Acquisition of Minority Stake in Arrowhead

Acquisition of minority stake in Arrowhead Pharmaceuticals

9th January 2017

London, 9th January 2017 - Silence Therapeutics plc, AIM:SLN ("Silence" or 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 it has acquired a stake, on-market, in Arrowhead Pharmaceuticals, Inc. (NASDAQ: ARWR) ("Arrowhead") of 6,006,359 common shares, representing 8.4% of the common share capital of Arrowhead, for a total cash consideration of $9.6 million (£7.8 million(1)), excluding transaction costs.

Since the capital raise of May 2015, Silence has been actively evaluating a number of RNAi assets, including technologies within both listed and unlisted RNAi companies. Arrowhead is a US based NASDAQ listed company that develops medicines to treat intractable diseases by silencing the genes that cause them by means of a broad portfolio of RNA chemistries and efficient modes of delivery. The Company believes that Arrowhead's IP, technology and pipeline is among the leading platform technologies in a sector that promises huge potential advances by generating novel medicines.

Silence has acquired the equity position in order to facilitate future discussions regarding a possible transaction with Arrowhead, which could include, but is not limited to, product licensing, R&D collaboration, technology sharing or a potential corporate transaction. Silence and Arrowhead are not currently engaged in any discussions regarding a possible transaction. Silence will update the market at the appropriate time should any discussions progress to a transaction.

Silence has acquired the stake using its existing cash resources. The stake will not be consolidated and will be held as an investment asset on the Company's balance sheet, as such there are no profits to attribute to the assets being held. There will be no contribution from the investment to Silence's net loss. The Company confirms that it reported net cash of £47.6 million as at 30 June in its interim results.

1 Exchange rate used 1.234

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

"We believe that the recent technological advancements in RNA therapeutics have been underestimated and undervalued. We are confident that the recent market approval of medicines in our field are the beginning of the emergence of an important new class of therapeutics. We look forward to opening a constructive dialogue with Arrowhead."

THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION AS STIPULATED UNDER THE MARKET ABUSE REGULATION (EU No. 596/2014). UPON THE PUBLICATION OF THIS ANNOUNCEMENT VIA REGULATORY INFORMATION SERVICE THIS INSIDE INFORMATION IS NOW CONSIDERED TO BE IN THE PUBLIC DOMAIN.

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About Silence Therapeutics plc

Our technology harnesses the body's natural mechanisms to create therapeutic effects within its cells. This technology can selectively silence or replace any gene in the genome, modulating gene expression up as well as down in a variety of organs and cell types, in vivo. We have developed proprietary modifications to improve the robustness of RNA sequences, as well as advanced chemistries to enhance the effective delivery of therapeutic RNA molecules to target cells.