Correlative analyses of patients with T-cell lymphoma treated with ibrutinib. (A) Ibrutinib therapy achieved 50% ITK occupancy within 4 hours, which was stable over time. (B) Ibrutinib did not increase the percentage of Th1 cells (CD4⁺/CXCR3⁺/CCR6⁻) in the peripheral blood. (C) Ibrutinib did not increase the percentage of cells producing interferon-γ (IFN-γ) in response to restimulation. (D-F) Ibrutinib did not significantly alter serum levels of interferon-γ (Th1), tumor necrosis factor-α (TNF-α; Th1), or interleukin-10 (IL-10; Th2). (G) Patients in whom ibrutinib therapy resulted in higher ITK occupancy (50% or higher, as measured on C2D1) were more likely to increase Th1 skewing in the peripheral blood in response to ibrutinib monotherapy as compared with patients in whom ibrutinib achieved lower ITK occupancy. P value by unpaired Student t test.