Aim:
The BTK inhibitors ibrutinib and pirtobrutinib have demonstrated clinical success in treating B cell malignancies. However, their impact on T cell function remains underexplored. Ibrutinib has off-target kinase effects, whilst pirtobrutinib is a second-generation BTK inhibitor which has not been tested for its effects on T cell function. This study established a multi-assay platform to investigate the immunomodulatory effects of BTK inhibitors and their impacts in sequential or novel combination therapies with bispecific antibodies which are being used in clinical trials to treat haematological malignancies.
Method:
Peripheral blood mononuclear cells from healthy donors and mantle cell lymphoma patients were stimulated in presence of either ibrutinib or pirtobrutinib (1 μM), in combination with dexamethasone (10 μM) and the bispecific antibody glofitamab (10 nM). T cell proliferation (CellTrace Violet), intracellular cytokine staining (IL-2, TNFa, IFNg) and T:B synapse formation assays were performed. Samples were acquired using a BD Fortessa flow cytometer, and analysis was performed using FlowJo and PRISM software.
Results:
Preliminary data demonstrated that short-term ibrutinib treatment modulated T cell function. In a 5-day assay, a ~3-fold reduction in proportion of proliferating cells was observed relative to vehicle controls. Cytokine production was also impaired, with a ~3-fold reduction in TNFα and ~2-fold reductions in IFNγ and IL-2. In contrast, pirtobrutinib exhibited minimal effects, maintaining proliferative capacity and cytokine output comparable to controls. The effects of long-term BTK inhibitor administration in combination with dexamethasone and glofitamab are under investigation.
Conclusion:
Ibrutinib exerted broad immunomodulatory effects on T cells, whilst pirtobrutinib showed limited effects. These findings indicate that choice of BTK inhibitor may influence T cell responses in the setting of immunotherapies. These assays provide a multi-parameter framework for further evaluation of immunological responses to BTK inhibitors, informing design of clinical treatment strategies.
Conflict of Interest:
No conflict of interest to disclose.