Thomas, Sheeba K.

Abstract Introduction: Waldenström's macroglobulinemia (WM) is a rare, indolent B-cell lymphoma characterized by lymphoplasmacytic cell infiltration of bone marrow and elevated serum levels of immunoglobulin M (IgM) protein. Despite recent advances in treatment the disease relapses in most patients. About 90% of WM patients harbor the MYD88 L265P oncogenic mutation. MYD88 is an adapter protein in the Toll-like receptor (TLR) pathway. The MYD88 L265P oncoprotein has been shown to amplify TLR 7 and 9 signaling, leading to downstream activation of NF-κB and cytokine signaling pathways that promote tumor cell survival and proliferation (Lim, AACR 2013). IMO-8400 is an investigational oligonucleotide antagonist of endosomal TLRs 7, 8 and 9. In preclinical studies in a human cell line and animal models of WM, IMO-8400 inhibited key cell signaling pathways, including NF-κB, BTK, STAT-3 and IRAK-4, and inhibited tumor growth and tumor IgM production. In Phase 1 and 2 clinical trials in healthy subjects (N=30) and in patients with autoimmune disease (N=35), IMO-8400 was generally well tolerated and demonstrated evidence of clinical activity. Based on these data, we initiated a Phase 1/2 clinical trial of IMO-8400 in WM, the first study of a drug candidate specifically targeting the MYD88 L265P mutation. Methods: This Phase 1/2 multicenter, open-label, dose-escalation clinical trial continues to recruit adult patients with relapsed or refractory WM (NCT Identifier: NCT02092909). In a classic 3x3 dose escalation scheme, patients are enrolled in one of three sequential escalating dose cohorts and receive subcutaneous IMO-8400 at dosages of 0.6, 1.2 or 2.4 mg/kg per week, respectively, for 24 weeks. The presence of the MYD88 L265P mutation is assessed by PCR-based genetic screening following enrollment. Patients who complete the 24-week treatment period are eligible to enroll in an extension trial. The primary study objective is to evaluate the safety and tolerability of escalating IMO-8400 dosages. Secondary objectives include preliminary evaluation of clinical response based on international guidelines and identification of an optimal dose for further evaluation (Kimby, Clin Lymphoma Myeloma 2006). Results: Overall, 17 patients (6 female, 11 male) have been enrolled in three dose cohorts to date. Median baseline characteristics include: age 66 years, prior therapies 4 (range 1-13), serum IgM 2,225 mg/dL, serum M protein 0.96 g/dL, and B2-microglobulin 3.42 mg/L. IMO-8400 has been generally well tolerated across all dose cohorts to date, with patient exposure ranging from 2-46 weeks in the Phase 1/2 and extension trials. The most common adverse events reported to date include transient flu-like symptoms and injection site reactions. One serious adverse event of worsening grade 3 arthritis, deemed possibly related to study drug, was reported in a patient with a pre-existing history of arthritis in the 2.4 mg/kg dose cohort. This patient discontinued study treatment. To date, no other patients have discontinued treatment due to treatment-related adverse events. Preliminary evidence of clinical activity for IMO-8400 has been observed in all dose cohorts. In June 2015, an independent Data Review Committee reviewed 4-week safety data from the highest dose cohort and agreed that 2.4 mg/kg was safe for further evaluation. Safety, pharmacokinetics and preliminary activity for all three dose cohorts will be presented. Conclusions: IMO-8400 is a mutation-targeted therapy in development for the treatment of patients with relapsed or refractory WM. In an ongoing Phase 1/2 clinical trial in WM, IMO-8400 has been generally well tolerated and has demonstrated preliminary evidence of clinical activity. Safety results support continued evaluation of IMO-8400 at 2.4 mg/kg/week in this patient population. Disclosures Thomas: Novartis, Celgene, Acerta Pharmaceuticals, Idera Pharmaceuticals: Research Funding. Harb:Astex Pharmaceuticals, Inc.: Research Funding; Idera Pharmaceuticals: Research Funding. Beck:Idera Pharmaceuticals: Research Funding. Nashat:Idera Pharmaceuticals: Research Funding. Ansell:Idera Pharmaceuticals: Research Funding. Eradat:Idera Pharmaceuticals: Research Funding. Libby:Idera Pharmaceuticals: Research Funding. Hajdenberg:Celgene: Speakers Bureau; Novartis: Speakers Bureau; Incyte: Speakers Bureau; AbbVie: Speakers Bureau; Gilead: Speakers Bureau; Janssen: Speakers Bureau; Idera Pharmaceuticals: Research Funding. Heffner:Idera Pharmaceuticals: Research Funding. Hoffman:Idera Pharmaceuticals: Research Funding. Vesole:Celgene Corporation: Speakers Bureau; Idera Pharmaceuticals: Research Funding. Simov:Idera Pharmaceuticals: Employment. Wyant:Idera Pharmaceuticals: Employment. Brevard:Idera Pharmaceuticals: Employment. O'Leary:Idera Pharmaceuticals: Employment. Agrawal:Idera Pharmaceuticals: Employment.

Abstract Background: LGH447 is a novel, specific pan-Pim kinase inhibitor in development for the treatment of patients with multiple myeloma (MM) and other hematologic malignancies. The PIM (Provirus Integration site for Moloney leukemia) kinase gene family encodes 3 serine/threonine protein kinases that have roles in cell cycle progression and survival. In human disease, elevated levels of Pim1 and Pim2 are associated with hematologic malignancies, with MM showing the highest level of Pim2 expression. In preclinical studies, a majority of MM cell lines proved sensitive in vitro to LGH447-mediated Pim inhibition, exhibiting a dose-dependent decrease in cell proliferation. LGH447 demonstrated significant tumor growth inhibition in xenograft mouse models of MM as compared with control animals, supporting the clinical development of LGH447 in MM patients. Methods: Patients with relapsed/refractory MM for whom no effective treatment options exist were enrolled on this first-in-human, multicenter, open-label phase 1 dose-escalation study (CLGH447X2101). Escalating doses of single-agent LGH447 were administered orally on a continuous daily dosing schedule. Treatment continued until disease progression, unacceptable toxicity, consent withdrawal, or death. The primary objective was to estimate the maximum tolerated dose (MTD) of LGH447 administered as a single agent, orally, once daily. Secondary objectives included assessing the safety, tolerability, preliminary anti-myeloma activity, and pharmacokinetics of LGH447. Dose escalation followed a Bayesian logistic regression model based on dose-limiting toxicities (DLTs) occurring in cycle 1. Adverse events (AEs) were graded according to NCI-CTCAE v4.03. Efficacy assessments were made by investigators according to International Myeloma Working Group (IMWG) uniform response criteria with modifications. Results:At the data cutoff, 54 patients have been treated at the following doses: 70 mg (n = 5), 150 mg (n = 6), 200 mg (n = 6), 250 mg (n = 7), 300 mg (n = 4), 350 mg (n=10), 500 mg (n=10), 700 mg (n=6), with the MTD determined to be 500 mg once daily. Median age was 65 years (range, 41-87 years). Most patients (92.6%) presented with baseline Eastern Cooperative Oncology Group performance status 0-1. Patients were heavily pretreated with a median of 4 prior lines of therapy (range, 1-16). 81.5% had received prior proteasome inhibitor therapy, 83.3% had received prior immunomodulatory therapy (70.4% lenalidomide and 48.1% thalidomide), 68.5% were treated with both proteasome inhibitor and immunomodulatory therapies, and 87.0% had received prior stem cell transplant. Seventeen patients are ongoing at doses between 250-700 mg, with a median duration of exposure of 10.6 weeks (range, 0.1-56.1 weeks), and 37 patients discontinued (disease progression [n = 29], AEs [n = 4], withdrawal of consent [n = 4]). There were 8 DLTs, consisting of four grade 3/4 thrombocytopenia (1 each at 200, 250, 350, 500 mg dose levels), two grade 3 fatigue (1 each at 500 and 700 mg dose levels), one grade 3 hypophosphatemia (300 mg), and one episode of vaso-vagal syncope (700 mg). This last event was the only reported unexpected serious AE that was suspected to be due to LGH447 treatment. The majority of AEs regardless of study drug relationship were grade 1/2. Most common grade 3/4 AEs were thrombocytopenia (18.5%), anemia (18.5%), neutropenia (13%), and fatigue (11.1%). No deaths have occurred on study. Forty-eight individuals (70-500 mg) were evaluable for disease response assessments. Evidence of single agent activity was noted at doses ≥ 150 mg, including 1 VGPR at 200 mg (exposure duration > 55 weeks) and 4 PRs noted at doses ranging from 150-500 mg (respective exposure durations of 32, 29, 24, and 21 weeks). Five additional patients achieved MR, resulting in a clinical benefit rate (≥ MR) of 20.8%, and 23 patients were noted to have SD, resulting in a remarkable disease control rate (≥ SD) of 68.8%. In addition, of those patients with SD, 8 had exposure durations for > 20 weeks. Conclusions:In heavily treated patients with relapsed/refractory MM, LGH447 was generally well tolerated and exhibited evidence of durable single-agent efficacy in multiple patients, with the best response being a VGPR. These findings validate Pim kinase inhibition as a promising therapeutic rationale in MM patients and support further clinical development in patients. Disclosures Ocio: Novartis: Honoraria. Thomas:Novartis: Research Funding; Celgene: Consultancy, Research Funding; Millennium: Research Funding; Idera Pharmaceuticals: Research Funding; Immunomedics: Research Funding. Günther:Novartis: Consultancy, Research Funding. Goh:Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees; Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jannsen Pharmaceuticals: Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees. Lebovic:Celgene: Consultancy, Research Funding, Speakers Bureau; Onyx: Research Funding, Speakers Bureau; Millennium: Consultancy. Jakubowiak:Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; SkylineDx: Honoraria, Membership on an entity's Board of Directors or advisory committees; Onyx: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Song:Novartis: Employment. Xiang:Novartis: Employment. Patel:Novartis: Employment. Vanasse:Novartis: Employment, Equity Ownership. Kumar:Celgene: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Onyx: Consultancy, Research Funding; Novartis: Research Funding; Array: Research Funding; Cephalon: Research Funding.

Abstract Abstract 3723 Background: Waldenström macroglobulinemia (WM), a lymphoproliferative disorder with marrow infiltration by lymphoplasmacytic lymphoma cells and production of monoclonal IgM, is characterized clinically by good initial responses to standard therapeutic approaches. However, a minority of patients achieve a complete remission, and most inevitably relapse, indicating a need for validation of new, targeted therapies. Notably, B-cell receptor signaling has been linked to clonal evolution in WM, and Spleen tyrosine kinase (Syk) is over-expressed in primary patient cells. Also, a recent phase I/II study of the Syk inhibitor fostamatinib in patients with a variety of non-Hodgkin lymphomas showed evidence of activity in three patients with WM. These findings supported our central hypothesis, which proposed that Syk could be a rational new target for therapy of WM, which we pursued first with pre-clinical studies. Methods: Studies of fostamatinib were performed using the WM cell line MWCL-1, and the IgM-producing cell line BWCM.1, as well as in primary cells from patients with WM, and in a novel murine xenograft model utilizing MWCL-1 cells. Results: Fostamatinib induced a time- and dose-dependent reduction in viability of MWCL-1 and BWCM.1 cells, with median inhibitory concentrations (IC50) that were in the physiologically relevant range of approximately 0.25 and 1 μM, respectively, at 3 days. Cell cycle analysis showed a decrease in cells at S-phase and at G2/M, while an increase was seen in cells in G1, and in the sub-G1fraction, suggesting induction of apoptosis. Consistent with the possibility that there was activation of type I programmed cell death, increased staining was seen in fostamatinb-treated cells with an antibody to Annexin V. Interestingly, evidence was seen of the induction of type II programmed cell death, or autophagy, as measured by an increase in cells staining with the lysotropic dye acridine orange. At the molecular level, fostamatinib blocked signaling through p44/42 mitogen-activated protein kinase (MAPK), MAPK kinase (MEK), protein kinase B/Akt, and Zeta-chain-associated protein kinase (ZAP)-70/Syk, as judged by a reduction in the phosphorylated forms of these intermediates by Western blotting. Notably, the viability of primary cells isolated from patients with WM was also reduced in association with blockade of p44/42 MAPK. Finally, a novel murine xenograft model was generated by injection of MWCL-1 cells into immunodeficient mice, which developed measurable tumors. When these were treated with fostamatinib, a delay in tumor growth was demonstrable. Conclusions: Targeting Syk with fostamatinib is an attractive strategy against pre-clinical models of WM both in vitro and in vivo. These findings lend further support for translation of fostamatinib to the clinic for patients with relapsed, and possibly even newly diagnosed WM. Disclosures: No relevant conflicts of interest to declare.

Abstract Purpose: Waldenström's macroglobulinemia is an incurable lymphoproliferative disorder driven by an L265P mutation in the myeloid differentiation primary response gene 88 (MYD88), which activates downstream NF-κB signaling through the Myddosome. As this pathway depends in part on activity of interleukin-1 receptor-associated kinases (IRAKs)-1 and -4, we sought to evaluate the potential of the IRAK1/4 inhibitor R191 in preclinical models. Experimental Design: Patient-derived cell lines and primary samples were used in both in vitro and in vivo experiments to model Waldenström's macroglobulinemia and its response to IRAK1/4 inhibitors. Results: R191 induced a dose- and time-dependent reduction in viability of BCWM.1 and MWCL-1 Waldenström's cell lines, and suppressed activation of IRAK1/4. This was associated with cell-cycle arrest at G0–G1, reduced levels of cyclin-dependent kinases 4 and 6, and induction of apoptosis in cell lines and primary patient samples. Further downstream, R191 exposure led to reduced activation of NF-κB, and of protein kinase B/Akt/mammalian target of rapamycin signaling, whereas expression of a constitutively active Akt mutant induced R191 resistance. Gene expression profiling and gene set enrichment analysis revealed a signature consistent with inhibition of c-Myc and activation of the endoplasmic reticulum stress response. In both subcutaneous and systemic murine models of Waldenström's, R191 showed antitumor activity. Finally, the activity of R191 was enhanced when it was combined with novel chemotherapeutics such as bortezomib, afuresertib, and ibrutinib. Conclusions: Taken together, these data support the translation of R191 as an approach to target IRAK1/4 to the clinic for patients with Waldenström's macroglobulinemia.

Abstract Purpose: Waldenström macroglobulinemia (WMG) is a lymphoproliferative disorder characterized by good initial responses to standard therapeutics, but only a minority of patients achieve complete remissions, and most inevitably relapse, indicating a need for novel agents. B-cell receptor signaling has been linked to clonal evolution in WMG, and Spleen tyrosine kinase (Syk) is overexpressed in primary cells, suggesting that it could be a novel and rational target. Experimental Design: We studied the impact of the Syk inhibitor fostamatinib on BCWM.1 and MWCL-1 WMG-derived cell lines both in vitro and in vivo, as well as on primary patient cells. Results: In WMG-derived cell lines, fostamatinib induced a time- and dose-dependent reduction in viability, associated with activation of apoptosis. At the molecular level, fostamatinib reduced activation of Syk and Bruton's tyrosine kinase, and also downstream signaling through MAPK kinase (MEK), p44/42 MAPK, and protein kinase B/Akt. As a single agent, fostamatinib induced tumor growth delay in an in vivo model of WMG, and reduced viability of primary WMG cells, along with inhibition of p44/42 MAPK signaling. Finally, fostamatinib in combination with other agents, including dexamethasone, bortezomib, and rituximab, showed enhanced activity. Conclusions: Taken together, these data support the translation of approaches targeting Syk with fostamatinib to the clinic for patients with relapsed and possibly even newly diagnosed WMG. Clin Cancer Res; 21(11); 2538–45. ©2015 AACR.

Abstract Waldenström macroglobulinemia (WM) is a distinct B-cell lymphoproliferative disorder for which clearly defined criteria for the diagnosis, initiation of therapy, and treatment strategy have been proposed as part of the consensus panels of International Workshops on WM (IWWM). As part of the IWWM-7 and based on recently published and ongoing clinical trials, the panels updated treatment recommendations. Therapeutic strategy in WM should be based on individual patient and disease characteristics (age, comorbidities, need for rapid disease control, candidacy for autologous transplantation, cytopenias, IgM-related complications, hyperviscosity, and neuropathy). Mature data show that rituximab combinations with cyclophosphamide/dexamethasone, bendamustine, or bortezomib/dexamethasone provided durable responses and are indicated for most patients. New monoclonal antibodies (ofatumumab), second-generation proteasome inhibitors (carfilzomib), mammalian target of rapamycin inhibitors, and Bruton's tyrosine kinase inhibitors are promising and may expand future treatment options. A different regimen is typically recommended for relapsed or refractory disease. In selected patients with relapsed disease after long-lasting remission, reuse of a prior effective regimen may be appropriate. Autologous stem cell transplantation may be considered in young patients with chemosensitive disease and in newly diagnosed patients with very-high-risk features. Active enrollment of patients with WM in clinical trials is encouraged.