The efficacy of the benzimidazoles oxfendazole and flubendazole against Litomosoides sigmodontis is dependent on the adaptive and innate immune system

Abstract

Filarial nematodes can cause debilitating diseases such as lymphatic filariasis and onchocerciasis. Oxfendazole (OXF) is one promising macrofilaricidal candidate with improved oral availability compared to flubendazole (FBZ), and OXF is currently under preparation for phase 2 clinical trials in filariasis patients. This study aimed to investigate the immune system’s role during treatment with OXF and FBZ and explore the potential to boost the treatment efficacy via stimulation of the immune system. Wild type (WT) BALB/c, eosinophil-deficient ΔdblGata1, IL-4r/IL-5−/−, antibody-deficient μMT and B-, T-, NK-cell and ILC-deficient Rag2/IL-2rγ−/− mice were infected with the rodent filaria Litomosoides sigmodontis and treated with an optimal and suboptimal regimen of OXF and FBZ for up to 5 days. In the second part, WT mice were treated for 2–3 days with a combination of OXF and IL-4, IL-5, or IL-33. Treatment of WT mice reduced the adult worm burden by up to 94% (OXF) and 100% (FBZ) compared to vehicle controls. In contrast, treatment efficacy was lower in all immunodeficient strains with a reduction of up to 90% (OXF) and 75% (FBZ) for ΔdblGata1, 50 and 92% for IL-4r/IL-5−/−, 64 and 78% for μMT or 0% for Rag2/IL-2rγ−/− mice. The effect of OXF on microfilariae and embryogenesis displayed a similar pattern, while FBZ’s ability to prevent microfilaremia was independent of the host’s immune status. Furthermore, flow cytometric analysis revealed strain-and treatment-specific immunological changes. The efficacy of a shortened 3-day treatment of OXF (−33% adult worms vs. vehicle) could be boosted to a 91% worm burden reduction via combination with IL-5, but not IL-4 or IL-33. Our results suggest that various components of the immune system support the filaricidal effect of benzimidazoles in vivo and present an opportunity to boost treatment efficacy.

Onchocerciasis Drug Discovery: In Vitro Evaluation of FDA-Approved Drugs against Onchocerca gutturosa in Gambia

“…Similarly, oxfendazole is a drug that is used against intestinal helminths in the veterinary field over several decades. In vitro and in vivo animal studies showed that oxfendazole is also active against filarial nematodes [ 27 , 28 ]. Oxfendazole was tested in Phase 1 clinical trials [ 29 ] and will be tested in onchocerciasis, loiasis, mansonellosis and Trichuris trichiura patients in a Phase 2 clinical basket trial [ 30 ].…”

“…However, clinical studies in Mexico demonstrated that flubendazole has high macrofilaricidal activity [ 33 , 34 ] and in vivo laboratory studies confirmed this activity [ 35 ]. Recently, the important role of the immune system in supporting the macrofilaricidal efficacy for the related drug oxfendazole was demonstrated in the Litomosoides sigmodontis filarial mouse model [ 28 ]. Despite the limitation that some candidates may require an intact immune system for efficacy, several promising candidates were identified.…”

Combinations of the azaquinazoline anti-Wolbachia agent, AWZ1066S, with benzimidazole anthelmintics synergise to mediate sub-seven-day sterilising and curative efficacies in experimental models of filariasis

“…Upon combining humanised dose exposures of ABZ equivalent to standard 400 mg dosing (Turner et al, 2017 ) or matching doses of the veterinary OXF, which has higher systemic exposure and is being repurposed for human helminth indications (Lanusse et al, 1995 ; Gokbulut et al, 2007 ; Bach et al, 2020 ; Ehrens et al, 2022 ; Risch et al, 2023 ), we could demonstrate a pharmacological synergy of otherwise sub-optimal doses of AWZ1066S given alone for 5 days. The impact of ABZ “rescue” meant these otherwise ~2-fold sub-optimal 5-day doses could recapitulate profound sterilising and partial macrofilaricidal activities in the rodent models and washout periods tested.…”

“…Embryogram from adult worms was done as described elsewhere (Ziewer et al, 2012 ; Risch et al, 2023 ). Briefly, worms were fixed using 4% formaldehyde for 24 h and then stored in 60% ethanol until analysis.…”