Exhibit 10.52

THIRD AMENDMENT TO THE
AMGEN INC.
CHANGE OF CONTROL SEVERANCE PLAN

     The Amgen Inc. Change of Control Severance Plan (the “Plan”) is hereby
amended, effective as of January 1, 2004, unless otherwise provided herein, as
follows:

  1.   Section 1(M) shall be amended and restated in its entirety as follows:  
      “ (M) “Group I Participants” shall mean those senior executive-level staff
members of the Company, Amgen USA Inc., and Amgen Worldwide Services, Inc., and
effective on July 16, 2004, Immunex Corporation, Immunex Manufacturing
Corporation and Immunex Rhode Island Corporation, whom the Company has
designated as members of the Amgen Executive Committee, as such committee shall
be constituted immediately prior to a Change of Control. At or before the
occurrence of a Change of Control, the Company shall notify the Group I
Participants in writing of their status as Participants in the Plan.”     2.  
Section 1(N) shall be amended and restated in its entirety as follows:        
“(N) “Group II Participants” shall mean those management-level staff members of
the Company, Amgen USA Inc., and Amgen Worldwide Services, Inc., and effective
on July 16, 2004, Immunex Corporation, Immunex Manufacturing Corporation and
Immunex Rhode Island Corporation, at the level of Director or equivalent and
above (i.e., those employees of the Company or of Amgen USA Inc. whose positions
have been designated as Salary Grade 32 or Salary Grade EL4 and above) and who
are not Group I Participants, as such group shall be constituted immediately
prior to a Change of Control. At or before the occurrence of a Change of
Control, the
Company shall notify the Group II Participants in writing of their status as
Participants in the Plan.”     3.   Section 1(O) shall be amended and restated
in its entirety as follows:         “(O) “Group III Participants” shall mean
those management-level staff members of the Company, Amgen USA Inc., and Amgen
Worldwide Services, Inc., and effective on July 16, 2004, Immunex Corporation,
Immunex Manufacturing Corporation and Immunex Rhode Island Corporation, at the
level of Associate Director or equivalent (i.e., those employees of the Company
or of Amgen USA Inc. whose positions have been designated as Salary Grade 30 or
Salary Grade EL2 or Salary Grade EL3), as such group shall be constituted
immediately prior to a Change of Control. At or before the occurrence of a
Change of Control, the Company shall notify the Group III Participants in
writing of their status as Participants in the Plan.”

 

--------------------------------------------------------------------------------

 

  4.   Subsection 4.1(A)(II) shall be amended and restated in its entirety as
follows (the entire Section 4.1 (A) is included to provide context for the
amendment to subsection (II)):         “4.1 Termination After Change of Control.
If a Participant’s employment is terminated during a Change of Control Period
(a) by the Company other than for Cause or Disability, or (b) by the Participant
for Good Reason, the Company shall pay the Participant the amounts, and provide
the Participant with the benefits, described in this Section 4.1:

     (A) In lieu of any further salary payments to the Participants for periods
subsequent to the Date of Termination and in lieu of any severance benefit
otherwise payable to the Participant (other than accrued vacation and similar
benefits otherwise payable upon termination of employment pursuant to Company
policies and programs), the Company shall pay to the Participant a lump sum cash
payment (the “Cash Severance Payment”) in an amount equal to the excess, if any,
of

(I) the product of (x) the Participant’s Benefits Multiple, and (y) the sum of
(i) the Participant’s annual base salary in effect immediately prior to the Date
of Termination or, if higher, as in effect immediately prior to the Change of
Control, plus, (ii) the Participant’s targeted annual bonus for the year in
which such Date of Termination occurs, or, if higher, the Participant’s average
annual bonus for the three (3) years immediately prior to the Change of Control;
over

(II) the aggregate value of the acceleration of vesting or exercisability of any
unvested stock options held by the Participant under any of the Company’s equity
based plans as a result of or in connection with the Change of Control as such
value is determined by the Accountants (as defined below) in accordance with the
principles of Sections 280G(d)(3) and 280G(d)(4) of the Code and Question and
Answer 24 of Proposed Treasury Regulation Section 1.280G-1 or any successor
section of any successor regulation or statute; provided however, that any stock
or cash awarded to a Participant under the Performance Award Program under the
Amgen Inc. Amended and Restated Equity Incentive Plan shall not be included in
this calculation.”

[THIS SPACE INTENTIONALLY LEFT BLANK]

 

--------------------------------------------------------------------------------

 

     To record this Third Amendment to the Plan as set forth herein, the Company
has caused its Authorized officer to execute this document this 9th day of June,
2004.

            AMGEN INC.
      By:   /s/ Brian McNamee       Title: Senior Vice president, Human
Resources