Additional Relevant Details The FDA designation is for the combination of BPX-501 genetically modified T cells and activator agent rimiducid as replacement T-cell therapy for the treatment of immunodeficiency and graft versus host disease (GvHD) after allogeneic hematopoietic stem cell transplant. BPX-501 is an adjunct T-cell therapy incorporating the Company's proprietary CaspaCIDe® safety switch.