Shares of Ariad Pharmaceuticals (ARIA) soared Monday after Japan's Takeda Pharmaceutical (TKPYY) offered to buy the leukemia drug maker. Under the deal, Takeda will pay $24 a share in cash, which represents an enterprise value of approximately $5.2 billion.

With the deal, the Japanese drug giant also gains access to Ariad's leukemia drug, Iclusig, which is expected to generate sales of $170 million to $180 million in 2016. The transaction is expected to close by the end of February 2017.

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