Alpelisib/iNOS Inhibitor/Nab-paclitaxel in Patients With HER2 Negative Metaplastic Breast Cancer (MpBC)

This study tests a three-drug combination — alpelisib (a targeted therapy), an iNOS inhibitor (an experimental drug), and nab-paclitaxel (a chemotherapy) — in people with a rare and aggressive form of breast cancer called metaplastic breast cancer (MpBC) or triple-negative breast cancer (TNBC) that has spread or cannot be surgically removed. **You may be eligible if...** - You are 18 or older - You have been diagnosed with HER2-negative metaplastic breast cancer or triple-negative breast cancer with specific features (squamous, sarcomatoid, or similar elements) - Your cancer has spread or is locally advanced and cannot be operated on - You are in good health (ECOG 0–1) - Your blood counts, liver, and kidney function meet the study requirements - You may have had prior treatment, including immunotherapy **You may NOT be eligible if...** - Your cancer is HER2-positive - You do not have measurable disease on imaging - You have serious organ dysfunction or uncontrolled medical conditions - You are pregnant or breastfeeding - You have had certain prior treatments that conflict with the study drugs Talk to your doctor to see if this trial is right for you.