A preparation of autologous peripheral blood lymphocytes (PBLs) harvested from chronic lymphocytic leukemia (CLL) patients previously treated with the Brutons' tyrosine kinase (BTK) inhibitor ibrutinib with potential immunostimulating and antineoplastic activities. Upon intravenous administration, IOV-2001 generates an enhanced cytotoxic T-cell response against autologous leukemic B-cells in patients who have relapsed during treatment with ibrutinib. IOV-2001 is mostly comprised of T-cells of which the majority are of the effector memory phenotype which augments the specificity of the immune response.