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


                             SCHEDULE 13G

               Under the Securities Exchange Act of 1934


                           (Amendment No. )*


                               Allakos Inc.
                             (Name of Issuer)

                               Common Stock
                      (Title of Class of Securities)

                                01671P100
                              (CUSIP Number)

                            December 31, 2018
         (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).


















CUSIP: 01671P100                                                Page 1 of 4



 1   NAMES OF REPORTING PERSONS
     I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
     Capital Research Global 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

     Delaware

             5   SOLE VOTING POWER

                  3,486,468


             6   SHARED VOTING POWER
 NUMBER OF
   SHARES         NONE
BENEFICIALL
 Y OWNED BY
             7   SOLE DISPOSITIVE POWER
    EACH
 REPORTING        3,486,468
   PERSON
   WITH:
             8   SHARED DISPOSITIVE POWER

                  NONE

 9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

     3,486,468          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

     8.3%

 12  TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

     IA

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






CUSIP: 01671P100                                                Page 2 of 4


                  SECURITIES AND EXCHANGE COMMISSION
                         Washington, DC 20549

                             Schedule 13G
               Under the Securities Exchange Act of 1934

Amendment No.

Item 1(a)     Name of Issuer:
       Allakos Inc.

Item 1(b)     Address of Issuer's Principal Executive Offices:
       75 Shoreway Road, Suite A
       San Carlos, CA 94070

Item 2(a)     Name of Person(s) Filing:
       Capital Research Global Investors

Item 2(b)     Address of Principal Business Office or, if none,
       Residence:
       333 South Hope Street
       Los Angeles, CA 90071

Item 2(c)     Citizenship:   N/A

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

Item 2(e)     CUSIP Number:
       01671P100

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

       Capital Research Global Investors divisions of CRMC is deemed
       to be the beneficial owner of 3,486,468 shares or 8.3% of the
       42,113,059 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
CUSIP: 01671P100                                                Page 3 of 4
 

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 Research Global 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 Allakos Inc.. Capital Research Global Investors holds more than five percent of the outstanding Common Stock of Allakos Inc. as of December 31, 2018 on behalf of each of the following client(s): SMALLCAP World Fund, Inc. 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: February 13, 2019 Signature: /s/ Donald H. Rolfe Name/Title: Donald H. Rolfe - Senior Vice President and Senior Counsel, Fund Business Management Group Capital Research and Management Company CUSIP: 01671P100 Page 4 of 4