X0202 3 2004-06-21 0 0001235010 MOMENTA PHARMACEUTICALS INC MNTA 0001291895 Barrett Peter C/O MOMENTA PHARMACEUTICALS INC. 43 MOULTON STREET CAMBRIDGE MA 02138 1 0 1 0 Series B Convertible Preferred Stock Common Stock 977497 I See Footnote Series B Convertible Preferred Stock Common Stock 121420 I See Footnote Series B Convertible Preferred Stock Common Stock 121420 I See Footnote Series B Convertible Preferred Stock Common Stock 16271 I See Footnote Series B Convertible Preferred Stock Common Stock 1768453 I See Footnote Series B Convertible Preferred Stock Common Stock 54080 I See Footnote Series B Convertible Preferred Stock Common Stock 32381 I See Footnote Series C Convertible Preferred Stock Common Stock 186191 I See Footnote Series C Convertible Preferred Stock Common Stock 23128 I See Footnote Series C Convertible Preferred Stock Common Stock 23128 I See Footnote Series C Convertible Preferred Stock Common Stock 3097 I See Footnote Series C Convertible Preferred Stock Common Stock 336852 I See Footnote Series C Convertible Preferred Stock Common Stock 10301 I See Footnote Series C Convertible Preferred Stock Common Stock 6168 I See Footnote Automatically converts into common stock upon the closing of the Issuer's initial public offering of common stock. N/A Reflects a 1.28 for 1 forward stock split, which became effective on May 10, 2004, pursuant to which each share of Series B Convertible Preferred Stock and Series C Convertible Preferred Stock will automatically convert into approximately 1.28 shares of common stock upon the closing of the Issuer's initial public offering of common stock. These shares are owned directly by Atlas Venture Fund V, L.P. Peter Barrett is a Senior Partner of Atlas Venture. Mr. Barrett disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest therein. These shares are owned directly by Atlas Venture Parallel Fund V-A, C.V. Peter Barrett is a Senior Partner of Atlas Venture. Mr. Barrett disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest therein. These shares are owned directly by Atlas Venture Parallel Fund V-B, C.V. Peter Barrett is a Senior Partner of Atlas Venture. Mr. Barrett disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest therein. These shares are owned directly by Atlas Venture Entrepreneurs' Fund V, L.P. Peter Barrett is a Senior Partner of Atlas Venture. Mr. Barrett disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest therein. These shares are owned directly by Atlas Venture Fund VI, L.P. Peter Barrett is a Senior Partner of Atlas Venture. Mr. Barrett disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest therein. These shares are owned directly by Atlas Venture Entrepreneurs' Fund VI, L.P. Peter Barrett is a Senior Partner of Atlas Venture. Mr. Barrett disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest therein. These shares are owned directly by Atlas Venture Fund VI GmbH & Co. KG. Peter Barrett is a Senior Partner of Atlas Venture. Mr. Barrett disclaims beneficial ownership of such shares except to the extent of his proportionate pecuniary interest therein. /s/ Peter Barrett 2004-06-21