Pelabresib Plus Ruxolitinib Improves Spleen Responses in Myelofibrosis

By Roman Fabbricatore
Fact checked by Russ Conroy

Pelabresib (CPI 0610) in combination with ruxolitinib (Jakafi) significantly improved spleen responses and elicited robust clinical activity compared with placebo/ruxolitinib in patients with JAK inhibitor-naïve myelofibrosis, according to results from the phase 3 MANIFEST-2 trial (NCT04603495) published in Nature Medicine.1

Efficacy data from the trial revealed that the primary end point of spleen volume reduction of at least 35% at week 24 favored the investigational combination vs the placebo arm: 65.9% vs 35.2%, respectively (difference, 30.4%; 95% CI, 21.6%-39.3%; P <.001). Additionally, the mean percent change at week 24 in the respective arms was –50.6% (95% CI, –53.2% to –48.0%) vs –30.6% (95% CI, –33.7% to –27.5%). Spleen volume response was consistently higher with pelabresib vs placebo across predefined subgroups.

Furthermore, the hemoglobin response rate, defined as a 1.5 g/dl or greater mean increase, occurred in in 10.7% of the pelabresib arm (95% CI, 6.60%-14.90%) vs 6.0% of the placebo arm (95% CI, 2.85%-9.19%). Transfusions were received in the first 24 weeks of treatment in 27.6% and 37.5% of respective arms.

Greater reductions in NF-κB-regulated cytokines (–32.1% [95% CI, –34.9% to –29.2%] vs –19.4% [95% CI, –22.5% to –16.2%]), tumor necrosis factor (TNF; –43.5% [95% CI, –47.0% to –39.8%] vs –26.4% [95% CI, –30.5% to –22.1%]), and interleukin-6 (IL-6; –35.4% [95% CI, –44.2% to –25.2%] vs –14.5% [95% CI, –25.2% to –2.3%]) were seen in the investigational arm vs the placebo arm. Of note, a reduction in IL-8 levels was observed with pelabresib (–14.3% [95% CI, –22.3% to –5.5%]), but an increase was observed in the placebo arm (31.2% [95% CI, 17.5%-46.5%).

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Dr Rampal on ​Emerging Therapies Under Investigation in Myelofibrosis

March 17, 2025

Author(s): Raajit K. Rampal, MD, PhD

Fact checked by: Ashling Wahner ,Chris Ryan

Raajit Rampal, MD, director of the Center for Hematologic Malignancies and director of the Myeloproliferative Neoplasms Program at Memorial Sloan Kettering Cancer Center, discusses emerging treatments for patients with myelofibrosis.

The therapeutic paradigm for myelofibrosis continues to expand with emerging treatment options, particularly with combination therapies, novel JAK inhibitors, and immunotherapeutic agents, Rampal begins. Among these, pelabresib (CPI-0610), a BET inhibitor, has completed phase 3 trials. Preliminary data from the phase 3 MANIFEST-2 trial (NCT04603495), which were presented in December 2023, demonstrated improved spleen responses and a trend toward better symptom management with the combination of pelabresib and ruxolitinib (Jakafi) vs placebo plus ruxolitinib in patients with JAK inhibitor–naive myelofibrosis. Updated findings from MANIFEST-2 were published in Nature Medicine in March 2025.

Beyond pelabresib, several other agents are currently in phase 3 trials for patients with myelofibrosis, Rampal says. Selinexor (Xpovio), which is currently FDA approved for the treatment of patients with relapsed/refractory multiple myeloma, is being studied in combination with ruxolitinib in patients with myelofibrosis in the phase 3 XPORT-MF-034 trial (NCT04562389). Additionally, navtemadlin (KRT-232), an MDM2 inhibitor, is undergoing clinical evaluation in patients with myelofibrosis. Notably, these trials are ongoing, and no conclusive data are available at this time, Rampal emphasizes.

The development of next-generation JAK inhibitors also represents a promising area of investigation, according to Rampal. These newer inhibitors are anticipated to demonstrate greater potency and selectivity compared with existing agents, though they remain in early-phase clinical trials, he notes.

Rampal states that one of the most exciting advancements in this setting is the emergence of immunotherapies. Calreticulin-targeted antibodies are currently being evaluated in clinical trials, and 2 candidates are in development, he reports. If these agents prove effective, they could significantly alter the treatment paradigm, he concludes.

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Jakafi May Not Associate with Long-Term Benefits in Myelofibrosis Subset

March 16, 2025

Author(s): Spencer Feldman

Fact checked by: Alex Biese

Among patients with calreticulin (CALR)-mutated myelofibrosis, real-world data reveal insights into those with splenomegaly and/or symptoms requiring therapy with Janus kinase 2 (JAK2) inhibitors.

The findings suggest that while Jakafi (ruxolitinib) shows some initial benefits, CALR-mutated patients may require more targeted and innovative therapeutic approaches for better long-term outcomes, according to study findings published in Annals of Hematology.

“Overall, despite the initial benefits of [Jakafi], CALR-mutated patients may require more innovative therapeutic interventions to achieve optimal outcomes. This further emphasizes the necessity of exploring alternative or adjunctive therapies tailored specifically for CALR-mutated individuals,” lead study author Dr. Francesca Palandri and colleagues wrote in the study.

Palandri is currently an adjunct professor primarily based in the Department of Experimental, Diagnostic and Specialty Medicine at the Università di Bologna, Bologna, Italy. She is also a junior researcher at Azienda Ospedaliero-Universitaria di Bologna, Institute of Hematology, Bologna, Italy.

Patients with CALR mutations began Jakafi with more severe disease, including higher peripheral blast counts, lower hemoglobin levels and worse marrow fibrosis, and after a longer median time from diagnosis (2.6 versus 0.7 years) compared to patients with JAK2 mutations. At six months, spleen responses were numerically lower in CALR-mutated patients, who also had lower rates of symptom responses (56.1% versus 66.7%, respectively). However, CALR-mutated patients experienced lower rates of high white blood cell counts.

Furthermore, in patients with delayed Jakafi initiation, anemia and reduced starting doses correlated with poorer survival. Managing anemia through interventions like danazol, erythropoiesis-stimulating agents, iron chelation and optimized Jakafi dosing may improve outcomes, according to study authors. The study also highlights the potential benefits of alternative JAK2 inhibitors with lower hematological toxicity.

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Optimizing Treatment in Patients With Myelofibrosis and Transfusion-Dependent Anemia

By Clinical Content Hub

In patients with MF, greater anemia severity and transfusion dependency have been linked to worse overall survival and quality of life (QOL). Historically, the only available treatment strategies for MF-related anemia have shown limited efficacy and an increased risk for numerous adverse effects.1,2

In September 2023, the US Food and Drug Administration (FDA) approved momelotinib, an oral inhibitor of JAK1 and JAK2 as well as activin A receptor type 1 (ACVR1), for the treatment of adults with anemia and intermediate or high-risk MF. Momelotinib is currently the only FDA-approved therapy indicated for the treatment of MF patients with anemia.3 In clinical trials, this first-in-class treatment has shown efficacy in treating anemia and other key manifestations of MF.4

Douglas Tremblay, MD, is an assistant professor of medicine at the Icahn School of Medicine at Mount Sinai in New York City, New York, specializing in hematologic malignancies such as myelodysplastic/myeloproliferative overlap syndromes, myeloproliferative neoplasms, and acute myeloid leukemia. He serves as the principal investigator on multiple clinical trials focused on myeloid neoplasms. In this article, Dr Tremblay discusses treatment strategies for MF patients, with a particular focus on those with transfusion-dependent anemia, as well as emerging developments in the MF treatment landscape.

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Promising New Treatment for Myelofibrosis Blood Cancer Using a Combination Targeted Therapy 

By 

An international phase 3 clinical trial of a new drug combination for treating the blood cancer myelofibrosis found that adding a second, experimental drug to standard treatment was more effective than the standard treatment alone. Further, adding the second drug did not significantly increase side effects. Memorial Sloan Kettering Cancer Center (MSK) enrolled the most patients in the trial.

“This is one of the largest myelofibrosis clinical trials to date,” says MSK leukemia specialist Raajit Rampal, MD, PhD, lead author of the study, published March 10 in Nature Medicine. “There is a real unmet need for patients with this disease, and the findings from this trial represent an exciting advance.”

This study looked at adding an experimental drug called pelebresib to the drug ruxolitinib (Jakafi®), which is the current treatment for myelofibrosis. Both drugs are targeted therapies. Pelebrisib blocks the action of proteins involved in inflammation and cancer; ruxolitinib blocks a protein called JAK. This combination approach was based on ongoing research from the lab of MSK leukemia specialist and physician-scientist Ross Levine, MD.

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New MF Study Recruiting Participants for Its Phase 3 Portion

A phase 1/3 clinical trial testing the safety and efficacy of selinexor plus ruxolitinib in patients with myelofibrosis (MF) who are Janus kinase (JAK) inhibitor-naïve is now recruiting participants for its phase 3 portion.

The global, multicenter, 2-part study aims to recruit an estimated 350 participants with MF. Participants were all at least 18 years of age.

The study consists of an experimental phase 1a, experimental phase 1b, and experimental phase 3 portion.

In the experimental phase 1a portion, 1 group of patients were given 40 mg of oral selinexor once a week on days 1, 8, 15, and 22 of each 28-day cycle together with 15 or 20 mg of ruxolitinib twice a day based on their platelet count at baseline while another group was given 60 mg of oral selinexor on the same days and the same dose of ruxolitinib as the first group.

In the experimental phase 1b, patients were given either 40 or 60 mg of oral selinexor once a week on days 1, 8, 15, and 22 of each 28-day cycle and the same dose of ruxolitinib.

In the experimental phase 3 portion, patients will either be given a fixed starting dose of 60 mg of oral selinexor or a placebo once a week on days 1, 8, 15, and 22 of each 28-day cycle together with the same dose of ruxolitinib.

The primary outcome measures of the phase 1 portion of the trial was the maximum tolerated dose and recommended phase 2 dose of selinexor and the number of participants with adverse events by severity, nature, and occurrence.

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Patients With MF May Benefit From Interdisciplinary Care and Personalized Treatment

A new position paper combining insights from a panel discussion of German experts about the diagnosis and treatment of patients with myelofibrosis (MF) was published in the scientific journal Annals of Hematology. The paper highlights the need for an interdisciplinary approach, adherence to updated World Health Organization (WHO) and the International Consensus Classification (ICC) diagnostic criteria, and personalized treatment approaches for each patient.

The team of authors led by Florian H. Heidel, MD, from the Department of Hematology, Hemostasis, Oncology and Stem Cell Transplantation at Hannover Medical School in Hannover, Germany said that by addressing diagnostic challenges and therapeutic nuances, the paper aims to improve outcomes and quality of life for patients in the prefibrotic phase of primary MF.

The panel discussions were grouped under 3 main areas which were:

  • The definition and diagnosis of prefibrotic primary MF, its clinical characteristics, and how they separate from other subentities of myeloproliferative neoplasms.
  • Whether essential thrombocythemia and prefibrotic primary MF are distinguishable entities or part of a continuous spectrum.
  • The therapeutic options and how Janus kinase (JAK)-inhibitor therapy ranks among therapies of prefibrotic primary MF.

The relevant aspects of the panel discussion for each area were then outlined in detail.

It was concluded that profibrotic primary MF has unique morphological, clinical, and molecular characteristics that distinguish it from essential thrombocythemia and overt primary MF and that the diagnostic process relies on the histological analysis of the bone marrow, the identification of genetic mutations, and the exclusion of other myeloid neoplasms.

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Ruxolitinib Plus SOC Prophylaxis Is Associated With Lower Rates of GVHD in Myelofibrosis

February 14, 2025

Author(s): Dylann Cohn-Emery

Fact checked by: Jonah Feldman

Treatment with the combination of ruxolitinib (Jakafi) and standard-of-care graft-vs-host disease (GVHD) prophylaxis led to a reduction in the rates of acute and chronic GVHD without compromising survival rates in patients with myelofibrosis undergoing hematopoietic stem cell transplantation (HCT), according to data from a phase 2 prospective study (NCT04384692) presented at the 2025 Transplantation and Cellular Therapy Meetings.1

The study conducted at Fred Hutchinson Cancer Center showed grade II to IV acute GVHD occurred in 32% of patients receiving peri-transplant ruxolitinib, whereas it occurred in 71% in a pre-transplant ruxolitinib group of a similar preliminary study. The percentage of patients with chronic GVHD at 1 year with peri-transplant ruxolitinib 12%, whereas it was 25% with pre-transplant ruxolitinib. These rates of GVHD also coincided with high overall survival (OS) rates at year 1 and 2 of 100% and 87%, respectively, in the peri-transplant ruxolitinib trial.

“The incidence of acute and chronic GVHD was markedly reduced without the expense of non-relapse mortality, relapse, or survival. It doesn’t appear that infections or transfusion needs were increased,” Rachel B. Salit, MD, associate professor at Fred Hutchinson Cancer Center, said in her presentation.

Janus kinase (JAK) inhibitors prevent activation of the JAK domain by binding to the kinase, in turn preventing STAT phosphorylation and translocation of the nucleus. This process reduces the production of pro-inflammatory cytokines. GVHD pathogenesis has shown to be affected by the JAK-STAT pathway, and JAK signaling is key in the process leading to tissue damage and inflammation.

In previous trials of ruxolitinib, such as COMFORT-I (NCT00952289) and COMFORT-II (NCT00934544), this JAK inhibition showed significantly better results in reducing symptoms and splenomegaly compared with best available therapy in patients with myelofibrosis. Additionally, the REACH1 (NCT02953678), REACH2 (NCT02913261), and REACH3 (NCT03112603) trials demonstrated significantly improved response with ruxolitinib vs best available therapy when treating patients with acute and chronic GVHD.

The preliminary study (NCT02251821) of ruxolitinib pre-transplant showed improved survival in this patient population. With a median time of 7 months on ruxolitinib, 38% of patients had more than a 10% decrease in spleen size and 36% were stable. In patients with symptoms prior to ruxolitinib, 55% had stable or improved symptoms by the time of HCT.

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Patients With Cytopenic Primary Myelofibrosis Face Unique Therapeutic Challenges, Poor Prognosis

February 12, 2025

Author(s): Luke Halpern, Assistant Editor

Patients with primary myelofibrosis (PMF) harboring the cytopenic phenotype called cytopenic (CyP) PMF face greater unmet needs and worsened prognosis compared with other myeloproliferative neoplasms (MPNs), including polycythemia vera (PV) and essential thrombocytopenia (ET), according to an analysis of data from the European multicenter collaborative ERNEST registry.1

Myelofibrosis that advances to blast phase worsens outcomes for patients affected. | Image Credit: © tonaquatic – stock.adobe.com

Disease behavior of MF can vary widely based on clinical phenotype. Two distinct subgroups comprise MF: proliferative MF and cytopenic MF, which is also called myelodepletive MF. For patients with cytopenic MF, disease presentation can encompass lower blood counts—specifically thrombocytopenia and anemia—additional somatic mutations, and a worse prognosis compared with proliferative MF.2

Additionally, approved Janus kinase (JAK) inhibitors that can improve constitutional symptoms of MF carry risks of worsening anemia and thrombocytopenia in CyP MF, making treatment uniquely challenging for patients. Severe anemia is known to further worsen patient prognosis, and measures to relieve disease burden, such as transfusions, can lead to disease progression into blast phase (BP) MF. Given the poor outcomes MF patients with CyP face, describing the clinical characteristics and outcomes of this population is critical.1,3

The current investigators analyzed data gathered from the European multicenter collaborative ERNEST registry, with a focus on the clinical outcomes and characteristics of MF patients with CyP. In total, 559 patients comprised the study population; a CyP was defined by the presence of at least 1 cytopenia at diagnosis, including sex-adjusted anemia, thrombocytopenia, or leukopenia. Patients who showed none of these characteristics were considered MyP.1

Median follow-up was 5.4 years. A CyP was identified in 275 patients (49.2%); these patients were more likely to be older, less frequently JAK2V617F-mutated, and included in higher risk categories. In total, 392 patients (70.1%) died, including 59.9% of MyP patients and 80.7% of CyP patients, and the incidence rate of death among patients with both anemia and thrombocytopenia was the highest among the subgroups analyzed.1

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Allogeneic Hematopoietic Stem Cell Transplantation May Resolve Osteosclerosis in MF

Allogeneic hematopoietic stem cell transplantation leads to extensive skeletal homeostasis reconstruction and subsequent resolution of osteosclerosis in patients with myelofibrosis (MF), according to a new study published in the peer-reviewed journal Nature Communications.

For the study, a team of German researchers outlined the skeletal characteristics of patients with MF before and after allogeneic hematopoietic stem cell transplantation using clinical high-resolution imaging, laboratory analyses, and bone marrow biopsy studies.

The team reported that even though the bone microarchitecture was not impaired at peripheral skeletal sites, there was a marked increase in bone mineral density at the lumbar spine and proximal femur.

This, the researchers said, is histologically related to severe bone marrow fibrosis and osteosclerosis.

Following allogeneic hematopoietic stem cell transplantation, the bone marrow fibrosis was fully normalized.

The team also reported that the regression of fibrosis was accompanied by vanishing osteosclerosis together with restored osteoclastic resorption activity and whole-body calcium homeostasis.

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