Thermo Fisher Scientific Inc. initiated an underwritten public offering of $1.5 billion of its common stock.

The company plans to grant the underwriters an option to buy up to $225.0 million of additional shares.

Thermo Fisher plans to use all of the net proceeds of the offering to fund a portion of the consideration payable for its acquisition of Patheon NV, including the repayment of Patheon's debt to be assumed by Thermo Fisher. The company expects to complete the transaction around the end of third quarter 2017, subject to the satisfaction of customary closing conditions.

The offering is not conditioned upon the completion of the acquisition of Patheon.

Goldman Sachs & Co. LLC is acting as lead book-running manager, while BofA Merrill Lynch and Citigroup are acting as joint book-running managers for the offering.