Protherics, the biotechnology company, has given warning that American approval for Voraxaze, its cancer drug, could be delayed by a year.

The company said yesterday that it had been forced to withdraw an application for a US licence for the drug, which is used to alleviate the toxic side-effects of methotrexate, a widely used chemotherapy drug, after America’s Food and Drug Administration (FDA) asked for more manufacturing data.

Protherics said that it planned to reapply for a licence in 2007 once it had obtained the additional information.

“Protherics now anticipates that approval could be granted in the US from the second half of 2008, depending on the FDA’s exact requirements, rather than the second half of 2007,” the company said in a statement.

Protherics hopes that the drug will be granted a priority review by the FDA on compassionate grounds. This would reduce the approval wait once the application has been submitted from ten months to six.

“We will work with the FDA to minimize the impact on approval time in the US,” Andrew Heath, the chief executive, said.

“It’s disappointing for them, but there is no issue with the drug’s safety or efficacy,” Dr Robin Campbell, pharmaceuticals analyst at Jefferies, said. “This is more to do with administrative bookkeeping by the FDA. It’s nitpicking.”

Protherics expects regulators to approve the drug for use in Europe in the first half of next year.

CytoFab, another Protherics product, which is being developed to combat anti- sepsis in partnership with AstraZeneca, the pharmaceutical giant, is also facing delays to its Phase-III development trials.

Analysts said that the latest delay was unlikely to cause significant financial damage to Protherics.

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