WASHINGTON, April 5 (UPI) -- A study released Wednesday indicates GlaxoSmithKline's cervical-cancer vaccine Cervarix protects women for up to 4.5 years, a finding that could give it an important advantage over Merck's vaccine Gardasil.
The study, which was published online by The Lancet, found that women given Cervarix showed sustained high levels of antibodies against human papillomavirus types 16 and 18 for up to 4.5 years. In addition, Cervarix appears to cross-protect against HPV-45 and 31, two other strains of the virus associated with cancer, a benefit not provided by Gardasil.
"This is so exciting," Diane Harper, of Dartmouth Medical School and a principal investigator in the trial, told United Press International. "We saw sustained immune titers that did not drop," Harper added, noting that with other vaccines in general, the immune response is dropping by four years after the last shot.
The long-term response appears to be due to the use of the adjuvant ASO4 with Cervarix rather than the adjuvant alum that is typically used with vaccines, including Merck's Gardasil.
"So potentially it wouldn't matter at what age you give the vaccine to women because potentially they're protected for decades" without requiring booster shots, Harper said, although she acknowledged that this was speculation at this point and still needed to be proven.
This doesn't hold for Gardasil and could be a potential negative for it, added Harper, who has also worked as a principal investigator in clinical trials of Merck's vaccine.
"Merck's vaccine is alum-based so you want to make sure you give it to women around the time when they are most exposed to virus (because) if you give it to them too soon, they're not going to have protection during their peak period of exposure," she said. "That's got to be something that physicians and patients know about before they get the vaccine."
Gardasil does, however, offer protection against HPV strains associated with genital warts, a benefit that Cervarix does not provide. But both vaccines are likely to win Food and Drug Administration approval, Harper said. "Both are very effective, both are very safe, and there shouldn't be anything that should cause any regulatory body to have any concerns," she said.
The Cervarix study is the first that looks at long-term safety of a potential HPV vaccine and it is "very striking at how safe the vaccine is," Harper said. "We can say the women who received the vaccine are not having any more of any kind of medical problems because of the vaccine," she said.
Prudential analyst Tim Anderson gave Merck a neutral rating in a research report released Tuesday and raised his EPS forecast for 2006 from $2.36 to $2.41.
The EPS increase was based on Merck's announcement that it will report higher first-quarter EPS than previously anticipated -- from $0.62-0.66 to $0.71-0.75 -- predominantly due to better than expected Zocor revenues.
Prudential's EPS is still below the group average and this "reflects the uncertainties that lay ahead for MRK such as Vioxx legal liability, offset partly by a higher-than-average dividend yield," Anderson wrote in the report. Other factors that could reduce the EPS estimate include "the possibility that MRK has an extended run of bad luck in trying to commercialize its various pipeline products, including its HPV vaccine," he added.
Citigroup analyst George Grofik wrote in a detailed analysis of both HPV vaccines issued last June that he saw no major difference between the inoculations, aside from Gardasil's ability to prevent genital warts.
However, Gardasil's development lead of 12-18 months could make it first to market and give Merck control over pricing, Grofik stated. Ultimately, Grofik estimated a HPV vaccine market that will be worth $4.5 billion by 2012.
"Our model indicates levels of vaccination consistent with other major vaccines, and peak global market sales of $4.5 bn in 2012 are divided between Gardasil $2.5 bn and Cervarix $2 bn," he stated.
Philippe Monteyne, head of global vaccine development of GSK Biologicals, called the data "extremely encouraging."
Monteyne declined to say whether the findings gave GSK's vaccine an advantage over Gardasil, but he told UPI they do provide several unique findings about Cervarix. This includes the cross-protection seen against HPV 45 and 31 and that the 4.5 year follow-up in this study is the longest follow-up for any HPV vaccine.
Monteyne said the data will be submitted to the regulatory authorities as part of their submission for approval to market Cervarix. GSK filed in Europe last month and intends to file with the FDA by the end of the year.
