arGEN-X SIMPLE Antibody(TM) Platform set to Transform Therapeutic Antibody Discovery & Development

ROTTERDAM, The Netherlands, March 1, 2010 -

    - SIMPLE Antibody(TM) Platform Delivers Unprecedented Choice
      of Ultra-Potent Functional Antibody Leads Against Challenging Soluble
      and Cell Surface Targets.

    - ARGX-109, a Fully Human mAb Targeting Autoimmune,
      Inflammation and Oncology Indications, Enters Preclinical Development
      in Less Than 12 Months From Start of Discovery.

arGEN-X, a biopharmaceutical company focused on the discovery
and development of human monoclonal antibodies using its proprietary SIMPLE
Antibody(TM) platform, announces that it will provide an update on the
development of this unique platform and its own antibody pipeline during the
BIO-Europe Spring event in Barcelona (March 8-10, 2010).

Tim Van Hauwermeiren, the CEO of arGEN-X, will highlight a
series of important technical breakthroughs during his presentation,
demonstrating the power of the Company's SIMPLE Antibody(TM) platform to
deliver multiple, diverse, ultra-potent functional antibodies that are able
to blanket any target, regardless of its complexity.

He will also outline the very rapid progress that arGEN-X has
made in building its own pipeline with its lead product ARGX-109, which
entered preclinical development less than 12 months from the start of the
discovery process. ARGX-109 was chosen from a panel of 65 functional
antagonists generated against IL-6, a cytokine that plays an important role
in several autoimmune, inflammation and oncology indications.

arGEN-X' SIMPLE Antibody(TM) Platform is based on the active
immunisation of outbred Camelids with target antigen to deliver antibodies
whose variable regions are virtually identical to those of human antibodies.
These variable domains are combined with human constant domains to generate
full size, fully human therapeutic antibodies.

SIMPLE Antibodies routinely exhibit gold-standard potency and
manufacturability without the need for additional engineering, making them an
ideal starting point for a therapeutic antibody development program.

Prof. Hans de Haard, CSO of arGEN-X commenting on the SIMPLE
Antibody(TM) platorm said:

"The work that we have conducted in the past six months has
clearly demonstrated the power of our SIMPLE Antibody(TM) platform and its
potential to transform the development of therapeutic antibodies. We have
tested its full potential by selecting as targets two highly challenging
receptors known to play a pivotal role in cancer. In just a matter of weeks,
we managed to generate an incredibly diverse panel of ultra-potent antagonist
antibodies, effectively blanketing these targets in a way that, according to
our expert collaborators, has never been seen before. Given the outstanding
manufacturability of our human antibody leads, we are now in a position to
further develop candidates with the best possible drug characteristics in
record time."

arGEN-X intends to use the power of the SIMPLE Antibody(TM)
platform to build its business by making its technology and know-how
available to biopharmaceutical companies through selective strategic
partnerships and adding more exciting programs to its preclinical portfolio.

Tim Van Hauwermeiren, CEO of arGEN-X commenting on the
progress with the Company's own antibody pipeline said:

"Our lead program has already been remarkably productive,
identifying 65 unique IL-6 antagonists with potencies in the picomolar to
femtomolar range. Both lead and back-up molecules in this program have shown
impressive performance in in vivo efficacy studies less than a year from
project commencement, and are now being progressed into preclinical
development. We are extremely pleased with how quickly we have progressed all
four of our internal programs. The progress that we have made so far with our
platform and pipeline gives us great confidence in building a high-value
business that makes us an attractive partner for big pharma."

The power of the SIMPLE Antibody(TM) platform has enabled
arGEN-X to close a recent EUR12.5 milion Series A fund raising. The round was
backed by a range of leading European life science investors including
Forbion Capital Partners, LSP, Credit Agricole Private Equity, KBC Private
Equity, BioGeneration Ventures, Erasmus MC Biomedical Fund, Thuja Capital
Healthcare Funds, as well as the prestigious Belgian life sciences research
institute VIB.

Note for the editor

About arGEN-X - www.arGEN-X.com

arGEN-X is a preclinical stage biopharmaceutical company with
a broadly applicable, proprietary SIMPLE Antibody(TM) 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 and
has broad patent claims in place covering its technology.

arGEN-X' SIMPLE Antibody(TM) Platform is based on the active
immunisation of outbred Camelids with target antigens to deliver antibody
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(TM) Platform enjoys an independent,
unencumbered patent position and is free of target gatekeeping restrictions.

arGEN-X(TM) and SIMPLE Antibody(TM) 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
    David Dible
    Mark Swallow
    Nina Enegren
    T: +44-207-282-2949/2948
    E: David.Dible@citigatedr.co.uk

    arGEN-X
    Tim Van Hauwermeiren, MSc, eMBA
    Chief Executive Officer
    T: +31-6-122-85-257
    E: tim.vh@arGEN-X.com

Citigate Dewe Rogerson: David Dible, Mark Swallow, Nina Enegren, T: +44-207-282-2949/2948, E: David.Dible at citigatedr.co.uk; arGEN-X, Tim Van Hauwermeiren, MSc, eMBA, Chief Executive Officer, T: +31-6-122-85-257, E: tim.vh at arGEN-X.com