The European Patent Offices's Opposition Division has found in favour of Oxford Gene Technology in the 6-year opposition to its European patent for DNA microarrays.

OGT's European patent number 0373203 was granted on 31 August 1994, and had been opposed after grant by Affymetrix, Abbott, Roche, Nanogen and three others. OGT's European array patent has emerged almost entirely unscathed from the opposition process after a three-day oral hearing at the EPO in Munich, which ended on 15 November. Although Affymetrix had withdrawn its opposition after a settlement brokered in March this year, its written arguments were still before the Opposition Division.

OGT introduced amendments both prior to and during the hearing to limit the patent's coverage to arrays of oligonucleotides covalently attached to a smooth impermeable surface, and these amendments were accepted by the Opposition Division. The patent covers most oligonucleotide arrays currently on the market, whether made by in situ synthesis or deposition of presynthesised oligonucleotides, and irrespective of their density.

Professor Ed Southern, owner of OGT and the patent's inventor, said, "We are very pleased with the Opposition Division's decision, and with the very broad claims that have emerged. This has been a long process, but the decision greatly strengthens the patent, and we intend to pursue the many licensing opportunities with renewed determination: it has always been my aim to make this technology as widely available as possible."

OGT's existing licensees under its microarray patents include Affymetrix, Agilent Technologies, Rosetta Inpharmatics (now part of Merck) and Incyte Genomics.

OGT was represented at the European Patent Office by Huw Hallybone and Cameron Marshall of London-based patent agents, Carpmaels & Ransford.