Workshop report and follow-up--AAPS Workshop on current topics in GLP bioanalysis: Assay reproducibility for incurred samples--implications of Crystal City recommendations.

The Conference Report of the 3rd AAPS/FDA Bioanalytical Workshop (Crystal City III) endorsed the concept that assay methods supporting bioanalytical data in submissions must demonstrate assay reproducibility by using incurred samples. The present Workshop was convened to provide a forum for discussion and consensus building about incurred sample assay reproducibility for both nonclinical and clinical studies. Information about current regulatory perspectives on incurred sample reanalysis (ISR) was presented, implications of ISR for both large and small molecules were discussed, and the steering committee put forth recommendations for performing ISR. These recommendations from the Workshop, along with the subsequent evolution of approaches leading to a robust ISR program, may be used by scientists performing bioanalytical assays for regulated studies to provide additional confirmation of assay reproducibility for incurred samples.

Criteria for selecting pharmacokinetic repeat study samples.

The pharmacokinetic (PK) repeat study sample, selected by the study pharmacokineticist, requires repeat bioanalysis because the concentration is incongruous with drug plasma concentration versus time profile. The inconsistency could be due to a number of reasons, including the detectable drug concentration in a predose sample or a sample from a placebo control group or a significant double peak in the terminal phase of an individual plasma concentration versus time profile that is not consistent with the profiles from other subjects in the same dose group. The justification for selecting the PK repeat sample should be clearly documented. The repeat analysis should be conducted in duplicate or triplicate as allowed by sample volume. To avoid subjectively selecting PK repeat samples, standard operating procedures should be prepared prior to the start of the study in order to define the criteria for selecting PK repeat study samples and also the procedure for conducting repeat analysis and reporting repeat assay values. The incurred sample re-analysis (ISR) assessment and the repeat analysis of pharmacokinetically anomalous samples are different in terms of purpose and conduct; the ISR assessment alone cannot accept or reject the results from a study for analytical reasons. Therefore, the results from the ISR assessment for assuring the reliability and reproducibility of a validated bioanalytical method in animal or human plasma or other biological matrices should not be used to substitute the results of repeat analysis of pharmacokinetically anomalous samples from a nonclinical or clinical study.

The 2nd Calibration and Validation Group workshop on recent issues in good laboratory practice bioanalysis.

This event was organized by the Calibration and Validation Group (a scientific nonprofit organization based in Toronto, Canada) as a 1.5-day workshop for contract research organizations and pharmaceutical companies involved in providing bioanalytical data for bioavailability, bioequivalence, pharmacokinetic and comparability studies.

Distribution of radioactivity in bone and related structures following administration of [14C]dalbavancin to New Zealand white rabbits.

Penetration of dalbavancin into noninfected bone and joint tissues was assessed after an intravenous dose of 20 mg/kg (of body weight) [(14)C]dalbavancin given to rabbits. Drug-derived radioactivity, determined over 14 days by either liquid scintillation counting or autoradiography, remained above the MIC for common gram-positive pathogens that cause bone and joint infections.

Protein binding and its potential for eliciting minimal systemic side effects with a novel inhaled corticosteroid, ciclesonide.

Freely circulating, protein unbound, active inhaled corticosteroid (ICS) can cause systemic adverse effects. Desisobutyryl-ciclesonide (des-CIC) is the active metabolite of ciclesonide, an effective, novel ICS for persistent asthma. This study examines the free fraction of ciclesonide and des-CIC and determines whether the presence of other agents or disease states affects protein binding. Protein binding of des-CIC (0.5, 5.0, 25, 100, and 500 ng/mL) was determined, using both equilibrium dialysis and ultrafiltration, in plasma from humans (healthy and either renally or hepatically impaired) and several animal species and in the presence of either salicylates or warfarin. Dialyzed samples were analyzed by liquid chromatography with tandem mass spectroscopy to determine both free and bound concentrations of des-CIC. After ultrafiltration, spiked plasma plus H-des-CIC was separated into free and bound fractions by centrifugation and quantified by scintillation counting. Additionally, in another study, protein binding of ciclesonide was determined by equilibrium dialysis. For equilibrium dialysis, the mean percentages of des-CIC (0.5-500 ng/mL) plasma protein binding across species were high, approximately 99%, and no apparent saturation of protein binding was observed. Results were similar for ultrafiltration analysis. Protein binding of des-CIC did not change in the presence of warfarin or salicylates or in the plasma of renally or hepatically impaired patients. The protein binding of ciclesonide was 99.4% in human serum. The very low fraction of unbound des-CIC in the systemic circulation suggests minimal systemic exposure of unbound des-CIC, thus suggesting a low potential for systemic adverse effects after administration of inhaled ciclesonide.

The conduct of in vitro and in vivo drug-drug interaction studies: a Pharmaceutical Research and Manufacturers of America (PhRMA) perspective.

Current regulatory guidances do not address specific study designs for in vitro and in vivo drug-drug interaction studies. There is a common desire by regulatory authorities and by industry sponsors to harmonize approaches, to allow for a better assessment of the significance of findings across different studies and drugs. There is also a growing consensus for the standardization of cytochrome P450 (P450) probe substrates, inhibitors and inducers and for the development of classification systems to improve the communication of risk to health care providers and to patients. While existing guidances cover mainly P450-mediated drug interactions, the importance of other mechanisms, such as transporters, has been recognized more recently, and should also be addressed. This article was prepared by the Pharmaceutical Research and Manufacturers of America (PhRMA) Drug Metabolism and Clinical Pharmacology Technical Working Groups and represents the current industry position. The intent is to define a minimal best practice for in vitro and in vivo pharmacokinetic drug-drug interaction studies targeted to development (not discovery support) and to define a data package that can be expected by regulatory agencies in compound registration dossiers.

The conduct of in vitro and in vivo drug-drug interaction studies: a PhRMA perspective.

Current regulatory guidances do not address specific study designs for in vitro and in vivo drug-drug interaction studies. There is a common desire by regulatory authorities and by industry sponsors to harmonize approaches to allow for a better assessment of the significance of findings across different studies and drugs. There is also a growing consensus for the standardization of cytochrome P450 (CYP) probe substrates, inhibitors, and inducers and for the development of classification systems to improve the communication of risk to health care providers and patients. While existing guidances cover mainly CYP-mediated drug interactions, the importance of other mechanisms, such as transporters, has been recognized more recently and should also be addressed. This paper was prepared by the Pharmaceutical Research and Manufacturers of America (PhRMA) Drug Metabolism and Clinical Pharmacology Technical Working Groups and represents the current industry position. The intent is to define a minimal best practice for in vitro and in vivo pharmacokinetic drug-drug interaction studies targeted to development (not discovery support) and to define a data package that can be expected by regulatory agencies in compound registration dossiers.