Pfizer and Allergan will join in a $160 billion deal to create the world's largest drugmaker.
The transaction is valued at $363.63 per Allergan share. Allergan shareholders will receive 11.3 shares of the combined company for each of their shares. Pfizer stockholders get one share of the combined company for each of theirs.
It's the biggest health care deal ever and the largest so-called inversion in history, a tax-saving maneuver in which a U.S. company reorganizes in a country with a lower corporate tax rate. U.S. efforts to curb the practice have so far proven ineffectual.
Botox maker Allergan is based in Ireland but runs much of its operations out of New Jersey.
Pfizer and Allergan will be combined under Allergan PLC, which will be renamed Pfizer PLC.