FDA OKs New Drug for Triple-Negative Breast Cancer

Nick Mulcahy

April 22, 2020

The US Food and Drug Administration (FDA) granted accelerated approval to sacituzumab govitecan (Trodelvy, Immunomedics) for the treatment of metastatic triple-negative breast cancer (TNBC).

Eligible patients must have received at least two prior therapies.

TNBC is so-called because it lacks the three cellular targets present in more common forms of breast cancer. It is usually treated with chemotherapy.

Sacituzumab govitecan offers a new approach — and it has a target.

Given intravenously, the new drug is an antibody–drug conjugate in which SN-38, an active metabolite of the chemotherapy drug irinotecan (multiple brands), is coupled to a monoclonal antibody that targets an antigen that has high expression in TNBC and induces cancer cell growth.

"Metastatic triple-negative breast cancer is an aggressive form of breast cancer with limited treatment options," observed Richard Pazdur, MD, director of the FDA's Oncology Center of Excellence and acting director of the Office of Oncologic Diseases in the FDA's Center for Drug Evaluation and Research in a press statement. "There is intense interest in finding new medications" for this patient population, he added.

The new approval is based on safety and efficacy results from a phase 1/2 clinical trial of 108 patients (median age, 56 years) who had received at least two prior treatments for metastatic disease.

The overall response rate was 33% (n = 36), including three complete responses. Median duration of response was 7.7 months. Of responders, 55.6% maintained their response for ≥ 6 months and 16.7% for ≥ 12 months.

Median progression-free survival was 5.5 months, and median overall survival was 13.0 months.

The study data were published last year in the New England Journal of Medicine.

"It's not every day that we see this sort of clinical activity in this aggressive subtype of breast cancer," said senior study author Kevin Kalinsky, MD, in an interview at that time. He is a medical oncologist at New York–Presbyterian Hospital and Columbia University Medical Center in New York City.

The most common side effects of the new therapy were nausea, neutropenia, diarrhea, fatigue, anemia, vomiting, alopecia, constipation, decreased appetite, rash, and abdominal pain.

No peripheral neuropathy of grade 3 or higher was reported.

In the study, patients received sacituzumab govitecan intravenously (10 mg/kg body weight) on days 1 and 8 of each 21-day cycle until disease progression or unacceptable toxicity.

The 108 participants received a mean 18.7 doses of sacituzumab govitecan, or 9.6 cycles. The median duration of exposure was 5.1 months.

Three patients discontinued treatment because of adverse events, and two patients discontinued because of drug-related events.

The prescribing information includes a boxed warning regarding the risks of severe neutropenia and severe diarrhea. Blood cell counts should be monitored during treatment and granulocyte-colony stimulating factor (G-CSF) therapy should be considered. Anti-infective treatment should be initiated in the event of febrile neutropenia. Patients with reduced uridine diphosphate-glucuronosyltransferase 1A1 (UGT1A1) activity are at increased risk for neutropenia following initiation of treatment.

The new drug can also cause hypersensitivity reactions including severe anaphylactic reactions.

Women who are pregnant should not take sacituzumab govitecan.

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