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We aimed to evaluate the efficacy and toxicity of paclitaxel combined with pazopanib in advanced angiosarcoma (AS). The primary end point was progression-free survival (PFS) rate at six months (PFSR6). Planned accrual was 44 patients in order to detect a PFSR6 of &gt, 55%, with an interim futility analysis of the first 14 patients. The study did not meet its predetermined interim target of 6/14 patients progression-free at 6 months. At the time of this finding, 26 patients had been enrolled between July 2014 and April 2016, resulting in an overrunning of 12 patients. After a median follow-up of 9.5 (IQR 7.7–15.4) months, PFSR6 amounted to 46%. Two patients had a complete and seven patients a partial response. Patients with superficial AS had a significantly higher PFSR6 (61% vs. 13%, p = 0.0247) and PFS (11.3 vs. 2.7 months, p &lt, 0.0001) compared to patients with visceral AS. The median overall survival in the entire cohort was 21.6 months. A total of 10 drug-related serious adverse effects were reported in 5 patients, including a fatal hepatic failure. Although our study did not meet its primary endpoint, the median PFS of 11.6 months in patients with superficial AS appears to be promising. Taking recent reports into consideration, future studies should evaluate the safety and efficacy of VEGFR and immune checkpoint inhibitors with or without paclitaxel in a randomized, multiarm setting.

Introduction Selinexor is an exportin-1 (XPO1) inhibitor which forces the nuclear retention and functional activation of tumor suppressor proteins, inducing apoptosis in cancer cells. Overexpression of XPO-1 is common in many tumors, including acute myeloid leukemia (AML). A phase II study, "SAIL", of selinexor with cytarabine and idarubicin in patients with relapsed/refractory AML was conducted by Fiedler et al. showing a high remission rate. To identify molecular predictors of response and survival we evaluated the molecular mutations and their course in selinexor treated patients. Methods All 42 patients treated in the SAIL trial were eligible to participate in this translational study. The main criterion for inclusion in the present study was availability of DNA from bone marrow or peripheral blood at 3 time points: initial AML diagnosis, screening for the SAIL trial and first response assessment on day 28 of cycle 1. A custom TruSight myeloid sequencing panel was used to identify molecular mutations at diagnosis. Molecular response was defined as variant-allele frequency (VAF) Results Eighteen patients were included for whom DNA was available for all three time points. The median age was 47.5 years (29-72), median prior therapies was 3 (1-9). 13 patients had de novo and 5 secondary/therapy-related AML. ELN risk at first diagnosis was favorable in eight, intermediate in five and adverse in three patients. Only one course of SAIL treatment was administered to all patients. 8 patients achieved morphologic complete remission (CR) or CR with incomplete hematologic recovery (CRi). 13 patients proceeded to allogeneic hematopoietic cell transplantation (alloHCT) or donor lymphocyte infusion. The median overall survival was 0.69 years. The molecular profile showed a predominance of secondary AML-type mutations. No clear pattern was found between mutation status and morphologic CR or CRi (Figure 1). Molecular response to the SAIL induction treatment was found in 6 of 14 patients who had a molecular marker. Mutations in FLT3 (FLT3-TKD=1, FLT3-ITD=2), SF3B1 and TP53 were associated with molecular response, whereas mutations in GATA2, CUX1, TET2, BCOR, DNMT3A, RAD21, ASXL1, SRSF2, and WT1 were associated with resistance. When comparing the molecular characteristics of patients achieving CR/CRi (n=8) and all other patients (n=10), a trend to achieve CR was observed among patients with NPM1 mutations (P=0.094), whereas mutations in ASXL1 (P=0.09) and SRSF2 (P=0.09) were associated with refractoriness. One of the responding patients received selinexor as maintenance therapy for four years. The patient was diagnosed with de novo AML with normal cytogenetics, with SF3B1 and SRSF2 mutations. The patient received an HLA-identical transplant after myeloablative conditioning, but relapsed 6 years after alloHCT. One cycle of selinexor/chemotherapy was administered and the patient achieved CR. The patient continued selinexor maintenance treatment with 60 mg selinexor twice a week. SF3B1 and SRSF2 mutations were still present at the time of relapse and declined under SAIL treatment (Figure 2). The patient received one course of DLI (1x10 7CD3 +), which was tolerated well without signs of GvHD. MRD remained detectable 17 days after DLI. At 30 days after DLI treatment both MRD markers were negative. Under continued selinexor maintenance treatment MRD remained negative until last follow-up at 4.9 years after SAIL treatment. The patient tolerated selinexor well with short-term nausea and dysgeusia after selinexor intake. Selinexor maintenance treatment was stopped 4 years after SAIL treatment and the patient remains in CR 14 months after the end of maintenance. Conclusion In this small series, we found a correlation between FLT3, TP53 and SF3B1 mutation status and molecular response to selinexor/chemotherapy (SAIL). NPM1 mutations were associated with morphologic response to SAIL by trend. Finally, selinexor maintenance may have contributed to long-term disease control in a patient with relapsed AML, and long term therapy with selinexor is feasible. Figure 1 Figure 1. Disclosures Fiedler: Servier: Consultancy, Other: Meeting attendance, Preparation of information material; Stemline: Consultancy; Daiichi Sanyko: Consultancy, Other: Meeting attendance, Preparation of information material; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Honoraria; MorphoSys: Consultancy, Honoraria; Jazz: Consultancy, Honoraria, Other: Meeting attendance, Preparation of information material; Celgene: Consultancy, Honoraria; Ariad/Incyte: Honoraria; Amgen: Consultancy, Honoraria, Other: Meeting attendance, Preparation of information material, Patents & Royalties, Research Funding; Abbvie: Consultancy, Honoraria, Other: Meeting attendance, Preparation of information material. Modemann: Servier: Honoraria, Other: Travel accomodation; Incyte: Other: Travel accomodation; Gilead: Other: Travel accomodation; Jazz Pharmaceuticals: Other: Travel accomodation; Novartis: Other: Travel accomodation; Teva: Other: Travel accomodation; Pfizer: Other: Travel accomodation; Amgen: Other: Travel accomodation; Daiichi Sankyo: Research Funding; Abbvie: Honoraria, Other: Travel accomodation. Bokemeyer: Merck KGaA: Honoraria; Sanofi: Consultancy, Honoraria, Other: Travel accomodation; Roche: Honoraria, Research Funding; Bayer: Honoraria, Research Funding; BMS: Honoraria, Other: Travel accomodation, Research Funding; AstraZeneca: Honoraria, Research Funding; Merck Sharp Dohme: Consultancy, Honoraria; Lilly/ImClone: Consultancy; Merck Serono: Consultancy, Other: Travel accomodation ; Bayer Schering Pharma: Consultancy; GSO: Consultancy; AOK Health insurance: Consultancy; Abbvie: Research Funding; ADC Therapeutics: Research Funding; Agile Therapeutics: Research Funding; Alexion Pharmaceuticals: Research Funding; Amgen: Research Funding; Apellis Pharmaceuticals: Research Funding; Astellas: Research Funding; BerGenBio: Research Funding; Blueprint Medicine: Research Funding; Boehringer Ingelheim: Research Funding; Celgene: Research Funding; Daiichi Sankyo: Research Funding; Eisai: Research Funding; Gilead Sciences: Research Funding; Gylcotope GmbH: Research Funding; GlaxoSmithKline: Research Funding; Inside: Research Funding; IO Biotech: Research Funding; Isofol Medical: Research Funding; Janssen-Cilag: Research Funding; Karyopharm Therapeutics: Research Funding; Lilly: Research Funding; Millenium: Research Funding; MSD: Research Funding; Nektar: Research Funding; Rafael Pharmaceuticals: Research Funding; Springworks Therapeutics: Research Funding; Taiho Pharmaceutical: Research Funding; Pfizer: Other. Ganser: Celgene: Honoraria; Novartis: Honoraria; Jazz Pharmaceuticals: Honoraria. Thol: Astellas: Honoraria; Jazz: Honoraria; Novartis: Honoraria; Pfizer: Honoraria; BMS/Celgene: Honoraria, Research Funding; Abbvie: Honoraria. Heuser: Karyopharm: Research Funding; AbbVie: Membership on an entity's Board of Directors or advisory committees, Research Funding; Astellas: Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tolremo: Membership on an entity's Board of Directors or advisory committees; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Honoraria; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer Pharma AG: Research Funding; BMS/Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; BergenBio: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees, Research Funding. OffLabel Disclosure: Selinexor in patients with relapsed or refractory AML

2524 Background: The phase I GATTO study explored the feasibility, tolerability and preliminary activity of combining gatipotuzumab (GAT), a novel humanized monoclonal antibody binding to the tumor-associated epitope of mucin-1 (TA-MUC1) and an anti-EGFR antibody. Preclinical evidence suggests a complex interaction between TA-MUC1 and EGFR on the cell surface of epithelial tumors driving carcinogenesis processes and synergistic antibody dependent cell cytotoxicity activity with the dual targeting. Methods: Initially the study enrolled in a primary phase (PP) 20 patients with EGFR positive metastatic solid tumors, for whom no standard treatment was available. The first 6 patients were enrolled into a safety run-in phase and the number of dose-limiting toxicities (DLTs) was evaluated, in order to de-escalate the doses if needed. Patients received GAT administered at 1400 mg Q2W in combination with the glyco-optimized anti-EGFR antibody tomuzotuximab (TOM) at 1200 mg Q2W. Due to the risk of infusion related reactions (IRR), the first dose of TOM was reduced to 720 mg split over 2 consecutive days and three cycles of TOM monotherapy were given before start of treatment with GAT. As this regimen was proven safe, no DLT was observed and the initial dose remained unchanged, the study was amended to enroll in an expansion phase (EP) 30 additional patients with refractory colorectal cancer (CRC), non-small cell lung cancer (NSCLC), head and neck and breast cancers. TOM and GAT were given at the same doses and GAT treatment started already one week after the first dose of the anti-EGFR antibody. Additionally investigator had the choice to use a commercial anti-EGFR antibody in place of TOM. Results: By the time of the final analysis in January 2021, 52 refractory patients were enrolled and 50 received at least one dose of both GAT and anti-EGFR antibodies. Panitumumab (PAN) was used in 9 CRC patients. Because of the difference in treatment schedule, results are summarized separately for the 20 and 30 patients in PP and EP. Overall, the combined treatment was well tolerated and no DLT was observed in the whole study, nor related SAE or death. There were no treatment emergent adverse events (TEAEs) leading to dose interruptions or reductions in the PP and 2/30 (6.7%) patients in EP stopped both TOM and GAT. 16 IRRs were reported in 8/20 (40%) PP patients, and 40 IRRs in 10 (33.3%) EP patients. Only one event of chills was severe and only 6 events were related to GAT in the EP, all others to TOM. Other frequent TEAEs were those commonly observed with anti-EGFR treatment such as skin toxicity in 17 (85%) PP and 26 (86.7%) EP patients and hypomagnesemia in 10 (50%) PP and 7 (23.3%) EP patients. Conclusions: Combination of TA-MUC1 and EGFR targeting antibody is safe and feasible. Future studies should test this combination together with chemotherapy Clinical trial information: NCT03360734.

2522 Background: The phase I GATTO study explored the feasibility, tolerability and preliminary activity of combining Gatipotuzumab (GAT), a novel humanized monoclonal antibody binding to the tumor-associated epitope of mucin-1 (TA-MUC1), and an anti-EGFR antibody. Preclinical evidence suggests a complex interaction between TA-MUC1 and EGFR on the cell surface of epithelial tumors and synergistic antibody dependent cell cytotoxicity activity with the double targeting. Methods: Initially 20 patients with refractory metastatic disease were treated with GAT administered at 1400 mg Q2W in combination with the glyco-optimized anti-EGFR antibody Tomuzotuximab (TOM) at 1200 mg Q2W. Due to the risk of infusion related reactions, three cycles of TOM were given before start of combined treatment with GAT. After this regimen was proven safe and no DLT was observed, 30 additional patients including colorectal cancer (CRC) already treated with anti-EGFR antibodies, non-small cell lung cancer (NSCLC), head and neck and breast cancers received TOM and GAT administered at the same doses, with GAT treatment starting already one week after the first dose of the anti-EGFR antibody. As allowed in the study expansion, Panitumumab (PAN) was used in place of TOM in 9 CRC patients at investigator’s choice. Results: By the time of the final analysis in January 2021, 52 patients were enrolled, and 50 received at least one dose of both GAT and anti-EGFR antibodies. Safety was overall good and results are reported in a separate abstract. Because of the difference in treatment schedule, activity results of the two parts of the study are summarized separately. There were 2 and 4 RECIST partial responses in the first and second part of the study, all in CRC patients. In the expansion phase, the median Progression Free Survival (PFS) of CRC patients who received TOM (10) and PAN (9) was 1.9 and 5.5 months, respectively. There were 2 responses in each subgroup and the duration of response was 3.8 and 7.2 months in patients receiving TOM and PAN, respectively. The PFS for NSCLC was 5.3 months and 2 heavily pretreated patients achieved a prolonged control of disease of 10.6 and 9.4 months. The trial was accompanied by a comprehensive translational research program for identification of biomarkers, including soluble TA-MUC1 in serum. In the extension phase patients with baseline values above median appeared to have improved PFS and overall survival; this was not the case for patients of the first part of the study who received GAT only after 3 doses of TOM. Conclusions: Combination of TA-MUC1 and EGFR targeting antibody is safe and feasible. Interesting anti-tumor activity was observed in heavily pretreated CRC and NSCLC patients. Levels of soluble TA-MUC1 may have predictive value and potentially be a companion biomarker for further development of the combination Clinical trial information: NCT03360734.

// Emily-Marie Latuske 1 , Hauke Stamm 1 , Marianne Klokow 1 , Gabi Vohwinkel 1 , Jana Muschhammer 1 , Carsten Bokemeyer 1 , Manfred Jucker 2 , Maxim Kebenko 1 , Walter Fiedler 1 , Jasmin Wellbrock 1 1 Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald University Cancer Center, University Medical Center Hamburg-Eppendorf, Hamburg, Germany 2 Institute of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, Hamburg, Germany Correspondence to: Walter Fiedler, email: fiedler@uke.de Keywords: Hedgehog, non-canonical, GLI, FLT3, AML Received: July 22, 2016 Accepted: February 20, 2017 Published: March 16, 2017 ABSTRACT Activation of the Hedgehog pathway has been implicated in the pathogenesis of several tumor types including myeloid leukemia. Previously we demonstrated that overexpression of Hedgehog downstream mediators GLI1/2 confers an adverse prognosis to patients with acute myeloid leukemia (AML) and is correlated with a FLT3 mutated status. To analyze a possible non-canonical activation of the Hedgehog pathway via FLT3 and PI3K, we performed blocking experiments utilizing inhibitors for FLT3 (sunitinib), PI3K (PF-04691502) and GLI1/2 (GANT61) in FLT3-mutated and FLT3 wildtype AML cell lines and primary blasts. Combination of all three compounds had stronger anti-leukemic effects in FLT3-mutated compared to FLT3 wildtype AML cells in vitro . Interestingly, the colony growth of normal CD34 + cells from healthy donors was not impeded by the triple inhibitor combination possibly opening a therapeutic window for the clinical use of inhibitor combinations. Besides, combined treatment with sunitinib, PF-04691502 and GANT61 significantly prolonged the survival of mice transplanted with FLT3-mutated MV4-11 cells compared to the single agent treatments. Furthermore, the inhibition of FLT3 and PI3K resulted in reduced GLI protein expression and promotor activity in FLT3-mutated but not in FLT3 wildtype AML cell lines in western blotting and GLI1/2 promoter assays supporting our hypothesis of non-canonical GLI activation via FLT3. In summary, FLT3-mutated in contrast to FLT3 wildtype cells or normal human hematopoietic progenitor cells are exquisitely sensitive to combined inhibition by FLT3, PI3K and GLI1/2 overcoming some of the limitations of current FLT3 directed therapy in AML. The development of GLI1/2 inhibitors is highly desirable.

This open-label, multicentre phase I/II study determined the maximum tolerated dose (MTD), safety and efficacy of clofarabine administered with cytarabine and idarubicin in newly diagnosed acute myeloid leukaemia (AML) patients lacking favourable genetic aberrations. The MTD was 30 mg/m2 clofarabine for patients below and above 60 years. The most frequently reported grade 3-4 non-haematological adverse events were infectious and gastrointestinal toxicities. Complete remission (CR)/CR with incomplete recovery rate was 67%. Allogeneic haematopoietic cell transplantation in first remission was feasible in a high proportion of younger AML patients and probably contributed to the favourable outcome compared to historical controls.

The Hedgehog pathway plays an important role in the pathogenesis of several tumor types, including esophageal cancer. In our study, we show an expression of the ligand Indian hedgehog (Ihh) and its downstream mediator Gli-1 in primary resected adenocarcinoma tissue by immunohistochemistry and quantitative PCR in fifty percent of the cases, while matching healthy esophagus mucosa was negative for both proteins. Moreover, a functionally important regulation of Gli-1 by ErbB2-PI3K-mTORC signaling as well as a Gli-1-dependent regulation of Ihh in the ErbB2 amplified esophageal adenocarcinoma cell line OE19 was observed. Treatment of OE19 cells with the Her2 antibody trastuzumab, the PI3K-mTORC1 inhibitor NVP BEZ235 (BEZ235) or the knockdown of Akt1 resulted in a downregulation of Gli-1 and Ihh as well as in a reduction of viable OE19 cells in vitro. Interestingly, the Hedgehog receptor Smo, which acts upstream of Gli-1, was not expressed in OE19 cells and in the majority of primary human esophageal adenocarcinoma, suggesting a non-canonical upregulation of Gli-1 expression by the ErbB2-PI3K axis. To translate our findings into a therapeutic concept, we targeted ErbB2-PI3K-mTORC1 by trastuzumab and BEZ235, combining both compounds with the Gli-1/2 inhibitor GANT61. The triple combination led to significantly stronger reduction of tumor cell viability than cisplatinum or each biological alone. Therefore, concomitant blockage of the ErbB2-PI3K pathway and the Hedgehog downstream mediator Gli-1 may provide a new therapeutic strategy for esophageal cancer.

Background AXL has been established as an independent prognostic factor in AML. AXL also represents a novel immune checkpoint because it directly inhibits NK cells and suppresses antigen presentation by antigen-presenting cells. Bemcentinib is a first-in-class, selective, orally bioavailable, AXL kinase inhibitor which is being evaluated as a therapy for solid tumours and myeloid malignancies in multiple phase II clinical trials. Increased levels of the plasma soluble, shed form of the AXL receptor (sAXL) upon bemcentinib exposure have been found across the clinical trial programme. The Phase I/II trial BGBC003 (NCT02488408) evaluates the anti-leukaemic effect of bemcentinib in patients with relapsed / refractory AML and int-2 and high-risk MDS. Methods Part A of the BGBC003 consisted of a dose escalation part per standard 3+3 design, followed by cohort expansion at the recommended phase 2 dose. Plasma protein biomarker levels were measured using the DiscoveryMap v3.3 panel (Myriad RBM) at pre-dose and after one cycle of treatment. Gene expression analysis was carried out on RNA extracted from BM-MNCs by qPCR using TaqMan. The presence of phosphorylated AXL was measured using Western blotting. The TCRß repertoire was quantified by NGS of DNA isolated from PBMNCs using an Illumina MiSeq sequencer. TCRß genes and the IGH repertoire were analysed with BIOMED2-TCRß-A and -B and BIOMED2-FR1/-FR3 primer pools, respectively. Using genomic DNA as template, the amplicons were tagged with Illumina adapters and indices in two consecutive PCR reactions. Demultiplexing and FastQ formated data output was generated by the MiSeq reporter. Analysis of TCRß and IGH data was performed on a Microsoft Cloud using our in-house analysis pipeline Pippa. Results In total, 36 patients were enrolled in part A of the study: 27 male (75%), median age of 72 years old (51 - 85), 3 patients with MDS (8%), median of 2 lines of prior therapy (0 - 6). A loading dose of 400 mg on days one to three followed by 200 mg daily thereafter has been established as safe and recommended phase 2 dose. In patients who received treatment for at least 21 days (n=28), an ORR (CR/Cri/PR) of 25% (7/28) was observed. Median DoR was 63 days. In the subset of patients with available plasma measurements at screening (n=19), 12 showed low levels of plasma soluble shed AXL and an ORR of 58% (sAXL-low; 7 of 12 patients) was observed. No responses occurred in patients with high levels of sAXL at screening (sAXL-high; 0 out of 7). sAXL levels were correlated with exposure and one cycle of treatment with bemcentinib significantly increased sAXL protein levels, particularly in responders to treatment indicating on-target activity of the drug. Median PFS from the day of randomisation until evidence of disease progression (PD) per bone marrow assessment or discontinuation due to PD whichever occurred earlier, was 62 days overall (95% CI: 18 - 106 d), 124 days in sAXL-low patients and 63 days in sAXL-high patients, respectively. Adverse events were mostly gastrointestinal and mild or moderate in severity congruent with bemcentinib monotherapy being well-tolerated in this patient population. There were no grade 4 or 5 events. We observed a diversification of the TCR repertoire in the bone marrow in 75% of evaluable patients (6/8). In the peripheral blood we detected increased TCR diversification in 44% of evaluable patients (4/9). These data indicate that the contribution of the Gas6-AXL axis to immunosuppression might be particularly pronounced in the bone marrow microenvironment. This notion is in concordance with earlier data indicating a specific upregulation of Gas6 by bone marrow stroma cells upon paracrine interaction with AML cells leading to locally increased Gas6 levels. We also observed diversification of the BCR, however less frequently (bone marrow 42%, peripheral blood 11%). Conclusions Bemcentinib is well tolerated in relapsed / refractory MDS and AML patients and exhibits anti-leukaemic activity. Furthermore, we observed a diversification of the TCR repertoire particularly in the bone marrow thereby supporting a role of AXL as immune checkpoint. Patient benefit was correlated with the level of the plasma marker soluble AXL at screening. This predictive biomarker candidate warrants further exploration in larger cohorts and has potential for development as companion diagnostics to select patient populations more likely to respond to bemcentinib treatment. Disclosures Loges: BerGenBio: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Paschka:Agios: Membership on an entity's Board of Directors or advisory committees; Astex: Membership on an entity's Board of Directors or advisory committees; Otsuka: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Speakers Bureau; Astellas: Membership on an entity's Board of Directors or advisory committees, Travel support; Novartis: Membership on an entity's Board of Directors or advisory committees, Other: Travel support, Speakers Bureau; Bristol-Meyers Squibb: Other: Travel support, Speakers Bureau; Takeda: Other: Travel support; Jazz: Speakers Bureau; Sunesis: Membership on an entity's Board of Directors or advisory committees; Amgen: Other: Travel support; Pfizer: Membership on an entity's Board of Directors or advisory committees; Janssen: Other: Travel support. Micklem:BerGenBio ASA: Employment, Equity Ownership, Patents & Royalties. Holt:BerGenBio ASA: Employment, Patents & Royalties. Brown:BerGenBio ASA: Employment, Equity Ownership, Patents & Royalties. Lorens:BerGenBio ASA: Employment, Equity Ownership, Patents & Royalties. Yule:BerGenBio ASA: Employment, Equity Ownership, Patents & Royalties. Fiedler:Amgen: Research Funding; GSO: Other: support for meeting attendance; Amgen: Other: support for meetíng attendance; Daiichi Sankyo: Other: support for meeting attendance; JAZZ Pharmaceuticals: Other: support for meeting attendance; Pfizer: Research Funding; Teva: Other: support for meeting attendance; Amgen: Patents & Royalties; Gilead: Other: support for meeting attendance; Pfizer: Membership on an entity's Board of Directors or advisory committees, Research Funding; ARIAD/Incyte: Membership on an entity's Board of Directors or advisory committees, support for meeting attendance; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Cortes:novartis: Research Funding. Gjertsen:Alden Cancer Therapy 2: Equity Ownership; Alden Cancer Therapy 2: Patents & Royalties: Alden Cancer Therapy II patent application in relation to CryoIT trial.; Kinn Therapeutics: Equity Ownership; Seattle Genetics: Consultancy; Boehringer Ingelheim: Research Funding; BerGenBio: Consultancy; Alden Cancer Therapy 2: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Kinn Therapeutics: Membership on an entity's Board of Directors or advisory committees.

RG7356, a recombinant anti-CD44 immunoglobulin G1 humanized monoclonal antibody, inhibits cell adhesion and has been associated with macrophage activation in preclinical models. We report results of a phase I dose-escalation study of RG7356 in relapsed/refractory acute myeloid leukemia (AML). Eligible patients with refractory AML, relapsed AML after induction chemotherapy, or previously untreated AML not eligible for intensive chemotherapy were enrolled and received intravenous RG7356 at dosages ≤ 2400 mg every other week or ≤ 1200 mg weekly or twice weekly; dose escalation started at 300 mg. Forty-four patients (median age, 69 years) were enrolled. One dose-limiting toxicity occurred (grade 3 hemolysis exacerbation) after one 1200 mg dose (twice-weekly cohort). The majority of adverse events were mild/moderate. Infusion-related reactions occurred in 64% of patients mainly during cycle 1. Two patients experienced grade 3 drug-induced aseptic meningitis. Pharmacokinetics increased supraproportionally, suggesting a target-mediated drug disposition (TMDD) at ≥ 1200 mg. Two patients achieved complete response with incomplete platelet recovery or partial response, respectively. One patient had stable disease with hematologic improvement. RG7356 was generally safe and well tolerated. Maximum tolerated dose was not reached, but saturation of TMDD was achieved. The recommended dose for future AML evaluations is 2400 mg every other week.

7020Background: Bemcentinib (BGB324) is a first-in-class, oral selective inhibitor of the RTK AXL currently in ph II clinical development across several cancer types. AXL overexpression has been es...

TPS2596Background: TO (CetuGEX) is a second-generation anti-EGFR antibody that specifically binds to EGFR and acts as a competitive antagonist at the ligand binding site. GAT (PankoMab-GEX) is a no...

70 Background: The tyrosine kinase AXL acts as suppressive immune checkpoint of the innate immune system. AXL signalling leads to immunosuppression and tumour immune escape by downregulating dendritic cell activity, modulating efferocytosis as well as favouring an immunosuppressive chemokine profile and M-MDSC expansion. Therefore it represents an interesting novel immune oncology target. Bemcentinib (BGB324) is a first-in-class, highly selective and orally bioavailable small molecule AXL inhibitor in phase II clinical development. In pre-clinical models, inhibition of AXL signalling with bemcentinib reversed multiple established immune suppressive mechanisms leading to increased infiltration of CTLs, NK and NKT cells and decreased infiltration of M-MDSCs (Wnuk-Lipinska, 2017). We explored safety, PK, efficacy and the effects of treatment with bemcentinib on the T- and B cell repertoire in patients with relapsed AML or MDS. Methods: BGBC003 (NCT02488408) is an open-label, dose finding study of bemcentinib in patients with R/R AML or MDS. Three dose levels have been explored and a loading dose of 400 mg on days one to three followed by 200 mg daily thereafter has been established as safe and recommended phase 2 dose. The TCRß repertoire was quantified by NGS of DNA isolated from PBMNCs using an Illumina MiSeq sequencer. TCRß genes and the IGH repertoire were analysed with BIOMED2-TCRß-A and –B and BIOMED2-FR1/-FR3 primer pools, respectively. Using genomic DNA as template, the amplicons were tagged with Illumina adapters and indices in two consecutive PCR reactions. Demultiplexing and FastQ formated data output was generated by the MiSeq reporter. Analysis of TCRß and IGH data was performed on a Microsoft Cloud using our in-house analysis pipeline Pippa. Results: Early evidence of antileukemic activity was seen. Diversification of the TCR and IGH repertoire could be detected in peripheral blood at day 21 of therapy compared to pre-treatment in three and two out of five matched samples, respectively. Conclusions: Bemcentinib shows preliminary evidence of immune modulation in AML. Clinical trial information: NCT02488408.

Thyroid hormone (T3) has a profound influence on normal development, differentiation and metabolism. T3 induces complex gene expression patterns raises the question of how these expression patterns might be regulated. Since the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) induces very similar cellular energy metabolic pathways, we investigated the molecular mechanism of T3 regulation of PGC-1alpha. PGC-1alpha is rapidly regulated by T3, both in vivo and in cell culture. Transient transfection experiments demonstrated binding of the thyroid hormone receptor (TR) to a response element located at -4kb upstream of the transcriptional start site within the PGC-1alpha gene. Introducing of a single copy of the -4kb TRE in a heterologous promoter context is sufficient to maintain T3 responsiveness. Chromatin immunoprecipitation analysis revealed increased histone acetylation upon stimulation of T3. Finally, TR binds the -4kb TRE in electrophoretic mobility shift assays, identifying PGC-1alpha as a direct target of TR action. Since T3 directly regulates PGC-1alpha and PGC-1alpha coactivates liganded TR, we suggest an autoregulatory feed-forward loop of PGC-1alpha activation upon T3 treatment.

7059 Background: The interplay with bone marrow stroma plays an important role in the pathobiology of MDS. Gas6 is secreted by mesenchymal bone marrow stroma cells and promotes survival and therapy resistance of AML cells expressing the Axl receptor. We hypothesized that inhibiting Axl by the small molecule inhibitor BGB324 might hold therapeutic potential in MDS. Methods: We investigated the inhibitory effect of BGB324 on primary bone marrow mononucleated cells (BMMNC) and mesenchymal stroma cells (MSC) from MDS patients in comparison to healthy donors. In the ongoing first-in-patient Phase 1a/b trial BGBC003 A standard 3 + 3 dose escalation study was performed to identify the maximum tolerated dose of BGB324 in patients with previously treated high risk MDS or AML. BGB324 was administered as an oral loading dose on days one and two followed by a reduced daily maintenance. Three dose levels were explored 400/100mg, 600/200mg and 900/300mg. Results: We found that BGB324 inhibited BMMNC from low- and high-risk MDS patients with an IC50 of 2.1 µM and 3.8 µM, respectively (n = 5). In comparison, BMNNC from healthy donors were resistant to BGB324 (IC50 9.4 µM, p < 0.05, n = 10). Axl expression was present in MSC isolated from the BM of MDS patients and BGB324 inhibited the proliferation of MSC from low- and high-risk MDS patients (IC50 2.5 µM and 2.7 µM, respectively; n = 7/5).To date, 3 patients with MDS were treated with 400 mg loading dose and 100 mg maintenance dose of BGB324. Therapy has been well-tolerated and the MTD has not yet been reached. The majority of adverse events reported have been Grade 1 and 2. The most common related adverse events are diarrhea and fatigue. One patient with MDS was treated for 80 weeks and experienced a PR. Evidence of target inhibition was demonstrated by almost complete inhibition of Axl phosphorylation accompanied by reduction in phosphoErk and phosphoAkt signalling at day 21 of treatment. Conclusions: BGB324 is well-tolerated and might represent a promising novel treatment approach in MDS. Safety and efficacy of BGB324 will be explored further in clinical trials. Clinical trial information: NCT02488408.

Background: Clofarabine is a second-generation purine nucleoside analogue, which has shown synergistic activity with cytarabine. We determined the maximum tolerated dose (MTD, primary endpoint), safety and efficacy (secondary endpoints) of clofarabine in combination with cytarabine and idarubicin in newly diagnosed acute myeloid leukemia (AML) patients with high-risk for induction failure stratified in two age groups (< 60 years and ≥ 60 years). Methods: In this prospective, open-label, multicenter phase I/II study (EudraCT 2010-021719-18, CIARA trial), newly diagnosed AML patients with high risk of induction failure (NPM1 wildtype, FLT3-ITD negative), who were eligible for intensive chemotherapy, received two induction courses (cytarabine 750 mg/m2 d1-5, idarubicin 7.5 mg/m2 in patients Results: Forty-two patients with de novo (n=32) or secondary (n=10) AML were included. Median age was 58.5 years (range 28-73, 24 patients < 60 years, 18 patients ≥ 60 years). Intermediate/adverse risk cytogenetics were found in 22 and 12 patients, respectively (karyotype missing in 8 patients). All patients received induction 1, 27 (64%) received induction 2; 4 (10%) patients died during induction courses 1 or 2. Eight patients developed a dose-limiting toxicity (6 patients with grade 3/4 non-hematologic toxicity and 3 patients with grade 4/5 hematologic toxicity) and the MTD was determined at 30 mg/m2 clofarabine for both age cohorts (younger patients: 2 of 6 patients with DLT at 35 mg/m2, no DLT at 30 mg/m2 (n=9); older patients: 4 of 6 patients with DLT at 35 mg/m2 in the extension phase, no DLT at 30 mg/m2 (n=3). The most frequent grade 3-5 non-hematologic adverse events were febrile neutropenia, sepsis, increased liver enzymes, pneumonia, decreased appetite and diarrhea occurring in 55, 24, 21, 21, 10 and 10% of patients. The median time to neutrophils ≥0.5/nl and platelets ≥50/nl after induction 1 was 25 and 24 days, respectively. Sixteen patients (38%) proceeded to allogeneic HCT in first CR and 8 (19%) received at least one course of high-dose cytarabine consolidation. Complete remission (CR) or CR with incomplete recovery (CRi) was achieved in 67%. After a median follow up of 2.2 years the 2-year overall survival (OS) was 56% and the 2-year event-free survival was 38% (median EFS 11.4 months). Compared to a matched historical control of 197 younger AML patients (SHG 0199 trial, Schlenk et al. NEJM 2008), the CR rate was 79% in the 24 younger CIARA patients compared to 66% in the control cohort (P=.18), and 2-year OS was higher for CIARA than for control patients (74% vs 49%, P=.021, Figure A). The allogeneic HCT rate in first CR (CR1) was higher in younger CIARA compared to younger control patients (58% vs 27%, P=.002). The CR rate in older CIARA patients was 50% compared to 36% in a historical control of 191 older patients, who were selected using the same genetic inclusion criteria as for CIARA patients (HD98B trial, Schlenk et al. Haematologica 2009, P=.23). Two-year OS in older patients was similar between CIARA and control patients (33% vs 17%, P=.31, Figure B). The allogeneic HCT rate in CR1 was 11% vs 2% in CIARA vs control patients (P=.029). Conclusion: Clofarabine can be safely administered at 30 mg/m2 in combination with cytarabine and idarubicin in younger and older newly diagnosed AML patients. Allogeneic HCT in CR1 was feasible in a high proportion of younger AML patients and likely contributed to the favorable outcome compared to historical control patients. Figure Overall survival in younger and older AML patients of the CIARA trial compared to historical controls. Figure. Overall survival in younger and older AML patients of the CIARA trial compared to historical controls. Disclosures Krauter: Genzyme: Research Funding. Schlenk:Amgen: Research Funding; Pfizer: Honoraria, Research Funding. Paschka:Novartis: Consultancy; Medupdate GmbH: Honoraria; Bristol-Myers Squibb: Honoraria; Pfizer Pharma GmbH: Honoraria; Celgene: Honoraria; ASTEX Pharmaceuticals: Consultancy. Lübbert:Ratiopharm: Other: Study drug valproic acid; Celgene: Other: Travel Funding; Janssen-Cilag: Other: Travel Funding, Research Funding. Janning:Teva: Honoraria. Becker:BMS: Honoraria; Novartis: Honoraria. Heuser:Tetralogic: Research Funding; Novartis: Consultancy, Research Funding; Celgene: Honoraria; Pfizer: Research Funding; Bayer Pharma AG: Research Funding; BerGenBio: Research Funding; Karyopharm Therapeutics Inc: Research Funding.

Introduction: The RTK Axl represents a therapeutic target promoting AML cell proliferation and survival by pleiotropic mechanisms. Signalling through Axl is also known to suppress immune reactions mainly by inhibiting pro-inflammatory responses of antigen presenting cells. BGB324 is an orally available selective potent inhibitor of Axl, which is currently being investigated in a Phase 1 a/b trial in AML and MDS. We report here the clinical data and the impact of BGB324 on the Axl signalling pathway. Furthermore, we evaluated the T cell receptor (TCR) repertoire in order to assess potential effects of BGB324 on the immune response in AML patients. Methods: Twenty-five patients (twenty-one with relapsed/refractory AML and four with MDS) were treated in a classical 3+3 dose escalation design. Three dose levels were explored 400/100 mg (loading dose d1-2/maintenance dose), 600/200 mg and 900/300 mg. Serial bone marrow samples (BM) were available from n=5 patients. By means of immunoblotting and ELISA we analyzed phosphorylation of Axl and its downstream targets Erk/MapK and Akt as well as the levels of soluble Axl (sAxl) and osteopontin in plasma. The TCRß repertoire was quantified by Next Generation Sequencing of DNA isolated from peripheral blood MNCs using an Illumina MiSeq sequencer. TCRß gene containing the entire Vß, Dß and Jß segments were amplified with BIOMED2-TCRß-A and -B primer pools. Using genomic DNA as template, the amplicons were tagged with Illumina adapters and indices in two consecutive PCR reactions. Demultiplexing and FastQ formated data output was generated by the MiSeq reporter. Analysis of TCRß data was performed on a Microsoft Cloud using our in-house analysis pipeline Pippa, which relies on MiXCR analysis tools. Results: Treatment was generally well-tolerated. Diarrhea and fatigue represented the most frequent adverse events, which were mostly CTC Grade 1 or 2. One DLT (QTc prolongation) occurred and the MTD has not yet been reached. Steady-state levels of BGB324 were reached between three and six days after initiation of treatment. One AML patient achieved a CRi of 5 months, a second achieved a PR and another achieved clearance of circulating blasts accompanied by peripheral blood count recovery > 3 months (ORR 10%). Four additional AML patients (25%) experienced disease stabilisation for more than four months. Two MDS patients experienced a PR. From the five patients in whom BM samples were available three experienced either an objective response or disease stabilization for more than four months and two had progressive disease. We could detect phosphorylated Axl (pAxl) before treatment and decreased pAxl level after 21 days of treatment in 3 out of 3 responders/patients with SD while could not detect pAxl before treatment in the patients with PD (n=5; p=0.025). The patients with response or SD showed inhibition of pErk and pAxl (2 out of 3) or no change of the activity of these Axl downstream pathways (1 out of 3). The patients with PD showed increased pErk and pAkt level after treatment (n=5; p=0.082). Treatment with BGB324 led to an increase in the levels of sAxl after 21 days of treatment in the plasma of 67% of analyzed patients (n=12). SAxl levels were positively correlated to compound exposure (n=12; r=0.829), indicating that sAxl might be used as a biomarker of target engagement. The highest level of sAxl was seen in the patient who achieved a PR. Osteopontin levels decreased in 67% of analyzed patients after three weeks of treatment with BGB324 indicating modulation of this protein by BGB324. However, there was no correlation between increases of sAxl and decreases of osteopontin in this patient cohort. Interestingly, we could demonstrate diversification of the TCR repertoire by higher abundance of small T cell clones after three weeks of therapy with BGB324 compared to pre-treatment levels in two out of four analysed patients. Conclusion: BGB324 is well tolerated in AML patients and exhibits anti-leukemic activity. BGB324 has on-target activity in AML patients and blocks the phosphorylation of Axl and its downstream pathways. Furthermore, BGB324 can induce a diversification of the TCR repertoire in AML patients and might hold potential as an immune-activating drug. Disclosures Sonja: BergenBio: Honoraria, Other: Travel Support, Research Funding. Gjertsen:BerGenBio AS: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees; Kinn Therapeutics AS: Equity Ownership. Micklem:BerGenBio AS: Employment, Equity Ownership. Janning:Teva: Honoraria. Fiedler:Pfizer: Research Funding; GSO: Other: Travel; Amgen: Consultancy, Other: Travel, Patents & Royalties, Research Funding; Kolltan: Research Funding; Ariad/Incyte: Consultancy; Novartis: Consultancy; Gilead: Other: Travel; Teva: Other: Travel. Cortes:ARIAD: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Research Funding.

Background: Acute myeloid leukemia (AML) is the second most common form of leukemia and the most frequent cause of leukemia-related deaths in the United States. While complete response rates can be as high as 80% in patients undergoing initial induction chemotherapy, the majority of AML patients will relapse. Refractory or relapsed patients have a bleak prognosis. As there is currently no standard regimen for these patients, a great clinical need exists for new treatment options. Selinexor, an oral first-in-class Selective Inhibitor of Nuclear Export (SINE), inhibits XPO1 mediated nuclear export inducing cytotoxicity in cells with genomic damage. Preclinical data with Ara-C and selinexor significantly prolonged the survival of leukemic mice. A phase I clinical study demonstrated encouraging results in AML patients. The role of selinexor as mono-therapy or in combination is currently under investigation in phase II trials of AML. Aims: This phase II trial investigates the efficacy & tolerability of Ara-C and Idarubicin in combination with selinexor in patients with relapsed or refractory AML. Methods: Patients with relapsed/refractory AML were treated with Ara-C (100 mg/m2, continuous infusion, day 1-7), idarubicin (10 mg/m2, day 1, 3, 5) every 4 weeks. Selinexor was administered twice weekly orally starting on day 2 (40 mg/m2). A small cohort of patients received selinexor after registration and before first induction cycle for correlative studies. The primary endpoint was percentage of patients achieving a complete remission or complete remission without normalization of peripheral blood counts (CRi). Secondary endpoints were partial remission rate, percentage of patients undergoing subsequent allogeneic stem cell transplantion, early death rate, overall survival (OS), event-free survival and toxicity. Results: As of June-16-2015, 21 patients with AML have been enrolled at 3 sites in Germany (NCT02249091) after obtaining informed consent of which 20 had received ≥ 1 induction cycle and were evaluable for efficacy and toxicity. Median age was 60 (range 34-78) years. Seven patients had a complex and 6 a normal karyotype (unknown in 7 cases). On average, patients had received 3.5 (range 1-6) prior therapies. 2 patients had primary refractory disease and 11 patients an early relapse and 7 patients a late relapse. 7 patients had prior allogeneic transplantation. Overall response rate was 60% (25% of patients achieved CR, 25% of patients achieved CRi, 10% of patients achieved PR). Sixty percent of patients received or were planned for stem cell transplantion or donor lymphocyte infusion. The most frequent non-hematologic AES were vomiting, diarrhoea, nausea, fatigue, anorexia and neutropenic fever. One treatment-related death occurred. The patient developed subarachnoid haemorrhage during thrombocytopenia grade 4 and died. Summary / Conclusion: The prognosis of relapsed/refractory AML patients is remarkably poor. Our findings suggest that Ara-C and Idarubicin in combination with selinexor resulted in a remarkable response rate and is a promising regimen in this particularly unfavourable cohort of patients without unexpected toxicities enabling the majority of them to proceed to first or second allogeneic stem cell transplantation. Disclosures Fiedler: Teva, Amgen, Astellas: Other: Travel Grant; Pfizer, Amgen, Kolltan: Research Funding; Karyopharm: Research Funding. Off Label Use: Selinexor has been used in combination with AraC and idarubicin in relapsed/refractory AML patients.. Chromik:Karyopharm: Research Funding. Theile:GSO Hamburg: Employment. Kranich:GSO Global: Employment. Heuser:Karyopharm: Research Funding.

Thyroid hormone 3,3′,5-tri-iodothyronine (T3) regulates gene expression in a positive and negative manner. Here, we analyzed the regulation of a positively (mitochondrial glycerol-3-phosphate dehydrogenase) and negatively T3-regulated target gene (TSHα). Thyroid hormone receptor (TR) activates mGPDH but not TSH promoter fragments in a mammalian one-hybrid assay. Furthermore, we investigated functional consequences of targeting TR to DNA independent of its own DNA-binding domain (DBD). Using a chimeric fusion protein of the DBD of yeast transcription factor Gal4 with TR, we demonstrated a positive regulation of gene transcription in response to T3. T3-mediated activation of this chimeric protein is further increased after an introduction of point mutations within the DBD of TR. Moreover, we investigated the capacity of TR to negatively regulate gene transcription on a DNA-tethered cofactor platform. A direct binding of TR to DNA via its own DBD is dispensable in this assay. We investigated functional consequences of point mutations affecting different domains of TR. Our data indicate that the DBD of TR plays a key role in direct DNA binding on positively but not on negatively T3-regulated target genes. Nevertheless, the DBD is involved in mediating negative gene regulation independent of its capacity to bind DNA.

Abstract 1483 Background: Activating FLT3 mutations including internal tandem duplications (FLT3-ITD) and tyrosine-kinase domain mutation (FLT3-TKD) occur in approximately one third of patients with acute myeloid leukemia (AML) and are particularly associated with a poor outcome in case of FLT3-ITD. Sunitinib is a multitargeted FLT3 inhibitor approved for the treatment of advanced/metastatic renal cancer and metastatic/unresectable malignant GIST after failure of imatinib. Sunitinib has been evaluated in refractory AML as single agent treatment resulting in transient blast count reduction and in several cases of partial response in AML with activating FLT3 mutations. Aims: To evaluate the feasibility of a standard induction and consolidation therapy in combination with orally administered sunitinib in elderly AML patients with activating FLT3 mutations. Methods: Patients aged 60 years or higher with AML with activating FLT3 mutations (FLT3-ITD, FLT3-TKD) and fit enough for intensive chemotherapy were eligible. Induction therapy included cytarabine 100 mg/m2 per continuous infusion on days 1–7 and daunorubicin 60 mg/m2 i.v. on days 1–3 (DA). A second course was allowed in responding patients, who did not achieve a complete remission (CR). In patients achieving a CR after induction therapy three consolidation cycles were intended (cytarabine 1 g/m2 i.v. bid, on days 1,3,5). A 3+3 dose escalation/de-escalation scheme was used to define the dose and scheduling of sunitinib. The first cohort of three patients received oral sunitinib continuously starting from day 1 in a dose of 25 mg/day (level 1). Dose escalation to level 2 with sunitinib 37.5 mg/day continuously or dose de-escalation to level −1 with 25 mg day 1 to 7 had been defined in the protocol. After definition of the maximally tolerated dose (MTD) an extension of the cohort at that dose was intended. Results: A total of twenty-two patients were enrolled between January 2009 and March 2011. The median age was 70 years (range 60–78), 13 were female. The type of AML was de novo in 16 pts., s-AMLin one patient and t-AML in 4 pts. Fifteen patients had a FLT3-ITD (68%) and 7 a FLT3-TKD (32%) mutation. A NPM1 mutation was present in 11 patients (50%), 15 patients exhibited a normal karyotype, 3 an intermediate-2 risk karyotype according to ELN guidelines and 2 a complex karyotype and 2 had no evaluable metaphases. In the first cohort 5 patients were treated and two experienced dose-limiting toxicity (DLT), i) prolonged hematological recovery beyond day 35 in a patient achieving a CR and ii) a hand-foot-syndrome grade III. Four of the 5 patients achieved a CR. According to the protocol the following patients received treatment at dose level −1 with sunitinib 25mg days 1 to 7. In this cohort only one DLT occurred, again prolonged hematological recovery. Thus the MTD was defined at dose level −1. Response to induction therapy in all patients was CR in 13 pts. (59%), partial remission in 1 pt. (4.5%), refractory disease in 5 pts. (23%), death in 3 pts. (13.5%). CR rate in AML with FLT3-ITD was 53% (8/15) and 71% (5/7) in those with FLT3-TKD. All 13 patients achieving CR received repetitive cycles of high-dose cytarabine consolidation therapy and 7 proceeded to single agent sunitinib maintenance therapy (median 11 months, range 1–24 months). In these patients relapse occurred in 10, one patient died due to severe colitis during consolidation therapy and two patients are in sustained CR. Two patients not achieving a CR after induction therapy underwent allogeneic stem cell transplantation form matched unrelated donors. Twelve of the 22 patients died leading to a median survival of 18.8 months and a 2 year survival of 36% (95%-CI, 19–70%). Median relapse-free survival was 11 months. Conclusion: Combination of intensive induction and consolidation therapy with oral sunitinib in AML with activating FLT3 mutations is feasible with 25 mg sunitinib given during intensive therapy on days 1 to 7 and continuously during maintenance. Disclosures: Fiedler: Novartis: Consultancy, Research Funding; Pfizer Inc.: Consultancy, Research Funding.

2504 Background: MT110 is a bispecific T cell engaging antibody construct (BiTE) that directs CD3 expressing T cells to kill target cells that express EpCAM, which is widely found on solid tumors. Methods: Safety, tolerability, pharmacokinetics and anti-tumor activity of MT110 in patients (pts) with advanced solid tumors were studied using a 3+3 design. Continuous IV infusions for at least 28 days of doses ranging from 1 to 48 µg/d have been tested. Stepwise intra-patient dose escalations within cycle 1 or at start of cycle 2 have been explored. Results: 51 pts (6 gastric cancers, 32 CRC, 2 SCLC, 5 NSCLC, 3 HRPC, 1 ovarian cancer) have been treated in 12 dose cohorts. The maximally administered dose includes day 1 dose of 3 µg/d escalated up to 48 µg/d. The maximum tolerable dose (MTD) has not yet been established. Diarrhea and elevations in liver function tests have been reported as dose limiting toxicity (DLT) for individual patients. Transaminase elevations were fully reversible and mitigated by dexamethasone at initiation or escalation of dose. Other adverse events of grade 3 or higher included transient lymphopenia, increase in lipase or amylase, nausea, vomiting, and hypoalbuminaemia. No CNS safety signal was observed. The mean serum half-life of MT110 was 4.5 hours. Mean steady state serum concentrations of MT110 were linear with dose across treatment cycles. At 48 µg/d, the mean Css was 3.2 ng/mL. This compares to preclinical EC90 of 1.35 – 3.85 ng/ml in CRC cell lines. Sixteen pts who received a dose of ≥ 24 µg/d were evaluable for anti-tumor response. Best response of SD was reported in 38%; median duration was 155 days (95% CI 92; 161). Anti-tumor activity was demonstrated on biopsy of liver metastases in one patient. Following at least 1 week of MT110 treatment at 48 µg/d, a decrease in circulating tumor cells was observed with a median nadir 74% below baseline. Conclusions: The use of stepwise dose escalation and concomitant dexamethasone resulted in improved tolerability. A dose of 48 µg/d appears tolerable. Tumor biopsy evaluation on treatment and pharmacodynamic evidence of anti-tumor activity are encouraging. Additional dose cohorts will seek to identify the recommended phase II dose and further evidence of anti-tumor activity.