BTN3A1 and cancer: However, previous in vivo studies using a phosphoantigen mimic termed bromohydrin pyrophosphate (BrHPP),43 which activates Vγ9/Vδ2 T cells43via the involvement of BTN3A1,44 found this compound to be safe and well tolerated in cancer patients when used in combination with a low dose of IL-2.45,46 While further investigation of cancer cell selectivity for our HMBP ProPAgens is required, these previous findings establish a precedent that at least some phosphoantigens can achieve acceptable safety profiles in patients when used in combination with IL-2.