Litigation Update (Portugal and US)

Litigation Update (Portugal and US)

London, 3rd April 2018

Silence Therapeutics plc, AIM:SLN ("the Company") a leader in the discovery, delivery, and development of novel RNA therapeutics for the treatment of serious diseases with unmet medical need, announces that, through Silence Therapeutics Gmbh (together "Silence"), it has yesterday brought patent infringement proceedings in Portugal against Alnylam's Patisiran product, and that on March 29th Alnylam Pharmaceuticals Inc. ("Alnylam") filed a Declaratory Judgement (DJ) against Silence Therapeutics plc and Silence Therapeutics Gmbh.

Regarding Portugal, Silence has previously stated that it is committed to defending its Intellectual Property (IP) and to secure the appropriate value for this IP it will act to enforce its patent estate as necessary. The next phase in the Portuguese legal process is that the Court will serve the claim on the defendant. The claim asks the Court to determine whether Patisiran infringes the Silence patent EP 1857547.

Regarding the US, Alnylam filed the Declaratory Judgment action in the U.S. federal district court in Boston, Massachusetts. The action seeks a finding of non-infringement of certain Silence patents. Silence's most recently-issued U.S. patents, such as those identified in Silence's updates dated August 15, 2017, October 11, 2017, and October 18, 2017, are not named in the lawsuit. The complaint has not yet been served on Silence. More information on the lawsuit can be found on the court's docket, at case number mad-1-18-cv-10613.

 Ali Mortazavi, Chief Executive Officer of Silence Therapeutics plc, commented:

"We reiterate that we will defend the Silence patent estate where we consider third parties to be infringing the company's patent rights. As such, in Portugal we consider this process to be important in recognizing the contribution Silence has made to this field. Furthermore, we see Alnylam's filing of a DJ as an acknowledgment of the significance of our patent position."

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About Silence Therapeutics plc

Silence Therapeutics develops a new generation of medicines by harnessing the body's natural mechanism of RNA interference, or RNAi, within its cells. Our proprietary technology can selectively inhibit any gene in the genome, specifically silencing the production of disease-causing proteins. Using our enabling delivery systems, we have achieved an additional level of specificity by delivering our therapeutic RNA molecules exclusively to target cells. Silence's proprietary RNA chemistries and delivery systems are designed to improve the stability of our molecules and enhance effective delivery to target cells, providing a powerful modular technology well suited to tackle life-threatening diseases. For more information, please visit: http://www.silence-therapeutics.com/