A Clinical Trial to Evaluate the Efficacy and Safety of TQB2102 for Injection Versus Investigator-Selected Chemotherapy in HER2 Low-Expressing Recurrent/Metastatic Breast Cancer

Inclusion Criteria:

• Subjects voluntarily enrolled in this study with good compliance;

• Age: 18-75 years old; Eastern Cooperative Oncology Group Performance Status (ECOGPS) score: 0-1;

• Pathologically confirmed locally advanced or metastatic breast cancer with low HER2expression and unresectable:

• Defined hormone receptor (HR) status.

• Imaging-confirmed disease progression (during or after completion of the most recenttreatment);

• Have at least one measurable lesion according to RECIST 1.1 criteria;

• Good major organ function.

Exclusion Criteria:

• The presence or current concurrent presence of other malignant tumors within 5 yearsprior to randomization. ;

• Unresolved toxic reactions above Common Terminology Criteria for Adverse Events (CTCAE) grade 1 due to any prior therapy;

• Major surgical treatment, incisional biopsy, or significant traumatic injury within 28 days prior to the start of the pre-randomization period;

• Prolonged unhealed wounds or fractures;

• Previous history of interstitial lung disease/pneumonia requiring steroidal drugintervention;

• The presence of moderate to severe pulmonary dysfunction/disease within 3 monthsprior to randomization;

• The presence of an arterial/deep vein thrombotic event within 6 months prior torandomization;

• The presence of a medical condition that interferes with intravenous administration,intravenous blood collection, or inability to swallow, chronic diarrhea, intestinalobstruction, or the presence of other factors that interfere with the administrationand absorption of medications;

• The presence of grade ≥2 myocardial ischemia or myocardial infarction, cardiacarrhythmias (including QT corrected (QTc) ≥450ms (men) and QTc ≥470ms (women)) andgrade ≥2 congestive heart failure (New York Heart Association (NYHA)classification); angina pectoris requiring antianginal medication; and clinicallysignificant heart valve disease;

• Active or uncontrolled ≥ CTC AE grade 2 infection present within 14 days prior torandomization;

• Cirrhosis of the liver, active hepatitis that is not well controlled;

• Renal failure requiring hemodialysis or peritoneal dialysis;

• History of immunodeficiency, including HIV-positive or other acquired or congenitalimmunodeficiency diseases, or history of organ transplantation;

• Those with routine urinalysis suggestive of urinary protein ≥++ and confirmed 24-hour urine protein quantification >1.0 g;

• Those who have used immunosuppressive or systemic hormone therapy forimmunosuppression within 2 weeks prior to randomization;

• Those with a history of psychotropic substance abuse that cannot be abstained fromor those with psychiatric disorders;

• Tumor-related symptoms and treatments:

1. Subjects who have been treated with other antineoplastic agents such aschemotherapy, radical radiotherapy, or immunotherapy within 4 weeks prior torandomization, or who are still within 5 half-lives of the drug (whicheveroccurs shortest);

2. Treatment with endocrine therapy, molecularly targeted therapy, or aproprietary Chinese medicine with an anti-tumor indication as specified in theNational Medical Products Administration (NMPA) approved drug insert within 2weeks prior to randomization;

3. Presence of carcinomatous lymphadenitis, or uncontrollable pleural effusion,ascites, and pericardial effusion of moderate volume or greater that requiresrepeated drainage to relieve clinical symptoms, or who have received drainageof plasmapheresis for therapeutic purposes within 2 weeks prior torandomization;

4. Known carcinomatous meningitis or clinically active central nervous systemmetastases;

5. Severe bone damage resulting from tumor bone metastases;

• Those who have received a control chemotherapeutic agent of the investigator'schoice during the recurrent metastatic phase or for whom a control chemotherapeuticagent of the investigator's choice is inappropriate for reasons such as intoleranceor contraindication to that agent;

• Has received prior anti-HER2 therapy;

• Who have developed hypersensitivity to humanized monoclonal antibody products;

• Those who have developed an allergy to any of the study drugs or any component orexcipient in the drugs;

• Who have participated in and used another antitumor clinical trial drug within 4weeks prior to randomization;

• Subjects who, in the judgment of the investigator, have a concomitant disease thatseriously jeopardizes the safety of the subject or interferes with the completion ofthe study, or who are deemed to have other reasons for being unsuitable forenrollment.