Sapu003 in Advanced mTOR-sensitive Solid Tumors

The study will include two cohorts: * Cohort A: Patients with HR+/HER2-negative breast cancer who will receive Sapu003 in combination with exemestane. * Cohort B: Patients with RCC, NETs, TSC-associated tumors, or HCC who will receive Sapu003 without exemestane. The dose levels planned for this study are 5 mg/m², 7.5 mg/m², and 10 mg/m² administered as weekly 30-minute IV infusions, with each treatment cycle lasting 4 weeks (28 days). The primary purpose of this study is to determine the maximum tolerated dose (MTD) of weekly intravenous Sapu003. Secondary objectives include characterizing the pharmacokinetic profile of Sapu003, evaluating its safety and tolerability, and assessing preliminary antitumor activity.