The U.S. Food and Drug Administration has warned that breast cancer drugs manufactured by Pfizer Inc., Novartis AG and Eli Lilly and Co. may cause rare but severe inflammation of the lungs in certain patients.
Noted in a new warning from the regulator was Pfizer's Ibrance, Novartis' Kisqali and Lilly's Verzenio. These drugs belong to a class of medicines called cyclin-dependent kinase, or CDK, inhibitors that target the CDK 4 and 6 proteins.
The U.S. regulator has approved new label information to be printed on packaging for drugs in the CDK inhibitor class warning of the lung risks.
Patients taking the drugs are asked to immediately notify their doctors if they experience discomfort with breathing and shortness of breath at rest or slow activity, as these side effects may lead to a rare but potentially fatal condition.
Patients should not stop taking these medicines because the benefit of CDK inhibitors is greater than the risks, the FDA said in the safety announcement. Additionally, the agency has asked healthcare professionals to look out for symptoms such as hypoxia, cough and shortness of breath in patients taking this type of drug, and discontinue treatment in patients with interstitial lung disease or lung inflammation.
The FDA reviewed cases from clinical trials for the therapies, discovering reports of serious illnesses and fatalities that showed inflammation of the lungs.
Ibrance was first approved to treat women with breast cancer in 2015 and the FDA authorized it as a treatment for men with a subtype of the disease in April. Verzenio is approved for the treatment of certain breast cancer patients in more than 50 countries worldwide including the U.S. Kisqali gained approval in 2017 for the treatment of postmenopausal women with hormone receptor-positive, human epidermal growth factor receptor-2 negative advanced or metastatic breast cancer.

