Fedratinib demonstrates promising clinical activity in patients with myelodysplastic syndrome (MDS)/myeloproliferative neoplasms (MPN) and chronic neutrophilic leukemia (CNL), according to data presented at the 2023 ASH Annual Meeting.

Fedratinib is a JAK2 inhibitor that is currently approved by the FDA for the treatment of higher-risk myelofibrosis. Given fedratinib potential inhibition of FLT3 and BRD4 and suppression of c-Myc expression, researchers hypothesize that the drug could have biologic relevance in MDS/MPN.

Andrew Kuykendall, MD, Moffitt Cancer Center, Tampa, Florida, presented results from the ongoing phase 2, multinational investigator-initiated clinical trial that evaluated the efficacy of fedratinib in atypical chronic myeloid leukemia (CML), CNL, MDS/MPN-unclassifiable, and MDS/MPN-ring sideroblasts and thrombocytosis. The primary end point of this trial is overall response rate, which is defined as complete or partial response or clinical benefit at 24 weeks.

Bone marrow was collected at baseline and week 24 and stained for c-Myc. C-myc expression was scored by multiplying the percentage of positive cells by intensity.

Eligible patients had splenomegaly ≥5 cm below left costal margin or ≥450 cc and/or an MPN total symptom score ≥10. Patients were excluded if they had a platelet count higher than 35 x10⁹/L or peripheral peripheral/marrow blasts >10%. The planned trial enrollment is 25 patients with an interim analysis completed after 9 patients are eligible for efficacy.

At data cutoff, 10 patients have been enrolled in the trial (1 with atypical CML, 4 with CNL, 4 with MDS/MPN-ring sideroblasts and thrombocytosis, and 1 with MDS/MPN-unclassifiable) with a median follow-up of 5 months. Of whom, 8 patients remain on treatment.

Overall, 5 patients were evaluable for response. Of whom, 3 had a response at week 24, including 3 symptom responses and 1 spleen response. A total of 6 patients completed 12 weeks of treatment with 1 spleen response and 2 symptom responses. Among these 6 patients, spleen volume decreased in 5 by an average of -23%. Among 5 patients with significant baseline symptom burden, 4 experienced an improvement in symptom burden by an average of -43%. 

IHC staining was done in a median of 10% of cells to demonstrate c-Myc expression at baseline. The average baseline c-Myc expression was 26.5. Among 4 patients with paired samples, c-Myc expression decreased in all cases by an average of 51% (P = .02).

For safety analysis, 10 patients were evaluable. The most common adverse events (AEs) were anemia, platelet count decrease, diarrhea, nausea, muscle cramp, and constipation. Grade ≥3 AEs included anemia and neutropenia. One patient discontinued treatment due to disease progression after initial response and another due to patient decision unrelated to disease or treatment.

“Fedratinib demonstrates promising clinical efficacy in MDS/MPN and CNL patients with proliferative features. The safety profile is consistent with prior experience,” concluded Dr Kuykendall and colleagues, adding “fedratinib’s unique kinase inhibition profile may provide a mechanism for enhanced effectiveness in this patient population.”

Source:

Kukendall AT, Pettit KM, Singh A, et al. A Phase 2 Study of Fedratinib in Patients with MDS/MPN and Chronic Neutrophilic Leukemia; December 9-12, 2023; San Diego, CA. Abstract 73.