X0202 4 2008-04-16 0 0001069308 Opexa Therapeutics, Inc. OPXA 0001044321 MARXE AUSTIN W & GREENHOUSE DAVID M C/O SPECIAL SITUATIONS FUNDS 527 MADISON AVENUE, SUITE 2600 NEW YORK NY 10022 0 0 1 0 Common Stock 2008-04-16 4 S 0 5499 1.3036 D 772848 I By Limited Partnerships This is a joint filing by Austin W. Marxe (Marxe) and David M. Greenhouse (Greenhouse). They share voting and investment control over all securities owned by Special Situations Fund III QP, L.P. (QP), Special Situations Cayman Fund, L.P. (Cayman), Special Situations Private Equity Fund, LP (PE) and Special Situations Life Sciences Fund, L.P. (LS), respectively. 266,004 shares of Common Stock are held by QP, 71,683 shares of Common Stock are held by Cayman, 316,481 shares of Common Stock are held by PE and 118,680 shares of Common Stock are held by LS. The interest of Marxe and Greenhouse in the shares of Common Stock owned by QP, Cayman, PE, and LS is limited to the extent of his pecuniary interest. Austin W. Marxe 2008-04-18 David M. Greenhouse 2008-04-18