Real-World Data for Pacritinib Show Improvement in Thrombocytopenia, Anemia in Myelofibrosis

Michael Marrone, PhD, MPH

Pacritinib (Vonjo) generated improvements in thrombocytopenia and anemia in patients with myelofibrosis treated in the real-world setting, according to data from a retrospective study presented at the 2024 SOHO Annual Meeting.¹

Findings showed that patients with a platelet count below 100 x 109/L at baseline (n = 74) experienced an early increase in platelet count following treatment initiation that was maintained throughout the observation period. Additionally, an early increase in median hemoglobin was reported in all patients, and this increase was sustained throughout the observation period. Patients with hemoglobin level of less than 8.0 g/dL at the start of treatment (n = 35) experienced a hemoglobin increase of nearly 1 g/dL by day 30.

Notably, patients who received prior treatment with ruxolitinib (Jakafi; n = 69) experienced an increase in platelet counts and hemoglobin levels following initiation of pacritinib. At baseline, the median platelet count and median hemoglobin level in this population was 91.0 x 109/L and 8.7 g/dL, respectively. At day 360, the median platelet count and median hemoglobin were 97.0 x 109/L and 10.4 g/dL, respectively.

“In addition to spleen and symptom benefits observed in previous clinical trials, real-world outcomes demonstrate stability or improvement in thrombocytopenia and/or anemia in patients with myelofibrosis treated with pacritinib,” lead study author Michael Marrone, PhD, MPH, and colleagues, wrote in a poster presentation of the data. Marrone is an assistant professor in the College of Medicine, Department of Public Health Sciences, at the Medical University of South Carolina in Charleston.

This retrospective study evaluated the clinical and demographic characteristics, treatment patterns, and outcomes of patients with myelofibrosis treated with pacritinib in the United States. In February 2022, the FDA granted accelerated approval to pacritinib for the treatment of adult patients with intermediate or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis with a platelet count below 50 x 109/L.²

Data for the retrospective study were extracted from the Integra-PrecisionQ database, which includes de-identified electronic medical records and practice management data, from June 2022 to August 2023.¹

Primary outcomes assessed were changes in platelet count and hemoglobin levels at the initiation of pacritinib—the index date—and in 30-day intervals post-index. Overall survival (OS) was assessed from index date through the end of the observation period in October 2023 using the Kaplan-Meier method.

The study included 142 patients with myelofibrosis treated with pacritinib at a median follow-up of 6 months (interquartile range [IQR], 4-11). In this population, 119 patients had complete laboratory values available at the index date and at least 1 once during follow-up.

Notably, at treatment initiation, 28.5% of patients had severe thrombocytopenia with a platelet count of less than 50 x 109/L, and 29% had severe anemia with a hemoglobin level of less than 8.0 g/dL. The median age was 72 years (IQR, 64-79), and the median time from diagnosis to pacritinib initiation was 13.4 months (IQR, 0.6-49.6). The median time from index to the last dose of pacritinib or the end of the observation period was 5.3 months (IQR, 2.4-9.1). In patients with a median follow-up of more than 6 months (n = 78), the median duration of pacritinib treatment was 8.5 months (IQR, 5.9-11.2).

Additional data showed that the 12-month OS probability for patients with myelofibrosis treated with pacritinib was 69.4% (95% CI, 56.8%-79.0%) in the overall cohort, which study authors noted was a favorable outcome compared with historical JAK inhibitor controls.

Patients who received pacritinib as a first-line therapy (n = 52) had a 12-month OS probability of 77.3% (95% CI, 61.5%-87.3%). Those with severe thrombocytopenia treated in the first-line setting (n = 19) had a 12-month OS probability of 75.2% (95% CI,46.3%- 90.0%).

Among patients treated with pacritinib in the second-line (n = 59), the 12-month OS probability was 72.1% (95% CI: 42.4 to 88.2). Patients previously treated with ruxolitinib prior to pacritinib had a 12-month OS probability of 65.3% (95% CI, 47.2%-78.5%).

References

1. Marrone M, Geller R, Oladapo A, et al. Real-world treatment patterns and outcomes in patients with myelofibrosis treated with pacritinib in the United States. Presented at: 2024 SOHO Annual Meeting; September 4-7, 2024; Houston, TX. Abstract MPN-497.
2. FDA approves drug for adults with rare form of bone marrow disorder. FDA. March 1, 2022. Accessed September 9, 2024. https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-drug-adults-rare-form-bone-marrow-disorder