CAMBRIDGE ANTIBODY TECHNOLOGY

In August 1999, we entered into an antibody license agreement with Cambridge Antibody Technology for the development of fully human antibody therapeutics for up to three of our target human proteins. Pursuant to this agreement, we entered into an exclusive license agreement for BENLYSTA™ (belimumab), which was generated in collaboration with CAT. In February 2000, we entered into a broader agreement with CAT that provides us with the right to use its technology to develop and sell an unlimited number of fully human antibodies for therapeutic and diagnostic purposes. Pursuant to this agreement, we have obtained an exclusive license with respect to TRAIL receptor 1, TRAIL receptor 2 and raxibacumab. CAT has the right to select up to 24 of our proprietary antigens for preclinical development. We have the option to share clinical development costs and to share the profits equally with them on up to 18 such products. CAT has rights to develop six such products on its own. We are entitled to clinical development milestone and royalty payments on those six products. In June 2006, CAT was acquired by AstraZeneca.

XENCOR

On February 7, 2008, HGS and Xencor, Inc. announced a collaboration agreement under which Xencor will apply its proprietary technologies to enhance the pharmacologic properties of monoclonal antibodies developed by HGS that specifically target antigens discovered by HGS. Under the terms of the agreement, Xencor will receive an upfront payment and is eligible to receive additional payments including development and commercial milestones, and royalties on any products commercialized under the agreement. HGS will be responsible for all preclinical and clinical development, manufacturing and commercialization. Financial terms were not disclosed. This agreement demonstrates the continuing HGS commitment to targeted innovation based on HGS discoveries and the Company’s extensive intellectual property estate.

ABGENIX

In November 1999, we entered into a collaboration and license agreement with Abgenix relating to the field of fully human antibody drug candidates, which was amended in 2001; the research term of this agreement expired in November 2005. In May 2003, we announced the acquisition of an exclusive worldwide license from Abgenix to develop and commercialize a fully human monoclonal antibody to the CCR5 receptor. We received clearance from the FDA to initiate clinical development of CCR5 mAb (HGS004) in December 2004, and we completed and reported the results of a Phase 1 trial of CCR5 mAb in patients infected with the HIV-1 virus in September 2006. We will pay milestone and royalty payments for this product as it is developed and if it is commercialized. In April 2006, Abgenix was acquired by Amgen.