Page 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K Annual report pursuant to Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 For the fiscal year ended December 31 , 2020 or Transition report pursuant to Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 For the transition period from to Commission file number : 0-27756 ALEXION ALEXION PHARMACEUTICALS , INC . ( Exact Name of Registrant as Specified in Its Charter ) Delaware ( State or Other Jurisdiction of Incorporation or Organization ) 121 Seaport Boulevard , Boston Massachusetts 02210 ( Address of Principal Executive Offices ) ( Zip Code ) 475-230-2596 ( Registrant's telephone number , including area code ) Trading Symbol ( s ) ( I.R.S. Employer Identification No. ) Securities registered pursuant to Section 12 ( b ) of the Act : Yes > No Title of each class Common Stock $ 0.0001 par value Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes No > Indicate by check mark whether the registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes > No Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( § 232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes > No 13-3648318 ALXN Common Stock $ 0.0001 par value Class Name of each exchange on which registered NASDAQ Stock Market LLC Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a smaller reporting company , or an emerging growth company . See the definitions of “ large accelerated filer , ” “ accelerated filer , " " smaller reporting company , " and " emerging growth company " in Rule 12b - 2 of the Exchange Act . Large accelerated filer 0 Smaller reporting company Emerging growth company 0 Accelerated filer Non - accelerated filer If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . < Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes No > The aggregate market value of the Common Stock held by non - affiliates of the registrant , based upon the last sale price of the Common Stock reported on The Nasdaq Stock Market LLC on June 30 , 2020 , was $ 23,569,192,552 . ( 1 ) 219,711,754 Outstanding as of February 4 , 2021 ( 1 ) Excludes 9,150,840 shares of common stock held by directors , executive officers and their respective affiliates at June 30 , 2020 . Exclusion of shares held by any person should not be construed to indicate that such person possesses the power , directly or indirectly , to