By Bill Berkrot
(Reuters) - A U.S. Food and Drug Administration advisory panel on Wednesday voted 11-0 that the safety and efficacy of GlaxoSmithKline's (L:GSK) Shingrix shingles vaccine warrants approval for its use in adults aged 50 and over.
Panel members said they were "very impressed" by efficacy data from Shingrix clinical trials, and that it represents an improvement over Zostavax, the only marketed shingles prevention vaccine from Merck & Co (N:MRK).
While the FDA is not required to follow recommendations of its advisory panels, the enthusiasm expressed would seem to indicate that approval is a virtual certainty in coming weeks.
Shingrix is considered one of the more important products in GSK's pipeline, with annual sales forecast to reach $1 billion (757.69 million pounds) by 2023, according to Thomson Reuters data.
Zostavax, approved in 2006, is expected to generate sales of about $730 million this year, with declining sales forecast for ensuing years with the introduction of serious competition.
Shingrix contains a component used to help boost efficacy from Agenus Inc (O:AGEN), which is entitled to royalties on future sales.
Older people are most at risk of an outbreak of shingles, a painful, often debilitating blistering rash. Shingles is the result of reactivation of the varicella-zoster virus, which causes chickenpox and remains latent in those who have had that disease.
In clinical trials, Shingrix has shown greater protection against shingles among older recipients than that demonstrated by Zostavax. Four years after injection, the GSK vaccine remained about 90 percent effective in people over age 70, while the efficacy of Zostavax declines noticeably over time.
"This is a new generation of vaccine, which really has overcome the age-related decline in immunity," Thomas Breuer, chief medical officer of GSK Vaccines, said in an interview.
Shingrix, given in two doses two months apart, also reduces incidence of nerve pain following a shingles outbreak known as postherpetic neuralgia.
In two pivotal Phase III studies involving more than 29,000 subjects, serious side effects were similar for Shingrix and a placebo. Panelists had questions about a small but greater incidence of certain reported adverse health issues among Shingrix recipients, including gout and stroke.
GSK said it did not believe those were related to Shingrix but has proposed a post-approval safety monitoring plan.
Panelists also expressed concern that the vast majority of trial subjects were white, saying they would like to see more data for other populations.
GSK is expected to announce a U.S. price for Shingrix upon approval. It is also awaiting approval decisions from Europe, Japan, Australia and Canada.