Lurbinectedin is a drug that has been approved for the treatment of small cell lung cancer (SCLC). However, there is limited information available on its effectiveness against breast cancer.
A study published in The Lancet Oncology  investigated the efficacy of lurbinectedin in patients with advanced solid tumors, including breast cancer. The study found that lurbinectedin showed promising antitumor activity in patients with advanced breast cancer. However, the sample size was small, and further studies are needed to confirm these findings.
Another study published in the Journal of Clinical Oncology  evaluated the efficacy of lurbinectedin in patients with metastatic breast cancer. The study found that lurbinectedin had limited activity as a single agent in patients with heavily pretreated metastatic breast cancer. However, the study suggested that lurbinectedin could be a potential candidate for combination therapy with other agents.
In conclusion, while there is limited information available on the effectiveness of lurbinectedin against breast cancer, some studies have suggested that it could have antitumor activity in advanced breast cancer. However, further studies are needed to confirm these findings and determine the optimal use of lurbinectedin in breast cancer treatment.
 The Lancet Oncology: https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(18)30737-X/fulltext
 Journal of Clinical Oncology: https://ascopubs.org/doi/10.1200/JCO.2018.78.6558