New approaches to the modulation of Hedgehog signalling pathway with small molecules and bioconjugates

Antibody-Drug Conjugates (ADCs) are at the forefront of targeted therapy, designed to enhance the therapeutic index of drugs. This approach leverages the high selectivity of a monoclonal antibody (mAb) to deliver a payload, covalently bound by a linker, to a specific target, thereby reducing off-target toxicity and improving pharmacokinetics. It is now recognized that the use of highly cytotoxic payloads is not essential for ADC efficacy, a realization that has expanded interest to a new range of payloads with diverse pharmacological activities. In this context, our efforts focused on the Hedgehog (Hh) signalling pathway, whose aberrant activation is implicated in a variety of human cancers by promoting proliferation and invasion of cancer cells. While few Hh inhibitors are approved for Hh-dependent diseases, the rapid emergence of drug resistance is a significant clinical challenge. Our research group has developed a library of Hh inhibitors active against resistant receptor mutants; however, these compounds display suboptimal pharmacokinetic profiles. Therefore, the first section of this thesis details the design, synthesis, and evaluation of novel ADCs. This work centered on the development of conjugates incorporating in-house payloads, specifically Hh pathway inhibitors, ProTide-Gemcitabine systems, and ERK inhibitors, to overcome pharmacokinetic limitations and enhance therapeutic efficacy by targeted delivery. Additionally, the modulation of Hh can also play a role in promoting the repair of tissues and osteogenesis processes. In this context, agonists of the Hh pathway can find application in regenerative medicine. Our research group has developed Hh agonists that were evaluated on mesenchimal cells for their osteogenic potential. The second section of this thesis investigates a distinct project in green chemistry: the use of Sulfur Hexafluoride (SF6) as a fluorinating agent. This work, carried out in the research group of Prof. Tanja Gulder at Saarland University, was driven by the need to find applications for SF6, a potent yet non-toxic and chemically inert greenhouse gas. A novel photochemical methodology was developed and optimized to exploit SF6 as a reagent for the nucleophilic fluorination of organic compounds. A preliminary substrate scope evaluation yielded promising data and established future perspectives for the valorization of this abundant gas.