Selective PI3Kδ Inhibitor Research Articles

PI3K Signaling in B Cell and T Cell Biology.

The drug Idelalisib is the first PI3K inhibitor to be approved by the FDA for clinical use. It is therefore timely to take stock of our current understanding of the role of PI3Ks in the immune system. The phosphoinositide 3-kinases (PI3Ks) control many key functions in immune cells (1). PI3Ks phosphorylate PtdIns(4,5)P2 to yield PtdIns(3,4,5)P3, which acts as a second messenger signaling molecule that controls the activation of Akt and other proteins with PH domains. Initially, PI3K inhibitors such as Wortmannin, LY294002, and Rapamycin were used to establish a central role for PI3K pathway in immune cells. More recent progress in understanding the role of this pathway in cells of the immune system has been made through the generation of wide range of gene-targeted mouse models as well as with the development of highly selective small molecule inhibitors, culminating in the FDA approval of the PI3Kδ inhibitor Idelalisib in 2014. Together, lab experiments, preclinical, and clinical trials have revealed how PI3Ks control B cell and T cell development, T helper cell differentiation, regulatory T cell (Treg) development and function, B cell and T cell trafficking, immunoglobulin class switching, and much more.

Evaluation of WO2014075392 and WO2014075393, Merck’s first PI3Kδ inhibitor filings

Introduction: There is considerable interest in the development of selective PI3Kδ inhibitors for the treatment of inflammatory diseases and haematological cancers. Merck has no previous filings in this field but licensed Exelixis' programme, including its lead compound XL-499, in December 2011.Areas covered: Both applications claim novel 9-alkyl-6,8-disubstituted purine derivatives as selective δ inhibitors for the treatment of asthma, obstructive airways disease, arthritis and cancer. The two applications differ in the range of exemplified substituents, the first focusing on 8-heteroaryl substituted purines, the second on 8-aminopurine derivatives. Many of the exemplified compounds have IC50 values < 10 nM against PI3Kδ with a number having sub-nanomolar potency.Expert Opinion: The compounds appear to be XL-499 derivatives, some of which are more potent than XL-499. The compounds claimed by Merck are some of the most potent PI3Kδ inhibitors yet described but it is unclear whether a development compound has been identified.

PP-055 EVALUATION THE RELATIONSHIP BETWEEN MTHFR GENE POLYMORPHISM AND PREGNANCY LOSS

Background: Idelalisib (IDELA) is a potent and selective inhibitor of PI3Kδ, which is critical for activation, proliferation and survival of B cells and their homing and retention in lymphoid tissues. An unmet need exists for effective therapies in patients with CLL positive for del(17p) and other adverse prognostic factors. This report describes the efficacy of IDELA in combination with rituximab (R) in such high-risk relapsed patients. Methods: Samples for del(17p), del(11q), TP53mut, IGHVmut, ZAP70 and CD38 expression, and β2-microglobulin were collected prospectively and tested using standard methods. Patients were stratified based on presence of del(17p) and/or TP53mut, and on IGHV mutational status. The endpoints evaluated in the high-risk subpopulations in the preplanned 1st interim analysis include progression-free-survival (PFS) and overall response rate (ORR). The primary study analysis was reported in NEJM 2014. Results: IDELA+R retained robust efficacy across all high-risk subpopulations. Importantly, IDELA+R achieved 76.5% ORR and PFS HR 0.13 in the highest risk patients who were positive for both del(17p) and TP53mut, compared to 80.4% ORR and PFS HR 0.17 in those who had neither present. Conclusions: These results confirm the retained robust efficacy of IDELA in high-risk CLL subpopulations and support IDELA as a potentially important novel treatment for patients with CLL positive for del(17p) and other adverse prognostic factors.

Abstract 4531: INCB40093 is a selective PI3Kδ inhibitor with potent antiproliferative activity against human B-cell tumors

Abstract Phosphatidylinositol 3-kinases (PI3Ks) belong to a family of lipid signaling kinases that phosphorylate phosphatidylinositol-4,5-bisphosphate, giving rise to phosphatidylinositol-3,4,5-trisphosphate (PIP3). PIP3 functions as a second messenger that controls a number of cellular processes, including growth, survival, adhesion and migration. The delta isoform of PI3K (PI3Kδ) plays an essential role in B-cell development and functions by mediating the signaling of key receptors on B cells including BCR, BAFF-R, IL-4R, CD40 and TLRs. In addition, increased malignant B cell proliferation and survival has been associated with aberrant activation of PI3Kδ, and data from recent clinical studies using idelalisib, a PI3Kδ specific inhibitor, indicate that the enzyme is a therapeutic target for the treatment of B cell lymphomas. INCB40093 is a novel, potent small molecule inhibitor of PI3Kδ with 74 to &amp;gt; 900-fold selectivity over the other PI3K family members. It also does not inhibit (&amp;lt; 30% inhibition) a broad panel of 196 other kinases when tested at a concentration of 1 μM. INCB40093 blocks the proliferation of primary B cells induced by the activation of PI3Kδ-mediated signaling through several key receptors (e.g. BCR, CD40). More importantly, INCB40093 is potent (IC50 values of ∼10-100 nM) in cell-based assays relevant to the pathogenesis of B cell malignancies, such as PI3Kδ-mediated signaling and growth of human B cell lines. This effect is not due to general cytotoxicity because 10 μM INCB40093 had no significant effect on the growth of non-lymphoid cell lines. Compared to the inhibition of primary B cell proliferation, INCB40093 is at least 50 times less potent in assays that measure human T cell or NK cell proliferation, and neutrophil and macrophage function, suggesting that the impact of INCB40093 on the human immune system will likely be restricted to B cells. In vivo, the effects of INCB40093 were evaluated in two human hematological cancer xenograft models. In the Pfeiffer model of non-Hodgkin's lymphoma, oral administration of INCB40093 inhibited tumor growth as a single agent. INCB40093 also potentiated the anti-tumor effects of the clinically relevant chemotherapeutic agent, bendamustine. The tumor growth inhibitory effects of INCB40093 were also demonstrated in a myeloma tumor xenograft model, INA-6.Tu1. Taken together, pharmacological data obtained in both in vitro and in vivo model systems support the potential utility of orally administered INCB40093 in the treatment of B cell malignancies. Citation Format: Niu Shin, Kathy Wang, Leslie Hall, Qian Wang, Gengjie Yang, Yanlong Li, Yun-Long Li, Maryanne Covington, Jordan Fridman, Robert Newton, Peggy Scherle. INCB40093 is a selective PI3Kδ inhibitor with potent antiproliferative activity against human B-cell tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4531. doi:10.1158/1538-7445.AM2014-4531

Abstract 4529: The PI3Kδ inhibitor, idelalisib, inhibits transcription and translation through PI3K/Akt pathway in mantle cell lymphoma

Abstract PI3Kδ is the major PI3K family class I isoform expressed in B-cells that is known to promote cancer cell growth and survival. PI3Kδ pathway is activated through cell surface receptors, e.g. B-cell receptor signaling. This suggests that PI3Kδ is a therapeutic target for B-cell hematological malignancies. Idelalisib is a potent and selective PI3Kδ inhibitor (IC50=19nM) that is currently under investigation in Phase II/III trials in B-cell neoplasms. In solid tumors, it has been established that PI3K/Akt axis regulates transcription and translation processes. Based on the overexpression and hyperactivity of PI3Kδ in B-cell lymphoma such as mantle cell lymphoma (MCL), and PI3Kδ-specific inhibition by idelalisib, we hypothesized that idelalisib treatment will 1) impact the transcription and translation processes that are PI3K/Akt-dependent, 2) disrupt RNA and protein synthetic capacity, and 3) decrease short-lived oncogenic mRNA and proteins levels that are important for MCL cell survival. Idelalisib (0.5 to 5μM) induced modest levels of apoptosis (&amp;lt;15%) in MCL cell lines and primary cells. A reverse-phase protein array (RPPA) study suggested that idelalisib treatment resulted in a decrease in phosphorylation of transcription regulators (GSK-3αβ and c-Myc), and protein synthesis regulators (S6, p70S6K, 4E-BP1, eIF4 and mTOR) in MCL cell lines and primary cells. Immunoblot analysis suggests that a 4hr treatment with idelalisib (0.5 or 1μM) resulted in a decrease of phosphorylated Akt (T308 and S473) levels in both JeKo-1 and Mino cells following IgM stimulation. In parallel, phospho-levels of GSK-3β (S9), 4E-BP1 (S65) and S6 (S235/236) were also decreased. In IgM-stimulated MCL cell lines, moderate to significant decrease in global RNA synthesis (10-15% decrease in JeKo-1, 50% decrease in Mino) and protein synthesis (15% decrease in JeKo-1, &amp;gt;20% decrease in Mino) were detected with 72hr incubation of idelalisib (0.5 to 1μM). Consistent with cell line data, in B-cell lymphoma primary cells, transcription levels were decreased by 20% or &amp;gt;50% following a 24hr treatment with 1 or 5µM idelalisib, respectively; and a 40% decrease of translation level was detected with 5µM idelalisib. In Jeko-1, early response genes MCL1 mRNA level was reduced following 24hr idelalisib treatment, whereas the other mRNAs (PIM2, MYC, CCND1) were decreased to a lesser extent. Mcl-1 and cyclin D1 protein levels were decreased in JeKo-1 and Mino cells following short incubation of idelalisib (0.5 or 1µM). In summary, idelalisib was effective in reducing phosphorylation of Akt and its downstream effectors in MCL cell lines (GSK-3β, 4E-BP1 and S6). Idelalisib inhibits global RNA and protein synthesis, and decreases the levels of short-lived survival proteins. Collectively, these data imply that similar to solid tumors, PI3K regulates key factors involved in gene transcription and protein translation in MCL. Citation Format: Qingshan Yang, Lisa S. Chen, Sattva S. Neelapu, Varsha Gandhi. The PI3Kδ inhibitor, idelalisib, inhibits transcription and translation through PI3K/Akt pathway in mantle cell lymphoma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4529. doi:10.1158/1538-7445.AM2014-4529

Abstract 4207: JAK inhibition reverses IL10-mediated resistance to B cell receptor (BCR) pathway inhibition in DLBCL

Abstract Diffuse large B cell lymphoma (DLBCL) is the most common form of non-Hodgkin's lymphoma, and can be classified into activated B-cell like (ABC) and germinal center B-cell like (GCB) DLBCL according to gene expression profiling. In both subtypes, dysregulation of the B cell receptor (BCR) signaling pathway plays a critical role in tumorigenesis and survival. BCR activation induces phosphorylation of CD79A/B by Src family tyrosine kinases, which leads to the activation of the BTK and PI3Kδ/Akt pathways. Oncogenic mutations have been identified in DLBCL impacting CD79A/B (BCR complex), PTEN (negative regulator of PI3K), CARD11 and MYD88 (NF-kB activating factors) function. The influence of these mutations on the DLBCL phenotype appears to be further modified by aberrant cytokine signaling and JAK/Stat pathway activation. High levels of JAK/Stat-activating cytokines such as IL6 and IL10 are present in DLBCL, and patients with high serum IL10 have been shown to have shorter event-free survival and a higher international Prognostic Index score. Therefore, concurrent inhibition of both the BCR and JAK/Stat pathways may provide an attractive therapeutic approach in DLBCL. We have developed and characterized a potent and selective PI3Kδ inhibitor INCB040093 and have established that DLBCL cells are sensitive to INCB040093 treatment. We demonstrate that IL10 activates the JAK/Stat signaling pathway in DLBCL cells, which renders the cells resistant to INCB040093 in cell proliferation assays. This resistance can be reversed by co-treatment with a JAK1/JAK2 inhibitor. Although INCB040093 induces apoptosis in DLBCL cells, concurrent activation of the JAK/Stat pathway by IL10 prevents INCB040093-induced apoptosis, an effect that can be abrogated by a JAK1/JAK2 inhibitor. Similar resistance to IL-10 is observed with the BTK inhibitor, ibrutinib, which can also be reversed by a JAK1/JAK2 inhibitor. Interestingly, a JAK1 selective inhibitor is as effective as a JAK1/JAK2 inhibitor in reversing the IL10-mediated resistance to PI3Kδ and BTK inhibition. Combination treatment blocks both PI3K/Akt and JAK/Stat signaling pathways and results in the down-regulation of pro-survival proteins, including Pim2 and c-myc. These data illustrate the functional cross-talk that exists in DLBCL between the BCR and JAK/Stat signaling pathways, and support the clinical evaluation of combined BCR and JAK inhibition as a novel approach to targeted therapy. Citation Format: Xuesong (Mike) Liu, Margaret Favata, Jun Li, Niu Shin, Kathy He Wang, Qian Wang, Yun-Long Li, Andrew Combs, Chu-Biao Xue, Robert Newton, Kris Vaddi, Peggy Scherle. JAK inhibition reverses IL10-mediated resistance to B cell receptor (BCR) pathway inhibition in DLBCL. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4207. doi:10.1158/1538-7445.AM2014-4207

PI3K inhibitors LY294002 and IC87114 reduce inflammation in carrageenan-induced paw oedema and down-regulate inflammatory gene expression in activated macrophages.

PI3K/Akt pathway is a well-characterized pathway controlling cellular processes such as proliferation, migration and survival, and its role in cancer is vastly studied. There is also evidence to suggest the involvement of this pathway in the regulation of inflammatory responses. In this study, an attempt was made to investigate the role of PI3Ks in acute inflammation in vivo using pharmacological inhibitors against PI3Ks in the carrageenan-induced paw oedema model. A non-selective PI3K inhibitor LY294002 and a PI3Kδ-selective inhibitor IC87114 were used. Both of these inhibitors reduced inflammatory oedema upon carrageenan challenge in the mouse paw. To explain this result, the effects of the two inhibitors on inflammatory gene expression were investigated in activated macrophages. LY294002 and IC87114 prevented Akt phosphorylation as expected and down-regulated the expression of inflammatory factors IL-6, MCP-1,TNFα and iNOS. These findings suggest that PI3K inhibitors could be used to attenuate inflammatory responses and that the mechanism of action behind this effect is the down-regulation of inflammatory gene expression.

Idelalisib, an inhibitor of phosphatidylinositol 3-kinase p110δ, for relapsed/refractory chronic lymphocytic leukemia

AbstractIn a phase 1 trial, idelalisib (GS-1101, CAL-101), a selective inhibitor of the lipid kinase PI3Kδ, was evaluated in 54 patients with relapsed/refractory chronic lymphocytic leukemia (CLL) with adverse characteristics including bulky lymphadenopathy (80%), extensive prior therapy (median 5 [range 2-14] prior regimens), treatment-refractory disease (70%), unmutated IGHV (91%), and del17p and/or TP53 mutations (24%). Patients were treated at 6 dose levels of oral idelalisib (range 50-350 mg once or twice daily) and remained on continuous therapy while deriving clinical benefit. Idelalisib-mediated inhibition of PI3Kδ led to abrogation of Akt phosphorylation in patient CLL cells and significantly reduced serum levels of CLL-related chemokines. The most commonly observed grade ≥3 adverse events were pneumonia (20%), neutropenic fever (11%), and diarrhea (6%). Idelalisib treatment resulted in nodal responses in 81% of patients. The overall response rate was 72%, with 39% of patients meeting the criteria for partial response per IWCLL 2008 and 33% meeting the recently updated criteria of PR with treatment-induced lymphocytosis.1,2 The median progression-free survival for all patients was 15.8 months. This study demonstrates the clinical utility of inhibiting the PI3Kδ pathway with idelalisib. Our findings support the further development of idelalisib in patients with CLL. These trials were registered at clinicaltrials.gov as #NCT00710528 and #NCT01090414.

Characterization of Novel PI3Kδ Inhibitors as Potential Therapeutics for SLE and Lupus Nephritis in Pre-Clinical Studies.

SLE is a complex autoimmune inflammatory disease characterized by pathogenic autoantibody production as a consequence of uncontrolled T–B cell activity and immune-complex deposition in various organs, including kidney, leading to tissue damage and function loss. There is a high unmet need for better treatment options other than corticosteroids and immunosuppressants. Phosphoinositol-3 kinase δ (PI3Kδ) is a promising target in this respect as it is essential in mediating B- and T-cell function in mouse and human. We report the identification of selective PI3Kδ inhibitors that blocked B-, T-, and plasmacytoid dendritic cell activities in human peripheral blood and in primary cell co-cultures (BioMAP®) without detecting signs of undesired toxicity. In an IFNα-accelerated mouse SLE model, our PI3Kδ inhibitors blocked nephritis development, whether administered at the onset of autoantibody appearance or the onset of proteinuria. Disease amelioration correlated with normalized immune cell numbers in the spleen, reduced immune-complex deposition as well as reduced inflammation, fibrosis, and tissue damage in the kidney. Improvements were similar to those achieved with a frequently prescribed drug for lupus nephritis, the potent immunosuppressant mycophenolate mofetil. Finally, we established a pharmacodynamics/pharmacokinetic/efficacy model that revealed that a sustained PI3Kδ inhibition of 50% is sufficient to achieve full efficacy in our disease model. These data demonstrate the therapeutic potential of PI3Kδ inhibitors in SLE and lupus nephritis.

Efficacy of idelalisib in CLL subpopulations harboring del(17p) and other adverse prognostic factors: Results from a phase 3, randomized, double-blind, placebo-controlled trial.

7011^ Background: Idelalisib (IDELA) is a potent and selective inhibitor of PI3Kδ, which is critical for activation, proliferation and survival of B cells and their homing and retention in lymphoid...

Patient-reported outcomes data from a phase 2 study of idelalisib in patients with refractory indolent B-cell non-Hodgkin lymphoma (iNHL).

e19554 Background: Idelalisib, a selective oral inhibitor of PI3Kδ, demonstrated considerable anti-tumor activity in patients with relapsed/refractory iNHL in a phase 2 trial (Gopal, 2014). The purpose of this analysis was to evaluate patient-reported outcomes (PRO) data to determine whether drug treatment was associated with a change in health-related quality of life (HRQL). Methods: Eligible iNHL patients (pts) were refractory to both rituximab and an alkylating agent. Idelalisib 150 mg PO BID was administered continuously until disease progression. HRQL was measured by the 42-item Functional Assessment of Cancer Therapy-Lymphoma (FACT-Lym), comprising FACT-G subscales: Physical Well-being (PWB), Social/Family Well-being (SWB), Emotional Well-being (EWB), Functional Well-being (FWB), and the Lymphoma Subscale (LymS). Trial Outcome Index (TOI) is PWB + FWB + LymS. Higher scores reflect better HRQL. Minimally important differences (MID) on the FACT-G ranged 3-7 points (2-5 points for subscales). The FACT-...

PI3Kδ Inhibition by Idelalisib in Patients with Relapsed Indolent Lymphoma

BackgroundPhosphatidylinositol-3-kinase delta (PI3Kδ) mediates B-cell receptor signaling and microenvironmental support signals that promote the growth and survival of malignant B lymphocytes. In a phase 1 study, idelalisib, an orally active selective PI3Kδ inhibitor, showed antitumor activity in patients with previously treated indolent non-Hodgkin's lymphomas.MethodsIn this single-group, open-label, phase 2 study, 125 patients with indolent non-Hodgkin's lymphomas who had not had a response to rituximab and an alkylating agent or had had a relapse within 6 months after receipt of those therapies were administered idelalisib, 150 mg twice daily, until the disease progressed or the patient withdrew from the study. The primary end point was the overall rate of response; secondary end points included the duration of response, progression-free survival, and safety.ResultsThe median age of the patients was 64 years (range, 33 to 87); patients had received a median of four prior therapies (range, 2 to 12). Subtypes of indolent non-Hodgkin's lymphoma included follicular lymphoma (72 patients), small lymphocytic lymphoma (28), marginal-zone lymphoma (15), and lymphoplasmacytic lymphoma with or without Waldenström's macroglobulinemia (10). The response rate was 57% (71 of 125 patients), with 6% meeting the criteria for a complete response. The median time to a response was 1.9 months, the median duration of response was 12.5 months, and the median progression-free survival was 11 months. Similar response rates were observed across all subtypes of indolent non-Hodgkin's lymphoma, though the numbers were small for some categories. The most common adverse events of grade 3 or higher were neutropenia (in 27% of the patients), elevations in aminotransferase levels (in 13%), diarrhea (in 13%), and pneumonia (in 7%).ConclusionsIn this single-group study, idelalisib showed antitumor activity with an acceptable safety profile in patients with indolent non-Hodgkin's lymphoma who had received extensive prior treatment. (Funded by Gilead Sciences and others; ClinicalTrials.gov number, NCT01282424.)

PI3Kδ Inhibition Hits a Sensitive Spot in B Cell Malignancies

A PI3Kδ-selective inhibitor shows impressive clinical activity in chronic lymphocytic leukemia and indolent Bcell non-Hodgkin's lymphomas. In these malignancies, the PI3K pathway is not mutationally activated as in many other cancers, but it is important for mediating supportive cues from the cancer microenvironment and the B cell antigen receptor.

Inhibition of PI3Kδ Improves Systemic Lupus in Mice

Systemic lupus erythematosus (SLE) is an autoimmune disease accompanying excessive inflammatory responses. Phosphoinositide 3-kinase p110δ (PI3Kδ) is reported to associate with autoimmune conditions. We here aimed to determine whether selective inhibition of PI3Kδ is effective in a lupus model of BXSB mice, using the selective PI3Kδ inhibitor IC87114, which was intraperitoneally administrated to BXSB mice aged from 14 to 22weeks. We showed that IC87114 improved renal function by decreasing the levels of proteinuria and serum creatinine, ameliorating the pathologic changes of kidneys and IgG and C3 deposition. Serum anti-autoantibody to nuclear antigen, anti-dsDNA, IL-1β, and IL-17 were markedly reduced by IC87114 therapy. Hepatic damage was also inhibited by administration of IC87114. Expression of phosphorylated AKT (p-AKT) and monocyte chemoattractant protein-1 was inhibited and mouse survival improved. In sum, PI3Kδ activation may be a critical factor for escalating autoimmune renal and hepatic damage, and its inhibition may alleviate the autoimmune damage. Our study reveals that the selective blockade of PI3Kδ is effective for mouse SLE.

Effects of Isoform-selective Phosphatidylinositol 3-Kinase Inhibitors on Osteoclasts: ACTIONS ON CYTOSKELETAL ORGANIZATION, SURVIVAL, AND RESORPTION

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.

Clinical Activity Of Idelalisib (GS-1101), a Selective Inhibitor Of PI3Kδ, In Phase 1 and 2 Trials In Chronic Lymphocytic Leukemia (CLL): Effect Of Del(17p)/TP53 Mutation, Del(11q), IGHV Mutation, and NOTCH1 Mutation

BackgroundPI3K-delta (δ) is critical for activation, proliferation and survival of B cells and plays a role in homing and retention in lymphoid tissues. PI3Kδ signaling is hyperactive in many B-cell malignancies. Idelalisib (IDELA) is a potent and selective orally administered inhibitor of PI3Kδ with demonstrated activity in patients with relapsed or refractory (R/R) CLL either as a single agent (Brown, ASCO 2013) or in combination (Barrientos et al, ASCO 2013; Coutre et al, EHA 2013; Barrientos et al, EHA 2013), and in previously untreated patients in combination with rituximab (R) (O'Brien et al, ASCO 2013). This report describes the effect of established high risk prognostic markers on the clinical activity of idelalisib based therapy in CLL patients enrolled in 3 clinical trials. MethodsSubjects were enrolled into one of three trials: 1) phase 1 monotherapy dose escalation, dosing from 50 mg bid to 350 mg bid (N=54, R/R); 2) phase 1 combination with either R, ofatumumab, bendamustine ± R, fludarabine or chlorambucil±R (N= 114, R/R) ; 3) phase 2 combination with R (N=64, age≥ 65 yrs, previously untreated). Response was assessed by investigators per IWCLL 2008. Genetic markers were assessed in a central lab using archived DNA obtained at study enrollment. ResultsORR and CR results are shown in the table below, with data grouped per either R/R or previously untreated patients. ConclusionIDELA shows robust activity independent of the four genetic markers evaluated. Thus, patients can be considered for idelalisib-based treatment in clinical trials regardless of these high-risk features. Disclosures:Coutre:Gilead Sciences: Research Funding. Off Label Use: Idelalisib is a PI3K-delta inhibitor currently in phase III trials for multiple hematologic malignancies. Leonard:Gilead Sciences: Research Funding. Barrientos:Gilead Sciences: Research Funding. De Vos:Gilead Sciences: Research Funding. Flinn:Gilead Sciences: Research Funding. Furman:Gilead Sciences: Research Funding. Brown:Gilead Sciences: Research Funding. Wagner-Johnston:Gilead Sciences: Research Funding. Benson:Gilead Sciences: Research Funding. Schreeder:Gilead Sciences: Research Funding. Sharman:Gilead Sciences: Research Funding. Boyd:Gilead Sciences: Research Funding. Spurgeon:Gilead Sciences: Research Funding. Zelenetz:Gilead Sciences: Research Funding. Lamanna:Gilead Sciences: Research Funding. Kipps:Gilead Sciences: Research Funding. Kahl:Gilead Sciences: Research Funding. Bello:Gilead Sciences: Research Funding. Burger:Gilead Sciences: Research Funding. Rai:Gilead Sciences: Research Funding. Dansey:Gilead Sciences: Employment. Kim:Gilead Sciences: Employment. Holes:Gilead Sciences: Employment. Lazarov:Gilead Sciences: Employment. Dubowy:Gilead Sciences: Employment. O'Brien:Gilead Sciences: Research Funding.

Combined Carfilzomib and Selective PI3Kδ Inhibition (TGR1202) Results In Enhanced Myeloma Cell Apoptosis

IntroductionThe PI3K signaling pathway plays a vital role in regulating cell growth, proliferation and survival in multiple myeloma (MM) as well as in many other cancers. TGR-1202, an isoform-specific PI3Kδ inhibitor, with efficacy in preclinical models of hematologic malignancies, is currently in Phase I clinical development. In multiple myeloma, PI3K signaling appears to be very important for many extracellular signals, yet inhibition with -pan PI3K inhibitors have not exhibited significant activity. However, literature reports indicate that there are several MM cell lines that express PI3K -δ, and do appear to have differential sensitivity to specific isoform inhibition as opposed to pan PI3K inhibition. In this report, we sought to evaluate the effects of TGR-1202 alone and in combination with the proteasome inhibitor carfilzomib, with the intent of further understanding the mechanism of action and evaluating the impact of the combination. MethodsHuman myeloma cell lines (MM.1S, MY5, RPMI8226, U266, KMS11, ARH-77, OPM1, OPM2, LP1, JJN3 and L363) were treated with TGR-1202 alone, carfilzomib alone, or with the combination of TGR-1202 and carfilzomib. Annexin V/PI staining and Western blot were used to identify the cellular and molecular sequelae of the combination. Result10 µM TGR-1202 alone did not cause significant cell death in the MM cell lines tested at 48 hours. When cells were treated with the combination of TGR-1202 and 3 nM carfilzomib, we observed enhanced apoptosis in all of the tested cell lines. In the U266 cell line, 3 nM carfilzomib and 10 µM TGR-1202 induced 16% and 14% cell apoptosis respectively. In the combination treatment, apoptosis increased to 75%. To explore the molecular mechanisms underlying the combination, we used a Western blot assay to evaluate the impact of the combination on the mTOR signaling pathway, a known reciprocal feedback loop when PI3K is blocked. TGR-1202 alone did not have an obvious effect on the mTOR signaling pathway, yet combining TGR-1202 with carfilzomib, significantly inhibited phospho-mTOR, suggesting total pathway blockade. ConclusionThe combination of TGR-1202 with carfilzomib induces synergistic apoptosis in MM cell lines. Preliminary data suggests that this occurs through blockade of the entire reciprocal feedback loop of mTOR activation. Additional data from primary patient samples and underlying mechanisms will be presented at the meeting. These findings support the rationale for future clinical studies of TGR-1202, a selective PI3K-δ inhibitor in combination with the proteasome inhibitor carfilzomib. Disclosures:Boise:Onyx: Consultancy. Lonial:Millennium: Consultancy; Celgene: Consultancy; Novartis: Consultancy; BMS: Consultancy; Sanofi: Consultancy; Onyx: Consultancy.

Mature Response Data From a Phase 2 Study Of PI3K-Delta Inhibitor Idelalisib In Patients With Double (Rituximab and Alkylating Agent)-Refractory Indolent B-Cell Non-Hodgkin Lymphoma (iNHL)

IntroductionAlkylating agent-rituximab combinations are a current standard of care for patients with iNHL. Most iNHL will eventually become refractory to current therapies. Particularly, once iNHL becomes “double-refractory” to rituximab + alkylating agents, there are few data available on beneficial therapeutic options and development of novel therapies is essential for this patient population. PI3K-delta signaling is critical for activation, proliferation and survival of B cells, and is hyperactive in many B-cell malignancies. Idelalisib, a selective oral inhibitor of PI3Kδ, demonstrated considerable activity in recurrent iNHL in a phase 1 trial (Kahl, ICML 2011). We thus evaluated idelalisib in a phase 2 trial for patients with double-refractory iNHL, an area of unmet medical need. We present mature response data and extended follow-up of this study. MethodsEligible iNHL patients (pts) included those with measurable disease who were refractory to both rituximab and an alkylating agent. Refractory status was defined as lack of response to, or progression of lymphoma within 6 months of completion of therapy, documented by imaging. Idelalisib 150 mg PO BID was administered continuously until disease progression or intolerance. Responses were evaluated by an independent review committee, using standard criteria (Cheson, 2007). The new data cutoff date for this analysis was June 2013, 8 months after the last patient enrolled. ResultsEnrolled pts (N=125) had a median age of 64 years [range 33-87] and were 64% male. Indolent NHL subtypes included follicular lymphoma (FL) n=72 (58%), small lymphocytic lymphoma (SLL) n=28 (22%), marginal zone lymphoma (MZL) n=15 (12%) and lymphoplasmacytic lymphoma (LPL)/Waldenstrom's macroglobulinemia (WM) n=10 (8%). The median number of prior therapies was 4 [range 2-12], most common regimens included bendamustine/rituximab (BR) (n=60) and rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone (R-CHOP) (n=56) and 14 pts (11%) had a prior autologous transplant. 81 pts (65%) had prior bendamustine, of which 61/81 (75%) were refractory. 112 pts (90%) were refractory to their last regimen, and 99 pts (79%) were refractory to ≥2 regimens. Median time since completion of last regimen was 3.9 months. At baseline, pts had elevated LDH (30%), bulky disease >7 cm (26%), anemia ≥grade 1 (51%), neutropenia ≥ grade 1 (24%), and thrombocytopenia ≥grade 1 (34%).With a median follow up 9.4 months, the overall response rate (ORR) was 57% (95% CI = 47.6, 65.6) with 71 responders, comprising 7 CRs (6%), 63 PRs (50%), and 1 minor response (MR) in a WM pt. There were 42 pts with stable disease (SD) (33%). 90% of pts experienced some decrease in tumor burden (Figure 1). Median time to response was 1.9 months (range 1.6-8.3), median time to CR was 3.7 months (range 1.9-12). ORR for iNHL subtypes was: FL (54%), SLL (61%), LPL/WM (80%), and MZL (47%). ORR for bendamustine refractory pts was 59%. ORR for pts with <4 /≥4 prior therapies was 50%/62%, and for bulky disease <7cm/≥7cm was 57/57%. Among responders, median DOR was 12.5 months. Median PFS for all pts was 11.0 months and median overall survival was 20.4 months. [Display omitted] The most common adverse events were (total%/≥ grade 3%) diarrhea (43/13), fatigue (30/2), nausea (30/2), cough (29/0), pyrexia (28/2), dyspnea (18/3), rash (13/2), and pneumonia (11/7). Based on central laboratory measurements, Grade ≥3 ALT/AST elevations occurred in 16 pts (13%). Drug was held for these pts, and 11/14 pts (79%) were re-treated without recurrence of ALT/AST elevation. Grade ≥3 neutropenia occurred in 27%, thrombocytopenia in 6%, and anemia in 2%. 20% of pts have discontinued therapy due to adverse events. ConclusionsIdelalisib was well tolerated, had an acceptable safety profile, and was highly effective in this double-refractory iNHL population with an ORR of 57%. The ORR was consistent across all subgroups, regardless of disease histology, number of prior regimens, refractoriness to bendamustine, or tumor bulk. With continued administration of idelalisib, responses were durable beyond one year, substantially exceeding the median DOR for the last prior therapy. Mature response data demonstrate that idelalisib can provide clinical benefit to patients with the unmet medical need of double-refractory iNHL. Disclosures:Gopal:Gilead Sciences: Research Funding. Off Label Use: Idelalisib is a PI3K-delta inhibitor currently in phase III trials for multiple hematologic malignancies. Kahl:Gilead Sciences: Advisory Board Other, Research Funding. De Vos:Gilead Sciences: Advisory Board Other, Research Funding. Wagner-Johnston:Gilead Sciences: Research Funding. Schuster:Gilead Sciences: Research Funding. Blum:Gilead Sciences: Research Funding. Jurczak:Gilead Sciences: Research Funding. Flinn:Gilead Sciences: Research Funding. Flowers:Gilead Sciences: Research Funding. Martin:Gilead Sciences: Research Funding. Viardot:Gilead Sciences: Research Funding. Goy:Gilead Sciences: Research Funding. Davies:Gilead Sciences: Research Funding. Zinzani:Gilead Sciences: Research Funding. Dreyling:Gilead Sciences: Research Funding. Holes:Gilead Sciences: Employment. Li:Gilead Sciences: Employment. Dansey:Gilead Sciences: Employment. Godfrey:Gilead Sciences: Employment. Salles:Gilead Sciences: Research Funding.

Development and validation of a highly sensitive LC–MS/MS method for quantification of IC87114 in mice plasma, bronchoalveolar lavage and lung samples: Application to pharmacokinetic study

IC87114 is a selective PI3Kδ inhibitor. A simple, sensitive and reliable LC–MS/MS method with rapid sample preparation was developed and validated for the determination of IC87114 in mouse plasma, bronchoalveolar lavage, and lung. Chromatographic separation was achieved using an Agilent Zorbax Eclipse XDB-C18 column (150mm×2.1mm internal diameter, 3.5μm particle size). Mass spectrometric detection was conducted by electrospray ionization in positive ion multiple reaction monitoring modes. The calibration curve was linear over a concentration range of 0.01–1000ng/mL for plasma/BAL and 0.1–250ng/mL for lung tissue. Recoveries were as high as 97.29%, 102.81% and 89.70% for plasma, BAL fluid and lung sample, respectively. The lower limit of quantification was 0.01ng/mL. Intra-day and inter-day accuracy and precision were within the acceptable limits of ±15% at all concentrations. Finally, the method was successfully used in a pharmacokinetic study that measured IC87114 in mouse plasma, BAL fluid and lung tissue after administration of a single 1mg/kg intratracheal dose of IC87114. The percentage change for incurred sample reanalysis (ISR) was within ±15.0% and met the acceptance criteria for ISR.

PI3Kδ Inhibition Augments the Efficacy of Rapamycin in Suppressing Proliferation of Epstein−Barr Virus (EBV)+ B Cell Lymphomas

Posttransplant lymphoproliferative disorder (PTLD) continues to be a devastating and potentially life-threatening complication in organ transplant recipients. PTLD is associated with EBV infection and can result in malignant B cell lymphomas. Here we demonstrate that the PI3K/Akt/mTOR pathway is highly activated in EBV+ B cell lymphoma lines derived from patients with PTLD. Treatment with the mTORC1 inhibitor Rapamycin (RAPA) partially inhibited the proliferation of EBV+ B cell lines. Resistance to RAPA treatment correlated with high levels of Akt phosphorylation. An mTORC1/2 inhibitor and a PI3K/mTOR dual inhibitor suppressed Akt phosphorylation and showed a greater anti-proliferative effect on EBV+ B lymphoma lines compared to RAPA. EBV+ B cell lymphoma lines expressed high levels of PI3Kδ. We demonstrate that PI3Kδ is responsible for Akt activation in EBV+ B cell lymphomas, and that selective inhibition of PI3Kδ by either siRNA, or a small molecule inhibitor, augmented the anti-proliferative effect of RAPA on EBV+ B cell lymphomas. These results suggest that PI3Kδ is a novel, potential therapeutic target for the treatment of EBV-associated PTLD and that combined blockade of PI3Kδ and mTOR provides increased efficacy in inhibiting proliferation of EBV+ B cell lymphomas.