Abstract A016: Phase 1 study of hypofractionated radiation in combination with tremelimumab and durvalumab in refractory metastatic pancreatic adenocarcinoma
Authors: O'Hara Mark H. , Bear Adham S. , Wattenberg Max M. , Teitelbaum Ursina R. , Reiss Kim A. , Karasic Thomas B. , Schneider Charles J. , O'Dwyer Peter J. , Ben-Josef Edgar H. , Wojcieszynski Andrzej P. , Maity Amit H. , Mick Rosemarie H. , Vonderheide Robert H. 
Published: November 2022

Immune checkpoint inhibitors have limited clinical activity in pancreatic cancer. Based on preclinical data, we hypothesized that hypofractionated radiation may cooperate with dual checkpoint inhibition in patients (Rech AJ, et al, Cancer Research, 2018). We therefore designed a phase 1 study to evaluate the safety and feasibility of two schedules of hypofractionated radiation with durvalumab (anti-PDL1) and tremelimumab (anti-CTLA-4) in patients with metastatic pancreatic, lung, and breast cancers and melanoma. Here, we present the data for pancreatic adenocarcinoma. Methods: Patients with metastatic pancreatic cancer treated with at least one prior line of therapy with measurable disease by RECIST in addition to an index lesion amenable to hypofractionated radiation were enrolled sequentially to two cohorts – cohort A evaluating 3 fractions of 8 Gy or cohort B evaluating 1 fraction of 17 Gy. Patients received 4 cycles of tremelimumab 1 mg/kg IV and durvalumab 20 mg/kg IV every 4 weeks for 4 doses followed by durvalumab 10 mg/kg IV every 2 weeks until progression. Radiation was given in week 2 of treatment. Patients were replaced if they did not receive week 5 of therapy on trial, but were included in safety/feasibility analysis. Blood and, when feasible, baseline and on-treatment biopsies were obtained for exploratory biomarker evaluation. Results: 10 patients were treated in cohort A and 21 patients in cohort B. All patients were included in the safety and feasibility assessment. Overall, treatment was well tolerated in both cohorts. The most common adverse events were grade 1 or 2 fatigue (A 30%, B 23.8%), diarrhea (A 10%, B 14.3%), pruritis (A 10%, B 14.3%), AST/ALT elevation and constipation (each A 10%, B 9.5%). Grade 3 diarrhea, elevated bilirubin, pneumonitis, and syncope were noted in 1 patient each, all in cohort B. Grade 5 pneumothorax occurred after baseline biopsy in 1 patient. Grade 2 hyperthyroidism (A) and pneumonitis (B) were noted each in 1 patient. 8 patients in cohort A and 13 patients in cohort B were evaluable for response. In cohort A, 50% of patients had stable disease as best response, and median overall survival was 4.9 months. In cohort B, 23.1% had PR and 30.8% had SD as best response and mOS was 5.2 months. Responses occurred more frequently when metastatic lung nodules were radiated – SD in 3/5 (60%) patients in cohort A, PR in 3/10 (30%) and SD in 4/10 (40%) patients in cohort B, compared to SD in 1/3 (33%) patients in cohort A and 0/3 (0%) patients in cohort B who underwent radiation to a liver lesion. Biomarker analysis will be presented. Conclusions: The combination of durvalumab, tremelimumab with hypofractionated radiation is safe and feasible in a refractory pancreatic adenocarcinoma patient population. Encouraging clinical activity warrants further evaluation, especially when hypofractionated radiation is delivered to lung nodules.

Citation Format: Mark H. O'Hara, Adham S. Bear, Max M. Wattenberg, Ursina R. Teitelbaum, Kim A. Reiss, Thomas B. Karasic, Charles J. Schneider, Peter J. O'Dwyer, Edgar H. Ben-Josef, Andrzej P. Wojcieszynski, Amit H. Maity, Rosemarie H. Mick, Robert H. Vonderheide. Phase 1 study of hypofractionated radiation in combination with tremelimumab and durvalumab in refractory metastatic pancreatic adenocarcinoma [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A016.