After making a $43.7 billion offer yesterday (July 21) to buy the 44% of Genentech stock it didn't already own, the Swiss pharmaceutical company announced another biotech purchase today. Roche will acquire Mirus Bio Corporation for $125 million.

Roche's half-year financial results, released on Monday but eclipsed by the Genentech offer, showed a six percent decline in pharmaceutical sales. Roche intends to borrow half the funds required for the Genentech takeover, according to a report published Monday by Global Insight pharmaceutical analyst Gaelle Marinoni, which "implies that the Swiss giant is keeping its options and cash stash open for further smaller acquisitions."

Mirus, one of those smaller acquisitions, is a private US-owned company based in Madison, Wisconsin that specializes in RNA interference (RNAi) technologies. Their products include nucleic acid reagents, kits, and protocols, and the company has siRNA delivery platforms in the pipeline. This is not Roche's first move toward RNAi therapeutics: last year, Roche struck a deal Alnylam Pharmaceuticals Inc., a German company, for the rights to their RNAi technology, an alliance the companies claimed to be worth $1 billion.

"The race is on" for successful use of the RNAi technology, according to a Global Insight analysis, "and any breakthrough could prove very lucrative." Roche plans to maintain Mirus's research station in Madison. The takeover is scheduled to be completed by the end of the year.

Meanwhile, Genentech and Roche leaders met today to informally discuss the buyout, but some analysts are expecting that Roche will to have to increase its offer to take over the biotech giant. The offer is at $89 a share, but Genentech stock jumped to $92.91 by the end of the day on Monday, a possible sign that investors expect a raise on the offer, according to the Associated Press.