Scientists at the Cleveland Clinic are now testing out something that could become a huge milestone in cancer research: a vaccine for the most aggressive and deadly form of breast cancer. The small Phase I trial, which began this week, will give the vaccine to cancer survivors in order to gauge its safety and optimal dose. Ideally, the vaccine could be used both as a therapeutic booster for survivors as well as a preventative treatment for those at high risk.
The vaccine is intended to stop triple-negative breast cancer, a form of cancer where the tumor has few or no receptors for estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2). Though only about 10-15% of breast cancers are triple negative, these tumors are harder to treat due to the lack of receptors that current treatments can target; they’re also faster-growing and more likely to spread elsewhere in the body. The five-year survival rate of a triple-negative cancer varies but is only around 12% for cancers that have spread far across the body.
The principle behind the vaccine relies on training the immune system to target a certain protein called α-lactalbumin. This protein is expressed by breast cells when a woman is producing breast milk. The majority of triple-negative tumors also produce α-lactalbumin, however, making the protein a sort of homing beacon for the immune system to go after wayward tumor cells while leaving healthy breast tissue alone. Because of the way the vaccine works, it would be most suited for “women in their post-child-bearing, premenopausal years, when lactation is readily avoidable and risk for developing breast cancer is high,” as the scientists wrote in previous research.
In this Phase I trial, 18 to 24 people who survived triple-negative breast cancer and are currently tumor-free will be given a three-dose schedule of the vaccine. Though their cancer was treated early, they remain at high risk for a recurrence. Researchers will primarily be looking at the safety of the vaccine, but they’ll also be tracking the patients’ immune response post-vaccination.
Most vaccines for cancer being developed right now are therapeutic, meaning that their purpose is to prevent a cancer from returning. But because triple-negative cancers are so often characterized by α-lactalbumin, the researchers do think that it could be used as a preventive vaccine as well, particularly for people with a high genetic risk of breast cancer via mutations in the BRCA1 gene. These high-risk patients tend to develop triple-negative cancer more than other forms, and African American women are also twice as likely to develop this form than other racial and ethnic groups.
“Long term, we are hoping that this can be a true preventive vaccine that would be administered to healthy women to prevent them from developing triple-negative breast cancer, the form of breast cancer for which we have the least effective treatments,” said principal study investigator, G. Thomas Budd, a doctor with the Cleveland Clinic’s Taussig Cancer Institute, in a statement from the medical center.
The study is expected to wrap up by September 2022. Should things go well, the next phase of research would involve high-risk patients who have yet to develop breast cancer and would track whether the vaccine prevented later development of the cancer.