A new drug that uses the body's immune system to fight metastatic melanoma, called Keytruda, was developed by Merck pharmaceuticals and approved Thursday by US regulators.
Also known as pembrolizumab, the drug is the sixth new therapy to be approved against the deadly skin cancer since 2011, the US Food and Drug Administration said.
"Keytruda is the first approved drug that blocks a cellular pathway known as PD-1, which restricts the body's immune system from attacking melanoma cells," the FDA said in a statement.
"Keytruda is intended for use following treatment with ipilimumab, a type of immunotherapy."
More than 76,000 Americans are diagnosed with melanoma each year and nearly 10,000 die, the agency said.
The Melanoma Research Alliance described the approval as a "major breakthrough" and noted that 69 percent of melanoma patients treated with pembrolizumab were alive after one year.
"The news of FDA's first approval of an anti-PD-1 drug is extremely exciting and shows just how far the field has come in the last few years," said Debra Black, MRA co-founder and chair of the board.
"Today we are seeing a real sea change, with several new therapies and proof of concept that these new treatments can save lives."
The other recent FDA approvals for melanoma include ipilimumab (2011), peginterferon alfa-2b (2011), vemurafenib (2011), dabrafenib (2013), and trametinib (2013).
Keytruda was granted a breakthrough therapy designation and an accelerated review by the FDA because of "preliminary clinical evidence that the drug may offer a substantial improvement over available therapies," the FDA said.
Tom Stutz, a patient whose melanoma had spread throughout his body, was among those who enrolled in a clinical trial at the University of California, Los Angeles (UCLA).
"The drug saved my life, that is the bottom line," he said.