Metabolic Disposition of Osimertinib in Rats, Dogs, and Humans: Insights into a Drug Designed to Bind Covalently to a Cysteine Residue of Epidermal Growth Factor Receptor.

Preclinical and clinical studies were conducted to determine the metabolism and pharmacokinetics of osimertinib and key metabolites AZ5104 and AZ7550. Osimertinib was designed to covalently bind to epidermal growth factor receptors, allowing it to achieve nanomolar cellular potency (Finlay et al., 2014). Covalent binding was observed in incubations of radiolabeled osimertinib with human and rat hepatocytes, human and rat plasma, and human serum albumin. Osimertinib, AZ5104, and AZ7550 were predominantly metabolized by CYP3A. Seven metabolites were detected in human hepatocytes, also observed in rat or dog hepatocytes at similar or higher levels. After oral administration of radiolabeled osimertinib to rats, drug-related material was widely distributed, with the highest radioactivity concentrations measured at 6 hours postdose in most tissues; radioactivity was detectable in 42% of tissues 60 days postdose. Concentrations of [(14)C]-radioactivity in blood were lower than in most tissues. After the administration of a single oral dose of 20 mg of radiolabeled osimertinib to healthy male volunteers, ∼19% of the dose was recovered by 3 days postdose. At 84 days postdose, mean total radioactivity recovery was 14.2% and 67.8% of the dose in urine and feces. The most abundant metabolite identified in feces was AZ5104 (∼6% of dose). Osimertinib accounted for ∼1% of total radioactivity in the plasma of non-small cell lung cancer patients after 22 days of 80-mg osimertinib once-daily treatment; the most abundant circulatory metabolites were AZ7550 and AZ5104 (<10% of total osimertinib-related material). Osimertinib is extensively distributed and metabolized in humans and is eliminated primarily via the fecal route.

Metabolic disposition of AZD8931, an oral equipotent inhibitor of EGFR, HER2 and HER3 signalling, in rat, dog and man.

1. This series of studies in rats, dogs and humans (Clinicaltrials.gov identifier: NCT01284595) investigated the pharmacokinetics, tissue distribution, metabolism and excretion of the EGFR, HER2 and HER3 signalling inhibitor AZD8931. 2. Single oral or intravenous doses of 2-(4-[4-(3-chloro-2-fluoro[U-(14)C]-phenylamino)-7-methoxy-quinazolin-6-yloxy]-piperidin-1-yl)-N-methyl-acetamide difumarate ([(14)C]-AZD8931) were administered. 3. AZD8931 absorption was rapid in all species. Following [(14)C]-AZD8931 administration to rats, radioactivity was widely and rapidly distributed, with the highest levels in organs of metabolism and excretion (gastrointestinal tract, liver). Following oral and intravenous [(14)C]-AZD8931 administration, excretion of radioactivity by all species occurred predominantly via the bile into faeces, with <5% of the dose being eliminated in urine. In all species, AZD8931 was principally cleared by metabolism. The major route of metabolism was hydroxylation and O-demethylation in rat, and aryl ring oxidation in dog. Metabolism of AZD8931 in humans was attributed to three pathways; oxidation and amine or ether cleavage around the piperidine ring with subsequent glucuronide or sulphate conjugation. 4. AZD8931 is largely cleared by metabolism in the rat, dog and human. Excretory profiles indicate that there are no unique human metabolites.

Absence of developmental and reproductive toxicity in rats, rabbits, and zebrafish embryos exposed to antimalarial drug cabamiquine.

BACKGROUND: When developing new antimalarial drugs, considering their potential use during pregnancy as preventive or curative therapy is crucial. This prevents the parasite from affecting embryonic development and reduces maternal and fetal death risks. Consequently, understanding the exposure and safety of antimalarial drugs during pregnancy is crucial, with well-designed animal studies playing a key role in this assessment. METHODS: As part of the drug development program for cabamiquine, a series of developmental and reproductive toxicity studies were conducted in rats and rabbits. Additionally, the zebrafish embryo model was used to further improve embryo exposure, minimize confounding factors related to maternal toxicity, and assess developmental risks of cabamiquine. RESULTS: In these studies, although maternal toxicity was observed, there were no cabamiquine-related adverse effects on fertility, embryonic, or fetal development at maternal exposures representing significant multiples (up to five and 10 times higher in rabbit and rats, respectively) than the exposure at the anticipated efficacious human dose. Similarly, no adverse effects were observed on ZF embryonic development, even though cabamiquine concentrations in the embryos were 10-fold higher than nominal concentrations. CONCLUSIONS: The results obtained in a full set of reproductive toxicity studies did not provide evidence of detrimental effects on the conceptuses and progeny at maternally nontoxic doses and exposures, still representing a multiple of the anticipated systemic exposures in women of childbearing potential (WOCBP). Cabamiquine can therefore be considered a suitable therapeutic option for WOCBP and pregnant women living in malaria-endemic regions by significantly reducing maternal and infant malaria death rates.

Metabolism of (R)-Praziquantel versus the Activation of a Parasite Transient Receptor Potential Melastatin Ion Channel.

Praziquantel (PZQ) is an essential anthelmintic drug recently established to be an activator of a Transient Receptor Potential Melastatin (TRPMPZQ ) ion channel in trematode worms. Bioinformatic, mutagenesis and drug metabolism work indicate that the cyclohexyl ring of PZQ is a key pharmacophore for activation of trematode TRPMPZQ , as well as serving as the primary site of oxidative metabolism which results in PZQ being a short-lived drug. Based on our recent findings, the hydrophobic cleft in schistosome TRPMPZQ defined by three hydrophobic residues surrounding the cyclohexyl ring has little tolerance for polarity. Here we evaluate the in vitro and in vivo activities of PZQ analogues with improved metabolic stability relative to the challenge of maintaining activity on the channel. Finally, an estimation of the respective contribution to the overall activity of both the parent and the main metabolite of PZQ in humans is reported.

The right compound in the right assay at the right time: an integrated discovery DMPK strategy.

The high rate of attrition during drug development and its associated high research and development (R&D) cost have put pressure on pharmaceutical companies to ensure that candidate drugs going to clinical testing have the appropriate quality such that the biological hypothesis could be evaluated. To help achieve this ambition, drug metabolism and pharmacokinetic (DMPK) science and increasing investment have been deployed earlier in the R&D process. To gain maximum return on investment, it is essential that DMPK concepts are both appropriately integrated into the compound design process and that compound selection is focused on accurate prediction of likely outcomes in patients. This article describes key principles that underpin the contribution of DMPK science for small-molecule research based on 15 years of discovery support in a major pharmaceutical company. It does not aim to describe the breadth and depth of DMPK science, but more the practical application for decision making in real-world situations.

Correction for nonspecific binding to various components of ultrafiltration apparatus and impact on estimating in vivo rat clearance for a congeneric series of 5-ethyl, 5-n-alkyl barbituric acids.

Accurately predicting in vivo metabolic clearance from in vitro liver microsomes or hepatocytes requires a good understanding of the factors contributing to the prediction. Although much work has concentrated on deriving scaling factors and optimizing the metabolic stability techniques for consistency and rigor, it is only relatively recently that the importance of binding to microsomes and hepatocytes has been appreciated. Ultrafiltration is often used to estimate binding to plasma proteins and microsomes, but the level of nonspecific binding (NSB) to the ultrafiltration apparatus has not been adequately described. We derive an equation to correct for NSB and demonstrate that this can significantly affect the estimate of binding to microsomes and improve the accuracy of scaling to in vivo clearance for a series of barbiturates.

Small-molecule androgen receptor downregulators as an approach to treatment of advanced prostate cancer.

Chemical starting points were investigated for downregulation of the androgen receptor as an approach to treatment of advanced prostate cancer. Although prototypic steroidal downregulators such as 6a designed for intramuscular administration showed insufficient cellular potency, a medicinal chemistry program derived from a novel androgen receptor ligand 8a led to 6-[4-(4-cyanobenzyl)piperazin-1-yl]-3-(trifluoromethyl)[1,2,4]triazolo[4,3-b]pyridazine (10b), for which high plasma levels following oral administration in a preclinical model compensate for moderate cellular potency.

Development of an influenza pandemic decision support tool linking situational analytics to national response policy.

National influenza pandemic plans have evolved substantially over recent decades, as has the scientific research that underpins the advice contained within them. While the knowledge generated by many research activities has been directly incorporated into the current generation of pandemic plans, scientists and policymakers are yet to capitalise fully on the potential for near real-time analytics to formally contribute to epidemic decision-making. Theoretical studies demonstrate that it is now possible to make robust estimates of pandemic impact in the earliest stages of a pandemic using first few hundred household cohort (FFX) studies and algorithms designed specifically for analysing FFX data. Pandemic plans already recognise the importance of both situational awareness i.e., knowing pandemic impact and its key drivers, and the need for pandemic special studies and related analytic methods for estimating these drivers. An important next step is considering how information from these situational assessment activities can be integrated into the decision-making processes articulated in pandemic planning documents. Here we introduce a decision support tool that directly uses outputs from FFX algorithms to present recommendations on response options, including a quantification of uncertainty, to decision makers. We illustrate this approach using response information from within the Australian influenza pandemic plan.

Novel thienopyrimidine and thiazolopyrimidine kinase inhibitors with activity against Tie-2 in vitro and in vivo.

The SAR and improvement in potency against Tie2 of novel thienopyrimidine and thiazolopyrimidine kinase inhibitors are reported. The crystal structure of one of these compounds bound to the Tie-2 kinase domain is consistent with the SAR. These compounds have moderate potency in cellular assays of Tie-2 inhibition, good physical properties, DMPK, and show evidence of in vivo inhibition of Tie-2.

Acute-onset Flu Encephalopathy in an Adolescent Female.

Flu encephalopathy is a rare and poorly understood complication of the influenza virus. In children, it presents most commonly in the 6-18 months age range and most often in the first 26 hours of flu symptoms. Here, we present a case of a 13-year old black female who presented with acute-onset encephalopathy two weeks into flu symptoms. As we begin this flu season, this case serves as a reminder that flu encephalopathy should be on the differential for acute-onset altered mental status.

Novel 3-alkoxy-1H-pyrazolo[3,4-d]pyrimidines as EGFR and erbB2 receptor tyrosine kinase inhibitors.

Novel 4-anilino-1H-pyrazolo[3,4-d]pyrimidines have been synthesized and evaluated in vitro for erbB2 and EGFR kinase inhibition. A representative compound displaying oral bioavailability in rat and dog illustrates the potential of this series to provide orally active erbB2 inhibitors.

Neutral 5-substituted 4-indazolylaminoquinazolines as potent, orally active inhibitors of erbB2 receptor tyrosine kinase.

We have identified a new series of C-5 substituted indazolylaminoquinazolines as potent erbB2 kinase inhibitors. The lead compound 22 showed excellent in vitro potency, good physical properties, acceptable oral pharmacokinetics in rat and dog, and low human in vitro clearance. It showed at least equivalent activity dose for dose compared to lapatinib in various erbB2- or EGFR-driven xenograft models after chronic oral administration.

A new series of neutral 5-substituted 4-anilinoquinazolines as potent, orally active inhibitors of erbB2 receptor tyrosine kinase.

Starting from initial lead 1 containing a basic 5-substituent, optimisation of the glycolamide-derived neutral 5-substituent led to potent inhibitors of erbB2 with good pharmacokinetics. Representative compounds 19 and 21 inhibited phosphorylation of erbB2 in a mouse BT474C xenograft model after oral administration.

Development, Verification, and Prediction of Osimertinib Drug-Drug Interactions Using PBPK Modeling Approach to Inform Drug Label.

Osimertinib is a potent, highly selective, irreversible inhibitor of epidermal growth factor receptor (EGFR) and T790M resistance mutation. In vitro metabolism data suggested osimertinib is a substrate of cytochrome P450 (CYP)3A4/5, a weak inducer of CYP3A, and an inhibitor of breast cancer resistance protein (BCRP). A combination of in vitro data, clinical pharmacokinetic data, and drug-drug interaction (DDI) data of osimertinib in oncology patients were used to develop the physiologically based pharmacokinetic (PBPK) model and verify the DDI data of osimertinib. The model predicted the observed monotherapy concentration profile of osimertinib within 1.1-fold, and showed good predictability (within 1.7-fold) to the observed peak plasma concentration (Cmax ) and area under the curve (AUC) DDI ratio changes, when co-administered with rifampicin, itraconazole, and simvastatin, but not with rosuvastatin. Based on observed clinical data and PBPK simulations, the recommended dose of osimertinib when dosed with strong CYP3A inducers is 160 mg once daily. PBPK modeling suggested no dose adjustment with moderate and weak CYP3A inducers.

Irreversible Inhibition of EGFR: Modeling the Combined Pharmacokinetic-Pharmacodynamic Relationship of Osimertinib and Its Active Metabolite AZ5104.

Osimertinib (AZD9291) is a potent, selective, irreversible inhibitor of EGFR-sensitizing (exon 19 and L858R) and T790M-resistant mutation. In vivo, in the mouse, it is metabolized to an active des-methyl metabolite, AZ5104. To understand the therapeutic potential in patients, this study aimed to assess the relationship between osimertinib pharmacokinetics, the pharmacokinetics of the active metabolite, the pharmacodynamics of phosphorylated EGFR reduction, and efficacy in mouse xenograft models of EGFR-driven cancers, including two NSCLC lines. Osimertinib was dosed in xenografted models of EGFR-driven cancers. In one set of experiments, changes in phosphorylated EGFR were measured to confirm target engagement. In a second set of efficacy studies, the resulting changes in tumor volume over time after repeat dosing of osimertinib were observed. To account for the contributions of both molecules, a mathematical modeling approach was taken to integrate the resulting datasets. The model was able to describe the pharmacokinetics, pharmacodynamics, and efficacy in A431, PC9, and NCI-H1975 xenografts, with the differences in sensitivity described by the varying potency against wild-type, sensitizing, and T790M-mutant EGFR and the phosphorylated EGFR reduction required to reduce tumor volume. It was inferred that recovery of pEGFR is slower after chronic dosing due to reduced resynthesis. It was predicted and further demonstrated that although inhibition is irreversible, the resynthesis of EGFR is such that infrequent intermittent dosing is not as efficacious as once daily dosing. Mol Cancer Ther; 15(10); 2378-87. ©2016 AACR.

Preclinical Comparison of Osimertinib with Other EGFR-TKIs in EGFR-Mutant NSCLC Brain Metastases Models, and Early Evidence of Clinical Brain Metastases Activity.

PURPOSE: Approximately one-third of patients with non-small cell lung cancer (NSCLC) harboring tumors with EGFR-tyrosine kinase inhibitor (TKI)-sensitizing mutations (EGFRm) experience disease progression during treatment due to brain metastases. Despite anecdotal reports of EGFR-TKIs providing benefit in some patients with EGFRm NSCLC brain metastases, there is a clinical need for novel EGFR-TKIs with improved efficacy against brain lesions. EXPERIMENTAL DESIGN: We performed preclinical assessments of brain penetration and activity of osimertinib (AZD9291), an oral, potent, irreversible EGFR-TKI selective for EGFRm and T790M resistance mutations, and other EGFR-TKIs in various animal models of EGFR-mutant NSCLC brain metastases. We also present case reports of previously treated patients with EGFRm-advanced NSCLC and brain metastases who received osimertinib in the phase I/II AURA study (NCT01802632). RESULTS: Osimertinib demonstrated greater penetration of the mouse blood-brain barrier than gefitinib, rociletinib (CO-1686), or afatinib, and at clinically relevant doses induced sustained tumor regression in an EGFRm PC9 mouse brain metastases model; rociletinib did not achieve tumor regression. Under positron emission tomography micro-dosing conditions, [11C]osimertinib showed markedly greater exposure in the cynomolgus monkey brain than [11C]rociletinib and [11C]gefitinib. Early clinical evidence of osimertinib activity in previously treated patients with EGFRm-advanced NSCLC and brain metastases is also reported. CONCLUSIONS: Osimertinib may represent a clinically significant treatment option for patients with EGFRm NSCLC and brain metastases. Further investigation of osimertinib in this patient population is ongoing. Clin Cancer Res; 22(20); 5130-40. ©2016 AACR.

AZD9496: An Oral Estrogen Receptor Inhibitor That Blocks the Growth of ER-Positive and ESR1-Mutant Breast Tumors in Preclinical Models.

Fulvestrant is an estrogen receptor (ER) antagonist administered to breast cancer patients by monthly intramuscular injection. Given its present limitations of dosing and route of administration, a more flexible orally available compound has been sought to pursue the potential benefits of this drug in patients with advanced metastatic disease. Here we report the identification and characterization of AZD9496, a nonsteroidal small-molecule inhibitor of ERα, which is a potent and selective antagonist and downregulator of ERα in vitro and in vivo in ER-positive models of breast cancer. Significant tumor growth inhibition was observed as low as 0.5 mg/kg dose in the estrogen-dependent MCF-7 xenograft model, where this effect was accompanied by a dose-dependent decrease in PR protein levels, demonstrating potent antagonist activity. Combining AZD9496 with PI3K pathway and CDK4/6 inhibitors led to further growth-inhibitory effects compared with monotherapy alone. Tumor regressions were also seen in a long-term estrogen-deprived breast model, where significant downregulation of ERα protein was observed. AZD9496 bound and downregulated clinically relevant ESR1 mutants in vitro and inhibited tumor growth in an ESR1-mutant patient-derived xenograft model that included a D538G mutation. Collectively, the pharmacologic evidence showed that AZD9496 is an oral, nonsteroidal, selective estrogen receptor antagonist and downregulator in ER(+) breast cells that could provide meaningful benefit to ER(+) breast cancer patients. AZD9496 is currently being evaluated in a phase I clinical trial. Cancer Res; 76(11); 3307-18. ©2016 AACR.

Discovery and optimization of a novel series of Dyrk1B kinase inhibitors to explore a MEK resistance hypothesis.

Potent and selective inhibitors of Dyrk1B kinase were developed to explore the hypothesis, based on siRNA studies, that Dyrk1B may be a resistance mechanism in cells undergoing a stress response.

Optimization of a Novel Binding Motif to (E)-3-(3,5-Difluoro-4-((1R,3R)-2-(2-fluoro-2-methylpropyl)-3-methyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-yl)phenyl)acrylic Acid (AZD9496), a Potent and Orally Bioavailable Selective Estrogen Receptor Downregulator and Antagonist.

The discovery of an orally bioavailable selective estrogen receptor downregulator (SERD) with equivalent potency and preclinical pharmacology to the intramuscular SERD fulvestrant is described. A directed screen identified the 1-aryl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole motif as a novel, druglike ER ligand. Aided by crystal structures of novel ligands bound to an ER construct, medicinal chemistry iterations led to (E)-3-(3,5-difluoro-4-((1R,3R)-2-(2-fluoro-2-methylpropyl)-3-methyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-yl)phenyl)acrylic acid (30b, AZD9496), a clinical candidate with high oral bioavailability across preclinical species that is currently being evaluated in phase I clinical trials for the treatment of advanced estrogen receptor (ER) positive breast cancer.