Pooled biomarker analysis of the association of baseline T regulatory cells with response and T-cell recovery profiles with blinatumomab treatment.

Introduction: Blinatumomab, a bispecific T-cell engager, requires the activity of CD3+ T-cells for tumor lysis. This pooled analysis aimed to re-examine baseline T regulatory cells (Tregs) as a biomarker of blinatumomab efficacy across multiple clinical trials and provide insights into peripheral T-cell dynamics during blinatumomab therapy in hematological malignancies.

Methods: Tregs and peripheral T-cells were enumerated by fluorescence-activated cell sorting and were statistically evaluated using the Wilcoxon rank-sum test and linear mixed effect modeling, respectively.

Results: Comparable baseline percentages of Tregs were observed in responders and non-responders of blinatumomab treatment (N = 325) in adults with leukemia or lymphoma. Peripheral T-cell count recovery occurred early during blinatumomab dosing, and before blinatumomab-free interval in patients (N = 233) from 4 clinical trials.

Conclusion: The pooled analysis revealed that baseline Treg levels do not serve as a predictive marker for blinatumomab response and that there is rapid peripheral T-cell recovery following blinatumomab dosing. These results suggest that patients with varying levels of Tregs can benefit from blinatumomab treatment and that blinatumomab-free intervals of 7 days may suffice in blinatumomab treatment regimens.