Abstract CT182: Neoadjuvant cemiplimab demonstrates complete pathological responses in hepatocellular carcinoma

Introduction: Hepatic resection is the accepted treatment of early-stage hepatocellular carcinoma (HCC), however, the majority of tumors recur despite surgery and no perioperative intervention has demonstrated a survival advantage. Neoadjuvant immunotherapy has shown success in inducing pathological responses alongside induction of immune memory in multiple tumor types and is being evaluated to determine its potential in HCC. Methods: We recently completed accrual into a trial of perioperative cemiplimab (anti-PD-1) for resectable HCC (NCT03916627, Cohort B). This trial enrolled 21 patients to receive 2 cycles of neoadjuvant cemiplimab (350 mg Q3W) followed by surgical resection and an additional 8 adjuvant cycles. The primary endpoint was significant tumor necrosis, defined as >70% necrosis of the resected tumor. Secondary endpoints included delay of surgery, overall response rate, adverse events (AEs), and change in lymphocyte infiltration. Patients underwent pre-treatment biopsies and regular blood collection throughout treatment to enable exploratory analyses including multiplex IHC and single-cell proteomic and transcriptomic analysis. The final patient enrolled underwent resection on December 28, 2020. Results: Over the course of 18 months, 21 patients were enrolled. All patients received 2 cycles of preoperative cemiplimab, and all but 1 patient underwent successful resection; 1 patient was found to have metastatic disease at the time of surgery and resection was aborted. Cemiplimab demonstrated an acceptable risk-benefit profile: 90.5% of patients experienced any treatment-emergent AE (TEAE) of any grade during the neoadjuvant treatment period through the perioperative period; 28.6% of patients experienced any Grade 3 TEAE. One patient experienced Grade 3 pneumonitis during neoadjuvant therapy and surgery was delayed by 2 weeks past protocol defined surgical window. Of the 20 patients with resected tumors, 4 (20%) met the predefined endpoint of >70% tumor necrosis and 7 (35%) had ≥50% tumor necrosis. Three (15%) of the 4 patients with >70% tumor necrosis had a pathological complete response, defined as 100% tumor necrosis. We observed similar patterns of change in degree of necrosis on pathological assessment and 3D MRI at baseline and following completion of immunotherapy. Initial pathological assessment suggests an association between immune cell infiltration and tumor response. Tissue analysis is ongoing and multiplex IHC relating myeloid and lymphoid infiltration patterns with response to cemiplimab will be presented at the meeting. Conclusion: This is the largest trial reported to date of neoadjuvant PD-1 targeted monotherapy in HCC. Pathological response data support larger trials to identify optimal clinical endpoints that correlate with improvement in survival, and to establish the utility and safety of perioperative PD-1 blockade. Citation Format: Thomas Urban Marron, Ganesh Gunasekaran, Parissa Tabrizian, Edward Kim, Maria Isabel Fiel, Stephen Ward, Zhen Zhao, Deborah Doroshow, Meredith Legg, Ashley Hammad, Paul Kennedy, Guray Akturk, Pauline Hamon, Antoinette Bonaccorso, Daniel Labow, Sacha Gnjatic, Bachir Taouli, Elizabeth Miller, Pradeep Thanigaimani, Nathalie Fiaschi, Jennifer Sims, Jayakumar Mani, Nicola James, Sara Hamon, Vladimir Jankovic, Siyu Li, Hung Kam Cheung, Gavin Thurston, Israel Lowy, Myron Schwartz, Miriam Merad. Neoadjuvant cemiplimab demonstrates complete pathological responses in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT182.