Chimeric antigen receptor T (CART) cells targeting CD19 have shown promising 
results in the treatment of chronic lymphocytic leukemia (CLL). However, 
efficacy seems to be inferior compared to diffuse large B-cell lymphoma or acute 
lymphoblastic leukemia. Impaired T-cell fitness of CLL patients may be involved 
in treatment failure. Less-differentiated naïve-like T cells play an important 
role in CART expansion and long-term persistence in vivo. These cells are sparse 
in CLL patients. Therefore, optimization of CART cell production protocols 
enriching less differentiated T cell subsets may overcome treatment resistance. 
The B-cell receptor inhibitor ibrutinib targeting Bruton's tyrosine kinase (BTK) 
is approved for the treatment of CLL. Besides BTK, ibrutinib additionally 
inhibits interleukin-2-inducible T-cell kinase (ITK) which is involved in T-cell 
differentiation. To evaluate the effect of ibrutinib on CART cell production, 
peripheral blood mononuclear cells from nine healthy donors and eight CLL 
patients were used to generate CART cells. T-cell expansion and phenotype, 
expression of homing and exhaustion makers as well as functionality of CART 
cells were evaluated. CART cell generation in the presence of ibrutinib resulted 
in increased cell viability and expansion of CLL patient-derived CART cells. 
Furthermore, ibrutinib enriched CART cells with less-differentiated naïve-like 
phenotype and decreased expression of exhaustion markers including PD-1, TIM-3 
and LAG-3. In addition, ibrutinib increased the cytokine release capacity of CLL 
patient-derived CART cells. In summary, BTK/ITK inhibition with ibrutinib during 
CART cell culture can improve yield and function of CLL patient-derived CART 
cell products.