Roche extended its $5.7 billion cash bid for U.S. gene decoder Illumina for a second time as the Swiss drugmaker sticks to its tried and tested M&A strategy of playing a long game.

Roche is offering $44.50 per share for Illumina, but analysts expect the company ultimately to raise its offer for the San Diego-based group.

Illumina, which has adopted a "poison pill" defence strategy for Roche's unsolicited bid, said that Roche's offer remained "grossly inadequate."

"Illumina is positioned to create far more value than Roche has offered. Our shareholders clearly agree," the company said in a statement.

Only about 0.1% of Illumina's shares outstanding have so far been tendered to Roche, the Basel-based company said.

Roche urged Illumina shareholders last week to take up its offer, originally made in January, which it views as "full and fair."

Investors have said Roche may have to raise its bid to around $60 per share to win Illumina, whose shares have come down from a six-month high of $55.39 hit when the offer was announced to close at $50.46 on Friday

Waiting Game

The next stage in Roche's hostile bid is Illumina's annual general meeting on April 18, for which Roche has named a slate of director candidates for election to Illumina's board in a bid to gain control.

It is vying to fill the seats of four directors, whose terms will expire at the meeting this year. Roche will also try to convince shareholders to expand the board to 11 members by adding two more Roche-nominated directors in an attempt to win a majority.

Roche, the world's largest maker of cancer drugs, has already extended its offer for Illumina once as it digs in and plays a waiting game before possibly stepping in with a higher offer, a strategy that has paid off in the past.

The group took seven months to buy U.S. diagnostic test-maker Ventana for $3.4 billion in 2008. It first made an unsolicited, low-end bid before increasing its original offer by 19%.

"We see the acquisition of Illumina as a good strategic fit and expect further six to eighteen months for the deal to be settled," said Vontobel analyst Andrew Weiss.

Illumina makes machines that decode a person's entire genome and would give Roche a leading position in the market for gene sequencing, which can help better identify which patients benefit from a given drug.

Roche has been pushing ahead in developing targeted therapies and Illumina's technology would help it to progress further in this field as gene sequencing is central to "personalised" medicine, particularly in cancer.

The Basel-based company extended its offer until 6.00 p.m. New York time on April 20. Roche said all other terms of the offer remained the same.

Greenhill & Co. and Citigroup Markets are advising Roche on the deal and Davis Polk & Wardell is acting as legal counsel.