Lurbinectedin is a type of chemotherapy drug that is used to treat certain types of cancer. According to the sources provided, Lurbinectedin is primarily used to treat two types of cancer: small cell lung cancer (SCLC) and metastatic breast cancer (MBC).

Small cell lung cancer is a type of lung cancer that is characterized by the rapid growth of small cells in the lung tissue. Lurbinectedin has been shown to be effective in treating SCLC, both as a first-line treatment and as a second-line treatment for patients who have already received chemotherapy [2]. Lurbinectedin works by inhibiting the activity of a protein called RNA polymerase II, which is involved in the transcription of DNA into RNA. By inhibiting this protein, Lurbinectedin can prevent the growth and proliferation of cancer cells [3].

Metastatic breast cancer is a type of breast cancer that has spread to other parts of the body, such as the lungs, liver, or bones. Lurbinectedin has been approved by the FDA for the treatment of MBC in patients who have received at least two prior therapies for their disease [1]. Lurbinectedin has been shown to be effective in shrinking tumors and improving progression-free survival in patients with MBC [3].

In summary, Lurbinectedin is primarily used to treat small cell lung cancer and metastatic breast cancer. It works by inhibiting the activity of RNA polymerase II, which is involved in the transcription of DNA into RNA. Lurbinectedin has been shown to be effective in treating these types of cancer, both as a first-line treatment and as a second-line treatment for patients who have already received chemotherapy.

Sources:
[1] https://www.zepzelca.com/
[2] https://www.cancer.gov/about-cancer/treatment/drugs/lurbinectedin
[3] https://www.drugpatentwatch.com/p/tradename/LURBINECTEDIN