Anemia Protocol Does Not Reduce Ruxolitinib Efficacy in Myelofibrosis

Patients were not receiving anemia management medication at the time of enrollment and began danazol or ESA within 3 months of enrollment.

The addition of danazol or erythropoiesis-stimulating agents (ESAs) for anemia management to treatment with ruxolitinib (Jakafi) for myelofibrosis did not reduce spleen and symptom response rates of ruxolitinib, according to results from a post hoc analysis of the phase 3b JUMP trial (NCT01493414) shared at the European Hematology Association 2025 Congress.¹

For patients with a hemoglobin (Hb) of less than 12.0 g/dL (n = 101), the spleen length response rate at 12 weeks was 41.6% and 36.6% at 24 weeks. For those with an Hb of less than 10 g/dL (n = 52), the spleen length response rate at 12 weeks was 42.3% and 34.6% at 12 weeks. For reference, the spleen length response in the JUMP trial at 12 weeks was 39.1% and 31.5% at 24 weeks.

Symptom response rates were found to be comparable between patients with an Hb less than 12 g/dL at 25.7% vs 23.1% for those with an Hb less than 10 g/dL. The symptom response rate in JUMP overall was 26.9%.

At week 4, the mean Hb reached a nadir that steadily increased to week 48. The percentage of change from baseline to week 48 in those with a Hb less than 12 g/dL was +1.5%; in those with a Hb less than 10 g/dL, it was +6.5%.

From baseline to week 48, requirement rates for transfusions declined. Overall, 57% (n = 4) of patients in the Hb less than 10 g/dL subset and had transfusion dependency at baseline were no longer transfusion dependent at 24 weeks. Three of the 4 patients became transfusion independent.

“These results support the use of an ESA or danazol as an option for anemia supportive care in combination with ruxolitinib and may allow for maintenance of ruxolitinib dose intensity for patients with myelofibrosis with anemia,” lead study author Pankit Vachhani, MD, assistant professor of medicine and associate scientist of Experimental Therapeutics, at the University of Alabama at Birmingham, said during the presentation.

JUMP was a single-arm, phase 3b, expanded access trial looking at the safety and efficacy of ruxolitinib for patients with myelofibrosis. To be eligible for enrollment, patients must have had primary or secondary myelofibrosis with baseline platelets of 50x10⁹/L or greater. Ruxolitinib was administered at 5 mg to 20 mg twice daily based on the baseline platelet count.

In JUMP, patients were included if they had baseline anemia with either Hb less than 12 g/dL or an Hb less than 10 g/dL subset. At enrollment, patients should not have been receiving anemia medication but were initiated on an ESA or danazol within 3 months of enrollment and continued therapy for at least 3 months.

In the post hoc analysis, investigators evaluated 1384 patients with a HB less than 12 g/dL and 755 with Hb of less than 10 g/dL who did not receive supportive care for anemia at the time of enrollment. Of note, 101 patients were given ESA (n = 98) or danazol (n = 3) within 3 months of enrollment and were included in the analysis.

In the HB less than 12 g/dL group, the median age was 70 years (range, 45-86), 73.3% of patients were 65 years or older, and 45.5% were female. Via the Dynamic International Prognostic Scoring System, patients’ disease were either had high risk (12.9%), intermediate-2 risk (35.6%), intermediate-1 risk (31.7%), low risk (1.0%), or missing (18.8%). The median time since initial diagnosis was 18.6 months (range, 0.3-312).

In those with an HB less than 10 g/dL group, the median age was 71.5 years (range, 45-84), 69.2% were at least 65 years old, and 48.1% were female. The DIPSS risk breakdown was high risk (25.0%), intermediate-2 risk (51.9%), intermediate-1 risk (3.8%), low risk (0.0%), and missing (19.2%). The time since initial diagnosis was 12.9 months (range, 0.3-158).

The median time from enrollment to the first dose of an ESA or danazol was 43 days (range, 2-91) in the Hb less than 12 g/dL group and 34 days (range, 2-90) in the Hb less than 10 g/dL group. At baseline, 10 patients with a Hb less than 12 g/dL (9.9%) were transfusion dependent vs 7 in the Hb less than 10 g/dL subset.

Between each group, respectively, the mean platelet count was 322 x 10⁹/L vs 297 x 10⁹/L, and the mean white blood cell counts were 14.5 x 10⁹/L vs 15.6 x 10⁹/L. The mean palpable spleen length was 13.0 cm below the left central margin vs 12.1 cm below the left central margin.

The median follow-up was 17.5 months (range, 4.6-57.1) for those with a Hb less than 12 g/dL and 16.7 months (range, 4.6-53.7) in the Hb less than 10 g/dL group. The median duration of ESA/danazol treatment was 10.2 months (range, 3.3-44.3) and 9.2 months (range, 3.4-40.8), respectively.

The 4-week average of ruxolitinib doses remained above 25 mg for most study visits, while the mean total daily dose decreased over time. At 48 weeks, the doses were 25.3 mg and 25.0 mg in the Hb less than 12 g/dL and less than 10 g/dL subsets, respectively.

Reference

Vachhani P, Repp J, Hamer-Maansson JE, et al. Clinical outcomes in patients with myelofibrosis treated with ruxolitinib and anemia supporting medications. Presented at: European Hematology Association 2025 Congress; June 12-15, 2025; Milan, Italy. Abstract S218.