Homoharringtonine and Mebendazole Are Preferentially Lethal Against Models of Myeloid Malignancy Associated with Germline Mutant RUNX1

Abstract RUNX1 is a master-transcriptional regulator involved in normal and malignant hematopoiesis. Majority of mono-allelic germline mutations in RUNX1 are missense, large deletions or truncation mutations, behaving mostly as loss of function (LOF) mutations. They are ~40%-penetrant and cause Familial Platelet Disorder (RUNX1-FPD) that has a propensity to evolve into myeloid malignancy (FPD-MM), i.e., MDS or AML. FPD-MM harbors co-mutations, most commonly on the second allele of RUNX1, and on BCOR, PHF6, K-RAS, WT1 or TET2, which confer relative resistance to standard therapy for MDS or AML. Although curative in some patients with FPD-MM, allogeneic transplantation from matched, un-related donors carries risk of graft versus host disease and frequent AML relapse. This creates a strong rationale and an unmet need to develop novel targeted therapies for FPD-MM. We previously reported on utilizing the RNA-Seq signature of RUNX1 knockdown, which exerted more lethality in AML cells with mutant (mt) RUNX1 compared to AML harboring two copies of wild-type RUNX1, for conducting LINCS1000-CMap analysis. This identified several expression mimickers (EMs), including the protein synthesis inhibitor homoharringtonine (HHT or omacetaxine) and anthelmintic fenbendazole (analog of mebendazole). Present studies demonstrate that treatment with HHT or mebendazole (MB) dose-dependently induced significantly greater loss of viability in four patient-derived (PD) bone marrow aspirate (BMA) samples of FPD-MM (3 AML and 1 MDS) compared to RUNX1-FPD (3 samples) or in normal CD34+ progenitor cells. In a patient with RUNX1-FPD (expressing mtRUNX1 K194N), who developed FPD-MM, following co-mutations were documented by NGS: BCOR A1437fs, PHF6 L324fs, SF3B1 D781G and SRSF2 P95R/L. From BMA of this patient, we successfully established the first ever, continuously cultured cell line (GMR-AML1) expressing the same germline mtRUNX1. GMR-AML1 cells were cytogenetically diploid and lacked MYC or MLL1 rearrangement, or any copy number gains or losses on array CGH. However whole exome sequencing (WES) identified additional mutations in TP53 (P72R), AIM2 (K340fs), NELFB (L523F), CEP152 (Y370X), SUGP2 (H23L), RRM2B (R71fs), TADA3 (T27R), SPDYE6 (G292C) and PRDM9 (S814R) with % VAF ranging between 33 to 55%. GMR-AML1 cells exhibited high surface expression of CD117 (c-KIT), CD123 (IL3R), CD86 and CD33, but without expression of CD34, CD14, CD11b, MPO or CD135 (FLT3). Compared to the AML OCI-AML5 cells with somatic mtRUNX1, GMR-AML1 cells demonstrated markedly reduced protein expression of RUNX1, RUNX2, PU.1, c-Myb, GFI1, GFI1B, FLT3, MEIS1 and CEBPα (p42), but much higher protein expression of RUNX3 and NOTCH (p120). CRISPR-Cas9 knockout of RUNX3 in GMR-AML1 cells restored RUNX1 expression, while significantly increasing % of differentiated cells. Although dose-dependently sensitive to daunorubicin, etoposide, cytarabine and panobinostat (class I and II HDAC inhibitor), GMR-AML1 cells were relatively insensitive to venetoclax, A1155463 (Bcl-xL inhibitor), AZD-5991 (MCL1 inhibitor), azacytidine or decitabine. Notably, treatment with HHT or MB dose-dependently induced loss of viability of GMR-AML1 cells (LD50: 40 and 330 nM, respectively). Additionally, co-treatment with HHT and venetoclax synergistically induced apoptosis in GMR-AML1 cells, as determined by the SynergyFinder algorithm. This synergy in GMR-AML1 cells was associated with abrogation of venetoclax-induced increase in MCL1 and Bcl-xL levels, as well as greater decline in levels of RUNX3, PU.1, c-Myb, c-Myc, MPL and CDK4/6. Tail vein infusion and engraftment of luciferase-transduced GMR-AML1 (10 6 cells) caused marked splenomegaly and 100% mortality of NSG mice by day-18, post-infusion. We will present at the ASH meeting findings of ongoing in vivo studies determining effects of treatment with HHT and/or venetoclax, versus vehicle control, on AML burden and overall survival of NSG mice engrafted with GMR-AML1 cells. Overall, preclinical findings presented here highlight the molecular and genetic features associated with progression of RUNX1-FPD to FPD-MM, especially in the newly established GMR-AML1 cell line. They also demonstrate that HHT or MB are preferentially more lethal against FPD-MM versus RUNX1-FPD cells and exert synergistic lethality with venetoclax against GMR-AML1 cells. Disclosures DiNardo: GlaxoSmithKline: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; AbbVie: Consultancy, Research Funding; Agios/Servier: Consultancy, Honoraria, Research Funding; Notable Labs: Current holder of stock options in a privately-held company, Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Honoraria, Research Funding; Takeda: Honoraria; ImmuneOnc: Honoraria, Research Funding; Forma: Honoraria, Research Funding; Foghorn: Honoraria, Research Funding; Celgene, a Bristol Myers Squibb company: Honoraria, Research Funding. Takahashi: GSK: Consultancy; Celgene/BMS: Consultancy; Symbio Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy. Khoury: Stemline Therapeutics: Research Funding; Angle: Research Funding; Kiromic: Research Funding.

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Efficacy Outcomes of Treatments for Double Relapsed/Refractory Follicular Lymphoma (R/R FL): A Systematic Literature Review

Blood ◽

10.1182/blood-2020-136228 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 42-43

Author(s):

Brad S. Kahl ◽

Anik R. Patel ◽

Omer Zaidi ◽

Sonya J. Snedecor ◽

Anna G. Purdum

Keyword(s):

Clinical Trials ◽

Follicular Lymphoma ◽

Board Of Directors ◽

Clinical Data ◽

Research Funding ◽

Treatment Options ◽

Unmet Need ◽

Progression Free Survival ◽

Disease Stage ◽

Advisory Committees

ABSTRACT Introduction: Patients with indolent non-Hodgkin lymphomas (iNHL), including follicular lymphoma (FL), have high response to first-line treatment. However, retreatment is often required when relapses occur, and those with multiple relapses represent a patient population with an unmet need for effective treatment. Clinical data for several treatment options exist for the general relapsed and refractory (R/R) population; however, there are relatively fewer data specific to FL patients with ≥2 lines of prior treatment. This work systematically identified the available efficacy data in the double R/R FL population. Methods: The MEDLINE and EMBASE databases were searched through February 10, 2020. Studies were limited to interventional clinical trials of R/R FL patients (or mixed histologies with a predominance of FL) and articles published in English. Studies also must have reported one or more efficacy measures, such as overall response rate (ORR), complete response (CR), duration of response (DoR), time to next treatment (TTNT), progression-free survival (PFS), and overall survival (OS). Potential interventions of interest were lenalidomide ± rituximab (R), duvelisib, ibrutinib, venetoclax, polatuzumab vedotin + R, obinutuzumab, copanlisib, umbralisib, idelalisib, and tazemetostat. Results: Of 35 publications examining treatment outcomes in R/R FL patients, only 14 (representing 5 unique clinical trials) were specific to the ≥ 2-line population. These trials were: CHRONOS Part B (copanlisib), DAWN (ibrutinib), DELTA (idelalisib), DYNAMO (duvelisib), and Morschhauser et al. 2019 (tazemetostat) and included a total of 605 participants. All studies used similar inclusion criteria, and patients included were similar in age (median 62-65), disease stage (III/IV), and ECOG score (0-2). Patients in the CHRONOS study had a median number of prior treatments of 2, whereas those in the DELTA study had 5. ORR ranged from 21% (ibrutinib) to 59% (copanlisib) (Table). The DoR ranged from 8.3 months in tazemetostat patients with EZH2 gene mutation to 19.4 months for ibrutinib. PFS ranged from 5.7 months in tazemetostat patients with wild-type EZH2 to 11.2 months for copanlisib. Median TTNT was only reported in the DAWN study (16 months). Conclusions: Very few clinical data exist reporting efficacy outcomes specific to the double R/R FL population. The limited data indicate that current treatments do not produce durable responses for most double R/R FL patients, demonstrating an unmet need. Further research is needed to fully understand the efficacy and safety of other potential interventions for this population. Disclosures Kahl: Genentech:Consultancy;Pharmacyclics LLC:Consultancy;AstraZeneca Pharmaceuticals LP:Consultancy, Membership on an entity's Board of Directors or advisory committees;ADC Therapeutics:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Celgene Corporation:Consultancy;AbbVie:Consultancy;Roche Laboratories Inc:Consultancy;BeiGene:Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding;Janssen:Consultancy, Membership on an entity's Board of Directors or advisory committees;Acerta:Consultancy, Research Funding.Patel:Kite, a Gilead Company:Current Employment.Zaidi:BMS:Consultancy.Snedecor:Pharmerit - an OPEN Health Company:Other: Employment at consultancy paid by Kite Pharma to conduct this work.Purdum:Kite, a Gilead Company:Current Employment.

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The Interaction of Bortezomib with P-Gp, MRP-1 and BCRP Drug Transporters: Implications for Therapeutic Applications of Bortezomib in Advanced Multiple Myeloma and Other Neoplasias.

Blood ◽

10.1182/blood.v114.22.1729.1729 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1729-1729

Author(s):

Melissa G Ooi ◽

Robert O'Connor ◽

Jana Jakubikova ◽

Justine Meiller ◽

Steffen Klippel ◽

...

Keyword(s):

Lung Cancer ◽

Multiple Myeloma ◽

Cell Line ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Significant Activity ◽

Cancer Resistance ◽

Advisory Committees ◽

Bortezomib Treatment

Abstract Abstract 1729 Poster Board I-755 Background Multidrug transporters are energy-dependent transmembrane proteins which can efflux a broad range of anticancer drugs and thereby play a role in resistance to the actions of substrate agents. Classically, three transporters, p-glycoprotein (Pgp; MDR-1; ABCB1), multidrug resistant protein-1 (MRP-1; ABCC1) and breast cancer resistance protein (BCRP; MXR; ABCG2), have been found to have the broadest substrate specificity and a strong correlation with drug resistance in vitro and in vivo in many models and forms of cancer. We have sought to characterize the interaction of bortezomib with these transporters and thereby explore the potential for these agents to play a role in resistance. Bortezomib is a novel proteosome inhibitor with significant activity in multiple myeloma, although subsets of patients remain refractory to the activity of the drug. Hence, better characterization of the interactions of this drug with classical resistance mechanisms may identify improved treatment applications. Methods and Results We investigated the role of these transporters by using isogenic cell line models which are resistant due to overexpression of a particular transporter: DLKP lung cancer cell line that overexpresses MRP-1; DLKP-A which overexpresses Pgp; and DLKP-SQ-Mitox which overexpresses BCRP. DLKP-A cells exhibited a 4.6-fold decrease in responsiveness to bortezomib compared to parental DLKP cells. In DLKP-SQ-Mitox, bortezomib-induced cytotoxicity was comparable to DLKP. When bortezomib was combined with elacridar, a Pgp and BCRP inhibitor, significant synergy was evident in DLKP-A (100% viable cells with single agent treatment versus 11% with the combination), but not DLKP-SQ-Mitox. Sulindac, an MRP-1 inhibitor, combined with bortezomib failed to produce any synergy in MRP-1 positive DLKP cells. Conversely, combination assays of Pgp substrate cytotoxics such as doxorubicin with Bortezomib were largely additive in nature. This indicates that bortezomib has little, if any, direct Pgp inhibitory activity, as combinations of a traditional Pgp inhibitor (such as elacridar) and doxorubicin would show marked synergy rather than just an additive effect in Pgp positive cells. To further characterize the extent of this interaction with Pgp, we conducted cytotoxicity assays in cell lines with varying levels of Pgp overexpression. NCI/Adr-res (ovarian cancer, high Pgp overexpression), RPMI-Dox40 (multiple myeloma, moderate Pgp overexpression) and A549-taxol (lung cancer, low Pgp overexpression). The combination of bortezomib and elacridar that produced the most synergy was in cell lines expressing moderate to high levels of Pgp expression. Cell lines with lower Pgp expression produced an additive cytotoxicity. We next examined whether bortezomib had any direct effect on Pgp expression. In RPMI-Dox40 cells, Pgp expression is reduced in a time-dependent manner with bortezomib treatment. Conclusions Our studies therefore show that bortezomib is a substrate for Pgp but not the other drug efflux pumps. In tumor cells expressing high levels of Pgp, the efficacy of bortezomib is synergistically enhanced by combinations with a Pgp inhibitor, while bortezomib treatment itself can reduce the expression of Pgp. This study suggests that in the subset of patients with advanced multiple myeloma or solid tumors which express high levels of Pgp, inhibition of its function could contribute to enhanced responsiveness to bortezomib. Disclosures Richardson: millenium: Membership on an entity's Board of Directors or advisory committees, Research Funding; celgene: Membership on an entity's Board of Directors or advisory committees, speakers bureau up to 7/1/09; MLNM: speakers bureau up to 7/1/09. Mitsiades:Millennium Pharmaceuticals : Consultancy, Honoraria; Novartis Pharmaceuticals : Consultancy, Honoraria; Bristol-Myers Squibb : Consultancy, Honoraria; Merck &Co: Consultancy, Honoraria; Kosan Pharmaceuticals : Consultancy, Honoraria; Pharmion: Consultancy, Honoraria; PharmaMar: licensing royalties ; Amgen Pharmaceuticals: Research Funding; AVEO Pharma: Research Funding; EMD Serono : Research Funding; Sunesis Pharmaceuticals: Research Funding. Anderson:Celgene: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Millennium: Consultancy, Research Funding; Biotest AG: Consultancy, Research Funding.

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CYC065, a Potent Derivative of Seliciclib Is Active In Multiple Myeloma In Preclinical Studies

Blood ◽

10.1182/blood.v116.21.2999.2999 ◽

2010 ◽

Vol 116 (21) ◽

pp. 2999-2999 ◽

Cited By ~ 1

Author(s):

Samantha Pozzi ◽

Diana Cirstea ◽

Loredana Santo ◽

Doris M Nabikejje ◽

Kishan Patel ◽

...

Keyword(s):

Cell Cycle ◽

Multiple Myeloma ◽

Cell Line ◽

Board Of Directors ◽

Cell Lines ◽

Preliminary Data ◽

Research Funding ◽

Preclinical Studies ◽

Dependent Manner ◽

Advisory Committees

Abstract Abstract 2999 Multiple myeloma (MM) is a treatable but incurable hematological malignancy and novel targeted therapies are under investigation. MM is characterized by dysregulation of the cell cycle, consequent to the overexpression of cyclins and their related kinases, the cyclins dependent kinases (CDK), a group of Ser/Thr proteine kinases. CDKs represent a promising therapeutic target, and inhibitors have been developed for anticancer treatment. We have previously studied seliciclib in the context of MM. CYC065, a second generation CDK inhibitor is the more potent derivative of seliciclib. It is mainly active on CDK 2, 5 and 9, involved in progression of the cell cycle and protein transcription. It has already shown promising results in preclinical studies in breast cancer and acute leukemia. We tested CYC065 in in vitro experiments in MM. Our preliminary data in 7 MM cell lines showed cytotoxicity of CYC065, both in MM cell lines sensitive as well as resistant to conventional chemotherapy, with an IC50 ranging between 0.06 and 2μ M, at 24 and 48h. Tritiated thymidine uptake assay confirmed the antiproliferative effects of CYC065 in MM, and its ability to overcome the growth advantage conferred by co-culture with bone marrow stromal cells derived from MM patients, and cytokines like interleukin 6 (10ng/ml) and insulin like growth factor-1 (50ng/ml). The anti-proliferative effect was evident both at 24 and 48h, starting at concentrations as low as 0.015μ M. The AnnexinV/PI assay in the MM1.s cell line confirmed CYC065's ability to induce apoptosis in a time dependent manner starting at 9 hours of treatment, at a concentration of 0.125 μ M, inducing 82% of apoptosis after 48h of exposure. Cell cycle analysis in the same MM1.s cell line showed an increase of subG1 phase, starting at 9 hours of treatment, at 0.125 μ M of CYC065. Preliminary results of western blot analysis confirmed the apoptotic effect of CYC065 in the MM1s cell line, highlighted by the cleavage of caspase 3, 8, 9 and PARP. The compound was tested in primary CD138+ cells isolated from three refractory MM patients, confirming its efficacy at 0.125 μ M, both at 24 and 48h. Comparative analysis in PBMCs from normal donors, for the evaluation of the drug toxicity is ongoing and will be presented. In conclusion our preliminary data confirm the efficacy of CYC065 in MM cell lines and primary MM cells, at nanomolar concentrations. Ongoing mechanistic and in vivo studies will delineate its role in the now increasing spectrum of CDK inhibitors in MM and better define its potential for clinical development in MM. Disclosures: Green: Cyclacel: Employment. Anderson:Millennium Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Scadden:Fate Therapeutics: Consultancy, Equity Ownership, Patents & Royalties. Raje:Celgene: Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Research Funding; Acetylon: Research Funding.

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Inhibition of Chronic Myeloid Leukemia Stem Cells by the Combination of the Hedgehog Pathway Inhibitor LDE225 with Nilotinib

Blood ◽

10.1182/blood.v116.21.514.514 ◽

2010 ◽

Vol 116 (21) ◽

pp. 514-514 ◽

Cited By ~ 6

Author(s):

Bin Zhang ◽

David Irvine ◽

Yin Wei Ho ◽

Silvia Buonamici ◽

Paul Manley ◽

...

Keyword(s):

Stem Cells ◽

Board Of Directors ◽

Colony Formation ◽

Research Funding ◽

Leukemia Stem Cells ◽

Advisory Committees ◽

Nsg Mice ◽

Cd34 Cells ◽

Hh Signaling

Abstract Abstract 514 Background: Tyrosine kinase inhibitors (TKI), although effective in inducing remissions and improving survival in CML patients, fail to eliminate leukemia stem cells (LSC), which remain a potential source of relapse on stopping treatment. Additional strategies to enhance elimination of LSC in TKI-treated CML patients are required. The Hedgehog (Hh) pathway, important for developmental hematopoiesis, has been shown to be activated in BCR-ABL-expressing LSC, in association with upregulation of Smoothened (SMO), and contributes to maintenance of BCR-ABL+ LSC. However the role of Hh signaling in chronic phase (CP) CML LSC is not clear. LDE225 (LDE, Novartis Pharma) is a small molecule SMO antagonist which is being clinically evaluated in patients with solid tumors. We have reported that LDE does not significantly affect proliferation and apoptosis of primary CP CML CD34+ cells, or reduce colony growth in CFC assays, but results in significant reduction in CML CFC replating efficiency and secondary colony formation. Treatment with LDE + Nilotinib resulted in significant reduction in colony formation from CD34+ CML cells in LTCIC assays compared to Nilotinib alone or untreated controls. These observations suggest that LDE may preferentially inhibit growth of primitive CML progenitors and progenitor self-renewal. We therefore further investigated the effect of LDE on growth of primitive CML LSC in vivo. Methods and Results: 1) CP CML CD34+ cells were treated with LDE (10nM), Nilotinib (5μ M) or LDE + Nilotinib for 72 hours followed by transplantation into NOD-SCID γ-chain- (NSG) mice. Treatment with LDE + Nilotinib resulted in reduced engraftment of CML CD45+ cells (p=0.06) and CD34+ cells (p=0.02) compared with controls, and significantly reduced engraftment of CML cells with CFC capacity (p=0.005). In contrast LDE or Nilotinib alone did not reduce CML cell engraftment in the bone marrow (BM) compared with untreated controls. LDE, Nilotinib, or LDE + Nilotinib treatment did not significantly inhibit engraftment of normal human CD34+ cells in NSG mice compared to controls. 2) We also used the transgenic Scl-tTa-BCR-ABL mouse model of CP CML to investigate the effect of in vivo treatment with LDE on CML LSC. BM cells from GFP-SCL-tTA/BCR-ABL mice were transplanted into wild type congenic recipients to establish a cohort of mice with CML-like disease. Recipient mice developed CML-like disease 3–4 weeks after transplantation. Transplanted CML cells were identifiable through GFP expression. Mice were treated with LDE225 (80mg/kg/d by gavage), Nilotinib (50 mg/kg/d by gavage), LDE + Nilotinib, or vehicle alone (control) for 3 weeks. Treatment with Nilotinib, LDE, and LDE + Nilotinib resulted in normalization of WBC and neutrophil counts in peripheral blood. LDE + Nilotinib treatment significantly reduced the number of splenic long term hematopoietic stem cells (LT-HSC, Lin-Sca-1+Kit+Flt3-CD150+CD48-, p<0.01) and granulocyte-macrophage progenitors (GMP) compared to controls, but did not significantly alter LT-HSC numbers in the BM. LDE alone reduced splenic LT-HSC but not GMP, whereas Nilotinib alone did not reduce LT-HSC numbers in spleen or BM but significantly reduced splenic GMP numbers. The mechanisms underlying enhanced targeting of LSC in the spleen compared to the BM are not clear but could reflect greater dependence on Hh signaling in the context of the splenic microenvironment and/or relocalization of LDE treated LT-HSC to BM. Experiments in which BM and spleen cells from treated mice were transplanted into secondary recipients to determine functional stem cell capacity of remaining LT-HSC are ongoing. Importantly mice treated with LDE + Nilotinib demonstrated enhanced survival on follow up after discontinuation of treatment compared with control mice or mice treated with LDE or Nilotinib alone. Conclusions: We conclude that LDE225 can target LSC from CP CML patients and in a transgenic BCR-ABL model of CP CML, and that LDE + Nilotinib treatment may represent a promising strategy to enhance elimination of residual LSC in TKI-treated CML patients. Disclosures: Buonamici: Novartis: Employment. Manley:Novartis: Employment. Holyoake:Novartis: Consultancy, Research Funding. Copland:Novartis Pharma: Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees. Bhatia:Novartis: Consultancy, Honoraria.

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An Update On The Clinical Activity Of Resimmune, a Targeted Therapy Directed To CD3 Receptor, In Patients With Cutaneous T Cell Lymphomas--CTCL

Blood ◽

10.1182/blood.v122.21.4381.4381 ◽

2013 ◽

Vol 122 (21) ◽

pp. 4381-4381 ◽

Cited By ~ 2

Author(s):

Arthur E. Frankel ◽

Jung H Woo ◽

Jeremy P Mauldin ◽

Francine M. Foss ◽

Madeleine Duvic ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Pichia Pastoris ◽

Cell Line ◽

Board Of Directors ◽

Research Funding ◽

Response Rate ◽

The United States ◽

Advisory Committees ◽

Systemic Therapies

Abstract Cutaneous T cell lymphoma—CTCL is a malignancy of skin-tropic T cells. CTCL cells have ubiquitous overexpression of CD3. Although uncommon, CTCL has been estimated to affect 1,500 patients per year in the United States. There are multiple approved systemic therapies for CTCL, but responses are brief lasting months. Allogeneic stem cell transplantation may provide long-term remissions, but is suitable for only rare CTCL patients. Overall, CTCL has a long clinical course with relentless progression over months to years with estimated median survival of 3-5 years for stage IB-IIB patients. The CD3 targeted agent, Resimmune, was synthesized and prepared for clinical use. It consists of the catalytic and translocation domains of diphtheria toxin fused to two anti-human CD3 Fv fragments. DNA encoding Resimmune protein was integrated into the Pichia pastoris genome, and recombinant protein was produced in Pichia pastoris via the secretory route (Woo, Protein Expr Purif 25, 270, 2002). Protein was purified by anion exchange and size exclusion chromatography. The CD3+ Jurkat cell line incubated with Resimmune yielded an IC50 for protein synthesis inhibition of 0.017pM. The CD3- Vero cell line incubated with Resimmune showed an IC50 >10pM. Mice, rats, and monkeys given total doses of >200mg/kg over four days showed only transient transaminasemia without histopathologic tissue injury or clinical signs or symptoms (Woo, Cancer Immunol Immunother 57, 1225, 2008). In a mouse model with human CD3e transfected lymphocytes, four logs of antigen positive cells were reproducibly depleted from nodes and spleen with 100mg/kg total dose of Resimmune (Thompson, Protein Eng 14, 1035, 2001). Based on these findings, a phase 1 study was initiated and this report serves to update the results of a single cycle of Resimmune given at 2.5-11.25mg/kg 15 min IV infusion twice daily for 8 doses to 18 CTCL patients. There were 10 females and 8 males with ages 20-81 years. Two patients were naïve to systemic therapies, and all others had failed 1-4 prior treatments including interferon, bexarotene, gemcitabine, vorinostat, chlorambucil, etoposide, pralatrexate, doxil, romidepsin, methotrexate, CHOP, and brentuximab vedotin. None of the Resimmune treated CTCL patients had dose-limiting toxicities. Side effects were mild-moderate and transient with fevers, chills, nausea, transaminasemia, hypoalbuminemia, lymphopenia, reactivation of EBV and CMV, and hypophosphatemia. Toxicities responded to antipyretics, anti-emetics, albumin infusions, rituximab treatment and valgancyclovir. Among measured patients, there was a 3 log decline in normal, circulating T cells by day 5 that recovered by day 14. Because of vascular leak syndrome toxicities in non-CTCL patients, the MTD was defined as 7.5mg/kg x 8 doses. Cmax ranged from 1.9-40.7ng/mL and half-life from 5-66min. Pretreatment anti-DT titers were 0.9-251mg/mL and day 30 post-therapy increased to 5-4059 mg/mL. 17 CTCL patients were evaluable for response. There were six responses for a response rate of 35%. There were four CRs (24% CR rate). Three of the CRs are over 4-years duration. Patients with IB or IIB disease and mSWAT<50 had an overall response rate of 86% and CR rate of 56%. The long time required to convert from a PR to a CR in the absence of any additional therapy beyond the four treatment days suggest an additional anti-tumor mechanism beyond immunotoxin-induced killing such as immunomodulation. Accrual of patients with mSWAT scores of 50 or less is ongoing. Disclosures: Woo: Angimmune: Patents & Royalties, Research Funding. Foss:celgene: Honoraria, Research Funding; millenium: Honoraria, Membership on an entity’s Board of Directors or advisory committees; eisai: Membership on an entity’s Board of Directors or advisory committees; spectrum: Research Funding; merck: Research Funding; seattle genetics: Research Funding. Neville:Angimmune: Employment, Equity Ownership, Patents & Royalties.

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FLT3 Splice Variant (FLT3Va) As a Potential Immunotherapeutic Target in Patients with Acute Myeloid Leukemia (AML)

Blood ◽

10.1182/blood.v128.22.1681.1681 ◽

2016 ◽

Vol 128 (22) ◽

pp. 1681-1681

Author(s):

Sophia Adamia ◽

Jeffrey Nemeth ◽

Shruti Bhatt ◽

Sarah R Walker ◽

Natalie I Voeks ◽

...

Keyword(s):

Flow Cytometry ◽

Cell Surface ◽

Board Of Directors ◽

Research Funding ◽

Leukemic Cells ◽

Advisory Committees ◽

Gm Csf ◽

Nsg Mice ◽

Blocking Antibodies ◽

Pdx Models

Abstract Alternative pre-mRNA splicing (AS) is a normal epigenetic phenomenon, a key regulator of gene expression, yields multiple transcripts and thus a variety of proteins from a single gene. Mutations in the spliceosome components resulting in aberrant splicing isoforms are common in AML, and other myeloid neoplasms, and may generate leukemia-specific neoantigens targetable with an antibody-drug conjugates (ADCs) or blocking antibodies. Our previous studies revealed that the FLT3 cell surface receptor is one of the most commonly misspliced genes in AML (54-63% of ~400 AML patients). We conducted cloning and sequencing analyses in AML cells and identified multiple aberrant splice-variants of FLT3 that resulted from either skipping of one or more exons or activation of cryptic splicing sites. Transfection of cDNA with three of these variants in TF-1 (AML cell line) cells resulted in expression of Flt3 variant proteins on the cell surface. We successfully generated rabbit polyclonal antiserum against a unique peptide sequence present in the most commonly expressed abnormal splice variant, which we termed Flt3Va. Immunoblots performed with the polyclonal antibody identified a ~160 kDa protein expressed by TF-1 cells transfected with FLT3Va, and the antibody did not react with untransfected TF-1 cell lysate. Using standard techniques, we generated rabbit hybridomas and evaluated the clones by flow cytometry and western blotting experiments. Based on these data, we selected one antibody clone (15-7) for further experiments. The 15-7 anti-Flt3Va rabbit monoclonal antibody identified Flt3Va protein expressed on the cell surface and within the cytoplasm of transfected TF-1 cells by flow cytometry and western blotting. However, no Flt3Va protein was detected in untransfected TF-1 cells or normal CD34+ bone marrow cells. The 15-7 antibody bound to 26 of 52 primary AML samples and 5 of 10 primagraft samples (PDX models) of human AML. Immunoblotting analyses of PDX models and patient samples confirmed binding to a protein of the expected size (130-160 kDa). Additionally, multi-parameter flow cytometry in 10 PDX models and 52 primary demonstrated that putative AML stem cells (as defined by the CD45dim, CD34, CD38, CD33, c-Kit cell surface expression) co-expressed Flt3Va antigen in 50% samples evaluated. An analysis of Flt3Va protein localization by live cell imaging showed a punctate distribution of Flt3Va on the cell surface. Furthermore, we observed that overexpression of Flt3Va in TF-1 cells led to GM-CSF growth factor independence. Analysis of TF-1 cells in the absence of GM-CSF and Flt3 ligand demonstrated constitutive activation of STAT5, an important mediator of Flt3 signaling, in Flt3Va overexpressing cells. In addition, Erk1/2 phosphorylation was also increased in Flt3Va overexpressing cells, another downstream effector of Flt3. In an effort to determine if Flt3Va+ cells had tumor repopulating ability, we sorted 0.3X10^6 Flt3Va+ and Flt3Va- cells from a PDX sample and injected the sorted populations or unsorted bulk tumor cells into NSG mice. The human cell engraftment in the mice was detected by the expression of human CD45, CD33, CD34, CD38, and c-kit antigens in the peripheral blood. In two experiments, mice injected with Flt3Va+ cells had detectable circulating leukemic cells by ~18 days after injection, while those injected with Flt3Va- cells had detectable circulating leukemic cells after the 4th week. These results suggest both Flt3Va+ and Flt3Va- cell populations are able to reconstitute leukemia after transplantation in NSG mice. However, Flt3Va+ may be expressed by an aggressive AML clone that facilitate early tumor engraftment. Overall, these studies suggest that Flt3Va is a leukemia-specific neoantigen and is an attractive potential immunotherapeutic target in AML. Proteins such as Flt3Va generated by alternative splicing are common in AML and may be targets for of novel blocking antibodies or ADCs, minimizing effects on normal tissues. Disclosures Adamia: Janssen: Research Funding. Nemeth:Janssen: Employment. Attar:Janssen: Employment. Letai:AbbVie: Consultancy, Research Funding; Tetralogic: Consultancy, Research Funding; Astra-Zeneca: Consultancy, Research Funding. Steensma:Millenium/Takeda: Consultancy; Celgene: Consultancy; Amgen: Consultancy; Janssen: Consultancy; Ariad: Equity Ownership; Genoptix: Consultancy. Weinstock:Novartis: Consultancy, Research Funding. DeAngelo:Novartis: Consultancy; Ariad: Consultancy; Pfizer: Consultancy; Baxter: Consultancy; Celgene: Consultancy; Incyte: Consultancy; Amgen: Consultancy. Stone:Agios: Consultancy; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celator: Consultancy; Juno Therapeutics: Consultancy; Roche: Consultancy; Jansen: Consultancy; Pfizer: Consultancy; ONO: Consultancy; Sunesis Pharmaceuticals: Consultancy; Merck: Consultancy; Xenetic Biosciences: Consultancy; Abbvie: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Amgen: Consultancy; Karyopharm: Consultancy; Seattle Genetics: Consultancy. Griffin:Janssen: Research Funding; Novartis: Consultancy, Research Funding.

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Identification of Qualitative Platelet Disorders in Adolescent Women with Heavy Menstrual Bleeding

Blood ◽

10.1182/blood.v128.22.4922.4922 ◽

2016 ◽

Vol 128 (22) ◽

pp. 4922-4922

Author(s):

Kristina M. Haley ◽

Susan Lattimore ◽

Cara McDavitt ◽

Ayesha Khader ◽

Colin Boehnlein ◽

...

Keyword(s):

Platelet Aggregation ◽

Board Of Directors ◽

Platelet Function ◽

Research Funding ◽

Blood Platelet ◽

Bleeding Disorder ◽

Advisory Committees ◽

Adolescent Women ◽

Platelet Disorder ◽

Platelet Function Assays

Abstract Introduction: Nearly 40% of adolescent women experience heavy menstrual bleeding (HMB), and identifiable bleeding disorders are diagnosed in only 20-60% of these patients. We suspect that qualitative platelet disorders contribute to HMB, but are under-diagnosed. A pilot study was conducted to evaluate platelet function in adolescent women with HMB employing four novel, small-volume, whole blood platelet function assays. In addition, primary and secondary hemostasis, bleeding phenotype, and quality of life were assessed. Methods: Patients referred to the Young Women's Hematology Clinic at Oregon Health & Science University for evaluation of HMB were offered participation in the study. Participants underwent standard review of their medical and family history and physical exam. Standard lab evaluation included CBC, PT, PTT, fibrinogen, thrombin time, Von Willebrand Panel, PFA-100, and iron studies with platelet aggregation or phenotyping performed if clinically indicated. Using less than 0.5 mL of whole blood, platelet function was assessed with four novel platelet function assays: assessment of platelet activation, secretion, and aggregation was assessed by flow cytometry analysis, while platelet adhesion and aggregation was assessed under shear in a capillary tube. Quality of life (QOL) was assessed using the PedsQL tool. Bleeding phenotype was assessed with the ISTH Bleeding Assessment Tool (ISTH BAT). Menorrhagia was assessed with the Pictorial Bleeding Assessment Chart (PBAC), the Philipp Tool and the clinical history. Results: Nine participants have enrolled on study to date, with 2 completing the 3-month visit. The median age of the cohort was 16 years (14-18 years). Eight out of nine categorized their period as heavy, 6 also had epistaxis, and 7 reported excessive bruising. The median ISTH BAT score was 4 (3-7). Of the 7 patients who had a Philipp Score obtained, 5 were positive. Median PBAC score was 161 (64-196). Median ferritin was 13 ng/mL (4-65 ng/mL). Median QOL psychosocial score was 70 (68.36-88.25), comparable to that of pediatric patients with cancer. Of the 9 participants, 6 had platelet aggregation and phenotyping. Four participants did not receive a bleeding disorder diagnosis, 1 was diagnosed with Type 1 VWD, 1 was diagnosed with bleeding disorder, NOS, and 1 was diagnosed with Ehlers Danlos Syndrome. Two participants were diagnosed with a qualitative platelet disorder (QPD): one based on platelet aggregation and one based on thromboelastography. The four novel platelet function assays confirmed platelet function abnormalities in the participants diagnosed with QPD's (Figure 1&2). Impaired platelet response to agonist stimulation was also observed in participants with non-platelet disorder bleeding disorder diagnoses and in participants without a bleeding disorder diagnosis. Conclusions: In this pilot study, the etiology of HMB in adolescent women was evaluated with four novel platelet assays in addition to standard assays of hemostasis. A bleeding disorder diagnosis was not made with standard evaluations in 4 out of 9 participants. The novel assays detected platelet abnormalities not observed using currently available clinical labs, and confirmed the presence of abnormal platelet function in participants with abnormal platelet function testing. These assays require significantly less blood volume than currently available assays and expand investigation of platelet function to platelet adhesion and platelet interactions in whole and flowing blood. Further work is needed to determine the sensitivity and specificity of the novel assays in detecting platelet dysfunction. Continued investigation into the impact of HMB on the adolescent female population is needed. Disclosures Haley: CSL Behring: Honoraria; Baxalta: Membership on an entity's Board of Directors or advisory committees. Recht:Biogen: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Biogen: Research Funding; Genentech: Research Funding; Novo Nordisk: Research Funding; Baxalta: Research Funding; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees.

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Tolinapant (ASTX660), a Non-Peptidomimetic Antagonist of cIAP1/2 and XIAP, and the HDAC Inhibitor Romidepsin Are Synergistic in in Vitro Models of T Cell Lymphoma

Blood ◽

10.1182/blood-2021-153451 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 4356-4356

Author(s):

John S Manavalan ◽

Ipsita Pal ◽

Aidan Pursley ◽

George A. Ward ◽

Tomoko Smyth ◽

...

Keyword(s):

T Cell ◽

Cell Line ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Cell Lymphoma ◽

T Cell Lymphoma ◽

Tnf Alpha ◽

Sensitive Cell ◽

Advisory Committees

Abstract Background: The PTCL are a heterogeneous group of non-Hodgkin lymphomas originating from mature T-lymphocytes. They are aggressive diseases, often resistant to conventional chemotherapy. Despite the fact that a number of new agents have been approved, treatment paradigms tailored to the biology of the disease have yet to emerge. Tolinapant (ASTX660) is a potent antagonist of both cellular and X-linked inhibitors of apoptosis proteins (cIAP1/2 and XIAP), and is presently in phase I/II trials in patients with advanced solid tumors and lymphomas (NCT02503423). IAP antagonists enhance tumor necrosis factor (TNF) receptor superfamily mediated apoptosis (Ward GA, et al. Mol Cancer Ther. 2018), are potent anti-tumor immune enhancers and induce markers of immunogenic cell death such as damage associated molecular patterns (DAMPs; Ye W, et al, Oncoimmunology, 2020). Objectives: We explored the sensitivity of a range of T-cell lymphoma (TCL) cell lines to tolinapant. We establish the synergy coefficient between tolinapant and the HDAC inhibitor, romidepsin, and interrogated the molecular basis of their synergistic interaction. Methods: A panel of human T-cell lymphoma cell lines were tested in proliferation assays (CellTiterGlo) for sensitivity to tolinapant in the presence or absence of 10ng/ml of TNF alpha. For combination studies, with tolinapant and romidepsin, each drug was tested at the IC10 and IC40 concentrations in the presence or absence of TNF alpha. Synergy scores using the Excess over Bliss (EOB) model were calculated using SynergyFinder (Aleksandr Ianevski et al; Nucleic Acids Research, 2020). Additionally, the effects of tolinapant and romidepsin on the IAPs and caspases were analyzed by western blots. TNFR1 receptor expression and induction of DAMPs were also analyzed by flow cytometry. Results: TCL Lines demonstrated varying sensitivities to tolinapant in the presence or absence of TNF alpha. The most sensitive cell lines, ALK+ ALCL and SUP-M2, had IC50 concentrations ranging from 200nM ± 100nM to 20nM ± 1nM in the absence or presence of TNF alpha, respectively, at 24, 48 and 72hrs, while a resistant CTCL cell line HH had an IC50 concentration of over 20mM, even in the presence of TNF alpha. Interestingly, using western blot analysis, we found that the presence of TNF alpha increased the levels of cIAP1 in the tolinapant sensitive SUP-M2 cell line, but not in the resistant HH cell line. However, there was a concentration dependent decrease in cIAP1 but not in XIAP in both cell lines treated with tolinapant. Flow cytometry analysis demonstrated that tolinapant increases the expression of TNFR1 and DAMPs in a dose dependent manner on the sensitive SUP-M2, but not in the resistant HH cells. In combination experiments, using the EOB model, tolinapant plus romidepsin was found to be synergistic in the absence of TNF alpha, at 36hrs, in both the sensitive cell line SUP-M2 and the resistant cell line HH. In the presence of TNF alpha, synergism was seen only in the sensitive cell line SUP-M2 and antagonistic in the HH cell line (Fig. 3). In the tolinapant plus romidepsin treated samples, cIAP1 levels decreased in the SUP-M2 cell line, in the absence of TNF alpha, however, addition of TNF alpha did not alter the levels of cIAP1 in the SUP-M2 cells. The cIAP1 levels decreased in the HH cells treated with the combination, in both the presence or absence of TNF alpha (Figure). Our findings indicate that the synergy of the tolinapant plus romidepsin is not dependent on the presence of TNF alpha. Conclusion: Tolinapant has demonstrated potent cytotoxic effects against a broad range of TCL lines both as a monotherapy and in combination with the HDAC Inhibitor, romidepsin. In in vitro studies, T cell lymphoma cell lines demonstrated varying sensitivity to tolinapant with certain cell lines being more resistant, even in the presence of TNF alpha. Interestingly, the addition of romidepsin appeared to overcome the intrinsic resistance to tolinapant in the absence of TNF alpha. These data provide the rationale to continue to explore the combination of tolinapant and romidepsin in vivo and to investigate additional combinations with T-cell specific agents (e.g. pralatrexate, belinostat, azacitidine and decitabine). Figure 1 Figure 1. Disclosures Smyth: Astex Pharmaceuticals: Current Employment. Sims: Astex Pharmaceuticals: Current Employment. Loughran: Kymera Therapeutics: Membership on an entity's Board of Directors or advisory committees; Bioniz Therapeutics: Membership on an entity's Board of Directors or advisory committees; Keystone Nano: Membership on an entity's Board of Directors or advisory committees; Dren Bio: Membership on an entity's Board of Directors or advisory committees. Marchi: Kyowa Kirin: Honoraria; Myeloid Therapeutics: Honoraria; Astex: Research Funding; BMS: Research Funding; Merck: Research Funding; Kymera Therapeutics: Other: Scientific Advisor.

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Genotype-Phenotype Relationships and Therapeutic Targets in Acute Erythroid Leukemia

Blood ◽

10.1182/blood-2020-141750 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 17-18

Author(s):

June Takeda ◽

Kenichi Yoshida ◽

Akinori Yoda ◽

Lee-Yung Shih ◽

Yasuhito Nannya ◽

...

Keyword(s):

Cell Line ◽

Board Of Directors ◽

Research Funding ◽

Pharmaceutical Research ◽

Private Company ◽

Advisory Committees ◽

Otsuka Pharmaceutical ◽

Group A ◽

Genetic Profiles ◽

Stat Pathway

Background: Acute erythroid leukemia (AEL) is a rare subtype of AML characterized by erythroid predominant proliferation and classified into two subtypes with pure erythroid (PEL) and myeloid/erythroid (MEL) phenotypes. Although gene mutations in AEL have been described in several reports, genotype phenotype correlations are not fully understood with little knowledge about the feasible molecular targets for therapy. Methods: To understand the mechanism of the erythroid dominant phenotype of AEL and identify potential therapeutic targets for AEL, we analyzed a total of 105 AEL cases with the median age of 60 (23-86), using targeted-capture sequencing of commonly mutated genes in myeloid neoplasms, together with 1,279 SNPs for copy number measurements. Among these 105 cases, 13 were also analyzed by RNA sequencing. Genetic profiles of these 105 AEL cases were compared to those of 775 cases with non-erythroid AML (NEL) including 561 cases from The Cancer Genome Atlas and Beat AML study. An immature erythroid cell line (TF1) and three patient-derived xenografts (PDX) established from AEL with JAK2 and/or EPOR amplification. Cell line and samples from patients were inoculated into immune-deficient mice and tested for their response to JAK1/2 inhibitor. Results: According to unique genetic alterations, AEL was classified into 4 subgroups (A-D). Characterized by TP53 mutations and complex karyotype, Group A was the most common subtype and showed very poor prognosis. Remarkably, all PEL cases were categorized into Group A. Conspicuously, 80% of PEL cases had amplifications of JAK2 (6/10; 60%), EPOR (7/10;70%), and ERG (6/10;60%) loci on chromosomes 9p, 19q, and 21q, respectively, frequently in combination, although they were rarely seen in NEL cases. All cases in Group B (n=19, 18%), another prevalent form of AEL, had STAG2 mutations and classified in MEL. To further characterize this subgroup, we compared genetic profiles of STAG2-mutated AEL and NEL. Prominently, 70% (14/20) of STAG2-mutated cases in AEL had KMT2A-PTD, whereas it was found only in 8.8% (3/34) of NEL. CEBPA mutations were also more common in AEL (6/21; 29%) than NEL (4/34; 12%). While Group C was characterized by frequent NPM1 mutations, in contrast to the frequent co-mutation of FLT3 in the corresponding subgroup of NPM1-mutated cases in NEL, NPM1-mutated patents in this subgroup lacked FLT3 mutations but had frequent PTPN11 mutations (8/16; 50%), which were much less common in NEL (25/209; 12%). The remaining cases were categorized into Group D, which was enriched for mutations in ASXL1, BCOR, PHF6, U2AF1 and KMT2C. Recurrent loss-of-function mutations in USP9X were unique to this subtype, although USP9X mutations have been reported in ALL with upregulation of JAK-STAT pathway. In RNA sequencing analysis, AEL cases exhibited gene expression profiles implicated in an upregulated STAT5 signaling pathway, which was seen not only those cases with JAK2 or EPOR amplification, but also those without, suggesting that aberrantly upregulated STAT5 activation might represent a common defect in AEL. Based on this finding, we evaluated the effect of a JAK inhibitior, ruxolitinib, on an AEL-derived cell line and three PDX models established from AEL having TP53 mutations and JAK2 and EPOR mutation/amplification. Of interest, ruxolitinib significantly suppressed cell growth and prolonged overall survival in mice engrafted with TF1 and 2 PDX models with STAT5 downregulation, although the other model was resistant to JAK2 inhibition with persistent STAT5 activation. Conclusion: AEL is a heterogeneous group of AML, of which PEL is characterized by frequent amplifications/mutations in JAK2, EPOR and/or ERG. Frequent involvement of EPOR/JAK/STAT pathway is a common feature of AEL, in which a role of JAK inhibition was suggested. Disclosures Yoda: Chordia Therapeutics Inc.: Research Funding. Shih:Novartis: Research Funding; Celgene: Research Funding; PharmaEssentia: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees. Ishiyama:Alexion: Research Funding; Novartis: Honoraria. Miyazaki:Astellas Pharma Inc.: Honoraria; Sumitomo Dainippon Pharma Co., Ltd.: Honoraria; NIPPON SHINYAKU CO.,LTD.: Honoraria; Celgene: Honoraria; Otsuka Pharmaceutical: Honoraria; Chugai Pharmaceutical Co., Ltd.: Honoraria; Novartis Pharma KK: Honoraria; Kyowa Kirin Co., Ltd.: Honoraria. Nakagawa:Sumitomo Dainippon Pharma Co., Ltd.: Research Funding. Takaori-Kondo:Celgene: Honoraria, Research Funding; Ono Pharmaceutical: Research Funding; Thyas Co. Ltd.: Research Funding; Takeda: Research Funding; CHUGAI: Research Funding; OHARA Pharmaceutical: Research Funding; Sanofi: Research Funding; Novartis Pharma: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; Pfizer: Research Funding; Otsuka Pharmaceutical: Research Funding; Eisai: Research Funding; Astellas Pharma: Honoraria, Research Funding; Kyowa Kirin: Honoraria, Research Funding; Nippon Shinyaku: Research Funding; MSD: Honoraria. Kataoka:Asahi Genomics: Current equity holder in private company; Otsuka Pharmaceutical: Research Funding; Takeda Pharmaceutical Company: Research Funding; CHUGAI PHARMACEUTICAL CO., LTD.: Research Funding. Usuki:Alexion: Research Funding, Speakers Bureau; Apellis: Research Funding; Novartis: Research Funding, Speakers Bureau; Chugai: Research Funding. Maciejewski:Novartis, Roche: Consultancy, Honoraria; Alexion, BMS: Speakers Bureau. Ganser:Novartis: Consultancy; Celgene: Consultancy. Thol:Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Ogawa:Sumitomo Dainippon Pharma Co., Ltd.: Research Funding; Otsuka Pharmaceutical Co., Ltd.: Research Funding; Asahi Genomics Co., Ltd.: Current equity holder in private company; Eisai Co., Ltd.: Research Funding; Chordia Therapeutics, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding; KAN Research Institute, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. OffLabel Disclosure: Ruxolitinib is used for drug efficacy test using patient-derived xenografts established from acute erythroid leukemia.

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CD38low Natural Killer Cells Transiently Expressing CD16F158V m-RNA Potentiates the Therapeutic Activity of Daratumumab Against Multiple Myeloma with Minimal Effector NK Cell Fratricide

Blood ◽

10.1182/blood-2018-99-118926 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 3199-3199 ◽

Cited By ~ 2

Author(s):

Subhashis Sarkar ◽

Sachin Chauhan ◽

Arwen Stikvoort ◽

Alessandro Natoni ◽

John Daly ◽

...

Keyword(s):

Nk Cells ◽

Cell Line ◽

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Nk Cell ◽

Ex Vivo ◽

Advisory Committees ◽

Cd38 Expression ◽

Rpmi 8226

Abstract Introduction: Multiple Myeloma (MM) is a clonal plasma cell malignancy typically associated with the high and uniform expression of CD38 transmembrane glycoprotein. Daratumumab is a humanized IgG1κ CD38 monoclonal antibody (moAb) which has demonstrated impressive single agent activity even in relapsed refractory MM patients as well as strong synergy with other anti-MM drugs. Natural Killer (NK) cells are cytotoxic immune effector cells mediating tumour immunosurveillance in vivo. NK cells also play an important role during moAb therapy by inducing antibody dependent cellular cytotoxicity (ADCC) via their Fcγ RIII (CD16) receptor. Furthermore, 15% of the population express a naturally occurring high affinity variant of CD16 harbouring a single point polymorphism (F158V), and this variant has been linked to improved ADCC. However, the contribution of NK cells to the efficacy of Daratumumab remains debatable as clinical data clearly indicate rapid depletion of CD38high peripheral blood NK cells in patients upon Daratumumab administration. Therefore, we hypothesize that transiently expressing the CD16F158V receptor using a "safe" mRNA electroporation-based approach, on CD38low NK cells could significantly enhance therapeutic efficacy of Daratumumab in MM patients. In the present study, we investigate the optimal NK cell platform for generating CD38low CD16F158V NK cells which can be administered as an "off-the-shelf"cell therapy product to target both CD38high and CD38low expressing MM patients in combination with Daratumumab. Methods: MM cell lines (n=5) (MM.1S, RPMI-8226, JJN3, H929, and U266) and NK cells (n=3) (primary expanded, NK-92, and KHYG1) were immunophenotyped for CD38 expression. CD16F158V coding m-RNA transcripts were synthesized using in-vitro transcription (IVT). CD16F158V expression was determined by flow cytometry over a period of 120 hours (n=5). 24-hours post electroporation, CD16F158V expressing KHYG1 cells were co-cultured with MM cell lines (n=4; RPMI-8226, JJN3, H929, and U266) either alone or in combination with Daratumumab in a 14-hour assay. Daratumumab induced NK cell fratricide and cytokine production (IFN-γ and TNF-α) were investigated at an E:T ratio of 1:1 in a 14-hour assay (n=3). CD38+CD138+ primary MM cells from newly diagnosed or relapsed-refractory MM patients were isolated by positive selection (n=5), and co-cultured with mock electroporated or CD16F158V m-RNA electroporated KHYG1 cells. CD16F158V KHYG1 were also co-cultured with primary MM cells from Daratumumab relapsed-refractory (RR) patients. Results: MM cell lines were classified as CD38hi (RPMI-8226, H929), and CD38lo (JJN3, U266) based on immunophenotyping (n=4). KHYG1 NK cell line had significantly lower CD38 expression as compared to primary expanded NK cells and NK-92 cell line (Figure 1a). KHYG1 electroporated with CD16F158V m-RNA expressed CD16 over a period of 120-hours post-transfection (n=5) (Figure 1b). CD16F158V KHYG1 in-combination with Daratumumab were significantly more cytotoxic towards both CD38hi and CD38lo MM cell lines as compared to CD16F158V KHYG1 alone at multiple E:T ratios (n=4) (Figure 1c, 1d). More importantly, Daratumumab had no significant effect on the viability of CD38low CD16F158V KHYG1. Moreover, CD16F158V KHYG1 in combination with Daratumumab produced significantly higher levels of IFN-γ (p=0.01) upon co-culture with CD38hi H929 cell line as compared to co-culture with mock KHYG1 and Daratumumab. The combination of CD16F158V KHYG1 with Daratumumab was also significantly more cytotoxic to primary MM cell ex vivo as compared to mock KHYG1 with Daratumumab at E:T ratio of 0.5:1 (p=0.01), 1:1 (p=0.005), 2.5:1 (p=0.003) and 5:1 (p=0.004) (Figure 1e). Preliminary data (n=2) also suggests that CD16F158V expressing KHYG1 can eliminate 15-17% of primary MM cells from Daratumumab RR patients ex vivo. Analysis of more Daratumumab RR samples are currently ongoing. Conclusions: Our study provides the proof-of-concept for combination therapy of Daratumumab with "off-the-shelf" CD38low NK cells transiently expressing CD16F158V for treatment of MM. Notably, this approach was effective against MM cell lines even with low CD38 expression (JJN3) and primary MM cells cultured ex vivo. Moreover, the enhanced cytokine production by CD16F158V KHYG1 cells has the potential to improve immunosurveillance and stimulate adaptive immune responses in vivo. Disclosures Sarkar: Onkimmune: Research Funding. Chauhan:Onkimmune: Research Funding. Stikvoort:Onkimmune: Research Funding. Mutis:Genmab: Research Funding; OnkImmune: Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Research Funding; Celgene: Research Funding; Novartis: Research Funding. O'Dwyer:Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; BMS: Research Funding; Glycomimetics: Research Funding; Onkimmune: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding.

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