Targeted Therapy Could Help Patients With Rare Bone Marrow Cancer

A targeted drug already used for one type of bone marrow cancer may also help ease symptoms in patients with a rarer, harder-to-treat group of related blood disorders, new research suggests.  

Andrew Kuykendall, MD

Data presented at the American Society of Clinical Oncology Annual Meeting found that fedratinib could benefit people living with myelodysplastic syndrome/myeloproliferative neoplasm overlap syndromes, or MDS/MPN overlap. These rare conditions cause the body to produce abnormal or excessive blood cells and often lead to severe fatigue, abdominal discomfort and an enlarged spleen. Treatment options are limited, and many patients continue to struggle with symptoms. 

The phase 2 study looked at whether fedratinib, already approved to treat myelofibrosis, could also reduce symptoms and shrink spleen size in patients with these related diseases. 

“Patients with these diagnoses often face significant symptoms, and there are very few treatments that reliably improve them,” said Andrew Kuykendall, MD, lead investigator and a medical oncologist in Moffitt Cancer Center’s Malignant Hematology Department. “This study gave us an opportunity to evaluate whether a therapy like fedratinib, which targets pathways active in these diseases, could offer meaningful benefit.”  

Understanding the Diseases  

MDS/MPN overlap syndromes are rare blood cancers that disrupt normal blood cell production. Patients may experience fatigue, abdominal discomfort, other systemic symptoms and an enlarged spleen. Some forms, such as atypical chronic myeloid leukemia and chronic neutrophilic leukemia, can progress quickly and have few effective treatments. 

 “These conditions can significantly affect quality of life,” Kuykendall said. “Patients often deal with heavy symptom burdens and very few therapies that reliably help.”  

What the Study Found 

The trial enrolled 25 adults with four types of MDS/MPN overlap syndromes. Most patients had multiple genetic mutations, which can make the diseases more difficult to treat. Participants received fedratinib daily in 28-day cycles. 

 At 24 weeks, 18 of 20 evaluable patients had a reduction in spleen size, with six achieving at least a 35% reduction. Among 19 patients who had significant symptoms before treatment, 13 reported improvement and nine saw their symptom scores cut in half. 

Overall, spleen volume decreased by an average of 30%, while symptom scores improved by 41% among those who reported symptoms at the start of treatment. 

 Some patients experienced serious side effects, including kidney injury, low thiamine levels and gastrointestinal issues. More common side effects included nausea, diarrhea and constipation. 

 “These outcomes were particularly encouraging given the molecular features of this patient population, which typically predict lower response rates and poor prognosis,” Kuykendall said. 

Why This Matters for Patients  

Fedratinib works by blocking JAK2, a key signaling pathway that drives many of these cancers. It also targets additional pathways that may play a role in more complex disease biology. The drug has previously received priority review from the U.S. Food and Drug Administration for related conditions, reflecting the need for more effective therapies. 

“Patients with these diseases need more options,” Kuykendall said. “Fedratinib may offer a path forward for people who have had very few treatments available to them.”