FDA Added Three Breast Cancer Drugs to Safety Watchlist

The agency is evaluating potential links between colitis and the medications Ibrance, Kisqali, and Verzenio.

Updated on Oct. 5, 2026 in Cancer

Isometric editorial illustration of a laboratory beaker containing a geometric molecular structure, symbolizing a pharmaceutical safety investigation. — The FDA has added breast cancer treatments Ibrance, Kisqali, and Verzenio to its safety watchlist to investigate potential links to colitis. AI Illustration. Upload story photo >

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The FDA has included the breast cancer treatments Ibrance, Kisqali, and Verzenio on its latest quarterly list of potential safety signals. Officials are currently investigating whether these medications carry a risk of colitis.

Why it matters

This evaluation is part of a routine regulatory process to determine if the drugs require updated safety labeling. The FDA has not concluded that the treatments cause colitis, and patients have not been advised to stop taking them.

Verzenio labeling reports that 81% to 90% of patients experience diarrhea, with 8% to 20% of cases classified as severe. These medications are used to treat hormone receptor-positive, HER2-negative breast cancer, a diagnosis affecting 140,230 women in the U.S.

The players

FDA

The Food and Drug Administration is the federal agency responsible for protecting public health by ensuring the safety and efficacy of human drugs.

The details

The FDA reviews potential safety issues using its Adverse Event Monitoring System to identify patterns in side effect reports. While diarrhea is already listed as a side effect for all three medications, colitis is not currently included on their labels.

The FDA issued a prior warning regarding lung inflammation in 2019.
The quarterly report covers safety data from April 2026 through June 2026.
The safety report was considered current as of September 30, 2026.

Health Landscape

This investigative step follows a pattern established by the agency when it previously assessed lung inflammation risks for the same class of drugs in 2019. It reflects the ongoing commitment to monitoring adverse events as medical usage of these targeted therapies continues to evolve.

Patients currently prescribed these medications should not stop treatment or alter their dosage without consulting their physician. Because diarrhea is a known side effect, patients should continue to report any new or worsening gastrointestinal symptoms to their healthcare provider.

The takeaway

The FDA's watchlist is an early-stage monitoring tool and does not represent a confirmed medical finding or a recall of these life-saving drugs. Patients are encouraged to maintain open communication with their oncologists regarding any changes in their daily health status.