Drug repurposing: From the discovery of a useful pharmacological effect to making the treatment available to the patient.

The repurposing of a medicine already on the market to a new indication could be an opportunity to respond rapidly to a therapeutic need not yet covered, particularly in the context of rare and neglected diseases, or health emergencies. However, at each stage, difficulties may arise that will prevent the repurposed drug from being provided to patients. Beyond fortuity or a systematic strategy to detect a useful pharmacological effect, the implementation of the preclinical and clinical stages is sometimes complicated by the difficulty of accessing the molecule and its pharmaceutical data. Furthermore, relevant clinical results will not always be sufficient to ensure that a marketing authorisation is obtained or that patients receive satisfactory care. In addition to describing these various obstacles, the round table provided an opportunity to put forward recommendations for overcoming them, in particular the creation of a public-private partnership structure with sufficient funding to be able to offer individualised support for projects up to and including the marketing application.

Clofoctol inhibits SARS-CoV-2 replication and reduces lung pathology in mice.

Drug repurposing has the advantage of shortening regulatory preclinical development steps. Here, we screened a library of drug compounds, already registered in one or several geographical areas, to identify those exhibiting antiviral activity against SARS-CoV-2 with relevant potency. Of the 1,942 compounds tested, 21 exhibited a substantial antiviral activity in Vero-81 cells. Among them, clofoctol, an antibacterial drug used for the treatment of bacterial respiratory tract infections, was further investigated due to its favorable safety profile and pharmacokinetic properties. Notably, the peak concentration of clofoctol that can be achieved in human lungs is more than 20 times higher than its IC50 measured against SARS-CoV-2 in human pulmonary cells. This compound inhibits SARS-CoV-2 at a post-entry step. Lastly, therapeutic treatment of human ACE2 receptor transgenic mice decreased viral load, reduced inflammatory gene expression and lowered pulmonary pathology. Altogether, these data strongly support clofoctol as a therapeutic candidate for the treatment of COVID-19 patients.

Identification of ebselen as a potent inhibitor of insulin degrading enzyme by a drug repurposing screening.

Insulin-degrading enzyme, IDE, is a metalloprotease implicated in the metabolism of key peptides such as insulin, glucagon, ß-amyloid peptide. Recent studies have pointed out its broader role in the cell physiology. In order to identify new drug-like inhibitors of IDE with optimal pharmacokinetic properties to probe its multiple roles, we ran a high-throughput drug repurposing screening. Ebselen, cefmetazole and rabeprazole were identified as reversible inhibitors of IDE. Ebselen is the most potent inhibitor (IC50(insulin) = 14 nM). The molecular mode of action of ebselen was investigated by biophysical methods. We show that ebselen induces the disorder of the IDE catalytic cleft, which significantly differs from the previously reported IDE inhibitors. IDE inhibition by ebselen can explain some of its reported activities in metabolism as well as in neuroprotection.

Characterization of monoclonal antibodies by a fast and easy liquid chromatography-mass spectrometry time-of-flight analysis on culture supernatant.

Rapid and efficient structural analysis is key to the development of new monoclonal antibodies. We have developed a fast and easy process to obtain mass spectrometry profiles of antibodies from culture supernatant. Treatment of the supernatant with IdeS generates three fragments of 25 kDa that can be analyzed by liquid chromatography-mass spectrometry time-of-flight (LC-MS TOF) in one run: LC, Fd, and Fc/2. This process gives rapid access to isoform and glycoform profiles. To specifically measure the fucosylation yield, we included a one-pot treatment with EndoS that removes the distal glycan heterogeneity. Our process was successfully compared with high-performance capillary electrophoresis with laser-induced fluorescence detection (HPCE-LIF), currently considered as the "gold standard" method.

Rescue of nonsense mutations by amlexanox in human cells.

BACKGROUND: Nonsense mutations are at the origin of many cancers and inherited genetic diseases. The consequence of nonsense mutations is often the absence of mutant gene expression due to the activation of an mRNA surveillance mechanism called nonsense-mediated mRNA decay (NMD). Strategies to rescue the expression of nonsense-containing mRNAs have been developed such as NMD inhibition or nonsense mutation readthrough. METHODS: Using a dedicated screening system, we sought molecules capable to block NMD. Additionally, 3 cell lines derived from patient cells and harboring a nonsense mutation were used to study the effect of the selected molecule on the level of nonsense-containing mRNAs and the synthesis of proteins from these mutant mRNAs. RESULTS: We demonstrate here that amlexanox, a drug used for decades, not only induces an increase in nonsense-containing mRNAs amount in treated cells, but also leads to the synthesis of the full-length protein in an efficient manner. We also demonstrated that these full length proteins are functional. CONCLUSIONS: As a result of this dual activity, amlexanox may be useful as a therapeutic approach for diseases caused by nonsense mutations.

Drug-to-genome-to-drug, step 2: reversing selectivity in a series of antiplasmodial compounds.

In a recent paper, we have described the discovery of antimalarial compounds derived from tadalafil, using a drug-to-genome-to-drug approach ( J. Med. Chem. 2011 , 54 ( 9 ), pp 3222 - 3240 ). We have shown that these derivatives inhibit the phosphodiesterase activity of Plasmodium falciparum and the parasite growth in culture. In this paper, we describe the optimization of these compounds. A direct consequence of our approach based on gene orthology is the lack of selectivity of the compounds over the original activity on the human target. We demonstrate here that it is possible to take advantage of subtle differences in SAR between HsPDE5 inhibition and antiplasmodial activity to improve significantly the selectivity. In particular, the replacement of the piperonyl group in compound 2 by a dimethoxyphenyl group was the best way to optimize selectivity. This observation is consistent with the differences between human and plasmodial sequences in the Q2 pocket receiving this group.

Drug to genome to drug: discovery of new antiplasmodial compounds.

The dominant strategy for discovery of new antimalarial drugs relies on cell-free assays on specific biochemical pathways of Plasmodium falciparum . However, it appears that screening directly on the parasite is a more rewarding approach. The "drug to genome to drug" approach consists of testing a small set of structural analogues of a drug acting on human proteins that have plasmodial orthologues. Both man and plasmodium possess cyclic nucleotide phosphodiesterases (PDEs) that are key players of cell homeostasis. We synthesized and tested 40 analogues of tadalafil, a human PDE5 inhibitor, on P. falciparum in culture and obtained potent inhibitors of parasite growth. We discuss the structure-activity relationships, which support the hypothesis that our compounds kill the parasite via inhibition of plasmodial PDE activity. We also prove that antiplasmodial derivatives inhibit the hydrolysis of cyclic nucleotides of the parasite, validating the cAMP/cGMP pathways as therapeutic targets against Plasmodium falciparum.

Natural compounds: leads or ideas? Bioinspired molecules for drug discovery.

In this article, we compare drugs of natural origin to synthetic compounds and analyze the reasons why natural compounds occupy a place of choice in the current pharmacopoeia. The observations reported here support the design of synthetic compounds inspired from plant alkaloids and their biosynthetic pathway. Our reasoning leads to very efficient syntheses of compounds which complexity matches that of indolomonoterpenic alkaloids.

Novel selective inhibitors of the zinc plasmodial aminopeptidase PfA-M1 as potential antimalarial agents.

Proteases that are expressed during the erythocytic stage of Plasmodium falciparum are newly explored drug targets for the treatment of malaria. We report here the discovery of potent inhibitors of PfA-M1, a metallo-aminopeptidase of the parasite. These compounds are based on a malonic hydroxamic template and present a very good selectivity toward neutral aminopeptidase (APN-CD13), a related protease in mammals. Structure-activity relationships in these series are described. Further optimization of the best inhibitor yielded a nanomolar, selective inhibitor of PfA-M1. This inhibitor displays good physicochemical and pharmacokinetic properties and a promising antimalarial activity.

PDE5 inhibitors: An original access to novel potent arylated analogues of tadalafil.

A method to access totally new analogues of tadalafil was explored. The Buchwald reaction was adapted and used to replace the methyl group of tadalafil by various aryl groups. Inhibition potencies on PDE5 of these analogues were determined and proved to be comparable to the one of tadalafil. Using the same route, compounds with the same level of activity but improved water solubility were produced by introducing a pyridine or a pyrimidine ring. This original route also opens access to new unpatented compounds.

A library of novel hydroxamic acids targeting the metallo-protease family: design, parallel synthesis and screening.

We report here the design and parallel synthesis of 217 compounds based on a malonic-hydroxamic acid template. These compounds are obtained via a two-step solution-phase procedure. The set of diverse building-blocks used makes this strategy suitable for the search of inhibitors of various metallo-proteases and for the investigation of the biological role of new metallo-proteases. As a proof of concept, we screened this library on Neutral Aminopeptidase (APN; EC 3.4.11.2), the prototypal enzyme of the M1 family. Several submicromolar inhibitors were identified.