Antibody Drug Conjugates (ADCs) are an emerging class of chemologics which have wide ranging applications from target validation to new therapeutics. Currently, only a limited palette of synthetic approaches have been employed to attach the drug payload to the parent mAb. The proposed study aims to exploit novel reactivity and selectivity patterns identified in our laboratories using a key reactive intermediate generated photochemically in order to create a modular, convergent synthesis of ADC with tuneable linker properties. The approach will be exemplified using a workhorse mAb in conjunction with a variety of linker-payload combinations to enable convergent synthesis of ADC systems. Potential additional applications of this approach also exist in screening of fragments - small efficient ligands which can target a protein of relevance to disease. Equipping a library of such fragments with the reactive warhead of the type outlined above enables these to covalently modify a protein. This binding event may be detected by mass spectrometry and the hits obtained validated by biochemical assays before being evolved into mature leads.