Roche Holding AG (ROG.VX) Chairman Franz Humer said Tuesday the Swiss drugmaker doesn't consider as realistic the $112 a share price for Genentech Inc. (DNA) proposed by directors of the biotechnology company as a condition to agree to a takeover.

Humer was speaking to shareholders at the company's annual general meeting in Basel, Switzerland.

On Friday, Roche increased its offer to buy the roughly 44% of U.S. biotechnology company Genentech Inc. (DNA) it doesn't already own, in a deal worth around $45.7 billion. The price reflects a price of $93 per share. On Monday, the Wall Street Journal reported that the two companies are close to agreeing a deal at a price of $95 per share.

The bid was again rejected as too low by Genentech's special committee of independent board members. But Humer said assumptions on which the committee bases its asking price are flawed.

"We feel the price proposed by the special committee, $112 per share, isn't based on realistic assumptions," Humer said.

Overly optimistic assumptions include, the committee's view about the potential impact from follow-on biologics, or generic copies of biotechnology drugs that lost patent protection. The committee also overestimates productivity gains and the potential increase in success rates in research and development, he added.

Roche also considers the committee's view on the market potential of cancer drug Avastin in new uses, and possibilities for price increases in the U.S. market as either inadequate or overly optimistic, Humer said.

Roche has raised close to $40 billion through various bond offerings to finance the deal. Given that the Swiss drugmaker commands around $7 billion in liquid funds already, financing of the deal looks secure, analysts say.

Company Web site: www.roche.com

-By Anita Greil, Dow Jones Newswires; +41 43 443 8044 ; anita.greil@dowjones.com