Allogeneic hematopoietic stem cell transplantation (aHSCT) provides curative therapy for hematologic malignancies. However, graft vs. host disease (GVHD) remains a serious clinical problem threatening anti-tumor (GVL) immune function and patient survival. Dr.Levy’s lab is developing novel approaches to suppress GVHD while maintaining GVL including targeting the MEK pathway that specifically inhibits alloreactive T cells while sparing pathogen and cancer-specific donor T cells. They recently discovered a novel 2-pathway strategy for Treg expansion in donors which spares GVL while suppressing GVHD. Their recent work demonstrates this Treg strategy is superior to post-transplant Cytoxan for GVHD prophylaxis. Based on STING’s role in modulating anti-tumor immunity, they discovered HSCT is reduced in recipients of MUD transplants in the absence of STING and worsened using STING agonists. This suggests that inhibition of STING in recipient cells can be a novel strategy to reduce GVHD and maintain GVL.