The antimalarial MMV688533 provides potential for single-dose cures with a high barrier to Plasmodium falciparum parasite resistance.

The emergence and spread of Plasmodium falciparum resistance to first-line antimalarials creates an imperative to identify and develop potent preclinical candidates with distinct modes of action. Here, we report the identification of MMV688533, an acylguanidine that was developed following a whole-cell screen with compounds known to hit high-value targets in human cells. MMV688533 displays fast parasite clearance in vitro and is not cross-resistant with known antimalarials. In a P. falciparum NSG mouse model, MMV688533 displays a long-lasting pharmacokinetic profile and excellent safety. Selection studies reveal a low propensity for resistance, with modest loss of potency mediated by point mutations in PfACG1 and PfEHD. These proteins are implicated in intracellular trafficking, lipid utilization, and endocytosis, suggesting interference with these pathways as a potential mode of action. This preclinical candidate may offer the potential for a single low-dose cure for malaria.

Identification and optimization of a new series of anti-tubercular quinazolinones.

A high throughput phenotypic screening against Mycobacterium smegmatis led us to the discovery of a new class of bacteriostatic, highly hydrophobic antitubercular quinazolinones that potently inhibited the in vitro growth of either extracellular or intramacrophagic M. tuberculosis (Mtb), via modulation of an unidentified but yet novel target. Optimization of the initial hit compound culminated in the identification of potent but poorly soluble Mtb growth inhibitors, three of which were progressed to in vivo efficacy studies. Despite nanomolar in vitro potency and attractive PK properties, none of these compounds was convincingly potent in our in vivo mouse tuberculosis models. This lack of efficacy may be linked to the poor drug-likeness of the test molecules and/or to the properties of the target.

Synthesis and multiparametric evaluation of thiadiazoles and oxadiazoles as diacylglycerol acyltransferase type 1 inhibitors.

Chemical modulation of a formerly disclosed DGAT-1 inhibitor resulted in the identification of a compound with a suitable profile for preclinical development. Optimisation of solubility is discussed and a PK/PD study is presented.

Stabilization of rasburicase and physico-chemical characterization of the resulting injectable formulation.

Rasburicase (Fasturtec/Elitek) is a new generation of recombinant urate oxidase administred therapeutically by intravenous infusion for the prevention or treatment of hyperuricemia during chemotherapy. To ensure a long storage period, a freeze-dried formulation was developed to guarantee the molecular integrity and enzyme activity. Screening of potential excipients was the first stage of the preformulation study. The selection was based on stability results (rasburicase solution with excipient) obtained with the isoelectric focusing profiles and residual enzyme activity. The different excipients were classified as stabilising, neutral or destabilising. A stability study was then carried out on different freeze-dried formulations containing the usual bulking agents for freeze-drying, excipients with a high glass transition temperature or competitive enzyme inhibitors having a stabilising effect. A mannitol/alanine mixture in phosphate buffer was selected from these preliminary results. Finally, the optimal content of mannitol and alanine in the freeze-dried powder was determined by an experimental design study. The water content and the appearance of the "cake", the osmolality, pH, clarity, and enzyme activity of the reconstituted solution were assessed. The formula with a mannitol/alanine ratio of 0.7 was found to be the best composition. Differential scanning calorimetry and ThermoStimulated Current technique experiments were carried out to study the amorphous phase. A glass transition temperature of about 45-500 degrees C was found. Glassy state is known to preserve stability, which was verified by the real stability data. X-ray diffraction studies have shown that alanine is in a crystallised state and that mannitol remains amorphous. Crystallised excipients participate in forming the structure of the powder and therefore help to prevent any collapse. Amorphous mannitol creates a surrounding medium favourable to the stability of the protein.

Molecular mobility study of amorphous and crystalline phases of a pharmaceutical product by thermally stimulated current spectrometry.

Two crystalline forms and the amorphous state of irbesartan, a pharmaceutical drug chosen as a model, were analyzed by Thermally Stimulated Current (TSC) spectroscopy, a powerful technique currently used in polymer science to investigate the molecular dynamics of heterogeneous and complex materials. Whereas no specific dielectric response was noted for the B crystalline form, the A form of irbesartan exhibited molecular motions localized inside its channel structure. The dynamics involved in the dielectric glass transition of amorphous samples followed a compensation law characteristic of highly cooperative relaxation processes. Concerning the amorphous content in physical mixtures, a calibration curve and a limit of detection (2.5%) were established. The limit of detection could be improved by optimizing the TSC experimental parameters. The amorphous sample recrystallized at a single temperature was interpreted by the "idealized one-state model" defined here to describe systems composed of identical semicrystalline particles in which amorphous and crystalline phases are independent of each other (i.e., no chemical and physical interaction between the two phases). Therefore, the idealized one-state model may be simulated by a two-state model, which is representative of the two-phase model. Other samples recrystallized through a complex annealing stage were explained by the classical one-state model in agreement with the three-phase model used to describe bulk semicrystalline systems. These results demonstrate that, as for polymers, the semicrystalline state of pharmaceutical drugs should not be considered as a single state but as a more complex system that can be described as an idealized one-state model or a one-state model depending on the applied thermal treatment. These results give a new view that should be taken into account in the development of amorphous pharmaceutical drugs and formulations.