The latest chapter in GlaxoSmithKline's hostile $2.60 billion takeover attempt to buy Human Genome Sciences has seen the UK drugs major once again extend its offer.

GSK has again chosen not up its $13 a share bid and pushed back the closing date from June 29 to July 20. The extension comes after HGS set a deadline of July 16 for offers to acquire the company in connection with its ongoing strategic alternatives review, a process that GSK has refused to get involved with.

GSK said that extension of the tender offer "will provide HGS shareholders the opportunity to evaluate the outcome of the HGS board's process" relative to its offer. The company added that "based on circumstances at that time, GSK will consider all available options regarding its offer but can make no assurance that the tender offer will be further extended".

HGS noted that less than 1% of its outstanding shares have been tendered into the GSK offer, adding that its review "continues to be active and fully underway". The firm adds that although it would welcome GSK's participation but it has twice declined to enter the process.

Although HGS says it has been in talks with other potential buyers/partners, no other firms have made their interest public. Analysts believe that any potential purchasers will be put off by the existing relationship between HGS and GSK which developed the lupus drug Benlysta (belimumab) together.

The firms are also partners on the late-stage cardiovascular treatment darapladib and albiglutide, currently in Phase III for type 2 diabetes.