Preliminary results of an early, multicenter study showed an experimental immune therapy drug was safe in patients with metastatic, triple-negative breast cancer. These early findings offer new hope in the fight against this particularly aggressive and difficult-to-treat disease.

The study involved 54 patients with advanced triple-negative breast cancer from the Kimmel Cancer Center and other cancer centers. The patients received an experimental drug, known as a PD-1 blockade, designed to disrupt a pathway that hides tumor cells from immune system.

“Early data in this trial show that the drug is generally safe and well-tolerated, and it appears to be able to control disease in some of these patients,” says study leader Leisha Emens, M.D., Ph.D. “Now we’ll need to test it further in more patients and compare it with standard therapies to establish its therapeutic value.”

The drug binds to an immune-regulating protein known as PD-L1, disrupting an interaction between it and a related protein known as PD-1, enabling an immune response against the cancer cells. The researchers determined that 37 of the 54 patients expressed the PD-L1 protein in some immune cells within their tumors, and 21 of these patients were evaluated to assess the impact of the drug. Six patients survived at least 24 weeks without disease progression, an unusual result among patients with this type of advanced and resistant cancer. Two patients saw their cancers disappear, and tumors shrunk in another two patients.

Next steps include testing the drug’s benefit in groups of patients and comparing it with standard treatments to determine its therapeutic value. A large global study to evaluate it as a possible standard therapy is underway.

“Engaging the immune system to fight breast cancer is a game changer,” says Emens. “This is especially true for triple-negative breast cancer, for which chemotherapy is currently the only standard treatment option outside of a clinical trial. Identifying a way to predict ahead of treatment which patients are more likely to respond is critically important, and there are ongoing efforts to identify biomarkers for patients who are more likely to respond to this therapy.”