BTK and B-cell chronic lymphocytic leukemia: However, basal pSTAT5 levels were significantly higher when the samples from patients treated with chemoimmunotherapy (CIT) were compared to samples from patients receiving Bruton Tyrosine Kinase Inhibitor (BTKi) therapy (Figure 4C) and CLL patients not receiving therapy (p = 0.04) and HC (p = 0.02).