Some Triple Negative Breast Cancers Show Response To New Drug Conjugate

Aditya Bardia MBBS, MPH Attending Physician, Massachusetts General Hospital Cancer Center, Assistant Professor, Harvard Medical School Boston, MA 02114

Dr. Bardia Interview with:
Aditya Bardia MD, MPH
Attending Physician, Massachusetts General Hospital Cancer Center,
Assistant Professor, Harvard Medical School,
Boston, MA 02114 

Medical Research: What is the background for this study? What are the main findings?

Dr. Bardia: Triple negative breast cancer (TNBC) represents breast cancers that are negative for estrogen and progesterone receptors, as well as human epidermal growth factor receptor 2, or HER2. This type of breast cancer comprises about 15-20% of all invasive breast cancers and is more prevalent in young and African-American women.Triple negative breast cancer characteristically has a high recurrence rate and is perhaps the most difficult type of breast cancer to treat successfully with current cytotoxic agents. Trop-2 is a protein present in limited amounts in normal human tissues but widely found in many human cancers. It is expressed in more than 80 percent of Triple negative breast cancer, making it an attractive therapeutic target.

Sacituzumab govitecan (IMMU-132) is a first-in-class ADC developed by Immunomedics, Inc. by linking moderately-toxic drug, SN-38, to an antibody that binds to the Trop-2 target found in many solid cancers. We conducted a clinical trial with this drug for patients with advanced tumors, including patients with TNBC who either had failed their previous treatments for Triple negative breast cancer or their cancer had returned.

We have found that even though patients who participated in this trial had very advanced stages of the disease, approximately 30% of these patients responded with 30% or more tumor shrinkage. The response rate to standard agents is usually 10 to 20 percent, while the response rate with IMMU-132 was approximately 30 percent. If you include patients with stable disease, the clinical disease control rate, which is complete response [CR] + partial response [PR] + stable disease, was about 75 percent.

Medical Research: What should clinicians and patients take away from your report?

Dr. Bardia: Patients treated with other agents used to treat heavily pretreated metastatic Triple negative breast cancer  have a median progression-free survival [PFS] of three to four months in general, while in the phase II clinical trial, patients on IMMU-132 had an interim median PFS of seven months. The agent was well tolerated by patients, and toxicity was much lower than one would anticipate with chemotherapy agents such as irinotecan. Grade 3 to 4 toxicities included neutropenia (in 15 percent of the patients), anemia (6 percent), diarrhea (6 percent), and febrile neutropenia (4 percent), and no patient discontinued treatment because of toxicity issues.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Bardia: Limitations of the study include lack of a placebo arm and small sample size. Additional research is needed to develop this drug further and develop strategies to improve outcomes for women with metastatic breast cancer.


Phase II clinical trial Results presented at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics, held Nov. 5–9 2015

Safety and tumor responses of the anti-Trop-2 antibody drug conjugate, sacituzumab govitecan (IMMU-132), in refractory, metastatic, triple-negative breast cancer (TNBC): An ongoing Phase II trial

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Aditya Bardia MD, MPH (2015). Some Triple Negative Breast Cancers Show Response To New Drug Conjugate 

Last Updated on November 10, 2015 by Marie Benz MD FAAD