A modified form of vitamin D may one day make pancreatic cancer respond to immunotherapy, researchers say. The drug is called paricalcitol.Pancreatic cancer is one of the deadliest cancers, with only about 13 percent of patients alive five years after diagnosis. The tumour builds a dense shield that keeps immune cells and drugs out.Writing in The Journal of Immunology, the team reports that paricalcitol softens that shield.

It reprograms the fibroblast cells that build the barrier, letting cancer-killing T cells get inside.The study was done in mouse models. In some of them, the combination with immunotherapy produced long-lasting tumour control.The researchers are planning human trials that would combine paricalcitol with existing immune drugs. They stress it is not a cure yet, and vitamin D supplements are not a substitute for the therapy being tested.

The researchers say paricalcitol alone cannot cure the cancer. Its value lies in opening the tumour to existing immunotherapy drugs.