The medical aid group said at an international AIDS meeting here that prices of older drugs long used to treat patients have fallen sharply as India and other countries make generics.
But newer drugs that are more effective against the AIDS virus are too expensive, costing up to 15 times more.
"It's good news that the price of key HIV drugs continues to fall as more generic companies compete for the market, but the newer medicines are still priced far too high," said Jennifer Cohn, medical director for Doctors Without Borders' access campaign.
Patients can be treated with a combination of three or four older drugs, but those who develop resistance to them need the expensive newer medicines.
Also Read
According to Doctors Without Borders, the governments of Thailand and Jamaica pay USD 4,760 and USD 6,570, respectively, a year per patient for the new drug darunavir alone.
Paraguay pays USD 7,782 for etravirine, while Armenia pays USD 13,213 for raltegravir. In comparison, a cocktail of older generic drugs costs as little as USD 139 per person a year.
It warned that the pact will increase intellectual property rights across Asia and the Americas, expanding monopoly protection for medicines and threatening cheap access to drugs.
It said the World Health Organizsation's new guidelines, which recommend earlier treatment for adults, means that an additional 9 million people in developing countries will now be eligible for treatment.
At the moment, only about 60 percent of those who need the drugs are getting them. "Scaling up HIV treatment and sustaining people on treatment for life will depend on bringing the price of newer drugs down," said Arax Bozadijan, an HIV pharmacist for Doctors Without Borders.