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Equivocal Results With Hepatitis C Vaccine, ChronVac-C, in Phase II Trial

Outcomes not significantly different between vaccinated and non-vaccinated subjects (Apr. 2)

Preliminary results have been reported from an open-label phase II study of ChronVac-C (Inovio Pharmaceuticals), an investigational DNA vaccine for the treatment of hepatitis C virus (HCV) infection. The vaccine was administered with the MedPulser-DDS electroporation device (Inovio) followed by a drug regimen (pegylated interferon-alpha [PEG-IFN-alpha] plus ribavirin) in chronic HCV-positive subjects. Initial results did not show a statistically significant difference between treatment outcomes in the vaccinated and non-vaccinated groups.

Seventeen patients received two monthly vaccinations of ChronVac-C (500 mcg) followed by PEG-IFN-alpha and ribavirin. In the control arm, 12 additional patients were treated with PEG-IFN-alpha and ribavirin alone. Results were reported from an interim analysis at 12 weeks after treatment. Reduction or elimination of the HCV viral load was assessed by measuring HCV RNA levels.

At week 12, 71% of the vaccinated group had less than 15 international units (IUs) of HCV RNA compared with 58% of the non-vaccinated group, and 65% of vaccinated subjects were HCV RNA-negative compared with 58% of the non-vaccinated subjects. The number of patients with moderate AEs was significantly lower in the vaccinated group compared with the non-vaccinated group (P < 0.05). There was no difference in mild AEs between the two groups.

In 2007, a phase I dose-escalation study of ChronVac-C DNA vaccine (167 mcg, 500 mcg, and 1,500 mcg) delivered with the MedPulser device targeted genotype-1a and NS3/4A antigens. The treatment regimen of four vaccinations delivered with electroporation demonstrated transient reductions in viral loads. Eight patients were subsequently treated with standard-of-care PEG-IFN-alpha plus ribavirin. Of this group, six patients (75%) achieved a complete early viral response (cEVR) and a sustained viral response (SVR), compared with typical 40% to 50% response rates with the PEG-IFN-alpha/ribavirin regimen alone in genotype-1 patients. In the new phase II study, only two vaccine administrations at the medium-dose level used in the phase I study were used to assess the potential for a clinically meaningful result.

“The major hurdle to developing therapeutic vaccines for any disease area has been the inability to generate a meaningful level of functional T-cell response and, in the case of HCV, one that is directed to the liver,” a company spokesman said.

Source: Inovio Pharmaceuticals; April 2, 2013.

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