X0306 4 2014-03-10 1 0001509190 ARATANA THERAPEUTICS, INC. PETX 0001482716 MPM BIOVENTURES V, L.P. C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 0001356950 Scopa James Paul C/O MPM ASSET MANAGEMENT 601 GATEWAY BOULEVARD, SUITE 350 SOUTH SAN FRANCISCO CA 94080 0 0 1 0 0001134657 EVNIN LUKE C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 0001473930 Foley Todd C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 0001134655 GADICKE ANSBERT C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 0001180429 KAILIAN VAUGHN M C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 0001541412 MPM ASSET MANAGEMENT INVESTORS BV5 LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 0001482714 MPM BIOVENTURES V GP LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 0001482715 MPM BIOVENTURES V LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON STREET, 54TH FLOOR BOSTON MA 02116 0 0 1 0 Common Stock 2014-03-10 4 S 0 600000 20.02 D 2751048 I See Footnote Common Stock 38386 I By Luke Evnin Common Stock 22767 I By James Paul Scopa Common Stock 17937 I By Vaughn Kailian Common Stock 37117 I By MPM Capital LLC The shares were sold as follows: 577,520 by MPM BioVentures V, L.P. ("BV V") and 22,480 by MPM Asset Management Investors BV5 LLC ("AM BV5"). MPM BioVentures V GP LLC and MPM BioVentures V LLC ("BV LLC") are the direct and indirect general partners of BV V and BV LLC is the manager of AM BV5. Ansbert Gadicke, Luke Evnin, Vaughn M. Kailian, James Paul Scopa and Todd Foley are the members of BV LLC. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its respective pecuniary interest therein. The shares are held as follows: 2,647,974 by BV V and 103,074 by AM BV5. Each Reporting Person disclaims beneficial ownership of the securities except to the extent of his or its respective pecuniary interest therein. Includes 2,627 shares held by The Vaughn and Patricia Kailian Revocable Trust u/a/dtd 12/18/1992, of which the Reporting Person is trustee. Medical Portfolio Management LLC ("MPM Medical") is the managing member of MPM Capital LLC, and Messrs. Evnin and Gadicke are members of MPM Medical. Messrs. Evnin and Gadicke disclaim beneficial ownership of the shares held by MPM Capital LLC except to the extent of their respective pecuniary interests therein. By Ansbert Gadicke, member of MPM BioVentures V LLC, the managing member of MPM BioVentures V GP LLC, the general partner of MPM BioVentures V, L.P. /s/ Ansbert Gadicke 2014-03-12 /s/ James Paul Scopa 2014-03-12 /s/ Luke Evnin 2014-03-12 /s/ Todd Foley 2014-03-12 /s/ Ansbert Gadicke 2014-03-12 /s/ Vaughn Kailian 2014-03-12 By Ansbert Gadicke, member of MPM BioVentures V LLC, the manager of MPM Asset Management Investors BV5 LLC /s/ Ansbert Gadicke 2014-03-12 By Ansbert Gadicke, member of MPM BioVentures V LLC, the managing member of MPM BioVentures V GP LLC /s/ Ansbert Gadicke 2014-03-12 By Ansbert Gadicke, member of MPM BioVentures V LLC /s/ Ansbert Gadicke 2014-03-12