Tremelimumab in Combination With Microwave Ablation in Patients With Refractory Biliary Tract Cancer

Abstract

Treatment options for patients with advanced biliary tract cancer are limited. Dysregulation of the immune system plays an important role in the pathogenesis of biliary tract cancer (BTC). This study aimed to investigate whether tremelimumab, an anti-CTLA4 (cytotoxic T-lymphocyte-associated protein 4) inhibitor, could be combined safely with microwave ablation to enhance the effect of anti-CTLA4 treatment in patients with advanced BTC. Patients were enrolled to receive monthly tremelimumab (10 mg/kg, intravenously) for six doses, followed by infusions every 3 months until off-treatment criteria were met. Thirty-six days after the first tremelimumab dose, patients underwent subtotal microwave ablation. Interval imaging studies were performed every 8 weeks. Adverse events (AEs) were noted and managed. Tumor and peripheral blood samples were collected to perform immune monitoring and whole-exome sequencing (WES). Twenty patients with refractory BTC were enrolled (median age, 56.5 years). No dose-limiting toxicities were encountered. The common treatment-related AEs included lymphopenia, diarrhea, and elevated transaminases. Among 16 patients evaluable for efficacy analysis, 2 (12.5%) patients achieved a confirmed partial response (lasting for 8.0 and 18.1 months, respectively) and 5 patients (31.3%) achieved stable disease. Median progression free survival (PFS) and overall survival (OS) were 3.4 months (95% confidence interval [CI], 2.5-5.2) and 6.0 months (95% CI, 3.8-8.8), respectively. Peripheral blood immune cell subset profiling showed increased circulating activated human leukocyte antigen, DR isotype ([HLA-DR] positive) CD8⁺ T cells. T-cell receptor (TCR)β screening showed tremelimumab expanded TCR repertoire, but not reaching statistical significance (P = 0.057). Conclusion: Tremelimumab in combination with tumor ablation is a potential treatment strategy for patients with advanced BTC. Increased circulating activated CD8⁺ T cells and TCR repertoire expansion induced by tremelimumab may contribute to treatment benefit.

Figure 1:. Efficacy data from study population.

(A) Spider plot from left to right tracks the change in the overall disease burden of patients on treatment, and the rise or fall in the line represents a relative increase or decrease, respectively, in the overall size of measurable “target” lesions on imaging for each patient. These lines demonstrate the variability of the patterns seen, as well as the potential for prolonged response that may be of delayed onset. (B) Waterfall plot of all radiographic responses. Tumor responses were measured at regular intervals and values show the best fractional change of the sum of longest diameters from the baseline measurements of each measurable tumor. (C) Swimmer plot showed time on study and response status. The arrow indicates patients still alive. Gray represents as unevaluable case, black as progressive disease case, blue as stable disease case, red as partial response case. (D) Tumor marker CA 19.9 level change of patients during the treatment and follow-up.

Figure 2:. Patient survival to CTLA-4 blockade and microwave ablation

(A) PFS and (B) OS was assessed by Kaplan-Meier

Figure 3:. Immune cell profiling determined by flow cytometry

(A) Significantly increased HLA-DR positive CD8+ T cells at D28 compared with D0 (P=0.0002) as well as D56 compared with D0 (P=0.046). Horizon line represented median. (B) Suppressed 4–1BB–positive CD8 T cell count after the treatment (P=0.012 and P=0.038). Horizon line represented median. (C) Comparison of the change of immune cell profiling between BTC and HCC cohort treated with CTLA-4 blockade and microawave ablation. Bar represented upper and lower limit of cell count of individual subset and dot symbol as mean.

Figure 3:. Immune cell profiling determined by flow cytometry

(A) Significantly increased HLA-DR positive CD8+ T cells at D28 compared with D0 (P=0.0002) as well as D56 compared with D0 (P=0.046). Horizon line represented median. (B) Suppressed 4–1BB–positive CD8 T cell count after the treatment (P=0.012 and P=0.038). Horizon line represented median. (C) Comparison of the change of immune cell profiling between BTC and HCC cohort treated with CTLA-4 blockade and microawave ablation. Bar represented upper and lower limit of cell count of individual subset and dot symbol as mean.

Figure 4.. Data of patient #2

(A) Clinical events. Upper panel showed the timeline of clinical events, including therapy and disease status. Lower panel shows representative axial CT images at baseline, 2 months, 3 months, 5 months and 15 months after the tremelimumab infusion initiated. Arrow indicates liver abscess, confirmed with biopsy. (B–C): Representative H/E staining of biopsied tumor samples determined by immunohistochemistry (200x) (B: liver metastasis of putative ampullary carcinoma showed a moderately differentiated adenocarcinoma with minimal inflammatory infiltrate. C: follow-up liver biopsy of tissue near cyst. Only necrotizing granulomas were seen. There was no normal hepatic parenchyma and no tumor). (D): Heatmap based on immune cell signatures from RNA-seq. AC represents Patient #2 (arrow). (E): A Circos plot showed germline (Blue) and somatic (Black) mutation landscape for whole genome sequenced sample from one cholangiocarcinoma patient.

Figure 4.. Data of patient #2

(A) Clinical events. Upper panel showed the timeline of clinical events, including therapy and disease status. Lower panel shows representative axial CT images at baseline, 2 months, 3 months, 5 months and 15 months after the tremelimumab infusion initiated. Arrow indicates liver abscess, confirmed with biopsy. (B–C): Representative H/E staining of biopsied tumor samples determined by immunohistochemistry (200x) (B: liver metastasis of putative ampullary carcinoma showed a moderately differentiated adenocarcinoma with minimal inflammatory infiltrate. C: follow-up liver biopsy of tissue near cyst. Only necrotizing granulomas were seen. There was no normal hepatic parenchyma and no tumor). (D): Heatmap based on immune cell signatures from RNA-seq. AC represents Patient #2 (arrow). (E): A Circos plot showed germline (Blue) and somatic (Black) mutation landscape for whole genome sequenced sample from one cholangiocarcinoma patient.