Hookworm disease is a major global health problem and principal among a number of soil-transmitted
helminthiases (STHs) for the chronic disability inflicted that impacts both personal and societal productivity.
Mass drug administration most often employs single-dose
therapy with just two drugs of the same chemical class to which resistance is a growing concern. New chemical entities with the appropriate single-dose efficacy are needed.
METHODS AND FINDINGS: Using various life-cycle stages of the hookworm Ancylostoma ceylanicum in vitro and a hamster model of
infection, we report the potent, dose-dependent cidal activities of the peptidyl
cysteine protease inhibitors (CPIs)
K11002 (4-mopholino-carbonyl-phenylalanyl-homophenylalanyl- vinyl sulfone phenyl) and
K11777 (N-methylpiperazine-phenylalanyl-homophenylalanyl-vinylsulfone phenyl). The latter is in late pre-clinical testing for submission as an
Investigational New Drug (IND) with the US Federal
Drug Administration as an anti-chagasic. In vitro,
K11002 killed hookworm eggs but was without activity against first-stage larvae. The reverse was true for
K11777 with a larvicidal potency equal to that of the current anti-hookworm
drug,
albendazole (ABZ). Both CPIs produced morbidity in ex vivo adult hookworms with the activity of
K11777 again being at least the equivalent of ABZ. Combinations of either
CPI with ABZ enhanced morbidity compared to single compounds. Strikingly, oral treatment of infected hamsters with 100 mg/kg
K11777 b.i.d. (i.e., a total daily dose of 200 mg/kg) for one day cured
infection: a single 100 mg/kg treatment removed >90% of worms. Treatment also reversed the otherwise fatal decrease in blood
hemoglobin levels and
body weights of hosts. Consistent with its mechanism of action,
K11777 decreased by >95% the resident CP activity in parasites harvested from hamsters 8 h post-treatment with a single 100 mg/kg oral dose.
CONCLUSION: A new, oral single-dose
anthelmintic that is active in an animal model of
hookworm infection and that possesses a distinct mechanism of action from current
anthelmintics is discovered. The data highlight both the possibility of repurposing the anti-chagasic
K11777 as a treatment for
hookworm infection and the opportunity to further develop CPIs as a novel
anthelmintic class to target hookworms and, possibly, other helminths.