Late Wednesday, March 28, the Basel, Switzerland pharma company succumbed to the inevitable and lifted its hostile offer for Illumina Inc. by almost 15% to value the stock at close to $6.3 billion.

Roche raised its offer to $51 per share, up from the $44.50 it offered on Feb. 7, and a premium to a stock price that had consistently traded above Roche's offer. The San Diego-based gene-sequencing specialist's shares closed Wednesday at $49.88.

Roche has secured little more than 0.1% of Illumina in its tender to date but CEO Severin Schwan claimed Illumina investors were warming to the takeover.

"Based on our discussions with Illumina shareholders we have seen interest to accelerate the takeover process," he said in a statement. "As a result, we are increasing our offer price to US$ 51.00 per share. Roche's preference continues to be a negotiated transaction. We look forward to the possibility of a swift completion that offers immediate value to Illumina's shareholders."

Illumina shareholders will vote on the proposal during the company's general meeting April 18. To circumvent the board's resistance, Roche has asked investors to expand the target's board by two seats to 11 and replace four executives up for re-election with four of its nominees. Roche also wants investors to appoint two additional nominees to the newly created seats, giving it a majority that could then agree to a deal.

Illumina is asking investors to ignore Roche's approval and re-elect the four executives, including CEO Jay Flatley. The target has resisted Roche's overtures from the beginning and accuses the Swiss suitor of exploiting a dip in its share price to buy the company cheaply.

The San Diego company late Wednesday said it didn't yet have an opinion on the sweetener and told shareholders to take no action.

"Illumina's board of directors will thoroughly review Roche's revised proposal and make a recommendation to stockholders regarding the proposal in due course," the company said.

The Swiss company first announced its interest Jan. 25 and was swiftly met with resistance by Illumina. Although Roche insisted the $44.50 was its last and final offer, history may have tipped its hand - the company has at least twice boosted offers to convert hostile approaches to agreed deals.

Roche has already extended the offer twice and repeatedly called for Illumina to enter discussions. Analysts have said the companies are an excellent match and ruled out a white-knight suitor since no other company could benefit from Illumina as much as Roche.

The acquisition would allow the Swiss company to identify and target specific tumors in cancer patients, taking over a promising market for personalized oncology medicines.

Greenhill & Co. and Citigroup Inc. are providing financial advice to Roche, and Davis Polk & Wardwell LLP is serving as legal counsel.

Goldman, Sachs & Co. and Bank of America Merrill Lynch are Illumina's financial advisers. Dewey & LeBoeuf LLP is the company's legal counsel.

-Laura Board contributed to this report