Artemisone effective against murine cerebral malaria

<p>Abstract</p> <p>Background</p> <p>Artemisinins are the newest class of drug approved for malaria treatment. Due to their unique mechanism of action, rapid effect on Plasmodium, and high efficacy in vivo, artemisinins have become essential components of malaria treatment. Administration of artemisinin derivatives in combination with other anti-plasmodials has become the first-line treatment for uncomplicated falciparum malaria. However, their efficiency in cases of cerebral malaria (CM) remains to be determined.</p> <p>Methods</p> <p>The efficacy of several artemisinin derivatives for treatment of experimental CM was evaluated in ICR or C57BL/6 mice infected by <it>Plasmodium berghei </it>ANKA. Both mouse strains serve as murine models for CM.</p> <p>Results</p> <p>Artemisone was the most efficient drug tested, and could prevent death even when administered at relatively late stages of cerebral pathogenesis. No parasite resistance to artemisone was detected in recrudescence. Co-administration of artemisone together with chloroquine was more effective than monotherapy with either drug, and led to complete cure. Artemiside was even more effective than artemisone, but this substance has yet to be submitted to preclinical toxicological evaluation.</p> <p>Conclusions</p> <p>Altogether, the results support the use of artemisone for combined therapy of CM.</p

Synthesis of Artemiside and Its Effects in Combination with Conventional Drugs against Severe Murine Malaria

This research describes the use of novel antimalarial combinations of the new artemisinin derivative artemiside, a 10-alkylamino artemisinin. It is a stable, highly crystalline compound that is economically prepared from dihydroartemisinin in a one-step process. Artemiside activity was more pronounced than that of any antimalarial drug in use, both in Plasmodium falciparum culture and in vivo in a murine malaria model depicting cerebral malaria (CM). In vitro high-throughput testing of artemiside combinations revealed a large number of conventional antimalarial drugs with which it was additive. Following monotherapy in mice, individual drugs reduced parasitemias to nondetectable levels. However, after a period of latency, parasites again were seen and eventually all mice became terminally ill. Treatment with individual drugs did not prevent CM in mice with recrudescent malaria, except for piperaquine at high concentrations. Even when CM was prevented, the mice developed later of severe anemia. In contrast, most of the mice treated with drug combinations survived. A combination of artemiside and mefloquine or piperaquine may confer an optimal result because of the longer half life of both conventional drugs. The use of artemiside combinations revealed a significant safety margin of the effective artemiside doses. Likewise, a combination of 1.3 mg/kg of body weight artemiside and 10 mg/kg piperaquine administered for 3 days from the seventh day postinfection was completely curative. It appears possible to increase drug concentrations in the combination therapy without reaching toxic levels. Using the drug combinations as little as 1 day before the expected death of control animals, we could prevent further parasite development and death due to CM or anemic malaria. Earlier treatment may prevent cognitive dysfunctions which might occur after recovery from CM

Glucocorticosteroids in Nano-Sterically Stabilized Liposomes Are Efficacious for Elimination of the Acute Symptoms of Experimental Cerebral Malaria

Cerebral malaria is the most severe complication of Plasmodium falciparum infection, and a leading cause of death in children under the age of five in malaria-endemic areas. We report high therapeutic efficacy of a novel formulation of liposome-encapsulated water-soluble glucocorticoid prodrugs, and in particular beta-methasone hemisuccinate (BMS), for treatment of experimental cerebral malaria (ECM), using the murine P. berghei ANKA model. BMS is a novel derivative of the potent steroid beta-methasone, and was specially synthesized to enable remote loading into nano-sterically stabilized liposomes (nSSL), to form nSSL-BMS. The novel nano-drug, composed of nSSL remote loaded with BMS, dramatically improves drug efficacy and abolishes the high toxicity seen upon administration of free BMS. nSSL-BMS reduces ECM rates in a dose-dependent manner and creates a survival time-window, enabling administration of an antiplasmodial drug, such as artemisone. Administration of artemisone after treatment with the nSSL-BMS results in complete cure. Treatment with BMS leads to lower levels of cerebral inflammation, demonstrated by changes in cytokines, chemokines, and cell markers, as well as diminished hemorrhage and edema, correlating with reduced clinical score. Administration of the liposomal formulation results in accumulation of BMS in the brains of sick mice but not of healthy mice. This steroidal nano-drug effectively eliminates the adverse effects of the cerebral syndrome even when the treatment is started at late stages of disease, in which disruption of the blood-brain barrier has occurred and mice show clear signs of neurological impairment. Overall, sequential treatment with nSSL-BMS and artemisone may be an efficacious and well-tolerated therapy for prevention of CM, elimination of parasites, and prevention of long-term cognitive damage

Characterization of nSSL before and after GC loading.

<p>Values shown in each category are the average±SD for at least 10 formulations (13 empty nSSL, 27 nSSL-BMS, and 17 nSSL-MPS formulations). No significant differences were observed when comparing size according to intensity, number, or volume. No significant differences were observed when comparing nSSL-MPS and nSSL-BMS. PdI: an indication of size distribution variance between different batches prepared. A low PdI (<0.2) indicates that the sample is monodispersed.% drug encapsulated  = 100×([drug]/[lipid]_{after Dowex anion exchanger})/([drug]/[lipid]_{after dialysis}).</p

Levels of BMS originating from nSSL-BMS or free BMS in tissues of naive healthy mice and mice with ECM.

<p>Mice at initial clinical stages of ECM were injected (on day 6 p.i.) with either free or nSSL-BMS. Healthy mice were injected with nSSL-BMS. *n.d, not done.</p

Survival rates after early treatment with 10 mg/kg free or nSSL-encapsulated MPS (upper graph) or BMS (lower graph).

<p>Representative results for ICR mice infected with PbA are presented. Arrows denote treatment administration. ECM prevention is reflected in longer survival times, due to the development of severe anemic malaria, and as a result creation of a survival time-window for anti-plasmodial administration. Significant differences in survival were seen between non-treated and nSSL-MPS-treated groups (p = 0.01) and between non-treated mice and mice administered free or nSSL-BMS (p<0.01).</p

The effect of nSSL-BMS treatment at late stages of ECM, followed by artemisone.

<p>PbAus-infected C57Bl/6 mice (n = 10 per group, non-treated; n = 6 per group, nSSL-BMS) were administered 5% dextrose or 20 mg/kg nSSL-BMS (arrows) every other day, starting on day 5p.i., followed by 2×10 mg/kg/d artemisone after the cerebral phase, on days 11–15 p.i. (double arrows). No effect on the development of parasitemia was observed following administration of 5% dextrose. Administration of nSSL-BMS significantly reduced clinical score when started on day 5 p.i. or day 6 p.i. (p<0.001, p<0.05 vs. no treatment, respectively) and increased survival (p<0.01 and p<0.001 vs. non-treated), creating a time-window for antiplasmodial treatment and cure. *Day 15 p.i. nSSL-BMS: n = 6 (days 5,7,9 p.i. and days 6,8 p.i.).</p

Effect of sequential steroid-artemisone treatment on the development of infection.

<p>PbAus-infected C57Bl/6 mice (n = 10 per group) were treated with 10 mg/kg free or nSSL-BMS on days 3, 5, 7, and 9 post-inoculation. Although parasitemias were not affected (p>0.05, all groups), treatment led to reduced clinical scores (p<0.05, non-treated vs. free BMS; p<0.001, vs. nSSL-BMS, days 1–12 p.i.), an effect more pronounced in liposome-treated mice (p<0.05, free vs. nSSL). Administration of 2×20 mg/kg/d artemisone on days 11–15p.i. led to cure. *One mouse (of the total 17 administered artemisone) relapsed and died of ECM. Arrows represent free or nSSL-BMS injections; double arrows represent artemisone injections.</p

Scoring of clinical signs of ECM.

<p>Scoring of clinical signs of ECM.</p