Is a Preventive Breast Cancer Vaccine in Our Future?

Experts have long looked for ways to improve treatment options for people with breast cancer, which remains one of the most common types of cancer in the United States and beyond. But what about preventing the disease?

Cleveland Clinic has taken the next step in studying a novel vaccine designed to prevent triple-negative breast cancer (TNBC). A new phase of the clinical trial follows ongoing work from the first phase of the study.

Oncologist G. Thomas Budd, MD, the trial’s principal investigator, explains what’s happening and how the future of breast cancer prevention may look.

What started the breast cancer vaccine trial?

The groundbreaking breast cancer vaccine clinical trial is based on two decades of research and laboratory studies at Cleveland Clinic Lerner Research Institute by the late immunologist Vincent Tuohy, PhD.

Dr. Tuohy showed that activating the immune system against a protein called α-lactalbumin prevented breast cancer in mice at risk for the disease. The research, originally published in Nature Medicine, was funded in part by philanthropic gifts from more than 20,000 people.

In 2021, the research advanced into people with the first phase of a clinical trial. A second phase began in early 2023. (More on that in a bit.)

What will the breast cancer vaccine do?

The vaccine targets the milk protein α-lactalbumin, which is typically expressed only when a person is lactating. It’s no longer present after lactation in normal, aging breast tissue — but that doesn’t mean it’s forever gone.

Tumors can make this “retired” protein when they’re not supposed to. Studies have found that 70% to 80% of TNBCs produce too much α-lactalbumin.

“The general idea behind the vaccine is that α-lactalbumin could be a so-called immunologic target — where we can stimulate the immune system to attack cells that make that protein,” says Dr. Budd.

The vaccine also includes another drug, an immunologic adjuvant, which essentially calls your immune system’s attention to α-lactalbumin and flags it for an immune response to prevent an emerging tumor from growing.

Why target triple-negative breast cancer?

Triple-negative breast cancer (TNBC) is so named because peoples’ cancer cells test negative for estrogen and progesterone receptors and the human epidermal growth factor receptor 2 (HER2) protein.

Hormone therapy and other targeted drugs are ineffective against TNBC. Right now, the only effective prevention method available to those at high risk for TNBC is a mastectomy.

TNBC accounts for 12% to 15% of all breast cancers and is the most aggressive and deadly subtype, with nearly one-quarter of all patients dying within five years of diagnosis. TNBC also disproportionately affects Black people and those with BRCA1 gene mutations.

“Triple-negative breast cancer is the form of the disease for which we have the least effective treatments,” notes Dr. Budd. “Long term, we are hoping that this can be a true preventive vaccine that would be administered to cancer-free individuals to prevent them from developing this highly aggressive disease.”

What is the focus of the new phase of the clinical trial?

The vaccine study’s second phase will focus on cancer-free individuals who:

• Are at high risk for developing breast cancer.
• Have opted to undergo a prophylactic mastectomy to lower breast cancer risk.

People in this group typically carry genetic mutations that put them at risk of developing TNBC or they have a family history of breast cancer.

Six to 12 patients will be included in this trial phase. Participants will receive three vaccinations given two weeks apart. Their immune system response will be closely monitored, and they’ll undergo blood tests and physical exams to make sure there are no undue side effects.

The expectation is to complete this portion of the clinical trial by the end of 2023. This phase is being funded by the U.S. Department of Defense and conducted in partnership with Anixa Biosciences, Inc. (Cleveland Clinic licensed the vaccine technology to Anixa Biosciences.)

The U.S. Food and Drug Administration (FDA) approved an investigational new drug application for the vaccine, allowing the clinical trial to move forward.

Is the first phase of the trial complete?

Not yet, but it should be done by the end of 2023. This phase, which began two years ago, focused on individuals who have completed treatment for TNBC and are at risk of their cancer returning.

The goal of the phase-one trial is to determine the proper dosage in patients with early-stage TNBC and to optimize the body’s immune response to the vaccine.

Are there potential side effects of the breast cancer vaccine?

The vaccine is still experimental and under study, so there is a potential for as-yet-unknown side effects. And, of course, there’s the possibility that it may not prevent participants’ cancer from returning.

“We don’t know whether it will have a significant effect on the chance of their cancer coming back,” Dr. Budd says.

When might a breast cancer vaccine be available?

Even with a second phase of testing underway, it’s still far too soon to tell when or if a breast cancer vaccine may be made broadly available. It often takes years to develop and test a vaccine, notes Dr. Budd.

This vaccine strategy also has the potential to be applied to other types of tumors, including ovarian and endometrial cancers.

“The trial is part of a long road that we hope will lead to a vaccine that can prevent at least some breast cancer,” says Dr. Budd. “Our long-term goal is to determine if this vaccine can prevent breast cancer — especially the more aggressive forms of the disease — before it occurs.”

Information about this clinical trial, including a description of the study and patient eligibility criteria, can be found on the ClinicalTrials.gov website. If you have additional questions, you can contact Cleveland Clinic Cancer Answer Line at 216.444.7923 Monday through Friday 8 a.m. to 4:30 p.m. EST or by email at CancerAnswer@ccf.org.

For more background on the trial and how it started, listen to the Health Essentials Podcast episode, “Breast Cancer Vaccine Trial: What You Need to Know,” featuring Dr. Budd. New episodes of the podcast publish every Wednesday.