Background: Chimeric Antigen Receptor (CAR) T-cell therapy has shown promising results in cancer treatment, especially the use of CD19 CAR T-cell in B-lineage Acute Lymphoblastic Leukemia (B-ALL) which was recently approved for clinical use. Nonetheless, studies performed to date are relatively small. Major differences in CAR T-cell design and the specifics of the treatment protocols utilized suggest results from these studies are not necessarily comparable. Aims: To summarize the results of CD19 CAR T-cell trials performed to date, and explore the possibility of a systematic review of existing data on use in B-ALL, including treatment efficacy and key variables of potential relevance to treatment efficacy. Materials and methods: Based on a systematic review of publications available from MEDLINE, we included eight studies reporting on the use of CD19 CAR T-cells in relapsed/refractory B-ALL. Results: Eight published clinical studies were identified and analyzed, including 170 patients with B-ALL and one patient with T-ALL. 138 patients achieved MRD-negative status (ORR 80,7%, 95% CI: 74,7-86,7%) following therapy. We observed that use of 4-1BB versus CD28 costimulatory domain (84,7% vs. 68,3%), longer T-cell persistence (90,0 vs. 77,2%) and preconditioning by lymphodepletion (81,9% vs. 71,4%) were all positively correlated with improved MRD rate. The use of allogenic versus autologous CAR T-cells (81,8% vs 80,6%), and a high infused CAR T-cell number (83,3% vs 82,2%) might also confer benefit. Conclusion: Clinical trials of CD19 CAR T-cell therapy in B-ALL present promising results. Reported data appears to indicate a potential impact of T cell dosage, preconditioning and choice of CAR costimulatory domain on therapeutic efficacy. Existing studies include few patients and differ greatly in study design, which limits our ability to draw firm conclusions. Larger and more standardized studies, as well as an improved understanding of pharmacokinetics/dynamics are warranted. This will assist in further advancing this new form of therapy by providing more robust data on efficacy and side effects.