• Breast cancer; must have received at least one prior chemotherapy in neoadjuvant/adjuvant/metastatic setting, must have received hormonal therapy if HR+,

• HGSOC or high grade endometrioid EOC, fallopian tube or primary peritoneal cancer; must have received at least one prior platinum-based chemotherapy for advanced disease

• mCRPC with ongoing ADT, must have received NHA and up to 1 prior line of taxane chemotherapy

• Age ≥ 18 years at the time of informed consent

• Eastern Cooperative Oncology Group (ECOG) performance status ≤1

• Adequate organ function

• Life expectancy ≥ 12 weeks

• Should have evaluable disease as defined by RECIST1.1 and/or CA125 or PSA

• Female subjects of childbearing potential and male subjects must agree to use an effective method of contraception from study entry up to 6 months after the last dose of IMP1734

• deleterious or suspected deleterious germline or somatic mutations of select HRR genes

• up to 1 prior line of PARP inhibitor containing treatment