Case Report: An EGFR-Targeted 4-1BB-agonistic Trimerbody Does Not Induce Hepatotoxicity in Transgenic Mice With Liver Expression of Human EGFR.

Agonistic monoclonal antibodies (mAbs) targeting the co-stimulatory receptor 4-1BB are among the most effective immunotherapeutic agents across pre-clinical cancer models. However, clinical development of full-length 4-1BB agonistic mAbs, has been hampered by dose-limiting liver toxicity. We have previously developed an EGFR-targeted 4-1BB-agonistic trimerbody (1D8N/CEGa1) that induces potent anti-tumor immunity without systemic toxicity, in immunocompetent mice bearing murine colorectal carcinoma cells expressing human EGFR. Here, we study the impact of human EGFR expression on mouse liver in the toxicity profile of 1D8N/CEGa1. Systemic administration of IgG-based anti-4-1BB agonist resulted in nonspecific immune stimulation and hepatotoxicity in a liver-specific human EGFR-transgenic immunocompetent mouse, whereas in 1D8N/CEGa1-treated mice no such immune-related adverse effects were observed. Collectively, these data support the role of FcγR interactions in the major off-tumor toxicities associated with IgG-based 4-1BB agonists and further validate the safety profile of EGFR-targeted Fc-less 4-1BB-agonistic trimerbodies in systemic cancer immunotherapy protocols.

A novel form of 4-1BBL has better immunomodulatory activity than an agonistic anti-4-1BB Ab without Ab-associated severe toxicity.

Agonistic Abs to select costimulatory members of CD28 and TNFR family have shown efficacy in various preclinical cancer immunotherapeutic settings. However, the use of agonistic Abs is often associated with severe toxicity due to non-specific activation of lymphocytes. We hypothesized that natural costimulatory ligands may serve as more potent and safer alternative to agonistic Abs for immunotherapy. In this communication, we focused on 4-1BBL as the molecule of choice because of the pleiotropic effects of 4-1BB signaling in the immune system and the demonstrated therapeutic efficacy of 4-1BB agonistic Abs in preclinical cancer and infection models. We report that a novel form of soluble ligand, SA-4-1BBL, delivered more potent and qualitatively different signals to T cells than an agonistic Ab. Importantly, while treatment of naïve mice with the agonistic Ab resulted in severe toxicity, as assessed by enlarged spleen and peripheral LNs, non-specific T cell proliferation, hepatitis, and systemic inflammatory cytokine production, treatment with SA-4-1BBL lacked these immune anomalies. Agonistic Ab treatment produced full toxicity in FcgammaR(-/-) or complement C1q(-/-) or C3(-/-) knockout mice, suggesting lack of involvement of stimulatory FcgammaRs or complement system in the observed toxicity. Naïve and memory T cells served as direct targets of anti-4-1BB Ab-mediated toxicity. Potent immunostimulatory activity combined with lack of toxicity rationalizes further development of soluble SA-4-1BBL as an immunomodulatory component of therapeutic vaccines against cancer and chronic infections.