Target discovery and mode of action studies of dehydrodieugenol B analogues in Leishmania

Thesis

Leishmaniasis is a neglected parasitic disease that places a substantial burden on endemic communities. There is an urgent need for new anti leishmanial compounds due to the toxic side effects of current therapies and emerging drug resistance undermining their effectiveness. Central to this is understanding a compound’s mode of action (MoA) – how it interacts with the parasite at the molecular level and which target(s) it binds. The MoA is unknown for many anti leishmanial compounds, despite well established phenotypic, biochemical, and omics methods with proven success in this application. This thesis contributes to the ongoing search by investigating the MoA of three compound families with potent activity. Here we show that the dehydrodieugenol B (DDB) compound family (primarily using analogue DDB 1) localises to the mitochondrion indicating a mitochondrial MoA, Ascididemin carries out reactive oxygen species (ROS) generation and metal ion chelation, while the benzyltetrahydroisoquinoline (BI) alkaloids disrupt the cell cycle. DDB 1 was unable to select for in vitro drug resistance, contrary to expectation for a drug like compound in this often successful method to elucidate compound MoA. Ascididemin, as expected, selected for specific genes in a specialist genome wide knockdown library enabling MoA identification. Our results demonstrate that different MoA elucidation techniques are best suited to different compound families. Based on the MoA proposed here, Ascididemin and the BI compounds are rendered unsuitable hit compounds, while DDB 1 has an unusual yet promising MoA, with the potential to become a valuable lead compound following further target identification and medicinal chemistry efforts.

Authors: Asiki, H

• DOI: 10.5287/ora-yxrxmzrqj
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Dehydrodieugenol B; mode of action studies; Leishmaniasis; target identification
• Subjects: Organic compounds--Synthesis; Parasitology; Mechanism of action (Biochemistry)