In order to attain a dominant position in the hereditary angioedema (HAE) market and to increase the size of its rare disease business unit, Shire has agreed to acquire ViroPharma for approximately US$4.2 B in cash. With the acquisition, Shire will gain Cinryze® (C1 esterase inhibitor [human]), a prophylactic HAE treatment that will complement its existing portfolio product Firazyr® (icatibant), which is indicated for acute HAE attacks. The acquisition also offers Shire the potential for annual cost synergies of approximately US$150 M by 2015 and sizeable tax savings.