Letter regarding employment arrangement of Douglas E. Williams



 Exhibit 10.57 
 [Biogen Idec Logo] 
 December 7, 2010 

Dear Doug: 
 I am pleased to extend you this
offer of employment to join Biogen Idec as Executive Vice President, Research and Development. This position will report to me, George Scangos, Chief Executive Officer. The position will be based at our Weston, Massachusetts facility. 

Base Salary: Your starting bi-weekly salary will be $24,230.77, which is equivalent to an annual salary of $630,000.02, and which will be paid in
accordance with our standard payroll policies. 
 One-Time Cash Sign-on Bonus: Upon employment, you will receive $250,000 as a one-time
cash bonus. The bonus will be paid to you within two pay periods after your start date provided that you sign the enclosed Cash Sign-On Bonus Agreement, which describes the terms and conditions of the cash sign-on bonus. 

Annual Bonus Plan: You will be eligible to participate in the Biogen Idec Annual Bonus Plan, with a target bonus opportunity of 55% of your
annualized base salary. Based upon your start date, your target bonus amount may be pro-rated. Eligibility details and other terms of the Plan are included in the current year’s Plan document, which will be made available upon your employment
with the Company. 
 Long-Term Incentive: You will be granted Cash-Settled Performance Shares (CSPS) in connection with the commencement
of your employment. The approximate grant date value of your CSPS award will be $1,000,000. You will also be granted Market Stock Units (MSU) in connection with the commencement of your employment. The approximate grant date value of your MSU award
will be $1,000,000. Your CSPS and MSU awards will be granted on the first trading day of the month following your start date. 
 The actual
terms of your CSPS and MSU awards will be communicated to you following the grant date. Your grants will be awarded under the Biogen Idec Inc. 2008 Omnibus Equity Plan. You are considered a “designated employee,” as defined in the 2008
Omnibus Equity Plan. Our 2008 Omnibus Equity Plan and Prospectus are available to you on Biogen Idec’s benefits website at www.mybenergy.com. Please read these documents for information about your Long-term Incentive grants. 

Stock Trading Plan: As an Executive Vice President of the Company, you are required to enter into a 10b5-1 stock trading plan for all open market
trades in Biogen Idec stock. A 10b5-1 plan allows you to buy or sell Biogen Idec securities at pre-defined times and/or prices and provides an affirmative defense against insider trading liability. More information on 10b5-1 trading plans will be
made available upon your employment with the Company. 
 Employee Benefits: Biogen Idec offers a robust and highly competitive employee
benefits program. As an employee, you will be able to choose from a menu of options through our flexible benefits program. These benefits include a 401(k) savings plan; group health care, including medical, dental, prescription drug and vision
coverage; life, dependent life and disability insurance; as well as flexible spending accounts for eligible medical and dependent care expenses. You are also entitled to 20 vacation days per year, accrued on a per pay period basis. Additional
benefit offerings include an Employee Stock Purchase Plan (ESPP) and work/life benefits such as a concierge service and access to subsidized backup dependent care. Please visit Biogen Idec’s benefits website at www.mybenergy.com to familiarize
yourself with Biogen Idec’s complete benefit plan offerings. 







 Additional Executive Benefits 
 Supplemental Savings Plan: You will be entitled to participate in Biogen Idec’s Supplemental Savings Plan (SSP). This plan allows you to make pre-tax deferrals of up to 80% of your base salary
and up to 100% of your Annual Bonus payment and certain other eligible incentive payments. Your contributions to this plan may be limited by your contributions towards other plans (e.g., 401(k), ESPP, medical, etc.). You will be provided with SSP
enrollment information upon your employment with the Company. 
 Life Insurance: You will be provided life insurance coverage equal to
three times your annual base salary, subject to meeting the medical standards stated in the group term life insurance policy for U.S. employees. Biogen Idec pays the premium for this insurance. The IRS requires employers to impute the value of
company-paid life insurance for coverage over $50,000. This imputed income will be displayed on your pay stub. 
 Severance: Under
certain circumstances, you will be entitled to receive severance benefits. Your severance benefits are explained in detail in the attached executive severance document. If your total severance benefits will trigger 280G excise taxes, you may elect
to have Biogen Idec reduce the amount of your total payment to reduce your total payments to an amount below the 280G trigger. To facilitate your decision, Biogen Idec will estimate whether any 280G excise tax will be owed on severance and the
amount of that excise tax. 
 Tax Preparation, Financial and Estate Planning: You are entitled to reimbursement of up to $7,500 per
calendar year (January 1—December 31) for expenses incurred due to tax preparation, financial and/or estate planning services, as well as the purchase of tax preparation and/or financial planning software. You will be provided with details of
this benefit upon your employment with the Company. Reimbursement must be made no later than the end of the calendar year following the year in which the expense is incurred, and must be requested within the deadlines and processes established in
the policy. 
 You are required to satisfy the following contingencies prior to employment at Biogen Idec. 

• Drug Screen: A completed drug-screening test is required within 48 hours of accepting this offer of employment. Please see the enclosed
information regarding Biogen Idec’s Pre-Employment Drug Testing program. Your employment is subject to Biogen Idec receiving negative results (i.e., no drugs found) from your drug test. If you have not received confirmation of your test results
from Human Resources within a week prior to your start date, please contact me to confirm your test results prior to starting. 
 •
Background Check: Your employment is subject to satisfactory completion of Biogen Idec’s background check, which includes verification of employment history, educational and professional licenses, degrees and/or credentials, a criminal
records check, a Social Security Number search and verification of any other professional qualifications that your position responsibilities at Biogen Idec may warrant. Completion of your online Application for Employment authorizes Biogen Idec to
conduct these background checks. If you have any questions about the background check, please contact me. 
 • New Employee Forms:
Upon your acceptance of Biogen Idec’s offer of employment, please visit our Company website, www.biogenidec.com. Under·’Careers,’ click·’New Employees.’ This site contains the forms you must complete in
order to add you to Biogen Idec’s Payroll and Human Resources systems. Completion of these forms is required within 48 hours of accepting this offer of employment at Biogen Idec. Your username is your Social Security Number (without dashes) and
your password is L83348R. 







 • Authorization to Work in the United States: The Federal government requires you to provide
proper identification verifying your eligibility to work in the United States. Please bring documents necessary to complete the Employment Eligibility Verification Form I-9 on your first day of employment. 

• Signed Proprietary Agreement: In order to protect Biogen Idec’s substantial investment in creating and maintaining its confidential
and proprietary information, and to maintain goodwill with our customers, vendors and other business partners, you will be required to sign our ‘Employee Proprietary Information and Inventions and Dispute Resolution Agreement’ as a
condition of employment. A copy of the Agreement is enclosed with this letter for your reference. Please sign and return this Agreement with your signed acceptance of our offer. 
 Your employment at Biogen Idec is employment at-will. This means that just as you are free to leave your employment at any time, with or without cause or notice, Biogen Idec also has the same right to
terminate your employment at any time, with or without cause or notice. 
 To confirm your acceptance of this offer of employment, please
sign and return this letter and keep the other copy for your records. Review and complete the enclosed New Employee Checklist with actions required in order to begin your acceptance process. Your new employee paperwork and drug screen should be
completed within 48 hours of accepting this offer of employment. The New Employee Checklist provides instructions for your first day of employment. 
 We are very excited about the prospect of you joining Biogen Idec. We encourage you to accept this offer of employment by December 15, 2010. 
 Best regards, 
 /s/ George Scangos 
 George Scangos, Ph.D. 
 Chief Executive Officer 

I accept this offer of employment and acknowledge the contingencies of employment described above, including the at-will nature of my employment.

 ACCEPTED: 
  

					
	 /s/ Douglas Williams
	  	 December 11, 2010
	  	 January 10, 2011

			
	 Douglas Williams
	  	 Signature Date
	  	 Start Date