Alexion, AstraZeneca Rare Disease, has completed a definitive purchase and licence agreement for a portfolio of preclinical rare disease gene therapy programmes and enabling technologies from Pfizer Inc. These new resources build on the combined capabilities of Alexion and AstraZeneca in genomic medicine, with the objective to develop new genetic therapies with improved safety and efficacy profiles. Additionally, several of the Pfizer employees associated with the portfolio will join Alexion as employees. Financial considerations: Alexion has purchased and licenced the assets of Pfizer's early-stage rare disease gene therapy portfolio for a total consideration of up to $1 billion, plus tiered royalties on sales.