Synergy of water soluble prodrug triptolide (minnelide) with gemcitabine and nab-paclitaxel in pancreatic cancer.

Abstract

259 Background: Gemcitabine with nab-paclitaxel is the standard of care for metastatic Pancreatic Ductal Adenocarcinoma (PDAC). Addition of nab-paclitaxel to gemcitabine improves the survival of patients with metastatic pancreatic cancer by only 6 weeks while increasing toxicity. Meaningful combinations that reduce the doses while improving efficacy are required. Water soluble prodrug of triptolide (Minnelide) is effective against PDAC in preclinical studies and has demonstrated activity in the ongoing phase I trial. We have evaluated the combination of low dose triptolide prodrug with lowered doses of Abraxane and gemcitabine in PDAC. Methods: Pancreatic cancer cell lines S2-013 and S2-VP10 were xenografted both subcutaneously as well as orthotopically in athymic nude mice. Efficacy of a combination of triptolide prodrug (Minnelide: 0.21mg/kg) with reduced dose of gemcitabine 100mg/kg + Abraxane 10mg/kg (~40% of the clinically effective dose) was evaluated and compared with both standard of care gemcitabine 250mg/kg + Abraxane 25mg/kg as well as reduced dose of gemcitabine + Abraxane in animal models. We also used the immunocompetent model where murine PDAC cell line KPC001 implanted subcutaneously in C57/bl6 mice. Results: In subcutaneous syngeneic model, combination of triptolide prodrug and paclitaxel significantly inhibited tumor growth (tumor volumes expressed as % of Control, Mean±SEM: triptolide prodrug: 75.4±25, paclitaxel: 50.0 ±3, triptolide prodrug + paclitaxel: 11.0 ±1). In metastasis model combination therapy markedly improved survival (median survival in days: Vehicle-13, triptolide prodrug -20, standard of care -45, reduced dose standard of care-30, and Minnelide + reduced dose standard of care (all mice alive at 90 days). Combination of triptolide prodrug and low dose gemcitabine + nab-paclitaxel decreased tumor size, increased survival, reduced metastases and malignant ascites in orthotopic model of PDAC. Conclusions: Triptolide prodrug synergizes with reduced dose standard of care (gemcitabine and nab-paclitaxel) and helps in reducing the doses of these toxic drugs all the while achieving same or better efficacy in animal models of PDAC.