argenx raises approximately $231 million in gross proceeds in an upsized U.S. public offering

Regulated information - Inside information

Breda, the Netherlands / Ghent, Belgium - argenx (Euronext & Nasdaq: ARGX) a clinical-stage biotechnology company developing a deep pipeline of differentiated antibody-based therapies for the treatment of severe autoimmune diseases and cancer, announced today the pricing of its public offering in the United States (the Offering) with anticipated gross proceeds totalling approximately $231 million from the sale of 4,440,000 American Depository Shares (ADSs), at a price to the public of $52.00 per ADS. argenx increased the Offering from the initially filed offering size of $150 million.

All of the ADSs are being offered by argenx, and each of the ADSs offered represents the right to receive one ordinary share, nominal value of €0.10 per share.

argenx has granted the underwriters an option to purchase up to an additional 666,000 ADSs, representing 15% of the ADSs sold in the Offering. This option can be exercised during the 30-day period commencing December 13, 2017. The Offering is expected to close on December 18, 2017, subject to customary closing conditions.

argenx`s ADSs are currently listed on the Nasdaq Global Select Market under the symbol "ARGX," and argenx`s ordinary shares are currently listed on Euronext Brussels.

Cowen and Piper Jaffray & Co. are acting as joint bookrunning managers for the Offering, and JMP Securities and Wedbush PacGrow are acting as co-managers. Kempen & Co is argenx`s advisor in connection with the Offering.

A registration statement relating to and describing the terms of the Offering has been filed with, and was declared effective by, the U.S. Securities and Exchange Commission (SEC) on December 13, 2017. This registration statement can be accessed through the SEC`s website at.

The Offering is being made only by means of a prospectus forming part of the effective registration statement. When available, copies of the final prospectus can be obtained for free from Cowen and Company, LLC, c/o Broadridge Financial Services, 1155 Long Island Avenue, Edgewood, NY 11717, Attn: Prospectus Department, by telephone at (631) 274-2806 or by fax at (631) 254-7140 or from Piper Jaffray & Co., Attn: Prospectus Department, 800 Nicollet Mall, J12S03, Minneapolis, MN 55403, or by telephone at (800)747-3924, or by email at prospectus@pjc.com.

This press release is for information purposes only and does not constitute, and should not be construed as, an offer to sell or the solicitation of an offer to buy or subscribe to any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale is not permitted or to any person or entity to whom it is unlawful to make such offer, solicitation or sale. Reference is also made to the restrictions set out in "Important information" below. This press release is not for publication or distribution, directly or indirectly, in or into any state or jurisdiction into which doing so would be unlawful or where a prior registration or approval is required for such purpose.