A single dose of MEDI0641 led to long-term tumor regression in patient-derived xenograft (PDX) models of HNSCC, even after tumors were already established. MEDI0641 effectively targets and reduces the fraction of CSCs, which express high levels of 5T4, in both HNSCC cell lines in vitro and in vivo. The gene discussed is TPBG; the disease is neoplasm.