PAC/SIR/TAC suppresses STAT3 and enhances STAT5 phosphorylation in CD4⁺ T cells. (A) Percentage (%) of pSTAT3⁺ CD4⁺ T cells pretransplant and at days +21 and +100 among patients treated on phase 2 PAC/SIR/TAC. (B) %pSTAT3⁺ CD4⁺ T cells at day +21 among patients treated with PAC/SIR/TAC at dose level 1 with ineffective JAK2 inhibition vs PAC/SIR/TAC at the recommended phase 2 dose (RP2D) of PAC (primary end point: %pSTAT3⁺ CD4⁺ T cells ≤ 35%). (C) %pSTAT3⁺ CD4⁺ T at days +21 and +100 based on pacritinib dosing. (D) %pSTAT5⁺ CD4⁺ T (IL-2 receptor signaling element) cells pretransplant and at days +21 and +100 on phase 2 PAC/SIR/TAC. (E) %pSTAT5⁺ CD4⁺ T cells at day +21 among patients treated with dose level 1 PAC/SIR/TAC vs RP2D PAC/SIR/TAC. (F) Graph demonstrating the ratio of pSTAT5⁺ to pSTAT3⁺ CD4⁺ T cells at day +21 based on dose level 1 PAC/SIR/TAC vs RP2D PAC/SIR/TAC. (G) %pS6⁺ CD4⁺ T cells (CD28 signaling element) pretransplant and at days +21 and +100 on phase 2 PAC/SIR/TAC. (H) %pS6⁺ CD4⁺ T cells at day +21 among patients treated with dose level 1 PAC/SIR/TAC vs RP2D PAC/SIR/TAC. (I) %pH3 Ser10⁺ CD4⁺ T cells (CD28 signaling element) pretransplant and at days +21 and +100 on phase 2 PAC/SIR/TAC. (J) %pH3 Ser10⁺ CD4⁺ T cells at day +21 among patients treated with dose level 1 PAC/SIR/TAC vs RP2D PAC/SIR/TAC. ∗P < .05, ∗∗P = .01-.001, ∗∗∗P = .001-.0001, ∗∗∗∗P < .0001. NS, not significant.