Human Genome Sciences, Inc. (Nasdaq: HGSI) today issued the following statement regarding the extension by GlaxoSmithKline plc (GSK) of its unsolicited tender offer to acquire all the outstanding common shares of HGS at a price of $13.00 per share in cash and GSK’s statement that approximately 474,029 shares of HGS common stock have been tendered into their offer. HGS noted that less than one percent of its shares outstanding tendered into the GSK offer. The HGS Board of Directors has rejected GSK’s unsolicited $13.00 per share tender offer after determining, in consultation with financial and legal advisors, that the GSK offer price is inadequate and does not reflect the value inherent in HGS. As previously announced, our Board has authorized the exploration of strategic alternatives in the best interests of stockholders, including a potential sale of the Company. This process continues to be active and fully underway. GSK declined to enter the process and, through its unsolicited tender offer, seeks to circumvent, disrupt and prematurely end the Company’s process to the disadvantage of HGS stockholders. We are committed to completing our exploration of strategic alternatives as expeditiously as possible, and the HGS Board of Directors recommends that HGS stockholders reject GSK’s tender offer and not tender any of their shares to GSK. Goldman, Sachs & Co. and Credit Suisse Securities (USA) LLC are serving as financial advisors to HGS, and Skadden, Arps, Slate, Meagher & Flom LLP and DLA Piper LLP (US) are serving as legal counsel. ABOUT HUMAN GENOME SCIENCES Human Genome Sciences exists to place new therapies into the hands of those battling serious disease. For more information about HGS, please visit the Company’s web site at www.hgsi.com. Health professionals and patients interested in clinical trials of HGS products may inquire via email to firstname.lastname@example.org or by calling HGS at 1-240-314-4430. HGS, Human Genome Sciences and BENLYSTA® are trademarks of Human Genome Sciences, Inc. Other trademarks referenced are the property of their respective owners.