X0206 3 2014-05-14 0 0001274792 MERRIMACK PHARMACEUTICALS INC MACK 0001608541 Laivins Peter N C/O MERRIMACK PHARMACEUTICALS, INC. ONE KENDALL SQUARE, SUITE B7201 CAMBRIDGE MA 02139 0 1 0 0 SVP of Development Common Stock 2000 D Stock Option (right to buy) 6.78 2021-11-01 Common Stock 40000 D Stock Option (right to buy) 6.80 2022-06-12 Common Stock 10000 D Stock Option (right to buy) 7.53 2022-08-22 Common Stock 22300 D Stock Option (right to buy) 6.35 2023-03-11 Common Stock 35000 D Stock Option (right to buy) 5.02 2024-02-10 Common Stock 100000 D This option vested as to 1/6th of the shares on 4/17/12 and vests in equal quarterly installments thereafter until 10/17/14. This option vested as to 1/12th of the shares on 9/13/12 and vests in equal quarterly installments thereafter until 6/13/15. This option vested as to 1/12th of the shares on 11/23/12 and vests in equal quarterly installments thereafter until 8/23/15. This option vested as to 1/12th of the shares on 6/12/13 and vests in equal quarterly installments thereafter until 3/12/16. This option vested as to 1/12th of the shares on 5/11/14 and vests in equal quarterly installments thereafter until 2/11/17. /s/ Jeffrey A. Munsie, attorney-in-fact 2014-05-21