Vical’s bivalent vaccine reduces genital herpes lesions, showing durability to nine months

SAN DIEGO—Vical Inc. presented data from its randomized, double-blind, placebo-controlled Phase 1/2 clinical trial of a therapeutic genital herpes vaccine in symptomatic herpes simplex virus type 2 (HSV-2)-infected patients in an oral late-breaker presentation at the American Society for Microbiology (ASM) 2016 meeting held in Boston.

The study analyses included 131 evaluable patients: 54 receiving the monovalent (gD) vaccine, 56 receiving the bivalent vaccine (gD + UL46) and 21 receiving placebo. Initial top line three-month data announced in June 2015 showed that neither the monovalent nor the bivalent vaccine met the primary endpoint of viral shedding rate reduction from baseline.

However, the bivalent vaccine achieved statistically significant reduction in a prospectively defined secondary endpoint of genital lesion rate at three months versus baseline. In the nine-month analysis presented at ASM 2016, the statistically significant reduction in lesion rate compared to baseline for the bivalent vaccine was sustained. Furthermore, at the nine-month time point, the bivalent vaccine showed a favorable trend in recurrence rate, time to first recurrence and proportion of patients who are recurrence-free. Vical’s vaccines reportedly elicited significant increases in antigen-specific interferon gamma-producing T cells, indicating biologic activity.

An independent safety monitoring board reviewed all adverse events (AEs) and deemed the vaccines to be safe and tolerable in this trial. No serious adverse events, Grade 4 AEs or AEs of special interest related to vaccinations were observed during the study period. Grade 3 AEs were reported in 13 percent of subjects, the most common of which were fatigue and injection site pain.

“There remains considerable unmet medical need in the treatment of genital herpes, as there have been no new therapeutic breakthroughs in the past several decades,” said Dr. Peter Leone, professor of medicine at the University of North Carolina and an external program advisor for Vical. “A therapeutic HSV-2 vaccine could represent a very attractive treatment option to reduce outbreaks in individuals who suffer chronically from this disease. The data generated to date with the bivalent HSV-2 vaccine indicate that it is not only immunogenic, but also provides evidence for reducing lesion rate, a clinically meaningful endpoint for patients and physicians. Therefore, the bivalent vaccine warrants further clinical investigation.”

“We have consulted with multiple experts involved in treating patients with genital herpes and conducting clinical trials,” said Vijay Samant, president and CEO of Vical. “Our advisors have encouraged us to evaluate the bivalent vaccine further in a follow-on study powered to measure a clinically-relevant endpoint. We have established a continuing dialogue with the FDA about potential next steps and are currently finalizing a clinical protocol based on those discussions. We plan to initiate a Phase 2 trial of the bivalent vaccine during the second half of 2016. Importantly, we expect to be able to execute this study using our current resources and under our operational plan, and maintain our guidance for net cash burn of between $8 million and $11 million during 2016.”

Samant further said, "We anticipate a number of additional clinical milestones this year. In our CMV [cytomegalovirus] program with Astellas, we expect that in the third quarter of 2016, enrollment will be completed in the Phase 3 registration trial in hematopoietic cell transplant recipients and that top line data should be available from the Phase 2 trial in kidney transplant recipients. In addition, we also anticipate completing the Phase 1 trial of our novel antifungal, VL-2397, by year end.”