Vonjo Approved for Myelofibrosis With Severe Thrombocytopenia

The approval was based on data from the randomized, controlled, phase 3 PERSIST-2 trial.

The Food and Drug Administration (FDA) has granted accelerated approval to Vonjo (pacritinib) for the treatment of adults with intermediate or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis with a platelet count below 50×109/L.

Vonjo is an oral kinase inhibitor with activity against wild type Janus associated kinase 2 (JAK2), mutant JAK2V617F, and FMS-like tyrosine kinase 3. Myelofibrosis is often associated with dysregulated JAK2 signaling.

The approval was based on data from the randomized, controlled, phase 3 PERSIST-2 trial (ClinicalTrials.gov Identifier: NCT02055781), which evaluated the efficacy and safety of pacritinib in adults with thrombocytopenia and primary or secondary myelofibrosis. Patients were randomly assigned to receive 1:1:1 to receive pacritinib 400mg orally once daily (n=104), 200mg twice daily (n=107), or best available therapy (BAT; n=100). 

Among 31 evaluable patients who received pacritinib 200mg twice daily and had a platelet count less than 50×109/L, findings showed that 29% (95% CI, 14.2-48.0) of patients achieved a reduction in spleen volume of at least 35% at week 24 (as measured by magnetic resonance imaging or computed tomography) vs 3.1% (95% CI, 0.1-16.2) of those treated with BAT (most common agents included ruxolitinib, watchful waiting, and hydroxyurea).

The median reduction in spleen volume for patients with a platelet count less than 50×109/L was 27.3% for patients treated with pacritinib 200mg twice daily compared with 0.9% for those treated with BAT.

The most common adverse reactions reported with pacritinib were diarrhea, thrombocytopenia, nausea, anemia, and peripheral edema. The benefits and risks of treatment should be discussed with patients as another JAK inhibitor was shown to increase the risk for major adverse cardiac events, thrombosis, secondary malignancies, and serious infections.

Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory clinical trial. To fulfill the post-approval requirement, the Company expects to complete its confirmatory PACIFICA trial (ClinicalTrials.gov Identifier: NCT03165734), with results expected by mid-2025.

Vonjo is supplied as 100mg capsules of pacritinib in 120-count bottles.


  1. CTI BioPharma announces FDA accelerated approval of Vonjo (pacritinib) for the treatment of adult patients with myelofibrosis and thrombocytopenia. News release. CTI BioPharma Corp. February 28, 2022. Accessed March 1, 2022. https://www.prnewswire.com/news-releases/cti-biopharma-announces-fda-accelerated-approval-of-vonjo-pacritinib-for-the-treatment-of-adult-patients-with-myelofibrosis-and-thrombocytopenia-301492159.html
  2. Vonjo. Package insert. CTI BioPharma Corp.; 2022. Accessed March 1, 2022. https://www.ctibiopharma.com/wp-content/uploads/2022/02/CTI_VONJO_USPI.pdf