Approaches for predicting human pharmacokinetics using interspecies pharmacokinetic scaling

Glossary and tutorial of xenobiotic metabolism terms used during small molecule drug discovery and development (IUPAC Technical Report)

This project originated more than 15 years ago with the intent to produce a glossary of drug metabolism terms having definitions especially applicable for use by practicing medicinal chemists. A first-draft version underwent extensive beta-testing that, fortuitously, engaged international audiences in a wide range of disciplines involved in drug discovery and development. It became clear that the inclusion of information to enhance discussions among this mix of participants would be even more valuable. The present version retains a chemical structure theme while expanding tutorial comments that aim to bridge the various perspectives that may arise during interdisciplinary communications about a given term. This glossary is intended to be educational for early stage researchers, as well as useful for investigators at various levels who participate on today’s highly multidisciplinary, collaborative small molecule drug discovery teams.

A phase 1 trial of 4-(N-(S-penicillaminylacetyl)amino)-phenylarsonous acid (PENAO) in patients with advanced solid tumours

PURPOSE

This phase I study was conducted to evaluate the safety and Maximum Tolerated Dose of PENAO (4-(N-(S-penicillaminylacetyl)amino)-phenylarsonous acid), a second-generation organic arsenical with anti-mitochondrial activity, when given as a continuous intravenous infusion (CIVI), in patients with advanced solid tumours.

METHODS

Eligibility criteria for this trial included age ≥ 18 years, advanced solid tumour, ECOG Performance Status ≤ 1 and adequate organ function. PENAO was administered by CIVI, with dose levels initially increased by infusion duration in a 21-day cycle at a fixed daily dose and then increased daily dose. Standard dose-limiting toxicity (DLT) definitions were used in a "3 + 3" design. Patients had regular monitoring of toxicity and efficacy. Pharmacokinetic assays of serum and urine As were performed.

RESULTS

Twenty-six patients were treated across 8 dose levels. The only dose-limiting toxicity (DLT) observed was fatigue, that occurred in one patient treated at the highest dose level of 9 mg/m²/day. No significant organ toxicity or objective responses were observed, although there were two patients with stable disease lasting up to 7 months. Pharmacokinetic analysis unexpectedly indicated a half-life of 9-19 days, invalidating the CIVI dosing resulting in discontinuation of the study before the RP2D was defined.

CONCLUSIONS

PENAO was administered by CIVI at dose levels up to 9 mg/m²/day with only one DLT noted. Pharmacokinetic studies invalidated the rationale for continuous dosing and led to discontinuation of the trial without defining a RP2D. Future clinical development of PENAO will use intermittent dosing schedule, alone and in combination with rapamycin.

First dose in neonates: pharmacokinetic bridging study from juvenile mice to neonates for drugs metabolized by CYP3A

First dose prediction is challenging in neonates. Our objective in this proof-of-concept study was to perform a pharmacokinetic (PK) bridging study from juvenile mice to neonates for drugs metabolized by CYP3A. We selected midazolam and clindamycin as model drugs. We developed juvenile mice population PK models using NONMEM. The PK parameters of these two drugs in juvenile mice were used to bridge PK parameters in neonates using different correction methods. The bridging results were evaluated by the fold-error of 0.5- to 1.5-fold. Simple allometry with and without a correction factor for maximum lifespan potential could be used for a bridging of clearance (CL) and volume of distribution (V_d), respectively, from juvenile mice to neonates. Simulation results demonstrated that for midazolam, 100% of clinical studies for which both the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. For clindamycin, 75% and 100% of clinical studies for which the predictive CL and V_d were within 0.5- to 1.5-fold of the observed. A PK bridging of drugs metabolized by CYP3A is feasible from juvenile mice to neonates. It could be a complement to the ADE and PBPK models to support the first dose in neonates.

Aldehyde oxidase and its role as a drug metabolizing enzyme

Aldehyde oxidase (AO) is a cytosolic enzyme that belongs to the family of structurally related molybdoflavoproteins like xanthine oxidase (XO). The enzyme is characterized by broad substrate specificity and marked species differences. It catalyzes the oxidation of aromatic and aliphatic aldehydes and various heteroaromatic rings as well as reduction of several functional groups. The references to AO and its role in metabolism date back to the 1950s, but the importance of this enzyme in the metabolism of drugs has emerged in the past fifteen years. Several reviews on the role of AO in drug metabolism have been published in the past decade indicative of the growing interest in the enzyme and its influence in drug metabolism. Here, we present a comprehensive monograph of AO as a drug metabolizing enzyme with emphasis on marketed drugs as well as other xenobiotics, as substrates and inhibitors. Although the number of drugs that are primarily metabolized by AO are few, the impact of AO on drug development has been extensive. We also discuss the effect of AO on the systemic exposure and clearance these clinical candidates. The review provides a comprehensive analysis of drug discovery compounds involving AO with the focus on developmental candidates that were reported in the past five years with regards to pharmacokinetics and toxicity. While there is only one known report of AO-mediated clinically relevant drug-drug interaction (DDI), a detailed description of inhibitors and inducers of AO known to date has been presented here and the potential risks associated with DDI. The increasing recognition of the importance of AO has led to significant progress in predicting the site of AO-mediated metabolism using computational methods. Additionally, marked species difference in expression of AO makes it is difficult to predict human clearance with high confidence. The progress made towards developing in vivo, in vitro and in silico approaches for predicting AO metabolism and estimating human clearance of compounds that are metabolized by AO have also been discussed.

Systems Biology, Systems Medicine, Systems Pharmacology: The What and The Why

Systems biology is today such a widespread discipline that it becomes difficult to propose a clear definition of what it really is. For some, it remains restricted to the genomic field. For many, it designates the integrated approach or the corpus of computational methods employed to handle the vast amount of biological or medical data and investigate the complexity of the living. Although defining systems biology might be difficult, on the other hand its purpose is clear: systems biology, with its emerging subfields systems medicine and systems pharmacology, clearly aims at making sense of complex observations/experimental and clinical datasets to improve our understanding of diseases and their treatments without putting aside the context in which they appear and develop. In this short review, we aim to specifically focus on these new subfields with the new theoretical tools and approaches that were developed in the context of cancer. Systems pharmacology and medicine now give hope for major improvements in cancer therapy, making personalized medicine closer to reality. As we will see, the current challenge is to be able to improve the clinical practice according to the paradigm shift of systems sciences.

Pharmacokinetics of β-Lactam Antibiotics: Clues from the Past To Help Discover Long-Acting Oral Drugs in the Future

β-Lactams represent perhaps the most important class of antibiotics yet discovered. However, despite many years of active research, none of the currently approved drugs in this class combine oral activity with long duration of action. Recent developments suggest that new β-lactam antibiotics with such a profile would have utility in the treatment of tuberculosis. Consequently, the historical β-lactam pharmacokinetic data have been compiled and analyzed to identify possible directions and drug discovery strategies aimed toward new β-lactam antibiotics with this profile.

Pharmacotherapy in pediatric epilepsy: from trial and error to rational drug and dose selection - a long way to go

INTRODUCTION

Whereas ongoing efforts in epilepsy research focus on the underlying disease processes, the lack of a physiologically based rationale for drug and dose selection contributes to inadequate treatment response in children. In fact, limited information on the interindividual variation in pharmacokinetics and pharmacodynamics of anti-epileptic drugs (AEDs) in children drive prescription practice, which relies primarily on dose regimens according to a mg/kg basis. Such practice has evolved despite advancements in pediatric pharmacology showing that growth and maturation processes do not correlate linearly with changes in body size.

AREAS COVERED

In this review we aim to provide 1) a comprehensive overview of the sources of variability in the response to AEDs, 2) insight into novel methodologies to characterise such variation and 3) recommendations for treatment personalisation.

EXPERT OPINION

The use of pharmacokinetic-pharmacodynamic principles in clinical practice is hindered by the lack of biomarkers and by practical constraints in the evaluation of polytherapy. The identification of biomarkers and their validation as tools for drug development and therapeutics will require some time. Meanwhile, one should not miss the opportunity to integrate the available pharmacokinetic data with modeling and simulation concepts to prevent further delays in the development of personalised treatments for pediatric patients.

Pharmacokinetics and pharmacodynamics of rilotumumab: a decade of experience in preclinical and clinical cancer research

Rilotumumab is a fully human monoclonal antibody against hepatocyte growth factor, the only known ligand of the MET receptor. Over the last decade, rilotumumab has been extensively tested in preclinical studies and in clinical studies in a variety of cancer types. In this review, we examine the pharmacokinetic and pharmacodynamic data that have been collected in the rilotumumab programme to date, and discuss retrospectively how the knowledge acquired in this programme can be applied to a number of key issues in oncology drug development, including: (i) using preclinical data to inform first-in-human study design; (ii) the role of biomarkers in the identification of a target patient population; (iii) the potential for drug interactions between therapeutic proteins and other anticancer agents; and (iv) pharmacokinetic and pharmacodynamic considerations in phase 3 study design.

Population pharmacokinetics of maslinic acid, a triterpene from olives, after intravenous and oral administration in rats

SCOPE

Maslinic acid is a bioactive minor component of Olea europaea L. with health-enhancing activities and no harmful effects. A pharmacokinetic (PK) study was conducted to determine its bioavailability for future studies of maslinic acid in humans.

METHODS AND RESULTS

Intravenous (1 mg/kg) and oral (50 mg/kg) administrations to Sprague-Dawley rats were performed. Blood was obtained several times over 24 h and PKs were analyzed with NONMEM 7.2, applying a population approach. Body weight was included a priori in the model with fixed allometric exponents, based on allometric principles. Plasma concentrations versus time were best characterized by a two-open compartment model with first-order absorption and linear elimination. Maslinic acid had a relative rapid oral absorption with a peak concentration after administration at 0.51 h and a bioavailability of 5.13%. Once in bloodstream, it distributed extensively into tissues, since the central and peripheral distribution volumes were 8.41 L/70 kg and 63.6 L/70 kg, respectively. The clearance (8 L/h/70 kg) was related to unaltered renal excretion. The prediction-corrected visual predictive check confirmed its stability and predictive ability.

CONCLUSION

An allometric population PK model was performed for maslinic acid, which adequately described and predicted plasma concentrations.