GSK Plc is in talks to buy biotech company IDRx, people with knowledge of the matter said, a deal that would see the British drugmaker further boost its growing oncology portfolio.

British pharma giant GSK (NYSE:GSK) is closing in on a $1B buyout deal to acquire IDRx, a U.S. biotech focused on developing drugs for rare gastrointestinal tumors, The Financial Times reported Wednesday.

GSK is reportedly in late-stage negotiations about a $1 billion deal to acquire IDRx and its experimental targeted therapy for a form of rare gastrointestinal stromal tumour (GIST).