Abstract 5465: Immune cell dynamics of patients and mice with hepatocellular carcinoma treated with anti-PD-L1 plus anti-CTLA-4 combination therapy

Abstract Background: Hepatocellular carcinoma (HCC) is one of the major causes for cancer-related death. Single agent immunotherapy or combined immunotherapy have become the standard of care in advanced HCC. Recently, the combination of durvalumab (dur) plus a single dose of 300 mg tremelimumab (trem) (STRIDE regimen) have received FDA approval based on results from the HIMALAYA trial. However, immune responses have not been studied in detail. We tested the combination of 4 × 75 mg trem plus dur and locoregional therapies in HCC at and conducted correlative studies. Methods: We enrolled 28 patients with biopsy proven advanced HCC in an open-labeled phase 2 trial using dur and trem combined with ablative therapies (NCT02821754). Patients received four doses of 75mg trem every 4 weeks and 1500mg dur every 4 weeks until progression. Patients underwent an interventional radiologic procedure (RFA/TACE) on day 36. Peripheral blood mononuclear cells (PBMC) and serum from patients enrolled were collected at baseline and after 1 cycle (day 28). PBMC was analyzed by multicolor spectral cytometry using a 17 antibody pan immune cell panel and a 25 antibody T cell panel. Serum samples from patients were collected at baseline and on day 28. Serum samples were analyzed with a 34-plex cytokine/chemokine array. Mice with orthotopically injected HCC (RIL-175 and Hep55.1C) were treated with anti-PD-L1 plus anti-CTLA4 and followed for tumor responses. Hepatic lymphocytes, tumor infiltrating lymphocytes (TILs), and splenocytes were analyzed by spectral cytometry from mice treated with immune checkpoint inhibitors. Results: 28 patients with advanced HCC were enrolled in this study. The best clinical response for treatment was the following, partial response (PR, n=5), stable disease (SD, n=12), progressive disease (PD, n=8), and not evaluable (n=3). Median PFS and OS were 4.5 and 20.8 months respectively. Patient PBMC analysis demonstrated an increase of regulatory T cells 1.65 times from baseline after 28 days in all patients. The frequency of Tbet+CD4+ T cells showed a non-significant increase in patients demonstrating a PR. Serum cytokine analysis revealed the levels of IL-18, IL-10, CCL-2, and VEGF-a increased in responders after treatment. in contrast, an increase of IL-6 and TNF-alpha after treatment was found only in patients with PD. In animal experiments, the size of liver tumors treated with anti-PDL1 and anti-CTLA4 were significantly smaller than that with isotype controls. The lymphocytes in the adjacent livers and tumor-infiltrating lymphocytes (TILs) were analyzed. PD1+CD8+ T cells and Tbet+CD4+ T cells in the liver and TILs increased with combination treatment. Conclusion: Anti-PD-L1 and anti-CTLA4 combination therapy have an anti-tumor effect on HCC. We observed an expansion of PD1+ CD8+ T cells and Tbet+ CD4+ T cells. Citation Format: Yuta Myojin, Benjamin Ruf, Mohamed-Reda Benmebarek, Kylynda Bauer, Rajiv Trehan, Kelley Coffman, Chi Ma, Cecilia B. Monge, Changqing Xie, Tim Greten. Immune cell dynamics of patients and mice with hepatocellular carcinoma treated with anti-PD-L1 plus anti-CTLA-4 combination therapy. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5465.