PDCD1 and neoplasm: The NCT03399448 [49] trial targeting multiple myeloma [49] is one of the first trials to publish data on safety and efficacy of CRISPR-Cas9-engineered T cells where, in addition to removing α and β chains of the endogenous TCR, the immune checkpoint regulator PD1 was also removed to enhance the anti-tumor activity of these cells with engineered TCRs [51].