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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 No. 001-36276 Ultragenyx Pharmaceutical Inc. ( Exact name of registrant as specified in its charter ) Delaware ( State or other jurisdiction of incorporation or organization ) 60 Leveroni Court Novato , California ( Address of principal executive offices ) 27-2546083 Title of each class Common Stock , $ 0.001 par value ( I.R.S. Employer Identification No. ) 94949 ( Zip Code ) ( 415 ) 483-8800 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : Trading Symbol RARE Securities registered pursuant to Section 12 ( g ) of the Act : None . Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . YES NO 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 Name of each exchange on which registered The Nasdaq Global Select Market 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 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 . Accelerated filer Large accelerated filer ✔ Non- accelerated filer Emerging growth company Smaller reporting company 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 Exchange Act ) . YES NO The aggregate market value of the voting and non - voting common equity held by non - affiliates of the Company as of June 30 , 2020 was approximately $ 4.7 billion , based upon the closing price on The Nasdaq Global Select Market reported for such date . Shares of common stock held by each executive officer and director and by each person who is known to own 10 % or more of the outstanding common stock have been excluded in that such persons may be deemed to be affiliates of the Company . This determination of affiliate status is not necessarily a conclusive determination for other purposes . As of February 8 , 2021 , the Company had 66,949,244 shares of common stock issued and outstanding .