Silence Therapeutics Announces Collaboration with AstraZeneca to Discover and Develop siRNA Therapeutics for Cardiovascular, Renal, Metabolic and Respiratory Diseases 25 March 2020 AstraZeneca to invest $80 million through upfront cash and equity investment in Silence For each disease target, Silence is eligible to receive up to $400 million in milestones, plus tiered royalties Companies to collaborate to achieve delivery of siRNA molecules to liver, heart, lung and other tissues Silence retains the option to co-develop two programs discovered through the collaboration Webcast and conference call today at 1pm GMT LONDON - Silence Therapeutics plc (LON: SLN) (?Silence?) today announced a strategic collaboration with AstraZeneca to discover, develop and commercialize small interfering RNA (siRNA) therapeutics for the treatment of Cardiovascular, Renal, Metabolic and Respiratory diseases. The collaboration draws on Silence?s extensive experience as a leader in the discovery, development and delivery of siRNA therapeutics together with AstraZeneca?s industry leading expertise in disease biology and target identification with the aim of developing first-in-class and differentiated therapeutics to address significant unmet need. AstraZeneca will make an upfront cash payment of $60 million and an equity investment of $20 million in Silence. The parties anticipate initiating work on five targets within the first three years of the collaboration, with AstraZeneca having the option to extend the collaboration to a further five targets. Silence will harness its established GalNAc-siRNA platform to inhibit liver expressed gene targets and the companies will collaborate to achieve targeted delivery of siRNA molecules to other tissues including heart, kidney and lung. Delivery of siRNA molecules to the liver hepatocytes is an established approach; targeted delivery to these other tissue types represents a new and compelling opportunity to treat Cardiovascular, Renal, Metabolic and Respiratory diseases. Under the collaboration, Silence will be responsible for designing siRNA molecules against gene targets selected by AstraZeneca, and for manufacturing of material to support GLP toxicology studies and Phase I clinical studies. AstraZeneca and Silence will collaborate during discovery phase and AstraZeneca will lead clinical development and commercialization of molecules arising from the collaboration. Silence will have the option to negotiate for co-development of two programs of their choice starting from Phase II. AstraZeneca will pay Silence an option fee of $10 million for each selected target at the point of candidate nomination and thereafter for each target selected Silence will be eligible for up to $140 million in development milestones and up to $250 million in commercialization milestones as well as tiered royalties on net sales ranging from high single digit to low double digit. Iain Ross, Executive Chairman at Silence said ?We are delighted to announce this collaboration with AstraZeneca as it is a further validation of our proprietary siRNA platform. It not only provides us with an? opportunity to collaborate on specific liver expressed gene targets but also to work with a leading company to achieve targeted delivery of siRNA molecules to other tissues including heart, kidney and lung.? Mene Pangalos, EVP BioPharmaceuticals R&D, AstraZeneca said ?This collaboration with Silence adds an exciting new modality, siRNA, into our drug discovery toolbox. Importantly we can apply this drug modality across our key therapy areas in cardiovascular, renal and metabolism and respiratory to target novel pathways not amenable to more traditional drug discovery approaches.? The Silence management team will host a conference call accompanied by a live presentation and Q&A for analysts and investors at 13:00 GMT (09:00 ET) today, Wednesday 25 March 2020 to discuss this announcement. Dial-in details are below: Participant Dial-in (UK): 08002796619 Participant Dial-in (USA): 18778709135 Conference ID: 2937529 Link to the live webcast: https://edge.media-server.com/mmc/p/9oyktpze. A replay will be available on the investor page of our website. A copy of the presentation can be downloaded from the investor page of our website. For more information, please contact: Silence Therapeutics plc Iain Ross, Executive Chairman Rob Quinn, Chief Financial Officer Tel: +44 (0)20 3457 6900 Peel Hunt LLP (Nominated Adviser and Broker) James Steel/Oliver Jackson Tel: +44 (0)20 7418 8900 European IR Consilium Strategic Communications Mary-Jane Elliott/Chris Welsh/Angela Gray silencetherapeutics@consilium-comms.com Tel: +44 (0) 20 3709 5700 US IR Westwicke Partners Peter Vozzo peter.vozzo@westwicke.com Tel: +1 (443) 213-0505 About Silence Therapeutics plc Silence Therapeutics is developing a new generation of medicines by harnessing the body?s natural mechanism of RNA interference, or RNAi, within its cells. Its proprietary technology can selectively inhibit any gene in the genome, specifically silencing the production of disease-causing proteins. Using its enabling delivery systems, it has achieved an additional level of specificity by delivering its 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. Silence Therapeutics remains focused and is determined to be responsive to creating shareholder value as well as the appropriate growth and development of its business. Silence Therapeutics continues to assess a number of options in addition to its organic plan which it believes would be additive to the Company's future growth prospects and shareholder value, which may include equity fundraisings as well as other strategic licensing and collaboration opportunities. For more information, please visit: https://www.silence-therapeutics.com/ Admission of Shares Application will be made for 4,276,580 new Ordinary Shares in Silence to be admitted to trading on AIM and dealings are expected to commence on 30th March 2020. The new Ordinary Shares will rank pari passu with the existing shares of the Company. Following the issuance the Company's issued share capital consists of 82,646,845 Ordinary Shares. Accordingly, the figure of 82,646,845 may be used by shareholders as the denominator for the calculations by which they will determine if they are required to notify their interest in, or a change to their interest in the Company under the FCA's Disclosure Guidance and Transparency Rules. Inside Information The information contained within this announcement is deemed by the Silence Therapeutics plc to constitute inside information as stipulated under the Market Abuse Regulation (EU) No. 596/2014. Upon the publication of this announcement via the Regulatory Information Service, this inside information is now considered to be in the public domain.