Design and synthesis of RAD51/RAD52 inhibitors to achieve synthetic lethality in combination with PARP inhibitors in pancreatic cancer

My main PhD research project focused on the discovery of potential disruptors of the RAD51-BRCA2 protein-protein interaction, with the goal of triggering synthetic lethality in BRCA2-proficient pancreatic cancer, in combination with PARPi. SL has been clinically validated as a therapeutic approach for cancer due to the efficacy of olaparib in BRCA2-deficient patients. In this scenario, we suggested to trigger a “fully small-molecule-induced SL” by combining a RAD51-BRCA2 PPI disruptor with PARPi to target pancreatic cancer cells. The interaction between RAD51 and BRCA2 is crucial in DNA damage repair by homologous recombination and is mediated by two key “hotspots” on RAD51 surface, identified as Zone I and Zone II, which have been previously confirmed as ideal sites to design small molecule inhibitors. Initially, a virtual screening campaign on Zone II was exploited as hit identification strategy, followed by chemical modifications that led to the creation of a library of analogues. Derivative 14 proved to be a promising lead compound inhibiting RAD51-BRCA2 interaction, reducing HR and inducing cell death in combination with olaparib in BRCA2-proficient pancreatic cancer cell lines, fully reproducing the paradigm of SL. The second part of the thesis concerned the experience I carried out during the six-month secondment at EPFL in Lausanne in Professor Heinis' Laboratory. The project focused on the synthesis of dipeptides aimed at inhibiting the monomer-monomer interaction of RAD52. RAD52 inhibition proved to induce SL in cancer cells with defective DNA repair-related proteins, such as BRCA1/2 proteins. After a VS on an identified RAD52 monomer-monomer interaction pocket, the best 10 dipeptides had been synthesized. Preliminary biophysical assays have been carried out to evaluate their efficacy in binding RAD52. The final goal will be triggering a three-pathways SL by a PARPi, a RAD51-BRCA2 PPI disruptor and a potential RAD52i in BRCA2-proficient pancreatic cancer cells.