Salix Pharmaceuticals Ltd. and Cosmo Pharmaceuticals SpA have called off their $2.6 billion merger, which would have made Salix a wholly owned subsidiary of Cosmo Technologies Ltd., an Irish subsidiary of Cosmo. In a statement, Salix president and CEO Carolyn Logan cited the "uncertainty" created by the "changed political environment" after the U.S. Treasury proposed plans last month to make corporate tax inversions less attractive and even to halt such deals.