HS-20089 is an investigational antibody-drug conjugate (ADC) composed of a humanized IgG1 anti-B7-H4 monoclonal antibody conjugated to the topoisomerase I inhibitor payload via a protease-cleavable linker, with an average drug-to-antibody ratio of about 6. This is a phase 2, open-label, multi-center study to evaluate the efficacy, safety, pharmacokinetics (PK) and immunogenicity of HS-20089 as monotherapy in patients with recurrent or metastatic ovarian cancer and endometrial cancer.