MONROVIA, Calif., USA and INGELHEIM, Germany – February 21, 2012 – Xencor, Inc., a company using its proprietary Protein Design Automation® (PDA) platform technology to engineer next-generation antibodies, and Boehringer Ingelheim announced today a collaboration agreement for certain Xencor biosuperior monoclonal antibodies. Under the terms of the agreement, Boehringer Ingelheim will provide all manufacturing and product supply from preclinical through Phase 1 development. Xencor is responsible for preclinical and clinical studies and retains all development and commercial rights to products under the agreement. Upon successful advancement of clinical programs beyond Phase 1 development, Boehringer Ingelheim has certain manufacturing rights to supply clinical and commercial material to Xencor.

"Xencor has developed a deep portfolio of biosuperior antibodies with the potential for superior clinical and commercial performance, and this collaboration agreement with Boehringer Ingelheim allows us to establish an important relationship with the leading global contract manufacturer of biologics," said Bassil Dahiyat, Ph.D., president and CEO of Xencor. "Xencor and Boehringer Ingelheim will share the financial risk in early preclinical and clinical development with the incentive of sharing in future success of the programs."

"We are delighted to start this collaboration with Xencor. It reflects one of our new business models in the contract manufacturing in which both parties are enabled to focus on their core competencies," stated Corporate Senior Vice President Simon Sturge at Boehringer Ingelheim Biopharmaceuticals."We are convinced that this creates a win-win situation for both parties."

Xencor's lead biosuperior compound is an anti-TNF antibody engineered using the company's proprietary Xtend&#8482 antibody engineering technology for increasing antibody half-life. Xencor expects to initiate a Phase 1 trial in 2013 potentially resulting in key human pharmacokinetic data validating Xtend technology.

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, Centocor, 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.

About Boehringer Ingelheim
The Boehringer Ingelheim group is one of the world's 20 leading pharmaceutical companies. Headquartered in Ingelheim, Germany, it operates globally with 145 affiliates in 50 countries and more than 42,000 employees. Since it was founded in 1885, the family-owned company has been committed for 125 years to researching, developing, manufacturing and marketing novel products of high therapeutic value for human and veterinary medicine.

Today, Boehringer Ingelheim is one of the world's leading companies for contract development and manufacture of biopharmaceuticals. All types of services from mammalian cell line or microbial strain development to final drug production can be delivered within a one-stop-shop concept. Boehringer Ingelheim delivers services for pre-clinical development up to global market supply with a strong commitment to its customers at its global manufacturing facilities for mammalian cell culture and microbial fermentation. Boehringer Ingelheim has brought 19 molecules to market and has many years of experience in multiple molecule classes such as monoclonal antibodies, recombinant proteins, interferons, enzymes, fusion molecules and plasmid DNA. Furthermore, high-titer platform technologies for new antibody mimetic formats such as scaffold proteins and antibody fragments are available for the manufacture of customer products. www.biopharma-cmo.com.

For more information, please contact:
Xencor Inc.
Heidi Chokeir, Ph.D.
Canale Communications for Xencor
Tel: 619-849-5377
heidi@canalecomm.com

Boehringer Ingelheim GmbH
Heidrun Thoma
Corporate Communications
Boehringer Ingelheim GmbH
55216 Ingelheim/Germany
Phone: +49/6132 77 3966

Twitter: www.twitter.com/boehringer
More information:
bio-cmo@boehringer-ingelheim.com