Marcks Marks Resistance to Proteasome Inhibitors: Exocytosis of Polyubiquitinated Proteins in Bortezomib-Resistant Leukemia Cells

Abstract Despite the proven efficacy of proteasome inhibitors like bortezomib (BTZ) in multiple myeloma, mantle cell lymphoma, and in an experimental setting in pediatric acute leukemia, development of drug resistance remains a primary hindrance. To further understand the molecular basis underlying this chemoresistance phenomenon, various leukemia cell line models with acquired resistance to BTZ were developed and characterized. One common characteristic was that acquisition of point mutations in PSMB5 and upregulation of the β5-subunit of the proteasome were key determinants of BTZ-resistance in vitro. However, it remains unclear how these drug resistance modalities translate to the overcoming of proteolytic stress imposed by proteasome inhibition. From this perspective, we here undertook a multi-modality (DNA, mRNA, miRNA) array-based analyses of human CCRF-CEM acute leukemia cells and two BTZ-resistant subclones [one with a low resistance level [(10-fold, CEM/BTZ7) and another subline with a high resistance level (140-fold, CEM/BTZ200)] to determine whether or not complementary mechanisms contribute to BTZ resistance. Gene expression profiling studies revealed markedly reduced proteolytic stress induction in drug resistant cells over a broad BTZ concentration range. Moreover, several genes involved in cytoskeleton regulation and vesicle migration were increased in resistant cells. Of all genes, myristoylated alanine-rich C-kinase substrate (MARCKS) was the most differentially overexpressed gene with 25- to 42-fold upregulation in CEM/BTZ7 and CEM/BTZ200 cells, respectively. These observations were corroborated at the protein level and solely included unphosphorylated MARCKS rather than phosphorylated MARCKS, which was marginally expressed in CEM/BTZ cells. Interestingly, MARCKS upregulation was also observed in other BTZ-resistant and leukemia cells (CEM and THP1) with acquired resistance to the proteasome inhibitor salinosporamide A and the immunoproteasome inhibitor PR924. Given the overexpression of MARCKS in proteasome inhibitor-resistant leukemia cells, we further explored whether or not MARCKS overexpression may serve as a predictive marker of BTZ resistance in clinical samples of acute leukemia patients. To this end, we examined primary patient specimens from a phase II childhood refractory/relapsed ALL trial in which BTZ is administered in two intensive re-induction regimens containing vincristine, prednisone, PEG-asparaginase, doxorubicin or cyclophosphamide and etoposide followed by methotrexate treatment. MARCKS expression was demonstrated in 64% of therapy-refractory pediatric leukemia specimens (n=44) wherein higher MARCKS expression trended (p=0.09) towards a dismal response to BTZ-containing chemotherapy. Finally, from a mechanistic perspective, we showed a concentration-dependent association of MARCKS protein with the emergence of ubiquitin-containing vesicles in the resistant cells. This association with MARCKS protein was lost upon exocytosis of these vesicles, which were found to be extruded and taken up in co-cultures with recipient HeLa cells. Collectively, we propose a role for MARCKS in a novel mechanism of BTZ resistance through vesicular exocytosis of ubiquitinated proteins in BTZ-resistant cells to overcome proteolytic stress over a broad range of cytotoxic BTZ concentrations. Disclosures Kaspers: Janssen-Cilag: Research Funding. Smeets:Novartis: Employment. Zweegman:Celgene: 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; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding. Cloos:Takeda: Honoraria.

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Results of a Phase I Trial of Lenalidomide, Rituximab (R2) and Ixazomib for Frontline Treatment of High Risk Follicular and Indolent Non-Hodgkin Lymphoma

Blood ◽

10.1182/blood-2020-136370 ◽

2020 ◽

Vol 136 (Supplement 1) ◽

pp. 1-2

Author(s):

Brian T. Hill ◽

Deepa Jagadeesh ◽

Alex V. Mejia Garcia ◽

Robert M. Dean ◽

Omer N. Koc ◽

...

Keyword(s):

High Risk ◽

Phase I ◽

Board Of Directors ◽

Research Funding ◽

Marginal Zone ◽

Proteasome Inhibitors ◽

Marginal Zone Lymphoma ◽

Aggressive Lymphoma ◽

Advisory Committees ◽

Frontline Treatment

INTRODUCTION: Lenalidomide and Rituximab (R2) is an effective frontline treatment regimen for patients (pts) with indolent B-cell lymphoma including follicular lymphoma (FL). Recent phase III data from the RELEVANCE trial comparing R2 to traditional chemoimmunotherapy showed that this regimen is generally well-tolerated and has favorable clinical efficacy [61% overall response, 53% CR rate, 77% 3-year progression free survival (PFS) (Morschhauser, et al)]. Proteasome inhibitors such as bortezomib disrupt NF-KB signaling and have shown clinical activity in indolent NHL. Although randomized trials have failed to demonstrate clinical benefit of adding bortezomib to standard chemoimmunotherapy regimen bendamustine + rituximab (BR) for frontline treatment of FL, the addition of proteasome inhibitors to lenalidomide is a mainstay of treatment for plasma cell neoplasms due to synergistic antitumor effect. The oral proteasome inhibitor ixazomib has less potential for dose-limiting neuropathy than bortezomib, making it an attractive option to incorporate into the R2 regimen. We sought to investigate the safety and efficacy of the addition of ixazomib to R2 for FL and indolent B-cell NHL through a phase I clinical trial of this combination for patients with high risk disease. METHODS: Adult (age ≥ 18) pts with untreated FL or other indolent lymphoma, adequate organ function and performance status were enrolled. To be enrolled, FL patients were required to have stage 2, 3 or 4 disease, with high tumor burden by GELF criteria and/or FLIPI score of 3-5. During 3 x 3 dose escalation, ixazomib was given at a dose of 2 mg (n=3), 3 mg (n=3) or 4 mg (n=12) PO on days 1, 8, and 15 with lenalidomide 20 mg PO on days 1-21 every 28 days. Rituximab was administered at standard dosing on days 1,8,15,21 for cycle 1, once every 28 days for cycles 2-6 and then once every 2 months for cycles 7-12. Treatment was continued for 12 cycles and no maintenance therapy was specified per protocol. All pts received low dose aspirin for venous thromboembolism prophylaxis and acyclovir for prevention of VZV reactivation. Response assessments by CT were performed after cycle 3 and 6 and by PET/CT at the end-of-treatment (cycle 12). RESULTS: 20 pts were enrolled and 18 were eligible for treatment [15 FL (14 grade 1-2, 1 grade 3A), 2 splenic marginal zone lymphoma and 1 nodal marginal zone lymphoma].The median age of treated pts was 61 (range 40-83) years old. 55% of patients were female. Stage at diagnosis was II (n =2), III (n = 4) and IV (n = 12). For FL pts, FLIPI scores at enrollment were low (n=2), intermediate (n = 5) and high risk (n=8) and FLIPI-2 scores were low (n=3), intermediate (n = 2) and high risk (n=10). There were no dose limiting toxicities during 3 x 3 dose escalation. Grade (G) 1/2 and G3/4 treatment-related hematologic adverse events (AEs) included neutropenia (6%, 28%), thrombocytopenia (16.7%, 5.6%) and anemia (16.7%, 0%). The most common treatment-related AEs included nausea/vomiting (44% G1, 11% G2), diarrhea, (50% G1, 22% G2, 5% G3), rash (33% G1, 6% G2, 11%G3), peripheral neuropathy (22% G1, 6% G2), myalgia/arthralgia (17% G1, 17% G2), and infection (33% G2, 17% G3). There was one pulmonary embolism and no cases of febrile neutropenia. As of June, 2020, median follow-up among living pts was 21 months. 4 pts discontinued treatment due to disease progression; 2 with transformation to aggressive lymphoma. Of the transformed cases, one subject died on study due to progression disease and one developed CNS disease on study treatment but proceeded to autologous stem cell transplant. The best overall response rate was 61.2% [55.6% CR, 5.6% PR): 22.2% had stable disease and 16.7% had disease progression. 18-month Kaplan-Meier estimates of PFS and overall survival were 71% and 94%, respectively (Figure). CONCLUSION: R2 can safely be combined with at the target dose of 4 mg of ixazomib for treatment-naïve indolent NHL patients. Non-hematologic AEs were generally consistent with known toxicity of each component of therapy. CR rate and PFS were was similar to the outcomes reported in the RELEVANCE trial despite enrolling high risk patient. R2 may serve as backbone for future studies of novel treatment combinations for high risk FL after thorough evaluation for occult transformation to aggressive lymphoma. Disclosures Hill: Abbvie: Consultancy, Honoraria, Research Funding; Genentech: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria; BMS: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Takeda: Research Funding; Karyopharm: Consultancy, Honoraria, Research Funding; AstraZenica: Consultancy, Honoraria, Research Funding; Kite, a Gilead Company: Consultancy, Honoraria, Research Funding; Beigene: Consultancy, Honoraria, Research Funding; Pharmacyclics: Consultancy, Honoraria, Research Funding. Jagadeesh:MEI Pharma: Research Funding; Regeneron: Research Funding; Seattle Genetics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Debiopharm Group: Research Funding; Verastem: Membership on an entity's Board of Directors or advisory committees. Caimi:Celgene Corp: Other: Incyte Corporation - Ownership - Pharmacyclics, Inc. - Ownership - Celgene Corp. - Other, Speakers Bureau; ADC Therapeutics: Research Funding; Genentech: Research Funding. Smith:Takeda: Research Funding; Celgene: Research Funding. OffLabel Disclosure: Ixazomib is off-label for treatment of NHL

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Alkaline Phosphatase (ALP) Variation During Carfilzomib Treatment Is Associated to Best Response in Multiple Myeloma.

Blood ◽

10.1182/blood.v114.22.2865.2865 ◽

2009 ◽

Vol 114 (22) ◽

pp. 2865-2865 ◽

Cited By ~ 2

Author(s):

Maurizio Zangari ◽

Latha Polavaram ◽

Fenghuang Zhan ◽

Guido J. Tricot ◽

Ravi Vij ◽

...

Keyword(s):

Retrospective Analysis ◽

Board Of Directors ◽

Research Funding ◽

Single Agent ◽

Proteasome Inhibitors ◽

Phase 2 ◽

Two Phase ◽

Advisory Committees ◽

Best Response ◽

Ortho Biotech

Abstract Abstract 2865 Poster Board II-841 BACKGROUND: The ubiquitin-proteasome pathway, which has been shown to be an essential cellular degradative system in myeloma cells, can also regulate bone formation through its effects on osteoblast differentiation. Retrospective analysis of variation of ALP during treatment with bortezomib indicates a close correlation between myeloma response and serum ALP levels which multiple studies have shown to be of bone origin. To determine if this effect is a class effect of proteasome inhibitors (PIs), this retrospective study analyzed variation of ALP in relationship to myeloma response during treatment with carfilzomib, the first in a new class of selective epoxyketone PIs that has demonstrated encouraging safety and efficacy in two phase 2 studies of relapsed or refractory myeloma patients. METHODS: Retrospective analysis of serum ALP was performed on relapsed or refractory myeloma patients enrolled on two phase 2 studies (PX-171-003 and PX- 171-004) evaluating the safety and efficacy of single agent carfilzomib. We analyzed data from 38 patients in the first cohort of the PX-171-003 study, a relapsed and refractory myeloma trial for patients who have received ≥ 3 prior therapies including bortezomib and an IMiD and 29 patients in PX-171-004, a relapsed or refractory myeloma trial that included bortezomib naïve patients. All patients received 20 mg/m2 of carfilzomib on Days 1, 2, 8, 9, 15, and 16 of a 28-day cycle. RESULTS: Seventy-seven patients were enrolled. The median age was 63 years with a median time since diagnosis of 4.6 years, 52% were male, 84.% had relapsed after autologous transplants, 82.% were previously exposed to bortezomib, and 92% were previously exposed to an IMiD. Sixty seven patients with ALP data were evaluable for response. In PX-171-003 the ORR (≥PR) was 18% and the clinical benefit response (CBR; ≥MR) was 26%, while in PX-171-004 the ORR was 35.5% overall and 57% in bortezomib naive patients. ALP increment from baseline, which was most evident during the second cycle of treatment, was statistically different in patients who achieved ≥VGPR compared to all others on Days 1 (P=0.0049) and 8 (P=0.006) of Cycle 2. In all patients achieving a VGPR or better, ALP increased more than 15 units per liter at Cycle 2 Day 1 over baseline An ALP increase over the same period of time was seen in 26 %, 13%, and 11% of patients achieving PR, MR, and SD, respectively. None of the patients with progressive disease exhibited a similar increase. Our study indicates that response first assessed on Day 15 of Cycle 1 parallels the ALP elevation which returned to baseline levels at the end of Cycle 3. CONCLUSIONS: This retrospective analysis on a subset of patients in these ongoing phase 2 studies of single agent carfilzomib in relapsed or refractory multiple myeloma suggests that elevation in ALP may be associated with best response. Taken with previous publications describing bortezomib treatment, these results suggest that this specific anabolic bone phenomenon could be a class effect of proteasome inhibitors. These phase 2 studies are ongoing with a higher dose of carfilzomib (27 mg/m2) being evaluated. The data from this small subset analysis suggests that further exploration of this relationship is warranted. Disclosures: Zangari: Milllennium: Honoraria, Research Funding; Novartis: Research Funding; Celgene: Honoraria; OrthoBiotech: Honoraria; Optum Health: Honoraria; Educational Concepts Group, LLC: Membership on an entity's Board of Directors or advisory committees. Vij:Proteolix: Consultancy, Research Funding. Jagannath:Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria; Merck: Honoraria. Siegel:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Millennium: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Stewart:Millennium: Consultancy, Research Funding; Proteolix: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Celgene: Honoraria. Wang:Proteolix: Honoraria, Research Funding. Belch:Ortho Biotech: Honoraria, Research Funding. Jakubowiak:Millennium Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Centocor Ortho Biotech: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Exelixis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers-Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Trudel:Celgene: Honoraria, Speakers Bureau; Ortho Biotech: Honoraria. Bahlis:Celgene: Honoraria, Speakers Bureau; Ortho Biotech: Honoraria, Speakers Bureau. Lonial:Celgene: Consultancy; Millennium: Consultancy, Research Funding; BMS: Consultancy; Novartis: Consultancy; Gloucester: Research Funding. Singhal:Celgene: Speakers Bureau; Millennium: Speakers Bureau.

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The 3-Drug Combination Treatment ART838, ABT199 Plus Sorafenib Is Effective Against AML Xenografts, Possibly Via Cooperative Targeting of MCL1

Blood ◽

10.1182/blood-2018-99-113040 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 4044-4044

Author(s):

Blake S Moses ◽

Jennifer Fox ◽

Xiaochun Chen ◽

Samantha McCullough ◽

Sang Ngoc Tran ◽

...

Keyword(s):

Acute Leukemia ◽

Board Of Directors ◽

Cell Lines ◽

Drug Combination ◽

Research Funding ◽

Leukemia Cell ◽

Advisory Committees ◽

Leukemia Cell Lines ◽

Equity Ownership

Abstract Antimalarial artemisinins have broad antineoplastic activity in vitro, are well tolerated and inexpensive, and can be parenterally or orally administered in humans. Artemisinin-derived trioxane diphenylphosphate dimer 838 (ART838; a potent artemisinin-derivative) inhibited acute leukemia growth in vivo and in vitro, at doses where normal human CD34+ hematopoietic stem-progenitor cell clonogenicity was essentially unaffected (Fox et al, Oncotarget 2016, PMID: 26771236). In our focused drug combination screen for drugs that synergize with ART838, the only BCL2 inhibitors in the screen library of 111 emerging antineoplastic compounds, navitoclax (ABT737) and venetoclax (ABT199; FDA-approved), were identified as 2 of the top 3 candidates. Synergies between ART838 and BCL2 inhibitors were validated in multiple acute leukemia cell lines and primary cases. This ART838-BCL2 inhibitor synergy may be due to reduced levels of MCL1 protein that we and others have observed in multiple acute leukemia cell lines and primary cases treated with artemisinins (Budhraja et al, Clin Cancer Res 2017, PMID: 28974549). Treatment of acute leukemia xenografts with the ART838 plus ABT199 combination reduced leukemia growth rates and prolonged survivals, compared to vehicle or either ART838 or ABT199 alone. To add to the efficacy of this ART838 plus ABT199 treatment regimen, we sought to rationally add a third low-toxicity active antileukemic agent. Sorafenib (SOR; FDA-approved) inhibits multiple kinases which may mediate its antileukemic activity, with the importance of the targets varying from case to case; e.g. FLT3 is an important target in many AMLs. In addition, several reports have found that SOR reduces MCL1 protein stability and translation through inhibition of the ERK and PI3K pathways (Wang et al, Clin Cancer Res 2016, PMID: 26459180; Huber et al, Leukemia 2011, PMID: 21293487). In all acute leukemia cell lines tested, we observed large reductions in MCL1 protein levels with SOR treatment, which may further rationalize the addition of SOR to our ART838 plus ABT199 antileukemic regimen. We had previously observed strong in vitro synergy between ART838 and SOR (PMID: 26771236). Treatment of acute leukemia xenografts with the ART838 plus SOR combination reduced leukemia xenograft growth rates and prolonged survivals, compared to single drugs. Mice bearing luciferase-labelled acute leukemia xenografts were treated (PO daily x5) with single drug or 2-drug or 3-drug combinations of ART838, ABT199, and SOR, each at their individual maximally tolerated doses. Treatment with this 3-drug combination caused rapid regression of luciferase-labelled MV4;11 AML xenografts (Fig 1A). The 5-day treatment cycles were repeated every other week, and mice receiving this 3-drug combination survived >4 times longer than vehicle-treated mice (Fig 1B). Mouse body weights were stable during treatment. Although myelosuppression is the human clinical dose-limiting toxicity of each of these 3 drugs, mouse blood cell counts during 3-drug combination treatment were in the normal range. Treatment of a luciferase-labelled primary AML leukemia xenograft with this 3-drug combination reduced leukemia growth more than the single drugs or 2-drug combinations (Fig 1C). Assessment of efficacy and pharmacokinetics-pharmacodynamics against diverse acute leukemia xenografts will test this combination of ART838, ABT199 plus SOR as a rational low-toxicity drug triad for treatment of acute leukemias and potentially other cancers. Disclosures Fox: Intrexon Corporation: Employment. Tyner:Genentech: Research Funding; Janssen: Research Funding; AstraZeneca: Research Funding; Gilead: Research Funding; Incyte: Research Funding; Constellation: Research Funding; Array: Research Funding; Takeda: Research Funding; Vivid Biosciences: Membership on an entity's Board of Directors or advisory committees; Aptose: Research Funding. Civin:ConverGene LLC: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding; GPB Scientific LLC: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; 3DBioWorks Inc: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; BD (Becton Dickinson): Honoraria.

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Patient Reported Financial Toxicity in Acute Leukemia

Blood ◽

10.1182/blood-2018-99-119163 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 4796-4796 ◽

Cited By ~ 1

Author(s):

Thomas G. Knight ◽

Myra Robinson ◽

Michael R. Grunwald ◽

Lauren M. Bohannon ◽

Erin Blackwell ◽

...

Keyword(s):

Acute Leukemia ◽

Board Of Directors ◽

Research Funding ◽

Safety Monitoring ◽

Data Safety Monitoring Board ◽

Financial Toxicity ◽

Advisory Committees ◽

Data Safety ◽

Safety Monitoring Board ◽

Data Safety Monitoring

Abstract Background: Financial Toxicity (FT) is increasingly recognized as a major contributor to morbidity and mortality in a variety of cancers. Treatment of acute leukemia is associated with heavy healthcare utilization and high costs. The purpose of this study was to define rates, risk factors, and mortality implications for FT in patients with acute leukemia using patient reported data. Methods: All patients seen at the Levine Cancer Institute, a tertiary hospital-based leukemia practice, were surveyed prior to each visit over a six-month period. All patients were aged ≥18 years and were diagnosed with acute myeloid leukemia (AML) or acute lymphoblastic leukemia (ALL). The survey consisted of the PROMIS Global-10 measure and two questions from the COST measure. FT was defined as scoring 4 or less (maximum: 10) in agreement with the COST questions: "I know that I have enough money in savings, retirement, or assets to cover the costs of my treatment" and "I am satisfied with my current financial situation." Demographic data and disease characteristics were abstracted from the medical record. Model selection was carried out using logistic regression to identify factors impacting the incidence of financial toxicity. Correlation of numerical financial toxicity scores with PROMIS scores and with mortality data was assessed using linear regression. Results: Of the 106 patients, 58 (54%) met the definition of exhibiting FT. The factors associated with incidence of FT included: age, race, and insurance type. The odds of FT in those patients <65 years of age were 2.7 times the odds of FT in those ≥65, adjusting for race, insurance, and time since first treatment (95% CI: 0.884 - 8.438, p = .081). The odds of FT in African American patients were 4.3 times the odds of FT in Caucasian patients, adjusting for age, insurance, and time since first treatment (CI: 0.408 - 44.824, p = .150). The odds of FT in patients with Medicaid insurance were 14.2 times the odds of FT in patients with commercial insurance, adjusting for age, race, and time since first treatment (CI: 1.658 - 121.862, p = .106). Gender, distance from the hospital, type of acute leukemia, history of blood/marrow transplant, and history of relapsed disease were not found to be significant. There was a significant correlation for both the PROMIS global physical (p < .001) and mental (p < .001) scores with the FT score. Lower FT score (higher degree of FT) was associated with lower mental and physical scores. There was no statistically significant difference in survival between patients with FT scores >4 compared to patients with FT scores <=4; however, there was a trend toward decreased survival in those with lower FT scores (Figures 1 and 2). Conclusions: Patients with acute leukemia represent an extremely vulnerable population for financial toxicity with rates of distress even higher than other reported malignancies. Urgent interventions are indicated in this population. Disclosures Grunwald: Medtronic: Equity Ownership; Cardinal Health: Consultancy, Membership on an entity's Board of Directors or advisory committees; Genentech: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forma Therapeutics: Research Funding; Janssen: Research Funding; Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Alexion: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agios: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees. Avalos:Juno: Membership on an entity's Board of Directors or advisory committees. Symanowski:Five Prime Therapeutics: Other: Data Safety Monitoring Board ; Boston Biomedical: Other: Data Safety Monitoring Board ; Eli Lily & Co: Other: Data Safety Monitoring Board; Immatics: Other: Data Safety Monitoring Board.

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Bitter Taste Receptors System Is Expressed and Functional in Both HSCs and Leukemic Cells

Blood ◽

10.1182/blood-2018-99-111806 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 2560-2560

Author(s):

Valentina Salvestrini ◽

Valentina Pensato ◽

Marilena Ciciarello ◽

Giorgia Simonetti ◽

Dorian Forte ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Bitter Taste ◽

Leukemic Cells ◽

Leukemia Cells ◽

High Dose ◽

Taste Receptors ◽

Advisory Committees ◽

Hematopoietic Stem

Abstract Acute Myeloid Leukemia (AML) is a clonal disease sprouting from a rare population of leukemic stem cells. Over the past years, increasing interest is gaining the contribution that cell-extrinsic factors have in AML generation and maintenance. In this context, the ability of leukemia cells to detect changes in the microenvironment is important in responsiveness to environmental fluctuations. Bitter taste receptors (T2Rs) are typical G-protein coupled receptors and are normally found on the surface of the tongue. Recent studies showed that T2Rs are widely expressed in various parts of human anatomy and have been shown to be involved in physiology of respiratory system, gastrointestinal tract and endocrine system. thus suggesting a wider function in "sensing microenvironment". We recently reported that AML cell lines OCI-AML3, THP-1, and AML primary cells expressed fully functional T2Rs subtypes. Gene expression profile analysis showed that after T2Rs activation, leukemic cell lines underwent down-regulation of genes involved in positive regulation of cell proliferation, migration, and cell-cycle. Whereas genes involved in cell adhesion and DNA repair were up-regulated. Functional assays supported these results (Blood 2017 130:3949). In the present work, we further investigated the role of T2Rs in BM microenvironment by extending the analysis to AML primary samples and to normal hematopoietic stem cells (HSCs). Similarly to AML cell lines, T2Rs activation with high dose of agonist induced a reduction of cell viability associated to apoptosis induction, while non-toxic doses reduced cell migration and clonogenic capacity. In addition, T2Rs stimulation with agonist makes AML cell lines more prone to oxidative and metabolic stress. Leukemia cells displayed a quiescent phenotype in response to T2Rs activation suggesting that mitochondrial activity is significantly limited by T2Rs agonist treatment. Since no data are available on the presence and the function of T2Rs on normal hematopoietic stem cell counterpart, we characterized T2Rs expression on CD34+ cell isolated from healthy donor. CD34+ cells express several T2Rs subtype without significant differences compare to AML cells. Their activation with high dose of agonist reduced HSCs viability inducing apoptosis, while non-cytotoxic doses reduced clonogenic capacity and promoted migration. Given the effect of T2Rs activation on crucial AML cell function, we tested the therapeutical potential of T2R agonist with and without conventional chemioterapic agent. Interestingly we observed that T2Rs agonist have a synergistic effect with cytarabine, reducing leukemia cell viability when combined with ARA-C compared to their use as single compound. The combination allowed to reach a high toxicity using lower doses of chemotherapic agent. Overall our results indicate that T2Rs receptor system is expressed and functional in both leukemic cells and HSCs. In particular, in AML cells T2Rs activation is associated with quiescence induction and prevention of migration. T2Rs stimulation modulates HSCs function but their role need to be further deepen. These data may suggest a role for microenvironment "bitter" molecules in regulating normal and leukemic hematopoiesis. Disclosures Cavo: AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees.

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The MP0250-CP201 Mirror Study: A Phase 2 Study Update of MP0250 Plus Bortezomib and Dexamethasone in Relapse/Refractory Multiple Myeloma (RRMM) Patients Previously Exposed to Proteasome Inhibitors and Immunomodulatory Drugs

Blood ◽

10.1182/blood-2019-129827 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 1899-1899 ◽

Cited By ~ 2

Author(s):

Norbert Grząśko ◽

Stefan Knop ◽

Hartmut Goldschmidt ◽

Marc S Raab ◽

Jan Dürig ◽

...

Keyword(s):

Multiple Myeloma ◽

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Proteasome Inhibitors ◽

Immunomodulatory Drugs ◽

Phase 2 ◽

Advisory Committees ◽

Phase 2 Study ◽

Grade 3

Background Bone marrow neovascularization is a hallmark of multiple myeloma and progression is associated with a substantial increase in pro-angiogenic factors that promote bone marrow angiogenesis, including vascular endothelial growth factor (VEGF-A) and hepatocyte growth factor (HGF). At present, anti-angiogenic agents are not part of treatment strategies in multiple myeloma, neither alone nor in combination with approved agents. MP0250 is a first-in-class, tri-specific multi-DARPin® drug candidate neutralizing VEGF-A and HGF as well as binding to human serum albumin to increase plasma half-life. This is a report on early safety and efficacy of MP0250 in combination with bortezomib plus dexamethasone (Vd) in RRMM patients that have previously been exposed to proteasome inhibitors (PIs) and immunomodulatory drugs (IMiDs). Aims To assess the efficacy and safety of MP0250 in combination with bortezomib and dexamethasone in patients with RRMM (MiRRoR, NCT03136653). Trial Design This trial is recruiting adults ≥18 years of age with RRMM who have progressed after at least two prior treatment regimens including bortezomib and an IMiD. Patients were enrolled to receive iv MP0250 on day 1 + subcutaneous bortezomib 1.3 mg/m² on days 1, 4, 8, 11, oral dexamethasone 20 mg on days 1-2, 4-5, 8-9, 11-12 of each 21-day cycle. Patients will receive treatment until there is documented disease progression or unacceptable toxicity. Methods The primary endpoint is efficacy in terms of overall response rate (ORR) per International Myeloma Working Group criteria. Secondary endpoints include safety, immunogenicity, progression-free survival (PFS) and duration of response (DOR). Exploratory endpoints include overall survival, and pharmacokinetics. Exploratory biomarkers for HGF and cMET in bone marrow biopsies are detected by IHC; MM specific markers, circulating HGF and VEGF levels are measured using patient plasma samples. Results As of 01 July 2019, 20 patients (7 ongoing) received a total of 137 doses (1-33 cycles) of MP0250 at the maximum tolerated dose of 8 mg/kg on Day 1 of each 21-day cycle in combination with Vd. Median age was 61 years (46-76), median time since diagnosis was 6.7 years. Median number of prior therapies was 4 (range, 2-9). All 20 patients had prior exposure to IMiDs and PIs and 9 patients received PI-based regimens as their immediate prior line of therapy before start of MP0250 + Vd. Importantly, 6 out of these 9 patients achieved responses ≥ Partial Response (PR). Treatment had been discontinued in 40% of patients due to PD, 15% due to Adverse Event (AE), 5% due to physician's decision and in 1 case at patient's request. The most frequent drug-related grade 3/4 AEs were hypertension in 7/1 patients, thrombocytopenia in 4/1 patients, grade 3 proteinuria in 4 patients and grade 3 anemia in 4 patients. There were no infusion-related reactions. No treatment-related deaths were reported. 20 patients received ≥ 1 dose of MP0250 + Vd and had at least 1 assessment of response and were included in the efficacy analysis. 1 patient (5%) achieved Complete Response, 4 patients achieved Very Good Partial Response (20%) and 3 patients achieved PR (15%) for an ORR of 40%. DOR at cutoff date is 6 months (range, 2-21). Pharmacokinetic data show sustained exposure over multiple cycles with a mean half-life of 11 days (range, 6-17). No indication of ADA-mediated drug clearance was observed. Summary Combining MP250 at 8 mg/kg with standard doses of bortezomib and dexamethasone was generally well tolerated with discontinuation due to AE in only 15% of patients. No unexpected toxicity was observed and AEs consistent with the toxicity profile of the individual agents. Analysis of the preliminary efficacy results showed an encouraging ORR of 40%. Recruitment to this Phase 2 study is ongoing. Disclosures Knop: Janssen, AMGEN, Bristol-Myers Squibb, Celgene: Consultancy, Honoraria. Goldschmidt:Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Research Funding; John-Hopkins University: Research Funding; MSD: Research Funding; Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Adaptive Biotechnology: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Research Funding; John-Hopkins University: Research Funding; Chugai: Honoraria, Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Dietmar-Hopp-Stiftung: Research Funding; Molecular Partners: Research Funding; Mundipharma: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding. Dürig:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel support; Celgene: Consultancy, Other: Travel or accommodations, Speakers Bureau. Bringhen:Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Karyopharm: Membership on an entity's Board of Directors or advisory committees; Takeda: Consultancy; Bristol-Myers Squibb: Honoraria; Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees. Gamberi:Amgen: Honoraria; Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Sanofi: Consultancy, Membership on an entity's Board of Directors or advisory committees. Castellano Acosta:Molecular Partners AG: Employment. Lang:Molecular Partners AG: Employment. Lemaillet:Molecular Partners AG: Employment. Sudhir:Molecular Partners AG: Employment.

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Acute Leukemia of Ambiguous Lineage: A Comprehensive Survival Analysis Enables Designing New Treatment Strategies

Blood ◽

10.1182/blood.v128.22.584.584 ◽

2016 ◽

Vol 128 (22) ◽

pp. 584-584 ◽

Cited By ~ 1

Author(s):

Ondrej Hrusak ◽

Valerie De Haas ◽

Ales Luks ◽

Iveta Janotova ◽

Ester Mejstrikova ◽

...

Keyword(s):

Acute Leukemia ◽

Board Of Directors ◽

Molecular Genetics ◽

Financial Support ◽

Research Funding ◽

Residual Disease ◽

Inadequate Response ◽

Advisory Committees ◽

Travel Costs ◽

All Treatment

Abstract Acute leukemia (AL) of ambiguous lineage (AMBI-L) comprises up to 5% of AL cases in both children and adults. Although several definitions exist, a general treatment guideline has been missing. Single country studies usually report fewer than 50 cases of children or adults. Accordingly, the international iBFM AMBI2012 Study/Registry collected 275 AMBI-L cases in patients <18y from Australia, Austria, Brazil, Czechia, Germany, Greece, Israel, Italy, Netherlands, NOPHO (Denmark, Estonia, Finland, Norway, Sweden, Iceland, Latvia and Lithuania), PINDA (Chile), Poland, SAHOP (Argentina), Slovakia, St. Jude's Children Research Hospital (USA), Texas Children's Cancer Center (USA), Ukraine and United Kingdom. Each center/country reported all consecutive patients with AMBI-L from a 2 to 13 year period ending May 31, 2015. Apart from the study itself, the central database served also as a basis for consulting individual patients during the diagnostic workup. Preliminary results of this study were first introduced in ASH 2015 and now the complete detailed analysis of updated findings including significance of immunophenotype, molecular genetics, blast clearance and transplant are shown. In total, 275 patients were included in the study. Of these, 240 fulfilled the definitions of biphenotypic/mixed phenotype AL, partially overlapping with cases in whom two clones had been identified (n=68) and 15 cases presented with undifferentiated AL. Most patients started their treatment with an ALL-type protocol (n=161), 79 with AML therapy, 27 with a combined regimen, including the Interfant protocols, 2 patients were not treated, 2 received other treatment, and in 4 patients such information was missing. The 5yEFS of the entire cohort was 56±3.7% and 5y overall survival was 67±3.3%. Patients treated by ALL-type protocols had superior 5 year event free survival (5yEFS) (70±4.6%, n=158) compared to those who started AML-type treatment (5yEFS: 40±6.4%, n=78) or hybrid ALL/AML treatment (5yEFS: 50±11%, n=27). Although protocol selection was likely biased, we recommend ALL treatment, when diagnostic findings, including molecular genetics, fail to indicate AML therapy. Although myeloperoxidase (MPO) has been used as the ultimate marker of myeloid lineage, patients who started with ALL-type treatment demonstrated a better prognosis even among cases classified as MPOpos/part pos (Fig. 1). These differences by initial choice of treatment are most prominent when CD19pos/part pos cases are analyzed regardless of the overall lineage (Fig. 2). This shows that at least for CD19pos/part pos cases in the absence of RUNX1/RUNX1T1 fusion, treatment should not start with current AML-type protocols. Until week 12, patients with higher leukemia burden were slightly overrepresented compared to non-AMBI ALL patients (data not shown). In addition, patients with higher residual disease had a much poorer prognosis. Thus, Prednisone poor and good responders (based on day 8 blood blast counts) had a 5yEFS of 50±9.7%, n=38 and 81±5.8%, n=82, respectively (p=0.005). By day 15 bone marrow (BM), only cutoffs of 10-4 and 10-3 were analyzed and neither showed significant associations with EFS. At the end of induction, patients with BM residual disease ≥10-3 had a 5yEFS of 51±10%, n=49 compared to 90±4.3% for those with lower levels, n=75 (p=0.0002). Especially higher residual disease at week 12 was associated with an extremely poor EFS (Fig. 3). Early identification of patients with inadequate response and designing alternative treatment for them is our important challenge. No overall benefit of transplantation was seen in patients who started on ALL treatment or hybrid ALL/AML treatment. Again, this may be caused by a biased selection of more severe cases for transplant. In patients who started with AML treatment, transplant appeared to improve prognosis (Fig. 4). This study provides the basis for improved treatment of future patients with AMBI-L, with more accurate diagnostics. OH, AL, IJ, EM and JS were supported by Czech Health Research Council 15-28525A. Disclosures Bleckmann: JazzPharma: Other: financial support of travel costs. Moricke:JazzPharma: Honoraria, Other: financial support of travel costs. Inaba:Arog: Research Funding. Kattamis:Novartis: Honoraria, Research Funding; ApoPharma: Honoraria. Reinhardt:Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Jazz Pharma: Other: Travel Accomodation; Celgene: 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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Amino Acid Stress Response Genes Promote L-Asparaginase Resistance in Pediatric Acute Lymphoblastic Leukemia

Blood ◽

10.1182/blood-2021-152940 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3304-3304

Author(s):

Daniel Ferguson ◽

J. Robert McCorkle ◽

Qian Dong ◽

Erik Bonten ◽

Wenjian Yang ◽

...

Keyword(s):

Board Of Directors ◽

Cell Lines ◽

Research Funding ◽

Lymphoblastic Leukemia ◽

Acid Stress ◽

Leukemia Cells ◽

P Value ◽

Newly Diagnosed ◽

Advisory Committees ◽

Primary Leukemia

Abstract Understanding the genomic and epigenetic mechanisms of drug resistance in pediatric acute lymphoblastic leukemia (ALL) is critical for further improvements in treatment outcome. The role of transcriptomic response in conferring resistance to l-asparaginase (LASP) is poorly understood, beyond asparagine synthetase (ASNS). We defined reproducible LASP response genes in LASP resistant and sensitive ALL cell lines (n = 7) as well as primary leukemia samples from newly diagnosed patients. We identified 2219 response genes (absolute log 2FC > 1.5, FDR p-value <0.05) with ~16.5% being reproduced in more than one cell line. Defining target genes of the amino acid stress response related transcription factor ATF4 in ALL cell lines using ChIP-seq revealed 25% of genes that changed expression after LASP treatment were direct targets of the ATF4 transcription factor. A total of 17,117 significantly differentially bound ATF4 sites were identified (FDR p-value <0.01) and 97.8% of these sites displayed an increase in ATF4 binding following LASP treatment. SLC7A11 was found to be a response gene in cell lines and patient samples as well as a direct target of ATF4. SLC7A11 was also one of only 2.4% of response genes with basal level gene expression that also correlated with LASP ex vivo resistance in primary leukemia cells from 212 newly diagnosed children enrolled on St. Jude Total Therapy 16. Experiments using chemical inhibition of SLC7A11 with sulfasalazine, gene overexpression, and partial gene knockout recapitulated LASP resistance or sensitivity in ALL cell lines. These findings show the importance of assessing changes in gene expression following treatment with an antileukemic agent for its association with drug resistance and highlights that many response genes may not differ in their basal expression in drug resistant leukemia cells. Disclosures Stock: Pfizer: Consultancy, Honoraria, Research Funding; amgen: Honoraria; agios: Honoraria; jazz: Honoraria; kura: Honoraria; kite: Honoraria; morphosys: Honoraria; servier: Honoraria; syndax: Consultancy, Honoraria; Pluristeem: Consultancy, Honoraria. Mullighan: Amgen: Current equity holder in publicly-traded company; Illumina: Membership on an entity's Board of Directors or advisory committees; AbbVie: Research Funding; Pfizer: Research Funding. Pui: Adaptive Biotechnologies: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: Data Monitoring Committee. Evans: Princess Máxima Center for Pediatric Oncology, Scientific Advisory Board, Chair: Membership on an entity's Board of Directors or advisory committees; BioSkryb, Inc.: Membership on an entity's Board of Directors or advisory committees; St. Jude Children's Research Hospital, Emeritus Member (began Jan 2021): Ended employment in the past 24 months.

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Resistance to Danusertib (formerly PHA-739358) in BCR-ABL-Positive Cells Is Mediated by Upregulation of the Drug Transporter Abcg2 and Can Be Suppressed in Vitro by Combination Treatment with Imatinib.

Blood ◽

10.1182/blood.v114.22.1724.1724 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1724-1724

Author(s):

Tim H Brummendorf ◽

Artur Gontarewicz ◽

Gunhild Keller ◽

Jürgen Moll ◽

Melanie Braig ◽

...

Keyword(s):

Stem Cells ◽

Combination Therapy ◽

Board Of Directors ◽

Research Funding ◽

Aurora Kinase ◽

Epigenetic Mechanism ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Resistant Cells

Abstract Abstract 1724 Poster Board I-750 The success of imatinib (IM, formerly STI571, Gleevec®) in the treatment of chronic myeloid leukemia (CML) is compromised by the development of primary or acquired IM-resistance, particularly in advanced phase disease as well as by a limited IM-effect on immature hematopoietic stem cells, emphasizing the need for novel therapeutic strategies. The small molecule inhibitor Danusertib (formerly PHA-739358) potently inhibits Aurora and ABL kinases. Here, the individual contribution of each pathway to the effect of Danusertib was investigated. Starting at very low concentration, a dose-dependent reduction of BCR-ABL activity was observed, whereas inhibition of Aurora kinase activity, assessed by phosphorylation of histone H3-Ser10, required substantially higher concentrations. In primary CD34+ CML cells, including initially quiescent leukemic stem cells, combination therapy with IM and Danusertib revealed a synergistic anti-proliferative activity, which also affected immature CD34+38- cells. Neither mono- nor combination therapy led to substantial induction of apoptosis in quiescent stem cells. Interestingly, under treatment with Danusertib, the emergence of resistant clones in a well-established murine Ba/F3-p210 cell model was considerably less frequent than with IM. Surprisingly, Danusertib-resistant cells did not have mutations in BCR-ABL or Aurora kinase domains and remained IM-sensitive. Analysis of resistance mechanisms using DNA-microarray suggests an overexpression of Abcg2 efflux transporter to be causative for the resistance arising under Danusertib treatment. In support of this finding, stable retroviral overexpression of Abcg2 in parental Ba/F3-p210 cells induced a resistant phenotype against Danusertib. Furthermore, the Abcg2 inhibitor Fumitremorgin C (FTC) could restore the sensitivity of resistant cells to Danusertib. Finally, significant re-expression of Abcg2 in parental Ba/F3-p210 cells upon treatment with the demethylating agent 5-Azacytidine suggests that an epigenetic mechanism might play a role in the regulation of Abcg2 gene expression in resistant clones. Detailed analyses of the methylation patterns of the Abcg2 promoter region are currently being performed. In conclusion, simultaneous in vitro exposure of Ba/F3-p210 cells to Danusertib and IM significantly reduced the emergence of drug resistance, raising hope that both epigenetic modulation of drug transporters involved in development of resistance as well as hypothesis-driven combinations of kinase inhibitors may eventually achieve durable disease control even in 2nd and 3rd line treatment of CML. Disclosures Brummendorf: Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Moll:Nerviano MS: Employment. Jost:MSD: Research Funding. Bokemeyer:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees. Holyoake:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol Myers Squib: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Balabanov:Novartis : Research Funding; Bristol Myers Squibb: Research Funding.

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Vemurafenib (VEM) in Relapsed Refractory Multiple Myeloma Harboring BRAFV600 Mutations (V600m): A Cohort of the Histology-Independent VE-Basket Study

Blood ◽

10.1182/blood.v126.23.4263.4263 ◽

2015 ◽

Vol 126 (23) ◽

pp. 4263-4263 ◽

Cited By ~ 7

Author(s):

Noopur Raje ◽

Ian Chau ◽

David M. Hyman ◽

Vincent Ribrag ◽

Jean-Yves Blay ◽

...

Keyword(s):

Multiple Myeloma ◽

Board Of Directors ◽

Clinical Benefit ◽

Research Funding ◽

Progressive Disease ◽

Single Agent ◽

Proteasome Inhibitors ◽

Advisory Committees ◽

Equity Ownership ◽

Stage 1

Abstract Background: Whole-genome sequencing has identified a 4-6% incidence of BRAF mutations in multiple myeloma (MM). We undertook a histology-independent, "basket" study of VEM in BRAF V600m-positive cancers (NCT01524978). Six disease cohorts were prespecified; remaining tumors were classified in a 7th "all-comers" cohort. Here we present preliminary efficacy and safety data for the MM cohort. Methods: A multicenter, Simon, 2-stage adaptive design in patients with relapsed refractory BRAF V600m-positive MM who were receiving VEM (960 mg bid) until disease progression (PD) or unacceptable toxicity was used. Primary end point is investigator-assessed response rate (RR) at week 8 by International Myeloma Working Group criteria. Secondary objectives include overall RR, clinical benefit rate, duration of response, progression-free survival, overall survival, and safety. Stage 1 was complete after the 7th patient received a minimum of 8 weeks of treatment, died, or withdrew early from the study. Results: Eight patients had been enrolled in the MM cohort at the time of the data cutoff (December 3, 2014). Data are presented on patients in stage 1. Twelve patients were screened, of which 4 patients did not meet eligibility criteria. Of the 8 patients enrolled in the study, 6 were men and 2 were women, with a median age of 64 years (range, 55-68). High-risk features were seen in 3 patients by cytogenetics and fluorescence in situ hybridization (FISH). Prior treatment included immunomodulators (IMiDs) in 100% of patients, proteasome inhibitors in 75%, and chemotherapy (melphalan, bendamustine, cytoxan, doxorubicin, etoposide, and cisplatin) in 87.5%. Patients had received between 2 and 7 lines of treatment before enrolling in the BASKET trial, and 5 were refractory to IMiDs or proteasome inhibitors, or both. Median duration of treatment was 3.3 months (range, 1-5) at the time of data cutoff; 3 patients continue to be treated and 5 patients discontinued study drug. Response data were available for 7 patients at the end of 2 cycles. One patient achieved partial response (PR); 4 patients had stable disease; 1 patient had progressive disease; and 1 patient response was reported as not evaluable (objective response rate [ORR] week 8, 14%; 95% confidence interval [CI], 0.4-57.9). Of the patients enrolled, 71% (95% CI, 29.0-96.3) had clinical benefit with single-agent VEM. Responses occurred beyond 2 cycles: 1 patient went on to achieve very good PR (after cutoff date, January 2015). Three patients experienced disease progression between study days 57 and 85, and 1 of these patients died as a result of progressive disease. Single-agent VEM was well tolerated, with a safety profile similar to that observed in melanoma patients. Seven patients (88%) had at least 1 adverse event (AE) of grade 3 or 4, and 3 patients (38%) had at least 1 serious AE, including sepsis and lower respiratory tract infection, that was attributable to the underlying disease. Toxicity was manageable, and 1 patient discontinued treatment because of lower respiratory tract infection and skin lesions. Dose modification was necessary in 5 of 8 patients because of toxicity. Conclusions: This is the first mutation-specific clinical trial in MM. VEM has promising activity in patients with BRAF V600m-positive MM despite these patients being heavily pretreated. Because obvious clinical benefit for patients has been observed, the decision to recruit additional patients was made, and recruitment is ongoing. Updated efficacy results from all patients currently participating in the study will be presented. Disclosures Raje: Amgen: Consultancy; Celgene: Consultancy; Astra Zeneca: Research Funding; Eli Lilly: Research Funding; BMS: Consultancy; Roche: Consultancy; Takeda: Consultancy; Onyx: Consultancy. Off Label Use: Vemurafenib is a potent inhibitor of BRAF mutated at codon 600 (BRAFV600). Here we explored the efficacy of vemurafenib in multiple myeloma patients with BRAFV600 mutations.. Chau:Roche: Research Funding. Hyman:Chugai Pharma: Consultancy; Biotherapeutics: Consultancy; Atara: Consultancy, Honoraria. Ribrag:Gilead: Membership on an entity's Board of Directors or advisory committees; Esai: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; Servier: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmamar: Honoraria, Membership on an entity's Board of Directors or advisory committees. Blay:roche: Research Funding. Tabernero:Taiho: Consultancy; Millennium: Consultancy; Merck: Consultancy; Amgen: Consultancy; Imclone: Consultancy; Chugai: Consultancy; Merck Serono: Consultancy; Boehringer Ingelheim: Consultancy; Eli Lilly: Consultancy; Celgene: Consultancy; Sanofi: Consultancy; Roche: Consultancy; Novartis: Consultancy; Symphgen: Consultancy. Wolf:Roche: Consultancy, Equity Ownership, Honoraria, Research Funding. Sirzen:F. Hoffmann-La Roche: Employment, Equity Ownership. Faris:Merrimack Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Roche: Research Funding; N-of-One-Therapeutics: Consultancy. Kaiser:Bristol-Myers Squibb: Consultancy; Amgen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Janssen: Honoraria; Chugai: Consultancy. Veronese:F. Hoffmann-La Roche: Employment. Makrutzki:F. Hoffmann-La Roche: Employment. Lasserre:F. Hoffmann-La Roche: Employment, Other: Unspecified, Patents & Royalties. Puzanov:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Baselga:Roche: Consultancy.

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