Cleary Gottlieb Steen & Hamilton has served as legal counsel to Japan‘s Takeda Pharmaceutical on a $5.2 billion deal to acquire U.S.-based rare cancer drugmaker Ariad Pharmaceuticals, represented by Paul, Weiss, Rifkind, Wharton & Garrison.

The transaction is expected to close by the end of February 2017. With this deal, Takeda gains access to Iclusig, Ariad’s leukemia drug, which is estimated to generate sales of $170 million-$180 million in 2016, according to Reuters.

Cancer drugs are attractive to pharma giants, which pay high prices promising assets, reported Reuters. In September, Takeda announced it was seeking multi-billion dollar acquisitions to cut back its dependence on domestic sales.

Velcade, Takeda's blockbuster blood cancer medicine, is expected to face market competition from generic drugmakers this year. In addition, other key Takeda products will go off patent from 2020.

Takeda said it will finance the acquisition by taking on $4 billion in new debt.