ARX788 in HER2-positive Metastatic Breast Cancer Patients

Inclusion Criteria:

* 18 to 75 years old (including upper and lower limits), male or female;
* Unresectable locally advanced, recurrent or metastatic BC;
* Has previously received ≤ two lines of chemotherapy (excluding hormone therapy) for recurrent or metastatic BC;
* Tissue samples determined to be HER2 positive (defined as IHC3+ or FISH+);
* Has at least one measurable target lesion as per RECIST1.1 criteria;
* Has recovered from any AE (≤ Grade 1) related to prior surgery and prior cancer treatment;
* Adequate bone marrow, liver, kidney and coagulation function;
* ECOG Performance Status Score of 0-1;
* Voluntarily sign the informed consent, have good compliance and are willing to comply with the follow-up visit.

Exclusion Criteria:

* Has known history to be allergic to any active ingredient or excipient of ARX788;
* With meningeal metastases or disseminated brain metastases or active brain metastases, who need radiation, surgery or drug therapy;
* Has pericardial effusion, pleural effusion or ascites effusion with clinical symptoms, signs or require symptomatic treatment;
* Has interstitial lung disease requiring steroid therapy, a history of drug-induced interstitial lung disease, a history of radiation pneumonitis, or any evidence indicating clinically active interstitial lung disease;
* Has any eye disease that require medical intervention such as keratitis, corneal diseases or active eye infection;
* Has cardiac insufficiency;
* Uncontrolled hypertension;
* Has evidence of severe or uncontrollable systemic diseases;
* Received live vaccines within 4 weeks before the first use of the investigational product or plans to receive live vaccines during the trial;
* Breastfeeding female, or who has childbearing potential with a positive baseline pregnancy test or who is unwilling to use effective contraception during the trial;
* Is unwilling or unable to stop wearing corneal contact lens during the trial;
* Has received any systemic anti-tumor therapy (with the exception of endocrine therapy, with an interval of at least 7 days) within 28 days (or at least 5 half-lives) before the first use of the investigational product;
* Has any mental or cognitive disorder that may restrict his/her understanding and execution of the informed consent form;
* Other conditions that the Investigator considers inappropriate for participation in this trial, such as poor compliance.