Cubist Pharmaceuticals Inc. is buying a pair of antibiotics companies to gain two compounds as revenue drivers to fill the gap between Cubicin daptomycin and the company's Phase III pipeline. Cubist's task now is to wrestle scrips away from lower priced generics by convincing hospitals of the value of Optimer Pharmaceuticals Inc.'s Dificid fidaxomicin and, if approved next year, Trius Therapeutics Inc.'s tedizolid.

With an existing U.S. sales force and plans to establish one in Europe, Cubist seized an opportunity last week to gain two products it believes line up well with the company's marketing expertise.