FDA Evaluated Breast Cancer Drugs for Colitis Link
The agency is investigating potential colitis risks for three breast cancer therapies commonly used by patients.
Updated on Oct. 5, 2026 in Cancer
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The FDA has added three widely used breast cancer medications—Ibrance, Kisqali, and Verzenio—to its quarterly safety signal report. Federal regulators are now evaluating whether these drugs, which treat hormone receptor-positive, HER2-negative breast cancer, may be linked to cases of colitis.
Why it matters
The agency is investigating this potential side effect to determine if regulatory updates are needed for the drug labels. This review is part of an ongoing safety evaluation, as colitis is not currently listed as a known risk for these specific medications.
The FDA identified a pattern of reports through its Adverse Event Monitoring System during the period of April through June 2026. While the agency is now assessing these findings, it has not yet determined if the drugs are responsible for the reported cases.
The players
FDA
The federal agency responsible for overseeing the safety and efficacy of medical products in the United States.
The details
These drugs, known as CDK4/6 inhibitors, are used to treat hormone receptor-positive, HER2-negative breast cancer. While diarrhea is already a recognized side effect for all three treatments, the FDA is specifically examining whether some experiences might indicate underlying colitis. The agency uses its monitoring system to flag patterns in patient reports that warrant a deeper investigation into potential regulatory actions.
Timeline
2019: The FDA previously issued warnings regarding lung inflammation for these therapies.
April 2026 - June 2026: Period covered by the current FDA quarterly safety report.
September 30, 2026: The date the FDA report was considered current.
Health Landscape
This safety review marks an evolution in the oversight of CDK4/6 inhibitors as their clinical use remains standard for metastatic breast cancer. It reflects the ongoing scientific scrutiny of treatment-related side effects following the 2019 FDA safety warning for lung inflammation.
The FDA has not advised patients to stop taking these medications, and you should continue your current treatment plan as prescribed. If you experience persistent or severe diarrhea, have a conversation with your physician to discuss your symptoms and any concerns.
The takeaway
The FDA is currently investigating a potential link between colitis and three common breast cancer medications. Patients should monitor for new or worsening gastrointestinal symptoms and report them to their oncologist during regularly scheduled visits.
Further reading
For more information on the latest developments in oncology treatments, visit our Cancer section.
Source note: This article includes information reported by Medical Daily.
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