A new batch of counterfeit cancer drug Avastin discovered in the United States was bought in Turkey and shipped through Britain by a UK-based business, officials said on Wednesday, revealing a shipment pattern very similar to an earlier episode.

The first discovery of fake supplies of the Roche drug shipped into the United States from the Middle East via Europe hit the headlines in February, although the middlemen involved this time are different.

The repetition of the illegal trade highlights vulnerabilities in the global medicine supply chain, which leaves patients at risk of receiving ineffective or contaminated products.

Britain's Medicines and Healthcare products Regulatory Agency (MHRA) said it was looking into how the latest counterfeit batch entered Britain before being sold in the U.S. market.

"It's an ongoing investigation," said spokeswoman Jennifer Kyne. "We're helping the FDA (Food and Drug Administration) with their investigation and doing all we can on our side."

The British wholesaler purchased 120 packs of the medicine from a Turkish supplier, 38 of which were exported direct to the United States and the remainder were sold to another British firm, also for the purpose of export to the U.S., she added.

There is no evidence to suggest that any of the counterfeit product reached patients in Britain.

Scrutiny of the supply chain has grown since the first episode of fake Avastin set alarm bells ringing by underscoring the lack of a clear system to track medicines as they change hands.

The Avastin case is viewed as particularly serious because it marks a step change by criminal counterfeiters, who until now have tended to focus on simple pills. Avastin, by contrast, is a complex injectable biotech drug with annual sales of $6 billion.

No active ingredient

The FDA said on Tuesday the new batch of bogus vials of the cancer treatment contained none of Avastin's active ingredient, bevacizumab.

The fake versions of the Swiss drugmaker's top-selling product were labelled as Altuzan, which is the brand name that Avastin is sold under in Turkey. Kyne said the MHRA was informed on March 28 by the FDA that Altuzan batch B6021 was counterfeit.

A Roche spokesman said that authentic Altuzan only had Turkish-language packaging, whereas images of the fake medicine posted by the FDA on its website showed English-language packaging.

The FDA said U.S. medical practices had bought the latest counterfeit Avastin from overseas suppliers, in particular "Richards Pharma", while the MHRA said it was following up all potential lines of inquiry, including with Richard's Pharma, based in Warwick, central England.

A spokeswoman for the company, which is registered as a business involved in the "wholesale of pharmaceutical goods", said no-one was immediately available to comment.

In the case of the fake Avastin that came to light in U.S. clinics in February, the source of supply was also Turkey - but the wholesalers then were different. That network involved middlemen based in Egypt, Switzerland, Denmark and Britain.

The World Health Organisation estimates that less than 1% of medicines available in the developed world are likely to be counterfeit. Globally, however, the figure is around 10%, while in some developing countries as much as a third of medicines are estimated to be bogus.