MONROVIA, CA – September 11, 2006 – Xencor, Inc., a biotherapeutics company developing protein and antibody therapeutics, announced today that it has been named by The Wall Street Journal as a 2006 Wall Street Journal Technology Innovation Awards winner. Xencor was selected from among 600 of the most innovative companies and technologies from around the world as a runner-up in the Biotech-Medical category for the company’s innovative XmAb™ technologies. Coverage of the awards appears in The Journal Report section of today’s Wall Street Journal and online at www.wsj.com.

“Our XmAb™ technologies are a suite of proprietary antibody Fc domains and antibody engineering tools that enable us to create humanized therapeutic antibody candidates with unprecedented potency, affinity and ease of production,” said Bassil Dahiyat, Ph.D., President and CEO of Xencor. “We are greatly honored by the Wall Street Journal’s recognition of XmAb™ technology and its impact on the development of new, more potent antibody treatments, such as XmAb™2513, our proprietary drug candidate expected to enter clinical development for treatment of Hodgkin’s Disease next year.”

Xencor’s proprietary XmAb™ technology is addressing a substantial need for structural and functional optimization of monoclonal antibodies as cytotoxic agents through use of its Fc domains. These engineered components of the constant region of an antibody have a wide range of immunological properties and have shown to improve potency of antibodies against tumor cells by more than 100-fold. XmAb™ technology is also being applied to engineering other areas of the antibody therapeutic including the variable region, which imparts specificity for the antibody-target antigen binding. Xencor has entered into numerous license agreements with large pharmaceutical and biotechnology companies based on its XmAb technologies, and the company is generating a strong internal product portfolio of antibody and protein therapeutic candidates.

About Xencor

Xencor, Inc., engineers superior biotherapeutics using its proprietary Protein Design Automation® technology platform and is a leader in the field of antibody Fc engineering to significantly improve antibody potency. The company is internally advancing both XPro™ protein therapeutic candidates and XmAb™ antibody drug candidates optimized for activity against biologically validated targets. Xencor’s product development is led by a protein therapeutic drug candidate, XPro™1595, for the treatment of inflammatory disorders and an antibody candidate, XmAb™2513, for the treatment of Hodgkin’s Disease and T-cell lymphoma. With multiple partners, such as industry leaders Genentech, Roche, Centocor and MedImmune, Xencor is applying its suite of XmAb antibody Fc domains to improve antibody drug candidates for traits such as potency and sustained half-life. Xencor also develops therapeutic protein variants in collaboration with major pharmaceutical partners. For more information, please visit www.xencor.com.