The goal of this clinical trial is to learn if drug regimen pegylated liposomal doxorubicin and adebrelimab with or without mirabegron works to treat relapsed ovarian cancer in adults. It will also learn about the safety of drug regimen pegylated liposomal doxorubicin and adebrelimab with or without mirabegron. The main questions it aims to answer are:

Does drug pegylated liposomal doxorubicin and adebrelimab with or without mirabegron reduce tumor volume? What medical problems do participants have when taking drug pegylated liposomal doxorubicin and adebrelimab with or without mirabegron?

Researchers will compare drug regimen pegylated liposomal doxorubicin and adebrelimab with mirabegron to a drug regimen pegylated liposomal doxorubicin and adebrelimab without mirabegron to see which drug regimen works better to treat relapsed ovarian cancer.

Participants will:

Take drug pegylated liposomal doxorubicin and adebrelimab every 21 days with or without everyday mirabegron Visit the clinic once every 2 months for checkups and tests Keep a diary of their symptoms

Inclusion Criteria:

• Has provided documented informed consent for the study.
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1.
• Has histologically confirmed epithelial ovarian, fallopian tube, or primary peritoneal carcinoma.
• Has received a front line platinum-based regimen (administered via either intravenous or intraperitoneal route) per local standard of care or treatment guideline following the primary or interval debulking surgery with documented disease recurrence (note: Maintenance treatment following the front line treatment is permitted and counted together as part of the front line treatment).
• Has a platinum-free interval (PFI) of < 12 months if the last regimen received is a platinum-based, or a treatment-free interval (TFI) of < 12 months if the last regimen received is a non-platinum-based.
• Has measurable disease at baseline based on Response Evaluation Criteria in Solid Tumors (RECIST) 1.1.
• Has a life expectancy of ≥12 weeks.
• Has provided a tumor tissue sample either collected from prior cytoreductive surgery or fresh newly obtained tumor tissue at screening.
• Has adequate organ function.
• Has not recovered from AEs to ≤ Grade 1 or prior treatment level due to a previously administered agent.

Exclusion Criteria:

• Has nonepithelial cancers, borderline tumors, mucinous, seromucinous that is predominantly mucinous, malignant Brenner's tumor and undifferentiated carcinoma.
• Has received prior therapy with an anti-programmed cell death (PD)-1, anti-PD-L1, anti-PD-L2 agent or with an agent directed to another co-inhibitory T-cell receptor (e.g. cytotoxic T-lymphocyte-associated antigen-4 [CTLA-4], tumor necrosis factor receptors OX-40 or CD137) or has participated in prior adebrelimab studies.
• Has received prior systemic anticancer therapy including radiation therapy or maintenance therapy within 4 weeks before randomization.
• Has severe hypersensitivity (≥Grade 3) or uncontrolled hypertension to pegylated liposomal doxorubicin, adebrelimab, mirabegron and any of their excipients.
• Has undergone major surgery within 3 weeks before randomization or has complications/sequelae that have not yet recovered.
• Has a known additional malignancy that progressed or required active treatment within the last 5 years.
• Is pregnant or breastfeeding.
• Has a history of allogenic tissue/solid organ transplant.
• Has a history of thrombotic disorders, hemorrhage, hemoptysis, or active gastrointestinal bleeding within 6 months before randomization.
• Has a history of active autoimmune disease.
• Has an active infection requiring systemic therapy.
• Has a history of human immunodeficiency virus (HIV) infection.
• Has a history of Hepatitis B or C virus infection.
• Has a history or current evidence of any condition, therapy, laboratory abnormality, or other circumstance that might confound the results of the study.
• Has a known psychiatric or substance abuse disorder that would interfere with the participant's ability to cooperate with the requirements of the study.