Abstract: Factor V Leiden, (FVL) is the most common known inherited thrombotic risk factor and is present in approximately 5% of most Western populations and 25–50% of patients presenting with venous thrombosis. However, FVL is incompletely penetrant, with only approximately 10% of FVL carriers developing thrombosis in their lifetimes. Though interactions between FVL and other known prothrombotic mutations have been documented in a few cases, the genetic factors responsible for the incomplete penetrance of FVL remain largely unknown. We previously reported a remarkable synthetic lethality in mice carrying the FVL mutation and partial deficiency of a key coagulation component, tissue factor pathway inhibitor (TFPI). Complete TFPI deficiency in mice is embryonic lethal, whereas heterozygosity is compatible with normal survival. However, homozygosity for FVL (FvQ/Q) in the context of heterozygosity for TFPI (Tfpi+/−) is uniformly lethal due to disseminated perinatal thrombosis. In order to identify potential modifier genes contributing to FVL penetrance, we have utilized this lethal genetic interaction as a phenotyping tool for a sensitized ENU mutagenesis screen in laboratory mice. We hypothesize that dominant mutations in key components of the coagulation system will improve hemostatic balance and allow survival in mice carrying the lethal FvQ/Q Tfpi+/− genotype combination. As an example, we propose that loss of one tissue factor allele might compensate for reduced TFPI and rescue FvQ/Q Tfpi+/− . To test this hypothesis, we bred tissue factor heterozygous mice (Tf+/−) with FvQ/Q Tfpi+/− mice and observed complete rescue, with normal survival and the expected number (8 of 57) of FvQ/Q Tfpi+/− Tf+/− mice from a FvQ/+ Tfpi+/− Tf+/−x FvQ/Q cross. In order to identify candidate modifier genes, we performed a whole genome mutagenesis screen. In this screen, male FvQ/Q mice were mutagenized with ENU and bred to FvQ/+ Tfpi+/− double heterozygous females. DNAs from surviving offspring were PCR assayed to identify rescued mice with the FvQ/Q Tfpi+/− genotype. Analysis of 2250 offspring, corresponding to approximately half genome coverage, has identified 15 mice that survived to weaning. Heritability was demonstrated for the 5 mutant lines subjected to progeny testing to date. Genetic crosses are in progress to map the mutant genes in 3 of the 5 progeny tested lines. These preliminary results demonstrate the feasibility of this sensitized screen for the identification of dominant suppressors of thrombosis. Based on our data, we estimate that there are likely 10–20 mammalian genes for which a 〈 50% reduction in expression could result in a major shift in hemostatic balance sufficient to rescue the lethal thrombosis associated with the FvQ/Q Tfpi+/− lethal genotype. Each of these loci represent a candidate for a human modifier gene in patients with FVL and other thrombophilic mutations. Finally, the biologic pathways uncovered by these studies should provide new insights into the overall regulation of hemostatic balance and identify potential new targets for therapeutic intervention.

Abstract: Abstract 287 Purpose: Farnesyltransferases are key cellular enzymes involved in the prenylation of proteins. Prenylated proteins are important for malignant cell growth. The purpose of this phase II study (NCT00082888) was to assess tumor response and toxicity associated with the oral farnesyltransferase inhibitor tipifarnib (R115777, Johnson and Johnson) in patients with relapsed aggressive, indolent, or uncommon lymphoma. The uncommon group included low incidence lymphoma types such as Hodgkin lymphoma (HL) and T-cell non-Hodgkin lymphoma- cutaneous T-cell lymphoma (CTCL) and peripheral T-cell lymphoma (PTCL). Patients and Methods: Patients with relapsed or refractory non-Hodgkin (NHL) or Hodgkin (HL) were eligible if they had measurable disease, performance status ≤2, platelet count ≥75,000 × 10(6)/L, an absolute neutrophil count ≥1000 × 10(6)/L and a creatinine ≤2 × upper limit of normal. Patients initially received tipifarnib 300 mg twice daily, days 1–21 every 28 days. The trial was conducted by the University of Iowa/Mayo Clinic Lymphoma SPORE. Results: Ninety-three patients with lymphoma (42 aggressive, 15 indolent, and 36 uncommon) enrolled in the trial between March 2004 and November 2008. The median age was 62 years (range, 18–91). The median number of prior therapies was 5 (range, 1–17). The overall response rate (ORR) was 20% (19/93) with 6% (6/93) complete responses (CR) and 14% (13/93) partial responses (PR). The ORR was 17%, 7%, and 31% for the aggressive, indolent, and uncommon groups, respectively (Table). Among the 19 responders were 7 diffuse large B-cell lymphoma (DLBCL), 7 T-cell NHL, 1 follicular grade II, and 4 HL. The overall median response duration for the 19 responders was 7.5 months (mean, 12.8; range, 1.8 – 48.1 months). The median response duration was 11.3 months (mean, 10.1; range, 1.8 – 18.5 months), 2 months, and 7.5 months (mean, 15.5; range, 1.9 – 48.1 months) for the aggressive (7), indolent (1), and uncommon (11) groups, respectively. Five patients in the uncommon group are still receiving treatment with a range of treatment duration between 25 – 60+ months. Among the 5 still receiving treatment 4 responded and 1 is stable. The range of response duration is 15.4, 17.7, 43.1, and 48.1 months. These five patients (2 with HL, 1 anaplastic large cell cutaneous, and 2 PTCL) are currently receiving doses of 400 (1), 200 (2), and 100 (2) mg twice daily. The median time to progression for all patients was 3.6 months (95% CI: 2.1 – 4.5 months). The grade 3,4 toxicities observed were primarily fatigue (10%) and reversible myelosuppression with 11% anemia, 37% neutropenia, and 32% thrombocytopenia. Correlative studies demonstrated tipifarnib-induced upregulation of Bim, a marker of tipifarnib action in lymphoma cell lines, in 7 of 9 paired lymphoma biopsies. Conclusions: Tipifarnib has activity in lymphoma, with responses in patients with heavily pretreated DLBCL, HL and T-cell types, but little activity in follicular NHL. This agent has an excellent toxicity profile and targets a novel pathway. Further studies in combination with other agents are warranted for patients with DLBCL, HL or T-cell NHL. Disclosures: No relevant conflicts of interest to declare.

Abstract: Alvocidib has demonstrated a significant improvement in the complete response rates of newly diagnosed acute myeloid leukemia (AML) patients when administered before cytarabine and mitoxantrone (FLAM regimen) in a randomized Phase 2 study compared to 7+3, the current standard of care. Although the mechanism of action of alvocidib as a single agent is documented, the mechanism underlying synergy found in the FLAM regimen is still not fully understood. The FLAM regimen was originally developed based on the perceived benefit of time-sequential cell cycle arrest (alvocidib) followed by release of the cells from cell cycle arrest and inhibition of DNA replication (cytarabine) during S-phase. However, recent reports suggest that the transcriptional repression of key anti-apoptotic proteins (eg., MCL-1) mediated by alvocidib's CDK9 inhibition, drive the activity in the FLAM regimen. We, therefore, hypothesized that MCL-1 transcriptional repression constitutes the primary mechanism for the synergism observed with the treatment of the FLAM regimen. Here, we demonstrate that treatment with alvocidib, followed by treatment with cytarabine and mitoxantrone, is synergistic in vitro and correlates with the downregulation of MCL-1 expression. The FLAM regimen results in significant increases in caspase activity in comparison to any single agent within the combination. As has been previously reported, we also observe that increased activity of cytarabine in alvocidib-treated cells corresponds with progression into the S-phase of the cell cycle, following the washout of alvocidib. However, this observation accounts for only a small portion of the inhibition of cell proliferation. This is further confirmed by the observation that CDK4/6 (cell cycle) specific inhibitors, such as palbociclib, do not show synergistic increases in caspase activity following treatment in the same setting. In various AML cell lines treated with MCL-1 siRNA, followed by cytarabine and mitoxantrone treatment, we also observe a synergistic increase in the inhibition of cell proliferation. Therefore, considering our earlier work showing that MCL-1 dependence predicts AML patient response to the FLAM regimen, we propose that MCL-1 repression is the primary mechanism of alvocidib's biological activity and also a primary mechanism conferring resistance to cytarabine. We also conclude that the FLAM regimen is an effective regimen, clinically, in treating patients with high-risk AML, as a consequence of its inhibition of transcription via CDK9. Disclosures Kim: Tolero Pharmaceuticals: Employment. Bahr:Tolero Pharmaceuticals: Employment. Soh:Tolero Pharmaceuticals: Employment. Bearss:Tolero Pharmaceuticals: Employment. Lee:Tolero Pharmaceuticals: Employment. Peterson:Tolero Pharmaceuticals: Employment. Whatcott:Tolero Pharmaceuticals: Employment. Siddiqui-Jain:Tolero Pharmaceuticals: Employment. Weitman:Tolero Pharmaceuticals: Employment. Bearss:Tolero Pharmaceuticals: Employment. Warner:Tolero Pharmaceuticals: Employment.

Abstract: Introduction: There remains no clear standard first-line therapy for MCL. VcR-CVAD is a novel, intermediate-intensity chemoimmunotherapy regimen which incorporates bortezomib into modified hyper-CVAD chemotherapy. We hypothesized that the addition of bortezomib would improve the complete response (CR) rate, and maintenance rituximab (MR) would improve the remission duration. The results of this study were previously reported (Chang JE, et al. Br J Haematol 2011), with an observed overall response rate (ORR) of 90% (CR/unconfirmed CR in 77%), and 3-year progression-free survival (PFS) and overall survival (OS) of 63% and 86%, respectively. Long-term follow-up (LTFU) is reported from this multicenter trial. Methods: The study enrolled patients ≥18 years of age with histologically confirmed MCL. Patients were previously untreated, with the exception of 1 cycle of CHOP/CHOP-like chemotherapy. Patients received VcR-CVAD induction chemotherapy every 21 days for 6 cycles: rituximab (R) 375 mg/m2 intravenously (IV) on day 1; bortezomib/Velcade® (Vc) 1.3 mg/m2 IV, days 1 & 4; cyclophosphamide 300 mg/m2 IV every 12 hours, days 1-3 (total of 6 doses); doxorubicin 50 mg/m2 IV continuous infusion days 1-2 (total dose over 48 hours equal to 50 mg/m2); vincristine 1 mg IV day 3; and dexamethasone 40 mg orally days 1-4. Patients received G-CSF support beginning day 5-6 of each induction cycle, and all appropriate supportive care measures were permitted throughout treatment including tumor lysis prophylaxis, transfusion support and antibiotics. Patients achieving at least a partial response to induction therapy received R consolidation (R 375 mg/m2 IV X 4 weekly doses) and MR (R 375 mg/m2 IV every 12 weeks for a total of 5 years; total of 20 doses). Restaging CT scans were performed after cycles 2, 4, and 6 of induction, 12 weeks after consolidation, every 6 months during maintenance, and yearly during LTFU. The primary endpoint was ORR and CR to induction chemotherapy; secondary endpoints were PFS and OS. Results: Thirty patients were enrolled from 7/2005-5/2008. Median age was 61 years (range 48-74), 80% male, all patients had advanced stage disease, and 60% had MIPI score of medium- or high-risk disease. Six patients had blastic morphology. Long-term results are reported after a median follow-up of 7.8 years in surviving patients. Twenty patients are alive, and 15 (50%) are alive in ongoing remission (Figure 1). Estimates of 6-year PFS and OS are 53.1% and 69.8%, respectively (Table 1). The observed PFS and OS differences between patients 〈 age 60 and those ≥age 60 were not statistically significant. The observed PFS and OS differences by MIPI score were not statistically significant, although there was a trend towards worse PFS and OS for high-risk MIPI patients. Five patients have died from confirmed progression of MCL. Two deaths occurred from complications post-allogeneic transplant, and 3 deaths occurred from unrelated causes with MCL in remission. No MCL relapses have been observed beyond 5 years. No late toxicities from VcR-CVAD or from MR have emerged during the LTFU. Conclusions: VcR-CVAD is a moderate intensity chemotherapy regimen that is tolerable for many older and less fit adult patients as first-line therapy of MCL. LTFU of patients receiving VcR-CVAD induction followed by 5 years of MR demonstrates high rates of durable remission that are comparable with more intensive chemotherapy and consolidative autologous stem cell transplant (ASCT). The highly promising activity of the VcR-CVAD regimen was recapitulated in ECOG-ACRIN protocol E1405 (Chang et al, Blood 2014). A randomized phase 3 trial has recently confirmed the beneficial effects of bortezomib incorporation into standard immunochemotherapy (Robak et al, NEJM 2015). VcR-CVAD remains an effective therapy choice for initial treatment of MCL, both in younger and older MCL populations. Disclosures Kahl: Celgene: Consultancy; Seattle Genetics: Consultancy; Infinity: Consultancy; Gilead: Consultancy; Juno: Consultancy; Pharmacyclics: Consultancy.

Abstract: Mesenchymal stem cells (MSCs) contribute to the regeneration of mesenchymal tissues, and are essential in providing support for the growth and differentiation of primitive hemopoietic cells within the bone marrow microenvironment. It is becoming increasingly clear that the tumor microenvironment plays a very important role in tumor progression and drug resistance, and the selection of cancer cells possessing the mesenchymal phenotype leads to drug resistance in many different tumor types. We have been exploring the role of the protein Axl in promoting the mesenchymal phenotype in both myeloid and lymphoid malignancies, and the role of Axl in promoting drug resistance in these malignancies. The signaling downstream of Axl that leads to the acquisition of the mesenchymal phenotype has not been well elucidated. Following results from a genetic screen using a zebrafish model, we have discovered a role for retinoic acid (RA) signaling which is regulated by Axl and controls the mesenchymal phenotype in leukemic cells. In addition, recent reports have shown an interaction between a retinoic acid regulated gene, RARRES1, and Axl, leading our group to seek to understand the role of retinoic acid signaling in the control of AXL. We hypothesized that treatment with our AXL inhibitor, TP-0903, would disrupt RA signaling and lead to a reversal of the mesenchymal phenotype in leukemia cells. Following TP-0903 treatment, we interrogated changes in mRNA expression using RT-PCR, protein expression using standard immunoblotting, and endogenous RA levels using a competitive ELISA. We also assessed the effect of TP-0903 on tumor growth in an in vivo model, assessing efficacy of TP-0903 in an MV4-11 xenograft mouse model. One of the genes that we detected being dramatically changed by treatment with TP-0903 was the RA metabolizing protein CYP26A1, suggesting that Axl inhibition indeed leads to changes in RA metabolism. We observed a strong induction of CYP26 mRNA expression following RA treatment in MV4-11 leukemia cells which was also observed in treatment with our AXL inhibitor, TP-0903, at levels as low as 100 nM. We also assessed TP-0903 activity in additional cell lines (HL60, A549, and H1650), and with an alternative AXL inhibitor, R428. Importantly, TP-0903 treatment correlated with increased CYP26 expression and reduced levels of endogenous RA. In vivo, TP-0903 strongly inhibited xenograft tumor volumes by up to 100% with multiple dose levels and treatment schedules. CYP26 expression in fixed tissues correlated well with mRNA levels observed in xenograft tumors following treatment. Taken together, our observations support our hypothesis that inhibition of AXL kinase by TP-0903 can disrupt RA metabolism by inducing CYP26 expression and this disruption of RA metabolism leads to reversal of the mesenchymal phenotype in leukemic cells. Disclosures Soh: Tolero Pharmaceuticals: Employment. Bahr:Tolero Pharmaceuticals: Employment. Bearss:Tolero Pharmaceuticals: Employment. Kim:Tolero Pharmaceuticals: Employment. Peterson:Tolero Pharmaceuticals: Employment. Whatcott:Tolero Pharmaceuticals: Employment. Siddiqui-Jain:Tolero Pharmaceuticals: Employment. Bearss:Tolero Pharmaceuticals: Employment. Warner:Tolero Pharmaceuticals: Employment.

Abstract: Accurate classification and risk stratification are critical for clinical decision making in patients with acute myeloid leukemia (AML). In the newly proposed World Health Organization and International Consensus classifications of hematolymphoid neoplasms, the presence of myelodysplasia-related (MR) gene mutations is included as 1 of the diagnostic criteria for AML, AML-MR, based largely on the assumption that these mutations are specific for AML with an antecedent myelodysplastic syndrome. ICC also prioritizes MR gene mutations over ontogeny (as defined in the clinical history). Furthermore, European LeukemiaNet (ELN) 2022 stratifies these MR gene mutations into the adverse-risk group. By thoroughly annotating a cohort of 344 newly diagnosed patients with AML treated at the Memorial Sloan Kettering Cancer Center, we show that ontogeny assignments based on the database registry lack accuracy. MR gene mutations are frequently observed in de novo AML. Among the MR gene mutations, only EZH2 and SF3B1 were associated with an inferior outcome in the univariate analysis. In a multivariate analysis, AML ontogeny had independent prognostic values even after adjusting for age, treatment, allo-transplant and genomic classes or ELN risks. Ontogeny also helped stratify the outcome of AML with MR gene mutations. Finally, de novo AML with MR gene mutations did not show an adverse outcome. In summary, our study emphasizes the importance of accurate ontogeny designation in clinical studies, demonstrates the independent prognostic value of AML ontogeny, and questions the current classification and risk stratification of AML with MR gene mutations.

Abstract: The CALGB conducted a series of clinical trials with azacitidine (Vidaza®) administered subcutaneously or intravenously in patients with MDS using the FAB classification (JCO2002;20:2429). Since completion of these CALGB studies (8421, 8921, 9221), a new classification system was developed by the WHO that distinguishes MDS from AML (blasts 〉 20%). Although studies with azacitidine in patients with AML had previously shown activity, the 75 mg/m2/day dose in the CALGB studies was lower than previously studied. Using the WHO system, the diagnosis for CALGB study patients was redefined and patients with AML were analyzed separately. Most of the 105 patients were previously considered refractory anemia with excess blasts in transformation (RAEB-T). Also, new treatment response criteria for MDS were published by the IWG (Blood2000; 96:3671). Using IWG response criteria, azacitidine patients with WHO AML in studies 8421, 8921, or 9221 had an overall response rate (CR+PR+HI) of 48% (12/25), 32% (9/28), and 37% (10/27), respectively. Best Response using IWG Response Criteria for WHO AML Patients in Studies 8421, 8921, and 9221 Median duration of any response (CR, PR or HI) in the 33 azacitidine-treated responders was 279 days (range: 61 to 724 days). The median duration of CR in the 8 azacitidine-treated responders was not achieved; however, the 25th percentile was 115 days (range: 92 to 274+ days). In Study 9221, the median duration of transfusion independence (defined as ≥56 days) in patients independent at baseline was significantly longer in the azacitidine group compared with supportive care for red blood cells (azacitidine [n=8]: 411 days vs. supportive care [n=9] : 133 days, p=0.02) and platelets (azacitidine [n=13]: 363 days vs. supportive care [n=18] : 125 days, p=0.004). In the azacitidine group, 22% (6/27) of patients had a hemoglobin improvement to 〉 11 g/dL that was maintained for ≥56 days compared with 8% (2/25) in the supportive care group (p=0.2). The proportions of patients with ANC 〉 1500/m3 and platelets 〉 100,000/mm3 lasting for ≥56 days were similar between the treatment arms. Azacitidine patients with WHO AML had a longer median survival (19.3 months) compared with the supportive care group (12.9 months) (p=0.2). Further studies investigating azacitidine in patients with AML with dysplasia are warranted.

Abstract: Background. Consensus from prior studies shows that the use of maintenance therapy after completion of combination therapy leads to longer progression-free survival (PFS) for patients with multiple myeloma with some studies showing an overall survival (OS) benefit. Currently, lenalidomide is the standard of care; however, there are limited published data on long-term use regarding ability to sustain minimal residual disease (MRD)-negativity and late toxicities. We were motivated to develop a study focusing on continuous, induction-agnostic lenalidomide maintenance with integration of clinical and correlative data. Here, we report formal results of this phase II study with focus on MRD dynamics and tolerability. Methods. This single arm, phase II trial enrolled 100 evaluable patients. Lenalidomide 10 mg is given days 1-21 on a 28-day cycle. Per protocol, patients underwent bone marrow biopsies and aspirates as well as PET/CT at baseline, annually, at progression/end of study; blood work was done every 3 months. The study was statistically powered for the primary endpoint of PFS at 36 months. Correlative assays included MRD testing (10-color single-tube flow cytometry and IGHV sequencing; sensitivity ≤10-5), genomic characterization of detectable disease, and profiling of the bone marrow microenvironment performed on serially banked samples. Results. 100 evaluable patients were enrolled (63% males) between September 2015 and January 2019. Baseline characteristics include median age 63 years (range 38-87 years) and median ECOG score 1 (range 0-1). Prior to enrollment, 22 (30%) patients had high-risk FISH/SNP signature defined as one or more of: 1q+, t(4;14), t(14;16), t(14;20), and 17p- and 48 patients had undergone autologous hematopoietic cell transplantation (AHCT). At abstract submission, median cycles delivered is 39 (range 9-62). 74% of patients have completed ³24 cycles and 55% have completed ³36 cycles. Overall PFS at 36 months was 77% (95% CI: 0.69-0.87) and PFS at 60 months was 63% (95% CI: 0.51-0.78). All patients had MRD testing at least once. 46% were MRD-negative at enrollment. 7 patients who were MRD+ at enrollment converted to MRD-negative. At median follow up 39.4 months (range 7-56 months), 20/100 patients (20%) have progressed. In consideration of the entire follow-up time from initial MRD-negativity, 44 (of 95 tested; 46%) and 37 (of 73 tested; 51%) achieved sustained MRD-negativity at 1 and 2 years, respectively. 22 patients were MRD-negative at 3 years (of 51 tested; 43%). Among those who sustained MRD-negativity for 2 years, with median follow-up of 19 months past the 2-year landmark analysis (max 120 months), there were no progression events. Age, induction regimen, and MRD status at enrollment were the only significant variables associated with PFS regardless of cytogenetic risk or transplant status. At 1 and 2-year landmark analysis, MRD-negativity superseded all else as the most significant factor associated with PFS with HR 0.06(p=0.0004) and HR 1/Inf (p=0.015), respectively. Toxicities (grade 3) included neutrophil count decrease (20%), hypertension (3%), diarrhea (3%), lung infection (2%), and maculo-papular rash (2%), and toxicities (grade 4) include sepsis (2%) and platelet count decrease (7%). The most common non-grade 3/4 toxicities were diarrhea (55%), fatigue (36%), and upper respiratory infection (30%). 7% developed a secondary malignancy on study: 3 adenocarcinoma, 1 squamous cell carcinoma, 1 CMML, 1 MDS, 1 ALL, and 1 glioblastoma. One evaluable patient required dose reduction due to toxicities/tolerability. Conclusions. This prospective study of continuous lenalidomide maintenance, agnostic to induction regimen or AHCT usage, was designed to evaluate the dynamics of MRD-negativity in relation to PFS. It expands on the importance of MRD as a predictor of outcome and illustrates how continuous maintenance therapy can deepen and sustain MRD-negative responses achieved with modern combination therapy. For this cohort, MRD-negativity at each landmark profoundly outweighed the impact of all other variates. Among those who had sustained MRD-negativity at 2 years (37% of the cohort), regardless of MRD status at enrollment, none have had progression events at median 43 months. Our results support cross-sectional MRD testing as a surrogate endpoint for drug approval, and the use of longitudinal MRD tracking in clinical management. Disclosures Korde: Amgen: Research Funding; Astra Zeneca: Other: Advisory Board. Lesokhin:Genentech: Research Funding; Janssen: Research Funding; GenMab: Consultancy, Honoraria; Juno: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Serametrix Inc.: Patents & Royalties; BMS: Consultancy, Honoraria, Research Funding. Smith:Precision Biosciences: Consultancy; Bristol Myers Squibb: Consultancy, Patents & Royalties, Research Funding; Fate Therapeutics: Consultancy. Shah:Physicians Education Resource: Honoraria; Celgene/BMS: Research Funding. Mailankody:Physician Education Resource: Honoraria; PleXus Communications: Honoraria; Takeda Oncology: Research Funding; Janssen Oncology: Research Funding; Allogene Therapeutics: Research Funding; Juno Therapeutics, a Bristol-Myers Squibb Company: Research Funding. Hultcrantz:Intellisphere LLC: Consultancy; Amgen: Research Funding; Daiichi Sankyo: Research Funding; GSK: Research Funding. Hassoun:Takeda: Research Funding; Celgene: Research Funding; Novartis: Consultancy. Scordo:McKinsey & Company: Consultancy; Angiocrine Bioscience, Inc.: Consultancy, Research Funding; Omeros Corporation: Consultancy; Kite - A Gilead Company: Other: Ad-hoc advisory board. Chung:Genentech: Research Funding. Shah:Amgen: Research Funding; Janssen Pharmaceutica: Research Funding. Lahoud:MorphoSys: Other: Advisory Board. Thoren:Sebia: Research Funding; The Binding Site: Research Funding. Ho:Invivoscribe, Inc.: Honoraria. Dogan:AbbVie: Consultancy; EUSA Pharma: Consultancy; Takeda: Consultancy; Seattle Genetics: Consultancy; Corvus Pharmaceuticals: Consultancy; Physicians Education Resource: Consultancy; Roche: Consultancy, Research Funding; National Cancer Institute: Research Funding. Giralt:MILTENYI: Consultancy, Research Funding; ACTINUUM: Consultancy, Research Funding; KITE: Consultancy; OMEROS: Consultancy, Honoraria; NOVARTIS: Consultancy, Honoraria, Research Funding; CELGENE: Consultancy, Honoraria, Research Funding; JAZZ: Consultancy, Honoraria; AMGEN: Consultancy, Research Funding; TAKEDA: Research Funding. Landgren:Takeda: Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Binding Site: Consultancy, Honoraria; Karyopharma: Research Funding; Janssen: Consultancy, Honoraria, Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Seattle Genetics: Research Funding; Glenmark: Consultancy, Honoraria, Research Funding; Takeda: Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Janssen: Consultancy, Honoraria, Other: Independent Data Monitoring Committees for clinical trials, Research Funding; Pfizer: Consultancy, Honoraria; Merck: Other; Cellectis: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Juno: Consultancy, Honoraria; Glenmark: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Seattle Genetics: Research Funding; Karyopharma: Research Funding; Merck: Other; Adaptive: Consultancy, Honoraria; Amgen: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Binding Site: Consultancy, Honoraria; BMS: Consultancy, Honoraria; Cellectis: Consultancy, Honoraria; Juno: Consultancy, Honoraria.

Abstract: Background: Bortezomib, a proteasome inhibitor, has shown efficacy in the treatment of newly diagnosed and relapsed light chain (AL) amyloidosis, and the combination of bortezomib, cyclophosphamide and dexamethasone is a commonly used regimen in AL. Ixazomib is the first oral proteasome inhibitor to be approved, and the combination of ixazomib with cyclophosphamide and dexamethasone is an all oral effective regimen for the treatment of multiple myeloma. This phase 2 trial was designed to evaluate the efficacy of this regimen in patients with AL, who have not received any therapy. Patients and methods: Newly diagnosed patients with biopsy proven AL amyloidosis, with organ involvement requiring therapy, were enrolled if they had measurable disease (Serum immunoglobulin free light chain ≥5 mg/dL AND abnormal serum free light chain ratio) and adequate organ function. Patients with severe organ involvement were excluded (Alkaline phosphatase & gt;750 U/L, creatinine clearance & lt;30 mL/min or NT-ProBNP ≥ 7500 ng/dL). Treatment consisted of ixazomib 4 mg days 1, 8, 15; cyclophosphamide 500 mg PO weekly and dexamethasone 40 mg, weekly for twelve 28-day cycles, followed by ixazomib maintenance (days 1, 8, 15) at the last tolerated dose till progression. The primary objective was to determine the hematologic response rate of ixazomib, used in combination with cyclophosphamide and dexamethasone in patients with previously untreated AL. A one-stage binomial design was utilized to test the null hypothesis that the hematologic response rate is at most 30% against the alternative hypothesis that it is at least 50%, with 85% power and 9% type I error. Results: Thirty-five patients were enrolled, median age was 67 (range 38-78) years; 69% were male. Organ involvement included cardiac in 23 (65.7%), renal in 19 (54.3%), and nervous system involvement in 5 (14.3%). At data cutoff 8 patients still remain on study with a median follow up of 4.4 months for those who are alive. Across the trial a median of 4 cycles (range 0-23) of treatment have been completed; the most common reason for going off study was institution of alternate therapy in 17 patients (63%). The overall hematologic response was 57% (20/35) and included amyloid CR in 5 (14%), VGPR in 9 (26%) and a PR in 6 (17%) patients. Confirmed organ responses have been observed in 5 patients so far, 2 each for cardiac and renal and 1 hepatic. The median PFS and OS have not been reached; 4 patients had hematological progression; 6 patients (17%) have died. Across 193 cycles of treatment administered, dose modification was required in 5, 3, and 10 patients, respectively, for ixazomib, cyclophosphamide and dexamethasone. A grade 3 or higher adverse event (AE), at least possibly attributed to the study drugs, was observed in 41% of patients. The figure shows the maximum grade of adverse events for individual patients seen in more than one patient across the study. Conclusions: The all-oral regimen of ixazomib, cyclophosphamide, and dexamethasone is active in patients with previously untreated AL amyloidosis with hematologic responses observed in 57% of patients, including complete responses. Organ response has been observed but will likely need longer follow up for accurate assessment, given the delay in organ responses in this disease. Further evaluation of this combination is warranted. Disclosures Gertz: Alnylam: Consultancy; Ionis/Akcea: Consultancy; Amgen: Consultancy; Medscape: Consultancy, Speakers Bureau; Physicians Education Resource: Consultancy; Data Safety Monitoring board from Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy; Johnson and Johnson: Speakers Bureau; DAVA oncology: Speakers Bureau; Advisory Board for Pharmacyclics: Membership on an entity's Board of Directors or advisory committees; Advisory Board for Proclara: Membership on an entity's Board of Directors or advisory committees; i3Health: Consultancy; Springer Publishing: Patents & Royalties; Amyloidosis Foundation: Research Funding; International Waldenstrom Foundation: Research Funding; NCI SPORE MM: Research Funding; Prothena: Consultancy; Sanofi: Consultancy; Janssen: Consultancy; Spectrum: Consultancy, Research Funding; Annexon: Consultancy; Appellis: Consultancy. Kapoor:Celgene: Honoraria; GlaxoSmithKline: Research Funding; Takeda: Honoraria, Research Funding; Amgen: Research Funding; Sanofi: Consultancy, Research Funding; Janssen: Research Funding; Cellectar: Consultancy. Larsen:Janssen Oncology: 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. Dingli:Apellis: Consultancy; Janssen: Consultancy; Sanofi-Genzyme: Consultancy; Rigel: Consultancy; Bristol Myers Squibb: Research Funding; Karyopharm Therapeutics: Research Funding; Alexion: Consultancy; Millenium: Consultancy. Dispenzieri:Janssen: Research Funding; Intellia: Research Funding; Alnylam: Research Funding; Celgene: Research Funding; Pfizer: Research Funding; Takeda: Research Funding. Kumar:Adaptive Biotechnologies: Consultancy; Carsgen: Other, Research Funding; AbbVie: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Janssen Oncology: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Genecentrix: Consultancy; Dr. Reddy's Laboratories: Honoraria; Tenebio: Other, Research Funding; Takeda: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; BMS: Consultancy, Research Funding; Sanofi: Research Funding; Novartis: Research Funding; Kite Pharma: Consultancy, Research Funding; Karyopharm: Consultancy; Oncopeptides: Consultancy, Other: Independent Review Committee; IRC member; Merck: Consultancy, Research Funding; Amgen: Consultancy, Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments, Research Funding; Genentech/Roche: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Celgene/BMS: Other: Research funding for clinical trials to the institution, Consulting/Advisory Board participation with no personal payments; Cellectar: Other; MedImmune: Research Funding.

Abstract: The prognosis for patients with refractory anemia with excess blasts (RAEB) or RAEB in transformation (RAEB-T) ≥ 65 years of age has been poor. These high-risk patients are often not eligible for intensive induction/transplantation regimens or combination chemotherapies, leaving few treatment options besides supportive or palliative care. In the publication of the CALGB trial by Silverman et al (JCO2002;20:2429), no age- and/or risk- related subgroup analyses for azacitidine (Vidaza®) were presented. To assess the treatment effect of azacitidine versus supportive care on survival and time to AML transformation in a homogeneous sample of high-risk patients with MDS, we performed a subgroup analysis on the 191 patients included in the CALGB trial. All patients with a baseline diagnosis of RAEB or RAEB-T who were ≥ 65 years of age were included in the comparative analysis, using intent-to-treat (ITT) principles based on randomization to azacitidine or supportive care. Efficacy was analyzed using three survival endpoints: overall survival, time to death or AML transformation, and time to AML transformation. In all, 31 azacitidine patients and 37 supportive care patients met the criteria for this high-risk subgroup analysis. No significant differences in demographics or disease characteristics between the two groups were observed. For all three survival analyses, a statistically significant difference was observed for patients in the azacitidine group compared with those in the supportive care group. (Table) Median time to transformation to AML, in particular, was prolonged for 24 months in azacitidine patients compared with patients in the supportive care group. A sensitivity analysis of the overall survival results was conducted by performing 10 additional subgroup analyses based on ages ≥ 60 through ≥ 70 years in increments of one year with all overall survival results remaining significant (p & lt; 0.05, except for 2 subgroup analyses based on ages ≥ 60 and ≥ 66 where both p-values were 0.051). The sensitivity results demonstrated robust patient benefit in the subgroup ≥ 65 years of age. The most common adverse event observed with azacitidine was myelosuppression, which decreased in frequency as therapy continued. Azacitidine provided clear treatment effect and patient benefit to this difficult-to-treat, high-risk group of RAEB and RAEB-T patients ≥ 65 years of age by significantly prolonging overall survival and time to AML transformation. Time of Even Analysis