Hetero Drugs has withdrawn all six of its antiretroviral drugs from the WHO’s list of approved drugs following concerns about their laboratory tests, the World Health Organisation (WHO) said on Friday.

It was the third time since June that an Indian company has removed anti-AIDS drugs following WHO inspections that revealed faulty bioequivalence tests meant to show the drugs have the same effect as name brands.

There are still some 48 antiretrovirals - generic and patented - on WHO’s list of so-called “prequalified” generic drugs, a key weapon in the international fight against the global epidemic.

“All six drugs on WHO’s prequalified list have been withdrawn by them (Hetero),” WHO spokesman Iain Simpson said. “There are certainly major concerns about the lab testing, about the quality of it, about the situation that has been found by these (WHO) inspections,” he added.

Hetero, which is based in Hyderabad, will redo the studies and hoped to resubmit the results for consideration early next year, according to the WHO spokesman.

In a statement, the WHO said that Hetero had acknowledged that there were “deficiencies in the data submitted” and had pledged to hire different contract research organisations (CROs) to carry out fresh testing.

“The irregularities found during the CRO inspections do not undermine the proven pharmaceutical quality of the medicines - including their purity and stability,” the WHO said.

However, it showed that not all CROs can be relied upon for evidence on the medicines’ bioequivalence with their originating products, according to the United Nations agency.

The WHO also reiterated its advice that countries should suspend the use of de-listed medicines and switch to other prequalified products. But if alternative prequalified products were difficult to obtain immediately, it was recommended that patients continued the use of de-listed products.

“The risk of withholding treatment is higher than that of providing medicines whose bioequivalence is not proven but which have demonstrated quality and safety,” the WHO added.

Earlier this month Ranbaxy of India pulled its AIDS drugs off the WHO’s list after also finding discrepancies in the equivalency tests. It followed the removal by India’s Cipla of two HIV/AIDS drugs in June for similar problems.

“Our findings and the companies’ admission of responsibility by withdrawing their products, show that CRO inspections are necessary,” said Lembit Rago, coordinator of quality, safety and efficacy of medicines at WHO.

“Current WHO procedures are ultimately improving medicines monitoring mechanisms which will, in the long term, ensure better quality treatment for patients,” he said.