X0204 3 2012-01-31 0 0001274792 MERRIMACK PHARMACEUTICALS INC MACK 0001531563 Mulroy Robert J. C/O MERRIMACK PHARMACEUTICALS, INC. ONE KENDALL SQUARE, SUITE B7201 CAMBRIDGE MA 02139 1 1 0 0 President and CEO Common Stock 474603 D Series B Convertible Preferred Stock Common Stock 26173 D Series C Convertible Preferred Stock Common Stock 29019 D Series D Convertible Preferred Stock Common Stock 57143 I By Wife Series E Convertible Preferred Stock Common Stock 4657 I By Wife Stock Option (right to buy) 2.1900 2012-08-02 Common Stock 75000 D Stock Option (right to buy) 2.1900 2013-05-08 Common Stock 50000 D Stock Option (right to buy) 1.2500 2014-08-30 Common Stock 158048 D Stock Option (right to buy) 1.2500 2014-08-30 Common Stock 141952 D Stock Option (right to buy) 1.2500 2015-02-02 Common Stock 25837 D Stock Option (right to buy) 1.2500 2015-02-02 Common Stock 224163 D Stock Option (right to buy) 1.7100 2015-08-03 Common Stock 43247 D Stock Option (right to buy) 1.7100 2015-08-03 Common Stock 456753 D Stock Option (right to buy) 2.4700 2017-01-23 Common Stock 52985 D Stock Option (right to buy) 2.4700 2017-01-23 Common Stock 97015 D Stock Option (right to buy) 2.5900 2017-10-04 Common Stock 26689 D Stock Option (right to buy) 2.5900 2017-10-04 Common Stock 248311 D Stock Option (right to buy) 2.1200 2019-11-04 Common Stock 775000 D Stock Option (right to buy) 5.5400 2021-05-02 Common Stock 50000 D Each share of Series B Convertible Preferred Stock will automatically convert into approximately 1.5435 shares of Common Stock upon the closing of the issuer's initial public offering. The shares have no expiration date. Each share of Series C 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. 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. Each share of Series E 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. This option vested as to 1/12th of the shares on each of November 5, 2009 and February 1, 2010 and vests in equal quarterly installments thereafter until August 1, 2012. This option vested as to 1/12th of the shares on August 1, 2011 and vests in equal quarterly installments thereafter until May 1, 2014. /s/ Jeffrey A. Munsie, attorney-in-fact 2012-02-01