Researchers at the National Cancer Institute (NCI) developed novel groups of cyanine (Cy) based antibody-drug conjugate (ADC) chemical linkers that undergo photolytic cleavage upon irradiation with near-IR light. By using the fluorescent properties of the Cy linker to monitor localization of the ADC, and subsequent near-IR irradiation of cancerous tissue, drug release could be confined to the tumor microenvironment.