Cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors: Risk of severe lung inflammation


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Palbociclib, ribociclib and abemaciclib are cyclin-dependent kinase 4/6 (CDK 4/6) inhibitors used in combination with hormone therapies to treat advanced breast cancers.  In Malaysia, there are currently three (3) registered products containing palbociclib and one (1) containing ribociclib.


Background of Safety Issue

The National Pharmaceutical Regulatory Agency (NPRA) received information from the United States Food and Drug Administration (US FDA) on the risk of rare but severe inflammation of the lungs with use of palbociclib, ribociclib and abemaciclib.1 Although rare, cases of interstitial lung disease (ILD) and pneumonitis which were serious or fatal have been identified in clinical trials and postmarketing reports related to CDK 4/6 inhibitor use. Across clinical trials of the three CDK 4/6 inhibitors, 1-3% of patients had ILD or pneumonitis of any grade, and less than 1% had fatal outcomes.


The Malaysian product registration holders are in the process of updating the product package inserts with warnings on the risk of ILD and pneumonitis. When used as prescribed, the overall benefits of CDK 4/6 inhibitors remain greater than the risks.


Adverse Drug Reaction Reports

NPRA has received 53 ADR reports with 66 adverse events suspected to be related to palbociclib, and 29 ADR reports with 36 adverse events suspected to be related to ribociclib. To date, no ILD and pneumonitis-related adverse event has been reported to NPRA.2


Advice for Healthcare Professionals



  1. United States Food and Drug Administration (2019). Drug Safety Communication: FDA warns about rare but severe lung inflammation with Ibrance, Kisqali, and Verzenio for breast cancer. Retrieved from
  2. The Malaysian Adverse Drug Reaction database, NPRA [Accessed: 11 November 2019]



This publication is aimed at health professionals. The information is meant to provide updates on medication safety issues, and not as a substitute for clinical judgement. While reasonable care has been taken to verify the accuracy of the information at the time of publication, the NPRA shall not be held liable for any loss whatsoever arising from the use of or reliance on this publication.