Abstract 4301: A systemically administered detoxified TLR4 agonist displays potent antitumor activity across multiple tumor models and favorable preclinical tolerance profile

Abstract Background: TLR4 agonists have shown potent anti-tumor activity, but their clinical use is limited by toxicity issues preventing their systemic administration at effective doses in humans. HEPHA-440 is an innovative chemically detoxified TLR4 agonist formulated in liposomes with an optimized safety and solubility profile for systemic administration. HEPHA-440 demonstrated potent antitumor and adjuvant properties with capacity to address primary tumors and metastases associated with its capacity to preferentially activate the TRIF dependent TLR4 pathway, to activate and polarize Tumor Associated Macrophages and to trigger a Th1-type adaptive immune response. Methods: In these studies, we further explored the antitumor and adjuvant activities of HEPHA-440 across multiple murine tumor models, as well as in MyD88 KO and TRIF KO mice. We analyzed its cytokine profile in mice and rabbits and its tolerance profile on patient liver biopsies and through a dose range finding (DRF) study in rabbits. Results: HEPHA-440 antitumor activity was confirmed across multiple murine tumor models, including solid tumors (EMT6, CT26, Panc02) and lymphoma (A20), in monotherapy and/or in combination with anti-PD1 or anti CD20 monoclonal antibodies, respectively. In mice, HEPHA-440 mainly produced TRIF-related Type 1 Interferon cytokines compared to a natural TLR4 agonist, but its antitumor activity was found to depend on both MyD88 and TRIF-TLR4 pathways. In rabbits, repeated administration of high doses (200 µg/kg) of HEPHA-440 did not induce macroscopic or acute hepatic toxicity, while triggering transient and controlled production of pro-inflammatory cytokines (IL-8, MIP-1b, IL-1b), at similar levels after repeated administration and consistent with induction of innate immune responses. Ex vivo toxicity data on patient liver biopsies showed that HEPHA-440 does not alter liver functions unlike a natural TLR4 agonist, with a moderate inflammation and no increase of transaminases even at very high concentrations. Finally, a DRF study demonstrated good safety and favorable pharmacokinetics supporting progression to regulatory studies. Conclusions: HEPHA-440 combines potent systemic antitumor efficacy with an excellent safety profile. These findings support its development as a tumor type-independent immunotherapy, with first-in-human clinical trials planned for 2027. Citation Format: Laury-Anne Leroy, Capucine Phelip, Armando Andres Roca Suarez, Sabine Beaumel, Anais Debesset, Abdelkamel Chettab, Martine Caroff, Audrey Diederichs, Alexey Novikov, Barbara Testoni, Frédérique Brune, Fabien Zoulim, Jérôme Kerzerho, Juliette Humeau, Charles Dumontet. A systemically administered detoxified TLR4 agonist displays potent antitumor activity across multiple tumor models and favorable preclinical tolerance profile abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4301.