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

This study tests MRG003, a new targeted drug called an antibody-drug conjugate, in patients with squamous cell carcinoma of the head and neck that has come back or spread and cannot be surgically removed. The drug is designed to deliver chemotherapy directly to cancer cells while sparing healthy tissue. **You may be eligible if...** - You have confirmed squamous cell cancer of the head and neck that has returned or spread - You have already tried platinum-based chemotherapy and/or an immunotherapy drug (anti-PD-1) that didn't work - You are in generally good health (ECOG score 0 or 1) - You have at least one measurable tumor on scans - You are willing to use effective contraception during and for 6 months after treatment **You may NOT be eligible if...** - You have had 4 or more prior systemic cancer treatments - You have significant nerve damage (grade 2 or higher peripheral neuropathy) - You have previously been treated with a similar type of targeted drug (MMAE/MMAF antibody-drug conjugate) - You have a very low BMI (17 or under) - You have active brain metastases, HIV, active hepatitis B or C, or an uncontrolled autoimmune disease - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.