JPC-2997, a new aminomethylphenol with high in vitro and in vivo antimalarial activities against blood stages of Plasmodium.

4-(tert-Butyl)-2-((tert-butylamino)methyl)-6-(6-(trifluoromethyl)pyridin-3-yl)-phenol (JPC-2997) is a new aminomethylphenol compound that is highly active in vitro against the chloroquine-sensitive D6, the chloroquine-resistant W2, and the multidrug-resistant TM90-C2B Plasmodium falciparum lines, with 50% inhibitory concentrations (IC50s) ranging from 7 nM to 34 nM. JPC-2997 is >2,500 times less cytotoxic (IC50s > 35 µM) to human (HepG2 and HEK293) and rodent (BHK) cell lines than the D6 parasite line. In comparison to the chemically related WR-194,965, a drug that had advanced to clinical studies, JPC-2997 was 2-fold more active in vitro against P. falciparum lines and 3-fold less cytotoxic. The compound possesses potent in vivo suppression activity against Plasmodium berghei, with a 50% effective dose (ED50) of 0.5 mg/kg of body weight/day following oral dosing in the Peters 4-day test. The radical curative dose of JPC-2997 was remarkably low, at a total dose of 24 mg/kg, using the modified Thompson test. JPC-2997 was effective in curing three Aotus monkeys infected with a chloroquine- and pyrimethamine-resistant strain of Plasmodium vivax at a dose of 20 mg/kg daily for 3 days. At the doses administered, JPC-2997 appeared to be well tolerated in mice and monkeys. Preliminary studies of JPC-2997 in mice show linear pharmacokinetics over the range 2.5 to 40 mg/kg, a low clearance of 0.22 liters/h/kg, a volume of distribution of 15.6 liters/kg, and an elimination half-life of 49.8 h. The high in vivo potency data and lengthy elimination half-life of JPC-2997 suggest that it is worthy of further preclinical assessment as a partner drug.

Novel diaryl ureas with efficacy in a mouse model of malaria.

Exploration of triclosan analogs has led to novel diaryl ureas with significant potency against in vitro cultures of drug-resistant and drug-sensitive strains of the human malaria parasite Plasmodium falciparum. Compound 18 demonstrated EC(50) values of 37 and 55 nM versus in vitro cultured parasite strains and promising in vivo efficacy in a Plasmodium berghei antimalarial mouse model, with >50% survival at day 31 post-treatment when administered subcutaneously at 256 mg/kg. This series of compounds provides a chemical scaffold of novel architecture, as validated by cheminformatics analysis, to pursue antimalarial drug discovery efforts.

Identification of the optimal third generation antifolate against P. falciparum and P. vivax.

Inhibitors of dihydrofolate reductase (DHFR) have been mainstays in the treatment of falciparum malaria. Resistance to one of these antifolates, pyrimethamine, is now common in Plasmodium falciparum populations. Antifolates have not traditionally been recommended for treatment of vivax malaria. However, recent studies have suggested that a third-generation antifolate, WR99210, is remarkably effective even against highly pyrimethamine-resistant parasites from both species. Two methods were used to identify a compound that is effective against quadruple mutant alleles from P. falciparum (N51I/C59R/S108N/I164L) and from Plasmodium vivax (57L/111L/117T/173F). The first was simple yeast system used to screen a panel of WR99210 analogs. The biguanide prodrug, JPC-2056, of the 2-chloro-4-trifluoromethoxy analog of WR99210 was effective against both the P. falciparum and P. vivax enzymes, and has been selected for further development. The second method compared the analogs in silico by docking them in the known structure of the P. falciparum DHFR-thymidylate synthase. The program reproduced well the position of the triazine ring, but the calculated energies of ligand binding were very similar for different compounds and therefore did not reproduce the observed trends in biological activity. The WR99210 family of molecules is flexible due to a long bridge between the triazine ring and the substituted benzene. During docking, multiple conformations were observed for the benzene ring part of the molecules in the DHFR active site, making computer-based predictions of binding energy less informative than for more rigid ligands. This flexibility is a key factor in their effectiveness against the highly mutant forms of DHFR.