Long-term results from a phase 1b immunotherapy trial have ended with "encouraging results."

The results of the trial proved the therapy to be long-lasting and to significantly increase the patients' life spans, a Yale University news release reported.

The trial looked at the safety and efficiency of a regimen of the drug nivolumab (anti-PD-1), which is an "investigational PD-1 immune checkpoint inhibitor. The trial also included ipilimumab (anti-CTLA-4; Yervoy). The drugs were given to the patients either at the same time or sequentially.

The participants in the study all had melanoma that had progressed after the initial treatments. The one-year survival rate proved to be 94 percent and the two-year survival rates was 88 percent.

"The treatment of advanced melanoma has changed dramatically in the last few years, but there continues to be a need to increase the number of patients who experience a long-term survival benefit," first author Mario Sznol, M.D., professor of medical oncology at Yale Cancer Center, said in the news release. "While these are phase 1b data, the duration of response and one- and two-year survival rates observed with the combination regimen of nivolumab and Yervoy are very encouraging and support the rationale for the ongoing, late-stage trials of this combination regimen."

CTLA-4 and PD-1 are treatment targets because they restrict the immune system's ability to fight tumors. Antibodies that block CTLA-4 and PD-1 allow for a strong immune system response to the cancer by "removing the brakes," the news release reported.

"Nivolumab targets the PD-1 receptor on the surface of T-cells, and ipilimumab targets CTLA-4 receptors," the news release reported.

Both of the drugs are manufactured by Bristol-Myers Squibb; the company also sponsored the trial with the Ono Pharmaceutical Company, Ltd. The work was published in the New England Journal of Medicine and presented at ASCO in 2013.