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Abstract Background Optimum duration of antimicrobial therapy for acute bacteremic cholangitis is not well established; however, 4–7 days is recommended by the 2018 Tokyo guidelines in those without Gram-positive bacteremia. Methods A retrospective study performed at Mayo Clinic - Rochester, Florida and Arizona sites was conducted, reviewing all adult patients with the first episode of acute cholangitis secondary to biliary stone obstruction, between January 1, 2012 and December 31, 2017. We reviewed the duration of prescribed antimicrobials. Results Among 331 included cases, 197(60%) were men, 66 (20%) were immuno-compromised. Presenting symptoms included fever in 202 (61.5%), abdominal pain in 289 (87%), jaundice 128(38.7%), and altered mentation in 49 (15%). Among these, 256 (77%) were classified as “definite” and 38 (11.5%) were “suspected” using the 2018 Tokyo guideline classification. Cholangitis grade was grade III in 134 (40.5%); grade II in 115 (34.7%); and grade I in 82 (24.8%). Majority of cases, 321 (97%), underwent source control—most commonly 309 (96%) achieved by endoscopic retrograde cholangiopancreatography (ERCP). Source control occurred within 24 hr of presentation in 197 (61.4%) of the cases. Bacteremia was documented in 131/277 (47%). Majority of bacteremias were due to Gram-negative organisms in 119 (91%). Mean duration of antibiotic therapy following “source control” was 9.6 days (SD 7.0). Cases with bacteremia, resulted in longer treatment duration, mean of 13 days (SD 5.6), regardless of the isolated organism. Overall 30 day mortality was 14/331 (4.2%). No mortality difference was noted in patients who underwent early (within 12 hours) vs. later source control (4.55% Vs. 4.53%), nor in those who received more or less than 6 days of antibiotic therapy after source control (4.7% Vs. 3.9%, P = 0.76). No difference in mortality was observed in those with or without bacteremia. Conclusion Our results note the use of longer courses of antimicrobials for management of bacteremic cholangitis, regardless of the organism type. This population could be a prime target for an antimicrobial stewardship intervention, to decrease the duration of prescribed antimicrobials in accordance with recent guidelines. Disclosures All authors: No reported disclosures.

Abstract Abstract 880 Pulmonary marginal zone lymphoma is a distinct subgroup of B-cell non-Hodgkin's lymphomas originating from the bronchial-associated lymphoid tissue (BALT) and characterized by an indolent clinical course. Here we present the data of the IELSG-28 study of the International Extranodal Lymphoma Study Group (IELSG) on primary pulmonary lymphoma patients. Clinical records and histological material of 186 patients diagnosed with pulmonary marginal zone lymphoma from December 1986 to June 2009 were collected. The pathology was reviewed centrally and the diagnosis was confirmed in 180 (96%) patients. The median age at diagnosis was 62 (30 – 88). The majority of the patients (149/180) had localized disease at diagnosis with a good performance status (0–1) and low prognostic index (IPI 0–2). Eighty-one patients (45%) received local treatment, including surgery (74%) or radiotherapy (4%). Ninety-nine patients with advanced stage disease or incomplete surgical resection received an additional systemic treatment. Most of these patients (66; 66%) received an alkylating containing regimen, 22 (22%) patients were treated with an anthracycline containing regimen and 29 (29%) received the anti-CD20 monoclonal antibody in combination with chemotherapy. With a median follow up of 67 (range 1–256) months, 47/180 patients (26%) experienced disease progression. (median time to progression 30 months, range 0–109). Progression free survival analysis showed a trend in favour of patients treated with immuno-chemotherapy versus those receiving chemotherapy alone (HR 0.53–95%CI: 0.21, 1.33), while no difference in terms of OS and PFS was observed between patients receiving systemic anthracycline or alkylating containing regimens. In twenty five cases a specific PCR-assay was carried out for detecting the presence of Achromobacter (Alcaligenes) xylosoxidans. The presence of Achromobacter was detected in 50% of patients. Our results confirm that local therapy (surgery or radiotherapy) is the treatment of choice for patients with localized disease. Chemotherapy has to be considered in case of relapse, incomplete surgical excision or advanced disease. In this setting, alkylating containing regimens plus rituximab is the most effective option. Further studies are ongoing to confirm the relevance of infection/colonization with Achromobacter (Alcaligenes) xylosoxidans for pathogenesis of BALT lymphoma. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 769 Despite the many and diverse therapeutic approaches used to treat patients with mantle cell lymphoma (MCL), it remains an incurable disease. Recently, attention has turned into novel therapies targeting MCL-specific oncogenic pathways important for the growth and maintenance of the transformed phenotype. The chromosomal translocation t(11;14)(q13;q32) leading to cyclin-D1 over-expression is the hallmark of MCL. Constitute cyclin-D1 activation in B-lymphocytes maintains retinoblastoma protein in a phosphorylated state and promotes cell cycling, thus initiating the tumorigenesis process. Cyclin-D1 has been postulated as a putative target for therapeutic intervention, however its evaluation has been hampered by the incomplete understanding of the mechanism underlying this cyclin oncogenic function and by the lack of valid MCL models. To investigate these issues, we developed a combined cellular-genomics screening whereby responses to known cytotoxic compounds targeting cancer-related molecular pathways were correlated with genomic, gene expression and proteomic profiles of human MCL cells. Results showed that cyclin-D1 silencing had minimal antitumoral effects but significantly increased the therapeutic efficacy of several compounds, especially the BH3 mimetics that inhibited anti-apoptotic protein BCL-2. To further evaluate this finding we generated a MCL mouse model by transducing a tetracycline-regulatable cyclin-D1-expressing vector in murine pro-B cells, which allowed modulating cyclin-D1 expression levels. These mice generated lymphomas recapitulating most of the cellular, histopathological and molecular features of human MCL. Similar to the previous in vitro findings, cyclin-D1 inhibition in this model did not induce lymphoma regression, but sensitized cells to apoptosis. Analysis of the mechanisms underlying this therapeutic synergy identified a novel role for cyclin-D1 as a pro-survival molecule. Specifically, cyclin-D1 sequestrated the pro-apoptotic effector protein BAX in MCL cells, thereby favoring BCL2 anti-apoptotic function. Accordingly, therapeutic cyclin-D1 inactivation released BAX, thus sensitizing cells to apoptosis and inducing lymphoma regression. Interestingly, pharmacological blockade in vivo of cyclin-D1 with Roscovitine synergistically cooperated with the BH3 mimetic ABT-737 to effectively inhibit MCL tumor growth. In summary, our study reveals a novel role for cyclin-D1 in deregulating apoptosis in MCL cells and highlights the potential benefit of cyclin-D1 targeting, thus providing the rationale for the clinical evaluation of drugs targeting cell proliferation and survival pathways in MCL. Disclosures: Siebert: Abbott: Honoraria.

Abstract Background Fedratinib (SAR302503) is a JAK2-selective inhibitor that has provided clinically meaningful reductions in MF-associated splenomegaly and symptoms in Phase I and II studies (J Clin Oncol 2011;29:789. Haematologica 2013;98:S1113). Here, we present efficacy and safety data from the Phase III JAKARTA study of fedratinib versus placebo in patients with MF (NCT01437787). Methods In this international double-blind, placebo-controlled, 3-arm study, patients aged ≥18 years with IPSS intermediate-2 or high-risk MF, platelet count ≥50 × 109/L, and splenomegaly were randomized (1:1:1) to receive placebo or fedratinib 400 mg or 500 mg, orally, once daily, in consecutive 4-week cycles. Patients who received placebo were eligible to cross-over to fedratinib (randomized 1:1 to 400 mg or 500 mg) following 6 cycles of treatment, or prior to Cycle 6 if the patient had disease progression. The primary endpoint was spleen response rate (RR) (≥35% reduction in spleen volume from baseline measured by MRI or CT at Week 24, and confirmed 4 weeks later). Secondary endpoints included symptom RR (≥50% reduction in total symptom score from baseline at Week 24, measured through a daily electronic eDiary using the modified Myelofibrosis Symptom Assessment Form [Cancer 2011;117:4869. Blood 2011;118:401]), and safety of fedratinib. Results A total of 289 patients were randomized: median age 65 years; 59% male; 63% primary MF; 48% high-risk MF; 67% JAK2V617F positive; 16% platelet count <100 × 109/L; median baseline spleen volume 2568 mL (range 316–8244); median baseline total symptom score 14.7 (0–57). Median (range) exposures for placebo, 400 mg and 500 mg groups were 24 (2–34), 30 (1–55) and 28 (1–60) weeks, respectively. Spleen RRs at Week 24 (placebo 1%; 400 mg 47%; 500 mg 49%), and confirmed at Week 28 (placebo 1%; 400 mg 36%; 500 mg 40%), were significantly (p<0.0001) higher in both fedratinib groups compared with placebo (Table). Nineteen patients had a spleen response at Week 24 not confirmed 4 weeks later (spleen reduction 25–35% [n=10]; image not available/evaluable [n=8]; image taken outside time window [n=1]). Spleen RRs by baseline platelet level are shown in the table. Patients treated with fedratinib had significantly (p<0.0001) greater improvements in MF symptoms compared with placebo (Table). The most common all grade non-hematologic treatment-emergent adverse event (TEAE) was diarrhea (16%, 66% and 56% of patients in the placebo, 400 mg and 500 mg groups, respectively). Grade 3/4 diarrhea was reported in 5% of patients in both the 400 mg and 500 mg dose groups. The most common hematologic TEAE was anemia (any grade 91%, 99% and 98%; Grade 3/4 25%, 43% and 60% in the placebo, 400 mg and 500 mg groups, respectively). Rates of Grade 3/4 thrombocytopenia were 9% (placebo), 17% (400 mg), and 27% (500 mg). Incidences of Grade 3/4 liver function tests (placebo/400 mg/500 mg) were: bilirubin, 2%/2%/1%; ALT, 0%/3%/3%; and AST, 1%/2%/2%. Overall treatment discontinuation rates up to 24 weeks of treatment were 25% (placebo), 22% (400 mg) and 32% (500 mg). Twenty-five patients died during the study (10, 5 and 10 in the placebo, 400 mg and 500 mg groups, respectively); the most common causes of death: disease progression (placebo [n=5]; 400 mg [n=3]; 500 mg [n=4]) and adverse events (placebo [n=4]; 400 mg [n=1]; 500 mg [n=4]). Conclusions In this Phase III, randomized, placebo-controlled, 3-arm study of 289 MF patients, treatment with fedratinib 400 mg or 500 mg once-daily demonstrated clinically meaningful and statistically significant reductions in splenic volume and MF-associated symptom burden versus placebo. Fedratinib had an acceptable safety profile, with the adverse events reported consistent with those observed in previous studies. This study was sponsored by Sanofi. Disclosures: Pardanani: Sanofi, Bristol Myers Squibb, PharmaMar and JW Pharma: Clinical trial support Other. Harrison:Novartis: Research Funding; Novartis, Sanofi, YM Bioscience, Celgene, SBio, Gilead: Honoraria; Novartis, Sanofi, Shire: Speakers Bureau; Novartis, Sanofi, YM Bioscience, SBio, Gilead: Membership on an entity’s Board of Directors or advisory committees. Cortes:Incyte, Sanofi: Consultancy; Incyte, Sanofi: Research Funding. Cervantes:Novartis: Speakers Bureau; Novartis and Sanofi: Membership on an entity’s Board of Directors or advisory committees. Mesa:Incyte, Genentech, Lilly, MS Pharma, Gilead: Research Funding. Jourdan:Sanofi: Honoraria. Vannucchi:Novartis: Membership on an entity’s Board of Directors or advisory committees. Drummond:Sanofi, Novartis, Celgene: Honoraria; TargeGen, Novartis: Speakers Bureau; Sanofi, Novartis, Celgene: Consultancy. Passamonti:Novartis, Celgene, Incyte, Sanofi, Roche: Honoraria. Neumann:Sanofi: Employment. Gao:Sanofi: Employment.

Abstract Philadelphia-negative Myeloproliferative Neoplasms (MPN) include Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Myelofibrosis Primary (PMF) and secondary to PV and ET (PPV-, PET-MF); included are also some less characterized entities defined as unclassified MPN (U-MPN). Risk of arterial and venous thrombosis is increased in MPN patients, and thrombosis is one of most important causes of mortality and morbidity. The risk of venous thrombosis in unusual sites, such as splanchnic vessels (SVT), is particularly associated with MPN; SVT can lead to complications such as portal hypertension, esophageal and gastric varices, ascites and hepatic failure. A recent meta-analysis reported that a MPN is the underlying cause of portal vein thrombosis in 31.5% and of Budd Chiari syndrome in 40.9% of cases (Smalberg, 2012). A significant association of SVT with JAK2V617F mutated MPN was reported (Dentali, 2009) but study of other correlations has been hampered by heterogeneity of available patient cohorts comprising relatively small number of cases. We conducted a retrospective multicenter study collecting clinical and biological data of patients (pts) with SVT associated with MPN diagnosed according to WHO2008 criteria, aiming to describe patients’ characteristics, trends and prognostic factors, and their potential implications for clinical practice. Data were collected from 15 international hematology centers in the framework of IWG-MRT. We collected 475 cases of pts with portal, splenic or mesenteric vein thrombosis (75.2%) or Budd Chiari syndrome (24.8%) associated with MPN. In 32% of cases, simultaneous involvement of portal (69.1% of total thrombosis), splenic (30.5%) and mesenteric (25.3%) veins occurred, and in 1.7% they were associated with Budd Chiari syndrome. Frequency of MPN subtype: 38.1% ET (n=181), 34.9% PV (n=166), 16.2% MF (n=77), 10.8% U-MPN (n=51). Median follow-up 87.9 mo (range 0.5-430); female 61.3% (n=292; P<0.0001 vs male); median age at MPN diagnosis (dg) 44.4 y (range 12-90), at SVT dg 44.9 y (range 17-85). In 229 cases (48%) MPN and SVT dg were coincident, while in 104 (22%) SVT occurred before MPN dg (median 40 mo, range 5-335) and in 129 (27%) during MPN follow up (median 79 mo, range 5-394). JAK2V617F mutational status is available for 361 pts: 99% PV, 84.7% ET, 88.1% PMF and 92.9% U-MPN pts were JAK2V617F positive, with a mean allele burden of 56±27.4%, 33.1±25.5%, 39.3±19.4% and 23.8±11.9%, respectively. Erythropoietin-independent colonies (EEC) were present at diagnosis in 80/110 evaluated cases (72.7%), 38/47 PV (84.4%), 32/45 ET (71.1%), 8/11 PMF (72.7%) and 2/7 U-MPN (28.6%). A concurrent thrombophilic state was found in 38.9% of cases. A 12.3% of pts experienced a recurrence of SVT after a median of 29 mo (range 1-378.3) and 35.8% developed thrombosis in other sites (17.7% arterial, 19.3% venous). Esophageal varices were found in 70.6% from which 31.9% bled. MF transformation occurred in 32/166 PV (19%) and in 23/181 ET (13%) pts, with median time to progression of 122.3 mo (range 5.4-377.3) and 125.1 mo (range 39.3-255.3), respectively. Evolution to acute leukemia (AL) occurred in 12 pts (2.7%), of which 2 PMF, 6 PV and 4 ET. In 3 PV and 1 ET pts a PPV and PET-MF transformation occurred before AL. After SVT, 77% of pts received anticoagulation, 23.5% antiaggregant therapy and 1.5% both; 68.8% received cytotoxic drugs, 11.4% of pts were treated with trans jugular porto-systemic shunt. No differences in survival were noted with these approaches. Beta blocker therapy was used in 48.5% of pts and correlated with improved survival (p=0.041) At last follow up 70/473 pts (14.8%) died; causes of death are evolution to AL (16.4%), other cancers (14.5%), disease progression without AL (12.7%), SVT (10.9%), hepatic failure and venous thrombosis other than SVT (9.1% each), heart failure and arterial thrombosis (7.3% each), hemorrhage (5.5%), renal failure and infection (3.6% each). After 10 y follow up 8/166 PV (5%), 14/181 ET (8%), 14/77 PMF (18%) and 1/51 U-MPN (1.96%) pts died (p<0.01). Survival was significantly affected by occurrence of thrombosis other than SVT (p<0.0001) but not recurrence in splanchnic vessels (p=0.068). This large study confirms the strong association between JAK2V617F-mutated MPN and SVT and identifies the category of U-MPN as the prognostically more favorable; thrombosis at sites outside the splanchnic vasculature remains the leading cause of death. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 487FN2 Background: Given the life-threatening nature of severe VOD (sVOD) and multi-organ failure (MOF), DF was made available in the US through a prospective treatment IND protocol (T-IND) to gather additional safety and response data from SCT patients (pts) with sVOD who were not eligible for a pivotal Phase 3 trial. Following completion of this Phase 3 trial, the T-IND protocol has continued and been amended to include pts who would have met eligibility criteria for the completed phase 3 trial, as well as pts with non-severe VOD and non-SCT pts who develop VOD after chemotherapy (chemo). This is the largest prospective evaluation of DF for the treatment of sVOD/MOF post SCT and non-SCT pts to date. Methods: Pts were initially required to have a diagnosis of VOD by Baltimore criteria (total bilirubin > 2.0 mg/dL with > 2 of the following: hepatomegaly, ascites or 5% weight gain) with MOF (either renal and/or pulmonary failure) that followed SCT. Following treatment of 104 pts, an amendment expanded eligibility criteria to include pts with VOD after chemo and pts with non-severe VOD (defined as no MOF). Key exclusion criteria included clinically significant bleeding or >1 pressor to maintain BP. CR was defined as bilirubin < 2 mg/dL + resolution of MOF (if applicable). Mortality was assessed at Day +100 (D+100) in all pts. DF was given at 6.25 mg/kg IV q6h (25 mg/kg/d) with treatment duration recommended for at least 21d. Results: This interim analysis is based on 269 pts enrolled between December 2007 and March 2011 at 67 centers. Nearly all pts (n=251) had undergone SCT (with allogeneic SCT in 225, 90%); 18 developed VOD after chemo alone. Of the 269 cases of VOD, 200 were severe at study entry, with 25% (66/269) of all pts dialysis dependent and 31% (83/269) ventilator dependent. Median age was 16 years (range 0.1 – 70); 55% were male. In the SCT pts, the most common diagnosis was leukemia (29% AML; 22% ALL; CML 3%; 4% other), with conditioning of CY (71%), BU (46%) and TBI (38%) respectively; 18% had undergone multiple SCTs (>1 SCT). Median onset of VOD was 15 d post-SCT. When presenting after chemo alone (n=18), median onset of VOD was 16 d after the first dose, most frequently after CY (61%), cytarabine (44%) and vincristine (39%), and for treatment of leukemia (AML 33%, ALL 33%, other 6%). Overall mean number of days of DF administration in all pts was 22 (range 1–88).Of 269 pts, 32% (85/269) achieved a CR and 50% [ by Kaplan-Meier estimate] survived to D+100. In the subgroup of SCT pts, 31% (78/251) achieved CR and 50% survived to D+100; 134 pts met entry criteria for the original Phase 3 trial and comparison to the Phase 3 historical control showed a statistically improved outcome in CR (30% vs 9%, p=0.0006) and D+100 survival (46% vs 25%; p=0.006). Of 200 pts with sVOD, CR was 28% and D+100 survival was 44%. In the 18 chemo only pts, CR was 39% and D+100 survival was 50%. CR rate and D+100 survival for the 69 pts with non-severe VOD were 42% and 62%, respectively. Delay of >2 d (vs < 2 d) in the start of DF after VOD diagnosis resulted in reduced CR (23% vs 35%, p=0.0339) and survival (37% vs 56%, p=0.01). Children as compared to adults had higher rates in CR (35% vs 29%) and survival (55% vs 43%). Toxicity proved generally manageable: 22% of pts experienced a total of 81 related AEs, primarily consisting of hemorrhage (19%) and hypotension (4%). Hemorrhage included pulmonary bleeding (6%), GI hemorrhage (3%), epistaxis (3%) and hematuria (3%). Similar to the observation of decreased GvHD in other studies, the incidence of all grade GvHD in the allogeneic SCT pts was 8%. Conclusions: In 269 pts with mainly sVOD/MOF, DF therapy achieved significantly improved outcome compared to an untreated historical control. Importantly, CR and survival were improved in pts who were treated within 2d of VOD diagnosis (vs. later) and in pts who had not yet progressed to sVOD. As with prior studies, there was a low incidence of DF-associated toxicities. Interestingly, the incidence of GvHD in allo-SCT pts was low, consistent with the reduction of GvHD seen in the large randomized EBMT pediatric prevention study. These results confirm the findings of previous trials and strongly support early intervention with DF once the diagnosis of VOD is made after SCT, as well as its use in pts who have not progressed to advanced MOF. The use of DF for VOD following intensive chemotherapy without SCT also appears promising, but more research in this patient population is needed. Enrollment to the T-IND study continues. Disclosures: Richardson: Gentium: Membership on an entity's Board of Directors or advisory committees. Arai:Gentium: Research Funding. Symons:Otsuka Pharmaceuticals: Research Funding. Martin:Gentium: Research Funding. Massaro:Gentium: Consultancy. D'Agostino:Gentium: Membership on an entity's Board of Directors or advisory committees. Hannah:Gentium: Consultancy. Tudone:Gentium: Employment. Hume:Gentium: Employment. Iacobelli:Gentium SpA: Employment. Soiffer:Gentium: Honoraria.

Abstract While multiple myeloma (MM) is almost invariably preceded by asymptomatic monoclonal gammopathy of undetermined significance (MGUS) and/or smoldering MM (SMM), the alterations of the bone marrow (BM) microenvironment that establish progression to symptomatic disease are circumstantial. Our aim was to identify changes in the BM microenvironment eliciting angiogenesis in MM. We have found that in Vk*MYC mice harboring oncogene-driven plasma cell proliferative disorder, the progression from asymptomatic to symptomatic MM was characterized by substantial modifications of the BM microenvironment, including a switch from a T helper type 1 (Th1) to a Th2 response, and accumulation of CD206+Tie2+ macrophages, which eventually favored angiogenesis and increased in microvessel density (MVD). Notably, MVD was also increased at diagnosis in the BM of MGUS and SMM patients that subsequently progressed to MM when compared with MGUS and SMM that remained quiescent. These findings suggest a multistep pathogenic process in MM, in which the immune system may contribute to angiogenesis and disease progression. They also suggest investigating MVD in asymptomatic patients as prognostic factor for the progression and outcome of this disease. Disclosures No relevant conflicts of interest to declare.

Abstract Background: ENESTop, an ongoing, single-arm, phase 2 study (ClinicalTrials.gov, NCT01698905), is the first trial specifically evaluating treatment-free remission (TFR; ie, stopping tyrosine kinase inhibitor [TKI] treatment without a loss of response) in patients with chronic myeloid leukemia in chronic phase (CML-CP) who achieved a sustained deep molecular response after switching from imatinib (IM) to nilotinib (NIL). Of 126 patients in ENESTop who were eligible to stop NIL, 57.9% (95% CI, 48.8%-66.7%) maintained TFR at 48 weeks. Here we present results from a subgroup analysis based on reasons for switching from IM to NIL, categorized as intolerance, resistance, and physician preference. Methods:Eligible patients were adults with CML-CP who received ≥ 3 years of total TKI therapy (> 4 weeks of IM, followed by ≥ 2 years of NIL) and achieved a sustained MR4.5 (BCR-ABL1 ≤ 0.0032% on the International Scale [BCR-ABL1IS]) on NIL therapy; patients with a documented MR4.5 at the time of switch from IM to NIL were not eligible. Enrolled patients continued NIL treatment in a 1-year consolidation phase, and those without confirmed loss of MR4.5 (ie, consecutive BCR-ABL1IS > 0.0032%) were eligible to stop NIL in the TFR phase. Patients with loss of major molecular response (MMR; ie, BCR-ABL1IS > 0.1%) or confirmed loss of MR4 (ie, consecutive BCR-ABL1IS > 0.01%) during the TFR phase reinitiated NIL treatment. The primary endpoint was the proportion of patients who maintained TFR (ie, no loss of MMR, confirmed loss of MR4, or treatment reinitiation) at 48 weeks after stopping NIL. In this post hoc analysis, rates of TFR at 48 weeks after stopping NIL and a Kaplan-Meier (KM) analysis of treatment-free survival (TFS; defined as the time from the start of TFR to the earliest occurrence of any of the following: loss of MMR, confirmed loss of MR4, reinitiation of NIL due to any cause, progression to accelerated phase/blast crisis, death due to any cause) were evaluated in subgroups of patients who switched from IM to NIL due to intolerance, resistance, or physician preference. These categories were determined by grouping the reasons for switching from IM to NIL, as reported by the investigators, based on relatedness to safety (intolerance), loss of response/treatment failure (resistance), and the physician's clinical judgment (physician preference); individual reasons included within each category are presented in the Figure. Results:A total of 125 patients who entered the TFR phase were included in this analysis; 1 patient who was found to have had atypical transcripts was excluded. Among these 125 patients, the reasons for switching to NIL were categorized as intolerance in 51 patients (40.8%), resistance in 30 patients (24.0%), and physician preference in 44 patients (35.2%). The proportion of patients who maintained TFR at 48 weeks after stopping NIL was generally similar across the 3 subgroups: 30 of 51 (58.8%; 95% CI, 44.2%-72.4%) in the intolerance subgroup, 16 of 30 (53.3%; 95% CI, 34.3%-71.7%) in the resistance subgroup, and 27 of 44 (61.4%; 95% CI, 45.5%-75.6%) in the physician preference subgroup. KM analysis of TFS showed that in all 3 subgroups, the majority of TFS events occurred within the first 24 weeks after stopping NIL (Figure). There were no notable differences in the kinetics of TFS events among subgroups. The KM-estimated median duration of TFS was not reached by the data cutoff date in all 3 subgroups. Conclusion: Primary analysis from ENESTop showed that among patients with CML-CP who achieved a sustained MR4.5after switching from IM to NIL, 57.9% of those who stopped NIL maintained TFR at 48 weeks. In the present analysis, TFR was maintained at 48 weeks after stopping NIL by > 50% of patients in the intolerance, resistance, and physician preference subgroups, with generally similar results across subgroups. These findings suggest that the rate of successful TFR following second-line NIL does not differ based on the reasons for switching from IM to NIL. Figure. Figure. Disclosures Hughes: Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Australasian Leukaemia and Lymphoma Group (ALLG): Other: Chair of the CML/MPN Disease Group. Boquimpani:Novartis: Research Funding, Speakers Bureau; BMS: Speakers Bureau. Takahashi:Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; BMS: Honoraria. Shuvaev:Pfizer: Honoraria; BMS: Honoraria; Novartis pharma: Honoraria. Ailawadhi:Pharmacyclics: Consultancy; Novartis: Consultancy; Amgen Inc: Consultancy; Takeda Oncology: Consultancy. Lipton:Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Ariad: Consultancy, Research Funding. Turkina:Pfizer: Honoraria; Novartis Pharma: Honoraria; BMS: Honoraria. Moiraghi:BMS: Speakers Bureau; NOVARTIS: Speakers Bureau. Nicolini:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria; Ariad pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees. Sacha:BMS: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Adamed: Consultancy, Honoraria. Kim:Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; ILYANG: Consultancy, Honoraria, Research Funding. Fellague-Chebra:Novartis: Employment. Acharya:Novartis Healthcare Pvt. Ltd.: Employment. Krunic:Novartis: Employment, Equity Ownership. Jin:Novartis: Employment, Equity Ownership. Mahon:BMS: Honoraria; PFIZER: Honoraria; NOVARTIS PHARMA: Honoraria, Research Funding; ARIAD: Honoraria.

Abstract Background: ENESTop (NCT01698905) is an ongoing, single-arm, phase 2 study evaluating treatment-free remission (TFR) in patients (pts) with chronic myeloid leukemia in chronic phase (CML-CP) who achieved sustained molecular response 4.5 (MR4.5; BCR-ABL1 ≤ 0.0032% on the International Scale [BCR-ABL1IS]) on second-line nilotinib (NIL). In the primary analysis, 57.9% (95% CI, 48.8%-66.7%) of pts who stopped NIL maintained TFR (no loss of major molecular response [MMR; ie, BCR-ABL1IS > 0.1%], confirmed loss of MR4 [ie, consecutive BCR-ABL1IS > 0.01%], or treatment reinitiation) at 48 weeks. Adverse events (AEs) were reported in 73.8% of pts during the first 48 weeks of TFR vs 77.0% during the year prior to stopping treatment. The incidence of musculoskeletal pain-related AEs was higher during TFR (42.1% vs 14.3%). To assess the potential effect of stopping NIL on quality of life (QOL), pt-reported outcomes were assessed before and during TFR. Methods: ENESTop enrolled adult pts with CML-CP with ≥ 3 years of prior tyrosine kinase inhibitor (TKI) therapy (> 4 weeks of imatinib [IM], then ≥ 2 years of NIL). Pts must have achieved sustained MR4.5 on NIL after switching from IM. Enrolled pts entered a 1-year NIL treatment consolidation phase; those without confirmed loss of MR4.5 (ie, consecutive BCR-ABL1IS > 0.0032%) entered the TFR phase and stopped NIL. Pts with loss of MMR or confirmed loss of MR4 during the TFR phase reinitiated NIL. QOL was assessed via questionnaires completed by pts at specified time points. The MD Anderson Symptom Inventory for CML (MDASI-CML) questionnaire assessed, for a defined set of symptoms, the levels of severity and interference with daily life on a scale of 0 to 10, with 0 being the lowest level. The EQ-5D-5L questionnaire assessed problems experienced by pts (no, slight, moderate, severe, or extreme [ie, interfering with functioning] problems) in 5 dimensions: mobility, self-care, usual activities, anxiety/depression, and pain/discomfort; additionally, overall level of health was assessed on a scale of 0 to 100 using the EQ VAS, with 0 being the lowest level. Results: Of 163 enrolled pts, 126 met the criteria for stopping NIL in the TFR phase; of these 126, 53 had loss of MMR or confirmed loss of MR4, of whom 51 reinitiated NIL. Among pts who completed each questionnaire at week 48 of the consolidation phase, week 12 of the TFR phase, or week 48 of the TFR phase, mean MDASI-CML severity scores were 1.7, 1.5, and 1.2, respectively; mean MDASI-CML interference scores were 1.7, 1.6, and 1.4, respectively; and mean EQ VAS scores were 82.2, 78.8, and 82.3, respectively (Table). Among pts with sustained TFR and scores at both week 48 of the consolidation phase and week 12 or 48 of the TFR phase, minimal changes were observed in MDASI-CML and EQ VAS scores during TFR vs week 48 of the consolidation phase. Among pts who reinitiated NIL, mean MDASI-CML severity and interference scores and mean EQ VAS scores at 24 weeks after the start of retreatment were 1.6, 1.5, and 78.8, respectively; changes in scores between week 24 after treatment reinitiation and week 48 of the consolidation phase were minimal among pts with scores at both time points. Among pts who completed the EQ-5D-5L questionnaire, the proportions who reported problems (any level of severity) in the 5 dimensions were generally similar across time points, although problems with mobility and pain/discomfort were more common during TFR vs week 48 of the consolidation phase, particularly at week 12 of the TFR phase (Table). Conclusion: Changes in QOL after stopping NIL, as assessed using these questionnaires, were minimal. This may be related to pts having a relatively high QOL prior to stopping treatment given that they had tolerated ≥ 3 years of TKI therapy, including ≥ 2 years of NIL, prior to enrollment. Despite the higher incidence of musculoskeletal pain-related AEs observed during TFR (42.1% vs 14.3%), the overall QOL was generally similar between the TFR and consolidation phases. This suggests that these AEs did not have a significant negative impact on QOL. Longer follow-up in ENESTop will be needed to further evaluate trends in QOL after stopping second-line NIL. Disclosures Mahon: NOVARTIS PHARMA: Honoraria, Research Funding; BMS: Honoraria; ARIAD: Honoraria; PFIZER: Honoraria. Boquimpani:BMS: Speakers Bureau; Novartis: Research Funding, Speakers Bureau. Takahashi:Novartis: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; BMS: Honoraria. Shuvaev:Novartis pharma: Honoraria; Pfizer: Honoraria; BMS: Honoraria. Ailawadhi:Pharmacyclics: Consultancy; Novartis: Consultancy; Amgen Inc: Consultancy; Takeda Oncology: Consultancy. Lipton:Novartis: Consultancy, Research Funding; Ariad: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding. Turkina:Novartis Pharma: Honoraria; Pfizer: Honoraria; BMS: Honoraria. Moiraghi:NOVARTIS: Speakers Bureau; BMS: Speakers Bureau. Nicolini:Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria. Sacha:Pfizer: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Adamed: Consultancy, Honoraria. Kim:BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; ILYANG: Consultancy, Honoraria, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau. Fellague-Chebra:Novartis: Employment. Acharya:Novartis Healthcare Pvt. Ltd.: Employment. Brandt:Novartis: Employment. Gnanasakthy:Novartis: Consultancy, Equity Ownership, Research Funding. Jin:Novartis: Employment, Equity Ownership. Hughes:Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding.