Bristol-Myers Squibb Co. will develop a once-a-day pill to treat the HIV virus that combines its popular Reyataz with an experimental drug from Gilead Sciences Inc.

Under the licensing deal, Bristol-Myers will formulate, manufacture and sell the pill. It will include Reyataz, a drug in the class called protease inhibitors, and Gilead's cobicistat, which is designed to boost blood levels of some HIV drugs.

Gilead currently is doing mid- and late-stage human tests using the two drugs together to treat new HIV patients.

Bristol is to pay Gilead an undisclosed royalty from sales of the combination medicine.

The two companies already have a joint venture selling the three-drug combination pill Atripla, the top-selling HIV pill in the U.S.