The metabolism of piperaquine to its antiplasmodial metabolites and their pharmacokinetic profiles in healthy volunteers [PublishAheadOfPrint]

As a partner antimalarial for artemisinin drug-based combination therapy (ACT), piperaquine (PQ) can be metabolized into two major metabolites, including piperaquine N-oxide (M1) and N,N-dioxide (M2). To better understand the antimalarial potency of PQ, the antimalarial activity of PQ metabolites (M1 and M2) was studied in vitro (Plasmodium strains Pf3D7 and PfDd2) and in vivo (murine Plasmodium yoelii) in this study. The recrudescence and survival time of infected mice were also recorded after drug treatment. The pharmacokinetic profiles of PQ and its two metabolites (M1 and M2) were investigated in healthy subjects after oral doses of two widely used ACT regimens, i.e., Duo-Cotecxin (dihydroartemisinin plus piperaquine phosphate) and Artequick (artemisinin plus piperaquine). Remarkable antiplasmodial activity was found for PQ (IC₅₀ 4.5 nM against Pf3D7 and IC₅₀ 6.9 nM against PfDd2 strain; ED₉₀ of 1.3 mg/kg), M1 (IC₅₀ 25.5 nM against Pf3D7 and IC₅₀ 38.7 nM against PfDd2 strain; ED₉₀ of 1.3 mg/kg) and M2 (IC₅₀ 31.2 nM against Pf3D7 and IC₅₀ 33.8 nM against PfDd2 strain; ED₉₀ of 2.9 mg/kg). Compared with PQ, M1 showed comparable efficacy, in terms of recrudescence and survival time, and M2 had relatively weaker antimalarial potency. PQ and its two metabolites displayed a long elimination half-life (~11 days for PQ, ~9 days for M1 and ~4 days for M2), and they accumulated after repeated administrations. The contribution of two PQ metabolites to the efficacy of piperaquine as a partner drug of ACT for the treatment of malaria should be considered for PQ dose optimization.

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