A new drug targeting the deadliest form of skin cancer has helped some patients live for at least three years, according to a new study. Take it from former U.S. President Jimmy Carter himself, whose melanoma has spread to the brain.

Around 40 percent of melanoma patients in the study on Merck drug Keytruda stayed alive after three years. The medication, part of a new class of genetically engineered antibody-based drugs, blocks proteins that prevent the immune system from destroying cancer cells.

Also known as pembrolizumab, Keytruda is an immunotherapeutic approach that transforms treatment for several cancer types using drugs that are usually less toxic than chemotherapy.

“This is incredible. I spend my time telling my residents that these patients would be dead if it was five years ago,” study lead author Dr. Caroline Robert said in an AP report of the results released Wednesday.

Carter received Keytruda as one of his treatments after his 2015 diagnosis. Last weekend, the 91-year-old was spotted helping give an honorary humanities degree to rock personality Gregg Allman at Mercer University, where he stays a trustee.

The latest findings on 655 patients showed a 40 percent survival rate at three years as well as an 85 percent cancer-free rate. The study was a follow-up to one previously conducted and leading to the drug’s approval for advanced melanoma back in 2014.

Last December, Merck announced the promising performance of Keytruda for advanced lung cancer in its second set of results from a three-phase trial.

Another drug demonstrated the same positive results and seeming advantage over older oncology treatments. Bristol-Myers’ Opdivo drug was also shown to prolong the life of a significant number of patients afflicted with advanced lung cancer by at least two years.

Like Keytruda, Opdivo is part of the first wave of immune-oncology medications with a list price of around $150,000 per year, also blocking the PD-1 protein that tumors use for evading detection by the immune system. It was approved Tuesday for Hodgkin lymphoma as well.

Further, an experimental drug from Pfizer assisted the immune system in a small clinical trial. Utomilumab, targeting the antibody 4-1BB, incited an intense immune system attack, reflecting encouraging results early on against a blood cancer type when used alongside Roche’s Rituxan.

All new data will be presented at the American Society of Clinical Oncology’s annual meeting next month in Chicago.

Photo: Ed Uthman | Flickr