GLAXOSMITHKLINE

BENLYSTA® (belimumab)

We entered into an agreement with GlaxoSmithKline (GSK) in 2006 for the co-development and commercialization of BENLYSTA. GSK is one of the world’s leading research-based pharmaceutical and healthcare companies, and brings global development and marketing capabilities to the BENLYSTA program.

On March 9, 2011, HGS and GlaxoSmithKline PLC (GSK) announced FDA approval of BENLYSTA® (belimumab) for the treatment of autoantibody-positive adult patients with active, systemic lupus erythematosus who are receiving standard therapy. BENLYSTA is the first new approved drug for lupus in more than 50 years – and the first HGS product to receive FDA approval.

GSK submitted a Marketing Authorization Application (MAA) for BENLYSTA to the European Medicines Agency (EMA) in June 2010, and a decision on European approval is expected in the second half of 2011. Regulatory applications have also been submitted and are currently under consideration in Canada, Australia, Switzerland, Russia, Brazil and The Philippines.

HGS and GSK will share equally in Phase 3 and 4 development costs, sales and marketing expenses, and profits associated with BENLYSTA.

Darapladib

Darapladib, a small-molecule Lp-PLA2 inhibitor discovered by GSK based on HGS technology, is in Phase 3 development by GSK for the treatment of coronary heart disease. We will receive a 10% royalty on worldwide sales of darapladib if it is commercialized, and we have a 20% co-promotion option in North America and Europe, under which we would pay 20% of commercialization costs in exchange for 20% of darapladib profits. We are also entitled to receive a milestone payment if darapladib moves through clinical development into registration.

Syncria® (albiglutide)

Syncria, an albumin-fusion protein created by HGS using our proprietary albumin-fusion technology, is in Phase 3 development by GSK for the treatment of type 2 diabetes. We licensed Syncria to GSK in October 2004, and are entitled to fees and milestone payments that could amount to as much as $183 million, some of which has already been received, in addition to royalties on worldwide sales if Syncria is commercialized.

UNITED STATES GOVERNMENT

Raxibacumab

In September 2005, we entered into a contract with the Biomedical Advanced Research and Development Authority (BARDA) of the Office of the Assistant Secretary for Preparedness and Response (ASPR) of the U.S. Department of Health and Human Services (HHS) to supply raxibacumab to the U.S. Strategic National Stockpile for emergency use in the treatment of inhalation anthrax. Under the first phase of our contract, we supplied ten grams of raxibacumab to HHS for comparative in vitro and in vivo testing. In June 2006, under the second phase of our contract, the U.S. Government exercised its option to purchase raxibacumab.

In the first half of 2009, we achieved our first product sales by delivering 20,000 doses of raxibacumab to the U.S. Strategic National Stockpile for use in the event of an emergency to treat inhalation anthrax. In July 2009, we secured a new purchase order for 45,000 additional doses to be delivered over a three-year period. Approximately 21,000 doses have been delivered to date under the new purchase order, and we expect to deliver approximately 15,000 additional doses to the Stockpile in 2011.