Dose Escalation Study of ZG006 in Participants With Advanced Small Cell Lung Cancer or Neuroendocrine Carcinoma, Followed by Dose Expansion Study in Participants With Neuroendocrine Carcinoma.

This study tests ZG006, a new targeted treatment for people with advanced small cell lung cancer or neuroendocrine carcinoma — rare but aggressive cancers that often come back after initial treatment. The study first checks the safest dose and then expands to test effectiveness. **You may be eligible if...** - You are between 18 and 75 years old - You have advanced small cell lung cancer or neuroendocrine carcinoma - You are in reasonably good physical condition (able to carry out normal activities with minimal assistance) - Your life expectancy is at least 3 months **You may NOT be eligible if...** - Your cancer has spread to the brain and is untreated or unstable - You have serious heart, liver, or kidney problems - You have had major surgery or another investigational drug treatment recently - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.