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Pembrolizumab Pregnancy and Breastfeeding Warnings

Pembrolizumab is also known as: Keytruda

Pembrolizumab Pregnancy Warnings

Animal studies have not been reported; however, based on its mechanism of actions, this drug can cause fetal harm. In animal models, the programmed death receptor-1/ligand-1 (PD-1/PD-L1) signaling pathway is important in the maintenance of pregnancy through induction of maternal immune tolerance to fetal tissue. Blockade of PD-L1 signaling has been shown in murine models to disrupt tolerance to the fetus and to result in an increase in fetal loss; therefore, potential risks of administering this drug during pregnancy include increased rates of abortion/stillbirth. No malformations related to the blockade of PD-1 signaling were reported in the offspring of these animals, but immune-mediated disorders occurred in PD-1 knockout mice. Based on its mechanism of action, fetal exposure to this drug may increase the risk of developing immune-mediated disorders or of altering the normal immune response. There are no controlled data in human pregnancy.

AU TGA pregnancy category D: Drugs which have caused, are suspected to have caused or may be expected to cause, an increased incidence of human fetal malformations or irreversible damage. These drugs may also have adverse pharmacological effects. Accompanying texts should be consulted for further details.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

This drug should not be used during pregnancy unless clearly needed and the benefit outweighs the risk to the fetus.

AU TGA pregnancy category: D
US FDA pregnancy category: Not assigned.

Risk summary: Based on its mechanism of action, this drug can cause fetal harm when administered to a pregnant woman; no human data are available informing the risk of embryofetal toxicity.

-Human immunoglobulin G4 (IgG4) is known to cross the placental barrier; because this drug is an IgG4, it may be transmitted from the mother to the developing fetus.
-If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential harm to the fetus.
-Pregnancy status of patients of childbearing potential should be verified before starting this drug.
-Patients of childbearing potential should be advised to use effective contraception during therapy and for 4 months after the last dose.

See references

Pembrolizumab Breastfeeding Warnings

Because this drug is a large protein molecule (molecular weight about 149 kilodaltons), the amount in milk is likely to be very low. It is also likely to be partially destroyed in the infant's gastrointestinal tract; absorption by the infant is probably minimal.

Until more data are available, caution is recommended, particularly while breastfeeding newborn or preterm infants.
-According to some authorities: Breastfeeding is not recommended during use of this drug and for 4 months after the last dose.
-According to some authorities: A decision should be made to discontinue breastfeeding or discontinue the drug, taking into account the importance of the drug to the mother and the benefit of breastfeeding for the child.

Excreted into human milk: Unknown
Excreted into animal milk: Unknown

-No information is available on the clinical use of this drug during breastfeeding.
-The effects in the nursing infant are unknown; there is the potential for serious adverse reactions.
-The effects of local gastrointestinal exposure and limited systemic exposure to this drug on the nursing infant are unknown.
-Maternal immunoglobulin G (IgG) is present in human milk. Because antibodies can be secreted in human milk, a risk to newborns/infants cannot be excluded.

See references

References for pregnancy information

  1. Product Information. Keytruda (pembrolizumab). Merck Sharp & Dohme LLC. 2023.
  2. Product Information. Keytruda (pembrolizumab). Merck Sharp & Dohme (Australia) Pty Ltd. 2023.
  3. Product Information. Keytruda (pembrolizumab). Merck Sharp & Dohme (UK) Ltd. 2022.

References for breastfeeding information

  1. National Library of Medicine (US), National Center for Biotechnology Information. Pembrolizumab - Drugs and Lactation Database (LactMed) 2023.
  2. Product Information. Keytruda (pembrolizumab). Merck Sharp & Dohme LLC. 2023.
  3. Product Information. Keytruda (pembrolizumab). Merck Sharp & Dohme (Australia) Pty Ltd. 2023.
  4. Product Information. Keytruda (pembrolizumab). Merck Sharp & Dohme (UK) Ltd. 2022.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.