Last reviewed 2026-04-20 · How we verify

Vonjo (PACRITINIB)

Vonjo works by blocking the activity of the JAK2 enzyme, which is overactive in myelofibrosis patients.

Vonjo (Pacritinib) is a small molecule kinase inhibitor developed by Marinus Pharma Inc and currently owned by Sobi. It targets the Tyrosine-protein kinase JAK2, a key enzyme involved in the signaling pathways that regulate blood cell production. Vonjo is FDA-approved for the treatment of myelofibrosis, a type of bone marrow disorder. The drug is patented and not yet available as a generic. Key safety considerations include the potential for gastrointestinal and hematologic adverse effects.

At a glance

Mechanism of action

Pacritinib is an oral kinase inhibitor with activity against wild type Janus associated kinase (JAK2), mutant JAK2V617F, and FMS-like tyrosine kinase (FLT3), which contribute to signaling of number of cytokines and growth factors that are important for hematopoiesis and immune function. MF is often associated with dysregulated JAK2 signaling. Pacritinib has higher inhibitory activity for JAK2 compared to JAK3 and TYK2. At clinically relevant concentrations, pacritinib does not inhibit JAK1. Pacritinib exhibits inhibitory activity against additional cellular kinases (such as CSF1R and IRAK1) the clinical relevance of which is unknown.

Approved indications

• Myelofibrosis

Common side effects

• Diarrhea
• Thrombocytopenia
• Nausea
• Anemia
• Peripheral edema
• Vomiting
• Dizziness
• Pyrexia
• Epistaxis
• Dyspnea
• Pruritus
• Upper respiratory tract infection

Key clinical trials

• Pacritinib, a Kinase Inhibitor of CSF1R, IRAK1, JAK2, and FLT3, in Adults and Pediatric Participants 12 Years of Age or Older With Myelodysplastic Syndromes or Myelodysplastic/Myeloproliferative Neoplasms (PHASE1,PHASE2)
• Phase I/II Study of Pacritinib, A JAK2/IRAK1/CSF1R Inhibitor, in Refractory Chronic Graft-Versus-Host Disease (cGVHD) After Allogeneic Hematopoietic Stem Cell Transplantation (HSCT) (PHASE1,PHASE2)
• Selinexor and Pacritinib in JAK Inhibitor-naïve MF Patients With Cytopenias (PHASE2)
• Pacritinib With Aza for Upfront Myelodysplastic Syndrome (PHASE1,PHASE2)
• Decitabine With Ruxolitinib, Fedratinib or Pacritinib for the Treatment of Accelerated/Blast Phase Myeloproliferative Neoplasms (PHASE2)
• Phase II Study of Pacritinib in Kaposi Sarcoma Herpesvirus (KSHV)-Associated Multicentric Castleman Disease and KSHV-Associated Inflammatory Cytokine Syndrome (KICS) (PHASE2)
• A Study to Assess the Effectiveness and Safety of Pacritinib in Patients With VEXAS Syndrome (PAXIS) (PHASE2)
• Pacritinib vs. Hydroxyurea in Advanced Proliferative Chronic Myelomonocytic Leukemia (PHASE2)

Patents

Primary sources

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