RTX-321

RTX-321 is an investigational allogeneic artificial antigen-presenting cell (aAPC) therapy designed as a red cell therapeutic for the treatment of human papillomavirus (HPV) 16-positive cancers. It consists of cultured, enucleated human red cells engineered to express three key components on their surface: - An HPV peptide antigen bound to major histocompatibility complex (MHC) class I proteins, - The costimulatory molecule 4-1BB ligand (4-1BBL), - The cytokine interleukin 12 (IL-12). This configuration mimics natural T cell-antigen presenting cell interactions and is intended to induce a tumor-specific immune response by expanding and activating antigen-specific CD8+ T cells. Preclinical studies show that RTX-321 can promote epitope spreading—broadening the immune response beyond the presented antigen—and induce both innate and adaptive immunity. Its dual mechanism aims to boost HPV16-specific cytotoxic T lymphocyte responses while also stimulating broader anti-tumor immunity. Developed as an "off-the-shelf" product with potential long shelf life, it targets persistent, recurrent, or metastatic unresectable HPV16-positive cancers including cervical cancer, head and neck squamous cell carcinoma (HNSCC), and anal cancer[2][5][6][7][8].