What will (and should) be improved in CAR immunotherapy?

Chimeric antigen receptor (CAR) is probably one of the most successful proposals for cancer treatment, especially hematological diseases for which several Advanced Therapies Medicinal Products (ATMP) have been approved worldwide by drug agencies. But, despite this unprecedented success in the oncology and cell/gene therapy fields, there are a lot of aspects that could (and should) be improved in the multiple aspects that involve this complex therapy: from the design of the chimeric molecule to the clinical protocols of use of the engineered T-cells, including even the regulatory rules that they are currently restricting the development of these hopeful therapies. In this chapter, we will try to summarize the main aspects that can (and probably should) be improved for the expansion of immunotherapy with CAR proposals beyond onco-hematology.