Dainippon Sumitomo Pharma has filed suit today against Pfizer after the US drug giant sought to end a licensing deal for the blood pressure drug, Amlodin (amlodipine besylate). The Japanese firm argues that Pfizer has “no justifiable ground” for seeking an injunction against the manufacture and sale of the drug, which is Dainippon Sumitomo’s biggest-selling offering, pulling in almost $500 million dollars annually.

Dainippon Sumitomo, and its parent company, Sumitomo Chemical are hoping the district court in Tokyo will rubber stamp the validity of the deal with Pfizer: the US firm had argued that the merger between Dainippon and Sumitomo, which came into effect on October 1, overruled the original agreement signed in 1991 [[26/11/04c]]. In contrast, Dainippon Sumitomo stresses that the contract was transferred to the newly-merged company and that it therefore has the right to continue manufacturing and selling Amlodin.