GlaxoSmithKline (GSK) began its previously announced tender offer to acquire all of the outstanding shares of Human Genome Sciences (HGS) for $13.00 per share in cash or $2.6 billion. GSK, which first made the unsolicited bid for HGS in mid-April, is proceeding with its offer despite having the bid rejected by HGS when it was first made.

The closing of the tender offer is subject to the terms and conditions detailed in the offer document. The tender offer and withdrawal rights are scheduled to expire on June 7, 2012, unless otherwise extended.

In a press statement, HGS confirmed that it was aware of GSK’s intention to proceed with the $2.6-billion offer. The company will review the offer with its board of directors in consultation with independent financial and legal advisors. HGS says it plans to advise stockholders within 10 days of when GSK commenced the offer, which was May 10, 2012.

The proposed $13.00-per-share price is the same price that GSK had offered in mid-April when HGS rejected the bid. At that time, HGS authorized the exploration of strategic alternatives, including, but not limited to, a potential sale of the company, and invited GSK to participate in that process.

HGS posted a net loss of $381.1 million in 2011 on revenues of $131 million and also posted a loss in 2010 of $233 million. Last year, HGS received FDA approval for Benlysta (belimumab), a drug to treat lupus. The drug was approved by FDA in March 2011 and posted 2011 revenues of $52.3 million. In 2006, HGS and GSK entered into a codevelopment and commercialization agreement under which HGS conducted the Benlysta Phase II trials, with assistance from GSK. The companies share equally in Phase III/IV development costs, sales, and marketing expenses, and profits of any product commercialized under the agreement. GSK also has two late-stage candidates to which HGS has substantial financial rights, darapladib, in Phase III development for treating cardiovascular disease, and albiglutide, in Phase III development for treating Type II diabetes.

See related article, GlaxoSmithKline: A Rebuffed Suitor for the Moment (PharmTech blog)