Abstract: Introduction Ixazomib, a second generation proteasome inhibitor provides the advantage of combining oral administration with pronounced activity and a favorable toxicity profile. Phase II studies employing ixazomib-dexamethasone established a once weekly dosing regimen and showed substantial activity in RRMM yielding response rates of up to 58% when combined with lenalidomide-dexamethasone (Ld). A recent phase III trial proved the superiority of the triple combination ixazomib-Ld compared to Ld in patients with RRMM. Here, we evaluate the activity and tolerability of the all oral combination ixazomib-thalidomide-dexamethasone in patients with RRMM. Methods Patients with RRMM with at least 1 prior line of therapy were enrolled. Patients had to have measurable disease, ECOG performance status ≤2, ANC ≥1000/µL, platelet count ≥50000µL, GFR ≥15mL/min. The treatment regimen consisted of ixazomib (4mg, d 1, 8 and 15), thalidomide (100mg daily) and dexamethasone (40mg once weekly). Patients aged ≥75 years received a reduced dose of both thalidomide (50mg daily) and of dexamethasone (20mg, once weekly). A total of 8 cycles was planned, followed by ixazomib maintenance therapy (4mg, days 1, 8, 15 of a 28 cycle and 3mg in patients aged ≥75 years) for one year. Progression-free survival curves were estimated using the Kaplan-Meier method. The EORTC Q30 instrument was used for evaluation of changes in overall health and global QoL during therapy. Results Thirty-nine of 77 planned patients have been enrolled so far. Intent-to treat group (ITT), age, median: 67, range 42 to 85; ISS stage I: 13, II 14, III: 10, not known: 2, number of prior treatment lines, median: 2, (range: 1-5). Seven patients have discontinued treatment before completion of 2 cycles (early death: 3, progressive disease: 2, protocol violation: 1, patients request: 1). At present, 8 patients are too early (not yet completed 2 cycles) for evaluation per protocol (PP). Full documentation of at least 2 cycles of therapy is available for 24 patients. In this group, the median number of cycles administered is 4, and the median follow up is 4.5 months. Responses to IxaThalDex were seen in 14 patients (35.8% and 58.3% of ITT and PP group, respectively), 3 achieved ≥ VGPR (8%/ITT, 13%/PP), 10 PR (26%/ITT, 42%/PP) and 2 MR (5%/ITT, 8%/PP), yielding a clinical benefit rate of 38.5%/ITT, 62.5%/PP. FISH data are available in 17 of the 24 PP patients. Responses (≥PR) were seen in 5/6 patients with t (4;14) and/or t (14;16) and/or del17p and in 5/8 with standard risk cytogenetics. Median PFS at the time of reporting is 5.7 and 6.4 months in the ITT and PP group, respectively. An improvement in overall health and of general QoL was noted in 6 and 7 of the 14 responders, respectively. Toxicity data are presented for the PP group. Neutropenia was the most common hematologic toxicity noted in 20 (83.3%) patients; all of them had grade 1/2, and none higher grade neutropenia. Leukopenia was seen in 15 (62.5%) patients, (14 grade 1/2 and one grade 3). Sixteen (66.7%) had grade 1/2 anemia. Grade 1/2 thrombocytopenia was noted in 8 (33.3%) patients. The most frequent non hematological toxicity was infection seen in 7 (29%) patients. Six were grade 3; pneumonia was seen in 4, sepsis in 1 and other infections in 2 patients. Polyneuropathy at baseline was seen in 7 patients (grade 1 in 2, and grade 2 without pain in 6 patients). During the study the incidence of new PNP was relatively rare (3 new and one worsening PNP) with presently 9 (37.5%) patients with grade 1-2 and only 1 (4.2%) with grade 3. Other notable toxicities were acute renal failure (grade 3) in 2 (8.3%), fatigue in 8 (4 grade 1, 4 grade 2), constipation and diarrhea (all grade 1) each in 4, and edema and vision impairment (all grade 1), each in 3 patients. Conclusion The entirely oral IxaThalDex regimen resulted in an ORR of 58.3 in the PP and of 35.8% in the ITT population (with 8 patients being too early for PP evaluation and not having reached 2 cycles as yet). The clinical benefit rate was 62.5% and 38.5% for the PP and ITT group, respectively. Median PFS was 6.4 months in the PP group. General health and QoL improved in 42.8% and 50% of the responders. The ixazomib-thalidomide-dexamethasone regimen was well tolerated and with relatively few side effects being noted. As exposure to therapy is still short at this point of time it is anticipated that efficacy data will further improve with longer therapy and follow up. Updated results will be presented at the meeting. Disclosures Ludwig: Takeda: Research Funding, Speakers Bureau; Amgen: Research Funding, Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Janssen: Speakers Bureau. Gunsilius:Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria; Novartis: Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Greil:Celgene: Research Funding; Takeda: Honoraria, Research Funding; Novartis: Research Funding; BMS: Honoraria; Celgene: Honoraria; Roche: Honoraria, Speakers Bureau. Petzer:Roche: Honoraria. Knop:Takeda: Consultancy. Poenisch:Mundipharma: Research Funding.

Abstract: Background Rapid induction of remission is a favorable factor in pts with Hodgkin's disease and DLBCL. In MM, only few data are available on the impact of response kinetics on outcome in newly diagnosed transplant ineligible MM pts. Recently, (Abstract EP971, EHA 2021) we described a significant correlation between time to response and progression-free survival (PFS) and overall survival in this patient population. Response and time to response depend on several factors such as the biology of the underlying myeloma clone(s), the activity of the treatment regimen, and on the composition of the bone marrow immune environment. Here, we evaluated possible interconnections between the bone marrow immune environment at baseline and the time to response to therapy in a series of pts randomized to either 9 cycles KRd or KTd induction therapy followed by a second randomization to carfilzomib maintenance or observation. Patients and Methods Composition of the immune environment at baseline was analyzed in 55 pts with newly diagnosed transplant ineligible MM enrolled in a randomized phase II trial (AGMT_MM 02). Median age: 74 years (range: 58-84 years), ISS I: 21.8%, ISS II: 41.8%, and ISS III: 36.4%, cytogenetics: 30.9% high risk, 40% standard risk, 29.1% unknown, ECOG Status 0: 54.5%, 1: 45.6%. Treatment: Carfilzomib : Cycle 1 day 1+2: 20mg/m 2, days 8+9 and 15+16: 27 mg/m 2 ; Cycle 2 day 1,2,8,9,15 + 16: 27 mg/m 2 Cycle 3-9: 56mg/m 2 on days 1, 8 and 15. Lenalidomide: 25mg p.o. on days 1-21/cycle or thalidomide: 100 mg p.o. on days 1-28; in pts ≥75 years of age 50mg p.o. on days 1-28, dexamethasone: 40 mg p.o. on days 1, 8, 15, 22 (± 1 day), in pts ≥ 75 years of age 20 mg p.o. this treatment was administered for nine cycles. Thereafter, pts were randomized to carfilzomib maintenance at last tolerated dose on days 1+15 or to observation for 12 cycles. BM samples were stained with 3 different antibody combinations for the analysis of T, B and NK cells (T cells: CD45RA, CD127, CD8, TCRgd, CD25, CD197, CD4, CD3, B/NK cells: CD57, CCR7, CD314, CD85j, CD62L, CD3, CD16, CD56, CD335, HLADR, CD337). We used a semi-automated pipeline to unveil full cellular diversity based on unbiased clustering. The median and range of each cellular subgroup was calculated and compared between pts with short or longer time to response ( & lt; or ≥119 days (median)). Statistical significance of these comparisons was calculated using the Wilcoxon test. Results Median FU was 20.5 months. Twenty of the 55 pts achieved a CR (36.7%) and 16 (57.1%) of the 28 who had MRD testing were shown to be MRD negative at a sensitivity of 10 -6. Twenty-three pts achieved a VGPR (41.8%), while only 12 pts achieved a PR (21.8%). Pts were subdivided into two groups according to time to best response. Group A (n=26), median time 56 (26-112) days, group B (n=29), 265 (119-675) days. PFS was significantly longer in group B (19.1 months vs not reached, p=0.007), while for OS only a trend for better survival was noted for group B pts (median survival not reached, p=0.129). High numbers of total CD3 + cells (p=0.033) and CD4 T cells with a CD 197 loCD45RA -CD127 + phenotype (p=0.022) were associated with longer time to best response and longer PFS. An opposite result was noted for the following T cell subsets, which correlated with a shorter time to best response and shorter PFS: CD56 + T cells with (p=0.01) or without (p=0.024) HLADR and CD8 Naïve CD127 + T cells (p=0.041). Diverse results were noted when the NK cell compartment was analyzed. Higher levels of circulatory CD314 - (p & lt;0.0001) and circulatory CD314 + (p=0.049) NK cells correlated with longer time to best response and longer PFS. By contrast, lower levels of cytotoxic HLADR + NK cells (p=0.044) were associated with better outcome. Conclusion Our data show significant correlations between the composition of bone marrow immune cells at start of therapy with time to best response and PFS in newly diagnosed transplant ineligible MM pts uniformly treated with carfilzomib-based therapy. High numbers of total lymphocytes CD3 and CD4 Tcells with a CD197 loCD45RA -CD127 + phenotype correlated with significantly longer PFS and longer time to response. Furthermore, higher numbers of specific NK subsets such as those with a circulatory phenotype, correlated with better outcome. These results highlight the prognostic potential of immune monitoring and the interconnection between specific subsets of the immune environment with the course of the disease. Figure 1 Figure 1. Disclosures Greil: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; AstraZeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Janssen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses; MSD: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Gilead: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Daiichi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Sankyo: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Accommodations, Expenses, Research Funding; Sanofi: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Other: Travel, Accommodations, Expenses, Research Funding; Sandoz: Honoraria, Research Funding. Podar: Amgen Inc.: Consultancy, Honoraria; Janssen Pharmaceuticals: Consultancy, Honoraria; Roche Pharmaceuticals: Research Funding; Celgene: Consultancy, Honoraria. Petzer: Pfizer: 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; Kite-Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sandoz: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene-BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: 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; Daiichi Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Saegen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Zojer: Celgene-BMS, Amgen, Takeda, Sanofi, Janssen: Consultancy, Speakers Bureau. Schreder: BMS-Celgene, Amgen: Consultancy. Melchardt: Abbvie, Celgene, Novartis: Honoraria. Knop: BMS/Celgene: Consultancy, Honoraria, Research Funding; Amgen: Research Funding; Janssen: Consultancy; Oncopeptides: Consultancy; Pfizer: Consultancy; Sanofi: Consultancy. Paiva: Bristol-Myers Squibb-Celgene, Janssen, and Sanofi: Consultancy; Adaptive, Amgen, Bristol-Myers Squibb-Celgene, Janssen, Kite Pharma, Sanofi and Takeda: Honoraria; Celgene, EngMab, Roche, Sanofi, Takeda: Research Funding. Ludwig: Janssen, Celgene-BMS, Sanofi, Seattle Genetics: Consultancy, Speakers Bureau; Amgen, Takeda: Consultancy, Research Funding, Speakers Bureau. OffLabel Disclosure: Carfilzomib in first-line therapy

Abstract: Homing to secondary lymphoid organs and re-entry to bone marrow (BM) are central aspects of leukemic pathophysiology. We investigated the roles of the two major lymphocyte integrins LFA-1 and VLA-4 on B-cell chronic lymphocytic leukaemia (CLL) cells in these processes. We found that CLL cells expressed significantly reduced LFA-1 due to low beta2 integrin transcripts and displayed diminished adhesiveness to ICAM-1-expressing endothelium in vitro. VLA-4 expression was heterogenous but underwent rapid activation by the BM chemokine CXCL12. Nevertheless, CLL cells failed to transmigrate across VCAM-1, ICAM-1 and CXCL12 expressing endothelium due to their deficient LFA-1 expression. Furthermore, when injected into tail veins of immunodeficient mice, normal B cells rapidly homed to lymph nodes (LNs) in a LFA-1 dependent manner whereas CLL cells did not. CLL alike normal B lymphocytes used VLA-4 rather than LFA-1 to reenter the BM. In contrast, both normal and CLL B cells homed to mice spleen in an LFA-1- and VLA-4-independent manner. Our results suggest that CLL cells are deficient in LFA-1-dependent trafficking to LNs but residual subsets can still re-enter the BM. Integrin blocking could be therefore an efficient strategy to prevent circulating CLL cells from reaching prosurvival niches in LNs and BM and directing these cells to the spleen.

Abstract: Introduction: Panobinostat (PAN) is a potent pan-deacetylase inhibitor that targets multiple myeloma (MM) cells via its epigenetic effects as well as its effect on the aggresome. In the PANORAMA 1 phase 3 trial, the combination of PAN, bortezomib (BTZ), and dexamethasone (Dex; PAN+BTZ+Dex) significantly increased progression-free survival compared with placebo plus BTZ and Dex, leading to approval in Europe of the combination for the treatment of patients with MM who have received ≥ 2 prior regimens, including BTZ and an immunomodulatory agent. The purpose of this expanded treatment protocol (ETP) is to further evaluate safety and to provide panobinostat prior to commercial availability to patients with relapsed/refractory MM who have received ≥ 2 prior lines of therapy but for whom satisfactory treatment alternatives are not available. Methods: Panobinostat-ETP is a multicenter, open-label, ETP study of PAN+BTZ+Dex in adult patients with MM relapsed and/or refractory to ≥ 2 prior lines of therapy. During treatment phase (TP) 1 of the study, patients received oral PAN 20 mg (days 1, 3, 5, 8, 10, and 12) plus intravenous or subcutaneous BTZ 1.3 mg/m2 (days 1, 4, 8, and 11) for eight 21-day cycles. Patients with ≥ stable disease proceeded to TP2, with maintained PAN and less frequent BTZ dosing (days 1 and 8) for an additional 8 cycles. In both phases, oral Dex 20 mg was administered on the days of and after BTZ treatment. Reduction to once-weekly BTZ was allowed prior to TP2 as a dose reduction strategy. Results: A total of 49 patients with a median age of 67 years (range, 45-85 years) were enrolled in the study. Patients were heavily pretreated; 73.5% received ≥ 3 prior lines of therapy. Most patients (n = 43 [87.8%]) received subcutaneous BTZ, while 3 (6.1%) received intravenous BTZ, and another 3 (6.1%) received both. The median duration of treatment with PAN+BTZ+Dex was 67 days (range, 12-305 days). The most common grade 3/4 hematologic laboratory abnormalities were thrombocytopenia (51.0%), anemia (12.2%), and neutropenia (10.2%). The most common nonhematologic grade 3/4 treatment-emergent adverse events (AEs) were diarrhea (14.3%), fatigue (8.2%), infection (6.1%), and nausea (6.1%). Common gastrointestinal treatment-emergent AEs of any grade included diarrhea (51.0%), constipation (16.3%), and nausea (16.3%). Interestingly, in the patients receiving subcutaneous BTZ, the rates of grade 3/4 diarrhea (11.6%), thrombocytopenia (48.8%), anemia (14.0%), and neutropenia (11.6%) were lower than those seen with intravenous BTZ administration in the phase 3 PANORAMA 1 trial (25%, 57%, 16.8%, and 24.1%, respectively). Two patients died while on treatment; one due to disease progression and the other due to infection. Common serious AEs included diarrhea (12.2%) and thrombocytopenia, atrial fibrillation, infection, pneumonia, and syncope (all 6.1%); serious AEs of atrial fibrillation and syncope were higher than in PANORAMA 1 (1.0% and 1.3%, respectively). AEs led to PAN, BTZ, and Dex dose adjustment in 36.7%, 42.9%, and 16.3% of patients, respectively; the most common AE leading to dose adjustment or temporary interruption was thrombocytopenia (all-grade, 30.6%; grade 3/4, 28.6%). Efficacy data will be reported after sufficient follow-up. Conclusions: Overall, the safety results from panobinostat-ETP, albeit in an older population of patients with more advanced MM, support those generated in PANORAMA 1, with only a slight increase in atrial fibrillation, potentially because of the older population. In the subgroup of patients receiving subcutaneous BTZ, rates of diarrhea and hematologic toxicities, AEs of interest with PAN+BTZ+Dex therapy, appear to be reduced compared with PANORAMA 1 data with intravenous BTZ administration; however, because of the small size of this study, these results should be interpreted with caution. Further clinical experience with the use of subcutaneous BTZ in this combination will help to determine the potential impact of the route of BTZ administration on tolerability. Disclosures Guenther: Takeda: Consultancy, Honoraria; Celgene: Honoraria; Novartis: Consultancy, Honoraria. Mügge:Celgene: Honoraria, Research Funding; Janssen: Honoraria; Cilag: Honoraria; Novartis: Honoraria; Amgen: Honoraria; Bristol Myers-Suibb: Honoraria. Schjesvold:Janssen: Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Lechner:Novartis: Honoraria. Gisslinger:Novartis: Consultancy, Honoraria; AOP Orphan: Consultancy, Honoraria; Baxalta: Consultancy, Honoraria. Greil:Novartis: Honoraria, Research Funding; Janssen Cilag: Honoraria, Research Funding. Gunsilius:Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria; Novartis: Membership on an entity's Board of Directors or advisory committees. Weisel:Amgen: Consultancy, Honoraria; Bristol Myer-Squibb: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria. Munder:Janssen: Honoraria; Amgen: Honoraria; Bristol Myers Squibb: Honoraria; Takeda: Honoraria. Kiani:Novartis: Consultancy, Honoraria, Speakers Bureau. Campello-Iddison:Novartis: Employment, Equity Ownership. Einsele:Janssen: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Speakers Bureau; Amgen: Consultancy, Honoraria, Speakers Bureau.

Abstract: Morbidity and mortality of Philadelphia chromosome–negative myeloproliferative neoplasms (MPNs) are mainly determined by thromboembolic complications. Thrombus formation is facilitated by a neutrophil-specific form of cell death linked to neutrophil extracellular trap (NET) formation (NETosis). Preclinical and clinical data suggested a potential link between NETosis and thrombosis in MPNs. In this study, we aimed to define the impact of NETosis on clinical end points in a large MPN cohort. NETosis was induced in vitro by ionomycin and quantified by enzyme-linked immunosorbent assay–based nucleosome release assays as well as fluorescent staining of free DNA in samples from 103 MPN patients and 28 healthy donors. NETosis rate was correlated with a broad set of clinical data, such as MPN subtype, mutational status, laboratory variables, history of thrombotic events, and treatment types. Triggered NETosis levels were clearly higher in MPN patients than in healthy donors. Positivity for JAK2 V617F or exon 12 as well as CALR mutations correlate with increased NET formation. However, neither JAK2 allelic burden nor history of thromboembolic complication nor the presence of other risk factors for thrombosis (eg, leukocytosis) were associated with the rate of NETosis. In addition, none of the analyzed laboratory parameters nor the type of treatment significantly impacted the rate of NETosis formation. The biology of MPNs has an impact on NET formation because genetic driver mutations favor induction of NETosis, but this does not seems to translate into important clinical end points such as thromboembolic complications. Therefore, NETosis may play a role in facilitating thrombosis, but it is not a sole causative determinant in MPN-associated thrombophilia.

Abstract: Introduction Ixazomib is an effective PI that combines the advantage of oral administration with a favorable toxicity profile. Recent results showed significant activity, both in newly diagnosed, and in pretreated patients (pts). Ixazomib in combination with lenalidomide-dexamethasone (IRd) was significantly superior over Rd in pts with relapsed/refractory multiple myeloma (RRMM), and was able to overcome the negative impact of poor risk cytogenetics. Ixazomib-thalidomide-dexamethasone (IxaThalDex) has been shown to be effective in pts with newly diagnosed MM and is used in this trial in pts with RRMM. Here, we evaluate the impact of cytogenetic risk factors on outcome in pts with RRMM treated with IxaThalDex. Patients and Methods Ninety pts with RRMM and one or more prior lines of therapy (TX) were enrolled. Treatment regimen: Ixazomib (4mg, d 1, 8 and 15), thalidomide (100mg/d), and dexamethasone (40mg once/week). Pts aged ≥75 years received lower doses of thalidomide (50mg/d) and of dexamethasone (20mg). Pts were scheduled for 8 cycles followed by ixazomib maintenance therapy (4mg, days 1, 8, 15 of a 28 cycle and 3mg in pts aged ≥75 years) for one year. Preplanned FISH analysis was performed on CD138 selected bone marrow plasma cells. The cut-off level for positivity was 10% for t(4;14), and 20% for del(17p) and 1q21 gain, respectively. The previously defined primary endpoint was progression-free survival (PFS), and secondary objectives were overall response rate, overall survival (OS), and impact of cytogenetic risk and of renal impairment, safety and myeloma frailty status. PFS and OS was estimated according to Kaplan-Meier and differences evaluated by log-rank test. Response rates were compared using Fisher's Exact Test. Findings Seventy-six of the 90 pts of the intent to treat group (ITT) received at least two cycles and comprise the per protocol population (PP). Complete FISH data are available in 61 pts. Pt characteristics of the ITT group: Age, median 67 (44 -84) years, ISS stage I: 37, II 30, III: 22, not known: 1, median number of prior TX lines: 1 (range: 1-8). Forty-three pts have completed all 8 cycles of induction therapy (median number of cycles: 6). Forty-one pts started Ixazomib maintenance therapy and 6 completed the planned 12 cycles as yet. Median follow-up is 15.3 months. PR or better was achieved in 46 pts (60.5%), CR in 8 (10.5%), VGPR in 13 (17.1%), PR in 25 (32.9%), and MR in 6 (7.9%) pts, yielding a clinical benefit rate of 68.4%. Thirteen (21.3%) pts of the 61 pts with FISH data available presented with t(4;14), 5 (8.1%) with del(17p), and 32 (52.5%) with 1q21 gain. Response rates (≥PR) did not differ significantly (p values not shown) between pts with high-risk (HR) [t(4;14) and/or del(17p)], and standard-risk (SR) cytogenetic risk profile: 64.7% vs. 53.2%, nor in those with and without 1q21 gain: 46.9% vs. 69.2%, or those with HR cytogenetics and/or 1q21 gain 48.7% vs. 68.2, and were comparable to those of the entire PP patient group (60.5%). Median PFS at the time of reporting is 8.8 mos. in the ITT and 10.2 mos. in the PP group. PFS did not differ in pts with HR and SR cytogenetics (10.3 vs. 9.3 months, p=0.703). In contrast, a tendency for shorter PFS was noted in pts with 1q21 gain (6.9 vs. 11.6 months, p=0.067). Similar findings were observed in pts with HR and/or 1q21 gain vs. those without these features (7.0 vs. 10.8 months; p=0.117). Median OS has not been reached, neither in the ITT nor in the PP group. OS did not differ between pts with HR and SR cytogenetics (p=0.961), similarly, Pts with 1q21 gain had significantly shorter OS (median: 19.6 vs. not reached, p=0.001); a similar reduction in OS was noted when pts with HR cytogenetics and/or 1q21 gain were compared to those without these features (median: 19.6 months vs. not reached, p=0.003) Discussion and Conclusion The all oral IxaThalDex regimen overcame the negative impact of HR cytogenetics [t(4;14) and del(17p)] both in terms of PFS and OS. Similarly, there was no difference in the depth of response between the groups. However, in those with 1q21 gain alone, or with a HR feature and/or 1q21 gain, a tendency of shorter PFS was noted. OS was significantly shorter in the latter groups. These findings suggest that 1q21 gain should be included in the HR category in pts exposed to ixazomib plus thalidomide-dexamethasone. Figure 1: PFS and OS in pts with and without HR cytogenetics (1A and 1B) and in those with and without HR cytogenetics and/or 1q21 gain (1C and 1D). Disclosures Ludwig: BMS: Speakers Bureau; Takeda: Research Funding, Speakers Bureau; Celgene: Speakers Bureau; Amgen: Research Funding, Speakers Bureau; Cilag-Janssen: Speakers Bureau. Knop:Bristol Myers Squibb: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding. Hajek:Amgen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding. Gunsilius:Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen-Cilag: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; BMS: Honoraria. Petzer:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees. Weisel:Amgen, Celgene, Janssen, and Sanofi: Research Funding; Amgen, BMS, Celgene, Janssen, Juno, Sanofi, and Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen, BMS, Celgene, Janssen, and Takeda: Honoraria. Greil:Takeda: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Astra Zeneca: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; MSD: Honoraria, Research Funding; Sandoz: Honoraria, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Honoraria, Other: TRAVEL, ACCOMMODATIONS, EXPENSES, Research Funding; Merck: Honoraria, Research Funding; Janssen: Other: TRAVEL, ACCOMMODATIONS, EXPENSES; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Abstract: The selective tyrosine kinase inhibitor imatinib eradicates bcr-abl+ cells in chronic myeloid leukemia patients (pts). Although a previous clinical trial showed superiority of an imatinib therapy over an interferon-α containing regimen, a significant number of pts eventually relapse with leukemia because of either point mutations within the imatinib-binding site, amplification of the Philadelphia chromosome or other mechanisms, e.g. clonal evolution. AMN107 (Novartis Pharma AG) is a new anilino-pyrimidine derivative (MW: 529.5) structurally related to imatinib. AMN107 was tested in three human bcr-abl positive lines (K562, KCL-22, Lama-84) and in primary cells derived from two bcr-abl + CML pts who were resistant to imatinib, as well as in one newly diagnosed chronic phase patient. In all pts sequencing of the bcr-abl kinase domain excluded any point mutations, but cytogenetic analysis of the bone marrow revealed clonal evolution in the resistant pts including t(1;5) and t(3;21) translocations, trisomy of chromosome 8 and monosomy of chromosome 7. Determination of the proliferative activity by XTT-assay in cell lines demonstrated a decrease of the IC50 in imatinib versus AMN107 treated samples from 0.08μM to 0.0075μM in Lama 84, from 0.25μM to 0.08μM in K562 and from 0.45μM to 0.03 in KCL-22 cells. No activity of either compound was observed in the bcr-abl negative HL-60 and KG-1 cells. In primary cells from imatinib-resistant pts, a decrease of the IC50 in imatinib versus AMN107 treated peripheral blood cells from 0.75μM to 0.1μM and from 4 to 0.4μM was detected. In addition, in primary cells from one newly diagnozed CML patient the IC50 of AMN107 (2.5μM) was reduced when compared to imatinib (5μM). Immunoblotting showed that in LAMA84 cells a concentration of 0.01μM AMN107 completely inhibited the tyrosine kinase activity as detected by use of an anti-phosphotyrosine antibody in contrast to almost 5μM in imatinib treated samples. Further, induction of apoptosis was detected using annexin V and propidium iodide by double fluorescence. After 48 hours of incubation with either 0.25 μM imatinib or 0.005 μM AMN107 induction of early apoptosis was detected in 8.8% of imatinib treated and 26% of AMN107 treated cells. Finally, HPLC analysis in HL-60 cells showed increased uptake by 1,5 fold for AMN107 when compared to imatinib. In addition, in MDR1 over-expressing CCRF cells co-culture with either AMN107 or imatinib revealed elevated AMN107 levels (3.7 fold) indicating that this substance is less susceptible to MDR1 driven resistance than imatinib. Conclusions: 1. AMN107 showed elevated activity when compared to imatinib in bcr-abl + cell lines and primary cells derived from imatinib resistant leukemic pts. 2. Complete inhibition of the bcr-abl tyrosine kinase activity and induction of apoptosis was achieved at lower concentrations in AMN107 treated samples when compared to imatinib. 3. Preliminary data indicate favourable cellular uptake of AMN107 when compared to imatinib. 4. AMN107 may be useful in the treatment of bcr-abl + leukemic pts.