Gardasil and Cervarix help prevent cancer by blocking infections by the most common forms of the human papilloma virus (HPV), but what if cancerous cells have already begun growing? A new experimental HPV vaccine shows promise of reversing the course of the tumor cells in a small clinical trial reported today in the New England Journal of Medicine.
The vaccine is targeted against a condition called vulvar intraepithelial neoplasia, a precursor of vulvar cancer in which lesions appear on the vulva. About three-quarters of the growths are caused by the strain of virus called HPV-16. Existing treatments include topical chemotherapy, laser removal or surgery, but all are frequently unsuccessful. Such lesions progress to cancer in about 3,200 American women each year, killing about 800.
Dr. Gemma Kenter of Leiden University in the Netherlands and her colleagues have been studying a vaccine composed of synthetic peptides (amino acid chains or fragments of proteins) encompassing specific sites on HPV-16. The peptides are added to an adjuvant that stimulates a stronger immune response to the peptides when they are injected into the body.
Twenty women were vaccinated three or four times each with the preparation. The lesions disappeared completely in nine of the 20 women, including one patient who had been carrying the lesions for 10 years. They had not returned after two years of monitoring. The growths shrank by at least 50% in six of the women. One woman died of an unrelated heart attack. Two of the other women went on to develop full-fledged cancer, and one who showed significant improvement had a relapse.
The primary side effect was the occurrence of bumps at the injection site. Some of the bumps persisted for as long as two years.
The team now plans to test the vaccine in larger numbers of patients. They are also working to develop vaccines that are more potent and that target other strains of HPV as well.
-- Thomas H. Maugh II