Bioactivity Comments

The interaction table below provides data from whole cell assays and gives the antiparasite activity of ELQ-300 against a number of Plasmodium lifecycle stages. The results include an evaluation of asexual blood stage activity using a panel of P. falciparum strains, with ELQ-300 demonstrating no evidence of reduced potency against drug-resistant strains. In addition, ex vivo testing of drug-resistant field isolates of the two most significant human malaria species, P. falciparum and P. vivax, were found to be sensitive to ELQ-300 (EC50 values 14.9 and 17.9 nM respectively) [4]. ELQ-300 is not cytotoxic vs. various mammalian cell lines which is indicative of an excellent in vitro selectivity index, nor does it inhibit ATP production in mammalian cells lines or from the human cytochrome bc1 complex isolated from HEK293 cells.

Whole organism assay data
Key to terms and symbols	Click on species/strain names for details	Click column headers to sort
MOA/likely target Sp. Assay description Type Action Value Parameter Concentration range (M) Reference Plasmodium falciparum cytochrome b Pb Plasmodium berghei P. berghei (Pb) is a malaria parasite that infects mammals other than humans with the natural mammalian host being the thicket rat (G. surdaster) from Central Africa. Pb is used in rodent model studies of malaria. ✖ Parasite liver stage assay - - 9.0 pEC50 - 4 ⤷ pEC50 9.0 (EC50 1.02x10-9 M) Luciferase bioluminescence assay to measure viability of exoerythrocytic forms [4] Lifecycle stages: Plasmodium liver stage (sporozoite, hepatic schizont, hepatic merozoite) Plasmodium falciparum cytochrome b PfW2 Plasmodium falciparum W2 P. falciparum strain W2 (PfW2) was cloned from the Indochina III/CDC isolate, originally derived from a Laotian patient who failed chloroquine therapy. PfW2 can be obtained from the European Malaria Reagent Repository or the Malaria Research and Reference Reagent Resource Center (MR4) and is reported to be resistant to chloroquine and susceptible to mefloquine. ✖ Parasite growth inhibition assay - - 8.6 – 8.7 pIC50 - 4 ⤷ pIC50 8.7 (IC50 1.8x10-9 M) SYBR green method, measured at 72h [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) pIC50 8.6 (IC50 2.27x10-9 M) [3H]-hypoxanthine incorporation [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) Plasmodium falciparum cytochrome b PfTM90C2B Plasmodium falciparum TM90C2B P. falciparum TM90C2B (PfTM90C2B) is a clinical isolate, first described during a Phase 2 clinical trial to determine atovaquone efficacy in Thailand (PMID:8651372). A point mutation (Y268S) at the Qo site of cytochrome b results in a 3,000-fold loss of atovaquone sensitivity. It is used as a screening tool for the development of new cytochrome b inhibitors. ✖ Parasite growth inhibition assay - - 8.6 – 8.8 pIC50 - 4 ⤷ pIC50 8.8 (IC50 1.7x10-9 M) SYBR green method, measured at 72h [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) pIC50 8.6 (IC50 2.84x10-9 M) [3H]-hypoxanthine incorporation [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) Plasmodium falciparum cytochrome b PfDd2 Plasmodium falciparum Dd2 P. falciparum strain Dd2 (PfDd2) is a clone derived from PfW2, following continuous culture in mefloquine. PfW2 was cloned from the Indochina III/CDC isolate, originally derived from a Laotian patient who failed chloroquine therapy. PfDd2 can be obtained from the Malaria Research and Reference Reagent Resource Center (MR4) and is reported to be resistant to chloroquine, pyrimethamine and mefloquine. ✖ Parasite growth inhibition assay - - 8.6 pIC50 - 4 ⤷ pIC50 8.6 (IC50 2.5x10-9 M) SYBR green method, measured at 72h [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) Plasmodium falciparum cytochrome b PfD6 Plasmodium falciparum D6 P. falciparum strain D6 (PfD6) was collected in Sierra Leone. PfD6 can be obtained from the European Malaria Reagent Repository or the Malaria Research and Reference Reagent Resource Center (MR4) and is generally considered drug sensitive with minor mefloquine resistance. ✖ Parasite growth inhibition assay - - 8.5 – 8.7 pIC50 - 4 ⤷ pIC50 8.7 (IC50 2.2x10-9 M) SYBR green method, measured at 72h [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) pIC50 8.5 (IC50 3.06x10-9 M) [3H]-hypoxanthine incorporation [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) Plasmodium falciparum cytochrome b PfTM91C235 Plasmodium falciparum TM91C235 P. falciparum TM91C235 (PfTM91C235) is a clinical isolate from a patient in Thailand who failed mefloquine treatment twice. It can be obtained from the Malaria Research and Reference Reagent Resource Center (MR4) and is reported to be resistant to chloroquine, sulfadoxime, pyrimethamine and quinine. ✖ Parasite growth inhibition assay - - 8.4 pIC50 - 4 ⤷ pIC50 8.4 (IC50 4.34x10-9 M) [3H]-hypoxanthine incorporation [4] Lifecycle stages: Plasmodium asexual blood stage (erythrocytic merozoite, trophozoite, erythrocytic schizont) Plasmodium falciparum cytochrome b PfNF54 Plasmodium falciparum NF54 P. falciparum strain NF54 (PfNF54) was derived from a patient who had never left the Netherlands. PfNF54 can be obtained from the European Malaria Reagent Repository or the Malaria Research and Reference Reagent Resource Center (MR4) and is sensitive to a panel of antimalarial compounds including chloroquine and pyrimethamine. ✖ Parasite late stage (IV–V) gametocyte assay - - 7.1 pIC50 - 4 ⤷ pIC50 7.1 (IC50 7.19x10-8 M) High-content fluorescence-based image analysis of gametocyte viability throughout a period of 72 hours [4] Lifecycle stages: Plasmodium sexual blood stage (gametocyte) Plasmodium falciparum cytochrome b Pc Plasmodium cynomolgi P. cynomolgi (Pc) is a malaria parasite that infects non-human primate species with the natural mammalian host being Asian Old World monkeys. Pc is used as a model for human P. vivax infection because these species are phylogenetically close and share a similar lifecycle, including the dormant liver form (hypnozoite). ✖ Parasite liver stage assay - - ~7.0 pIC50 - 4 ⤷ pIC50 ~7.0 (IC50 ~1x10-7 M) High-content fluorescence imaging to quantify the number of developing hepatic schizonts in primary rhesus hepatocytes infected with sporozoites from the M strain of P. cynomolgi [4] Lifecycle stages: Plasmodium liver stage (sporozoite, hepatic schizont, hepatic merozoite) Plasmodium falciparum cytochrome b PfNF54 Plasmodium falciparum NF54 P. falciparum strain NF54 (PfNF54) was derived from a patient who had never left the Netherlands. PfNF54 can be obtained from the European Malaria Reagent Repository or the Malaria Research and Reference Reagent Resource Center (MR4) and is sensitive to a panel of antimalarial compounds including chloroquine and pyrimethamine. ✖ Parasite early stage (I–III) gametocyte assay - - - - - 4 ⤷ Giemsa-stained blood film counts: treated gametocytes did not develop past stage III, even at 0.1 μM, the lowest dose tested [4] Lifecycle stages: Plasmodium sexual blood stage (gametocyte)