Successful European patent appeal

12 February 2015

Silence Therapeutics plc

Successful Appeal at European Patent Office hearing

Silence Therapeutics plc, AIM: SLN ('Silence' or 'the Company'), a leader in the development and delivery of novel RNA therapeutics for the treatment of serious diseases announces that the Board of Appeal of the European Patent Office, on 11 February 2015, upheld the key RNA interference (RNAi) trigger modification patent of the Company against challenges by four parties including Alnylam Pharmaceuticals Inc, its subsidiary Sirna Therapeutics Inc, Alcon Laboratories Inc, and an independent attorney.

At the oral hearing (number T1094/10-3-308), the Board of Appeal validated Silence's patent covering an alternating pattern of modified and unmodified nucleotides.

Silence's modification technology of alternating 2'-O-methly modified nucleotides is designed to increase the robustness of the trigger whilst maintaining its activity in efficient gene knockdown.

This granted European patent covers triggers of 15 to 23 base pairs with the modification pattern and covers one of the Company's products already in clinical trial.

Equivalent patents have already been granted to the Company in the USA, China, Israel, India, Japan, Korea and Mexico.

Silence is vigorously pursuing, on a worldwide basis, further patent applications on both triggers and delivery to fully protect its innovations in the field.

Ali Mortazavi, CEO of Silence Therapeutics, said:

"This is a very important victory for Silence Therapeutics and it strengthens our already broad IP portfolio covering both RNAi triggers and delivery. We have demonstrated that our stabilisation technology materially enhances the performance of RNAi. We will protect our position robustly whilst always ready to engage in licensing discussions."

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About Silence Therapeutics (www.silence-therapeutics.com)

Silence Therapeutics is a leading RNA therapeutics company. It has developed proprietary modifications to improve the robustness of RNA sequences together with advanced liposomal chemistries to enhance the delivery of its therapeutics. Its technology can selectively silence or replace the expression of any gene in the genome, modulating expression up as well as down in a variety of organs and cell types, in vivo. This allows the development of therapeutics for diseases with high unmet clinical need