The first combination of breakthrough drugs that boost the immune system to fight cancer has been approved, giving maker Bristol-Myers Squibb an early lead over competitors testing their own combos in a pharmaceutical gold rush of sorts.

The Food and Drug Administration has given accelerated approval to a regimen combining the New York-based drugmaker's two immuno-oncology drugs, Opdivo and Yervoy, to treat patients with advanced melanoma who have a particular genetic variation.

Together, the drugs slowed or temporarily stopped in 60 percent of patients, versus 11 percent who only received Yervoy, in a study.

But with a list price of up to a quarter-million dollars for the combo treatment, unless insurance plans negotiate huge discounts, many likely won't be able to afford their portion of the cost.