Targeting radionuclides to tumors expressing extracellular Hsp90 using rationally designed peptide probes

Radiopharmaceuticals are a powerful class of drugs that requires new molecular probes to expand the array of targets it can be used for. Peptides are a perfect fit for the role of a molecular probe due to their high target specificity and favorable pharmacodynamics. Hsp90a was identified as a biomarker of cancer with ectopic cellular localization. Targeting the pool of extracellular Hsp90 provides a promising strategy for cancer diagnosis and treatment, but to date there is no available radiotracer approved for human use beyond clinical trials. The goal of this project is to develop a cell-impermeable peptide probe against Hsp90a and investigate its potential as a radiopharmaceutical vector for diagnostics and therapy of cancer using two distinct approaches. The first approach is based on the targeted aggregation technology Pept-InTM developed by the SWITCH laboratory, while the second relies on the computational design using the force field mutation engine FoldX, directed at the two distinct binding interfaces of Hsp90. The binding of the Pet-Ins probes will be examined in vitro in two different breast cancer lines known to secrete Hsp90a, followed by affinity studies with recombinant protein using Monolith instrument that relies on the Microscale Thermophoresis technology. FoldX-generated peptides will be screened using a pooled library with FRET signal as a readout of protein-peptide interactions. Peptides with high binding specificity and affinity to Hsp90 will be radiolabeled and their pharmacokinetics examined in vivo using mouse tumour models.