approval process is presently on-going. This has the potential to allow for a more flexible regulatory approach based on understanding and optimisation of how design of a product and its manufacturing process may affect product quality. Thus, adding restrictions to manufacturing beyond what can be motivated by clinical quality brings no benefits but only additional costs. This leads to a challenge for biopharmaceutical scientists to link clinical product performance to critical manufacturing attributes. In vitro dissolution testing is clearly a key tool for this purpose and the present bioequivalence guidelines and biopharmaceutical classification system (BCS) provides a platform for regulatory applications of in vitro dissolution as a marker for consistency in clinical outcomes. However, the application of these concepts might need to be further developed in the context of QbD to take advantage of the higher level of understanding that is implied and displayed in regulatory documentation utilising QbD concepts. Aspects that should be considered include identification of rate limiting steps in the absorption process that can be linked to pharmacokinetic variables and used for prediction of bioavailability variables, in vivo relevance of in vitro dissolution test conditions and performance/interpretation of specific bioavailability studies on critical formulation/process variables. This article will give some examples and suggestions how clinical relevance of dissolution testing can be achieved in the context of QbD derived from a specific case study for a BCS II compound.

Oral bioavailability of cinnarizine in dogs : relation to SNEDDS droplet size, drug solubility and in vitro precipitation

The in vivo performance of self-nanoemulsifying drug delivery systems (SNEDDSs) with different in vitro physicochemical properties were determined with the purpose of elucidating the parameters determining the in vivo performance of SNEDDSs. The in vitro characterisation included the use of pulsed field gradient NMR and the dynamic lipolysis model. In vivo characterisation was carried out in dogs with elevated gastric pH. Four SNEDDSs containing cinnarizine were dosed orally, and the obtained PK profiles were related to in vitro characterisation data. The SNEDDSs with the lowest solubility of cinnarizine in the preconcentrates and the smallest droplet size had the highest AUC values after oral administration. No difference in C(max) and t(max) was observed between the SNEDDSs. Despite of precipitation occurring during in vitro lipolysis of one of the SNEDDS this SNEDDS performed as well in vivo as another SNEDDS that did not show any precipitation. The area under the colloidal dispersion curves as well as under the lipolysis curves could be used to rank order the in vivo performance of the SNEDDSs. Selection of in vitro optimisation parameters for SNEDDSs should be done carefully. It may not always be best to aim for the highest solubility in the preconcentrate and to avoid precipitation during in vitro lipolysis.

An Investigation into the Utility of a Multi-compartmental, Dynamic, System of the Upper Gastrointestinal Tract to Support Formulation Development and Establish Bioequivalence of Poorly Soluble Drugs

In recent years mechanical systems have been developed that more closely mimic the full dynamic, physical and biochemical complexity of the GI Tract. The development of these complex systems raises the possibility that they could be used to support formulation development of poorly soluble compounds and importantly may be able to replace clinical BE studies in certain circumstances. The ability of the TNO Simulated Gastro-Intestinal Tract Model 1 (TIM-1) Dynamic Artificial Gastrointestinal System in the ‘lipid membrane’ configuration to support the development of Biopharmaceutics Classification System Class 2 compounds was investigated by assessing the performance of various AZD8055 drug forms and formulations in the TIM-1 system under standard fasting and achlorhydric physiological conditions. The performance data were compared with exposure data from the phase 1 clinical study. Analysis of the AZD8055 plasma concentrations after tablet administration supported the conclusions drawn from the TIM-1 experiments and confirmed that these complex systems can effectively support the product development of poorly soluble drugs. Particularly, the TIM-1 system was able to show that AZD8055 exposure would increase in an approximately dose proportional manner and not be limited by the solubility or dissolution. Additionally, the investigations also showed that the exposure produced by a solution and a tablet would be the same. Specific instances when the TIM-1 system may not be predictive of clinical product performance have also been identified.

Drug metabolism of CYP3A4, CYP2C9 and CYP2D6 substrates in pigs and humans

Pigs are becoming increasingly used as a test animal both in pharmacological and toxicological assessment of new drug compounds. For interspecies comparisons and predictions it is important to characterize the expression and function of membrane transport and enzymatic proteins in pigs, particularly at a mechanistic level which will make extrapolation of observation between pig and man to be made with more confidence. The major objective of this report was to increase the integrative knowledge of drug metabolism in pigs and to compare with corresponding data from human liver microsomes. This was done by using human substrates of CYP3A4 (verapamil and testosterone), CYP2C9 (diclofenac) and CYP2D6 (dextromethorphan). In addition, the mRNA expression of important drug metabolizing enzymes and carrier-mediated transporters were assessed in intestine and liver tissues from pigs. It was shown that CYP3A4 activity is quantitatively comparable between the two species but data suggest that qualitative differences may exist. Verapamil showed similar metabolism pattern as in humans and the CYP3A4 inhibitor ketoconazole was able to inhibit the depletion of both R- and S-verapamil. A correlation between individual pig CYP3A mRNA expression and in vivo hepatic extraction ratio was established which indicates that CYP3A is the major determinant factor in both pigs and humans. However, investigations of the metabolism of testosterone resulted in qualitative different metabolite pattern between pigs and humans. The metabolism of diclofenac was very low in pig liver microsomes and did not correlate to corresponding activity in human liver microsomes. In contrast dextromethorphan exhibited a very extensive and rapid metabolism in pig liver microsomes compared to human data. Together with previously determined gene expression data it confirms that CYP2D6 substrates will be very rapidly metabolized in pigs. The mRNA data increased the knowledge of the interindividual variability and the relative expression of different enzymes and transporters in pig intestine and liver. In conclusion, this study has increased the understanding of similarities and differences between pig and human biotransformation of drugs by providing new data for four different model compounds.

Meeting report: applied biopharmaceutics and quality by design for dissolution/release specification setting: product quality for patient benefit.

A biopharmaceutics and Quality by Design (QbD) conference was held on June 10–12, 2009 in Rockville, Maryland, USA to provide a forum and identify approaches for enhancing product quality for patient benefit. Presentations concerned the current biopharmaceutical toolbox (i.e., in vitro, in silico, pre-clinical, in vivo, and statistical approaches), as well as case studies, and reflections on new paradigms. Plenary and breakout session discussions evaluated the current state and envisioned a future state that more effectively integrates QbD and biopharmaceutics. Breakout groups discussed the following four topics: Integrating Biopharmaceutical Assessment into the QbD Paradigm, Predictive Statistical Tools, Predictive Mechanistic Tools, and Predictive Analytical Tools. Nine priority areas, further described in this report, were identified for advancing integration of biopharmaceutics and support a more fundamentally based, integrated approach to setting product dissolution/release acceptance criteria. Collaboration among a broad range of disciplines and fostering a knowledge sharing environment that places the patients needs as the focus of drug development, consistent with science- and risk-based spirit of QbD, were identified as key components of the path forward.

Do gastrointestinal transit parameters influence the pharmacokinetics of gefitinib

The selective EGFR tyrosine kinase inhibitor, gefitinib has been shown to be active against certain human carcinomas. It had been noted that a proportion of volunteers consistently had lower gefitinib exposure following oral administration. The shape of the elimination profile in this subset was also different, showing a monophasic elimination pattern rather than the biphasic pattern observed in the majority of subjects. A gamma scintigraphic study was conducted to examine the relationship of gastrointestinal transit and drug absorption in a cohort of rapid clearance subjects (n=5) and normal profile volunteers (n=7). The fasted volunteer panel received a 250 mg gefitinib tablet labelled with [(111)In]-DTPA together with 240 mL [(99m)Tc]-labelled water. The rapid clearance cohorts were shown to have a faster mean gastric emptying T90 (37 min vs 74 min) and shorter small intestinal transit time (156 min vs 204 min), resulting in an earlier colonic arrival time (181 min vs 244 min). Mean plasma C(max) was lower (99.2 ng/mL vs 116 ng/mL) and AUC almost half in the rapid clearance group (2162+/-81 ngh/mL vs 4996+/-64 ngh/mL). These data suggest that gastrointestinal transit parameters play a role in the differences in the rapid clearance profile group, also contributing to the biphasic to monophasic switch. However, historical data show, at the recommended dose of 250 mg/day steady-state plasma concentrations adequate for clinical benefit are achieved in patients with non-small cell lung cancer.

Different Effects of Ketoconazole on the Stereoselective First- Pass Metabolism of R/S-Verapamil in the Intestine and the Liver: Important for the Mechanistic Understanding of First-Pass Drug-Drug Interactions

In this acute study a pig jejunal intestinal perfusion model with multiple plasma sampling sites and three different administration routes was used to investigate the quantitative contribution of the intestine versus liver to the first-pass extraction of each enantiomer of verapamil (VER). A subclinical dose of ketoconazole (8 mg) was coadministered in the perfusion solution to selectively inhibit gut wall CYP3A. Both enantiomers of VER and its main metabolite norverapamil (NOR) as well as the inhibitor ketoconazole were quantified in all plasma compartments by liquid chromatography-tandem mass spectrometry. The overall first-pass metabolic extraction of VER and the metabolite NOR was shown to be stereoselective with the S-isomer being more extensively extracted. For VER the ratio of R- enantiomer to S-enantiomer was greater in the hepatic vein than in the portal vein (∼2.2 versus 1.4), indicating that the stereoselective metabolism of VER in pigs mainly occurs on the first pass through the liver and not in the intestine. Ketoconazole increased the area under the curve from time 0 to 6 h and Cmax of R- and S-VER at least 3-fold in the portal vein, most likely explained by inhibition of gut wall metabolism. Conversely, hepatic extraction was increased because the effect of gut wall metabolism was not observed at the peripheral sampling sites. In conclusion, this study provided novel and more direct information on the contribution of the intestine and the liver, respectively, to the overall first-pass extraction of racemic VER.

Summary Workshop Report: Facilitating Oral Product Development and Reducing Regulatory Burden Through Novel Approaches to Assess Bioavailability/ Bioequivalence

This summary workshop report highlights presentations and over-arching themes from an October 2011 workshop. Discussions focused on best practices in the application of biopharmaceutics in oral drug product development and evolving bioequivalence approaches. Best practices leverage biopharmaceutic data and other drug, formulation, and patient/disease data to identify drug development challenges in yielding a successfully performing product. Quality by design and product developability paradigms were discussed. Development tools include early development strategies to identify critical absorption factors and oral absorption modeling. An ongoing theme was the desire to comprehensively and systematically assess risk of product failure via the quality target product profile and root cause and risk analysis. However, a parallel need is reduced timelines and fewer resources. Several presentations discussed applying Biopharmaceutics Classification System (BCS) and in vitro–in vivo correlations in development and in post-development and discussed both resource savings and best scientific practices. The workshop also focused on evolving bioequivalence approaches, with emphasis on highly variable products (HVDP), as well as specialized modified-release products. In USA, two bioequivalence approaches for HVDP are the reference-scaled average bioequivalence approach and the two-stage group-sequential design. An adaptive sequential design approach is also acceptable in Canada. In European Union, two approaches for HVDP are a two-stage design and an approach to widen Cmax acceptance limits. For some specialized modified-release products, FDA now requests partial area under the curve. Rationale and limitations of such metrics were discussed (e.g., zolpidem and methylphenidate). A common theme was the benefit of the scientific and regulatory community developing, validating, and harmonizing newer bioequivalence methodologies (e.g., BCS-based waivers and HVDP trial designs).