FDA Approves First Immunotherapeutic for Breast Cancer

Last Friday, March 8, 2019, marked another milestone in immuno-oncology: The U.S. Food and Drug Administration (FDA) announced the first approval of an immunotherapeutic for use in the treatment of breast cancer.

Shown here in a mouse model of breast cancer are cytotoxic T cells attacking a breast tumor. Image courtesy of the National Cancer Institute.

The immunotherapeutic in question is atezolizumab (Tecentriq). It was approved for use in combination with a cytotoxic chemotherapeutic called nab-paclitaxel (Abraxane) for treating adults who have unresectable locally advanced or metastatic triple-negative breast cancer that expresses the protein PD-L1.

Triple-negative breast cancer accounts for about 12 percent of breast cancer cases diagnosed in the United States each year, which translates into about 32,000 new cases of the disease in 2019. Breast cancers are classed as triple-negative if they test negative for hormone receptors and the protein HER2. Until now, cytotoxic chemotherapeutics are the only systemic treatment options for patients with triple-negative breast cancers. Even with treatment, researchers estimate that the median overall survival for patients with triple-negative breast cancer is less than 18 months.

Atezolizumab is an immunotherapeutic that works by releasing a brake called PD-1 on natural cancer-fighting immune cells called T cells. It prevents a protein called PD-L1 from engaging the PD-1 brake, freeing T cells to destroy cancer cells. Triple-negative breast cancer is the third type of cancer for which atezolizumab has been approved; it was approved for treating certain patients with bladder cancer in May 2016 and for treating certain patients with non–small cell lung cancer in October 2016.

The new approval for atezolizumab was based on results from the phase III IMpassion130 randomized clinical trial. Among patients whose triple-negative breast cancer tested positive for PD-L1, adding atezolizumab to nab-paclitaxel significantly improved median progression-free survival, according to the FDA statement; median progression-free survival was 7.4 months for those receiving the combination treatment versus 4.8 months for those receiving placebo and nab-paclitaxel.

More detailed results of this trial were published recently in the New England Journal of Medicine. These results showed that 58.9 percent of patients with PD-L1–positive triple-negative breast cancer who received atezolizumab and nab-paclitaxel had partial or complete tumor shrinkage, compared with 42.6 percent of those who received placebo and nab-paclitaxel. The interim overall survival data also showed that patients who received atezolizumab and nab-paclitaxel did better than those receiving placebo and nab-paclitaxel (25.0 months versus 15.5 months), but the researchers need more time to be able to determine the final survival data.

Two additional expansions in the use of anticancer agents

The approval of atezolizumab was the third time in 2019 that the FDA has expanded the use of previously approved anticancer agents to new types of cancer. On January 14, use of the antiangiogenic therapeutic cabozantinib (Cabometyx) was expanded to include certain patients who have the most common type of liver cancer, hepatocellular carcinoma. On February 22, use of Lonsurf, which is a combination of drugs that are formulated together in a single pill, was expanded to include certain patients with gastric and gastroesophageal junction adenocarcinoma. These agents had previously been approved for treating certain patients with thyroid and kidney cancer, and colorectal cancer, respectively.

Many ongoing clinical trials are investigating whether anticancer agents already approved by the FDA and in clinical use for treating certain types of cancer can benefit patients with other types of cancer. It is likely, therefore, that there will be more expansions in the use of anticancer agents in the near future, and we look forward to keeping you up to date with these developments on Cancer Research Catalyst.