The World Health Organisation said last Wednesday it was removing three generic HIV/AIDS drugs made by India's Ranbaxy Laboratories Ltd from its recommended list amid concerns about quality.

Ranbaxy has not proved that the medicines are biologically equivalent to patented drugs, the Geneva-based UN Agency said in a statement.

The antiretrovirals in question are a triple combination pill containing lamivudine, stavudine and nevirapine in two different strengths and a tablet of lamivudine plus zidovudine.

The move follows similar action in late May against two drugs made by another Indian firm, Cipla Ltd. Cipla's three-in-one pill did meet equivalence standards and will continue to be listed.

Triple combination drugs have become standard therapy for fighting HIV, since the virus that causes AIDS mutates rapidly and must be attacked on several fronts at once. Ranbaxy and Cipla have pioneered the supply of generic versions of such pills in poor countries, particularly Africa, to cheers from AIDS activists, who see them as a cheap alternative to branded medicines.

But Western drug makers and US government officials have questioned whether such products are necessarily of the same standard as the originals.

Officials at Ranbaxy in New Delhi had no immediate comment on the WHO move. But the decision is a setback for the firm, which announced plans at the weekend to file its anti-AIDS drugs with the US Food and Drug Administration under a new fast-track approval scheme before the end of 2004.

The WHO's so-called prequalification list, which currently includes some 60 life-saving antiretrovirals, was set up two years ago to guide procurement by aid agencies battling the epidemic in African and Asian countries. It contains both generic and patented products.

The WHO has launched a campaign to get antiretrovirals to 3 million people in the developing world by the end of 2005. As of June 30 this year, however, only 440,000 were receiving them.

The WHO said it was dropping the three Ranbaxy products because the laboratory, which had carried out bioequivalence studies, did not meet international standards of good clinical and laboratory practices.

The three medicines from Ranbaxy will not be reinstated until the company submits data from new studies providing "unequivocal evidence" of bioequivalence with the originals, the WHO said.

The lack of proof of bioequivalence means the drugs may not offer the same therapeutic benefits as the originals on which they are based. Bioequivalence studies involve checking whether volunteers given the drugs have the right concentration of the drug in their blood.

GlaxoSmithKline Plc holds patents in major markets on lamivudine and zidovudine, while Bristol-Myers Squibb Co has patents on stavudine, and Boehringer Ingelheim has rights to nevirapine.

(Agencies August 19, 2004)