Roche has extended its $5.70 billion hostile takeover bid for Illumina, ie without raising its offer, a move that has not gone down well with the US gene specialist.

The Swiss major is sticking with its $44.50 per share bid and has extended the offer, which expired on Friday, to March 23. To date, shareholders of Illumina have taken the advice of the latter's board, which has dismissed Roche's offer, and just 0.1% of shares have been tendered.

Illumina, which in January adopted a 'poison pill', namely a shareholder-rights plan with a 15% trigger in an attempt to ward off Roche's advances, has previously dismissed the offer as "grossly inadequate in multiple respects" and "opportunistic". Now, the firm says that "the extension by Roche was expected," noting that "extremely low number of shares have been tendered".

The firm adds that this is "consistent with our view - and that of our stockholders - that Roche's offer does not reflect Illumina's unique leadership position, business performance and future prospects".

Analysts believe that Roche will finally get hold of Illumina but may have to sweeten the deal. However, it is clear that the Basel-headquartered giant is in no hurry, and this waiting approach has been successful in the past, resulting in the acquisition of US diagnostics company Ventana Medical Systems in 2008 and the buy-out of Genentech a year later.