Update on Acquisition of GE Healthcare Dharmacon

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Horizon Discovery Group plc ("Horizon" or the "Company")

Update on Acquisition of GE Healthcare Dharmacon, Inc.

Cambridge, UK, 22 August 2017: Horizon Discovery Group plc (LSE: HZD) ("Horizon" or "the Company"), a global leader in the application of gene editing technologies, is today providing an update on its acquisition of GE Healthcare Dharmacon, Inc. ("Dharmacon") which was announced on 19 July 2017 (the "Acquisition"). Horizon is pleased to announce that on 22 August 2017 the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976 for the Acquisition expired. Consequently, the Acquisition Agreement has now become unconditional in all respects save for completion of the Placing.

Application has been made to AIM for the admission of the Placing Shares (comprising 39,024,390 new Ordinary Shares) and the Consideration Shares (comprising 13,064,868 new Ordinary Shares) to trading. It is expected that the Placing Shares will be admitted to trading on AIM at 8.00 a.m. on 23 August 2017. It is expected that, following completion of the Acquisition expected to be on 31 August 2017, the Consideration Shares will be admitted to trading on AIM within 2 business days.

Unless otherwise indicated, capitalised terms in this announcement have the same meaning as in the Acquisition announcement released by Horizon on 19 July 2017.

ENDS

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

Horizon Discovery Group plc

Darrin Disley, Chief Executive Officer

Richard Vellacott, Chief Financial Officer

Chris Claxton, VP Investor Relations

Tel: +44 (0) 1223 655 580

Numis Securities Limited (Broker and NOMAD)

Michael Meade / Freddie Barnfield

Tel: +44 (0) 207 260 1000

Consilium Strategic Communications (Financial Media and Investor Relations)

Mary-Jane Elliott / Susan Stuart / Matthew Neal / Melissa Gardiner

Tel: +44 (0) 20 3709 5701

Email: [email protected]

About Horizon Discovery Group plc ‐ see www.horizondiscovery.com

Horizon Discovery Group plc (LSE: HZD) ("Horizon"), is a leading global gene editing company that designs and engineers genetically-modified cells and then applies them in research and clinical applications that advance human health.

Horizon's core capabilities are built around its proprietary translational genomics platform, a highly precise and flexible suite of gene editing tools (rAAV, ZFN, CRISPR and Transposon) able to alter almost any gene sequence in human or mammalian cell-lines.

Horizon offers over 23,000 catalogue products and related research services based on the generation and application of cell and animal models that accurately recapitulate the disease-causing genetic anomalies found in diseases like cancer. Horizon's commercial offering has been adopted by over 1,600 unique research organisations in over 50 countries, as well as in the Company's own pipeline of innovation, to support a greater understanding of the genetic drivers of disease and the development of molecular, cell and gene therapies that can be prescribed on a personalised basis.

Horizon is headquartered in Cambridge, UK, and is listed on the London Stock Exchange's AIM market under the ticker "HZD".