arGEN-X Presents Preliminary Efficacy and Expanded Safety Data from Phase I Trial of ARGX-111 at ASCO

• Safe dose established for next stage studies
• Biological activity observed in MET-amplified cancer patient

Breda, the Netherlands/Ghent, Belgium– arGEN-X N.V. (Euronext Brussels: ARGX), a clinical-stage biopharmaceutical company focused on creating and developing differentiated therapeutic antibodies to treat cancer and severe autoimmune diseases, will present the results of a Phase I, first-in-human dose escalation study of ARGX-111, a monoclonal antibody targeting c-Met in patients with solid tumors, at the Annual Meeting of the American Society of Clinical Oncology (ASCO) in Chicago. The company will present an abstract of the data on Saturday, May 30th, from 08:00am – 11:30am as part of the poster session on Development Therapeutics.

ARGX-111 is a c-Met-targeting human monoclonal SIMPLE Antibody™ that modulates all known mechanisms of action of the receptor. As well as the blocking of both ligand-dependent and -independent signaling through c-MET, ARGX-111 benefits from POTELLIGENT®-enhanced Antibody Dependent Cellular Cytotoxicity (ADCC), which drives the immune system to destroy c-MET positive cells of the primary tumor and the circulating tumor cells that are responsible for metastasis; and from NHance®, which drives tissue penetration in the hunt for tumor metastasis. This unique combination results in a potentially best-in-class drug candidate for
c-Met therapies.

ARGX-111 was investigated in a Phase I dose escalation study in 18 patients with advanced solid tumors over-expressing c-Met. The study yielded the initial safety profile and the dosing regimen for the next stage of clinical investigation. The maximum tolerated dose (MTD) was determined at 3 mg/kg every 3 weeks. Biological activity was clearly illustrated in a patient with gastric MET amplified cancer.

What is exciting about these ARGX-111 results is that the Phase I clinical data are a nice translation of the preclinical observations including successful depletion of circulation tumor cells and a marked impact on metastatic lesions in bone and lymph compartments , said Tim Van Hauwermeiren, Chief Executive Officer of arGEN-X. Together with the established safety profile, we have strong support for the further development of ARGX-111 in MET amplified malignancies.

Recruitment of MET amplified patients for the safety expansion cohort is ongoing. arGEN-X expects to report interim data on this safety expansion cohort in the second half of 2016.