Design, synthesis, and preliminary biological evaluation of novel small molecules modulating the HuR RNA-binding protein and other therapeutically relevant targets in immuno-oncology.

The International Agency for Research on Cancer (IARC) estimates that 25% of men and 17% of women worldwide develop cancer during their lifetime, making it the second leading cause of death in Europe and America. Many research efforts have been directed against cancer, both from pharmaceutical companies and governmental/private organizations, and several treatments are now available. Most aim to either directly kill/block the growth of cancer cells, or to the deprivation of signals needed for their survival (i.e., surgery, radiation therapy, chemotherapy). More recent, and possibly successful approaches stimulate the body's defences either by targeting pro-oncogenic transcription factors (TFs), or by eliciting immune responses against cancer cells (i.e., cancer immunotherapy). Both TF-targeted and immuno-stimulating agents are used as stand-alone or in combination, depending on the tumor microenvironment (TME), on genetic and epigenetic modifications of cancer cells, on the patient’s health and on many other factors. Clinical portraits related to oncology are extremely heterogeneous, as even the same cancer cell lines in different patients can be molecularly and genetically different. Thus, a universally effective therapy does not exist, and a complete, deep understanding of cancer development and growth is still difficult. Research is crucial for the development of more effective anticancer agents having different mechanisms of action, to be used in combination to improve the outcome of clinical treatments. Thus, during my Ph.D. thesis, I focused my research onto multiple cancer treatment approaches. The first part (Chapter 1) deals with the inhibition of the Human antigen R (HuR) protein, a member of the embryonic lethal abnormal vision (ELAV) family of RNA-binding proteins (RBPs). As HuR over-expression is correlated to advanced cancer development, my aim was to find novel small organic molecules to disrupt the mRNA-HuR interaction and act as cytotoxic agents. The second part of my Ph.D. thesis deals with two biological pathways related to cancer immunotherapy. PD-1 (Programmed Death receptor 1) – a type I cell−surface receptor expressed by T lymphocytes, B cells and macrophages – negatively regulates the activity of T cells upon binding to its ligand PD-L1 (Programmed Death-Ligand 1) on the surface of cancer cells. Recent studies demonstrated a key role for HuR in controlling the PD-L1 protein levels, promoting its stability and half-life through binding to discrete regions of the transcript 3’ untranslated region (UTR). Thus, I focused my attention on the design and synthesis of novel small organic molecules as putative inhibitors of the PD-1/PD-L1 axis, which will be extensively described in Chapter 2. Lastly, in Chapter 3 I will cover the direct activation of the STimulator of INterferon Genes (STING) pathway through small molecule binding with the adaptor protein for cancer immunotherapy, which is a complementary target to synergize with PD-1/PD-L1 and HuR. In fact, the STING pathway is known as a relevant player in re-activation of the native immune system, which is crucial to increase the therapeutic applicability of adaptive immunity-targeted cancer immunotherapy by both reducing its side effects and increasing its efficacy.