Opexa Reports Positive Data on T-Cell Vaccine for MS

Opexa Therapeutics has announced positive top-line data from an open-label, Phase I/II, dose-escalation clinical trial of its investigational T-cell vaccine, Tovaxin, for multiple sclerosis (MS).

In this one-year, 10-subject trial, Tovaxin therapy was shown to be safe and effective. The per-protocol analysis of Tovaxin therapy achieved a 90 percent reduction in annualized relapse rate (ARR) in subjects who received one of the three dosage levels. Subjects in the study received subcutaneous injections of Tovaxin over a period of 20 weeks and were monitored for an additional 32 weeks.

The safety profile for all dosage levels revealed no severe adverse reactions related to T-cell vaccination. With increasing dosage, an increase in mild injection site reactions was observed, and these resolved within 48 hours. All subjects are enrolled in an extension study to collect longitudinal safety and effectiveness data.

"We are particularly encouraged by the data from this dose escalation trial," David McWilliams, president and CEO of Opexa, said. "While all three dosage levels were safe and effective, the group treated with the 30 to 45 x 106 T-cell dose achieved a 100 percent reduction in ARR. The currently enrolling Tovaxin IIb clinical trial is being conducted with the 30 to 45 x 106 T-cell dose."

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, according to Opexa. Studies of T-cell vaccines have indicated that T-cell vaccination with peripheral-blood-derived, autologous, myelin-peptide-selected T-cells in MS 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. The observed regulatory immune responses have been shown to collectively correlate with clinical improvement in treated patients.