UK drug giant GlaxoSmithKline has kicked off the first study of its kind to compare the immunogenicity of its cervical cancer candidate vaccine Cervarix against Merck & Co’s marketed rival, Gardasil.

The main objective of this head-to-head trial is to compare the immune responses to human papillomavirus types 16 and 18 in women aged 18 to 26, while secondary goals will assess this in those aged 27 to 35 and 36 to 45. The study will also look at immune responses to other cancer-causing HPV types, such as 45 and 31 which, together with types 16 and 18, cause more that 80% of cervical cancers. First results are expected around 12 months after enrollment is complete.

"Vaccination to prevent cervical cancer may be the most significant healthcare breakthrough for women in our lifetime," commented Dr Mark M Blatter, Medical Director of Primary Physicians Research in Pittsburgh and study investigator. "This unprecedented trial, which will enroll more than 1,000 women, will provide the first scientific evidence to demonstrate how the two vaccines differ with respect to inducing strong and sustained immune responses in women who may be appropriate for vaccination," he explained.

Both vaccines employ the use of adjuvants, which boost the ability of an antigen to stimulate an immune response. But, while Merck's Gardasil uses an aluminum salt adjuvant, Cervarix uses a novel adjuvant known as AS04, which GSK is hoping to prove will give its vaccine an edge over its rival.

According to the group, data published in Vaccine in August last year showed that Cervarix “induced higher antibody levels and more robust immune memory response compared to the same HPV vaccine composition conventionally formulated with aluminium hydroxide adjuvant alone.”

Gardasil first to market

Merck’s Gardasil won the race to market last year, with a UK launch in October, shortly after it was given the green light by European regulators. Cervarix was filed in Europe in March last year, so could be approved in the near future. But Gardasil, which also protects against HPV strains 6 and 11 as well as 16 and 18, offers the benefit of tackling genital warts too, and this, together with its first-to-market advantage, could provide it with a competitive edge over its rival, helping it achieve the $3 billion peak sales target forecast by analysts. GSK, therefore, will be pushing hard to tout any benefits that its offering may have.