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HPV Vaccine Generates Immune Responses in Trial

T-cell lymphocyte

Colorized scanning electron micrograph of a T lymphocyte (NIAID)

20 Mar. 2023. Early results from a clinical trial show a vaccine for the human papillomavirus is safe and invokes immune responses in women with low-grade cervical lesions. Vaccitech plc in Oxford, U.K., developer of the vaccine, reported interim results from the trial today on the company web site, but plans to report the findings next month at the International Papillomavirus Conference in Washington D.C.

Infections from the human papillomavirus or HPV are common, and often transmitted through sexual contact. Most of the 200 known HPV infections are considered low risk, forming no more than warts on affected regions. According to National Cancer Institute, however, 14 types of HPV can cause cancer where infections occur, such as the cervix. World Health Organization says cervical cancer is the fourth most common cancer among women, with some 604,000 new cases in 2020 leading to 342,000 deaths worldwide. Because some cervical cancers develop slowly and cause few symptoms early on, pap test screening for the virus is encouraged among women, and vaccination of pre-teen girls.

Vaccitech is a spin-off company from the Jenner Institute at University of Oxford, developing vaccines for cancer and infectious disease prevention and treatment, often from research findings at the institute. The Vaccitech process generates two types of synthetic viral vaccine vectors, one derived from chimpanzee adenoviruses and another from vaccinia viruses, either weakened or modified to prevent replication. But the synthetic viruses encode enough of the target genetics to stimulate T-cell responses. The company uses synthetic chimpanzee adenoviruses, called Chimpanzee Adenovirus Oxford or ChAdOx, to produce prime vaccines designed to generate T-cells for initial immune responses, and Modified Vaccinia Ankara or MVA viruses to produce booster vaccines given one to 12 weeks later.

Designed to treat early-stage HPV infections

For HPV infections, Vaccitech is developing an immunotherapy vaccine code-named VTP-200, with a first dose made from ChAdOx and second dose from MVA synthetic viruses, for women with low-grade cervical lesions. The company says most of today’s HPV treatments are for women with more advanced HPV cases, thus meeting an unmet need. “Currently people with persistent HPV infections have no treatment options until they develop high grade lesions,” says Vaccitech CEO Bill Enright in a company statement, “Being told to return for a repeat cervical screening every 6 to 12 months without a treatment option can be frustrating and anxiety-provoking.” Enright adds, “VTP-200 is intended to treat HPV infections, potentially before the virus causes these high-grade lesions.”

The early- and mid-stage clinical trial is testing VTP-200 at several dosage levels and against a placebo, for both first and second doses, enrolling 96 women with low-grade HPV lesions in the U.K., Belgium, and Estonia. The study team is assessing the safety of the vaccine looking for any serious adverse effects it may cause among trial participants, as well as T-cell responses at three and 12 months after vaccination.

Vaccitech reported on results from the first 58 participants, six months after receiving the full vaccine. The company says the study team found no adverse effects from the vaccines rated serious or causing basic disruptions to participants’ lives. In addition, says Vaccitech, results of blood tests using enzyme-linked immunosorbent spot or ELISpot assays, a widely-used test of antigen-specific T-cells, found high responses in participants’ samples to the targeted antigens.

“These interim data are a promising step in the right direction,” notes Enright, “and we look forward to seeing the final data in early 2024.”

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