Mar. 12--A wave of multibillion-dollar deals this week signals the acceleration of a deal-making frenzy that will likely reshape the life-sciences industry.

In the two latest, South San Francisco-based Genentech Thursday finally agreed to a $46.8 billion deal with Roche, while Foster City-based Gilead Sciences moved the same day to snap up Palo Alto-based CV Therapeutics for $1.4 billion. Earlier this week pharmaceutical giant Merck agreed to buy Schering-Plough.

Failing in large measure to develop their own new medicines and facing a slew of generic competitors as their drug patents expire, companies like Roche -- often dubbed Big Pharma -- increasingly are bolstering their product lines by swallowing up biotech and other drug companies with hot products.

And Bay Area biotech companies are especially attractive take-over targets. Aside from Genentech and CV Therapeutics, firms whose names pop up as possible acquisitions for Big Pharma or other biotech suitors include Affymax of Palo Alto as well as Exelixis and Theravance, both of South San Francisco. Affymax is working on treatments for kidney diseases, Exelixis focuses heavily on combating cancer and Theravance is developing medicine for respiratory disease, bacterial infections and gastrointestinal ailments.

Some experts fear the trend might blunt the innovative, research-oriented cultures that long have been the hallmark of such legendary biotech firms as the venerable

Genentech. Others say Big Pharma may stop work on some promising but expensive-to-develop drugs at the companies they buy or could so dominate certain drug markets they could foist higher prices on consumers.

But others discount such concerns, noting the merger trend has been growing for nearly two decades without stifling biomedical research, and they predict that a lot more deals are likely to be in the works.

"I don't see any end in sight for the next two to three years," said Mark Edwards president of Deloitte Recap of Walnut Creek, which tracks these deals.

There were 31 such mergers and acquisitions in 2008, a record number, according to Edwards' company. That compares with 19 in 2007, 24 in 2006 and 23 in 2005.

Edwards noted that venture capital firms in recent years have tended to pump larger amounts of money into each biotech firm they fund, which has upped the expectations for those investors. And with initial public stock offerings rare these days, the easiest way those investors have of recouping their money is through acquisitions by other companies.