A Phase 2 interventional study of Pacritinib in Myelofibrosis，MF, sponsored by Grupo Español de Enfermedades Mieloproliferativas Crónicas PH Negativas. Recruiting at 13 sites in Spain. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-02.
Sponsored by Grupo Español de Enfermedades Mieloproliferativas Crónicas PH Negativas · Phase 2, Interventional, and Treatment
We hypothesize that pacritinib leads to modification of the myelofibrosis (MF) disease phenotype, especially related to BM fibrosis and cytopenias; due potentially to its dual effect as an inhibitor of the JAK and NFκB pathways, through its targets JAK2 and IRAK1 respectively, leading to a decrease of inflammatory cytokines and/or effects on stem/progenitor populations restoring hematopoiesis New evidence suggests that blocking simultaneously the JAK/STAT and NF-κB pathways might have a beneficial effect on aspects that only inhibition of the JAK pathway cannot achieve: partial recovery of BM histology and
PACRIMYEL is a multicenter, open-label, single arm, phase II, exploratory study including patients with MF and platelet count between 50 - 120 x 109/L. Clinic visits will occur on weeks 4, 8, 12, 24, 36 and 52 during the first year and every 12 weeks during the second year of the treatment, and pacritinib will be dispensed at every visit to the clinic.
Bone fibrosis will be assessed by biopsy and MRI imaging [mDixon Quant "(Philips), IDEAL IQ (General Electric) or qDixon (Siemens)] on weeks 24 and 52 after the first dose of study treatment. Splenomegaly and SVR (Splenic Volume Reduction) will be assessed by physical exam and MRI imaging on weeks 24 and 52 after the first dose of study treatment if splenomegaly at diagnosis. Same MRI to evaluate BM imaging will be used to measure spleen volume. Additionally, spleen size will be assessed by physical exam during the routine clinic visits. All patients should complete all efficacy assessments through Week 52, including patients who stop study treatment or have protocol-defined progressive disease prior to Week 24 and 52, unless the patient withdraws consent or dies. For patients who discontinue treatment before disease assessments on week 24 and week 52 for other reasons different than protocol-based progression of the disease (i.e. toxicity), and with no recent disease / fibrosis assessment (last BM biopsy > 12 weeks), disease and fibrosis assessments will be performed by the end of treatment visit. The trial includes the assessment of safety (AEs, comorbidities) throughout the study period at every visit.
Patient-reported symptoms through MPN-SAF TSS 2.0 will be collected screening, baseline (C1D1), and on Week 12, Week 24, Week 36, Week 52 and in 12-weeks intervals during the second year. Blood samples for translational research will be collected at screening and at week 24 for determination of cytokines.
418 studies on the registry are indexed under Primary Myelofibrosis; 116 are open to participants now.
This study's planned enrollment of 30 is below the median of 44 across 347 interventional studies indexed under Primary Myelofibrosis.
Browse Primary Myelofibrosis studies →This is the only study on the registry with Grupo Español de Enfermedades Mieloproliferativas Crónicas PH Negativas as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Patients who require JAK-2 inhibitor therapy in the opinion of the investigator and are eligible to start treatment with pacritinib either in the first line (JAK2 inhibitor-naive) or in second line setting (after no response or loss of response or intolerance to one prior JAK2 inhibitor ).
Note: patients should have recovered to grade ≤ 1 from any toxicity from previous treatment.
Adequate liver and renal function, defined by:
Exclusion Criteria:
Pacritinib administed 200 mg twice a day (BID)
Drug: Pacritinib
All patients enrolled will receive pacritinib 200 mg twice a day (BID). The maximum daily dose will be 400 mg of pacritinib. Pacritinib dose may be reduced by one level to 100 mg BID (200 mg total daily dose), or by two levels to 100 mg once daily (QD) for management of AEs. The treatment will be continued until progressive disease, unacceptable toxic effects, the patient no longer derives benefit from treatment, patients consent withdrawal or death, whichever occurs first.
Decrease in reticulin fibrosis in bone marrow (BM)
Measured in BM biopsy. Percentage of patients who experience a decrease of ≥1 grade in reticulin fibrosis from baseline to week 52. Definition of BM fibrosis grade will follow the European consensus that ranges from 0 (scattered, less fibrotic) to 3 (difuse and dense reticulin, more fibrotic). Patients will be classified as improvement (fibrosis decrease ≥1 grade), no change, or worsening (fibrosis increase \> 1 grade).
Time frame: from baseline to week 52 after first dose of study treatment
Improvement in BM fat fraction (FF)
measured by quantitative quantitative Dixon Quant MRI or equivalent. Changes in the bone marrow associated with MF, such as replacement of the bone marrow fat by fibrosis or elevated numbers of hematopoietic cells, reduce the abundance of fat. Here we will report the percentage of patient who had an improvement in the FF (increase from baseline at week 52).
Time frame: from baseline to week 52 after first dose of study treatment
red blood cell (RBC) transfusion independence
Percentage of patients who achieved no need of RBC transfusions during at least 12 week. RBC transfusion independence will be reported in subgroup of patients with the changes in the Bone Marrow (by MRI and/or BM biopsy) over the first 24 and 52 weeks of treatment.
Time frame: from baseline to week 24 and week 52 after first dose of study treatment
Improvement in hemoglobin level
Percentage of patients who improve their hemoglobin levels without transfusion. Improvement was defined as a ≥ 1.5 g/dL increase in hemoglobin from baseline. Changes in hemoglobin level without transfusion will be reported in subgroup of patients with the changes in the Bone Marrow (by MRI and/or BM biopsy) over the first 24 and 52 weeks of treatment.
Time frame: from baseline to week 24 and week 52 after first dose of study treatment
Improvement in platelet counts
increase of platelet count (without transfusions) in comparison to baseline of above 75 x 109/L (if platelet count was between 50 - 75 109/L at baseline) or above 100 x 109/L (if platelet count was between 75 - 100 x 109/L at baseline). Alternatively, the proportion of patients who increase platelet counts ≥25% above baseline will be measured.
Time frame: from baseline to week 24 and week 52 after first dose of study treatment
Myeloproliferative neoplasms (MPN) driver-gen Variant Allele Frequency (VAF)
JAK2, CALR, and MPL genes are drivers of myelofibrosis. Their VAF could be quantified in peripheral blood or bone marrow and its circulating levels are usually correlated with the course of the disease. We aim to find the percentage of patients who reduced their VAF at week 24 and 52.
Time frame: Baseline and at Week 24 and Week 52 after the first dose of study treatment
Cummulative dose
the sum of all doses of pacritinib taken from the start of study treatment, taken into consideration interruptions and reductions.
Time frame: Throughout the study period, up to approximately 2 years
Actual dose of pacritinib
defined as the real average daily dose administered. For its calculation, the cumulative dose will be divided by the duration of the treatment, considering also the interruption periods.
Time frame: Throughout the study period, up to approximately 2 years
Relative dose intensity of pacritinib
Defined as the percentage of the planned dose that has been actually administered. Calculated dividing actual dose by planned dose per day.
Time frame: Throughout the study period, up to approximately 2 years
Frequency of treatment-related adverse events
number of patients who experience a treatment-related adverse event. Events will be classified and graded according to National Cancer Institute (NCI) Common Terminology Criteria (CTCAE) version 5.0
Time frame: Throughout the study period, up to approximately 2 years
Plan to share: No
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From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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