Lurbinectedin is a chemotherapy drug used to treat small cell lung cancer (SCLC). Immunotherapy, such as pembrolizumab, is another type of treatment that can be used in combination with chemotherapy to improve the patient's outcome. According to the sources provided, there is no specific recommended dosage of lurbinectedin when used in combination with immunotherapy.

The first source, Drug Patent Watch [1], provides information about the patent status of lurbinectedin and its various formulations. However, it does not provide any information about the recommended dosage of the drug when used in combination with immunotherapy.

The second source, a study published in the Journal of Clinical Oncology [2], evaluated the efficacy and safety of lurbinectedin and pembrolizumab in patients with SCLC. The study found that the combination of lurbinectedin and pembrolizumab had promising preliminary activity in relapsed SCLC patients. However, the study did not mention any specific recommended dosage of lurbinectedin when used in combination with pembrolizumab.

The third source, an article published on Cancer Network [3], highlights the promising preliminary activity of lurbinectedin and pembrolizumab in relapsed SCLC patients. However, the article does not provide any information about the recommended dosage of lurbinectedin when used in combination with pembrolizumab.

In conclusion, based on the sources provided, there is no specific recommended dosage of lurbinectedin when used in combination with immunotherapy. It is important for patients to consult with their healthcare provider to determine the appropriate dosage and treatment plan for their specific condition.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LURBINECTEDIN
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8165873/
[3] https://www.cancernetwork.com/view/antonio-calles-md-highlights-promising-preliminary-activity-of-lurbinectedin-and-pembrolizumab-in-relapsed-sclc