Stein, Brady L.

Abstract We recently reported that the induction of polyploidization of malignant megakaryocytes shows great promise as a new therapy for acute leukemia. Polyploidization inducers such as dimethylfasudil (diMF) and MLN8237, both of which target Aurora A kinase (AURKA), induce proliferation arrest, polyploidization, expression of megakaryocyte differentiation markers and apoptosis of leukemic megakaryocytes in vitro and in vivo. Since megakaryocytes in primary myelofibrosis (PMF) show impaired polyploidization and maturation, and likely directly contribute to the disease, we predicted that polyploidization inducers would provide a new therapeutic strategy. To determine the effect of these compounds on the growth of MPN cells, we first treated the JAK2 V617F mutant megakaryocytic SET2 cell line with varying doses of MLN8237 and diMF. Both compounds effectively and dose dependently inhibited proliferation, induced polyploidization and upregulation of lineage specific markers CD41 and CD42, and increased apoptosis. Furthermore, MLN8237 synergized with ruxolitinib to induce apoptosis of the SET2 cells and also potently induced growth arrest of JAK2 inhibitor persistent SET2 cells. We observed a similar polyploidization and differentiating activity of MLN8237 and diMF on megakaryocytes derived from primary human PMF progenitors. The ability of these agents to induce polyploidization was specific, as the non-megakaryocyte fractions of the cultures were not affected. Next, we assayed the activity of polyploidization inducers on progression of MPNs in two mouse models: JAK2V617F conditional knockin mice and mice engrafted with MPLW515L expressing bone marrow progenitors. Of note, spleens from both mouse models displayed a robust increase in both total and phosphorylated forms of AURKA relative to control animals, further suggesting that AURKA is a rational target in this disease. We first assayed the activities of MLN8237 and diMF in the MPLW515L bone marrow transplantation model. Recipient mice develop a rapid MPN characterized by leukocytosis, thrombocytosis and bone marrow fibrosis. Both MLN8237 and diMF reduced the disease burden, as evidenced by significant reductions in the liver and spleen weights, white cell counts and platelet counts. Both compounds also led to a significant decrease of fibrosis in the bone marrow, diminished infiltration of megakaryocytes and granulocytes in the liver, and a profound reduction in the numbers of megakaryocytes within the spleen. Moreover, plasma levels of TGF-β a known myelofibrogenic cytokine, were decreased by more than 3-fold by the drug treatment. Both diMF and MLN8237 led to selective polyploidization of megakaryocytes in the spleen as well as marked reductions in the levels of p-AURKA. Of note, neither agent affected the extent of phosphorylation of STAT3 or STAT5. Therefore, we tested whether the combined use of a JAK inhibitor and a polyploidy inducer would show enhanced activity in vivo. Indeed, the combination of MLN8237 and ruxolitinib led to greater reductions in tumor burden in the MPLW515L mouse model than either agent alone. Similar results were obtained using the JAK2V617F knock-in model. To further validate our conclusion that AURKA is a target in PMF, we infected Aurkafl/fl floxed bone marrow progenitors with MPLW515L and transplanted the cells to irradiated recipients. Excision of both alleles of Aurka by Cre mediated recombination completely resolved the disease, while heterozygous deletion of Aurka significantly reduced the disease burden, in a manner similar to treatment with MLN8237. Given that heterozygous deletion of Aurka does not alter normal hematopoiesis in mice, the fact that a 50% reduction in kinase expression was associated with a significant decrease in disease burden suggests that there is an effective therapeutic window in which AURKA inhibitors will be effective against MPN while sparing normal hematopoiesis. Although JAK inhibitors provide symptomatic relief, it is becoming clear that they are not curative. Thus, there is an urgent need to develop new agents to use in combination with JAK inhibitors. Our data reveal that inducing polyploidization and differentiation of dysplastic megakaryocytes in PMF ameliorates features of the disease both in vitro and in vivo. These results support the initiation of clinical studies that combine a JAK inhibitor with an AURKA inhibitor. Disclosures: Crispino: Sanofi: Research Funding.

Abstract Background: NS-018 is an oral, selective, small molecule inhibitor of Janus kinase 2 (JAK2). OBJECTIVE: The purpose of this study is to determine the safety, tolerability and efficacy of orally administered NS-018 in patients with PMF, post-PV MF, or post-ET MF. METHODS: This multicenter, Phase 1/2, 3+3 dose-escalation study of NS-018 enrolled patients with IPSS intermediate-1, intermediate-2, or high risk PMF, post-PV MF, or post-ET MF. The study drug, NS-018, was given orally either daily (QD) or twice daily (BID) in 28-day cycles. In Phase 1, changes in spleen size were assessed by manual palpation, quality of life with the Myelofibrosis Symptom Assessment Form (MF-SAF), and responses were assessed according to the IWG-MRT/ELN consensus criteria. Bone marrow fibrosis (BMF) was evaluated by biopsy, according to WHO criteria. Changes in grade of BM fibrosis from baseline were categorized as improvement, stabilization, or worsening. The Phase 1 portion of the study has been completed and data are presented here. RESULTS: In this Phase 1 study, 48 patients were enrolled across 10 dosing cohorts (75-400 mg QD/100-400 mg BID). Characteristics: 37 PMF, 5 post-PV MF, 6 post-ET MF with a median age (range) 69.5 yrs (38-83); M/F:29/19; 35 JAK2V617F+, and 23 previously treated with a different JAK2 inhibitor. At 400 mg QD/BID, NS-018 dosing was associated with drug-related neurologic adverse events (AEs) including dizziness, peripheral neuropathy, headache, disturbance in attention, vertigo, dysesthesia, paresthesia, aphasia, and nervous system disorder (not otherwise specified). The 300 mg QD dose was better tolerated than 250 mg BID or 300 mg BID, with fewer neurologic AEs, and was selected as the recommended phase 2 dose (RP2D). For the 48 phase 1 patients, reductions in MF-SAF score were observed for all symptoms after 3 cycles, including for patients with prior JAK2 inhibitor treatment. In all dose cohorts, ≥ 50% patients achieved ≥ 50% score reduction from baseline in night sweats, pruritus and bone pain after 1 cycle. Moreover, ≥ 50% patients achieved ≥ 50% score reduction from baseline in abdominal pain and inactivity after 3 cycles. In patients who had received prior JAK2 inhibitor, ≥ 50% patients achieved ≥ 50% score reduction from baseline in filling up quickly, inactivity, night sweats and quality of life after 3 cycles. Among 36 patients with baseline splenomegaly ≥ 5 cm and treatment for ≥ 1 cycle, 20 (56%) showed ≥ 50% reduction in spleen size (confirmed for ≥ 8 weeks in 16 patients), including 9/19 (47%) patients with prior JAK2 treatment. According to IWG criteria, 14/36 (39%) patients showed splenic clinical improvement (CI) for ≥ 8 weeks, 4 had hemoglobin CI, and 1 had platelet CI. After 3 cycles of NS-018 treatment, 11/31 (37%) evaluable patients had a reduction in bone marrow fibrosis(BMF) by ≥ 1 grade. At any time during NS-018 treatment, 17/31 (55%) evaluable patients had a reduction in BMF by ≥ 1 grade. Overall, 23% (7/31) patients maintained improvement in BMF for ≥ 12 weeks. Reduction in BMF after 3 cycles was correlated with reduction in splenomegaly and hemoglobin responses. To date, 8 patients with prior JAK inhibitor treatment have been enrolled into the phase 2 portion of the trial. Updated Phase 2 data will presented at the meeting. CONCLUSIONS: The RP2D dose of NS-018 was 300 mg QD. This dose provided an acceptable safety and tolerability profile, and reduction in symptomatic splenomegaly. Phase 2 is ongoing and includes patients previously treated with other JAK2 inhibitors. Disclosures Talpaz: ARIAD: Research Funding; Bristol-Myers Squibb: Research Funding; Sanofi Aventis: Research Funding; Pfizer: Research Funding; Incyte: Research Funding. Ritchie:Incyte: Speakers Bureau; Celgene: Speakers Bureau. Odenike:Spectrum Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Algeta Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi-Aventis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Suneisis Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; CTI/Baxter: Honoraria, Membership on an entity's Board of Directors or advisory committees; Geron: Research Funding. Jamieson:GlaxoSmithKline: Research Funding; Johnson & Johnson: Research Funding. Stein:Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees. Mesa:Novartis Pharmaceuticals Corporation: Consultancy; Pfizer: Research Funding; CTI Biopharma: Research Funding; NS Pharma: Research Funding; Gilead: Research Funding; Incyte Corporation: Research Funding; Promedior: Research Funding; Genentech: Research Funding.

Abstract Background: Patients with polycythemia vera (PV) have an increased symptom burden (eg, fatigue, pruritus, and splenomegaly-related symptoms) and an increased risk of mortality compared with the general population, often resulting from thrombotic events, disease transformation to myelofibrosis, or secondary malignancies. There are limited data regarding PV burden and treatment patterns in a contemporary, real-world US setting. REVEAL is an ongoing observational study being conducted to describe contemporary demographics, burden of disease, clinical management, patient-reported outcomes, and healthcare resource utilization among patients with PV in the US. The objective of this assessment is to describe the clinical characteristics at enrollment among patients currently enrolled in REVEAL (enrollment from July 22, 2014 to June 9, 2015). Methods: REVEAL is a multicenter, noninterventional, nonrandomized, prospective, observational study. Eligible patients are ≥18 years of age with a PV diagnosis and currently under active management by a physician in the US. Data regarding disease and clinical characteristics, patient-reported outcomes, and health resource utilization are being collected at usual-care visits over a planned 36-month observation period. Analyses of these preliminary data were descriptive. Results: At data cutoff, 865 patients were enrolled (total planned enrollment, n=2000) from 174 sites (academic, n=27; community, n=147). Median (range) age at enrollment was 67 (22-95) years, 55.5% were male, 89.5% were white, and 45.4% had a history of smoking. Most patients (99.4%) had health insurance, including Medicare (56.0%), PPO (24.3%), or HMO (11.6%). Fifty-two percent were retired, 29.6% were employed, and 4.5% were unable to work or disabled. A total of 40.2% of patients completed a college/graduate degree, 19.9% had some college, and 32.5% completed high school or the equivalent. Documented major World Health Organization diagnostic criteria included JAK2V617F mutation in 50.9% of patients, elevated hemoglobin in 52.3%, and red cell mass in 5.5%. A bone marrow biopsy was conducted in 24.0% of patients, approximately half of whom (52.4% of the 24.0%) had trilineage myeloproliferation. Erythropoietin levels were abnormal in 19.7% of patients. Approximately half (46.6%) of patients had physician-reported PV-related symptoms at diagnosis, most frequently fatigue (25.2%) and pruritus (14.0%). At enrollment, median disease duration was 52.6 months; 42.3% of patients were diagnosed ≥5 years before enrollment. The most common comorbidities were hypertension (51.3%), obesity (14.2%), dyspnea (13.4%), myalgia (11.2%), and diabetes mellitus (11.1%). Mean hematocrit was 44.9%, hemoglobin was 14.5 g/dL, white blood cell count was 11.4×109/L, platelet count was 363.7×109/L, and absolute neutrophil count was 363.7×109/L. Twenty-one percent of patients had a history of thrombotic events, with 13.1% and 8.6% of patients experiencing ≥1 venous or arterial thromboembolic event, respectively. Of the 261 reported thrombotic events, 43.7% occurred after diagnosis of PV. The most common PV symptoms recorded at enrollment (using the Myeloproliferative Neoplasm Symptom Assessment Form) were fatigue (37.1%), pruritus (24.0%), headache (18.6%), insomnia (17.0%), dizziness (13.2%), bone pain (10.5%), and blurred vision (7.9%); 19.7% of 518 evaluable patients had palpable splenomegaly. Fewer than half of patients were receiving aspirin at enrollment (47.7%). The most common PV treatments ± aspirin were phlebotomy (PBT; 63.5%), hydroxyurea (HU; 42.2%), watchful waiting (5.3%), and ruxolitinib (3.1%); 23.0% of patients received PBT + HU. Conclusion: The REVEAL study is unique in that it captures data from both academic and community centers, and therefore includes a broader segment of the PV population typically not described in the literature. REVEAL can provide novel insights into questions related to the contemporary demographics of PV, practice patterns regarding diagnosis and therapy, and the real-world burden of PV and its impact on patients' quality of life and work productivity. Preliminary descriptive data from this early subset of patients suggest that a high proportion of patients report having PV-related symptoms at diagnosis, fewer patients are treated with aspirin than expected, and that thromboembolic event rates remain high after diagnosis. Disclosures Stein: Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees. Moliterno:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees. Boccia:Incyte Corporation: Honoraria. Naim:Incyte Corporation: Employment, Equity Ownership. Cordaro:Incyte Corporation: Employment, Equity Ownership. Peng:Incyte Corporation: Employment, Equity Ownership. Sun:Incyte Corporation: Employment, Equity Ownership. Parasuraman:Incyte Corporation: Employment, Equity Ownership. Mesa:Promedior: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; NS Pharma: Research Funding; CTI Biopharma: Research Funding; Gilead: Research Funding; Pfizer: Research Funding; Incyte Corporation: Research Funding; Genentech: Research Funding.

Abstract Background:Patients with polycythemia vera (PV) often present with a broad range of clinical characteristics that may contribute to increased risks of cardiovascular (CV) morbidity and mortality, including thrombotic events (TE). Limited contemporary real-world data have been reported about the clinical burden of PV and treatment patterns in the United States. The ongoing REVEAL study collects data on disease burden, clinical management, patient-reported outcomes, and healthcare resource utilization for patients with PV in the United States. This analysis reports clinical characteristics, including underlying CV risk factors, for patients enrolled in the REVEAL study as of April 28, 2016. Methods: REVEAL is a multicenter, nonrandomized, prospective, observational study enrolling patients ≥18 years of age with a PV diagnosis who are actively managed in an academic or community setting. For this analysis, data regarding PV disease and diagnosis, clinical characteristics, and treatment patterns were collected at enrollment during usual-care visits and were based on physician assessment, electronic medical records, and local laboratory values. Ten-year CV risk factors selected for this analysis were adapted from the Framingham Heart Study for CV diseases. Results: At data cutoff, 2307 patients were available for this analysis. Mean (SD) age was 66.3 (12.2) years, 54.4% were male, 89.9% were white, 62.7% had at least some college education, and 51.1% were retired. Approximately 6% of patients had a family history of PV, primarily in parents (35.1%) and siblings (33.8%). A history of second malignancies was reported for 344 patients (14.9%). The majority of patients (84.6%) were diagnosed with PV based on an abnormal blood test alone or in combination with a bone marrow test. Among patients who were diagnosed with a mutational test (n=1078), 95.2% were diagnosed via an abnormal JAK2V617F test result. Abnormal hemoglobin (57.3%), hematocrit (55.4%), or both (47.5%) were among the most common blood values assessed for PV diagnosis. At diagnosis, 58.5% of patients were classified with high-risk PV (age ≥60 years or history of a TE); this percentage increased to 77.3% at REVEAL enrollment. The average (SD) disease duration from diagnosis to enrollment was 5.8 (6.1) years. At enrollment, 91.5% of patients were under active management for PV (phlebotomy ± aspirin, 34.0%; hydroxyurea ± aspirin, 27.0%; and phlebotomy + hydroxyurea ± aspirin, 23.2%). Underlying CV risk factors that were either diagnosed or treated in 86.0% of enrolled patients included hypertension (66.5%), history of smoking (46.2%), current smoking at enrollment (10.9%), obesity (34.2%), hyperlipidemia (27.4%), and diabetes (14.8%). At enrollment, 431 (18.7%) patients reported having ≥1 TE, including 181 patients who had a TE between PV diagnosis and enrollment. Venous and arterial TEs were reported in 11.1% and 8.6% of patients, respectively. Most commonly reported venous TEs were deep vein thrombosis (5.9%) and pulmonary embolism (2.5%); most common arterial TEs were cerebrovascular arterial thrombosis including transient ischemic attack (5.1%) and acute myocardial infarction (1.7%). Increased rates of TEs were observed among patients with hyperlipidemia (23.6%) and hypertension (21.0%; Table 1), compared with patients who did not have any risk factors (10.5%). Conclusion: A large proportion of patients in the REVEAL study had 1 or more underlying CV risks, including age, hypertension, smoking, obesity, hyperlipidemia, and diabetes, which may contribute to the risk of thrombosis. Longitudinal data from REVEAL will provide a better understanding of how these factors affect CV outcomes over time. Disclosures Stein: Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding. Naim:Incyte Corporation: Employment, Equity Ownership. Grunwald:Janssen: Research Funding; Forma Therapeutics: Research Funding; Medtronic: Equity Ownership; Alexion: Membership on an entity's Board of Directors or advisory committees; Ariad: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Incyte Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Oh:Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Research Funding; CTI: Research Funding. Paranagama:Incyte Corporation: Employment, Equity Ownership. Cordaro:Incyte Corporation: Employment, Equity Ownership. Sun:Incyte Corporation: Employment, Equity Ownership. Parasuraman:Incyte Corporation: Employment, Equity Ownership. Boccia:Celgene: Consultancy, Honoraria, Speakers Bureau; Amgen/Onyx: Consultancy, Honoraria, Speakers Bureau; Gilead: Speakers Bureau; Genentech: Consultancy, Honoraria, Speakers Bureau; Eisai: Consultancy, Honoraria, Speakers Bureau. Mesa:Ariad: Consultancy; CTI: Research Funding; Gilead: Research Funding; Galena: Consultancy; Novartis: Consultancy; Promedior: Research Funding; Celgene: Research Funding; Incyte Corporation: 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: NS-018 is an oral, selective, small molecule inhibitor of Janus kinase 2 (JAK2).In the previously-reported Phase 1 portion, patients with myelofibrosis (MF) who received NS-018 achieved steady-state plasma levels above the IC50 for JAK2 at all doses (75mg QD - 400 mg BID). 300 mg QD was chosen as the recommended dose (RD) for Phase 2 portion of the study. OBJECTIVE: The purpose of this study was to determine the safety, tolerability and efficacy of orally-administered NS-018 in patients with PMF, post-PV MF, or post-ET MF. METHODS: This multicenter, Phase 1/2, 3+3 dose-escalation study of NS-018 enrolled patients with IPSS intermediate-1, intermediate-2, or high risk PMF, post-PV MF, or post-ET MF. NS-018 was dosed orally daily (QD) or twice daily (BID) in 28-day cycles. In Phase 1, changes in spleen size were assessed by manual palpation, quality of life with the Myelofibrosis Symptom Assessment Form (MF-SAF), and responses according to the IWG-MRT/ELN consensus criteria. Bone marrow fibrosis was evaluated by biopsy, according to standard practice at the sites. Changes from baseline in grade of BM fibrosis were categorized as improvement, stabilization, or worsening. The Phase 1 portion of the study is complete. In the ongoing Phase 2 portion, spleen size is being assessed by palpation and by centrally-read MRI, and quality of life evaluated by the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF). RESULTS: 48 patients were enrolled across 10 dosing cohorts (75-400 mg QD/100-400 mg BID) in Phase 1. Patient characteristics: 37 PMF, 5 post-PV MF, 6 post-ET MF; median age (range) 69.5 yrs (38-83); M/F:29/19; 35 JAK2V617F+, and 23 previously treated with a different JAK2 inhibitor. The data cutoff for this analysis was June 30, 2016 (median follow-up time of 279.5 [range 5-1806] days from screening), at which time 10 patients remained on treatment. The median number of treatment cycles was 10 (1-65). Reasons for treatment discontinuation were disease progression (PD, n = 13), adverse events (AE, n = 8), physician consideration (n = 6), patient request (n = 4), and protocol non-compliance (n = 1). The 300 mg QD dose was selected as the phase 2 recommended dose (P2RD) in terms of tolerability and efficacy. For the 48 patients, reductions in MF-SAF score were observed for all symptoms after 3 cycles, including patients with priorJAK2 inhibitor treatment. Among 36 splenic-evaluable patients with baseline splenomegaly > 5 cm and treatment for > 1 cycle, 20 (56%) showed > 50% reduction in spleen size (confirmed for > 8 weeks in 16 patients), including 9/19 (47%) patients with prior JAK2 treatment. According to IWG criteria, 14/36 (39%) patients showed splenic clinical improvement for > 8 weeks, 4 with hemoglobin CI, and 1 with platelet CI. Twenty-nine patients with prior JAK inhibitor treatment have been enrolled into the phase 2 portion of the trial. Patient characteristics: 13 PMF, 12 post-PV MF, 4 post-ET MF; median age (range) 67 yrs (48-86). The reason for discontinuation of prior JAK2 inhibitor treatment: AEs (62%) and PD (38%). To date, the median number of treatment cycles is 6 (1-20). The majority of grade 3/4 AEs were hematologic and the most common hematologic toxicities were anemia (21%) and thrombocytopenia (17%). Non-hematologic AEs were mostly grade 1/2, and the other AEs shown in > 10% of patients was nausea (14%). Updated Phase 2 efficacy and safety data will be presented at the meeting. CONCLUSIONS: The RP2D dose of NS-018 was 300 mg QD. This dose provided a durable dosing schedule, an acceptable safety profile, splenic size reductions and clinical symptom improvement. Phase 2 is ongoing and includes patients previously treated with a different JAK2 inhibitor. Disclosures Talpaz: Novartis: Research Funding; Incyte Corporation: Other: Travel expense reimbursement, Research Funding; Ariad: Other: Expense reimbursement, travel accomodation expenses, Research Funding; Pfizer: Consultancy, Other: travel accomodation expenses, Research Funding. Ritchie:Pfizer: Honoraria; Arian: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Honoraria; Incyte: Speakers Bureau. Odenike:Suneisis: Honoraria, Membership on an entity's Board of Directors or advisory committees; CTI/Baxter: Honoraria, Membership on an entity's Board of Directors or advisory committees; Geron: Research Funding; Spectrum: Honoraria, Membership on an entity's Board of Directors or advisory committees; Algeta: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi-Aventis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jamieson:GlaxoSmithKline: Research Funding; CTI Biopharma: Research Funding; Johnson & Johnson: Research Funding. Stein:Incyte: Membership on an entity's Board of Directors or advisory committees. Mesa:CTI: Research Funding; Promedior: Research Funding; Celgene: Research Funding; Gilead: Research Funding; Incyte: Research Funding; Galena: Consultancy; Ariad: Consultancy; Novartis: Consultancy.

Abstract Primary myelofibrosis (PMF) is a clonal hematologic malignancy resulting from the transformation of a pluripotent hematopoietic progenitor cell leading to increased hematopoiesis and overproduction of abnormal blood cells. PMF is characterized by bone marrow (BM) fibrosis, extramedullary hematopoiesis, increased numbers of circulating CD34+ cells, splenomegaly, and a propensity to evolve to AML. Patients also display anemia and thrombocytopenia and harbor abnormal, immature megakaryocytes (Mks) in their BM and spleen. Numerous mutations are associated with PMF including JAK2, CALR, MPL, TET2, CBL, ASXL1, and IDH. The presence of abnormal Mks in the BM of PMF patients is an important characteristic of the disease, as these cells are believed to contribute to the fibrosis.Here, we performed an analysis of Mk differentiation from individuals with PMF compared to healthy individuals as a way to better understand the mechanism leading to their defects. CD34+ cells obtained from PMF and healthy donors were cultivated in presence of thrombopoietin to induce Mks differentiation. Under these conditions, we observed that the proliferative capacity of CD34+ cells from PMF patients was increased as compared to normal CD34+ cells. At the same time, the percentage of mature Mks obtained was reduced. Semi-solid culture conditions confirmed the proliferative advantage of the PMF CD34+ cells. To investigate the mechanism responsible for this phenotype, we performed genome wide expression analysis of sorted Mks from patients versus controls. Nine PMF patients with different mutations (5 JAK2V617F, 1 MPLW515L, 2 CALR and 1 triple negative) and 4 healthy donors were included in the study. Gene Set Enrichment Analysis (GSEA) analysis revealed that the top scoring pathways included the RPS14 signature, ribosome biogenesis, rRNA metabolic process, and rRNA processing. We first studied the RPS14 geneset, which consists of a group of genes that were up-regulated in CD34+ cells after knock-down of RPS14, a component of the small ribosome subunit. Using shRNA against RPS14, we discovered that its knock down leads to a significant reduction in the development of mature Mks from normal CD34+ cells. The microarray data also revealed changes in the expression of several myeloid genes. CEBPa and GFI-1 were over-expressed in PMF Mks, whereas GFI-1b and PF4, which are associated with Mk differentiation, were down-regulated. Surprisingly the expression of GATA1, a master regulator of megakaryopoiesis, was not changed. However, consistent with previous report, we discovered that GATA1 protein level was reduced in PMF Mks. GATA1 deficient Mks are impaired in their maturation, so we reasoned that the reduction in GATA1 contributes to the defects in PMF. Indeed, we found that overexpression of GATA1 in PMF CD34+ cells rescued Mk differentiation. To understand how GATA1 protein but not mRNA, is reduced, we knocked down RPS14 in the JAK2 mutant SET2 megakaryoblastic cell line. As predicted, we observed a reduction in GATA1 protein, but not mRNA. By ribosomal profiling, we saw that the shRPS14 led to an abnormal ribosomal profile with a reduction of the 40s peak. Finally, by RT-PCR analysis of the ribosomal and polysomal fractions, we found that GATA1 mRNA was less abundant in the polysomal fraction in cells expressing the shRPS14. This finding is consistent with recent data showing that alterations in ribosomal genes cause a decrease in GATA1 protein in Diamond-Blackfan Anemia. Although we identified the RPS14 gene signature, we did not observe changes in RPS14 expression or in any of the ribosomal subunits. Since our GSEA analysis also identified deficiencies in three ribosomal biogenesis pathways, we looked for genes present in all three signatures. NOP58, a ribonucleoprotein required for ribosome biogenesis, was significantly reduced in all samples of PMF Mks. To link the reduction in NOP58 expression with PMF associated mutations, we expressed MPLW515L or the CALR type II mutant in hematopoietic progenitor cells and detected a reduction in NOP58 expression. Our findings suggest that the activation of JAK/STAT signaling leads to a reduction in NOP58, which contributes to defects in ribosome assembly, decreased GATA1 expression and subsequent impairment in Mk differentiation. This work reveals, for the first time, that defective ribosomes contribute to the pathogenesis of PMF and suggests new avenues for therapeutic intervention. Disclosures Stein: Incyte Corporation: Honoraria, Speakers Bureau; Sanofi Oncology: Honoraria.

Abstract Background: NS-018 is an oral, selective, small molecule inhibitor of Janus kinase 2 (JAK2). Pre-clinically NS-018 inhibited JAK2 kinase with an IC50 value in the subnanomolar range and demonstrated splenomegaly reduction at low doses in a JAK2V617F-bearing mouse model (Blood Cancer J 2011; 1: e29.). Methods: This multicenter, Phase 1/2, 3+3 dose-escalation study of NS-018 enrolled patients with IPSS intermediate-1, intermediate-2, or high risk PMF, postPV MF, or postET MF. Patients were ≥ 18 years, had ECOG PS ≤ 2 and required therapy but were not required to have splenomegaly in Phase 1. NS-018 was dosed orally daily (QD) or twice daily (BID) in 28-day cycles. Responses were assessed according to IWG consensus criteria, changes in spleen size by manual palpation and quality of life with the Myelofibrosis Symptom Assessment Form (MF-SAF). The Phase 1 portion of the study completed enrollment and is presented here. Results: Patients: 42 patients were enrolled across 10 cohorts. Patient characteristics: 33 PMF, 5 postPV MF, 4 postET MF; median age (range) 69 yrs (43-83); M/F:28/14; 31 JAK2V617F+, and 17 previously treated with a different JAK inhibitor. Dosing and tolerability: Dose levels included 75, 125, 200, 300 and 400 mg QD and 100, 200, 250, 300 and 400 mg BID. Systemic exposures based on Cmax were approximately dose proportional across the tested range from 75 to 400 mg. The recommended Phase 2 dose (RP2D) was 300 mg BID, based on drug-related neurological adverse events (AEs) at 400 mg BID including dizziness (Grade 2 or 3), dysphagia (Grade 2) or hypoesthesia (Grade 1) in one patient each that led to dose reduction or drug discontinuation. Study drug-related serious AEs (SAEs) included non-cardiac chest pain (Grade 2, 200 and 300 mg BID), lower GI hemorrhage (Grade 3, 300mg BID), paresthesia (Grade 3, 300mg BID), increased lipase (Grade 2, 300mg BID), and dizziness (Grade 3, 400 mg BID) in one patient each. For the 300 mg BID cohort (n=11), the most frequent drug-related AEs across all grades were nausea (Grade 1, 18%), decreased platelet count (≤ Grade 2, 18%), and dizziness (≤ Grade 2, 27%); Grade 3 related AEs included anemia, lower GI bleed, leukopenia, neutropenia or paresthesia (1 patient each, 9%); and no Grade 4 AEs. Overall, 22 patients (52%) discontinued treatment due to AEs (n=7), progressive disease (PD) (n=7), or MD/patient decision (n=8). The AEs leading to discontinuation included thrombocytopenia (Grade 4), transient ischemic attack (Grade 2), muscle contraction involuntary (Grade 2), light headedness (Grade 1), insomnia (Grade 1), hemolytic anemia (Grade 3), dizziness (Grade 2), dysphagia (Grade 2), and hypoesthesia (Grade 1). Nine patients had a hemoglobin decrease ≥ 2 g/dL and 8 patients a platelet decrease ≥ 50%. Responses: Of 33 evaluable patients with baseline splenomegaly ≥ 5 cm and treatment for ≥ 1 cycle, 16 (48%) patients showed ≥ 50% reduction in spleen size (confirmed for ≥ 8 weeks in 11 patients). In addition, 11 patients showed splenic clinical improvement (CI, for ≥ 8 weeks), 3 patients hemoglobin CI, and 2 patients platelet CI. Median (range) time to splenic response and duration of response: 1.5 cycle (1-12) and 4.5 cycles (1-29). Splenic reductions ≥50% are shown in the Table for the specified patient groups. Changes in MF-SAF and PK and PD results will be presented. Table Splenic reduction(in evaluable patients) All doses 16/33 (48%) 300mg BID 3/6 (50%) 300mg QD 4/7 (57%) Prior different JAK inhibitor treated 8/16 (50%) Conclusions: The dose of NS-018 determined to be the RP2D in Phase 1 was 300 mg BID. This dose provided a durable dosing schedule with an acceptable safety profile, and was associated with splenic size reduction and clinical improvements. The Phase 2 portion of the study is ongoing and includes only patients previously treated with a different JAK inhibitor. Disclosures Verstovsek: NS Pharma, Inc: Research Funding. Talpaz:Ariad, BMS, Sanofi, Pfizer, Incyte: Research Funding. Ritchie:Celgene, Incyte: Speakers Bureau. Odenike:Suneisis Pharmaceuticals, Incyte, Sanofi-Aventis, Algeta Pharmaceuticals, Spectrum Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jamieson:Roche, Johnson&Johnson, CTI: Research Funding. Stein:Incyte Corporation: Honoraria, Speakers Bureau; Sanofi Oncology: Honoraria. Tomonori:NS Pharma, Inc.: Employment. Mesa:Incyte, CTI, NS Pharma, Inc., Gilead, Celgene: Research Funding.

Abstract Purpose: Myelofibrosis is characterized by bone marrow fibrosis, atypical megakaryocytes, splenomegaly, constitutional symptoms, thrombotic and hemorrhagic complications, and a risk of evolution to acute leukemia. The JAK kinase inhibitor ruxolitinib provides therapeutic benefit, but the effects are limited. The purpose of this study was to determine whether targeting AURKA, which has been shown to increase maturation of atypical megakaryocytes, has potential benefit for patients with myelofibrosis. Patients and Methods: Twenty-four patients with myelofibrosis were enrolled in a phase I study at three centers. The objective of the study was to evaluate the safety and preliminary efficacy of alisertib. Correlative studies involved assessment of the effect of alisertib on the megakaryocyte lineage, allele burden, and fibrosis. Results: In addition to being well tolerated, alisertib reduced splenomegaly and symptom burden in 29% and 32% of patients, respectively, despite not consistently reducing the degree of inflammatory cytokines. Moreover, alisertib normalized megakaryocytes and reduced fibrosis in 5 of 7 patients for whom sequential marrows were available. Alisertib also decreased the mutant allele burden in a subset of patients. Conclusions: Given the limitations of ruxolitinib, novel therapies are needed for myelofibrosis. In this study, alisertib provided clinical benefit and exhibited the expected on-target effect on the megakaryocyte lineage, resulting in normalization of these cells and reduced fibrosis in the majority of patients for which sequential marrows were available. Thus, AURKA inhibition should be further developed as a therapeutic option in myelofibrosis. See related commentary by Piszczatowski and Steidl, p. 4868