ABSTRACT
Recombinant agonists that activate co-stimulatory and cytokine receptors have shown limited clinical anticancer utility, potentially due to narrow therapeutic windows, the need for coordinated activation of co-stimulatory and cytokine pathways and the failure of agonistic antibodies to recapitulate signaling by endogenous ligands. RTX-240 is a genetically engineered red blood cell expressing 4-1BBL and IL-15/IL-15Rα fusion (IL-15TP). RTX-240 is designed to potently and simultaneously stimulate the 4-1BB and IL-15 pathways, thereby activating and expanding T cells and NK cells, while potentially offering an improved safety profile through restricted biodistribution. We assessed the ability of RTX-240 to expand and activate T cells and NK cells and evaluated the in vivo efficacy, pharmacodynamics and tolerability using murine models. Treatment of PBMCs with RTX-240 induced T cell and NK cell activation and proliferation. In vivo studies using mRBC-240, a mouse surrogate for RTX-240, revealed biodistribution predominantly to the red pulp of the spleen, leading to CD8 + T cell and NK cell expansion. mRBC-240 was efficacious in a B16-F10 melanoma model and led to increased NK cell infiltration into the lungs. mRBC-240 significantly inhibited CT26 tumor growth, in association with an increase in tumor-infiltrating proliferating and cytotoxic CD8 + T cells. mRBC-240 was tolerated and showed no evidence of hepatic injury at the highest feasible dose, compared with a 4-1BB agonistic antibody. RTX-240 promotes T cell and NK cell activity in preclinical models and shows efficacy and an improved safety profile. Based on these data, RTX-240 is now being evaluated in a clinical trial.
Subject(s)
4-1BB Ligand/genetics , Cell- and Tissue-Based Therapy , Erythrocytes/metabolism , Gene Expression , Genetic Therapy , Interleukin-15/genetics , 4-1BB Ligand/metabolism , Animals , Cell- and Tissue-Based Therapy/methods , Erythroid Precursor Cells/metabolism , Female , Flow Cytometry , Genes, Reporter , Genetic Engineering , Genetic Therapy/methods , Humans , Interleukin-15/metabolism , Mice , Models, Animal , Protein Binding , Treatment Outcome , Xenograft Model Antitumor AssaysABSTRACT
Checkpoint inhibitors and T-cell therapies have highlighted the critical role of T cells in anti-cancer immunity. However, limitations associated with these treatments drive the need for alternative approaches. Here, we engineer red blood cells into artificial antigen-presenting cells (aAPCs) presenting a peptide bound to the major histocompatibility complex I, the costimulatory ligand 4-1BBL, and interleukin (IL)-12. This leads to robust, antigen-specific T-cell expansion, memory formation, additional immune activation, tumor control, and antigen spreading in tumor models in vivo. The presence of 4-1BBL and IL-12 induces minimal toxicities due to restriction to the vasculature and spleen. The allogeneic aAPC, RTX-321, comprised of human leukocyte antigen-A*02:01 presenting the human papilloma virus (HPV) peptide HPV16 E711-19, 4-1BBL, and IL-12 on the surface, activates HPV-specific T cells and promotes effector function in vitro. Thus, RTX-321 is a potential 'off-the-shelf' in vivo cellular immunotherapy for treating HPV + cancers, including cervical and head/neck cancers.
Subject(s)
Antigen-Presenting Cells/transplantation , Cell Engineering/methods , Erythrocytes/immunology , Immunotherapy, Adoptive/methods , Neoplasms/therapy , 4-1BB Ligand/genetics , 4-1BB Ligand/immunology , 4-1BB Ligand/metabolism , Animals , Antigen-Presenting Cells/immunology , Antigen-Presenting Cells/metabolism , Cell Line, Tumor , Coculture Techniques , Disease Models, Animal , Erythrocytes/metabolism , Female , HLA-A2 Antigen/genetics , HLA-A2 Antigen/immunology , HLA-A2 Antigen/metabolism , Histocompatibility Antigens Class I/genetics , Histocompatibility Antigens Class I/immunology , Histocompatibility Antigens Class I/metabolism , Humans , Interleukin-12/genetics , Interleukin-12/immunology , Interleukin-12/metabolism , Lymphocyte Activation , Neoplasms/immunology , Papillomavirus E7 Proteins/genetics , Papillomavirus E7 Proteins/immunology , Papillomavirus E7 Proteins/metabolism , Primary Cell Culture , T-Lymphocytes/immunology , T-Lymphocytes/transplantation , Transplantation, Homologous/methodsABSTRACT
Adnectins are targeted biologics derived from the tenth type III domain of human fibronectin (¹°Fn3), a member of the immunoglobulin superfamily. Target-specific binders are selected from libraries generated by diversifying the three ¹°Fn3 loops that are analogous to the complementarity determining regions of antibodies. The crystal structures of two Adnectins were determined, each in complex with its therapeutic target, EGFR or IL-23. Both Adnectins bind different epitopes than those bound by known monoclonal antibodies. Molecular modeling suggests that some of these epitopes might not be accessible to antibodies because of the size and concave shape of the antibody combining site. In addition to interactions from the Adnectin diversified loops, residues from the N terminus and/or the ß strands interact with the target proteins in both complexes. Alanine-scanning mutagenesis confirmed the calculated binding energies of these ß strand interactions, indicating that these nonloop residues can expand the available binding footprint.
