Myelofibrosis is a rare chronic disorder of the hematopoietic cells of the bone marrow that disrupts the body’s normal production of blood cells. For most patients, drugs from the JAK2 inhibitor class have represented a meaningful therapeutic advance, relieving symptoms, extending survival, and improving quality of life. However, a troubling pattern has emerged in clinical practice: two to three years after starting JAK2 inhibitor treatment, some myelofibrosis patients develop an aggressive B cell lymphoma. A new study conducted in close collaboration between researchers at MedUni Vienna and Vetmeduni Vienna has now identified why, and published its findings in the journal Blood.
How JAK2 Inhibitors Trigger Lymphoma in Myelofibrosis Patients
Using bone marrow biopsies taken at the very start of disease, the research team was able to demonstrate that primordia of lymphoma were already present in the form of a dormant B cell clone in a substantial subset of myelofibrosis patients. Sixteen percent of myelofibrosis patients in the study were found to carry these dormant aggressive lymphomas. In approximately six percent of those patients, administration of JAK2 inhibitors appeared to stimulate the dormant clone into active, aggressive disease.
According to hematologists Heinz Gisslinger and Ulrich Jager from the Division of Haematology at MedUni Vienna, the key finding is that JAK2 inhibitors do not cause lymphoma de novo but rather awaken a pre existing malignant clone that was already present in the bone marrow before treatment began. This distinction is critical for understanding both the mechanism of the risk and the strategies available to manage it.
Detecting Dormant Lymphoma Before Myelofibrosis Treatment Begins
The research team demonstrated that dormant lymphomas can be detected before treatment starts if clinicians actively look for them using sensitive molecular biological techniques. According to the investigators, this approach represents the best available predictive tool for identifying high risk patients. By screening for B cell clones at baseline, it becomes possible to identify the relevant 16 percent of myelofibrosis patients, categorize their risk level, and make more informed treatment decisions before JAK2 inhibitor therapy is initiated.
The findings from the clinical team at MedUni Vienna were validated by researchers at Vetmeduni Vienna, led by Veronika Sexl, who demonstrated in a mouse model that animals receiving bone marrow transplants similarly developed lymphomas under analogous conditions. Two additional individual cases from Hopital Saint Louis in Paris, an international collaborative partner, further supported the conclusions of the Vienna study.
What This Means for Myelofibrosis Drug Safety and Future Research
The investigators described their findings as a paradigm shift that improves the safety profile of JAK2 inhibitors as a drug class. Rather than withdrawing these effective therapies from use, the research points toward a risk stratification approach: identifying the subset of myelofibrosis patients who carry dormant lymphoma clones and applying heightened monitoring or alternative treatment strategies for that group.
The next phase of this work involves collecting international cases and associated data to further characterize the risk and refine clinical guidance. Researchers are already working in close collaboration with the pharmaceutical companies that manufacture JAK2 inhibitors to enhance drug safety protocols. The study exemplifies how coordinated basic, preclinical, and clinical research can translate rapidly into actionable safety improvements for patients with rare hematological conditions.
To read more about hematology and oncology research, visit the FOMAT blog. FOMAT conducts hematology clinical trials at sites across the United States. To learn more about active studies, visit FOMAT’s patient studies page.
For the full source, see the original release at MedUni Vienna.