Pfizer Inc. has decided to kill its planned $150 billion takeover of Allergan PLC, after the Obama administration took aim at a deal that would have moved the biggest drug company in the U.S. to Ireland to lower its taxes, according to people familiar with the matter.

The companies are expected to announce the deal’s termination as early as Wednesday morning, after Pfizer’s board voted Tuesday to halt the combination and the New York-based pharmaceutical company then notified Dublin-based Allergan, the people said.

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