A new chimeric antigen receptor (CAR) T-cell product had an acceptable safety profile and showed early signs of efficacy as a monotherapy and in combination with an mRNA vaccine in patients with solid tumors, according to preliminary data from a phase I/II clinical trial presented during the AACR Annual Meeting 2022, held April 8-13 in New Orleans. CAR T-cell therapy has revolutionized the treatment options for hematologic malignancies, but its application for solid tumors has been challenging. “One of the main limitations is that most of the proteins present on solid tumors that could be used as targets are also found at low levels on normal cells, making it difficult to specifically direct the CAR T cells against tumor cells and spare healthy ones,” said presenter John Haanen, MD, PhD, a medical oncologist at the Netherlands Cancer Institute (NKI), Amsterdam, Netherlands. “Other challenges include the limited persistence of CAR T cells observed in solid tumors and their difficulty reaching the tumors and penetrating the center of the mass.”