X0206 3 2015-01-01 0 0001274792 MERRIMACK PHARMACEUTICALS INC MACK 0001225960 RAY RUSSELL T C/O MERRIMACK PHARMACEUTICALS, INC. ONE KENDALL SQUARE, SUITE B7201 CAMBRIDGE MA 02139 1 0 0 0 Common Stock 10000 I By RBKD Enterprises, LLC /s/ Jeffrey A. Munsie, attorney-in-fact 2015-01-08