CAR T-cell therapy: is it prime time in myeloma?

Chimeric antigen receptor (CAR) T cells have shown promising activity in hematological malignancies and are being studied for the treatment of multiple myeloma, as well. B-cell maturation antigen, which is widely and almost exclusively expressed on plasma cells and B cells, is a promising target. Other targets being evaluated include CD19, CD38, CD138, signaling lymphocyte activation molecule or CS1, light chain, GPRC5D, and NKG2D. Early clinical studies have shown promising response rates in heavily pretreated patients, but relapses have occurred. Cytokine release syndrome and neurotoxicity have been observed in the majority of patients but are mostly grades 1 and 2. Relapse may be mediated by antigen escape and the limited persistence of CAR T cells. CAR T-cell constructs that target multiple antigens/epitopes or constructs with longer persistence due to a higher proportion of memory phenotype T cells may decrease the rates of relapse. Allogeneic CAR T cells that offer "off-the-shelf" options are also being developed. The challenges in integrating CAR T cells in myeloma therapy include disease relapse, adverse effects, cost, and identifying the right patient population. Longer-term data on efficacy and toxicity are needed before CAR T cells are ready for prime time in myeloma.