Efficacy and Safety of Eltrombopag for Treatment of Patients with Myelodysplastic Syndromes after Hypomethylating-Agent Failure: A Phase 2 Clinical Trial

Abstract Background: Myelodysplastic syndromes (MDS) are malignant clinical disorders characterized by ineffective hematopoiesis, bone marrow dysplasia, peripheral cytopenias and a property to transform into acute myeloid leukemia (AML). Standard of care for MDS includes the hypomethylating agents (HMAs) (i.e. azacitidine, decitabine) to improve quality of life, decrease transfusion requirements and improve clinical outcome. However not all patients (pts) respond to HMAs and even in responding pts, cytopenias may persist. HMA-failure MDS has extremely poor prognosis and currently there are no approved therapeutic options for such pts who are often of advanced age with frequent comorbidities. Objectives: The dual primary objectives of this study evaluate the safety and efficacy of the second-generation thrombopoietin-receptor agonist (TPO-RA) eltrombopag (EPAG) for the treatment of MDS pts at the time of HMA-failure. Secondary objectives include incidence of transformation to AML and evaluation of bone marrow fibrosis during therapy. Methods: Eligible pts for this 2-arm phase 2 open-label clinical trial included adults with MDS after completing >4 HMA cycles with failure to achieve at least a partial response, or the presence of ongoing cytopenias per IWG criteria. Arm A includes eltrombopag monotherapy and Arm B includes eltrombopag with continuation of the HMA at the previous dosing schedule. The starting eltrombopag dose is 200mg orally daily, which can be increased to 300mg in the absence of toxicity. First response is assessed after 2 cycles with each cycle lasting 28 days. The primary efficacy endpoint was overall response rate based on the IWG-2006 criteria. Results: To date, 23 pts with a median age of 72 years (range 42-84 years) have been enrolled. Prior to study entry, pts had received a median of 6 (range 4-25) HMA cycles. Cytogenetics were diploid in 12 (53%), intermediate in 7 (30%), and high risk in 4 (17%) pts by IPSS. Median bone marrow blasts at study start was 3% (range 0-15%). Arm A has enrolled 7 pts with a median age of 74 years; Arm B has enrolled 16 pts with median age of 69 years. In Arm B, ongoing HMA therapy includes azacitidine in 7 (44%) and decitabine in 9 (56%). Nine (39%) pts increased to 300mg EPAG after median of 8 weeks on study. Median total cycles received on study is 5 (1-17); median OS has not been reached. Overall, 16 pts are response-evaluable; 7 pts discontinued prior to the first response assessment at 2 months (4 due to AEs including myalgias/fatigue (n=2), hyperbilirubinemia (n=1), and pneumonia (n=1), 2 per pt request and 1 for pt inability to comply with protocol requirements). Of the 16 response-evaluable pts, 3 (19%) in Arm B demonstrated platelet improvement, including one pt necessitating EPAG dose-reduction to 100mg due to platelet count exceeding 450 x10⁹/L with concomitant ANC recovery at 200mg EPAG dose level. An additional 8 (35%) pts have remained on study for a median of 5 cycles (2-17) with stable disease. Two pts discontinued therapy due to disease progression, including 1 (4%) that progressed to AML. The most common non-hematologic AEs regardless of attribution included hyperbilirubinemia (n=14, 61%), fatigue (n=13, 56%) myalgias (n=11, 48%), fever (7, 30%), dyspnea (7, 30%), nausea (6, 26%) and transaminitis (4, 17%). No significant increase in bone marrow fibrosis has been observed. Conclusion: Eltrombopag orally daily appears to be a safe and beneficial supportive adjunct for pts with MDS while receiving HMA-therapy or after HMA-failure due to persistent cytopenias. Treatment on this study continues and larger prospective clinical trials are needed to confirm these preliminary findings. Disclosures Off Label Use: Eltrombopag for the treatment of MDS-related cytopenias". Pemmaraju:Stemline: Research Funding; Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; LFB: Consultancy, Honoraria. Konopleva:Novartis: Research Funding; AbbVie: Research Funding; Stemline: Research Funding; Calithera: Research Funding; Threshold: Research Funding. DiNardo:Novartis: Research Funding.

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A Phase 2 Study to Evaluate the Efficacy and Safety of Simtuzumab in Adult Subjects with Primary, Post Polycythemia Vera (PV) or Post Essential Thrombocythemia (ET) Myelofibrosis

Blood ◽

10.1182/blood.v126.23.2810.2810 ◽

2015 ◽

Vol 126 (23) ◽

pp. 2810-2810

Author(s):

Srdan Verstovsek ◽

Michael R. Savona ◽

Ruben A. Mesa ◽

Stephen Oh ◽

Hua Dong ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Phase 2 ◽

Fibrosis Score ◽

Bone Marrow Fibrosis ◽

Advisory Committees ◽

Equity Ownership ◽

Stage 1 ◽

Marrow Fibrosis

Abstract Background: Simtuzumab (SIM) is a humanized monoclonal antibody that inhibits lysyl oxidase-like molecule 2 (LOXL2), an extracellular matrix enzyme that catalyzes the covalent cross-linking of collagen and is widely expressed across many fibrotic diseases. In pre-clinical models, inhibition of LOXL2 blocks fibroblast activation, which plays an important role in the development of organ fibrosis. In Phase 1 studies, SIM was well-tolerated in patients (pts) with advanced solid tumors, liver fibrosis, and idiopathic pulmonary fibrosis (IPF). A Phase 2, open-label study to determine the efficacy of SIM alone (Stage 1) and combined with ruxolitinib (rux) (Stage 2) in pts with primary myelofibrosis (PMF) and post-ET/PV MF was initiated. Methods: Eligible pts had intermediate-1, intermediate-2, or high risk disease and Eastern Cooperative Oncology Group performance status of <2. The primary endpoint was rate of clinical response as defined by a reduction in bone marrow fibrosis score following 24 weeks of treatment with SIM. Patients were randomized in a 1:1 ratio to receive 200 mg or 700 mg SIM by intravenous infusion every 2 weeks as monotherapy (Stage 1, n=24) or combined with rux (Stage 2, n=30). Patients received SIM for up to 24 weeks. Bone marrow biopsies and aspirates were performed approximately every 3 months. Bone marrow fibrosis scoring was performed and quantified at local investigator sites using the European Consensus on Grading Bone Marrow Fibrosis. Myelofibrosis symptoms were evaluated using the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF) and changes in hematologic parameters and splenomegaly were assessed. Results: Between 7/14/11 and 9/22/14, 54 pts were randomized and treated (200 mg SIM [n=12], 700 mg SIM [n=12], 200 mg SIM/rux [n=15], and 700 mg SIM/rux [n=15]). In Stage 1, 0 subjects (0%) in the SIM 200 mg group and 2 subjects (16.7%; 90% CI 3.0%, 43.8%) in the SIM 700 mg group showed a reduction in bone marrow fibrosis score from Baseline to Week 24. In Stage 2, 1 subject (6.7%; 90% CI 0.3%, 27.9%) in the SIM 200 mg/rux group and 2 subjects (13.3%, 90% CI 2.4%, 36.3%) in the SIM 700 mg/rux group showed a reduction in bone marrow fibrosis score from Baseline to Week 24. In an exploratory analysis, similar numbers of subjects showed increases in bone marrow fibrosis scores. SIM treatment was not associated with meaningful improvements in hematologic parameters or reductions in MPN-SAF score or spleen size. The most frequent adverse events were those commonly associated with MF, including constitutional symptoms and reductions in hematological parameters. Conclusions: SIM treatment alone or in combination with rux is safe but does not reliably reduce bone marrow fibrosis in pts with MF. The reason for reduction of marrow fibrosis in some patients and increase in others is unclear and may be sampling variability. Clinical studies of SIM in IPF and liver fibrosis are ongoing. Disclosures Savona: Karyopharm: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Research Funding; Astex Pharmaceuticals, Inc: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Mesa:Incyte Corporation: Research Funding; CTI Biopharma: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; Pfizer: Research Funding; Promedior: Research Funding; Genentech: Research Funding; NS Pharma: Research Funding; Gilead: Research Funding. Oh:CTI Biopharma: Membership on an entity's Board of Directors or advisory committees; Incyte: Membership on an entity's Board of Directors or advisory committees. Dong:Gilead Sciences: Consultancy, Equity Ownership. Thai:Gilead Sciences: Employment, Equity Ownership. Gotlib:Allakos, Inc.: Consultancy.

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A Phase 2 Study of Cpi-0610, a Bromodomain and Extraterminal (BET) Inhibitor, in Patients with Myelofibrosis (MF)

Blood ◽

10.1182/blood-2018-99-119157 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 5481-5481 ◽

Cited By ~ 4

Author(s):

Marina Kremyanskaya ◽

Ronald Hoffman ◽

John Mascarenhas ◽

Srdan Verstovsek ◽

Jennifer Mertz ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Inadequate Response ◽

Phase 2 ◽

Spleen Volume ◽

Bone Marrow Fibrosis ◽

Advisory Committees ◽

Phase 2 Study ◽

Marrow Fibrosis

Abstract MF is a myeloproliferative neoplasm characterized by abnormal megakaryocytes and elevated proinflammatory cytokines which results in bone marrow fibrosis, progressive hepatosplenomegaly due to extramedullary hematopoiesis, and debilitating constitutional symptoms. Current treatments, including ruxolitinib (the only approved drug for MF), provide symptomatic relief but have limited effects on the underlying disease. Effective therapies with potential MF disease course modification and second line therapies are urgently needed. CPI-0610 has been evaluated in 3 Phase 1 studies in > 140 patients with lymphoma, multiple myeloma and acute leukemias/myelodysplastic syndrome/MF. Although CPI-0610 was tested at doses as high as 400 mg PO QD, the maximum tolerated dose was 225 mg PO QD for 2 weeks on, 1 week off. Clear anti-tumor activity was observed in patients with lymphomas, particularly ABC-DLBCL (Blum et al. TAT conference 2018). Preclinical data on CPI-0610 demonstrated downregulation of pro-inflammatory cytokines through its effects on NF-κB pathway as well as inhibition of megakaryocyte differentiation. Both of these features are thought to be important in the pathogenesis of MF. In addition, a recent preclinical publication using a mouse model of MF, suggests that BET inhibition reduces inflammatory cytokine production, platelet counts, spleen volume and bone marrow fibrosis, the effects of which were further magnified when combined with ruxolitinib (Kleppe et al. 2018). Taken together, these data suggest that BET inhibitors such as CPI-0610, administered with and without ruxolitinib, have the potential to affect the underlying MF disease and supports further clinical evaluation of CPI-0610 in patients with MF. Therefore, we have embarked on a Phase 2 trial of CPI-0610 as monotherapy or in combination with ruxolitinib. This Phase 2 study aims to evaluate CPI-0610 as a monotherapy and in combination with ruxolitinib in patients with MF who are not eligible to receive a JAK inhibitor or have had an inadequate response to ruxolitinib. The primary objectives are to evaluate spleen volume response by imaging after 24 weeks of therapy and to evaluate the effect on transfusion independence rate. Other key secondary objectives are to evaluate the change in patient reported outcomes and the duration of splenic response. Exploratory objectives include characterizing the effects of treatment on the bone marrow and blood biomarkers. The Phase 2 study has a 2-stage design to enroll up to 35 patients in each arm (monotherapy and combination therapy) if ≥2 responses are observed during stage 1. The study is registered at ClinicalTrials.gov NCT02158858. Disclosures Kremyanskaya: Incyte: Research Funding. Hoffman:Formation Biologics: Research Funding; Summer Road: Research Funding; Incyte: Research Funding; Merus: Research Funding; Janssen: Research Funding. Mascarenhas:CTI Biopharma: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Research Funding; Promedior: Research Funding; Merck: Research Funding; Janssen: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees. Verstovsek:Italfarmaco: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Incyte: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees. Mertz:Constellation Pharma: Employment. Garner:Constellation Pharma: Employment. Senderowicz:Constellation Pharma: Employment.

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Decoding Bone Marrow Fibrosis in Myelodysplastic Syndromes

Clinical Lymphoma Myeloma & Leukemia ◽

10.1016/j.clml.2020.01.003 ◽

2020 ◽

Vol 20 (5) ◽

pp. 324-328

Author(s):

Megan Melody ◽

Najla Al Ali ◽

Ling Zhang ◽

Hanadi Ramadan ◽

Eric Padron ◽

...

Keyword(s):

Bone Marrow ◽

Myelodysplastic Syndromes ◽

Bone Marrow Fibrosis ◽

Marrow Fibrosis

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(A7) Myelodysplastic syndromes with bone marrow fibrosis: A myelodysplastic disorder with proliferative features

Leukemia Research ◽

10.1016/0145-2126(91)90330-v ◽

1991 ◽

Vol 15 ◽

pp. 2

Keyword(s):

Bone Marrow ◽

Myelodysplastic Syndromes ◽

Bone Marrow Fibrosis ◽

Marrow Fibrosis

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Efficacy, Safety, and Confirmation of the Recommended Phase 2 Dose of Ruxolitinib Plus Panobinostat in Patients with Intermediate or High-Risk Myelofibrosis

Blood ◽

10.1182/blood.v124.21.711.711 ◽

2014 ◽

Vol 124 (21) ◽

pp. 711-711 ◽

Cited By ~ 6

Author(s):

Jean-Jacques Kiladjian ◽

Florian H Heidel ◽

Alessandro M. Vannucchi ◽

Vincent Ribrag ◽

Francesco Passamonti ◽

...

Keyword(s):

Bone Marrow ◽

High Risk ◽

Board Of Directors ◽

Research Funding ◽

Phase Iii ◽

Spleen Volume ◽

Bone Marrow Fibrosis ◽

Advisory Committees ◽

Expansion Phase ◽

Marrow Fibrosis

Abstract Background: Myelofibrosis (MF) is a clonal neoplastic disease resulting in bone marrow fibrosis, splenomegaly, and debilitating constitutional symptoms. The Janus kinase (JAK) pathway is often dysregulated in MF, and agents targeting this pathway have demonstrated efficacy in this disease. Ruxolitinib (RUX), a potent JAK1/JAK2 inhibitor, demonstrated superiority in spleen volume reduction, symptom improvement, and survival compared with the control arm in the phase III COMFORT-I and COMFORT-II studies. Panobinostat (PAN), a potent pan-deacetylase inhibitor (pan-DACi), inhibits JAK signaling through disruption of the interaction of JAK2 with the protein chaperone heat shock protein 90. In phase I/II studies, PAN has shown splenomegaly reduction and improvement of bone marrow fibrosis. The combination of RUX and PAN demonstrated synergistic anti-MF activity in preclinical studies. These preliminary results led to the initiation of a phase Ib study evaluating the combination of RUX and PAN in patients (pts) with MF. The updated results from the expansion phase of this trial are presented here. Methods: Eligible pts had intermediate-1, -2, or high-risk primary MF, post-polycythemia vera MF, or post-essential thrombocythemia MF by International Prognostic Scoring System criteria, with palpable splenomegaly (≥ 5 cm below the costal margin). The primary objective was determination of the maximum tolerated dose (MTD) and/or recommended phase II dose (RPIID). Secondary objectives included safety, efficacy, and pharmacokinetics. Exploratory endpoints included assessment of improvement in bone marrow fibrosis and reduction of JAK2 V617F allele burden. The treatment schedule was RUX (5-15 mg) twice daily (bid) every day and PAN (10-25 mg) once daily 3 times per week (tiw; days 2, 4, and 6) every other week (qow) in a 28-day cycle. Following dose escalation and identification of the potential RPIID, additional pts were enrolled into the expansion phase and treated at this dose. Results: As of March 14, 2014, a total of 61 pts were enrolled (38 escalation phase and 23 expansion phase). The median duration of exposure to PAN and to RUX was 24.6 weeks and 24.0 weeks, respectively, for pts treated in the expansion phase. Three DLTs were observed in the escalation phase (grade 4 thrombocytopenia [n = 2], grade 3 nausea [n = 1]). No MTD was reached. The RPIID was confirmed to be RUX 15 mg bid and PAN 25 mg tiw qow in May 2014. Among the 34 pts treated at the RPIID, grade 3/4 adverse events (AEs) regardless of causality included anemia (32%), thrombocytopenia (24%), diarrhea (12%), asthenia (9%), and fatigue (9%). AEs led to discontinuation in 6% of pts treated at the RPIID. Two pts treated at the RPIID died due to causes unrelated to study treatment (1 due to myocardial infarction and 1 due to progression of myelofibrosis). Among the pts treated at the RPIID, 79% showed a >50% decrease in palpable spleen length, with 100% decrease (non-palpable spleen) being observed in 53% of pts. Additionally, 48% of pts treated at the RPIID in the expansion phase achieved ≥35% reduction in spleen volume (Figure). These results are similar to those observed for spleen volume response at 24 weeks among pts who received single-agent RUX on the phase III COMFORT-I (41.9%) and COMFORT-II (32%) studies. Conclusions: The combination of the JAK1/JAK2 inhibitor RUX and the pan-DACi PAN was well tolerated and resulted in high rates of reductions in splenomegaly in pts with intermediate- and high-risk MF. Although a relatively larger proportion of patients experienced spleen volume reductions at week 24 as compared to the COMFORT studies, the smaller sample size, shorter follow up times and potential differences in the patient populations preclude definitive comparisons. Similar to COMFORT-I and II trials, hematological AEs, specifically anemia and thrombocytopenia, were the most common AEs observed in pts treated with the combination therapy. Pts continue to be treated in the expansion phase at the RPIID. Updated safety, efficacy, and exploratory analyses on bone marrow fibrosis, JAK V617F allele burden, and biomarkers, including cytokines, will be presented. Figure Change in Spleen Volume in Expansion Phase Figure. Change in Spleen Volume in Expansion Phase Disclosures Kiladjian: Novartis: Honoraria, Research Funding, Speakers Bureau; Shire: Membership on an entity's Board of Directors or advisory committees; AOP Orphan: Honoraria, Research Funding. Heidel:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Ribrag:Celgene: Consultancy; Pharmamar: Consultancy; Epizyme: Research Funding; Bayer: Consultancy, Research Funding; Servier: Consultancy, Honoraria, Research Funding. Conneally:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Honoraria, Speakers Bureau; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Kindler:Novartis: Consultancy. Acharyya:Novartis: Employment. Gopalakrishna:Novartis: Employment. Ide:Novartis: Employment, Equity Ownership. Loechner:Novartis: Employment. Mu:Novartis: Employment. Harrison:Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Sanofi: Consultancy, Honoraria; CTI: Consultancy, Honoraria; Gilead: Honoraria; SBio: Consultancy; Shire: Speakers Bureau.

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Myelodysplastic syndromes with bone marrow fibrosis: a myelodysplastic disorder with proliferative features

Annals of Hematology ◽

10.1007/bf01698371 ◽

1991 ◽

Vol 63 (5) ◽

pp. 235-241 ◽

Cited By ~ 44

Author(s):

G. E. G. Verhoef ◽

C. De Wolf-Peeters ◽

A. Ferrant ◽

S. Deprez ◽

P. Meeus ◽

...

Keyword(s):

Bone Marrow ◽

Myelodysplastic Syndromes ◽

Bone Marrow Fibrosis ◽

Marrow Fibrosis

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The implication of identifying JAK2 V617F in myeloproliferative neoplasms and myelodysplastic syndromes with bone marrow fibrosis

Journal of Hematopathology ◽

10.1007/s12308-008-0014-8 ◽

2008 ◽

Vol 1 (2) ◽

pp. 111-117 ◽

Cited By ~ 10

Author(s):

Randall J. Olsen ◽

Cherie H. Dunphy ◽

Dennis P. O’Malley ◽

Lawrence Rice ◽

April A. Ewton ◽

...

Keyword(s):

Bone Marrow ◽

Myelodysplastic Syndromes ◽

Myeloproliferative Neoplasms ◽

Jak2 V617f ◽

Bone Marrow Fibrosis ◽

Marrow Fibrosis

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Interim Results from Fight-203, a Phase 2, Open-Label, Multicenter Study Evaluating the Efficacy and Safety of Pemigatinib (INCB054828) in Patients with Myeloid/Lymphoid Neoplasms with Rearrangement of Fibroblast Growth Factor Receptor 1 (FGFR1)

Blood ◽

10.1182/blood-2018-99-110388 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 690-690 ◽

Cited By ~ 12

Author(s):

Srdan Verstovsek ◽

Alessandro M. Vannucchi ◽

Alessandro Rambaldi ◽

Jason R. Gotlib ◽

Adam J. Mead ◽

...

Keyword(s):

Bone Marrow ◽

Board Of Directors ◽

Research Funding ◽

Phosphate Binders ◽

Phase 2 ◽

Open Label ◽

Employment Equity ◽

Advisory Committees ◽

Lymphoid Neoplasms ◽

Equity Ownership

Abstract Introduction: Myeloid/lymphoid neoplasms (MLNs) with rearrangement of FGFR1 on chromosome band 8p11 are rare but aggressive neoplasms characterized by heterogeneous presentation with myeloid and/or lymphoid proliferation, extramedullary involvement, and rapid progression to blast phase (Strati P, et al., Leuk Lymphoma. 2018;59:1672-1676). FGFR1 gets constitutively activated through fusion genes involving various partner genes, most frequently ZMYM2-FGFR1 or BCR-FGFR1 as consequence of a t(8;13)(p11;q12) or a t(8;22)(p11;q11), respectively. Chemotherapy is usually ineffective, effective targeted treatment has not been described, and allogeneic hematopoietic stem cell transplant (alloHSCT) is the only potentially curative option. Pemigatinib, a selective, potent, oral inhibitor of FGFR1, 2, and 3, has shown efficacy in patients with FGF/FGFR-activated tumors, including cholangiocarcinoma and urothelial carcinoma. We report interim results from the ongoing fight-203 study (NCT03011372) of pemigatinib in patients with FGFR1-rearranged MLNs. Methods: Fight-203 is a phase 2, open-label study enrolling patients ≥ 18 years of age with FGFR1-rearranged MLN. Patients enrolled in the study must have progressed on ≥ 1 prior treatment and be ineligible for alloHSCT. Patients receive a daily oral dose of pemigatinib 13.5 mg on a 21-day cycle (2 weeks on, 1 week off) until disease progression or unacceptable toxicity. The primary endpoint is overall clinical benefit rate, which includes complete clinical (CR) or partial clinical response (PR), and either complete or partial cytogenetic response (CCyR, PCyR). Secondary endpoints include duration of response/benefit, progression-free survival, overall survival, and safety/tolerability. Efficacy is assessed by evaluation of bone marrow histomorphology changes, standard cytogenetic and FISH evaluation of the FGFR1 rearrangement, and PET/CT scan. Results: At data cutoff (July 23, 2018), 14 patients were enrolled. Ten patients who had ≥ 1 response assessment were included in the analysis (Table). Patients received an average of 6.9 cycles of pemigatinib (range, 2-12 cycles). Median number of prior lines of therapy was 3 (range, 0-5), including 2 patients who received alloHSCT. Eight patients (80%) had a major CyR, including 6 patients with CCyR and 2 with PCyR. Eight patients (80%) had a CR or PR in bone marrow, peripheral blood, and extramedullary disease. One patient died of progression to myeloid blast crisis, 2 patients were bridged to alloHSCT, and 7 patients are ongoing. The most common treatment-emergent adverse events (AEs) were hyperphosphatemia (n=7 [70%]), diarrhea (n=5 [50%]) and anemia (n=5 [50%]); hyperphosphatemia was managed with diet and phosphate binders. Nine events in 4 patients (40%) were grade 3/4; 2 of these events (diarrhea and leukopenia) in 2 patients were related to pemigatinib. There were no drug-related AEs leading to dose interruption, dose reduction, or discontinuation. Conclusions: Pemigatinib showed promising efficacy, with an 80% major CyR rate accompanied by complete or partial remission, and was generally well tolerated by patients with FGFR1-rearranged MLN. The protocol was amended to allow continuous dosing, and the study is currently enrolling. Disclosures Verstovsek: Celgene: Membership on an entity's Board of Directors or advisory committees; Italfarmaco: Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Gotlib:Blueprint Medicines: Consultancy, Honoraria, Research Funding; Deciphera: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Gilead: Consultancy, Research Funding; Promedior: Research Funding; Kartos: Consultancy; Incyte: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Mead:Celgene: Research Funding; Bristol-Myers Squibb: Consultancy; Evotek: Research Funding; ARIAD: Consultancy; Cell Therapeutics: Consultancy; Novartis: Consultancy, Honoraria, Research Funding, Speakers Bureau; Elstar: Research Funding. Hochhaus:Bristol-Myers Squibb: Research Funding; Novartis: Research Funding; Incyte: Research Funding; Takeda: Research Funding; Pfizer: Research Funding. Kiladjian:AOP Orphan: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees. Hernandez Boluda:Incyte: Consultancy; Novartis: Consultancy. Asatiani:Incyte: Employment, Equity Ownership. Lihou:Incyte: Employment, Equity Ownership. Zhen:Incyte: Employment, Equity Ownership. Reiter:Incyte: Consultancy, Honoraria.

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