Results from an interim analysis of a phase III study show that Cervarix, the GlaxoSmithKline (GSK) cervical cancer candidate vaccine, provides up to 100 per cent protection against advanced precancerous lesions caused by the most common types of human papillomavirus, types 16 and 18. The study also strengthens earlier preliminary evidence that the vaccine provides significant protection against infection with additional cancer-causing virus types. These results were published in the latest The Lancet.

"This landmark trial has provided important new insights into the natural history of cervical lesions, and helps us to more clearly understand the causal link between these lesions and the virus types detected within them," said Gary Dubin, M.D., vice president, North American Clinical Development, GSK.

"These results validate our previous clinical findings, and we believe that the data in this study show the GSK candidate vaccine provided 100 percent protection against precancerous lesions caused by virus types 16 and 18, which are responsible for 70 per cent of all cervical cancers," commented David Stout, President of Pharmaceuticals Operations, GSK.

In this study, the majority of precancerous lesions included in the primary analysis had multiple cancer-causing virus types detected, making it difficult to clearly determine which virus type was the cause of the lesion. The observation of such a high number of lesions with multiple virus types was not expected based on published data. This necessitated additional analyses to determine which virus type was the cause of the lesion. In these analyses, causality was determined by confirming the presence of the virus in both the lesion and in previous Pap smear samples.

When using the pre-specified analyses which only required detection of virus in the lesion, and not taking previous samples into account, vaccine efficacy in women with virus type 16 and/or 18 in the lesion was 90 percent.

When considering the virus type present in both the lesion and previous samples, the vaccine was 100 percent effective in preventing precancerous lesions caused by virus types 16 and/or 18.

"The findings are very encouraging because the women in the study are representative of the patients seen by physicians every day in their practice," said lead investigator Professor Jorma Paavonen, Department of Obstetrics and Gynecology at Helsinki University Central Hospital, Finland. "This provides a strong indication that this vaccine can protect women from the infections that may develop into cervical cancer."

This pivotal, phase III study involves 18,644 women aged 15-25 from 14 countries across Europe, Asia-Pacific and Latin and North America, making it the single largest cervical cancer vaccine efficacy trial to date.

In this clinical trial, the vaccine showed significant cross-protection against 6-month persistent infection caused by virus types 45, 31 and 52. Together with virus types 16 and 18, these types are collectively responsible for more than 80 percent of cervical cancer cases globally.

"These results suggest protection from persistent infection with additional cancer-causing virus types beyond those contained in the vaccine," said Professor Margaret Stanley, Pathology Department, University of Cambridge, UK. "This is important because persistent infection is a necessary first step in the development of precancerous lesions and cervical cancers."

The data also shows that the GSK candidate vaccine, formulated with the innovative adjuvant system AS04, produced a robust immune response for both virus types 16 and 18. This strong immune response has been shown to persist for up to 5.5 years in previous studies.

As in previous studies conducted over the past five years and involving over 40,000 women, the candidate vaccine has been shown to be generally well-tolerated.