Abstract 2997: Combination treatment with cIAP and WEE1 inhibitors exhibits synergism in HPV-positive and HPV-negative head and neck squamous carcinoma cells

Abstract Head and neck squamous cell carcinoma (HNSCC) remains a lethal and prevalent diagnosis with limited treatment options for recurrent metastatic cases, particularly in patients with sporadic, human papillomavirus (HPV) negative disease. Recently, the Human Cancer Genome Project identified cell death and NF-κB signaling alterations in a subset of HPV- and HPV+ HNSCC. Co-amplification of Fas-associated death domain (FADD) and cellular inhibitor of apoptosis protein 1 (cIAP1) was identified in HPV- HNSCC, whereas Tumor Necrosis Factor receptor-associated factor 3 (TRAF3) deletion was linked with HPV+ HNSCC. Birinapant, a cIAP inhibitor with primary affinity for cIAP1, functions as a SMAC mimetic to modulate downstream TNF death signaling and promote apoptosis. Clinical trials with Birinapant have demonstrated tolerability and favorable pharmacokinetics but limited activity as a single agent. Our lab recently demonstrated a key interaction between TNF-NF-κB signaling and the G2/M checkpoint kinase WEE1, providing a possible rationale for combination treatment targeting these pathways. We hypothesize that dual-antagonist therapy has the potential to synergistically inhibit TNF-induced canonical NF- κB pro-survival signaling, while enhancing sensitization to TNF-caspase and G2/M mitotic cell death. To investigate this, in vitro studies of Birinapant in combination with Adavosertib, a potent WEE1 inhibitor, were performed. Birinapant and Adavosertib demonstrated drug synergism to varying degrees in all HPV- and HPV+ cell lines tested, both in the presence and absence of tumor necrosis factor alpha (TNF-α), according to the Chou-Talalay method. In the majority of cell lines, synergistic drug activity, as indicated by a low combination index, was positively correlated with percent inhibition. These results were confirmed by increased levels of apoptosis as demonstrated by flow cytometry and both early and sustained cell growth inhibition over time in impedance assays. Ongoing studies include additional characterization of the downstream effects of these agents on NF-κB pro-survival signaling and the cell cycle, along with evaluation in a preclinical murine xenograft model with combined radiotherapy. Citation Format: Tiffany Toni, Ethan Morgan, Ramya Viswanathan, Xinping Yang, Hui Cheng, Carter Van Waes. Combination treatment with cIAP and WEE1 inhibitors exhibits synergism in HPV-positive and HPV-negative head and neck squamous carcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2997.