ViiV Healthcare, majority-owned by GSK, is the second research-based pharmaceutical business to sign up to the new Medicines Patent Pool, following a lead set in 2011 by Gilead Sciences.
Although more than half of people living with the human immunodeficiency virus (HIV) that causes AIDS now get the drugs they need - thanks to a major roll-out of treatment in Africa - an estimated 6.8 million still go without, according to UNAIDS.
The Medicines Patent Pool (MPP), launched in 2010 by the UNITAID health financing system that is funded by a levy on airline tickets, aims to address the remaining gap by getting patent holders to share know-how with makers of cheap generic drugs.
In the case of ViiV, a key pediatric medicine known as abacavir will be made available to generic manufacturers which will be able to take a license to make and sell it in 118 poor countries, the patent pool said on Wednesday.
ViiV and the patent pool have also agreed to negotiate further licenses that will allow generics firms to manufacture low-cost versions of an experimental drug, dolutegravir, that is currently awaiting regulatory approval in Western markets.
There are 3.4 million children living with HIV worldwide but only 562,000 have access to medicines. Treating them is challenging because many drugs are not adapted for use in children.
Abacavir and dolutegravir are both seen as priority products for fighting HIV in poor countries. ViiV also sells other older drugs, some of which are already off patent and available as cheaper generics.
ViiV - which is owned 76.5 percent by GSK, 13.5 percent by Pfizer and 10 percent by Shionogi - only signed up to the patent pool after lengthy negotiations.
Some other major drugmakers have yet to join.
Bristol-Myers Squibb, Roche and privately owned Boehringer-Ingelheim are currently discussing plans to join the scheme, but Abbott, Johnson & Johnson and Merck have so far remained outside.
J&J decided in November to take unilateral action by not enforcing its patents on HIV drug Prezista in a limited number of poor countries, in a move that disappointed campaigners who argued joining the pool would have been more effective.
(Reporting by Ben Hirschler, Editing by Kate Kelland and Mark Potter)