Vonjo Improves Blood Counts in Patients With Myelofibrosis and Anemia

Patients living with myelofibrosis who also experience anemia may see meaningful improvements in blood counts when treated with Vonjo (pacritinib), according to new real-world clinical findings which were presented at the 13th Annual Society of Hematologic Oncology (SOHO) Congress.

Investigators found that the study, which evaluated hemoglobin (Hb) and platelet (PLT) responses in patients with myelofibrosis receiving Vonjo in routine clinical practice, aligned with clinical guideline recommendations for its use in patients with anemia.

Anemia is a significant complication in myelofibrosis and can affect quality of life and overall health. Anemia occurs when the body lacks enough healthy red blood cells or hemoglobin to deliver oxygen to tissues. This can lead to fatigue, weakness, and shortness of breath, according to the Mayo Clinic website, which noted that anemia has many types and causes.

Vonjo, a JAK1-sparing inhibitor targeting JAK2/IRAK1/ACV1 pathways, has previously been shown in clinical trials to reduce the need for blood transfusions in patients who are not transfusion-dependent. Importantly, Vonjo can be administered at full dosage regardless of pre-existing cytopenias, making it a viable option for patients struggling with low blood counts.

The study used the Integra-PrecisionQ database, which includes electronic health records and practice management data from predominantly community oncology practices. Patients diagnosed with myelofibrosis who initiated Vonjo therapy between June 2022 and June 2024 were included. Only patients with at least 90 days of follow-up and complete laboratory data were analyzed. Outcomes assessed included Hb response, defined as an increase of at least 1.5 g/dL, PLT count, and changes in Hb levels over time. Patients were grouped by baseline Hb levels: severe anemia, moderate anemia, and mild or no anemia.

Majority of Patients Show Hemoglobin Improvement Within 90 Days

Among 148 patients with sufficient follow-up, 44% achieved a hemoglobin response, and 75% of these responders reached the target within 90 days. Patients with early Hb responses had moderate or severe anemia at baseline. The median age of patients with a 90-day Hb response (49 patients) was 76 years, and 55.1% were male. Race distribution included White (59.1%), Black or African American (4.2%), and Asian (2.0%).

Anemia severity at index included severe anemia in 61.2% of patients, moderate anemia in 22.4%, and mild or no anemia in 16.3%. Median time from myelofibrosis diagnosis to Vonjo initiation was 11.4 months, and median follow-up was 10 months. Among patients with at least nine months of follow-up, median Vonjo treatment duration was 5.2 months.

Median time to Hb response was 40 days among all responders (65 patients) and 33 days among patients achieving a 90-day response. Regarding line of therapy, 26.5% received Vonjo as first-line treatment, 44.9% as second-line, and 30.6% as third-line or later. Some patients received Vonjo across multiple lines of therapy.

Vonjo Supports Platelet Stability During Treatment

In addition to improvements in hemoglobin, platelet counts remained stable through six months of Vonjo therapy. Patients with moderate or mild/no anemia experienced modest improvements in PLT counts at day 90, while those with severe anemia maintained stable counts through day 180. This stability is particularly important for patients at risk of bleeding or other complications associated with low platelet counts, emphasizing Vonjo's potential role in supporting overall hematologic health in myelofibrosis.

“Patients with myelofibrosis and anemia treated with Vonjo in real-world clinical settings demonstrated improvements in hemoglobin levels and platelet counts,” study investigators concluded in their poster, adding that “These real-world findings align with the guideline recommendations for the use of PAC in patients with anemia.”

Reference

1. Hematologic Response in Patients With Myelofibrosis Treated With Pacritinib in Real-World Clinical Settings, by Dr. Raajit K Rampal, et al. Presented at: 13th Society of Hematologic Oncology (SOHO) Congress; September 3-6, 2025; Houston, Texas. Abstract MPN-1038.
2. “Anemia: Symptoms and Causes,” by Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/anemia/symptoms-causes/syc-20351360

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