LBA3010Background: T cells genetically-modified to express chimeric antigen receptors (CARs) targeting CD19 have potent activity against a variety of B-cell malignancies. Chemotherapy is administered prior to CAR T cells because depletion of recipient leukocytes enhances the anti-malignancy efficacy of adoptively-transferred T cells; an increase in serum interleukin (IL)-15 is one mechanism for this enhancement. Previously, we (Kochenderfer et al. Journal of Clinical Oncology, 2015) and others have reported patients treated with high-dose chemotherapy prior to anti-CD19 CAR T-cell infusions. This report describes treatment of 22 patients with low-dose conditioning chemotherapy followed by infusion of anti-CD19 CAR T-cells. Methods: Eighteen of 22 treated patients received 300 mg/m2 of cyclophosphamide (cy) daily for 3 days; 4 patients received 500 mg/m2 of cy on the same schedule. All patients received fludarabine 30 mg/m2daily for 3 days on the same days as cy. Patients received a single dose of CAR T ce...