arGEN-X Granted Broad Patent Covering Its Unique Simple Antibody(TM) Platform

Rotterdam, the Netherlands, July 8 2010 – arGEN-X, a biopharmaceutical company focused on the discovery and development of human monoclonal antibodies using its proprietary SIMPLE Antibody™ platform, announces that it has been granted the first patent covering the platform. The patent GB2461546B, has been granted by the UK Patent and Trademark Office (UKPTO).

The broad granted patent covers arGEN-X’s SIMPLE Antibody™ technology, which yields gold standard human therapeutic antibodies with an unmatched functional diversity. It also covers arGEN-X’s antibody products as well as methods of generating them. arGEN-X is prosecuting additional patent applications globally, which when granted will provide the company with an unrivalled IP position in the human antibody space.

arGEN-X’ SIMPLE Antibody™ platform utilizes the active immunization of outbred Camelids with a target antigen to rapidly deliver highly diverse antibodies whose variable regions are nearly identical to those of human antibodies. arGEN-X then uses these to produce variable antibody regions with 96-99% human sequence homology via minimal germlining (humanization). This is easily achieved without any loss in affinity and potency in just a matter of weeks. These variable domains are then combined with human constant domains to generate full size, fully human therapeutic antibodies.

A further key attraction of the SIMPLE Antibody™ platform is its unique ability to generate incredibly diverse panels of ultra-potent antibodies to a broad range of targets, including intractable and conserved targets. These antibody panels effectively blanket the target of interest providing pharma researchers with more choice in the drug discovery stage. This allows them to use more stringent lead selection criteria, increasing the probability of successful therapeutic antibody development.

arGEN-X has already demonstrated that human antibodies generated using its SIMPLE Antibody™ platform routinely exhibit gold standard potencies and affinities, without the need for additional engineering. These properties combined with their excellent manufacturability, make them an ideal starting point for a therapeutic antibody development program. Prof. Hans de Haard, CSO of arGEN-X commenting on today’s announcement said: “The UKPTO’s decision to grant the first patent for our SIMPLE Antibody™ platform is a major value-enhancing milestone in arGEN-X’ corporate development. It is also a key step in our goal to achieve a broad and unencumbered global IP position for our platform which will give us a highly competitive position in the human antibody space”.

“As we work with our SIMPLE Antibody™ platform, we are increasingly convinced that it will transform the discovery and development of human therapeutic antibodies. This is due to its ability to rapidly produce incredibly diverse panels of ultra potent antibodies that address a broad range of both intractable and conserved targets. These unique properties are already generating considerable interest amongst potential partners who are looking to access a platform around which they can build broadly based therapeutic antibody discovery and development programs.”

arGEN-X is currently using the power of the SIMPLE Antibody™ platform to build its business by making this unique technology and know-how available to biopharmaceutical companies through selective strategic partnerships and by developing its own portfolio of exciting therapeutic antibody candidates.

The power of the SIMPLE Antibody™ platform is enabling the Company to rapidly build its own pipeline. arGEN-X’ lead product, ARGX-109, a fully human mAb targeting autoimmune, inflammation and oncology indications, has already entered preclinical development in less than 12 months from start of the discovery process. ARGX-109, which targets the cytokine IL-6, has already shown very high potencies in a range of in vivo studies. arGEN-X currently has a further three therapeutic antibody candidates in its own development pipeline.

About arGEN-X – www.arGEN-X.com

arGEN-X is a preclinical stage biopharmaceutical company with a broadly applicable, proprietary SIMPLE Antibody™ platform. The platform allows arGEN-X to create an unparalleled diversity of in vivo generated antibody leads against a broad range of human disease targets. This superior choice of ultra-high affinity and highly potent leads, having best-in-class human homology, allows for more stringent lead selection criteria, thereby increasing the probability of success later in the drug development path. The Company has validated its platform on four human disease targets to date. The Company’s first patent was granted by the UK Patent and Trademark Office in July 2010. arGEN-X is globally prosecuting additional patent applications, which will provide it with broad protection of its technology.

arGEN-X’ SIMPLE Antibody™ Platform is based on the active immunization of outbred Camelids with target antigens to deliver antibodies whose variable regions are virtually identical to those of human antibodies. The combination of those variable domains with the constant domains of human antibodies, generates full size, human therapeutic antibodies.

The SIMPLE Antibody™ Platform enjoys an independent, unencumbered patent position and is free of target gatekeeping restrictions.

arGEN-X™ and SIMPLE Antibody™ are deposited trademarks of arGEN-X BV.

SIMPLE stands for Superior Immunodiversity with Minimal Protein Lead Engineering.

For further information, please contact:

Citigate Dewe Rogerson arGEN-X David Dible Mark Swallow Nina Enegren Tim Van Hauwermeiren, MSc, eMBA Chief Executive Officer

T: +44 207 282 2949/2948 E: David.Dible@citigatedr.co.uk T: +31 6 122 85 257 E: tim.vh@arGEN-X.com

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