Sonia Guedan, PhD, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain, addresses the main challenges of CAR T-cell therapy in solid tumors. Dr Guedan reveals one of the main limitations is that CAR-T cells need to reach the tumor and infiltrate it to later proliferate and persist in a highly immunosuppressed microenvironment. Additionally, solid tumors are very heterogeneous, and the antigens present are not specific since they can also be expressed in healthy tissue. This interview took place at the 2nd European CAR T-Cell Meeting in Sitges, Spain.