Onyx falls behind in cancer drug race

Onyx Pharmaceuticals - which is developing one of the most promising new cancer therapies on the horizon - has said it will not file for US approval of its kidney cancer drug as soon as some investors had anticipated.

Onyx is developing the drug, BAY43-9006, with Germany's Bayer. It is one of a new generation of "smart bomb" cancer therapies that attack tumours without destroying healthy cells as chemotherapy does.

BAY43-9006 blocks an enzyme called RAF kinase believed to be involved in controlling growth and division of cells. It also blocks the VEGF protein that helps produce blood vessels that supply nutrients to tumours.

The companies said the drug shrank tumours in a mid-stage, phase II trial, but said they would use the results to support data from an ongoing larger, phase III clinical trial.

Some investors had hoped Onyx would file on the phase II data, which would have accelerated the drug's approval.

The drug's official time to the market was 2006, but the companies had left the door open to the possibility of filing earlier. Now that door is closed, opening the way for a competitor drug in development by Pfizer to take the lead. Pfizer's drug could be approved by the end of 2005.

Onyx did not say precisely why it does not plan to file based on the phase II data, which the company said showed the drug met the main goal of the trial of 202 patients with advanced kidney cancer.

The trial showed a statistically significant percentage decrease in disease progression and 70 percent of patients had their disease stabilize or their tumors shrink. Still, the company did not release details of the data and analysts said the trial itself was designed in an unusual fashion.