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 disclosures provided in a prior cover page.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

   RiverVest Venture Fund II, L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  WC

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  817,257

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  817,257

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  817,257

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  1.7%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

The percentage set forth in row (13) is based on the 48,766,351 shares of common stock, par value $0.001 per share (“Common Stock”), of Allakos Inc., a Delaware corporation (the “Issuer”), reported by the Issuer to be outstanding as of May 6, 2020 on the Issuer’s Form 10-Q, filed with the Securities and Exchange Commission (“SEC”) on May 11, 2020.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

   RiverVest Venture Fund II (Ohio), L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  WC

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  221,982

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  221,982

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  221,982

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  0.5%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

   RiverVest Venture Partners II (Ohio), LLC

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  221,982 ⁽²⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  221,982 ⁽²⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  221,982 ⁽²⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  0.5%⁽¹⁾

  TYPE OF REPORTING PERSON

  OO

Represents 221,982 shares of Common Stock owned by RiverVest Venture Fund II (Ohio), L.P., a Delaware limited partnership (“RiverVest II (Ohio)”). RiverVest Venture Partners II (Ohio), LLC, a Delaware limited liability company (“RiverVest Partners II (Ohio)”), is the general partner of RiverVest II (Ohio).

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest Venture Partners II, L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  1,039,239 ⁽³⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  1,039,239 ⁽³⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  1,039,239 ⁽³⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  2.1%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

Represents 817,257 shares of Common Stock owned by RiverVest Venture Fund II, L.P., a Delaware limited partnership (“RiverVest II”), and 221,982 shares of Common Stock owned by RiverVest II (Ohio). RiverVest Venture Partners II, L.P., a Delaware limited partnership (“RiverVest Partners II”), is the general partner of RiverVest II and the sole member of RiverVest Partners II (Ohio), which is the general partner of RiverVest II (Ohio).

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest Venture Partners II, LLC

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  1,039,239 ⁽⁴⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  1,039,239 ⁽⁴⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  1,039,239 ⁽⁴⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  2.1%⁽¹⁾

  TYPE OF REPORTING PERSON

  OO

Represents 817,257 shares of Common Stock owned by RiverVest II and 221,982 shares of Common Stock owned by RiverVest II (Ohio). RiverVest Venture Partners II, LLC, a Delaware limited liability company, is the general partner of RiverVest Partners II, which is (a) the general partner of RiverVest II and (b) the sole member of RiverVest Partners II (Ohio), which is the general partner of RiverVest II (Ohio).    

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest Venture Fund III, L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  WC

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  2,754,816

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  2,754,816

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  2,754,816⁽⁵⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  5.6%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

Includes 1,139,537 shares of Common Stock that are pledged to secure a line of credit pursuant to a customary collateral agreement and promissory note. As of the date of this report, there is no outstanding balance on the line of credit.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest Venture Fund III (Ohio), L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  WC

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  146,206

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  146,206

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  146,206⁽⁶⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  0.3%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

Includes 60,463 shares of Common Stock that are pledged to secure a line of credit pursuant to a customary collateral agreement and promissory note. As of the date of this report, there is no outstanding balance on the line of credit.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest Venture Partners III (Ohio), LLC

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  146,206 ⁽⁷⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  146,206 ⁽⁷⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  146,206 ⁽⁷⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  0.3%⁽¹⁾

  TYPE OF REPORTING PERSON

  OO

Represents 146,206 shares of Common Stock owned by RiverVest Venture Fund III (Ohio), L.P., a Delaware limited partnership (“RiverVest III (Ohio)”). RiverVest Venture Partners III (Ohio), LLC, a Delaware limited liability company (“RiverVest Partners III (Ohio)”), is the general partner of RiverVest III (Ohio).

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest Venture Partners III, L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  2,901,022 ⁽⁸⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  2,901,022 ⁽⁸⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  2,901,022 ⁽⁸⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  5.9%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

Represents 2,754,816 shares of Common Stock owned by RiverVest Venture Fund III, L.P., a Delaware limited partnership (“RiverVest III”), and 146,206 shares of Common Stock owned by RiverVest III (Ohio). RiverVest Venture Partners III, L.P., a Delaware limited partnership (“RiverVest Partners III”), is the general partner of RiverVest III and the sole member of RiverVest Partners III (Ohio), which is the general partner of RiverVest III (Ohio).

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest Venture Partners III, LLC

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  2,901,022 ⁽⁹⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  2,901,022 ⁽⁹⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  2,901,022 ⁽⁹⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

5.9%⁽¹⁾

  TYPE OF REPORTING PERSON

  OO

Represents 2,754,816 shares of Common Stock owned by RiverVest III and 146,206 shares of Common Stock owned by RiverVest III (Ohio). RiverVest Venture Partners III, LLC, a Delaware limited liability company, is the general partner of RiverVest Partners III, which is (a) the general partner of RiverVest III and (b) the sole member of RiverVest Partners III (Ohio), which is the general partner of RiverVest III (Ohio).

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  3x5 RiverVest Fund II, L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  WC

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  1,744,827

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  1,744,827

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  1,744,827⁽¹⁰⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  3.6%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

Includes 1,517,479 shares of Common Stock that are pledged to secure a line of credit pursuant to a customary collateral agreement and promissory note. As of the date of this report, there is no outstanding balance on the line of credit.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  3x5 RiverVest Fund II-B, L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  WC

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  65,418

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  65,418

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  65,418

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  0.1%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  3x5 RiverVest Partners II, LLC

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  1,810,245 ⁽¹¹⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  1,810,245 ⁽¹¹⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  1,810,245 ⁽¹¹⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  3.7%⁽¹⁾

  TYPE OF REPORTING PERSON

  OO

Represents 1,744,827 shares of Common Stock owned by 3x5 RiverVest Fund II, L.P., a Delaware limited partnership (“3x5 RiverVest II”), and 65,418 shares of Common Stock owned by 3x5 RiverVest Fund II-B, L.P., a Delaware limited partnership (“3x5 RiverVest II-B”). 3x5 RiverVest Partners II, LLC, a Delaware limited liability company (“3x5 RiverVest Partners”), is the general partner of 3x5 RiverVest II and 3x5 RiverVest II-B.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

   RiverVest 3x5 Managers II, L.P.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  1,810,245 ⁽¹²⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  1,810,245 ⁽¹²⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  1,810,245 ⁽¹²⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  3.7%⁽¹⁾

  TYPE OF REPORTING PERSON

  PN

Represents 1,744,827 shares of Common Stock owned by 3x5 RiverVest II, and 65,418 shares of Common Stock owned by 3x5 RiverVest II-B. RiverVest 3x5 Managers II, L.P., a Delaware limited partnership (“RiverVest 3x5 Managers”), is one of two members of 3x5 RiverVest Partners, which is the general partner of 3x5 RiverVest II and 3x5 RiverVest II-B.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  RiverVest 3x5 Managers II, LLC

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  Delaware, USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  1,810,245 ⁽¹³⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  1,810,245 ⁽¹³⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  1,810,245 ⁽¹³⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  3.7%⁽¹⁾

  TYPE OF REPORTING PERSON

  OO

Represents 1,744,827 shares of Common Stock owned by 3x5 RiverVest II, and 65,418 shares of Common Stock owned by 3x5 RiverVest II-B. RiverVest 3x5 Managers II, LLC, a Delaware limited liability company (“RiverVest 3x5 Managers II”), is the general partner of RiverVest 3x5 Managers, which is one of two members of 3x5 RiverVest Partners. 3x5 RiverVest Partners is the general partner of 3x5 RiverVest II and 3x5 RiverVest II-B.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  John P. McKearn, Ph.D.

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  41,066 ⁽¹⁴⁾

  SHARED VOTING POWER

  5,750,506 ⁽¹⁵⁾

  SOLE DISPOSITIVE POWER

  41,066 ⁽¹⁴⁾

  SHARED DISPOSITIVE POWER

  5,750,506 ⁽¹⁵⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  5,791,572

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  11.9%⁽¹⁾

  TYPE OF REPORTING PERSON

  IN

In July 2018, the Issuer granted Dr. McKearn, as a non-employee director of the Issuer, an option to purchase 37,600 shares of Common Stock at a per share exercise price equal to $16.00. The option vests as to 1/36th of the shares subject to the option each month following July 2018, subject to continued service through each applicable vesting date. In june 2019, the Issuer granted Dr. McKearn an additional 16,000 options that 100% cliff vest upon the earlier of (i) the one-year anniversary of the date of grant of the annual option or (ii) the date of the next annual meeting of stockholders that occurs following the grant of such annual option, subject to continued service through the applicable vesting date. Dr. McKearn’s options have vested, or will vest within sixty (60) days of the date of this filing, with respect to 41,066 shares of Common Stock.

Includes 817,257 shares of Common Stock owned by RiverVest II, 221,982 shares of Common Stock owned by RiverVest II (Ohio), 2,754,816 shares of Common Stock owned by RiverVest III, 146,206 shares of Common Stock owned by RiverVest III (Ohio), 1,744,827 shares of Common Stock owned by 3x5 RiverVest II, and 65,418 shares of Common Stock owned by 3x5 RiverVest II-B.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  Jay Schmelter

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  5,750,506 ⁽¹⁶⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  5,750,506 ⁽¹⁶⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  5,750,506 ⁽¹⁶⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  11.8%⁽¹⁾

  TYPE OF REPORTING PERSON

  IN

Represents 817,257 shares of Common Stock owned by RiverVest II, 221,982 shares of Common Stock owned by RiverVest II (Ohio), 2,754,816 shares of Common Stock owned by RiverVest III, 146,206 shares of Common Stock owned by RiverVest III (Ohio), 1,744,827 shares of Common Stock owned by 3x5 RiverVest II, and 65,418 shares of Common Stock owned by 3x5 RiverVest II-B.

  NAME OF REPORTING PERSON

  I.R.S. IDENTIFICATION NO. (ENTITIES ONLY)

  Thomas C. Melzer

  CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

  (a)  ☐        (b)  ☐

  SEC USE ONLY

  SOURCE OF FUNDS

  AF

  CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED PURSUANT TO ITEMS 2(d) OR 2(e)

  ☐

  CITIZENSHIP OR PLACE OF ORGANIZATION

  USA

NUMBER OF

SHARES

  BENEFICIALLY  

OWNED BY

EACH

REPORTING

PERSON

WITH

  SOLE VOTING POWER

  0

  SHARED VOTING POWER

  5,750,506 ⁽¹⁷⁾

  SOLE DISPOSITIVE POWER

  0

  SHARED DISPOSITIVE POWER

  5,750,506 ⁽¹⁷⁾

  AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

  5,750,506 ⁽¹⁷⁾

  CHECK IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES CERTAIN SHARES

  ☐

  PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

  11.8%⁽¹⁾

  TYPE OF REPORTING PERSON

  IN

Represents 817,257 shares of Common Stock owned by RiverVest II, 221,982 shares of Common Stock owned by RiverVest II (Ohio), 2,754,816 shares of Common Stock owned by RiverVest III, 146,206 shares of Common Stock owned by RiverVest III (Ohio), 1,744,827 shares of Common Stock owned by 3x5 RiverVest II, and 65,418 shares of Common Stock owned by 3x5 RiverVest II-B.

Entity or Individual

RiverVest Venture Fund II, L.P.

RiverVest Venture Fund II (Ohio), L.P.

RiverVest Venture Partners II (Ohio), LLC⁽¹⁾

RiverVest Venture Partners II, L.P.⁽²⁾

RiverVest Venture Partners II, LLC⁽³⁾

RiverVest Venture Fund III, L.P.

RiverVest Venture Fund III (Ohio), L.P.

RiverVest Venture Partners III (Ohio), LLC⁽⁴⁾

RiverVest Venture Partners III, L.P.⁽⁵⁾

RiverVest Venture Partners III, LLC⁽⁶⁾

3x5 RiverVest Fund II, L.P.

3x5 RiverVest Fund II-B, L.P.

3x5 RiverVest Partners II, LLC⁽⁷⁾

RiverVest 3x5 Managers II, L.P.⁽⁸⁾

RiverVest 3x5 Managers II, LLC⁽⁹⁾

John P. McKearn, Ph.D.⁽¹⁰⁾

Jay Schmelter⁽¹¹⁾

Thomas C. Melzer⁽¹²⁾

Based on the 48,766,351 shares of Common Stock reported by the Issuer to be outstanding as of May 6, 2020 on the Issuer’s Form 10-Q, filed with the SEC on May 11, 2020.

RiverVest Partners II (Ohio), as the general partner of RiverVest II (Ohio), may be deemed to beneficially own the 221,982 shares of Common Stock owned by RiverVest II (Ohio).

RiverVest Partners II is the general partner of RiverVest II and the sole member of RiverVest Partners II (Ohio), which is the general partner of RiverVest II (Ohio), and as a result,, may be deemed to beneficially own the 817,257 shares of Common Stock owned by RiverVest II and the 221,982 shares of Common Stock owned by RiverVest II (Ohio).

RiverVest Venture Partners II, LLC, a Delaware limited liability company, is the general partner of RiverVest Partners II, which is (a) the general partner of RiverVest II and (b) the sole member of RiverVest Partners II (Ohio), which is the general partner of RiverVest II (Ohio), and as a result, may be deemed to beneficially own the 817,257 shares of Common Stock owned by RiverVest II and the 221,982 shares of Common Stock owned by RiverVest II (Ohio).

RiverVest Partners III (Ohio) is the general partner of RiverVest III (Ohio), and as a result, may be deemed to beneficially own the 146,206 shares of Common Stock owned by RiverVest III (Ohio).

RiverVest Partners III is the general partner of RiverVest III and the sole member of RiverVest Partners III (Ohio), which is the general partner of RiverVest III (Ohio), and as a result, may be deemed to beneficially own the 2,754,816 shares of Common Stock owned by RiverVest III and the 146,206 shares of Common Stock owned by RiverVest III (Ohio).

RiverVest Venture Partners III, LLC, a Delaware limited liability company, is the general partner of RiverVest Partners III, which is (a) the general partner of RiverVest III and (b) the sole member of RiverVest Partners III (Ohio), which is the general partner of RiverVest III (Ohio), and as a result, may be deemed to beneficially own the 2,754,816 shares of Common Stock owned by RiverVest III and the 146,206 shares of Common Stock owned by RiverVest III (Ohio).

3x5 RiverVest Partners is the general partner of 3x5 RiverVest II and 3x5 RiverVest II-B, and as a result, may be deemed to beneficially own the 1,744,827 shares of Common Stock owned by 3x5 RiverVest II and the 65,418 shares of Common Stock owned by 3x5 RiverVest II-B.

RiverVest 3x5 Managers is one of two members of 3x5 RiverVest Partners, which is the general partner of 3x5 RiverVest II and 3x5 RiverVest II-B, and as a result, may be deemed to beneficially own the 1,744,827 shares of Common Stock owned by 3x5 RiverVest II and the 65,418 shares of Common Stock owned by 3x5 RiverVest II-B.

RiverVest 3x5 Managers II is the general partner of RiverVest 3x5 Managers, which is one of two members of 3x5 RiverVest Partners. 3x5 RiverVest Partners is the general partner of 3x5 RiverVest II and 3x5 RiverVest II-B. As a result, RiverVest 3x5 Managers II may be deemed to beneficially own the 1,744,827 shares of Common Stock owned by 3x5 RiverVest II and the 65,418 shares of Common Stock owned by 3x5 RiverVest II-B.

Dr. McKearn is an authorized person of RiverVest Venture Partners II, LLC, a Delaware limited liability company, which is the general partner of RiverVest Partners II. RiverVest Partners II is (a) the general partner of RiverVest II and (b) the sole member of RiverVest Partners II (Ohio), which is the general partner of RiverVest II (Ohio). As a result, Dr. McKearn may be deemed to beneficially own the 817,257 shares of Common Stock owned by RiverVest II and the 221,982 shares of Common Stock owned by RiverVest II (Ohio).

Mr. Schmelter is a member of RiverVest Venture Partners II, LLC, a Delaware limited liability company, which is the general partner of RiverVest Partners II. RiverVest Partners II is (a) the general partner of RiverVest II and (b) the sole member of RiverVest Partners II (Ohio), which is the general partner of RiverVest II (Ohio). As a result, Mr. Schmelter may be deemed to beneficially own the 817,257 shares of Common Stock owned by RiverVest II and the 221,982 shares of Common Stock owned by RiverVest II (Ohio)

Mr. Melzer is a member of RiverVest Venture Partners II, LLC, a Delaware limited liability company, which is the general partner of RiverVest Partners II. RiverVest Partners II is (a) the general partner of RiverVest II and (b) the sole member of RiverVest Partners II (Ohio), which is the general partner of RiverVest II (Ohio). As a result, Mr. Melzer may be deemed to beneficially own the 817,257 shares of Common Stock owned by RiverVest II and the 221,982 shares of Common Stock owned by RiverVest II (Ohio).

Previously filed.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

Name: John P. McKearn, Ph.D.

Title:   Member

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ John P. McKearn, Ph.D.

/s/ Jay Schmelter

/s/ Thomas C. Melzer

Allakos Inc. (the “Company”)

& Gentlemen: