Biopharma giant Abbvie has announced the acquisition of Allergan for $63 billion in cash and stock. Abbvie said the deal would be “transformational” for both companies, allowing Abbvie to diversify its business while focusing on scientific research and the company’s pipeline.

Allergan has previously been a target for Pfizer, though the deal was called off after the US Department of Treasury implemented new tax inversion regulations. Since that point the company’s stock has slipped for a number of quarters in 2018, mostly due to generic competition in the US.

Allergan’s CEO said the deal would create a company with a combined revenue of around $48 billion in 2019, with a strong pipeline in multiple therapeutic areas and the ability to contribute more widely to global health than either Abbvie or Allergan could do on their own.

The combined companies will have strong franchises across immunology, haematologic oncology, neuroscience, eye care and virology, alongside other areas.

AbbVie is set to generate considerable annual operating cash flow after the deal, which will support a debt reduction target of $15 to $18 billion before the end of 2021.