X0204 3 2012-01-31 0 0001274792 MERRIMACK PHARMACEUTICALS INC MACK 0001213100 LOVENBERG WALTER M PHD C/O MERRIMACK PHARMACEUTICALS, INC. ONE KENDALL SQUARE, SUITE B7201 CAMBRIDGE MA 02139 1 0 0 0 Common Stock 70000 D Series D Convertible Preferred Stock Common Stock 7143 D Stock Option (right to buy) 2.1900 2012-05-03 Common Stock 5462 D Stock Option (right to buy) 2.1900 2012-08-02 Common Stock 20000 D Stock Option (right to buy) 2.1900 2013-05-08 Common Stock 15000 D Stock Option (right to buy) 1.2500 2014-08-30 Common Stock 25000 D Stock Option (right to buy) 1.7100 2015-08-03 Common Stock 20000 D Stock Option (right to buy) 2.4700 2016-08-01 Common Stock 20000 D Stock Option (right to buy) 2.5900 2017-10-04 Common Stock 20000 D Stock Option (right to buy) 1.8100 2018-09-21 Common Stock 20000 D Stock Option (right to buy) 2.1200 2019-11-04 Common Stock 20000 D Stock Option (right to buy) 5.5400 2021-05-02 Common Stock 53000 D Each share of Series D Convertible Preferred Stock will automatically convert into one share of Common Stock upon the closing of the issuer's initial public offering. The shares have no expiration date. This option is fully vested. /s/ Jeffrey A. Munsie, attorney-in-fact 2012-02-01