The deluge of bad news reported by Vical just won’t let up. The biotech confirmed today it has abandoned its lead genital herpes vaccine program after a negative phase 2 trial, following in the footsteps of earlier cancer and cytomegalovirus candidates.
It’s not a wholly unexpected development, as the herpes simplex virus-2 candidate VCL-HB01 hasn’t hit the mark in earlier studies. Still, Vical said it saw glimmerings of activity that it said should be improved by upping the dose form three to four injections.
That proved to be a false hope, as in the midstage trial, the vaccine was unable to show a significant effect in annualized recurrence rate for genital herpes lesions, its primary endpoint, said Vical. The company’s CEO, Vijay Samant, said the study was affected by a lower-than-expected relapse rate in the placebo group.
“As a result, there was significantly less power to show a vaccine effect in this trial,” he said. Shares in the company were down 17% after hours, as news of the setback filtered through. The biotech said recently it thought that a therapeutic HSV-2 vaccine could conservatively represent a commercial opportunity of more than $1 billion.
The decision leaves Vical with an ever-dwindling pipeline—now limited to its potentially first-in-class antifungal drug product VL-2397 licensed from Astellas in phase 2 and a chronic hepatitis B virus candidate called VR-CHB01 in preclinical development.
Samant said a phase 2 trial would compare VL-2397 to standard first-line treatment in invasive aspergillosis in immunocompromised adults, a small indication that he suggested would be eligible for a "limited use indication"—in other words, it could potentially be approved based on a single midstage study.
Earlier this year, Vical slashed 40 workers from its headcount after its CMV vaccine licensed from Astellas, ASP0113, failed to show a significant improvement in overall survival or reduction in CMV end-organ disease, missing the phase 3 trial’s primary endpoint.
The decision is also a blow to people affected by genital herpes, an incurable, contagious sexually-transmitted infection that causes a lifetime of painful outbreaks. One in six Americans are infected with HSV-2, and worldwide the virus affects a massive 400 million people.
Last year, another company with a genital herpes candidate—Genocea Biotech—also said it wouldn’t be progressing with the project, although it has offered its drug for licensing on the strength of phase 2b data.