Searching of Antagonist Ligands Switching of the Angiogenesis by interacting with the VEGFR-1 d2 domain. – SALSA

This project aims at designing new vascular endothelial growth factor (VEGF) antagonist raised again the VEGF receptors (VEGF-Rs). More precisely we will target the receptor 1 that is implicated in tumoral angiogenesis i.e the formation of new blood vessels that are widely up-regulated in cancer and metastasis. To this end we will use macrocyclic peptides or non peptidic heterocyclic compounds that are able to disrupt the interaction between the VEGF and its receptor. It is important to quote that these compounds are true antagonist and are not related to the tyrosine kinase inhibition associated to the receptor. The structure and nature of these antagonists, whose first prototype have already been synthesized and studied by the projects partners 1 and 2, will be optimized not only in order to increase their affinity and selectivity to their targets, but also to improve their in vivo properties i.e. their bioavailability.
This project is therefore organized in three main axes:
- chemistry
- structural biology
- pharmacology

The main tasks of each axes could be summarize as follow:
The chemistry part includes two partners. Partner 1 will pursue the development of already described antagonist and a particular attention will be paid to their optimization by merging in a single entity the peptide antagonist with the heterocyclic antagonist. This task will certainly induce a gain of affinity by interfering with two distal sites of the VEGF-R1. Partner 2 will develop the synthesis of the natural occurring peptide laxaphycin B issuing from marine specie. More particularly the laxaphycin B scaffold will be modified in order to introduce a pseudoproline which will stabilize its biological conformation.

In order to accurately develop and optimize the two series of antagonists we will rely on structural information. Indeed partner 3 has already expressed, purified and crystallized the VEGFR-1 domain 2 which entail the binding epitope to VEGF. Therefore, we have nowadays engaged co-crystallization assays of the antagonists with this receptor domain. Furthermore, in order to increase the selectivity of the antagonist a comparable structural study will be performed on VEGFR-2. In this context, a comparative study of VEGFR 1 and 2 co-crystallized with fragment 8-109 of VEGF will be undertaken to define which structural elements may allow selective binding to the receptor 1. This work is currently under progress and we have succeeded in expressing and purifying the receptor 2 and its ligand (VEGF 8-109). It is important to quote that the structure of this last receptor was never solved.

The last part of this project concern the biological evaluation of the synthesize antagonist. Partner 4 will be in charge of this task. The compounds will be firstly characterized for their effects on tumoral cell lines. Depending of this evaluation test the compounds will be investigated in vivo on nude mice xeno-transplanted with human angiogenesis dependent solid tumor.

This project represent thus a multidisciplinary approach spanning from synthetic chemistry to structural biology and pharmacology that will lead to the design of new tools for deciphering the VEGF-R1 role in angiogenesis. Finally, this new antagonist would constitute an innovative therapeutic strategy that would complement the existing ones.