design of potential antiMAlarial M1/M17 AMinopeptIdase Agents – MAMMAMIA
Novel antimalarial drug targets, New therapeutics
Malaria is a major cause of morbidity and mortality across the globe and there is an urgent need to develop new drugs against new targets. Trageting the aminopeptidases PfAM1 & PfAM17 essential for the parasite at various stages of its development, offers new opportunities in antimalarial therapeutics.
Hope for new therapies against Plasmodium falciparum
The situation is worrying as in most parts of the world, Plasmodium resistance rendered ineffective older low cost (average $ 0.37) antimalarial drugs (quinine and chloroquine),To fight against the emergence of resistance, the World Health Organism now recommends the use of drugs combination therapies based on artemisinin as first-line treatment. These artemisinin derivatives are highly effective, but remain very expensive (average $ 4.96) for the poorest populations. Furthermore, the neurotoxicity linked to their use as well as the emergence of clinical cases of resistance (confirmed in 2009 at the border between Cambodia and Thailand) strongly encourage the scientific community to discover viable alternatives to existing therapeutic options.<br />Due to this imperative need, the discovery of both new therapeutic targets and non-toxic, low cost molecules are required to expand the arsenal against malaria. <br />Recently two aminopeptidases, PfA-M1 and PfA-M17, involved in the last step of the hemoglobin degradation by Plasmodium, have emerged as potential candidates for the design of a new class of antimalarial drugs. They are expressed at different stages of the life cycle of Plasmodium and this opportunity to kill the parasite at different stages of its life cycle makes these two aminopeptidases more interesting to study and inactivate. Inhibition of these aminopeptidases is the main goal in this project.<br />
We plan to synthesize potent inhibitors of the recombinant PfAM1& PfAM17 based on the original benzosuberone sacffold, which will be selective, active in vivo and non-toxic to humans, To be more ambitious we intend to design low cost molecules (effort in synthesic methods) which can be orally administered to fight against malaria.
This is a «Hit to Lead« discovery phase project in which compounds that selectively inhibit monometallic and bimetallic enzymes, and if possible, a mixed mono-and bimetallic inhibitor are already under investagation. Their activities and specificities have also to be quickly evaluated as well as their pharmacological properties .
This project brings together two partners, each one with unique knowledge in their respective fields: the design of selective inhibitors of enzymes of the M1 and M17 family ( enzymology and organic synthesis) , the discovery and characterization of these new targets ( molecular biology ) as well as the in vitro and in vivo évaluation of new drugs on this family of parasites and parasistes models.
We have designed and evaluated a series of compounds targeting essential enzymes in P. falciparum survival. This 4 years multidisciplinary program has developed new skills to answer new questionings all along our research. We have combined organic synthesis, biochemistry and the molecular biology as well as structural biology and cellular and parasite biology, to design new drugs and validate the interest of our approach to fight malaria. We developed the necessary tools to concentrate on the role of the aminopeptidase PfA-M1 for the parasite Plasmodium falciparum. These compounds which inhibit specifically this malarial aminopeptidase, are capable of decreasing the in vivo parasitemia (40 %) in standardized murine models.
This work should continue in order to better adapt the intrinsic properties of the developed compounds to the new biological roles discovered during our work.
6 published publications , and 6 in the course of drafting
Malaria is still the most important parasitic infection and one of the major causes of mortality. The vast majority of victims are children under 5;even today, a child dies every 45 seconds. With more than a third of the world’s population living in endemic areas, malaria is a serious global health and developmental challenge in Africa, South-East Asia and the Amazon region of latin America, described as the “poverty belt”. The emergence of drug-resistant Plasmodiumstrains to current therapeutics, combined with the treatment cost and limited access to health care in these countries of great poverty, remains a major problem.We intend to participate in the fight against P. falciparum by developing original compounds, at a reasonable cost, targeting two aminopeptidases (PfA-M1 and-M17) essential at different stages of the reproductive cycle of the parasite.This multidisciplinary project brought together the unique expertise of both partners, the one with original compounds (to optimize for this application) of these specific families of metallo-aminopeptidases, the other with a detailed knowledge of the parasite(s) involved in the disease, and also at the origin of the discovery and characterization of PfA-M1.We have gathered all the necessary experience, from molecular chemistry to murine models of malaria. The consortium born by combining both laboratories (with their respective established collaborations) is an alternative approach to the current Australian-American consortium, which is currentlythe unique other pole worldwide addressing these targets(PfA-M1 and-M17).Our collaboration, already initiated, has showed that ouraminobenzosuberone-type compounds are safe Hits/Leads (flexible scaffold, attractive Ligand Efficiency and inhibitory activities of the parasite growth in the µM range) to develop more potent new drug-candidates. Thus, this 4-years research program is divided into 4 interactive phases (tasks) conducted in a parallel and/or successive manner, and requiring the expertise of each partner:
1. Production and characterization of recombinant enzymes PfA-M1/M17
2. Organic Synthesis, Medicinal Chemistry & ADME studies (TechmedIll, Strasbourg)
Enzymes crystallization with selected compounds in order to generate structural information (in collaboration with the SLS in Villingen (S))
3. Biological activities of compounds:
in vitro: Inhibition (Ki) of recombinant enzymes produced from P. falciparum and human enzymes of the same family in order to study the selectivity
- Selection of the most active compounds, with the best pharmacological profile
incellulo: inhibition of parasite growth in culture (IC50& IC90)
Toxicity to mammalian cells (CD50)
- Selection of compounds with the best therapeutic index.
in vivo: Determination of toxicity (MTD & MTTD) in animals. Inhibition of parasite development in vivo in mouse models of malaria.
4. Mode of action studies of new molecules: Evaluation of selected compounds at different stages of parasite development & evaluation of a possible synergy with existing antimalarials.
This work will lead to a clinical candidate within the end of this four years research timeline, a special effort in organic synthesis will be carried out to minimize the cost of the final molecule.
Madame Céline TARNUS (Ecole Nationale Supérieure de Chimie de Mulhouse - Laboratoire de Chimie Organique et Bioorganique - Université de Haute Alsace - EA 4566) – Celine.Tarnus@uha.fr
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
CNRS-MNHN-MCAM Muséum National d'Histoire Naturelle, Molécules de Communication et Adaptation des Micro-organismes, CNRS-MNHN, Equipe Adaptation des Protozoaires à leur Environnement / CNRS
ENSC - MUHA Ecole Nationale Supérieure de Chimie de Mulhouse - Laboratoire de Chimie Organique et Bioorganique - Université de Haute Alsace - EA 4566
Help of the ANR 448,760 euros
Beginning and duration of the scientific project: September 2012 - 48 Months