GlaxoSmithKline (NYSE:GSK) has made change in its offer to buy Human Genome Sciences (Nasdaq: HGSI) but it’s not sweetening the price.

The British pharmaceutical giant announced that it is changing the conditions of its cash offer to acquire HGS for $13 per share — nearly $2.6 billion. HGS last week adopted a “poison pill” to fend off GSK’s hostile bid. Under the shareholder rights plan, HGS shareholders would have the right to acquire additional shares at a discount, diluting GSK’s stake in the company.

GSK, which has its U.S. headquarters in Research Triangle Park, said today that because of the poison pill its tender offer comes with an added condition requiring HGS “to redeem the pill.”

In other words, GSK wants action taken to make the poison pill invalid or not applicable to a GSK acquisition of the company. The pill is triggered if GSK gets a 15 percent or greater stake in HGS.

GSK’s bid for HGS became public on April 19. On May 9, GSK took its offer directly to HGS shareholders arguing that the $13 per share price, an 80 percent premium over HGS share price before the offer became public, was “full and fair.” The offer was set to expire on June 7.
HGS countered last week by adopting the poison pill, which is in effect for a year, in order to buy time to find another buyer and consider its alternatives. But GSK is not budging on price or on its timeline. GSK said its offer still expires on June 7 at midnight, eastern time.