argenx SE

AGM Information • Apr 1, 2015

arGEN-X announces Annual General Meeting of Shareholders 13 May 2015

Breda, the Netherlands, 1 April 2015 - arGEN-X N.V. (Euronext Brussels: ARGX, hereinafter: the "Company"), a clinical-stage biopharmaceutical company focused on creating and developing differentiated therapeutic antibodies for the treatment of cancer and severe autoimmune diseases, today announces that an annual general meeting of shareholders will be held on Wednesday 13 May 2015.

The shareholders and all other persons with meeting rights to attend the annual general meeting of shareholders of the Company are invited to attend the annual general meeting of shareholders, to be held at 9:00 AM on Wednesday 13 May 2015 at Hilton Amsterdam Schiphol Airport, Schiphol Boulevard 701, 1118 BN Schiphol, the Netherlands.

AGENDA

Next to recurrent items on the agenda such as the adoption of the 2014 Annual Accounts and the authorisation of the board of directors to limit or exclude pre-emptive rights, the following is, amongst other, proposed:

• approval of the arGEN-X Option Plan, originally adopted by the board of directors on 13 November 2009 and as lastly amended on 18 December 2014 (agenda item 3a)
• appointment of Mr. J. D. deBethizy, PhD as a non-executive member of the board of directors (agenda item 7); and
• appointment of Deloitte Accountants B.V. as the Company's accountant for the 2015 financial year (agenda item 11).

RELEVANT DOCUMENTATION

Here you can find the notice of convocation, including information for shareholders regarding the attendance of the meeting and notification and registration for the meeting, the agenda and the explanatory notes. The 2014 Annual Report and the proposal for the arGEN-X Option Plan may be viewed and downloaded via www.argen-x.com and will be available for examination at the offices of arGEN-X, Technologiepark 30, 9052 Zwijnaarde, Belgium. Copies of these documents may be obtained free of charge at this address.

Breda, 1 April 2015 Board of directors arGEN-X N.V.

ABOUT arGEN-X

arGEN-X is a clinical-stage biopharmaceutical company focused on creating and developing differentiated therapeutic antibodies for the treatment of cancer and severe autoimmune diseases. arGEN-X has generated a pipeline of differentiated clinical and preclinical antibody candidates using its SIMPLE Antibody(TM) discovery platform. SIMPLE Antibody(TM) has a particular strength in addressing novel, complex disease targets that are difficult to access using established antibody technology platforms. Proprietary Fc engineering technologies (NHance® and ABDEG(TM)) and POTELLIGENT® technology (licensed from BioWa, Inc.) further enhance the therapeutic properties of SIMPLE Antibody(TM) leads in terms of tissue penetration/residence time in the body, ability to clear disease targets or pathogenic antibodies and cell-killing potency through Antibody-Dependent Cellmediated Cytotoxicity (ADCC), respectively. arGEN-X has leveraged its suite of antibody technologies in forging strategic collaborations with pharmaceutical and biotechnology companies to provide new approaches to diseases with unmet medical needs.

arGEN-X is listed on the Euronext Brussels exchange under the symbol ARGX.

www.argen-x.com

SIMPLE Antibody(TM), NHance® and ABDEG(TM) are trademarks of arGEN-X NV POTELLIGENT® is a trademark of BioWa Inc.

For further information, please contact:

Joke Comijn, Corporate Communications Manager +32 (0)477 77 29 44 +32 (0)9 243 40 70 info@argen-x.com

Mark Swallow/David Dible Citigate Dewe Rogerson +44 207 282 2948 arGEN-X@citigatedr.co.uk

Beth DelGiacco (US IR) Stern Investor Relations +1 212 362 1200 beth@sternir.com

Forward-looking Statements

The contents of this announcement include statements that are, or may be deemed to be, "forwardlooking statements". These forward-looking statements can be identified by the use of forward-looking terminology, including the terms "believes", "estimates", "anticipates", "expects", "intends", "may", "will", or "should", and include statements arGEN-X makes concerning the intended results of its strategy. By their nature, forward-looking statements involve risks and uncertainties and readers are cautioned that any such forward-looking statements are not guarantees of future performance. arGEN-X' actual results may differ materially from those predicted by the forward-looking statements. arGEN-X undertakes no obligation to publicly update or revise forward-looking statements, except as may be required by law. "Management's Discussion and Analysis of Financial Condition and Results of Operations"