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, 20 March 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 Baker Bros. Advisors LP on 15 March 2018.

Baker Bros. Advisors LP notified Ablynx that as a result of a disposal of voting securities, it has downward crossed the 5% threshold on 14 March 2018 and now holds 2,928,325 voting securities of Ablynx, representing 3.89% of the current 75,253,667 outstanding voting rights of Ablynx (versus 5.35% notified previously on 31 October 2017).

The notification contains the following information:

• Reason for the notification: acquisition or disposal of voting securities or voting rights
• Notification by: a parent undertaking or a controlling person
• Persons subject to the notification requirement: Julian C. Baker, Felix J. Baker, Baker Bros. Advisors (GP) LLC, Baker Bros. Advisors LP, 860 Washington Street, 3^rd Floor, New York, NY 10014, USA
• Transaction date: 14 March 2018
• Threshold that is crossed: 5%
• Denominator: 75,253,667
• Details of the notification: Baker Bros. Advisors LP holds 2,928,325 Ablynx shares with voting rights
• Chain of controlled undertakings through which the holding is effectively being held: Baker Bros. Advisors LP (the "Investment Adviser") is the Investment adviser to 667 LP and Baker Brothers Life Sciences LP (the "Funds").

             
More information is provided in the transparency notification. Full versions of both transparency notifications are 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.

For more information, please contact
Ablynx:
Dr Edwin Moses
CEO
t:   +32 (0)9 262 00 07
m: +32 (0)473 39 50 68
e:  edwin.moses@ablynx.com

Lies Vanneste
Director Investor Relations
t:   +32 (0)9 262 01 37
m: +32 (0)498 05 35 79
e:  lies.vanneste@ablynx.com