Tag Archives: mf

Fedratinib for the treatment of myelofibrosis: a critical appraisal of clinical trial and “real-world” data

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January 14, 2025

Adrian Duek, Ilona Leviatan, Osnat Jarchowsky Dolberg & Martin H. Ellis

Abstract

Fedratinib is a predominantly JAK2 inhibitor that has shown efficacy in untreated and ruxolitinib-exposed patients with myelofibrosis (MF). Based on randomized clinical trial data, it is approved for use in patients with International Prognostic Scoring System (IPSS) or Dynamic International Prognostic Scoring System (DIPSS) intermediate-2 or high-risk disease and is distinguished from ruxolitinib in that it can be administered without dose reduction in patients with thrombocytopenia, to a platelet count above 50,000/µL. In these trials, fedratinib achieved significant spleen volume reduction in ~30–45% of patients and improvement in total symptom scores in 35–40% with good tolerability. In contrast, recently published real-world data suggest that these responses may not be as robust outside clinical trials. In the context of routine clinical practice spleen responses are documented in only 13–68%, with varying degrees of symptom improvement. This may be due to the lack of a uniform definition of ruxolitinib failure, which may influence the timing of initiating fedratinib as a second-line treatment and result in a more prolonged exposure to ruxolitinib prior to intitaing fedratinib treatment. We suggest that given the growing number of drugs available for use in MF, recognizing the failure of first-line (and potentially subsequent) treatments is critical to allow timely transition to potentially more active agents, as highlighted by the data pertaining to fedratinib.

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Arterial and Venous Thrombosis May Be Linked to More Aggressive MF

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Özge Özkaya, MSc, PhD
Publish Date

The impact of thrombosis on myelofibrosis (MF), mortality, and formation of solid tumors in myeloproliferative neoplasms (MPN) has been discussed in a new review article published in the Blood Cancer Journal.

For the review, the authors, led by Alessandro M. Vannucchi, MD, from Università di Firenze in Florence, Italy, analyzed large personal patient databases of MPN.

Arterial and venous thrombosis seem to be associated with a more aggressive disease course, they said.

Moreover, biomarkers of inflammation like the neutrophil-to-lymphocyte ratio seem to be associated with the aggressiveness of polycythemia vera and essential thrombocythemia, linking thrombosis to the risk of secondary cancer, the researchers added.

They suggested that this means there may be a common inflammatory pathway shared between cardiovascular diseases and cancer.

“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 [myeloproliferative neoplasms],” they concluded.

They highlighted the limitations of the viewpoint, including the fact that most of the studies that they reviewed were retrospective and the lack of investigations on the effect of cytoreductive therapy and associated comorbidities.

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Bromodomain and BET Inhibitor INCB057643 Shows Benefit for Patients With Myelofibrosis

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12/19/24

Emily Estrada

According to research presented by Justin Watts, MD, Sylvester Cancer Center Institute, University of Miami, Miami, Florida at the 2024 American Society of Hematology (ASH) Annual Meeting & Exposition in San Diego, California, INCB057643 may improve patient outcomes in the treatment of hematologic malignancies, including myelofibrosis (MF).

A small-molecular bromodomain and extra-terminal BET protein inhibitor, INCB057643, has shown safety and tolerability as monotherapy and combination with Janus kinase (JAK) 1 and 2 inhibitors among patients with MF in previous phases of the ongoing phase 1/2 clinical trial. In this dose-escalation and expansion portion of the trial, the dose of INCB057643 in patients with MF receiving monotherapy was increased from 4mg to 12mg and for patients with MF who had an inadequate response to ruxolitinib, combination therapy dosage was increased from 4mg to total maximum dosage.

The primary end points were safety and tolerability, as well as dose-limiting toxicities of INCB057643 at 24 weeks. The secondary end points included spleen volume reduction greater than 35% from baseline (SVR35), symptom reduction by greater than 50% from baseline via MPN-Symptom Assessment Form (TSS50), and anemia response of a hemoglobin increase at least 1.5 g/dL from baseline in patients that were not receiving transfusions or transfusion-free for at least 12 weeks for patients dependent on transfusions at baseline.

Patients with relapsed/refractory MF (84.1%%), essential thrombocythemia ([ET]; 4.5%), myelodysplastic syndromes (MDS), or myeloproliferative neoplasm (MPN) syndromes (11.4%). were included in the study. In total, 18 patients were treated with a monotherapy dose escalation and 10 patients received dose expansion. Combination therapy dose escalation was received by 16 patients whose median age was 71 years and whose median ruxolitinib dose was 22.4mg per day. The median duration of INCB057643 exposure was 195.5 days for patients in the monotherapy dose-escalation cohort and 139.0 days for patients in the dose-expansion cohort. As for patients who were in the combination therapy dose-escalation cohort, median INCB057643 exposure was 194.0  days.

At 24 weeks, 3 out of 16 patients who received monotherapy achieved SVR35 and 5 out of 14 achieved TSS50 with any dose of INCB057643, of which 3 received a dose of at least 10 mg. During any time of treatment, improvements in spleen volume and TSS50 best response were demonstrated by 13/19 and 12/15 patients, respectively. Among patients who received combination therapy of INCB057643 and ruxolitinib, 3 out of 12 patients achieved SVR35 and 6 out of 11 achieved TSS50 at any combo dose. Improvements were seen at any time during treatment for both SVR35 and TSS50 in 13 out of 16 and 10 out of 15 patients, respectively. Of patients not dependent on blood transfusions, an anemia response was demonstrated by 3 patients in both the monotherapy and the combination group. Additionally, of 6 patients who were blood transfusion dependent at BL, 2 achieved transfusion independence.

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Combination of PXS-5505 With Standard Ruxolitinib Therapy Shows Potential Benefit for Patients With Myelofibrosis

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12/16/2024

According to data from an ongoing multicenter, open-label phase 1/2a trial, the addition of the pan-lysyl oxidase inhibitor PXS-5505 to standard Janus kinase (JAK) inhibitor therapy demonstrated safety and potential efficacy for patients with intermediate or high-risk myelofibrosis (MF).

Peter T Tan, MBSS, One Clinical Research Pty Ltd, Nedlands, Australia presented these findings at the 2024 American Society of Hematology (ASH) Annual Meeting & Exposition in San Diego, California.

Previous dose escalation and cohort expansion of PXS-5505 trial phases have established safety and tolerability of a monotherapy dose of 200 mg BID over 24 weeks in patients with MF. Researchers evaluated the safety and efficacy of a 200 mg BID dose of PXS-5505 as an add-on to standard JAK2 inhibitor, ruxolitinib (RUX), therapy among patients with MF.

Enrolled in the study were patients with MF with a Dynamic International Prognostic Scoring System (DIPPS) score of intermediate-2/high risk disease. Before initial PXS-5505 administration, patients had been under current RUX treatment for 12 or more weeks, with a stable dose for at least 8 weeks.  A bone marrow biopsy was completed within 3 months of start date for all patients. Patients received PXS-5505 for 52 weeks or until progressive disease, dose limiting toxicity, or unacceptable toxicity. Dosage of PXS-5505 remained consistent at 200 mg BID, however patients were entitled to change RUX dose or discontinue RUX therapy while continuing to receive PXS-5505.

In this add-on phase of the trial, 15 patients were included, of which 6 had primary MF, 2 had post-ET MF, 7 patients had post-PV MF, 3 patients were considered high risk, and all other patients were Int-2. Among patients, the median duration of RUX treatment was 26 months (range, 3.5-74) and a median of 58 months (range 6.5-120) since time of MF diagnosis. The median myeloproliferative neoplasms symptom asssessment form total symptom score (PMN-SAF TSS) was 22.5. The median baseline spleen volume was 1353 cm3 (n=14) and medial baseline hemoglobin was 94 g/dL.

Additionally, 11 patients had hemoglobin levels over 100 g/dL at baseline and almost half had platelet levels below 100×109/L, 2 of which were transfusion-dependent at the start of the study. Baseline mutation profiles for 11 patients revealed a JAK2 V617F mutation among 7 patients and 6 patients with more than 1 high risk mutation.

“The results from this trial using a novel combination of PXS-5505 and RUX will add to the existing safety profile of PXS-5505 and provide preliminary indicators of efficacy to help inform future investigations of PXS-5505 in patients with MF,” the researchers concluded.

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OB756 Showcases Favorable Tolerability in JAK Inhibitor–Naive Myelofibrosis

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December 16, 2024

Author(s): Kristi Rosa

The investigative JAK2 inhibitor OB756 was found to be well tolerated and to elicit meaningful clinical activity in the form of rapid and durable spleen reduction in Chinese patients with myelofibrosis who did not have prior exposure to JAK inhibition, according to data from a phase 1/2 study (CTR20201950) presented during the 2024 ASH Annual Meeting.

In the phase 1 portion of the research, no dose-limiting toxicities were reported when the agent was administered at twice daily doses ranging from 8 mg to 32 mg. Investigators ultimately identified 16 mg and 20 mg twice daily as the recommended phase 2 dose (RP2D) according to p-STAT3 inhibited percentage in an Imax model.

Of 66 evaluable patients, 54.5% achieved a spleen volume reduction (SVR) of at least 35% (SVR35) at the end of cycle 6. Moreover, 59.1% of patients achieved SVR35 at the time of the last follow-up; at the end of cycle 12, 50.0% had achieved SVR35. SVR occurred early, with 7 of 28 patients experiencing a reduction of greater than 5 cm from baseline by week 1 of treatment. Additionally, a 50% or higher reduction in total symptom score (TSS50) was achieved by 51.4% of 55 patients at the end of cycle 3, 64.2% of 53 patients at the end of cycle 6, and 87.5% of 8 patients at the end of cycle 20.

“OB756 can be a promising treatment option for patients with myelofibrosis, but we still need to wait for the final data analysis results after all patients complete follow-up,” Yile Zhou, MD, of the Department of Hematology, the First Affiliated Hospital, Zhejiang University School of Medicine, in Hangzhou, China, said in a poster presentation of the data.

In preclinical studies, OB756 was found to hinder cell proliferation and encourage cell apoptosis by acting on the JAK/STAT-signaling pathway. The open-label, multicenter, phase 1/2 study enrolled patients with primary myelofibrosis, post–polycythemia vera (post-PV) myelofibrosis, and post–essential thrombocytopenia (post-ET) myelofibrosis who were at least 18 years of age and whose disease was intermediate-1/2 or higher per the International Prognostic Scoring System (IPSS).

The trial utilized a 3+3 design for the dose-escalation portion of the research. OB756 was to be evaluated twice daily at the following 6 dosage levels: 8 mg, 16 mg, 24 mg, 32 mg, 40 mg, and 48 mg. The number of patients enrolled per dose level in phase 1 were as follows: 1 patient in the 8-mg group, 3 in the 16-mg group, 4 in the 24-mg group, and 1 in the 32-mg group.

The primary end point of phase 1 was to identify the maximum tolerated dose and the RP2D of OB756. For the second phase, investigators set out to determine the proportion of patients who achieved SVR35 from baseline at week 24. The key secondary end points in phase 2 included TSS50 from baseline at week 24, platelet and anemia improvements, and safety.

A total of 296 patients with myelofibrosis were assessed for eligibility between November 3, 2020, and May 16, 2024; 75 patients were enrolled and received the JAK2 inhibitor (phase 1, n = 9; phase 2, n = 66). The median age of patients included in the phase 2 portion of the research was 58 years (range, 55-69), and more than half were male (57.6%). Most patients had primary myelofibrosis (71.2%), and the remaining patients had post-PV disease (21.2%) or post-ET disease (7.6%). Regarding IPSS, 28.8% of patients had intermediate-1 disease, 39.4% had intermediate-2 disease, and 31.8% had high-risk disease. The median spleen volume was 1780.2 mL (range, 1132.5-2728.7). Moreover, 6.1% of patients had a history of red blood cell transfusion. Patients had EOG status of 0 (24.2%), 1 (68.7%), or 2 (6.1%). Most patients had JAK2 mutation (87.1%); other participants had CARL (12.1%) or MPL (1.6%) mutations. The mean MPN System Assessment Form TSS was 13.5 (range, 0-71). The mean number of days from diagnosis to enrollment was 298.5 (range, 4-4020).

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JAB-8263 Monotherapy Demonstrates Early Promise in Myelofibrosis

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December 13, 2024

Author(s): Kristi Rosa

The investigative BET inhibitor JAB-8263 was found to be well tolerated and to demonstrate preliminary efficacy in patients with myelofibrosis, according to data from a phase 1/2 study (NCT04686682) presented during the 2024 ASH Annual Meeting.1

Any treatment-emergent adverse effects (TEAEs) occurred in 93.8% of those who received the agent at any dose level (n = 16), with 37.5% experiencing grade 3 or higher TEAEs and 25.0% experiencing a serious TEAEs. Treatment-related AEs (TRAEs) occurred in 87.5% of patients, with 31.3% experiencing grade 3 or higher TRAEs, and 18.8% experiencing serious TRAEs. TRAEs led to dose interruption and reduction for 43.8% and 25.0% of patients, respectively. One patient experienced a TRAE that led to discontinuation of JAB-8263. No treatment-related events proved to be fatal.

Notably, 1 dose-limiting toxicity occurred in a patient who received the agent at a dose of 0.4 mg; this patient experienced grade 3 increases in alanine and aspartate aminotransferase levels.

In all evaluable patients (n = 13), the mean spleen volume reduction (SVR) was –19.95% (range, –39.4% to 3.6%) at week 24 and –26.16% (range, 56.6% to –11.0%) at best response. Notably, 2 patients achieved an SVR of 35% or higher, and 1 patient experienced an SVR of –34.9%. Moreover, at week 24, 60% of 10 patients had a tumor symptom score reduction of at least 50% (TSS50). Two of 8 patients who had received JAK inhibitors experienced a best response of SVR of –41.2% and 34.9%, respectively. Moreover, 50% of 6 evaluable patients who had received JAK inhibitors achieved TSS50 at week 24.

“JAB-8263 at 0.125 mg [once daily to] 0.3 mg [once daily] was well tolerated…Hematological and gastrointestinal AEs are mild with JAB-8263 continuous dosing [compared with] other BET inhibitors,” Junyuan Qi, MD, of the Institute of Hematology and Blood Disease Hospital, Chinese Academy of Medical Sciences, in Tianjin, China, and coauthors, wrote in the poster of the data. “The preliminary efficacy data in myelofibrosis for JAB-8263 monotherapy is promising. Most patients showed spleen reduction and TSS reduction.”

The early-phase study enrolled patients with confirmed primary myelofibrosis (PMF), post–polycythemia vera myelofibrosis (PV-MF), or post–essential thrombocytopenia myelofibrosis (ET-MF). Patients were at least 18 years of age, had spleen volume of at least 450 cm3, a Dynamic International Prognostic Score (DIPSS) of at least intermediate-1, and an ECOG performance status up to 2.

The median age in the 16 total patients was 62 years (range, 36-69) and 56.3% were female. All patients were Asian. Regarding ECOG performance status, 31.3% had a status of 0, 62.5% had a status of 1, and 6.3% had a status of 2. Regarding disease subtype, 68.8% of patients had PMF, 18.8% had PV-MF, and 12.5% had ET-MF. Half of patients had prior exposure to a JAK inhibitor. Most patients had a JAK2 mutation (93.8%). Regarding DIPSS, 68.8% had intermediate-1 disease and 25.0% had intermediate-2 disease. The median time since initial diagnosis was 13.5 months (range, 0.9-76.6).

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MAIC Points to Improved OS With Momelotinib in Ruxolitinib-Pretreated Myelofibrosis

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December 13, 2024

Author(s): Caroline Seymour, Kyle Doherty

Fact checked by: Courtney Flaherty

Momelotinib (Ojjaara) demonstrated improved overall survival (OS) vs best available therapy (BAT) in patients with ruxolitinib (Jakafi)–pretreated myelofibrosis, according to data from a matching-adjusted indirect comparison (MAIC) analysis that were presented at the 2024 ASH Annual Meeting & Exposition.1

Data from an unmatched analysis demonstrated that the median OS favored patients who received momelotinib (n = 383) compared with those who received BAT (n = 267; HR, 0.373; 95% CI, 0.297-0.469; P < .001). In the base case model (model 1), the median OS also favored momelotinib (n = 89) vs BAT (HR, 0.512; HR, 0.358-0.732; P < .001). In the alternative adjustment model (model 2), the median OS again favored momelotinib (n = 117) vs BAT (HR, 0.484; 95% CI, 0.347-0.675; P < .001).

Additionally, patients in the anemia subgroup who received momelotinib (n = 255) experienced a median OS benefit compared with those treated with BAT (n = 174; HR, 0.384; 95% CI, 0.293-0.504; P < .001). Data from model 1 also showed that patients treated with momelotinib in this subgroup (n = 98) achieved a median OS benefit vs those in the BAT arm (HR, 0.542; 95% CI, 0.387-0.759; P < .001). Findings from model 2 demonstrated a median OS benefit with momelotinib (n = 146) vs BAT (HR, 0.487; 95% CI, 0.360-0.660; P < .001).

“[Although] the trials used in this analysis do no provide long-term outcomes, this MAIC suggests that momelotinib may offer a greater OS benefit than BAT in patients with myelofibrosis previously treated with ruxolitinib, both in the overall cohort and the anemic population,” Francesca Palandri, MD, PhD, lead study author and an adjunct professor in the Department of Medical and Surgical Sciences at the University of Bologna in Italy, said in a poster presentation of the data.

In September 2023, the FDA approved momelotinib for the treatment of adult patients with intermediate or high-risk myelofibrosis, including primary myelofibrosis or secondary myelofibrosis, and anemia.2 The regulatory decision was supported by findings from the phase 3 MOMENTUM (NCT04173494) and SIMPLIFY-1 trials (NCT01969838).

To conduct their analysis, Palandri and colleagues performed a MAIC analysis comparing patients who received momelotinib during MOMENTUM, SIMPLIFY-1, or the phase 3 SIMPLIFY-2 trial (NCT02101268) with 267 patients who received BAT across 26 European hematology centers in the real-world, retrospective RUX-MF study.1 Notably, the overall study included 1055 patients treated with ruxolitinib across 26 European hematology centers from 2013 until death or the data cutoff of February 2, 2024.

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Pacritinib and Momelotinib Display Positive Real-World Impact on Anemia and Transfusion Needs in Myelofibrosis

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December 12, 2024

Author(s): Kyle Doherty

Fact checked by: Caroline Seymour

Although long-term follow-up was limited, treatment with the JAK2 inhibitors pacritinib (Vonjo) and/or momelotinib (Ojjaara) led to favorable effects on anemia and transfusion requirements among patients with myelofibrosis, according to findings from a real-world study presented in a poster during the 2024 ASH Annual Meeting.1

Patients who received momelotinib (n = 32) had a median hemoglobin count of 8.7 g/dL (range, 6.5-1.2) at the start of therapy which increased to 9.0 g/dL after 3 months of treatment (P = .021). The median platelet count at the start of therapy was 141 x 109/L (range 15 x 109-504 x 109) and increased to 116 x 109/L after 3 months (P = .317). Patients required a mean of 1.9 red blood cell (RBC) units/month at the start of therapy and 0.47 units/month after 3 months of treatment (P = .015).

Patients treated with pacritinib (n = 27) had a median hemoglobin count of 8.5 g/dL (range, 6.9-12.9) at the start of treatment and a median count of 9.1 g/dL following 3 months of therapy (P = .402). The median platelet count at the start of therapy was 65 x 109/L(range, 18 x 109-441 x 109) compared with 31 x 109/L after 3 months of treatment (P = .303). Patients required a mean of 2.4 RBC units/month at the start of therapy vs 0.75 RBC units/month after 3 months of therapy (P = .099).

“The goal of this project was to [examine] the patients who have been treated so far at Moffitt Cancer Center with either pacritinib and/or momelotinib to gain a better understanding of the hematologic responses of these therapies, the duration of treatment, and other real-world data regarding these agents after they got their approvals,” Jeremy DiGennaro, MD, said during the presentation. “Patients receiving momelotinib and pacritinib are typically older with extended disease duration, multiple prior lines of therapy, high-risk mutations, and cytopenia. Pacritinib-treated patients have more prominent baseline thrombocytopenia. [However], there were favorable impacts on anemia and transfusion requirements [with both agents], although we still do need more long-term follow-up.”

DiGennaro is an internal medicine resident physician at the University of South Florida Morsani College of Medicine in Tampa.

In February 2022, the FDA granted accelerated approval to pacritinib for the treatment of adult patients with intermediate or high-risk primary or secondary myelofibrosis with a platelet count below 50,000/µL.2 Momelotinib was approved by the FDA in September 2023 for the treatment of adult patients with intermediate or high-risk myelofibrosis, including primary myelofibrosis or secondary myelofibrosis, and anemia.3

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Optimizing Myelofibrosis Care in the Age of JAK Inhibitors

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December 12, 2024|Hematology and Oncology
Douglas Tremblay, MD

Myelofibrosis is a rare but serious bone marrow disorder that disrupts blood cell production and often leads to debilitating symptoms. In this interview, Douglas Tremblay, MD, Assistant Professor at the Tisch Cancer Institute, discusses the process for selecting the best treatment pathway for patients – from evaluating disease prognosis to navigating treatment resistance and intolerance.

Dr. Douglas Tremblay

How do you assess a patient’s prognosis at the time that they are diagnosed with myelofibrosis?
In the clinic, we use several scoring systems that have been developed based on the outcomes of hundreds of patients with myeloproliferative neoplasms (MPNs) to try to predict survival from time of diagnosis. Disease features associated with a poor prognosis include anemia, elevated white blood cell count, advanced age, constitutional symptoms, and increased peripheral blasts. Some of these scoring systems also incorporate chromosomal abnormalities as well as gene mutations to further refine prognostication.1

Determining prognosis can be important to creating a treatment plan, particularly to decide if curative allogeneic stem cell transplantation is necessary. However, I always caution patients that these prognostic scoring systems cannot tell the future and that each patient may respond differently to treatment.

How do you monitor for disease progression?
I will discuss with patients how they are feeling in order to determine if there are any new or developing symptoms that could be a sign that their disease is progressing. I will also review their laboratory work looking for changes in blood counts that could be a signal of disease evolution.

For instance, development of anemia or thrombocytopenia may signal worsening bone marrow function or progression to secondary acute leukemia. If there are concerning signs or symptoms, I will then perform a bone marrow biopsy with aspirate that will include assessment of mutations and chromosomal abnormalities to determine if their disease is progressing.

What are the first-line treatment options for a patient newly diagnosed with myelofibrosis, and how do you determine the best course of action?
For patients with myelofibrosis, the first-line treatment options include Janus kinase (JAK) inhibitors, which are effective at improving spleen size and reducing symptom burden. The US Food and Drug Administration (FDA) has approved 4 JAK inhibitors for the treatment of myelofibrosis: ruxolitinib, fedratinib, pacritinib, and momelotinib (Table).2-13 In general, ruxolitinib is the first-line treatment option unless there is thrombocytopenia, in which case pacritinib is more appropriate. In patients with baseline anemia, momelotinib may be the best choice.

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Navtemadlin Reduces Markers of Disease Burden in Relapsed/Refractory Myelofibrosis

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December 9, 2024

Author(s): Morgan Bayer

Treatment with navtemadlin (KRT-232) lowered the levels of biomarkers of disease burden in patients with relapsed/refractory myelofibrosis, according to findings from the phase 3 BOREAS trial (NCT03930732) that were presented at the 2024 ASH Annual Meeting.1

“I want to emphasize the biology that drives this approach. MDM2 is a negative regulator of wild-type p53, which is a master determinant of cell fate, and this becomes very critical when you consider its influence over the 4 hallmarks of myelofibrosis: CD34-positive myelofibrosis cell proliferation, myelofibrosis driver gene variant allele frequency (VAF), bone marrow fibrosis, and pro-inflammatory cytokines,” said John O. Mascarenhas, MD, during a presentation of the data.

Mascarenhas is professor of medicine, hematology and medical oncology, director of the Center of Excellence for Blood Cancers and Myeloid Disorders, and director of the Adult Leukemia Program at the Mount Sinai Tisch Cancer Center in New York, New York.

In the randomized, multicenter, global phase 3 BOREAS trial, navtemadlin monotherapy was compared with best available therapy (BAT) that included hydroxyurea, peginterferon, immunomodulatory drugs, or supportive care. Patients included in the trial had TP53 wild-type myelofibrosis and were refractory or had relapsed on prior therapy with a JAK inhibitor. The data cutoff date was September 30, 2024.

In the study, 183 patients were randomly assigned 2:1 to receive navtemadlin (n =1 23) at 240 mg 7 days in a row for a 28-day cycle (with 21 days of drug holiday) or 1 cycle of BAT (n = 60) for 28 days. “The patients who were on a JAK inhibitor at the time had a 28-day washout period so that from a spleen and symptom perspective they were clear on day 1 of navtemadlin dosing,” Mascarenhas explained.

“What we saw in terms of biomarkers was a very significant potent, rapid reduction in circulating CD34 cells as a hallmark of myelofibrosis even within 12 weeks and sustained over 24 and 36 weeks,” Mascarenhas stated. At 12 weeks, CD34-positive cells showed a median reduction of 68% from baseline in 50 patients in the navtemadlin arm and 52% in 25 patients in the BAT arm. This trend continued at 24 weeks (n = 48, 70% reduction vs n = 19, 38% reduction) and at 36 weeks (n = 21, 76% reduction vs n = 9, 33% reduction).

The reduction in driver gene VAF by 50% or greater was observed in 21% (n = 17/82) of patients in the navtemadlin arm and 12% (n = 4/33) of patients in the BAT arm at 24 weeks, “nearly doubling the molecular response at 24 weeks,” Mascarenhas noted.

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