Paris: US pharmaceutical giant Pfizer announced Monday it had reached a deal to buy biotech firm Seagen, specialising in innovative cancer treatment, for $43 billion.

"Pfizer is deploying its financial resources to advance the fight against cancer," said Pfizer CEO Albert Bourla.

Seagen -- leading in the research, development and commercialisation of cancer treatments -- is growing, with a 12 percent increase in revenue forecast in 2023 to $2.2 billion.

The deal has been approved by the boards of both firms.

Pfizer is offering $229 per share in cash, at a valuation of $43 billion for Seagan.

The pharmaceutical firm will finance the transaction by going into debt and dipping into its cash.

The company says it expects the deal to close late this year or early next year once it obtains various regulatory and shareholder approvals.