A Study of BL0175 Injection in Postmenopausal Female Adults With HR-positive, Locally Advanced or Metastatic Cancer

Inclusion Criteria:

1. Volunteer to participate in the study, be able to understand the requirements of aclinical study, and willingness to sign a written informed consent form.

2. Age ≥ 18 years.

3. HR-positive, HER2-negative (characterized by the absence of HER2 expression and thepresence of ER and/or PR expression) locally advanced or metastatic breast cancer (histological or cytological proven diagnosis) in postmenopausal women with diseaseprogression during or following endocrine therapy, or HR-positive, locally advancedor metastatic ovarian cancer or endometrial cancer in postmenopausal women thatprogressed during or following prior standard of care therapy.

4. Patients with at least one measurable or evaluable lesion: At least one lesion (measurable and/or non-measurable) that can be accurately assessed by CT/MRI/plainx-ray at baseline and follow up visit. Note: Measurable lesions cannot be selected from the following sites in principle:having received prior radiotherapy or having received other local therapy. If atarget lesion at a site that has received prior radiotherapy or other local therapyis the only optional lesion, the progression of the lesion shall be confirmed by theinvestigator.

5. Eastern Cooperative Oncology Group (ECOG) performance status score 0 or 1 atscreening.

6. Life expectancy period ≥ 12 weeks.

Exclusion Criteria:

1. Patients with symptomatic central nervous system (CNS) metastases or carcinomatousmeningitis. Note: patients with treated CNS metastases may participate in this study if thepatient has completed radiotherapy or surgery for CNS metastases ≥ 4 weeks prior to ≥ 2 weeks afterradiotherapy or surgery treatment (no new neurologic deficits from brain metastasison screening clinical examination, no new findings on CNS imaging, andcorticosteroids were not required within 2 weeks prior to enrollment).

2. Patients who have a history of another primary malignancy (with the exception ofparticipants with cured basal cell carcinoma of the skin, squamous cell carcinoma ofthe skin, or carcinoma in situ of uterine cervix). A patient who has had no evidenceof disease from another primary cancer for 3 or more years is allowed to participatein the study.

3. Patients whose pericardial effusion, pleural effusion or ascites remainuncontrollable after intervention.

4. Patients with a history of allogeneic transplantation of organs, bone marrow or stemcell.

5. A history of allergic or adverse response(s) to fulvestrant, or prone to allergicreactions (such as: prone to angioedema, urticaria, asthma, rash, etc.).

6. Patients who have impaired cardiac function or clinically significant cardiacdiseases, including any of the following:

• New York Heart Association class III-IV for cardiac insufficiency or leftventricular ejection fraction < 50% (if the LVEF data is available).

• Patients with poorly controlled arrhythmia: QTc interval > 480 ms calculated byFridericia's formula, or congenital syndrome of prolonged QT interval.

• Any of the following within 6 months prior to the enrollment: myocardialinfarction, severe or unstable angina, congestive heart failure,cerebrovascular accident (including transient ischemic attack), symptomaticpulmonary embolism or other clinically significant thromboembolic disease, orcoronary artery bypass graft.

• Clinically symptomatic bradycardia as assessed by the investigator.

• Patients with other clinically significant cardiovascular disease who wereassessed as unsuitable for this study by the investigator.

7. Patients who have a known diagnosis of Human Immunodeficiency Virus (HIV) infectionor HIV antibody test positive in screening.

8. Patients with active hepatitis C or chronic hepatitis B at screening ("activehepatitis" defined as HCV RNA level ≥ 200 IU/mL for hepatitis C or HBV DNA level ≥ 2000 IU/mL for hepatitis B at screening). In addition, eligible hepatitis B orhepatitis C patients must agree to antiviral treatment according to the treatmentguidelines.

9. Active infections requiring antibiotic intravenous therapy within 1 weeks prior toenrollment.

10. Moderate or severe hepatic impairment (Child-Pugh class B or C).

11. Patients who have not sufficient baseline organ function and whose laboratory datameet the following criteria at enrollment [No transfusion of blood products (including platelets or red blood cells) or use of colony-stimulating factors (including granulocyte colony-stimulating factor, granulocyte macrophagecolony-stimulating factor, or recombinant erythropoietin) within 14 days prior toscreening]:

• Absolute Neutrophil Count (ANC) < 1.5×109/L.

• Total bilirubin > 1.5×ULN.

• Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) > 3×ULNwithout liver metastases or primary liver cancer. AST or ALT > 5×ULN if thepatient has documented liver metastases.

• Hemoglobin < 90 g/L.

• Platelets < 100×109 /L.

• Creatinine clearance < 30 mL/min.

12. Prior to first dose of the investigational product, received an antitumor drug orinvestigational drug at the following time intervals:

• Chemotherapy, targeted small molecule therapy or radiotherapy (exceptpalliative radiotherapy and the radiotherapy area do not include the proposedtarget lesion) ≤ 14 days. The wash-out period for TKI drugs is more than 5half-lives could enroll for their shorter half-life.

• Immunotherapy or cell therapy (i.e. chimeric antigen receptor T cell therapy) ≤ 28 days; Other cell therapy must be discussed with the investigators todetermine eligibility.

• Monoclonal antibodies ≤ 28 days for anticancer therapy.

• Anti-tumor Chinese medicine which approved by the agency ≤ 14 days.

• Immunosuppressive therapy for any reason ≤ 7 days.

• Fulvestrant ≤ 250 days (5 half-lives).

• All other investigational drugs or devices ≤ 28 days or 5 half-lives before thefirst dosing administration (whichever is shorter).

13. Bleeding constitution (e.g., diffuse intravascular coagulation [DIC], clottingfactor deficiency), or long-term anticoagulant therapy (excluding antiplatelettherapy and low doses of warfarin and low molecular weight heparin).

14. Severe vascular embolism events requiring medical or surgical intervention.

15. Active autoimmune diseases that require systemic treatment (i.e. use ofimmunomodulators, corticosteroids, or immunosuppressive drugs). Note: Participants with hyperthyroidism/hypothyroidism could participate. Note:Hormone replacement therapy and symptomatic therapy (e.g., levothyroxine, insulin,or physiologic corticosteroid replacement therapy for adrenal or pituitaryinsufficiency, etc.) are not considered a form of systemic therapy and arepermitted.

16. Those who have received systemic corticosteroids within 4 weeks prior toadministration of BL0175 or active control (low doses of corticosteroids areexcluded, such as ≤ 20 mg prednisone daily or equivalent).

17. Those who underwent major surgery within 4 weeks before enrollment, or plan toundergo major surgery during the study.

18. Has not recovered from the toxic effects of prior treatment (including priorimmunotherapy) and/or complications of surgical intervention to CTCAE v5.0 ≤ 1. Note: Participants with stable chronic AE (≤ grade 2) that are not expected toresolve on their own (e.g., peripheral neuropathy and alopecia) are allowed.

19. Those who are determined disqualified to join clinical studies by investigator forother causes.