X0303 4 2011-02-22 0 0001235010 MOMENTA PHARMACEUTICALS INC MNTA 0001345695 Leicher Bruce 675 WEST KENDALL ST CAMBRIDGE MA 02142 0 1 0 0 SVP & General Counsel Common Stock 2011-02-22 4 S 0 761 13.45 D 38160 D Common Stock 2011-02-23 4 S 0 501 13.26 D 37659 D Common Stock 2011-02-22 4 A 0 9271 0 A 46930 D Stock Option (Right to Buy) 13.26 2011-02-22 4 A 0 23178 0 A 2011-05-22 2011-02-22 Common Stock 23178 160228 D This sale was effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on August 27, 2008. This transaction was executed in multiple trades at prices ranging from $13.37 to $13.45. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a security holder of the issuer full information regarding the number of shares and prices at which the transaction was effected. Represents 9,271 shares of restricted common stock, $0.0001 par value per share, awarded pursuant to the Company's 2004 Stock Incentive Plan, as amended, and subject to a restricted stock agreement to be entered into between the Company and Mr. Leicher. Pursuant to the restricted stock agreement, 25% of the shares of restricted Common Stock shall vest on February 22, 2012, and an additional 6.25% of the shares of restricted Common Stock shall vest at the end of each three-month period thereafter. Represents an option granted by the issuer pursuant to the issuer's 2004 Stock Incentive Plan. Subject to certain criteria, the shares subject to such option vest as to 6.25% of the shares at the end of each three-month period following the grant date. This balance of shares beneficially owned reflects 777 shares acquired under the employee stock purchase plan at a purchase price of $10.87 per share on January 31, 2011. Bruce Leicher 2011-02-23