oz-439 and arterolane

Ozonide antimalarials, OZ277 (arterolane) and OZ439 (artefenomel), are synthetic peroxide-based antimalarials with potent activity against the deadliest malaria parasite, Plasmodium falciparum. Here we used a "multi-omics" workflow, in combination with activity-based protein profiling (ABPP), to demonstrate that peroxide antimalarials initially target the haemoglobin (Hb) digestion pathway to kill malaria parasites. Time-dependent metabolomic profiling of ozonide-treated P. falciparum infected red blood cells revealed a rapid depletion of short Hb-derived peptides followed by subsequent alterations in lipid and nucleotide metabolism, while untargeted peptidomics showed accumulation of longer Hb-derived peptides. Quantitative proteomics and ABPP assays demonstrated that Hb-digesting proteases were increased in abundance and activity following treatment, respectively. Ozonide-induced depletion of short Hb-derived peptides was less extensive in a drug-treated K13-mutant artemisinin resistant parasite line (Cam3.IIR539T) than in the drug-treated isogenic sensitive strain (Cam3.IIrev), further confirming the association between ozonide activity and Hb catabolism. To demonstrate that compromised Hb catabolism may be a primary mechanism involved in ozonide antimalarial activity, we showed that parasites forced to rely solely on Hb digestion for amino acids became hypersensitive to short ozonide exposures. Quantitative proteomics analysis also revealed parasite proteins involved in translation and the ubiquitin-proteasome system were enriched following drug treatment, suggestive of the parasite engaging a stress response to mitigate ozonide-induced damage. Taken together, these data point to a mechanism of action involving initial impairment of Hb catabolism, and indicate that the parasite regulates protein turnover to manage ozonide-induced damage.

Topics: Adamantane; Antimalarials; Erythrocytes; Hemoglobins; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; Humans; Peroxides; Plasmodium falciparum; Proteomics; Spiro Compounds

The peroxide bond of the artemisinins inspired the development of a class of fully synthetic 1,2,4-trioxolane-based antimalarials, collectively known as the ozonides. Similar to the artemisinins, heme-mediated degradation of the ozonides generates highly reactive radical species that are thought to mediate parasite killing by damaging critical parasite biomolecules. We examined the relationship between parasite dependent degradation and antimalarial activity for two ozonides, OZ277 (arterolane) and OZ439 (artefenomel), using a combination of

Topics: Adamantane; Antimalarials; Erythrocytes; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; Humans; Peroxides; Plasmodium falciparum; Spiro Compounds; Trophozoites

We describe the first systematic study of antimalarial 1,2,4-trioxolanes bearing a substitution pattern regioisomeric to that of arterolane. Conformational analysis suggested that trans-3″-substituted trioxolanes would exhibit Fe(II) reactivity and antiparasitic activity similar to that achieved with canonical cis-4″ substitution. The chiral 3″ analogues were prepared as single stereoisomers and evaluated alongside their 4″ congeners against cultured malaria parasites and in a murine malaria model. As predicted, the trans-3″ analogues exhibited in vitro antiplasmodial activity remarkably similar to that of their cis-4″ comparators. In contrast, efficacy in the Plasmodium berghei mouse model differed dramatically for some of the congeneric pairs. The best of the novel 3″ analogues (e.g., 12i) outperformed arterolane itself, producing cures in mice after a single oral exposure. Overall, this study suggests new avenues for modulating Fe(II) reactivity and the pharmacokinetic and pharmacodynamic properties of 1,2,4-trioxolane antimalarials.

Topics: Animals; Antimalarials; Female; Ferrous Compounds; Heterocyclic Compounds, 1-Ring; Malaria; Mice; Peroxides; Plasmodium berghei; Plasmodium falciparum; Spiro Compounds; Stereoisomerism; Structure-Activity Relationship

Recently published data suggest that artemisinin derivatives and synthetic peroxides, such as the ozonides OZ277 and OZ439, have a similar mode of action. Here the cross-resistance of OZ277 and OZ439 and four additional next-generation ozonides was probed against the artemisinin-resistant clinical isolate Plasmodium falciparum Cam3.I, which carries the K13-propeller mutation R539T (Cam3.I. The previously described in vitro ring-stage survival assay (RSA. At the pharmacologically relevant concentration of 700 nM, all six ozonides were highly effective against the dihydroartemisinin-resistant P. falciparum Cam3.I. The absence of in vitro cross-resistance against the artemisinin-resistant clinical isolate Cam3.I

Topics: Adamantane; Antimalarials; Artemisinins; Drug Resistance; Heterocyclic Compounds, 1-Ring; Peroxides; Plasmodium falciparum; Spiro Compounds

The ring-stage susceptibility assay was modified to quantify the susceptibilities of multiple strains of control and delayed-clearance phenotype (DCP) Plasmodium falciparum strains to seven endoperoxide antimalarial drugs. The susceptibility of all of the DCP lines to six of the drugs was lower than that of the controls. In contrast, DCP parasites did not show reduced susceptibility to the synthetic endoperoxide drug OZ439. These data show that it is possible to circumvent emerging artemisinin resistance with a modified endoperoxide drug.

Topics: Adamantane; Antimalarials; Artemether; Artemisinins; Dose-Response Relationship, Drug; Drug Resistance; Heterocyclic Compounds, 1-Ring; Inactivation, Metabolic; Lethal Dose 50; Microbial Sensitivity Tests; Peroxides; Plasmodium falciparum; Spiro Compounds

To ascertain the structure-activity relationship of the core 1,2,4-trioxolane substructure of dispiro ozonides OZ277 and OZ439, we compared the antimalarial activities and ADME profiles of the 1,2-dioxolane, 1,2,4-trioxane, and 1,2,4,5-tetraoxane isosteres. Consistent with previous data, both dioxolanes had very weak antimalarial properties. For the OZ277 series, the trioxane isostere had the best ADME profile, but its overall antimalarial efficacy was not superior to that of the trioxolane or tetraoxane isosteres. For the OZ439 series, there was a good correlation between the antimalarial efficacy and ADME profiles in the rank order trioxolane > trioxane > tetraoxane. As we have previously observed for OZ439 versus OZ277, the OZ439 series peroxides had superior exposure and efficacy in mice compared to the corresponding OZ277 series peroxides.

Topics: Absorption; Adamantane; Animals; Antimalarials; Dioxolanes; Heterocyclic Compounds; Heterocyclic Compounds, 1-Ring; Male; Mice; Peroxides; Plasmodium berghei; Plasmodium falciparum; Spiro Compounds; Structure-Activity Relationship; Tetraoxanes

The declining efficacy of artemisinin derivatives against Plasmodium falciparum highlights the urgent need to identify alternative highly potent compounds for the treatment of malaria. In Papua Indonesia, where multidrug resistance has been documented against both P. falciparum and P. vivax malaria, comparative ex vivo antimalarial activity against Plasmodium isolates was assessed for the artemisinin derivatives artesunate (AS) and dihydroartemisinin (DHA), the synthetic peroxides OZ277 and OZ439, the semisynthetic 10-alkylaminoartemisinin derivatives artemisone and artemiside, and the conventional antimalarial drugs chloroquine (CQ), amodiaquine (AQ), and piperaquine (PIP). Ex vivo drug susceptibility was assessed in 46 field isolates (25 P. falciparum and 21 P. vivax). The novel endoperoxide compounds exhibited potent ex vivo activity against both species, but significant differences in intrinsic activity were observed. Compared to AS and its active metabolite DHA, all the novel compounds showed lower or equal 50% inhibitory concentrations (IC(50)s) in both species (median IC(50)s between 1.9 and 3.6 nM in P. falciparum and 0.7 and 4.6 nM in P. vivax). The antiplasmodial activity of novel endoperoxides showed different cross-susceptibility patterns in the two Plasmodium species: whereas their ex vivo activity correlated positively with CQ, PIP, AS, and DHA in P. falciparum, the same was not apparent in P. vivax. The current study demonstrates for the first time potent activity of novel endoperoxides against drug-resistant P. vivax. The high activity against drug-resistant strains of both Plasmodium species confirms these compounds to be promising candidates for future artemisinin-based combination therapy (ACT) regimens in regions of coendemicity.

Topics: Adamantane; Amodiaquine; Antimalarials; Artemisinins; Artesunate; Chloroquine; Drug Resistance, Multiple; Heterocyclic Compounds, 1-Ring; Microbial Sensitivity Tests; Peroxides; Plasmodium falciparum; Plasmodium vivax; Quinolines; Spiro Compounds