Research

The kiss of death for key apoptosis players: development of BCL-2 and BAX PROTACs

Code:

J1-2485

Range:

01. September 2020 - 31. August 2023

Range:

0,63 FTE

Leader:

Izidor Sosič

Field:

1-09 Natural sciences and Mathematics - Pharmacy

Abstract:

The intrinsic (mitochondrial) apoptosis pathway is a physiologically dominant form of cell death and is controlled by the BCL-2 family of proteins. The members of this family have opposing effects as some of them promote and others prevent mitochondria-dependent apoptosis. The cross-talk within this family, which is governed by protein-protein interactions between pro-apoptotic and anti-apoptotic proteins, dictates whether or not cells die in response to cell stress. Therefore, deregulation of apoptotic process leads to either pathological depletion or accumulation of cells, which are characteristics of many human disorders. The most studied proteins from this family are BCL-2 and BAX. The latter is a pro-apoptotic, whereas the former is a pro-survival protein. Overexpression of BCL-2 or BAX leads to either cancer, when cell death is down-regulated, or in bone marrow failure, autoimmune or neurodegenerative diseases, when apoptosis is increased.

Inhibition of BCL-2 or BAX, therefore, represents an appealing strategy for the development of apoptosis modulators as novel therapeutics. However, current inhibitor-based concept has limitations, mostly because high inhibitor concentrations must be maintained to ensure the target’s active site occupancy. Moreover, because interactions between BCL-2 family of proteins is based on protein-protein interactions, the development of high affinity inhibitors of such targets is very challenging. In the proposed project, we intend to utilize the proteolysis targeting chimera (PROTAC) strategy to achieve targeted degradation of BCL-2 or BAX, as oppose to their inhibition. From a medicinal chemistry perspective, PROTACs are heterobifunctional compounds consisting of an E3 ligase ligand, which is linked to a ligand that binds the desired target protein. Such molecules can recruit the target protein to the E3 ligase resulting in the formation of a ternary complex ‘target-PROTAC-E3 ligase’. This promotes ubiquitination of the target protein and its subsequent proteasomal degradation. PROTACs are currently recognized as the most promising modality in drug discovery, because they can very efficiently tackle protein-protein interactions and have the ability to cause degradation of overexpressed and mutated proteins.

The scientific objective of the proposed project is to develop PROTACs for the targeted degradation of two key apoptosis-regulating proteins BCL-2 and BAX as potential therapeutics or as tools to probe the dynamic interactions between BCL-2 family proteins. The ultimate project aims are:
(i) to design and synthesize new heterobifunctional molecules capable of binding and degrading BCL-2 and BAX using literature-guided knowledge, computational techniques and medicinal chemistry;
(ii) to evaluate the prepared BCL-2 PROTACs for their anticancer activity in different hematologic tumour models;
(iii) to evaluate the prepared BAX PROTACs for their cytoprotective properties;
(iv) to develop high quality lead compound(s) as BCL-2 and BAX degraders with potent anticancer and cytoprotective activity, respectively.

To achieve these goals, the rational design of PROTACs will be focused on achieving good cell-permeability, on-target activity, and ternary complex formation. The modular nature of PROTACs will enable efficient synthesis of a variety of heterobifunctional derivatives, which will subsequently be thoroughly evaluated in a number of in vitro functional cell-based assays. All tasks will be performed within a highly complementary consortium of four scientific partners demonstrating very good prospects in terms of the feasibility of the project and the potential for scientifically successful outcome. The advanced degraders of BCL-2 and BAX will undoubtedly be of paramount scientific importance as they will represent a valuable contribution to the development of both positive and negative modulators of apoptosis with great therapeutic potential.