To acquire Seragon Pharmaceuticals, Swiss pharmaceuticals Roche Holding AG has agreed to pay up to $1.725 billion. Seragon Pharmaceuticals which is a privately-held U.S. biotech company focuses on developing treatments for breast cancer.

Roche, which is based in Basel, will pay $725 million in cash and may hand another $1 billion based on the realization of certain drug development milestones.

With this deal, Roche is looking to boost its offering of breast cancer drugs. Roche has long had a dominant position in the field with drugs such as Herceptin and recently won approval for Perjeta and Kadcyla two other treatments for patients whose cancer cells contain increased amounts of the protein known as HER2.

Since walking away from a $6.8 billion deal to acquire Illumina, a U.S. gene sequencing company in 2012, Roche has avoided multi-billion deals and instead snapped up a couple of smaller diagnostic companies so far this year.

To develop antibiotics, Roche also partnered with various companies and it will work with Versant Ventures and Inception Sciences Inc on a new company to develop therapies for patients with multiple sclerosis.

For Roche, Seragon is the second notable acquisition in as many months. Roche acquired Genia Technologies, a U.S. gene-sequencing firm in June for $350 million. Seragon, which is based in San Diego, was last year spun off from Aragon Pharmaceuticals when that firm was bought for up to $1 billion by Johnson & Johnson.

Seragon is focused on developing a new generation of oral medicines that it believes present an improved way of tackling hormone receptor-positive breast cancer and other types of cancers. ARN-810, its most advanced experimental drug, is presently in initial Phase I clinical trials for breast cancer patients who have not responded to current hormonal agents.

Roche said that Seragon’s oral selective estrogen receptor degraders, or SERDs, would complement existing research and development programmes in breast cancer under way at the Swiss group’s Genentech unit.