[Show abstract][Hide abstract] ABSTRACT: Neuroblastoma (NB) is one of the most common and deadly pediatric solid tumors. NB is characterized by clinical heterogeneity, from spontaneous regression to relentless progression despite intensive multimodality therapy. There is compelling evidence that members of the tropomyosin receptor kinase (Trk) family play important roles in these disparate clinical behaviors. Indeed, TrkB and its ligand, brain-derived neurotrophic factor (BDNF), are expressed in 50-60 % of high-risk NBs. The BDNF/TrkB autocrine pathway enhances survival, invasion, metastasis, angiogenesis and drug resistance.
Cancer Chemotherapy and Pharmacology 11/2014; · 2.57 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The first disclosure of the synthesis, pre-clinical profile and in vivo efficacy in rat xenograft models of the novel and selective anaplastic lymphoma kinase inhibitor LDK378 (14b) is described. In this initial report, preliminary structure activity relationships (SAR) are described as well as the rational design strategy employed to overcome the de-velopment deficiencies of the first generation clinical candidate 4 (TAE684). Compound 14b is currently in Phase 1 and 2 clinical trials with substantial antitumor activity being observed in ALK-positive cancer patients.
Journal of Medicinal Chemistry 06/2013; · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Accumulation of β-amyloid (Aβ) in the brain is believed to contribute to the pathology of Alzheimer's Disease (AD). Aβ levels are controlled by the production of Aβ from amyloid precursor protein, degradation by proteases, and peripheral clearance. In this study we sought to determine whether enhancing clearance of plasma Aβ with a peripherally administered Aβ-degrading protease would reduce brain Aβ levels through a peripheral sink. Neprilysin (NEP) is a zinc-dependent metalloprotease that is one of the key Aβ-degrading enzymes in the brain. We developed a NEP fusion protein with in vitro degradation of Aβ and a 10 day plasma half-life in mouse. Intravenous administration of NEP to wild-type and APP23 transgenic mice resulted in dose-dependent clearance of plasma Aβ. However, this did not correspond to reduced levels of soluble brain Aβ with treatment up to 5 weeks in WT mice or formic acid-extractable brain Aβ with 3 month treatment in aged APP23. In contrast, intracranial injection of NEP resulted in an acute decrease in soluble brain Aβ. We found no change in amyloid precursor protein gene expression in mice treated with intravenous NEP, suggesting that the lack of effects in the brain following this route of administration was not caused by compensatory upregulation of Aβ production. Taken together, these results suggest a lack of a robust peripheral Aβ efflux sink through which brain amyloid burdens can be therapeutically reduced.
Journal of Neuroscience 02/2013; 33(6):2457-64. · 6.75 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Successful drug discovery relies on the selection of drug candidates with good in vivo pharmacokinetic (PK) properties as well as appropriate preclinical efficacy and safety profiles. In vivo PK profiling is often a bottleneck in the discovery process. In this review, we focus on the tiered in vivo PK approaches implemented at the Genomics Institute of the Novartis Research Foundation (GNF), which includes snapshot PK, rapid PK and full PK studies. These in vivo PK approaches are well integrated within discovery research, allow tremendous flexibility and are highly efficient in supporting the diverse needs and increasing demand for in vivo profiling. The tiered in vivo PK studies expedite compound profiling and help guide the selection of more desirable compounds into efficacy models and for progression into development.
Drug discovery today 09/2012; · 6.63 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: On the basis of the initial success of optimization of a novel series of imidazolopiperazines, a second generation of compounds involving changes in the core piperazine ring was synthesized to improve antimalarial properties. These changes were carried out to further improve the potency and metabolic stability of the compounds by leveraging the outcome of a set of in vitro metabolic identification studies. The optimized 8,8-dimethyl imidazolopiperazine analogues exhibited improved potency, in vitro metabolic stability profile and, as a result, enhanced oral exposure in vivo in mice. The optimized compounds were found to be more efficacious than the current antimalarials in a malaria mouse model. They exhibit moderate oral exposure in rat pharmacokinetic studies to achieve sufficient multiples of the oral exposure at the efficacious dose in toxicology studies.
Journal of Medicinal Chemistry 04/2012; 55(9):4244-73. · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Transient transfection of mammalian cells in suspension culture has recently emerged as a very useful method for production of research-scale quantities of recombinant proteins. The most commonly used cell lines for this purpose are suspension-adapted HEK and CHO cells. We report here that the plasma exposure in mice of an IL-23R extracellular domain Fc fusion protein (IL23R-Fc) differed dramatically depending on whether the protein was prepared by transient transfection of HEK or CHO cells. Specifically, IL23R-Fc expressed using CHO cells had about 30-fold higher in vivo plasma exposure compared to the HEK-expressed protein. In contrast to their differing plasma exposures, the HEK- and CHO-expressed proteins had equivalent in vitro biological activity. Characterization of the CHO- and HEK-expressed IL23R-Fc proteins indicated that the differences in in vivo plasma exposure between them are due to differential glycosylation.
Protein Expression and Purification 05/2010; 71(1):96-102. · 1.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A novel series of benzo[a]carbazole-based small molecule agonists of the thrombopoietin (Tpo) receptor is reported. Starting from a 3.4 microM high throughput screen hit, members of this series have been identified which are full agonists with functional potency <50 nM and oral bioavailability in mice.
[Show abstract][Hide abstract] ABSTRACT: Described in this article are strategies implemented to increase the throughput of in vivo rodent pharmacokinetic (PK) studies using the snapshot PK study design and automated methods for compound submission, sample processing, data analysis and reporting. Applying snapshot PK studies to categorize the oral exposure of >1300 discovery compounds as low, moderate or high resulted in an attrition rate of 86%. The follow up full PK studies on the remaining compounds found that 98% of the compounds were predicted in the correct (69%) or adjacent (29%) oral exposure category by the snapshot PK studies. These results demonstrate that the snapshot PK screen in rodents can serve as an effective and efficient in vivo tool in the compound selection process in drug discovery.
Drug Discovery Today 05/2008; 13(7-8):360-7. · 5.96 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The optimization of the pharmacokinetic performance of various 2-pyridone-containing human rhinovirus (HRV) 3C protease (3CP) inhibitors following oral administration to either beagle dogs or CM-monkeys is described. The molecules described in this work are composed of a 2-pyridone-containing peptidomimetic binding determinant and an alpha,beta-unsaturated ester Michael acceptor moiety which forms an irreversible covalent adduct with the active site cysteine residue of the 3C enzyme. Modification of the ester contained within these compounds is detailed along with alteration of the P(2) substituent present in the peptidomimetic portion of the inhibitors. The pharmacokinetics of several inhibitors in both dogs and monkeys are described (7 h plasma concentrations after oral administration) along with their human plasma stabilities, stabilities in incubations with human, dog, and monkey microsomes and hepatocytes, Caco-2 permeabilities, and aqueous solubilities. Compounds containing an alpha,beta-unsaturated ethyl ester fragment and either an ethyl or propargyl P(2) moiety displayed the most promising combination of 3C enzyme inhibition (k(obs)/[I] 170 000-223 000 M(-1) s(-1)), antiviral activity (EC(50) = 0.047-0.058 microM, mean vs seven HRV serotypes), and pharmacokinetics following oral administration (7 h dog plasma levels = 0.248-0.682 microM; 7 h CM-monkey plasma levels = 0.057-0.896 microM).
Journal of Medicinal Chemistry 11/2003; 46(21):4572-85. · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The structure-based design, chemical synthesis, and biological evaluation of various 2-pyridone-containing human rhinovirus (HRV) 3C protease (3CP) inhibitors are described. These compounds are comprised of a peptidomimetic binding determinant and a Michael acceptor moiety, which forms an irreversible covalent adduct with the active site cysteine residue of the 3C enzyme. The 2-pyridone-containing inhibitors typically display improved 3CP inhibition properties relative to related peptide-derived molecules along with more favorable antiviral properties. The cocrystal structure of one pyridone-derived 3CP inhibitor complexed with HRV-2 3CP is also described along with certain ab initio conformation analyses. Optimization of the 2-pyridone-containing compounds is shown to provide several highly active 3CP inhibitors (k(obs)/[I] > 500,00 M(-1) s(-1)) that function as potent antirhinoviral agents (EC(50) = <0.05 microM) against multiple virus serotypes in cell culture. One 2-pyridone-containing 3CP inhibitor is shown to be bioavailable in the dog after oral dosing (F = 48%).
Journal of Medicinal Chemistry 04/2002; 45(8):1607-23. · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In modern drug discovery, the implementation of high throughput in vitro absorption, distribution, metabolism and elimination (ADME) assays has greatly facilitated early elimination of poor drug-like compounds and allowed selection of potential candidates for in vivo pharmacokinetic profiling. Despite the advances in the in vitro technologies and in silico approaches for prediction of in vivo PK parameters, in vitro to in vivo extrapolation and predictive power of these approaches are not always reliable and accurate. In vivo rodent PK studies are critical to ensure compounds have appropriate pharmacokinetic properties to be evaluated in preclinical pharmacology and safety studies. However, in vivo animal pharmacokinetic studies are still conducted in a traditional low throughput manner, and therefore, are often the bottlenecks of discovery projects in many pharmaceutical companies.
We present a new paradigm which we call Rapid PK for preclinical rodent in vivo PK studies to support drug discovery projects. We have applied this approach for both mouse and rat in vivo PK studies, which typically include both IV and PO arms with 3 animals in each dosing arm. Six blood samples are collected for each dosing arm up to 24h via serial blood sampling, and blood or plasma samples for the same time point within a dosing arm were pooled, resulting in a total of 12 plasma samples per study. The rapid PK approach has several integrated components, including automated compound preparation; standardized formulation and protocols for dosing and sampling; sample pooling across animals to reduce number of samples; automated plasma sample preparation using a Beckman FXp liquid handler; automated LC/MS/MS tuning and analysis; incorporation of in house developed non-compartmental PK regression tool for batch analysis of multiple compounds, and PK reports generated to internal database using web publishing tools.
In this approach, compound is dosed and analyzed discretely, thereby eliminating any drug-drug interaction concerns and analysis complications typically associated with cassette dosing or cassette analysis. We have shown that this approach has significantly improved throughput and turn-around time of preclinical PK studies, yet generating high quality full set of pharmacokinetics parameters sufficient to support discovery drug projects. When compared with standard full PK studies, very good correlation of the PK parameters CL, Vss and T1/2 was obtained in rapid PK studies after IV dosing of 26 compounds to rodents when the rapid and full PK studies were done months apart. Moreover, excellent correlation of dose-normalized AUC and Cmax values between Rapid and Full PK studies was achieved after oral dosing of 33 compounds.
17th North American Regional International society for the study of xenobiotics Meeting;