Abstract 6734: Preclinical impact of pretreatment with CRS mitigation agents on pharmacodynamic response to TAK-500, a systemically delivered CCR2-targeted STING agonist iADC

Abstract Background: Stimulator of interferon genes (STING) agonists elicit potent innate immune enhancement and mobilize robust adaptive immune responses. Given the potential risk of immunotoxicity from associated cytokine release due to STING agonist treatment, there is a need to identify mitigation strategies that minimize immune-related toxicity while offering a therapeutic window for STING-mediated anti-tumor effects. This strategy is particularly relevant for myeloid-targeted immunotherapies, as cytokine release syndrome (CRS) can be myeloid cell-mediated. We utilized preclinical models to evaluate the pharmacological impact of pretreatment with agents routinely used for management of CRS in advance of delivering TAK-500, a novel, systemic, immune-cell directed STING agonist antibody drug conjugate (iADC) that selectively targets CCR2+ myeloid cells. Methods: Dexamethasone and anti-IL-6R antibodies were tested at clinically relevant doses 1 hour prior to treatment with TAK-500 or mTAK-500, a murine surrogate, to study immunomodulatory and anti-tumor effects in preclinical models. Induction of innate and adaptive immune responses and cytokine release was evaluated in human, ex vivo, and in tumor-bearing mouse models to characterize potential impact of premedication strategies on drug pharmacology and anti-tumor efficacy. Results: TAK-500 triggered dose-dependent monocyte activation and cytokine secretion ex vivo. Monocyte activation was minimally impacted by dexamethasone or anti-IL-6R pretreatment. Suppression of IL-6 and IFN-ƴ and increase in IL-10 were observed following dexamethasone pretreatment, whereas anti-IL-6R maintained a more proinflammatory milieu. In syngeneic mouse models, pretreatment with dexamethasone and anti-mouse IL-6R had minimal impact on mTAK-500 anti-tumor efficacy. Key pharmacodynamic effects, including innate immune cell activation in periphery and tumor-draining lymph node and intratumoral CD8+ T cell accumulation, were minimally impacted by either pretreatment agent. Serum cytokine analyses demonstrated suppression of IL-6, IFN-ƴ and increases in IL-10 with dexamethasone, but not with anti-IL-6R, similar to ex vivo findings. Conclusion: Premedication of TAK-500 and mTAK-500 with dexamethasone or anti-IL-6R antibodies does not substantially impact STING-mediated innate immune activation, mobilization of adaptive immune responses or anti-tumor efficacy, despite altered cytokine profiles compared to (m) TAK-500 without premedication. Clinically, these premedication strategies have been effective in mitigating immunotherapy-associated CRS with T cell therapeutics, and here resulted in maintained anti-tumor activity when used in combination with TAK-500, suggesting a viable potential strategy for mitigation of STING-induced immunotoxicities in patients. Citation Format: Emily Rosentrater, Michelle L. Ganno, Tiquella Hatten, Henry Mack, Arjun Reddy Bollampalli, Dong Mei Zhang, Alex Parent, Jeffrey Raizer, Richard C. Gregory, Neil Lineberry, Vicky Appleman. Preclinical impact of pretreatment with CRS mitigation agents on pharmacodynamic response to TAK-500, a systemically delivered CCR2-targeted STING agonist iADC abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 6734.