Corrigendum: Identification of novel anti-amoebic pharmacophores from kinase inhibitor chemotypes

[This corrects the article DOI: 10.3389/fmicb.2023.1149145.].

Identification of novel anti-amoebic pharmacophores from kinase inhibitor chemotypes

Acanthamoeba species, Naegleria fowleri, and Balamuthia mandrillaris are opportunistic pathogens that cause a range of brain, skin, eye, and disseminated diseases in humans and animals. These pathogenic free-living amoebae (pFLA) are commonly misdiagnosed and have sub-optimal treatment regimens which contribute to the extremely high mortality rates (>90%) when they infect the central nervous system. To address the unmet medical need for effective therapeutics, we screened kinase inhibitor chemotypes against three pFLA using phenotypic drug assays involving CellTiter-Glo 2.0. Herein, we report the activity of the compounds against the trophozoite stage of each of the three amoebae, ranging from nanomolar to low micromolar potency. The most potent compounds that were identified from this screening effort were: 2d (A. castellanii EC50: 0.92 ± 0.3 μM; and N. fowleri EC50: 0.43 ± 0.13 μM), 1c and 2b (N. fowleri EC50s: <0.63 μM, and 0.3 ± 0.21 μM), and 4b and 7b (B. mandrillaris EC50s: 1.0 ± 0.12 μM, and 1.4 ± 0.17 μM, respectively). With several of these pharmacophores already possessing blood-brain barrier (BBB) permeability properties, or are predicted to penetrate the BBB, these hits present novel starting points for optimization as future treatments for pFLA-caused diseases.

Chemical Optimization of CBL0137 for Human African Trypanosomiasis Lead Drug Discovery

The carbazole CBL0137 (1) is a lead for drug development against human African trypanosomiasis (HAT), a disease caused by Trypanosoma brucei. To advance 1 as a candidate drug, we synthesized new analogs that were evaluated for the physicochemical properties, antitrypanosome potency, selectivity against human cells, metabolism in microsomes or hepatocytes, and efflux ratios. Structure-activity/property analyses of analogs revealed eight new compounds with higher or equivalent selectivity indices (5j, 5t, 5v, 5w, 5y, 8d, 13i, and 22e). Based on the overall compound profiles, compounds 5v and 5w were selected for assessment in a mouse model of HAT; while 5v demonstrated a lead-like profile for HAT drug development, 5w showed a lack of efficacy. Lessons from these studies will inform further optimization of carbazoles for HAT and other indications.

Effects of terpenes and tannins on some physiological and biochemical parameters in two species of phalangerid possums (Marsupialia : Phalangeridae)

The common brushtail possum (Trichosurus vulpecula) and the short-eared possum (T. caninus) are closely related but differ in several aspects of their life-history strategy, habitat and diet preferences. Both are generalist herbivores, but T. vulpecula consumes significant amounts of Eucalyptus spp. foliage, while T. caninus instead feeds mainly on Acacia spp. Eucalypt foliage is protected against herbivory by several classes of plant secondary compounds, including terpenes and tannins, while acacia foliage is protected mainly by tannins. We compared the responses of these two possum species to the addition of either sesquiterpenes or a hydrolysable tannin to a basal diet free of these compounds. In both species, sesquiterpenes tended to reduce food intake, and increased plasma concentrations of albumin and decreased concentrations of bicarbonate, the latter consistent with changes in acid–base balance. Tannic acid significantly depressed food intake in both species, and depressed plasma concentrations of total protein, albumin, glucose, sodium and chloride, consistent with dehydration. T. vulpecula increased urinary glucuronic acid excretion three-fold in response to dietary sesquiterpenes but there was no increase in T. caninus. T. vulpecula had five- to six-fold greater plasma concentrations of bilirubin, a potent antioxidant, than did T. caninus across all treatments. Results suggest that T. vulpecula can better withstand the detrimental effects of plant secondary compounds, consistent with its wider spectrum of foods and broader habitat preferences.