Confidential submission of Form F-1 to SEC

Horizon Discovery Group plc

Confidential submission of Form F-1 to SEC relating to

proposed U.S. public offering

Cambridge, UK, 4 February 2020: Horizon Discovery Group plc (LSE: HZD) ("Horizon" "the Group" or "the Company") today announces that it has confidentially submitted a draft registration statement on Form F-1 with the Securities and Exchange Commission (the "SEC") relating to the proposed initial U.S. public offering of American depositary shares ("American Depositary Shares") representing its ordinary shares (the "Offering"). The number of American Depositary Shares to be offered and the price range for the proposed Offering have not yet been determined. Horizon expects to use the proceeds of the Offering for general corporate purposes. The Offering is expected to commence after the SEC completes its review process, subject to market and other conditions, and shareholders and potential investors should note that the potential Offering may or may not proceed.

This news release is being made pursuant to and in accordance with Rule 135 under the Securities Act of 1933, as amended, and does not constitute an offer to sell or the solicitation of an offer to buy securities, and shall not constitute an offer, solicitation or sale in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of that jurisdiction.

Ends

For further information from Horizon Discovery Group plc, please contact:

Horizon Discovery Group plc

Terry Pizzie, Chief Executive Officer

Jayesh Pankhania, Chief Financial Officer

Jon Davies, Head of Investor Relations

Tel: +44 (0) 1223 655 580

Numis Securities Limited (Broker and NOMAD)

Freddie Barnfield / Duncan Monteith

Tel: +44 (0) 207 260 1000

Consilium Strategic Communications (Financial Media and Investor Relations)

Mary-Jane Elliott / Matthew Neal / Melissa Gardiner

Tel: +44 (0) 20 3709 5700

Email: [email protected]

Westwicke, an ICR Company (US Investor Relations)

Stephanie Carrington

Tel. +1 646-277-1282

Email: [email protected]