Design and synthesis of novel heterocyclic compounds as receptor or protein/protein interaction modulators

Combination therapy has been the standard of care in several diseases, such as diabetes and immunoinflammatory disorders, since it is a rationale strategy to decrease drug resistance and to increase response and tolerability. The benefits of multi-target action are well established in cancer, because the process of oncogenesis is known to be multigenic, multifactorial and characterized by the misregulation of more than one protein.111 The multi-target strategy may be of great importance against glioblastoma multiforme (GBM), a particularly aggressive form of brain cancer. Despite massive research efforts, the surgical resection is the only cure for GBM, and the currently approved anti-GBM agents, such as Temozolamide, Bevacizumab, or Cilengitide offer a limited improvement in progression free survival. Evasion of cell death is a hallmark of cancers and a major cause of treatment failure; in this respect, apoptosis inducers that act through the mitochondria death pathway have been emerging as promising drugs in a large number of tumors, particularly in GBM. Activation of the cancer cell death machinery through the mitochondrial membrane permeabilization has been obtained so far also by the use of drugs targeting the mitochondrial translocator protein (TSPO). Ligands such as PK11195, Ro5-4864 and diazepam have demonstrated antitumor effects in vitro and in vivo, both as single agents or combined with the chemotherapeutic agents etoposide or ifosfamide.Importantly, in a variety of systems, PK11195 can reduce or abrogate the antiapoptotic effect of Bcl-2-family proteins, suggesting that TSPO could be exploited to bypass Bcl-2-imposed chemoresistance. In this respect, we have recently demonstrated that newly synthesized selective TSPO ligands are able to trigger apoptosis also in human GBM cell lines and in rat C6 glioma cells, modulating the opening of the mitochondrial permeability transition pore (MPTP), of which TSPO is an important constitutive protein. Another important role in mitochondria-mediated cell apoptosis involves the tumor suppression protein p53. Indeed, in addition to target gene regulation, p53 can directly induce permeabilization of the outer mitochondrial membrane, by forming complexes with the protective Bcl2-family proteins, resulting in cytochrome c release.120 The deregulation of this pro-apoptotic protein is widely described in literature, and the reactivation of its endogenous function represents an important anti-cancer therapeutic strategy, at least for those tumors with a no mutant p53. P53 is negatively regulated by the murine double minute 2 (MDM2), and thus inhibitors of p53-MDM2 interaction currently represent another viable approach in GBM therapy. Thus, while agents targeting either the TSPO or p53-MDM2 interaction have been already investigated and provided to have some survival benefit in cancers, molecules targeting both proteins are not known so far. With the perspective that co-targeting TSPO and p53-MDM2 with one molecule could maximize the anti-tumor efficacy, dual binders were rationally designed, synthesized and biologically characterized in human GBM cells.