Vitamin D Receptor Agonist Paricalcitol Plus Gemcitabine And Nab-Paclitaxel In Patients With Metastatic Pancreatic Cancer

TPS784 Background: Patients(pts) with metastatic pancreatic cancer (PC) have a median survival of less than one year even with use of multiagent chemotherapy programs. Pancreatic tumors are composed of multiple cell types and a dense extracellular matrix that may support cancer cell proliferation and impede chemotherapy delivery. Cancer-associated fibroblasts (CAF’s) in the tumor microenvironment secrete pro-inflammatory factors and components of the extracellular matrix. In PC laboratory models, engagement of the vitamin D receptor (VDR) by VDR agonists shifts CAFs toward a more quiescent phenotype with reduced tumor growth and improved chemotherapy penetration (Sherman. Cell, 2014). Paricalcitol is a synthetic VDR agonist used in patients with secondary hyperparathyroidism due to chronic kidney disease. A prior pilot study evaluated IV paricalcitol with gemcitabine (G) and nab-paclitaxel (A) before surgical resection in patients with resectable PC (NCT02030860). Methods: Pts with previously-untreated metastatic PC will be enrolled in a two-stage study consisting of a safety run-in and a randomized phase 2 study (NCT03520790). In the run-in stage, 36 pts will be randomized 1:1:1 to G (1000 mg/m2) and A (125 mg/m2) given 3 weeks on and 1 week off plus: (a) paricalcitol 25mcg IV thrice weekly, (b) paricalcitol 16mcg oral daily, or (c) placebo oral daily. Grade 3/4 hypercalcemia or genitourinary stones will be considered dose limiting toxicities.Pts will undergo paired pre- and on-treatment tumor biopsies to examine pharmacodynamic (PD) markers by bulk and single cell RNA sequencing and multiplex immunofluoresence.Assuming safety and supportive PD assessments, the phase 2 study will randomize an additional 76 pts to two treatment arms with GA plus: (a) paricalcitol or (b) placebo.Paricalcitol formulation (IV or oral) will be determined based on data from the run-in stage.The primary endpoint of the phase 2 study is overall survival, with a total of 100 pts needed to identify a hazard ratio of 0.6 with 80% power and one-sided alpha of 0.10.Secondary endpoints include safety, response rate, and progression free survival.Trial funding provided by SU2C, CRUK,Lustgarten Foundation, and AACR. Clinical trial information: NCT03520790.