LONDON, Dec 12 (Reuters) - Bristol-Myers Squibb is to share intellectual property rights on an important HIV/AIDS drug in a patent pool designed to make treatments more widely available in poor countries.

The licensing deal will enable generic drug firms around the world to produce affordable versions of atazanavir, which Bristol sells under the brand name Reyataz, and to combine it with other medicines to make treatment easier.

The agreement announced on Thursday by the United Nations-backed Medicines Patent Pool is the first covering an HIV drug designed for use after patients develop resistance to initial treatments.

The World Health Organisation estimates there will be over 1 million people on such second-line treatments by 2016 and many more will need access to these therapies in the future.