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14th June 2015 @ 21:46

Stephan Meister from Elizabeth Winzeler's laboratory at UCSD tested two Series 1 Compounds in a liver stage assay to provide some greater context for the first Open Source Malaria Paper.

The aryl pyrrole OSM-S-5 and near neighbour OSM-S-38 were both blood-stage active compounds from Series 1 and were both evaluated in this assay. OSM-S-5 showed an IC50 of 23 uM, whilst OSM-S-38 had an activity of 19 nM with no HepG2 cytotoxicity. These data may provide some evidence that these two series of compounds may have distinct mechanisms of action.

Previously OSM-S-111, another of the near neighbours (analogous to OSM-S-38) had shown moderate potency in the same assay:

Liver stage malaria activities of OSM-S-106 and OSM-S-111 in Plasmodium berghei.




General assay principle:

This assay is based on the murine Plasmodium berghei species transformed with Luciferase. Hepatic human transformed cells (HepG2), pretreated for two hours with the compound to investigate, are infected with freshly dissected P. berghei Luciferase sporozoites. After 48 hours of incubation with the compound to investigate, the viability of P. berghei exoerythrocytic forms (EEF) is measured by bioluminescence.

This assay allows us to identify compounds with an eventual activity against sporozoite infection of liver cell as well the viability of liver schizonts. 

Update Sept 10th 2015

The compounds were re-tested by Stephan and Jenya Antonova, giving broadly similar results: OSM-S-5 showed an IC50 of 14 uM, whilst OSM-S-38 had an activity of 13 nM.

Pberghei results_2015_08_OSDD.xlsx

This raises the question of whether OSM-S-38 should be tested in the Pc liver stage assay at the BPRC in the Netherlands.



This post originally authored by Alice Williamson. Edited by Mat Todd. Updated with new data by Mat Todd.



Plasmodium berghei Luciferase sporozoites were obtained by dissection of infected A. stephensi mosquito salivary glands supplied by the New York University Insectary. Dissected salivary glands were homogenized in a glass tissue grinder and filtered twice through Nylon cell strainers (40 μm pore size, BD Falcon) and counted using a hemocytometer. The sporozoites were kept on ice until needed. 


OSM-S-5: TCMDC-123812 CC(N1C2=CC=C(F)C=C2)=C(C(OCC(N)=O)=O)C=C1C InChI=1S/C15H15FN2O3/c1-9-7-13(15(20)21-8-14(17)19)10(2)18(9)12-5-3-11(16)4-6-12/h3-7H,8H2,1-2H3,(H2,17,19) YSUCFIZUNLQZDX-UHFFFAOYSA-N

OSM-S-38: CC1=CC(/C=C(C(N/2)=O)\SC2=N/C3=CC=CC=C3)=C(C)N1C(C=C4)=CC=C4C(F)(F)F InChI=1S/C23H18F3N3OS/c1-14-12-16(15(2)29(14)19-10-8-17(9-11-19)23(24,25)26)13-20-21(30)28-22(31-20)27-18-6-4-3-5-7-18/h3-13H,1-2H3,(H,27,28,30)/b20-13- YBBWTVGRVHTTDD-MOSHPQCFSA-N

OSM-S-111: O=C(/C(S/1)=C/C2=C(C)N(C3=CC=C(OC)C=C3)C(C)=C2)NC1=N\C4=CC=CC=C4 InChI=1S/C23H21N3O2S/c1-15-13-17(16(2)26(15)19-9-11-20(28-3)12-10-19)14-21-22(27)25-23(29-21)24-18-7-5-4-6-8-18/h4-14H,1-3H3,(H,24,25,27)/b21-14- KXIVXNPEYYNDHE-STZFKDTASA-N

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