Exhibit 10.4

Non-Employee Director Compensation Summary
 
The following is a summary of the compensation program for non-employee
directors of Momenta Pharmaceuticals, Inc. (the “Company”):
 
Stock Option Grant Upon Initial Appointment or Election

Each new non-employee director receives an option to purchase up to 33,000
shares of the Company’s common stock upon his or her initial election or
appointment to the Board of Directors (the “Board”), with 1/3 of such option to
vest on the first anniversary of the date of grant and an additional 8 1/3% to
vest at the end of every three-month period thereafter, subject to the
director’s continued service to the Company. Each option is granted pursuant to,
and subject to the terms of, the Company’s incentive award plan and a stock
option award agreement in substantially the form of the Company’s standard stock
option agreement approved by the Board.

Annual Option and Restricted Stock Unit Grant

Each non-employee director who served as a director at any time during in the
previous calendar year receives restricted stock units of the Company and an
option to purchase shares of the Company’s common stock. Each award is granted
on the date of the scheduled meeting of the Board coinciding with each annual
meeting of the Company’s stockholders. The number of shares subject to the
option and the number of restricted stock units is determined annually by the
Board so that the total value of the option and restricted stock units (i)
targets the 50th percentile of total value of equity grants made by the
Company’s peer group to their respective directors on an individual director
basis, and (ii) is comprised equally of restricted stock units and shares
subject to the option.

The option has a term of ten (10) years and vests in full on the first
anniversary of the date of grant, subject to the director’s continued service to
the Company. Each option is granted pursuant to, and subject to the terms of,
the Company’s incentive award plan and a stock option award agreement in
substantially the form of the Company’s standard stock option agreement approved
by the Board.

One hundred percent of the restricted stock units vests and becomes free from
forfeiture and transfer restrictions on the first anniversary of date of grant,
subject to the director’s continued service to the Company. The restricted stock
units are granted pursuant to, and subject to the terms of, the Company’s
incentive award plan and a restricted stock unit award agreement in
substantially the form of the Company’s standard restricted stock unit award
agreement approved by the Board.

Payment of Retainer Fee; Reimbursement of Travel and Other Expenses

Each non-employee director is entitled to receive an annual retainer for his or
her service on the Board as well as additional fees for committee service as
follows:

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Annual Retainer

$50,000

Non-Employee Board Chairperson

$30,000

Audit Committee Chairperson

$20,000

Audit Committee Members (other than the Chairperson)

$12,500

Compensation Committee Chairperson

$15,000

Compensation Committee Members (other than the Chairperson)

$10,000

Nominating and Corporate Governance Committee Chairperson

$12,000

Nominating and Corporate Governance Committee Members (other than the
Chairperson)

$7,000

Science Committee Chairperson

$17,500

Science Committee Members (other than the Chairperson)

$12,500

Retainers are paid quarterly in arrears during the fiscal year. Non-employee
directors also receive reimbursement for reasonable travel and other expenses in
connection with attending meetings of the Board of Directors.

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