Pacritinib vs. Hydroxyurea in Advanced Proliferative Chronic Myelomonocytic Leukemia

Inclusion Criteria

• Diagnosis of CMML-1 (5th WHO classification), with <10% bone marrow blasts on morphology and <5% peripheral blood blasts.
• Proliferative disease, defined as white blood cell count ≥13 × 10⁹/L.
• Advanced disease, defined as at least one of the following features during screening: spleen palpable ≥5cm below the lower costal margin in the midclavicular line; TSS ≥20; or platelet count <100 × 10⁹/L. For participants in whom spleen palpation is not feasible, an ultrasound exam may be performed for assessment of spleen craniocaudal length (length ≥12 cm by ultrasound is considered splenomegaly).
• ECOG performance status ≤2.
• Adequate organ function: AST and ALT ≤3 × ULN, total bilirubin ≤4 × ULN (≤8 × ULN in participants with Gilbert's syndrome), creatinine clearance >30 mL/min, absolute neutrophil count ≥0.5 × 10⁹/L, PT and PTT ≤1.5 × ULN.
• Women of child-bearing potential must have a negative serum pregnancy test within 7 days prior to enrollment and, along with male participants, must agree to use a highly effective method of contraception from the first dose through 90 days after the last dose.

Exclusion Criteria

• Active malignancy diagnosed within the past 2 years, except for curatively treated non-invasive cancers (e.g., basal/squamous cell skin cancer, low-risk prostate cancer on stable endocrine therapy with PSA stable ≥3 months).
• Allogeneic hematopoietic stem cell transplant within 12 months prior to enrollment, or requiring immunosuppressive therapy within 6 months before enrollment.
• Likely to undergo allogeneic hematopoietic stem cell transplant within 6 months, per investigator assessment.
• Prior systemic treatment with any JAK inhibitor.
• Treatment with hypomethylating agents or cytotoxic chemotherapy (excluding hydroxyurea) within 28 days prior to enrollment.
• Participation in another interventional study or use of experimental therapy within 28 days or 5 half-lives, whichever is longer.
• Use of hematologic support drugs within 28 days prior to enrollment. Supportive care permitted.
• Use of strong CYP3A4 inhibitors or inducers within 14 days or 5 half-lives before enrollment, whichever is shorter.
• Use of systemic anticoagulants or antiplatelets (except aspirin ≤100 mg/day) within 14 days prior. Therapeutic anticoagulation allowed if stable for ≥90 days without bleeding events.
• CTCAE Grade ≥2 bleeding within 3 months prior to enrollment, unless due to a reversible cause (e.g., trauma, surgery).
• QTcF >450 ms (men) or >470 ms (women); QTcF up to 480 ms allowed if QRS >100 ms. QTcF may be repeated if affected by reversible factors.
• CTCAE Grade ≥3 cardiac event within 3 months before enrollment.
• Symptomatic heart failure with limitations on ordinary activity.
• Uncontrolled infection at study entry.
• Moderate/severe hepatic impairment (Child-Pugh B or C), or active viral hepatitis:
• HBV: Exclude if HBsAg+ or HBV DNA detectable. HBV antiviral therapy allowed if HBV DNA undetectable.
• HCV: Allowed if HCV Ab+ but RNA negative.
• Uncontrolled HIV or detectable viral load while on antiretrovirals.
• Known hypersensitivity to pacritinib or its excipients (microcrystalline cellulose, polyethylene glycol, magnesium stearate).