The buyout will see Bristol-Myers shareholders own about 69% of the merged company, with 31% going to Celgene shareholders, according to the statement.

The new specialty firm will focus on treating people with serious conditions including cancer, offering nine products with “more than US$1 billion in annual sales,” the companies said.

Under the agreement Celgene shareholders will receive one Bristol-Myers Squibb share along with US$50 in cash for each Celgene share, the statement said.

Early US trading saw Bristol-Myers shares drop nearly 15% to US$44.75 — while the New Jersey-based Celgene spiked 32% to hit US$87.40.

In announcing the merger Bristol-Myers Squibb noted “significant potential for growth in the core disease areas of oncology, immunology and inflammation and cardiovascular disease.”

“Together with Celgene, we are creating an innovative biopharma leader, with leading franchises and a deep and broad pipeline that will drive sustainable growth and deliver new options for patients across a range of serious diseases,” said Bristol-Myers Squibb Chairman and CEO Giovanni Caforio in the statement.

Caforio will continue to serve in those capacities, while two members of Celgene’s board will hold spots on Bristol-Myers Squibb’s board of directors.