Pharma sparring over which HPV vaccine is better

Aside from the controversy that likely will shadow HPV vaccines' introduction, Merck and GSK are fully engaged in a not-so-friendly debate over whose vaccine is superior. Those in attendance at the last ACIP meeting in February caught a glimpse of this jockeying, and a piece in today's Philadelphia Inquirer covers the latest round of salvos.

First, the news. A paper was published today on the website of The Lancet (subscription required) reporting new trial data of the GSK vaccine, Cervarix. It is titled "Sustained efficacy up to 4·5 years of a bivalent L1 virus-like particle vaccine against human papillomavirus types 16 and 18: follow-up from a randomised control trial." Here's the GSK press release.

Two newsworthy items: (1) The follow-up study showed 100% efficacy over 4.5 years against the precancerous lesions caused by HPV. The data was gathered from a sample of 776 women who participated in an earlier vaccine trial, according to Forbes. For both vaccines, long-term efficacy data is not yet available, so it's unclear whether booster doses may be needed. 4.5 years of protection is a start, but ultimately, life-long protection is necessary.

(2) The paper also suggests broader protection against more subtypes of HPV than the two specifically included in the vaccine. From the press release:

"The study provided evidence that GSK’s candidate vaccine demonstrated substantial protection against infection with the third and fourth most prevalent cancer-causing types of HPV, namely types 45 and 31. This protection also extends over 4.5 years. GSK is conducting further large studies to determine the potential mechanism and extent of the demonstrated broader oncogenic protection."

If this finding holds up, it would mean that GSK's vaccine provides protection against up to 80% of cervical cancers in the U.S. (up from the 70% figure originally believed).

As the Inquirer reports, Merck scientists were skeptical of the GSK announcement:

"Merck...immediately questioned GlaxoSmithKline's study. One of its HPV researchers, Eliav Barr, called Dubin's analysis 'unorthodox' and emphasized that Merck also was testing for additional virus protections. Merck's vaccine already has been shown to help prevent HPV infections that cause genital warts.

Reacting to Merck's criticism, Dubin defended the study results as highly reliable and suggested that a reporter 'ignore' Merck's comment."

We've discussed the differences between each company's HPV vaccine and other recent developments previously (here, here, here, and here). While Merck's inclusion of additional HPV subtypes responsible for genital warts in their vaccine gave it the early competitive advantage (as males could also benefit from it), today's news signals that the battle for superiority is far from over.