Novartis said on Monday it would begin a second offer period for shares in U.S. cancer diagnostics company Genoptix after securing acceptances for 80% in the initial offer.

The holders of shares tendered in the second period, which closes on March 4, will be paid $25 per share, the same amount offered in the initial offer period, the Swiss drugmaker said.

Independent analysts had placed the stock's value as high as $28.00 per share, legal advisers The Briscoe Law Firm PLLC and Powers Taylor LLP, said in January, when the deal was first announced.

Genoptix, a laboratory specialising in diagnosing cancers in bone marrow, blood and lymph nodes, had sales of $184 million in 2009 and employs 500 staff, Novartis said in January.

Novartis wrapped up its $52 billion buyout of U.S. eyecare group Alcon last year after a protracted battle with the U.S.-listed company's minority shareholders. Novartis shareholders will vote on that merger and on a proposed capital increase at an extraordinary meeting on April 8.