arGEN-X advances a third therapeutic antibody program into preclinical development

• ARGX-111isan anti-c-Metantibody withbroadapplicability in cancer

Rotterdam, the Netherlands and Ghent, Belgium– arGEN-X, a biopharmaceutical company focused on the discovery and development of human monoclonal antibodies from its proprietary SIMPLE Antibody™ platform, announces that it has progressed ARGX-111, its third therapeutic candidate, into formal preclinical development.

ARGX-111 is a novel, fully human antibody specific for c-Met, a receptor tyrosine kinase involved in cell proliferation, angiogenesis and metastasis. c-Met is widely implicated in multiple cancers, including non small cell lung cancer (NSCLC), gastric, prostate and brain tumors. ARGX-111 has been shown in several preclinical models to outperform clinical-stage anti-c-Met antibodies in terms of potency and efficacy.

ARGX-111 was selected from a panel of more than 60 antagonistic anti-c-Met antibodies generated from the SIMPLE Antibody™ platform, several of which have specificity for previously unknown epitopes on c-Met. ARGX-111 exhibits the unique ability to block both ligand-dependent and independent receptor activation, while avoiding agonistic activity. In addition, the antibody demonstrates potent cytotoxic effects against c-Met over-expressing tumor cells.

Next to its ultra-high potency, ARGX-111 has other important characteristics that make it a very attractive development candidate. ARGX-111 has a fully human sequence and structure, and expression and stability studies indicate that it can be manufactured at consistently high quality and yield.

arGEN-X anticipates filing an IND application for ARGX-111 in 2013.

ARGX-111 is one of five therapeutic antibody programs under development at arGEN-X for the treatment of autoimmune disorders, inflammation and cancer. The initiation of formal preclinical development for ARGX-111 marks the third program to progress to this stage in only 26 months since the start of the Company’s operations.

arGEN-X’ most advanced preclinical program is ARGX-110, a fully human antibody with unprecedented neutralization potency for a novel T- and B-cell receptor involved in haematological malignancies, solid tumors and autoimmune indications. An IND application for ARGX-110 is anticipated in early 2013.

Commenting further on the Company’s progress, Tim Van Hauwermeiren, CEO of arGEN-X, said: To have identified an antibody with such potency, specificity and excellent development potential for a target as important as c-Met is a major step in the validation of our unique SIMPLE Antibody™ platform. The highly attractive profile of ARGX-111 was recognized as an exciting investment proposition in our EUR27.5 million fundraising in December 2011. Our progress in successfully applying our transformational technology and rapidly building a best-in-class product pipeline puts arGEN-X in pole position to deliver its business plan in the coming years.