The MDM2 Inhibitor NVP-CGM097 Is Highly Active in a Randomized Preclinical Trial of B-Cell Acute Lymphoblastic Leukemia Patient Derived Xenografts

Abstract The majority of drugs tested in clinical trials for hematologic malignancies ultimately fail to confer benefit. In many cases, this results from the inability to accurately identify patients most likely to benefit and mechanisms that mediate resistance. At the same time, clinical trials commonly fail to capture essential specimens at early and late timepoints that could be used to identify predictors of response, pharmacodynamic markers of on-target activity and targetable resistance pathways. To overcome these challenges, we have developed a repository of >200 patient-derived xenografts (PDXs) of leukemias and lymphomas now available through the DFCI Public Repository of Xenografts (PRoXe; http://www.proxe.org). Because PDX models can be developed and propagated from a large number of patients, randomized in vivo studies using adequate numbers of PDXs offer the first opportunity to capture the diversity of disease biology in pre-clinical drug testing. We tested the novel MDM2 inhibitor CGM097, which is currently undergoing clinical testing in solid tumors, in 24 B-cell acute lymphoblastic leukemia (B-ALL) PDXs (including hypodiploid, near haploid, MLL- rearranged, CRLF2-rearranged, and BCR-ABL models) in a randomized, phase II-like trial. Only a small subset of B-ALLs harbor de novo TP53 mutations, suggesting that MDM2 antagonists may have broad activity in this disease. Each PDX was injected into 4 NOD.SCID.IL2Rɣ-/- (NSG) mice. Upon engraftment (>2% hCD45+/hCD19+ cells in the peripheral blood), mice were randomized to vehicle or CGM097 treatment arms. One animal from each treatment arm was sacrificed 26 hours after beginning treatment to examine pharmacodynamic endpoints. The remaining two mice continued on daily therapy until moribund. CGM097 markedly improved overall survival (median 73 vs 28 days for vehicle; p=0.0008). All 19 models with survival benefit from CGM were TP53 wild-type. Among 6 models (all TP53 wild-type) derived from patients with relapsed disease, the median survival improvement compared to vehicle was 53 days (p=0.0059), consistent with robust single-agent activity in relapsed disease. Specimens at the 26 hour timepoint and upon progression to moribund were captured from the majority of mice in the trial, allowing for comprehensive characterization of the trial population. Dynamic BH3 profiling (Montero et al. Cell 2015), in which CGM097 or vehicle is added to leukemia cells harvested from mice and the effect of CGM097 on "priming" for apoptosis was performed on 10 models and demonstrated 100% accuracy in predicting response to CGM097. To characterize the effects of MDM2 inhibition on p53-dependent gene expression, we measured expression of 120 p53-related genes using a custom Nanostring gene expression panel. Differential expression analysis identified 11 genes that were significantly upregulated (p≤0.05) by CGM097 treatment at the 26 hour timepoint, including the canonical p53 targets BBC3, CDKN1A and MDM2. All mice treated with CGM097 ultimately became moribund from progressive leukemia. Targeted deep sequencing identified acquired TP53 mutations in only 2 leukemias after progression on CGM097. This indicates that p53 mutation is not the primary genetic driver of resistance to MDM2 inhibition in B-ALL PDXs. Despite this, CGM097-dependent transcriptional changes were largely abolished in the majority of leukemias collected from mice upon progression on CGM097. In summary, we established a paradigm for "Phase II-like" trials in panels of human leukemia PDX models. With this approach, we defined CGM097 as a highly active agent across the diverse spectrum of TP53-wildtype B-ALL, and established 19 independent models of acquired resistance that are the ideal reagents for defining mechanisms and then testing combinations in vivo that overcome those mechanisms. The same paradigm could be applied as a new standard for pre-clinical testing of drugs to minimize the empiric nature of current drug development strategies. Disclosures Barzaghi-Rinaudo: Novartis Institutes for Biomedical Research: Employment. Letai:AbbVie: Consultancy, Research Funding; Tetralogic: Consultancy, Research Funding; AstraZeneca: Consultancy, Research Funding. Jeay:Novartis: Employment, Equity Ownership. Wuerthner:Novartis: Employment, Equity Ownership. Halilovic:Novartis: Employment, Equity Ownership.

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CXCR4 Blockade By BL-8040 in T Cell Acute Lymphoblastic Leukemia Decreases Mitochondrial Mass and Induces Non-Apoptotic Cell Death

Blood ◽

10.1182/blood-2019-128881 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 2745-2745

Author(s):

Jun Xia ◽

Stephanie Sun ◽

Matthew RM Jotte ◽

Geoffrey L. Uy ◽

Osnat Bohana-Kashtan ◽

...

Keyword(s):

Cell Death ◽

Apoptotic Cell ◽

Lymphoblastic Leukemia ◽

Apoptotic Cell Death ◽

Employment Equity ◽

Cxcr4 Signaling ◽

Cell Acute Lymphoblastic Leukemia ◽

Equity Ownership

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy that accounts for 10-15% of pediatric and 25% of adult ALL cases. CXCL12 is a CXC chemokine that is constitutively expressed at high levels in the bone marrow. CXCR4 is the major receptor for CXCL12 and is by far the most highly expressed chemokine receptor on T-ALL cells. Two groups recently showed that genetic loss of CXCR4 signaling in murine or human T-ALL cells markedly suppressed their growth in vivo. We previously reported that BL-8040, a potent new CXCR4 antagonist with sustained receptor occupancy, is active as monotherapy against T-ALL in mice. Indeed, a 2-week course of daily BL-8040 resulted in a median reduction in tumor burden of 32.1-fold (range 6.8 to 176) across 5 different T-ALL xenografts. Preliminary data from a clinical trial of BL-8040 plus nelarabine for relapsed T-ALL also suggest therapeutic activity, with a complete remission rate observed in 4/8 patients (50%), which compares favorably to published response rates of approximately 30% with single agent nelarabine. Here, we explore molecular mechanisms by which CXCR4 blockade induces T-ALL death. NOD-scid IL2Rgammanull (NSG) mice were injected with P12-Ichikawa cells, a T-ALL cell line modified to express click beetle red luciferase and GFP. Following T-ALL engraftment, mice were treated with a single dose of BL-8040, and then leukemic cells in the bone marrow harvested 24-48 hours later. Treatment with BL-8040 resulted in a marked suppression of Akt and Erk1/2 phosphorylation, suggesting that signaling through CXCR4 is the major source of PI3 kinase pathway activation in T-ALL cells. Surprisingly, treatment with BL-8040 did not affect cellular proliferation, as measured by Ki67/FxCycle Violet staining or by EdU labeling. Moreover, no increase in apoptosis, as measured by annexin V or activated caspase 3 expression, was observed. These data suggest that CXCR4 blockade induces a non-apoptotic cell death. To explore this possibility further, we performed transcriptome sequencing on T-ALL cells recovered from mice 24 hours after 1 dose of BL-8040. A total of 151 differentially expressed genes (FDR of < 0.05% and ≥ 2-fold change) were identified. Gene set enrichment analysis was strongly positive for alterations in oxidative phosphorylation, ribosome biogenesis, and carbohydrate metabolism. Ribosome function was assessed using O-propargyl-puromycin (OPP), which monitors global protein translation. No difference in global protein synthesis in T-ALL cells was observed after CXCR4 blockade in vivo. T-ALL cells are dependent on glutamine as a source of carbon, and PI3 kinase signaling positively regulates glutaminolysis. Thus, we hypothesized that CXCR4 blockade may induce T-ALL cell death by reducing glutamine metabolism. However, treatment of T-ALL cells in vitro with BL-8040 did not alter the cellular levels of glutamine or glutamate, as measured using a commercial bioluminescent assay. Confirmatory metabolic tracing studies using 13C-labeled glutamine and glucose are in progress. Finally, to explore the reduction in oxidative phosphorylation, we examined mitochondria function using Mitotracker Green. Treatment of T-ALL cells in vitro with BL-8040 for 24-48 hours induced a significant decrease in mitochondria number, suggesting induction of mitophagy. Collectively, these data suggest that T-ALL cells are addicted to CXCR4 signaling in vivo. CXCR4 blockade with BL-8040 induces a non-apoptotic cell death that is characterized by a loss of mitochondria. Disclosures Uy: Astellas: Consultancy; Pfizer: Consultancy; Curis: Consultancy; GlycoMimetics: Consultancy. Bohana-Kashtan:BiolineRx: Employment, Equity Ownership. Sorani:BiolineRx: Employment, Equity Ownership. Vainstein:BiolineRx: Employment, Equity Ownership.

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Protein Translocation Inhibitors Overcome Cytokine-Induced Glucocorticoid Resistance in T-Cell Acute Lymphoblastic Leukemia

Blood ◽

10.1182/blood-2019-127537 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 805-805

Author(s):

Lauren K. Meyer ◽

Cristina Delgado-Martin ◽

Phillip P. Sharp ◽

Dustin McMinn ◽

Christopher J. Kirk ◽

...

Keyword(s):

Acute Lymphoblastic Leukemia ◽

Cell Surface ◽

Research Funding ◽

Secretory Pathway ◽

Signal Sequence ◽

Lymphoblastic Leukemia ◽

Life Sciences ◽

Employment Equity ◽

Cell Acute Lymphoblastic Leukemia ◽

Equity Ownership

Glucocorticoids (GCs) are central to the treatment of T-cell acute lymphoblastic leukemia (T-ALL), and upfront resistance to GCs is a poor prognostic factor. We previously demonstrated that over one-third of primary patient T-ALLs are resistant to the GC dexamethasone (DEX) when cultured in the presence of interleukin-7 (IL7), a cytokine that is abundant in the microenvironment of leukemic blasts and that plays a well-established role in leukemogenesis. Mechanistically, we demonstrated that GCs paradoxically induce their own resistance by promoting the upregulation of IL7 receptor (IL7R) expression. In the presence of IL7, this augments signal transduction through the JAK/STAT5 axis, ultimately leading to increased STAT5 transcriptional output. This promotes the upregulation of the pro-survival protein BCL-2, which opposes DEX-induced apoptosis. Given that IL7-induced GC resistance depends on de novo synthesis of IL7R in response to DEX, and that newly synthesized IL7R reaches the cell surface via trafficking through the secretory pathway, we hypothesized that inhibiting the translocation of nascent IL7R peptide into the secretory pathway would effectively overcome IL7-induced DEX resistance. Sec61 is a protein-conducting channel in the membrane of the endoplasmic reticulum (ER) that is required for the cotranslational insertion of nascent polypeptides into the ER upon recognition of the signal sequence on secreted and cell surface proteins. To test the hypothesis that Sec61 inhibition could overcome IL7-induced DEX resistance, we utilized the human T-ALL cell line CCRF-CEM, which recapitulates the resistance phenotype observed in primary patient samples. Using a series of structurally distinct small molecule inhibitors of the Sec61 translocon, we demonstrated that Sec61 inhibition effectively overcomes the increase in cell surface IL7R expression in response to DEX. This occurs despite a persistent elevation in IL7R transcript expression following DEX exposure, confirming that Sec61 inhibitors act post-transcriptionally to attenuate cell surface IL7R expression. To determine whether the sensitivity of IL7R to Sec61 inhibitors is due specifically to the interaction between the IL7R signal sequence and Sec61 inhibitors, we generated IL7R constructs containing hydrophobic amino acid substitutions in the signal sequence, which are predicted to confer resistance to Sec61 inhibitors. Upon transient transfection of these constructs into HEK293T cells, we found that these mutations rendered IL7R resistant to the effects of Sec61 inhibition, confirming that the IL7R signal sequence confers sensitivity to these inhibitors. Using the Bliss independence model of synergy in CCRF-CEM cells, we demonstrated that Sec61 inhibitors potently synergize with DEX to overcome IL7-induced DEX resistance. Importantly, at concentrations at which synergy occurs, Sec61 inhibitors demonstrate no single-agent effect on cell survival, suggesting that these effects are not due to an overall reduction in secretory and membrane protein biogenesis. Furthermore, Sec61 inhibitors failed to sensitize CCRF-CEM cells to other chemotherapies used in T-ALL, none of which demonstrate IL7-induced resistance, thereby suggesting that these effects on DEX sensitivity are due specifically to the reduction in cell surface IL7R. To determine if Sec61 inhibitors prevent the DEX-induced increase in STAT5 transcription, we analyzed BCL-2 expression in cells exposed to DEX and IL7, and found that Sec61 inhibitors attenuate the increase in BCL-2 expression in a dose-dependent manner. We next analyzed a cohort of 34 primary patient T-ALL samples. As in CCRF-CEM cells, we found that specifically in those samples with IL7-induced DEX resistance, Sec61 inhibitors synergized with DEX to induce cell death in the presence of IL7. This effect occurred concomitantly with a reduction in cell surface IL7R expression and BCL-2 expression. Taken together, these data demonstrate the efficacy and feasibility of Sec61 inhibition as a novel and rational therapeutic strategy to overcome the IL7-induced DEX resistance phenotype that affects over one-third of newly diagnosed T-ALL patients. Disclosures Sharp: Kezar Life Sciences: Patents & Royalties. McMinn:Kezar Life Sciences: Employment, Equity Ownership. Kirk:Kezar Life Sciences: Employment, Equity Ownership. Taunton:Global Blood Therapeutics: Equity Ownership; Principia Biopharma: Equity Ownership, Patents & Royalties; Cedilla Therapeutics: Consultancy, Equity Ownership; Pfizer: Research Funding; Kezar Life Sciences: Equity Ownership, Patents & Royalties, Research Funding.

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The CXCR4 Antagonist, BL8040, Is Highly Active Against Human T-ALL in Preclinical Models

Blood ◽

10.1182/blood-2018-99-117213 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 2700-2700

Author(s):

Jun Xia ◽

Matthew RM Jotte ◽

Stephanie Sun ◽

Geoffrey L. Uy ◽

Abi Vainstein ◽

...

Keyword(s):

Target Genes ◽

Hematologic Malignancy ◽

Lymphoblastic Leukemia ◽

Notch Pathway ◽

Cxcr4 Antagonist ◽

Employment Equity ◽

Cxcr4 Signaling ◽

Highly Active ◽

Equity Ownership

Abstract T cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy that accounts for 10-15% of pediatric and 25% of adult ALL cases. Approximately 20-25% of pediatric and 50% of adult patients with T-ALL relapse following induction therapy, and the prognosis after relapse is dismal, with 3-year event-free survival of only 10-15%. Thus, there is a clear unmet clinical need for better therapies for T-ALL. CXCL12 (stromal-derived factor-1, SDF1) is a CXC chemokine that is constitutively expressed at high levels in the bone marrow. CXCR4 is the major receptor for CXCL12 and is by far the most highly expressed chemokine receptor on T-ALL cells. Two groups recently showed that genetic loss of CXCR4 signaling in murine or human T-ALL cells markedly suppressed their growth in vivo. Here we explore the hypothesis that inhibition of the CXCR4 signaling with a potent new CXCR4 antagonist, BL-8040 alone, or in combination with ABT263 (navitoclax), a BCL2/BCLXL antagonist, will have therapeutic activity against T-ALL. To test this hypothesis, we xenotransplanted a human T-ALL cell line (P12/Ichikawa cells) or 5 different patient-derived T-ALL xenografts into non-irradiated NSG mice. In each case, the T-ALL cells were allowed to engraft and then mice were randomly assigned to one of four treatment groups: 1) vehicle control; 2) BL-8040 alone; 3) ABT263 alone; 4) combined BL-8040 and ABT263. Treatment was given for 2 weeks, and leukemia burden monitored weekly by bioluminescent imaging or by flow cytometry to quantify human CD45+ T-ALL cells in the blood. A minimum of 10 mice in each cohort from two independent experiments were analyzed (Figure 1). A significant reduction in T-ALL burden was observed in all T ALL samples after treatment with BL8040 alone, with a mean fold-decrease compared with control mice after 2 weeks of treatment of 966 ± 651 (range 16-3,486). Consistent with a prior report, the response to ABT263 alone was more variable, with responses seen in 4 of 6 T-ALL samples. All T-ALL samples had a marked response to the combination of BL-8040 and ABT263, with a mean fold decrease of 4,389 ± 2,602 (range, 139-15,199). A previous study suggested that inhibition of CXCR4 signaling may suppress Myc expression (Pitt et al, Cancer Cell, 2015), which is relevant, since overexpression of Myc secondary to mutations in the Notch pathway are common in T-ALL. However, we observed no difference in Myc protein expression or expression of Myc target genes following BL-8040 treatment. Consistent with this observation, treatment with BL8040 had no impact on the cell cycle status of T-ALL cells in vivo. Of note, we observed a marked decrease in Akt and Erk phosphorylation following BL8040, suggesting that CXCR4 signaling may regulate T ALL survival in vivo by suppressing these pathways. Conclusion. Collectively, these data suggest that BL-8040, either alone or in combination with ABT263, is highly active in T-ALL and support our ongoing clinical trial of BL-8040 in combination with nelarabine for patients with relapsed T-ALL (NCT02763384). Figure 1. Figure 1. Disclosures Uy: GlycoMimetics: Consultancy; Curis: Consultancy. Vainstein:Biolinerx: Employment. Sorani:BioLineRx Ltd.,: Employment. Bohana-Kashtan:BioLineRx Ltd.,: Employment, Equity Ownership; Cell Cure Neurosciences: Equity Ownership. Shaw:BioLineRx Ltd.: Employment, Equity Ownership.

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Role of Spleen Tyrosine Kinase Signaling in Early B Cell Acute Lymphoblastic Leukemia.

Blood ◽

10.1182/blood.v114.22.3092.3092 ◽

2009 ◽

Vol 114 (22) ◽

pp. 3092-3092

Author(s):

Tatiana Perova ◽

Lauryl Nutter ◽

Irina Matei ◽

Ildiko Grandal ◽

Polly Pine ◽

...

Keyword(s):

Acute Lymphoblastic Leukemia ◽

Tyrosine Kinase ◽

B Cell ◽

Molecular Mechanisms ◽

Lymphoblastic Leukemia ◽

Employment Equity ◽

Cell Acute Lymphoblastic Leukemia ◽

Equity Ownership ◽

All Treatment

Abstract Abstract 3092 Poster Board III-29 Introduction Early B cell acute lymphoblastic leukemia (B-ALL) is the most common type of childhood malignancy, characterized by abnormal accumulation and proliferation of progenitor-B or precursor-B (pre-B) cells. Current challenges associated with B-ALL treatment include fatal relapses, treatment-related toxicities and long-term morbidities underscoring a need to develop new targeted therapies aimed at eradicating leukemia cells and their stem cells. To achieve this, a better understanding of molecular mechanisms involved in leukemia initiation and progression is required. Our laboratory developed p53-/- PrkdcSCID/SCID double mutant (DM) strain as a mouse model of early B-ALL. We showed that DM leukemias progress through discrete developmental stages of leukemogenesis despite the absence of a pre-B cell receptor (pre-BCR), a crucial checkpoint in B cell development. Spleen tyrosine kinase (SYK), a key proximal component of pre-BCR signaling, was activated in the DM leukemias despite the absence of pre-BCR and was required for their survival. Approximately 70% of pediatric pre-B-ALLs also do not express pre-BCR, which lead us to investigate SYK signaling in human pre-B-ALL and to test potential therapeutic application of SYK inhibition in these leukemias. Patients and Methods We examined 22 viably frozen primary pediatric pre-B-ALL bone marrow samples to test their responses to SYK inhibition in vitro and in vivo and have investigated the molecular basis for aberrant SYK-mediated signaling in B-ALL. Results Western blot analyses revealed that SYK and BLNK, a dominant target of SYK, were expressed in pre-B-ALL patient samples. The majority of human pre-B ALL samples tested (14/22) displayed significantly attenuated proliferation in the presence of SYK inhibitors suggesting that SYK is necessary for their survival and/or proliferation. Treatment with SYK inhibitor R406 prevented phosphorylation of downstream SYK targets including BLNK and PLC-γ2. We are continuing to study the effects of SYK inhibition using phospho-flow cytometry and genome wide expression arrays. Preliminary data will also be presented on therapeutic efficacy of an orally bioavailable form of R406-mediated SYK inhibition in vivo by xenotransplantation of human leukemias into immuno-deficient mice. Conclusions Understanding the molecular mechanisms of pre-BCR-independent SYK activation involved in proliferation and survival of leukemic blasts may provide a rational basis for development of effective treatment for ALL. Specifically, targeted therapeutic inhibition of SYK signaling may be effective B-ALL treatment that may improve outcomes of current treatment regiments with minimal additional treatment-related toxicity. Disclosures Pine: Rigel Pharmaceuticals: Employment, Equity Ownership. Hitoshi:Rigel Pharmaceuticals: Employment, Equity Ownership.

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Phase II Study of the Cyclin-Dependent Kinase (CDK) Inhibitor Dinaciclib (SCH 727965) In Patients with Advanced Acute Leukemias

Blood ◽

10.1182/blood.v116.21.3287.3287 ◽

2010 ◽

Vol 116 (21) ◽

pp. 3287-3287 ◽

Cited By ~ 5

Author(s):

Ivana Gojo ◽

Alison Walker ◽

Maureen Cooper ◽

Eric J Feldman ◽

Swaminathan Padmanabhan ◽

...

Keyword(s):

Research Funding ◽

Post Treatment ◽

Parp Cleavage ◽

Employment Equity ◽

Acute Leukemias ◽

Early Management ◽

Tumor Lysis ◽

Equity Ownership ◽

Pre Treatment

Abstract Abstract 3287 Background: Dinaciclib is a potent and selective inhibitor of the CDKs 1, 2, 5, and 9 that has demonstrated anti-tumor activity against both myeloid and lymphoid leukemia cell lines in vitro and human tumor xenografts in vivo. Methods: A randomized, multicenter, open-label phase 2 study of dinaciclib 50 mg/m2 administered by 2-hour i.v. infusion once every 21 days was initiated with the goal of assessing its efficacy and safety in patients (pts) with advanced acute myeloid (AML, ≥60 years old) or lymphoid (ALL, ≥18 years old) leukemia. AML pts were randomized between dinaciclib and gemtuzumab ozogamicin (GO) with cross-over to dinaciclib if no response to GO, while ALL pts only received dinaciclib. Intra-patient dose escalation of dinaciclib to 70 mg/m2 in cycle 2 was allowed. Twenty-six pts were treated on study (20 AML, 6 ALL). Data on 14 AML (2 cross-over from GO) and 6 ALL pts treated with dinaciclib are presented. Their median age was 70 (range 38–76) years and 70% were male. Sixteen pts were refractory and 4 pts had relapsed after a median of one (range 1–4) chemotherapy regimens. Four AML pts had complex karyotypes (≥3 abnormalities), 2 monosomy 7, 2 trisomy 8, 1 der (1:7)(q10;p10), 1 trisomy 21, 1 deletion 9q, and 3 had normal karyotype. Two ALL pts had t(9;22). Response: Anti-leukemia activity was observed in 60% of pts. Ten of 13 pts with circulating blasts (7/7 AML and 3/6 ALL) had >50% and 6 pts (4 AML, 2 ALL) >80% decrease in the absolute blast count (ABC) within 24 hours of the first dinaciclib dose. An additional pt had a 29% decrease in ABC. The median pre-treatment ABC was 1085 (range 220–9975) and the median ABC nadir was 169 (range 0–1350). The median duration of blast nadir was 6 days (range 2–23). A representative graph from an AML patient (below) shows a rapid decrease of circulating blasts and WBC after treatment, followed by a gradual recovery. Two patients had >50% reduction of marrow blasts (35% on d1 to 17% on d 42 in an AML pt; 81% on d1 to 27% on d 21 in an ALL pt). However, no objective responses by International Working Group criteria were observed. The median number of treatment cycles was 1 (range 1–5), with 10 pts receiving more than one cycle of treatment. Eight pts were treated with dinaciclib 70 mg/m2 starting in cycle 2. Toxicity: Treatment related AE's occurring in >30% of pts included diarrhea, nausea, vomiting, anemia, elevated AST, fatigue, leukopenia, hypocalcemia, and hypotension. The most common CTCAE v3 treatment-related grade 3 and 4 toxicities, occurring in 3 or more pts, were anemia, leukopenia, febrile neutropenia, thrombocytopenia, fatigue, increased AST, and tumor lysis syndrome (TLS). Laboratory evidence of tumor lysis in cycle 1, using the Cairo-Bishop criteria, was seen in 6 pts in addition to 3 pts with clinical TLS (JCO 2008;26:2767). Hyperacute TLS requiring hemodialysis occurred in one pt with AML, who died of acute renal failure. Subsequently, all pts were aggressively managed to prevent and treat TLS (hospitalization, hydration, allopurinol, rasburicase, oral phosphate binder administration, and early management of hyperkalemia). An additional 9 pts died on study, 8 pts from leukemia progression and 1 pt from intracranial bleed due to disease-related thrombocytopenia. Pharmacodynamics: Pre-treatment, 4 and 24 hrs post end-of-infusion samples of circulating leukemic blasts were obtained from 1 AML and 3 ALL pts. By Western blot, post-treatment decrease in Mcl-1 and increase in PARP cleavage were seen in all 4 pts at 4 hrs post-treatment, confirming that in vivo inhibition of CDKs was achieved, but recovery of Mcl-1 at 24 hrs was observed in all 4 pts, suggesting that inhibition was lost at 24 hrs. Decline in p-Rb was observed in 1 pt, while 2 pts had almost undetectable p-Rb levels at baseline. Conclusion: Dinaciclib showed anti-leukemia activity in this heavily pre-treated patient population. TLS was a notable toxicity, but was manageable in most pts with aggressive prophylaxis, monitoring and treatment. Early blast recovery and short duration of nadir observed on this study, combined with PK data showing a short t1/2 (1.5-3.3 hours) for dinaciclib and PD data demonstrating rapid reexpression of Mcl-1, support either use of longer infusion schedules (currently explored in solid tumors) or more frequent drug administration. Further exploration of dinaciclib dose and schedules in AML and ALL is planned. Disclosures: Gojo: Merck & Co.: Research Funding. Off Label Use: SCH 727965 (dinaciclib) is an investigational drug. Padmanabhan:Schering-Plough: Consultancy; Merck & Co.: Research Funding. Small:Merck & Co.: Employment, Equity Ownership. Zhang:Merck & Co.: Employment. Sadowska:Merck & Co.: Research Funding. Bannerji:Merck & Co.: Employment, Equity Ownership.

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A Phase 1 Study of Prasugrel in Subjects with Sickle Cell Disease: Effects on In Vivo Markers of Platelet Activation and of Coagulation

Blood ◽

10.1182/blood.v118.21.1049.1049 ◽

2011 ◽

Vol 118 (21) ◽

pp. 1049-1049

Author(s):

Joseph A. Jakubowski ◽

Chunmei Zhou ◽

David S. Small ◽

Kenneth J. Winters ◽

D. Richard Lachno ◽

...

Keyword(s):

Sickle Cell Disease ◽

Platelet Activation ◽

Sickle Cell ◽

Research Funding ◽

Blood Platelet ◽

Cell Disease ◽

Employment Equity ◽

Equity Ownership ◽

Adp Receptor

Abstract Abstract 1049 Introduction: Evidence suggests that platelets are activated in sickle cell disease (SCD) and this appears to increase further during painful crises caused by vascular occlusions from sickled red blood cells. Antiplatelet therapy may be useful in reducing the frequency and severity of acute pain episodes and reducing the risk of thrombotic complications. Prasugrel, an ADP receptor antagonist, irreversibly inhibits the P2Y12 ADP receptor, blocking ADP-stimulated platelet activation and aggregation and reducing downstream procoagulant activities. Here we present the first evaluation of prasugrel's effects on markers of in vivo platelet activation and of coagulation in subjects with SCD. Methods: Twenty-six adult subjects were enrolled and 25 completed the study: 12 with SCD and 13 well-matched healthy controls. Subjects were examined before and after 12±2 days of treatment with oral prasugrel (5.0 mg/day for subjects weighing <60 kg and 7.5 mg/day for subjects weighing ≥60 kg). Markers of platelet activation and coagulation included whole-blood platelet-monocyte and -neutrophil aggregates, and whole blood platelet-associated P-selectin and platelet CD40L, all measured by flow cytometry and presented as percent (%) of marker positive cells. Plasma soluble (s) P-selectin, CD40L, and plasma prothrombin fragment 1.2 (F1.2) were evaluated by ELISA. Results: Results from the biomarkers are presented in the table. Prior to prasugrel administration (baseline), subjects with SCD had significantly higher levels of the following biomarkers compared to healthy subjects: Platelet-monocyte aggregates, platelet-neutrophil aggregates, platelet CD40L, and plasma F1.2. In addition, subjects with SCD had numerically higher values of sCD40L, as well as platelet-associated and sP-selectin. Prasugrel treatment resulted in numerical decreases in levels of all biomarkers (with the exception of platelet-associated CD40L for control subjects), most notably in SCD subjects with elevated baseline levels. Prasugrel was safe and well tolerated with no serious adverse events observed during the study. No subject discontinued the study due to an adverse event (AE) and the majority of AEs were mild. No subjects with SCD reported any bleeding-related AEs. Conclusion: In this study, compared to healthy controls, baseline elevation of several platelet-activation and coagulation markers among adult subjects with SCD is consistent with that seen in previous studies of both children and adults with SCD. The decrease in platelet activation biomarkers following 12 days of prasugrel treatment in subjects with SCD suggests prasugrel interrupts SCD-related platelet activation in vivo and raises the possibility that prasugrel may modulate the frequency and/or severity of painful crises associated with SCD. These data support additional studies of the safety and efficacy of prasugrel in the treatment of vascular complications associated with SCD. Disclosures: Jakubowski: Eli Lilly and Company: Employment, Equity Ownership. Off Label Use: This abstract discusses prasugrel treatment in patients with sickle cell disease. Please see USPI for most up-to-date information. Zhou:Eli Lilly and Company: Employment, Equity Ownership. Small:Eli Lilly and Company: Employment, Equity Ownership. Winters:Eli Lilly and Company: Employment, Equity Ownership. Lachno:Eli Lilly and Company: Employment, Equity Ownership. Frelinger:Takeda: Research Funding; Daiichi Sankyo Company, Ltd. and Eli Lilly and Company: Consultancy, Research Funding; GLSynthesis: Research Funding. Howard:Daiichi Sankyo Company, Ltd. and Eli Lilly and Company: Research Funding. Payne:Eli Lilly and Compnay: Employment, Equity Ownership.

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Stroma-Free Ex Vivo Expanded, CD34+ Cord Blood-Derived NK Cells Retain Lytic Activity After Long-Term Engraftment in NSGS Mice

Blood ◽

10.1182/blood.v120.21.580.580 ◽

2012 ◽

Vol 120 (21) ◽

pp. 580-580

Author(s):

Mark Wunderlich ◽

Mahesh Shrestha ◽

Lin Kang ◽

Eric Law ◽

Vladimir Jankovic ◽

...

Keyword(s):

Nk Cells ◽

Research Funding ◽

Nk Cell ◽

Ex Vivo ◽

Employment Equity ◽

Cell Product ◽

Equity Ownership ◽

Cellular Therapeutics

Abstract Abstract 580 Generating a large number of pure, functional immune cells that can be used in human patients has been a major challenge for NK cell-based immunotherapy. We have successfully established a cultivation method to generate human NK cells from CD34+ cells isolated from donor-matched cord blood and human placental derived stem cells, which were obtained from full-term human placenta. This cultivation method is feeder-free, based on progenitor expansion followed by NK differentiation supported by cytokines including thrombopoietin, stem cell factor, Flt3 ligand, IL-7, IL-15 and IL-2. A graded progression from CD34+ hematopoietic progenitor cells (HSC) to committed NK progenitor cells ultimately results in ∼90% CD3-CD56+ phenotype and is associated with an average 10,000-fold expansion achieved over 35 days. The resulting cells are CD16- and express low level of KIRs, indicating an immature NK cell phenotype, but show active in vitro cytotoxicity against a broad range of tumor cell line targets. The in vivo persistence, maturation and functional activity of HSC-derived NK cells was assessed in NSG mice engineered to express the human cytokines SCF, GM-CSF and IL-3 (NSGS mice). Human IL-2 or IL-15 was injected intraperitoneally three times per week to test the effect of cytokine supplementation on the in vivo transferred NK cells. The presence and detailed immunophenotype of NK cells was assessed in peripheral blood (PB), bone marrow (BM), spleen and liver samples at 7-day intervals up to 28 days post-transfer. Without cytokine supplementation, very few NK cells were detectable at any time-point. Administration of IL-2 resulted in a detectable but modest enhancement of human NK cell persistence. The effect of IL-15 supplementation was significantly greater, leading to the robust persistence of transferred NK cells in circulation, and likely specific homing and expansion in the liver of recipient mice. The discrete response to IL-15 versus IL-2, as well as the preferential accumulation in the liver have not been previously described following adoptive transfer of mature NK cells, and may be unique for the HSC-derived immature NK cell product. Following the in vivo transfer, a significant fraction of human CD56+ cells expressed CD16 and KIRs indicating full physiologic NK differentiation, which appears to be a unique potential of HSC-derived cells. Consistent with this, human CD56+ cells isolated ex vivo efficiently killed K562 targets in in vitro cytotoxicity assays. In contrast to PB, spleen and liver, BM contained a substantial portion of human cells that were CD56/CD16 double negative (DN) but positive for CD244 and CD117, indicating a residual progenitor function in the CD56- fraction of the CD34+ derived cell product. The BM engrafting population was higher in NK cultures at earlier stages of expansion, but was preserved in the day 35- cultured product. The frequency of these cells in the BM increased over time, and showed continued cycling based on in vivo BrdU labeling 28 days post-transfer, suggesting a significant progenitor potential in vivo. Interestingly, DN cells isolated from BM could be efficiently differentiated ex vivo to mature CD56+CD16+ NK cells with in vitro cytotoxic activity against K562. We speculate that under the optimal in vivo conditions these BM engrafting cells may provide a progenitor population to produce a mature NK cell pool in humans, and therefore could contribute to the therapeutic potential of the HSC-derived NK cell product. The in vivo activity of HSC-derived NK cells was further explored using a genetically engineered human AML xenograft model of minimal residual disease (MRD) and initial data indicates significant suppression of AML relapse in animals receiving NK cells following chemotherapy. Collectively, our data demonstrate the utility of humanized mice and in vivo xenograft models in characterizing the biodistribution, persistence, differentiation and functional assessment of human HSC-derived cell therapy products, and characterize the potential of HSC-derived NK cells to be developed as an effective off-the-shelf product for use in adoptive cell therapy approaches in AML. Disclosures: Wunderlich: Celgene Cellular Therapeutics: Research Funding. Shrestha:C: Research Funding. Kang:Celgene Cellular Therapeutics: Employment, Equity Ownership, Patents & Royalties. Law:Celgene Cellular Therapeutics: Employment, Equity Ownership, Patents & Royalties. Jankovic:Celgene Cellular Therapeutics: Employment, Equity Ownership, Patents & Royalties. Zhang:Celgene Cellular Therapeutics: Employment, Equity Ownership, Patents & Royalties. Herzberg:Celgene Cellular Therapeutics: Employment, Equity Ownership, Patents & Royalties. Abbot:Celgene Cellular Therapeutics: Employment, Equity Ownership, Patents & Royalties. Hariri:Celgene Cellular Therapeutics: Employment, Equity Ownership, Patents & Royalties. Mulloy:Celgene Cellular Therapeutics: Research Funding.

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Randomized, Phase II Dose Optimization Study Of Chimeric Antigen Receptor Modified T Cells Directed Against CD19 (CTL019) In Patients With Relapsed, Refractory CLL

Blood ◽

10.1182/blood.v122.21.873.873 ◽

2013 ◽

Vol 122 (21) ◽

pp. 873-873 ◽

Cited By ~ 7

Author(s):

David L. Porter ◽

Michael Kalos ◽

Noelle V. Frey ◽

Stephan A Grupp ◽

Alison W. Loren ◽

...

Keyword(s):

T Cells ◽

Dose Level ◽

Research Funding ◽

University Of Pennsylvania ◽

Employment Equity ◽

Lower Dose Level ◽

Equity Ownership ◽

Cell And Gene Therapy

Abstract Background Patients (pts) with relapsed, and/or refractory (R/R) CLL have a poor prognosis with few effective treatment options. We have shown that infusion of autologous T cells genetically modified to express a chimeric antigen receptor (CAR) consisting of an external anti-CD19 domain, with the CD3ζ and 4-1BB signaling domains (CTL019 cells), can mediate potent anti-tumor effects in pts with advanced, relapsed refractory CLL. In our initial pilot study, doses of 1.7-50, x 108 mononuclear cells, corresponding to 0.14-5.9 x 108genetically modified cells, were given as a split dose infusion on days 0, 1 and 2 to 14 pts with R/R CLL and overall response rate (PR plus CR) was 57%. The majority of responses were sustained, and associated with marked expansion and long-term persistence of transduced cells. Notably, there was no obvious dose:reponse or dose:toxicity effect noted over a wide range of cell doses. To better define an optimal CTL019 cell dose, we are performing a randomized phase II study of 2 doses of CTL019 cells in pts with R/R CLL. Methods Pts with R/R CLL are randomly assigned to receive either 5x108 vs. 5x107transduced CTL019 cells, with the rationale that both doses induced CRs in pts on our initial pilot trial. In the initial stage, 12 evaluable pts will be treated in each arm and in stage 2, an additional 8 pts will be treated with the selected dose level. Pts have to have relapsed or persistent disease after at least 2 previous treatments and progress within 2 years of their last therapy. All pts receive lymphodepleting chemotherapy ending 3-5 days before T cell infusion. Cell infusions are given as a single dose. Results As of 7/15/2013, 27 pts have been enrolled; T cells did not adequately expand in 3, 1 patient was not eligible after screening, and 10 pts have been treated including 7 men and 3 women with a median age of 63 yrs (range 59-76). 5 pts had a mutation of p53. All pts had active disease at the time of CTL019 cell infusion. Lymphodepleting chemotherapy was Fludarabine/cyclophosphamide (8), pentostatin/cyclophosphamide (1), or bendamustine (1). 4 pts have been randomized to the higher dose level (5 x 108 CTL019 cells) and 6 pts have been randomized to the lower dose level (5 x 107CTL019 cells). There were no significant infusional toxicities. Median follow-up as of July 15, 2013 was 3 mo (1.3-5) for all pts and 3.3 mo (1.3-4) for responding pts. 2 pts have achieved a CR and 2 pts achieved PR, both with clearance of CLL from the blood and marrow and >50 reduction in adenopathy, for an overall response rate of 40%. In other recipients of CTL019 cells, we have observed ongoing improvement in adenopathy over time implying there can be a continued anti-tumor response. No responding patient has progressed. Seven of 10 pts experienced a delayed cytokine release syndrome (CRS) manifested by symptoms that included high fevers, nausea, myalgias and in some cases, capillary leak, hypoxia, and hypotension, typically correlated with peak CTL019 cell expansion. We have noted that the CRS accompanying CTL019 therapy has been associated with marked increases of serum IL6 and can be rapidly reversed with the IL6-receptor antagonist tocilizumab. The CRS required intervention in 2 pts, one who responded and one who did not respond to CTL019. Treatment was initiated for hemodynamic or respiratory instability and was effective in reversing signs and symptoms of CRS in both pts. A preliminary analysis through July 15, 2013 does not yet suggest a dose:response or dose:toxicity relationship. 2 of 4 recipients of the higher dose CTL019 responded, and 2 of 6 recipients at the lower dose level responded. The 7 pts who experienced a CRS included all 4 responding pts and 3 pts who did not respond. The CRS occurred in 3/4 recipients of higher dose CTL019 cells and 4/6 of recipients of lower dose CTL019 cells. CTL019 expansion in-vivo and persistence over the follow up period was noted in all responding pts. Conclusions In this ongoing dose optimization study of CTL019 cells, 4 of the first 10 pts treated have responded within 3 months. With short follow-up, as yet there is no suggestion that there is a dose:response or dose:toxicity relationship at the dose ranges being studied. These cells can undergo robust in-vivo expansion and from other studies (ASH 2013) can persist for at least 3 yrs. This trial confirms that CTL019 cells can induce potent responses for pts with advanced, relapsed and refractory CLL. Disclosures: Porter: Novatis: IP and potential royalties with COI managed according to policies of the University of Pennsylvania, IP and potential royalties with COI managed according to policies of the University of Pennsylvania Patents & Royalties, Research Funding; Genentech: Spouse employment, Spouse employment Other. Off Label Use: CTL019 cells to treat CLL. Kalos:Novartis corporation: CART19 technology, CART19 technology Patents & Royalties; Adaptive biotechnologies: Member scientific advisory board , Member scientific advisory board Other. Grupp:Novartis: Research Funding. Chew:Novartis: Patents & Royalties. Shen:Novartis Pharmaceuticals: Employment, Equity Ownership. Wood:Novartis Pharmaceuticals: Employment, Equity Ownership. Litchman:Novartis Pharmaceuticals Corporation: Employment, Equity Ownership. Zheng:Novartis: Patents & Royalties. Levine:Novartis: cell and gene therapy IP, cell and gene therapy IP Patents & Royalties. June:Novartis: Patents & Royalties, Research Funding.

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Ublituximab (TG-1101), a Novel Glycoengineered Anti-CD20 Monoclonal Antibody, in Combination with Ibrutinib Is Highly Active in Patients with Relapsed and/or Refractory CLL and MCL; Results of a Phase II Trial

Blood ◽

10.1182/blood.v124.21.4679.4679 ◽

2014 ◽

Vol 124 (21) ◽

pp. 4679-4679 ◽

Cited By ~ 5

Author(s):

Jeff P. Sharman ◽

Charles M. Farber ◽

Daruka Mahadevan ◽

Marshall T. Schreeder ◽

Heather D. Brooks ◽

...

Keyword(s):

Board Of Directors ◽

Research Funding ◽

Alkylating Agent ◽

Single Agent ◽

Employment Equity ◽

Advisory Committees ◽

Highly Active ◽

Efficacy Assessment ◽

Equity Ownership ◽

Anti Cd20

Abstract Introduction: Ublituximab (UTX) is a novel, chimeric monoclonal antibody (mAb) which targets a unique epitope on the CD20 antigen and has been glycoengineered to enhance affinity for all variants of FcγRIIIa receptors, demonstrating greater antibody-dependent cellular cytotoxicity (ADCC) activity than rituximab and ofatumumab, particularly against cells that express low CD20 levels. Two Phase I trials of single agent UTX in relapsed/refractory CLL reported significant response rates with rapid and sustained lymphocyte depletion and a manageable safety profile. Ibrutinib, a novel oral BTK inhibitor approved for patients with previously treated CLL and MCL, displays high single agent activity and has reported increased activity in combination with non-glycoengineered anti-CD20 mAbs. Herein we report safety and efficacy data on the first combination of ibrutinib with a glycoengineered anti-CD20 mAb, UTX, from an ongoing Phase 2 trial. Methods: Eligible patients have relapsed or refractory CLL/SLL or MCL with an ECOG PS ≤ 2. The study was designed to assess safety, tolerability, and early overall response rate, with an initial safety run-in period consisting of 6 patients followed by open enrollment. UTX (Cohorts of 600 and 900 mg for CLL and at 900 mg for MCL patients) is administered on Days 1, 8, and 15 in Cycle 1 followed by Day 1 of Cycles 2 - 6. Ibrutinib is started on Day 1 and continues daily at 420 mg and 560 mg for CLL and MCL patients respectively. Following Cycle 6, patients come off study but remain on ibrutinib. Primary endpoint for safety: Adverse Events and Dose Limiting Toxicities (DLT) during safety run-in. Phase II primary efficacy endpoint: ORR with an emphasis on early activity with response assessments by CT scan scheduled prior to cycles 3 and 6 only. Results: 40 patients (33 CLL/ 7 MCL) have been enrolled to date with enrollment continuing. 23 M/17 F, median age 72 yr (range 52-86), ECOG 0/1/2: 20/19/1, median prior Tx = 2 (range 1-6), 38% with ≥ 2 prior anti-CD20 therapies; prior purine analog = 43%; prior alkylating agent = 68%; and prior purine and alkylating agent = 43%. No DLTs were observed during the safety run-in. Gr 3/4 AE’s occurring in at least 5% of patients and at least possibly related to UTX and/or ibrutinib included: neutropenia, thrombocytopenia, diarrhea, rash, leukocytosis, and infusion related reaction. There were no Grade 3/4 adverse events reported in ≥ 10% of patients. Ibrutinib was dose reduced due to an AE in 2 patients (1 diarrhea, 1 rash) and discontinued in 2 patients due to ibrutinib related AE’s (diarrhea and rash). IRR’s were managed with infusion interruptions with no patient requiring an ublituximab dose reduction. As of July 2014, 24/40 patients are evaluable for response. Best response to treatment is as follows: TableTypePts (n)CR (n)PR (n)SD (n)ORR (%)CLL non 17p/11q10-9190%17p/11q817-100%Total CLL18116194%MCL632183% The one CLL patient who achieved stable disease had a 46% nodal reduction. UTX appears to control ibrutinib related lymphocytosis with more than half of the patients within normal range for ALC by first efficacy assessment. Conclusions: Data suggests ublituximab, a glycoengineered anti-CD20 mAb, in combination with ibrutinib is both well-tolerated and highly active in patients with relapsed or refractory CLL and MCL. ORR was 94% in patients with CLL (100% in patients with high risk CLL: 17p, 11q del with 1 CR), with responses attained rapidly (median TTR: 8 weeks). In MCL, 83% of patients achieved a response at first efficacy assessment, with 50% of patients achieving a CR by week 20. For most patients, responses improved by the second efficacy assessment. The addition of ublituximab appears to mitigate ibrutinib related lymphocytosis producing earlier clinical responses than historically seen with ibrutinib monotherapy. Efficacy and safety will be updated on all enrolled patients. Disclosures Sharman: TG Therapeutics: Research Funding; Gilead: Consultancy, Research Funding; Roche: Research Funding; Pharmacyclics: Research Funding; Celgene: Consultancy, Research Funding. Farber:Leukemia Lymphoma Society NJ Chapter: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Alexion: Stock ownership Other. Schreeder:TG Therapeutics, Inc.: Research Funding. Kolibaba:TG Therapeutics: Research Funding; Gilead: Research Funding; Glaxo Smithkline: Research Funding. Sportelli:TG Therapeutics: Employment, Equity Ownership. Miskin:TG Therapeutics, Inc.: Employment, Equity Ownership. Weiss:TG Therapeutics, Inc.: Employment, Equity Ownership. Greenwald:TG Therapeutics: Research Funding.

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Ublituximab (TG-1101), a Novel Glycoengineered Anti-CD20 Monoclonal Antibody, in Combination with Ibrutinib Is Highly Active in Patients with Relapsed and/or Refractory Mantle Cell Lymphoma; Results of a Phase II Trial

Blood ◽

10.1182/blood.v126.23.3980.3980 ◽

2015 ◽

Vol 126 (23) ◽

pp. 3980-3980 ◽

Cited By ~ 4

Author(s):

Kathryn Kolibaba ◽

John M. Burke ◽

Heather D. Brooks ◽

Daruka Mahadevan ◽

Jason Melear ◽

...

Keyword(s):

Atrial Fibrillation ◽

Monoclonal Antibody ◽

Mantle Cell Lymphoma ◽

Research Funding ◽

Cell Lymphoma ◽

Employment Equity ◽

Highly Active ◽

Mantle Cell ◽

Equity Ownership ◽

Anti Cd20

Abstract Introduction: Ublituximab (UTX) is a novel, chimeric monoclonal antibody (mAb) which targets a unique epitope on the CD20 antigen and has been glycoengineered to enhance affinity for all variants of FcγRIIIa receptors, demonstrating greater ADCC than rituximab and ofatumumab. In patients (pts) with rel/ref CLL, the combination of UTX with ibrutinib was well-tolerated and highly active demonstrating an 88% ORR (95% ORR in high-risk CLL) with responses attained rapidly (median time to iwCLL response of 8 weeks). Ibrutinib has demonstrated single agent activity in Mantle Cell Lymphoma (MCL), achieving a 68% ORR (21% CR) in a single arm trial in relapsed or refractory patients (Wang et al, NEJM 2013). Herein we report on the first combination of ibrutinib with a glycoengineered anti-CD20 mAb, UTX, in patients with Mantle Cell Lymphoma (MCL). Methods: Eligible patients had rel/ref MCL with an ECOG PS < 3. Prior ibrutinib treatment was permitted. UTX (900 mg) was administered on Days 1, 8, and 15 in Cycle 1 followed by Day 1 of Cycles 2 - 6. Ibrutinib was started on Day 1 and continued daily at 560 mg. Following Cycle 6, patients came off study but could remain on ibrutinib. Primary endpoints were safety and ORR with an emphasis on early activity with response assessments by CT scan scheduled prior to cycles 3 and 6 only (criteria per Cheson 2007). Results: 15 patients were enrolled: 13 M/2 F, median age 71 yr (range 55-80), ECOG 0/1: 9/6, median prior Tx = 3 (range 1-8), 53% with ≥ 2 prior anti-CD20 therapies, 40% prior bortezomib. Gr 3/4 AE's occurring in at least 5% of patients and at least possibly related to UTX and/or ibrutinib included: neutropenia (13%), fatigue (7%), rash (7%) and atrial fibrillation (7%). Ibrutinib was dose reduced due to an AE in 1 patient (rash) and discontinued in 1 patient due to atrial fibrillation. No UTX dose reductions occurred. All 15 pts are evaluable for response with best response to treatment as follows: 87% (13/15) ORR with 33% (5/15) Complete Response. Three of the CR's occurred at week 8. Of the two patients not achieving an objective response, one patient was stable at first scan and came off treatment prior to second efficacy assessment (ibrutinib related A-Fib) and one patient progressed at first assessment. Responses generally improved from first to second assessment with median tumor reduction of 64% by week 8 and 82% by week 20. Conclusions: Ublituximab, a glycoengineered anti-CD20 mAb, in combination with ibrutinib is both well-tolerated and highly active in pts with rel/ref MCL. Response rate, depth of response, and time to response compare favorably to historical data with ibrutinib alone. A randomized phase 3 trial with ibrutinib +/- ublituximab is currently ongoing in high-risk CLL pts and future studies using this combination in MCL are being evaluated. Disclosures Kolibaba: Janssen: Research Funding; Novartis: Research Funding; Pharmacyclics: Research Funding; Seattle Genetics: Research Funding; Gilead: Consultancy, Honoraria, Research Funding; TG Therapeutics: Research Funding; GSK: Research Funding; Genentech: Research Funding; Cell Therapeutics: Research Funding; Celgene: Research Funding; Amgen: Research Funding; Amgen: Research Funding; Acerta: Research Funding. Burke:Gilead: Consultancy; Millenium/Takeda: Consultancy; Seattle Genetics, Inc.: Research Funding; Incyte: Consultancy; Janssen: Consultancy; TG Therapeutics: Other: Travel expenses. Farber:TG Therapeutics, Inc.: Research Funding. Fanning:Celgene and Millennium/Takeda: Speakers Bureau. Schreeder:TG Therapeutics, Inc: Research Funding. Boccia:Incyte Corporation: Honoraria. Sportelli:TG Therapeutics, Inc.: Employment, Equity Ownership. Miskin:TG Therapeutics, Inc.: Employment, Equity Ownership. Weiss:TG Therapeutics, Inc.: Employment, Equity Ownership. Sharman:Roche: Research Funding; Gilead: Consultancy, Honoraria, Research Funding, Speakers Bureau; Pharmacyclics: Consultancy, Honoraria, Research Funding; Calistoga: Honoraria; Janssen: Research Funding; TG Therapeutics, Inc.: Research Funding; Celgene Corporation: Consultancy, Research Funding.

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