San Diego

The European Patent Office (EPO) last week revoked a patent for an important thermally stable enzyme used in the polymerase chain reaction (PCR) process for DNA amplification. The decision brings with it the prospect that the price of the enzyme will fall.

Getting warmer: Tom Brock of the University of Wisconsin, who discovered Thermus aquaticus. Credit: PETER MENZEL/SPL

Hoffmann-La Roche's patent for naturally occurring Taq DNA polymerase —obtained from the bacterium Thermus aquaticus, which lives in hot springs — is invalid because it is not a novel invention and is based on previously published discoveries, EPO officials say. Roche says it will appeal against the decision next year once the formal written opinion is issued by the EPO in Munich.

Melinda Griffith, general counsel for Roche Molecular Systems in Pleasanton, California, downplayed what she called “an intermediate-level” decision. She said the panel of patent examiners responsible had made “many errors of law” during the three-day hearing, which ended on 30 May.

This is the second major Roche patent on PCR to be revoked. In 1999, a federal judge in San Francisco ruled that Roche's US patent for native Taq was invalid (see Nature 402, 709; 1999) because it had been obtained with “intent to mislead”. Switzerland-based Roche is appealing against that decision, and a court ruling is expected next year.

In both the EPO and San Francisco cases, the Roche patents were disputed by Promega, a Wisconsin-based company that markets native Taq and other reagents internationally. Three other companies — Bioline, New England Biolabs and Becton Dickinson — supported Promega in the EPO action. The companies argued that the EPO patent for native Taq, issued in 1997, should never have been allowed and was granted only after years of pressure by Roche and its subsidiaries.

Roche still holds an EPO patent for a recombinant version of Taq, which is created by inserting the gene for Taq into another species of bacterium. Recombinant Taq now accounts for a large proportion of the market. But that patent is being challenged by the London-based company Bioline.

Bioline declined to comment on the case. But Griffith claims Roche's EPO patent on recombinant Taq is valid and enforceable.

In a separate action, Roche is suing Promega in the German federal court for selling Taq in Europe, alleging that the company is infringing its patents. It remains unclear how the EPO will ruling will affect this action.

Promega lawyer Brenda Furlow claims that more companies are now likely to start selling native Taq, creating a more competitive market that will lower the price of the widely used reagent. Native Taq produced by the companies fighting Roche costs 20–30% less than Roche charges, she notes.