Anna B. Halpern, MD, physician, assistant professor, Clinical Research Division, Fred Hutch; assistant professor, hematology, University of Washington School of Medicine, discusses investigational efforts being developed to expand on the use of ruxolitinib and navitoclax in earlier treatment lines for patients with myelofibrosis.
In cohort 3 of the phase 2 REFINE trial (NCT03222609), the combination of ruxolitinib and navitoclax was evaluated in the upfront setting for patients (n=32) who had not been previously exposed to a JAK inhibitor. The study’s primary end point was spleen volume reduction of 35% or greater from baseline at week 24.
An exploratory analysis of this cohort was presented at the 2022 ASH Annual Meeting and Exposition, Halpern begins. Findings showed that navitoclax plus ruxolitinib produced a spleen volume reduction of at least 35% at week 24 across specific patient subsets, she details. These subsets consisted of patients 75 years of age or older, those with a high Dynamic International Prognostic Scoring System score, and those with HMR mutations. The percentage of patients who experienced optimal spleen volume reduction in these subgroups are 50%, 33%, and 47%, respectively.
Notably, changes in bone marrow fibrosis and reductions in the variant allele frequency (VAF) of the driver gene mutation were seen with the combination regimen in many patients, Halpern continues. Half of patients achieved a greater than 20% reduction in VAF from baseline at week 12 or 24, while a greater than 50% VAF reduction from baseline occurred in 18% of patients. When comparing those with or without HMR mutations, no differences in greater than 20% VAF reduction from baseline to week 12 or 24 were observed between populations.
These results indicate the potential disease-modifying ability of ruxolitinib and navitoclax, suggesting that reductions in bone marrow fibrosis and VAF may serve as biomarkers for disease modification, Halpern states. Notably, long-term outcomes cannot be definitively assessed as correlates for leukemia, progression, and survival, she adds. The viability of these 2 biomarker candidates should be assessed more short term, and in larger study populations, Halpern concludes.