X0305 4 2012-04-03 0 0001274792 MERRIMACK PHARMACEUTICALS INC MACK 0001108494 PORTER MICHAEL E C/O MERRIMACK PHARMACEUTICALS, INC. ONE KENDALL SQUARE, SUITE B7201 CAMBRIDGE MA 02139 1 0 0 0 Common Stock 2012-04-03 4 P 0 12500 7 A 75500 D Common Stock 2012-04-03 4 C 0 56509 A 132009 D Common Stock 2012-04-03 4 C 0 34286 A 166295 D Common Stock 2012-04-03 4 C 0 25000 A 191295 D Common Stock 2012-04-03 4 C 0 33000 A 224295 D Common Stock 2012-04-03 4 C 0 28570 A 252865 D Series C Convertible Preferred Stock 2012-04-03 4 C 0 56509 0 D Common Stock 56509 0 D Series D Convertible Preferred Stock 2012-04-03 4 C 0 34286 0 D Common Stock 34286 0 D Series E Convertible Preferred Stock 2012-04-03 4 C 0 25000 0 D Common Stock 25000 0 D Series F Convertible Preferred Stock 2012-04-03 4 C 0 33000 0 D Common Stock 33000 0 D Series G Convertible Preferred Stock 2012-04-03 4 C 0 28570 0 D Common Stock 28570 0 D Each share of Series C Convertible Preferred Stock automatically converted into one share of Common Stock upon the closing of the issuer's initial public offering and had no expiration date. Each share of Series D Convertible Preferred Stock automatically converted into one share of Common Stock upon the closing of the issuer's initial public offering and had no expiration date. Each share of Series E Convertible Preferred Stock automatically converted into one share of Common Stock upon the closing of the issuer's initial public offering and had no expiration date. Each share of Series F Convertible Preferred Stock automatically converted into one share of Common Stock upon the closing of the issuer's initial public offering and had no expiration date. Each share of Series G Convertible Preferred Stock automatically converted into one share of Common Stock upon the closing of the issuer's initial public offering and had no expiration date. /s/ Michael E. Porter 2012-04-05