The boards of Sanofi-Aventis SA and Genzyme Corp were scheduled to hold separate meetings on Sunday to discuss a potential deal, but talks may linger into the week, sources familiar with the situation said on Sunday.

Sanofi, close to clinching a more than $19 billion deal to buy Genzyme, continues to conduct due diligence and the two companies have not yet finalized an agreement, sources said.

The deal's timing remained unclear. Although an announcement could come as early as Monday, sources cautioned that discussions could linger into the week.

A deal may be priced at roughly $74 per share in cash, or $19.2 billion, based on Genzyme's outstanding shares of 258.99 million as of Oct. 29, plus a contingent value right, or CVR, with an intrinsic value of $5 to $6 a share, the sources said.

An agreement would come nearly nine months after the French drugmaker first put the idea to the U.S. biotech group.

Buying Genzyme will give Sanofi a new area for growth in the high-margin business of rare diseases as it seeks to diversify to make up for patent losses that will take out roughly a third of its 2008 sales base until 2013.

"A $74 cash deal makes financial and strategic sense for Sanofi. It removes a substantial overhang and gives a bridge over the patent cliff they face," said Marc Booty, a fund manager at Pictet.

Sanofi Chief Executive Chris Viehbacher, who first told Genzyme CEO Henri Termeer he was interested in a deal on May 23 last year, took an initial bid of $69 a share directly to Genzyme shareholders in October. But the two companies in recent weeks have entered direct negotiations on a higher price.

The CVR is a tradable instrument, which promises a payout to shareholders over time, based on the performance of Genzyme's experimental drug Lemtrada for multiple sclerosis. The drug is already sold under the brand name Campath for leukemia.

It is not possible to pin down what the CVR will begin to trade at, but assuming it trades for $2 a share - a reasonable estimate since many of Genzyme's shareholders are short-term investors who will want to sell immediately - the deal would give Genzyme a tradable value of about $19.68 billion.

The nominal value of the CVR is expected to be between $12 and $15 a share, to be paid out over seven or eight years, according to one source.

But a standard discount is applied to those figures to determine their present value. That figure is then risk-adjusted depending on investors' assessment of the likelihood of the company meeting its goals.

CONFIDENTIALITY PACT
A Sanofi spokesman said the French drugmaker was continuing to review Genzyme's business and declined to say when a deal might be concluded.
"As we have already indicated, we have signed a confidentiality agreement with Genzyme and we are still looking at non-public information. We have no further comment," he said.

Sanofi is due to release its full-year financial results on Wednesday and a deal could be announced before then, sources said.

The timing of the deal announcement is not dependent on the earnings date, however, one source cautioned.

The management and advisers for the two companies have been discussing a potential deal, including a CVR, for several weeks, trying to bridge a wide gap in their expectations for Lemtrada.

Genzyme has forecast peak annual sales of $3.5 billion, while Sanofi, using the average of several analyst estimates, expects only about $700 million.

Helvea analyst Karl-Heinz Koch said a CVR was a smart way for Sanofi to deal with the unknowns surrounding Lemtrada.

"They are not paying upfront for a lot of uncertainty --that's important," he said. "At $74 plus a CVR the deal terms would be within reason ... The earnings leverage to Sanofi is substantial. They can extract a couple of billions in profit by integratingGenzyme."

Credit Suisse and Goldman Sachs are advising Genzyme.
JPMorgan, Evercore Partners and Morgan Stanley are advising Sanofi.