Kenneth D. Rice

Synthesis of 3,5-disubstituted-1,2,4-oxadiazoles using tetrabutylammonium fluoride as a mild and efficient catalyst

Tetrabutylammonium fluoride (TBAF) was found to be a mild and efficient catalyst for the synthesis of 3,5-disubstituted-1,2,4-oxadiazoles. Using 0.1–1.0 equivalents of TBAF in THF for 1–24 h at room temperature, alkanoyl- and aroyloxyamidines were converted in high yield to the corresponding 3,5-disubstituted-1,2,4-oxadiazoles. A variety of R and R′ substituents were investigated.

Novel Carboxamide-Based Allosteric MEK Inhibitors: Discovery and Optimization Efforts toward XL518 (GDC-0973)

The ERK/MAP kinase cascade is a key mechanism subject to dysregulation in cancer and is constitutively activated or highly upregulated in many tumor types. Mutations associated with upstream pathway components RAS and Raf occur frequently and contribute to the oncogenic phenotype through activation of MEK and then ERK. Inhibitors of MEK have been shown to effectively block upregulated ERK/MAPK signaling in a range of cancer cell lines and have further demonstrated early evidence of efficacy in the clinic for the treatment of cancer. Guided by structural insight, a strategy aimed at the identification of an optimal diphenylamine-based MEK inhibitor with an improved metabolism and safety profile versus PD-0325901 led to the discovery of development candidate 1-({3,4-difluoro-2-[(2-fluoro-4-iodophenyl)amino]phenyl}carbonyl)-3-[(2S)-piperidin-2-yl]azetidin-3-ol (XL518, GDC-0973) (1). XL518 exhibits robust in vitro and in vivo potency and efficacy in preclinical models with sustained duration of action and is currently in early stage clinical trials.

Dibasic inhibitors of human mast cell tryptase. Part 2 : Structure-activity relationships and requirements for potent activity

Detailed structure activity relationships (SARs) for a series of dibasic human tryptase inhibitors are presented. The structural requirements for potent inhibitory activity are remarkably broad with a range of core template modifications being well tolerated. Optimized inhibitors demonstrate potent anti-asthmatic activity in a sheep model of allergic asthma. APC-2059, a dibasic tryptase inhibitor with subnanomolar activity, has been advanced to phase II clinical trials for the treatment of both psoriasis and ulcerative colitis.

An improved synthesis of 1,2,4-oxadiazoles on solid support.

The use of tetra-N-butylammonium fluoride (TBAF) as a mild and efficient reagent for the cyclodehydration of O-acyl amidoximes has been extended to the synthesis of 1,2,4-oxadiazoles on solid support. Argopore MB-CHO resin (Argonaut Technologies) was reductively aminated and subsequently acylated with 4-cyanobenzoyl chloride. Conversion of the nitrile to the amidoxime and acylation with a range of acid chlorides in parallel followed by treatment with TBAF under ambient conditions afforded a library of 3,5-disubstituted 1,2,4-oxadiazoles.

Dibasic inhibitors of human mast cell tryptase. Part 1: Synthesis and optimization of a novel class of inhibitors

The synthesis and optimization of a novel class of reversible and active-site directed dibasic inhibitors of human mast cell tryptase are described. The compounds were shown to be both remarkably potent and selective for tryptase with Ki values for optimized inhibitors in the picomolar range.

Discovery of XL888: A novel tropane-derived small molecule inhibitor of HSP90

With structural guidance, tropane-derived HTS hits were modified to optimize for HSP90 inhibition and a desirable in vivo profile. Through an iterative SAR development process 12i (XL888) was discovered and shown to reduce HSP90 client protein content in PD studies. Furthermore, efficacy experiments performed in a NCI-N87 mouse xenograft model demonstrated tumor regression in some dosing regimens.

Design and evaluation of a series of pyrazolopyrimidines as p70S6K inhibitors.

The 70-kDa ribosomal protein S6 kinase (p70S6K) is part of the PI3K/AKT/mTOR pathway and has been implicated in cancer. High throughput screening versus p70S6K led to the identification of aminopyrimidine 3a as active inhibitor. Lead optimization of 3a resulted in highly potent, selective, and orally bioavailable pyrazolopyrimidines. In this manuscript we report the structure-activity relationship of this series and pharmacokinetic, pharmacodynamic, and efficacy data of the lead compound 13c.

Raf modulators and methods of use

Exelixis claims a series of RAF kinase inhibitors based on a 3-oxo-2,3-dihydro-1H-isoindol-1-yl core structure. Both the chemical matter and the biochemical target appear to be new for Exelixis, and many examples have IC50 values < 100 nM. These compounds are claimed to have the potential to treat diseases that are associated with uncontrolled, abnormal and/or unwanted cellular activities such as cancer.

Dibasic Inhibitors of Human Mast Cell Tryptase. Part 3: Identification of a Series of Potent and Selective Inhibitors Containing the Benzamidine Functionality

A survey of charged groups and linkers for a series of symmetrical and unsymmetrical dibasic inhibitors is described, leading to several classes of potent and selective inhibitors. In particular, the benzamidine functionality was identified as the most potent charged group investigated.

Pyrazolopyrimidines as dual Akt/p70S6K inhibitors.

Activation of the PI3K/Akt/mTOR kinase pathway is frequently associated with human cancer. Selective inhibition of p70S6Kinase, which is the last kinase in the PI3K pathway, is not sufficient for strong tumor growth inhibition and can lead to activation of upstream proteins including Akt through relief of a negative feedback loop. Targeting multiple sites in the PI3K pathway might be beneficial for optimal activity. In this manuscript we report the design of dual Akt/p70S6K inhibitors and the evaluation of the lead compound 11b in vivo, which was eventually advanced into clinical development.