Opexa Therapeutics Completes Patient Enrollment in Phase IIb Trial of Tovaxin(TM) for Treatment of Multiple Sclerosis.

THE WOODLANDS, Texas -- Opexa Therapeutics, Inc. (NASDAQ:OPXA), a company involved in the development and commercialization of cell therapies, today announced the completion of patient enrollment in a 150-patient Phase IIb safety and efficacy study (TERMS). The trial design is a U.S. multicenter, randomized, double-blind, placebo-controlled study of subcutaneous Tovaxin[TM] in subjects with Clinically Isolated Syndrome (CIS) or Relapsing/Remitting Multiple Sclerosis (RRMS).

Patients participating in the study, which is being conducted under Opexa's U.S. Investigational New Drug (IND) application filed with the U.S. Food and Drug Administration (FDA), will receive 52 weeks of treatment and will undergo safety and efficacy assessments using primary criterion of gadolinium-enhancing lesions and secondary criterion of annualized relapse rate. The Company will collect descriptive analysis data on the first 75 subjects to reach 6 months evaluable later this year. This trial was specifically designed, with the assistance of well-known multiple sclerosis experts, to address three important objectives: to rigorously assess the safety and efficacy of Tovaxin, to maintain a robust clinical effect for the full study, and to provide a scientific and clinical database for advancement to Phase III.

David McWilliams, president and chief executive officer of Opexa Therapeutics, stated, "Full enrollment in this Phase IIb study is an important milestone in the commercialization of Tovaxin. With this milestone achieved, we now look forward to reporting a descriptive analysis in the fourth quarter of 2007 and the full data results in the second half of 2008." McWilliams continued, "I am convinced that the ability to rapidly enroll this study across 35 U.S. centers reflects the high level of interest by multiple sclerosis patients in new safe and effective treatments."

Edward Fox, MD, PhD and lead principal investigator for the Phase IIb study, commented, "If the results of this study can replicate the safety and effectiveness demonstrated in earlier studies, I believe Tovaxin could be an important advance in treating patients with MS. I'm pleased that the positive response from physicians and their MS patients across the country has resulted in the rapid enrollment of this study."

About T-cell Vaccination

For a T-cell vaccine to be effective, it should be able to induce T-cell cytotoxic and/or regulatory immune responses against the pathogenic T-cells. Studies of T-cell vaccine have indicated that T-cell vaccination with peripheral blood-derived autologous myelin-peptide selected T-cells in multiple sclerosis patients resulted in the in vivo induction of CD8+ cytotoxic T-cells and CD4+CD25+FoxP3 Tregs specific for T-cell vaccine. The induction of anti-idiotypic cytotoxic CD8+ effector T-cells and anti-ergotypic CD4+CD25+FoxP3 positive Tregs is believed to provide a therapeutically effective dual mechanism of protection to patients treated with Tovaxin[TM]. The observed regulatory immune responses have been shown to collectively correlate with clinical improvement in treated patients.

About TERMS

The Tovaxin Phase IIb clinical study will include 150 patients in a multicenter, randomized, double blind, placebo-controlled trial designed primarily to evaluate the efficacy, safety and tolerability of the Tovaxin T Cell vaccination with clinically isolated syndrome (CIS) and relapsing-remitting MS (RR-MS) patients. A total of 100 patients will receive Tovaxin, while 50 will receive placebo. The study is designed as a two-arm, 52-week, parallel-group study, whereby patients will be given five subcutaneous injections at 0, 4, 8, 12 and 24 weeks. The analyses will be performed at the end of the 52-week study to assess the safety and efficacy of Tovaxin. The primary efficacy variable is the cumulative number of gadolinium-enhancing lesions on T1-weighted MRI scans summed over the Week 28, 36, 44, and 52 MRIs. The secondary efficacy variables are the cumulative number of new gadolinium-enhancing lesions at Weeks 28-52, the change in T2-weighted lesion volume, and the annualized relapse rate.

All patients who complete the trial will be eligible to participate in an optional one-year extension study, in which they will receive Tovaxin under an open-label protocol. The open-label study is being planned under a different protocol that will be submitted to the FDA.

About Opexa Therapeutics

Opexa Therapeutics develops and commercializes cell therapies to treat autoimmune diseases such as MS, rheumatoid arthritis, and diabetes. The Company is focused on autologous cellular therapy applications of its proprietary T-cell and stem cell therapies. The Company's lead product, Tovaxin(TM), a T-cell therapy for multiple sclerosis is in Phase IIb trials. The Company holds the exclusive worldwide license for adult multipotent stem cells derived from mononuclear cells of peripheral blood. The technology allows large quantities of monocyte derived stem cells to be produced efficiently for use in autologous therapy, thus circumventing the threat of rejection. The Company is in preclinical development for diabetes mellitus. For more information, visit the Opexa Therapeutics website at www.opexatherapeutics.com.

Safe Harbor Statement

This press release contains "forward-looking statements," including statements about Opexa Therapeutics' growth and future operating results, discovery and development of products, strategic alliances and intellectual property, as well as other matters that are not historical facts or information. These forward-looking statements are based on management's current assumptions and expectations and involve risks, uncertainties and other important factors, specifically including those relating to Opexa Therapeutics' ability to obtain additional funding, develop its stem cell technologies, achieve its operational objectives, and obtain patent protection for its discoveries, that may cause Opexa Therapeutics' actual results to be materially different from any future results expressed or implied by such forward-looking statements. Opexa Therapeutics undertakes no obligation to update or revise any such forward-looking statements, whether as a result of new information, future events or otherwise.