Study of [212Pb]Pb-DOTAM-MAM279 ([212Pb]Pb-MP0712) in Patients With Small Cell Lung Cancer and Other DLL3 Expressing Solid Tumors

This trial is testing a new radioactive drug called [212Pb]Pb-MP0712 for people with small cell lung cancer or other hard-to-treat neuroendocrine cancers that have a protein called DLL3 on their cancer cells. **You may be eligible if...** - You are 18 or older - You have confirmed small cell lung cancer or another neuroendocrine cancer (such as certain stomach, cervical, bladder, or other cancers) that has progressed after prior treatment - Your cancer tests positive for DLL3 (a protein target for this drug) - You have at least one measurable tumor on scan - Your blood counts, kidney, and liver function are within acceptable ranges - Brain metastases are allowed if they are clinically stable **You may NOT be eligible if...** - You have an uncontrolled ongoing illness - You have significant side effects from prior treatment that haven't resolved - You have active serious heart disease - You have interstitial lung disease or pneumonitis - You have had another cancer in the past 2 years (some exceptions apply) Talk to your doctor to see if this trial is right for you.