Study of ERW316 as a Single Agent or in Combination With Endocrine Therapy in Patients With HR+/HER2- Breast Cancer and Other Advanced Solid Tumors

Inclusion Criteria: * Age ≥ 18 years old * Eastern Cooperative Oncology Group (ECOG) performance status of ≤ 1. * Patients with one of the following histologically or cytologically confirmed advanced cancers: Phase I (patients with one of the following cancers, for whom no standard therapy is available or appropriate in the judgment of the investigator): * HR+/HER2- advanced breast cancer (aBC) with disease progression on or following at least one line of hormone-based therapy in combination with a CDK4/6i and at least one additional line of systemic therapy for metastatic disease. * Locally advanced or metastatic cancer with CCNE1- amplification. For dose expansion only: no more than 5 prior lines of therapy (ovarian cancer) or 3 prior lines of therapy (gastric or esophageal adenocarcinoma). * Metastatic castration-resistant prostate adenocarcinoma (mCRPC), with no documented neuroendocrine component, castrate level of testosterone, disease progression on or after at least one line of androgen receptor pathway inhibitor therapy (ARPI) and at least one line of taxane-based chemotherapy, and no more than 3 total prior lines of systemic therapy for metastatic disease. Phase II: • HR+/HER2- aBC with disease progression on or after an endocrine therapy in combination with a CDK4/6 inhibitor for advanced disease, with no more than 2 total lines of endocrine therapy and no prior cytotoxic chemotherapy or antibody-drug conjugate therapy for advanced disease. Phase I and Phase …