Guillermo de la Cueva Méndez studied Biochemistry and Molecular Biology at the Universidad Autónoma de Madrid. He obtained his PhD at the Centro de Investigaciones Biológicas, also in Madrid, studying the regulation and mode of action of toxin Kid and its antitoxin Kis, two proteins that contribute to the survival of plasmid R1, an antibiotic resistance factor, in its bacterial hosts. Afterwards he joined Professor Ron Laskey´s group at the Wellcome/Cancer Research Campaign Institute in Cambridge, United Kingdom, were he analyzed the effects of bacterial Toxin-Antitoxin pairs in animal cells. His work showed that toxin Kid induces apoptosis in human cells, and that this effect is neutralized by the antitoxin Kis. These results led him to propose the possibility of creating synthetic genetic circuits that allow modulating precisely and differentially the relative amounts of Kid and Kis in different cells of an organisms, depending on their origin, differentiation state, environmental stimuli or genetic integrity, to achieve selective killing of target cells. The biotechnological and therapeutic potential of this proposal led Guillermo to join the Hutchison/MRC Research Centre, also in Cambridge, as principal investigator in the MRC Cancer Cell Unit. Since then, research in his group has focused on the design and development of synthetic systems using Kid and Kis that kill cancer cells in a controlled, precise and autonomous manner, without harming other cells, and of parallel technologies that allow the personalization and facilitate the implementation of these systems in the clinic. His efforts to understand the biology of Toxin-Antitoxin pairs and to apply this knowledge to the development of smart biopharmaceuticals using Synthetic Biology has produced a number of patents and publications. Currently, Guillermo is Principal Investigator in the Synthetic Biology and Smart Therapeutic Systems Laboratory in BIONAND.