Previous attempts have shown the potential of T cells in immunotherapy of cancer. Here, we report on the clinical activity of a bispecific antibody construct called blinatumomab, which has the potential to engage all cytotoxic T cells in patients for lysis of cancer cells. Doses as low as 0.005 milligrams per square meter per day in non-Hodgkin's lymphoma patients led to an elimination of target cells in blood. Partial and complete tumor regressions were first observed at a dose level of 0.015 milligrams, and all seven patients treated at a dose level of 0.06 milligrams experienced a tumor regression. Blinatumomab also led to clearance of tumor cells from bone marrow and liver. T cell-engaging antibodies appear to have therapeutic potential for the treatment of malignant diseases.

In this phase I study of relapsed/refractory NHL, continuous infusion with CD19-targeted immunotherapy blinatumomab at various doses and schedules was feasible, with an MTD of 60 μg/m(2)/day. Single-agent blinatumomab showed antilymphoma activity.

The common neurotrophin receptor, p75 NTR , has been shown to signal in the absence of Trk tyrosine kinase receptors, including induction of neural apoptosis and activation of NF-B. However, the mechanisms by which p75 NTR initiates these intracellular signal transduction pathways are unknown. Here we report interactions between p75NTR and the six members of TRAF (tumor necrosis factor receptor-associated factors) family proteins.

No abstract

CD40 is a member of the tumor necrosis factor receptor family that mediates a number of important signaling events in B-lymphocytes and some other types of cells through interaction of its cytoplasmic (ct) domain with tumor necrosis factor receptor-associated factor (TRAF) proteins. Alanine substitution and truncation mutants of the human CD40ct domain were generated, revealing residues critical for binding TRAF2, TRAF3, or both of these proteins. In contrast to TRAF2 and TRAF3, direct binding of TRAF1, TRAF4, TRAF5, or TRAF6 to CD40 was not detected. However, TRAF5 could be recruited to wild-type CD40 in a TRAF3-dependent manner but not to a CD40 mutant (Q263A) that selectively fails to bind TRAF3. CD40 mutants with impaired binding to TRAF2, TRAF3, or both of these proteins completely retained the ability to activate NF-B and Jun N-terminal kinase (JNK), implying that CD40 can stimulate TRAF2-and TRAF3-independent pathways for NF-B and JNK activation. A carboxyl-truncation mutant of CD40 lacking the last 32 amino acids required for TRAF2 and TRAF3 binding, CD40(⌬32), mediated NF-B induction through a mechanism that was suppressible by co-expression of TRAF6(⌬N), a dominant-negative version of TRAF6, but not by TRAF2(⌬N), implying that while TRAF6 does not directly bind CD40, it can participate in CD40 signaling. In contrast, TRAF6(⌬N) did not impair JNK activation by CD40(⌬32). Taken together, these findings reveal redundancy in the involvement of TRAF family proteins in CD40-mediated NF-B induction and suggest that the membrane-proximal region of CD40 may stimulate the JNK pathway through a TRAF-independent mechanism.

673 FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD) in acute myeloid leukemia (AML) are associated with early relapse after standard chemotherapy and poor survival. Quizartinib (AC220) is an oral FLT3 receptor tyrosine kinase inhibitor that is active against both ITD mutant and wild type FLT3, and has shown promising activity in a Phase 1 study of patients (pts) with AML. This Phase 2 study was conducted to assess the efficacy and safety of quizartinib monotherapy in FLT3-ITD positive (+) and FLT3-ITD negative (−) pts with a total of 333 pts included in two cohorts. Cohort 2 included pts aged ≥ 18 yrs with AML relapsed or refractory to 2nd-line, salvage chemotherapy or relapsed after hematopoietic stem cell transplantation (HSCT). A total of 137 pts were included in this cohort and constitute the basis for this analysis. Data through 31 January 2012 from 137 pts in this cohort were analyzed. These pts included 99 (72%) who were FLT3-ITD(+) and 38 (28%) who were FLT3-ITD(-). A total of 50% of the 99 FLT3-ITD(+) pts and 61% of the 38 FLT3-ITD(-) pts were male. The FLT3-ITD(+) pts had a median age of 50 yrs (range 19 to 77 yrs), and the FLT3-ITD(-) pts had a median age of 55 yrs (range 30 to 73 yrs). Pts received quizartinib at a starting dose of 90 mg/day (females) or 135 mg/day (males), and were treated continuously during 28-day cycles. The composite complete remission (CRc) rate included complete remission (CR), complete remission with incomplete platelet recovery (CRp), and complete remission with incomplete hematologic recovery (CRi). For FLT3-ITD(+) pts the CRc rate was 44% (4% CR, 0 CRp, and 40% CRi), with a median duration of response of 11.3 weeks and median overall survival of 23.1 weeks. Of those refractory to their last AML therapy, 47% achieved a CRc with quizartinib. For FLT3-ITD(-) pts the CRc rate was 34% (3% CR, 3% CRp, and 29% CRi), with a median duration of response of 5.0 weeks and median overall survival of 25.6 weeks. Of those refractory to their last AML therapy, 31% achieved a CRc with quizartinib. Efficacy Results in AML Pts Relapsed/Refractory to 2nd-line Therapy or HSCT FLT3-ITD(+) N = 99 FLT3-ITD(−) N = 38 Cumulative CRc, n (%) 44 (44) 13 (34) CRc + PR, n (%) 67 (68) 18 (47) Prior nonresponders achieving CRc to quizartinib, n (%) 27/57 (47) 9/29 (31) Subjects discontinuing quizartinib because of HSCT, n (%) 34 (34) 13 (34) Median CRc duration, weeks 11.3 5.0 Median overall survival, weeks 23.1 25.6 CRc = composite complete remission; HSCT = hematopoietic stem cell transplantation; NR = not reached; PR = partial remission. The most common (≥20%) treatment-related adverse events (AEs) were nausea (38%), anemia (29%), QT interval prolongation (26%), vomiting (26%), febrile neutropenia (25%), diarrhea (20%), and fatigue (20%). The most common (≥10%) Grade 3 or 4 treatment-related AEs were anemia (26%), febrile neutropenia (25%), thrombocytopenia (15%), neutropenia (12%), and QT interval prolongation (10%). An AE of QT interval prolongation occurred in 36/137 pts (26%) and was Grade 3 in 13 pts (10%). No Grade 4 QT interval prolongation occurred. A total of 14 pts (10%) experienced a treatment-related AE resulting in discontinuation of quizartinib. The final data from this Phase 2 study confirm the high degree of activity of quizartinib monotherapy in FLT3-ITD(+) and FLT3-ITD(-) AML pts relapsed/refractory to 2nd-line treatment or HSCT. These data represent the highest level of single agent activity observed to date for FLT3-targeted therapy in FLT3-ITD(+) relapsed/refractory AML. Of clinical significance in this heavily pretreated population, approximately 1/3 of pts were successfully bridged to potentially curative HSCT, and many pts who were refractory to prior therapy responded to quizartinib. Safety findings were manageable, and were primarily myelosuppression and QT prolongation that was mitigated with dose modifications. Further Phase 1 and 2 studies with lower doses of quizartinib as monotherapy and in combination with other agents in FLT3-ITD(+) and FLT3-ITD(-) AML are being planned/ongoing. Disclosures: Levis: Ambit Biosciences: Consultancy. Perl:Ambit Biosciences: Consultancy. Dombret:Celgene: Consultancy. Döhner:Celgene, Amgen, Lilly, Genzyme: Consultancy. Steffen:Novartis: Travel/accommodations/meeting expenses Other. Rousselot:Ambit Biosciences: Consultancy. Martinelli:BMS, Novartis; Pfizer, Roche: Consultancy. Estey:Ambit Biosciences: Consultancy. Burnett:Ambit Biosciences: Consultancy. Gammon:Ambit Biosciences: Employment. Trone:Ambit Biosciences: Employment. Leo:Ambit Biosciences: Employment. Cortes:Novartis: Consultancy.

48 FMS-like tyrosine kinase 3 internal tandem duplications (FLT3-ITD) in acute myeloid leukemia (AML) are associated with early relapse after standard chemotherapy and poor survival. Quizartinib (AC220) is an oral FLT3 receptor tyrosine kinase inhibitor that is active against both ITD mutant and wild type FLT3, and has shown promising activity in a Phase 1 study of patients (pts) with AML. This Phase 2 study was conducted to assess the efficacy and safety of quizartinib monotherapy in FLT3-ITD positive (+) and FLT3-ITD negative (-) pts with a total of 333 pts included in two cohorts. Cohort 1 included pts aged ≥ 60 yrs with AML relapsed in <1 yr or refractory to 1st-line chemotherapy. A total of 134 pts were included in this cohort and constitute the basis for this analysis. Data through 31 January 2012 from 134 pts in this cohort were analyzed. These pts included 92 (69%) who were FLT3 ITD(+), 41 (31%) who were FLT3-ITD(-), and 1 (1%) whose FLT3-ITD status was unknown. Half the 92 FLT3-ITD(+) pts and 46% of the 41 FLT3-ITD(-) pts were male. The FLT3-ITD(+) pts had a median age of 70 yrs (range 54 to 85 yrs), and the FLT3-ITD(-) pts had a median age of 69 yrs (range 60 to 78 yrs). Pts received quizartinib at a starting dose of 90 mg/day (females) or 135 mg/day (males and 1 female), and were treated continuously during 28-day cycles. The composite complete remission (CRc) rate included complete remission (CR), complete remission with incomplete platelet recovery (CRp), and complete remission with incomplete hematologic recovery (CRi). For FLT3-ITD(+) pts the CRc rate was 54% (0 CR, 3% CRp, and 51% CRi), with a median duration of response of 12.7 weeks and median overall survival of 25.3 weeks. Of those refractory to their last AML therapy, 39% achieved a CRc with quizartinib. For FLT3-ITD(-) pts the CRc rate was 32% (2% CR, 2% CRp, and 27% CRi), with a median duration of response of 22.1 weeks and median overall survival of 19.0 weeks. Of those refractory to their last AML therapy, 44% achieved a CRc with quizartinib. Efficacy Results in Relapsed/Refractory AML Pts ≥ 60 Yrs FLT3-ITD(+) (N = 92) FLT3-ITD(−) (N = 41) Cumulative CRc, n (%) 50 (54) 13 (32) CRc + PR, n (%) 66 (72) 17 (41) Prior nonresponders achieving CRc to quizartinib, n (%) 12/31 (39) 8/18 (44) Subjects discontinuing quizartinib because of HSCT, n (%) 9 (10) 1 (2) Median CRc duration, weeks 12.7 22.1 Median overall survival, weeks 25.3 19.0 CRc = composite complete remission; HSCT = hematopoietic stem cell transplantation; PR = partial remission. The most common (≥20%) treatment-related adverse events (AEs) were nausea (40%), fatigue (31%), anemia (28%), QT interval prolongation (25%), diarrhea (23%), vomiting (23%), dysgeusia (22%), and febrile neutropenia (20%). The most common (≥10%) Grade 3 or 4 treatment-related AEs were anemia (25%), febrile neutropenia (20%), QT interval prolongation (13%), and thrombocytopenia (12%). An AE of QT interval prolongation occurred in 33/134 pts (25%) and was Grade 3 or 4 in 17 pts (13%). There was 1 occurrence of Grade 4 QT prolongation with torsade de pointes. QT interval prolongations were transient, and none were fatal. A total of 17 pts (13%) experienced a treatment-related AE resulting in discontinuation of quizartinib. The final data from this Phase 2 study for elderly relapsed/refractory AML pts with few other available therapy options confirm the high degree of activity of quizartinib monotherapy in FLT3-ITD(+) pts and also suggest activity in FLT3-ITD(-) pts. These data represent the highest level of single agent activity observed to date for FLT3-targeted therapy in elderly pts with relapsed/refractory FLT3-ITD(+) AML. Of clinical significance in this elderly population, a number of pts refractory to prior therapy responded to quizartinib, with some pts (8%) able to bridge to potentially curative hematopoietic stem cell transplantation. Safety findings were manageable, and were primarily myelosuppression and QT prolongation that was mitigated with dose modifications. Results from the total study population will be presented. Further Phase 1 and 2 studies investigating lower doses of quizartinib as monotherapy and in combination with other agents in FLT3-ITD(+) and FLT3-ITD(-) AML are being planned/ongoing. Disclosures: Cortes: Novartis: Consultancy. Perl:Ambit Biosciences: Consultancy. Dombret:Celgene: Consultancy. Steffen:Novartis: Travel/accommodations/meeting expenses Other. Rousselot:Ambit Biosciences: Consultancy. Martinelli:BMS, Novartis; Pfizer, Roche: Consultancy. Estey:Ambit Biosciences: Consultancy. Burnett:Ambit Biosciences: Consultancy. Gammon:Ambit Biosciences: Employment. Trone:Ambit Biosciences: Employment. Leo:Ambit Biosciences: Employment. Levis:Ambit Biosciences: Consultancy.

Summary Pharmacological inhibitors of histone deacetylases (HDACs) are currently being developed and tested as anti‐cancer agents and may be useful to enhance the therapeutic efficiency of established anti‐myeloma treatments. This study preclinically evaluated the effects of the ‘second generation’ pan‐HDAC inhibitor JNJ‐26481585 on human multiple myeloma (MM) cells from established cell lines and primary MM samples (n = 42). Molecular responses in both groups of MM cells included histone acetylation, a shift in Bcl2‐family members towards proapoptotic bias, attenuation of growth and survival pathway activity and Hsp72 induction. Mcl‐1 depletion and Hsp72 induction were the most reliable features observed in JNJ‐26481585‐treated primary MM samples. The drug alone effectively induced myeloma cell death at low nanomolar concentrations. In vitro combination of JNJ‐26481585 with anti‐myeloma therapeutic agents generally resulted In effects close to additivity. In view of the favourable activity of this novel HDAC‐inhibitor towards primary myeloma cells further evaluation in a clinical setting is warranted.