Swiss pharmaceutical group Roche said on Wednesday that it was buying Seragon Pharmaceuticals, a US biotechnology firm specializing in a new way to fight breast cancer, in a deal worth up to $1.7 billion.

Seragon, a privately held outfit located in California, is developing a new generation of treatments for the most common form of breast cancer, the Basel-based company said in a statement.
   
Roche said its Genentech subsidiary would be acquiring Seragon, putting $725 million in cash upfront and adding up to another $1 billion if "certain predetermined milestones" are met.

The deal is expected to be sealed by the end of September if anti-trust regulators raise no objection.