European Patent Office Limits Kreutzer-Limmer RNAi Patent Claim

The patent, which is owned by RNAi drug company Alnylam, now only covers methods of making and using double-stranded RNA with lengths and structures of limited use as RNAi-based therapeutics, according to Sirna. The decision will also substantially limit the commercial utility of that patent.

The chemical structures now covered under the patent "are obsolete and essentially ineffective as viable RNAi-based therapeutics," said Bharat Chowrira, Sima's chief patent counsel. With the limitation, the Kreutzer-Limmer patent no longer provides "any meaningful intellectual property protection in the field of RNAi-based therapeutics," he said.

Granted in mid-2002, the patent, EP 1144623/WO 0044895, covers an invention made by founders of the German RNAi company Ribopharma and became part of Alnylam's IP estate when the two companies merged in July 2003.

The patent specifically covers "a medicament containing at least one double-stranded oligonucleotide (dsRNA) designed to inhibit the expression of a target gene." According to GenomeWeb News sister publication RNAi News, the patent's abstract notes that in the invention, "at least one strand of the dsRNA is at least in part complimentary to the target gene."

In 2003 eight parties -- Sirna Therapeutics, Atugen, Aventis Pharma, Janssen Pharmaceutica, AstraZeneca, Isis Pharmaceuticals, Novartis, and Munich-based patent attorney Martin Grund -- joined to oppose it in Europe. Grund and Isis have since withdrawn their opposition.