A trial involving Genentech began in London.

The litigation involves lawsuits between biotechnology companies that could influence the development of the international market for genetically engineered drugs. The patent dispute in Britain’s High Court concerns a new type of heart-attack medicine called tissue plasminogen activator, or TPA. San Francisco-based Genentech and London-based Wellcome separately devised genetic methods to produce the drug, but Genentech beat Wellcome to the British patent office last year. Now the companies are suing each other over whether Genentech’s patent also covers Wellcome’s own TPA.