Efforts to bring antiretroviral treatment to AIDS patients in developing countries are threatened by the looming implementation of new World Trade Organisation's patent rules, the charity Médecins Sans Frontières warned this week.

The organisation's TRIPS (trade related aspects of intellectual property rights) agreement comes into force for most signatories on 1 January 2005. It requires the organisation's members to grant 20 year patents to new pharmaceutical products. Only the least developed countries can postpone implementation until 2016.

Médecins Sans Frontières' international president, Dr Rowan Gillies, told the BMJ: "We're gravely concerned that our sources of affordable medicines will dry up. Not only are patents going to be granted on all new medicines, some existing medicines that we rely on will be reviewed for possible patent protection as well."

Dr Gillies said he is particularly worried about the effect on the generics industry in India, which produces most of the generic, fixed dose combination antiretrovirals currently used by his charity.

The charity is currently treating 23,000 HIV positive patients in 27 countries in Asia, Africa, Latin America, and eastern Europe more than double the number it treated last year. Dr Gillies said: "We're not ideologically attached to generics, but we've found it's what works best. At the moment, only generics can provide a treatment regimen of just two pills a day.

That's essential for compliance and good results." Dr Arnaud Leannin, who works with Médecins Sans Frontières' AIDS programme in Malawi, said: "Although they are not the final answer to AIDS, triple drug cocktails literally allow people to rise from their death beds and live normal, longer lives."

Two year survival rates in the programme attained 85%, he added. But Pietro di Mattei, medical coordinator of the charity's Mozambique AIDS programme, said that growing numbers of patients are now failing first line treatment and the charity has to buy patented medicines for second line therapy. The cost of annual treatment in these cases jumps from $250 a year to $700-$3,000.

Patients needed cheap, second line formulations adapted to resource poor settings, he said. Other priorities identified by the charity's fieldworkers were a simple blood test for CD4 count and viral load, more sensitive tests for tuberculosis, combination antiretrovirals that are not incompatible with tuberculosis drugs, and a fixed dose formulation for children.

Médecins Sans Frontières spelt out its concerns at a press conference in London on 30 November, the day before World AIDS day. "There are about five and a half million people in developing countries who need antiretroviral treatment now if they are to expect to survive two years," said Dr Gillies. "Only about 440,000 are getting it."