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Abstract BACKGROUND: Bone marrow fibrosis might represent either a primary myeloid malignancy such as myelofibrosis with myeloid metaplasia (MMM) or a reactive phenomenon associated with other malignancies or inflammatory/infectious processes. The development of myelofibrosis in the context of a plasma cell dyscrasia is uncommon and incompletely understood from the standpoint of both pathogenesis and clinical implications. We sought to determine the origin and clinical ramifications of this phenomenon based on a consecutive series of patients with plasma cell disorders (PCD). METHODS: A retrospective search of institutional databases was performed for clinical cases of PCD with the concomitant observation of myelofibrosis. Bone marrow aspirates and trephines from the time of diagnosis of both PCD and myelofibrosis were reviewed. Clinical history was abstracted for clinical manifestations as well as disease course. DNA from archived cytogenetic pellets, when available, from the time of diagnosis, was screened for the presence of JAK2V617F. RESULTS: Among 7587 patients with a PCD seen over the last 30 years at our institution, 29 (0.3%) displayed concomitant myelofibrosis (median age 59 years, range 27–77; 52% males). The specific PCD was multiple myeloma in 25 patients, smoldering myeloma in 2, plasmacytoma in 1, and heavy chain disease in 1. Four patients (14%) had organomegaly and bone marrow histological features most consistent with MMM. Otherwise, myeloproliferative disorder (MPD)-characteristic features were infrequent and included leukocytosis and/or thrombocytosis in only 2 patients. None of the patients displayed thrombohemorrhagic complications. Archived DNA was available in 7 cases without either clinical or bone marrow histological evidence of a MPD and yet revealed the presence of JAK2V617F in 6 of the 7 cases (86%). In addition, one other patient without MPD phenotype displayed a monosomy 5 abnormality. To date, 2 patients, one with and one without a MPD phenotype underwent leukemic transformation. All other causes of death were related to PCD-associated complications. Median survival (Kaplan-Meier) for the patients with multiple myeloma was 50 months. Survival stratified by the myeloma international staging system (ISS) was similar or better than expected (published controls of 62, 44, and 29 months): median survivals for this series of 73, 51 and 37 months for stage I, II, and III disease, respectively. CONCLUSIONS: Myelofibrosis that accompanies a PCD often represents an underlying MPD and does not negatively impact the natural history of the associated PCD.

Abstract Background It is widely recognized that advanced age and prior thrombosis predict recurrent thrombosis in essential thrombocythemia (ET) and are used to risk-stratify patients. However, the paucity of large sample size and long-term follow-up has limited the development of similar prognostic models for survival and leukemic transformation (LT). Methods Data was abstracted from the medical records of a consecutive cohort of patients with WHO-defined ET seen at the Mayo Clinic. Cox proportional hazards was used to determine the impact of clinical and laboratory variables on survival and LT. Overall survival and leukemia-free survival was estimated by Kaplan-Meier plots. Results i. Patient characteristics and outcome The study cohort included 605 patients of which 399 (66%) were females (median age, 57 years; range 5–91). Median follow-up was 84 months (range; 0–424). During this period, 155 patients (26%) have died and LT was documented in 20 patients (3.3%) occurring at a median of 138 months (range; 23–422) from ET diagnosis. ii. Prognostic variables for overall survival Univariate analysis of parameters at diagnosis identified age ≥ 60 years, hemoglobin less than normal (defined as < 12 g/dL in females and < 13.5 g/dL in males), leukocyte count ≥ 15 x 109/L, tobacco use, diabetes mellitus, thrombosis, male sex, and the absence of microvascular symptoms as independent predictors of inferior survival. All of the above except the last two (i.e. male sex and the absence of microvascular symptoms) sustained their prognostic significance on multivariate analysis. Based on the first three prognostic variables: age, hemoglobin level, and leukocyte count, we constructed a prognostic model for survival: low-risk (none of the risk factors), intermediate-risk (1of 3 risk factors), and high-risk (≥ 2 risk factors). The respective median survivals were 278, 200, and 111 months (p<0.0001; Figure 1) iii. Prognostic variables for leukemic transformation On univariate analysis of parameters at ET diagnosis, LT was significantly associated with platelet count ≥ 1000 x 109/L, hemoglobin less than normal, and exposure to P-32. However, on multivariate analysis, only hemoglobin less than normal and platelet count ≥ 1000 x 109/L maintained independent prognostic value. Accordingly, we utilized these two variables, to construct a prognostic model for LT: low-risk (none of the risk factors), intermediate-risk (1 risk factor), and high-risk (both risk factors). Only 1 of the 239 patients (0.4%) in the low-risk group vs. 14 of the 289 (4.8%) in the intermediate-risk and 5 of the 77 (6.5%) in the high-risk group underwent LT (p=0.0009; Figure 2). Conclusion The current study provides clinician-friendly prognostic models for both survival and LT in ET. Figure 1 Figure 1. Figure 2 Figure 2.

Abstract Abstract 1751 Background: JAK inhibitors have significant palliative benefit in myelofibrosis (MF), mainly in the form of improved constitutional symptoms and reduced splenomegaly. Preliminary data suggests that CYT387, a JAK-1/2 inhibitor, also has the ability to produce anemia responses (ASH Annual Meeting, 2011). In general, the mechanism(s) underlying treatment effects of JAK inhibitors remain unclear but likely represent a drug-specific balance between anti-clonal activity and modulation of immuno cellular-cytokine pathways. We conducted a gene expression profiling (GEP) study using primary cells from MF patients undergoing therapy with CYT387 followed by correlation with clinical data. Methods: Study subjects were enrolled in the Phase-1/2 study of CYT387 treatment in patients with primary (PMF), post-polycythemia vera (PPMF) or post-essential thrombocythemia (PTMF) myelofibrosis. Paired research samples were collected; the time points were pre-study and 12 weeks after commencing study treatment. PBMCs were purified from whole blood by Ficoll separation; RNA was isolated from this cell fraction for GEP analysis. Gene expression profiles were generated using Illumnia Human HT-12 v4 microarray. Pair wise analysis was conducted using the Wilcoxon signed-rank test with a p-value cutoff of 0.05 to generate lists of differentially expressed genes between assigned groups. Pathway analysis was conducted to identify relevant pathways enriched for differentially expressed genes. Comprehensive plasma cytokine profiling was performed using Multiplex Bead-Based Luminex technology (Invitrogen, Carlsbad, CA). Results: Seventeen patients were studied based on sample availability; 11 (65%) mere male with median age of 66 years (range 53–85). Twelve (71%) were JAK2V617F mutation positive and the DIPSS-plus risk categorization was 10 (59%) high and 7 (41%) intermediate-2. All patients were evaluable for anemia response; 14 (82%) were red cell transfusion dependent at study start. Nine (53%) patients achieved anemia response by IWG-MRT criteria; of these, 8 patients achieved transfusion independence (minimum non-transfused hemoglobin level of 8 g/dL maintained for at least 12 weeks) and 1 had a sustained >2 g/dL increase in hemoglobin level above baseline. The initial pair wise analysis to identify differential patterns of gene expression compared pre- and post-treatment groups (Figure 1A). This revealed a cluster of significantly (p <0.05) down-regulated genes (minimum 2-fold; median 17-fold) following treatment (displayed in green; upper left quadrant). Pathway enrichment analysis revealed significant associations of these genes with cytokine regulation of immune response, cell proliferation, chemotaxis and cytoskeleton remodeling. We then conducted a pair wise analysis of anemia responders versus non-responders; this revealed a predominance of over expressed gene targets (median 35-fold) in the anemia responder group (Figure 1B) (displayed in red; upper right quadrant). Similar pathway analysis identified enrichment for genes involved in immune system function in this cluster. Conclusions: The current preliminary analysis suggests that genes relevant to immune response-cytokine pathways are significantly over expressed in patients who achieve anemia response following CYT387 therapy. This further suggests a dominant immune component that underpins ineffective hematopoiesis in responding patients. On the basis of broad treatment-related changes in gene expression we suggest that an important component of CYT387's treatment effect is down regulation of these dysregulated pathways. Ongoing studies include validation of select gene targets which will be tested prospectively in future treatment protocols, as well as correlation of gene expression with circulating cytokine-chemokine levels. Disclosures: Pardanani: Bristol-Myers Squibb: Clinical trial support, Clinical trial support Other; YM BioSciences: Clinical trial support, Clinical trial support Other; Sanofi-Aventis: Clinical trial support Other. Off Label Use: Data from Phase −1/2 study of CYT387 use in myelofibrosis is mentioned.

Abstract INTRODUCTION: Among patients (pts) with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), the indications for liver biopsy are not known. Additionally, the histopathologic findings of CLL infiltration in the liver along with its clinical implications have not been thoroughly described in the literature. METHODS: We identified all pts with a diagnosis of CLL/SLL from the CLL Clinical Database at Mayo Clinic, Rochester, MN who underwent a liver biopsy. We also cross referenced the Mayo Clinic Hematopathology Database for all pts who underwent a liver biopsy. The indications for biopsy, description of the pathologic findings in the liver biopsy, CLL therapy and outcomes were abstracted from the clinical records. Retrospective pathology review was performed on cases with CLL involvement in which slides were available for review. RESULTS: Fifty-two CLL/SLL pts who underwent a liver biopsy were identified. The indications for liver biopsy were as follows: liver lesion identified on radiographic imaging in 21 (41%) pts, abnormal liver function tests (LFTs) in 17 (33%) pts, hepatosplenomegaly in 11 (21%) pts, and unknown in 3 (6%) pts. Among all 52 pts, there was concern for Richter transformation at time of biopsy in 7 (13%) pts. Types of biopsy were as follows: percutaneous in 20 (39%) pts, intraoperative in 17 (33%) pts, transjugular in 3 (6%) pts, and unknown in 12 (23%) pts. CLL/SLL involvement was identified in 38/52 (73%) pts undergoing liver biopsy. Among these, the diagnosis of CLL/SLL was made on liver biopsy in 8 pts, and 7 pts had additional findings on their liver biopsy including metastatic colon cancer (n=3), hemochromatosis (n=2), steatohepatitis (n=1), and cirrhosis (n=1). Liver biopsy revealed Richter transformation in 4 (8%) pts (3 pts with diffuse large B cell lymphoma (DLBCL) and 1 patient with Hodgkin lymphoma), other malignancy in the absence of CLL in 7 (15%) pts (2 metastatic colorectal, 2 metastatic esophageal, 1 hepatocellular carcinoma, 1 metastatic lung, and 1 neuroendocrine), and 1 patient with steatohepatitis. Two (4%) pts had normal findings on liver biopsy. Among the 38 pts with liver involvement by CLL, 27 had slides available for retrospective pathology review. CLL involvement ranged from 2-100% of the liver parenchyma. Seven pts (26%) underwent excisional biopsies or resections and 20 (74%) underwent core biopsies. The portal tracts were the most common region of the liver involved (22/26 pts, 85%). Of these, 8/22 (36%) pts had extension into the lobules or sinusoids, as well. Of the 4 cases without portal involvement, 2 showed extensive involvement such that it effaced the liver parenchyma in the region of involvement. One patient (4%) had a predominantly sinusoidal involvement. One patient (4%) showed small nodular infiltrates that were difficult to localize due to their size. Proliferation centers were noted in only 3 pts (11%). Most pts (29/38; 76%) whose liver biopsy demonstrated involvement by CLL did not receive immediate CLL-specific treatment. Nine of the 38 pts (24%) with CLL involvement on liver biopsy received therapy (Table): purine analog based therapy (n=4), rituximab and steroids (n=2), steroids only (n=1), alkylator and rituximab (n=1), and ibrutinib (n=1). Pts with extensive involvement of the liver by CLL were more likely to receive purine nucleoside analog based therapy compared to pts with portal infiltration by CLL (2/2 pts [100%] vs. 1/6 pts [17%]). The remaining pts were offered no therapy due to incidental finding of CLL in the liver biopsy (n=11), chemotherapy for other cancer (n=5), palliative care (n=3), or unknown (n=10). Pts with Richter's transformation received R-CHOP (n=2) and CHOP (n=1) for DLBCL, and ABVD (n=1) for Hodgkin lymphoma. Pts with other cancers without CLL received appropriate therapy for their underlying malignancy. CONCLUSION: Abnormal LFTs and radiographic abnormalities were the most common indications for a biopsy in this large cohort of CLL pts. Infiltration of the portal tracts by CLL/SLL was the most common histopathological finding. Proliferation centers were not commonly seen, which may make the diagnosis challenging for the pathologist if there is not a prior history of CLL/SLL. The mere presence of CLL/SLL infiltration did not mandate treatment and many pts were able to continue observation. Table Table. Disclosures Ding: Merck: Research Funding. Kenderian:Novartis: Patents & Royalties, Research Funding. Shanafelt:GlaxoSmithkKine: Research Funding; Celgene: Research Funding; Cephalon: Research Funding; Genentech: Research Funding; Janssen: Research Funding; Pharmacyclics: Research Funding; Hospira: Research Funding. Parikh:Pharmacyclics: Honoraria, Research Funding.

Abstract T is a farnesyltransferase inhibitor with clinical activity in elderly adults with newly diagnosed AML who are not candidates for TCC. For adults age ≥ 65 with poor-risk AML, T 600 mg BID for 21 out of 28–63 days induced complete remissions (CR) in 14%, median duration 7.3 mos, median survival 18.3 mos (Lancet JE, et al, Blood109:1387–1394,2007). In vitro, T+E exhibits synergistic anti-AML activity. In an attempt to increase CR rates in elderly AML pts, we conducted a Phase I trial of oral T+E, with escalation of both drugs and 14 vs. 21 days of T every 28–63 days (median 31 days, range 29–50). T+E resulted in a 25% CR rate (21/84 pts), duration 2 – 26+ mos, with best rates achieved with T dose ≥ 400 mg BID for 14 days (Karp JE, et al, Blood108:130a,2006). In the context of this trial, we have conducted longitudinal laboratory studies of changes in DNA damage and apoptosis in AML marrow blasts obtained from 84 patients prior to T+E (Day 0) and on Day 8 of T+E. Blasts were enriched by Ficoll density gradient separation and fixed in 70% ethanol. Persistent, unrepaired DNA damage was quantified by flow cytometry of cells stained with antibody to phosphorylated histone H2AX (γH2AX). Apoptosis was measured by flow cytometry of propidium iodide-stained cells with sub2n DNA content as observed in cell cycle distribution. To date, we have analyzed changes in in vivo γH2AX from 10 pts (4 CR, 6 stable disease or no response, SD/NR). CR pts had a 2-fold increase (range 1.91–2.22) in DNA damage induced by Day 8 of T+E relative to Day 0 values, while patients with SD/NR had no such increase (0–1.06) in DNA damage. Similarly, the apoptotic fraction of the cell cycle distributions of CR patients increase by 2-fold (range 1.2–5.3) for Day 8 marrow blasts. In contrast, changes in apoptosis were widely divergent for SD/NR patients (range 0.2–7.0). Taken together, these preliminary studies on AML marrow blasts obtained prior to and during T+E therapy suggest a possible linkage among induction of DNA damage, apoptotic response, and clinical outcome. Full analysis of all acquired specimens is ongoing.

Abstract The optimal source of donor hematopoietic stem cells (HSC) is controversial. Granulocyte colony stimulating factor (G-CSF) mobilized peripheral blood (G-PB) has replaced bone marrow (BM) as the most common allograft source in adults but is associated with donor morbidity and higher rates of chronic graft versus host disease (GVHD) compared to BM. The CXCR4 antagonist plerixafor (Px) mobilizes HSC into the PB (Px-PB) faster than G-CSF and preliminary data suggest both quantitative and qualitative differences in allograft content that may impact clinical outcomes. We sought to assess the efficacy and safety of transplanted allografts collected following mobilization with Px alone in HLA-identical sibling transplantation. This was a Phase II, two-strata, multi-center prospective trial (NCT01696461) to evaluate Px-PB allografts prior to reduced intensity conditioning (RIC) and myeloablative conditioning (MAC) based hematopoietic cell transplantation (HCT). Patients aged 18-65 years with an HLA-ID sibling donor and a hematological malignancy suitable for HCT were eligible. The primary objective was to determine the proportion of donors whose cells could be successfully mobilized and collected with a sufficient CD34+ cell dose using Px as the sole mobilizing agent. Px mobilization was considered successful if ≥ 2.0x10^6 CD34+ cells/kg recipient weight were collected in no more than two leukapheresis (LP) collections. All donors receiving Px were included in the analysis of the primary objective based on the intention-to-treat principle. Secondary objectives included the incidence of acute and chronic adverse events in donors, rates of hematopoietic engraftment, donor chimerism, rates of acute and chronic GVHD, non-relapse mortality (NRM), progression free survival (PFS) and overall survival (OS) for the recipients. From July 2013 to December 2014, 64 donor/recipient pairs were enrolled at 12 centers. Donors received Px at 240μg/kg subcutaneously 4 hours prior to LP. LP was performed processing at least 4X blood volume for up to two consecutive days (a third day was allowed for low CD34+ cell yields after 2 LP procedures) to achieve a target CD34+ cell dose of ≥ 4.0 x 10^6/kg recipient weight with a minimum goal of ≥ 2.0 x 10^6/kg. All allografts were cryopreserved. GVHD prophylaxis included cyclosporine or tacrolimus in combination with methotrexate, mycophenolate mofetil, or sirolimus. G-CSF was given routinely post HCT only to MAC recipients. Patient demographics are provided in Table 1. The median donor age was 56 years (18-65). 64% of the donors were male. Donors underwent one (23%), two (72%), or three (5%) LP procedures. 63 of 64 (98%) donors achieved the primary objective. The median total CD34+ cell dose/kg recipient weight collected within 2 days was 4.6 (0.9-9.6). Maximal donor toxicity following Px injection and LP was grades 0 (30%), 1 (52%), 2 (17%), and 3 (2%). Bloating, flatulence, abdominal pain, headache, paresthesisas, injection site reaction, and dizziness were the most commonly observed toxicities. Bone pain was not observed. The one grade 3 toxicity was a vasovagal episode felt related to LP and unlikely to Px. Toxicities typically resolved within a week of LP. The median follow up is 6.3 months. Median days to ANC (>0.5 x10^9/L) and Platelet count (>20 x 10^9/L) recovery were 13.5 (10-148) and 19 (1-76) after MAC and 14.5 (0-25) and 18 (0-141) after RIC, respectively. The cumulative incidence of acute GVHD grades 2-4 and 3-4 at day 100 were 47% (95% CI: 30-64) and 9% (95% CI: 2-22) after MAC and 19% (95% CI: 6-38) and 5% (95% CI: 0-18) after RIC. Probability of NRM at day 100 was 4% (95% CI: 0-13) and 0% after MAC and RIC, respectively. The probability of OS at day 100 was 97% (95% CI: 88-100) and 90% (95% CI: 78-98) after MAC and RIC, respectively. In conclusion, this is the first multi-center trial to demonstrate that as an alternative to G-CSF, Plerixafor rapidly, safely, and effectively mobilizes sufficient numbers of CD34+ cells from HLA-ID sibling donors for HCT following both RIC and MAC regimens. Engraftment was generally prompt and early results of secondary endpoints in recipients are encouraging. Longer follow-up and more extensive analysis of donor allografts and recipient outcomes will be presented at the time of the meeting. Research support was provided in part by Genzyme, a Sanofi Company. Table 1. Characteristics of recipients Table 1. Characteristics of recipients Disclosures Chen: Bayer: Consultancy, Research Funding. Devine:Genzyme: Research Funding.

Background and Purpose— Cardiovascular disease is a known risk factor for cognitive decline, although the mechanisms remain unclear. We hypothesize that Aβ (β-amyloid), a core pathology of Alzheimer's disease, will be associated with subclinical cardiac structure and function echocardiogram indices. Methods— Three hundred six nondemented participants from the ARIC study (Atherosclerosis Risk in Communities Study) underwent florbetapir positron emission tomography and 2D echocardiography (echo). Cross-sectional associations between echo markers of left ventricular structure and function and global cortical Aβ (≥1.2 standardized uptake value ratio were evaluated using multivariable logistic regression with interaction terms when appropriate. Results— Participants ranged in age from 67 to 88 years, were 57% female and 42% black. Per 1 cm increase in end-diastolic left ventricular diameter, the odds of elevated florbetapir standardized uptake value ratio doubled (odds ratio, 2.04 [95% CI, 1.10–3.77]), with similar findings when excluding mild cognitive impairment (odds ratio, 2.61 [95% CI, 1.22–5.59]). Conclusions— We have demonstrated a significant association between a marker of left ventricular structure and elevated florbetapir standardized uptake value ratio, identified using positron emission tomography. Ongoing prospective work will help determine if changes in cardiac structure and function either precede, or occur simultaneously with deposition of amyloid.

Abstract Background : CC-5013 (Revlimid™) is an immunomodulatory analog of thalidomide that is substantially more potent than the parent drug in terms of both anti-angiogenic and anti-TNF-α activity. CC-5013 has shown therapeutic activity in thalidomide-responsive hematological malignancies including relapsed multiple myeloma (Blood2002;100:3063) and myelodysplastic syndrome (Blood2002;100:96a). Myelofibrosis with myeloid metaplasia (MMM) has also been shown to respond to thalidomide (BJH2002;117:288). Furthermore, both angiogenesis and altered TNF-α activity have been pathogenetically implicated in MMM. Methods : The current report considers the first 15 patients in an ongoing phase II treatment trial of single agent CC-5013 in MMM based on a minimum of 3 month follow-up from day 1 of protocol treatment. Study eligibility criteria included no concomitant MMM-directed therapy, a hemoglobin (Hgb) level of < 10 g/dL, an absolute neutrophil count (ANC) of ≥ 1 x 109/L, and a platelet count of ≥ 100 x 109/L. Previous thalidomide therapy in the absence of high-grade skin toxicity was allowed. All patients were started with daily oral CC-5013 (10 mg/day) to be taken for three 28-day treatment cycles. Three additional treament cycles were planned in case of anemia response. Results : Median age was 64 years (range, 40–75) and 10 pts were males. Twelve of the 15 study pts (80%) were red cell transfusion-dependent, 14 (93%) were previously treated including 12 with cytoreductive and 4 with thalidomide therapy. The spleen was palpably enlarged in 13 pts (median 18 cm, range 7–23). Eight of the 15 pts (53%) successfully completed 3 months of protocol treatment. Treatment was discontinued in the remaining 7 pts because of drug toxicity (2 pts), disease progression (1 pt), other co-morbid condition (3 pts), or patient discretion (1 pt). Treatment response data : Clinically relevant responses were documented in 4 patients (27%) and consisted of measurable improvements in anemia (2 pts), splenomegaly (2 pts), and/or constitutional symptoms (3 pts). One pt experienced an increase in Hgb level from 8.3 to 13.4 g/dL, a decrease in leukocyte count from 66.2 to 7.7 x 109/L, and complete resolution of myelophthisis including disapperance of circulating blasts that measured 9% before treatment. Another pt became transfusion-independent (Hgb level increased to > 10 g/dL) as well as enjoyed a profound improvement in constitutional symptoms. Interestingly, serum lactate dehydrogenase (LDH) level decreased in 11 pts (73%) to either within the normal ramge (5 pts) or by more than 30 % (6 pts). Treatment toxicity data : Grade 3 or 4 adverse events that were possibly, probably, or definitely attributed to CC-5013 included rash (2 pts), neutropenia (5 pts), thrombocytopenia (3 pts), and fatigue (2 pts). In addition, 3 patients experienced drug-associated extreme thrombocytosis while a histologically-proven disseminated extramedullary hematopoiesis was documented in one patient after one month of CC-5013 treatment. Conclusion : The current preliminary report suggests a substantial biological activity of CC-5013 in MMM with a therapeutic potential for a subset of patients. Additional studies with a longer duration of therapy, different dose schedules, and combinations of CC-5013 and corticosteroids are warranted.

Abstract Abstract 677 Background: Activating mutations of NRAS and KRAS (‘RAS’) are found in 10–30% of myeloid malignancies. Evidence of constitutive activation of the RAS-RAF-MEK-ERK pathway, however, is more ubiquitous. Trametinib is a potent, selective, allosteric inhibitor of MEK1/2 that inhibits proliferation of myeloid cell lines in vitro. A Phase I/II study of single, daily, oral dosing of trametinib in myeloid malignancies is ongoing. Here we report the results from Phase I/II patients receiving the recommended Phase II dose (RP2D) of 2 mg. Methods: Patient eligibility was limited to patients with relapsed/refractory myeloid malignancies and adequate hepatic, renal and cardiac function. There were no hematologic eligibility criteria. Patients were prospectively screened for KRAS mutations at amino acids 12, 13 and for NRAS mutations at amino acids 12, 13 and 61. Clinical response was assessed using International Working Group (2003 and 2006) criteria for acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS), respectively. Pharmacodynamic marker (pERK) analysis was conducted in phase II patients with patient paired (pre/during treatment) blood and bone marrow samples. Results: Eighty-seven (9 in Phase I and 78 in Phase II) patients received 2 mg of trametinib daily: AML (n=66), MDS (n=11), chronic myelomonocytic leukemia (CMML) (n=7) or other (n=3) (RAS mutations, n=57; RAS wild type, n=15 and RAS unknown, n=15). Median age was 68 years (range 21–87) and for close to half of the patients, trametinib was 3 3rd line of therapy. Trametinib exhibited a long effective half-life with small peak/trough ratios, and the exposure profile maintained time above preclinical target threshold for the 24-hour dosing period. Results of the pharmacodynamic analysis indicated an on-target effect of trametinib. Responses by RAS mutation status for Phase I/II subjects are summarized in Table 1. Responding patients have continued therapy for median of 16.9 weeks (range, 10.9 – 36.7). Drug-related grade 3/4 adverse events (AEs) were encountered in 31/87 (36%) of the Phase I/II patients and there was one grade 5 drug-related AE,cerebrovascular accident. Hepatic toxicities (9%), gastrointestinal disorders (7%) and rash (5%) were the most frequent grade 3/4 AEs. AEs possibly related to inhibition of MEK signaling were blurred vision (total,13%; grade 3, 1%) and decreased cardiac ejection fraction (total, 9%; grade 3, 6%); events were generally reversible. Conclusion: At the RP2D of trametinib (2 mg orally daily), trametinib has shown promising clinical activity and responses (CR/CRp/Marrow CR/MLFS/PR) were almost exclusively seen in patients with refractory myeloid malignancies characterized by somatic RAS mutations. Expansion of the CMML cohort for RAS positive subjects is ongoing. Disclosures: Borthakur: GlaxoSmithKline, Sigma-Tau, Eisai, XBiotech: Research Funding. Off Label Use: Trametinib, to report outcome of clinicla trial to audience at ASH meeting. Foran:GlaxoSmithKline: Research Funding. Platzbecker:GlaxoSmithKline: Honoraria, Research Funding. Giagounidis:GlaxoSmithKline: Honoraria. Ottmann:GlaxoSmithKline: Clinical trial participation Other. Kadia:GlaxoSmithKline: Research Funding. Bauman:GlaxoSmithKline: Employment, Equity Ownership. Wu:GlaxoSmithKline: Employment. Liu:GlaxoSmithKline: Employment. Schramek:GlaxoSmithKline: Employment. Zhu:GlaxoSmithKline: Employment. Wissel:GlaxoSmithKline: Employment, Equity Ownership.

Abstract Abstract 430 Background: The Dynamic International Prognostic Scoring System (DIPSS-plus) uses eight risk factors to predict overall survival (OS) in primary myelofibrosis (PMF): unfavorable karyotype, peripheral blood (PB) blast count ≥1%, platelet count <100 × 109/L, white blood cell count (WBC) >25 × 109/L, hemoglobin level <10 g/dL, red blood cell transfusion need, constitutional symptoms, and age >65 years (JCO 2011;29:392). Among these risk factors, karyotype holds a dominant role in predicting both overall (OS) and leukemia-free (LFS) survival (Blood 2011;118:4595). More recently, certain PMF-associated somatic mutations (IDH, EZH2, ASXL1, SRSF2) have been reported (in print or at recent meetings) to carry prognostic relevance for OS or LFS in PMF while other mutations (JAK2, MPL, TET2, SF3B1) did not. The purpose of the current study was to examine the individual and combined prognostic relevance of the former in the context of cytogenetic risk stratification and DIPSS-plus. Methods: An updated Mayo Clinic database of 1008 karyotypically- and DIPSS-plus-annotated patients with PMF was used to identify study patients in whom DNA at time of referral was available for mutation analysis. OS and LFS were calculated from the time of referral, which was also the time of study sample collection. Results: In an ongoing project, a total of 397 PMF patients have so far been studied for IDH1/2 (n=367), SRSF2 (n=355), ASXL1 (n=260) and EZH2 (n=43) mutations. The corresponding mutational frequencies were 5.4% (20/367), 14.4% (51/355), 31.2% (81/260) and 7% (3/43). These mutations were not exclusive of either each other or JAK2 or MPL mutations and a significant clustering was noted between SRSF2 and IDH mutations; IDH mutational frequency was 21% (10/48) in SRSF2-mutated versus 3% (9/279) in unmutated cases (P<0.0001). Mutational hotspots were P95 in exon 1 for SRSF2 and exons 1, 2 and 5 for ASXL1. OS and LFS effect have so far been examined for ASXL1, SRSF2 and IDH 1/2 mutations; in univariate analysis, all three mutations significantly affected OS (ASXL1 RR 1.9, 95% CI 1.4–2.7; SRSF2 RR 1.7, 95% CI 1.2–2.5; IDH 1/2 RR 1.8, 95% CI 1.1–3.1) whereas only IDH 1/2 (RR 5.5, 95% CI 2.5–11.8) and SRSF2 (RR 3.5, 95% CI 1.7–7.0) but not ASXL1 (p=0.29) mutations affected LFS. The observed prognostic relevance for OS was sustained during multivariable analysis that included ASXL1 with either SRSF2 or IDH mutations, as co-variates, whereas both IDH and SRSF2 mutations remained significant for LFS. Based on the above observations, study patients were classified into two groups: i) unmutated for ASXL1, SRSF2 and IDH1/2 (all unmutated; n=146) and ii) mutated for at least one of the three mutations (one or more mutated; n=130); the latter group constituted 62%, 52%, 18% and 27% of DIPSS-plus high, intermediate-2, intermediate-1and low risk patients, respectively (p<0.0001). The corresponding rates for patients with favorable and unfavorable karyotype were 47% and 43% (p=0.7) and for normal vs. abnormal karyotype were 53% and 36% (p=0.008). The “all unmutated group”, compared to the “one or more mutated group” enjoyed a significantly superior OS (RR 0.5, 95% CI 0.4–0.7) and LFS (RR 0.3, 95% CI 0.2–0.7) that was DIPSS-plus-independent for OS (p=0.03) and karyotype-independent for LFS (p=0.004). The prognostic value of distinguishing “all unmutated” from “one or more mutated” patient groups was most evident for DIPSS-plus intermediate-2 or lower risk groups (p=0.002) and its added value for high-risk group was limited (p=0.23) (Figure). Conclusions: A concomitant analysis strategy reveals that SRSF2, ASXL1 and IDH mutations carry inter-independent prognostic relevance for overall or leukemia-free survival in PMF. Any one of these three mutations is more likely to occur in patients with normal karyotype and such an event predicts shortened survival that is not accounted for by DIPSS-plus and a higher risk of leukemic transformation that is independent of karyotype. The current study suggests that such information might be useful in treatment decisions involving intermediate-2 or lower risk patients. Disclosures: No relevant conflicts of interest to declare.