Lysogene announces the publication of its 2017 Registration Document

CAMBRIDGE, MA, US, and PARIS, France – June 4, 2018, at 7.30pm CEST – Lysogene (FR0013233475– LYS), a pioneering biopharmaceutical company specialized in gene therapy targeting central nervous system (CNS) diseases, is today announcing the publication of its 2017 Registration Document, recorded by the Autorité des Marchés Financiers (AMF – French Financial Markets Regulator) under no. R. 18-047 on June 4, 2018.

This 2017 Registration Document is now available on Lysogene’s (https://lysogene.com) and the Autorité des Marchés Financiers’ (http://www.amf-france.org/) websites. Copies are also available on request and free of charge from Lysogene’s registered office (18-20 rue Jacques Dulud, 92200 Neuilly-sur-Seine, France).

Investors’ attention is drawn to Chapter 4 – “Risk factors” of the Registration Document recorded by the AMF, especially the liquidity risks presented in section 4.4.2 of the Registration Document.

About Lysogene

Lysogene is a gene therapy company focused on the treatment of orphan diseases of the central nervous system (CNS). The company has built a unique capability to enable a safe and effective delivery of gene therapies to the CNS to treat lysosomal diseases and other genetic disorders of the CNS. A pivotal clinical trial in MPS IIIA is expected to start in 2018, a phase 1-2 clinical trial in GM1 Gangliosidosis in 2019, while we are currently collaborating with amajor partner to define the strategy of development for the treatment of Fragile X syndrome, a genetic disease related to autism. www.lysogene.com

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Forward looking statement

This press release may contain certain forward-looking statements. Although the Company believes its expectations are based on reasonable assumptions, all statements other than statements of historical fact included in this press release about future events are subject to (i) change without

notice and (ii) factors beyond the Company’s control. These statements may include, without limitation, any statements preceded by, followed by or including words such as “target,” “believe,” “expect,” “aim,” “intend,” “may,” “anticipate,” “estimate,” “plan,” “project,” “will,” “can have,” “likely,” “should,” “would,” “could” and other words and terms of similar meaning or the negative thereof. Forward-looking statements are subject to inherent risks and uncertainties beyond the Company’s control that could cause the Company’s actual results, performance or achievements to be materially different from the expected results, performance or achievements expressed or implied by such forward-looking statements. Except as required by law, the Company assumes no obligation to update these forward-looking statements publicly, or to update the reasons actual results could differ materially from those anticipated in the forward-looking statements, even if new information becomes available in the future. This press release has been prepared in both French and English. In the event of any differences between the two texts, the French language version shall supersede.