Chiron Corp. on Wednesday presented data showing its vaccine fortreating genital herpes failed to meet its primary endpoint but didhave statistically significant benefit in reducing the duration ofsymptoms and healing time.

The Emeryville, Calif., company reported last January that the PhaseIII study failed to meet its primary endpoint. But the presentation inNew Orleans at the 36th annual Interscience Conference onAntimicrobial Agents and Chemotherapy was the first detailedpresentation of the data.

Chiron has two separate Phase III trials ongoing studying the vaccineas a prophylactic for herpes simplex virus type II (HSV-2).Completion is expected by the end of the year in one study and nextspring in the other.

The completed trial was a randomized, controlled study involving202 patients with a primary endpoint of reducing the frequency ofoutbreaks. Patients with frequently occurring genital herpes (medianof seven outbreaks per year) received two doses of vaccine orplacebo at the start of the study and two months later. Detailedassessments were made on the first outbreak following the firstimmunization.

Patients on the vaccine, while not faring better on the monthly rate ofoutbreaks, did have significant reductions in the duration ofsymptoms (from 6.7 to 4.9 days, p=0.002), the number of days onwhich new lesions formed (from 6.9 to 4.1 days, p=0.04), and healingtime (from 8.8 to 6.8 days, p=0.004) during the first recurrence afterthe first immunization.

Larry Kurtz, vice president of corporate communications for Chiron,said, "We have to consider these results and study their medicalimplications as well as do some marketing research. It's possible wemay want to pursue additional studies that focus on the positiveresults that were observed."

The recombinant vaccine consists of gD and gB, the predominantglycoproteins in the HSV envelope, with the squalene-based adjuvantMF59. The gB glycoprotein is responsible for fusion of the viralmembrane and its target cell membrane, while gD binds to a receptoron that mucosal cell's surface. (See BioWorld Today, June 28, 1995,p. 1.)

One ongoing study involves 500 people (half vaccine, half placebo)who don't have the virus but their monogamous partner does. Despitesafe sex practices there still is a chance for exposure. The other studyinvolves nearly 2,000 sexually active people with multiple partners.They don't have HSV-2 but did go to a clinic for another sexuallytransmitted disease.

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