Antimalarial pharmacodynamics and pharmacokinetics of a third-generation antifolate--JPC2056--in cynomolgus monkeys using an in vivo in vitro model.

OBJECTIVES: To assess the antimalarial pharmacodynamics and pharmacokinetics of the novel dihydrofolate reductase (DHFR) inhibitor, JPC2056 and its principal active metabolite JPC2067 in cynomolgus monkeys using an in vivo-in vitro model.
METHODS: In a two-phase crossover design, five cynomolgus monkeys were administered a single dose (20 mg/kg) and multiple doses (20 mg/kg daily for 3 days) of JPC2056. Plasma samples collected from treated monkeys were assessed for in vitro antimalarial activity against Plasmodium falciparum lines having wild-type (D6), double-mutant (K1) and quadruple-mutant (TM90-C2A) DHFR-thymidylate synthase (TS) and a P. falciparum line transformed with a Plasmodium vivax dhfr-ts quadruple-mutant allele (D6-PvDHFR). Plasma JPC2056 and JPC2067 concentrations were measured by LC-mass spectrometry.
RESULTS: The mean inhibitory dilution (ID(90)) of monkey plasma at 3 h after drug administration against D6, K1 and TM90-C2A was, respectively, 1253, 585 and 869 after the single-dose regimen and 1613, 1120 and 1396 following the multiple-dose regimen. Less activity was observed with the same monkey plasma samples against the D6-PvDHFR line, with a mean ID(90) of 53 after multiple dosing. Geometric mean plasma concentrations of JPC2056 and JPC2067 at 3 h after drug administration were, respectively, 113 and 12 ng/mL after the single dose and 150 and 17 ng/mL after multiple dosing. The mean elimination half-life of JPC2056 was shorter than its metabolite after both regimens (single dose, 7.3 versus 11.8 h; multiple doses, 6.6 versus 11.1 h).
CONCLUSIONS: The high potency of JPC2056 against P. falciparum DHFR-TS quadruple-mutant lines provides optimism for the future development of JPC2056 for the treatment of malaria infections.