Bacterial enzymes and antibiotic resistance

1) Development of inhibitors directed against cytosolic 5'-nucleotidase II (cN-II)

This enzyme belongs to the HAD superfamily and is in charge of regulating the intracellular nucleotide pools; cN-II catalyzes the following reaction (see below) using preferentially purines (I, A and G) nucleotide 5'-monophosphate as substrates and converts them into their corresponding nucleoside and inorganic phosphate.

The major drawback is that cN-II is found overexpressed or hyperactive in hematological malignancies leading to shorter survival of patients.

Our objectives during the last five years were to develop new inhibitors by different approaches:

- Fragment-based Drug Design (FBDD)

- Substrate analogs (β-hydroxy-phosphonate nucleotides)

- Virtual screening


FBDD setup: experimental screening of small fragment library and then link together several hit fragments by combining molecular modeling and docking approaches (selection of non-overlapping fragments) and chemical synthesis (for linking all together).
 

Marton Z. et al. “Identification of non-competitive inhibitors of cytosolic 5'-nucleotidase II using a fragment-based approach.” J. Med Chem. (2015) 58, 9680-96. Pubmed

2) Development of new and selective CD73 inhibitors to restore the anticancer immune response

CD73 or ecto-5'-nucleotidase is the only extracellular member of this family, attached to cell surface through a GPI anchor. CD73 has become a major therapeutic target in oncology as this enzyme is overexpressed on tumor and certain immune cells (Teff) and catalyzes the reaction of AMP hydrolysis in adenosine (ADO). The main pitfall is that ADO is a potent immunosuppressor leading to cancer cells development in absence of efficient immune defenses.

Adapted from Knapp et al, Cell (2012)

An original approach was investigated to find out new and selective CD73 inhibitors, this includes molecular dynamics simulations to reproduce the large collective motions occurring during active site formation of the enzyme and therefore constituting dynamical motions required for the enzymatic function.

The strategy, here was to block the functional dynamics by screening on various conformations of the enzyme. After the selection of an unidentified target binding site located at the dimerization interface, several chemical libraries were in silico screened.

a) Selection of a druggable and allosteric cavity from molecular dynamics simulations
 

b) In vitro evaluation of CD73 inhibition (kinetics inhibition assays) and lead optimization by using chemoinformatics approaches

Our final objective is to recover the anticancer immune system by blocking CD73 activity and to bring up our drug candidates to the preclinical developmental stage.

     
   

   

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IRIM
Institut de Recherche en Infectiologie de Montpellier
UMR 9004 - CNRS / UM
1919 route de Mende - 34293 Montpellier cedex 5
FRANCE

 

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