“The counterfeit version of Avastin does not contain the medicine’s active ingredient, bevacizumab, which may have resulted in patients not receiving needed therapy,” the US Food and Drug Administration said in a statement.

Charlotte Arnold, spokeswoman for the Roche US-based unit Genentech, said that because the counterfeit lacks the active ingredient, “it’s not safe or effective for use. It should not be used. We are still analyzing what is in the product. We know that there is no biological product in it.”

In a related action, FDA said it had issued letters to 19 medical practices in the United States that purchased unapproved cancer medicines that may include the counterfeit Avastin.

The 19 medical practices purchased unapproved cancer medicines and, potentially, the counterfeit Avastin, from Quality Specialty Products (QSP), a foreign supplier that is also known as Montana Health Care Solutions.

The FDA asked QSP’s US distributor in Tennessee to stop using any remaining products from the supplier.

Genentech said some of the counterfeit US lots are believed to be labeled as Avastin 400 mg/16 ml and have the serial numbers B86017, B6011 and B6010.

Genentech said the suspect batches differ from the official product, which is certified by the FDA. Genuine Avastin boxes are normally marked with six digit serial numbers and have no letters, stated the company.

Avastin is among Roche’s top-selling drugs with sales of 5.3 billion francs ($5.8 billion) in 2011.

Last year, the FDA revoked the authorization of Avastin for breast cancer treatment, saying its effectiveness was not proven, but allowed it to remain on the market as an approved treatment for certain types of colon, lung, kidney and brain cancer.