MAGEA3 and plasma cell myeloma: In another phase I trial using another TCR targeting MAGE-A3, two patients experienced cardiovascular toxicity after receiving TCR gene-modified T cells for the treatment of melanoma or myeloma, leading to death.38, 39 Subsequent investigations revealed a previously undefined cross-reactivity of the MAGE-A3 TCR with a muscle-specific protein, Titin, expressed in the heart.