By Grant Ferrett
BBC World Service
The cost of drugs to tackle the effects of Aids is again soaring, five years after trade negotiators made what was thought to be a breakthrough at talks in Doha to allow greater access to drugs for those living in developing countries.
World Aids Day has seen protests over second-line drugs costs
Since the Doha deal, the price of HIV treatments in developing countries - where the majority of HIV-positive people live - has come down dramatically, in some areas from $10,000 a year per person to $150.
"Those medicines were very expensive because they were all under patent," explained Sarah Bowsley, health correspondent of the UK's Guardian newspaper.
"The Doha declaration was thought to be a way of actually allowing generics - cheap, copycat versions - into the field."
This is not only because of the availability of generic products, but because many of the pharmaceutical companies lowered the price of their own branded drugs as well. There are now five times as many people receiving drug treatment for HIV compared with five years ago.
But the world is still far short of providing drugs for all of the estimated six million who need them.
And Tido von Schoen-Angerer of Medecins Sans Frontieres said the old problem of expensive drugs is now reappearing.
"What we are seeing, five years after Doha, is that prices are again on the increase," he said.
"If patients need newer drugs, that means costs go up 10 times - or, in some countries, up to 50 times. This is a very worrying trend."
Prices are going up because these new treatments - known as second-line drugs - are more expensive than their predecessors.
The new medicines are needed because HIV is changing - and for some patients, existing drugs lose their effectiveness.
The new versions are often either more expensive or simply not available to patients in poorer countries.
Until now, India has been the main producer of generic drugs - but in 2005, the country was obliged to change its legislation to comply with World Trade Organisation rules, meaning that drugs invented after that point cannot be made in India by the generic companies.
The Guardian's Sarah Bowsley said that there is "a lot of pressure" on the Indian government by the pharmaceutical companies, to stop them producing generic versions of the newer drugs.
"They know that after the second-line Aids drugs we're also talking about cancer drugs, diabetes, heart disease," she said.
"It is all the things that affect us in the West - and actually affect populations in developing countries too."
Drug manufacturers argue that patents are needed to protect their investments. They spend years developing drugs - and if these are simply copied, they lose out.
Dirk van Eeden, spokesman for one of the world's biggest drugs companies, US-based Abbott, said that price is "not the real stumbling block" - insisting the problem is the lack of healthcare workers and infrastructure.
India is under pressure to stop generics of new drugs being created
"Sub-Saharan Africa has a quarter of the global HIV burden - yet only 3% of all of the healthcare workers in the world," he said.
"Pharmacies could be fully stocked, but without enough doctors and nurses, there's just no way that people waiting outside the clinic can get the medicine."
Certainly, where campaigners and pharmaceutical companies agree is that what is needed is the political will at the highest levels to take co-ordinated, global action.
If the world is to help the millions living with HIV in poorer countries, a massive injection of cash and commitment is needed.
"There is only so much you can expect from companies... there is a great need for public leadership on this issue," said Mr von Schoen-Angerer.
"There is an absence of government support for these kind of initiatives, and without public leadership this will not be resolved."