Disclosure of cinnamic acid/4,9-diaminoacridine conjugates as multi-stage antiplasmodial hits

4,9-diaminoacridines with reported antiplasmodial activity were coupled to different trans-cinnamic acids, delivering a new series of conjugates inspired by the covalent bitherapy concept. The new compounds were more potent than primaquine against hepatic stages of Plasmodium berghei, although this was accompanied by cytotoxic effects on Huh-7 hepatocytes. Relevantly, the conjugates displayed nanomolar activities against blood stage P. falciparum parasites, with no evidence of hemolytic effects below 100 µM. Moreover, the new compounds were at least 25-fold more potent than primaquine against P. falciparum gametocytes. Thus, the new antiplasmodial hits disclosed herein emerge as valuable templates for the development of multi-stage antiplasmodial drug candidates.

Improved synthesis of antiplasmodial 4-aminoacridines and 4,9-diaminoacridines

Acridines are one of the most important nitrogen-containing heterocycle systems and have many applications in the therapeutic field. However, the synthesis of acridine-based scaffolds is not always straightforward. Herein, we report the optimization of two multi-step synthetic routes towards 4,9-diaminoacridines and 4-aminoacridines, which have shown promising antiplasmodial properties. The improved synthesis pathways make use of greener, simpler, and more efficient methods, with less reaction steps and increased overall yields, which were doubled in some cases. These are impactful results towards future approaches to the chemical synthesis of acridine-based compounds.

New 4-(N-cinnamoylbutyl)aminoacridines as potential multi-stage antiplasmodial leads

A novel family of 4-aminoacridine derivatives was obtained by linking this heteroaromatic core to different trans-cinnamic acids. The 4-(N-cinnamoylbutyl)aminoacridines obtained exhibited in vitro activity in the low- or sub-micromolar range against (i) hepatic stages of Plasmodium berghei, (ii) erythrocytic forms of Plasmodium falciparum, and (iii) early and mature gametocytes of Plasmodium falciparum. The most active compound, having a meta-fluorocinnamoyl group linked to the acridine core, was 20- and 120-fold more potent, respectively, against the hepatic and gametocyte stages of Plasmodium infection than the reference drug, primaquine. Moreover, no cytotoxicity towards mammalian and red blood cells at the concentrations tested was observed for any of the compounds under investigation. These novel conjugates represent promising leads for the development of new multi-target antiplasmodials.

Acridine-Based Antimalarials-From the Very First Synthetic Antimalarial to Recent Developments

Malaria is among the deadliest infectious diseases in the world caused by Plasmodium parasites. Due to the high complexity of the parasite’s life cycle, we partly depend on antimalarial drugs to fight this disease. However, the emergence of resistance, mainly by Plasmodium falciparum, has dethroned most of the antimalarials developed to date. Given recent reports of resistance to artemisinin combination therapies, first-line treatment currently recommended by the World Health Organization, in Western Cambodia and across the Greater Mekong sub-region, it seems very likely that artemisinin and its derivatives will follow the same path of other antimalarial drugs. Consequently, novel, safe and efficient antimalarial drugs are urgently needed. One fast and low-cost strategy to accelerate antimalarial development is by recycling classical pharmacophores. Quinacrine, an acridine-based compound and the first clinically tested synthetic antimalarial drug with potent blood schizonticide but serious side effects, has attracted attention due to its broad spectrum of biological activity. In this sense, the present review will focus on efforts made in the last 20 years for the development of more efficient, safer and affordable antimalarial compounds, through recycling the classical quinacrine drug.

4,9-Diaminoacridines and 4-Aminoacridines as Dual-Stage Antiplasmodial Hits

Multi-stage drugs have been prioritized in antimalarial drug discovery, as targeting more than one process in the Plasmodium life cycle is likely to increase efficiency, while decreasing the chances of emergence of resistance by the parasite. Herein, we disclose two novel acridine-based families of compounds that combine the structural features of primaquine and chloroquine. Compounds prepared and studied thus far retained the in vitro activity displayed by the parent drugs against the erythrocytic stages of chloroquine-sensitive and -resistant Plasmodium falciparum strains, and against the hepatic stages of Plasmodium berghei, hence acting as dual-stage antiplasmodial hits.

[Thromboprophylaxis in critically ill children in Spain and Portugal]

INTRODUCTION

Although critically ill children may be at risk from developing deep venous thrombosis (DVT), data on its incidence and effectiveness of thromboprophylaxis are lacking.

OBJECTIVE

To describe the use of thromboprophylaxis in critically ill children in Spain and Portugal, and to compare the results with international data.

MATERIAL AND METHODS

Secondary analysis of the multinational study PROTRACT, carried out in 59 PICUs from 7 developed countries (4 from Portugal and 6 in Spain). Data were collected from patients less than 18 years old, who did not receive therapeutic thromboprophylaxis.

RESULTS

A total of 308 patients in Spanish and Portuguese (Iberian) PICUS were compared with 2176 admitted to international PICUs. Risk factors such as femoral vein (P=.01), jugular vein central catheter (P<.001), cancer (P=.03), and sepsis (P<.001), were more frequent in Iberian PICUs. The percentage of patients with pharmacological thromboprophylaxis was similar in both groups (15.3% vs. 12.0%). Low molecular weight heparin was used more frequently in Iberian patients (P<.001). In treated children, prior history of thrombosis (P=.02), femoral vein catheter (P<.001), cancer (P=.02) and cranial trauma or craniectomy (P=.006), were more frequent in Iberian PICUs. Mechanical thromboprophylaxis was used in only 6.8% of candidates in Iberian PICUs, compared with 23.8% in the international PICUs (P<.001).

CONCLUSIONS

Despite the presence of risk factors for DVT in many patients, thromboprophylaxis is rarely prescribed, with low molecular weight heparin being the most used drug. Passive thromboprophylaxis use is anecdotal. There should be a consensus on guidelines of thromboprophylaxis in critically ill children.