X0303 4 2011-03-08 0 0001235010 MOMENTA PHARMACEUTICALS INC MNTA 0001373605 Koestler Thomas P 675 WEST KENDALL ST CAMBRIDGE MA 02172 1 0 0 0 Stock Option (Right to Buy) 14.17 2011-03-08 4 A 0 30000 0 A 2011-06-08 2021-03-08 Common Stock 30000 30000 D 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 8.33% on June 8, 2011 and an additional 8.33% of the shares shall vest at the end of each three-month period thereafter. /s/ Michael Flanagan as attorney in fact 2011-03-09