ALBERT

Description: Key Points Infiltrating FLT3-ITD neutrophils identified in skin confirms terminal differentiation of FLT3-ITD blasts after FLT3 inhibitor therapy. Neutrophilic dermatosis after FLT3 inhibition may be a manifestation of a differentiation syndrome associated with this treatment.

Description: Background: Patients with acute myeloid leukemia (AML) presenting with hyperleukocytosis have frequent complications and early mortality. Pulmonary, central nervous system, and cardiovascular complications are common. Attempts to improve outcomes in the 10% of AML patients arriving with hyperleukocytosis have included leukapheresis. No prospective randomized study has supported the use of leukapheresis, and retrospective reports have revealed persistently poor outcomes as well as emerging concerns of acquired coagulopathy and worsening hypoxemia after leukapheresis. While many centers use a leukapheresis protocol processing two blood volumes, Johns Hopkins protocol routinely processes three-five blood volumes. This study aimed to assess coagulopathy, hypoxemia, and mortality with large volume leukapheresis. Methods: 32 patients with newly diagnosed AML treated with large volume leukapheresis for WBC depletion are included in this report. Demographic, clinical, laboratory, and apheresis-related data were collected. Coagulopathy and hypoxemia-related metrics were evaluated within 6 hours before leukapheresis and within 6 hours of completion of leukapheresis. Descriptive and inferential statistics (chi square and Mann-Whitney U test) were used to compare pre and post-leukapheresis findings and assess clinical outcomes. Results: Twenty-nine of 32 (93.8%) patients presented with symptomatic leukostasis (with pulmonary and/or CNS symptoms in 26/29). Median blood volume processed was 14.8 liters (range 4-23.4L). Mean platelet count decreased from 60x109/L to 37x109/L after leukapheresis (p

Description: Background: Fms-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutations in acute myeloid leukemia (AML) are a common indication for allogeneic hematopoietic stem cell transplant (HCT) in first complete remission (CR1). Despite HCT, relapses are common and cure rates are limited thereafter. The use of FLT3 inhibitors as post-HSCT maintenance therapy has not been prospectively evaluated in the phase 3 setting. Gilteritinib is a selective, potent FLT3 inhibitor with robust activity and favorable tolerability in relapsed/refractory AML. This trial will compare the safety and efficacy of 2-year maintenance therapy with gilteritinib versus placebo in patients with FLT3-ITD+ AML in CR1 after allogeneic HSCT. The broad goal of this study is to determine if there is a benefit to FLT3 inhibition as maintenance therapy post-HCT and to identify which patients, if any, benefit. We will use a novel NGS-based assay for FLT3-ITD mutations to detect minimal residual disease (MRD) in order to stratify patients pre-HSCT and correlate with relapse post-HCT. Study Design and Methods: This Phase 3, randomized, double-blind, placebo-controlled multicenter trial (NCT02997202; Blood and Marrow Transplant Clinical Trials Network Protocol 1506), is being conducted at 149 sites worldwide. The target enrollment is 532 adult subjects (aged ≥18 years) with FLT3-ITD+ AML in CR1 who are ≥30 days and ≤90 days from scheduled allogeneic HSCT. Of these 532 subjects, 346 subjects who have achieved successful engraftment without uncontrolled graft-versus-host disease (GVHD) or other serious toxicity will be randomized (1:1; stratified by conditioning regimen intensity, time from HSCT [Day 0] to randomization [30-60 days vs 61-90 days], and presence of minimal residual disease [MRD] in the pre-transplant bone marrow sample) to receive oral gilteritinib (120 mg) or matching placebo as maintenance therapy for 2 years. The primary endpoint is relapse-free survival (RFS) in the two treatment arms; RFS will be assessed from the time of randomization to the time of death or morphologic leukemia relapse (as defined by Revised IWG criteria). MRD status will continue to be monitored over the duration of the maintenance therapy, although investigators will be blinded to the MRD assay results. Overall survival is a key secondary endpoint. Other endpoints include safety/tolerability, non-relapse mortality, event-free survival, incidences of acute/chronic GVHD, and MRD. As of July 31, 2019, 341 patients have been registered and 236 have been randomized. To achieve a target number of 346 subjects for randomization (n=173 per treatment arm), we estimated that enrollment of 532 subjects would be required given an expected dropout rate of 35% between the time of registration to the time of randomization. The RFS rate in the placebo arm (control) is assumed to be 67% at 1 year, 59% at 2 years, and 55% at 3 years (according to the Center for International Blood & Marrow Transplant Research data for FLT3-ITD+ patients transplanted in CR1 who were alive and were progression free at 60 days). A total of 122 events will provide 85% power to detect a hazard ratio (HR) of 0.57 (corresponding to a 15% difference in 2-year RFS) with two-sided significance level of 0.05. With a 2-year accrual period and a 5% annual dropout rate, enrollment of 346 subjects will ensure a high probability of obtaining 122 events. The primary efficacy analysis will be performed using the intention-to-treat (ITT) population, which is defined as all subjects who are randomized. RFS will be compared across the treatment groups using the stratified Log-rank test. A stratified Cox model with treatment as covariate will be used to determine HR and confidence intervals at 1, 2, and 3 years. Kaplan-Meier estimates of RFS will be reported at 1, 2, and 3 years. No interim efficacy or futility analyses are planned. Figure Disclosures Levis: Daiichi Sankyo Inc: Consultancy, Honoraria; Menarini: Consultancy, Honoraria; Novartis: Consultancy, Research Funding; Agios: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Astellas: Consultancy, Research Funding; FUJIFILM: Consultancy, Research Funding. Hamadani:Otsuka: Research Funding; ADC Therapeutics: Consultancy, Research Funding; Medimmune: Consultancy, Research Funding; Pharmacyclics: Consultancy; Takeda: Research Funding; Sanofi Genzyme: Research Funding, Speakers Bureau; Celgene: Consultancy; Merck: Research Funding; Janssen: Consultancy. Rosales:Astellas: Employment. Delgado:Astellas: Employment. Bahceci:Astellas: Employment, Patents & Royalties. Devine:Kiadis Pharma: Other: Protocol development (via institution); Bristol Myers: Other: Grant for monitoring support & travel support; Magenta Therapeutics: Other: Travel support for advisory board; My employer (National Marrow Donor Program) has equity interest in Magenta. Horowitz:Actinium: Other: Unrestricted educational and research grant; Gamida Cell: Other: Unrestricted educational and research grant, Research Funding; Oncoimmune: Other: Unrestricted educational and research grant; Miltenyi Biotech: Other: Unrestricted educational and research grant, Research Funding; Janssen: Other: Unrestricted educational and research grant, Research Funding; Kite Pharma/Gilead: Other: Unrestricted educational and research grant, Research Funding; Magenta: Consultancy, Other: Unrestricted educational and research grant; GlaxoSmithKline: Other: Unrestricted educational and research grant; Shire: Other: Unrestricted educational and research grant; CSL Behring: Other: Unrestricted educational and research grant, Research Funding; Seattle Genetics: Other: Unrestricted educational and research grant; Mesoblast: Other: Unrestricted educational and research grant, Research Funding; Bristol-Myers Squibb: Other: Unrestricted educational and research grant, Research Funding; Daiichi Sankyo: Other: Unrestricted educational and research grant; Sanofi: Other: Unrestricted educational and research grant, Research Funding; Pharmacyclics: Other: Unrestricted educational and research grant; Amgen: Other: Unrestricted educational and research grant; Chimerix: Other: Unrestricted educational and research grant; Regeneron: Other: Unrestricted educational and research grant. Chen:Incyte: Consultancy; Kiadis: Consultancy; Magenta: Consultancy; Abbvie: Consultancy; Takeda: Consultancy.

Description: Background AlloBMT is a potentially curative treatment for multiple myeloma (MM). However, its effectiveness has been compromised by high transplant related mortality (TRM) and acute and/or chronic graft-versus host disease (GvHD). Our development of PTCy has reduced the incidence of GvHD allowing safe and effective related haploidentical alloBMT. PTCy promotes tolerance in both alloreactive host and donor T cells, leading to suppression of both graft rejection and GVHD after alloBMT. Patients and Methods As part of an IRB-approved study we performed a retrospective analysis on all patients with MM who underwent alloBMT followed by PTCy. A total of 39 patients who were transplanted between 2003 and 2011 were identified. All patients received 2 doses of PTCy 50mg/kg on days 3 and 4 after alloBMT. High risk MM was defined as having any one of the following: del(13q) by cytogenetics or t(4;14), t(14;16), t(14;20), -17p ,+1q21 on FISH/cytogenetics. International Staging System (ISS) stage was based on beta2 microglobulin and albumin at diagnosis of symptomatic MM. The definitions of progression, stable disease and response were as per the International Myeloma Working Group criteria. Survival probability was determined using Kaplan-Meier method and differences assessed with the log-rank test. Cox regression was used to model prognostic factors with respect to progression-free (PFS) and overall survival (OS) rates. Results The median follow-up for living patients was 80 months (22-115). The minimum follow up was 23 months. The median age at BMT was 54 (range 37-70). 30 patients (77%) received a transplant from a matched sibling donor. Of the remaining 9 patients, 7 (18%) received a transplant from a haploidentical donor and 2 (5%) from a matched unrelated donor. 28 patients (72%) were in 〉 PR at the time of alloBMT. Only 1 patient (3%) was in a CR prior to alloBMT. Thirty patients (77%) received reduced intensity conditioning and the remaining 9 patients (23%) received myeloablative conditioning. 28 patients (72%) received unmanipulated bone marrow, while remaining 11 patients (28%) received mobilized peripheral blood cells. The median time between diagnosis and alloBMT was 10.6 months (4.1-178.7). Cytogenetics and FISH for evaluating high risk MM were available for 26 patients (66.6%) and of those 15 patients (58%) had high risk features. 28 patients (72%) were evaluable for ISS at diagnosis and of those 13 patients (46%) had ISS III at diagnosis. 36 patients (92%) had been treated with either bortezomib based or immunomodulatory (Imid) based therapy prior to alloBMT. 7 patients (18%) had received an autologous transplant prior to alloBMT. 20 patients (51%) are alive after a median follow up of 〉 6 years after alloBMT. Only 1 (2.5%) patient died from complications related to alloBMT. At last follow up, 6 patients (15%) are in sustained first complete remission after alloBMT. Of the 9 patients who received myeloablative prep, 6 are alive and 3 are in sustained CR. At 6 months following alloBMT, 12 patients (31%) were in a deeper response compared to their pre-transplant status. 15 patients (38%) developed 〉 grade 2 acute GvHD at a median of 1.5 (range 0.6-4.5) months. Only 3 patients (8%) developed grade 3 acute GvHD and there was no grade 4 acute GVHD. 14 (36%) patients received systemic treatment for acute GvHD. 5 (13%) patients developed chronic GvHD. The median OS was 96 months, and the median PFS was 14 months (95% CI 6.2-32.8). Chronic GvHD was significantly associated with PFS, with a median PFS of 90 months in patients who developed cGvHD compared to 11 months in patients who did not (hazard ratio = 0.3, 95% CI 0.07-1.25). The major cause of death was disease progression. Conclusion The use of PTCy led to a very low TRM in MM, including with related haploidentical donors. Although only a minority of patients maintained long-term PFS, the prolonged OS allows incorporation of novel post-alloBMT strategies to improve disease control. Disclosures: Off Label Use: Outcomes of Allogeneic Blood Or Marrow Transplantation (AlloBMT) In Multiple Myeloma With Post-Transplantation Cyclophosphamide (PTCy).

Description: Key Points Posttransplantation cyclophosphamide is effective as sole GVHD prophylaxis for myeloablative HLA-matched–related or –unrelated BMT. Despite low chronic GVHD with PTCy, relapse and survival are comparable with outcomes reported using other GVHD prophylactic approaches.

Description: Abstract 866 Acute myeloid leukemia (AML) is a hematologic malignancy characterized by increased myeloproliferation and a block in differentiation of hematopoietic stem/progenitor cells, leading to infiltration of immature blasts in the bone marrow and peripheral blood. FMS-like tyrosine kinase-3 (FLT3) is a receptor tyrosine kinase expressed in hematopoietic stem/progenitor cells. It can activate cell growth/proliferation pathways via STAT5, AKT/PI3K, and RAS/MAPK signaling. Greater than 35% of AML patients harbor a constitutively activating mutation in the FLT3 gene, and the most common type, an internal tandem duplication (ITD), confers poor prognosis. These ITD mutations typically occur in the juxtamembrane domain and consist of variable length sequence repeats. In addition, activating mutations in the kinase domain are observed in 7–10% of patients. Thus, FLT3 is a validated target for the treatment of AML. Towards this end there have been a number of clinical trials testing the clinical efficacy of FLT3 tyrosine kinase inhibitors (TKIs) in FLT3 mutant AML, either alone or combined with chemotherapy. While some patients have responded, there have been many others who fail to demonstrate significant improvement. Additionally, many patients who initially respond to FLT3 TKI have developed resistance. Inadequate achievement of FLT3 inhibition has been one of the factors limiting efficacy in these trials. This appears most often to be due to a combination of insufficiently potent drugs, decreased efficacy against some FLT3 activating mutations, high plasma protein binding, and the selection for resistance-conferring point mutations within the FLT3/ITD gene. For all of these reasons, there is the need to develop additional FLT3 TKIs able to overcome some of these limitations. We report for the first time on TTT-3002, a kinase inhibitor that has activity against FLT3 and may overcome some of the limitations that current FLT3 TKIs have demonstrated in clinical trials. TTT-3002 is one of the most potent FLT3 inhibitors discovered to date with regard to both inhibition of FLT3 autophosphorylation and cell proliferation. Utilizing human FLT3/ITD mutant leukemia cell lines the half maximal inhibitory concentration (IC50) for inhibiting FLT3 autophosphorylation was less than 250 pM. The IC50 for TTT-3002 in inhibiting proliferation in these same FLT3/ITD expressing cells was 490–920 pM. TTT-3002 also showed potent activity when tested against a broad spectrum of known, non-ITD FLT3 activating mutations, including the most frequently occurring D835Y mutation. It also shows potent activity against a number of FLT3/ITD resistance mutations that have been selected for in patients from clinical trials of other FLT3 TKI or through in vitro drug screening. Studies utilizing human plasma samples from healthy donors and AML patients determined that TTT-3002 is only moderately protein bound, resulting in high levels of free drug able to bind target, and thus maintain activity, in the presence of physiological concentrations of major human plasma proteins including alpha-1-acid glycoprotein and human serum albumin. Therefore, relatively low levels of total drug would need to be achieved in vivo to achieve an effective concentration of free drug in clinical trials. These encouraging findings have been validated both ex vivo and in vivo utilizing mouse models of FLT3-associated AML. Survival and tumor burden of mice in a number of FLT3/ITD transplant models is significantly improved by administration of TTT-3002 via oral dosing. Finally, we demonstrate that TTT-3002 is cytotoxic to leukemic blasts isolated from FLT3/ITD expressing AML patients, while displaying minimal toxicity against normal hematopoietic stem/progenitor cells from healthy bone marrow donors. Therefore, TTT-3002 has demonstrated preclinical potential as a promising new FLT3 TKI that may overcome some of the limitations of other TKI in the treatment of FLT3-mutant AML. Disclosures: No relevant conflicts of interest to declare.

Description: Key Points No overall clinical benefit was seen after the addition of lestaurtinib to standard chemotherapy for newly diagnosed FLT3-mutated AML. Lower rates of relapse and improved overall survival were seen in patients who achieved sustained levels of FLT3 inhibitory activity.

Description: Abstract 1516 Background: Sorafenib is a potent inhibitor of FLT3 kinase with demonstrable clinical activity in patients with acute myeloid leukemia (AML) and FLT3-ITD mutation, but not those with FLT3-D835 mutation. Objectives: To determine the long term outcome of patients with AML treated with the combination of Sorafenib, cytarabine and idarubicin, and in particular those with FLT3-ITD mutation. Method: Between October 2007 to March 2010, 62 patients with newly diagnosed, previously untreated AML, were treated with Sorafenib 400 mg orally twice daily (BID) for 7 days, cytarabine 1.5 g/m2 by continuous intravenous (IV) infusion daily for 4 days (3 days if 〉 60 years of age), and idarubicin at 12 mg/m2 IV daily for 3 days on an IRB-approved clinical trial. After achieving remission, patients received up to 5 cycles of consolidation with sorafenib 400 mg BID continuously and abbreviated doses of cytarabine and idarubicin given at approximately one month intervals. Results: 62 patients were treated on the phase II portion of the study. Median age was 53 years (range, 18 – 66) and 12 (19%) patients were 〉 60 years. 23 (37%) had FLT3 mutations including 17 with FLT3-ITD, 4 with FLT3-D835, and 2 with both mutations. Cytogenetics was diploid in 36 (58%), chromosome 5 and 7 deletion in 4 (6%) and 1 (2%) respectively, complex in 8 (13%), miscellaneous in 13 (21%). Median white blood cell count (WBC) at diagnosis was 7.25 × 109/L (range, 0.6 – 225), and 28 (45%) patients had WBC 〉 10 × 109/L; among these, 12 (43 %) had FLT3-ITD. After induction, 49 (79 %) patients achieved CR and 5 (8%) CR with incomplete platelet recovery (CRp). 1 (2%) patient died before response assessment could be performed and 7 (11%) were non responders. Patients with FLT3-ITD were more likely to achieve a CR/CRp than patients without FLT3-ITD [18/19 (95%) patients vs. 36/43 (83%) patients, respectively (p=0.23)]. To date, 32 (59%) of the responders have relapsed including 10 of 18 (56%) patients with FLT3-ITD and 22 of 36 (61%) patients without FLT3-ITD (P=0.86). 35 patients received salvage therapy; 14 died after receiving salvage therapy, 11 achieved a second CR and 10 were refractory. After a median follow up of 40.6 months (range, 5.7 to 50 months), the median DFS and OS were 13 months and 29 months, respectively. Hematopoietic stem cell transplantation (HSCT) was performed in 34 (55 %) patients, including 23 in CR, and 11 with active disease. Stem cell source was from related donors in 15 (44%), unrelated donors in 9 (26%), cord blood in 7 (21%), and haploidentical donors in 3 (9%) patients. Overall, 35 (56%) patients have died; 16 (26%) had infectious complications, 12 (19%) multi-organ failure, 9 (15%) graft versus host disease, and 10 (16%) other causes with some patients having overlapping causes. Three-year disease free survival (DFS)(in patients achieving CR, n=54) and overall survival (OS) (n=62) were 34% and 47%, respectively (Figures 1 and 2). Conclusion: Combination of sorafenib, idarubicin and cytarabine is an effective regimen with durable responses in patients with newly diagnosed AML, particularly those with FLT3-ITD. Disclosures: Ravandi: Bayer: Research Funding; Onyx: Research Funding.

Description: Tipifarnib (T) exhibits modest activity in elderly adults with newly diagnosed acute myelogenous leukemia (AML). Based on preclinical synergy, a phase 1 trial of T plus etoposide (E) yielded 25% complete remission (CR). We selected 2 comparable dose levels for a randomized phase 2 trial in 84 adults (age range, 70-90 years; median, 76 years) who were not candidates for conventional chemotherapy. Arm A (T 600 mg twice a day × 14 days, E 100 mg days 1-3 and 8-10) and arm B (T 400 mg twice a day × 14 days, E 200 mg days 1-3 and 8-10) yielded similar CR, but arm B had greater toxicity. Total CR was 25%, day 30 death rate 7%. A 2-gene signature of high RASGRP1 and low aprataxin (APTX) expression previously predicted for T response. Assays using blasts from a subset of 40 patients treated with T plus E on this study showed that AMLs with a RASGRP1/APTX ratio of more than 5.2 had a 78% CR rate and negative predictive value 87%. This ratio did not correlate with outcome in 41 patients treated with conventional chemotherapies. The next T-based clinical trials will test the ability of the 2-gene signature to enrich for T responders prospectively. This study is registered at www.clinicaltrials.gov as #NCT00602771.

Description: We examined 6 different FMS-like tyrosine kinase-3 (FLT3) inhibitors (lestaurtinib, midostaurin, AC220, KW-2449, sorafenib, and sunitinib) for potency against mutant and wild-type FLT3, as well as for cytotoxic effect against a series of primary blast samples obtained from patients with acute myeloid leukemia (AML) harboring internal tandem duplication (FLT3/ITD) mutations. We found that inhibition of FLT3 autophosphorylation in a FLT3/ITD specimen does not always induce cell death, suggesting that some FLT3/ITD AML may not be addicted to FLT3 signaling. Relapsed samples and samples with a high mutant allelic burden were more likely to be responsive to cytotoxicity from FLT3 inhibition compared with the samples obtained at diagnosis or those with a low mutant allelic burden. These FLT3 inhibitors varied to a considerable degree in their selectivity for FLT3, and this selectivity influenced the cytotoxic effect. These results have important implications for the potential therapeutic use of FLT3 inhibitors in that patients with newly diagnosed FLT3-mutant AML might be less likely to respond clinically to highly selective FLT3 inhibition.