Tefferi, Ayalew

Abstract Venetoclax (Ven) combined with a hypomethylating agent (HMA) has now emerged as an effective treatment regimen for acute myeloid leukemia, in both de novo and relapsed/refractory setting. The current multicenter study retrospectively examined Ven + HMA treatment outcome among 32 patients (median age 69 years; 59% males) with blast‐phase myeloproliferative neoplasm (MPN‐BP). Pre‐leukemic phenotype included essential thrombocythemia (ET)/post‐ET myelofibrosis (34%), polycythemia vera (PV)/post‐PV myelofibrosis (38%) and primary myelofibrosis (28%). Twenty‐nine study patients were fully annotated cytogenetically and molecularly (NGS): 69% harbored complex karyotype and/or mutations, including TP53 (41%), IDH1/2 (21%), ASXL1 (21%), N/KRAS (14%), SRSF2 (10%), EZH2 (10%) and U2AF1 (7%). All patients received Ven combined with either azacitidine ( n = 12) or decitabine ( n = 20); either up front ( n = 23) or after failing another induction therapy ( n = 9). Complete remission with (CR) or without (CRi) count recovery was achieved in 14 (44%) patients and was more likely to occur in the absence of pre‐leukemic PV/post‐PV myelofibrosis phenotype ( p < .01), complex karyotype ( p < .01) or K/NRAS ( p = .03) mutations; seven of eight patients (88%) without vs four of 21 (19%) with complex karyotype or K/NRAS mutation achieved CR/CRi ( p < .01); all 11 informative patients with pre‐leukemic PV/post‐PV myelofibrosis phenotype displayed complex karyotype ( p < .01). In contrast, neither TP53 ( p = .45) nor IDH1/2 ( p = .63) mutations affected response. Compared to historical controls treated with HMA alone ( n = 26), the CR/CRi rate (44% vs 4%) and median survival (8 vs 5.5 months) were more favorable with Ven + HMA, but without significant difference in overall survival. Importantly, six patients with CR/CRi subsequently received allogeneic hematopoietic stem cell transplant (AHSCT). Note, Ven + HMA produces robust CR/CRi rates in MPN‐BP, especially in the absence of RAS mutations and complex karyotype, thus enabling AHSCT, in some patients.

Abstract The myeloproliferative neoplasms (MPN) frequently progress to blast phase disease, an aggressive form of acute myeloid leukemia. To identify genes that suppress disease progression, we performed a focused CRISPR/Cas9 screen and discovered that depletion of LKB1/Stk11 led to enhanced in vitro self-renewal of murine MPN cells. Deletion of Stk11 in a mouse MPN model caused rapid lethality with enhanced fibrosis, osteosclerosis, and an accumulation of immature cells in the bone marrow, as well as enhanced engraftment of primary human MPN cells in vivo. LKB1 loss was associated with increased mitochondrial reactive oxygen species and stabilization of HIF1α, and downregulation of LKB1 and increased levels of HIF1α were observed in human blast phase MPN specimens. Of note, we observed strong concordance of pathways that were enriched in murine MPN cells with LKB1 loss with those enriched in blast phase MPN patient specimens, supporting the conclusion that STK11 is a tumor suppressor in the MPNs. Significance: Progression of the myeloproliferative neoplasms to acute myeloid leukemia occurs in a substantial number of cases, but the genetic basis has been unclear. We discovered that loss of LKB1/STK11 leads to stabilization of HIF1a and promotes disease progression. This observation provides a potential therapeutic avenue for targeting progression. This article is highlighted in the In This Issue feature, p. 1307

Abstract Context. —Systemic mastocytosis is characterized by abnormal growth and accumulation of neoplastic mast cells in various organs. The clinical presentation is varied and may include skin rash, symptoms related to release of mast cell mediators, and/or organopathy from involvement of bone, liver, spleen, bowel, or bone marrow. Objective. —To concisely review pathogenesis, disease classification, clinical features, diagnosis, and treatment of mast cell disorders. Data Sources. —Pertinent literature emerging during the last 20 years in the field of mast cell disorders. Conclusions. —The cornerstone of diagnosis is careful bone marrow histologic examination with appropriate immunohistochemical studies. Ancillary tests such as mast cell immunophenotyping, cytogenetic/molecular studies, and serum tryptase levels assist in confirming the diagnosis. Patients with cutaneous disease or with low systemic mast cell burden are generally managed symptomatically. In the patients requiring mast cell cytoreductive therapy, treatment decisions are increasingly being guided by results of molecular studies. Most patients carry the kit D816V mutation and are predicted to be resistant to imatinib mesylate (Gleevec) therapy. In contrast, patients carrying the FIP1L1-PDGFRA mutation achieve complete responses with low-dose imatinib therapy. Other therapeutic options include use of interferon-α, chemotherapy (2-chlorodeoxyadenosine), or novel small molecule tyrosine kinase inhibitors currently in clinical trials.

Background: Elevated serum ferritin (SF) is common in patients with myelofibrosis (MF) given the frequent red-cell transfusion requirements and impaired iron metabolism. The dysregulation of iron metabolism is associated with increased hepcidin levels which predict for inferior survival in patients with MF (Pardanani et al AJH 2013). High pre-transplant SF negatively impacts overall survival and non-relapse mortality in patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT) for hematological malignancies (Chee et al BMT 2017 & Yan et al 2018). However, the impact of elevated pre-transplant SF specifically on post-alloHCT outcomes has not been described in MF. Methods: We conducted a retrospective study of patients with MF undergoing allo-HCT at Mayo clinic Rochester, Arizona, and Florida from January 1st 2012 - December 31st 2019. We abstracted demographic and outcome variables to evaluate the impact of pre-transplant ferritin levels on post-transplant outcomes. We used a Receiver Operand Characteristic Curve to identify a pre-transplant serum ferritin (SF) of ≥ 1,123 ng/mL as the cutoff which best correlated with poor survival. Results: We identified 67 patients with MF who underwent allo-HCT during the study period with readily available data. Patients with a pre-transplant ferritin ≥ 1,123 ng/mL (n=18) had a median age of 59.4 years and were predominantly male (n=9, 50%) with primary myelofibrosis (n=12, 67%), had a DIPSS-plus int-2 (n=10, 56%) and high (n=6, 33%) risk categories and received a reduced-intensity conditioning (n=14, 78%) from a matched-unrelated donor (n=7, 50%) Table1. Patients with SF ≥ 1,123 ng/mL had a worse overall survival (OS) (median OS= 12.64 months [95%CI=6.08-19.20 months] vs. not-reached (NR) p=0.001). Patients with elevated SF had an increased non-relapse mortality (NRM) rate at 6 months (16.7%, [95%CI=0.4-37.2%]) vs 8.2%,[95%CI= 2.6-18.1%] p=0.021) and 12 months (33.3% [95%CI=13.0-55.4%] vs 10.4% [95%CI=3.8-21.0%] p=0.021) Patients with ≥ 1,123 ng/mL SF had a non-statistically significant higher rate of acute graft-vs-host disease grades 3-4 (28% vs 12.2% p=0.13) but similar rates of moderate to severe chronic graft-vs-host disease (31% vs 28% p=0.78). In the univariate analysis, SF ≥1,123 ng/mL and a Hematopoietic stem cell transplant comorbidity index (HCT-CI) ≥3 were associated with an increased risk of mortality (Hazard ratio [HR]=4.18 [95%CI=1.64-10.62] p=0.003] and HR=4.42 [95%CI=1.70-11.46] p=0.003, respectively). Both retained significance in multivariate analysis SF ≥1,123 ng/mL (HR= 2.80 [95%CI= 1.0-7.6], p=0.04)] and HCT-CI score ≥ 3 (HR 3.10 [95%CI= 1.12-8.62, p=0.03]) after adjusting for age, DIPSS-plus score, conditioning regimen intensity, donor type, CMV risk, prior use of ruxolitinib, and ABO mismatch. We grouped the patients into low, intermediate and high risk categories using SF level and HCT-CI scores as detailed in Figure 1. The risk category based on SF and HCT-CI was statistically significant in impacting OS and NRM in this cohort. The 12 month OS rate was lower in the high risk category (44.4% [95%CI= 13.6%-71.9%]) when compared to the intermediate (64.6%, [95%CI=39.7%-81.3%]) and low risk (91.9%, [95%CI= 76.9%-97.3%], p=0.0002) categories. Similarly, the 12 month NRM rate was higher in the high risk category (44.4%, [95%CI=11.0%-74.2%]) when compared to the intermediate (25%, [95%CI=8.7%-45.5%]) and low risk (5.3% [95%CI=0.9%-15.9%], p=0.0046) categories. Conclusion: In patients undergoing allogeneic SCT for myelofibrosis, serum ferritin ≥ 1,123 ng/mL is a predictor of high NRM and inferior OS. Combining ferritin serum levels with HCT-CI may help in better patient selection for allo-HCT in MF population. Larger patient cohort is warranted to confirm our findings. Disclosures Kharfan-Dabaja: Daiichi Sankyo: Consultancy; Pharmacyclics: Consultancy. Shah:Dren Bio: Consultancy.

Introduction: Polycythemia Vera (PV), Essential Thrombocythemia (ET), and Primary Myelofibrosis (PMF) are BCR/ABL1-negative myeloproliferative neoplasms (MPN) that are associated with morbidity and increased mortality. Limited data regarding population-based outcomes for these MPNs have been reported. Our aim was to use the Surveillance, Epidemiology, and End Results (SEER) registry to investigate population based outcomes for PV, ET, and PMF. Methods: The SEER 18 registries were used to identify patients with ICD-O-3 diagnosis codes for PV (9950/3), ET (9962/3), and PMF (9961/3) from 2001-2015. For ET and PMF, histologic diagnosis was required for inclusion. Incidence was age-adjusted to the U.S. 2000 standard population. Causes of death were obtained and MPN-related death was defined as death from any myeloid disorder (ET, PV, PMF, acute myeloid leukemia [AML], acute monocytic leukemia, other myeloid/monocytic leukemia, and aleukemic, subleukemic and NOS). Relative survival (RS) was defined as the ratio of the proportion of observed survivors in a cohort of PV, ET, PMF patients to the proportion of expected survivors in a comparable set of individuals that did not respectively have PV, ET, or PMF, adjusting for the general survival of the US population for race, sex, age, and time when the diagnosis was established. Time to leukemic transformation was calculated using the left-truncated life tables session with a 3-month latency period used to prevent misattribution. Overall survival (OS) was calculated between the date of diagnosis and the date of death, date last known to be alive, or date of the study cut-off (31 December 2018). Variables significant in univariate analysis were included in a multivariate analysis. The Kaplan-Meier method was used to calculate overall survival (OS), and Cox regression model was used to identify predictors of survival. Statistical analyses were performed using JMP version 14.0. Results: 10,988 patients with PV, 9,146 with ET, and 4,022 with PMF were identified in SEER. The median age of diagnosis (interquartile range [IQR]) was 65 years (IQR 54-76), 67 years (IQR 54-77), and 69 years (IQR 60-78) for PV, ET, and PMF respectively. Overall incidence rates (cases/100,000) were 0.86 for PV, 0.72 for ET, and 0.30 for PMF. With a median follow up (in years, 95% confidence interval [CI]) of 7.6 (7.4-7.8), 7.9 (7.8-8.2), and 7.25 (7.0-7.5), the median OS was 11.4 (11.2-11.7), 11.75 (11.3-12.0), and 3.5 (3.3-3.7), for PV, ET, and PMF respectively. RS was better than expected survival for PV and ET, while less than expected survival for PMF (Figure 1). 3853 of PV patients died (35.1%) by the end of the study period, with 4.1% and 34.1% of deaths from PV-related and cardiovascular disease respectively (Table 1). 3142 of ET patients died (34.4%), with 7.2% and 32.2% of deaths from ET-related and cardiovascular disease respectively. 2578 patients with MF died (64.1%), with 13.2%, and 51.9% of deaths from PMF-related and other malignancies respectively. 106 patients (1.0%) with PV, 135 patients (1.5%) with ET, and 127 patients (3.2%) with PMF transformed to AML. Median time to transformation was 4.8, 6.3, and 2.3 years for PV, ET, and PMF respectively. Factors indicating inferior OS on multivariate analysis (Table 2) included age ≥ 65, female sex, and year of diagnosis for PV, age ≥ 65, male sex, and year of diagnosis for ET, and age ≥ 65, and male sex for PMF. Conclusion: Incidence rates for PV, ET, and PMF were similar to previous reports. RS was better than expected survival for PV and ET, while less than expected survival for PMF. The majority of deaths in ET and PV occurred from cardiovascular disease; a finding likely related to these MPNs. Patients with PMF were more likely to die from their disease or a subsequent malignancy. Transformation to AML occurred less frequently than prior large case series, noting a limitation in the current study. Patients with PMF were more likely to transform to AML with a shorter time interval. Older age was associated with worse OS in all patients. Male sex was predictive of worse survival for ET and PMF, while female sex was associated with worse survival in PV. Over the years, survival has improved for PV and remained essentially unchanged for ET and PMF. Figure Disclosures Shah: Dren Bio: Consultancy.

Study Rationale: At present there are no effective therapies for patients with primary or secondary myelofibrosis (MF) after the failure of the JAK inhibitory class of therapies. Furthermore, patients with monocytosis, thrombocytopenia, accelerated phase, or high-risk genetic features fare poorly with JAK inhibitors (JAKi), as intolerance, resistance, and/or ineligibility often limit treatment options. Median overall survival in most studies post-JAKi demonstrate poor outcomes (14-28 months) among patients with MF. Consequently, there is a considerable need in identifying new therapeutic targets beyond JAK-STAT inhibition. One potential cancer target is CD123, aberrantly expressed on leukemia stem cells and aberrant/malignant microenvironmental plasmacytoid dendritic cells (pDC) in certain myeloid cancers including MF. Tagraxofusp (TAG), a CD123-targeted therapy FDA-approved for patients with blastic plasmacytoid dendritic cell neoplasm, a pDC-derived malignancy, has demonstrated preclinical proof-of-concept in MF. We now report the updated results of an ongoing study of TAG monotherapy in patients with relapsed/refractory MF, or who were unable to tolerate currently approved JAKi. (NCT02268253) Experimental Design: A multicenter Phase 1/2 trial with TAG administered as a daily IV infusion at 7, 9, or 12 mcg/kg on days 1-3 every 21 days (cycle 1-4), 28 days (cycles 5-7), and 42 days (cycles 8+) in stage 1, and 12 mcg/kg every 21 days (C1-4), 28 days (C5+) in the currently ongoing stage 2. Results: Thirty-five patients (pts) with a median age 69 years (range: 54-87) have been treated thus far: 26% had baseline monocytosis and 69% had baseline thrombocytopenia, which impacts optimal dosing of JAKi, including 37% with platelets &lt;50x109/L including 7 pts with platelets ≤20; 75% had baseline palpable splenomegaly. Baseline genomic analysis in 35 pts revealed: JAK2 V617F (n=21); CALR (n=3); MPL (n=2); 7 of 21 pts who had comprehensive NGS, had an ASXL1 mutation. Most common treatment-related adverse events (incidence ≥15%) include hypoalbuminemia (23%), headache (17%), and elevated alanine aminotransferase (17%). Notably, capillary leak syndrome (CLS) was reported in 3 pts (1 was grade 4). Twenty-one pts (60%) achieved stable disease (SD) by IWG-MRT revised 2013 criteria, including 4 who had substantial clinical benefits; SD was noted in 7 of 9 (78%) with monocytosis, 7 of 13 (54%) with baseline platelets ≤50x109/L, including 3 of 7 (43%) with baseline platelets ≤20x109/L, and 2 of 3 (67%) pts with accelerated phase. At week 24, spleen responses by palpation were observed in 10 (45%), including 2 with &gt;50% spleen reduction; 12 of 26 (46%) had symptom burden reduction, including 3 pts who met the IWG-MRT criteria. There have been three deaths, all deemed to be unrelated to study drug, occurring in cycles 1, 6, 13, respectively. The median overall survival of our cohort was 31 months (range: 0.6-42 months). Conclusions: Interim results demonstrate clinical efficacy and safety of TAG monotherapy in JAKi relapse/refractory/intolerant MF patients, including those associated with recognized poor-risk biological and clinical features, such as monocytosis. Some patients have experienced clinical benefit, including reduction in splenomegaly and improvement in quality of life and enrollment continues. Disclosures Pemmaraju: Celgene: Honoraria; DAVA Oncology: Honoraria; Roche Diagnostics: Honoraria; Blueprint Medicines: Honoraria; AbbVie: Honoraria, Research Funding; MustangBio: Honoraria; SagerStrong Foundation: Other: Grant Support; Pacylex Pharmaceuticals: Consultancy; Novartis: Honoraria, Research Funding; LFB Biotechnologies: Honoraria; Stemline Therapeutics: Honoraria, Research Funding; Plexxikon: Research Funding; Cellectis: Research Funding; Incyte Corporation: Honoraria; Affymetrix: Other: Grant Support, Research Funding; Daiichi Sankyo: Research Funding; Samus Therapeutics: Research Funding. Gupta:Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bristol MyersSquibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Incyte: Honoraria, Research Funding. Ali:Incyte Corporation: Consultancy. Yacoub:Hylapharm: Current equity holder in private company; Incyte: Speakers Bureau; Agios: Honoraria, Speakers Bureau; Novartis: Speakers Bureau; Roche: Other: Support of parent study and funding of editorial support; Dynavax: Current equity holder in publicly-traded company; Ardelyx: Current equity holder in publicly-traded company; Cara Therapeutics: Current equity holder in publicly-traded company. Wang:PTC Therapeutics: Consultancy; Stemline: Speakers Bureau; Macrogenics: Consultancy; Astellas: Consultancy; Genentech: Consultancy; Pfizer: Speakers Bureau; Abbvie: Consultancy; Jazz Pharmaceuticals: Consultancy; Bristol Meyers Squibb (Celgene): Consultancy. Lee:Roche Molecular Systems: Consultancy; Jazz: Consultancy; AstraZeneca: Consultancy; Helsinn: Other: Member -DSMB; BMS: Consultancy. Schiller:Pfizer: Current equity holder in publicly-traded company, Research Funding; Regimmune: Research Funding; Samus: Research Funding; Sangamo: Research Funding; Tolero: Research Funding; Trovagene: Research Funding; Kaiser Permanente: Consultancy; Johnson & Johnson: Current equity holder in publicly-traded company; Jazz Pharmaceuticals: Research Funding; Geron: Research Funding; Genentech-Roche: Research Funding; Gamida: Research Funding; FujiFilm: Research Funding; Forma: Research Funding; Bristol-Myers Squibb: Current equity holder in publicly-traded company, Research Funding; DeltaFly: Research Funding; Deciphera: Research Funding; Daiichi Sankyo: Research Funding; Cyclacel: Research Funding; Constellation: Research Funding; Celator: Research Funding; Astellas Pharma: Honoraria, Research Funding; Ariad: Research Funding; Actinium: Research Funding; Abbvie: Research Funding; Stemline: Speakers Bureau; Gilead: Speakers Bureau; Agios: Consultancy, Research Funding, Speakers Bureau; Sanofi: Speakers Bureau; Amgen: Consultancy, Current equity holder in publicly-traded company, Research Funding, Speakers Bureau; AstraZeneca: Consultancy; Incyte: Consultancy, Research Funding, Speakers Bureau; Novartis: Consultancy, Research Funding; Ono Pharma: Consultancy; Celgene: Research Funding, Speakers Bureau; Karyopharm: Research Funding; Kite Pharma: Research Funding; Mateon: Research Funding; MedImmune: Research Funding; Onconova: Research Funding. Brooks:Stemline: Current Employment. Rupprecht:Stemline: Current Employment. Talpaz:Takeda: Research Funding; IMAGO: Consultancy; Constellation Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; BMS: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding. Mughal:Stemline: Current Employment. Verstovsek:PharmaEssentia: Research Funding; AstraZeneca: Research Funding; ItalPharma: Research Funding; Incyte Corporation: Consultancy, Research Funding; Gilead: Research Funding; Promedior: Research Funding; CTI Biopharma Corp: Research Funding; Genentech: Research Funding; Blueprint Medicines Corp: Research Funding; Novartis: Consultancy, Research Funding; Sierra Oncology: Consultancy, Research Funding; Roche: Research Funding; NS Pharma: Research Funding; Celgene: Consultancy, Research Funding; Protagonist Therapeutics: Research Funding.