A new type of cervical cancer vaccine made by Inovio Pharmaceuticals has shown early promise as a potential treatment for pre-cancerous changes in the cervix, researchers at the company said.
Instead of preventing infections caused by certain strains of the human papillomavirus (HPV), as is the aim of Merck's Gardasil and GlaxoSmithKline's Cervarix vaccine, the Inovio vaccine is designed to train the immune system to kill cells that spur cancer growth in women who are already infected.
In about 10% to 25% of women who develop moderate to severe cervical intraepithelial neoplasia, the condition resolves spontaneously.
"It was not clear why that happens," said Joseph Kim, chief executive of Inovio Pharmaceuticals, which funded the study.
But many of these women tend to have higher levels of T cells against two HPV-specific oncogenes, E6 and E7. The company set out to develop a vaccine to train a patient's immune system to make large quantities of these T cells.
How the study was done
In a phase I trial reported online in Science Translational Medicine, the team studied the effects of three intramuscular injections of "highly engineered plasmid DNA encoding HPV16 and HPV18 E6/E7 antigens" in 18 women whose cancers had already been treated surgically.
The vaccine, dubbed VGX-3100, produced CD8-positive T cells that "exhibited full cytolytic functionality" in 14 of the 18 women, which lasted for two years.
"These T cells were not only abundant in number; they were able to do what they were designed to do. They were able to seek out and kill the target cells," Kim said.
The study found no major side effects in any of the three doses tested.
But because surgery to remove abnormal cells works well in women with pre-cancerous lesions, the bar for success is high.
A therapeutic vaccine for this indication made by French company Transgene SA that was formerly licenced by Swiss drugmaker Roche Holding AG was discontinued earlier this year because not enough women benefited.
How the vaccine works
Inovio's vaccine works a bit like gene therapy in that it inserts a bit of specific DNA into patients' cells, which triggers an immune response.
But rather than using a conventional viral vector to deliver genes into cells, Inovio uses a process called electroporation: a brief electrical pulse coaxes cells into opening their doors to the vaccine.
Inovio is now testing its vaccine in a phase 2 trial of 150 women with previously untreated pre-cancerous lesions, and results are expected in by the end of 2013.
(Reuters Health, October 2012)
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