A Study to Evaluate the Efficacy and Safety of MRG003 in Patients With Recurrent or Metastatic Squamous Cell Carcinoma of Head and Neck

Inclusion Criteria:

• Willing to sign the ICF and follow the requirements specified in the protocol.

• Expected survival time≥3 months.

• Patients with histologically confirmed unresectable recurrent or metastatic squamouscell carcinoma of head and neck.

• Failed prior platinum and/or anti-PD-1 treatment (Part A); failed or intolerant toat least one prior line of standard therapy (platinum-based regimen) (Part B)

• Patients must have at least one measurable lesion according to the ResponseEvaluation Criteria in Solid Tumors (RECIST v1.1).

• ECOG performance score 0 or 1.

• Organ functions and coagulation function must meet the basic requirements.

• Serum or urine pregnancy test negative within 7 days before the first dose ofinvestigational drug.

• Patients with childbearing potential must use effective contraception during thetreatment and for 6 months after the last dose of treatment.

Exclusion Criteria:

• History of 4 or more systemic anti-tumor therapies for the recurrent or metastaticsquamous cell carcinoma of head and neck.

• ≥Grade 2 peripheral neuropathy

• Prior anti-tumor therapy with MMAE/MMAF ADCs

• BMI≤17

• Expected surgery or any other form of systemic or local anti-tumor therapy.

• History of systemic chemotherapy within 3 weeks before the first administration ofthe investigational drug, targeted small molecule therapy within 2 weeks or 5half-life periods before the first administration (whichever is shorter), antitumorbiological therapy or immunotherapy within 4 weeks before the first administration,or major surgery.

• Known active CNS metastasis and/or cancerous meningitis.

• Residual toxicity reactions caused by previous anti-tumor treatment or abnormalvalues of laboratory tests higher than grade 1 (CTCAE v5.0). Prior Grade 3 to 4immune-related AE (irAE) or ≥Grade 2 heart-related irAE.

• Uncontrolled or poorly controlled heart disease.

• History of pulmonary embolism or deep vein thrombosis within 3 months before thefirst administration of the investigational drug.

• Known history of malignancy.

• History of severe dermatosis.

• Uncontrolled or poorly controlled hypertension.

• Patients with a history of active bleeding, coagulopathy, or receiving coumarinanticoagulation therapy.

• Known allergic reaction to any ingredients or excipients of investigational drugs.

• Known active hepatitis B or C.

• Complicated with severe, uncontrolled infection or known human immunodeficiencyvirus (HIV) infection, or diagnosed as acquired immunodeficiency syndrome (AIDS); oruncontrolled autoimmune disease; or history of allogeneic tissue/organtransplantation, stem cell or bone marrow transplantation, or solid organtransplantation.

• Active bacterial, viral, fungal, rickettsia, or parasitic infections that requiresystemic anti-infective treatment.

• Vaccination of live virus vaccine within 30 days before the first administration ofthe study drug. Inactivated seasonal influenza vaccine or approved COVID-19 vaccineis allowed.

• History of previous or concurrent interstitial pneumonia, radiation pneumonitis,severe chronic obstructive pulmonary disease, severe pulmonary dysfunction,symptomatic bronchospasm, etc.

• Patients receiving immunology-based treatment for any reason.

• Uncontrolled pleural effusion, pericardial effusion or recurrent ascites.

• Potent CYP3A4 inhibitors or inducers are in use and cannot be discontinued.

• Women who are lactating or pregnant.

• Other conditions that in the clinical judgement of the investigator make the patientnot suitable for participation in this study.