B2M and cancer: In order to treat patients with HPV16+ cancers, we developed RTX-321 consisting of allogeneic, cultured, human enucleated RBCs engineered to express a single chain trimer of HLA-A*02:01 and β2M fused with HPV 16 E711–19 peptide (HLA-A2-HPV; signal 1), 4-1BBL (signal 2), and IL-12 (signal 3) on the cell surface (Fig. 6a).