Abstract 1377: The role of TIM3 and PD1 blockades in head and neck cancer

Abstract Background: Our group has recently developed and validated a novel prognostic score for human papillomavirus (HPV+) oropharyngeal cancer called UWO3, which stratifies patients into low risk (immune rich), intermediate risk (immune mixed), and high risk (immune desert) groups. The high-risk immune desert group had a paucity of immune cells, however, that population of lymphocytes expressed high levels of the checkpoint molecule TIM3. To follow up on this, we assessed the therapeutic effect of anti-TIM3 mAb alone and in combination with anti-PD-1 in a syngenic murine HPV+ head and neck cancer model using the mERR. T-cell immunoglobulin mucin 3 (TIM3) and Programmed death 1 (PD-1) are negative immune checkpoint receptors that are expressed on tumor-infiltrating lymphocytes (TIL), play a crucial role in tumor-induced immune suppression. Given the critical role that the tumour microenvironment (TME) has on the prognosis of head and neck squamous cell carcinoma (HNSCC), immune checkpoint inhibitor immunotherapy approaches, specifically anti-PD1 and/or anti-TIM3 antibody therapy, may be very effective treatment strategies and may offer improved survival outcomes. Methods:Immunocompetent C57BL/6 mice were injected in one flank with the syngeneic mouse HPV+ cell line, mEERL (106 cells), for tumour generation. Mice were then treated with either IgG2a isotype control, anti-PD1 (200μg), anti-TIM3 (200 μg) antibodies or a combination of anti-PD-1 and anti-TIM3 were administered via intraperitoneal injection 3 times per week following tumour establishement for 6 weeks (n = 7 mice per arm, total of 28 mice). Tumour volumes were measured every 2 days. Three representative tumors from each treatment group were collected for bulk RNA sequencing, scRNA-seq, and flow cytometry to characterise immune cell populations and transcriptional changes and monitor their impact on the TME of HNSCC. Results:Anti-PD1 and anti-TIM3 both restricted tumour growth by size and weight relative to the IgG2a control (p<0.01, linear mixed model [lmm]). The combination of anti-PD1 and anti-TIM3 was more effective than either monotherapy alone (p<0.05, lmm). RNA sequencing analysis revealed differential abundance in CCL6, CCL9, CFD, and MAP3K5 transcripts relative to control for anti-PD1, anti-TIM3, and combination checkpoint inhibition. Conclusion:Targeting both PD-1 and TIM3 enhanced the anti-tumor immune response in HPV+ head and neck tumours, providing further support for dual targeting of these molecules for more effective cancer immunotherapy. Our results suggest that immune checkpoint inhibitor therapy (PD1 and TIM3 blockades) could be a promising treatment strategy for HPV+ HNSCC, and the expression of these immune checkpoint molecules could serve as a predictive biomarker of patient outcome in HPV+ HNSCC. Citation Format: Mushfiq Shaikh, Amir Karimi, Peter Zeng, Harrison Pan, John Barrett, Anthony Nichols. The role of TIM3 and PD1 blockades in head and neck cancer [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(6_Suppl):Abstract nr 1377.