Researchers from the SWOG Cancer Research Network have found that adding ruxolitinib to standard tyrosine kinase inhibitor (TKI) treatment significantly increased the percentage of patients who had a molecular response deep enough to warrant discontinuing treatment for patients with chronic-phase chronic myeloid leukemia (CP-CML). The findings were presented at the European School of Haematology's 26th Annual John Goldman Conference on Chronic Myeloid Leukemia.
S1712 Trial Results
The SWOG S1712 clinical trial, led by Kendra L. Sweet, MD, a SWOG investigator at Moffitt Cancer Center, randomized 75 patients with CML whose disease was still molecularly detectable on current therapy and who had been undergoing treatment with a TKI for at least one year. Patients continued their TKI treatment, with one half also receiving ruxolitinib.
After 12 months, the rate of patients achieving MR4.0 (a reduction in leukemic RNA to 0.01% or less of baseline) was significantly higher in the ruxolitinib arm: 46% versus 26% in the TKI-only arm. Similarly, the rate of patients scoring MR4.5 (no detectable leukemic RNA) at 12 months was also significantly higher with ruxolitinib: 14% versus 3% in the control arm.
Impact on Treatment-Free Remission
Notably, two years after randomization, 29% of patients on the ruxolitinib arm met the National Comprehensive Cancer Network (NCCN) guidelines criteria for discontinuing treatment, compared to only 11% on the TKI-only arm. According to Sweet, this could lead to more patients successfully discontinuing treatment, which has been shown to significantly reduce health care costs and improve health-related quality of life.
Mechanism of Action and Rationale
CML is commonly treated with TKIs; however, leukemic stem cells can evade TKIs by hiding in the bone marrow. Preclinical data suggested that ruxolitinib could alter the bone marrow microenvironment, sensitizing these stem cells to TKIs. The researchers hypothesized that combining ruxolitinib with TKI treatment would enhance the effectiveness of TKIs against leukemic stem cells, ultimately eradicating measurable residual disease in a greater number of patients.
Safety Profile
Toxicity profiles were similar between the two arms. Two patients on the ruxolitinib arm experienced grade 3 treatment-related adverse events, while three patients on the TKI-only arm had grade 3 events, and one patient had a grade 4 event. Grade 1/2 anemia was more common in patients treated with ruxolitinib.
Future Directions
Sweet's team is now focused on identifying which CML patients are most likely to benefit from the addition of ruxolitinib to their TKI treatment. Further trials are planned to assess whether this combination can further increase the percentage of patients achieving treatment-free remission.
