X0306 4 2013-08-19 0 0001528129 Laredo Petroleum Holdings, Inc. LPI 0001332737 Warburg Pincus Private Equity IX, L.P. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001342445 Warburg Pincus IX LLC C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001322709 Warburg Pincus Partners LLC C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0000929408 WARBURG PINCUS & CO. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 1 0 1 0 0001162870 WARBURG PINCUS LLC C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 0 0 1 0 0001239318 KAYE CHARLES R C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 0 0 1 0 0001220638 Landy Joseph P. C/O WARBURG PINCUS & CO. 450 LEXINGTON AVENUE NEW YORK NY 10017 0 0 1 0 Common Stock, par value $0.01 per share (''Common Stock'') 2013-08-19 4 S 0 2304513 22.9781 D 64672966 D See Exhibit 99.1, note (1) See Exhibit 99.1, note (2) Exhibit List: Exhibit 99.1 - Explanation of Responses Exhibit 99.2 - Joint Filers' Names and Addresses Exhibit 99.3 - Joint Filers' Signatures *** The Power of Attorney given by Warburg Pincus & Co. was previously filed with the U.S. Securities & Exchange Commission on January 15, 2013 as an exhibit to a statement on Schedule 13D/A filed by Warburg Pincus Private Equity X, L.P. with respect to Talon Therapeutics, Inc. and is hereby incorporated by reference. WARBURG PINCUS PRIVATE EQUITY IX, L.P. By: Warburg Pincus IX LLC, its General Partner By: Warburg Pincus Partners LLC, its Sole Member By: Warburg Pincus & Co., its Managing Member /s/ Scott A. Arenare Name: Scott A. Arenare Title: Attorney-in-Fact*** 2013-08-19