Tecelra (afamitresgene autoleucel) is a T-cell immunotherapy used to treat synovial sarcoma in certain patients. It involves a one-time infusion where the patient's own white blood cells are collected, modified to include T cell receptors (TCR) targeting the MAGE-A4 protein on cancer cells, and then reintroduced to destroy the cancer. Tecelra works by using genetically modified T cells to recognize and attack synovial sarcoma cells expressing MAGE-A4.