This single-arm, multi-center clinical trial aimed to evaluate the safety, tolerability, DLT, recommended dose (RD), preliminary efficacy, and pharmacokinetics (PK) characteristics of lurbinectedin, a selective inhibitor of oncogenic transcription, in Chinese patients with advanced solid tumors, including relapsed SCLC. Patients with advanced solid tumors were recruited in the dose-escalation stage and received lurbinectedin in a 3 + 3 design (two cohorts: 2.5 mg/m2 and 3.2 mg/m2, IV, q3wk). The RD was expanded in the following dose-expansion stage, including relapsed SCLC patients after first-line platinum-based chemotherapy. The primary endpoints included safety profile, tolerability, DLT, RD, and preliminary efficacy profile, while the secondary endpoints included PK characteristics. In the dose-escalation stage, ten patients were included, while one patient had DLT in the 3.2 mg/m2 cohort, which was also the RD for the dose-expansion stage. At cutoff (May 31, 2022), 22 SCLC patients were treated in the ongoing dose-expansion stage, and the median follow-up was 8.1 months (range 3.0-11.7). The most common grade >= 3 treatment-related adverse events (TRAEs) included neutropenia (77.3%), leukopenia (63.6%), thrombocytopenia (40.9%), anemia (18.2%), and ALT increased (18.2%). The most common severe adverse events (SAEs) included neutropenia (27.3%), leukopenia (22.7%), thrombocytopenia (18.2%), and vomiting (9.1%). No treatment-related deaths occurred. The Independent Review Committee (IRC)-assessed ORR was 45.5% (95% CI 26.9-65.3). Lurbinectedin at the RD (3.2 mg/m2) showed manageable safety and acceptable tolerability in Chinese patients with advanced solid tumors, and demonstrates promising efficacy in Chinese patients with SCLC as second-line therapy.Trial registration: This study was registered with ClinicalTrials.gov NCT04638491, 20/11/2020.