GSK (GSK) has agreed to acquire Boston Pharmaceuticals' investigational steatotic liver disease treatment efimosfermin alfa for up to $2 billion in cash, the companies said Wednesday.

The company will pay $1.2 billion upfront, with potential for certain additional milestone payments amounting to $800 million. Under the terms of the deal, GSK will buy Boston Pharmaceuticals unit BP Asset IX to access efimosfermin.

GSK will be responsible for success-based milestone payments, as well as tiered royalties for efimosfermin owed to Novartis Pharma, the companies said.

GSK shares were up 2.1% in recent premarket activity.