MONROVIA, Calif., January 17, 2013—Xencor, Inc. today announced it has received a milestone payment from Janssen Research & Development, LLC (Janssen R&D) resulting from the exercised option for the use of Xencor's Xtend™ half-life extension technology in a therapeutic antibody. This triggered a payment to Xencor under the terms of a technology license agreement that the company entered into with Janssen R&D (f/k/a Centocor Research & Development, Inc.) in 2009. The antibody target and the amount of the payment were not disclosed.

"There has been significant interest in Xtend technology because of the impact it has on the pharmacokinetic properties of antibodies, and we are seeing Xencor technology license agreements with partners translate into promising pipeline programs," said Bassil Dahiyat, Ph.D., president and CEO of Xencor.

Using its Xtend technology, Xencor has developed an extensive pipeline of best-in-class proprietary and partnered antibody therapeutics, as well as biosuperior versions of blockbuster antibody drugs.

About Xtend™ technology
Xencor's proprietary Xtend™ antibody technology platform provides a validated solution to enhancing the serum half-life of immunoglobulin molecules. Using its proprietary series of antibody Fc variants, antibody half-life can be readily prolonged to enhance performance in a number of different therapeutic indications. By prolonging the serum half-life of antibody drug molecules the opportunity arises to address chronic indications with an antibody drug product that potentially i) enhances drug exposure and patient responses, ii) is administered at more than monthly intervals, greatly enhancing patient convenience, reducing administration costs and improving market positioning, and iii) has a reduced dose required to maintain effective drug levels, potentially improving the cost, profitability and capital expense profile of the product.

About Xencor, Inc.
Xencor, Inc. engineers superior biotherapeutics using its proprietary Protein Design Automation® technology platform, and is a leader in the field of antibody engineering to significantly improve antibody half-life, immune-regulatory function and potency. The company is advancing multiple XmAb® antibody drug candidates in the clinic, including XmAb®5871 targeting CD32b and CD19 for autoimmune diseases, and an anti-CD30 candidate XmAb®2513 for the treatment of Hodgkin's lymphoma. Xencor is also advancing a portfolio of biosuperior versions of blockbuster antibody drugs engineered for superior half-life and dosing schedule. Xencor has entered into multiple partnerships with industry leaders such as Amgen, Pfizer, MorphoSys, Boehringer Ingelheim, CSL Ltd. and Human Genome Sciences. In these partnerships Xencor is applying its suite of proprietary antibody Fc domains to improve antibody drug candidates for traits such as sustained half-life and/or potency. For more information, please visit www.xencor.com.

Xencor Media Contact
Jason I. Spark
Canale Communications for Xencor
Tel: 619-849-6005
jason@canalecomm.com