Background Glioblastoma is one of the most aggressive brain tumors for which to date there is no valuable treatment. The tumor's infiltrative nature and evasion of the immune system make surgical resection extremely challenging and often followed by a recurrence of the disease, on top of conferring resilience to chemo and radiotherapy. Photodynamic therapies (PDT) have emerged as promising strategies to reach beyond the surgical incision area, while preserving low systemic toxicity. PDT usually exploits indeed photosensitizers such as 5-ALA which are specifically uptaken by cancer cells and induce apoptosis upon reactive oxygen species production. Notwithstanding the potential of state-of-the-art PDT, the therapy is hampered by the low penetration of visible radiation in the cerebral tissue. Hypothesis Here we propose a therapy based on i) a novel mechanism for inducing cell death, ii) a targeted PDT, and iii) the ability to rely on bioluminescence instead of an external light-source. The strategy consists primarily in the administration of a photoswitchable conjugated compound (BV-1) that spontaneously partitions into the cell membrane and undergoes a charge transfer upon light stimulation as photosensitizer for the proposed PDT. BV-1 has in fact been proven to induce an oxidation of membrane phospholipids that promotes the progressive and irreversible formation of pores and eventual cell death. Aims Once in contact with cancer cells, the molecule will be photostimulated by endogenous light generated by a luciferase/GFP variant chimera expressed in cancer cells under the control of the promoter for Nestin, a glioblastoma marker, thus avoiding the need of an external or intra-operative illumination source. Experimental Design. To render the photosensitizer orthogonally specific for glioblastoma cells that produce a strongly acidic tumormicroenvironment (TME), a ratiometric GFP variant (coGFP) characterized by acidic pH-dependent emission to excite BV-1 and fused with luciferase will be exposed at the extracellular terminus of the single transmembrane domain of the PDGF receptor. Expected Results Such glioblastoma-expressed chemogenetic nanosensor can be activated "on-demand" by the administration of the proper luciferase substrate and its light emission, matching the peak absorption of BV-1, will be amplified by coGFP in the acidic TME. Thus, together with the targeting of nesting-expressing cells, the ONE therapy aims at the reduction of off-targets effects with the synergistic action of both genetic targeting and bio-chemical sensing. Impact On Cancer The ONE project envisions the engineering and in vitro testing of the chimera and its constructs on rodent GBM primary cell cultures and primary neuronal cultures and finally the application of the whole ONE therapy in an in vivo rodent model of GBM chronic treatment. The research outcome of this project will pave the way towards a novel strategy for the cure of GBM and will support the advances in GBM understanding and modelling investing in young researchers' potential and interdisciplinarity between chemistry, molecular biology and medicine.