Paricalcitol shows tumor microenvironment effects in small pancreatic cancer trial

A randomized clinical trial published in Nature Cancer evaluated adding the vitamin D analog paricalcitol to gemcitabine plus nab-paclitaxel in 36 patients with previously untreated metastatic pancreatic cancer. Participants received chemotherapy with placebo, intravenous paricalcitol, or oral paricalcitol. The primary objective was safety, with tumor biopsies assessing whether vitamin D receptor activation could modify the tumor microenvironment.

The combination was generally administrable, although five of 12 patients receiving oral paricalcitol developed hypercalcemia, managed with dose reductions. Biopsies collected at baseline and after four to six weeks showed reduced fibroblast activation, without reduced fibroblast numbers, and increased T-cell infiltration with paricalcitol.

Partial responses occurred in 10 of 24 patients receiving paricalcitol (42%), compared with one of 12 receiving placebo. Five paricalcitol-treated patients remained progression-free at one year, versus none receiving placebo. Among paricalcitol recipients, high tumor vitamin D receptor levels were associated with better chemotherapy responses and the longest overall survival; numerical survival estimates were not provided in the source.

These findings suggest biological activity but do not establish clinical benefit. The small trial was not designed to compare efficacy or determine whether paricalcitol extends survival. Larger trials are needed to confirm outcomes and evaluate vitamin D receptor expression as a predictive biomarker. This account is based on Salk Institute material summarized by ScienceDaily; paricalcitol’s existing FDA approval concerns secondary hyperparathyroidism in chronic kidney disease, not pancreatic cancer.