There was no joy in Paris, at least at sanofi-aventis (Paris) headquarters, on Friday. When the company’s offer to acquire Genzyme (Cambridge, MA) at $69 per share expired that day, fewer than 1% of the biopharmaceutical company’s outstanding shares had been tendered. In response, sanofi extended its deadline to January 21, 2011 without modifying the terms of its offer. Why should the company expect a different result in six weeks’ time?

Genzyme shareholders don’t like sanofi’s offer and are unlikely to pressure CEO Henri Termeer to accept it. sanofi should offer more money, Fabrice Seiman, portfolio manager of Lutetia Capital and a Genzyme shareholder, told The Wall Street Journal. A fairer price would be $75–80 per share, Seiman said.

Genzyme’s shareholders are not the only ones to consider sanofi’s bid too low. “Investors value Genzyme higher than the current offer from sanofi,” Michael Obuchowski, chief investment officer at First Empire Asset Management, told Bloomberg. sanofi may be alone in considering $69 per share a good price.

A disagreement about the value of Genzyme’s efforts to correct manufacturing-quality violations at its Allston, Massachusetts, plant has prevented the companies from agreeing on a share price. Nor have the companies seen eye to eye about the potential of Campath, a new product that Genzyme wants to market to treat multiple sclerosis.

An acquisition could be a boon to sanofi, which will soon face generic competition for major products such as Plavix and Taxotere. Buying Genzyme would help sanofi develop a pipeline of biopharmaceuticals and establish its position on the increasingly important large-molecule playing field.

Because no alternative bidder has emerged, sanofi might think that if it bides its time, Genzyme’s shareholders ultimately will give in. I think this is a miscalculation. The shareholders’ consensus has held strong for two months. I don’t see it dissolving during the next six weeks in the absence of a sweeter deal.

sanofi could compromise by agreeing to pay Genzyme compensation according to the future performance of Campath. The companies’ financial advisors recently discussed this idea, but it has not borne fruit so far, according to The Wall Street Journal. Driving a hard bargain might backfire for sanofi, and offering a higher price per share now could keep the company from losing more money in the future.