Citations

Abstract Background: SL-401 is a novel targeted therapy directed to the interleukin-3 receptor (CD123), a target overexpressed by many hematologic malignancies. SL-401 is currently being advanced through clinical trials in patients with a variety of CD123+ malignancies including blastic plasmacytoid dendritic cell neoplasm (BPDCN), acute myeloid leukemia (AML) in remission with high relapse risk, and multiple myeloma. CD123 has been shown to be expressed on myeloproliferative neoplasm (MPN) cells as well as microenvironmental immune cells, namely plasmacytoid dendritic cells (pDCs), in the bone marrows of some patients with MPN including chronic myelomonocytic leukemia (CMML). Microenvironmental pDCs have been implicated in promoting plasma cell disorders and preliminary data suggest that pDCs could play a related role in some myeloid neoplasms. Accordingly, a therapy directed at both CD123-expressing myeloid cells and neighboring CD123-expressing pDCs could provide therapeutic benefit. SL-401 is being evaluated in patients with advanced, high-risk MPN, including systemic mastocytosis (SM), myelofibrosis (MF), primary eosinophilic disorders (PED), and CMML. Preliminary results are reported here. Methods & Results: This multicenter, single-arm Phase 2 trial of patients with advanced, high risk MPN includes a lead-in (stage 1) and expansion (stage 2). In stage 1, patients receive SL-401 as a daily IV infusion at 7, 9, 12 ug/kg/day, or higher for days 1-3 of a 21-28 day cycle in a 3x3 design. In stage 2, patients receive SL-401 at the dose determined in stage 1. Study objectives include characterization of the safety profile, including determination of the maximum tolerated or tested dose, and detection of preliminary efficacy signals including evaluation of tumor response and progression free survival by standard criteria. As of 7/20/16, 6 patients with MPN (MF, n=3; CMML-2, n=2; CMML-1, n=1) received SL-401 (7 ug/kg, n=3; 9 ug/kg, n=3). The median age was 66 years (range: 42-81 years). Patients treated at all doses received 1+ to 2+ cycles (ongoing) of SL-401. The most common treatment-related adverse events (AEs) were thrombocytopenia (2/6; 33%) and fatigue (2/6; 33%); the most common ≥ Grade 3 treatment-related AEs were thrombocytopenia (2/6; 33%) and anemia (1/6; 17%); there has been no DLT. Efficacy assessments are ongoing. Patients are currently enrolling in the 12 ug/kg/day cohort. Conclusions: Initial dosing of SL-401 appears to be well-tolerated in patients with MPN and CMML, with no unexpected AEs observed. Given CD123 expression on myeloid neoplastic cells as well as microenvironmental immune cells (namely, pDCs), SL-401 may offer a novel, targeted therapeutic approach in patients with high-risk MPN and CMML of unmet medical need. Enrollment continues in stage 1 of this ongoing Phase 2 trial and updated safety and efficacy data will be presented. Clinical trial information: NCT02268253. Disclosures Gupta: Novartis: Consultancy, Honoraria, Research Funding; Incyte Corporation: Consultancy, Research Funding. Carraway:Incyte: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Baxalta: Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees. Schiller:Incyte Corporation: Research Funding. Talpaz:Incyte Corporation: Other: Travel expense reimbursement, Research Funding; Ariad: Other: Expense reimbursement, travel accomodation expenses, Research Funding; Novartis: Research Funding; Pfizer: Consultancy, Other: travel accomodation expenses, Research Funding. McCloskey:Novartis: Speakers Bureau; Incyte: Consultancy; Ariad: Consultancy, Speakers Bureau; Amgen: Speakers Bureau. Lee:Alexion Pharmaceuticals: Consultancy; Amgen: Consultancy; Baxalta: Consultancy; Boehringer Ingelheim: Consultancy; Pfizer Inc: Consultancy. Yacoub:Alexion: Honoraria; Seattle Genetics: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau. Ali:Incyte Corporation: Research Funding. Chen:Stemline Therapeutics, Inc.: Employment, Equity Ownership. Shemesh:Stemline Therapeutics: Employment, Equity Ownership. Brooks:Stemline Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties.

Abstract Background: Myelofibrosis (MF) is a myeloproliferative neoplasm associated with splenomegaly, debilitating symptoms, progressive bone marrow fibrosis and shortened survival. Inflammatory cytokines are associated with the disease and monitoring cytokine levels provides information about response to therapy. Momelotinib (MMB) is a JAK1/2 inhibitor under investigation for the treatment of MF that has been shown to be safe and efficacious while providing an anemia benefit to MF patients in the phase I/II studies: CCL09101 (ASH 2013) and YM387-II (EHA 2014). AIMS: To perform an exploratory analysis of the association between cytokines and anemia-related laboratories, 8 week transfusion response, spleen response by MRI at 24 weeks and total symptom score (TSS) reduction (≥50% decrease at week 24) and JAK2 mutation status, in the phase I/II, open-label YM387II trial. METHODS: 61 patients were enrolled and received MMB treatment. Whole blood samples were collected at baseline, 6 and 24 hours post-dose on day 1, and weeks 8 and 20. Plasma levels of 25 cytokines were analyzed by ELISA or MSD. Comparison of post-treatment data with baseline was carried out using Wilcoxon signed rank tests. Significant change from baseline was declared when ≥ 20% change from baseline was observed with Bonferroni adjusted p < 0.05. As this was an exploratory evaluation, comparison between treatment responders and non-responders was carried out using Wilcoxon rank sum test with no multiple testing corrections. Correlations between the cytokines and main biological parameters were investigated using Spearman correlation coefficients. RESULTS: JAK2V617F allele burden. The prevalence of JAK2V617F-positive patients was 68%. A statistically significant decline in JAK2V617F allele burden from baseline in this subgroup was observed at week 12 (median decrease 16.6%; p = 0.0063; n=21) and week 24 (median decrease 21.1%; p = 0.0019; n=18). Higher baseline IGFBP1 was associated with JAK2V617 mutation (48.2% higher in JAK2 mutated patients than in wildtype patients; p = 0.027). Cytokines and iron metabolism markers at baseline At baseline, hepcidin and IL-8 were anti-correlated with anemia-related markers such as transferrin and hemoglobin (Hb) (Spearman correlation coefficients < -0.5). IL-6, CRP and IL-10 showed strong, positive correlation (Spearman correlation coefficients > 0.5). Lower baseline IL-6 was associated with 24 week spleen response (42.3% lower in responders, p = 0.005); higher baseline thrombopoeitin (TPO) was associated with transfusion response at 8 week (3-fold higher in responders, p = 0.002). Baseline ferritin was 63.7% lower in TSS responders compared to non-responders (p = 0.015). On-treatment changes of cytokines and iron markers A significant decrease was observed in CRP, EPO, IL-6, IL-10, IL-12, TNFRII and TNFα following MMB treatment. IL-6 was reduced 30.3% as early as 6 hrs after first dose of MMB and CRP levels were reduced 27.3% after 24 hrs after treatment and continued to decline to 75% by week 4. A peak of IGFBP1 at 24h and increased TPO were observed. Decreased IL-12 and increased IL-8 at week 8 was significantly associated with 24 week spleen response (p < 0.05). Decline of CRP at week 8 was associated with TSS response (p = 0.045). Hb stayed at or above baseline for 6 months. An early peak of Hb was observed at Day 15 which was correlated with a significant increase in red blood cells and decrease in reticulocytes. CONCLUSIONS: In this exploratory analysis, a rapid and sustained reduction in inflammatory cytokines was observed with MMB treatment as expected based on the mechanism of action of MMB through JAK1/2 inhibition. Data from this study suggest an association between IGFBP1 and JAK/STAT signaling in myelofibrosis that will need to be explored in future studies with larger sample sets. Individual baseline biomarkers were correlated with MMB response, but no single biomarker was associated with all responses. Changes in IL-12 and IL-8 were significantly correlated with 24 week spleen response. The Day 15 data suggest that MMB treatment facilitates erythrocyte maturation. These observations, as well as a panel of iron metabolism markers and cellular signaling pathways, will be investigated in a planned Phase 2 translational biology study of MMB in transfusion-dependent subjects with MF (Gilead Sci: GS-US-352-1672). Disclosures Gupta: Incyte: Honoraria, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Mesa:Novartis Pharmaceuticals Corporation: Consultancy; NS Pharma: Research Funding; Gilead: Research Funding; Promedior: Research Funding; CTI Biopharma: Research Funding; Incyte Corporation: Research Funding; Genentech: Research Funding; Pfizer: Research Funding. Deininger:Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees. Zhang:Gilead Sciences: Employment. Xiao:Gilead Sciences: Employment. Collins:Gilead Science: Employment. Kwei:Gilead Sciences: Employment. Joshi:Gilead Sciences: Employment. Brachmann:Gilead Sciences: Employment.

Abstract Background: PRM-151 (PRM) is a recombinant form of pentraxin-2, an endogenous human protein that acts at sites of tissue damage, inducing macrophage differentiation to prevent and reverse fibrosis. 27 patients with primary myelofibrosis (MF), post-essential thrombocythemia MF, or post-polycythemia vera MF and Grade 2 or 3 bone marrow (BM) fibrosis enrolled in the first stage of a 2-stage adaptive trial in which PRM-151 10 mg/kg IV was administered for 24 weeks in four different arms: PRM-151 QW (n=8), PRM-151 Q4W (n=7), PRM-151 QW + ruxolitinib (RUX) (n=6), or PRM-151 Q4W + RUX (n=6). At 24 weeks, reductions in BM fibrosis, improvements in hemoglobin (Hgb) and platelets (PLT), decreases in symptoms (MPN-SAF Total Symptom Score [TSS]), and modest reductions in spleen size by palpation were observed in all arms, with a favorable safety profile (Verstovsek, ASH 2014, Abstract 713). Patients experiencing clinical benefit were allowed to continue beyond 24 weeks. We now report efficacy and safety in 13 patients who have completed at least 72 weeks of treatment. Bone marrow fibrosis status by morphologic WHO grading and computer-assisted image analysis (CIA) are available up to 48 weeks in some patients, as assessed by central hematopathologist reviewers blinded to patient, treatment, and timepoint. BM data through 72 weeks is pending. WHO response was defined as ≥1 grade reduction in MF grade at any time and CIA response was defined as a decrease in the % fibrosis compared to baseline with a negative slope > 1. (Pozdnyakova, EHA 2015, Abstract P677). Baseline Demographics (N=13): Median age 60 (51-76); 46% DIPSS Int-1, 54% DIPSS Int-2; 62% PMF, 15% post-ET MF, 23% post-PV MF; 46% grade 3 BM fibrosis, Hgb < 100 g/L in 38%, PLT < 100 x 109/L in 69% and <50 x 109/L in 38%; 31% JAK inhibitor-naive and 69% received a prior or current JAK inhibitor. Study treatment (N=13): In the first 24 weeks, treatment was PRM-151 QW (n=5), PRM-151 Q4W (n=3), PRM-151 QW + RUX (n=2), PRM-151 Q4W + RUX (n=3). At 28 weeks, treatment changed to PRM-151 QW (n=2), PRM-151 Q4W (n=7), and PRM-151 Q4W + RUX (n=4), with 1 patient stopping RUX for thrombocytopenia. Both PRM-151 QW patients switched to PRM-151 Q4W after 40 and 52 weeks. Two patients missed weeks 64 and 68 due to complications of a motor vehicle accident and abdominal surgery, respectively, but are continuing treatment as of week 72. BM (n=13): 54% had a morphologic response, and 85% had a CIA response. Hgb (g/L): In 5 pts with baseline Hgb < 100, median Hgb increased by 24% from 86 (range 77-97) at baseline to 107 (range 71-113) at Week 72. 3 of 5 patients who were receiving transfusions at baseline became transfusion independent, with durations of 32-60 weeks. (Figure 1) PLT (x 109/L): In 9 pts with baseline < 100, median PLT count increased by 37% from 38 (range 10-89) at baseline to 52 (range 26-159) at Week 72. All 4 patients who were receiving PLT transfusions at baseline became transfusion independent, with durations of 24-44 weeks. (Figure 2) Symptoms (N=13): 69% and 38% of patients had ≥ 50% and 100% reductions from baseline in TSS between 24 and 72 weeks, with durations of up to 48 and 12 weeks, respectively. (Figure 3) Spleen (N= 9 with palpable spleens at baseline): 50% of pts had ≥25% reduction, 2 of whom had ≥50% reduction lasting > 12 weeks. (Figure 4) Safety (N=13): Most common adverse events (AEs) regardless of relatedness were fatigue (4), nausea (3), fever (3), cough (2), diarrhea (2), tooth infection (2), headache (2), upper respiratory infection (2), hyperglycemia (2), and hyperuricemia (2). There were 13 possibly or probably related adverse events in 3 patients from beginning of study through 71 weeks, 11 Grade 1, 1 Grade 2 and 1 Grade 3, with no event occurring in > 1 patient. There were no related serious AEs in these patients. Conclusion: In 13 patients completing at least 72 weeks, PRM-151 treatment was well tolerated, and improvements in Hgb, PLT, symptoms and spleen appeared to increase with longer treatment duration. Disclosures Mesa: Novartis Pharmaceuticals Corporation: Consultancy; NS Pharma: Research Funding; Gilead: Research Funding; Promedior: Research Funding; Genentech: Research Funding; CTI Biopharma: Research Funding; Incyte Corporation: Research Funding; Pfizer: Research Funding. Foltz:Promedior: Research Funding. Gupta:Incyte Corporation: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Promedior: Research Funding. Mascarenhas:Kalobios: Research Funding; Roche: Research Funding; Promedior: Research Funding; Novartis Pharmaceuticals Corporation: Research Funding; CTI Biopharma: Research Funding; Incyte Corporation: Research Funding. Ritchie:Incyte: Speakers Bureau; Celgene: Speakers Bureau. Hoffman:All Cells, LLC: Consultancy, Membership on an entity's Board of Directors or advisory committees; Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; Promedior: Research Funding. Silver:Promedior: Research Funding. Pozdnyakova:Promedior: Consultancy. Hasserjian:Promedior: Consultancy. Trehu:Promedior: Employment, Equity Ownership. Salama:Promedior: Consultancy. Gotlib:Allakos, Inc.: Consultancy.

Abstract Background Momelotinib (MMB, GS-0387, CYT387) is a JAK1 and JAK2 inhibitor under investigation for the treatment of myelofibrosis. Preliminary results of a phase I/II core study (n=166) were previously reported. Subjects who achieved at least stable disease in the core study could continue MMB treatment in an extension study (n=120). Final data from the phase I/II core study and updated data from the extension study are presented. Methods Subjects with myelofibrosis categorized as IPSS intermediate-2 or high risk, or intermediate-1 risk with symptomatic splenomegaly or hepatomegaly and/or unresponsive to available therapy, were enrolled. Following a dose escalation phase, subjects were treated on a dose expansion phase in the core study with MMB at either 150 mg or 300 mg once-daily, or 150 mg twice-daily for 9 months. In the extension study, MMB was at the same dose the subject tolerated and derived clinical benefit from in the core study. Clinical responses were adjudicated according to IWG-MRT criteria. Spleen Response was defined as ≥ 50% reduction in palpable splenomegaly that lasted ≥ 8 weeks (wks) for baseline splenomegaly ≥ 10 cm, plus resolution of palpable splenomegaly that lasted ≥ 8 wks for baseline splenomegaly > 5 to < 10 cm. Anemia Response was defined as transfusion-free interval of ≥ 12 wks for baseline transfusion dependence, plus ≥ 2 g/dL rise in hemoglobin (Hb) for baseline transfusion independence and Hb < 10 g/dL. Baseline transfusion dependence was defined as ≥ 2U RBC transfusion in the 30 days prior to first dose of MMB or identified as transfusion dependent in medical history. Results As of April 2013, 58 of 120 subjects remained on treatment in the open-label extension study, with median treatment duration of 507 days (range 23-1036) for both core and extension studies. Based on interim analysis, the most common reasons for discontinuation from the extension study were disease progression (n=13), investigator's decision (n=12), and consent withdrawal (n=10), with 2 drug-related adverse events (both peripheral neuropathy) that led to study discontinuation. Efficacy data for the core and extension studies are depicted in table below. Median time to onset of Spleen Response was not yet reached (range 6-693 days), median duration of Spleen Response was 324 days (range 56-936). Median duration of 12-week transfusion independence was not yet reached (91-987 days), median duration of Anemia Response was not yet reached (57-987). Constitutional symptoms assessment at 3 months for the core study showed ≥ 50% improvement in 72%, 46%, 77%, 100%, and 74% of subjects with pruritis, cough, bone pain, fever, and night sweats respectively. Most common Grade 3 or 4 treatment-related events were thrombocytopenia (29%), neutropenia (5%), and elevated lipase (4%) without clinical pancreatitis. Peripheral neuropathy was reported by 38% of subjects, all ≤ Grade 2, with 17 subjects experiencing neuropathy at baseline. Four subjects transformed into acute leukemia (1 in core study, 3 in extension study). There was no treatment-related death. Conclusion Prolonged administration of MMB for treatment of myelofibrosis is well tolerated and has an acceptable safety profile. MMB is efficacious in durably reducing myelofibrosis-related splenomegaly as well as improving transfusion requirement and disease-related symptoms. These data form the basis for the phase 3 randomized study of MMB in myelofibrosis. Disclosures: Gupta: Novartis: Lecture fee, Lecture fee Other; Novartis: Consultancy; Incyte: Consultancy; Novartis: Research Funding; Incyte: Research Funding. Bavisotto:YM Biosciences: Consultancy. Kawashima:Gilead Sciences: Employment. Lee:Gilead Sciences: Employment. Kowalski:Gilead Sciences: Employment. Deng:Gilead Sciences: Employment. Niforos:Gilead Sciences: Employment.

Abstract PRM-151 (PRM) is a recombinant form of Pentraxin-2, an endogenous human protein that acts at sites of tissue damage, inducing macrophage differentiation to prevent and reverse fibrosis. PRM has broad anti-fibrotic activity in multiple preclinical models of established fibrotic diseases and no dose limiting toxicities in phase 1 trials. Myelofibrosis (MF: primary (PMF), post-essential thrombocythemia (post-ET MF), and post polycythemia vera (Post PV MF)) is a myeloid malignancy characterized by progressive bone marrow (BM) fibrosis with resultant anemia, abnormal platelet and leukocyte counts, extramedullary hematopoiesis, and a well-defined symptom complex. This study investigated the potential of PRM in MF to reduce BM fibrosis and to improve key disease features including abnormal blood counts, symptoms, and splenomegaly. MF patients (pts) with Dynamic International Prognostic Scoring System (DIPSS) intermediate-1, intermediate-2, or high-risk disease and grade ≥ 2 BM fibrosis, either on no current therapy or on a stable dose of ruxolitinib (RUX) for ≥ 12 weeks and no improvement in spleen for ≥ 4 weeks, were eligible for stage 1 of this open-label adaptive trial. Assignment to one of the 4 treatment arms was per investigator and pt choice: PRM 10 mg/kg IV 1-hour infusion days 1, 3, 5, then weekly (QW) or every 4 weeks (Q4W), alone or with RUX, for 24 weeks. Primary endpoint was overall response rate by IWG-MRT (symptoms by MPN-SAF Total Symptom Score (TSS), spleen by palpation) and/or decrease in BM fibrosis by ≥ 1 grade with otherwise stable disease. BM biopsies were obtained at baseline, 3 and 6 months, and were evaluated centrally by two blinded hematopathologists. Pts with clinical benefit were allowed to continue treatment in an extension. At least one response in any arm was required for that regimen to be evaluated in Stage 2. Twenty seven pts were enrolled: 8 PRM QW, 7 PRM Q4W, 6 PRM QW + RUX, 6 PRM Q4W + RUX. Median age 67 years (52-85); 70% DIPSS Int-2 or High Risk; 52% PMF, 15% post-ET MF, 33% post-PV MF; 63% grade 3 BM fibrosis, Hemoglobin (Hgb) < 100 g/L in 56% and < 85 g/L in 26%, platelet count (PLT)< 100 x 109/L in 52% and < 25 x 109/L in 30%; 22% were JAK inhibitor-naive and 52% had received a prior JAK inhibitor (not including ongoing RUX). Twenty pts completed 24 weeks of therapy; 18 continued extension treatment. PRM-151 was well-tolerated alone and with RUX; most adverse events (AEs) were Grade 1/2 and unrelated, with 3 Grade 3 possibly related AEs and 5 possibly related serious AEs. Nine of 26 evaluable pts responded, for an overall response rate (ORR) of 35%, with 4 IWG symptom clinical improvements (CI) and 6 BM fibrosis responses (Table 1), with ≥ 1 response in each arm. One pt had a CI and BM response. Reduction in BM fibrosis was associated with normal erythroid microarchitecture, normal or decreased myeloid:erythroid ratio, and fewer paratrabecular megakaryocytes, all potential surrogates of improved bone marrow microenvironment. IWG stable disease was observed in 77% of pts, with trends of clinical benefit in Hgb, PLT, peripheral blood blasts, spleen, and symptoms (Table 2). In 14 patients (54%), all parameters were stable or improved. Conclusion: PRM-151 was well-tolerated in patients with advanced MF, with no evidence of drug-related myelosuppression and encouraging trends in both clinical and histologic aspects of the disease. Reduction in BM fibrosis, stable to improved hematologic parameters, symptom responses, and stable to reduced spleen size support further development of PRM-151 in MF. Table 1 Two additional subjects had decrease in bone marrow fibrosis but progressive disease. Number of Patients BM Fibrosis Grade at Last Study Timepoint 3 2 1 BM Fibrosis Grade at Baseline 3 8 3 1 2 1 4 2 Abstract 713. Table 2 Outcome Parameter Denominator (n) Clinical Benefit Pts with Improvement (n/%) ORR (primary endpoint) All evaluable pts (26) IWG-MRT CI AND/OR reduction in BM fibrosis by ≥ 1 grade 9 (35%) Hgb Hgb < 100 g/L (15) ≥10 g/L increase from baseline AND no transfusions or 50% reduction in transfusions if transfusion dependent 6 (40%) PLT PLT < 100 x 109/L (13) > 100 x 109/L AND increase of ≥20 x 109/L ; increase of ≥20 x 109/L if baseline < 50, AND/OR increase of ≥ 10 x 109/L with discontinuation of transfusions 8 (62%) Blasts ≥ 1% peripheral blasts (14) No peripheral blasts 3 (21%) Symptoms All evaluable pts (26) ≥ 25% reduction in TSS ≥ 12 weeks 10 (38%) Spleen Palpable spleen (19) ≥ 25% decrease ≥ 4 weeks AND any decrease ≥ 12 weeks 5 (26%) Disclosures Verstovsek: Incyte: Research Funding; Astrazeneca: Research Funding; Lilly Oncology: Research Funding; Roche: Research Funding; Geron: Research Funding; NS Pharma: Research Funding; Bristol Myers Squibb: Research Funding; Novartis: Research Funding; Celgene: Research Funding; Gilead: Research Funding; Seattle Genetics: Research Funding; Promedior: Research Funding; Cell Therapeutics: Research Funding. Mesa:Incyte, CTI, NS pharma, Gilead, Celgene: Research Funding; Promedior: Research Funding. Foltz:Janssen: Consultancy; Promedior: Research Funding; Gilead: Research Funding; Incyte: Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Gupta:Incyte Corporation: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Promedior: Research Funding. Mascarenhas:Novartis Pharmaceuticals Corporation: Research Funding; Incyte Corporation: Consultancy, Research Funding; Promedior: Research Funding. Ritchie:Celgene, Incyte: Speakers Bureau; Promedior: Research Funding. Hoffman:Geron: Consultancy, Membership on an entity's Board of Directors or advisory committees; All Cells LLC: Consultancy, Membership on an entity's Board of Directors or advisory committees; Promedior: Research Funding. Pozdnyakova:Sanofi: Consultancy; Incyte: Consultancy; Promedior: Consultancy. Hasserjian:Sanofi: Consultancy; Incyte: Consultancy; Promedior: Consultancy. Trehu:Promedior: Employment, Equity Ownership. Kantarjian:ARIAD, Pfizer, Amgen: Research Funding. Gotlib:Novartis: Research Funding, Travel Reimbursement, Travel Reimbursement Other; Sanofi: Research Funding; Gilead: Research Funding; Incyte: Consultancy, Honoraria, Research Funding, Travel Reimbursement Other; Promedior: Research Funding.

Abstract Abstract 1733 Background: Patients with myelofibrosis (MF) suffer from cytopenias, debilitating symptoms, and splenomegaly, all of which may contribute to shortened life expectancy. Cachexia is a common manifestation of MF. Its causes are multifactorial and include elevated inflammatory cytokines and mechanical effects of splenomegaly. It is a predictor of poor survival in patients with MF. Cachexia manifests as weight loss with low body-mass index (BMI; <20–21 kg/m2) (Strasser F. Sixth Research Congress of the European Association of Palliative Care; Wagner PD. Eur Respir J. 2008;31:492–501) and with metabolic indicators of poor nutritional status including hypocholesterolemia (total cholesterol <150 mg/dL or <3.89 mmol/L), which has been linked to poor prognosis in MF (Mesa et al. Blood 2007;110:abstract 2548). In the phase III, placebo-controlled, COMFORT-I study, ruxolitinib treatment significantly reduced spleen volume, improved MF-related symptoms, and exhibited a survival advantage compared with placebo in patients with MF. In this post hoc analysis, we investigated the effects of ruxolitinib treatment on weight and total cholesterol and the association of these changes with survival in COMFORT-I. Methods: Eligible patients in COMFORT-I were randomized to receive placebo (n=154) or ruxolitinib (n=155) at starting doses of 15 and 20 mg PO BID depending on baseline platelet count. Body weight was measured at baseline, and weeks 4, 8, 12, 16, and 24 and then every 12 weeks thereafter. Total serum cholesterol was measured at baseline and weeks 4, 12, 24, and then every 24 weeks thereafter. All patients receiving PBO completed crossover or discontinued within 3 months of the primary data analysis (when all patients completed 24 weeks and when half the patients remaining on study completed 36 weeks of treatment); thus, data for these patients were available for up to week 36 for weight and week 24 for total cholesterol. Kaplan-Meier analyses of overall survival were conducted in patients randomized to ruxolitinib stratified into 2 groups based on the median values separately for maximum weight gain and for maximum increase in total cholesterol during randomized treatment. Results: At baseline, mean body weight was similar between the treatment groups (72 kg, both) and mean total cholesterol was low (<150 mg/dL) in both treatment groups (ruxolitinib: 118 mg/dL; placebo: 115 mg/dL). The proportion of patients with BMI <22 were similar between the treatment groups (ruxolitinib: 23%; placebo: 28%) as was the proportion with total cholesterol <150 mg/dL (82%, both). Patients randomized to ruxolitinib experienced a gradual increase in body weight that stabilized by week 36 of treatment whereas patients receiving placebo experienced decreases in body weight over time (Figure 1). Similarly, total cholesterol increased in patients randomized to ruxolitinib and decreased in patients receiving placebo (Figure 2). Although total cholesterol increased over time in ruxolitinib-treated patients, increases did not exceed the upper limit of normal (199 mg/dL or 5.15 mmol/L). Nearly all patients randomized to ruxolitinib experienced weight gain (96% of patients) or an increase in total cholesterol (97% of patients). In patients randomized to ruxolitinib, weight gain above the median was associated with prolonged survival relative to lesser degrees of weight gain (HR=0.40; 95% CI: 0.18, 0.90; P=0.022; Figure 3). Similarly, increase in total cholesterol above the median was also associated with prolonged survival relative to a lesser degree of total cholesterol increase (HR=0.46; 95% CI: 0.21, 1.01; P=0.048; Figure 4). Meaningful comparisons with the placebo group based on the same stratification criteria could not be conducted as the majority of such patients experienced weight loss and decreases in total cholesterol while on the study; however, overall survival favored both ruxolitinib groups relative to all patients randomized to placebo even for ruxolitinib-treated patients with lower than median levels of weight gain or increase in total cholesterol. Conclusions: Ruxolitinib therapy promotes weight gain and improves total cholesterol in MF patients. These results suggest that the survival advantage exhibited by ruxolitinib over placebo in MF patients may be partly explained by reversal of the catabolic state and cachexia. Disclosures: Mesa: Incyte: Research Funding; Lilly: Research Funding; Sanofi: Research Funding; NS Pharma: Research Funding; YM Bioscience: Research Funding. Verstovsek:Incyte Corporation: Research Funding. Gupta:Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; YM Biosciences: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi#x2610;#x0025; Aventis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Mascarenhas:Incyte Corporation: Consultancy; Novartis: Clinical Trial Support, Clinical Trial Support Other. Atallah:Incyte: Consultancy, Research Funding. Sun:Incyte Corporation: Employment, Equity Ownership. Sandor:Incyte Corporation: Employment, Equity Ownership. Gotlib:Incyte Corporation: Consultancy, Honoraria, Support for travel to meeting for the study or other purposes from Incyte Other.

Abstract Abstract 178 Background: CYT387 is a potent and selective small molecule inhibitor of JAK 1 and JAK 2 which is in clinical development for the treatment of myelofibrosis. Previously reported preliminary results from a phase I/II multicenter study demonstrated improvements in splenomegaly and constitutional symptoms as well as in RBC transfusion requirements. Enrollment has been completed and all subjects have now reached a minimum of 9 months on study. Updated safety and efficacy results are presented. Methods: Subjects with high or intermediate-risk primary myelofibrosis (PMF) and post-polycythemia vera (post-PV) or post-essential thrombocythemia (ET) myelofibrosis were enrolled. Following an initial dose expansion phase, subjects were treated in a 9 month core study at an initial dose of 150 mg QD, 300 mg QD or 150 mg BID. Continued treatment with CYT387 was permitted in an extension phase for subjects who maintained at least stable disease. Responses were assessed by International Working Group (IWG) criteria with transfusion independence response defined as achieving a minimum 12 week transfusion-free period. Results: Enrollment of 166 subjects was completed at 6 study sites. Initial doses included 52 subjects at 150 mg QD, 60 subjects at 300 mg QD and 42 subjects at 150 mg BID. An additional 12 subjects were enrolled in other dose groups (100 mg QD, 200 mg QD, 400 mg QD) during the initial dose escalation phase. The median duration (range) of follow-up is 16.1 months (0.7 to 31.0 months). Durable transfusion independence responses were observed in more than half of the RBC transfusion dependent subjects with a maximal transfusion-free period exceeding 2 years and ongoing. In addition, the percentage of all subjects requiring RBC transfusions substantially decreased over the treatment period. Treatment with CYT387 resulted in rapid and sustained reductions in splenomegaly with a maximal response duration approaching 2 years. The majority of subjects reporting constitutional symptoms at baseline experienced complete resolution or marked improvement by 6 months with measurable improvement within the first month of therapy. Higher transfusion independence and spleen response rates were seen in the 300 mg dose group compared to the 150 mg QD or 150 mg BID dose groups. For the first 60 consecutively enrolled subjects for whom the most mature data is available, the median follow-up period (range) is 21.5 months (2.9–31.0 months). The anemia and spleen response rates in these subjects, per IWG-MRT, were 59% and 48%, respectively; among 33 of these subjects who were RBC transfusion dependent by IWG-MRT criteria, 70% achieved a minimum 12-week period without transfusions with a maximal transfusion-free period of greater than 2 years and ongoing. While 90% of subjects reported at least one treatment-related AE, the majority were reported as Grade 1. The most common treatment-related AEs were thrombocytopenia, peripheral neuropathy, dizziness, diarrhea, nausea, and headache. Treatment-related peripheral neuropathy was sensory, with almost all events reported as Grade 1. The most common Grade 3–4 treatment-related AEs included thrombocytopenia and hyperlipasemia. Only 5% of subjects reported treatment-related AEs resulting in study drug discontinuation. There were no treatment-related deaths. Conclusions: CYT387 has proven safe and well tolerated even with prolonged administration for over 2.5 years. Treatment with CYT387 results in clinical improvement by effecting a rapid, meaningful and durable reduction of splenomegaly and the achievement of sustained RBC transfusion independence in a substantial number of subjects. CYT387 is also effective in improving constitutional symptoms. These results support the development of CYT387 at a dose of 300 mg QD for the treatment of myelofibrosis. Final analyses of safety and efficacy will be available at the time of the meeting. 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 the ongoing Phase-1/2 study of CYT387 use in myelofibrosis treatment will be described. Gotlib:YM Biosciences: Research Funding. Gupta:Celgene: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; YM Biosciences: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sanofi-Aventis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Roberts:YM BioSciences: clinical trial support Other. Wadleigh:Incyte: Membership on an entity's Board of Directors or advisory committees. Sirhan:Novartis: Consultancy, Honoraria. Bavisotto:YM BioSciences: Consultancy. Kawashima:YM BioSciences: Employment. Kowalski:YM BioSciences: Employment.

Abstract Introduction: The impact of genomic alterations, such as mutations in ASXL1, on the risk of disease progression and leukemic transformation in patients with myelofibrosis (MF) is well established. Further, emerging data suggests that the number and type of mutations may impact response to therapies such as ruxolitinib or imetelstat. Allogeneic hematopoietic stem cell transplant (allo-HSCT) remains the only potentially curative treatment for MF patients. However, the impact of somatic mutations on overall survival (OS) and relapse-free survival (RFS) is poorly understood. Using next-generation sequencing of pre-transplant blood and bone marrow samples from a well clinically-annotated cohort of MF patients who underwent allo-HSCT, we sought to determine the impact of mutational burden on outcomes. Methods: A multicenter retrospective analysis of a cohort of 84 patients was carried out. This included 52 patients treated on the MPD-RC 101 prospective study (NCT00572897), 18 patients treated at Prince Margaret Hospital, and 14 patients treated at Memorial Sloan Kettering Cancer Center. Patient and transplant characteristics are displayed in Table 1. DNA was extracted from pre-transplant bone marrow aspirate samples or peripheral blood samples. High-throughput sequencing of a panel of genes was performed. Average coverage of 829x (standard deviation of ±130) was obtained. Mutect was utilized to call single point variants (comparing our samples to a pool of normal samples) and PINDEL was used to call short insertions and deletions. We excluded all mutations present in at least one database of known non-somatic variants (DBSNP and 1000 genomes) and absent from COSMIC. Univariate Cox regression and Kaplan-Meier graphics were used to investigate the association of patient, transplant, and disease characteristics with OS and RFS. Results: JAK2V617F was the most frequent mutation detected in 41(48.8%) patients (Table 2). Eighteen patients (21.4%) had triple negative disease (negative for JAK2, MPL, and CALR mutations). Univariate analysis included the following: patient characteristics (age, gender), transplant characteristics (related vs. unrelated donor, matched vs. mismatched donor and myeloablative vs. reduced intensity conditioning) and disease characteristics (DIPSS and presence of mutations). Decreased OS was associated with unrelated donor status (HR 2.09, 95% CI: 1.03-4.23, p=0.04), reduced intensity conditioning (HR 4.21, 95% CI: 1.01-17.59, p=0.049), triple negative disease (HR 2.09, 95% CI: 1.02-4.30, p=0.04), and presence of U2AF1 (HR 2.53, 95% CI: 1.10-5.81, p=0.03) or SUZ12 mutations (HR 3.92, 95% CI: 1.19-12.21, p=0.02). Decreased RFS was associated with unrelated donor status (HR 2.27, 95% CI: 1.16-4.45, p=0.02), and the presence of SUZ12 mutation (HR 6.97, 95% CI: 2.37-20.49, p<0.001). A descriptive decrease in RFS in patients with U2AF1 (HR 2.15, 95% CI: 0.94-4.88, p=0.07) was observed but did not reach statistical significance. Importantly, mutations previously reported to be associated with reduced OS and RFS in the non-transplant setting, such as ASXL1, EZH2, IDH1/2, and SRSF2, were not associated with poorer outcomes in this analysis in transplanted patients. In an exploratory multivariate analysis including donor type (related vs. unrelated) and presence of U2AF1 and SUZ12 mutations, there was a significantly reduced OS and RFS in patients who harbor these mutations regardless of donor type (OS: HR 5.30, 95% CI: 2.08-13.47, p<0.001; RFS: HR 5.49, 95% CI: 2.27-13.30, p<0.001). In patients without the above mutations, having an unrelated donor was associated with worse OS (HR 2.55, 95% CI: 1.09-5.96, p=0.03) and RFS (HR 2.61, 95% CI: 1.17-5.83, p=0.02, Figure 1). Conclusions: Our analysis demonstrates that mutations previously associated with poor prognosis in MF, such as ASXL1, do not appear to confer a worsened prognosis in patients undergoing allo-HSCT, suggesting transplant may be able to overcome the impact of these mutations. However, mutations in SUZ12 and U2AF1 are associated with reduced OS in univariate and multivariate analysis (together with donor type). Further studies with larger cohorts of patients are indicated to validate these findings, and to elucidate the impact of these mutations on disease biology. Disclosures Rampal: Incye and CTI: Consultancy. Mascarenhas:Janssen: Research Funding; CTi Biopharma: Research Funding; Promedior: Research Funding; Merk: Research Funding; Incyte: Research Funding. Mesa:Galena: Consultancy; Gilead: Research Funding; Promedior: Research Funding; Incyte: Research Funding; CTI Biopharma: Research Funding; Celgene: Research Funding; Ariad: Consultancy; Novartis: Consultancy. Gupta:Novartis: Consultancy, Honoraria, Research Funding; Incyte Corporation: Consultancy, Research Funding.

Abstract Background: PAC is an oral kinase inhibitor with specificity for JAK2, FLT3, IRAK1, and CSF1R that has demonstrated significant and sustained spleen volume reduction (SVR) and symptom control vs BAT (excluding JAK2 inhibitors) in MF pts regardless of platelet count (PERSIST-1). The PERSIST-2 study was a randomized, controlled, open-label, phase 3 trial of PAC 200 mg BID and PAC 400 mg QD vs BAT (including JAK1/JAK2 inhibitor ruxolitinib [RUX]) in pts with 10 or 20 MF whose platelet counts were ≤100,000/µL, a recognized adverse prognostic variable. Prior JAK2 inhibitor use was allowed. Methods: Pts were randomized 1:1:1 to PAC BID, PAC QD, or BAT. The co-primary efficacy endpoints were the percentages of pts achieving ≥35% SVR (MRI or CT) and ≥50% reduction in total symptom score (TSS; MPN-SAF TSS 2.0), both from baseline to Week 24. The primary objective was to compare the efficacy of pooled PAC (BID+QD) to BAT and the secondary objectives were to compare PAC BID and PAC QD individually to BAT. PK samples were collected and analyzed for PAC. Safety analyses were based on all pts exposed to study treatment of any duration (safety population); efficacy analyses were based on ITT pts with a randomization date allowing Week 24 endpoint evaluations prior to the full clinical hold* (ITT efficacy population). Results: 311 pts were randomized (107 PAC BID, 104 PAC QD, 100 BAT), 308 received study drug, and 221 were included in the ITT efficacy population (74 PAC BID, 75 PAC QD, 72 BAT). Demographics and baseline disease characteristics were generally balanced among the treatment arms (Table) and analysis populations. A total of 32 (44%) BAT pts in the ITT efficacy population received RUX as treatment at some point on study. Population PK analyses showed that the steady-state plasma levels achieved with BID were higher than with QD, however the Cmax levels were lower. A significantly higher percentage of pts in the pooled PAC arm achieved SVR ≥35% (18% [27/149]) vs the BAT arm (3% [2/72]; p=0.001; Figure 1A). 25% of PAC pts (37/149) had ≥50% reduction in TSS vs 14% of BAT pts (p=0.079; Figure 1B). In secondary analyses vs BAT, PAC BID demonstrated significant improvement over BAT for both efficacy endpoints with 22% achieving SVR ≥35% (BAT=3%; p=0.001) and 32% achieving ≥50% reduction in TSS (BAT=14%; p=0.011). The PAC QD arm had a significant SVR ≥35% (15% v 3%, respectively; p=0.017), but a similar proportion with ≥50% reduction in TSS (17% v 14%, respectively; p=0.652). More PAC pts reduced their red blood cell transfusion dependence at Week 24 (defined as a ≥50% reduction in average transfusions/month for 3 months relative to baseline) with 19% (7/37) in the PAC QD arm, 22% (8/36) in PAC BID, and 9% (3/35) in BAT. There was no significant difference observed in OS across the treatment arms (Figure 2). Hazard ratios for OS (95% confidence intervals) were 0.68 (0.30, 1.53) for PAC BID v BAT, 1.18 (0.57, 2.44) for PAC QD v BAT, and 0.61 (0.27, 1.35) for PAC BID v QD. PAC BID maintained this survival advantage vs BAT across nearly all demographic and MF-associated risk factors. During the course of the study, 10 (9%), 15 (14%), and 15 (14%) died on PAC BID, PAC QD, and BAT, respectively. The most common treatment-emergent adverse events (AEs) associated with PAC were gastrointestinal (diarrhea, nausea, vomiting) and hematologic (anemia and thrombocytopenia), and were generally less frequent for BID vs QD administration. Grade 3/4 cardiac AEs occurred in 7%, 13% and 9% of PAC BID, PAC QD, and BAT pts, respectively, and grade 3/4 bleeding AEs occurred in 14%, 7%, and 7%, respectively. Grade 3/4 bleeding AEs were associated with grade 3/4 thrombocytopenia, which was also more common in the PAC BID group. Nine pts had cardiac failure (2% PAC QD, 4% PAC BID, 3% BAT) and 1 (1%, PAC QD) had intracranial hemorrhage.* Conclusions: The PERSIST-2 study is the only randomized, controlled trial to date in pts with MF and thrombocytopenia (platelets ≤100,000/µL), allowed prior JAK2 inhibitor treatment exposure (including RUX), and allowed RUX as BAT comparator. Irrespective of prior JAK2 inhibitor treatment, both PAC arms were more effective at SVR than BAT; however, PAC BID appeared more active than QD dosing and achieved significance versus BAT for both SVR and TSS. The most frequent AEs with PAC were gastrointestinal and hematologic toxicities. *PAC on full clinical hold by the FDA on 2/8/2016 based on concerns around excess deaths and cardiac and hemorrhagic events in PERSIST-1. Disclosures Mascarenhas: Incyte: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; CTI BioPharma: Research Funding; Janssen: Research Funding; Roche: Research Funding; Promedior: Research Funding. Talpaz:CTI BioPharma: Research Funding; Pfizer: Research Funding; Incyte Corporation: Research Funding; Ariad: Other: Expense reimbursement, travel accomodation expenses, Research Funding; Gilead: Other: Travel, Accommodations, Expenses, Research Funding; BMS - Canada: Consultancy. Gerds:CTI BioPharma: Research Funding; Astra-Zeneca: Research Funding; Roche: Research Funding; Incyte: Research Funding. Stein:Incyte Corporation: Consultancy. Gupta:Incyte Corporation: Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Drummond:CTI BioPharma: Honoraria; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; BMS: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; Roche: Speakers Bureau. Granston:CTI BioPharma Corp.: Employment. Daly:CTI BioPharma Corp.: Employment. Dean:CTI BioPharma Corp.: Employment, Equity Ownership. Al-Fayoumi:CTI BioPharma Corp.: Employment, Equity Ownership. Callahan:CTI BioPharma: Employment. Singer:CTI BioPharma Corp.: Employment, Equity Ownership, Other: Leadership . Gotlib:Novartis: Other: Travel, Accommodations, Expenses; Steering Committee Chairman, Research Funding; Promedior: Research Funding; CTI BioPharma: Research Funding; Gilead: Research Funding; Incyte: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding. Jamieson:GSK: Research Funding; Johnson & Johnson: Research Funding; CTI BioPharma: Research Funding. Harrison:Novartis: Consultancy, Honoraria, Other: Travel, Accommodations, Expenses, Research Funding, Speakers Bureau; CTI BioPharma: Consultancy, Honoraria, Speakers Bureau; Baxter: Consultancy, Honoraria; Shire: Speakers Bureau; Gilead: Speakers Bureau; Incyte: Speakers Bureau. Mesa:Novartis: Consultancy, Honoraria; Incyte: Research Funding; Gilead: Research Funding; CTI BioPharma: Research Funding; Celgene: Research Funding; Genetech: Research Funding; Promedior: Research Funding. Verstovsek:CTI BioPharma Corp: Research Funding.

Abstract Background:The Janus kinase (JAK) 1/JAK2 inhibitor ruxolitinib has been evaluated for patients with MF in the phase 3 COMFORT studies. In both trials, ruxolitinib prolonged OS, reduced splenomegaly, and improved MF-related symptoms and quality of life compared with controls. Here, we report the results of an exploratory pooled analysis of OS in the COMFORT studies at 5 years of follow-up. Methods: The double-blind COMFORT-I trial and the open-label COMFORT-II trial were randomized phase 3 studies that evaluated the safety and efficacy of ruxolitinib in patients with intermediate-2 (int-2) or high-risk primary MF (PMF), post-polycythemia vera MF (PPV-MF), or post-essential thrombocythemia MF (PET-MF). The comparator was placebo in COMFORT-I and best available therapy (BAT) in COMFORT-II. The ruxolitinib starting dose was 15 or 20 mg twice daily based on baseline platelet counts (100-200 and >200 × 109/L, respectively); dose modifications were permitted for safety and efficacy. Patients were allowed to cross over to ruxolitinib from the control arm for progressive splenomegaly, defined as a ≥25% increase in spleen volume from baseline (COMFORT-I) or study nadir (COMFORT-II), or select protocol-defined progression events; crossover was mandatory following treatment unblinding in COMFORT-I. OS was a secondary endpoint in both studies and was evaluated in an intent-to-treat (ITT) analysis using a Cox proportional hazard model that estimated the treatment effect stratified by clinical trial and International Prognostic Scoring System (IPSS) risk. The crossover-corrected treatment effect was estimated using a rank-preserving structural failure time (RPSFT) method. Results: Overall, 528 patients were randomized: 301 to ruxolitinib (COMFORT-I, n=155; COMFORT-II, n=146) and 227 to placebo (n=154) or BAT (n=73). All ongoing patients in the control arms crossed over to ruxolitinib by the 3-year follow-up. Patient populations were similar between the two trials and their details were previously published. In the combined ruxolitinib group, 162 patients (53.8%) had high-risk MF and 139 (46.2%) had int-2 risk MF based on IPSS criteria. At the 5-year ITT analysis, 128 patients (42.5%) died in the ruxolitinib group compared with 117 (51.5%) in the control group. The risk of death was reduced by 30% with ruxolitinib compared with control (median OS: ruxolitinib, 63.5 mo; control, 45.9 mo; HR, 0.70; 95% CI, 0.54-0.91; P=0.0065; Figure A). After correcting for crossover using RPSFT, OS advantage was more pronounced for patients originally randomized to ruxolitinib (median OS: ruxolitinib, 63.5 mo; control, 27 mo; HR, 0.35; 95% CI, 0.23-0.59; Figure B). An analysis of OS censoring patients at the time of crossover also demonstrated that ruxolitinib prolonged survival compared with control (median OS: ruxolitinib, 63.5 mo; control, 28.3 mo; HR, 0.53; 95% CI, 0.36−0.78; P=0.0013; Figure C). Among all patients treated with ruxolitinib, those with lower-risk disease had longer survival compared with those with high-risk disease (median OS: int-2, not reached [estimated, 102 mo]; high-risk, 50 mo; HR, 2.86; 95% CI, 1.95-4.20; P<0.0001; Figure D). In a subgroup analysis, OS favored ruxolitinib compared with placebo for patients with int-2 or high-risk MF (data not shown). At 5 years, median OS appeared to favor patients with int-2 (n=58) or high-risk (n=89) PMF who were originally randomized to ruxolitinib compared with historical (Cervantes et al; J Clin Oncol 30:2981-2987) controls (int-2 PMF, not reached [estimated, 70 mo] vs 48 mo; high-risk PMF, 34 vs 27 mo); OS was longer among patients with int-2 vs high-risk PMF (P=0.0003). Subgroup analyses showed that ruxolitinib provided an OS advantage regardless of age (>65 or ≤65 y), sex, disease type (PMF, PPV-MF, PET-MF), risk status (int-2 or high), JAK2V617F mutation status, baseline spleen volume (>10 or ≤10 cm), anemia, white blood cell count (>25 or ≤25 × 109L), or platelet count (>200 or ≤200 × 109/L). Conclusion: Long-term treatment with ruxolitinib up to 5 years prolonged survival in patients with MF compared with BAT or placebo. Corrections for patients who crossed over to ruxolitinib suggested that the separation between ruxolitinib and control OS curves was primarily caused by a delay in ruxolitinib treatment. The results suggest that earlier treatment with ruxolitinib may provide a greater survival advantage for patients with MF. Disclosures Gupta: Incyte Corporation: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Mesa:Incyte: Research Funding; Ariad: Consultancy; Novartis: Consultancy; Celgene: Research Funding; CTI: Research Funding; Promedior: Research Funding; Galena: Consultancy; Gilead: Research Funding. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Kiladjian:AOP Orphan: Research Funding; Novartis: Research Funding. Cervantes:AOP Orphan: Membership on an entity's Board of Directors or advisory committees; Baxalta: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Sun:Incyte Corporation: Employment, Equity Ownership. Gao:Incyte Corporation: Employment, Equity Ownership. Dong:Novartis Pharmaceutical Corporation: Employment, Equity Ownership. Naim:Incyte Corporation: Employment, Equity Ownership. Gopalakrishna:Novartis Pharma AG: Employment, Equity Ownership. Harrison:Incyte Corporation: Honoraria, Speakers Bureau; Baxaltra: Consultancy, Honoraria, Speakers Bureau; Gilead: Honoraria, Speakers Bureau; CTI Biopharma: Consultancy, Honoraria, Speakers Bureau; Shire: Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Other: travel, accommodations, expenses, Research Funding, Speakers Bureau.