The GlaxoSmithKline will develop and commercialize HGS-ETR1 (mapatumumab) jointly with Human Genome Sciences.

HGS-ETR1 is a human monoclonal antibody that specifically binds to the TRAIL-receptor 1 protein, induces apoptosis in human cancer cell lines expressing TRAIL receptor 1, and has anti-tumour activity in a broad range of tumour types, both as a single agent and in combination with chemotherapy. As HGS-ETR1 mimics the activity of the natural TRAIL-receptor 1 protein, it is considered an agonistic antibody.

As part of its June 1996 agreement with GSK, Human Genome Sciences granted a 50/50 co-development and co-promotion option to GSK for certain Human Genome Sciences human therapeutic products that complete Phase 2a clinical trials. Under the terms of the agreement, GSK and Human Genome Sciences will share equally in Phase 3 and 4 development costs, and will share equally in sales and marketing expenses and profits of any product that is commercialized, under a co-development and co-promotion agreement, the remaining terms of which are being negotiated by the parties. In July 2005, Human Genome Sciences announced that GSK exercised its option to co-develop and co-commercialize LymphoStat-B (belimumab), which is currently in Phase 2 clinical trials in systemic lupus erythematosus and rheumatoid arthritis.

H. Thomas Watkins, Chief Executive Officer, Human Genome Sciences, said, "We are delighted that GSK has exercised its option to develop and commercialize HGS-ETR1 jointly with Human Genome Sciences. We look forward to a productive collaboration for the development and commercialization of this novel anti-cancer agent."