ASP-1929 Photoimmunotherapy (PIT) Study in Recurrent Head/Neck Cancer for Patients Who Have Failed at Least Two Lines of Therapy

The study will have an Experimental Arm and a Control Arm. Experimental Arm: Patients may receive repeated ASP-1929 PIT interventions for up to a maximum of 8 cycles within a period of up to 12 months after randomization until the patient has complete remission, progressive disease that is no longer amendable to study treatment, patient experiences intolerable side effects, patient discontinues study treatment, or chooses to withdraw. Repeat ASP-1929 treatment cycles will be administered no less than 4 weeks from the previous ASP-1929 infusion. Control Arm: Patients may be treated with physician's choice standard of care until the patient has progressive disease, patient experiences intolerable side effects, discontinues study treatment, or chooses to withdraw.