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Background: Pancreatic cancer portends a poor prognosis with ~4% long-term survival. Among the estimated 20% of patients who have resectable disease, the 1/3/5-year survival rates approximate only 70%/30%/18%, even with adjuvant therapy. Better treatment options are needed, and addition of algenpantucel-L immunotherapy to standard adjuvant therapy is proposed to improve prospects for survival. Algenpantucel-L is composed of irradiated, live, allogeneic human pancreatic cancer cells expressing the enzyme α-1,3 galactosyl transferase (α-GT), which is the major barrier to xenotransplantation from lower mammals to humans (e.g., hyperacute rejection). Up to 2% of circulating human antibodies are directed against the α-GT epitope of algenpantucel-L and are the proposed mechanism of initiating the anti-tumor immune response.
Methods: Open-label, dose-finding, multi-institutional Phase 2 study evaluating algenpantucel-L (100 or 300 million cells per dose) + standard adjuvant therapy (RTOG-9704, JAMA, 2008: gemcitabine + 5-FU-XRT) for pancreatic cancer patients undergoing R0/R1 resection. Disease-free survival (DFS) was the primary endpoint with overall survival (OS) and toxicity being secondary endpoints.
Results: 70 patients with a 21-month median follow-up received gemcitabine + 5-FU-XRT + algenpantucel-L (mean 12 doses, range 1-14). Demographics and prognostic factors: median age 62 years, 47% female, 81% lymph node positive, median tumor size 3.2 cm (range 2-15 cm; 25% > 4cm), and 17% post-operative CA 19-9 ≥ 180. The primary endpoints of median and 12-month DFS were 14.3 months and 63%, respectively, for the entire cohort. These compare favorably to rates of 11.4 months and < 50% in historical controls treated with standard adjuvant therapy alone. Subgroup analysis showed that patients receiving 300 million cells per dose had a longer 12-month DFS compared to those receiving 100 million cells per dose, 81% vs. 52% (p = 0.02). Overall survival at one year in the entire cohort was 86% and compares favorably to 69% in historical controls. Subgroup analysis showed that patients receiving 300 million cells per dose tended toward a longer OS compared to those receiving 100 million cells per dose, 96% vs. 80% (p = 0.053). As of this analysis, median overall survival has not been reached. Algenpantucel-L was well tolerated with no grade 4 or 5 adverse events. There were nine grade 3 adverse events directly or possibly due to the immunotherapy. The most common adverse events were injection site pain and induration.
Conclusion: Addition of algenpantucel-L to standard adjuvant therapy for resected pancreatic cancer may improve survival. A multi-institutional, phase 3 study began patient enrollment in May 2010.