A Study of BL-B01D1, SI-B003 and BL-B01D1+SI-B003 in Patients With Extensive Stage Small Cell Lung Cancer

This study is testing new treatment options for people with extensive-stage small cell lung cancer (ES-SCLC) — a fast-growing type of lung cancer that has spread beyond the chest. The trial tests three separate approaches: a drug called BL-B01D1 alone, a drug called SI-B003 alone, and the combination of both. Different groups are enrolled based on how many prior treatments they have received. **You may be eligible if:** - You are 18–75 years old in good physical health (ECOG 0–1) - You have been diagnosed with extensive-stage small cell lung cancer confirmed by biopsy - Depending on which group applies to you: you have failed 3 or more prior treatment lines, OR failed or could not tolerate standard first-line therapy, OR you have not received any prior systemic therapy for this cancer - You have at least one measurable tumor on imaging - Your expected survival is at least 3 months **You may NOT be eligible if:** - You do not have the right number of prior treatment lines for the cohort you are applying for - You have serious uncontrolled medical conditions or inadequate organ function - You are unable to provide tumor tissue samples (in some cases this can be waived) Talk to your doctor to see if this trial is right for you.