Integrative approach for accelerating filarial worm drug discovery to treat river blindness

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Abstract River blindness (onchocerciasis) is a major neglected chronic tropical disease that has been selected by the WHO for elimination by 2030. Currently, international control programs attempt to interrupt transmission of infection with annual mass drug administration (MDA), over the 10-14 years lifetime of the adult worms, using the microfilaricidal drug ivermectin that kills the microfilariae (mf) of Onchocerca volvulus, the causative agent of onchocerciasis. However, MDA with ivermectin is confounded in Africa because it cannot be used in areas co- endemic for loiasis due to the risk of severe adverse events. The overall goal of our project is to develop a novel direct macrofilaricidal (lethal to adult worms directly) preclinical candidate drug as targeted therapy for onchocerciasis using a multidimensional interdisciplinary experimental approach. Our proposal is based on two main resources we have established: a) an extensive omics resource that allowed the identification of defined conserved and diversified essential molecular targets in adult filarial worms, and b) a multifaceted screening funnel that was used successfully to phenotypically screen in vitro a library of drugs approved for clinical use, resulting in the identification of drugs with macrofilaricidal activity. In silico prioritization interfaced with the experimental identification of drugs that were active against the adult stage of filarial nematodes resulted in a short list of inhibitors with known drug-indication and putative target indication pairs that form the basis for our rational optimization of new compounds with direct macrofilaricidal potential. Our proposed aims thus build on our significant progress starting with validating the canonical targets in filarial nematodes, further expanding the list of our five high priority hit scaffolds with similar compounds by using pharmacophore searches, followed by discovery and rational design of innovative adult filarial nematode- selective drugs. The newly synthesized compounds will be optimized for potency and selectivity against the parasites vs. the host as well as against the cognate filarial nematode targets using a systems biology approach. We will also confirm the mode of action for the most promising lead compounds which will also be assessed for in vivo efficacy in two filarial small animal models that we have developed to facilitate assessing drug candidates in vivo (Brugia pahangi/jirds and Onchocerca ochengi/jirds). The overall approach deploys iterative optimization of two chemical series of compounds, and by the end of the project we plan to have at least one macrofilaricidal drug candidate to move into late stage preclinical studies. Overall, this project will emphatically address a critical research and thus operational gap; the identification and development of novel potent and safe macrofilaricidal drugs. Our rational discovery approach has the potential of providing macrofilaricidal drugs that kill directly adult worms needed to achieve the elimination goals for the human onchocerciasis.