Testing the Safety and Efficacy of the Combination of Two Anti-cancer Drugs, ZEN003694 and Abemaciclib, for Adult and Pediatric Patients (12-17 Years) With Metastatic or Unresectable NUT Carcinoma, Breast Cancer and Other Solid Tumors

This study is testing two cancer drugs — ZEN003694 and abemaciclib — used together for adults and teenagers (12–17) with advanced cancers including NUT carcinoma (a rare, aggressive cancer), breast cancer, and other solid tumors that are no longer responding to standard treatment. **You may be eligible if...** - You are 12 years or older (adolescents 12–17 must weigh at least 40 kg) - You have a confirmed cancer that is metastatic (spread) or cannot be surgically removed, and standard treatments are no longer working - You can swallow oral medications - Your organ function (blood, liver, kidneys, heart) meets study requirements - You are in reasonably good health (ECOG 0–2 for adults; Lansky score 50% or higher for those under 16) **You may NOT be eligible if...** - You have received chemotherapy, immunotherapy, or radiotherapy within the past 2 weeks - You have had major surgery within the past 3 weeks - You are taking strong CYP3A4 inhibitors or inducers (certain medications) or proton pump inhibitors - You have uncontrolled heart disease or a recent heart attack - You are pregnant or breastfeeding - You have impaired bowel absorption (e.g., Crohn's disease, total stomach removal) Talk to your doctor to see if this trial is right for you.