A drug previously approved to treat different skin cancers recently got a Food and Drug Administration greenlight to treat a few more.

Dr. Davor Vugrin, a hematologist and oncologist in Lubbock, said Keytruda already proved to be effective against several skin cancers. The FDA’s approval now includes treatment for types of colorectal cancer, gastrointestinal cancer, breast cancer, prostate cancer, bladder cancer, thyroid cancer and more.

The FDA granted an accelerated approval of Keytruda in May to treat tumors that originate from specific genetic biomarkers.

A press release from the FDA says about 39.6 percent of the 149 patients who participated in clinical trials for Keytruda showed a complete or partial tumor shrinkage. The response lasted for six months or more for about 78 percent of those patients, according to the press release.

“It’s quite an exciting drug,” Vugrin said.

Cancer treatment drugs have traditionally been approved by the FDA based on their location on the body, Vugrin said. This is the first time a drug has received FDA approval based on a genetic feature.

Dr. Patrick Reynolds, professor and director of the cancer center for the Texas Tech’s Health Sciences Center, said the accelerated approval means responses in the clinical trials were favorable.

It’s not unusual for drugs to be placed in the accelerated approval track, he said. Keytruda is unique.

It works by targeting the root of a genetic-based cancer and blocks T cells in the body from allowing it to replicate, he said.

T cells are an essential part of the immune system, Reynolds said.

“T cells are the immune cells in our body that recognize cells that are not supposed to be there,” he said. “If you transplant tissue from somebody else in you, that’s what’s going to reject it.”

When a mutation slips into a DNA strand, it often leads to cancer, he said.

“When we get mutations, you don’t usually get Wolverine or X-Men,” Reynolds said. “You get cancer.”

That’s why T cells are important in controlling cancers, he said.

Vugrin said Keytruda targets the T cells and makes them aware of the cancer and blocks them from aiding in the production of more cancer cells.

“The basic mechanism of how it works is by sort of helping the immune system to fight the cancer cell,” Vugrin said.

Keytruda has been effective in treating skin cancers like melanoma, he said. It’s also been approved to treat lung cancers and colorectal cancers.