Testing the Combination of DS-8201a and Olaparib in HER2-Expressing Cancers With Expansion in Patients With Platinum Resistant Ovarian Cancer

Inclusion Criteria: * DOSE ESCALATION PHASE * Patients must have histologically confirmed malignancy that is metastatic or unresectable and for which standard curative or palliative measures do not exist or are no longer effective * Patients must have HER2-positive or HER2-expressing tumors determined by a Clinical Laboratory Improvement Act (CLIA)-certified laboratory. Specific requirement of HER2 status is outlined below: * Dose Escalation Module 1 and Module 2: * HER2 1-3+ expression by IHC OR * HER2 amplification by next generation sequencing panel (NGS) or in situ hybridization (ISH) OR * If local testing is not feasible, patients will submit archival tissue for central HER2 testing to determine eligibility. Patients with unknown or negative HER2 testing will not be eligible * Dose Escalation Module 3: * HER2 1-2+ expression by IHC OR * HER2 amplification by next generation sequencing panel (NGS) or in situ hybridization (ISH) OR * If local testing is not feasible, patients will submit archival tissue for central HER2 testing to determine eligibility. Patients with unknown or negative HER2 testing will not be eligible * DOSE EXPANSION PHASE * Patients must have histologically confirmed platinum resistant, high grade serous ovarian carcinoma. Platinum resistant is defined as radiographic progression \< 6 months following the last dose of platinum therapy * HER2 IHC 1+ per local or central testing * There must be least one lesion suitable fo…