Exhibit 21.1

SUBSIDIARIES OF ALEXION PHARMACEUTICALS, INC.

Alexion Delaware Holding LLC is organized in the State of Delaware

Alexion Services Latin America, Inc. is organized in the State of Delaware

Alexion US Holdings LLC is organized in the State of Delaware

Alexion US1 LLC is organized in the State of Delaware

Alexion Pharma LLC is organized in the State of Delaware

Alexion Holding LLC is organized in the State of Delaware

Wilson Therapeutics USA, Inc. is organized in the State of Delaware

Syntimmune, Inc. is organized in the State of Delaware

Alexion Pharma Argentina SRL is organized in Argentina

Alexion Pharmaceuticals Australasia PTY LTD is organized in Australia

Alexion Pharma Belgium Sprl is organized in Belgium

Alexion Services Europe Sprl is organized in Belgium

Alexion Bermuda L.P. is organized in Bermuda

Alexion Bermuda II L.P. is organized in Bermuda

Alexion Bermuda Holding ULC is organized in Bermuda

Alexion 1609 Partners, LP is organized in Bermuda

Alexion Bermuda Partners L.P. is organized in Bermuda

Alexion Farmacêutica Brasil Importação e Distribuição de Produtos e Serviços de Administração de Vendas Ltda. (doing business as Alexion Brasil) is organized in Brazil

Alexion Farmacêutica América Latina Serviços de Administração de Vendas Ltda. (doing business as Alexion Latina America) is organized in Brazil

Alexion Pharma Canada Corp. is organized in Canada

Alexion Pharmaceuticals (Shanghai) Company Limited is organized in Shanghai

Alexion Pharma Colombia SAS is organized in Colombia

Alexion Pharma Czech s.r.o is organized in the Czech Republic

Alexion Pharma Middle East FZ-LLC is organized in Dubai

Alexion Europe SAS is organized in France

Alexion Pharma France SAS is organized in France

Alexion R&D France SAS is organized in France

Alexion Pharma Germany GmbH is organized in Germany

Alexion Business Services Private Limited is organized in India

Alexion Pharma International Operations Unlimited Company is organized in Ireland

Alexion Pharma Holding Unlimited Company is organized in Ireland

Alexion Pharma Israel Ltd. is organized in Israel

Alexion Pharma Italy Sarl is organized in Italy

Alexion Pharma GK is organized in Japan

Alexion Pharma Mexico, S. de R.L. de C.V. is organized in Mexico

Alexion Holding B.V. is organized in the Netherlands

Alexion Pharma Netherlands B.V. is organized in the Netherlands

Alexion Pharma Foreign Holdings B.V. is organized in the Netherlands

Alexion Pharma Nordics Holding AB is organized in Sweden

Alexion Bermuda Limited is organized in Bermuda

Synageva BioPharma Limited is organized in the United Kingdom

Savoy Therapeutics Corp. is organized in the State of Delaware

Synageva BioPharma Mexico S. de R.L. de C.V. is organized in Mexico

Alexion Pharma OOO is organized in Russia

Alexion Pharma Spain S.L. is organized in Spain

Alexion Pharma Nordics AB is organized in Sweden

Alexion Pharma GmbH is organized in Switzerland

Alexion Ilaç Ticaret Limited Þirketi is organized in Turkey

Alexion Pharma UK Ltd.is organized in the United Kingdom

Alexion Pharma Austria GmbH is organized in Austria

Alexion Pharma Taiwan LTD is organized in Taiwan

Alexion Pharma Korea LLC is organized in South Korea

Alexion Pharma Chile Limitada is organized in Chile

Wilson Therapeutics Incentive AB is organized in Sweden

TTM Europe Development AB is organized in Sweden

Wilson Therapeutics AB is organized in Sweden

Syntimmune, Ltd. is organized in the United Kingdom