Additional Listing

The following amendment has been made to the Additional Listing announcement released on 24 March 2016 at 08:54 under RNS No 1674T and is replaced as follows:

Horizon Discovery Group plc 

Additional Listing

The Company has issued and allotted 28,386 new ordinary shares pursuant to the exercise of options.

Accordingly, application has been made for 28,386 new ordinary shares to be admitted to trading on AIM and it is expected that admission will take place on 5 April 2016.

The new ordinary shares will rank pari passu with the existing shares of the Company.

Following Admission, the Company's enlarged issued share capital will comprise 94,123,503 ordinary shares with one voting right per share. No shares are held in Treasury. The total number of voting rights in the Company is therefore 94,123,503.

This figure of 94,123,503 ordinary shares may be used by shareholders in the Company as the denominator for the calculations by which they will determine if they are required to notify their interest in, or a change in their interest in, the share capital of the Company under the FCA's Disclosure and Transparency Rules.

For further information, please contact:

Consilium Strategic Communications

Amber Fennell / Jessica Hodgson / Matthew Neal / Laura Thornton

[email protected]

+44 207 920 2352

Panmure Gordon & Co.

As Nominated Adviser and Broker

Corporate Finance

Freddy Crossley / Fabien Holler / Duncan Monteith

Broking

Tom Salvesen

Tel: +44 20 7886 2500

About Horizon Discovery Group plc

Horizon is a leading international gene-editing company that supplies products, services and research programmes that enable genomics research and the development of personalised and genomic medicines. Horizon has a diverse and global customer base of over 1,400 unique organisations across more than 50 countries, including major pharmaceutical, biotechnology and diagnostic companies as well as leading academic research centres. The Group supplies its products and services into multiple markets, estimated to total in excess of £29 billion in 2015.

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

Horizon offers over 23,000 catalogue products, almost all of which are based on the application of gene editing to generate in vitro and in-vivo models that accurately model the disease-causing genetic anomalies found in diseases like cancer. These 'patients-in-a-test-tube' are being used by customers to: understand the genetic drivers of disease; identify targets of therapeutic intervention that can moderate or correct these genetic drivers; develop novel medicines and companion diagnostic tests that result in the right patient getting the right medicine.

Horizon also provides custom in vitro and in vivo disease model generation services, biopharmaceutical manufacturing cell lines and generation services, quantitative molecular reference standards and contract research and custom screening services.

In addition, Horizon through its Research Biotech business deploys the Company's intellectual property, gene-editing platform, products, services and know-how in cancer research, drug discovery and immunology to develop its immuno-oncology, synthetic lethality and cell therapy platforms which aim to deliver novel drug treatments into the pharmaceutical pipeline.

Horizon is headquartered in Cambridge, UK, and is listed on the London Stock Exchange's AIM market under the ticker "HZD". For further information please visit:www.horizondiscovery.com.