How antitrust watchdogs will receive Shire plc's plan to grab Dyax Corp. for $5.9 billion cash – with $646 million more if the FDA clears DX-2930, a late-stage prophylactic antibody treatment for hereditary angioedema (HAE) – remains to be seen, but the FTC likely will want the combined firm to get rid of Kalbitor (ecallantide), approved for acute attacks of HAE, since Shire already has the bradykinin receptor antagonist Firazyr (icatibant) approved for that indication.