Table 1 Nitroheterocyclic drug efficacy in BALB/c and C3H mice infected with Trypanosoma cruzi CL Brener and JR strains.

Effectiveness of nitroheterocyclic drugs in treating acute stage Trypanosoma cruzi infections when administered for 5 days at 50 mg kg⁻¹ bid.

(a) In vivo imaging of BALB/c mice infected with bioluminescent T. cruzi (CL Brener strain) and treated twice daily by the oral route with benznidazole (BZ), nifurtimox (NF), fexinidazole (FX), or fexinidazole sulfone (FXS). Treatment was initiated 14 days post-infection (n = 6). Representative ventral images of 2 mice are shown for each drug, at various time points. NT, non-treated (vehicle only). Where necessary, to confirm curative outcomes, mice were immunosuppressed by cyclophosphamide treatment on days 28, 32 and 36 post-infection (underlined with a red bar). (b) Assessment of drug activity by ex vivo imaging. Representative images of organs/images isolated 50 days post-infection from NT (i), NF-treated (ii and iii), FX-treated (iv), and FXS-treated (v) mice. In the case of NF treatment, examples of cured (ii) and non-cured (iii) mice are illustrated.

Treatment of chronic (a) and acute (b) stage Trypanosoma cruzi infections with 30 mg kg⁻¹ benznidazole. Treatment of infected BALB/c mice (n = 6) with bioluminescent parasites (CL Brener strain) was initiated 124 or 126 days (chronic), or 14 days (acute) post-infection, once daily by the oral route, for the number of days indicated. Representative ventral images of the same pair of mice are shown for each drug, at various points post-infection. NT, non-treated (vehicle only). Where required to confirm curative outcomes, mice were immunosuppressed by cyclophosphamide treatment on days 42 and 46 (acute stage experiment), 138, 142 and 146 (chronic stage experiment, 5 days treatment), and 154, 158 and 162 (chronic stage experiment, 10 and 20 days treatment) (underlined with red bar). All mice scored as cured were bioluminescence negative by both in vivo and ex vivo imaging.

Nitroheterocylic drug activity in other experimental models of Chagas disease.

(a) BALB/c mice infected with bioluminescent T. cruzi JR strain were treated with benznidazole (BZ) or fexinidazole sulfone (FXS) 14 days post-infection. NT, non-treated (vehicle only). Drugs were administered orally, for 5 days at 100 mg kg⁻¹. FXS-treated mice were also immunosuppressed by cyclophosphamide treatment on days 32, 36 and 40 to promote the reactivation of any residual parasites (underlined with red bar). BZ was non-curative in all cases, (n = 6), whereas 4/5 mice treated with FXS were judged parasite-free after both in vivo and ex vivo imaging. (b) C3H mice infected with bioluminescent JR strain were treated orally with BZ or FXS 14 days post-infection, for 5 days at 100 mg kg⁻¹. Where necessary, to confirm curative outcomes, mice were immunosuppressed by cyclophosphamide treatment on days 28, 32 and 36 post-infection (underlined with a red bar). BZ was non-curative (n = 5), whereas 4/5 mice treated with FXS were parasite-free after both in vivo and ex vivo imaging. (c) C3H mice, chronically infected with bioluminescent JR strain were treated orally with BZ or FXS for 5 days at 100 mg kg⁻¹, commencing 161 days post-infection. Where required, cyclophosphamide treatment commencing on day 175, was used to promote reactivation. BZ-treatment cured 3/5 mice, whereas 5/5 mice were cured with FXS. (d) Assessment of drug-activity by ex vivo imaging. Organs/tissues from mice treated in the acute stage were removed 50 days post-infection (Methods) from NT (i), BZ-treated (ii) and FXS-treated (iii and iv) mice. Organs/tissues are arranged as described in Figs 1a and 2b. In the case of FXS treatment, examples of non-cured (iii) and cured (iv) mice are illustrated.