A Study to Evaluate Safety, Tolerability, Pharmacokinetics and Potential Anti-tumor Effects of SSGJ-705 in Patients With Advanced or Metastatic HER2-expressing Solid Tumors

Inclusion Criteria:

* ≥18 year, male or female.
* Life expectancy ≥12 weeks (according to Investigator's judgement).
* Patients with histologically or cytologically confirmed locally advanced or metastatic non resectable HER2-expressing Solid Tumors
* Patients who have at least one measurable lesion (radiation-naïve) according to RECIST v1.1
* ECOG performance status 0-1
* Adequate organ and bone marrow function evaluated by laboratory tests
* Male patients who are surgically sterilized or who agree to use highly effective contraceptive measures during the study and for at least 6 months after administration of the last study drug dose
* Willing to provide written informed consent and willing and able to comply with all study procedures.

Exclusion Criteria:

* Receive chemotherapy, targeted therapy, or other antitumor therapy within 3 weeks prior to initial dosing
* Patients whose toxicity due to previous anticancer therapy has not been reduced to NCI CTCAE Grade 1 or lower, or any greater than NCI CTCAE 1 AE exists within 2 weeks before enrollment, not including hair loss and fatigue
* Patients requiring systemic systemic therapy with systemic hormones or other immunosuppressive agents within 4 weeks prior to initial administration and during the study period
* Previous cumulative doses of adriamycin \> 720 mg/m2, adriamycin \>360 mg/m2 or other cumulative doses of adriamycin were converted to equal doses of adriamycin \>360 mg/m2
* Patients who underwent major surgery within 4 weeks of initial dosing and have not fully recovered or who plan to undergo major surgery during the trial
* In addition to palliative radiotherapy, other anticancer treatments not specified in the protocol are planned for the duration of the trial
* Always received total pelvic radiotherapy
* Had an active or prior autoimmune or inflammatory disease within the last 3 years prior to study treatment
* Severe disease of cardiovascular and cerebrovascular diseases
* History of active tuberculosis
* A history of (non-infectious) pneumonia/interstitial pneumonia or a history of present pneumonia/interstitial pneumonia requiring steroid treatment
* Severe dyspnea or the need for supplemental oxygen therapy at rest due to complications of advanced malignancy; Newly diagnosed or symptomatic central nervous system (CNS) metastasis, spinal cord compression, or cancerous meningitis
* Persons with a history of primary immunodeficiency disease, including but not limited to HIV-positive serum
* Hepatitis B virus (HBV) and hepatitis C virus (HCV) positive subjects
* Women/men who are pregnant or breast-feeding or planning to give birth
* A history of mental or substance abuse that may affect study compliance
* Allergy to other antibody drugs or to any excipients in the study drug
* Who received live vaccine within 30 days prior to initial administration (within 72 hours for COVID-19 vaccine), or who plan to receive any live vaccine during the study
* Previous organ and allogeneic stem cell transplants (except transplants that do not require immunosuppressive therapy, such as corneal and hair transplants)
* Participated in any medical device or drug clinical study within 1 month prior to screening
* The inestigators considered that this would significantly increase the risk of administration of the investigational drug, or that it would affect efficacy evaluation or other conditions requiring exclusion