Discovery of 6-(2,4-difluorophenoxy)-2-[3-hydroxy-1-(2-hydroxyethyl)propylamino]-8-methyl-8H-pyrido[2,3-d]pyrimidin-7-one (pamapimod) and 6-(2,4-difluorophenoxy)-8-methyl-2-(tetrahydro-2H-pyran-4-ylamino)pyrido[2,3-d]pyrimidin-7(8H)-one (R1487) as orally bioavailable and highly selective inhibitors of p38α mitogen-activated protein kinase.

The development of a new series of p38α inhibitors resulted in the identification of two clinical candidates, one of which was advanced into a phase 2 clinical study for rheumatoid arthritis. The original lead, an lck inhibitor that also potently inhibited p38α, was a screening hit from our kinase inhibitor library. This manuscript describes the optimization of the lead to p38-selective examples with good pharmacokinetic properties.

Identification and pre-clinical testing of a reversible cathepsin protease inhibitor reveals anti-tumor efficacy in a pancreatic cancer model.

Proteolytic activity is required for several key processes in cancer development and progression, including tumor growth, invasion and metastasis. Accordingly, high levels of protease expression and activity have been found to correlate with malignant progression and poor patient prognosis in a wide variety of human cancers. Members of the papain family of cysteine cathepsins are among the protease classes that have been functionally implicated in cancer. Therefore, the discovery of effective cathepsin inhibitors has considerable potential for anti-cancer therapy. In this study we describe the identification of a novel, reversible cathepsin inhibitor, VBY-825, which has high potency against cathepsins B, L, S and V. VBY-825 was tested in a pre-clinical model of pancreatic islet cancer and found to significantly decrease tumor burden and tumor number. Thus, the identification of VBY-825 as a new and effective anti-tumor drug encourages the therapeutic application of cathepsin inhibitors in cancer.

CRA-026440: a potent, broad-spectrum, hydroxamic histone deacetylase inhibitor with antiproliferative and antiangiogenic activity in vitro and in vivo.

CRA-026440 is a novel, broad-spectrum, hydroxamic acid-based inhibitor of histone deacetylase (HDAC) that shows antitumor and antiangiogenic activities in vitro and in vivo preclinically. CRA-026440 inhibited pure recombinant isozymes HDAC1, HDAC2, HDAC3/SMRT, HDAC6, HDAC8, and HDAC10 in the nanomolar range. Treatment of cultured tumor cell lines grown in vitro with CRA-026440 resulted in the accumulation of acetylated histone and acetylated tubulin, leading to an inhibition of tumor cell growth and the induction of apoptosis. CRA-026440 inhibited ex vivo angiogenesis in a dose-dependent manner. CRA-026440 parenterally given to mice harboring HCT116 or U937 human tumor xenografts resulted in a statistically significant reduction in tumor growth. CRA-026440, when used in combination with Avastin, achieved greater preclinical efficacy in HCT 116 colorectal tumor model. Inhibition of tumor growth was accompanied by an increase in the acetylation of alpha-tubulin in peripheral blood mononuclear cells and an alteration in the expression of many genes in the tumors, including several involved in angiogenesis, apoptosis, and cell growth. These results reveal CRA-026440 to be a novel HDAC inhibitor with potent antitumor activity.

Evaluation of antitumor properties of novel saframycin analogs in vitro and in vivo.

Novel analogs of (-)-saframycin A are described. The analogs are shown to be potent inhibitors of the in vitro growth of several tumor cells in a broad panel and promising as leads for further optimization. The first in vivo studies in a solid tumor model (HCT-116) reveal potent antitumor activity with associated toxicity of daily administration.

CRA-024781: a novel synthetic inhibitor of histone deacetylase enzymes with antitumor activity in vitro and in vivo.

CRA-024781 is a novel, broad spectrum hydroxamic acid-based inhibitor of histone deacetylase (HDAC) that shows antitumor activity in vitro and in vivo preclinically and is under evaluation in phase I clinical trials for cancer. CRA-024781 inhibited pure recombinant HDAC1 with a K(i) of 0.007 mumol/L, and also inhibited the other HDAC isozymes HDAC2, HDAC3/SMRT, HDAC6, HDAC8, and HDAC10 in the nanomolar range. Treatment of cultured tumor cell lines grown in vitro with CRA-024781 resulted in the accumulation of acetylated histone and acetylated tubulin, resulting in an inhibition of tumor cell growth and the induction of apoptosis. CRA-024781 parenterally administered to mice harboring HCT116 or DLD-1 colon tumor xenografts resulted in a statistically significant reduction in tumor growth at doses that were well tolerated as measured by body weight. Inhibition of tumor growth was accompanied by an increase in the acetylation of alpha-tubulin in peripheral blood mononuclear cells, and an alteration in the expression of many genes in the tumors, including several involved in apoptosis and cell growth. These results reveal CRA-024781 to be a novel HDAC inhibitor with potent antitumor activity.

Discovery of S-[5-amino-1-(4-fluorophenyl)-1H-pyrazol-4-yl]-[3-(2,3-dihydroxypropoxy)phenyl]methanone (RO3201195), an orally bioavailable and highly selective inhibitor of p38 MAP kinase.

A novel class of highly selective inhibitors of p38 MAP kinase was discovered from high throughput screening. The synthesis and optimization of a series of 5-amino-N-phenyl-1H-pyrazol-4-yl-3-phenylmethanones is described. An X-ray crystal structure of this series bound in the ATP binding pocket of unphosphorylated p38alpha established the presence of a unique hydrogen bond between the exocyclic amine of the inhibitor and threonine 106 which likely contributes to the selectivity for p38. The crystallographic information was used to optimize the potency and physicochemical properties of the series. The incorporation of the 2,3-dihydroxypropoxy moiety on the pyrazole scaffold resulted in a compound with excellent drug-like properties including high oral bioavailability. These efforts identified 63 (RO3201195) as an orally bioavailable and highly selective inhibitor of p38 which was selected for advancement into Phase I clinical trials.

Design and synthesis of 4-azaindoles as inhibitors of p38 MAP kinase.

Inhibition of the biosynthesis of proinflammatory cytokines such as tumor necrosis factor and interleukin-1 via p38 has been an approach toward the development of a disease modifying agent for the treatment of chronic inflammation and autoimmune diseases. The development of a new core structure of p38 inhibitors, 3-(4-fluorophenyl)-2-(pyridin-4-yl)-1H-pyrrolo[3,2-b] pyridine, is described. X-ray crystallographic data of the lead bound to the active site of p38 was used to guide the optimization of the series. Specific focus was placed on modulating the physical properties of the core while maintaining potent inhibition of p38. These efforts identified 42c as a potent inhibitor of p38, which also possessed the required physical properties worthy of advanced studies.

Targeting B cells for the treatment of rheumatoid arthritis.

The role of B cells in rheumatoid arthritis (RA) has been debated for decades. However, recent clinical trial data indicating that depletion of B cells in RA patients is of therapeutic benefit has validated the importance of this cell type in the pathogenesis of the disease. Elucidation of the molecular basis of B cell development and activation has allowed the identification of a number of possible therapeutic targets that are appealing for drug development. This review discusses briefly a number of these molecules and the rationale for targeting them for the treatment of RA.

A small molecule ubiquitination inhibitor blocks NF-kappa B-dependent cytokine expression in cells and rats.

A small molecule inhibitor of NF-kappaB-dependent cytokine expression was discovered that blocked tumor necrosis factor (TNF) alpha-induced IkappaB(alpha) degradation in MM6 cells but not the degradation of beta-catenin in Jurkat cells. Ro106-9920 blocked lipopolysaccharide (LPS)-dependent expression of TNFalpha, interleukin-1beta, and interleukin-6 in fresh human peripheral blood mononuclear cells with IC(50) values below 1 microm. Ro106-9920 also blocked TNFalpha production in a dose-dependent manner following oral administration in two acute models of inflammation (air pouch and LPS challenge). Ro106-9920 was observed to inhibit an ubiquitination activity that does not require betaTRCP but associates with IkappaB(alpha) and will ubiquitinate IkappaB(alpha) S32E,S36E (IkappaB(alpha)(ee)) specifically at lysine 21 or 22. Ro106-9920 was identified in a cell-free system as a time-dependent inhibitor of IkappaB(alpha)(ee) ubiquitination with an IC(50) value of 2.3 +/- 0.09 microm. The ubiquitin E3 ligase activity is inhibited by cysteine-alkylating reagents, supported by E2UBCH7, and requires cIAP2 or a cIAP2-associated protein for activity. These activities are inconsistent with what has been reported for SCF(betaTRCP), the putative E3 for IkappaB(alpha) ubiquitination. Ro106-9920 was observed to be selective for IkappaB(alpha)(ee) ubiquitination over the ubiquitin-activating enzyme (E1), E2UBCH7, nonspecific ubiquitination of cellular proteins, and 97 other molecular targets. We propose that Ro106-9920 selectively inhibits an uncharacterized but essential ubiquitination activity associated with LPS- and TNFalpha-induced IkappaB(alpha) degradation and NF-kappaB activation.

p38 mitogen activated protein kinase as a therapeutic target for Alzheimer's disease.

The characteristic pathological hallmarks of Alzheimer's disease (AD) include neuritic plaques, neurofibrillary tangles, and inflammatory changes. Current therapies, such as molecules that target enhancing cholinergic activity, can improve cognitive function in the short term but, unfortunately, have no impact on progression of the disease. Although many molecular targets have been suggested to play a causative role in AD progression, clinical data demonstrating a link between the blockade of such targets and amelioration or halting of disease progression are lacking. Even so, there are many interesting candidate targets, and current research efforts in these areas promises to deliver a wealth of new possibilities for treating AD in the future. This brief review will focus on p38 mitogen-activated protein kinase as a possible target for therapeutic intervention in AD.