GlaxoSmithKline’s waiting period under the Hart-Scott-Rodino Antitrust Improvement Act of 1976, as amended, expired as of June 1, 2012, giving GSK clearance to acquire all outstanding shares of Human Genome Sciences.

GSK’s tender offer to acquire HGS, made on May 10, 2012, was for $13.00 per share in cash. The offer represents a premium of 81% to HGS's closing share price of $7.17 on April 18, 2012, the last trading day before HGS publicly disclosed GSK’s private offer. The tender offer and withdrawal rights are scheduled to expire at midnight EST on June 7, 2012.

Lazard and Morgan Stanley are acting as financial advisors to GSK and Cleary Gottlieb Steen & Hamilton and Wachtell, Lipton, Rosen & Katz are providing legal advice.