Randomized, Open-label Study of the Bria-IMT regimen and Check Point Inhibitor vs Physician’s Choice in Advanced Metastatic Breast Cancer (BRIA-ABC)

• SV-BR-1-GM is a GM-CSF-secreting breast cancer vaccine

In this study, the sponsor and investigators want to learn:

• How much of the study agent can be given with an acceptable level of side effects when given in combination with Retifanlimab
• The effects of the study agent (good and bad) when given in combination with Retifanlimab
• If research tests can be used in the future to predict who will benefit from SV-BR-1-GM
• How the study agent is acting on your body
• Whether or not the study agent helps boost your immune system and/or helps control or shrink your cancer along with the other drugs that also boost the immune system

Research participants will be randomly assigned to receive the study agent alone (Cohort A), in combination with Retifanlimab (Cohort B), or a standard of care therapy (Cohort C) that is commonly used to treat breast cancer.

The study regimen for Cohorts A & B will be given in cycles. Each cycle is 3 weeks. If you are assigned to Cohort A or B, you will receive the following:

• Cyclophosphamide, a medication to prepare your immune system, 2-3 days before you receive the study agent. This will be given as an infusion into your vein (IV) over about 60 minutes.

• Retifanlimab on days that you receive Cyclophosphamide. This will be given as an IV infusion over 30-60 minutes (Cohort B Only).

• The study agent will be given as an injection just under the skin (intradermal) in up to four locations (One in each thigh and two locations on the upper back).

• Interferon-alpha (Interferon), a drug widely used to improve immune function. This will be given as an injection into each of the same locations that you received the study agent injections. This dose will be given 2 days after you receive the study agent.

If you are assigned to Cohort C, your study doctor will determine the standard of care therapy you will receive, as well as the frequency of administration.