"This study uses vitamin D analogs to engage the body's natural system for dampening fibrotic and inflammatory responses." – Ronald Evans, PhD, Salk Institute

Rewiring the Tumor’s Defenses: Vitamin D Analog Shows Promise in Pancreatic Cancer Trial

A Phase I/II clinical trial led by Dana-Farber Cancer Institute researchers has tested a novel approach to treating pancreatic cancer: activating the vitamin D receptor to modify the tumor’s microenvironment.

The randomized, safety-focused trial enrolled 36 patients with previously untreated metastatic pancreatic cancer. All patients received standard chemotherapy (gemcitabine plus nab-paclitaxel) alongside either a placebo, intravenous paricalcitol, or oral paricalcitol.

Safety and Mechanistic Validation

Paricalcitol, an FDA-approved vitamin D analog, was found to be safe when combined with chemotherapy. Notably, five of the 12 patients receiving oral paricalcitol experienced manageable hypercalcemia.

Paired biopsies provided a critical validation of preclinical findings. The trial demonstrated that paricalcitol reduced fibroblast activation and increased T cell infiltration within the tumor, confirming the hypothesis that the drug could remodel the tumor's supportive tissue.

Encouraging Efficacy Signals

While the study was not designed to measure efficacy, the results were notable. The response rate was 42% in the paricalcitol group versus 9% in the placebo group. Furthermore, five patients receiving paricalcitol showed progression-free survival at one year, compared to zero patients in the placebo group.

Patients with high vitamin D receptor expression who received paricalcitol experienced the longest overall survival.

Scientific Background

The research traces its origins to Ronald Evans' discovery of the nuclear receptor superfamily and the vitamin D receptor’s role in regulating fibroblasts in the liver and pancreas. Preclinical models had shown that vitamin D analogs could reverse cancer-associated fibroblast activation and enhance chemotherapy.

This is particularly relevant because pancreatic tumors are characterized by a dense, fibrotic microenvironment that contributes to therapeutic resistance.

Next Steps

• Larger clinical studies are now needed to evaluate the impact on survival outcomes.
• Further research should test whether baseline vitamin D receptor expression can serve as a biomarker for patient response.

Kimberly Perez, MD, co-lead of the trial, described the study as "an important step forward for stromal remodeling therapy."

The study was published in Nature Cancer on May 25, 2026, and was funded by federal grants and private foundations.