This project addresses the problem that several rounds of varied immunotherapy treatments over an extended period are often needed to find one that is effective in treating tumors in a particular patient. The proposed solution is an Immunotherapy Response Indication System (IRIS) to monitor treatment response directly in a patient’s own tumor while testing sub therapeutic doses of multiple candidate drugs to determine the best therapeutic option rapidly and safely. The intratumoral monitoring capabilities of the proposed IRIS implantable biosensor and wireless magnetic reader are key to enabling this pharmacotyping strategy. The work plan in this Phase II contract focuses on preclinical safety and performance testing that is foundational to future clinical translation. This pharmacotyping capability enabled by IRIS will allow clinicians to optimize treatment decisions in the early stages of treatment, and during the later stages of treatment in cases of acquired resistance. Our initial clinical product development goal is to track real-time responses within the tumor to immunotherapy in glioblastomas and melanoma brain metastases. Enabling faster selection of patient-specific treatments could increase cancer survival rates in the future