Pfizer Inc. and and Allergan Plc will mutually end their planned $160 billion merger amid the US crackdown on corporate inversions, CNBC reported Tuesday night, without naming its sources.

Allergan, which is run from New Jersey but has a legal domicile in Dublin, last year agreed to merge with Pfizer Inc. in a $160 billion deal that would give New York-based Pfizer a foreign address and a lower tax rate. Representatives for Pfizer and Allergan declined to comment.

The Treasury Department said Monday that new rules would limit companies’ ability to participate in inversion transactions if they’ve already done them within the past 36 months. Allergan has been involved in several such acquisitions in that time frame. In a corporate inversion, a US company merges with a smaller foreign firm and then transfers the new company’s tax address offshore.


Pfizer has been examining how it might be able to challenge new rules from the US Treasury Department, Bloomberg News reported earlier Wednesday, citing people with knowledge of the matter. Fighting the decision in court was one of the options under discussion, as well as restructuring the deal to reduce what Pfizer would pay, the people said.

Earlier in the day, investors seemed to view the deal as dead, and were trading shares in the two companies at a furious pace Tuesday. Allergan’s US shares fell $41, or 15 percent, to close at $236.55 Tuesday. Pfizer shares rose 64 cents, or 2.1 percent, to $31.36.

Tax inversions and the need to overhaul the US tax structure have become a hot issue in the presidential campaign, with some candidates calling Pfizer and other companies considering such deals ‘‘unpatriotic.’’ President Obama held a news conference Tuesday afternoon, saying the Treasury rules are meant to prevent ‘‘one of the most insidious tax loopholes out there’’ and prevent wealthy corporations from shirking their tax responsibility.


In an inversion, a big company buys a smaller one in another country, usually with a lower tax rate, then moves the combined company’s address on paper — but little else — to that country. Allergan is the result of multiple inversions, and despite its Dublin address is operated from offices in Parsippany, N.J.

Shares also fell Tuesday for other companies that have been planning inversion deals: Milwaukee-based Johnson Controls Inc. and Ireland’s Tyco International, makers of heating and other building control systems that announced a $14.6 billion deal in January, and drugmakers Baxalta Inc. of Bannockburn, Ill., and Shire PLC of Ireland, which are planning a $32 billion inversion deal.

As for Pfizer, experts disagree on what its Plan B will be and on its value and future prospects without the deal.

Cowen and Co. analyst Steve Scala wrote to investors that Pfizer’s ‘‘innovative engine is starting to deliver, as evidenced by the success’’ of new breast cancer drug Ibrance, the promise of its immune system-boosting cancer drugs, and growing sales of its pneumonia vaccine Prevnar-13 and blood thinner Eliquis.

Scala wrote Tuesday that Pfizer ‘‘has one of the industry’s most expansive pipelines’’ and forecast that the standalone company would have earnings-per-share growth of 11 percent from 2016 through 2020, ‘‘among the best in the group.’’

Jeffries International analyst Jeffrey Holford, on the other hand, sees ‘‘few other key catalysts for Pfizer in 2016 outside the Allergan merger and potential’’ separation of its global established products business, which sells older, mostly off-patent drugs, particularly outside the United States.

The Allergan deal was Pfizer’s third attempt at pulling off an inversion, including its failed hostile attempt to acquire Britain’s AstraZeneca PLC in 2014. Pfizer’s top management has been desperately seeking a way to quickly boost the company’s value and stock price amid years of relentless pressure from analysts and others to break up the company so growth and profits could accelerate. If that happened, Pfizer likely would spin off the established products business.


The company has a history in this century of doing mega-acquisitions that allow it to cut costs and increase sales to boost profits quickly. That has kept Pfizer among the top global drugmakers but hasn’t pleased investors enough, which ultimately led to the ouster of CEO Ian Read’s predecessor late in 2010.