Abstract LB400: Identification of potential biomarkers and immune characteristics in patients with non-small cell lung cancer treated with CJRB-101 plus pembrolizumab

Abstract Background: Gut microbiota is associated with efficacy of immune checkpoint inhibitors. We aim to identify immune characteristics and biomarkers between the six clinical benefit samples (CB; PR + SD) and the six non-clinical benefit samples (NCB; PD) from patients with stage III/IV non-small cell lung cancer. The patients were either treatment naïve or had relapsed after prior immune checkpoint inhibitor treatment and were treated with combination of CJRB-101, a live biotherapeutic product containing a Leuconostoc mesenteroides strain, and pembrolizumab in an ongoing phase 1 trial. Methods: Peripheral blood mononuclear cells (PBMCs) and tumor formalin-fixed, paraffin-embedded (FFPE) samples were obtained from 12 patients. PBMCs were analyzed using flow cytometry, and FFPE samples through bulk RNA sequencing and multiplex IHC to identify unique differences among clinical outcomes. Results: The biological pathway analysis using bulk RNA sequencing of baseline tumor FFPE samples (N=10) from CB and NCB groups revealed that T cell activation, response to cytokine (adaptive immunity) and innate immune response were significantly increased in CB group compared to NCB group. Of note, the canonical T cell activation genes (PRF1, GZMB), inflammation genes (PYCARD, TLR8) and the target of pembrolizumab, PDCD1 (PD-1), were significantly higher in the CB group compared to NCB group (P <0.05). Similarly, in the baseline PBMCs samples (N=12), the proliferation marker Ki-67 was significantly higher in CD8 (P=0.004) and CD4 (P=0.002) T cells and NK cells (P=0.018) in CB group compared to NCB group. Additionally, NK cells showed elevated IFN-γ expression (P=0.018). Next, to investigate the pharmacodynamics, we compared C1D1 (pre-treatment) and C2D1 (post-treatment) samples. A significant decrease in PD-1+Tim-3+ CD4 (P=0.002) and CD8 (P=0.006) T cells was exhibited in CB group compared to NCB group. In particular, a longitudinal decrease in PD-1+Tim-3+ T cells was observed. However, no significant longitudinal differences were observed in innate cells. To validate the characteristics of infiltrated T cells in matched tissues (N=6), we conducted a multiplex IHC analysis. An increase in infiltrated GZMB+ CD8 T cell was observed in CB group, while regulatory CD4 T cell (CD4 Treg) was decreased in the CB group compared to the NCB group. As a result, (CD4 Treg / GZMB+ CD8 T cell) ratio revealed lower levels in CB group than in NCB group. To evaluate the effects of CJRB-101, we conducted in vitro assays, demonstrating an increase in macrophage antigen-presenting machinery (P<0.05) and enhanced phagocytosis (P<0.05). Conclusion: We demonstrated that clinical response to CJRB-101 plus pembrolizumab and its association with enhanced macrophage function, increased GZMB+ T cell, and reduced Treg. Further analysis is in progress with additional clinical samples. Citation Format: Arim Min, Bo-Eun Kwon, Dong Kwon Kim, Hyunkyung Park, Jieun Im, Hyunjeong Kim, Jaemin Kim, Ji-Eun Kwon, So-Yeong Kang, Sujeong Baek, So Young Park, Jii Bum Lee, Jae Hwan Kim, Byoung Chul Cho. Identification of potential biomarkers and immune characteristics in patients with non-small cell lung cancer treated with CJRB-101 plus pembrolizumab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB400.