Lurbinectedin is a drug used to treat certain types of cancer, including small cell lung cancer. There is limited information on the safety of lurbinectedin for infants exposed to the drug through breast milk. The drug is not recommended for use in pregnant women or nursing mothers due to potential risks to the developing fetus or infant. According to the drug label [2], it is unknown whether lurbinectedin is excreted in human milk, and there is a potential for serious adverse reactions in nursing infants. Therefore, women who are breastfeeding should not breastfeed during treatment with lurbinectedin and for at least 2 weeks after the last dose. Additionally, women who are considering breastfeeding should discuss the potential risks and benefits with their healthcare provider before starting treatment with lurbinectedin. It is important to follow the healthcare provider's instructions carefully and to report any side effects or concerns about the safety of the drug to the healthcare provider.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LURBINECTEDIN
[2] https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/213702s000lbl.pdf
[3] https://pp.jazzpharma.com/pi/zepzelca.ca.PM-en.pdf