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Background: Phosphatidylinositol 3-kinase p110δ isoform (PI3K p110δ) activity is essential for mast cell activation, suggesting that inhibition of PI3K p110δ might be useful in treating allergic diseases., Objective: We sought to determine the effect of the PI3K p110δ-selective inhibitor idelalisib on allergic responses., Methods: This phase 1 randomized, double-blind, placebo-controlled, 2-period crossover study was conducted with the Vienna Challenge Chamber. Grass pollen-induced allergic symptoms were documented during screening. Eligible subjects received idelalisib (100 mg twice daily) or placebo for 7 days, with allergen challenge on day 7. After a 2-week washout period, subjects received the alternate treatment and repeated allergen challenge. Study measures included safety, nasal and nonnasal symptoms, nasal airflow, nasal secretions, basophil activation, and plasma cytokine levels., Results: Forty-one patients with allergic rhinitis received idelalisib/placebo (n = 21) or placebo/idelalisib (n = 20). Idelalisib treatment was well tolerated. Mean total nasal symptom scores were lower during the combined idelalisib treatment periods compared with placebo (treatment difference [idelalisib - placebo], -1.78; 95% CI, -2.53 to -1.03; P < .001). Statistically significant differences were also observed for the combined treatment periods for total symptom scores, nasal airflow, nasal secretion weight, and nasal congestion scores. The percentage of ex vivo-activated basophils (CD63(+)/CCR3(+) cells; after stimulation with grass pollen) was substantially lower for idelalisib-treated compared with placebo-treated subjects. Plasma CCL17 and CCL22 levels were reduced after idelalisib treatment., Conclusion: Idelalisib treatment was well tolerated in patients with allergic rhinitis and appears to reduce allergic responses clinically and immunologically after an environmental allergen challenge., (Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Systemic lupus erythematosus (SLE) is a human chronic inflammatory disease generated and maintained throughout life by autoreactive T and B cells. Class I phosphoinositide 3-kinases (PI3K) are heterodimers composed of a regulatory and a catalytic subunit that catalyze phosphoinositide-3,4,5-P3 formation and regulate cell survival, migration, and division. Activity of the PI3Kδ isoform is enhanced in human SLE patient PBLs. In this study, we analyzed the effect of inhibiting PI3Kδ in MRL/lpr mice, a model of human SLE. We found that PI3Kδ inhibition ameliorated lupus progression. Treatment of these mice with a PI3Kδ inhibitor reduced the excessive numbers of CD4(+) effector/memory cells and B cells. In addition, this treatment reduced serum TNF-α levels and the number of macrophages infiltrating the kidney. Expression of inactive PI3Kδ, but not deletion of the other hematopoietic isoform PI3Kγ, reduced the ability of macrophages to cross the basement membrane, a process required to infiltrate the kidney, explaining MRL/lpr mice improvement by pharmacologic inhibition of PI3Kδ. The observations that p110δ inhibitor prolonged mouse life span, reduced disease symptoms, and showed no obvious secondary effects indicates that PI3Kδ is a promising target for SLE., (Copyright © 2014 by The American Association of Immunologists, Inc.)

Phosphatidylinositol 3-kinases (PI3K) participate in numerous signaling pathways, and control distinct biological functions. Studies using pan-PI3K inhibitors suggest roles for PI3K in osteoclasts, but little is known about specific PI3K isoforms in these cells. Our objective was to determine effects of isoform-selective PI3K inhibitors on osteoclasts. The following inhibitors were investigated (targets in parentheses): wortmannin and LY294002 (pan-p110), PIK75 (α), GDC0941 (α, δ), TGX221 (β), AS252424 (γ), and IC87114 (δ). In addition, we characterized a new potent and selective PI3Kδ inhibitor, GS-9820, and explored roles of PI3K isoforms in regulating osteoclast function. Osteoclasts were isolated from long bones of neonatal rats and rabbits. Wortmannin, LY294002, GDC0941, IC87114, and GS-9820 induced a dramatic retraction of osteoclasts within 15-20 min to 65-75% of the initial area. In contrast, there was no significant retraction in response to vehicle, PIK75, TGX221, or AS252424. Moreover, wortmannin and GS-9820, but not PIK75 or TGX221, disrupted actin belts. We examined effects of PI3K inhibitors on osteoclast survival. Whereas PIK75, TGX221, and GS-9820 had no significant effect on basal survival, all blocked RANKL-stimulated survival. When studied on resorbable substrates, osteoclastic resorption was suppressed by wortmannin and inhibitors of PI3Kβ and PI3Kδ, but not other isoforms. These data are consistent with a critical role for PI3Kδ in regulating osteoclast cytoskeleton and resorptive activity. In contrast, multiple PI3K isoforms contribute to the control of osteoclast survival. Thus, the PI3Kδ isoform, which is predominantly expressed in cells of hematopoietic origin, is an attractive target for anti-resorptive therapeutics.

During the progression of autoimmune (type 1) diabetes, T cells and macrophages infiltrate the pancreas, disrupt islet function, and destroy insulin-producing beta cells. B-lymphocytes, particularly innate like B-cell populations such as marginal zone B cells and B-1 cells, have been implicated in many autoimmune diseases, and non-obese diabetic (NOD) mice that lack B cells do not develop spontaneous autoimmune diabetes. Hence, inhibitors of B cell signaling pathways could be useful for limiting the autoimmune processes that contribute to type 1 diabetes. Signaling via phosphoinositide 3-kinase (PI3K) regulates many cellular processes. The p110δ isoform of PI3K is expressed primarily in cells of hematopoietic origin and the catalytic activity of p110δ is important for B cell migration, activation, proliferation, and antigen presentation. Because innate-like B cells are particularly sensitive to inhibition of p110δ activity, and p110δ inhibitors also suppress pro-inflammatory functions of other cell types that contribute to autoimmunity, we tested whether a p110δ inhibitor could delay the onset or reduce the incidence of autoimmune diabetes in NOD mice. We found that long-term preventative treatment of pre-diabetic NOD mice with IC87114, a highly selective small molecule inhibitor of p110δ, reduced the infiltration of inflammatory cells into the pancreatic islets and, accordingly, delayed and reduced the loss of glucose homeostasis. Moreover in a therapeutic treatment mode, IC87114 treatment conferred prolonged protection from progression to overt diabetes in a number of animals. These findings suggest that PI3Kδ inhibitors could be useful for managing type 1 diabetes.

In patients with chronic lymphocytic leukemia (CLL), lenalidomide can promote humoral immune responses but also induces a distinct disease-specific toxicity of tumor flare and cytokine release. These CLL-specific events result from increased expression of costimulatory molecules on B cells. Here we demonstrate that lenalidomide activation of CLL cells depends on the phosphatidylinositol 3-kinase p110δ (PI3K-δ) pathway. Inhibition of PI3K-δ signaling by the PI3K-δ-inhibiting drug, CAL-101, or by siRNA knockdown of p110δ, abrogates CLL cell activation, costimulatory molecule expression, and vascular endothelial growth factor and basic fibroblast growth factor gene expression that is induced by lenalidomide. In addition, CAL-101 attenuates lenalidomide-mediated increases in immunoglobulin M production by normal B cells. Collectively, these data demonstrate the importance of PI3K-δ signaling for lenalidomide immune modulation. These findings may guide development of strategies for the treatment of CLL that combine lenalidomide with CAL-101, with other inhibitors of the PI3K-δ pathway, or with other agents that target downstream kinases of this signaling pathway.

Phosphoinositide 3-kinases (PI3Ks) contribute to the pathogenesis of asthma by regulating the activation of inflammatory mediators, inflammatory cell recruitment and immune cell function. Recent findings have indicated that PI3Ks also regulate the expression of interleukin (IL)-17, which has been recognised as an important cytokine involved in airway inflammation. In the present study, we investigated a role of PI3Kδ in the regulation of IL-17 expression in allergic airway disease using a murine model of asthma. After ovalbumin inhalation, administration of a selective p110δ inhibitor, IC87114, significantly attenuated airway infiltration of total cells, lymphocytes, neutrophils and eosinophils, as well as airway hyperresponsiveness, and attenuated the increase in IL-17 protein and mRNA expression. Moreover, IC87114 reduced levels of IL-4, -5 and -13, expression of keratinocyte chemoattractant protein and mRNA, and nuclear factor (NF)-κB activity. In addition, a NF-κB inhibitor, BAY 11-7085 substantially reduced the increase in IL-17 protein levels. Our results also showed that inhibition of IL-17 activity with an anti-IL-17 antibody remarkably reduced airway inflammation and hyperresponsiveness. These findings suggest that inhibition of the p110δ signalling pathway suppresses IL-17 expression through regulation of NF-κB activity and, thus, has therapeutic potential in asthma.

Targeted therapy with imatinib in chronic myeloid leukemia (CML) prompted a new treatment paradigm. Unlike CML, chronic lymphocytic leukemia (CLL) lacks an aberrant fusion protein kinase but instead displays increased phosphatidylinositol 3-kinase (PI3K) activity. To date, PI3K inhibitor development has been limited because of the requirement of this pathway for many essential cellular functions. Identification of the hematopoietic-selective isoform PI3K-δ unlocks a new therapeutic potential for B-cell malignancies. Herein, we demonstrate that PI3K has increased enzymatic activity and that PI3K-δ is expressed in CLL cells. A PI3K-δ selective inhibitor CAL-101 promoted apoptosis in primary CLL cells ex vivo in a dose- and time-dependent fashion that was independent of common prognostic markers. CAL-101-mediated cytotoxicity was caspase dependent and was not diminished by coculture on stromal cells. In addition, CAL-101 abrogated protection from spontaneous apoptosis induced by B cell-activating factors CD40L, TNF-α, and fibronectin. In contrast to malignant cells, CAL-101 does not promote apoptosis in normal T cells or natural killer cells, nor does it diminish antibody-dependent cellular cytotoxicity. However, CAL-101 did decrease activated T-cell production of various inflammatory and antiapoptotic cytokines. Collectively, these studies provide rationale for the clinical development of CAL-101 as a first-in-class targeted therapy for CLL and related B-cell lymphoproliferative disorders.

Background: Recent studies indicate that pharmaceutical blockade of phosphoinositide 3-kinase (PI3K) signaling enzymes might be effective in reducing allergic airway inflammation. Signals generated by the p110delta PI3K isoform play critical roles in signaling through antigen and cytokine receptors and were shown to be required for induction of type 2, but not type 1, cytokine responses., Objective: We sought to determine the effect of genetic or pharmaceutical inactivation of p110delta PI3K on induction of IgE responses., Methods: We determined the effect of p110delta inactivation on induction of systemic IgE responses and on the ability of purified B lymphocytes to undergo IgE isotype switch in vitro. IgG and IgE germline transcription, postswitch transcription, protein expression, and secretion were measured, as well as cell division and expression of activation-induced cytidine deaminase, an enzyme required for isotype switch., Results: Paradoxically, inactivation of p110delta PI3K led to markedly increased IgE responses, despite reduced production of other antibody isotypes. This result was seen by using genetic inactivation of p110delta inhibition with IC87114 compound or blockade with the broad-spectrum PI3K inhibitors PIK-90 and PI-103. Significant increases in IgG1/IgE double-positive cells were observed, indicating that inactivation of PI3K leads to uncontrolled sequential switching from IgG1 to IgE. Disruption of p110delta signaling results in increased germline transcription at the epsilon locus and increased activation-induced cytidine deaminase expression, suggesting deregulation at the level of the isotype switch process., Conclusion: Blockade of PI3K signaling leads to markedly enhanced B-cell switch to IgE and increased IgE levels in vivo, despite reduced type 2 cytokine production.

Background: Bronchial asthma is characterized by inflammation of the airways, which is usually accompanied by increased vascular permeability, resulting in plasma exudation. Vascular endothelial growth factor (VEGF) has been implicated in contributing to asthmatic tissue edema through its effect on vascular permeability. Many cellular responses of VEGF are regulated by the lipid products of phosphoinositide 3-kinase (PI3K). However, the effect of PI3K catalytic subunit p110delta on VEGF-mediated signaling is unknown. Recently, an isoform-specific small molecule inhibitor, IC87114, which is selective for p110delta catalytic activity, has been identified., Objective: We have sought to investigate the role of PI3K-delta, more specifically in the increase of vascular permeability., Methods: Female BALB/c mice were sensitized and challenged with ovalbumin. We have investigated the effect of IC87114 on airway inflammation, T(H)2 cytokines expression, airway hyperresponsiveness, plasma extravasation, hypoxia-inducible factor 1alpha expression, and VEGF expression in a murine model of asthma., Results: Our current study has revealed that IC87114 reduces antigen-induced airway infiltration of inflammatory cells, secretion of T(H)2 cytokines in lungs, airway hyperresponsiveness, and vascular permeability. Moreover, we have found that inhibition of p110delta reduces ovalbumin-induced upregulation of VEGF level., Conclusion: These results suggest that PI3K-delta inhibitor attenuates antigen-induced airway inflammation and hyperresponsiveness by preventing vascular leakage in mice., Clinical Implications: These findings provide a crucial molecular mechanism for the potential role of PI3K-delta in asthma and other airway inflammatory disorders.

P110delta phosphoinositide 3-kinase (PI3K) plays a pivotal role in the recruitment and activation of certain inflammatory cells. Recent findings revealed that the activity of p110delta also contributes to allergen-IgE-induced mast cell activation and vascular permeability. We investigated the role of p110delta in allergic airway inflammation and hyperresponsiveness using IC87114, a selective p110delta inhibitor, in a mouse asthma model. BALB/c mice were sensitized with OVA and, upon OVA aerosol challenge, developed airway eosinophilia, mucus hypersecretion, elevation in cytokine and chemokine levels, up-regulation of ICAM-1 and VCAM-1 expression, and airway hyperresponsiveness. Intratracheal administration of IC87114 significantly (P<0.05) attenuated OVA-induced influx into lungs of total leukocytes, eosinophils, neutrophils, and lymphocytes, as well as levels of IL-4, IL-5, IL-13, and RANTES in a dose-dependent manner. IC87114 also significantly (P<0.05) reduced the serum levels of total IgE and OVA-specific IgE and LTC(4) release into the airspace. Histological studies show that IC87114 inhibited OVA-induced lung tissue eosinophilia, airway mucus production, and inflammation score. In addition, IC87114 significantly (P<0.05) suppressed OVA-induced airway hyperresponsiveness to inhaled methacholine. Western blot analyses of whole lung tissue lysates shows that IC87114 markedly attenuated the OVA-induced increase in expression of IL-4, IL-5, IL-13, ICAM-1, VCAM-1, RANTES, and eotaxin. Furthermore, IC87114 treatment markedly attenuated OVA-induced serine phosphorylation of Akt, a downstream effector of PI3K signaling. Taken together, our findings implicate that inhibition of p110delta signaling pathway may have therapeutic potential for the treatment of allergic airway inflammation.