Ultragenyx Pharmaceutical Inc.
Ultragenyx Pharmaceutical Inc. (Form: SC 13G, Received: 01/10/2018 16:49:30)

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934

(Amendment No. )*

Ultragenyx Pharmaceutical Inc.
(Name of Issuer)

Common Stock
(Title of Class of Securities)

90400D108
(CUSIP Number)

December 29, 2017
(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this
Schedule is filed:
[X] Rule 13d-1(b)
[ ] Rule 13d-1(c)
[ ] Rule 13d-1(d)

*The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

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1 NAMES OF REPORTING PERSONS I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
Capital International Investors **

2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS) (a)

(b)

3 SEC USE ONLY

4 CITIZENSHIP OR PLACE OF ORGANIZATION

California

5 SOLE VOTING POWER

4,139,700

             6   SHARED VOTING POWER
 NUMBER OF
   SHARES         NONE
BENEFICIALL
 Y OWNED BY
             7   SOLE DISPOSITIVE POWER
    EACH
 REPORTING        4,411,165
   PERSON
   WITH:
             8   SHARED DISPOSITIVE POWER

                  NONE

9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

4,411,165 Beneficial ownership disclaimed pursuant to Rule 13d-4

10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES
(SEE INSTRUCTIONS)

11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW 9

10.3%

12 TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

IA

** A division of Capital Research and Management Company (CRMC)

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SECURITIES AND EXCHANGE COMMISSION
Washington, DC 20549

Schedule 13G

Under the Securities Exchange Act of 1934

Amendment No.

Item 1(a) Name of Issuer:
Ultragenyx Pharmaceutical Inc.

Item 1(b) Address of Issuer's Principal Executive Offices:
60 Leveroni Court
Novato, CA 94949

Item 2(a) Name of Person(s) Filing:
Capital International Investors, division of Capital Research and Management Company

Item 2(b) Address of Principal Business Office or, if none,
Residence:
11100 Santa Monica Boulevard
16th Floor
Los Angeles, CA 90025

Item 2(c) Citizenship: N/A

Item 2(d) Title of Class of Securities:
Common Stock

Item 2(e) CUSIP Number:
90400D108

Item 3 If this statement is filed pursuant to sections 240.13d-1(b)
or 240.13d-2(b) or (c), check whether the person filing is a:
(e) [X] An investment adviser in accordance with section 240.13d-1(b)(1)(ii)(E).

Item 4 Ownership

Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

(a) Amount beneficially owned:
(b) Percent of class:
(c) Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
(ii) Shared power to vote or to direct the vote:
(iii) Sole power to dispose or to direct the disposition of:
(iv) Shared power to dispose or to direct the disposition of:

See page 2

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Capital International Investors divisions of Capital Research and Management Company ("CRMC") and Capital Bank and Trust, as well as the following CRMC subsidiaries: Capital Guardian Trust Company, Capital International Limited, Capital International Sarl, Capital International K.K. and Capital International, Inc., collectively provide investment management services under the name "Capital International Investors." Please see Items 5 through 11 of each reporting person's cover sheet in this Schedule 13G filing for such person's deemed beneficial ownership of 4,411,165 shares or 10.3% of the 42,589,056 shares believed to be outstanding.

Item 5 Ownership of Five Percent or Less of a Class. If this
statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following: [ ]

Item 6 Ownership of More than Five Percent on Behalf of Another
Person: One or more clients of Capital International Investors have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Common Stock of Ultragenyx Pharmaceutical Inc.. Capital International Investors holds more than five percent of the outstanding Common Stock of Ultragenyx Pharmaceutical Inc. as of December 29, 2017 on behalf of each of the following client(s):

New Perspective Fund

Item 7 Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent Holding Company or Control Person: N/A

Item 8 Identification and Classification of Members of the Group:
N/A

Item 9 Notice of Dissolution of Group: N/A

Item 10 Certification

By signing below, I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

Signature

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

        Date:          January 10, 2018

        Signature:     **Robert W. Lovelace
        Name/Title:    Robert W. Lovelace, Partner
                       Capital International Investors

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***By  /s/ Walter R. Burkley
       Walter R. Burkley
       Attorney-in-fact

Signed pursuant to a Power of Attorney dated January 4, 2017 included as an Exhibit to Schedule 13G filed with the Securities and Exchange Commission by Capital International Investors on January 10, 2017 with respect to Agios Pharmaceuticals, Inc.

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