Mutated Calreticulin Could Lead to MF Onset

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Brian Murphy, PhD

Mutations in the CALR gene, including a 52 base pair (bp; CALR Del52) deletion and 5 bp insertion (CALR Ins5), affect several signaling pathways in cells leading to the pathogenesis of myelofibrosis (MF) and other myeloproliferative neoplasms (MPNs), according to a study published in the International Journal of Molecular Sciences.

Cells carrying CALR Del52 and CALR Ins5 mutations had increased activation of the Janus kinase/signal transducer and activator of the transcription (JAK/STAT) and the phosphatidylinositol 3-kinase/Protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR) pathways which have been previously implicated in the pathogenesis of MPNs. These effects were still present in a cell culture model lacking MPL gene (thrombopoietin receptor) expression.

The CALR mutations resulted in reduced functionality of calreticulin proteins. Calreticulin generally functions as a major chaperone in the endoplasmic reticulum and is involved in several processes, including control of protein folding, calcium homeostasis, and responses to cellular stress.

The study found cells with CALR Del52 mutations had statistically significant higher levels of DNA damage compared to controls when exposed to hydrogen peroxide. Cells with CALR Ins5 had significantly higher levels of phosphorylated ATM and H2AX than controls. Both cell types were not able to repair DNA damage after 24 hours following oxidative stress.

Apoptosis levels were also significantly higher in cells with the CALR Ins5 mutation compared to controls. Those with CALR Del52 also had higher rates of apoptosis, but it did not reach significance. Further analysis found that the CALR mutations not only led to increased apoptosis after hydrogen peroxide exposure-induced oxidative stress but also tended to arrest the cells in the G2/M phase.

“Functional analysis revealed that the accumulation of G2/M-CALR-mutated cells indicates that oxidative stress-induced DNA damage is difficult to repair. The mentioned cell cycle delay has not been shown in other studies analyzing mutated calreticulin,” the authors said.

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Exploring Possibilities in Disease Modification in MPNs

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October 25, 2024

Author(s): Mary Caffrey

Treatment of myeloproliferative neoplasms (MPNs) has historically focused on delaying or avoiding transformation to acute myeloid leukemia (AML) as well as symptom relief and improving quality of life; strategies addressed thrombosis or enlarged spleen both with therapy and with nonpharmacological strategies such as smoking cessation or encouraging patients to lose weight.

Although these strategies were associated with improving life expectancy, they did not measure disease modification through molecular responses that signal survival benefits, in the way that trials do with AML and chronic myeloid leukemia (CML).

Claire N. Harrison, MD, FRCP, FRCPath | Image credit: Guy’s and St Thomas

Now, in an essay appearing in HemaSphere, a publication of the European Hematology Association (EHA), investigator Claire N. Harrison, MD, FRCP, FRCPath, of the Department of Haematology, Guy’s and St Thomas NHS Foundation Trust, asks whether the study and treatment of MPNs is ready for a new era with new end points, with data that show how survival benefits are biologically linked to changes in the spleen, reduction in fibrosis, or other responses.

The challenge, Harrison writes, is that the requirements will be different from today’s standards. “These data should hopefully influence a paradigm shift for the regulatory agencies and the field toward a focus instead of disease modification, but this will certainly require data extending beyond the recent standard of 24 weeks,” she writes.

In the perspective piece, “Are we ready for disease modification in myeloproliferative neoplasms?” Harrison notes that a dramatic shift that came with arrival of Janus kinase (JAK) inhibitor–based therapy for patients with myelofibrosis (MF) who could not receive a stem cell transplant. Therapy shows the capacity to reduce spleen size and symptoms. “Both of these facets of MF do probably reflect underlying pathophysiology and, furthermore, spleen size reduction has been shown to correlate with overall survival advantage.”

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INCA033989 May Address Need for Disease-Modifying Therapies in Myelofibrosis

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October 25, 2024

Author(s): Courtney Flaherty

Fact checked by: Megan Hollasch

Unlike the array of JAK inhibitors available for the treatment of patients with myelofibrosis, the novel monoclonal antibody INCA033989 may have disease-modifying potential among those expressing CALR type 1 mutations, potentially addressing an area of need in myeloproliferative neoplasm (MPN) management, according to Daniel J. DeAngelo MD, PhD.

“With the 4 [FDA-approved] JAK inhibitors, we see clear improvements in symptoms, reduction in spleen [volume], and decreased counts for patients with polycythemia or essential thrombocytopenia, but we’re not seeing eradication and normalization of the bone marrow,” DeAngelo said in an interview with OncLive®. “We don’t know if this agent is going to change that, but the hypothesis is that [INCA033989] may be getting at the heart of the disease, although only for patients with CALR type 1 mutations.”

In engineered cell lines and primary CD34-positive cells from patients with MPN, INCA033989 was shown to antagonize mutant CALR–driven signaling and cellular proliferation. Moreover, in a mouse model of MPN with mutant CALR, administration of an INCA033989 mouse surrogate antibody prevented the development of thrombocytosis and accumulation of platelet-producing megakaryocytes in the bone marrow. The agent’s disease-modifying potential is supported by its reduction of pathogenic self-renewal among MPN cells expressing CALR mutations in both primary and secondary transplantations.1

These preclinical data support the agent’s ongoing investigation in a phase 1 study (NCT06034002) for patients with MPN.2

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Recognizing Symptoms of Myeloproliferative Neoplasms and Clinical Trial Challenges

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October 24, 2024

Author(s): Mary Caffrey, Laura Joszt, MA

The symptoms of myeloproliferative neoplasms can be variable and common, which can make it difficult to diagnose if you aren’t looking for the right thing, said Ruben Mesa, MD, FACP, executive director of Atrium Health Wake Forest Baptist Comprehensive Cancer Center and president of Atrium Health Levine Cancer.

He also discusses the challenges with getting patients enrolled in clinical trials, such as the limited availability of them and patient factors that make it difficult to participate.

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Thrombosis in myeloproliferative neoplasms: a viewpoint on its impact on myelofibrosis, mortality, and solid tumors

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October 25, 2024

Tiziano Barbui, Arianna Ghirardi, Alessandra Carobbio, Valerio De Stefano, Alessandro Rambaldi, Ayalew Tefferi & Alessandro M. Vannucchi

Abstract

This viewpoint summarizes findings from analyses of large personal patient databases of myeloproliferative neoplasms (MPNs) to assess the impact of thrombosis on mortality, disease progression, and second cancers (SC). Despite advances, the current incidence of arterial and venous thrombosis remains a challenge. These events appear to signal a more aggressive disease course, as evidenced by their association with myelofibrosis progression and mortality using multistate models and time-dependent multivariable analysis. Inflammatory biomarkers, such as the neutrophil-to-lymphocyte ratio (NLR), are associated with the aggressiveness of polycythemia vera (PV) and essential thrombocythemia (ET), linking thrombosis to SC risk. This suggests a common inflammatory pathway likely influencing cardiovascular disease and cancer incidence. Notably, this is observed more frequently in younger patients, likely due to prolonged exposure to MPN and environmental inflammatory triggers. These data underscore the need for new studies to validate these associations, delineate the sequence of events, and identify therapeutic targets to mitigate thrombotic events and potentially improve overall patient outcomes in MPN.

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FREEDOM2 Trial Shows Fedratinib’s Efficacy and Safety in Myelofibrosis

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By Jordyn Sava
Fact checked by Sabrina Serani

When given as a second-line JAK inhibitor option in patients with myelofibrosis, fedratinib (Inrebic) showed its effectiveness in achieving spleen volume reduction (SVR) while highlighting strategies for managing gastrointestinal adverse effects (AEs) and thiamine deficiency, according to findings from the FREEDOM2 study (NCT03952039).1

The FREEDOM2 study, a multicenter, open-label, randomized controlled trial, involved 316 patients with intermediate-2 or high-risk myelofibrosis who were either relapsed, refractory, or intolerant to ruxolitinib (Jakafi).2 The median follow-up for survival at the data cutoff on December 27, 2022, was 64.5 weeks (IQR, 37.9-104.9). The primary end point was the proportion of patients achieving an SVR of at least 35% (SVR35) at the end of cycle 6.

Results from the study demonstrated a significant difference in SVR35 between the fedratinib and best available therapy (BAT) groups, with 36% of patients in the fedratinib group achieving the primary end point compared with only 6% in the BAT group (30% difference; 95% CI 20%-39%; 1-sided P <.0001).1

“Findings from FREEDOM2 support fedratinib as a second-line Janus kinase inhibitor option to reduce spleen size after ruxolitinib failure or intolerance in patients with myelofibrosis,” wrote study authors in findings published in The Lancet Hematology.

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Dr Scandura on the SENTRY-2 Trial of Single-Agent Selinexor in JAK Inhibitor–Naive Myelofibrosis

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October 16, 2024

Author(s): Joe Scandura, MD, PhD

Fact checked by: Ryan Scott, Courtney Flaherty

Joseph M. Scandura, MD, PhD, associate attending physician, NewYork-Presbyterian Hospital; associate professor, medicine, Weill Cornell Medical College, Cornell University, discusses the phase 2 SENTRY-2 study (XPORT-MF-044; NCT05980806) evaluating single-agent selinexor (Xpovio) in JAK inhibitor–naive myelofibrosis.

The FDA granted fast track designation to single-agent selinexor for the treatment of patients with primary myelofibrosis, post-essential thrombocythemia myelofibrosis, and post-polycythemia vera myelofibrosis in July 2023. Notably, selinexor will be assessed in combination with ruxolitinib (Jakafi) in the phase 3 portion of the SENTRY trial (NCT04562389) and as a monotherapy in the phase 2 SENTRY-2 study for JAK inhibitor–naive patients.

The primary aim of the SENTRY-2 study is to evaluate the efficacy of selinexor as a standalone treatment for patients with myelofibrosis who have not previously been treated with a JAK inhibitor, Scandura begins. Currently, JAK inhibitors are the only FDA-approved class of drugs for this condition, complicating the ability to test alternative treatments like selinexor independently, he states. However, evidence suggests that selinexor demonstrates activity, prompting the FDA to permit the study’s initiation, Scandura says. In SENTRY-2, patients will start treatment with selinexor, and responses will be measured based on spleen volume reduction and symptom improvement, particularly anemia, he details.

An innovative aspect of the study is its flexibility, Scandura notes. If a patient shows some degree of response but it is not deemed significant, they may have a JAK inhibitor added to their treatment regimen, he explains. This could include ruxolitinib or newer agents such as pacritinib (Vonjoy), which does not suppress platelet counts, making it suitable for patients with low platelets. Momelotinib (Ojjaara), known for its efficacy in improving anemia, will be added if patients are anemic and maintain adequate platelet counts.

The importance of safety and rigorous science is emphasized in clinical trials, especially when evaluating new treatments, Scandura continues. With selinexor already recognized as safe, the focus shifts to optimizing its use in the treatment landscape of myelofibrosis, he says. If selinexor gains FDA approval for myelofibrosis, it could play a significant role in a more nuanced treatment approach, reflecting the complexities of managing this condition amidst financial considerations and the availability of multiple JAK inhibitors, Scandura concludes.

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Persian Gulf War Service Linked to High Rates of Myeloproliferative Neoplasms

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by Mary Anne Dunkin | Sep 15, 2024

WASHINGTON, DC — A study of almost a half-million veterans has found for the first time a link between environmental exposures during military service and the development of myeloproliferative neoplasms (MPNs).

MPNs—including polycythemia vera (PV), essential thrombocythemia (ET) and primary myelofibrosis (PMF)—are a group of rare, heterogeneous and acquired clonal stem-cell disorders, which lead to uncontrolled proliferation of myeloid cells and complications including arterial and venous thrombosis, bleeding, cardiovascular disease and potentially the development of leukemia. The study’s findings could open MPNs to be recognized as presumptive conditions under the Promise to Address Comprehensive Toxics (PACT) Act, suggested Maneesh R. Jain, MD, one of the study’s leaders.

Jain, a hematologist/oncologist at the Washington, DC VAMC, became intrigued with a possible connection between military exposures and MPN when three of his female patients who had served in the Korean War were diagnosed with MPNs. All three believed their disease was related to exposure to Agent Orange (a tactical herbicide used by the U.S. military for the control of vegetation), as were a number of other veterans they communicated with thought an MPN advocacy group.

To better understand a possible connection, Jain and colleagues at Georgetown University and George Washington University, including hematology/oncology fellow Andrew Tiu, MD, turned to the DoD and VA Infrastructure for Clinical Intelligence (DaVINCI). DaVINCI is an electronic network that provides a consolidated view of electronic medical record data for both service members and veterans.

Their retrospective cohort study, published in the American Journal of Hematology, included 65,425 Korean War era veterans, 211,927 Vietnam War era veterans, and 214,007 Persian Gulf War era veterans from Jan. 1, 2006, to Jan. 26, 2023. Veterans with MPN, thrombosis, bleeding, and cardiovascular risk factors were identified through ICD-9 and -10 codes. Illinois was selected as the state of residence, as it best mirrored the demographics of the entire U.S. cohort in terms of age, race, ethnicity and educational attainment according to the American Community Survey from the U.S. Census Bureau.1

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Pacritinib Demonstrates Efficacy, Tolerability in Patients with Myelofibrosis and Thrombocytopenia

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October 16, 2024

Author(s): Alexandra Gerlach, Associate Editor

Pacritinib (Vonjo; CTI BioPharma Corp) demonstrated improved spleen volume reduction (SVR) and was tolerable in patients with myelofibrosis (MF) and thrombocytopenia, according to data published in the European Journal of Hematology. The findings offer deeper insights into the capabilities of Janus kinase (JAK) inhibitors to improve SVR and overall survival (OS), contradicting prior studies advising against use of JAK inhibitors for thrombocytopenia.1

Further studies are needed to identify the long-term safety and efficacy of the therapy.

Image Credit: © AkuAku – stock.adobe.com

Thrombocytopenia, a condition that occurs when blood platelet counts are too low, is a disease-related feature of MF that leads to poorer prognoses impacting both OS and leukemia-free survival. It can be caused by a variety of factors including ineffective hematopoiesis, splenic sequestration, and treatment-related effects. Allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curable treatment for MF but is only available for a minority of patients. However, the development of JAK inhibitors has expanded treatment options for patients with MF and may show promise for treatment of thrombocytopenia.2

Pacritinib is a JAK inhibitor used to treat intermediate or high-risk MF that targets JAK2 and FMS-like tyrosine kinase 3. It was approved by the FDA in 2022 for treatment of both primary and secondary MF in patients with platelet counts < 50 x 109/L. In the phase 3, randomized, controlled PERSIST-2 trial (NCT02055781), pacritinib demonstrated favorable efficacy and tolerability compared with best available therapy (BAT) in patients with MF and thrombocytopenia.3-5

In the study, approximately 300 patients with thrombocytopenia and primary or secondary myelofibrosis were randomized in a 1:1:1 ratio to receive either pacritinib 400 mg once daily, pacritinib 200 mg twice daily, or BAT. The primary end points included SVR of ≥ 35% reduction in spleen volume from baseline to week 24 as measured by MRI or computed tomography, as well as ≥ 50% reduction in the total symptom score from baseline to week 24 on the Myeloproliferative Neoplasm Symptom Assessment Form 2.0.1,5

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Dr Klisovic on a Case Discussion of Momelotinib in Myelofibrosis With Anemia

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October 16, 2024

Author(s): Rebecca Klisovic, MD

Fact checked by: Ashling Wahner, Ryan Scott

Rebecca Klisovic, MD, chief medical information officer, University Hospitals Seidman Cancer Center, discusses 3 case studies about patients with myelofibrosis that were presented during an OncLive® State of the Science Summit™ on hematologic oncology, which she chaired.

The first case that was discussed was on a 71-year-old male patient with newly diagnosed myelofibrosis with splenomegaly, mild anemia, a high symptom burden, and intermediate-2–risk disease, Klisovic begins. The consensus among the panelists was that this patient required treatment due to his spleen size, symptoms, and anemia, she says. Although some oncologists who participated in the discussion considered using ruxolitinib (Jakafi) because of its early survival data, the panel predominantly favored momelotinib (Ojjaara), given this agent’s potential benefit in patients with anemia, she explains.

The second case was on a 62-year-old female patient with myelofibrosis who had already received ruxolitinib and had comorbidities including symptom scoring and a large spleen, according to Klisovic. This patient also had anemia, with a hemoglobin level of 7.2 g/dL, she reports. Therefore, the focus on improving anemia made momelotinib a clear treatment choice in this setting, she adds. Whereas other case presentations prompted treatment debates between the panelists, this case was more clear cut, especially since this patient was refractory to ruxolitinib, Klisovic emphasizes.

The third case was on a 54-year-old female patient with newly diagnosed myelofibrosis that was characterized by both anemia and thrombocytopenia, as well as a platelet count of 34/µL, Klisovic says. This discussion centered around the use of pacritinib vs momelotinib, informed by the patient’s low platelet count, she explains. Some discussants raised concerns about the patient’s eligibility for momelotinib clinical trials, which have enrollment criteria with varying platelet cutoffs, she notes. Despite these concerns, most participants favored the use of pacritinib (Vonjo) due to this agent’s efficacy in managing thrombocytopenia, she reports. However, some discussants noted that momelotinib could also be a viable treatment option for patients similar to the one in this case, depending on clinical trial criteria and individual patient factors, she concludes.

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