nitd-609 and artemisinin

Malaria is a life threatening disease caused by microscopic parasites called Plasmodium that are transmitted to human beings by mosquitoes. Single celled Eukaryotic plasmodium parasite is responsible to cause malaria in human beings and is transmitted by bite of Anopheles species mosquitoes. Resurgence of malaria towards the end of 20th Century is due to failure of its eradication completely. Parasite recurrence occurs due to high densities of parasite, low immunity and non opimized drug concentration. The ineffective eradications strategies were due to indefinable complex life cycle of Plasmodium and emergence of drugs resistant strains of Plasmodium falciparum (Pf) including Artemisinin and Artemisinin based combination therapy (ACT). The vector of the disease i.e. mosquitoes became resistive towards Pyrethroids, which are only class of insecticides recommended for vector control. Artemisinin based combination therapy gained acceptance as an effective approach to counter the spread of disease resistance to chloroquine, sulfadoxine, pyrimethamine and other anti malarial drugs. Understanding the underlying molecular basis of the pathogenesis led to the development of some new diagnostic, drugs and insecticides. Reports on the use of new combination therapies reduced the burden of disease worldwide. Some of the new combination therapies are in clinical stage of development that have efficacy against drug resistant parasites and the potential to use in single dose regimens to improve compliance. The current review represents the recent anti-malarial research carried out globally especially in the class of synthesis of small molecule and natural product derivatives as potent anti-malarial drugs. The review also covers the advancement in the anti-malarial vaccine development although goal for vaccine development still remains elusive.

Topics: Animals; Antimalarials; Artemisinins; Drug Resistance; Humans; Malaria; Plasmodium falciparum

Malaria control efforts have been continuously stymied by drug-resistant strains of Plasmodium falciparum, which typically originate in Southeast Asia prior to spreading into high-transmission settings in Africa. One earlier proposed explanation for Southeast Asia being a hotbed of resistance has been the hypermutability or "Accelerated Resistance to Multiple Drugs" (ARMD) phenotype, whereby multidrug-resistant Southeast Asian parasites were reported to exhibit 1,000-fold higher rates of resistance to unrelated antimalarial agents when compared to drug-sensitive parasites. However, three recent studies do not recapitulate this hypermutability phenotype. Intriguingly, genome sequencing of recently derived multidrug-resistant Cambodian isolates has identified a high proportion of DNA repair gene mutations in multidrug-resistant parasites, suggesting their potential role in shaping local parasite evolution. By adapting fluctuation assays for use in P. falciparum, we have examined the in vitro mutation rates of five recent Cambodian isolates and three reference laboratory strains. For these studies we also generated a knockout parasite line lacking the DNA repair factor Exonuclease I. In these assays, parasites were typed for their ability to acquire resistance to KAE609, currently in advanced clinical trials, yielding 13 novel mutations in the Na+/H+-ATPase PfATP4, the primary resistance determinant. We observed no evidence of hypermutability. Instead, we found evidence of a mild mutator (up to a 3.4-fold increase in mutation rate) phenotype in two artemisinin-resistant Cambodian isolates, which carry DNA repair gene mutations. We observed that one such mutation in the Mismatch Repair protein Mlh1 contributes to the mild mutator phenotype when modeled in yeast (scmlh1-P157S). Compared to basal rates of mutation, a mild mutator phenotype may provide a greater overall benefit for parasites in Southeast Asia in terms of generating drug resistance without incurring detrimental fitness costs.

Topics: Alleles; Antimalarials; Artemisinins; Cambodia; Drug Resistance, Multiple; Gene Frequency; Humans; Indoles; Malaria, Falciparum; Mutation; MutL Protein Homolog 1; Phenotype; Plasmodium falciparum; Protozoan Proteins; Sodium-Potassium-Exchanging ATPase; Spiro Compounds