Shares of Bristol-Myers Squibb Inc. and Merck & Co. are up about 5 percent each after the drugmakers announced encouraging results on experimental cancer medicines over the weekend.

Both companies’ drugs for advanced cases of melanoma are in a new class that helps the patient’s immune system identify and destroy tumor cells that otherwise would evade detection.

And both drugs are part of a promising new area of cancer research called immuno-oncology in which drugs rev up the patient’s immune system to fight their cancer, rather than killing cancer and healthy cells, as chemotherapy does.

Industry analysts say such drugs could become the new standard for treating many cancer types.

In midday trading, Bristol-Myers shares were up 5.7 percent at $48.61, while Merck shares were up 4.7 percent at $48.90.