X0306 4 2018-06-20 0 0001235010 MOMENTA PHARMACEUTICALS INC MNTA 0001415739 Stoner Elizabeth C/O MOMENTA PHARMACEUTICALS, INC. 301 BINNEY STREET CAMBRIDGE MA 02142 1 0 0 0 Common Stock 2018-06-20 4 M 0 5734 0 A 28541 D Common Stock 2018-06-21 4 S 0 2288 22.20 D 26253 D Stock Option (Right to Buy) 22.30 2018-06-20 4 A 0 8855 0 A 2028-06-20 Common Stock 8855 8855 D Restricted Stock Units 2018-06-20 4 A 0 4356 0 A Common Stock 4356 4356 D Restricted Stock Units 2018-06-20 4 M 0 5734 0 D Common Stock 5734 0 D This transaction was effected pursuant to a Rule 10b5-1 trading plan. This transaction was executed in multiple trades at prices ranging from $22.15 to $22.20. 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 sold at each separate price within the ranges set forth in this footnote. Represents an option granted by the Company pursuant to the Company's 2013 Incentive Award Plan. The stock option will vest and become exercisable on the first anniversary of the grant date, subject to Dr. Stoner's continued service to the Company. Each restricted stock unit represents a contingent right to receive one share of MNTA common stock. Represents 4,356 restricted stock units, awarded pursuant to the Company's 2013 Incentive Award Plan, 100% of the restricted stock units shall vest on the first anniversary of the grant date, subject to Dr. Stoner's continued service to the Company. Restricted Stock Units convert into common stock on a one-for-one basis. Subject to certain criteria, 100% of the restricted stock units shall vest on the first anniversary of the grant date. /s/ Marie T. Washburn as attorney in fact 2018-06-22