PUBLICATION IN ACCORDANCE WITH ARTICLE 14 OF THE BELGIAN LAW OF 2 MAY 2007 REGARDING THE PUBLICATION OF MAJOR SHAREHOLDINGS (THE "TRANSPARENCY LAW")

REGULATED INFORMATION

GHENT, Belgium, 28 May 2018 - Ablynx [Euronext Brussels and Nasdaq: ABLX] today announced, in accordance with Article 14 of the Belgian Law of 2 May 2007 regarding the publication of major shareholdings in issuers whose securities are admitted to trading on a regulated market (the "Transparency Law"), that it received a notification of shareholdings from Sanofi S.A. on 24 May 2018.

Sanofi S.A. notified Ablynx that on 18 May 2018 it has upward crossed the 95% threshold of total voting rights of Ablynx.

Sanofi S.A. now holds a total of 74,567,835 voting rights of Ablynx, representing 95.60% of the current 78,001,392 outstanding voting rights of Ablynx.

The notification contains the following information:

• Reason for the notification: acquisition or disposal of voting securities or voting rights
• Notification by: a person that notifies alone
• Persons subject to the notification requirement: Sanofi S.A., 54 rue La Boétie, 75008 Paris, France
• Transaction date: 18 May 2018
• Threshold that is crossed: 95%
• Denominator: 78,001,392
• Chain of controlled undertakings through which the holding is effectively being held: Sanofi is not a controlled entity

A full version of the transparency notification is available on Ablynx website, under the section Investors.

The Articles of the Association of Ablynx NV provide for shareholders notification threshold of 3%, 5% or a multiple of 5% of the total number of existing voting rights.

About Ablynx

Ablynx is a biopharmaceutical company engaged in the development of Nanobodies, proprietary therapeutic proteins based on single-domain antibody fragments, which combine the advantages of conventional antibody drugs with some of the features of small-molecule drugs. Ablynx is dedicated to creating new medicines which will make a real difference to society. Today, the Company has more than 45 proprietary and partnered programmes in development in various therapeutic areas including inflammation, haematology, immuno-oncology, oncology and respiratory disease. The Company has collaborations with multiple pharmaceutical companies including AbbVie; Boehringer Ingelheim; Eddingpharm; Merck & Co., Inc., Kenilworth, New Jersey, USA; Merck KGaA; Novo Nordisk; Sanofi and Taisho Pharmaceuticals. The Company is headquartered in Ghent, Belgium. More information can be found on www.ablynx.com.