Key Inclusion Criteria

• 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

Key Exclusion Criteria:

• Any investigational or approved anti-cancer therapies administered within 28 days/ before the first dose of IMP1734

• Have received prior PARP1 selective inhibitors

• Mean resting QTcF > 470 ms or QTcF < 340 ms

• Active or untreated central nervous system (CNS) metastases and/or carcinomatous meningitis.

• Infections

  - An active hepatitis B/C infection

• Any known predisposition to bleeding

• Unable to swallow oral medications OR have malabsorption syndrome or any other uncontrolled gastrointestinal condition that might impair the bioavailability