Naphthoquine phosphate

IC50: 0.1-5.2 nM for various P. falciparum strains [1]

Malaria remains a disease of devastating global impact, killing more than 800,000 people every year-the vast majority being children under the age of 5. Naphthoquine phosphate is a antimalarial drug developed in China.

In vitro: Naphthoquine phosphate showed promising antimalaria acitivities against various P. falciparum strains. Moreover, previoius study highlighted that naphthoquine did not lose potency when tested against chloroquine resistant strains [1].

In vivo: In an study aiming to investigate the antimalarial activity of naphthoquine phosphate combined with artemisinine against Plasmodium knowlesi in rhesus monkey, it was found that the combination of naphthoquine phosphate and artemisinine was superior to the single component and the optimum proportion in the combination is 1 : 2.5 in treating P. knowlesi infection in monkeys [2].

Clinical trial: An oral single dose of the combination drug (400 mg of naphthoquine + 1000mg artemisinin) was administered to adult uncomplicated falciparum malaria patients. Mean fever clearance time, parasite clearance time were 18.2 ± 8.6 h and 34.6 ± 14.3 h, respectively. Adequate clinical and parasitological response was achieved in 52 out of 54 cases, the rate being 98.1%. The drug was well tolerated and no adverse reactionswere detected in the patients [3].

References:
[1] Delves M, Plouffe D, Scheurer C, Meister S, Wittlin S, Winzeler EA, Sinden RE, Leroy D.  The activities of current antimalarial drugs on the life cycle stages of Plasmodium: a comparative study with human and rodent parasites. PLoS Med. 2012;9(2):e1001169.
[2] Wang JY, Ding DB, Li GF, Zhao JH.  Therapeutic efficacy of naphthoquine phosphate combined with artemisinine against Plasmodium knowlesi. Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi. 2008;26(6):442-4.
[3] Tun T, Tint HS, Lin K, Kyaw TT, Myint MK, Khaing W, Tun ZW.   Efficacy of oral single dose therapy with artemisinin-naphthoquine phosphate in uncomplicated falciparum malaria. Acta Trop. 2009;111(3):275-8.

Spotlight on the in vitro effect of artemisinin-naphthoquine phosphate on Schistosoma mansoni and its snail host Biomphalaria alexandrina.[Pubmed:25291045]

Acta Trop. 2015 Jan;141(Pt A):37-45.

Malaria and schistosomiasis are the two most important parasitic diseases in the tropics and sub-tropics with geographic overlap. Efforts have been made for developing new schistosomicidal drugs, or testing existing drugs originally used for non-related diseases. The antimalarial artemisinin-Naphthoquine phosphate combination (CO-ArNp) was recently reported to be a promising novel antischistosomal therapy with potent in vivo activity against Schistosoma mansoni. In this work, we report the in vitro dose- and time-response effect of CO-ArNp against the Egyptian strain of S. mansoni, and its snail host, Biomphalaria alexandrina. Incubation of adult S. mansoni with CO-ArNp at 40 or 20 mug/ml for 48 or 72 h killed all worms. Exposure of S. mansoni miracidia and cercariae to the molluscicidal LC50 of CO-ArNp (16.8 mug/ml) resulted in 100% mortality of the free larval stages within 90 and 15 min, respectively. Moreover, incubation of adult B. alexandrina snails with this drug combination killed all snails at 40 mug/ml within 24h. Scanning electron microscope revealed marked morphological and tegumental alterations on the different stages of the parasite and its snail soft tissue. Our study highlights the schistosomicidal and molluscicidal effects of artemisinin-Naphthoquine phosphate. No doubt more studies are needed to clarify its potential value to control schistosomiasis.

First insight into the effect of single oral dose therapy with artemisinin-naphthoquine phosphate combination in a mouse model of Schistosoma mansoni infection.[Pubmed:23500074]

Int J Parasitol. 2013 Jun;43(7):521-30.

Praziquantel is the current drug of choice against schistosomiasis. The dependency on praziquantel exclusively is problematic, given the spread of the disease and the threat of drug resistance. This study investigates an alternative antischistosomal drug using the compound Naphthoquine phosphate tablet, which is a novel single oral dose antimalarial drug, containing a combination of Naphthoquine phosphate and artemisinin. In the present study, the therapeutic efficacies of different artemisinin-Naphthoquine phosphate combination-dosing protocols were evaluated in experimentally infected mice harbouring juvenile or adult stages of Schistosoma mansoni (Egyptian strain). The study shows that the oral administration of artemisinin-Naphthoquine phosphate combination in a single dose of 400 mg/kg on day 7 p.i. resulted in a significant worm burden reduction of 95.07%. When used at a dose of 600 mg/kg on day 21 p.i., all female worms were killed before depositing eggs, resulting in complete absence of eggs in hepatic and intestinal tissues. The same dose given on day 42 p.i. reduced total and female worm burdens by 93.36% and 94.17%, respectively. In addition, artemisinin-Naphthoquine phosphate combination induced significant reductions of 80.18% and 76.73% in the hepatic and intestinal tissue egg loads, respectively. Artemisinin-Naphthoquine phosphate combination also induced significant alterations in the oogram pattern with elevated levels of dead eggs. Antipathological activities were evident in the amelioration of hepatic granulomata. Our findings hold promise for the development of a novel antischistosomal drug using an artemisinin-Naphthoquine phosphate combination. Further in vitro and in vivo studies should be launched to elucidate the possible mechanism/s of action and to study the effect of artemisinin-Naphthoquine phosphate combination on other human schistosomes.

Single-dose safety, pharmacokinetics, and food effects studies of compound naphthoquine phosphate tablets in healthy volunteers.[Pubmed:20197487]

J Clin Pharmacol. 2010 Nov;50(11):1310-8.

The compound Naphthoquine phosphate is a novel antimalaria drug tablet containing a fixed-dose combination of Naphthoquine phosphate and artemisinin in a 1:2.5 ratio. A randomized, open study on the safety and tolerability was conducted in 28 healthy male volunteers using a single oral dose of 350 mg, 700 mg, 1400 mg, or 2100 mg of artemisinin-Naphthoquine phosphate. Pharmacokinetics at the last 3 doses were examined in 30 volunteers. Food effects were also determined. Serial blood samples up to 216 hours after single oral dose administration were analyzed for plasma concentrations using a validated high-performance liquid chromatography-tandem mass spectrometry assay. The compound was well tolerated at single doses up to 2100 mg. Increased exposure to Naphthoquine phosphate and artemisinin was less than dose proportional and linear. The half-life of Naphthoquine phosphate was approximately 255 hours. The combination increased the AUC(0-t) and C(max) of both artemisinin (by 71% and 49%) and Naphthoquine phosphate (by 135% and 104%) compared with monotherapy. Food intake greatly increased the AUC(0-t) of artemisinin with a ratio of 77% and reduced that of Naphthoquine phosphate from 955 +/- 352 microg.h/L under the fasted state to 446 +/- 231 microg.h/L in the fed condition. The pharmacokinetics and safety profile of the drug support its continued investigation in future clinical studies.

Efficacy of oral single dose therapy with artemisinin-naphthoquine phosphate in uncomplicated falciparum malaria.[Pubmed:19464245]

Acta Trop. 2009 Sep;111(3):275-8.

All artemisinin-based combination therapies (ACTs), recommended by the World Health Organization, are 3-day regimens. A considerable level of non-compliance on ACTs has been reported from some countries. The study aimed to assess the therapeutic efficacy of single dose treatment with new generation ACT containing artemisinin plus naphthoquine. An oral single dose of eight tablets (400 mg of naphthoquine+1000 mg artemisinin) of the combination drug was administered to adult uncomplicated falciparum malaria patients. Observations of fever, parasite clearance and reappearance, and other clinical manifestations were made on Days 0, 1, 2, 3, 7, 14, 21 and 28. Fifty-three adult falciparum positive cases, with fever or history of fever within the previous 24 h, were included in the final evaluation of the study. Mean fever clearance time, parasite clearance time were 18.2+/-8.6 h and 34.6+/-14.3 h, respectively. Adequate clinical and parasitological response was achieved in 52 cases, the rate being 98.1% (95% CI, 91.1-99.9). One patient was classified as late parasitological failure because of the reappearance of falciparum parasite on Day 14. The drug was well tolerated and no adverse reactions were detected in the patients. Since it is a single dose therapy, health workers can administer the drug as directly observed treatment.