Targeting of colony-stimulating factor 1 receptor (CSF1R) in the CLL microenvironment yields antineoplastic activity in primary patient samples.

In many malignancies, the tumor microenvironment includes CSF1R-expressing supportive monocyte/macrophages that promote tumor cell survival. For chronic lymphocytic leukemia (CLL), these supportive monocyte/macrophages are known as nurse-like cells (NLCs), although the potential effectiveness of selective small-molecule inhibitors of CSF1R against CLL is understudied. Here, we demonstrate the preclinical activity of two inhibitors of CSF1R, GW-2580 and ARRY-382, in primary CLL patient samples. We observed at least 25% of CLL samples showed sub-micromolar sensitivity to CSF1R inhibitors. This sensitivity was observed in samples with varying genetic and clinical backgrounds, although higher white cell count and monocyte cell percentage was associated with increased sensitivity. Depleting CD14-expressing monocytes preferentially decreased viability in samples sensitive to CSF1R inhibitors, and treating samples with CSF1R inhibitors eliminated the presence of NLCs in long-term culture conditions. These results indicate that CSF1R small-molecule inhibitors target CD14-expressing monocytes in the CLL microenvironment, thereby depriving leukemia cells of extrinsic support signals. In addition, significant synergy was observed combining CSF1R inhibitors with idelalisib or ibrutinib, two current CLL therapies that disrupt tumor cell intrinsic B-cell receptor signaling. These findings support the concept of simultaneously targeting supportive NLCs and CLL cells and demonstrate the potential clinical utility of this combination.

Pexmetinib: A Novel Dual Inhibitor of Tie2 and p38 MAPK with Efficacy in Preclinical Models of Myelodysplastic Syndromes and Acute Myeloid Leukemia.

Myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML) suppress normal hematopoietic activity in part by enabling a pathogenic inflammatory milieu in the bone marrow. In this report, we show that elevation of angiopoietin-1 in myelodysplastic CD34(+) stem-like cells is associated with higher risk disease and reduced overall survival in MDS and AML patients. Increased angiopoietin-1 expression was associated with a transcriptomic signature similar to known MDS/AML stem-like cell profiles. In seeking a small-molecule inhibitor of this pathway, we discovered and validated pexmetinib (ARRY-614), an inhibitor of the angiopoietin-1 receptor Tie-2, which was also found to inhibit the proinflammatory kinase p38 MAPK (which is overactivated in MDS). Pexmetinib inhibited leukemic proliferation, prevented activation of downstream effector kinases, and abrogated the effects of TNFα on healthy hematopoietic stem cells. Notably, treatment of primary MDS specimens with this compound stimulated hematopoiesis. Our results provide preclinical proof of concept for pexmetinib as a Tie-2/p38 MAPK dual inhibitor applicable to the treatment of MDS/AML. Cancer Res; 76(16); 4841-9. ©2016 AACR.

Potent and highly selective benzimidazole inhibitors of PI3-kinase delta.

Inhibition of PI3Kδ is considered to be an attractive mechanism for the treatment of inflammatory diseases and leukocyte malignancies. Using a structure-based design approach, we have identified a series of potent and selective benzimidazole-based inhibitors of PI3Kδ. These inhibitors do not occupy the selectivity pocket between Trp760 and Met752 that is induced by other families of PI3Kδ inhibitors. Instead, the selectivity of the compounds for inhibition of PI3Kδ relative to other PI3K isoforms appears to be due primarily to the strong interactions these inhibitors are able to make with Trp760 in the PI3Kδ binding pocket. The pharmacokinetic properties and the ability of compound 5 to inhibit the function of B-cells in vivo are described.

Potent and selective inhibitors of PI3Kδ: obtaining isoform selectivity from the affinity pocket and tryptophan shelf.

A potent inhibitor of PI3Kδ that is ≥ 200 fold selective for the remaining three Class I PI3K isoforms and additional kinases is described. The hypothesis for selectivity is illustrated through structure activity relationships and crystal structures of compounds bound to a K802T mutant of PI3Kγ. Pharmacokinetic data in rats and mice support the use of 3 as a useful tool compound to use for in vivo studies.

Inflammation Research Association: 12th international conference.

The Inflammation Research Association held its 12th international meeting at the Sagamore at Bolton Landing in New York State (3 - 7 October 2004). These meetings were originally intended for scientists from the pharmaceutical industry to get together and discuss the latest developments in inflammation drug discovery, and it remains an industry-dominated affair. The conference covered some highly topical issues such as cyclooxygenase-2 inhibitors (rofecoxib/Vioxx [Merck & Co., Inc.] was withdrawn from the market only a few days before the conference), along with areas of ongoing interest to the pharmaceutical and biotechnology industry, including p38 MAPK inhibitors, nuclear hormone receptor modulators and prostaglandin receptor antagonists. This review will cover the main themes that emerged during the meeting.

Racemic and chiral lactams as potent, selective and functionally active CCR4 antagonists.

A series of racemic and chiral, nonracemic lactams that display high binding affinities, functional chemotaxis antagonism, and selectivity toward CCR4 are described. Compound 41, which provides reasonably high blood levels in mice when dosed intraperitoneally, was identified as a useful pharmacological tool to explore the role of CCR4 antagonism in animal models of allergic disease.

HIV entry and fusion inhibitors.

Human immunodeficiency virus (HIV) is a retrovirus that is the causative agent of acquired immunodeficiency syndrome (AIDS). Current HIV therapy is based on targeting two critical enzymes in the viral replication machinery: reverse transcriptase and a virally encoded protease. Although mortality rates due to HIV infection have been dramatically reduced, AIDS remains a major health problem throughout the world. The emergence of HIV variants that are resistant to current therapies and potential toxicity associated with their chronic use has highlighted the need for new approaches to HIV inhibition. Identification of the mechanisms underlying viral entry into the host cell has provided a number of novel therapeutic targets and the first of these HIV fusion inhibitors (enfuvirtide [pentafuside, T-20, Fuzeon; Roche Laboratories and Trimeris]) has recently been approved in the US and Europe. This review will focus on recent progress in the development of therapeutics that target the HIV entry process.

Discovery and SAR of trisubstituted thiazolidinones as CCR4 antagonists.

Substituted thiazolidinones were identified as CCR4 antagonists from high throughput screening. Subsequent lead optimization efforts resulted in defined structure-activity relationships and the identification of potent antagonists (compounds 90 and 91) that inhibited the chemotaxis of Th2 T-cells in vitro.

G protein-coupled receptors: from ligand identification to drug targets. 14-16 October 2002, San Diego, CA, USA.

IBC advertised their seventh annual symposium on G protein-coupled receptors (GPCRs) under the heading 'GPCRs still the best drug targets' and, at the end of the 3-day meeting which took place at the Hilton San Diego Resort (October 14-16 2002), it seemed like an appropriate description. The meeting brought together researchers from a wide range of disciplines, and from both academia and industry, to discuss recent advances in GPCR biology, pharmacology and drug design. This review will cover the main themes that emerged during the meeting, with an emphasis on those areas that impact drug discovery.

CCR4-bearing T cells participate in autoimmune diabetes.

Chemokine receptor expression is exquisitely regulated on T cell subsets during the course of their migration to inflammatory sites. In the present study we demonstrate that CCR4 expression marks a pathogenic population of autoimmune T cells. CCR4 was found exclusively on memory CD4(+) T cells during the progression of disease in NOD mice. Cells expressing the CCR4 ligand TARC (thymus- and activation-regulated chemokine) were detected within infiltrated islets from prediabetic mice. Interestingly, neutralization of macrophage-derived chemokine (MDC) with Ab caused a significant reduction of CCR4-positive T cells within the pancreatic infiltrates and inhibited the development of insulitis and diabetes. Furthermore, enhanced recruitment of CCR4-bearing cells in NOD mice resulting from transgenic expression of MDC resulted in acceleration of clinical disease. Cumulatively, the results demonstrate that CCR4-bearing T cells participate in the development of such tissue-driven autoimmune reactions.

A crucial role for the p110delta subunit of phosphatidylinositol 3-kinase in B cell development and activation.

Mice lacking the p110delta catalytic subunit of phosphatidylinositol 3-kinase have reduced numbers of B1 and marginal zone B cells, reduced levels of serum immunoglobulins, respond poorly to immunization with type II thymus-independent antigen, and are defective in their primary and secondary responses to thymus-dependent antigen. p110delta(-/-) B cells proliferate poorly in response to B cell receptor (BCR) or CD40 signals in vitro, fail to activate protein kinase B, and are prone to apoptosis. p110delta function is required for BCR-mediated calcium flux, activation of phosphlipaseCgamma2, and Bruton's tyrosine kinase. Thus, p110delta plays a critical role in B cell homeostasis and function.

Presence of high contents of thymus and activation-regulated chemokine in platelets and elevated plasma levels of thymus and activation-regulated chemokine and macrophage-derived chemokine in patients with atopic dermatitis.

BACKGROUND: T(H)2 cells and eosinophils selectively express CC chemokine receptor 4 and CCR3, respectively, and their chemokine ligands are likely to play important roles in the pathogenesis of atopic dermatitis (AD). OBJECTIVE: The purpose of this study was to demonstrate the presence of thymus and activation-regulated chemokine (TARC) in platelets and its release during clotting and to evaluate the circulating levels of TARC, macrophage-derived chemokine (MDC), and eotaxin in control subjects and patients with AD. METHODS: We compared plasma and serum contents of TARC, MDC, and eotaxin. We measured TARC contents in platelet lysates. We analyzed the correlation of plasma levels of TARC, MDC, and eotaxin with various clinicolaboratory parameters in patients with AD. RESULTS: Serum contents of TARC rapidly increased during clotting, whereas those of MDC and eotaxin increased only slightly. We demonstrated that platelets contained TARC, and its levels were dramatically elevated in patients with AD. Platelets also released TARC on stimulation with thrombin. We therefore evaluated circulating levels of these chemokines in control subjects and patients with AD by using plasma samples. Plasma TARC levels were significantly increased in patients with AD (P <.0001) and showed significant correlations with severity scoring of atopic dermatitis (SCORAD) index (r = 0.665, P <.00001), serum lactate dehydrogenese levels (r = 0.696, P =.00001), eosinophil counts (r = 0.381, P =.007), and platelet counts (r = 0.562, P <.0001). Similarly, plasma MDC levels were significantly increased in patients with AD (P <.0001) and showed significant correlations with SCORAD index (r = 0.727, P <.0001), serum lactate dehydrogenese levels (r = 0.861, P <.0001), eosinophil counts (r = 0.505, P =.005), and platelet counts (r = 0.370, P =.01). On treatment, plasma TARC and MDC levels were dramatically decreased in accordance with improved SCORAD scores (P =.0012 and P =.0007, respectively). On the other hand, plasma eotaxin levels did not show any significant increase or correlation with any of the clinical parameters in patients with AD. CONCLUSION: Platelets from patients with AD contain high levels of TARC. Thus platelets might play an important role in AD pathogenesis by releasing T(H)2-attracting TARC on activation. Furthermore, circulating levels of TARC and MDC, but not those of eotaxin, correlate well with the disease activity of AD.

IFN-gamma-inducible expression of thymus and activation-regulated chemokine/CCL17 and macrophage-derived chemokine/CCL22 in epidermal keratinocytes and their roles in atopic dermatitis.

Thymus and activation-regulated chemokine (TARC)/CCL17 and macrophage-derived chemokine (MDC)/CCL22 are a pair of CC chemokines known to selectively attract T(h)2 type memory T cells via CCR4. Here we examined circulating levels of TARC and MDC in patients with atopic dermatitis (AD) and control subjects by using plasma samples, which reflect blood contents of chemokines more accurately than serum samples. The plasma levels of TARC and MDC were significantly elevated in AD patients. These values also strongly correlated with disease severity and serum lactate dehydrogenase levels, and weakly correlated with serum total IgE levels and blood eosinophilia. Previous studies demonstrated TARC immunoreactivity in the epidermal layer of AD lesional skin and production of TARC by a human keratinocytic cell line HaCaT upon stimulation with IFN-gamma. Here we demonstrated MDC immunoreactivity in the epidermal layer of AD skin at levels stronger than that of TARC. Furthermore, primary epidermal keratinocytes expressed both TARC and MDC mRNA upon stimulation with IFN-gamma, but efficiently secreted only MDC. These results suggest a post-transcriptional regulation in TARC production. IFN-gamma also induced TARC and MDC mRNA in mouse skin. Collectively, both TARC and MDC play important roles in the local accumulation of T(h)2 cells in AD lesional skin. Production of T(h)2-attracting chemokines by epidermal keratinocytes upon treatment with IFN-gamma, which is also the potent inducer of T(h)1-attracting chemokines, may underline the pivotal role of IFN-gamma in the chronic phase of AD where both T(h)1 and T(h)2 responses are mixed.

Chemokines in allergy.

Allergic diseases such as atopic dermatitis, asthma, and allergic rhinitis represent a significant healthcare problem. Understanding these diseases as dysregulated inflammatory responses has led to many new targets for therapeutic intervention. Recent data concerning soluble IL-4 receptor, monoclonal antibodies against IL-5 and an antibody toward IgE have lead to an appreciation of the crucial role played by Th2 subset of CD4(+) T cells and their corresponding cytokines. While these potential drugs are presently in clinical trials and may be valuable therapeutics, orally bioavailable small molecule inhibitors of Th2 cell responses would be desirable for treatment of these chronic diseases. One strategy is to prevent effector cell migration (Th2 cells, mast cells, and eosinophils) via chemokine receptor antagonism with a suitable small molecule. Chemokine receptors are a subset of the seven transmembrane-spanning family, which mediate their effects through interaction with heterotrimeric G-proteins. The ligands are a structurally related set of proteins that are selectively expressed in certain disease settings. Three chemokine receptors CCR3, CCR4, and CCR8 are preferentially expressed by Th2 cells, mast cells and eosinophils and therefore represent therapeutic targets for allergy. This mini-review will focus on new research involving CCR3, CCR4 and CCR8. The cellular distribution of each receptor, the corresponding chemokine ligands, and various validation studies are discussed. Recent drug discovery advances concerning pharmacological tools and small molecule receptor antagonists will also be presented.