FLT3 Receptor Tyrosine Kinase Inhibitor Research Articles

Synergistic effect of a novel autophagy inhibitor and Quizartinib enhances cancer cell death

Drug combinations have been increasingly applied in chemotherapy as a strategy to enhance the efficacy of anti-cancer treatment. The appropriate drug combinations may achieve synergistic effects beyond monotherapies alone. AC220 (Quizartinib), an FLT3 receptor tyrosine kinase inhibitor, developed for the treatment of AML, has been tested in phase II human clinical trials. However, AC220 as a monotherapy is not efficacious enough. In this study, we performed a small-molecule screening of 12 640 compounds in order to find a compound that increase the AC220 efficacy in chemotherapy. We identified that TAK-165, a HER2 inhibitor, even when used at low nanomolar doses in combination with AC220, was able to induce cell death in different cancer cells, but not in non-cancer cell lines. We showed that TAK-165 and AC220 act synergistically to downregulate key signaling pathways and potently induce cancer cell death. Furthermore, we demonstrated that TAK-165 inhibited autophagy in a HER2-independent manner. Finally, we showed that the combination of TAK-165 and AC220 induced cell death in cancer cells through the activation of chaperone-mediated autophagy. Overall, these findings support the strategy for using AC220 and an autophagy inhibitor such as TAK-165 in a combinatorial treatment to enhance the efficacy of cancer therapies.

Quizartinib Significantly Improves Overall Survival in FLT3-ITD Positive AML Patients Relapsed after Stem Cell Transplantation or after Failure of Salvage Chemotherapy: A Comparison with Historical AML Database (UK NCRI data)

Introduction: The prognosis of patients with a FLT3-ITD mutation in acute myeloid leukemia (AML) is worse than FLT3 wild type patients, with increased early relapse including after allogeneic stem cell transplantation (SCT) and with a poor response to salvage. FLT3-ITD mutant patients who relapse after SCT or fail salvage chemotherapy have a dismal prognosis with no approved treatment options. Quizartinib (AC220), an oral FLT3 receptor tyrosine kinase inhibitor, has shown a remission rate of 44%, and median overall survival of 23 weeks in FLT3-ITD mutant patients who were relapsed or refractory to 2nd line treatment, or relapsed following SCT in a non-randomised phase 2 study [1]. While these outcomes compare favourably to published data, which give a median survival of 1.5 months in all comers [2], and median survival in FLT3-ITD mutant patients of 13 weeks following first relapse [3], there is an overall paucity of data available for the FLT3-ITD+ subpopulation examined in the quizartinib studies . The UK NCRI database is the largest dataset for FLT3-ITD+ AML patients, containing 6872 patients with ITD status (1388 mutant) and systematic collection of data from diagnosis with follow-up for at least 5 years or to death.Methods: 97 FLT3-ITD+ patients from the AC220-002 study who had received intensive chemotherapy, and had either relapsed following SCT (n=39); or were relapsed (n=53) or refractory (n=5) following salvage therapy prior to enrolment were identified. The equivalent eligibility criteria were applied to the UK MRC/NCRI database of AML trial patients treated intensively from 1988-2013 who had confirmed FLT3-ITD mutation: 183 patients matching the same criteria were identified (post-SCT n= 65; relapsed n=99; refractory n=19). Patients in this group received only recognised intensive chemotherapy regimens prior to fulfilling the eligibility criteria. To reflect the screening period in AC220-002, patients in the MRC/NCRI cohort entered the analysis 14 days following being identified as relapsed/refractory. The primary endpoint was overall survival. Multivariable Cox/logistic regression was performed stratified for known prognostic factors, including route to eligibility (post SCT/relapsed/refractory). Sensitivity analyses were performed excluding deaths within 14 and 28 days from eligibility from the MRC/NCRI cohort only to allow for patients who might not have been considered for quizartinib treatment on grounds of fitness.Results: There was no significant difference in the ages of the two cohorts (median age AC220-002 47y vs. MRC 48y). Outcomes in the MRC/NCRI cohort did not improve over time from 1988-2013 (p=0.7). Analyses were performed adjusted for route to eligibility, ITD allelic ratio, duration of remission (in relapsed patients), and cytogenetics. Overall survival was improved in the Quizartinib patients (adjusted hazard ratio (HR) 0.40 (0.29-0.55) p<.0001), with no interaction with route to eligibility (p=0.4). Median survival was 231 vs 60 d for relapse post SCT, 128 vs 53 d in relapsed patients, and 146 vs 61 d in refractory patients. Response rates (CRc) overall were 43% vs 11% (adjusted OR 0.24 (0.10-0.61) p=0.002). In sensitivity analyses excluding deaths within 14 days (HR 0.50 (0.36-0.69), p<.0001) and 28 days (HR 0.5 (0.38-0.76) p=0.0004) within the MRC/NCRI cohorts quizartinib retained superiority.Discussion: Quizartinib has previously shown activity in relapsed/refractory patients in a large Phase 2 single arm study, and is currently being studied in a randomized Phase 3 study vs. standard salvage chemotherapy. This analysis examines a patient population that has failed salvage therapy or SCT and for whom there is no standard therapy. It confirms the prolonged overall survival seen in the Phase 2 study when compared to an equivalent large historical cohort of previously intensively treated patients from the UK MRC/NCRI trials, with median survival in quizartinib patients was 159 days compared to 56 days in the historical cohort. Even if deaths within 28 days are excluded entirely from the MRC/NCRI group, there is a highly significant survival benefit for quizartinib. Overall, the activity seen in the AC220-002 Phase 2 study is greater than that seen in comparable patients in a large historical cohort.[1] Levis M et al. ASH meeting Abstr 615, 2014. [2] Giles F et al. Cancer 104 (3), p547, 2005. [3] Ravandi F et al. Leukemia Research 34, p752, 2010. [Display omitted] DisclosuresOff Label Use: Quizartinib for AML. Gammon:Ambit: Employment. Trone:Ambit: Employment.

Results of a Phase 1 Study of Quizartinib (AC220) As Maintenance Therapy in Subjects with Acute Myeloid Leukemia in Remission Following Allogeneic Hematopoietic Cell Transplantation

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. Hematopoietic cell transplantation (HCT) is a recommended treatment for patients with FLT3-ITD(+) AML. However, a high rate of relapse after a HCT is observed when compared to FLT3-ITD(-) patients with the 2 year relapse rate of 30% vs. 16% in FLT3-ITD(+) and FLT3-ITD(-) patients, respectively (Brunet, J. Clin. Oncol. 2012). Quizartinib (AC220) is an oral FLT3 receptor tyrosine kinase inhibitor that has shown a high level of single agent activity in nearly 500 patients with FLT3(+) relapsed or refractory AML and is currently in a Phase 3 study.This Phase 1 study examined maintenance therapy with quizartinib in AML patients (aged 18 years or older) in remission after receipt of an allogeneic HCT. Dose escalation was conducted using a modified 3+3 design, where 6 subjects were enrolled at each dose level. Two dose levels were tested; dose level 1 (DL1) at 40 mg and dose level 2 (DL2) at 60 mg given daily in continuous 28 day cycles. Dose limiting toxicities (DLTs) were assessed for the first 2 cycles and subjects were allowed to continue up to a maximum of 24 cycles.Thirteen subjects were recruited and enrollment was completed in June 2013. The median age was 43 (range 23 to 61) years. All subjects had received an HLA-matched allogeneic HCT (3 related and 10 unrelated) a median of 56 (range 41 – 70) days before study enrollment. All subjects were positive for the FLT3-ITD mutation by local testing at the time of diagnosis.Seven subjects were enrolled at DL1, including one who relapsed after 22 days on study and was replaced per protocol as deemed not evaluable for DLTs. There was 1 DLT of Grade 3 gastric hemorrhage which resolved and the subject was able to continue on a reduced dose (30 mg) of quizartinib. Six subjects were enrolled at DL2, including one subject who experienced 1 DLT of Grade 3 anemia but was able to continue on a reduced dose (30 mg).Of the 13 total subjects, 10 (77%) received quizartinib for more than a year. Six (45%) subjects are continuing to receive quizartinib currently (15, 16, 18, 18, 23, and 23 cycles) and 2 (15%) subjects have completed 24 cycles. Three subjects (23%) discontinued due to AE: Grade 4 neutropenia (Cycle 4), Grade 2 corneal epithelium defect (Cycle 9), and Grade 3 autoimmune hemolysis (Cycle 15); 1(8%) discontinued for disease relapse (Cycle 1) and 1 (8%) for protocol non-compliance (Cycle 13).The most common (≥20%) treatment-related adverse events (AEs) were diarrhea (38%; 5 subjects), neutropenia (31%; 4 subjects), nausea (23%; 3 subjects) and leukopenia (23%; 3 subjects).This is the first study conducted to determine whether or not quizartinib can be safely administered as post-transplant maintenance therapy in patients with AML. The data from this study support the use of post-transplant maintenance therapy with quizartinib and show early evidence indicating a reduced relapse rate with only 1 relapse reported out of 13 subjects, which compares favorably to historical reference data. No MTD was identified but 60 mg daily was selected as the highest dose for continuous daily administration based on Phase 2 study data in relapsed or refractory subjects (J Cortes, Blood (ASH Annual Meeting Abstracts) 2013 [Abstract]). Quizartinib maintenance has been included in the current Phase 3 QUANTUM-R study comparing quizartinib vs. salvage chemotherapy in relapsed or refractory FLT3-ITD(+) AML. DisclosuresSandmaier:Astellas Pharma, Inc: Research Funding; Ambit Bioscience Corporation: Research Funding. Khaled:Ambit Bioscience Corporation: Research Funding; Astellas Pharma, Inc: Research Funding. Oran:Astellas Pharma, Inc: Research Funding; Ambit Bioscience Corporation: Research Funding. Gammon:Ambit Bioscience Corporation: Employment, Equity Ownership. Trone:Ambit Bioscience Corporation: Employment, Equity Ownership. Frankfurt:Astellas Pharma, Inc: Research Funding; Ambit Bioscience Corporation: Research Funding.

Over-expression of FoxM1 is associated with adverse prognosis and FLT3-ITD in acute myeloid leukemia

Forkhead box M1 (FoxM1) drives cell cycle progression and the prevention of growth arrest and is over-expressed in many human malignancies. However, the characteristics of FoxM1 in acute myeloid leukemia (AML) are not clearly understood. We investigated the expression level of FoxM1 and analyzed the correlation of FoxM1 expression with AML patient characteristics and prognoses. Changes in FoxM1 expression were detected after MV4–11 cells, which have an internal tandem duplication (ITD) of the fms-like tyrosine kinase 3 gene (FLT3-ITD), and control THP1 cells (encoding wild-type FLT3) were treated with the FLT3 receptor tyrosine kinase inhibitor AC220 (quizartinib) or FLT3 ligand (FL). Finally, we determined the apoptosis rates after the addition of the FoxM1 inhibitor thiostrepton (TST) to AML cells with or without FLT3-ITD. The expression of FoxM1 in AML patients was correlated with the presence of FLT3-ITD, genetic groups, and possibly overall survival. Inhibition of FLT3-ITD by AC220 down-regulated FoxM1 expression in MV4–11 cells, and stimulation of FLT3 by FL up-regulated FoxM1 expression in MV4–11 and THP1 cells. TST induced the apoptosis of MV4–11 and THP1 cells in a dose-dependent manner. Thus, FoxM1 is a potential prognostic marker and a promising therapeutic target in AML.

Results Of a Phase 1 Study Of Quizartinib (AC220, ASP2689) In Combination With Induction and Consolidation Chemotherapy In Younger Patients With Newly Diagnosed Acute Myeloid Leukemia

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 has shown the highest level of single agent activity seen with a FLT3 targeted agent in FLT3+ relapsed AML to date. This Phase 1 dose escalation study is the first study to report data with quizartinib in combination with standard induction and consolidation chemotherapy in patients aged 18-60 years with newly diagnosed AML, regardless of FLT3-ITD status. The dose escalation was conducted using a modified 3+3 design, where 6 pts were enrolled at each dose level. The pts were given cytarabine 200 mg/m2 x 7 days and daunorubicin 60 mg/m2 x 3 days (7+3) for induction and high dose cytarabine 3 g/m2(HiDAC) q12hours on days 1, 3, and 5 for consolidation. Quizartinib was administered daily for either 7 or 14 days, starting at Day 4 of induction and/or consolidation chemotherapy. Patients were allowed to proceed directly to a stem cell transplant after achieving a response or receive further quizartinib as maintenance therapy after consolidation if they were not transplant eligible. Three dose levels were tested; dose level 1 (DL1) at 60 mg for 7 days, dose level 2 (DL2) 60 mg for 14 days, and dose level -1 (DL-1), 40 mg for 14 days. Through May 31, 2013 18 pts were enrolled in the study, and the safety information at all 3 dose levels are presented.The median age of pts was 43 years (range 22 to 60). Of the 18 patients, 16 had the FLT-ITD mutation.At DL1, one of the 6 patients had a DLT (grade 3 hyponatremia). At DL2, two of the 6 patients had a DLT (grade 3 QTc prolongation and grade 4 pericarditis) which exceeded the pre-specified criteria so DL-1 was then explored. At DL-1, one of the 6 patients had a DLT (grade 3 constrictive pericarditis).The most common (20%) treatment-related adverse events (AEs) were nausea (42%), diarrhea (32%), anemia (26%), febrile neutropenia (26%), neutropenia (21%), fatigue (21%), pyrexia (21%) and thrombocytopenia (21%). The most common (10%) Grade 3 or 4 treatment-related AEs were febrile neutropenia (26%), thrombocytopenia (21%) anemia (21%)), neutropenia (21%), leucopenia (16%), and nausea (11%).The data from this Phase 1 study demonstrates for the first time that quizartinib can be safely administered with induction and/or consolidation chemotherapy in newly diagnosed younger patients with AML. The MTD was identified as 40 mg for 14 days or 60 mg for 7 days. The efficacy results from this Phase 1 study will be available at the time of presentation. Based on these findings, multiple Phase 3 studies in newly diagnosed AML patients are planned. Disclosures:Altman:Novartis: Consultancy; Araid: Consultancy; BMS: Consultancy; Teva: Consultancy; Astellas: Consultancy. Foran:Astellas: Research Funding. Trone:Ambit: Employment. Gammon:Ambit: Employment. Cortes:Ambit: Research Funding.

Results Of a Phase 2 Randomized, Open-Label, Study Of Lower Doses Of Quizartinib (AC220; ASP2689) In Subjects With FLT3-ITD Positive Relapsed Or Refractory Acute Myeloid Leukemia (AML)

▪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 has shown the highest level of single agent activity seen with a FLT3 targeted agent in FLT3+ relapsed AML to date. This Phase 2 study was conducted to assess the efficacy and safety of two lower doses of quizartinib monotherapy in FLT3-ITD positive (+) pts aged 18 yrs or older with AML relapsed or refractory to 2nd-line, salvage chemotherapy or relapsed after hematopoietic stem cell transplantation (HSCT) to identify the optimal dose for future studies. The co-primary endpoints of the study were the composite complete remission (CRc) rate, which included complete remission (CR), complete remission with incomplete platelet recovery (CRp), and complete remission with incomplete hematologic recovery (CRi) and the rate of grade ³2 QTc prolongation. The Phase 2 study enrolled a total of 76 pts who were randomized to either 30 mg or 60 mg daily.Preliminary data from the entire study of 76 pts are included here; updated information will be provided for presentation. Thirty eight patients each were randomized to each arm and treated continuously during 28-day cycles. 58% of the randomized patients were male. The pts had a median age of 53 yrs (range 19 to 77).For 30 mg pts the derived CRc rate was 50% (5% CR, and 45% CRi). For 60 mg pts the CRc rate was 50 % (3% CR, 3% CRp, and 45% CRi). 29% of pts at 30mg and 37% of pts at 60mg were successfully bridged to HSCT.Efficacy Results in AML Pts Relapsed/Refractory to 2nd-line Therapy or HSCTThe rate of grade 2 or higher QTc prolongation assessed by central reading was 11% and 17% in 30 mg and 60 mg arms respectively, grade 3 QT prolongation was 3% in both arms and there was no grade 4. The mean maximum prolongation from baseline was 31.5 ms and 39.7 ms in 30 mg and 60 mg arms respectively.A majority of patients (78%) had a treatment related adverse event. The most common (10%) treatment-related adverse events (AEs) were anemia (18%), nausea (15%), fatigue (12%) and diarrhea (11%). Sixteen patients (22%) had a serious adverse event (SAE) possibly related to study drug. The most common (5%) treatment-related SAE was febrile neutropenia (5%). A total of 4 pts (5%) experienced a treatment-related AE resulting in discontinuation of quizartinib.The data from this Phase 2 study confirm the high degree of activity of quizartinib monotherapy in FLT3-ITD(+) AML pts relapsed/refractory to 2nd-line treatment or HSCT, previously shown in the larger Phase 2 ACE study of 333 patients treated at higher doses (90mg, 135mg or 200mg). Importantly, 25 of 76 pts (33%) were successfully bridged to a potentially curative HSCT, an almost identical rate to that seen with higher doses. The safety profile is improved specifically decreasing QT prolongation rate at lower doses. Other safety findings were manageable, and were primarily gastrointestinal adverse events and myelosuppression. The data from this Phase 2 study confirms an improved risk:benefit profile with lower doses of quizartinib and multiple randomized Phase 3 studies with quizartinib in both relapsed and newly diagnosed AML patients are planned. Disclosures:Cortes:Ambit: Research Funding. Schiller:Astellas: Consultancy. Trone:Ambit: Employment. Gammon:Ambit: Employment. Goldberg:Astellas: Research Funding. Marie:Astellas: Travel expenses and medical writing services provided by Astellas Other. Martinelli:Pfizer: Consultancy; BMS: Consultancy, Speakers Bureau; Ariad: Consultancy; Novartis: Consultancy, Speakers Bureau. Levis:Ambit Biosciences: Consultancy, Research Funding.

Final Results of a Phase 2 Open-Label, Monotherapy Efficacy and Safety Study of Quizartinib (AC220) in Patients ≥ 60 Years of Age with FLT3 ITD Positive or Negative Relapsed/Refractory Acute Myeloid Leukemia

AbstractAbstract 48FMS-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 YrsFLT3-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, weeks12.722.1Median overall survival, weeks25.319.0CRc = 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.

Final Results of a Phase 2 Open-Label, Monotherapy Efficacy and Safety Study of Quizartinib (AC220) in Patients with FLT3-ITD Positive or Negative Relapsed/Refractory Acute Myeloid Leukemia After Second-Line Chemotherapy or Hematopoietic Stem Cell Transplantation

AbstractAbstract 673FMS-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 HSCTFLT3-ITD(+) N = 99FLT3-ITD(−) N = 38Cumulative 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, weeks11.35.0Median overall survival, weeks23.125.6CRc = 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.

Anticancer imidazoacridinone C-1311 inhibits hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and angiogenesis

Antitumor imidazoacridinone C-1311 is a DNA-reactive topoisomerase II and FLT3 receptor tyrosine kinase inhibitor. Here, we demonstrate the mechanism of C-1311 inhibitory action on novel targets: hypoxia-inducible factor-1α (HIF-1α), vascular-endothelial growth factor (VEGF), and angiogenesis. In a cell-free system, C-1311 prevented HIF-1α binding to an oligonucleotide encompassing a canonical hypoxia-responsive element (HRE), but did not directly interfere with HIF-1α protein. Whereas C-1311 did not affect HIF-1α transcription, at higher concentrations (10 µM), it decreased HIF-1α protein accumulation. Furthermore, C-1311 potently reduced the transcription of HIF-1-dependent reporter gene as well as endogenous HIF-1 target gene encoding vascular endothelial growth factor. In colon cancer HCT116 and murine melanoma B16/F10 cells, C-1311-induced down-regulation of VEGF, resulted in decreased VEGF protein expression. C-1311 did not alter normoxic VEGF secretion. Consistent with VEGF depletion, C-1311 significantly affected angiogenesis in vivo. A single dose of C-1311 (40 mg/kg), inhibited angiogenesis by 70%, as measured by vascularization of Matrigel plugs in mice. Continuous low C-1311 dosing (8 mg/kg/day for 5 days) gave similar inhibition of angiogenesis (80%), suggesting that low-dose, frequent C-1311 administration may be more effective in terms of reducing toxicity. Anti-angiogenic activity of C-1311 was further demonstrated in an experimental model in which B16/F10 cells were encapsulated in alginate beads and implanted into mice. C-1311 (8 mg/kg/day for 9 days), completely abrogated vascularization of the alginate implants. Our findings indicate that C-1311 is an effective inhibitor of HIF-1α, VEGF, and angiogenesis and provide new perspectives into the mechanism of its anticancer activity