Since it was approved by the United States Food and Drug Administration in 2015, a modified form of the herpes virus has been used as a standard treatment for melanoma patients at Moffitt Cancer Center.

And according to data presented at this year’s American Society of Clinical Oncology annual meeting, talimogene laherparepvec, or T-VEC, could next target triple-negative breast cancer.

“For years, we’ve known that the immune system plays an important role in regulating how well a woman does on treatment,” said Dr. Hatem Soliman, lead study author and medical oncologist in the Breast Oncology Program. “So, we hypothesized that by using an oncolytic virus during treatment with chemotherapy prior to surgery, we could activate a woman’s immune response and hopefully create a favorable response that results in a higher chance of cure.”

T-VEC is a modified form of the herpes simplex 1 virus that works by killing cancer in two ways: by directly causing cancer cells to burst and by activating the immune system to attack tumors. The virus has been modified so it can’t replicate in healthy cells, and it is administered by injection directly into a tumor, sometimes under ultrasound guidance, while the patient is awake.

This trial enrolled 40 triple-negative breast cancer patients whose breast tumors were injected with the modified herpes virus while undergoing chemotherapy. The results showed the virus was able to increase the proportion of women who had no viable cancer left in their breasts or lymph nodes when the tissue was surgically removed, which predicts a higher likelihood of cure.

Researchers then followed the women to monitor longer-term outcomes. Some women have been followed for more than three years, and over 90% of the women are still alive and have had no cancer recurrence.

“The treatment was well tolerated and we do see evidence that the immune system is being activated by the use of the oncolytic virus during treatment,” said Soliman. “We think the results are really promising and encouraging and that this approach needs to be investigated in further trials to see if it can become a new standard of care for women with triple-negative breast cancer.”