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CHICAGO -- Two studies indicate that using investigative immunotherapy drugs improves survival and response in patients with metastatic melanoma, researchers said here.

In one study, the agent pembrolizumab (MK-3475) which targets the programmed death (PD-1) pathway produced a 1-year 69% survival rate, said , professor of medicine at the UCLA Jonsson Comprehensive Cancer Center in Los Angeles.

In a second study reported in a press conference at the annual meeting of the American Society of Clinical Oncology, , professor of medicine at the Yale Cancer Center, demonstrated that a combination of the investigative PD-1 inhibitor nivolumab in combination with another targeted agent ipilimumab (Yervoy) produced a 1-year survival rate of 85% and 2-year survival rate of 79% for advanced melanoma patients.

"PD-1-blocking antibodies unleash an immune response against cancer by releasing a brake on antitumor T cells," Ribas explained in his presentation. Basically, he explained, the cancer cells throw up a stop sign which is obeyed by anticancer cells; pembrolizumab and other PD-1 inhibitors remove that stop signal, allowing the immune system cells to attack the tumor.

And with pembrolizumab, the effect was great enough that after more than 2 years of treatment, the median overall survival figure had not been reached, Ribas said. He illustrated that tumor reductions were observed in 72% of patients; and in 88% of patients who achieved objective responses the achieved response was durable and was ongoing.

Overall, Ribas said there was a 34% objective response to treatment based on RECIST (Response Evaluation Criteria In Solid Tumors) criteria. That included a 40% objective response rate to patients who had not been treated with ipilimumab; a 44% objective response to patients who were previously untreated with any regimen, and a 28% response rate among patients previously treated with ipilimumab.

"This is probably the biggest phase I trial ever conducted in oncology. We were excited to see that pembrolizumab was effective in previously untreated patients as well as in those who had multiple prior therapies, including ipilimumab," said Ribas. "These are early data, but they tell us we are on to something really important."

The study enrolled 221 patients with prior ipilimumab treatment and 190 patients who had not previously received ipilimumab. All patients had advanced melanoma that had spread to the skin, lungs, or other major organs. Three different dosing schedules as a single agent were tested.

In his study, Ribas said that patients with advanced melanoma achieved responses that occurred across seven different pembrolizumab dosing strategies and various subgroups of patients, including those patients who had been previously treated with ipilimumab.

Overall, 8% of patients experienced serious treatment-related side effects, but only 4% of patients discontinued treatment due to a drug-related side effect. Median follow-up is 12 months, Ribas said.

"I think that this drug is the best new anticancer drug that is available today," said , instructor in medicine at Harvard Medical School/Massachusetts General Hospital.

"Pembrolizumab is now available through an expanded access program," he told 番茄社区app. "We are getting phone calls from patients who want to be treated with this drug. We want to treat these patients."

"This large phase I clinical trial demonstrates continued excitement for anti- PD-1 therapy. We're seeing that pembrolizumab results in long-lasting clinical responses in the majority of patients, and impressive overall survival with low toxicity," said press conference moderator , director of clinical research at the Los Angeles Skin Cancer Institute at Beverly Hills Cancer Center in California. "Importantly, it's effective regardless of prior ipilimumab treatment. Anti-PD-1 as a single agent is a major breakthrough and improves on the initial success of ipilimumab in metastatic melanoma."

In the combination study, Yale's Sznol reported at the press briefing that confirmed complete responses were observed in nine of 53 patients with advanced metastatic melanoma -- 17% of the patients. "Tumor reductions of 80% or greater were observed in 22 of the patients (42%)," he said. And 18 of those objective responses were ongoing, he noted. The median duration of response has not yet been reached, Sznol said.

Grade 3-4 drug-related adverse events occurred in 58 of 94 patients that included 41 more patients in an extended study, but most of those adverse events were observed in laboratory tests. One patient in the study died, a fatal multi-organ failure precipitated by colitis linked to treatment, he reported.

"Just a few years ago, median survival for patients diagnosed with advanced melanoma was as little as a year or less, and only approximately 20% to 25% survived 2 years, so it's truly remarkable that we're seeing a median survival over 3 years in this trial. Even in the latest era of targeted and immunotherapy agents, the median survival is on average only about 16 to 18 months with any new treatment alone," said Sznol. "While we're encouraged by what we're seeing with the use of these two drugs together, this trial was small, so a randomized phase III trial will be important to validate our initial results."

The updated data are based on a median follow-up of 22 months and reflect an additional year of follow-up from patients initially enrolled in the trial.

In commenting on the study, press conference moderator O'Day said, "Anti-CTLA-4 and anti-PD1 single-agent therapies for metastatic melanoma have made significant contributions in recent years. This study combines the two checkpoint inhibitors concurrently in efforts to improve clinical outcomes further.

"This update on the initial group of 53 patients treated with ipilimumab and nivolumab confirms continued excitement, with remarkable clinical benefit and longer survival than we've typically seen. Phase III trials will be necessary to determine the benefit of combination checkpoint therapy versus sequential single-agent therapy and delineate the price of additional toxicities."