1


                                                                   Exhibit 10.57
July 19, 1999





Mr. Kees Been
121 Whitebridge Meadows Lane
St. Louis, MO 63141

Dear Kees:

This letter supersedes my previous letter to you dated July 9, 1999 and
represents Jim Vincent's amended offer to you on behalf of Biogen. You are
offered the position of Vice President, Business Development at an annual salary
of $250,000. You will report directly to Jim Vincent. Consistent with Biogen's
compensation policy, you will be eligible for a pro-rated merit salary review at
year-end 1999 and annually thereafter. You will be eligible to participate in
Biogen's annual incentive compensation plan with a 30% target bonus beginning in
the year ending December 31, 2000.

Upon employment you will receive $200,000 as a one-time special cash bonus,
which will be treated as a forgivable loan. The bonus will be forgiven over a
thirty-six month, straight-line schedule. In the event you voluntarily terminate
your employment or your employment is terminated for performance prior to the
thirty-six months from the date of the loan, the unforgiven portion of the loan
would be payable to Biogen within six months of your termination date.

Upon employment you will be granted an option to purchase up to 100,000 shares
of the common stock of Biogen, Inc. This option grant is subject to the approval
of the Stock and Option Plan Administration Committee of the Board of Directors,
which we expect to be forthcoming. The exercise price per share will be the
average of the high and low sale prices as reported in the National Association
of Securities Dealers Automated Quotation System ("NASDAQ") on the date you
commence employment. The option will have a ten-year term and vest over a
five-year period at the rate of 20% per year starting on the anniversary of the
date you commence employment.

You will be able to choose from a menu of benefit options through our flexible
benefits program, BioChoice. These include health care, life, dependent life,
and disability insurance as well as two flexible spending accounts, Med-Flex and
D-Flex, for eligible medical or dependent care expenses. At the beginning of the
calendar quarter following your date of hire you will be eligible to participate
in Biogen's pension and 401(k) savings plans. You are also entitled to twenty
vacation days per year accrued on a monthly pro-rated basis. Biogen also offers
a variety of additional benefits including tuition reimbursement, childcare and
elder care referral service, educational matching gifts, credit union, and group
homeowners and automobile insurance. You will receive more detailed information
regarding your benefits on your first day at work.

   2


Mr. Kees Been
Page 2
July 19, 1999



Biogen will provide relocation benefits to facilitate your move from St. Louis,
MO. A relocation counselor will contact you to discuss the relocation program,
and will send you a package detailing the relocation policy to you. Please read
the policy carefully as it will outline the parameters of these benefits and
detail the reimbursement process. These benefits will include the reimbursement
of many of the costs associated with both the sale of your current house and the
purchase of a new house in the Boston area; home-finding; and movement of your
household goods.

As an additional provision of your relocation benefits, Biogen will pay you a
lump sum of $40,000 on employment to be used for your temporary living in Boston
and to also allow you round trip flights to St. Louis pending your family's
eventual relocation to the Boston area. In the event your family relocates to
the Boston area prior to your fully expending the $40,000, any unused amount of
this lump sum payment will be yours to retain with no repayment obligation to
Biogen.

In the event you voluntarily terminate your employment or your employment is
terminated for performance within two years from the date that you start your
new job, you will be required to repay to Biogen some or all of the relocation
expenses that you have incurred.

As an officer of the company, you will be required to participate in our program
for executive stock ownership. We believe it is very important that our key
leaders have personal stock ownership. I will outline the program to you.

Additionally, in your new role you will be eligible for the following:

-    SUPPLEMENTAL SAVINGS PLAN: You are entitled to participate in the Voluntary
     Executive Supplemental Savings Plan. This plan allows you to defer from
     your current taxation up to 50% of your base salary and 100% of your bonus,
     if there is one. I can outline the details of the program if you are
     interested in participating.

-    LIFE INSURANCE: You will be provided Biogen's Executive Term Life Insurance
     coverage for a total of $1,000,000. This coverage is based on your
     successfully meeting the medical standards as stated in the Executive Term
     insurance policy.

-    TAX REVIEW/PREPARATION: You are entitled to the preparation and/or review,
     including review of estimated taxes of your annual Federal and State tax
     returns, which is currently administered through PricewaterhouseCoopers.
     The cost of this service is covered by Biogen. In the event you choose to
     continue the services provided by your current tax advisor, Biogen will
     reimburse you the cost of these services up to but not exceeding the amount
     incurred by Biogen through PricewaterhouseCoopers.


   3



Mr. Kees Been
Page 3
July 19, 1999



-    INVOLUNTARY TERMINATION: If you are involuntarily terminated from
     employment with Biogen (other than for cause), Biogen will protect you by
     paying you a supplementary amount (the "Supplementary Amount") equal to
     your then present BASE salary for a period (the "Extra Period") ending on
     the earlier of (i) the date twelve months from your termination and (ii)
     the date you start another job. During such period, Biogen will also pay to
     continue your health benefits (i.e., health and dental plan coverage),
     provided such benefits are accorded employees generally and Biogen can
     obtain the relevant coverage. If you need continued coverage to prevent a
     gap in health coverage between your Biogen coverage and that at your new
     job, Biogen will extend such coverage for up to 30 days (to the extent that
     the Extra Period is less than twelve months) after you start your new job.
     The Supplementary Amount will be paid on the same schedule as your salary
     would have been paid. You will not be an employee of Biogen during the time
     of such payments and will not accrue any benefits or other rights (such as,
     but not limited to, pension plan vesting or accrual, stock option vesting,
     vacation pay, etc.) during such period except health benefits as described
     above. You agree to notify us when you accept a new job.

Employment with Biogen is contingent on the satisfactory completion of a
pre-employment drug screening test at least five business days prior to your
start date. We require all new employees to sign an Intellectual
Property/Confidentiality Agreement on the first day of employment. You will also
be required to complete a medical history review with our occupational health
department, which is scheduled after your first day of employment.

It is Biogen's policy to comply with federal, state and local guidelines
applicable to its facilities and to take all reasonable steps to ensure the
health and safety of Biogen employees. Consistent with this policy, your normal
duties may require you from time to time to attend meetings or perform functions
in any or all of Biogen's facilities.

The Federal Government requires you to provide proper identification verifying
your eligibility to work in the United States. Please bring the appropriate
identification with you on your first day of employment.

On behalf of Jim Vincent, we very much look forward to your positive response
and to your joining us as early as practical. We are confident that you will
make a significant contribution to Biogen's future success.


   4


Mr. Kees Been
Page 4
July 19, 1999




Please confirm your acceptance by signing this offer letter and noting your
preferred start date. Also, please sign the enclosed drug screen authorization
form and then return both signed documents to me in the enclosed self addressed,
stamped envelope. The other original offer letter is for your records.

                                               Sincerely,

                                               /s/ Frank A. Burke, Jr.

                                               Frank A. Burke, Jr.


FAB:bk
cc:    Mr. James L. Vincent


 I am pleased to accept the offer of employment described above.


ACCEPTED:

/s/ Kees Been
------------------------------------------------------------------------
Kees Been                                           Preferred Start Date