SHR-A1811 for HER2-positive Breast Cancer With Suboptimal Neoadjuvant Response

Patients will receive SHR-A1811, until completion or treatment discontinuation due to progression, toxicity, or withdrawal. The primary endpoint is tpCR (ypT0/is ypN0). Secondary endpoints include bpCR, RCB, EFS, and safety. The study will recruit 30 eligible patients from multiple centers in China.

• SHR-A1811 (Drug): Drug: SHR-A1811 4.8mg/kg

Primary outcomes

• tpCR [immediately after surgery]: It is defined as the absence of residual invasive carcinoma in the resected breast cancer specimens stained with hematoxylin and eosin, and no cancer metastasis in all ipsilateral lymph node samples, after completion of neoadjuvant therapy and surgery.

Secondary outcomes

• Breast Pathological Complete Response [immediately after surgery]: It is defined as the absence of residual invasive carcinoma in the primary breast lesion after neoadjuvant therapy, with the permission of residual ductal carcinoma in situ within the primary breast lesion.
• event free survival [until the end of the study]
• residual cancer burden [immediately after surgery]

Sex: Female, ages: 18 Years to 70 Years

Inclusion Criteria:

* 1.Female patients with newly diagnosed breast cancer aged 18 to 70 years old;
* 2.Early or locally advanced HER2-positive invasive breast cancer;
* 3.Known hormone receptor status;
* 4.ECOG score of 0-1;
* 5.Patients who were determined by the researchers to have poor therapeutic effect after 4 cycles of neoadjuvant therapy;
* 6.Organ function levels must meet the following requirements:
* 7.Women of childbearing age must undergo a serum pregnancy test within 7 days before enrollment, with a negative result, and be willing to use a medically approved highly effective contraceptive method during the study and within 3 months after the last administration of the study drug.
* 8.The subjects voluntarily participate in this study and sign the informed consent form.

Exclusion Criteria:

* 1\. Patients with metastatic or bilateral breast cancer, or inflammatory breast cancer
* 2\. Patients with grade 3 or higher thrombocytopenia during previous treatment, or grade 3 or higher nausea and vomiting despite primary prevention
* 3\. History of other malignant tumors (except cured carcinoma in situ of the cervix, basal cell carcinoma, etc.) and related treatment history
* 4\. Patients who received major non-breast cancer surgery within 4 weeks before enrollment and have not recovered (except biopsy and PICC)
* 5\. Autoimmune diseases (except special cases such as hypothyroidism and stable type 1 diabetes)
* 6\. Interstitial lung disease, non-infectious pneumonia, uncontrolled systemic diseases
* 7\. History of or planned administration of live attenuated vaccines within 28 days
* 8\. HIV infection, active hepatitis (hepatitis B, hepatitis C, etc.), autoimmune hepatitis
* 9\. Severe infection within 4 weeks, CTCAE grade ≥ 2 active infection within 2 weeks (except neoplastic fever), or evidence of active tuberculosis within 1 year
* 10\. History of allogeneic bone marrow or solid organ transplantation
* 11\. Peripheral neuropathy of grade ≥ 2
* 12\. Severe heart diseases
* 13\. Receipt of systemic immunostimulant therapy within 4 weeks
* 14\. Receipt of systemic immunosuppressant therapy within 2 weeks (except local or physiological dose of hormones)
* 15\. Allergy to study drugs/excipients, or history of severe allergic reaction to other monoclonal antibodies
* 16\. Pregnant or lactating women; fertile women with positive pregnancy test or unwilling to take effective contraception throughout the trial
* 17\. History of neurological/psychiatric disorders , or history of substance abuse, alcoholism, or drug addiction
* 18\. Other circumstances deemed unsuitable for enrollment by the researcher