Inhibition of the Non-Mevalonate Isoprenoid Pathway by Reverse Hydroxamate Analogues of Fosmidomycin

Synthesis of Novel Artemisinin, Ciprofloxacin, and Norfloxacin Hybrids with Potent Antiplasmodial Activity

The synthesis and antiplasmodial evaluation of new hybrids combining the pharmacophore structures of artemisinin, ciprofloxacin or norfloxacin, and 7-chloroquinoline are reported in this study. The first step for all of the syntheses is the obtainment of key piperazine esters intermediates bearing the drugs ciprofloxacin and norfloxacin. Using these platforms, 18 final compounds were synthesized through a multistep procedure with overall yields ranging between 8 and 20%. All compounds were screened for their antiplasmodial activity against the chloroquine-resistant Plasmodium falciparum FcB1 strain. Compounds 20, 21, 22, and 28, bearing an artesunate fragment with ciprofloxacin, exhibited IC50 values in the range of 3.5-5.4 nM and excellent selectivity indices. Among the compounds bearing the artesunate moiety on the norfloxacin, two of them, 23 and 24, afforded IC50 values of 1.5 nM and 1.9 nM, respectively. They also showed excellent selectivity indices. The most potent compounds were also evaluated against the CQ-resistant Dd2 strain of Plasmodium falciparum, demonstrating that those compounds incorporating the artesunate fragment were the most potent. Finally, the combination of artesunate with either ciprofloxacin or norfloxacin moieties in a single molecular entity proved to substantially enhance the activity and selectivity when compared to the administration of the unconjugated counterparts artesunate/ciprofloxacin and artesunate/norfloxacin.

Efforts Made to Eliminate Drug-Resistant Malaria and Its Challenges

Since 2000, a good deal of progress has been made in malaria control. However, there is still an unacceptably high burden of the disease and numerous challenges limiting advancement towards its elimination and ultimate eradication. Among the challenges is the antimalarial drug resistance, which has been documented for almost all antimalarial drugs in current use. As a result, the malaria research community is working on the modification of existing treatments as well as the discovery and development of new drugs to counter the resistance challenges. To this effect, many products are in the pipeline and expected to be marketed soon. In addition to drug and vaccine development, mass drug administration (MDA) is under scientific scrutiny as an important strategy for effective utilization of the developed products. This review discusses the challenges related to malaria elimination, ongoing approaches to tackle the impact of drug-resistant malaria, and upcoming antimalarial drugs.

Synthesis and anti-parasitic activity of achiral N-benzylated phosphoramidic acid derivatives

Synthetic pathways have been developed to access a series of N-benzylated phosphoramidic acid derivatives as novel, achiral analogues of the established Plasmodium falciparum 1-deoxy-d-xylulose-5-phosphate reductase (PfDXR) enzyme inhibitor, FR900098. Bioassays of the targeted compounds and their synthetic precursors have revealed minimal antimalarial activity but encouraging anti-trypanosomal activity - in one case with an IC₅₀ value of 5.4 µM against Trypanosoma brucei, the parasite responsible for Nagana (African cattle sleeping sickness). The results of relevant in silico modelling and docking studies undertaken in the design and evaluation of these compounds are discussed.