AstraZeneca’s mega $39 billion takeover of Alexion Pharmaceuticals has come to a close, delivering the British pharma a lucrative portfolio of immunology medicines and a towering presence in rare diseases.

AZ on Wednesday announced the completion of its Alexion acquisition, a week after securing a pivotal nod from the U.K.’s Competition and Markets Authority (CMA).

Industry watchers were concerned that the deal, the largest announced among pharma players last year, could become a target for an emboldened, Democrat-led Federal Trade Commission (FTC). But those fears were eventually wiped away as AZ secured blessings from the U.S. in April, then from the EU in early July.

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