Allergan PLC and Pfizer Inc. will merge in a deal worth about $155 billion.

Allergan will be the surviving corporate entity, while the new company will be named Pfizer PLC, trade under the ‘PFE’ ticker, and be based in Ireland for tax purposes.

Allergan is currently based in Ireland for that reason, has U.S. operations in New Jersey, and maintains an aesthetics and eye-care drug hub in Irvine.

The fate of Allergan’s local operations weren’t yet known, but news reports said the new company would decide by 2018 on whether to split into two businesses: patent-protected drugs and those that have lost protection or are about to.

The deal is said to be centered on tax benefits, integrating top-selling products into one company, Allergan bringing Pfizer a high commitment to research and development, and Pfizer bringing Allergan access to international markets.

The merger offers Allergan shareholders 11.3 shares in Pfizer for each Allergan share they own and includes a total of $6 billion to $12 billion in cash.

The newly combined company would have about $60 billion in sales.

Allergan PLC was formed via the acquisition this year of the former Allergan Inc. by Actavis PLC for $72.5 billion.