What seems to be going on with RNAi related patents in the US

Reciting Table 1 from Ref 1 and Table 3 from Ref 2:

Fire and Mello US 6,506,55:	RNAi with siRNA >24 nucleotidesr
Tuschl et al. US 108,923 (Tuschl I, pending):	synthetic or in vitro produced siRNA 21-23 bps
Tuschl et al US 7,056,704 and 7,078,196 (Tuschl II):	synthetic siRNA 19-23, with 3′ overhangs;
Kreutzer-Limmer EP 1,144,623:	siRNA 15-21 bps;
Benitec, DNA-driven RNAi DNA driven:	granted in 2003, then became under re-examination.

By the end Nov 2008 it appears that Allele’s patent (US 7,294,504 and 7,422,896) are the only currently granted DNA based RNAi patents. The focus of Allele’s technology is siRNA of 21-23, either in separate sense and antisense strands, or shRNA or miRNA format, thus not covered by the Fire patent or the Kreutzer-Limmer patent. Since these RNAi inducers are not synthesized by chemical reactions, or produced with enzymes or cell lysate in vitro, they do not relate to Tuschl I or II patent groups. Allele Biotech can not guarantee that its interpretation is correct or final by any means; commercial user of any of the related technologies should perform own due diligence.

[1] Charlie Schmidt. March 2007 “Negotiating the RNAi patent thicket” Nature Biotechnology 25 (3): 273-275

[2] Dirk Haussecker. May 2008 “The Business of RNAi Therapeutics” Human Gene Therapy 19: 451-462

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Tags: gene silencing, H1, lentiviral vector, miRNA, PCR cassette, plasmid vector, pol III, retroviral vector, RNAi, shRNA, siRNA, U6